Comparison of space-time block code and layered space-time MIMO systems for an underwater acoustic channel

The paper considers the viability of exploiting the spatial diversity that exists in shallow water, doubly-spread, underwater acoustic communications channels to use space-time methods. Using a simple 2D geometric ray model of an underwater acoustic channel, it is shown that sufficient spatial diversity exists for the underwater channel to be treated as a MIMO channel supporting space-time processing. Two different types of space-time communications system are examined: a space-time block code and a layered space-time system. Depending on the separation of the transducers, it is shown that the bit error probability performance of the two systems for the simple 2D acoustic channel can be close to that provided by an ideal Rayleigh channel in which each path suffers independent and uncorrelated fading.