On the design of spectrally overlaid multiple-symbol-rate multicarrier CDMA systems supporting multirate services

Two types of spectrally overlaid multiple-symbol-rate (MSR) asynchronous multicarrier code division multiple access (MC-CDMA) systems are proposed. One type of systems has constant spreading gain (CSG) and the other has variable spreading gain (VSG) for different services; both systems have different symbol rates at each subcarrier for different services. Two possible configurations of CSG systems are also proposed. An adaptive power control is proposed to maintain the link quality and improve the system capacity. The multiple access interference, and hence system capacity, for each type of MSR MC-CDMA system is investigated. From the numerical results obtained, it can be concluded that the MSR MC-CDMA systems with VSG and with CSG configuration 2 can both obtain much steadier performance and system capacity than the system with CSG configuration 1.