Resource Allocation Scheme for Spectral Efficiency Enhancement of OFDMA WLAN Systems
Resource Allocation Scheme for Spectral Efficiency Enhancement of OFDMA WLAN Systems
- 주제(키워드) OFDMA , resource allocation , fragmentation , heterogeneous packet lengths.
- 발행기관 아주대학교
- 지도교수 김재현
- 발행년도 2017
- 학위수여년월 2017. 2
- 학위명 석사
- 학과 및 전공 일반대학원 전자공학과
- 실제URI http://www.dcollection.net/handler/ajou/000000024281
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
As the number of users of wireless devices, not only smartphones but also tablets are increasing exponentially, WLANs will be playing a crucial role in next generation wireless communications. The MAC protocol and MA scheme play a very important role in determining the efficiency and scalability of a WLAN. In comparison to other access technologies such as TDMA and CDMA, OFDMA is emerging as a promising solution for wireless networks. OFDMA assigns sets of subcarriers to different users, this is how multiple access is achieved. As a result, simultaneous data transmission can take place from several users. Moreover, OFDMA can overcome one of the major drawbacks in wireless networks, frequency selective fading. The existing MAC schemes for wireless local area networks lack proper utilization of idle or unused sub-channels. One of the key challenges is an efficient radio resource management which can exploit the channel bandwidth to the maximum extent. In this thesis we propose resource allocation scheme based on grouping and fragmentation for improvement of spectral efficiency in OFDMA WLAN environment. The scheme is applicable to systems with stations of heterogeneous packet lengths. Earlier the studies have been done in systems with homogeneous packet lengths. However, packet lengths are quite heterogeneous in real networks. We demonstrate the effectiveness of the schemes in handling heterogeneous packet lengths and improving spectral efficiency and compare it with existing ones through simulation.
more목차
Acknowledgement…………………………………………… i
Abstract……………………………………………………………… ii
Table of Contents……………………………………… iii
List of Figures…...…………………………………… v
List of Tables……….………………………………………… vii
Chapter 1.Introduction………………………………………… 1
1.1 Background and Motivation...... 1
1.2 Contributions............... 3
1.3 Overview…...................... 3
Chapter 2.OFDMA based MAC protocols……… 5
2.1 Overview of OFDMA…………………… 5
2.2 Hybrid OFDMA/CSMA Based MAC........ 7
2.2.1 Hybrid MAC design………………………………….. 8
2.3 Novel DCF-based MAC................... 10
2.3.1 Novel-DCF protocol...... 10
2.3.2 Performance evaluation……………………………... 14
2.4 C-OFDMA…... 14
2.5 OMAX protocol....... 16
2.5.1 Protocol design……………………………………… 17
2.5.2 Performance evaluation……………………………... 19
2.6 OFDMA based Multiple access protocol…………………... 19
Chapter 3. Resource Allocation Scheme………………………………… 22
3.1 System Model………………………………………………. 22
3.2 MAC protocol procedure…………………………… 23
3.3 Grouping based resource allocation……………. 24
3.3.1 Grouping based resource allocation algorithm. 25
3.3.2 Example of proposed scheme.... 26
3.4 Fragmentation based resource allocation.. 27
3.4.1 Fragmentation based resource allocation algorithm.. 27
3.4.2 Example of proposed scheme…………… 31
3.5 Frame Structure………..…………………………… 32
3.6 Fragmentation………………………….………….. 33
Chapter 4. Performance Evaluation……………… 35
Chapter 5. Conclusion…………………………………………… 45
References………………………………………………………….. 46
