Modulation and Coding Classification for Adaptive Power Control in 5G Cognitive Communications

A key concept suggested for 5G networks is spectrum sharing within the context of Cognitive Communications (CC). This efficient spectrum usage has been explored intensively the last years. In this paper, a mechanism is proposed to allow a cognitive user, also called Secondary User (SU), to access the frequency band of a Primary User (PU) operating based on an Adaptive Coding and Modulation (ACM) protocol. The Spectrum Sensing (SS) technique used considers Higher Order Statistical (HOS) features of the signal and log-likelihood ratios (LLRs) of the code syndromes in order to constantly monitor the modulation and coding scheme (MODCOD) of the PU respectively. Once the Modulation and Coding Classification (MCC) is completed, a Power Control (PC) scheme is enabled. The SU can attempt to access the frequency band of the PU and increase its transmitting power until it causes a change of the PU´s transmission scheme due to interference. When the SU detects the change of the PU´s MODCOD, then it reduces its transmitting power to a lower level so as to regulate the induced interference. The proposed blind Adaptive Power Control (APC) algorithm converges without any interference channel information to the aforementioned interference limit and guarantees the preservation of the PU link throughput.