Improved Resource Awareness Channel for Cognitive Radio

Cognitive radio has been considered as an efficient approach to opportunistic spectrum sharing between primary users and cognitive radio users. The most important challenge of a cognitive radio system is to identify the primary users over a wide rage of the spectrum. Considering that the existing sensing techniques would be time-consuming and wasteful of power, Holland etc. give the concept of Resource Awareness Channel (RAC) - a fixed frequency random access channel on which all radios periodically transmit information about which resources are being used by the data that are receiving. In this paper, we propose an improvement on the scheme, for the radio´s transmission on the RAC, we use five different channel access protocols for the control field. Meanwhile, the transmitter-based code assignment is applied for spreading the data portion of each packet based on the idea of joint detection. The success probability for a radio trying to transmit on the RAC is analyzed and the effects on the performance for the transmission power, the period of radio´s transmission on the RAC, and the ratio of data signal lengths in bits for a transmission packet are evaluated. Also, the throughput per packet length is deduced and simulated for different channel access protocols and joint detection capacity.