Design of an all-digital receiver for narrowband continuous-phase asynchronous CDMA systems

The authors analyze a full-digital receiver for band-limited spread-spectrum signals in a radio communication network employing asynchronous code-division multiplexing and constant-envelope continuous-phase modulation (CPM). They present a detailed analysis of the code synchronization strategy, both in the acquisition and in the tracking mode. They also consider the issue of chip timing recovery, discussing first the impact of chip timing errors on code acquisition, and then evaluating the performance of three different code tracking loops. In particular, the acquisition performance is assessed in terms of false alarm and miss probabilities as well as average lock-in time, while in the analysis of the tracking behavior the root mean square chip timing jitter is assumed as the quality factor. A special subset of CPM, known as generalized minimum shift keying (GenMSK), encompassing Gaussian-filtered MSK modulation as well as traditional MSK, has been emphasized