Adaptive Demodulation in Differentially Coherent Phase Systems: Design and Performance Analysis

TL;DR

This paper introduces an adaptive demodulation system for differentially coherent phase modulation schemes that does not require channel state information, improving spectral efficiency and robustness over fading channels.

Contribution

It presents the design and analysis of an adaptive demodulation scheme for M-DPSK and M-DAPSK, including optimal and near-optimal bit recovery methods without CSI.

Findings

Enhanced spectral efficiency over Rayleigh fading channels.

Effective bit reliability determination methods.

Rate-adaptive system without CSI requirement.

Abstract

Adaptive Demodulation (ADM) is a newly proposed rate-adaptive system which operates without requiring Channel State Information (CSI) at the transmitter (unlike adaptive modulation) by using adaptive decision region boundaries at the receiver and encoding the data with a rateless code. This paper addresses the design and performance of an ADM scheme for two common differentially coherent schemes: M-DPSK (M-ary Differential Phase Shift Keying) and M-DAPSK (M-ary Differential Amplitude and Phase Shift Keying) operating over AWGN and Rayleigh fading channels. The optimal method for determining the most reliable bits for a given differential detection scheme is presented. In addition, simple (near-optimal) implementations are provided for recovering the most reliable bits from a received pair of differentially encoded symbols for systems using 16-DPSK and 16- DAPSK. The new receivers offer the advantages of a rate-adaptive system, without requiring CSI at the transmitter and a coherent phase reference at the receiver. Bit error analysis for the ADM system in both cases is presented along with numerical results of the spectral efficiency for the rate-adaptive systems operating over a Rayleigh fading channel.