Semi-Random Access in Small Cells With User Priority

In a small cell system, centralized control can be a problem for the visiting users (VUs) who randomly enter and leave with high mobility. In this letter, we propose a semi-random access scheme to achieve the coexistence of users with different control modes: centralized control for local users (LUs) and decentralized control for VUs. We adopt randomized power control and successive interference cancellation techniques to optimize the system within a quality of service (QoS) constraint of LUs. Simulation results show that most VU throughput gain can be achieved at the cost of marginal LUs' outage performance loss. The two types of users can well coexist under a proper QoS constraint, bringing about increased total throughput.