Serially Concatenated Space-Time Coded Continuous Phase Modulation

Doktorsavhandling, 2006

Certain problems associated with reliable digital wireless communication over a frequency-flat slow Rayleigh fading channel are treated, when the transmitted signal is modulated using continuous phase modulation (CPM) due to the desirable properties of CPM. The primary focus of attention is on detection strategies, and the thesis proposes iterative detection algorithms for CPM signals transmitted over frequency-flat slow Rayleigh fading channels. First, detection of space-time coded CPM (STC-CPM) signals is investigated, and a symbol-by-symbol iterative detector with an optimum front-end is derived. According to numerical examples, the proposed detector performs around 1 dB away from the no-fading scenario suggesting its effectiveness to mitigate adverse effects of fading. The detection algorithms are later extended to multiuser CPM communication, where the transmitter multiplexes several users into the same frequency band. The proposed multiuser detector performs very close to a single user detector when each user has more than one receiving antenna. Also, when the ratio between the number of users and the number of receiving antennas decreases, the performance difference between the single user system and the multiuser system becomes small. The study is further extended to propose new detection procedures for serially concatenated CPM (SCCPM) when the receiver has no information of the channel state information (CSI). The proposed receiver adds a separate low-complexity module to the iterative SCCPM detector, to systematically handle the detection process using the sum-product algorithm (SPA) running on a factor graph (FG). Two algorithms based on SPA are proposed, for Wiener phase noise (PN), and flat-fading.