Adaptive Resource Allocation for Spectral Efficiency Maximization in Uplink WCDMA

In this contribution we examine the joint optimization of the outer-loop power control (OLPC) and spreading factor in order to improve the spectral efficiency in the uplink of wideband code-division multiple-access (WCDMA) systems, in the presence of additive white Gaussian noise (AWGN) and multiple access interference (MAI), and while maintaining an average transmit power constraint. The variable spreading factors (VSF) and the target signal-to-noise ratio (SNR) -set by the OLPC - are adapted according to the interference-to-noise ratio (INR) and the target instantaneous bit error rate (BER). We use the standardized orthogonal VSF (OVSF) codes used for the uplink dedicated physical data channel (UL-DPDCH) and evaluate the performance over Nakagami flat fading channels. It is shown that the proposed scheme improves the spectral efficiency compared to systems that use constant spreading factor and OLPC, for a wide range of practical SNRs and signal-to-interference ratios (SIRs)