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Bandwidth Partitioning in Decentralized Wireless Networks
"... This paper addresses the following question, which is of interest in the design of a multiuser decentralized network. Given a total system bandwidth of W Hz and a fixed data rate constraint of R bps for each transmission, how many frequency slots N of size W/N should the band be partitioned into in ..."
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Cited by 38 (12 self)
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This paper addresses the following question, which is of interest in the design of a multiuser decentralized network. Given a total system bandwidth of W Hz and a fixed data rate constraint of R bps for each transmission, how many frequency slots N of size W/N should the band be partitioned into in order to maximize the number of simultaneous links in the network? Dividing the available spectrum results in two competing effects. On the positive side, a larger N allows for more parallel, noninterfering communications to take place in the same area. On the negative side, a larger N increases the SINR requirement for each link because the same information rate must be achieved over less bandwidth, which in turn increases the area consumed by each transmission. Exploring this tradeoff and determining the optimum value of N in terms of the system parameters is the focus of the paper. Using stochastic geometry, the optimal SINR threshold – which directly corresponds to the optimal spectral efficiency – is derived for both the low SNR (powerlimited) and high SNR (interferencelimited) regimes. This leads to the optimum choice of the number of frequency bands N in terms of the path loss exponent, power and noise spectral density, desired rate, and total bandwidth. I.
Multihop Relaying for Broadband Wireless Mesh Networks: From Theory to Practice ∗
"... We summarize capacity results to show merits of multihop relaying in broadband cellular mesh networks. Under the guidance of these results, we provide design perspectives on relay deployment, spectrum allocation and endtoend optimization of certain QoS measures such as throughput, coverage, reliab ..."
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Cited by 35 (1 self)
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We summarize capacity results to show merits of multihop relaying in broadband cellular mesh networks. Under the guidance of these results, we provide design perspectives on relay deployment, spectrum allocation and endtoend optimization of certain QoS measures such as throughput, coverage, reliability and robustness. We conclude with an overview of recent standardization activities and remarks on remaining open problems and design challenges. I.
Ad hoc networks: To spread or not to spread
 IEEE Communications Magazine
"... Spread spectrum communication – often called Code Division Multiple Access (CDMA) – has been widely adopted over the years for many types interferencechallenged wireless communication systems including cellular and cordless telephones, wireless LANs and PANs, military applications, and global posi ..."
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Cited by 29 (9 self)
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Spread spectrum communication – often called Code Division Multiple Access (CDMA) – has been widely adopted over the years for many types interferencechallenged wireless communication systems including cellular and cordless telephones, wireless LANs and PANs, military applications, and global positioning systems. In this paper, we explore whether CDMA – in either its frequency hopping (FH) or direct sequence (DS) forms – is an appropriate design approach for wireless ad hoc, or mesh, networks. CDMA’s merits for centralized cellular networks were widely debated in the late 1980s through the 1990s, and greatly increased the understanding of CDMA in particular and interferencelimited cellular networks in general. Such a discussion has not occurred for decentralized (ad hoc) networks, and one goal of this paper is to help provoke this debate by explaining the main advantages and disadvantages of CDMA in the context of ad hoc networks as exposed by recent research. We will argue that CDMA does not inherently improve the spectral efficiency of ad hoc networks; on the contrary, its valued interference averaging effect is not appreciable in ad hoc networks due to the irregular distribution of both the transmitters and receivers. On the positive side, both types (FH and DS) of spread spectrum allow for (i) longer hop distances and (ii) a reversal of the usual relationship that the desired transmitter must be closer to the receiver than interfering transmitters. These two facts allow for significant advantages over narrowband (NB) systems in terms of energy efficiency and endtoend delay. We also examine the considerable effect that a spread spectrum physical layer has on MAC protocols. 1
Distributed energyefficient cooperative routing in wireless networks
 IEEE Trans. on Wireless Communications
, 2008
"... Abstract — Recently, cooperative routing in wireless networks has gained much interest due to its ability to exploit the broadcast nature of the wireless medium in designing powerefficient routing algorithms. Most of the existing cooperationbased routing algorithms are implemented by finding a short ..."
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Cited by 28 (1 self)
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Abstract — Recently, cooperative routing in wireless networks has gained much interest due to its ability to exploit the broadcast nature of the wireless medium in designing powerefficient routing algorithms. Most of the existing cooperationbased routing algorithms are implemented by finding a shortestpath route first. As such, these routing algorithms do not fully exploit the merits of cooperative communications at the physical layer. In this paper, we propose a cooperationbased routing algorithm, namely, Minimum Power Cooperative Routing (MPCR) algorithm, which makes full use of the cooperative communications while constructing the minimumpower route. The MPCR algorithm constructs the minimumpower route as a cascade of the minimumpower singlerelay building blocks from the source to the destination. Hence, any distributed shortestpath algorithm can be utilized to find the optimal route with polynomial complexity, while guaranteeing certain throughput. We show that the MPCR algorithm can achieve power saving of 57.36 % compared to the conventional shortestpath routing algorithms. Furthermore, the MPCR algorithm can achieve power saving of 37.64 % compared to the existing cooperative routing algorithms, in which the selected routes are constructed based on the noncooperative routes. I.
1 Distance Distributions in Finite Uniformly Random Networks: Theory and Applications
, 2008
"... In wireless networks, the knowledge of nodal distances is essential for several areas such as system configuration, performance analysis and protocol design. In order to evaluate distance distributions in random networks, the underlying nodal arrangement is almost universally taken to be an infinite ..."
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Cited by 26 (2 self)
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In wireless networks, the knowledge of nodal distances is essential for several areas such as system configuration, performance analysis and protocol design. In order to evaluate distance distributions in random networks, the underlying nodal arrangement is almost universally taken to be an infinite Poisson point process. While this assumption is valid in some cases, there are also certain impracticalities to this model. For example, practical networks are nonstationary, and the number of nodes in disjoint areas are not independent. This paper considers a more realistic network model where a finite number of nodes are uniformly randomly distributed in a general ddimensional ball of radius R and characterizes the distribution of Euclidean distances in the system. The key result is that the probability density function of the distance from the center of the network to its nth nearest neighbor follows a generalized beta distribution. This finding is applied to study network characteristics such as energy consumption, interference, outage and connectivity.
Distributed SpectrumEfficient Routing Algorithms in Wireless Networks
 IEEE Trans. Wireless Commun., Apr
"... This paper applies spectral efficiency as a performance measure for routing schemes and considers how to obtain a good route in a wireless network. The objective for this study is to combine different perspectives from networking and information theory in the design of routing schemes. The problem o ..."
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Cited by 19 (1 self)
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This paper applies spectral efficiency as a performance measure for routing schemes and considers how to obtain a good route in a wireless network. The objective for this study is to combine different perspectives from networking and information theory in the design of routing schemes. The problem of finding the optimum route with the maximum spectral efficiency is difficult to solve in a distributed fashion. Motivated by an informationtheoretic analysis, this paper proposes two suboptimal alternatives, namely, the approximatelyidealpath routing (AIPR) scheme and the distributed spectrumefficient routing (DSER) scheme. AIPR finds a path to approximate an optimum regular path and requires location information. DSER is more amenable to distributed implementations based on BellmanFord or Dijkstra’s algorithms. The spectral efficiencies of AIPR and DSER for random networks approach that of nearestneighbor routing in the low signaltonoise ratio (SNR) regime and that of singlehop routing in the high SNR regime. In the moderate SNR regime, the spectral efficiency of DSER is up to twice that of nearestneighbor or singlehop routing. I. BACKGROUND AND MOTIVATION As wireless communications are extended beyond the last hop of networks, a better understanding of wireless relaying (including routing as a special case) is needed to deploy efficient multihop wireless networks. Research from different perspectives, e.g., networking and information theory, yields in different relaying paradigms for wireless networks [1]–[7]. The goal of this
Random Access Transport Capacity
, 2009
"... We develop a new metric for quantifying endtoend throughput in multihop wireless networks, which we term random access transport capacity, since the interference model presumes uncoordinated transmissions. The metric quantifies the average maximum rate of successful endtoend transmissions, multi ..."
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Cited by 19 (3 self)
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We develop a new metric for quantifying endtoend throughput in multihop wireless networks, which we term random access transport capacity, since the interference model presumes uncoordinated transmissions. The metric quantifies the average maximum rate of successful endtoend transmissions, multiplied by the communication distance, and normalized by the network area. We show that a simple upper bound on this quantity is computable in closedform in terms of key network parameters when the number of retransmissions is not restricted and the hops are assumed to be equally spaced on a line between the source and destination. We also derive the optimum number of hops and optimal per hop success probability and show that our result follows the wellknown square root scaling law while providing exact expressions for the preconstants as well. Numerical results demonstrate that the upper bound is accurate for the purpose of determining the optimal hop count and success (or outage) probability.
Optimization of AmplifyandForward Multicarrier TwoHop Transmission
, 2008
"... Member, IEEE In this paper, frequencydomain relay processing in a twohop transmission system is investigated. The relay is constrained to be “nonregenerative”; that is, the relay is only allowed to perform symbolbysymbol memoryless transformation of its received signals. Multicarrier modulation ..."
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Cited by 14 (0 self)
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Member, IEEE In this paper, frequencydomain relay processing in a twohop transmission system is investigated. The relay is constrained to be “nonregenerative”; that is, the relay is only allowed to perform symbolbysymbol memoryless transformation of its received signals. Multicarrier modulation, e.g., orthogonal frequency division multiplexing (OFDM), is utilized to convert each hop link into a collection of noninterfering parallel subcarriers. In contrast to conventional scalar amplifyandforward (AF) relays that scale all the subcarriers uniformly, it is possible to suppress relay noise and to exploit frequencydomain diversity by optimizing the relay scaling coefficients of different subcarriers jointly with subcarrier power allocation at the source transmitter. Although the endtoend achievable rate is a nonconcave function of the power allocation vectors, its optimization is accomplished with an algorithm whose computational complexity grows linearly with the number of subcarriers, by utilizing a structural property of the problem. Further motivated by the problem structure, a suboptimal algorithm with even lower complexity is also proposed, in which each hop link performs waterfilling separately over a selected subset of subcarriers. For hop links with a frequencyflat channel profile, the maximum achievable rate
Cooperative Strategies and Achievable Rate for Tree Networks With Optimal Spatial Reuse
"... Abstract—In this paper, a lowcomplexity cooperative protocol that significantly increases the average throughput of multihop upstream transmissions for wireless tree networks is developed and analyzed. A system in which transmissions are assigned to nodes in a collision free, spatial time division ..."
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Cited by 11 (0 self)
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Abstract—In this paper, a lowcomplexity cooperative protocol that significantly increases the average throughput of multihop upstream transmissions for wireless tree networks is developed and analyzed. A system in which transmissions are assigned to nodes in a collision free, spatial time division fashion is considered. The suggested protocol exploits the broadcast nature of wireless networks where the communication channel is shared between multiple adjacent nodes within interference range. For any upstream endtoend flow in the tree, each intermediate node receives information from both onehop and twohop neighbors and transmits only sufficient information such that the next upstream onehop neighbor will be able to decode the packet. This approach can be viewed as the generalization of the classical three node relay channel for endtoend flows in which each intermediate node becomes successively source, relay and destination. The achievable rate for any regular tree network is derived and an optimal schedule that realizes this rate in most cases is proposed. Our protocol is shown to dramatically outperform the conventional scheme where intermediate nodes simply forward the packets hop by hop. At high signaltonoise ratio (SNR), it yields approximately 66 % throughput gain for practical scenarios. Index Terms—Fairness, relay channel, time division multiaccess, user cooperation, wireless networks. I.
A DelayReliability Analysis for Multihop Underwater Acoustic Communication ABSTRACT
"... This paper investigates the delayreliability tradeoff for multihop underwater acoustic networks. The propagation medium of underwater acoustic channel exhibits distinct characteristics when contrasted with other common propagation media such as copper, fiber, and radio. In particular there are the ..."
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This paper investigates the delayreliability tradeoff for multihop underwater acoustic networks. The propagation medium of underwater acoustic channel exhibits distinct characteristics when contrasted with other common propagation media such as copper, fiber, and radio. In particular there are the extremely slow propagation speed of sound in water, high signal attenuation due to absorption, significant delay spreads and intersymbol interference, and rangedependent transmission bandwidth. These features make the delayreliability tradeoff for underwater acoustic channels fundamentally different from other channels. The approach is based on errorexponents which enable a physicallayer comparison of multihopping versus no hops while considering the overall throughput. The analysis shows that for typical network parameters, increasing the number of hops dramatically improves both the achievable information rate and the achievable reliability function, which quantitatively captures the decay rate of the decoding error probability as the coding block length increases asymptotically. Numerical results are presented to illustrate the analysis.