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분산형 무선 인지 네트워크에서 QoS 보장을 위한 효율적인 스펙트럼 접속 프로토콜 연구
- Alternative Title
- Bosung Kim
- Author(s)
- Kim Bosung
- Alternative Author(s)
- Bosung Kim
- Advisor
- 노병희
- Department
- 일반대학원 컴퓨터공학과
- Publisher
- The Graduate School, Ajou University
- Publication Year
- 2015-02
- Language
- eng
- Keyword
- 분산형 무선 인지 네트워크
- Alternative Abstract
- Cognitive radio (CR) is considered as a prospective technology to resolve the spectrum shortage problem in future wireless network. According to the network architecture, the cognitive radio networks (CRNs) are classified into centralized cognitive radio networks (CCRNs) and distributed cognitive radio networks (DCRNs). Unlicensed users, or secondary users (SUs), in DCRNs are not supported by central network unit, and thus have very limited local information. In order to overcome the constraints, the DCRNs necessitate the spectrum management functions: spectrum sensing, spectrum decision, spectrum sharing, and spectrum mobility. These are indispensable and correlated functions, and thus the functions are required for an SU to collaborate with others. In this dissertation, we propose spectrum access protocols to improve the spectrum efficiency and satisfy the QoS requirements in DCRNs. They are classified into three schemes according to spectrum management functions and their roles. Firstly, we propose an adaptive sensing period adjustment scheme, shortly ASPA, to improve the spectral efficiency in DCRNs. With the proposed scheme, SUs can share and maintain their sensing period information adaptively using a linearly-increase and exponentially-decrease (LIED) mechanism. An analytical model for the efficiency of the proposed scheme is also proposed and compared with simulation results. It is shown that the proposed scheme outperforms the fixed sensing period scheme in terms of sensing overhead and throughput performance. Next, we propose a non-overlapping channel medium access control protocol, shortly NC-MAC, in DCRNs. The proposed scheme consists of three main phases, namely network initialization, reporting, and contention phases. Each SU senses the PU channel assigned exclusively to it, and then reports the sensed results to all other SUs, without collisions, during the reporting phase. Using the sensing results, SUs can estimate the available PU channels and access the channels with contention based access method. It is demonstrated that the proposed scheme outperforms the existing CR MAC protocols in terms of saturation throughput and average packet delay. Besides the spectrum sensing or access schemes, the provision of VoIP traffic service for SUs in limited spectrum resources is a very important issue. Hence, we propose a VoIP call assignment and management scheme, shortly VoCAM, with VoIP QoS requirements in DCRNs. As the system model, the time structure considering the network structure is addressed. And, applying to the structure, a selection for bandwidth broker (BB) is proposed. Moreover, based on available bandwidth estimated by the BB, a connection admission control (CAC) for SUs is developed. It is shown that the provision of VoIP QoS is greatly affected by the channel utilization, the number of channels, and the length of timeslot.
- Fulltext
- Appears in Collections:
- Graduate School of Ajou University > Department of Computer Engineering > 4. Theses(Ph.D)
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