Research On Cognitive Radio Based Spectrum Aggregation Technology In BWT System

The industria l users require that trunking communicat ion systems can offer broadband services with the rapid development of wireless communication tec hniques while they offer voice services, inc lud ing data services, picture services, video services, and so on. In order to meet the requirements of industria l users, the development of a project called broadband wireless trunking(BWT) is put on the agenda. BWT is a wireless professional communication system, which is based on broadband wireless communication techniques, offers broadband services and its major function is the command and dispatch function. However, there is a problem to be notified that BWT has no suffic ient frequency bandwith and enough spectrum resources for broadband wireless data transmission, which is one of urgent pro blems to be solved in the development of BWT. Therefore, the dissertation studies the cognit ive radio based spectrum aggregation. In this dissertation, the cognit ive radio technology and spectrum aggregation technology are used to solve the pro blem that BWT has no sufficient frequency bandwith and enough spectrum resources.Firstly, the key technologies about spectrum sensing algor ithms of the cogn itive radio technology and resource scheduling schemes of the spectrum aggregation technology are introduced at the beginning as the theoretical princ iple of this dissertation. Aimming at spectrum sensing algorit hms, the energy detection and matched filter detection are presented and the performance indicators of the two spectrum sensing algorit hms are analyzed in detail. Besides that, t he dissertation introduces the key technologies of resource scheduling schemes in the spectrum aggregation, inc lud ing scheduler structures, component carrier selection(CC S election) schemes, and resource block assignment(RB Assignment) schemes. The research results of spectrum sensing a lgorithms and resource scheduling schemes supply theoretical supports for the theoretical analyses and simulat ions in the rest of this dissertation.Secondly, this dissertation proposes a joint DC offsets adaptive energy detection(Joint DC- AED) scheme to solve two problems in the BWT system, one is that it is difficult to sense the primary user(PU) signal for current spectrum sensing algorithms when PUs signa l coexists with the secondary user(SU) signal, and the other is that there are DC offsets in the received signal w hen the spectrum sensing receiver is a direct-conversion receiver. Based on the known BWT users priori information, the proposed scheme can sense the PUs signal in the case of the coexistence of the PU and SU signa l in the same spectrum band which is led by the hidden primary user proble m. Simulation results show that the proposed scheme can obtain a good detection performance when the PU signa l coexists with the SU signa l in the same spectrum band, and remove the influence of the DC offset without having the knowledge of the actual DC offset.Thirdly, the current resource scheduling schemes in spectrum aggregation are not suitable for spectrum aggregation in BWT. To overcome the drawbacks of e xisting schemes, the dissertation proposes a novel resource scheduling scheme, termed as cognit ive radio based resource scheduling(C R- RS) scheme, for optimizing the performance of spectrum aggregation in t he BWT system. A novel three- level scheduling structure is propo sed and an equivalent throughput of the CCs is given based on the knowledge of PUs. O n this basis, the users in BWT system can obtain not only better load balance, but also the fairness among diffe rent BWT users. The simulation results show that the proposed scheme successfully achieves the better performance than the current resource scheduling schemes for spectrum aggregation of the BWT system in terms of average throughput of the CCs, average user throughput, average user service rate, and average sojour n time.Finally, the current resource scheduling schemes of spectrum aggregation cannot meet the delay requirement of the BWT system. Due to the lack, the dissertation proposes a component carrier configuration and switching scheme for real- time traffic(RT-CCC S) to solve the problem that the current resource scheduling schemes cannot guarantee the certain delay requirements of the BWT system. On the basis of guaranteeing the load balance and fairness, the proposed scheme calculates the spectrum bandwidth in cognitive radio to meet the delay requirement. On this basis, the proposed scheme configurates the number of C Cs and aggregates the appropriate CCs for spectrum aggregation. If the current configured CCs ca nnot meet the delay requirement, the proposed scheme automatically adjusts the number of the configured CCs unt il these CCs can meet the delay require ment of BWT users. Simulation results prove that the proposed scheme can obtain the better delay performance and satisfy the average delay requirement of BWT users.