Kalman Filtering With Relays Over Wireless Fading Channels

This note studies the use of relays to improve the performance of Kalman filtering over packet dropping links. Packet reception probabilities are governed by time-varying fading channel gains, and the sensor and relay transmit powers. We consider situations with multiple sensors and relays, where each relay can either forward one of the sensors' measurements to the gateway/fusion center, or perform a simple linear network coding operation on some of the sensor measurements. Using an expected error covariance performance measure, we consider optimal and suboptimal methods for finding the best relay configuration, and power control problems for optimizing the Kalman filter performance. Our methods show that significant performance gains can be obtained through the use of relays, network coding and power control, with at least 30-40$\%$ less power consumption for a given expected error covariance specification.Comment: 7 page

Distributed Detection and Estimation in Wireless Sensor Networks

In this article we consider the problems of distributed detection and estimation in wireless sensor networks. In the first part, we provide a general framework aimed to show how an efficient design of a sensor network requires a joint organization of in-network processing and communication. Then, we recall the basic features of consensus algorithm, which is a basic tool to reach globally optimal decisions through a distributed approach. The main part of the paper starts addressing the distributed estimation problem. We show first an entirely decentralized approach, where observations and estimations are performed without the intervention of a fusion center. Then, we consider the case where the estimation is performed at a fusion center, showing how to allocate quantization bits and transmit powers in the links between the nodes and the fusion center, in order to accommodate the requirement on the maximum estimation variance, under a constraint on the global transmit power. We extend the approach to the detection problem. Also in this case, we consider the distributed approach, where every node can achieve a globally optimal decision, and the case where the decision is taken at a central node. In the latter case, we show how to allocate coding bits and transmit power in order to maximize the detection probability, under constraints on the false alarm rate and the global transmit power. Then, we generalize consensus algorithms illustrating a distributed procedure that converges to the projection of the observation vector onto a signal subspace. We then address the issue of energy consumption in sensor networks, thus showing how to optimize the network topology in order to minimize the energy necessary to achieve a global consensus. Finally, we address the problem of matching the topology of the network to the graph describing the statistical dependencies among the observed variables.Comment: 92 pages, 24 figures. To appear in E-Reference Signal Processing, R. Chellapa and S. Theodoridis, Eds., Elsevier, 201

A Practical Scheme for Wireless Network Operation

In many problems in wireline networks, it is known that achieving capacity on each link or subnetwork is optimal for the entire network operation. In this paper, we present examples of wireless networks in which decoding and achieving capacity on certain links or subnetworks gives us lower rates than other simple schemes, like forwarding. This implies that the separation of channel and network coding that holds for many classes of wireline networks does not, in general, hold for wireless networks. Next, we consider Gaussian and erasure wireless networks where nodes are permitted only two possible operations: nodes can either decode what they receive (and then re-encode and transmit the message) or simply forward it. We present a simple greedy algorithm that returns the optimal scheme from the exponential-sized set of possible schemes. This algorithm will go over each node at most once to determine its operation, and hence, is very efficient. We also present a decentralized algorithm whose performance can approach the optimum arbitrarily closely in an iterative fashion

A Hybrid Approach to Reduction of Packet Loss in Wireless Sensor Network

Wireless sensor networks are spatially distributed autonomous sensors to monitor physical or environmental conditions, such as temperature, sound, pressure, etc. and to cooperatively pass their data through the network to a main location The major role of sensor networks is sensing and delivering data to sink node, reliability is an important characteristic. However WSNs are associated with packet loss, which gets worse through multi-hop routing paths in wireless sensor networks, nodes near the destination have higher packet delivery performance. Numerous reasons for packet loss such as: signal attenuation due to the distance between the nodes, asymmetry in wireless communication links, non-uniform radio signal strength, wireless propagation effects (fading and multipath), interference due to hidden terminal problem, in addition to being  greatly affected by the deployment environment, and the behavior of wireless communication have been noticed. In an attempt to reduce packet loss via WSN, this research study proposes a combined approach of distributed storage system algorithm for wireless sensor networks coupled with Replacing Lost Packets (Packet Loss Concealment)  methods. . In an attempt to reduce packet loss via WSN, this research study proposes a combined approach of Modified distributed storage algorithm for wireless sensor networks (MDSA) coupled with Replacing Lost Packets (Packet Loss Concealment)  methods. During this study, a DSS was designed with both repetition code and regeneration code in case there is a link failure. Results from this study showed that for both codes the success probability of both theory and implementation correlate, while the regeneration code showed the highest success probability. And therefore it was chosen for further study. The implementation of regeneration code results showed that the increasing of field size also correlate with the increasing of success probability for both theory and implementation. The implementation of the proposed PLC results showed that showed that the proposed PLC algorithm improves significantly the quality of speech transmitted over an unreliable network with high packet loss rate. Though, the proposed PLC introduces additional delay which needs to be considered but the increased delay is often a necessary expense if the signal quality is a priority. Key words: Wireless Sensor Network,  Distributed Storage System algorithm, packet loss concealmen