Performance of multi-code CDMA wireless personal communications networks

Multi-code CDMA (MC-CDMA) was proposed as a technique to provide variable rate services with different quality requirements by varying the number of codes assigned to a user. When all other users are idle, a single user is able to use the full bit rate available in that cell. The system retains the CDMA advantage in combating multipath and does not require significant modifications of the radio frequency (RF) circuitry. It can evolve from commercial digital cellular systems based on IS-95. The paper presents preliminary results on the performance of MC-CDMA. The authors consider both voice and data users. Voice users are delay sensitive whereas the authors assume that data users can tolerate delay but require a lower bit error rate. They evaluate the instantaneous capacity as well as the average capacity which accounts for user activity factors and the control channel overhead needed for inactive users to maintain synchronization. Unrestricted access to the channel is given to voice bursts. Data bursts are required to wait until they are permitted to transmit. The authors show that the multi-code capability significantly improves the delay throughput performance of data users.