A fast cell search algorithm for inter-cell asynchronous W-CDMA system using code hopping method

Abstract

We propose a new method for fast cell search for inter-cell asynchronous W-CDMA systems. This method utilizes a code hopping technique to distinguish each cell; that is, each cell is identified by a cell specific M-ary hopping code and this hopping code is used to hop some of binary code pairs. There are M+1 binary code pairs, one pair out of M+1 binary code pairs is used as a common binary code and the rest are used as the alphabets of the M-ary hopping codes. This proposal uses a subset of R-S codewords as M-ary hopping codes and uses extended Gold codes as binary codes. A mobile station searches the initial phase of the pilot PN sequence by using a common binary code matched filter, then identifies the M-ary hopping code using the M-ary parallel correlators. The mobile station can identify the hopping code by checking only k elements among the total hopping code of length L (where k is the maximum number of overlaps between any two hopping codes). This is a good property of the subset of R-S codewords. Also, a mobile station can be quickly synchronized with the pilot PN sequence even if there is no group identity coding concept. We present some simulation results and compare the properties of the proposed method with that of previously proposed methods.