Performance of Orthogonal Uplink Multiple Access for Beyond 3G/4G Systems

The uplink access in the current 3G systems optimized primarily for voice applications is based on CDMA technology. The uplink transmissions in CDMA are non-orthogonal due to different propagation delays for signals received from different mobile station in the cell. Therefore, the users experience large amount of intra-cell interference in addition to the inter-cell interference. This limits the achievable data rates and capacity in a CDMA uplink In this paper, we explore potential capacity and performance benefits due to orthogonal multiple access schemes such as TDMA OFDMA and IFDMA for future beyond 3G/4G wireless systems. An orthogonal approach eliminates intra-cell interference and allows users to transmit at very high data rates without tight requirement on power control resulting in overall higher spectral efficiency.