Performance Evaluation of Space–Time Block Codes Over Keyhole Weibull Fading Channels

Abstract

It is well known that degenerate channel phenomena known as keyholes may significantly reduce the capacity of multiple-input and multiple-output (mimo) channels. Keyhole mimo channels were predicted theoretically and also observed experimentally. In this paper, a novel method of analyzing the performance of keyhole mimo channels is proposed. The proposed method is based on the assumption that the received signal at the keyhole encompasses an arbitrary number of multipath components and the propagation environment is such that the resulting signal is observed as a non-linear function of the modulus of the sum of these components. Based on this assumption, we initially introduce the double Weibull fading model, constructed by the product of two independent Weibull distributed fading envelopes. Closed-form expressions for its moments-generating function, probability density function, cumulative distribution function, and moments are also derived. Based on these formulas, we analytically evaluate the performance of a 2 × 2 mimo space---time block-coding (stbc) system, where performance metrics such as the average symbol error probability for several modulation schemes, outage probability, amount of fading and ergodic capacity are given in closed form. Various performance evaluation results are presented in order to verify the proposed analysis.