||The stationary and exclusive allocation of radio spectrum cause low spectral efficiency and, therefore, waste spectrum. In order to improve the usage of spectrum in time and space domains, dynamic spectrum access (DSA) has become a popular research topic in recent years. Hence cognitive radio (CR), which has spectrum-sensing ability, has become one of the mainstream researches in the field.|
The idea of CR is basically to raise utilization of spectrum by using the radio spectrum that is temporaly unused, but it still remains a lot of problems needed to be overcomed. For examples, increasing debug baud rate, improving collision frequency, and advancing overall performance are all significant directions for future researches. Furthermore, when operating the wireless cognitive radio network in ad hoc applications, either secondary user (SU), who wants to deliver data, needs to rendezvous with its peer firstly. Although the fusion center or common control approaches can provide effective management for the rendezvous process, the centralized approach introduces the dwawback of scalability and reliability issue, especially for the loose-managed CR network. In this thesis, we propose a fully distributed rendezvous algorithm and the associated data delivery method for ad hoc communication in CR network.
Throughout this paper, we assume that the SU have two antennae so that the transmission and receiving can be performed simultaneously without dead lock. In addition, we also propose the relay concept to decrease the time to rendezvous. Exhaustive simulations were conducted to show that the proposed relay based schemes can effectively reduce the time to rendezvous and the data delivery time and, therefore, the system throughput is improved as well when compared with the no-relay scheme.
|| FCC, “Notice of proposed rule making and order”, FCC Doc, ET Docket No 03-222, December 2003. |
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