We study the joint source-channel coding problem of transmitting a Gaussian source over a Gaussian channel in two cases: (i) the presence of interference known only to the transmitter and (ii) in the presence of side information about the source known only to the receiver. We introduce hybrid digital analog forms of the Costa and Wyner-Ziv coding schemes. We present the random coding counterpart of schemes based on lattices proposed by Kochman and Zamir. Then, we discuss applications of the hybrid digital analog schemes in the case of channel signal-to-noise ratio mismatch and for lossy multicasting of a common source with bandwidth compression.

We consider a communication system where two transmitters wish to exchange information through a central relay. The transmitter and relay nodes exchange data over synchronized, average power constrained additive white Gaussian noise channels with a real input with signal-to-noise ratio (SNR) of snr. An upper bound on the capacity is 1/2 log(1 + snr) bits per transmitter per use of the multiple access phase and broadcast phase of the bidirectional relay channel. We show that, using lattice codes and lattice decoding, we can obtain a rate of 1/2 log(1/2 + snr) bits per transmitter, which is essentially optimal at high SNR. The main idea is to decode the sum of the codewords modulo a lattice at the relay followed by a broadcast phase which performs Slepian-Wolf coding. We also show that if the two transmitters use identical lattices with minimum angle decoding, we can achieve the same rate of 1/2 log(1/2 + snr). The proposed scheme can be thought of as a joint physical-layer network-layer code which outperforms other recently proposed analog network coding schemes.

We consider a communication system where two transmitters wish to exchange information through a half-duplex relay in the middle. The channels between the transmitters and the relay have asymmetric channel gains. More specifically, the channels are assumed to be synchronized with complex inputs and complex fading coefficients with an average power constraint on the inputs to the channels. The noise at the receivers have the same power spectral density and are assumed to be white and Gaussian. We restrict our attention to transmission schemes where information from the two nodes are simultaneously sent to the relay during a medium access phase followed by a broadcast phase where the relay broadcasts information to both the nodes. An upper bound on the capacity for the two phase protocol under a sum power constraint on the transmit power from all the nodes is obtained as a solution to a convex optimization problem. We show that a scheme using channel inversion with lattice decoding can obtain a rate a small constant 0:09 bits from the upper bound at high signal-to-noise ratios. Numerical results show that the proposed scheme can perform very close to the upper bound.

We consider the problem of broadcasting kldr samples of an independent identically distributed (i.i.d) Gaussian source to two users in n = lambdakldr uses of an AWGN channel. We develop a framework which shows a duality between a source-channel coding scheme for the case of lambda > 1 and that for lambda < 1. Using this duality, we derive a scheme for the case of lambda < 1, which is the dual of a scheme proposed by Reznic, Zamir and Feder (2006). This scheme, which provides the largest known achievable distortion region currently known, is also the same as that proposed by Prabhakaran et al (2005) specialized to the case of an i.i.d source with lambda < 1. We also provide an explanation for why this scheme performs well by first analyzing the performance of source-channel coding schemes in the presence of a signal-to- noise ratio mismatch.