Multichannel Broadcast Via Channel Hopping in Cognitive Radio Networks

Broadcast is a mandatory service for wireless communications, through which the signals or contents are usually propagated as broadcasts to groups of users that subscribe to the service. However, in cognitive radio networks where secondary users (SUs) opportunistically access the licensed spectrum bands, the broadcast delivery via a single broadcast channel cannot be reliably guaranteed when the broadcast channel is reclaimed by a primary user (PU, or licensed user) that has a higher priority of accessing the spectrum or when an SU moves into a region where PU transmissions are active. As a result, broadcast failures occur between the base station (BS) and the SU. To address this problem, the BS has to broadcast on more than one channel to avoid colliding with PUs and ensure that all users can correctly receive the broadcasted content. In this paper, we propose a multichannel broadcast protocol, i.e., Mc-Broadcast, that enables a network BS to broadcast over multiple channels via a channel hopping (CH) process such that the broadcasts can be successfully delivered to SUs. The CH sequence for Mc-Broadcast is generated using a mathematical construct called Langford pairing, which allows the BS to significantly reduce the broadcast latency and given a customized number of broadcast channels. Our analytical and simulation results show that the proposed method reduces the broadcast latency, and it is robust to the broadcast failure caused by PU transmissions under various network conditions.