BURST COHERENT DEMODULATION WITH COMBINED SYMBOL TIMING, FREQUENCY OFFSET ESTIMATION, AND DIVERSITY SELECTION

A low-overhead burst coherent demodulation method that jointly estimates symbol timing and carrier frequency offset and then performs diversity selection is studied. This method is suitable for applications that require simultaneous estimation of carrier phase, frequency offset, and symbol timing in a multipath fading (possibly frequency-selective) environment such as TDMA portable radio communications. It coherently demodulates individual bursts of TDMA symbols by operating solely on random data within the burst without requiring training sequences. Its performance is robust against frequency offset between transmitter and receiver, thereby eliminating the need for a highly stable frequency reference. The performance of this demodulation method in a fading channel can be further improved by employing a diversity selection technique based on a quality measure derived as part of the joint timing/frequency offset estimation process. It is found that this diversity selection technique is more effective in mitigating frequency selective fading than a conventional technique based on power and that it performs almost as well as diversity selection after channel decoding.