On the Distortion Exponent of Some Layered Transmission Schemes
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We consider the problem of joint source-channel coding for transmitting K samples of a complex Gaussian source over T = bK uses of a quasi-static multiple input multiple output (MIMO) channel with M transmit and N receive antennas. The performance measure of interest is the rate of decay of the expected mean squared error with the signal-to-noise ratio (SNR), called the distortion exponent. We first show that using a broadcast strategy as in , but with a different power and rate allocation policy, the optimal distortion exponent can be achieved for bandwidth efficiencies, O ≤ b < (|N - M| + 1)/min(M, N). This is the first time the optimal exponent for 1/min(M, N) < b < (| N - M| +1)/ min(M, N) is characterized. We then propose a digital layered transmission scheme that uses both time layering and superposition. This includes many known schemes in [1, 2] as special cases. The proposed scheme is at least as good as the currently best known schemes for the entire range of bandwidth efficiencies, whereas at least for some M , N, and b, it is strictly better than the currently best known schemes.
author list (cited authors)
Bhattad, K., Narayan, K., & Caire, G.