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315
Reliable physical layer network coding
 PROCEEDINGS OF THE IEEE
, 2011
"... 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 typicall ..."
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Cited by 54 (5 self)
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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.
Approximately achieving Gaussian relay network capacity with latticebased QMF codes
, 2010
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An Algebraic Approach to PhysicalLayer Network Coding
 IEEE TRANS. INFORM. THEORY
, 2010
"... The problem of designing new physicallayer network coding (PNC) schemes via lattice partitions is considered. Building on recent work by Nazer and Gastpar, who demonstrated its asymptotic gain using informationtheoretic tools, we take an algebraic approach to show its potential in nonasymptotic ..."
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Cited by 41 (4 self)
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The problem of designing new physicallayer network coding (PNC) schemes via lattice partitions is considered. Building on recent work by Nazer and Gastpar, who demonstrated its asymptotic gain using informationtheoretic tools, we take an algebraic approach to show its potential in nonasymptotic settings. We first relate NazerGastpar’s approach to the fundamental theorem of finitely generated modules over a principle ideal domain. Based on this connection, we generalize their code construction and simplify their encoding and decoding methods. This not only provides a transparent understanding of their approach, but more importantly, it opens up the opportunity to design efficient and practical PNC schemes. Finally, we apply our framework to the Gaussian relay network and demonstrate its advantage over conventional PNC schemes.
Interference mitigation through limited receiver cooperation: Symmetric case
 IEEE TRANSACTIONS ON INFORMATION THEORY
, 2009
"... Interference is a major issue that limits the performance in wireless networks, and the cooperation among receivers can help mitigate interference by forming distributed MIMO systems. The rate at which receivers cooperate, however, is limited in most scenarios. How much interference can one bit of ..."
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Cited by 39 (5 self)
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Interference is a major issue that limits the performance in wireless networks, and the cooperation among receivers can help mitigate interference by forming distributed MIMO systems. The rate at which receivers cooperate, however, is limited in most scenarios. How much interference can one bit of receiver cooperation mitigate? In this paper, we study the twouser Gaussian interference channel with conferencing decoders to answer this question in a simple setting. We characterize the fundamental gain from cooperation: at high SNR, when INR is below 50 % of SNR in dB scale, onebit cooperation per direction buys roughly onebit gain per user until full receiver cooperation performance is reached, while when INR is between 67 % and 200 % of SNR in dB scale, onebit cooperation per direction buys roughly halfbit gain per user. The conclusion is drawn based on the approximate characterization of the symmetric capacity in the symmetric setup. We propose strategies achieving the symmetric capacity universally to within 3 bits. The strategy consists of two parts: (1) the transmission scheme, where superposition encoding with a simple power split is employed, and (2) the cooperative protocol, where quantizebinning is used for relaying.
TwoUnicast Wireless Networks: Characterizing the DegreesofFreedom
, 2012
"... We consider twosource twodestination (i.e., twounicast) multihop wireless networks that have a layered structure with arbitrary connectivity. We show that, if the channel gains are chosen independently according to continuous distributions, then, with probability 1, twounicast layered Gaussi ..."
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Cited by 33 (9 self)
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We consider twosource twodestination (i.e., twounicast) multihop wireless networks that have a layered structure with arbitrary connectivity. We show that, if the channel gains are chosen independently according to continuous distributions, then, with probability 1, twounicast layered Gaussian networks can only have 1, 3/2 or 2 sum degreesoffreedom (unless both sourcedestination pairs are disconnected, in which case no degreesoffreedom can be achieved). We provide sufficient and necessary conditions for each case based on network connectivity and a new notion of sourcedestination paths with manageable interference. Our achievability scheme is based on forwarding the received signals at all nodes, except for a small fraction of them in at most two key layers. Hence, we effectively create a “condensed network” that has at most four layers (including the sources layer and the destinations layer). We design the transmission strategies based on the structure of this condensed network. The converse results are obtained by developing informationtheoretic inequalities that capture the structures of the network connectivity. Finally, we extend this result and characterize the full degreesoffreedom region of twounicast layered wireless networks.
Topological interference management through index coding
, 2013
"... While much recent progress on interference networks has come about under the assumption of abundant channel state information at the transmitters (CSIT), a complementary perspective is sought in this work through the study of interference networks with no CSIT except a coarse knowledge of the topolo ..."
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Cited by 30 (14 self)
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While much recent progress on interference networks has come about under the assumption of abundant channel state information at the transmitters (CSIT), a complementary perspective is sought in this work through the study of interference networks with no CSIT except a coarse knowledge of the topology of the network that only allows a distinction between weak and significant channels and no further knowledge of the channel coefficients ’ realizations. Modeled as a degreesoffreedom (DoF) study of a partially connected interference network with no CSIT, the problem is found to have a counterpart in the capacity analysis of wired networks with arbitrary linear network coding at intermediate nodes, under the assumption that the sources are aware only of the end to end topology of the network. The wireless (wired) network DoF (capacity) region, expressed in dimensionless units as a multiple of the DoF (capacity) of a single point to point channel (link), is found to be bounded above by the capacity of an index coding problem where the antidotes graph is the complement of the interference graph of the original network and the bottleneck link capacity is normalized to unity. The problems are shown to be equivalent under linear solutions over the same field. An interference alignment
Interference Channels with RateLimited Feedback
, 2011
"... We consider the twouser interference channel with ratelimited feedback. Related prior works focus on the case where feedback links have infinite capacity, while no research has been done for the ratelimited feedback problem. Several new challenges arise due to the capacity limitations of the fee ..."
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Cited by 24 (6 self)
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We consider the twouser interference channel with ratelimited feedback. Related prior works focus on the case where feedback links have infinite capacity, while no research has been done for the ratelimited feedback problem. Several new challenges arise due to the capacity limitations of the feedback links, both in deriving innerbounds and outerbounds. We study this problem under three different interference models: the El GamalCosta deterministic model, the linear deterministic model, and the Gaussian model. For the first two models, we develop an achievable scheme that employs three techniques: HanKobayashi message splitting, quantizeandbinning, and decodeandforward. We also derive new outerbounds for all three models and we show the optimality of our scheme under the linear deterministic model. In the Gaussian case, we propose a transmission strategy that incorporates lattice codes, inspired by the ideas developed in the first two models. For symmetric channel gains, we prove that the gap between the achievable sumrate of the proposed scheme and our new outerbounds is bounded by a constant number of bits, independent of the channel gains.
Gaussian Zinterference channel with a relay link: Achievable rate region and asymptotic sum capacity
 in Proc.Int.Symp. Inf. Theory and Its App
, 2008
"... Abstract — This paper studies the Gaussian Zinterference channel with a ratelimited digital relay link from one receiver to the other receiver. In a companion paper, we dealt with the Type I channel, where the relay link goes from the interferencefree receiver to the interfered receiver. It was s ..."
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Cited by 22 (5 self)
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Abstract — This paper studies the Gaussian Zinterference channel with a ratelimited digital relay link from one receiver to the other receiver. In a companion paper, we dealt with the Type I channel, where the relay link goes from the interferencefree receiver to the interfered receiver. It was shown that in the weak interference regime, each relay bit can improve the sum capacity by up to one bit asymptotically in the high signaltonoiseratio and interferencetonoiseratio limit. In this paper, we study the Type II channel where the relay link goes from the interfered receiver to the interferencefree receiver. The capacity region for such a channel is established in the strong interference regime; achievable rate regions are established in the moderately strong and weak interference regimes. In the weak interference regime, we show that in contrast to the Type I channel, the sum capacity improvement due to relaying for the Type II channel is upper bounded by at most half a bit, even as the relay link rate goes to infinity. I.