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113
Joint Physical Layer Coding and Network Coding for BiDirectional Relaying
 45th Annual Allerton Conference on Communication, Control and Computing
, 2007
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Computeandforward: Harnessing interference through structured codes
 IEEE TRANS. INF. THEORY
, 2009
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Computation over MultipleAccess Channels
 IEEE TRANSACTIONS ON INFORMATION THEORY
, 2007
"... The problem of reliably reconstructing a function of sources over a multipleaccess channel is considered. It is shown that there is no sourcechannel separation theorem even when the individual sources are independent. Joint sourcechannel strategies are developed that are optimal when the structure ..."
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Cited by 142 (24 self)
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The problem of reliably reconstructing a function of sources over a multipleaccess channel is considered. It is shown that there is no sourcechannel separation theorem even when the individual sources are independent. Joint sourcechannel strategies are developed that are optimal when the structure of the channel probability transition matrix and the function are appropriately matched. Even when the channel and function are mismatched, these computation codes often outperform separationbased strategies. Achievable distortions are given for the distributed refinement of the sum of Gaussian sources over a Gaussian multipleaccess channel with a joint sourcechannel lattice code. Finally, computation codes are used to determine the multicast capacity of finite field multipleaccess networks, thus linking them to network coding.
Capacity of the Gaussian Twoway Relay Channel to within 1 2 Bit
, 902
"... In this paper, a Gaussian twoway relay channel, where two source nodes exchange messages with each other through a relay, is considered. We assume that all nodes operate in fullduplex mode and there is no direct channel between the source nodes. We propose an achievable scheme composed of nested l ..."
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Cited by 103 (2 self)
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In this paper, a Gaussian twoway relay channel, where two source nodes exchange messages with each other through a relay, is considered. We assume that all nodes operate in fullduplex mode and there is no direct channel between the source nodes. We propose an achievable scheme composed of nested lattice codes for the uplink and structured binning for the downlink. We show that the scheme achieves within 1 2 bit from the cutset bound for all channel parameters and becomes asymptotically optimal as the signal to noise ratios increase. Index Terms Twoway relay channel, wireless networks, network coding, lattice codes
Capacity bounds for twoway relay channels
 in International Zurich Seminar on Communications (IZS 2008
, 2008
"... Abstract—We provide achievable rate regions for twoway relay channels (TRC). At first, for a binary TRC, we show that the subspacesharing of linear codes can achieve the capacity region. And, for a Gaussian TRC, we propose the subsetsharing of lattice codes. In some cases, the proposed lattice co ..."
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Cited by 63 (5 self)
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Abstract—We provide achievable rate regions for twoway relay channels (TRC). At first, for a binary TRC, we show that the subspacesharing of linear codes can achieve the capacity region. And, for a Gaussian TRC, we propose the subsetsharing of lattice codes. In some cases, the proposed lattice coding scheme can achieve within 1/2bit the capacity and is asymptotically optimal at high signaltonoise ratio (SNR) regimes. I.
The wiretap channel with feedback: Encryption over the channel
 IEEE TRANS. INF. THEORY
, 2008
"... In this work, the critical role of noisy feedback in enhancing the secrecy capacity of the wiretap channel is established. Unlike previous works, where a noiseless public discussion channel is used for feedback, the feedforward and feedback signals share the same noisy channel in the present model ..."
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Cited by 59 (8 self)
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In this work, the critical role of noisy feedback in enhancing the secrecy capacity of the wiretap channel is established. Unlike previous works, where a noiseless public discussion channel is used for feedback, the feedforward and feedback signals share the same noisy channel in the present model. Quite interestingly, this noisy feedback model is shown to be more advantageous in the current setting. More specifically, the discrete memoryless moduloadditive channel with a fullduplex destination node is considered first, and it is shown that the judicious use of feedback increases the secrecy capacity to the capacity of the source–destination channel in the absence of the wiretapper. In the achievability scheme, the feedback signal corresponds to a private key, known only to the destination. In the halfduplex scheme, a novel feedback technique that always achieves a positive perfect secrecy rate (even when the source–wiretapper channel is less noisy than the source–destination channel) is proposed. These results hinge on the moduloadditive property of the channel, which is exploited by the destination to perform encryption over the channel without revealing its key to the source. Finally, this scheme is extended to the continuous real valued modulo channel where it is shown that the secrecy capacity with feedback is also equal to the capacity in the absence of the wiretapper.
Lattice strategies for the dirty multiple access channel
 in Proceedings of IEEE International Symposium on Information Theory
, 2007
"... A generalization of the Gaussian dirtypaper problem to a multiple access setup is considered. There are two additive interference signals, one known to each transmitter but none to the receiver. The rates achievable using Costa’s strategies (i.e. by a random binning scheme induced by Costa’s auxili ..."
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Cited by 59 (10 self)
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A generalization of the Gaussian dirtypaper problem to a multiple access setup is considered. There are two additive interference signals, one known to each transmitter but none to the receiver. The rates achievable using Costa’s strategies (i.e. by a random binning scheme induced by Costa’s auxiliary random variables) vanish in the limit when the interference signals are strong. In contrast, it is shown that lattice strategies (“lattice precoding”) can achieve positive rates independent of the interferences, and in fact in some cases which depend on the noise variance and power constraints they are optimal. In particular, lattice strategies are optimal in the limit of high SNR. It is also shown that the gap between the achievable rate region and the capacity region is at most 0.167 bit. Thus, the dirty MAC is another instance of a network setup, like the KornerMarton modulotwo sum problem, where linear coding is potentially better than random binning. Lattice transmission schemes and conditions for optimality for the asymmetric case, where there is only one interference which is known to one of the users (who serves as a “helper ” to the other user), and for the “common interference ” case are also derived. In the former case the gap between the helper achievable rate and its capacity is at most 0.085 bit.
Reliable physical layer network coding
 Proceedings of the IEEE
, 2011
"... Abstract—When two or more users in a wireless network transmit simultaneously, their electromagnetic signals are linearly superimposed on the channel. As a result, a receiver that is interested in one of these signals sees the others as unwanted interference. This property of the wireless medium is ..."
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Cited by 55 (6 self)
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Abstract—When two or more users in a wireless network transmit simultaneously, their electromagnetic signals are linearly superimposed on the channel. As a result, a receiver that is interested in one of these signals sees the others as unwanted interference. This property of the wireless medium is typically viewed as a hindrance to reliable communication over a network. However, using a recently developed coding strategy, interference can in fact be harnessed for network coding. In a wired network, (linear) network coding refers to each intermediate node taking its received packets, computing a linear combination over a finite field, and forwarding the outcome towards the destinations. Then, given an appropriate set of linear combinations, a destination can solve for its desired packets. For certain topologies, this strategy can attain significantly higher throughputs over routingbased strategies. Reliable physical layer network coding takes this idea one step further: using judiciously chosen linear errorcorrecting codes, intermediate nodes in a wireless network can directly recover linear combinations of the packets from the observed noisy superpositions of transmitted signals. Starting with some simple examples, this survey explores the core ideas behind this new technique and the possibilities it offers for communication over interferencelimited wireless networks. Index Terms—Digital communication, wireless networks, interference, network coding, channel coding, linear code, modulation, physical layer, fading, multiuser channels, multiple access, broadcast. I.
The case for structured random codes in network capacity theorems
 in Proceedings of the IEEE Information Theory Workshop (ITW 2007), (Lake Tahoe, CA
, 2007
"... Random coding arguments are the backbone of most channel capacity achievability proofs. In this paper, we show that in their standard form, such arguments are insufficient for proving some network capacity theorems: structured coding arguments, such as random linear or lattice codes, attain higher r ..."
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Cited by 54 (10 self)
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Random coding arguments are the backbone of most channel capacity achievability proofs. In this paper, we show that in their standard form, such arguments are insufficient for proving some network capacity theorems: structured coding arguments, such as random linear or lattice codes, attain higher rates. Historically, structured codes have been studied as a stepping stone to practical constructions. However, Körner and Marton demonstrated their usefulness for capacity theorems through the derivation of the optimal rate region of a distributed functional source coding problem. Here, we use multicasting over finite field and Gaussian multipleaccess networks as canonical examples to demonstrate that even if we want to send bits over a network, structured codes succeed where simple random codes fail. Beyond network coding, we also consider distributed computation over noisy channels and a special relaytype problem. I.
Approximately achieving Gaussian relay network capacity with lattice codes, eprint  arXiv.org, May 2010. 2 An alternative way to upper bound (16) is to randomly choose the quantization lattices at each relay instead of using a fixed lattice
"... Abstract—Recently, it has been shown that a quantizemapandforward scheme approximately achieves (within a constant number of bits) the Gaussian relay network capacity for arbitrary topologies [1]. This was established using Gaussian codebooks for transmission and random mappings at the relays. In ..."
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Cited by 47 (11 self)
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Abstract—Recently, it has been shown that a quantizemapandforward scheme approximately achieves (within a constant number of bits) the Gaussian relay network capacity for arbitrary topologies [1]. This was established using Gaussian codebooks for transmission and random mappings at the relays. In this paper, we show that the same approximation result can be established by using lattices for transmission and quantization along with structured mappings at the relays. I.