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35
Wireless Network Information Flow: A Deterministic Approach
, 2009
"... In contrast to wireline networks, not much is known about the flow of information over wireless networks. The main barrier is the complexity of the signal interaction in wireless channels in addition to the noise in the channel. A widely accepted model is the the additive Gaussian channel model, and ..."
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Cited by 298 (46 self)
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In contrast to wireline networks, not much is known about the flow of information over wireless networks. The main barrier is the complexity of the signal interaction in wireless channels in addition to the noise in the channel. A widely accepted model is the the additive Gaussian channel model, and for this model, the capacity of even a network with a single relay node is open for 30 years. In this paper, we present a deterministic approach to this problem by focusing on the signal interaction rather than the noise. To this end, we propose a deterministic channel model which is analytically simpler than the Gaussian model but still captures two key wireless channel properties of broadcast and superposition. We consider a model for a wireless relay network with nodes connected by such deterministic channels, and present an exact characterization of the endtoend capacity when there is a single source and one or more destinations (all interested in the same information) and an arbitrary number of relay nodes. This result is a natural generalization of the celebrated maxflow mincut theorem for wireline networks. We then use the insights obtained from the analysis of the deterministic model to study information flow for the Gaussian wireless relay network. We present an achievable rate for general Gaussian relay networks and show that it is within a constant number of bits from the cutset bound on the capacity of these networks. This constant depends on the number of nodes in the network, but not the values of the channel gains or the signaltonoise ratios. We show that existing strategies cannot achieve such a constantgap approximation for arbitrary networks and propose a new quantizemapandforward scheme that does. We also give several extensions of the approximation framework including robustness results (through compound channels), halfduplex constraints and ergodic channel variations.
SpaceTime Diversity Enhancements Using Collaborative Communications
 IEEE TRANS. INFORM. THEORY
, 2005
"... The use of the spatial dimension is known to greatly increase the reliability of quasistatic (i.e., nonergodic) wireless channels. In this paper, it is demonstrated that most of this gain can also be achieved through collaborative communications with singleantenna/multipleantenna nodes when ther ..."
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Cited by 54 (7 self)
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The use of the spatial dimension is known to greatly increase the reliability of quasistatic (i.e., nonergodic) wireless channels. In this paper, it is demonstrated that most of this gain can also be achieved through collaborative communications with singleantenna/multipleantenna nodes when there is one receiving agent. In particular, for the single antenna case, communication is considered to take place between clusters of nearby nodes. The existence of collaborative codes for which the intracluster negotiation penalty is in principle small (and almost all the diversity gain of traditional spacetime codes may be realized) is shown. For example, for a single transmitter node with two collaborators and one receiver node, if the collaborators have as little as 10 dB path loss advantage over the receiver, the penalty for collaboration over traditional spacetime systems is negligible.
The capacity of average and peak power constrained fading channel with channel side information
 IEEEWireless Communications and Networking Conference
, 2004
"... Abstract — We derive the ergodic capacity of discretetime fading channel with additive Gaussian noise subject to both peak and average power constraint. The average power can be interpreted as the cost that we incur to achieve a certain rate. On the other hand, the motivation of this analysis comes ..."
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Cited by 13 (1 self)
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Abstract — We derive the ergodic capacity of discretetime fading channel with additive Gaussian noise subject to both peak and average power constraint. The average power can be interpreted as the cost that we incur to achieve a certain rate. On the other hand, the motivation of this analysis comes from the fact that there is also a peak power limitation in practical communication system. It is been shown that the optimal power adaption is no longer waterfilling or constant power adaption which is the case where there is no limitation on the peak power. The numerical results show that the importance of peak power constraint become negligible for relatively low available average power, while it is limiting the capacity to be finite even as available average power goes to infinity. I.
On achievable rates of complexity constrained relay channels
 in Proc 41st Allerton Conf. Communication, Control and Computing
, 2003
"... We consider the achievable rates of a special instantiation of a network of cooperating nodes, mainly motivated by the sensor network application. Sensor networks are distinguished from more classical ad hoc networks due to strict limitations on power consumption, the density ..."
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Cited by 11 (3 self)
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We consider the achievable rates of a special instantiation of a network of cooperating nodes, mainly motivated by the sensor network application. Sensor networks are distinguished from more classical ad hoc networks due to strict limitations on power consumption, the density
Achievable rates and optimal schedules for half duplex multiplerelay networks
 in Proc. 46th Allerton Conf. on Commun., Control, and Comput
"... Abstract — We study the half duplex multiplerelay channel (MRC) where every node can either transmit or listen but not both at the same time. We derive a capacity upper bound based on a maxflow mincut argument and achievable transmission rates based on the decodeforward coding strategy (DF), for ..."
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Cited by 9 (4 self)
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Abstract — We study the half duplex multiplerelay channel (MRC) where every node can either transmit or listen but not both at the same time. We derive a capacity upper bound based on a maxflow mincut argument and achievable transmission rates based on the decodeforward coding strategy (DF), for both the half duplex discrete memoryless MRC and the half duplex phase fading Gaussian MRC. The upper bound and achievable rates are functions of the transmit state vector (a description of which nodes transmit and which receive). More precisely, they are functions of the time fraction of different transmit state vectors, which we term a schedule. We formulate the optimal scheduling problem as a maxmin optimization to find the schedule that maximizes the DF rate for the half duplex MRC. We use a technique based on minimax hypothesis testing to solve this problem and demonstrate it on a fournode MRC, getting closed form solutions in certain scenarios. For the phase fading Gaussian channel, surprisingly, we discover that optimal schedules can be solved using linear programming. I.
A new relaying scheme for cheap wireless relay nodes
, 2005
"... Wireless networks consist of senders, receivers, and intermediate nodes that collaborating (more or less) to establish the communication paths. Most of the researches in the domain of wireless network have focused on routing based approaches. In such an approach wireless network is reduced to a dyna ..."
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Cited by 6 (2 self)
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Wireless networks consist of senders, receivers, and intermediate nodes that collaborating (more or less) to establish the communication paths. Most of the researches in the domain of wireless network have focused on routing based approaches. In such an approach wireless network is reduced to a dynamic graph, and a minimum cost routing mechanism is applied. These approaches have led to several routing mechanisms as OLSR and AODV. However, the fundamental nature of wireless network is the broadcast. In the wireless network all the tuned receivers potentially receive every transmission. This basic property is not well captured by graphbased approaches where packets follow a single path from sender to receiver. In this paper we will propose a relaying scheme for wireless multihop networks. It is based on collaboration of intermediate relays at network layer to forward useful side information in place of dumbly forwarding packets. In our scheme we assume that the nodes are not able to benefit from any interference cancellation mechanism. The channels from sender to relay nodes and from sender to receiver are logically separated through a temporal scheduling. This model is realistic for many practical scenarios in the context of wireless networks. We will show in this paper the information theoretic bounds and show that they are achievable using practical codes. The proposed coding scheme is simulated in realistic scenarios. The obtained results show a remarkable improvement in throughput, relay load and reliability compared to network using classical routing approach.
On the capacity of erasure relay channel: Multirelay case
 in Proc. 2005 IEEE Information Theory Workshop (ITW 2005
, 2005
"... Abstract — We consider here a single senderdestination multirelay channel. The links connecting the nodes are supposed to be erasure where symbols are received correctly without any error, or lost. We consider that the nodes are not able to use any interference cancellation mechanism. The interfere ..."
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Cited by 3 (1 self)
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Abstract — We consider here a single senderdestination multirelay channel. The links connecting the nodes are supposed to be erasure where symbols are received correctly without any error, or lost. We consider that the nodes are not able to use any interference cancellation mechanism. The interference might be suppressed through using separated physical channel or thought a timesharing mechanism. This model is realistic for many practical scenarios in the context of wireless networks. In previous works, the capacity region of broadcast erasure channels as well as the capacity of the singlesender relay channel (under degraded and nondegraded hypothesis) has been derived. This paper extends the previous results to the more general case of multirelay channels. We derive the cutset bound for a general (stationary ergodic) multirelay erasure channel, and we show that it can be reached through a practical linear coding scheme based on MDS codes. I.
A decode and forward protocol for twostage Gaussian relay networks
 IEEE Trans. on Comm
, 2012
"... Abstract—We propose a multihopping decode and forward relaying protocol for twostage Gaussian relay networks with halfduplex nodes. We analytically show that the achievable rates in suitably defined strong and weak interference regimes are close to the cutset bound. Index Terms—Twostage relay ne ..."
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Cited by 3 (3 self)
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Abstract—We propose a multihopping decode and forward relaying protocol for twostage Gaussian relay networks with halfduplex nodes. We analytically show that the achievable rates in suitably defined strong and weak interference regimes are close to the cutset bound. Index Terms—Twostage relay network, decode and forward protocol, halfduplex relays. I.
Protocols and performance limits for halfduplex relay networks,” http://arxiv.org/abs/0907.2309
, 2009
"... ar ..."
Protocols For HalfDuplex Multiple Relay Networks
, 2008
"... In this paper we present several strategies for multiple relay networks which are constrained by a halfduplex operation, i. e., each node either transmits or receives on a particular resource. Using the discrete memoryless multiple relay channel we present achievable rates for a multilevel partia ..."
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Cited by 3 (1 self)
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In this paper we present several strategies for multiple relay networks which are constrained by a halfduplex operation, i. e., each node either transmits or receives on a particular resource. Using the discrete memoryless multiple relay channel we present achievable rates for a multilevel partial decodeandforward approach which generalizes previous results presented by Kramer and Khojastepour et al.. Furthermore, we derive a compressandforward approach using a regular encoding scheme which simplifies the encoding and decoding procedure and improves the achievable rates in general. Finally, we give achievable rates for a mixed strategy used in a fourterminal network with alternately transmitting relay nodes.