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Stability and Delay of FiniteUser Slotted ALOHA With Multipacket Reception
 IEEE TRANS. INFORM. THEORY
, 2005
"... The effect of multipacket reception (MPR) on stability and delay of slotted ALOHA based randomaccess systems is considered. A general asymmetric MPR model is introduced and the mediumaccess control (MAC) capacity region is specified. An explicit characterization of the ALOHA stability region for t ..."
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Cited by 56 (1 self)
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The effect of multipacket reception (MPR) on stability and delay of slotted ALOHA based randomaccess systems is considered. A general asymmetric MPR model is introduced and the mediumaccess control (MAC) capacity region is specified. An explicit characterization of the ALOHA stability region for the twouser system is given. It is shown that the stability region undergoes a phase transition from a concave region to a convex polyhedral region as the MPR capability improves. It is also shown that after this phase transition, slotted ALOHA is optimal i.e., the ALOHA stability region coincides with the MAC capacity region. Further, it is observed that there is no need for transmission control when ALOHA is optimal i.e., ALOHA with transmission probability one is optimal. Next, these results are extended to a symmetric P user ALOHA system. Finally, a complete characterization of average delay in capture channels for the twouser system is given. It is shown that in certain capture scenarios, ALOHA with transmission probability one is delay optimal for all stable arrival rates. Further, it is also shown that ALOHA with transmission probability one is optimal for stability and delay simultaneously in the twouser capture channel.
Challenges: Towards Truly Scalable Ad Hoc Networks
 MobiCom'07
, 2007
"... The protocols used in ad hoc networks today are based on the assumption that the best way to approach multiple access interference (MAI) is to avoid it. Unfortunately, as the seminal work by Gupta and Kumar has shown, this approach does not scale. Recently, Ahlswede, Ning, Li, and Yeung showed that ..."
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Cited by 43 (19 self)
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The protocols used in ad hoc networks today are based on the assumption that the best way to approach multiple access interference (MAI) is to avoid it. Unfortunately, as the seminal work by Gupta and Kumar has shown, this approach does not scale. Recently, Ahlswede, Ning, Li, and Yeung showed that network coding (NC) can attain the maxflow mincut throughput for multicast applications in directed graphs with pointtopoint links. Motivated by this result, many researchers have attempted to make ad hoc networks scale using NC. However, the work by Liu, Goeckel, and Towsley has shown that NC does not increase the order capacity of wireless ad hoc networks for multipair unicast applications. We demonstrate that protocol architectures that exploit multipacket reception (MPR) do increase the order capacity of random wireless ad hoc networks by a factor Θ(log n) under the protocol model. We also show that MPR provides a better capacity improvement for ad hoc networks than NC when the network experiences a singlesource multicast and multipair unicasts. Based on these results, we introduce design problems for channel access and routing based on MPR, such that nodes communicate with one another on a manytomany basis, rather than onetoone as it is done today, in order to make ad hoc networks truly scalable.
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.
Network Capacity Region and Minimum Energy Function for a DelayTolerant Mobile Ad Hoc Network
 IEEE TRANSACTIONS ON NETWORKING (TO APPEAR)
"... We investigate two quantities of interest in a delaytolerant mobile ad hoc network: the network capacity region and the minimum energy function. The network capacity region is defined as the set of all input rates that the network can stably support considering all possible scheduling and routing a ..."
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Cited by 10 (0 self)
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We investigate two quantities of interest in a delaytolerant mobile ad hoc network: the network capacity region and the minimum energy function. The network capacity region is defined as the set of all input rates that the network can stably support considering all possible scheduling and routing algorithms. Given any input rate vector in this region, the minimum energy function establishes the minimum time average power required to support it. In this work, we consider a cellpartitioned model of a delaytolerant mobile ad hoc network with general Markovian mobility. This simple model incorporates the essential features of locality of wireless transmissions as well as node mobility and enables us to exactly compute the corresponding network capacity and minimum energy function. Further, we propose simple schemes that offer performance guarantees that are arbitrarily close to these bounds at the cost of an increased delay.
Capacity region, minimum energy and delay for a mobile adhoc network
 in Proceedings of the 4th International Symposium on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks (WiOpt
, 2006
"... Abstract — We investigate two quantities of fundamental interest in a mobile adhoc network: the capacity region and the minimum energy function of the network. The capacity region is defined as the closure of the set of all input rates that the network can stably support. The minimum energy functio ..."
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Cited by 8 (3 self)
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Abstract — We investigate two quantities of fundamental interest in a mobile adhoc network: the capacity region and the minimum energy function of the network. The capacity region is defined as the closure of the set of all input rates that the network can stably support. The minimum energy function establishes a lower bound on the amount of energy required to support a given set of input rates. We consider a specific model of the mobile adhoc network that enables us to exactly compute these quantities. Further, we propose schemes that offer performance guarantees that are arbitrarily close to these bounds at the cost of an increased delay. The exact nature of the associated delay tradeoff when performance is pushed towards the minimum energy bound is another fundamental characteristic of the network that is discussed in this work. I.
An Admission Control Algorithm for Multihop 802.11e based WLANs
 COMPUTER COMMUNICATIONS
, 2008
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Algorithms for routing and centralized scheduling in IEEE 802.16 mesh networks
 In Proceedings of IEEE Wireless Communications and Networking Conference (WCNC
, 2006
"... Abstract — IEEE 802.16 standards for Wireless Metropolitan Area Networks (WMANs) include a mesh mode of operation for improving the coverage and throughput of the network. In this paper, we consider the problem of routing and centralized scheduling for such networks. We first fix the routing, which ..."
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Cited by 6 (0 self)
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Abstract — IEEE 802.16 standards for Wireless Metropolitan Area Networks (WMANs) include a mesh mode of operation for improving the coverage and throughput of the network. In this paper, we consider the problem of routing and centralized scheduling for such networks. We first fix the routing, which reduces the network to a tree. We then present a finite horizon dynamic programming framework. Using it we obtain various scheduling algorithms depending upon the cost function. Next we consider simpler suboptimal algorithms and compare their performances. I.
Towards a System Theoretic Approach to Wireless Network Capacity in Finite Time and Space
"... Abstract—In asymptotic regimes, both in time and space (network size), the derivation of network capacity results is grossly simplified by brushing aside queueing behavior in nonJackson networks. This simplifying doublelimit model, however, lends itself to conservative numerical results in finite ..."
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Cited by 3 (3 self)
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Abstract—In asymptotic regimes, both in time and space (network size), the derivation of network capacity results is grossly simplified by brushing aside queueing behavior in nonJackson networks. This simplifying doublelimit model, however, lends itself to conservative numerical results in finite regimes. To properly account for queueing behavior beyond a simple calculus based on average rates, we advocate a system theoretic methodology for the capacity problem in finite time and space regimes. This methodology also accounts for spatial correlations arising in networks with CSMA/CA scheduling and it delivers rigorous closedform capacity results in terms of probability distributions. Unlike numerous existing asymptotic results, subject to anecdotal practical concerns, our transient one can be used in practical settings: for example, to compute the time scales at which multihop routing is more advantageous than singlehop routing. I.
Throughput optimization in wireless networks under stability and packet loss constraints
 IEEE Trans. Mob. Comput
"... Abstract—The problem of throughput optimization in decentralized wireless networks with spatial randomness under queue stability and packet loss constraints is investigated in this paper. Two key performance measures are analyzed, namely the effective link throughput and the network spatial throughp ..."
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Cited by 2 (1 self)
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Abstract—The problem of throughput optimization in decentralized wireless networks with spatial randomness under queue stability and packet loss constraints is investigated in this paper. Two key performance measures are analyzed, namely the effective link throughput and the network spatial throughput. Specifically, the tuple of medium access probability, coding rate, and maximum number of retransmissions that maximize each throughput metric is analytically derived for a class of Poisson networks, in which packets arrive at the transmitters following a geometrical distribution. Necessary conditions so that the effective link throughput and the network spatial throughput are stable and achievable under bounded packet loss are determined, as well as upper bounds for both cases by considering the unconstrained optimization problem. Our results show in which system configuration stable achievable throughput can be obtained as a function of the network density and the arrival rate. They also evince conditions for which the perlink throughputmaximizing operating points coincide or not with the aggregate network throughputmaximizing operating regime. Index Terms—Ad hoc networks, interference, Poisson point process, stochastic geometry, queue stability, spatial throughput F 1
Proportionally Fair Rate Allocation in Regular Wireless Sensor Networks
 IEEE Conference on Computer Communications Workshops
, 2011
"... AbstractIn this paper, we consider the problem of fair rate allocation that maximizes the network throughput in regular topologies of Wireless Sensor Networks (WSNs). In order to monitor the entire coverage area of the WSN while maintaining acceptable network throughput, we need to find the optima ..."
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AbstractIn this paper, we consider the problem of fair rate allocation that maximizes the network throughput in regular topologies of Wireless Sensor Networks (WSNs). In order to monitor the entire coverage area of the WSN while maintaining acceptable network throughput, we need to find the optimal rate allocation for the individual/competing endtoend sessions that maximizes the total proportionally fair throughput of the network. We provide closed form expressions for the optimal endtoend session rates for square, triangular and hexagonal topologies as well as the bounds for the link layer transmission probabilities. We study the aforementioned problem for regular WSNs with a slotted Aloha MAC layer, which provides us with a lower bound for more realistic MAC protocols. Real world experiments using Telosb nodes validate our theories and results. Simulations carried out in Qualnet verify our comparisons of the different regular topologies as the size of network grows.