Capacity improvement for VoIP based two-tier CRN using space-time spectrum sensing

Cognitive Radio Network (CRN) provides a way for the improvement in the capacity and spectrum utilization with the use of idle spectrum band of licensed users (PUs). Currently, CRN has come to its upper bound limit which may restricts the progress in the area of CRN. This paper tries to take care of this issue by further exploring the idea of `Two Tier CRN (TT-CRN)' by using space-time spectrum sensing (STSS). In TT-CRN, the secondary users (SUs) of tier1 transmit their data based on Voice over IP (VoIP) communication. When these users are not transmitting the data (silence suppression), then SUs of tier2 transmit in that spectrum band. The TT-CRN increases the capacity and throughput of the network and also improves the spectrum utilization up to some extent. The space-time spectrum sensing based two tier CRN (STSS TT-CRN) mechanism further increases the utilization and the capacity of the existing TT-CRN. In this mechanism, different regions are divided into the tiers of the SUs and PUs. These regions are region 1 (RE Gl), region 2 (REG2), and region 3 (REG3). With the help of analytical results, the throughputs of basic CRN, TT-CRN, and STSS TT-CRN are compared. The performance evaluation confirms the improvement in the link utilization and results in higher throughput of STSS TT-CRN.