Cross-Layer Scheduling for OFDMA-Based Cognitive Radio Systems With Delay and Security Constraints

This paper considers the resource allocation problem in an orthogonal-frequency-division-multiple-access (OFDMA)-based cognitive radio (CR) network, where the CR base station adopts a full-overlay scheme to transmit both private and open information to multiple users with average delay and power constraints. A stochastic optimization problem is formulated to develop flow control and radio resource allocation to maximize the long-term system throughput of open and private information in a CR system and ensure the stability of the primary system. The corresponding optimal condition for employing full overlay is derived in the context of concurrent transmission of open and private information. An online resource allocation scheme is designed to adapt the transmission of open and private information based on monitoring the status of the primary system, as well as the channel and queue states in the CR network. The scheme is proven to be asymptotically optimal in solving the stochastic optimization problem without knowing any statistical information. Simulations are provided to verify the analytical results and efficiency of the scheme.