Coexistence of Dynamic Spectrum Access Based Heterogeneous Networks

This paper addresses the coexistence issue of distributed heterogeneous networks where the network nodes are cognitive radio terminals These nodes operating as secondary users (SUs) might Interfere with primary users (PUs) who are licensed to use a given frequency band Further due to the lack of coordination and the dissimilarity of the radio access technologies (RATs) among these wireless nodes they might interfere with each other To solve this coexistence problem we propose an architecture that enables coordination among the distributed nodes The architecture provides coexistence solutions and sends reconfiguration commands to SU networks As an example time sharing is considered as a solution Further the time slot allocation ratios and transmit powers are parameters encapsulated in the reconfiguration commands The performance of the proposed scheme is evaluated in terms of the coexistence between PUs and SUs as well as the coexistence among SUs The former addresses the interference from SUs to PUs whereas the latter addresses the sharing of an identified spectrum opportunity among heterogeneous SU networks for achieving an efficient spectrum usage In this study we first introduce a new parameter named as quality of coexistence (QoC) which is defined as the ratio between the quality of SU transmissions and the negative interference to PUs In this study we assume that the SUs have multiple antennas and employ fixed transmit power control (fixed TPC) By using the approximation to the distribution of a weighted sum of chi square random variables (RVs) we develop an analytical model for the time slot allocation among SU networks Using this analytical model we obtain the optimal time slot allocation ratios as well as transmit powers of the SU networks by maximizing the QoC This leads to an efficient spectrum usage among SUs and a minimized negative influence to the PUs Results show that in a particular scenario the QoC can be Increased by 30%