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136
The multi-way relay channel
- in Proc. IEEE Int. Symposium on Inf. Theory (ISIT), Seoul, Korea
"... Abstract—The multi-user communication channel, in which multiple users exchange information with the help of a single relay terminal, called the multi-way relay channel, is considered. In this model, multiple interfering clusters of users communicate simultaneously, where the users within the same c ..."
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Cited by 59 (3 self)
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Abstract—The multi-user communication channel, in which multiple users exchange information with the help of a single relay terminal, called the multi-way relay channel, is considered. In this model, multiple interfering clusters of users communicate simultaneously, where the users within the same cluster wish to exchange messages among themselves. It is assumed that the users cannot receive each other’s signals directly, and hence the relay terminal is the enabler of communication. A relevant metric to study in this scenario is the symmetric rate achievable by all users, which we identify for amplify-and-forward (AF), decodeand-forward (DF) and compress-and-forward (CF) protocols. We also present an upper bound for comparison. The two extreme cases, namely full data exchange, in which every user wants to receive messages of all other users, and pairwise data exchange, consisting of multiple two-way relay channels, are investigated and presented in detail. I.
An Algebraic Approach to Physical-Layer Network Coding
- IEEE TRANS. INFORM. THEORY
, 2010
"... The problem of designing new physical-layer net-work coding (PNC) schemes via lattice partitions is considered. Building on recent work by Nazer and Gastpar, who demonstrated its asymptotic gain using information-theoretic tools, we take an algebraic approach to show its potential in non-asymptotic ..."
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Cited by 41 (4 self)
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The problem of designing new physical-layer net-work coding (PNC) schemes via lattice partitions is considered. Building on recent work by Nazer and Gastpar, who demonstrated its asymptotic gain using information-theoretic tools, we take an algebraic approach to show its potential in non-asymptotic settings. We first relate Nazer-Gastpar’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.
Two-Unicast Wireless Networks: Characterizing the Degrees-of-Freedom
, 2012
"... We consider two-source two-destination (i.e., two-unicast) multi-hop wireless networks that have a layered struc-ture with arbitrary connectivity. We show that, if the channel gains are chosen independently according to continuous distribu-tions, then, with probability 1, two-unicast layered Gaussi ..."
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Cited by 33 (9 self)
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We consider two-source two-destination (i.e., two-unicast) multi-hop wireless networks that have a layered struc-ture with arbitrary connectivity. We show that, if the channel gains are chosen independently according to continuous distribu-tions, then, with probability 1, two-unicast layered Gaussian net-works can only have 1, 3/2 or 2 sum degrees-of-freedom (unless both source-destination pairs are disconnected, in which case no degrees-of-freedom can be achieved). We provide sufficient and necessary conditions for each case based on network connectivity and a new notion of source-destination 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 information-theoretic inequalities that capture the structures of the network connectivity. Finally, we extend this result and characterize the full degrees-of-freedom region of two-unicast layered wireless networks.
JMB: Scaling Wireless Capacity with User Demands
"... We present joint multi-user beamforming (JMB), a system that enables independent access points (APs) to beamform their signals, and communicate with their clients on the same channel as if they were one large MIMO transmitter. The key enabling technology behind JMB is a new low-overhead technique fo ..."
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Cited by 30 (3 self)
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We present joint multi-user beamforming (JMB), a system that enables independent access points (APs) to beamform their signals, and communicate with their clients on the same channel as if they were one large MIMO transmitter. The key enabling technology behind JMB is a new low-overhead technique for synchronizing the phase of multiple transmitters in a distributed manner. The design allows a wireless LAN to scale its throughput by continually adding more APs on the same channel. JMB is implemented and tested with both software radio clients and off-the-shelf 802.11n cards, and evaluated in a dense congested deployment resembling a conference room. Results from a 10-AP software-radio testbed show a linear increase in network throughput with a median gain of 8.1 to 9.4×. Our results also demonstrate that JMB’s joint multi-user beamforming can provide throughput gains with unmodified 802.11n cards.
Interference Networks With Point-to-Point Codes
"... Abstract—The paper establishes the capacity region of the Gaussian interference channel with many transmitter-receiver pairs constrained to use point-to-point codes. The capacity region is shown to be strictly larger in general than the achievable rate regions when treating interference as noise, us ..."
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Cited by 27 (4 self)
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Abstract—The paper establishes the capacity region of the Gaussian interference channel with many transmitter-receiver pairs constrained to use point-to-point codes. The capacity region is shown to be strictly larger in general than the achievable rate regions when treating interference as noise, using successive interference cancellation decoding, and using joint decoding. The gains in coverage and achievable rate using the optimal decoder are analyzed in terms of ensemble averages using stochastic geometry. In a spatial network where the nodes are distributed according to a Poisson point process and the channel path loss exponent is>2, it is shown that the density of users that can be supported by treating interference as noise can scale no faster than B 2= as the bandwidth B grows, while the density of users can scale linearly with B under optimal decoding. Index Terms—Ad hoc network, coverage, interference, joint decoding, network information theory, performance evaluation, stochastic geometry, stochastic network, successive interference cancelation. I.
Multiple access channels with states causally known at transmitters,” November 2010, submitted to IEEE Transactions on Information Theory, available online at http://arxiv.org/abs/1011.6639
"... Abstract—It has been recently shown by Lapidoth and Steinberg that strictly causal state information can be beneficial in multiple access channels (MACs). Specifically, it was proved that the capacity region of a two-user MAC with independent states, each known strictly causally to one encoder, can ..."
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Cited by 22 (3 self)
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Abstract—It has been recently shown by Lapidoth and Steinberg that strictly causal state information can be beneficial in multiple access channels (MACs). Specifically, it was proved that the capacity region of a two-user MAC with independent states, each known strictly causally to one encoder, can be enlarged by letting the encoders send compressed past state information to the decoder. In this study, a generalization of the said strategy is proposed whereby the encoders compress also the past transmitted codewords along with the past state sequences. The proposed scheme uses a combination of long-message encoding, compression of the past state sequences and codewords without binning, and joint decoding over all transmission blocks. The proposed strategy has been recently shown by Lapidoth and Steinbergtostrictlyimprove upon the original one. Capacity results are then derived for a class of channels that include two-user modulo-additive state-dependent MACs. Moreover, the proposed scheme is extended to state-dependent MACs with an arbitrary number of users. Finally, output feedback is introduced and an example is provided to illustrate the interplay between feedback and availability of strictly causal state information in enlarging the capacity region. Index Terms—Long-message encoding, multiple access channels (MACs), output feedback, quantize-forward, state-dependent channels, strictly causal state information. I.
On the optimal compressions in the compressand-forward relay schemes
- IEEE Trans. Inf. Theory
, 2013
"... Abstract—In the classical compress-and-forward relay scheme developed by Cover and El Gamal, the decoding process operates in a successive way: the destination first decodes the compression of the relay’s observation and then decodes the original message of the source. Recently, several modified com ..."
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Cited by 19 (1 self)
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Abstract—In the classical compress-and-forward relay scheme developed by Cover and El Gamal, the decoding process operates in a successive way: the destination first decodes the compression of the relay’s observation and then decodes the original message of the source. Recently, several modified compress-and-forward relay schemes were proposed, where the destination jointly decodes the compression and the message, instead of successively. Such a mod-ification on the decoding process was motivated by realizing that it is generally easier to decode the compression jointly with the orig-inal message, and more importantly, the original message can be decoded even without completely decoding the compression. Thus, joint decoding provides more freedom in choosing the compres-sion at the relay. However, the question remains in these modi-fied compress-and-forward relay schemes—whether this freedom of selecting the compression necessarily improves the achievable
MegaMIMO: Scaling Wireless Capacity with User Demands
"... We present MegaMIMO, a joint multi-user beamforming system that enables independent access points (APs) to beamform their signals, and communicate with their clients on the same channel as if they were one large MIMO transmitter. The key enabling technology behind MegaMIMO is a new low-overhead tech ..."
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Cited by 18 (8 self)
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We present MegaMIMO, a joint multi-user beamforming system that enables independent access points (APs) to beamform their signals, and communicate with their clients on the same channel as if they were one large MIMO transmitter. The key enabling technology behind MegaMIMO is a new low-overhead technique for synchronizing the phase of multiple transmitters in a distributed manner. The design allows a wireless LAN to scale its throughput by continually adding more APs on the same channel. MegaMIMO is implemented and tested with both software radio clients and off-the-shelf 802.11n cards, and evaluated in a dense congested deployment resembling a conference room. Results from a 10-AP software-radio testbed show a linear increase in network throughput with a median gain of 8.1 to 9.4×. Our results also demonstrate that MegaMIMO’s joint multi-user beamforming can provide throughput gains with unmodified 802.11n cards.
Degrees of freedom of two-hop wireless networks: Everyone gets the entire cake
- IEEE Trans. Inf. Theory
, 2014
"... Abstract—We show that fully connected two-hop 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 interference-alignment-based achievability scheme which we call aligned network ..."
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Cited by 18 (1 self)
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Abstract—We show that fully connected two-hop 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 interference-alignment-based achievability scheme which we call aligned network diagonalization. This scheme allows the data streams transmitted by the sources to undergo a diagonal linear transfor-mation from the sources to the destinations, thus being received free of interference by their intended destination. I.
