Hybrid multiple access coding with adaptive modulation

Abstract

Multiple access communication techniques havedirect impact on bandwidth and power efficiencies for future wireless networks. In this paper, a new multiple access scheme combining both adaptive modulation and multiple access coding is proposed to provide an efficient and robust method of combining signals from multiple users over fading channels. Hybrid Multiple Access Coding with Adaptive Modulation (H-MACwAM) allows independent users to share a common link without subdivision in time, frequency, or code. Users adapt the phase and power of their signal independently according to their respective channels to ensure that their combined transmission belongs a predesigned composite constellation known at the receiver. The size and minimum distance of this constellation is varied using multiple access coding. The scheme offers higher rates than those available with conventional multiple access coding or superposition modulation. It was shown that large numbers of users can share a common link and achieve higher than unity rate without any degradation in BER performance.