Power control and adaptive data transmission for SC/MC-CDMA systems

The capacity of CDMA (Code-Division Multiple Access) systems is limited by other-user interference because all users in a cell share the same frequency band and transmit at the same time. To improve system capacity, we propose a predictive power control scheme for SC/MC (Single Carrier/Multi Carrier)-CDMA systems and introduce adaptive band-selection (ABS) data transmission for MC-CDMA systems.; In CDMA systems, the near-far effect and the time-varying fading cause variation in the received power at the base station, causing capacity loss. To compensate for the near-far effect and fading while maintaining reliable QoS (Quality of Service), tight and accurate power control is required in SC/MC-CDMA systems. In this work, an upper bound for the reference SNR setting is derived to avoid potential instability in the power control operation and an efficient power control scheme with a simple predictive algorithm is proposed to improve system capacity in CDMA systems. We discuss the features of the proposed scheme and show that the performance of the proposed scheme outperforms those of some existing power control schemes.; For MC-CDMA systems where a number of subcarriers are used for high-rate transmission, an adaptive band-selection (ABS) scheme is introduced to improve system capacity. In ABS MC-CDMA systems, instead of using all sub-carriers, mobile stations transmit signals only through the selected frequency bands based on band-selection coefficients from the base station to avoid large channel attenuation. By using the adaptive band-selection scheme, ABS MC-CDMA systems accommodate more users than MC-CDMA systems that use all frequency bands for data transmission while transmitting the same amount data, using the same bandwidth, and consuming the same transmitted power as MC-CDMA systems. We show that the ABS scheme provides a significant capacity improvement compared to MC-CDMA systems.