We study the problem of target tracking in a sensor network environment. In particular, we consider a target that moves according to a Markov chain, and a tracker that queries sets of sensors to obtain tracking information. We are interested in finding the minimum number of queries per time step such that a target is trackable under three different requirements. First we investigate the case where the tracker is required to know the exact location of the target at each time step. We then relax this requirement and explore the case where the tracker may lose track of the target at a given time step, but it is able to ";catch-up"; at a later time, regaining up-to-date information about the target's track. Finally, we consider the case where tracking information is only known after a delay of d time steps. We provide necessary and sufficient conditions on the number of queries per time step to track in the above three cases. These conditions are stated in terms of the entropy rate of the target's Markov chain.

This paper introduces a novel merger of OFDM systems, MIMO systems, and carrier interferometry (CI) spreading codes. Specifically, previous works have illustrated the performance benefits of (1) applying CI spreading codes to OFDM and (2) merging MIMO and OFDM systems. In this paper, OFDM systems are combined with both a MIMO system and CI spreading codes, resulting in the so-called MIMO-CI/OFDM system, capable of very reliable communication at SNRs previously possible only with channel coding.