Adaptive algorithm for obtaining in-phase (I) and quadrature-phase (Q) pseudo-noise (PN) sequences in CDMA systems

In the CDMA wireless systems, the forward pilot channel is spread in quadrature spreading. The quadrature spreading is a spreading sequence of length 215 pseudo-noise (PN) chips. For spreading rate (SR) 1, each PN chip is about 0.813mus. This sequence is called the pilot PN sequence and consist of a pair of PN sequences called the In-phase ( I) and quadrature-phase (Q) sequences generated by a Linear Feedback Shift Register (LFSR). This pair of PN sequences is used to spread the forward and the reverse CDMA Channel. During the forward Pilot and Sync channel processing, the mobile station acquires and synchronizes to the CDMA system while it is in the initialization state. In the current CDMA systems, to obtain I and Q Pilot PN sequences for time alignment, a zero is inserted in the LFSR sequences after 14 consecutive ""0"" outputs. When the mobile station power is turned on, the MS synchronizes with the base station timing using Global Positioning System (GPS) timing reference on the Sync channel and the pilot channel. In this thesis, we propose an algorithm that reduces the computation time to find the I and Q Pilot PN sequences. We begin by developing evolutionary computation models to find the initial values (IV) and polynomial feedback coefficients (PFC) for the maximal-length LFSR that is used to generate the CDMA PN sequences. Next, we propose an adaptive algorithm for computing the I and Q pilot PN sequences in the CDMA systems that can result in a shorter synchronization time between the base station and mobile station. To study the performance of the proposed algorithm, many simulation experiments are carried out under noisy and non-noisy channel conditions. Our simulation test results show that the proposed algorithms cuts the synchronization time by a minimum of 32753 PN chips without degrading the channel performance, and with less computational complexity when compared to the currently used methods.