Opportunistic Spectrum Access to 3G Wireless CDMA Networks for Cognitive Radio

In this paper, we deal with the scenario that a single secondary user attempts to opportunistically access the 3G Wireless CDMA Networks licensed to primary users. Different from the former works merely consider the channel as two state Markov process,, we expand the channel's availability into a multiple-state Markov process according to the transmission power of SU. We propose a cyclical, but not periodic sensing and transmission strategy, which can be divided into two steps: 1) the SU acquires the estimation about how many PUs are in this networks during sensing period; 2) Based on the estimation, the SU determine how much transmission power and how long time period it can transmit? Further, we derive the optimal transmission strategy profile which consist of different transmission power and time corresponding to different number of PUs in service. Finally, the simulation results indicates that our optimal strategy is superior to the empirical strategy such as the maximum power transmission strategy and the maximum time transmission strategy, and achieve the highest throughput of SU in the long run.