The population declining AFSA based identification of active users for cooperative cognitive radio networks with DS-UWB based control channel

Cognitive radio (CR) has been considered as a promising technology to alleviate the spectrum scarcity problem and the spatial diversity gain can be obtained through cooperation among multiple secondary users (SUs). However, the multiuser control channel for exchanging control information among them becomes saturated, due to a significant number of cooperating SUs existing in this cooperative cognitive radio network (CRN). In this paper, the DS-UWB based control channel is applied to this scenario for its underlay nature and multiuser capability. In this multiuser DS-UWB framework, the active user identification problem is studied here for both the efficiency of multiuser detection (MUD) and the identification of malicious or redundant SUs. Then a novel population declining artificial fish swarm algorithm (PD-AFSA) based user identification scheme is proposed to make the logarithmic maximum a posterior (MAP) estimation of active SUs. This scheme employs a population declining mechanism to enlarge the searching range through initializing the large population of artificial fishes (AFs), and declining their population in successive iterations. Experimental results have testified the validity of this proposed PD-AFSA based scheme in both static and dynamic situations.