Performance evaluation of a joint CDMA/NC-PRMA protocol for wireless multimedia communications

A joint code division multiple access and noncollision packet reservation m ultiple access (CDMA/NC-PRMA) technique is proposed and investigated as an uplink protocol for the third-generation (3G) mobile systems. Being the und erlying time division multiple access (TDMA) architecture of the CDMA trans missions, NC-PRMA enables the base station (BS) to have a centralized contr ol over the slot allocation policy. In order to reduce the multiple access interference (MAI) variation in a CDMA transmission, two different slot ass ignment schemes, referred to as load-balancing (LB) and power-grouping (PG) schemes, are proposed and evaluated. Simulation results show that consider able improvement can be achieved over the joint CDMA/PRMA scheme, in which the MAI variation is reduced by way of a dynamic permission probability for contending terminals. Especially when an imperfect power control mechanism is considered, the proposed PG assignment scheme achieves significant perf ormance advantages.