Results 1 
9 of
9
1Optimal Routing with Mutual Information Accumulation in Wireless Networks
"... Abstract—We investigate optimal routing and scheduling strategies for multihop wireless networks with rateless codes. Rateless codes allow each node of the network to accumulate mutual information with every packet transmission. This enables a significant performance gain over conventional shortest ..."
Abstract

Cited by 4 (0 self)
 Add to MetaCart
Abstract—We investigate optimal routing and scheduling strategies for multihop wireless networks with rateless codes. Rateless codes allow each node of the network to accumulate mutual information with every packet transmission. This enables a significant performance gain over conventional shortest path routing. Further, it also outperforms cooperative communication techniques that are based on energy accumulation. However, it requires complex and combinatorial networking decisions concerning which nodes participate in transmission, and which decode ordering to use. We formulate three problems of interest in this setting: (i) minimum delay routing, (ii) minimum energy routing subject to delay constraint, and (iii) minimum delay broadcast. All of these are hard combinatorial optimization problems and we make use of several structural properties of their optimal solutions to simplify the problems and derive optimal greedy algorithms. Although the reduced problems still have exponential complexity, unlike prior works on such problems, our greedy algorithms are simple to use and do not require solving any linear programs. Further, using the insight obtained from the optimal solution to a line topology, we propose two simple heuristics that can be implemented in polynomial time and in a distributed fashion and compare them with the optimal solution. Simulations suggest that both heuristics perform very close to the optimal solution over random network topologies.
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 ..."
Abstract

Cited by 1 (0 self)
 Add to MetaCart
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.
Online Policies for Opportunistic Virtual MISO Routing in Wireless Ad Hoc Networks
"... Abstract—Cooperative routing has been shown to be an effective technique to improve the throughput/delay performance of multihop wireless ad hoc networks. In addition, suitable cooperation selection policies also allow for a reduction of the overall energy expenditure. In a previous study, we prop ..."
Abstract
 Add to MetaCart
(Show Context)
Abstract—Cooperative routing has been shown to be an effective technique to improve the throughput/delay performance of multihop wireless ad hoc networks. In addition, suitable cooperation selection policies also allow for a reduction of the overall energy expenditure. In a previous study, we proposed a centralized algorithm to obtain optimal cooperation selection policies in multihop networks with the aim of minimizing a linear combination of energy and delay costs. In this paper, we look at this problem from a different angle, devising three online and fully distributed algorithms which only exploit local interactions for the selection of the cooperators. The first technique selects at each hop a fixed number of nodes having the minimum distance with respect to the destination. The second one adopts a lookahead strategy, which selects a fixed number of nodes at each hop, according to their expected advancement toward
A Cooperative Routing Framework Based on Randomized Coding in Wireless Ad Hoc Networks
"... Abstract—A distributed cooperative forwarding framework based on randomized coding is proposed, where cooperative links are formed and packets are forwarded on the fly, without explicit relay selection, actuation or resource allocation. In this framework, a cooperative flooding method and two cooper ..."
Abstract
 Add to MetaCart
(Show Context)
Abstract—A distributed cooperative forwarding framework based on randomized coding is proposed, where cooperative links are formed and packets are forwarded on the fly, without explicit relay selection, actuation or resource allocation. In this framework, a cooperative flooding method and two cooperative forwarding schemes that actuate the cooperative transmissions of the nodes within an optimally formed progress region are described. It is shown that by assuring packets ’ progress cooperatively through a region instead of a string of predetermined nodes, progress of the packets towards the final destination is guaranteed even in sparse networks, under severe fading and mobility conditions. The proposed forwarding schemes are shown to provide reductions in the total number of hops, while causing minimal spatial footprint on the network. Index Terms—Cooperative communications, wireless ad hoc networks, cooperative routing. I.
Optimal Routing with Mutual Information 1 Accumulation in Wireless Networks
"... We investigate optimal routing and scheduling strategies for multihop wireless networks with rateless codes. Rateless codes allow each node of the network to accumulate mutual information with every packet transmission. This enables a significant performance gain over conventional shortest path rou ..."
Abstract
 Add to MetaCart
We investigate optimal routing and scheduling strategies for multihop wireless networks with rateless codes. Rateless codes allow each node of the network to accumulate mutual information with every packet transmission. This enables a significant performance gain over conventional shortest path routing. Further, it also outperforms cooperative communication techniques that are based on energy accumulation. However, it creates complex and combinatorial networking decisions concerning which nodes participate in transmission, and which decode ordering to use. We formulate three problems of interest in this setting: (i) minimum delay routing, (ii) minimum energy routing subject to delay constraint, and (iii) minimum delay broadcast. All of these are hard combinatorial optimization problems and we make use of several structural properties of their optimal solutions to simplify the problems and derive optimal greedy algorithms. Although the reduced problems still have exponential complexity, unlike prior works on such problems, our greedy algorithms are simple to use and do not require solving any linear programs. Further, using the insight obtained from the optimal solution to a linear network, we propose two simple heuristics that can be implemented in polynomial time in a distributed fashion and compare them with the optimal solution. Simulations suggest that both heuristics perform very close to the optimal solution over random network topologies.
Index Terms
"... This paper considers the problem of finding minimumenergy cooperative routes in a wireless network with variable wireless channels. We assume that each node in the network is equipped with a single omnidirectional antenna and, motivated by the large body of physical layer research indicating its po ..."
Abstract
 Add to MetaCart
(Show Context)
This paper considers the problem of finding minimumenergy cooperative routes in a wireless network with variable wireless channels. We assume that each node in the network is equipped with a single omnidirectional antenna and, motivated by the large body of physical layer research indicating its potential utility, that multiple nodes are able to coordinate their transmissions at the physical layer in order to take advantage of spatial diversity. Such coordination, however, is intrinsically intertwined with routing decisions, thus motivating the work. We first formulate the energy cost of forming a cooperative link between two nodes based on a twostage transmission strategy assuming that only statistical knowledge about channels is available. Utilizing the link cost formulation, we show that optimal static routes in a network can be computed by running Dijkstra’s algorithm over an extended network graph created by cooperative links. However, due to the variability of wireless channels, we argue that a manytoone cooperation model in static routing is suboptimal. Hence, we develop an opportunistic routing algorithm based on manytomany cooperation, and show that optimal routes in a network can be computed by a stochastic version of the BellmanFord algorithm. We use static and opportunistic optimal algorithms as baselines to develop heuristic link selection algorithms that are energy efficient while being computationally simpler than the optimal algorithms. We simulate our algorithms and show that while optimal cooperation and link selection can reduce energy consumption by almost an order of magnitude compared to noncooperative approaches, our simple heuristics achieve similar energy savings while being computationally efficient as well.
Perormance Of Different Cooperative Routing Algorithms In Wireless Networks
"... Abstract — Each node in the network is equipped with a single omnidirectional antenna and motivated by the large body of physical layer research indicating its potential utility, that multiple nodes are able to coordinate their transmissions at the physical layer in order to take advantage of spatia ..."
Abstract
 Add to MetaCart
(Show Context)
Abstract — Each node in the network is equipped with a single omnidirectional antenna and motivated by the large body of physical layer research indicating its potential utility, that multiple nodes are able to coordinate their transmissions at the physical layer in order to take advantage of spatial diversity. Such coordination, however, is intrinsically intertwined with routing decisions, thus motivating the work. The problem of finding minimum–energy cooperative routes in a wireless network with variable wireless channels. I first formulate the energy cost of forming a cooperative link between two nodes based on a twostage transmission strategy assuming that only statistical knowledge about channels is available. Utilizing the link cost formulation, optimal static routes in a network can be computed by running Dijkstra’s algorithm over an extended network graph created by cooperative link. However, due to the variability of wireless channels, a manytomany cooperative model in static routing is suboptimal. Hence, an opportunistic routing algorithm based on manytomany cooperation, is to be developed and optimal routes in a network can be computed by a stochastic version of the BellmanFord algorithm. Static and opportunistic optimal algorithms as baselines to develop heuristic link selection algorithms that are energy efficient while being computationally simpler than the optimal algorithms. Energy saving can be achieved through simple heuristics which are computationally efficient.