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32
Optimal Backpressure Routing for Wireless Networks with Multi-Receiver Diversity
, 2006
"... We consider the problem of optimal scheduling and routing in an ad-hoc wireless network with multiple traffic streams and time varying channel reliability. Each packet transmission can be overheard by a subset of receiver nodes, with a transmission success probability that may vary from receiver t ..."
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Cited by 60 (8 self)
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We consider the problem of optimal scheduling and routing in an ad-hoc wireless network with multiple traffic streams and time varying channel reliability. Each packet transmission can be overheard by a subset of receiver nodes, with a transmission success probability that may vary from receiver to receiver and may also vary with time. We develop a simple backpressure routing algorithm that maximizes network throughput and expends an average power that can be pushed arbitrarily close to the minimum average power required for network stability, with a corresponding tradeoff in network delay. The algorithm can be implemented in a distributed manner using only local link error probability information, and supports a “blind transmission” mode (where error probabilities are not required) in special cases when the power metric is neglected and when there is only a single destination for all traffic streams.
Energy-efficient cooperative relaying over fading channels with simple relay selection
- in EEE Global Telecommunications Conference (GLOBECOM
, 2006
"... We consider a cooperative wireless network where a set of nodes cooperate to relay in parallel the information from a source to a destination using a decode-and-forward approach. The source broadcasts the data to the relays, some or all of which cooperatively beamform to forward the data to the dest ..."
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Cited by 60 (16 self)
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We consider a cooperative wireless network where a set of nodes cooperate to relay in parallel the information from a source to a destination using a decode-and-forward approach. The source broadcasts the data to the relays, some or all of which cooperatively beamform to forward the data to the destination. We generalize the standard approaches for cooperative communications in two key respects: (i)we explicitly model and factor in the cost of acquiring channel state information (CSI), and (ii)we consider more general selection rules for the relays and compute the optimal one among them. In particular, we consider simple relay selection and outage criteria that exploit the inherent diversity of relay networks and satisfy a mandated outage constraint. These criteria include as special cases serveral relay selection criteria proposed in the literature. We obtain expressions for the total energy consumption for general relay selection and outage criteria for the non-homogeneous case, in which different relay links have different mean channel power gains, and the homogeneous case, in which the relay links statistics are identical. We characterize the structure of the optimal transmission scheme. Numerical results show that the cost of training and feedback of CSI is significant. The optimal strategy is to use a varying subset (and number) or relay nodes to cooperatively beamform at any given time. Depending on the relative location of the relays, the source, and the destination, numerical computations show energy savings of about 16 % when an optimal relay selection rule is used. We also study the impact of shadowing correlation on the energy consumption for a cooperative relay network.
Throughput optimal control of cooperative relay networks
- IEEE Trans. on Information Theory
, 2005
"... In cooperative relaying, packets are not forwarded by traditional hop-by-hop transmissions between pairs of nodes. Instead, several nodes cooperate with each other to forward a packet by, for example, forming a distributed antenna array. To date, such schemes have been primarily investigated at the ..."
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Cited by 50 (3 self)
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In cooperative relaying, packets are not forwarded by traditional hop-by-hop transmissions between pairs of nodes. Instead, several nodes cooperate with each other to forward a packet by, for example, forming a distributed antenna array. To date, such schemes have been primarily investigated at the physical layer with the focus on communication of a single end-to-end flow. In this paper, we consider cooperative relay networks with multiple stochastically varying end-to-end flows. The traffic from each flow is queued within the network until it can be forwarded. For such networks, we study network control policies that take into account queue dynamics to jointly optimize routing, scheduling and resource allocation. Specifically, we develop a throughput optimal policy, i.e., a policy that stabilizes the network for any arrival rate in its stability region. This policy is a generalization of the well-known Maximum Differential Backlog algorithms, which takes into account the cooperative gains in the network. Implementing this policy requires solving an optimization problem over the set of feasible transmission rates. We discuss several structural characteristics of this optimization problem for the special case of parallel relay cooperative networks. I.
A Framework for Distributed Spatio-Temporal
- Communications in Mobile Ad hoc Networks,” in Proceedings of IEEE INFOCOM’06
, 2006
"... Abstract — Space-time communications can help combat fading and hence can significantly increase the capacity of ad hoc networks. Cooperative diversity or virtual antenna arrays facilitate spatio-temporal communications without actually requiring the deployment of physical antenna arrays. Virtual MI ..."
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Cited by 35 (2 self)
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Abstract — Space-time communications can help combat fading and hence can significantly increase the capacity of ad hoc networks. Cooperative diversity or virtual antenna arrays facilitate spatio-temporal communications without actually requiring the deployment of physical antenna arrays. Virtual MISO entails the simultaneous transmission of appropriately encoded information by multiple nodes to effectively emulate a transmission on an antenna array. We present a novel multi-layer approach for exploiting virtual MISO links in ad hoc networks. The approach spans the physical, medium access control and routing layers and provides: (a) a significant improvement in the end-to-end performance in terms of throughput and delay and, (b) robustness to mobility and interference induced link failures. The key physical layer property that we exploit is an increased transmission range due to achieved the diversity gain. Except for space-time signal processing capabilities, our design does not require any additional hardware. We perform extensive simulations to quantify the benefits of our approach using virtual MISO links. As compared to using only SISO links, we achieve an increase of up to 150 % in terms of the end-to-end throughput and a decrease of up to 75 % in the incurred end-to-end delay. Our results also demonstrate a reduction in the route discovery attempts due to link failures by up to 60%, a direct consequence of the robustness that our approach provides to link failures. I.
Efficient Geographic Routing over Lossy Links in Wireless Sensor Networks
- ACM Transactions on Sensor Networks
"... Recent experimental studies have shown that wireless links in real sensor networks can be extremely unreliable, deviating to a large extent from the idealized perfect-reception-within-range models used in common network simulation tools. Previously proposed geographic routing protocols commonly empl ..."
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Cited by 22 (1 self)
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Recent experimental studies have shown that wireless links in real sensor networks can be extremely unreliable, deviating to a large extent from the idealized perfect-reception-within-range models used in common network simulation tools. Previously proposed geographic routing protocols commonly employ a maximum-distance greedy forwarding technique that works well in ideal conditions. However, such a forwarding technique performs poorly in realistic conditions as it tends to forward packets on lossy links. Based on a recently developed link loss model, we study the performance of a wide array of forwarding strategies, via analysis, extensive simulations and a set of experiments on motes. We find that the product of the packet reception rate and the distance improvement towards destination (P RR × d) is a highly suitable metric for geographic forwarding in realistic environments.
On Broadcasting with Cooperative Diversity in Multi-hop Wireless Networks
"... Abstract — Cooperative diversity facilitates spatio-temporal communications without requiring the deployment of physical antenna arrays. While physical layer studies on cooperative diversity have been extensive, higher layer protocols which translate the achievable reduction in the SNR per bit for a ..."
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Cited by 16 (1 self)
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Abstract — Cooperative diversity facilitates spatio-temporal communications without requiring the deployment of physical antenna arrays. While physical layer studies on cooperative diversity have been extensive, higher layer protocols which translate the achievable reduction in the SNR per bit for a given target BER, into system wide performance enhancements are yet to mature. The challenge is that appropriate higher layer functions are needed in order to enable cooperative diversity at the physical layer. We focus on network-wide broadcasting with the use of cooperative diversity in ad hoc networks. We design a novel distributed network-wide broadcasting protocol that takes into account the physical layer dependencies that arise with cooperative diversity. We perform extensive simulations that show that our protocol can outperform the best of the noncooperative broadcasting protocols by: (a) achieving up to a threefold increase in network coverage and, (b) by decreasing the latency incurred during the broadcast by about 50%. We also construct an analytical model that captures the behavior of our protocol. Furthermore, we show that computing the optimal solution to the cooperative broadcast problem is NP-complete and construct centralized approximation algorithms. Specifically, we construct an O(N ɛ)-approximation algorithm with a computational complexity of O(N 4 ɛ); we also construct a simpler greedy algorithm. The costs incurred with these algorithms serve as benchmarks with which one can compare that achieved by any distributed protocol.
On the Power Efficiency of Cooperative Broadcast in Dense Wireless Networks
, 2006
"... A fundamental problem in large scale wireless networks is the energy efficient broadcast of source messages to the whole network. The energy consumption increases as the network size grows, and the optimization of broadcast efficiency becomes more important. In this paper, we study the optimal power ..."
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Cited by 11 (0 self)
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A fundamental problem in large scale wireless networks is the energy efficient broadcast of source messages to the whole network. The energy consumption increases as the network size grows, and the optimization of broadcast efficiency becomes more important. In this paper, we study the optimal power allocation problem for cooperative broadcast in dense large-scale networks. In the considered cooperation protocol, a single source initiates the transmission and the rest of the nodes retransmit the source message if they have decoded it reliably. Each node is allocated an orthogonal channel and the nodes improve their receive signal-to-noise ratio (SNR), hence the energy efficiency, by maximal-ratio combining the receptions of the same packet from different transmitters. We assume that the decoding of the source message is correct as long as the receive SNR exceed a predetermined threshold. Under the optimal cooperative broadcasting, the transmission order (i.e., the schedule) and the transmission powers of the source and the relays are designed so that every node receives the source message reliably and the total power consumption is minimized. In general, finding the best scheduling in cooperative broadcast is known to be an NP-complete problem. In this paper, we show that the optimal scheduling problem can be solved for dense networks, which we approximate as a continuum of nodes.
Cooperation and routing in multi-hop networks
- in Proc. Int. Conf. on Communications
, 2007
"... Abstract — We study the cross-layer problem of combining routing and cooperative diversity in multi-hop, bandwidth-constrained, networks with dedicated multiple access. Previous work in cooperative diversity nearly always assumes cooperation to be a positive. We show that in a large scale multi-hop ..."
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Cited by 9 (0 self)
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Abstract — We study the cross-layer problem of combining routing and cooperative diversity in multi-hop, bandwidth-constrained, networks with dedicated multiple access. Previous work in cooperative diversity nearly always assumes cooperation to be a positive. We show that in a large scale multi-hop network, cooperation must only be used selectively. Our figure of merit is achievable data rate between a source and destination at a fixed probability of outage. We show that enforcing multiple hops is detrimental to performance, since each extra hop requires bandwidth expansion. This performance can be significantly im-proved by incorporating a selective cooperative diversity scheme on a one-hop link. On the other hand, the simulation results show that cooperative diversity does not improve performance over a dynamic routing protocol which searches for the optimal, non-diversity, route. Including the search for cooperative nodes into the dynamic route search, however, does further increase flow rates by decreasing the average number of hops and thus decreasing the required bandwidth expansion. This paper therefore points to the importance of an integrated approach to routing and the physical layer in cooperative networks. I.
Progressive accumulative routing: Fundamental concepts and protocol
- IEEE Trans. Wireless Comm
, 2008
"... This paper considers a multi-hop network in which relay nodes cooperate to minimize the total energy consumed in transmitting a (unicast) packet from a source to a destination. We propose the Progressive Accumulative Routing (PAR) algorithm, which progressively performs relay discovery, relay orderi ..."
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Cited by 7 (4 self)
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This paper considers a multi-hop network in which relay nodes cooperate to minimize the total energy consumed in transmitting a (unicast) packet from a source to a destination. We propose the Progressive Accumulative Routing (PAR) algorithm, which progressively performs relay discovery, relay ordering and relay power allocation in a distributed manner, such that each relay node only needs local information. We assume Destination Energy Accumulation, in which the destination accumulates the energy of multiple received copies of a packet, each of which is too weak to be reliably decoded by itself, while the lower-complexity relay nodes use a decodeand-forward approach. We also provide a closed-form analysis of the energy-saving achieved by the PAR when a relay node is added to an already existing DEA route. Simulations verify that the algorithm considerably reduces the total energy consumption, and can be implemented efficiently.
Robust Cooperative Routing Protocol in Mobile Wireless Sensor Networks
"... Abstract—In wireless sensor networks, path breakage occurs frequently due to node mobility, node failure, and channel impairments. It is challenging to combat path breakage with minimal control overhead, while adapting to rapid topological changes. Due to the Wireless Broadcast Advantage (WBA), all ..."
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Cited by 6 (0 self)
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Abstract—In wireless sensor networks, path breakage occurs frequently due to node mobility, node failure, and channel impairments. It is challenging to combat path breakage with minimal control overhead, while adapting to rapid topological changes. Due to the Wireless Broadcast Advantage (WBA), all nodes inside the transmission range of a single transmitting node may receive the packet, hence naturally they can serve as cooperative caching and backup nodes if the intended receiver fails to receive the packet. In this paper, we present a distributed robust routing protocol in which nodes work cooperatively to enhance the robustness of routing against path breakage. We compare the energy efficiency of cooperative routing with noncooperative routing and show that our robust routing protocol can significantly improve robustness while achieving considerable energy efficiency. Index Terms—Robustness, routing, wireless sensor networks, mobility. I.
