RAPID ACQUISITION ALGORITHMS FOR SYNCHRONIZATION OF BURSTY TRANSMISSIONS IN CDMA MICROCELLULAR AND PERSONAL WIRELESS SYSTEMS

Two rapid synchronization acquisition algorithms applicable to spread spectrum links of code division multiple access (CDMA) personal commun ication systems are proposed and evaluated. The algorithms operate wit hin a self-referencing matched filter synchronizer structure, and are particularly useful in reducing synchronization overhead on links desi gned to carry packet-type services. The main distinguishing characteri stic between the two schemes is that one uses hard-decision while the other uses soft-decision detection. The proposed schemes are especiall y applicable to reverse link transmissions in quasisynchronous CDMA sy stems in which timing at portable terminals is established via pilot a nd synchronization signals received on respective code-division channe ls from the home base. If discontinuous (bursty) transmission is used on reverse links, the acquisition process is required for each transmi ssion burst because of the propagation time uncertainty. Analysis of t he algorithms on additive white Gaussian noise (AWGN) and Rayleigh fad ing channels reveals that their performance depends significantly on t he choice of synchronizer parameters and the average de-spread signal- to-interference ratio (SIR). When this choice is proper, acquisition o ver a single preamble of relatively short duration can be achieved wit h high probability. The soft-decision scheme introduces a performance advantage of between 4-9 dB depending on the length of the synchronizi ng preamble.