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291
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.
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.
Interference mitigation through limited receiver cooperation,” Submitted to
 IEEE Transactions on Information Theory
, 2009
"... Abstract—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 ..."
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Cited by 40 (5 self)
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Abstract—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. I.
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 34 (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
Analog network coding in the highsnr regime
 in Proc. IEEE Wireless Network Coding Workshop
"... Abstract—A node performing analog network coding simply forwards a signal it receives over a wireless channel. This allows for a (noisy) linear combination of signals simultaneously sent from multiple sources to be forwarded in the network. As such, analog network coding extends the idea of network ..."
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Cited by 20 (5 self)
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Abstract—A node performing analog network coding simply forwards a signal it receives over a wireless channel. This allows for a (noisy) linear combination of signals simultaneously sent from multiple sources to be forwarded in the network. As such, analog network coding extends the idea of network coding to wireless networks. However, the analog network coding performance is limited by propagated noise, and we expect this strategy to perform well only in high SNR. In this paper, we formalize this intuition and determine highSNR conditions under which analog network coding approaches capacity in a layered relay network. By relating the received SNR at the nodes with the propagated noise, we determine the rate achievable with analog network coding. In particular, when all the received powers are lower bounded by 1/δ, the propagated noise power in a network with L layers is of the order Lδ. The result demonstrates that the analog network coding approaches the cutset bound as the received powers at relays increase. As all powers in the network increase, the analog network coding rate is within a constant gap from the upper bound. The gap depends on number of nodes. We further demonstrate by an example that analog network coding can perform close to sumcapacity also in the multicast case. I.
Degrees of freedom of twohop wireless networks: Everyone gets the entire cake
 IEEE Trans. Inf. Theory
, 2014
"... Abstract—We show that fully connected twohop wireless networks with K sources, K relays and K destinations have K degrees of freedom for almost all values of constant channel coefficients. Our main contribution is a new interferencealignmentbased achievability scheme which we call aligned network ..."
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Cited by 19 (1 self)
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Abstract—We show that fully connected twohop wireless networks with K sources, K relays and K destinations have K degrees of freedom for almost all values of constant channel coefficients. Our main contribution is a new interferencealignmentbased achievability scheme which we call aligned network diagonalization. This scheme allows the data streams transmitted by the sources to undergo a diagonal linear transformation from the sources to the destinations, thus being received free of interference by their intended destination. I.
An outer bound region for interference channels with generalized feedback
 in Information Theory and Applications Workshop (ITA), 2010, Feb.2010,pp.1–5
"... (IFCGF) are a model for wireless communication systems with source cooperation. GF enables to enlarge the achievable rate region with respect to the noncooperative IFC without requiring an increase in system resources. This paper develops an outer bound region on the capacity of general IFCGF and ..."
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Cited by 19 (7 self)
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(IFCGF) are a model for wireless communication systems with source cooperation. GF enables to enlarge the achievable rate region with respect to the noncooperative IFC without requiring an increase in system resources. This paper develops an outer bound region on the capacity of general IFCGF and then tighten it further for a class of semideterministic IFCGF that include the “high SNR approximation ” of the Gaussian channel and the Gaussian channel as special cases.
Diversitymultiplexing tradeoff of the halfduplex relay channel
 in Proc. FortySixth Allerton Conf. Commun. Contr. Comput
, 2008
"... Abstract—We show that the diversitymultiplexing tradeoff of a halfduplex singlerelay channel with identically distributed Rayleigh fading channel gains meets the 2 by 1 MISO bound. We generalize the result to the case when there are N noninterfering relays and show that the diversitymultiplexin ..."
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Cited by 18 (3 self)
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Abstract—We show that the diversitymultiplexing tradeoff of a halfduplex singlerelay channel with identically distributed Rayleigh fading channel gains meets the 2 by 1 MISO bound. We generalize the result to the case when there are N noninterfering relays and show that the diversitymultiplexing tradeoff is equal to the N + 1 by 1 MISO bound. I.