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논문 기본 정보

자료유형
학위논문
저자정보

Anup Thapa (조선대학교, 조선대학교 대학원)

지도교수
신석주
발행연도
2013
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조선대학교 논문은 저작권에 의해 보호받습니다.

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이 논문의 연구 히스토리 (2)

2013

Performance Analysis and Enhancement of MIMO aware MAC Protocols in WLANs : 무선 LAN 시스템에서 MIMO aware MAC 프로토콜 성능특성 및 개선 연구
Anup Thapa 컴퓨터공학 2013.01 학위논문

2010

Performance Analysis of CSMA/CA adapted Multi-User MIMO aware MAC for WLANs
Anup Thapa ,  Subodh Pudasaini ,  Seokjoo Shin 한국통신학회 학술대회논문집 2010.06 학술대회자료

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Multiple Input Multiple Output (MIMO) is a radio communication technology that uses multiple antenna elements at both transmitting and receiving ends. Multiple antenna elements in MIMO systems could be exploited to boost up channel capacity or to attain transmission reliability without additional bandwidth and power. Wireless networks deployed with MIMO systems can utilize these features by employing spatial multiplexing and/or spatial diversity.
Recently, MIMO systems have gained increased interest. Most of the existing wireless networks are looking forward to meet their ever increasing capacity demand by exploiting MIMO offered spectral efficiency. With the IEEE 802.11n amendment, MIMO systems have already been introduced to Wireless Local Area Networks (WLANs). IEEE 802.11n supports both spatial multiplexing and spatial diversity.
Regarding spatial multiplexing, however, the latest WLAN standard only supports Single User spatial multiplexing based MIMO (SU-MIMO) transmission. SU-MIMO is point-to-point MIMO communication, where all concurrently transmitted data streams are destined for a single receiver. But due to various network characteristics, SU-MIMO is not always applicable. For instance, unless all the queues of corresponding antenna elements have enough packets to send, it''s not worth applying SU-MIMO. In addition, SU-MIMO is worthy only when the antenna elements are evenly distributed in a transmitter-receiver pair. Apart from that, SU-MIMO is advantageous mostly when the transmitting node also deals with data packets of only one node at a time. Otherwise, if a transmitting node deals with data packets of various nodes, like Access Point (AP), it requires to go through multiple transmission attempts, which ultimately increases delay.
To deal with inexpedient issues of SU-MIMO, Multi-User spatial multiplexing based MIMO (MU-MIMO) transmission is being widely studied. MU-MIMO refers to point-to-multipoint MIMO communication or vice versa. In downlink, it is point-to-multipoint MIMO communication, whereas, in uplink, it is multipoint-to-point MIMO communication.
Realizing MU-MIMO in existing WLANs requires significant changes in the MAC protocol. Either dominant MAC protocol Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) needs to be replaced by novel MU-MIMO aware MAC protocol or it should be upgraded into MU-MIMO aware CSMA/CA. Nevertheless, the simplest approach would be upgrading the widely deployed CSMA/CA. Therefore, in this dissertation, we investigate different modification approaches that best represent the possible modifications in CSMA/CA to upgrade it into MU-MIMO aware CSMA/CA. We consider both uplink and downlink MU-MIMO communications. We also provide detailed performance analysis to understand their performance benefits and trade-off.
As both theoretical and practical understanding have already shown the superiority of MU-MIMO in many cases, MU-MIMO can be expected to become one of the basic essentials of future wireless networks. Even so, MU-MIMO still has some limitations. For example, when the data transmission duration varies between the links due to difference in link quality or data length, MU-MIMO may fail to utilize the available MIMO capacity to its full potential. Therefore, in this dissertation, we also analyze a MAC layer solution to address such issues. We present a MAC layer protocol design that can switch between MU-MIMO and multiple SU-MIMO transmissions. After taking into account the achievable performance, presented protocol selects a transmission mode in such a way that the available MIMO capacity is maximally utilized.

목차

Abstract i
Abstract [Korean] iv
Accronyms xi
List of Tables xvi
List of Figures xiv
1 Introduction 1
1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.1 MIMO in WLANs . . . . . . . . . . . . . . . . . . . . . . .3
1.1.2 MIMO aware MAC protocols in WLANs . . . .. . . 3
1.1.3 MU-MIMO in WLANs . . . . . . . . . . . . . .. . ... . 6
1.2 Contributions of Dissertation . . . . . . . . . . . . . ........ 8
1.3 Organization of Dissertation . . . . . . . . . . . ...... . . . 10
2 Wireless Local Area Networks 12
2.1 Overview of WLANs . . . . . . . . . . . . . . . . . . . . . . . 12
2.2 WLANs Protocol Suite . . . . . . . . . . . . . . . . . . . . . 14
2.3 Standardization Activities in WLANs . . . . . . . . . . . .15
2.4 Latest WLAN Standard: IEEE 802.11n . . . . . . . . . . . 18
2.4.1 IEEE 802.11n PHY . . . . . . . . . . . . . . . . . . . . . 18
2.4.1.1 MIMO . . . . . . . . . . . . . . . . . . . . .. . . . 19
2.4.1.2 SU-MIMO . . . . . . . . . . . . . . . . . . . . . .21
2.4.1.3 SU-MIMO System Model . . . . . . . . . . . 22
2.4.2 IEEE 802.11n MAC . . . . . . . . . . . . . . . . . . . . .26
2.4.2.1 SU-MIMO aware MAC Protocol . . . . . . .27
2.4.2.2 Frame Aggregation . . . . . . . . . . . . . . . .29
2.4.2.3 Block Acknowledgement . . . . . . . . . . . 31
2.4.2.4 Bi-directional Data Flow . . . . . . . . . . . .32
2.4.3 Limitation of IEEE 802.11n . . . . . . . . . . .. . . .. . 32
2.4.3.1 MU-MIMO aware MAC Protocol . . . . . . .33
3 Performance Analysis of SU-MIMO aware MAC Protocol
34
3.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 34
3.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 35
3.3 Numerical Analysis . . . . . . . . . . . . . . . . . . . . 36
3.3.1 Maximum Achievable Throughput . . . . . . . . 38
3.3.2 Minimum Achievable Delay . . . . . . . . . . . 41
3.4 Performance Evaluation and Discussion . . . . . . . . . 42
3.5 Concluding Remarks . . . . . . . . . . . . . . . . . . . 46
4 Performance Analysis of MU-MIMO aware MAC Protocols
48
4.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 48
4.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 49
4.3 MU-MIMO System: Overview . . . . . . . . . . . . . . 52
4.4 MU-MIMO aware MAC Modification Requirements . . 57
4.5 MU-MIMO aware CSMA/CA . . . . . . . . . . . . . . 58
4.5.1 CSI Feedback From Serially Transmitted CTS
Packets (CSIF-STCP) . . . . . . . . . . . . . . 59
4.5.2 CSI Prediction From Serially Transmitted CTS
Packets (CSIP-STCP) . . . . . . . . . . . . . . 61
4.5.3 CSI Prediction From Simultaneously Transmitted
CTS Packets (CSIP-SmTCP) . . . . . . . . 62
4.6 Numerical Analysis . . . . . . . . . . . . . . . . . . . . 63
4.6.1 Mathematical Analysis for Achievable Performance
. . . . . . . . . . . . . . . . . . . . . . . 63
4.6.1.1 Maximum Achievable Throughput . . 64
4.6.1.2 Minimum Achievable Delay . . . . . . 65
4.6.2 Mathematical Analysis for Average Performance 66
4.6.2.1 Average Throughput . . . . . . . . . 69
4.6.2.2 Average Delay . . . . . . . . . . . . . 70
4.7 Performance Evaluation and Discussion . . . . . . . . . 70
4.8 Concluding Remarks . . . . . . . . . . . . . . . . . . . 79
5 Enhanced MIMO aware MAC Protocol for MU-MIMO
Reception 80
5.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 80
5.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 81
5.3 MIMO aware CSMA/CA for MU-MIMO Reception . . 82
5.4 Numerical Analysis . . . . . . . . . . . . . . . . . . . . 83
5.5 Performance Evaluation and Discussion . . . . . . . . . 87
5.6 Concluding Remarks . . . . . . . . . . . . . . . . . . . 90
6 Enhanced MIMO aware MAC Protocol for Efficient
Transmission Mode Selection 91
6.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 91
6.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 92
6.3 Proposed Protocol . . . . . . . . . . . . . . . . . . . . 96
6.3.1 MU-MIMO Transmission in VHT WLAN . . . . 96
6.3.2 Proposed Scheme . . . . . . . . . . . . . . . . . 97
6.4 Numerical Analysis . . . . . . . . . . . . . . . . . . . . 98
6.5 Performance Evaluation and Discussion . . . . . . . . . 101
6.6 Concluding Remarks . . . . . . . . . . . . . . . . . . . 106
7 Conclusions and Future Work 108
7.1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . 108
7.2 Future Work . . . . . . . . . . . . . . . . . . . . . . . . 110
References 112

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