The extremely long underwater channel delay spread causes severe inter-symbol interference (ISI) for underwater acoustic communications. Passive time reversal processing (PTRP) can effectively reduce the channel time dispersion in a simple way via convolving the received packet with a time reversed probe signal. However the probe signal itself may introduce extra noise and interference (self-co...

The estimation of channel coefficients constitutes a major function of the receiver. It is also an important step in the signal detection process at the receiver, in a wireless communication system. To describe the spacetime channel from multiple transmitters to a single receiver, many parameters are required. This means that in order to perform channel estimation and signal detection, the orde...

In this paper we consider a narrowband point-to-point communication system with many (input) transmitters and a single (output) receiver (ie, a “MISO” system). We assume the receiver has perfect knowledge of the channel but the transmitter has only limited channel information. We focus on two canonical classes of channel models: (a) the channel has zero mean with a fixed covariance matrix and (...

We consider the problem of multiple-input singleoutput Broadcast Channels with Rayleigh fading where the transmitter has access to delayed knowledge of the channel state information. We first characterize the capacity region of this channel with two users to within constant number of bits for all values of the transmit power. The proposed signaling strategy utilizes the delayed knowledge of the...