On-off keying assisted acquisition scheme for burst mode DS/SS packet radio

Code Division Multiple Access (CDMA) is a promising technology for future digital cellular and personal communications. To despread the pseudo noise (PN) code and thus understanding the message sent, synchronization (acquisition fluid tracking) is necessary in priori. As a matter of fact, the throughput of a packet mode CDMA system is directly related to the performance of its frame synchronization algorithm. In this paper, we propose a new acquisition technique for packet mode CDMA operating in the Rayleigh fading channel. The technique is based on on-off keying (during the preamble section) followed by a Markov chain search. The length of the preamble is a design parameter and the performance measure is the throughput of packets. We have tested our new scheme on a flat fading and a selective fading channel, based on a fixed blocking probability criterion. Specifically for the latter case, we adopt a RAKE receiver to combat the multipath effect, and introduce a windowing technique which we found effective in overcoming the temporary increase in noise level caused by partial correlation of the PN sequence used. Results in both cases show that the proposed on-off keying technique is more efficient than many others in the literature such as the coincidence detector or simple Markov search