We propose a MAC for wireless ad hoc cognitive radio networks where secondary users employ cooperative spectrum sensing to mitigate the degradation of the channel between primary transmitter and secondary users. The sensing reports and fused decisions are transmitted based on random access of CSMA/CA and 802.11e EDCA on the control channel, whose access scheme determines the overall achievable throughput among the multi-channels. We propose several schemes and derive the upper bound of overall throughput. The saturation problem is also studied to address the optimization of the channel selection and the trade-off between cooperative sensing gain and channel reuse efficiency.