Computer Science › Computer Networks and Communications

Cooperative Communication and Network Coding

Works Count: 56176

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Description

This cluster of papers focuses on cooperative diversity in wireless networks, exploring efficient protocols, outage behavior, network coding, relay networks, space-time coding, and amplify-and-forward techniques. It delves into topics such as physical layer network coding, MIMO relay channels, and the analysis of outage probability in multiuser communication scenarios.

Keywords

Cooperative Diversity; Wireless Networks; Network Coding; Relay Networks; Space-Time Coding; Amplify-and-Forward; Physical Layer Network Coding; MIMO Relay Channels; Outage Probability; Multiuser Communication

Device-to-device communication in 5G cellular networks: challenges, solutions, and future directions

2014-05-01

Mohsen Nader Tehrani , Murat Uysal , Halim Yanıkömeroğlu

In a conventional cellular system, devices are not allowed to directly communicate with each other in the licensed cellular bandwidth and all communications take place through the base stations. In … In a conventional cellular system, devices are not allowed to directly communicate with each other in the licensed cellular bandwidth and all communications take place through the base stations. In this article, we envision a two-tier cellular network that involves a macrocell tier (i.e., BS-to-device communications) and a device tier (i.e., device-to-device communications). Device terminal relaying makes it possible for devices in a network to function as transmission relays for each other and realize a massive ad hoc mesh network. This is obviously a dramatic departure from the conventional cellular architecture and brings unique technical challenges. In such a two-tier cellular system, since the user data is routed through other users' devices, security must be maintained for privacy. To ensure minimal impact on the performance of existing macrocell BSs, the two-tier network needs to be designed with smart interference management strategies and appropriate resource allocation schemes. Furthermore, novel pricing models should be designed to tempt devices to participate in this type of communication. Our article provides an overview of these major challenges in two-tier networks and proposes some pricing schemes for different types of device relaying.

Three-terminal communication channels

1971-01-01

Edward C. van der Meulen

The problem of transmitting information in a specified direction over a communication channel with three terminals is considered. Examples are given of the various ways of sending information. Basic inequalities … The problem of transmitting information in a specified direction over a communication channel with three terminals is considered. Examples are given of the various ways of sending information. Basic inequalities for average mutual information rates are obtained. A coding theorem and weak converse are proved and a necessary and sufficient condition for a positive capacity is derived. Upper and lower bounds on the capacity are obtained, which coincide for channels with symmetric structure.

Hot topic

2006-09-29

Shengli Zhang , Soung Chang Liew , Patrick P. Lam

A main distinguishing feature of a wireless network compared with a wired network is its broadcast nature, in which the signal transmitted by a node may reach several other nodes, … A main distinguishing feature of a wireless network compared with a wired network is its broadcast nature, in which the signal transmitted by a node may reach several other nodes, and a node may receive signals from several other nodes simultaneously. Rather than a blessing, this feature is treated more as an interference-inducing nuisance in most wireless networks today (e.g., IEEE 802.11). The goal of this paper is to show how the concept of network coding can be applied at the physical layer to turn the broadcast property into a capacity-boosting advantage in wireless ad hoc networks. Specifically, we propose a physical-layer network coding (PNC) scheme to coordinate transmissions among nodes. In contrast to "straightforward" network coding which performs coding arithmetic on digital bit streams after they have been received, PNC makes use of the additive nature of simultaneously arriving electromagnetic (EM) waves for equivalent coding operation. PNC can yield higher capacity than straight-forward network coding when applied to wireless networks. We believe this is a first paper that ventures into EM-wave-based network coding at the physical layer and demonstrates its potential for boosting network capacity. PNC opens up a whole new research area because of its implications and new design requirements for the physical, MAC, and network layers of ad hoc wireless stations. The resolution of the many outstanding but interesting issues in PNC may lead to a revolutionary new paradigm for wireless ad hoc networking.

Compute-and-Forward: Harnessing Interference Through Structured Codes

2011-10-01

Bobak Nazer , Michael Gastpar

Interference is usually viewed as an obstacle to communication in wireless networks. This paper proposes a new strategy, compute-and-forward, that exploits interference to obtain significantly higher rates between users in … Interference is usually viewed as an obstacle to communication in wireless networks. This paper proposes a new strategy, compute-and-forward, that exploits interference to obtain significantly higher rates between users in a network. The key idea is that relays should decode linear functions of transmitted messages according to their observed channel coefficients rather than ignoring the interference as noise. After decoding these linear equations, the relays simply send them towards the destinations, which given enough equations, can recover their desired messages. The underlying codes are based on nested lattices whose algebraic structure ensures that integer combinations of codewords can be decoded reliably. Encoders map messages from a finite field to a lattice and decoders recover equations of lattice points which are then mapped back to equations over the finite field. This scheme is applicable even if the transmitters lack channel state information.

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How Practical is Network Coding?

2006-06-01

Mea Wang , Baochun Li

With network coding, intermediate nodes between the source and the receivers of an end-to-end communication session are not only capable of relaying and replicating data messages, but also of coding … With network coding, intermediate nodes between the source and the receivers of an end-to-end communication session are not only capable of relaying and replicating data messages, but also of coding incoming messages to produce coded outgoing ones. Recent studies have shown that network coding is beneficial for peer-to-peer content distribution, since if eliminates the need for content reconciliation, and is highly resilient to peer failures. In this paper, we present our recent experiences with a highly optimized and high-performance C++ implementation of randomized network coding at the application layer. We present our observations based on an extensive series of experiments, draw conclusions from a wide range of scenarios, and are more cautious and less optimistic as compared to previous studies

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Distributed space-time-coded protocols for exploiting cooperative diversity in wireless networks

2003-10-01

J. Nicholas Laneman , Gregory W. Wornell

We develop and analyze space-time coded cooperative diversity protocols for combating multipath fading across multiple protocol layers in a wireless network. The protocols exploit spatial diversity available among a collection … We develop and analyze space-time coded cooperative diversity protocols for combating multipath fading across multiple protocol layers in a wireless network. The protocols exploit spatial diversity available among a collection of distributed terminals that relay messages for one another in such a manner that the destination terminal can average the fading, even though it is unknown a priori which terminals will be involved. In particular, a source initiates transmission to its destination, and many relays potentially receive the transmission. Those terminals that can fully decode the transmission utilize a space-time code to cooperatively relay to the destination. We demonstrate that these protocols achieve full spatial diversity in the number of cooperating terminals, not just the number of decoding relays, and can be used effectively for higher spectral efficiencies than repetition-based schemes. We discuss issues related to space-time code design for these protocols, emphasizing codes that readily allow for appealing distributed versions.

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A Random Linear Network Coding Approach to Multicast

2006-09-29

T. Ho , Muriel Médard , R. Koetter +4 more

We present a distributed random linear network coding approach for transmission and compression of information in general multisource multicast networks. Network nodes independently and randomly select linear mappings from inputs … We present a distributed random linear network coding approach for transmission and compression of information in general multisource multicast networks. Network nodes independently and randomly select linear mappings from inputs onto output links over some field. We show that this achieves capacity with probability exponentially approaching 1 with the code length. We also demonstrate that random linear coding performs compression when necessary in a network, generalizing error exponents for linear Slepian-Wolf coding in a natural way. Benefits of this approach are decentralized operation and robustness to network changes or link failures. We show that this approach can take advantage of redundant network capacity for improved success probability and robustness. We illustrate some potential advantages of random linear network coding over routing in two examples of practical scenarios: distributed network operation and networks with dynamically varying connections. Our derivation of these results also yields a new bound on required field size for centralized network coding on general multicast networks

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Cooperative Strategies and Capacity Theorems for Relay Networks

2005-08-24

Gerhard Kramer , Michael Gastpar , Piyush Gupta

Coding strategies that exploit node cooperation are developed for relay networks. Two basic schemes are studied: the relays decode-and-forward the source message to the destination, or they compress-and-forward their channel … Coding strategies that exploit node cooperation are developed for relay networks. Two basic schemes are studied: the relays decode-and-forward the source message to the destination, or they compress-and-forward their channel outputs to the destination. The decode-and-forward scheme is a variant of multihopping, but in addition to having the relays successively decode the message, the transmitters cooperate and each receiver uses several or all of its past channel output blocks to decode. For the compress-and-forward scheme, the relays take advantage of the statistical dependence between their channel outputs and the destination's channel output. The strategies are applied to wireless channels, and it is shown that decode-and-forward achieves the ergodic capacity with phase fading if phase information is available only locally, and if the relays are near the source node. The ergodic capacity coincides with the rate of a distributed antenna array with full cooperation even though the transmitting antennas are not colocated. The capacity results generalize broadly, including to multiantenna transmission with Rayleigh fading, single-bounce fading, certain quasi-static fading problems, cases where partial channel knowledge is available at the transmitters, and cases where local user cooperation is permitted. The results further extend to multisource and multidestination networks such as multiaccess and broadcast relay channels.

Achievable rates in cognitive radio channels

2006-04-28

Natasha Devroye , Patrick Mitran , Vahid Tarokh

Cognitive radio promises a low-cost, highly flexible alternative to the classic single-frequency band, single-protocol wireless device. By sensing and adapting to its environment, such a device is able to fill … Cognitive radio promises a low-cost, highly flexible alternative to the classic single-frequency band, single-protocol wireless device. By sensing and adapting to its environment, such a device is able to fill voids in the wireless spectrum and can dramatically increase spectral efficiency. In this paper, the cognitive radio channel is defined as a two-sender, two-receiver interference channel in which sender 2 obtains the encoded message sender 1 plans to transmit. We consider two cases: in the genie-aided cognitive radio channel, sender 2 is noncausally presented the data to be transmitted by sender 1 while in the causal cognitive radio channel, the data is obtained causally. The cognitive radio at sender 2 may then choose to transmit simultaneously over the same channel, as opposed to waiting for an idle channel as is traditional for a cognitive radio. Our main result is the development of an achievable region which combines Gel'fand-Pinkser coding with an achievable region construction for the interference channel. In the additive Gaussian noise case, this resembles dirty-paper coding, a technique used in the computation of the capacity of the Gaussian multiple-input multiple-output (MIMO) broadcast channel. Numerical evaluation of the region in the Gaussian noise case is performed, and compared to an inner bound, the interference channel, and an outer bound, a modified Gaussian MIMO broadcast channel. Results are also extended to the case in which the message is causally obtained.

Fading Relay Channels: Performance Limits and Space–Time Signal Design

2004-08-01

R.U. Nabar , Helmut Bölcskei , F.W. Kneubuhler

Cooperative diversity is a transmission technique, where multiple terminals pool their resources to form a virtual antenna array that realizes spatial diversity gain in a distributed fashion. In this paper, … Cooperative diversity is a transmission technique, where multiple terminals pool their resources to form a virtual antenna array that realizes spatial diversity gain in a distributed fashion. In this paper, we examine the basic building block of cooperative diversity systems, a simple fading relay channel where the source, destination, and relay terminals are each equipped with single antenna transceivers. We consider three different time-division multiple-access-based cooperative protocols that vary the degree of broadcasting and receive collision. The relay terminal operates in either the amplify-and-forward (AF) or decode-and-forward (DF) modes. For each protocol, we study the ergodic and outage capacity behavior (assuming Gaussian code books) under the AF and DF modes of relaying. We analyze the spatial diversity performance of the various protocols and find that full spatial diversity (second-order in this case) is achieved by certain protocols provided that appropriate power control is employed. Our analysis unifies previous results reported in the literature and establishes the superiority (both from a capacity, as well as a diversity point-of-view) of a new protocol proposed in this paper. The second part of the paper is devoted to (distributed) space-time code design for fading relay channels operating in the AF mode. We show that the corresponding code design criteria consist of the traditional rank and determinant criteria for the case of colocated antennas, as well as appropriate power control rules. Consequently space-time codes designed for the case of colocated multiantenna channels can be used to realize cooperative diversity provided that appropriate power control is employed.

Sum capacity of the vector Gaussian broadcast channel and uplink–downlink duality

2003-07-23

Pramod Viswanath , David Tse

We characterize the sum capacity of the vector Gaussian broadcast channel by showing that the existing inner bound of Marton and the existing upper bound of Sato are tight for … We characterize the sum capacity of the vector Gaussian broadcast channel by showing that the existing inner bound of Marton and the existing upper bound of Sato are tight for this channel. We exploit an intimate four-way connection between the vector broadcast channel, the corresponding point-to-point channel (where the receivers can cooperate), the multiple-access channel (MAC) (where the role of transmitters and receivers are reversed), and the corresponding point-to-point channel (where the transmitters can cooperate).

On the construction of energy-efficient broadcast and multicast trees in wireless networks

2002-11-07

Jeffrey E. Wieselthier , Gam D. Nguyen , Anthony Ephremides

The wireless networking environment presents formidable challenges to the study of broadcasting and multicasting problems. After addressing the characteristics of wireless networks that distinguish them from wired networks, we introduce … The wireless networking environment presents formidable challenges to the study of broadcasting and multicasting problems. After addressing the characteristics of wireless networks that distinguish them from wired networks, we introduce and evaluate algorithms for tree construction in infrastructureless, all-wireless applications. The performance metric used to evaluate broadcast and multicast trees is energy-efficiency. We develop the broadcast incremental power algorithm, and adapt it to multicast operation as well. This algorithm exploits the broadcast nature of the wireless communication environment, and addresses the need for energy-efficient operation. We demonstrate that our algorithm provides better performance than algorithms that have been developed for the link-based, wired environment.

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Network Coding for Distributed Storage Systems

2010-08-19

Alexandros G. Dimakis , P. Brighten Godfrey , Yunnan Wu +2 more

Distributed storage systems provide reliable access to data through redundancy spread over individually unreliable nodes. Application scenarios include data centers, peer-to-peer storage systems, and storage in wireless networks. Storing data … Distributed storage systems provide reliable access to data through redundancy spread over individually unreliable nodes. Application scenarios include data centers, peer-to-peer storage systems, and storage in wireless networks. Storing data using an erasure code, in fragments spread across nodes, requires less redundancy than simple replication for the same level of reliability. However, since fragments must be periodically replaced as nodes fail, a key question is how to generate encoded fragments in a distributed way while transferring as little data as possible across the network. For an erasure coded system, a common practice to repair from a single node failure is for a new node to reconstruct the whole encoded data object to generate just one encoded block. We show that this procedure is sub-optimal. We introduce the notion of regenerating codes, which allow a new node to communicate <emphasis emphasistype="boldital" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">functions</emphasis> of the stored data from the surviving nodes. We show that regenerating codes can significantly reduce the repair bandwidth. Further, we show that there is a fundamental tradeoff between storage and repair bandwidth which we theoretically characterize using flow arguments on an appropriately constructed graph. By invoking constructive results in network coding, we introduce regenerating codes that can achieve any point in this optimal tradeoff.

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Network information flow

2000-07-01

Rudolf Ahlswede , Ning Cai , Shuo Li +1 more

We introduce a new class of problems called network information flow which is inspired by computer network applications. Consider a point-to-point communication network on which a number of information sources … We introduce a new class of problems called network information flow which is inspired by computer network applications. Consider a point-to-point communication network on which a number of information sources are to be multicast to certain sets of destinations. We assume that the information sources are mutually independent. The problem is to characterize the admissible coding rate region. This model subsumes all previously studied models along the same line. We study the problem with one information source, and we have obtained a simple characterization of the admissible coding rate region. Our result can be regarded as the max-flow min-cut theorem for network information flow. Contrary to one's intuition, our work reveals that it is in general not optimal to regard the information to be multicast as a "fluid" which can simply be routed or replicated. Rather, by employing coding at the nodes, which we refer to as network coding, bandwidth can in general be saved. This finding may have significant impact on future design of switching systems.

Linear network coding

2003-02-01

Shuo Li , Raymond W. Yeung , Ning Cai

Consider a communication network in which certain source nodes multicast information to other nodes on the network in the multihop fashion where every node can pass on any of its … Consider a communication network in which certain source nodes multicast information to other nodes on the network in the multihop fashion where every node can pass on any of its received data to others. We are interested in how fast each node can receive the complete information, or equivalently, what the information rate arriving at each node is. Allowing a node to encode its received data before passing it on, the question involves optimization of the multicast mechanisms at the nodes. Among the simplest coding schemes is linear coding, which regards a block of data as a vector over a certain base field and allows a node to apply a linear transformation to a vector before passing it on. We formulate this multicast problem and prove that linear coding suffices to achieve the optimum, which is the max-flow from the source to each receiving node.

A simple transmit diversity technique for wireless communications

1998-01-01

S.M. Alamouti

This paper presents a simple two-branch transmit diversity scheme. Using two transmit antennas and one receive antenna the scheme provides the same diversity order as maximal-ratio receiver combining (MRRC) with … This paper presents a simple two-branch transmit diversity scheme. Using two transmit antennas and one receive antenna the scheme provides the same diversity order as maximal-ratio receiver combining (MRRC) with one transmit antenna, and two receive antennas. It is also shown that the scheme may easily be generalized to two transmit antennas and M receive antennas to provide a diversity order of 2M. The new scheme does not require any bandwidth expansion or any feedback from the receiver to the transmitter and its computation complexity is similar to MRRC.

Cooperative communication in wireless networks

2004-10-01

Aria Nosratinia , T.E. Hunter , A. Hedayat

Transmit diversity generally requires more than one antenna at the transmitter. However, many wireless devices are limited by size or hardware complexity to one antenna. Recently, a new class of … Transmit diversity generally requires more than one antenna at the transmitter. However, many wireless devices are limited by size or hardware complexity to one antenna. Recently, a new class of methods called cooperative communication has been proposed that enables single-antenna mobiles in a multi-user environment to share their antennas and generate a virtual multiple-antenna transmitter that allows them to achieve transmit diversity. This article presents an overview of the developments in this burgeoning field.

Capacity of a mobile multiple-antenna communication link in Rayleigh flat fading

1999-01-01

Thomas L. Marzetta , Bertrand M. Hochwald

We analyze a mobile wireless link comprising M transmitter and N receiver antennas operating in a Rayleigh flat-fading environment. The propagation coefficients between pairs of transmitter and receiver antennas are … We analyze a mobile wireless link comprising M transmitter and N receiver antennas operating in a Rayleigh flat-fading environment. The propagation coefficients between pairs of transmitter and receiver antennas are statistically independent and unknown; they remain constant for a coherence interval of T symbol periods, after which they change to new independent values which they maintain for another T symbol periods, and so on. Computing the link capacity, associated with channel coding over multiple fading intervals, requires an optimization over the joint density of T/spl middot/M complex transmitted signals. We prove that there is no point in making the number of transmitter antennas greater than the length of the coherence interval: the capacity for M>T is equal to the capacity for M=T. Capacity is achieved when the T/spl times/M transmitted signal matrix is equal to the product of two statistically independent matrices: a T/spl times/T isotropically distributed unitary matrix times a certain T/spl times/M random matrix that is diagonal, real, and nonnegative. This result enables us to determine capacity for many interesting cases. We conclude that, for a fixed number of antennas, as the length of the coherence interval increases, the capacity approaches the capacity obtained as if the receiver knew the propagation coefficients.

Capacity Bounds and Power Allocation for Wireless Relay Channels

2005-06-01

Anders Høst-Madsen , Jianzhong Zhang

We consider three-node wireless relay channels in a Rayleigh-fading environment. Assuming transmitter channel state information (CSI), we study upper bounds and lower bounds on the outage capacity and the ergodic … We consider three-node wireless relay channels in a Rayleigh-fading environment. Assuming transmitter channel state information (CSI), we study upper bounds and lower bounds on the outage capacity and the ergodic capacity. Our studies take into account practical constraints on the transmission/reception duplexing at the relay node and on the synchronization between the source node and the relay node. We also explore power allocation. Compared to the direct transmission and traditional multihop protocols, our results reveal that optimum relay channel signaling can significantly outperform multihop protocols, and that power allocation has a significant impact on the performance.

Femtocell networks: a survey

2008-09-01

Vikram Chandrasekhar , Jeffrey G. Andrews , Alan Gatherer

The surest way to increase the system capacity of a wireless link is by getting the transmitter and receiver closer to each other, which creates the dual benefits of higher-quality … The surest way to increase the system capacity of a wireless link is by getting the transmitter and receiver closer to each other, which creates the dual benefits of higher-quality links and more spatial reuse. In a network with nomadic users, this inevitably involves deploying more infrastructure, typically in the form of microcells, hot spots, distributed antennas, or relays. A less expensive alternative is the recent concept of femtocells - also called home base stations - which are data access points installed by home users to get better indoor voice and data coverage. In this article we overview the technical and business arguments for femtocells and describe the state of the art on each front. We also describe the technical challenges facing femtocell networks and give some preliminary ideas for how to overcome them.

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Multiaccess fading channels. I. Polymatroid structure, optimal resource allocation and throughput capacities

1998-01-01

David Tse , Stephen V. Hanly

In multiaccess wireless systems, dynamic allocation of resources such as transmit power, bandwidths, and rates is an important means to deal with the time-varying nature of the environment. We consider … In multiaccess wireless systems, dynamic allocation of resources such as transmit power, bandwidths, and rates is an important means to deal with the time-varying nature of the environment. We consider the problem of optimal resource allocation from an information-theoretic point of view. We focus on the multiaccess fading channel with Gaussian noise, and define two notions of capacity depending on whether the traffic is delay-sensitive or not. We characterize the throughput capacity region which contains the long-term achievable rates through the time-varying channel. We show that each point on the boundary of the region can be achieved by successive decoding. Moreover, the optimal rate and power allocations in each fading state can be explicitly obtained in a greedy manner. The solution can be viewed as the generalization of the water-filling construction for single-user channels to multiaccess channels with arbitrary number of users, and exploits the underlying polymatroid structure of the capacity region.

Cross-layer design: a survey and the road ahead

2005-12-01

Vineet Srivastava , Mehul Motani

Of late, there has been an avalanche of cross-layer design proposals for wireless networks. A number of researchers have looked at specific aspects of network performance and, approaching cross-layer design … Of late, there has been an avalanche of cross-layer design proposals for wireless networks. A number of researchers have looked at specific aspects of network performance and, approaching cross-layer design via their interpretation of what it implies, have presented several cross-layer design proposals. These proposals involve different layers of the protocol stack, and address both cellular and ad hoc networks. There has also been work relating to the implementation of cross-layer interactions. It is high time that these various individual efforts be put into perspective and a more holistic view be taken. In this article, we take a step in that direction by presenting a survey of the literature in the area of cross-layer design, and by taking stock of the ongoing work. We suggest a definition for cross-layer design, discuss the basic types of cross-layer design with examples drawn from the literature, and categorize the initial proposals on how cross-layer interactions may be implemented. We then highlight some open challenges and new opportunities for cross-layer design. Designers presenting cross-layer design proposals can start addressing these as they move ahead.

Trading structure for randomness in wireless opportunistic routing

2007-08-27

Szymon Chachulski , Michael Jennings , Sachin Katti +1 more

Opportunistic routing is a recent technique that achieves high throughput in the face of lossy wireless links. The current opportunistic routing protocol, ExOR, ties the MAC with routing, imposing a … Opportunistic routing is a recent technique that achieves high throughput in the face of lossy wireless links. The current opportunistic routing protocol, ExOR, ties the MAC with routing, imposing a strict schedule on routers' access to the medium. Although the scheduler delivers opportunistic gains, it misses some of the inherent features of the 802.11 MAC. For example, it prevents spatial reuse and thus may underutilize the wireless medium. It also eliminates the layering abstraction, making the protocol less amenable to extensions to alternate traffic types such as multicast.

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Low-density parity-check codes

1962-01-01

Robert G. Gallager

A low-density parity-check code is a code specified by a parity-check matrix with the following properties: each column contains a small fixed number <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j \geq 3</tex> of l's … A low-density parity-check code is a code specified by a parity-check matrix with the following properties: each column contains a small fixed number <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j \geq 3</tex> of l's and each row contains a small fixed number <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k > j</tex> of l's. The typical minimum distance of these codes increases linearly with block length for a fixed rate and fixed <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</tex> . When used with maximum likelihood decoding on a sufficiently quiet binary-input symmetric channel, the typical probability of decoding error decreases exponentially with block length for a fixed rate and fixed <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j</tex> . A simple but nonoptimum decoding scheme operating directly from the channel a posteriori probabilities is described. Both the equipment complexity and the data-handling capacity in bits per second of this decoder increase approximately linearly with block length. For <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">j > 3</tex> and a sufficiently low rate, the probability of error using this decoder on a binary symmetric channel is shown to decrease at least exponentially with a root of the block length. Some experimental results show that the actual probability of decoding error is much smaller than this theoretical bound.

User cooperation diversity-part II: implementation aspects and performance analysis

2003-11-01

A. Sendonaris , Elza Erkip , Behnaam Aazhang

For pt.I see ibid., p.1927-38. This is the second of a two-part paper on a new form of spatial diversity, where diversity gains are achieved through the cooperation of mobile … For pt.I see ibid., p.1927-38. This is the second of a two-part paper on a new form of spatial diversity, where diversity gains are achieved through the cooperation of mobile users. Part I described the user cooperation concept and proposed a cooperation strategy for a conventional code-division multiple-access (CDMA) system. Part II investigates the cooperation concept further and considers practical issues related to its implementation. In particular, we investigate the optimal and suboptimal receiver design, and present performance analysis for the conventional CDMA implementation proposed in Part I. We also consider a high-rate CDMA implementation and a cooperation strategy when assumptions about the channel state information at the transmitters are relaxed. We illustrate that, under all scenarios studied, cooperation is beneficial in terms of increasing system throughput and cell coverage, as well as decreasing sensitivity to channel variations.

The benefits of coding over routing in a randomized setting

2003-01-01

T. Ho , R. Koetter , Muriel Médard +2 more

A novel randomized network coding approach for robust, distributed transmission and compression of information in networks is presented, and its advantages over routing-based approaches is demonstrated. A novel randomized network coding approach for robust, distributed transmission and compression of information in networks is presented, and its advantages over routing-based approaches is demonstrated.

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Relay-based deployment concepts for wireless and mobile broadband radio

2004-09-01

Ralf Pabst , Bernhard Walke , Daniel C. Schultz +7 more

In recent years, there has been an upsurge of interest in multihop-augmented infrastructure-based networks in both the industry and academia, such as the seed concept in 3GPP, mesh networks in … In recent years, there has been an upsurge of interest in multihop-augmented infrastructure-based networks in both the industry and academia, such as the seed concept in 3GPP, mesh networks in IEEE 802.16, and converge extension of HiperLAN/2 through relays or user-cooperative diversity mesh networks. This article, a synopsis of numerous contributions to the working group 4 of the wireless world research forum and other research work, presents an overview of important topics and applications in the context of relaying. It covers different approaches to exploiting the benefits of multihop communications via relays, such as solutions for radio range extension in mobile and wireless broadband cellular networks (trading range for capacity), and solutions to combat shadowing at high radio frequencies. Furthermore, relaying is presented as a means to reduce infrastructure deployment costs. It is also shown that through the exploitation of spatial diversity, multihop relaying can enhance capacity in cellular networks. We wish to emphasize that while this article focuses on fixed relays, many of the concepts presented can also be applied to systems with moving relays.

Distributed Space-Time Coding in Wireless Relay Networks

2006-12-01

Yindi Jing , Babak Hassibi

We apply the idea of space-time coding devised for multiple-antenna systems to the problem of communications over a wireless relay network with Rayleigh fading channels. We use a two-stage protocol, … We apply the idea of space-time coding devised for multiple-antenna systems to the problem of communications over a wireless relay network with Rayleigh fading channels. We use a two-stage protocol, where in one stage the transmitter sends information and in the other, the relays encode their received signals into a "distributed" linear dispersion (LD) code, and then transmit the coded signals to the receive node. We show that for high SNR, the pairwise error probability (PEP) behaves as (logP/P) <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min{TH}</sup> , with T the coherence interval, that is, the number of symbol periods during which the channels keep constant, R the number of relay nodes, and P the total transmit power. Thus, apart from the log P factor, the system has the same diversity as a multiple-antenna system with R transmit antennas, which is the same as assuming that the R relays can fully cooperate and have full knowledge of the transmitted signal. We further show that for a network with a large number of relays and a fixed total transmit power across the entire network, the optimal power allocation is for the transmitter to expend half the power and for the relays to collectively expend the other half. We also show that at low and high SNR, the coding gain is the same as that of a multiple-antenna system with R antennas. However, at intermediate SNR, it can be quite different, which has implications for the design of distributed space-time codes

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On the Achievable Diversity–Multiplexing Tradeoff in Half-Duplex Cooperative Channels

2005-11-22

Kambiz Azarian , H. El Gamal , Philip Schniter

We propose novel cooperative transmission protocols for delay-limited coherent fading channels consisting of N (half-duplex and single-antenna) partners and one cell site. In our work, we differentiate between the relay, … We propose novel cooperative transmission protocols for delay-limited coherent fading channels consisting of N (half-duplex and single-antenna) partners and one cell site. In our work, we differentiate between the relay, cooperative broadcast (down-link), and cooperative multiple-access (CMA) (up-link) channels. The proposed protocols are evaluated using Zheng-Tse diversity-multiplexing tradeoff. For the relay channel, we investigate two classes of cooperation schemes; namely, amplify and forward (AF) protocols and decode and forward (DF) protocols. For the first class, we establish an upper bound on the achievable diversity-multiplexing tradeoff with a single relay. We then construct a new AF protocol that achieves this upper bound. The proposed algorithm is then extended to the general case with (N-1) relays where it is shown to outperform the space-time coded protocol of Laneman and Wornell without requiring decoding/encoding at the relays. For the class of DF protocols, we develop a dynamic decode and forward (DDF) protocol that achieves the optimal tradeoff for multiplexing gains 0lesrles1/N. Furthermore, with a single relay, the DDF protocol is shown to dominate the class of AF protocols for all multiplexing gains. The superiority of the DDF protocol is shown to be more significant in the cooperative broadcast channel. The situation is reversed in the CMA channel where we propose a new AF protocol that achieves the optimal tradeoff for all multiplexing gains. A distinguishing feature of the proposed protocols in the three scenarios is that they do not rely on orthogonal subspaces, allowing for a more efficient use of resources. In fact, using our results one can argue that the suboptimality of previously proposed protocols stems from their use of orthogonal subspaces rather than the half-duplex constraint.

Communication Over MIMO X Channels: Interference Alignment, Decomposition, and Performance Analysis

2008-07-24

Mohammad Ali Maddah-Ali , Seyed Abolfazl Motahari , Amir K. Khandani

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <?Pub Dtl=""?>In a multiple-antenna system with two transmitters and two receivers, a scenario of data communication, known as the X channel, is studied in which each receiver … <para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <?Pub Dtl=""?>In a multiple-antenna system with two transmitters and two receivers, a scenario of data communication, known as the X channel, is studied in which each receiver receives data from both transmitters. In this scenario, it is assumed that each transmitter is unaware of the other transmitter's data (noncooperative scenario). This system can be considered as a combination of two broadcast channels (from the transmitters' points of view) and two multiple-access channels (from the receivers' points of view). Taking advantage of both perspectives, two signaling schemes for such a scenario are developed. In these schemes, some linear filters are employed at the transmitters and at the receivers which decompose the system into either two noninterfering multiple-antenna broadcast subchannels or two noninterfering multiple-antenna multiple-access subchannels. The main objective in the design of the filters is to exploit the structure of the channel matrices to achieve the highest multiplexing gain (MG). It is shown that the proposed noncooperative signaling schemes outperform other known noncooperative schemes in terms of the achievable MG. In particular, it is shown that in some specific cases, the achieved MG is the same as the MG of the system if full cooperation is provided either between the transmitters or between the receivers. </para>

An algebraic approach to network coding

2003-10-01

R. Koetter , Muriel Médard

We take a new look at the issue of network capacity. It is shown that network coding is an essential ingredient in achieving the capacity of a network. Building on … We take a new look at the issue of network capacity. It is shown that network coding is an essential ingredient in achieving the capacity of a network. Building on recent work by Li et al.(see Proc. 2001 IEEE Int. Symp. Information Theory, p.102), who examined the network capacity of multicast networks, we extend the network coding framework to arbitrary networks and robust networking. For networks which are restricted to using linear network codes, we find necessary and sufficient conditions for the feasibility of any given set of connections over a given network. We also consider the problem of network recovery for nonergodic link failures. For the multicast setup we prove that there exist coding strategies that provide maximally robust networks and that do not require adaptation of the network interior to the failure pattern in question. The results are derived for both delay-free networks and networks with delays.

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Coding for Errors and Erasures in Random Network Coding

2008-07-24

R. Koetter , Frank R. Kschischang

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The problem of error-control in random linear network coding is considered. A "noncoherent" or "channel oblivious" model is assumed where neither transmitter nor receiver is assumed to … <para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The problem of error-control in random linear network coding is considered. A "noncoherent" or "channel oblivious" model is assumed where neither transmitter nor receiver is assumed to have knowledge of the channel transfer characteristic. Motivated by the property that linear network coding is vector-space preserving, information transmission is modeled as the injection into the network of a basis for a vector space <emphasis><formula formulatype="inline"><tex>$V$</tex></formula></emphasis> and the collection by the receiver of a basis for a vector space <emphasis><formula formulatype="inline"> <tex>$U$</tex></formula></emphasis>. A metric on the projective geometry associated with the packet space is introduced, and it is shown that a minimum-distance decoder for this metric achieves correct decoding if the dimension of the space <emphasis><formula formulatype="inline"><tex>$V \cap U$</tex></formula></emphasis> is sufficiently large. If the dimension of each codeword is restricted to a fixed integer, the code forms a subset of a finite-field Grassmannian, or, equivalently, a subset of the vertices of the corresponding Grassmann graph. Sphere-packing and sphere-covering bounds as well as a generalization of the Singleton bound are provided for such codes. Finally, a Reed–Solomon-like code construction, related to Gabidulin's construction of maximum rank-distance codes, is described and a Sudan-style "list-1" minimum-distance decoding algorithm is provided. </para>

Cooperative Communications with Outage-Optimal Opportunistic Relaying

2007-09-01

Aggelos Bletsas , Hyundong Shin , Moe Z. Win

In this paper, we present simple opportunistic relaying with decode-and-forward (DaF) and amplify-and-forward (AaF) strategies under an aggregate power constraint. In particular, we consider distributed relay-selection algorithms requiring only local … In this paper, we present simple opportunistic relaying with decode-and-forward (DaF) and amplify-and-forward (AaF) strategies under an aggregate power constraint. In particular, we consider distributed relay-selection algorithms requiring only local channel knowledge. We show that opportunistic DaF relaying is outage-optimal, that is, it is equivalent in outage behavior to the optimal DaF strategy that employs all potential relays. We further show that opportunistic AaF relaying is outage-optimal among single-relay selection methods and significantly outperforms an AaF strategy based on equal-power multiple-relay transmissions with local channel knowledge. These findings reveal that cooperation offers diversity benefits even when cooperative relays choose not to transmit but rather choose to cooperatively listen; they act as passive relays and give priority to the transmission of a single opportunistic relay. Numerical and simulation results are presented to verify our analysis.

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Spectral efficient protocols for half-duplex fading relay channels

2007-02-01

Boris Rankov , Armin Wittneben

We study two-hop communication protocols where one or several relay terminals assist in the communication between two or more terminals. All terminals operate in half-duplex mode, hence the transmission of … We study two-hop communication protocols where one or several relay terminals assist in the communication between two or more terminals. All terminals operate in half-duplex mode, hence the transmission of one information symbol from the source terminal to the destination terminal occupies two channel uses. This leads to a loss in spectral efficiency due to the pre-log factor one-half in corresponding capacity expressions. We propose two new half-duplex relaying protocols that avoid the pre-log factor one-half. Firstly, we consider a relaying protocol where a bidirectional connection between two terminals is established via one amplify-and-forward (AF) or decode-and-forward (DF) relay (two-way relaying). We also extend this protocol to a multi-user scenario, where multiple terminals communicate with multiple partner terminals via several orthogonalize-and-forward (OF) relay terminals, i.e., the relays orthogonalize the different two-way transmissions by a distributed zero-forcing algorithm. Secondly, we propose a relaying protocol where two relays, either AF or DF, alternately forward messages from a source terminal to a destination terminal (two-path relaying). It is shown that both protocols recover a significant portion of the half-duplex loss

XORs in the Air: Practical Wireless Network Coding

2008-06-01

S. Katti , Hariharan Rahul , Wenjun Hu +3 more

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper proposes COPE, a new architecture for wireless mesh networks. In addition to forwarding packets, routers mix (i.e., code) packets from different sources to increase the … <para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper proposes COPE, a new architecture for wireless mesh networks. In addition to forwarding packets, routers mix (i.e., code) packets from different sources to increase the information content of each transmission. We show that intelligently mixing packets increases network throughput. Our design is rooted in the theory of network coding. Prior work on network coding is mainly theoretical and focuses on multicast traffic. This paper aims to bridge theory with practice; it addresses the common case of unicast traffic, dynamic and potentially bursty flows, and practical issues facing the integration of network coding in the current network stack. We evaluate our design on a 20-node wireless network, and discuss the results of the first testbed deployment of wireless network coding. The results show that using COPE at the forwarding layer, without modifying routing and higher layers, increases network throughput. The gains vary from a few percent to several folds depending on the traffic pattern, congestion level, and transport protocol. </para>

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Mobility increases the capacity of ad hoc wireless networks

2002-08-01

Matthias Grossglauser , David Tse

The capacity of ad hoc wireless networks is constrained by the mutual interference of concurrent transmissions between nodes. We study a model of an ad hoc network where n nodes … The capacity of ad hoc wireless networks is constrained by the mutual interference of concurrent transmissions between nodes. We study a model of an ad hoc network where n nodes communicate in random source-destination pairs. These nodes are assumed to be mobile. We examine the per-session throughput for applications with loose delay constraints, such that the topology changes over the time-scale of packet delivery. Under this assumption, the per-user throughput can increase dramatically when nodes are mobile rather than fixed. This improvement can be achieved by exploiting a form of multiuser diversity via packet relaying.

Cooperative Diversity in Wireless Networks: Efficient Protocols and Outage Behavior

2004-11-30

J. Nicholas Laneman , David Tse , Gregory W. Wornell

We develop and analyze low-complexity cooperative diversity protocols that combat fading induced by multipath propagation in wireless networks. The underlying techniques exploit space diversity available through cooperating terminals' relaying signals … We develop and analyze low-complexity cooperative diversity protocols that combat fading induced by multipath propagation in wireless networks. The underlying techniques exploit space diversity available through cooperating terminals' relaying signals for one another. We outline several strategies employed by the cooperating radios, including fixed relaying schemes such as amplify-and-forward and decode-and-forward, selection relaying schemes that adapt based upon channel measurements between the cooperating terminals, and incremental relaying schemes that adapt based upon limited feedback from the destination terminal. We develop performance characterizations in terms of outage events and associated outage probabilities, which measure robustness of the transmissions to fading, focusing on the high signal-to-noise ratio (SNR) regime. Except for fixed decode-and-forward, all of our cooperative diversity protocols are efficient in the sense that they achieve full diversity (i.e., second-order diversity in the case of two terminals), and, moreover, are close to optimum (within 1.5 dB) in certain regimes. Thus, using distributed antennas, we can provide the powerful benefits of space diversity without need for physical arrays, though at a loss of spectral efficiency due to half-duplex operation and possibly at the cost of additional receive hardware. Applicable to any wireless setting, including cellular or ad hoc networks-wherever space constraints preclude the use of physical arrays-the performance characterizations reveal that large power or energy savings result from the use of these protocols.

Embracing wireless interference

2007-08-27

Sachin Katti , Shyamnath Gollakota , Dina Katabi

Traditionally, interference is considered harmful. Wireless networks strive to avoid scheduling multiple transmissions at the same time in order to prevent interference. This paper adopts the opposite approach; it encourages … Traditionally, interference is considered harmful. Wireless networks strive to avoid scheduling multiple transmissions at the same time in order to prevent interference. This paper adopts the opposite approach; it encourages strategically picked senders to interfere. Instead of forwarding packets, routers forward the interfering signals. The destination leverages network-level information to cancel the interference and recover the signal destined to it. The result is analog network coding because it mixes signals not bits.

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Multi-Cell MIMO Cooperative Networks: A New Look at Interference

2010-10-05

David Gesbert , Stephen V. Hanly , Howard Huang +3 more

This paper presents an overview of the theory and currently known techniques for multi-cell MIMO (multiple input multiple output) cooperation in wireless networks. In dense networks where interference emerges as … This paper presents an overview of the theory and currently known techniques for multi-cell MIMO (multiple input multiple output) cooperation in wireless networks. In dense networks where interference emerges as the key capacity-limiting factor, multi-cell cooperation can dramatically improve the system performance. Remarkably, such techniques literally exploit inter-cell interference by allowing the user data to be jointly processed by several interfering base stations, thus mimicking the benefits of a large virtual MIMO array. Multi-cell MIMO cooperation concepts are examined from different perspectives, including an examination of the fundamental information-theoretic limits, a review of the coding and signal processing algorithmic developments, and, going beyond that, consideration of very practical issues related to scalability and system-level integration. A few promising and quite fundamental research avenues are also suggested.

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Layering as Optimization Decomposition: A Mathematical Theory of Network Architectures

2007-01-01

Mung Chiang , Steven H. Low , A.R. Calderbank +1 more

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Network protocols in layered architectures have historically been obtained on an <emphasis emphasistype="boldital">ad hoc</emphasis> basis, and many of the recent cross-layer designs are also conducted through piecemeal … <para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Network protocols in layered architectures have historically been obtained on an <emphasis emphasistype="boldital">ad hoc</emphasis> basis, and many of the recent cross-layer designs are also conducted through piecemeal approaches. Network protocol stacks may instead be holistically analyzed and systematically designed as distributed solutions to some global optimization problems. This paper presents a survey of the recent efforts towards a systematic understanding of "layering" as "optimization decomposition," where the overall communication network is modeled by a generalized network utility maximization problem, each layer corresponds to a decomposed subproblem, and the interfaces among layers are quantified as functions of the optimization variables coordinating the subproblems. There can be many alternative decompositions, leading to a choice of different layering architectures. This paper surveys the current status of horizontal decomposition into distributed computation, and vertical decomposition into functional modules such as congestion control, routing, scheduling, random access, power control, and channel coding. Key messages and methods arising from many recent works are summarized, and open issues discussed. Through case studies, it is illustrated how "Layering as Optimization Decomposition" provides a common language to think about modularization in the face of complex, networked interactions, a unifying, top-down approach to design protocol stacks, and a mathematical theory of network architectures. </para>

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Green Cellular Networks: A Survey, Some Research Issues and Challenges

2011-01-01

Ziaul Hasan , Hamidreza Boostanimehr , Vijay K. Bhargava

Energy efficiency in cellular networks is a growing concern for cellular operators to not only maintain profitability, but also to reduce the overall environment effects. This emerging trend of achieving … Energy efficiency in cellular networks is a growing concern for cellular operators to not only maintain profitability, but also to reduce the overall environment effects. This emerging trend of achieving energy efficiency in cellular networks is motivating the standardization authorities and network operators to continuously explore future technologies in order to bring improvements in the entire network infrastructure. In this article, we present a brief survey of methods to improve the power efficiency of cellular networks, explore some research issues and challenges and suggest some techniques to enable an energy efficient or "green" cellular network. Since base stations consume a maximum portion of the total energy used in a cellular system, we will first provide a comprehensive survey on techniques to obtain energy savings in base stations. Next, we discuss how heterogenous network deployment based on micro, pico and femtocells can be used to achieve this goal. Since cognitive radio and cooperative relaying are undisputed future technologies in this regard, we propose a research vision to make these technologies more energy efficient. Lastly, we explore some broader perspectives in realizing a "green" cellular network technology.

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Capacity theorems for the relay channel

1979-09-01

Thomas M. Cover , Abbas El Gamal

A relay channel consists of an input <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x_{l}</tex> , a relay output <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y_{1}</tex> , a channel output <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</tex> , and a relay sender <tex … A relay channel consists of an input <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x_{l}</tex> , a relay output <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y_{1}</tex> , a channel output <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</tex> , and a relay sender <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x_{2}</tex> (whose transmission is allowed to depend on the past symbols <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y_{1}</tex> . The dependence of the received symbols upon the inputs is given by <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p(y,y_{1}|x_{1},x_{2})</tex> . The channel is assumed to be memoryless. In this paper the following capacity theorems are proved. 1)If <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</tex> is a degraded form of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y_{1}</tex> , then <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C \: = \: \max \!_{p(x_{1},x_{2})} \min \,{I(X_{1},X_{2};Y), I(X_{1}; Y_{1}|X_{2})}</tex> . 2)If <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y_{1}</tex> is a degraded form of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</tex> , then <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C \: = \: \max \!_{p(x_{1})} \max_{x_{2}} I(X_{1};Y|x_{2})</tex> . 3)If <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p(y,y_{1}|x_{1},x_{2})</tex> is an arbitrary relay channel with feedback from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(y,y_{1})</tex> to both <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x_{1} \and x_{2}</tex> , then <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C\: = \: \max_{p(x_{1},x_{2})} \min \,{I(X_{1},X_{2};Y),I \,(X_{1};Y,Y_{1}|X_{2})}</tex> . 4)For a general relay channel, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C \: \leq \: \max_{p(x_{1},x_{2})} \min \,{I \,(X_{1}, X_{2};Y),I(X_{1};Y,Y_{1}|X_{2})</tex> . Superposition block Markov encoding is used to show achievability of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</tex> , and converses are established. The capacities of the Gaussian relay channel and certain discrete relay channels are evaluated. Finally, an achievable lower bound to the capacity of the general relay channel is established.

End-to-end performance of transmission systems with relays over rayleigh-fading channels

2003-11-01

Mazen O. Hasna , Mohamed‐Slim Alouini

End-to-end performance of two-hop wireless communication systems with nonregenerative relays over flat Rayleigh-fading channels is presented. This is accomplished by deriving and applying some new closed-form expressions for the statistics … End-to-end performance of two-hop wireless communication systems with nonregenerative relays over flat Rayleigh-fading channels is presented. This is accomplished by deriving and applying some new closed-form expressions for the statistics of the harmonic mean of two independent exponential variates. It is shown that the presented results can either be exact or tight lower bounds on the performance of these systems depending on the choice of the relay gain. More specifically, average bit-error rate expressions for binary differential phase-shift keying, as well as outage probability formulas for noise limited systems are derived. Finally, comparisons between regenerative and nonregenerative systems are presented. Numerical results show that the former systems clearly outperform the latter ones for low average signal-to-noise-ratio (SNR). They also show that the two systems have similar performance at high average SNR.

Toward Massive, Ultrareliable, and Low-Latency Wireless Communication With Short Packets

2016-08-02

Giuseppe Durisi , Tobias Koch , Petar Popovski

Most of the recent advances in the design of high-speed wireless systems are based on information-theoretic principles that demonstrate how to efficiently transmit long data packets. However, the upcoming wireless … Most of the recent advances in the design of high-speed wireless systems are based on information-theoretic principles that demonstrate how to efficiently transmit long data packets. However, the upcoming wireless systems, notably the fifth-generation (5G) system, will need to support novel traffic types that use short packets. For example, short packets represent the most common form of traffic generated by sensors and other devices involved in machine-to-machine (M2M) communications. Furthermore, there are emerging applications in which small packets are expected to carry critical information that should be received with low latency and ultrahigh reliability. Current wireless systems are not designed to support short-packet transmissions. For example, the design of current systems relies on the assumption that the metadata (control information) is of negligible size compared to the actual information payload. Hence, transmitting metadata using heuristic methods does not affect the overall system performance. However, when the packets are short, metadata may be of the same size as the payload, and the conventional methods to transmit it may be highly suboptimal. In this paper, we review recent advances in information theory, which provide the theoretical principles that govern the transmission of short packets. We then apply these principles to three exemplary scenarios (the two-way channel, the downlink broadcast channel, and the uplink random access channel), thereby illustrating how the transmission of control information can be optimized when the packets are short. The insights brought by these examples suggest that new principles are needed for the design of wireless protocols supporting short packets. These principles will have a direct impact on the system design.

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Broadcast channels

1972-01-01

Thomas M. Cover

We introduce the problem of a single source attempting to communicate information simultaneously to several receivers. The intent is to model the situation of a broadcaster with multiple receivers or … We introduce the problem of a single source attempting to communicate information simultaneously to several receivers. The intent is to model the situation of a broadcaster with multiple receivers or a lecturer with many listeners. Thus several different channels with a common input alphabet are specified. We shall determine the families of simultaneously achievable transmission rates for many extreme classes of channels. Upper and lower bounds on the capacity region will be found, and it will be shown that the family of theoretically achievable rates dominates the family of rates achievable by previously known time-sharing and maximin procedures. This improvement is gained by superimposing high-rate information on low-rate information. All of these results lead to a new approach to the compound channels problem.

Throughput Maximization for UAV-Enabled Mobile Relaying Systems

2016-09-20

Yong Zeng , Rui Zhang , Teng Joon Lim

In this paper, we consider a novel mobile relaying technique, where the relay nodes are mounted on unmanned aerial vehicles (UAVs) and hence are capable of moving at high speed. … In this paper, we consider a novel mobile relaying technique, where the relay nodes are mounted on unmanned aerial vehicles (UAVs) and hence are capable of moving at high speed. Compared with conventional static relaying, mobile relaying offers a new degree of freedom for performance enhancement via careful relay trajectory design. We study the throughput maximization problem in mobile relaying systems by optimizing the source/relay transmit power along with the relay trajectory, subject to practical mobility constraints (on the UAV's speed and initial/final relay locations), as well as the information-causality constraint at the relay. It is shown that for the fixed relay trajectory, the throughput-optimal source/relay power allocations over time follow a “staircase” water filling structure, with non-increasing and non-decreasing water levels at the source and relay, respectively. On the other hand, with given power allocations, the throughput can be further improved by optimizing the UAV's trajectory via successive convex optimization. An iterative algorithm is thus proposed to optimize the power allocations and relay trajectory alternately. Furthermore, for the special case with free initial and final relay locations, the jointly optimal power allocation and relay trajectory are derived. Numerical results show that by optimizing the trajectory of the relay and power allocations adaptive to its induced channel variation, mobile relaying is able to achieve significant throughput gains over the conventional static relaying.

A simple Cooperative diversity method based on network path selection

2006-03-01

Aggelos Bletsas , Ashish Khisti , David P. Reed +1 more

Cooperative diversity has been recently proposed as a way to form virtual antenna arrays that provide dramatic gains in slow fading wireless environments. However, most of the proposed solutions require … Cooperative diversity has been recently proposed as a way to form virtual antenna arrays that provide dramatic gains in slow fading wireless environments. However, most of the proposed solutions require distributed space-time coding algorithms, the careful design of which is left for future investigation if there is more than one cooperative relay. We propose a novel scheme that alleviates these problems and provides diversity gains on the order of the number of relays in the network. Our scheme first selects the best relay from a set of M available relays and then uses this "best" relay for cooperation between the source and the destination. We develop and analyze a distributed method to select the best relay that requires no topology information and is based on local measurements of the instantaneous channel conditions. This method also requires no explicit communication among the relays. The success (or failure) to select the best available path depends on the statistics of the wireless channel, and a methodology to evaluate performance for any kind of wireless channel statistics, is provided. Information theoretic analysis of outage probability shows that our scheme achieves the same diversity-multiplexing tradeoff as achieved by more complex protocols, where coordination and distributed space-time coding for M relay nodes is required, such as those proposed by Laneman and Wornell (2003). The simplicity of the technique allows for immediate implementation in existing radio hardware and its adoption could provide for improved flexibility, reliability, and efficiency in future 4G wireless systems.

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Building Scalable and Robust Adaptive Capacity Arbitration Algorithms for the Next Generation of WCDMA Wireless Networks

2025-06-24

Haroon Rashid Hammood Al Dallal | Journal La Multiapp

The plans to improve execution in optical multi-transporter Code Division Different Access (CDMA) upstream correspondence frameworks. The review centers around defeating difficulties connected with further developing correspondence effectiveness, diminishing obstruction, … The plans to improve execution in optical multi-transporter Code Division Different Access (CDMA) upstream correspondence frameworks. The review centers around defeating difficulties connected with further developing correspondence effectiveness, diminishing obstruction, and expanding generally speaking throughput in optical multi-transporter CDMA organizations. Through the examination of various coding systems and improvement strategies, this exploration adds to the progression of optical correspondence advancements.

Guest Editorial: Passive Reflective Communication for Internet of Things: Part 2

2025-06-24

Xingwang Li , Arumugam Nallanathan , Yu Zhao +3 more | IEEE Internet of Things Magazine

An optimal construction for complete graph embeddings with duals of low connectivity

2025-06-20

Timothy Sun | Discrete Mathematics

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Multi‐Generation Mixing–Based Network Coding for Reliable Data Dissemination in IoMT Environment

2025-06-18

Malaram Kumhar , Jitendra Bhatia , Sudeep Tanwar +1 more | International Journal of Communication Systems

ABSTRACT Internet of Medical Things (IoMT) devices are gradually being incorporated into healthcare systems that requires the development of data dissemination frameworks that are both reliable and secure. A revolution … ABSTRACT Internet of Medical Things (IoMT) devices are gradually being incorporated into healthcare systems that requires the development of data dissemination frameworks that are both reliable and secure. A revolution in healthcare has been made possible by integrating IoMT and key emerging technologies such as fog computing, cloud computing, and network coding (NC). This paper proposed an extensive architecture for guaranteeing reliable data dissemination in the IoMT environment. Real‐time analytics and responses are made possible by the convergence of fog computing, cloud computing, and IoMT, which promises to improve processing capabilities at the network edge. The proposed architecture uses NC with multi‐generation mixing (MGM) to enhance the reliability of data dissemination. We developed an MGM‐based NC methodology for encoding and decoding data. We performed experiments in an IoMT environment to validate the effectiveness of the proposed architecture. The experimental results show substantial improvements in successful access ratio, average access latency, and reliability against the percentage of server failure. The success access ratio greater than 66% is attained for the generation size (GS) 4. The average access latency decreases as we increase the GS and mixing set size (MSS). The reliability of the proposed NC‐based approach is also improved by 15%–20% for different GS and MSS. The experimentation results highlight that the NC‐based approach outperforms traditional approaches.

Prediction of Budd-Chiari syndrome based on attention mechanisms of high-risk factors in multi-hop graph learning

2025-06-16

Lei Wang , Shengli Li , Xiaorui Su +6 more | Science China Information Sciences

Disjoint Connected Dominating Sets in Pseudorandom Graphs

2025-06-15

Nemanja Draganić , Michael Krivelevich

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Constant Degree Networks for Almost-Everywhere Reliable Transmission

2025-06-15

Mitali Bafna , Dor Minzer

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Performance Analysis and Optimization of Enterprise Wireless Networks Based on 802.11ax Technology

2025-06-13

Berkay Dağtaş , İsmail Hakkı Cedi̇moğlu | Sakarya University Journal of Computer and Information Sciences

This study focuses on performance analysis and optimization of enterprise wireless networks. Fundamental performance parameters of Wi-Fi networks such as signal strength, signal-to-noise ratio (SNR), data rate, and channel interference … This study focuses on performance analysis and optimization of enterprise wireless networks. Fundamental performance parameters of Wi-Fi networks such as signal strength, signal-to-noise ratio (SNR), data rate, and channel interference were evaluated in detail in the study. The analysis process was carried out using Ekahau AI Pro software and Ekahau Sidekick device in a corporate facility, consisting of three main buildings. The obtained data revealed that signal strength dropped to -85 dBm levels in certain areas, negatively affecting the network's coverage area. Particularly in the ground floor of building B-C, secondary signal levels were found to be insufficient for roaming. Across the campus, SNR levels were observed to be 30 dB and above, and these values were found to provide ideal connectivity. During the analysis, it was discovered that in some areas, the number of access points broadcasting signals on the same channel increased up to 6. It has been assessed that this situation may negatively affect network performance in areas where interference is intense. Data rates varied between 1 - 300 Mbps in the 2.4 GHz frequency band and 1 - 585 Mbps in the 5 GHz band. The study provides significant data for performance analysis and optimization of enterprise wireless networks.

Enhanced reliability in mobility scenarios using multi-connectivity with packet duplication for next-generation networks

2025-06-03

Prabodh Mishra , Snigdhaswin Kar , Kuang‐Ching Wang | EURASIP Journal on Wireless Communications and Networking

Abstract Modern cellular communication systems are expected to be capable of delivering high data rates with low latency and ultra-reliability. Using frequencies in the FR2 or millimeter wave (mmWave) range … Abstract Modern cellular communication systems are expected to be capable of delivering high data rates with low latency and ultra-reliability. Using frequencies in the FR2 or millimeter wave (mmWave) range for communication can provide large data rates and cover densely populated areas, but only over short distances as they are susceptible to blockages. Such architectures lack the reliability needed to support the stricter requirements of V2X applications, especially in mobility scenarios. In this work, we study how packet duplication can be used to meet the stringent reliability and latency requirements of modern cellular networks under various mobility scenarios. Simultaneously transmitting multiple instances (duplicates) of a packet over different uncorrelated channels, although resource-consuming, could effectively reduce the packet failure probability without increasing the system complexity. This paper therefore proposes and evaluates novel enhancements to the packet duplication process to improve radio resource utilization and meet requirements under mobility and varying network load conditions.

Modelling Directed Networks with Reciprocity

2025-06-02

Rui Feng , Chenlei Leng | Biometrika

Summary Asymmetric relational data are becoming increasingly prevalent in diverse fields, underscoring the need for developing directed network models to address the complex challenges posed by the unique structure of … Summary Asymmetric relational data are becoming increasingly prevalent in diverse fields, underscoring the need for developing directed network models to address the complex challenges posed by the unique structure of such data. Unlike undirected models, directed models can capture reciprocity, the tendency of nodes to form mutual links. This work addresses a fundamental question: what is the effective sample size for modelling reciprocity? We examine this question by analysing the Bernoulli model with reciprocity, allowing for varying sparsity levels between non-reciprocal and reciprocal effects. We then extend this framework to a model that incorporates node-specific heterogeneity and link-specific reciprocity using covariates. Our findings reveal the intriguing interplay between non-reciprocal and reciprocal effects in sparse networks. We propose a straightforward inference procedure based on maximum likelihood estimation that operates without prior knowledge of sparsity levels, whether covariates are included or not.

Trust-based symmetric game theory for physical layer security in wi-fi communication

2025-05-31

S M Mohammad Iliyas , M. Mohamed Surputheen , A. R. Mohamed Shanavas | THE SCIENTIFIC TEMPER

A major improvement in growth of cellular networks has been observed in recent years, being an integral of Internet as well as showing reliability in connectivity for decreased military applications … A major improvement in growth of cellular networks has been observed in recent years, being an integral of Internet as well as showing reliability in connectivity for decreased military applications and public LAN. This is primarily because of their versatility as well as fewer cost solutions; however they are also vulnerable to a range of attacks relating to data privacy, Denial of service as well as eavesdropping.To withstand the security demand for Wireless Communication this paper presented a trust-based game theory (TRUST-GT). The proposed TRUST-GTintroduces confidence assessment for the development of protected routing topology. Consider PDR, energy consumption and throughput, comprehensive simulations demonstrate that it is efficient. We formally characterize TRUST-GT as a method for iterated as well as demonstrated its co-operation compliance characteristic by using game theory principles. The findings of both mathematical analyses as well as evolutionary simulation demonstrate that TRUST-GT is an important tool for fostering the reliability and evolution of Wi-Fi security.

On Vector Random Linear Network Coding in Wireless Broadcasts

2025-05-26

Rina Su , Chengji Zhao , Qifu Tyler Sun +1 more | Entropy

Compared with scalar linear network coding (LNC) formulated over the finite field GF(2L), vector LNC offers enhanced flexibility in the code design by enabling linear operations over the vector space … Compared with scalar linear network coding (LNC) formulated over the finite field GF(2L), vector LNC offers enhanced flexibility in the code design by enabling linear operations over the vector space GF(2)L and demonstrates a number of advantages over scalar LNC. While random LNC (RLNC) has shown significant potential to improve the completion delay performance in wireless broadcasts, most prior studies focus on scalar RLNC. In particular, it is well known that, with increasing L, primitive scalar RLNC over GF(2L) asymptotically achieves the optimal completion delay. However, the completion delay performance of primitive vector RLNC remains unexplored. This work aims to fill in this blank. We derive closed-form expressions for the probability distribution and the expected value of both the completion delay at a single receiver and the system completion delay. We further unveil a fundamental limitation that is different from scalar RLNC: even for large enough L, primitive vector RLNC over GF(2)L inherently fails to reach optimal completion delay. In spite of this, the gap between the expected completion delay at a receiver and the optimal one is shown to be a constant smaller than 0.714, which implies that the expected completion delay normalized by the number P of original packets is asymptotically optimal with increasing P. We also validate our theoretical characterization through numerical simulations. Our theoretical characterization establishes primitive vector RLNC as a performance baseline for the future design of practical vector RLNC schemes with different design goals.

SC-Route: A Scalable Cross-Layer Secure Routing Method for Multi-Hop Inter-Domain Wireless Networks

2025-05-24

Yanbing Li , Yang Zhu , Shangpeng Wang

Multi-hop inter-domain wireless networks play a vital role in future heterogeneous communication systems by improving data transmission efficiency and security assurance. Despite the advances in secure routing techniques in areas … Multi-hop inter-domain wireless networks play a vital role in future heterogeneous communication systems by improving data transmission efficiency and security assurance. Despite the advances in secure routing techniques in areas such as node authentication and encryption, they still suffer from the shortcomings of frequent key updates, high computational overhead, and poor adaptability to large-scale dynamic topologies. To address these limitations, we propose a new routing method—the Secure Cross-Layer Route—designed for multi-hop inter-domain wireless networks to achieve unified optimization of security, delay, and throughput. First, we construct a multi-objective optimization model that integrates authentication delay, link load, and resource states, enabling balanced trade-offs between security and transmission performance in dynamic conditions. Second, we introduce a cross-layer information fusion mechanism that allows nodes to adapt routing costs in real time under heterogeneous network conditions, thereby improving path reliability and load balancing. Furthermore, a risk-aware dynamic key update strategy is developed to handle behavioral uncertainty among nodes, reducing authentication overhead and enhancing attack resilience. Experimental evaluations conducted on four datasets with varying network scales demonstrate the superior performance of the proposed method. Experimental results demonstrated that the proposed method achieves at least 28% improvement in effective throughput, reduces average authentication delay by approximately 30%, and increases the secure link ratio by at least 10%, outperforming mainstream routing algorithms under multi-constraint conditions.

Enhancing Adaptive Behavior in Federated Learning: The AdaptiveMesh Algorithm for Interactive Mobile and Bandwidth-Limited Resource-Constrained Wireless Environments

2025-05-22

Lamir Shkurti , Mennan Selimi

Federated learning (FL) enables decentralized model training while preserving data privacy, but its application in resource-constrained environments faces challenges, including computational load, slowing down CPU speed, and network bandwidth limitations. … Federated learning (FL) enables decentralized model training while preserving data privacy, but its application in resource-constrained environments faces challenges, including computational load, slowing down CPU speed, and network bandwidth limitations. This paper introduces and evaluates the AdaptiveMesh (Adaptive Federated Learning for Wireless Mesh Environments) algorithm, an adaptive approach designed to optimize resource usage in FL scenarios, with a focus on resource-constrained Internet of Things (IoT) devices, mobile applications, and commercial cloud systems. We compare the performance of AdaptiveMesh with a naive non-adaptive algorithm, focusing on key metrics such as CPU utilization, device temperature, accuracy, training time, and network bandwidth. Our study examines these algorithms’ effectiveness on both physical devices, including Raspberry Pis, mini PCs, and laptops, as well as virtual machine instances in the Google Cloud Platform. The results demonstrate that the AdaptiveMesh algorithm dynamically adjusts training parameters in response to real-time device metrics, thereby optimizing resource usage, preventing device overload, and reducing training time under constrained conditions, whereas the naive approach often leads to device inefficiencies and potential temporary shutdowns, as devices attempt to manage heat or workload by throttling performance. This comparison underscores the importance of adaptive mechanisms in FL, especially in resource-limited environments.

An algorithm for heterogeneous wireless network connections for user preferences and services

2025-05-19

Sriram Krishnan , A. V. Daniel , S. Ayyasamy +4 more

Heterogeneous wireless networks (HWNs) present a challenge in selecting the optimal network for user devices due to the overlapping availability of multiple networks. In order to help users choose the … Heterogeneous wireless networks (HWNs) present a challenge in selecting the optimal network for user devices due to the overlapping availability of multiple networks. In order to help users choose the best HWN connection, this research is trying to build a decision-making framework that takes user preferences and network performance characteristics into account. Using a multi-attribute decision-making (MADM) method that incorporates fuzzy logic and the Fuzzy Analytic Hierarchy Process (FAHP), our goal is to improve the decision-making process for network selection. The suggested system takes into account a number of network metrics, including latency, jitter, bandwidth, and cost, and uses user preferences to determine the relative importance of each to guarantee a tailored and adaptable recommendation. Our results demonstrate that the algorithm greatly enhances the efficiency of network selection and the level of user happiness, with UMTS being the best option for conversational services, WiMAX being the best for streaming, and LTE being the best for interactive services. Through the incorporation of user-centric decision-making into the network selection process, this research enhances adaptive wireless communication systems, leading to better user experience and network efficiency.

Energy Efficiency Optimization of Multi-Hop Relay Networks via a Joint Relay Selection and Power Allocation Strategy

2025-05-15

Dongxu Li , Lin Wan , Sheng He +1 more

Existing resource allocation models for multi-hop relay networks lack the systematic joint optimization of relay selection and power allocation. Therefore, a multi-hop relay network model based on a joint optimization … Existing resource allocation models for multi-hop relay networks lack the systematic joint optimization of relay selection and power allocation. Therefore, a multi-hop relay network model based on a joint optimization strategy is proposed, aimed at realizing the energy efficiency optimization of the system through the cooperative optimization of relay selection and power allocation. The proposed model not only takes into account the node transmitting power and communication link but also combines the specified system quality of service requirements. On this basis, the FD-Dink energy efficiency optimization algorithm is proposed. By integrating an enhanced D* algorithm with a forward maximum signal-to-noise ratio (FMSNR) and the Dinkelbach–Lagrange multiplier method, the proposed strategy resolves relay selection and power control problems in a coordinated framework so as to determine the optimal energy efficiency communication link of a multi-hop relay network model. Case studies demonstrate that this joint optimization strategy significantly improves the system energy efficiency of the multi-hop relay network and shows superiority in dynamic path planning and global power allocation, offering significant theoretical and practical implications.

Multi-level miscommunication

2025-05-15

Erica Russell , Ian Christie

Development and Evaluation of a Lightweight Encryption Algorithm for Mobile Ad Hoc Networks

2025-05-10

M Varsha | Journal of Information Systems Engineering & Management

Mobile Ad Hoc Networks are characterized by their dynamic topology and decentralized nature, which present unique challenges for ensuring secure communication. This paper presents the development and evaluation of a … Mobile Ad Hoc Networks are characterized by their dynamic topology and decentralized nature, which present unique challenges for ensuring secure communication. This paper presents the development and evaluation of a lightweight encryption algorithm tailored specifically for MANETs. The proposed algorithm is designed to balance security and efficiency, minimizing computational and energy overhead while maintaining robust protection against various security threats. The research methodology is divided into three primary phases. In Phase 1, a thorough literature review and requirement analysis lead to the design of the encryption algorithm using lightweight cryptographic techniques, followed by a comprehensive security analysis to identify and mitigate potential vulnerabilities. Phase 2 involves implementing the algorithm in the NS-2 simulation environment. The network topology is set up with varying node counts, and simulation scenarios are developed to test performance metrics such as encryption time, energy consumption, packet delivery ratio (PDR), and packet loss. Phase 3 focuses on the performance evaluation, where simulation data is analyzed, and the algorithm is optimized for better efficiency and security. The results demonstrate that the proposed algorithm significantly improves encryption time and energy consumption compared to existing solutions while maintaining high levels of security and data integrity. The performance metrics are thoroughly analyzed and presented through both tabular and graphical representations, highlighting the algorithm's advantages in various MANET scenarios. This research contributes to the field of network security by providing a practical and efficient encryption solution for MANETs, potentially paving the way for secure communication in future mobile networks.

Error analysis of quadruple-correlated cooperative communication systems

2025-05-07

S. Kirubakaran , M. D. Selvaraj

An efficient resource allocation mechanism with fuzzy C-means and adaptive RNNs for D2D communications in cellular networks

2025-05-01

Sambi Reddy Gottam , Udit Narayana Kar

Differential equation algorithms for distance relays in the presence of inverter-based resources

2025-05-01

Henrik Johansson , Qianli Xing , Nathaniel Taylor +1 more

A stochastic geometry approach for relay-assisted uplink multicell networks

2025-05-01

Moubachir Madani Fadoul , Mohammed S. M. Gismalla

Robust Overcurrent-Differential Agent-Based Relaying Scheme with a False Data Rejection Tool

2025-05-01

Mohamed Elgamal , Abdelfattah A. Eladl , Bishoy E. Sedhom +1 more

Heuristic method for relay node placement in heterogeneous wireless network

2025-04-30

Eliott Guffens , Vincent Le Nir , Ben Lauwens +1 more

Whether it is to initially deploy a network or to restore the connectivity in a partitioned one, the question of the optimal Relay Node (RN) placement arises. This problem is … Whether it is to initially deploy a network or to restore the connectivity in a partitioned one, the question of the optimal Relay Node (RN) placement arises. This problem is already challenging when considering a static homogeneous network. However, diversity in transmission parameters within the network can induce diversity in transmission ranges, imposing the consideration of heterogeneity in the network. Furthermore, if the nodes are moving, the RN placement scheme must manage a smooth repositioning of the RNs without any large jumps or major restructuring. This paper introduces an effective strategy for deploying the minimum number of RNs in order to restore the connectivity between the nodes of a partitioned heterogeneous network. Through the statistical analysis of results from numerous randomly generated scenarios, the proposed Barycenter-focused Relay nodes placement for Heterogeneous wireless Networks (BRHEN) algorithm is shown to be an improvement on other similar approaches in terms of the number of RNs and the latency. Additionally, BRHEN exhibits stability in the positions and number of RNs when small displacements are applied to the Initial Nodes (INs). This characteristic makes this method suitable for scenarios with moving INs.

Asymptotic BER Performance Comparison of MRC and SC Diversity Techniques with Binary Signaling over Rayleigh Fading Channels

2025-04-30

Jinu Gong , Hoojin Lee

Q Cells in Wireless Networks

2025-04-30

Martin Haenggi

For a given set of transmitters such as cellular base stations or WiFi access points, is it possible to analytically characterize the set of locations that are "covered" in the … For a given set of transmitters such as cellular base stations or WiFi access points, is it possible to analytically characterize the set of locations that are "covered" in the sense that users at these locations experience a certain minimum quality of service? In this paper, we affirmatively answer this question, by providing explicit simple outer bounds and estimates for the coverage manifold. The key geometric elements of our analytical method are the Q cells, defined as the intersections of a small number of disks. The Q cell of a transmitter is an outer bound to the service region of the transmitter, and, in turn, the union of Q cells is an outer bound to the coverage manifold. In infinite networks, connections to the meta distribution of the signal-to-interference ratio allow for a scaling of the Q cells to obtain accurate estimates of the coverage manifold.

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Kernels for storage capacity and dual index coding

2025-04-25

Ishay Haviv

Improving OFDM Maximum Transmission Rate Uplink Based on the Cognitive One-Way Af-Relay Networks via Genetic Algorithm

2025-04-22

Ghufran M. Hatem

In wireless communication systems the demand for spectrum resources are increasing rapidly due to increasing spectrum utilization that causes scarceness of the spectrum frequency bands, the Cognitive Radio Network is … In wireless communication systems the demand for spectrum resources are increasing rapidly due to increasing spectrum utilization that causes scarceness of the spectrum frequency bands, the Cognitive Radio Network is considered the best solution for this problem, and its cooperated network if it merges with Relay technology. The resource allocation for an OFDM (orthogonal frequency-division multiplexing) with N subcarrier-based-cognitive AF (amplify and forward) for relay network and relay selection is proposed in this paper, the Objective Function is to Maximization the sum transmission rate over the sub-carriers of the secondary user under the Interference constraints from the secondary users (SUs) to the primary users (PUs) and the power constraints for both (the secondary users and relays). The subcarrier allocation and power allocation for the secondary network with relay selection were solved by using a Genetic algorithm.

Secure Relay Networks in Text Semantic Communication

2025-04-18

Jianhua Cui | 4th International Conference on Information Science, Electrical, and Automation Engineering (ISEAE 2022)

Land ledger-A Secure and Immutable Ledger for Land Transactions

2025-04-04

S Anugraha , E K Abishek , K. Mohan +3 more

The "Land Ledger Management System" is a comprehensive digital platform designed to streamline the documentation, verification, and management of land records. This project focuses on creating a secure, transparent, and … The "Land Ledger Management System" is a comprehensive digital platform designed to streamline the documentation, verification, and management of land records. This project focuses on creating a secure, transparent, and user-friendly system that digitizes land ownership details and property transactions. It enables users to access land records, verify ownership, and initiate property transfers with ease. Administrators can manage user access, authenticate documents, and maintain up-to-date land registry data. By integrating technologies such as blockchain for data integrity and GIS for location mapping, the system aims to reduce fraud, increase transparency, and enhance efficiency in land administration. This project contributes to the modernization of land record systems, aligning with digital governance and smart city initiatives.

New constant dimension subspace codes via generalized coset construction

2025-04-03

K. John Singh , Sheo Kumar Singh

Spanning trees in pseudorandom graphs via sorting networks

2025-04-03

Joseph Hyde , Natasha Morrison , Alp Müyesser +1 more

We show that <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="left-parenthesis n comma d comma lamda right-parenthesis"> <mml:semantics> <mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:mi>n</mml:mi> <mml:mo>,</mml:mo> <mml:mi>d</mml:mi> <mml:mo>,</mml:mo> <mml:mi>λ</mml:mi> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:annotation encoding="application/x-tex">(n,d,\lambda )</mml:annotation> </mml:semantics> … We show that <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="left-parenthesis n comma d comma lamda right-parenthesis"> <mml:semantics> <mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:mi>n</mml:mi> <mml:mo>,</mml:mo> <mml:mi>d</mml:mi> <mml:mo>,</mml:mo> <mml:mi>λ</mml:mi> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:annotation encoding="application/x-tex">(n,d,\lambda )</mml:annotation> </mml:semantics> </mml:math> </inline-formula>-graphs with <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="lamda equals upper O left-parenthesis d slash log cubed n right-parenthesis"> <mml:semantics> <mml:mrow> <mml:mi>λ</mml:mi> <mml:mo>=</mml:mo> <mml:mi>O</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi>d</mml:mi> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>/</mml:mo> </mml:mrow> <mml:msup> <mml:mi>log</mml:mi> <mml:mn>3</mml:mn> </mml:msup> <mml:mo>⁡</mml:mo> <mml:mi>n</mml:mi> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:annotation encoding="application/x-tex">\lambda =O(d/\log ^3 n)</mml:annotation> </mml:semantics> </mml:math> </inline-formula> are universal with respect to all bounded degree spanning trees. This significantly improves upon the previous best bound due to Han and Yang of the form <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="lamda equals d slash exp left-parenthesis upper O left-parenthesis StartRoot log n EndRoot right-parenthesis right-parenthesis"> <mml:semantics> <mml:mrow> <mml:mi>λ</mml:mi> <mml:mo>=</mml:mo> <mml:mi>d</mml:mi> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>/</mml:mo> </mml:mrow> <mml:mi>exp</mml:mi> <mml:mo>⁡</mml:mo> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo stretchy="false">(</mml:mo> <mml:mi>O</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msqrt> <mml:mi>log</mml:mi> <mml:mo>⁡</mml:mo> <mml:mi>n</mml:mi> </mml:msqrt> <mml:mo stretchy="false">)</mml:mo> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> </mml:mrow> <mml:annotation encoding="application/x-tex">\lambda =d/\exp {(O(\sqrt {\log n}))}</mml:annotation> </mml:semantics> </mml:math> </inline-formula>, and makes progress towards a problem of Alon, Krivelevich, and Sudakov from 2007. Our proof relies on the existence of sorting networks of logarithmic depth, as given by a celebrated construction of Ajtai, Komlós and Szemerédi. Using this construction, we show that the classical vertex-disjoint paths problem can be solved for a set of vertices fixed in advance.

Coexistence in Wireless Networks: Challenges and Opportunities

2025-04-01

Nagma Parveen , Khaizuran Abdullah , Khairayu Badron +2 more

The potential consequences of interference on communication networks are one of the main challenges in the nature and efficiency of wireless communication links. The interruption is seen as additional noise … The potential consequences of interference on communication networks are one of the main challenges in the nature and efficiency of wireless communication links. The interruption is seen as additional noise to the device, which can have a major impact on the efficiency of the connection. The rapid expansion of broadband wireless networks and the increasing congestion of the radio frequency spectrum due to shared usage by terrestrial and satellite networks have heightened concerns about potential interference. To optimize spectrum utilization, multiple terrestrial and satellite networks often coexist within the same frequency bands allocated for satellite communications services. Spectrum interference in wireless networks is a topic of much interest in the current scenario as it can present a lot of challenges. This article provides a critical review of the coexistence and spectrum sharing in wireless networks. Along with this, mitigation techniques to avoid interference have also been discussed in detail. The article aims to give a detailed discussion on the challenges and opportunities in this field by reviewing significant recent works in this field.

Modelling of grid following inverter for performance evaluation of positive sequence memory polarized distance relay

2025-04-01

Meenu Jayamohan , Sarasij Das , Jose de Jesús Chávez +1 more

Relay Signal Optimization in Distributed GRS Codes

2025-04-01

Jiu Xiong , Fengfan Yang

Abstract In this paper, based on the idea of segmentation algorithm, a lightweight and reasonable signal optimization algorithm at the relay is proposed in the cooperation communication system with GRS … Abstract In this paper, based on the idea of segmentation algorithm, a lightweight and reasonable signal optimization algorithm at the relay is proposed in the cooperation communication system with GRS coding. This algorithm mainly splits the information bits of the relay signal several times and pre-selects some of them, while the remaining information bits are randomly selected. The algorithm has lower complexity than the traditional algorithm, and the relay information is more evenly distributed. This paper describes the general flow of this signal optimization algorithm, design examples. The optimization algorithm is simulated by Monte Carlo experiments to have similar transmission performance gains over the traversal search.

An embedding-based method for inferring novel interlayers in multilayer networks

2025-04-01

Pietro Cinaglia

Enhancing Security in Private Network Communications through Advanced Encryption Gateways: Innovations, Implementations and Performance Analysis

2025-04-01

ShangbinXu

Private network communications are critical for safeguarding sensitive data in sectors such as finance, healthcare, and defense. Encryption gateways serve as pivotal components in securing these networks by integrating encryption … Private network communications are critical for safeguarding sensitive data in sectors such as finance, healthcare, and defense. Encryption gateways serve as pivotal components in securing these networks by integrating encryption algorithms, protocol conversion, and secure tunnel establishment. This paper explores the technical architecture of modern encryption gateways, evaluates their performance across hybrid encryption models, and introduces a novel framework for dynamic algorithm selection. A healthcare case study demonstrated a ‌75% reduction in data breaches‌ while achieving ‌zero data loss‌ during FTP-to-SFTP migration. Research findings indicate that ‌data security significantly improves under encrypted gateways‌, with performance further optimized through machine learning algorithms.