  Two-wave with diffuse power (TWDP) is one of the most promising models for
description of small-scale fading effects in emerging wireless networks.
However, its current statistical characterization has several fundamental
issues. Primarily, conventional TWDP parameterization is not in accordance with
the model's underlying physical mechanisms. In addition, available TWDP
expressions for PDF, CDF, and MGF are given either in integral or approximate
forms, or as mathematically untractable closed-form expressions. Consequently,
the existing TWDP statistical characterization does not allow accurate
evaluation of system performance (such as error and outage probability) in all
fading conditions for most modulation and diversity techniques. In this paper,
the existing statistical characterization of the TWDP fading model is improved
by overcoming some of the noticed issues. In this regard, physically justified
TWDP parameterization is proposed and used for further calculations.
Additionally, exact infinite-series PDF and CDF are introduced. Based on these
expressions, the exact MGF of the SNR is derived in form suitable for
mathematical manipulations. The applicability of the proposed MGF for
derivation of the exact average symbol error probability (ASEP) is demonstrated
with the example of M-ary PSK modulation. Therefore, in this paper, M-ary PSK
ASEP is derived as an explicit expression for the first time in the literature.
The derived expression is further simplified for large SNR values in order to
obtain a closed-form asymptotic ASEP, which is shown to be applicable for SNR >
20 dB. All proposed expressions are verified by Monte Carlo simulation in a
variety of TWDP fading conditions.
