A generalization of differentially encoded transmit time diversity and its blind demodulation techniques

摘要

In order to improve both the bit error rate (BER) performance and the tracking capability on time-varying channels, this paper proposes a generalized version of differentially encoded transmit time diversity and associated blind demodulation techniques. At first, this paper assumes that the demodulator employs maximum-likelihood sequence estimation (MLSE) with per-survivor processing (PSP), and PSP-MLSE estimates the channel impulse response by means of the normal equation, i.e., the deterministic Wiener-Hopf equations. This paper then derives the requirement for the transmitted sequence according to the PSP-MLSE's demodulation constraints. Next, taking into account these requirements, this paper proposes a differentially encoded transmit time diversity scheme employing a different mapping for each transmit antenna. Computer simulations confirm that the proposed scheme has excellent tracking capability for fast time-varying fading without a reference sequence.