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Delay Constrained Minimum Energy Broadcast in Cooperative Wireless Networks
"... Abstract—We formulate the problem of delay constrained energyefficient broadcast in cooperative multihop wireless networks. We show that this important problem is not only NPcomplete, but also o(log(n)) inapproximable. We derive approximation results and an analytical lowerbound for this problem. ..."
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Abstract—We formulate the problem of delay constrained energyefficient broadcast in cooperative multihop wireless networks. We show that this important problem is not only NPcomplete, but also o(log(n)) inapproximable. We derive approximation results and an analytical lowerbound for this problem. We break this NP hard problem into three parts: ordering, scheduling and power control. We show that when the ordering is given, the joint scheduling and powercontrol problem can be solved in polynomial time by a novel algorithm that combines dynamic programming and linear programming to yield the minimum energy broadcast for a given delay constraint. We further show empirically that this algorithm used in conjunction with an ordering derived heuristically using the Dijkstra’s shortest path algorithm yields nearoptimal performance in typical settings. We use our algorithm to study numerically the tradeoff between delay and powerefficiency in cooperative broadcast and compare the performance of our cooperative algorithm with a smart noncooperative algorithm. I.
1 A Simple Cooperative Transmission Protocol for EnergyEfficient Broadcasting Over MultiHop Wireless Networks
, 903
"... Abstract—This paper analyzes a broadcasting technique for wireless multihop sensor networks that uses a form of cooperative diversity called opportunistic large arrays (OLAs). We propose a method for autonomous scheduling of the nodes, which limits the nodes that relay and saves as much as 32% of t ..."
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Abstract—This paper analyzes a broadcasting technique for wireless multihop sensor networks that uses a form of cooperative diversity called opportunistic large arrays (OLAs). We propose a method for autonomous scheduling of the nodes, which limits the nodes that relay and saves as much as 32% of the transmit energy compared to other broadcast approaches, without requiring Global Positioning System (GPS), individual node addressing, or internode interaction. This energysaving is a result of crosslayer interaction, in the sense that the Medium Access Control (MAC) and routing functions are partially executed in the Physical (PHY) layer. Our proposed method is called OLA with a transmission threshold (OLAT), where a node compares its received power to a threshold to decide if it should forward. We also investigate OLA with variable threshold (OLAVT), which optimizes the thresholds as a function of level. OLAT and OLAVT are compared with OLA broadcasting without a transmission threshold, each in their minimum energy configuration, using an analytical method under the orthogonal and continuum assumptions. The tradeoff between the number of OLA levels (or hops) required to achieve successful network broadcast and transmission energy saved is investigated. The results based on the analytical assumptions are confirmed with Monte Carlo simulations.
Reactive Routing For Multihop Dynamic Ad Hoc Networks Based On Opportunistic Large Arrays
"... Abstract: A mobile ad hoc network is an infrastructureless multihop system of wireless autonomous mobile nodes. Reactive routing protocols like Ad hoc On Demand Distance Vector Routing (AODV) and Dynamic Source Routing (DSR) are appropriate for mobile environments, because they cope quickly with to ..."
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Abstract: A mobile ad hoc network is an infrastructureless multihop system of wireless autonomous mobile nodes. Reactive routing protocols like Ad hoc On Demand Distance Vector Routing (AODV) and Dynamic Source Routing (DSR) are appropriate for mobile environments, because they cope quickly with topological changes. Lately cooperativetransmissionbased routing protocols have been proposed to further save energy and enhance reliability. However they require an existing conventional route and individual addressing of the cooperating nodes, which involves a lot of overhead. In this paper, we propose a new Opportunistic Large Array (OLA)based extension to AODV, which incorporates cooperative diversity into both route discovery and data transmission without requiring any preexisting route or any individual addressing of relay nodes. An OLA is a form of cooperative diversity in which a group of simple, inexpensive relays or forwarding nodes operate without any mutual coordination, but naturally fire together in response to energy received from a single source or another OLA. Our proposed scheme inherits from OLA lower transmit energy and low computational overhead. However, this paper highlights a newly discovered feature of OLAs, which is robustness against mobility. We show through extensive simulation that this new technique yields significantly longer route lifetimes compared to the traditional AODV scheme, assuming node mobility according to the Random Waypoint Mobility Model. We also compare the endtoend delays of the traditional and proposed schemes. To the best knowledge of the authors, this work is the only unicast, distributed, cooperative ad hoc routing scheme that does not require a preexisting route. 1.
Multicasting in Large Random Wireless Networks: Bounds on the Minimum Energy per Bit
"... Abstract—We consider scaling laws for maximal energy efficiency of communicating a message to all the nodes in a random wireless network, as the number of nodes in the network becomes large. Two cases of large wireless networks are studied — dense random networks and constant density (extended) rand ..."
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Abstract—We consider scaling laws for maximal energy efficiency of communicating a message to all the nodes in a random wireless network, as the number of nodes in the network becomes large. Two cases of large wireless networks are studied — dense random networks and constant density (extended) random networks. We first establish an informationtheoretic lower bound on the minimum energy per bit for multicasting that holds for arbitrary wireless networks when the channel state information is not available at the transmitters. These lower bounds are then evaluated for two cases of random networks. Upper bounds are also obtained by constructing a simple flooding scheme that requires no information at the receivers about the channel states or the locations and identities of the nodes. The gap between the upper and lower bounds is only a constant factor for dense random networks and differs by a polylogarithmic factor for extended random networks. Furthermore, the proposed upper and lower bounds hold almost surely in the node locations as the number of nodes approaches infinity. A. Prior Work I.
Minimum Energy per Bit for Wideband Wireless Multicasting: Performance of DecodeandForward
"... Abstract—We study the minimum energy per bit required for communicating a message to all the destination nodes in a wireless network. The physical layer is modeled as an additive white Gaussian noise channel affected by circularly symmetric fading. The fading coefficients are known at neither transm ..."
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Abstract—We study the minimum energy per bit required for communicating a message to all the destination nodes in a wireless network. The physical layer is modeled as an additive white Gaussian noise channel affected by circularly symmetric fading. The fading coefficients are known at neither transmitters nor receivers. We provide an informationtheoretic lower bound on the energy requirement of multicasting in arbitrary wireless networks as the solution of a linear program. We study the broadcast performance of decodeandforward operating in the noncoherent wideband scenario, and compare it with the lower bounds. For arbitrary networks with k nodes, the energy requirement of decodeandforward is within a factor of k − 1 of the lower bound regardless of the magnitude of channel gains. We also show that decodeandforward achieves the minimum energy per bit in networks that can be represented as directed acyclic graphs, thus establishing the exact minimum energy per bit for this class of networks. We also study regular networks where the area is divided into cells, each cell containing at least k and at most ¯ k nodes placed arbitrarily within the cell. A path loss model (with path loss exponent α> 2) dictates the channel gains between the nodes. It is shown that the ratio between the upper bound using decodeandforward based flooding, and the lower bound is at most a constant times ¯ k α+2 /k. I.
1 On Hardness of Multiflow Transmission in Delay Constrained Cooperative Wireless Networks
"... Abstract—We consider the problem of energyefficient transmission in multiflow multihop cooperative wireless networks. Although the performance gains of cooperative approaches are well known, the combinatorial nature of these schemes makes it difficult to design efficient polynomialtime algorithms ..."
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Abstract—We consider the problem of energyefficient transmission in multiflow multihop cooperative wireless networks. Although the performance gains of cooperative approaches are well known, the combinatorial nature of these schemes makes it difficult to design efficient polynomialtime algorithms for joint routing, scheduling and power control. This becomes more so when there is more than one flow in the network. It has been conjectured by many authors, in the literature, that the multiflow problem in cooperative networks is an NPhard problem. In this paper, we formulate the problem, as a combinatorial optimization problem, for a general setting of kflows, and formally prove that the problem not only NPhard but it is o(n 1/7−ɛ) inapproxmiable. To our knowledge, the results in this paper provide the first such inapproxmiablity proof in the context of multiflow cooperative wireless networks. We further prove that for a special case of k = 1 the solution is asimplepath,andofferapolynomialtimealgorithmfor jointly optimizing routing, scheduling and power control. I.
Algorithmic Aspects of EnergyDelay Tradeoff in Multihop Cooperative Wireless Networks
, 2011
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Multicasting in Large Wireless Networks: Bounds on the Minimum Energy per Bit 1
, 905
"... We consider scaling laws for maximal energy efficiency of communicating a message to all the nodes in a wireless network, as the number of nodes in the network becomes large. Two cases of large wireless networks are studied — dense random networks and constant density (extended) random networks. In ..."
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We consider scaling laws for maximal energy efficiency of communicating a message to all the nodes in a wireless network, as the number of nodes in the network becomes large. Two cases of large wireless networks are studied — dense random networks and constant density (extended) random networks. In addition, we also study finite size regular networks in order to understand how regularity in node placement affects energy consumption. We first establish an informationtheoretic lower bound on the minimum energy per bit for multicasting in arbitrary wireless networks when the channel state information is not available at the transmitters. Upper bounds are obtained by constructing a simple flooding scheme that requires no information at the receivers about the channel states or the locations and identities of the nodes. The gap between the upper and lower bounds is only a constant factor for dense random networks and regular networks, and differs by a polylogarithmic factor for extended random networks. Furthermore, we show that the proposed upper and lower bounds for random networks hold almost surely in the node locations as the number of nodes approaches infinity. I.
Multiflow Transmission in Delay Constrained Cooperative Wireless Networks
, 2012
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