Spectrum sharing in DS-CDMA/OFDM wireless mobile networks

In this chapter, we define DS-CDMA/OFDM spectrum sharing systems and investigate the impact of the primary service communication activity as well as other system parameters on the interference level at the secondary service receiver. The achieved capacity of the secondary service is directly related to the interference level at the secondary service receiver as well as the secondary service adopted sub-channel selection policy. The achievable capacity of the secondary service in such systems is obtained under different sub-channel selection policies in fading environments. Two general sub-channel selection policies are studied in this chapter: uniform sub-channel selection and non-uniform sub-channel selection. Uniform sub-channel selection fits into the cases where a priori knowledge on sub-channels state information is not available at the secondary transmitter. For cases with available a priori knowledge on sub-channels state information, a variety of non-uniform sub-channel selection policies are studied. We then present results on the scaling law of the opportunistic spectrum sharing in DS-CDMA/OFDM systems with multiple users. We provide numerical results to compare different sub-channel selection policies