Recently cognitive radio based dynamic spectrum access techniques have been anticipated to solve the problem of spectrum scarcity and spectrum under-utilization. With multiple cognitive radio network operating in a given region, a network has to mitigate the harmful effects of interference from licensed users and other cognitive radio networks. To this end we propose a self co-existence protocol for multi-channel cognitive radio based ad-hoc networks which guarantees a certain grade of QoS to the secondary users. The co-existence is provided on per channel basis by sharing the channel among multiple cognitive radio networks. Simulation results are drawn to show the performance of the protocol.