Trellis coded 2×MPSK modulation with transmit diversity

Abstract

Alamouti's diversity technique can achieve the maximum possible diversity order with a simple decoding algorithm. This paper combines this technique with trellis coded 2 × MPSK modulation to provide an additional coding gain on top of the diversity gain. The performance over Rayleigh and Rician fading channels is analyzed. It is shown that on fast Rayleigh fading channels the design of optimum trellis codes is guided by maximizing the minimum multidimensional symbol-wise Hamming distance δ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</inf> and the product of the branch distances d <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</inf> along the path corresponding to δ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</inf> . On slow Rayleigh fading channels, the design criteria is equivalent to the trellis code design for AWGN channels which is guided by maximizing the free Euclidean distance. The design criteria are applied to construct optimum trellis coded 2×4PSK and 2×8PSK in conjunction with transmit diversity. The performance of these codes on Rayleigh fading channels is evaluated through computer simulations.