Spectrum Sharing with Limited Channel Feedback

In this paper, an underlay spectrum sharing scheme is proposed where both primary and secondary users are discrete power-rate adaptive systems with limited feedback from receivers. By receiving secondary and overhearing primary quantized channel quality information from the secondary receiver and primary receiver, respectively, the secondary transmitter adapts its resource allocation to the current channel quality by selecting a proper power-rate pair from a pre-designed secondary quantization codebook. The secondary quantization codebook is designed to maximize the secondary average rate subject to the primary rate loss constraint and the average secondary transmit power constraint, which is discussed in three cases when different amount of side information of the primary codebook and the cross interference link are available at the secondary receiver side. Differential Evolution algorithm is employed to provide the global optimal solutions to the proposed secondary quantization codebook optimization problems. Numerical results show that, by introducing the secondary feedback, the secondary throughput is greatly improved. Furthermore, more secondary feedback bits or more primary side information result in better secondary performance.