Optimizing the Tradeoff Between Incumbent Protection and Secondary Transmissions with AFC

To allow unlicensed spectrum access and yet adequately protect incumbent wireless systems in the 6 GHz band, the Federal Communications Commission (FCC) requires an automated frequency coordination (AFC) procedure for standard power unlicensed (or secondary) transmitters to follow in order to gain channel access. Yet how to achieve a (near)-optimal tradeoff between incumbent protection and secondary transmitter (ST) channel and power allocation with AFC has not been adequately studied in the open literature. In this paper, we provide two AFC schemes that include a greedy ST channel and power allocation scheme, and a near-optimal balanced ST channel and power allocation scheme. For incumbent protection, we introduce the incumbent protection criterion (IPC) violation probability as a performance metric, which is expressed as a function of the ST to the primary (i.e., incumbent) receiver (PR) aggregate interference power and the antenna patterns. This analysis models the effects of channel uncertainty (e.g., channel shadowing), aggregate interference, and the issue of missing information of the PR antenna model in the AFC server database. Our results show that the proposed near-optimal AFC scheme provides a significantly better performance than the benchmark greedy allocation scheme. Furthermore, using a representative model to address the case of missing PR model information in the AFC servers may cause a significant degradation in the ST and PR performance tradeoff. Thus, this issue deserves a more thorough research and optimization. This result provides new insight into the AFC algorithm design and performance evaluation, and can support the optimization of spectrum sharing systems in the 6 GHz band and other unlicensed bands.