Design of cyclically permutable codes for PN code acquisition in WCDMA TDD mode

Abstract

The acquisition problem in the wideband-CDMA (WCDMA) system proposed by the 3rd Generation Partnership Project (3GPP) to the ITU consists of determining both the timing and the identity of the particular scrambling code being received. A fast search mechanism to tackle this problem, based on cyclically permutable (CP) codes is proposed by Sriram and Hosur (see IEEE Inter. Conf. on Communications (ICC), June 1999) for the frequency-division-duplex (FDD) component of WCDMA. The CP codes for the FDD mode of WCDMA are not optimum for the time-division duplex (TDD) mode and have to be redesigned. In this paper we design optimum CP codes for the TDD mode. The new CP codes can also identify both frame timing and long code group information using only one synchronization slot. Thus, they can be used for GSM to WCDMA TDD mode handover. The new CP codes have been incorporated into the 3GPP WCDMA TDD standard.