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Network Information Flow with Correlated Sources
 TO APPEAR IN THE IEEE TRANSACTIONS ON INFORMATION THEORY
, 2005
"... Consider the following network communication setup, originating in a sensor networking application we refer to as the “sensor reachback ” problem. We have a directed graph G = (V, E), where V = {v0v1...vn} and E ⊆ V × V. If (vi, vj) ∈ E, then node i can send messages to node j over a discrete memor ..."
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Cited by 93 (7 self)
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Consider the following network communication setup, originating in a sensor networking application we refer to as the “sensor reachback ” problem. We have a directed graph G = (V, E), where V = {v0v1...vn} and E ⊆ V × V. If (vi, vj) ∈ E, then node i can send messages to node j over a discrete memoryless channel (Xij, pij(yx), Yij), of capacity Cij. The channels are independent. Each node vi gets to observe a source of information Ui (i = 0...M), with joint distribution p(U0U1...UM). Our goal is to solve an incast problem in G: nodes exchange messages with their neighbors, and after a finite number of communication rounds, one of the M + 1 nodes (v0 by convention) must have received enough information to reproduce the entire field of observations (U0U1...UM), with arbitrarily small probability of error. In this paper, we prove that such perfect reconstruction is possible if and only if H(USUS c) < i∈S,j∈S c for all S ⊆ {0...M}, S = ∅, 0 ∈ S c. Our main finding is that in this setup a general source/channel separation theorem holds, and that Shannon information behaves as a classical network flow, identical in nature to the flow of water in pipes. At first glance, it might seem surprising that separation holds in a
Multipleantenna capacity in the lowpower regime
 IEEE TRANS. INFORM. THEORY
, 2003
"... This paper provides analytical characterizations of the impact on the multipleantenna capacity of several important features that fall outside the standard multipleantenna model, namely: i) antenna correlation, ii) Ricean factors, iii) polarization diversity, and iv) outofcell interference; all ..."
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Cited by 85 (11 self)
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This paper provides analytical characterizations of the impact on the multipleantenna capacity of several important features that fall outside the standard multipleantenna model, namely: i) antenna correlation, ii) Ricean factors, iii) polarization diversity, and iv) outofcell interference; all in the regime of low signaltonoise ratio. The interplay of rate, bandwidth, and power is analyzed in the region of energy per bit close to its minimum value. The analysis yields practical design lessons for arbitrary number of antennas in the transmit and receive arrays.
Optimal Power Control, Scheduling and Routing in UWB Networks
, 2004
"... UltraWide Band (UWB) is an emerging wireless physical layer technology that uses a very large bandwidth. We are interested in finding the design objectives of the medium access (MAC, namely, power control and scheduling) and routing protocols of a multihop, besteffort, UWB network. Our objective ..."
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Cited by 82 (5 self)
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UltraWide Band (UWB) is an emerging wireless physical layer technology that uses a very large bandwidth. We are interested in finding the design objectives of the medium access (MAC, namely, power control and scheduling) and routing protocols of a multihop, besteffort, UWB network. Our objective is to maximize flow rates (more precisely, logutility of flow rates) given node power constraints. The specificity of UWB is expressed by the linear dependence between rate and signaltonoise ratio at the receiver. It is known that, in wireless networks, different routing strategies can imply differences in MAC protocol design. Hence we search for the jointly optimal routing, scheduling and power control.
Ultrawideband radio design: The promise of highspeed, shortrange wireless connectivity
 in Proc. of the IEEE. Special Issue on Gigabit Wireless
, 2004
"... This paper provides a tutorial overview of ultrawideband (UWB) radio technology for highspeed wireless connectivity. Subsequent to establishing a historical and technological context, it describes the new impetus for UWB systems development and standardization resulting from the FCC’s recent decisi ..."
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Cited by 72 (1 self)
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This paper provides a tutorial overview of ultrawideband (UWB) radio technology for highspeed wireless connectivity. Subsequent to establishing a historical and technological context, it describes the new impetus for UWB systems development and standardization resulting from the FCC’s recent decision to permit unlicensed operation in the [3.1,10.6] GHz band subject to modified Part 15 rules and indicates the potential new applications that may result. Thereafter, the paper provides a system architect’s perspectives on the various issues and challenges involved in the design of link layer subsystems. Specifically, we outline current developments in UWB system design concepts that are oriented to highspeed applications and describe some of the design tradeoffs involved. Keywords—Personal area networks, wireless, ultrawide band. I. INTRODUCTION AND BACKGROUND
On the power efficiency of sensory and ad hoc wireless networks
 in Proc. Asilomar Conf. Signals, Systems, and Computing
, 2002
"... Abstract—We consider the power efficiency of a communications channel, i.e., the maximum bit rate that can be achieved per unit power (energy rate). For additive white Gaussian noise (AWGN) channels, it is well known that power efficiency is attained in the low signaltonoise ratio (SNR) regime whe ..."
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Cited by 70 (3 self)
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Abstract—We consider the power efficiency of a communications channel, i.e., the maximum bit rate that can be achieved per unit power (energy rate). For additive white Gaussian noise (AWGN) channels, it is well known that power efficiency is attained in the low signaltonoise ratio (SNR) regime where capacity is proportional to the transmit power. In this paper, we first show that for a random sensory wireless network with users (nodes) placed in a domain of fixed area, with probability converging to one as grows, the power efficiency scales at least by a factor of. In other words, each user in a wireless channel with nodes can support the same communication rate as a singleuser system, but by expending only 1 times the energy. Then we look at a random ad hoc network with relay nodes and simultaneous transmitter/receiver pairs located in a domain of fixed area. We show that as long as, we can achieve a power efficiency that scales by a factor of. We also give a description of how to achieve these gains. Index Terms—Capacity, sensor networks, wireless communication systems and networks. I.
Sum Rate Characterization of Joint Multiple CellSite Processing
, 2005
"... The sumrate capacity of a cellular system model is analyzed, considering the uplink and downlink channels, while addressing both nonfading and flatfading channels. The focus is on a simple Wynerlike multicell model, where the system cells are arranged on a circle, assuming the cellsites are lo ..."
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Cited by 68 (11 self)
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The sumrate capacity of a cellular system model is analyzed, considering the uplink and downlink channels, while addressing both nonfading and flatfading channels. The focus is on a simple Wynerlike multicell model, where the system cells are arranged on a circle, assuming the cellsites are located at the boundaries of the cells. For the uplink channel, analytical expressions of the sumrate capacities are derived for intracell TDMA scheduling, and a “WideBand ” (WB) scheme (where all users are active simultaneously utilizing all bandwidth for coding). Assuming individual percell power constraints, and using the Lagrangian uplinkdownlink duality principle, an analytical expression for the sumrate capacity of the downlink channel is derived for nonfading channels, and shown to coincide with the corresponding uplink result. Introducing flatfading, lower and upper bounds on the average percell sumrate capacity are derived. The bounds exhibit an O(loge K) multiuser diversity factor for a number of users percell K ≫ 1, in addition to the array diversity gain. Joint multicell processing is shown to eliminate outofcell interference, which is traditionally considered to be a limiting factor in highrate reliable communications. This paper was presented in part at the 9
Cooperative multihop broadcast for wireless networks
 IEEE J. Sel. Areas Commun
, 2004
"... Abstract—We address the minimumenergy broadcast problem under the assumption that nodes beyond the nominal range of a transmitter can collect the energy of unreliably received overheard signals. As a message is forwarded through the network, a node will have multiple opportunities to reliably recei ..."
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Cited by 67 (1 self)
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Abstract—We address the minimumenergy broadcast problem under the assumption that nodes beyond the nominal range of a transmitter can collect the energy of unreliably received overheard signals. As a message is forwarded through the network, a node will have multiple opportunities to reliably receive the message by collecting energy during each retransmission. We refer to this cooperative strategy as accumulative broadcast. We seek to employ accumulative broadcast in a large scale loosely synchronized, lowpower network. Therefore, we focus on distributed network layer approaches for accumulative broadcast in which loosely synchronized nodes use only local information. To further simplify the system architecture, we assume that nodes forward only reliably decoded messages. Under these assumptions, we formulate the minimumenergy accumulative broadcast problem. We present a solution employing two subproblems. First, we identify the ordering in which nodes should transmit. Second, we determine the optimum power levels for that ordering. While the second subproblem can be solved by means of linear programming, the ordering subproblem is found to be NPcomplete. We devise a heuristic algorithm to find a good ordering. Simulation results show the performance of the algorithm to be close to optimum and a significant improvement over the well known BIP algorithm for constructing energyefficient broadcast trees. We then formulate a distributed version of the accumulative broadcast algorithm that uses only local information at the nodes and has performance close to its centralized counterpart. Index Terms—Distributed algorithm, minimumenergy broadcast, reliable forwarding, wideband regime.
Bandwidth and powerefficient routing in linear wireless networks
 IEEE TRANS. INF. THEORY
, 2006
"... The goal of this paper is to establish which practical routing schemes for wireless networks are most suitable for powerlimited and bandwidthlimited communication regimes. We regard channel state information (CSI) at the receiver and pointtopoint capacityachieving codes for the additive white ..."
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Cited by 66 (10 self)
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The goal of this paper is to establish which practical routing schemes for wireless networks are most suitable for powerlimited and bandwidthlimited communication regimes. We regard channel state information (CSI) at the receiver and pointtopoint capacityachieving codes for the additive white Gaussian noise (AWGN) channel as practical features, interference cancellation (IC) as possible, but less practical, and synchronous cooperation (CSI at the transmitters) as impractical. We consider a communication network with a single source node, a single destination node, and I intermediate nodes placed equidistantly on a line between them. We analyze the minimum total transmit power needed to achieve a desired endtoend rate for several schemes and demonstrate that multihop communication with spatial reuse performs very well in the powerlimited regime, even without IC. However, within a class of schemes not performing IC, singlehop transmission (directly from source to destination) is more suitable for the bandwidthlimited regime, especially when higher spectral efficiencies are required. At such higher spectral efficiencies, the gap between singlehop and multihop can be closed by employing IC, and we present a scheme based upon backward decoding that can remove all interference from the multihop system with an arbitrarily small rate loss. This new scheme is also used to demonstrate that rates of @�� � A are achievable over linear wireless networks even without synchronous cooperation.
Capacity of multipletransmit multiplereceive antenna architectures
 IEEE Trans. Inf. Theory
, 2002
"... codes for high data rates wireless communications: Performance criteria in the presence of channel estimation errors, mobility and multiple ..."
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Cited by 56 (11 self)
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codes for high data rates wireless communications: Performance criteria in the presence of channel estimation errors, mobility and multiple
Feedback capacity of stationary Gaussian channels
"... The capacity of stationary additive Gaussian noise channels with feedback is characterized as the solution to a variational problem. Toward this end, it is proved that the optimal feedback coding scheme is stationary. When specialized to the firstorder autoregressive movingaverage noise spectrum, ..."
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Cited by 45 (10 self)
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The capacity of stationary additive Gaussian noise channels with feedback is characterized as the solution to a variational problem. Toward this end, it is proved that the optimal feedback coding scheme is stationary. When specialized to the firstorder autoregressive movingaverage noise spectrum, this variational characterization yields a closedform expression for the feedback capacity. In particular, this result shows that the celebrated Schalkwijk–Kailath coding scheme achieves the feedback capacity for the firstorder autoregressive movingaverage Gaussian channel, resolving a longstanding open problem studied by Butman, Schalkwijk– Tiernan, Wolfowitz, Ozarow, Ordentlich, Yang–Kavčić–Tatikonda, and others. 1 Introduction and