Low Complexity Near Optimum Multiple Symbol Differential Detection of DAPSK Based on Iterative Amplitude/Phase Processing
Differentially encoded and noncoherently detected transceivers exhibit low complexity since they dispense with a complex channel estimation. In pursuit of high bandwidth efficiency, differential amplitude/phase (A/P) shift keying (DAPSK) was devised using constellations of multiple concentric rings. To increase resilience against the typical high Doppler induced performance degradation of DAPSK and/or to enhance the maximum achievable error free transmission rate for DAPSK modulated systems, multiple symbol differential detection (MSDD) may be invoked. However, the complexity of the maximum a posteriori (MAP) MSDD exponentially increases with the detection window size and hence may become excessive upon increasing the window size, particularly in the context of an iterative detection aided channel coded system. To circumvent this excessive complexity, we conceive a decomposed two stage iterative A/P detection framework, where the challenge of having a nonconstant modulus constellation is tackled with the aid of a specifically designed information exchange between the independent A/P detection stages, thus allowing the incorporation of reduced complexity sphere detection (SD) Consequently, a near MAP MSDD performance can be achieved at significantly reduced complexity, which may be five orders of magnitude lower than that of the traditional MAP MSDD in the 16 DAPSK scenario that was considered.
IEEE Transactions on Vehicular Technology