Neural Network Prediction of Radio Propagation

Preliminary work for predicting signal distributions in a local area, using a feature-based neural network is presented. The neural network is trained by radio signal measurements at known positions. After appropriately setting the parameters of nodes o

On the Entropy Rate of Word-Valued Sources

Abstract — A word-valued source Y is any discrete finite alphabet random process that is created by encoding a discrete random process X with a symbol-to-word function f. The first result of this paper solves an open problem by proving an existence theorem for the entropy rate of word valued sources: If X is ergodic, then the entropy rate of the word valued source Y exists, and it is upper bound by the entropy rate of X divided by the expected codeword length. More generally, if X is Asymptotically Mean Stationary (AMS), then entropy rate of Y exists, and it is upper bound by the expectation of the entropy rate of each stationary ergodic sub-source divided by the expected codeword length of that sub-source. The second result of this paper proves a “conservation of entropy result ” for decodable word functions: If f is decodable and X is AMS, then the entropy rate of the word valued source Y is equal to the expectation of the entropy rate of each stationary ergodic sub-source divided by the expected codeword length of that sub-source. This result generalizes existing entropy conservation results for prefix free word functions. I

Body-area-network transmission power control using variable adaptive feedback periodicity

We propose a class of adaptive power control protocol, where the period between each feedback transmission is adaptively varied to accommodate run-time variation in the quality of each channel. Initial analyses suggest that transmission control protocols with adaptive feedback periodicity can outperform other comparable schemes. For certain measured channels the period can increase to once every few minutes (thousands of packets) and still provides substantial power savings. Adaptive power control protocols also provide the potential to reduce intra-cell interference. ©2010 IEEE

Reliable body area networks using relays: Restricted tree topology

This paper focuses on mechanisms that support the reliable transfer of data for medical applications in wireless Body Area Networks (BANs), in particular for the monitoring by sensors of vital life signs. Recent studies on path-loss models for BANs show that for some scenarios a Star Topology (ST) with a direct, single link, between sensor and coordinator is insufficient. It is thus beneficial to extend the ST to a Tree Topology with a restricted number of hops using relays. In this paper we provide an overview of relevant findings before presenting our Restricted Tree Topology (RTT) design. We then present an experiment that is set up to study the performance of RTT in terms of availability of connectivity, based on Received signal strength at 2.4 GHz using wearable channel sounders with various people sleeping - sleeping has been found to be one of the most difficult scenarios, in terms of reliability, for BAN. Our simulation results show that for certain sleeping positions, RTT improves connectivity by approximately 12% for a receiver sensitivity of -95 dBm. In addition we have shown that without RTT it is not possible to meet the reliability requirement as set out by the IEEE 802.15.6 Task Group for its draft standard. © 2012 IEEE