A fair, efficient, and exchangeable channelization code assignment scheme for IMT-2000

High data-rate and variable data-rate services are important features in third-generation mobile communication systems. International Mobile Telecommunication-2000 (IMT-2000) in the International Telecommunication Union (ITU) sets up the air interface objectives to support wideband data services as high as 2 Mb/s for limited coverage and mobility, and 144 kb/s to 384 kb/s for full coverage and mobility, with the same quality as in a fixed telecommunication network. Direct sequence code division multiple access (DS-CDMA) is widely investigated and accepted as the wireless access technique of IMT-2000 for its high spectrum efficiency, high flexibility, and high availability in offering different and time-varying data-rate services. No frequency planning among cells and no orthogonality coordination among users in the cell also make the DS-CDMA suitable for system implementation despite the need for rigorous transmit power control (TPC). In this paper, the channel assignment scheme of the forward link is investigated since the channelization codes are a scarce resource in the wireless environment. The FEX (Fair Efficient and eXchangeable) scheme is proposed to efficiently assign the orthogonal codes and to reduce the blocking rate of the system. The simulation result shows that the FEX scheme achieves its best performance for the system under medium/high data-rate requests.