A Joint Subcarrier Power Allocation and Interference Avoidance Code Assignment Strategy for Multi-Rate MC-DS-CDMA with TF-Domain Spreading

Abstract

In the multi-rate multi-carrier direct sequence code division multiple access (MC-DS-CDMA) system, how to allocate subcarrier power to improve the received signal quality, control the multiple access interference (MAI) at an acceptable level, and simultaneously maintain high call admission is an interesting and challenging issue. In this paper, we propose a joint subcarrier power allocation and code assignment scheme for the synchronous multi-rate MC-DS-CDMA system with time-and frequency-domain spreading. The proposed scheme consists of a subcarrier power allocation method to optimize the received signal power as well as an interference avoidance code assignment strategy to eliminate MAI. For this purpose, we define a performance metric called the MAI coefficient to quantitatively predict the incurred MAI before assigning a spreading code. The simulation results show that the proposed joint subcarrier power allocation and code assignment strategy not only can reach a better received signal quality but also achieve high call admission rate.