Wireless backhaul has emerged as a suitable and flexible alternative to wired backhaul, however, it is not as reliable as its wired counterpart. This paper presents for the first time a comprehensive model including a heterogeneous underlay cognitive network with small cells also acting as multiple secondary users, multiple primary users and unreliable wireless backhaul. In this system, a macro-base station connects to multiple secondary transmitters via wireless backhaul links. In addition, multiple secondary transmitters send information to a secondary receiver by sharing the same spectrum with multiple primary users. A Bernoulli process is adopted to model the backhaul reliability. A selection combining protocol is used at the secondary receiver side to maximize the received signal-to-noise ratio. We investigate the impact of the number of secondary transmitters, the number of primary users as well as the backhaul reliability on the system performance in Rayleigh fading channels. Two key constraints are considered on the system performance, namely, 1) maximum transmit power at the secondary transmitters. 2) peak interference power at the primary users caused by secondary transmitters. Closedform expressions for outage probability, ergodic capacity and symbol error rate and the asymptotic expressions for outage probability and symbol error rate are derived. Moreover, closedform expressions are also applicable to non-cooperative scenarios.
- Cognitive Radio
- Wireless Backhaul