Multisymbol with memory noncoherent detection of CPFSK

Abstract

Multisymbol receiver is an effective method to demodulate noncoherent sequences. However it is necessary to correlate an important number of symbols in a noncoherent scheme to reach the performances carried out by optimal coherent Maximum a Posteriori (MAP) detectors such as BCJR. In this paper, we propose an advanced multisymbol receiver by adding some memory to the decision process. The advanced receiver, called here Multisymbol With Memory (MWM) takes into account the cumulative phase information unlike multisymbol algorithm and thus it can be seen as a truncated BCJR. An exact mathematical derivation is performed for this truncated BCJR. Then an implementation of the MWM detector applied to a continuous phase frequency shift keying modulation is presented. Finally an asymptotic analysis is carried out based on the achievable Symmetric Mutual Information rate. The proposed system exhibits good performances compared to classical multisymbol receivers at the expense of increased complexity and can approach the performances of a coherent receiver.

Precoding for Non-Coherent Detection of Continuous Phase Modulations

“…The transition {δ k →δ k+1 } corresponds to the emitted symbol u k . Following [10], the conditional probability is written as follows…”

“…Transmission channels undergoing unknown phase shift are called non-coherent (by opposition to coherent channel). Detection methods for CPM adapted to both channels were studied in [5], [10], [13]. It appears that their associated receiver offers different behaviour regarding asymptotic performance illustrated by extrinsic information transfer (EXIT) charts [15].…”

On sparse graph coding for coherent and noncoherent demodulation

“…2) Multisymbol With Memory receiver: The multisymbol detector has been recently improved in [10] by including some memory within the decoding process (It has been originally proposed for CPFSK, but can be extended to other modulation schemes). MWM detector is based on a trellis state representation allowing to use a modified version of the BCJR algorithm to compute the conditional probability p(u k+N −1 |r Ns−1 0 ).…”

“…MWM [10] is strictly equivalent to BCJR in coherent channel but it can also demodulate in noncoherent channel by getting the best from multisymbol. Like BCJR, MWM is a trellis based detector.…”