Spread spectrum-based coordination design for spectrum-agile wireless ad hoc networks

Cognitive radios (CRs) have been proposed to improve spectrum utilization by enabling opportunistic and dynamic spectrum access for unlicensed users. To enable efficient CR communications, a reliable control channel (CC) for exchanging control information is needed. In this paper, a direct sequence spread spectrum (DSSS)-based underlay CC design for distributed coordination in CR networks (CRNs) is proposed. The proposed design provides immunity to licensed primary radio (PR) interference (reliable communication), low transmission power (PR users’ protection) and predefined-required transmission rate and range (network connectivity). The Proposed design ensures that both narrow-band data and wide-band control transmissions can be simultaneously proceeded while protecting the performance of PR users. To ensure reliable CR control communications, a closed-form expression is derived for the minimum required transmission power for control packet transmissions such that required transmission range and rate are achieved. Based on the derived expression, the maximum allowable transmission power for CR data transmissions is computed such that an enforced power mask constrain over the PR channels is not violated. Simulation results indicate that the proposed CC design enables efficient CR communications without relying on the existence of a dedicated CC.