PERFORMANCE OF OPPORTUNISTIC SPECTRUM ACCESS WITH SENSING ERROR IN COGNITIVE RADIO AD HOC NETWORKS

Sensing in opportunistic spectrum access (OSA) has a responsibility to detect the available channel by performing binary hypothesis as busy or idle states. If channel is busy, secondary user (SU) cannot access and refrain to transmit data. SU is allowed to access when primary user (PU) does not use it (idle states). However,
channel is sensed on imperfect communication link. Fading, noise and any obstacles existed can cause sensing errors in PU signal detection. False alarm detects idle states as a busy channel while miss-identification detects busy states as an idle channel. False detection makes SU refrain to transmit data and reduces number of bits transmitted. On the other hand, miss-identification causes SU collide to PU
transmission. This paper study the performance of OSA based on the greedy approach with sensing errors by the restriction of maximum collision probability allowed (collision threshold) by PU network. The throughput of SU and spectrum capacity metric is used to evaluate OSA performance and make comparisons to those ones without sensing error as function of number of slot based on the greedy approach. The relations between throughput and signal to noise ratio (SNR) with different collision probability as well as false detection with different SNR are presented. According to the obtained results show that CR users can gain the reward from the previous slot for both of with and without sensing errors. It is indicated by
the throughput improvement as slot number increases. However, sensing on imperfect channel with sensing errors can degrade the throughput performance. Moreover, the throughput of SUs and spectrum capacity improve by increasing maximum collision probability allowed by PU network as well. Due to frequent collision with PU, the throughput of SU and spectrum capacity decreases at certain
value of collision threshold. Computer simulation is used to evaluate and validate these works.