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39
Informationtheoretic Relaying for multicast in . . .
, 2007
"... A twosender, tworeceiver channel model with one relay node is considered for the case of multicast traffic. We examine two different cooperative approaches: relaying, in which the relay timeshares between helping two senders and employs traditional routing on the network layer, and more general e ..."
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Cited by 7 (2 self)
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A twosender, tworeceiver channel model with one relay node is considered for the case of multicast traffic. We examine two different cooperative approaches: relaying, in which the relay timeshares between helping two senders and employs traditional routing on the network layer, and more general encoding schemes in which the relay simultaneously forwards two data streams. Outer bounds are presented and then specialized to bound the performance of any relaying scheme. Two simple encoding schemes that allow for more general relaying are considered and compared to the relaying outer bound. We also consider the performance of an opportunistic network coding scheme that exploits interference at the receivers by interpreting it as a form of a network code.
Deterministic Network Model Revisited: An Algebraic Network Coding Approach
, 2010
"... The capacity of multiuser networks has been a longstanding problem in information theory. Recently, Avestimehr et al. have proposed a deterministic network model to approximate multiuser wireless networks. This model, known as the ADT network model, takes into account the broadcast nature of wirele ..."
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Cited by 5 (1 self)
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The capacity of multiuser networks has been a longstanding problem in information theory. Recently, Avestimehr et al. have proposed a deterministic network model to approximate multiuser wireless networks. This model, known as the ADT network model, takes into account the broadcast nature of wireless medium and interference. We show that the ADT network model can be described within the algebraic network coding framework introduced by Koetter and Médard. We prove that the ADT network problem can be captured by a single matrix, and show that the mincut of an ADT network is the rank of this matrix; thus, eliminating the need to optimize over exponential number of cuts between two nodes to compute the mincut of an ADT network. We extend the capacity characterization for ADT networks to a more general set of connections, including single unicast/multicast connection and nonmulticast connections such as multiple multicast, disjoint multicast, and twolevel multicast. We also provide sufficiency conditions for achievability in ADT networks for any general connection set. In addition, we show that random linear network coding, a randomized distributed algorithm for network code construction, achieves the capacity for the connections listed above. Furthermore, we extend the ADT networks to those with random erasures and cycles (thus, allowing bidirectional links). In addition, we propose an efficient linear code construction for the deterministic wireless multicast relay network model. Note that Avestimehr et al.’s proposed code construction is not guaranteed to be efficient and may potentially involve an infinite block length. Unlike several previous coding schemes, we do not attempt to find flows in the network. Instead, for a layered network, we maintain an invariant where it is required that at each stage of the code construction, certain sets of codewords are linearly independent.
AmplifyandForward in Wireless Relay Networks
"... Abstract—A general class of wireless relay networks with a single sourcedestination pair is considered. Intermediate nodes in the network employ an amplifyandforward scheme to relay their input signals. In this case the overall inputoutput channel from the source via the relays to the destinatio ..."
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Abstract—A general class of wireless relay networks with a single sourcedestination pair is considered. Intermediate nodes in the network employ an amplifyandforward scheme to relay their input signals. In this case the overall inputoutput channel from the source via the relays to the destination effectively behaves as an intersymbol interference channel with colored noise. Unlike previous work we formulate the problem of the maximum achievable rate in this setting as an optimization problem with no assumption on the network size, topology, and signaltonoise ratio. Previous work considered only scenarios wherein relays use all their power to amplify their received signals. We demonstrate that this may not always maximize the achievable rate in amplifyandforward relay networks. The proposed formulation allows us to not only recover known results on the performance of the amplifyandforward schemes for some simple relay networks but also characterize the performance of such schemes in more complex relay networks which cannot be addressed in a straightforward manner with existing approaches. Using cutset arguments, we derive simple upper bounds on the capacity of general wireless relay networks. Through various examples, we show that a large class of amplifyandforward relay networks can achieve rates within a constant factor of these upper bounds asymptotically in network parameters. I.
CostDelay Tradeoffs for TwoWay Relay Networks
"... Abstract—We consider two sources in a wireless network exchanging stochastically varying traffic using an intermediate relay. Each relay use incurs some cost, which, for example, could be transmission energy. This cost is shared between the sources when packets from both are transmitted simultaneous ..."
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Abstract—We consider two sources in a wireless network exchanging stochastically varying traffic using an intermediate relay. Each relay use incurs some cost, which, for example, could be transmission energy. This cost is shared between the sources when packets from both are transmitted simultaneously by the relay using network coding. If the relay transmits a packet originating from one source only, the cost is incurred by that source only. In this setting, we study transmission policies that tradeoff the average cost with the average packet delay. We first present the costdelay tradeoff for a centralized scheme using Lyapunov stability arguments. Next, we consider a distributed policy, where each source aims to optimize its own costdelay tradeoff. We determine the Nash equilibrium of the resulting noncooperative game and show that it performs worse than the centralized algorithm. To overcome this limitation, we introduce a pricing mechanism at the relay, which is shown to achieve the centralized performance. These algorithms, though oblivious to the arrival statistics, do require global knowledge of queue backlogs. Lastly, we consider distributed algorithms that overcome this requirement. Among those, we observe that simple queuelength threshold algorithms perform remarkably well. Index Terms—Cost sharing, delay, network coding, twoway relaying, queue stability, stochastic traffic, cooperation, competition.
Twoway Source Coding Through a Relay
"... Abstract — A 3node lossy source coding problem for a 2DMS (X1,X2) is considered. Source nodes 1 and 2 observe X1 and X2, respectively, and each wishes to reconstruct the other source with a prescribed distortion. To achieve these goals, nodes 1 and 2 send descriptions of their sources to relay nod ..."
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Abstract — A 3node lossy source coding problem for a 2DMS (X1,X2) is considered. Source nodes 1 and 2 observe X1 and X2, respectively, and each wishes to reconstruct the other source with a prescribed distortion. To achieve these goals, nodes 1 and 2 send descriptions of their sources to relay node 3. The relay node then broadcasts a joint description to the source nodes. A cutset outer bound and a compress–linear code inner bound are established and shown to coincide in several special cases. A compute–compress inner bound is then presented and shown to outperform the compress–linear code in some cases. An outer bound based on Kaspi’s converse for the twoway source coding problem is shown to be strictly tighter than the cutset outer bound. I.
Wireless Multicast Relay Networks with LimitedRate SourceConferencing
"... Abstract—We investigate capacity bounds for a wireless multicast relay network where two sources simultaneously multicast to two destinations with the help of a fullduplex relay node. The two sources and the relay use the same channel resources (i.e. cochannel transmission). We assume Gaussian cha ..."
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Abstract—We investigate capacity bounds for a wireless multicast relay network where two sources simultaneously multicast to two destinations with the help of a fullduplex relay node. The two sources and the relay use the same channel resources (i.e. cochannel transmission). We assume Gaussian channels with timeinvariant channel gains which are known by all nodes. The two source nodes are connected by orthogonal limitedrate errorfree conferencing links. By extending the proof of the converse for the Gaussian relay channel and introducing two lemmas on conditional (co)variance, we present two genieaided outer bounds of the capacity region for this multicast relay network. We extend noisy network coding to use source cooperation with the help of the theory of network equivalence. We also propose a new coding scheme, partialdecodeandforward based linear network coding, which is essentially a hybrid scheme utilizing ratesplitting and messages conferencing at the source nodes, partial decoding and linear network coding at the relay, and joint decoding at each destination. A lowcomplexity alternative scheme, analog network coding based on amplifyandforward relaying, is also investigated and shown to benefit greatly from the help of the conferencing links and can even outperform noisy network coding when the coherent combining gain is dominant. Index Terms—Relays, source cooperation, network coding, wireless multicast, cooperative communication. I.
FiniteSNR DiversityMultiplexing Tradeoff and Optimum Power Allocation in Bidirectional Cooperative Networks
, 810
"... This paper focuses on analog network coding (ANC) and time division broadcasting (TDBC) which are two major protocols used in bidirectional cooperative networks. Lower bounds of the outage probabilities of those two protocols are derived first. Those lower bounds are extremely tight in the whole sig ..."
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This paper focuses on analog network coding (ANC) and time division broadcasting (TDBC) which are two major protocols used in bidirectional cooperative networks. Lower bounds of the outage probabilities of those two protocols are derived first. Those lower bounds are extremely tight in the whole signaltonoise ratio (SNR) range irrespective of the values of channel variances. Based on those lower bounds, finiteSNR diversitymultiplexing tradeoffs of the ANC and TDBC protocols are obtained. Secondly, we investigate how to efficiently use channel state information (CSI) in those two protocols. Specifically, an optimum power allocation scheme is proposed for the ANC protocol. It simultaneously minimizes the outage probability and maximizes the total mutual information of this protocol. For the TDBC protocol, an optimum method to combine the received signals at the relay terminal is developed under an equal power allocation assumption. This method minimizes the outage probability and maximizes the total mutual information of the TDBC protocol at the same time. I.
Performance Analysis of Physical Layer Network Coding
, 2009
"... Network coding has emerged as an innovative approach to network operation that can significantly enhance network throughput. The key goal of this thesis is to understand fundamental aspects of physical layer network coding, where network coding is performed at the physical layer. As a simple but typ ..."
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Cited by 2 (0 self)
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Network coding has emerged as an innovative approach to network operation that can significantly enhance network throughput. The key goal of this thesis is to understand fundamental aspects of physical layer network coding, where network coding is performed at the physical layer. As a simple but typical example of network coding, we consider a network scenario where two users transmit messages through a common channel and the receiver reconstructs the exclusiveor of the two messages. For this channel, we investigate the error exponent which can provide guidelines for the design of efficient communication systems using network coding. From a practical point of view, we examine the performance of channel codes for this problem. Assuming that each user transmits data using the same lowdensity paritycheck (LDPC) code and each link is an additive white Gaussian noise channel, we evaluate the noise thresholds of LDPC codes via density evolution methods. Other important issues considered in this thesis are related to transmission over fading channels. First, we study the performance of LDPC codes over nonergodic
Cooperative strategies for relayaided multicell wireless networks with Backhaul
 in Proc. of IEEE ITW
, 2010
"... Abstract—We investigate cooperative strategies for relayaided multisource multidestination wireless networks with backhaul support. Each source multicasts information to all destinations using a shared relay. We study cooperative strategies based on different network coding (NC) schemes, namely, ..."
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Abstract—We investigate cooperative strategies for relayaided multisource multidestination wireless networks with backhaul support. Each source multicasts information to all destinations using a shared relay. We study cooperative strategies based on different network coding (NC) schemes, namely, finite field NC (FNC), linear NC (LNC), and lattice coding. To further exploit the backhaul connection, we also propose NCbased beamforming (NBF). We measure the performance in term of achievable rates over Gaussian channels and observe significant gains over a benchmark scheme. The benefit of using backhaul is also clearly demonstrated in most of scenarios. I.
Stability Regions of TwoWay Relaying with Network Coding (Invited Paper)
"... We consider a pair of nodes with stochastic traffic flows who wish to communicate in a bidirectional communication scenario using intermediate relays in twohop fashion. Intermediate relays are capable of XOR network coding. Transmission scheduling is done by tailoring the backpressure algorithm to ..."
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We consider a pair of nodes with stochastic traffic flows who wish to communicate in a bidirectional communication scenario using intermediate relays in twohop fashion. Intermediate relays are capable of XOR network coding. Transmission scheduling is done by tailoring the backpressure algorithm to the problem at hand. Two main alternatives for network operation are either to have queues at the relays (hopbyhop scheduling) or no queues at the relays (immediate forwarding). In this twoway network with stochastic flows, we formulate and show that the resulting stability regions of these two approaches are identical.