An improvement on opportunistic spectrum access MAC protocol

Radio spectrum resource is a finite resource and of fundamental importance for wireless communication. But the utilization of the spectrum became unbalanced, some spectrum is crowd with users and some is inefficiently used. The concept of cognitive radio is a good solution for this problem. One of the tasks to realize this technology is to design an efficient MAC protocol. OSA-MAC is one of the practical MAC protocol used for opportunistic spectrum access in cognitive wireless network. However, in this protocol after contention for channel, secondary users still have to use back off mechanism when transmitting data. As a result, the throughput and the channel utilization is low in OSA-MAC. We make some improvement on OSA-MAC protocol. In our protocol, the transmission process is divided into time slots. New competition mechanism is used for each secondary user who has data to send to access the channel. Using this mechanism, collision is avoided when transmission and channel utilization is increased. In the end of the paper, we make some analysis and comparison between the two protocols.