Cognitive Point-to-Point Network with Limited Feedback

In this chapter, we study an opportunistic spectrum sharing scheme in a point-to-point network, where both the primary user and secondary user are power-rate adaptive systems with a few bits of quantized channel feedback from the receivers. The secondary user detects the spectrum opportunities by overhearing the primary feedback and receiving the secondary feedback, and then adapts its power and rate accordingly. The secondary quantization codebook is designed offline by maximizing the secondary average throughput while not causing noticeable degradation to the primary throughput. The secondary quantization and transmission schemes are discussed in three cases when different primary interference information is available at the secondary receiver. Numerical results show that the secondary throughput is greatly improved by the introduction of even 1-bit feedback. Moreover, the secondary throughput increases with more secondary feedback bits or more primary side information.