이동통신 네트워크에서의 QoS 패킷 스케줄러 설계 및 고정 릴레이 관련 주파수 재사용 관리 기법 연구

학위논문 (박사)-- 서울대학교 대학원 공과대학 전기·컴퓨터공학부, 2017. 8. 박세웅.The main interest of this paper is to understand a basic approach to provide more efficient method to allocate radio resources in the mobile communication systems, especially in which radio resources could be allocated by both frequency and time division multiple access. So, we consider OFDMA system and the ideas described in this paper could be easily applied to the current and next generation mobile communication systems. This paper studies two basic research themesa QoS packet scheduler design and fixed relay resource management policies based on frequency reuse in mobile networks. This paper considers novel scheduler structures that are executable in the environments of multiple traffic classes and multiple frequency channels. To design a scheduler structure for multiple traffic classes, we first propose a scheduler selection rule that uses the priority of traffic class and the urgency level of each packet. Then we relax the barrier of traffic class priority when a high priority packet has some room in waiting time. This gives us a chance to exploit multiuser diversity, thereby giving more flexibility in scheduling. Our considered scheduler can achieve higher throughput compared to the simple extension of conventional modified largest weighted delay first (MLWDF) scheduler while maintaining the delay performance for QoS class traffic. We also design a scheduler structure for multiple frequency channels that chooses a good channel for each user whenever possible to exploit frequency diversity. The simulation results show that our proposed scheduler increases the total system throughput by up to 50% without degrading the delay performance. This paper also introduces radio resource management schemes based on frequency reuse for fixed relay stations in mobile cellular networks. Mobile stations in the cell boundary experience poor spectral efficiency due to the path loss and interference from adjacent cells. Therefore, satisfying QoS requirements of each MS at the cell boundary has been an important issue. To resolve this spectral efficiency problem at the cell boundary, deploying fixed relay stations has been actively considered. In this paper, we consider radio resource management policies based on frequency reuse for fixed relays that include path selection rules, frequency reuse pattern matching, and frame transmission pattern matching among cells. We evaluate performance of each policy by varying parameter values such as relay stations position and frequency reuse factor. Through Monte Carlo simulations and mathematical analysis, we suggest some optimal parameter values for each policy and discuss some implementation issues that need to be considered in practical deployment of relay stations. We also surveyed further works that many researchers have been studied to tackle the similar problems of QoS scheduling and resource management for relay with our proposed work. We expect that there would be more future works by priority-based approach and energy-aware approach for QoS scheduling. Also current trends such as the rising interest in IoT system, discussion of densification of cells and D2D communications in 5G systems make us expect that the researches in these topics related with relays would be popular in the future. We also think that there are many interesting problems regarding QoS support and resource management still waiting to be tackled, especially combined with recent key topics in mobile communication systems such as 5G standardization, AI and NFV/SDN.Chapter 1 Introduction 1 1.1 QoS Packet Scheduler 4 1.2 Fixed Relay Frequency Reuse Policies 6 Chapter 2 Scheduler Design for Multiple Traffic Classes in OFDMA Networks 10 2.1 Proposed Schedulers 10 2.1.1 Scheduler Structures 12 2.1.2 MLWDF scheduler for Multiple Traffic Classes 13 2.1.3 Joint Scheduler 13 2.2 System Model 18 2.3 Performance Evaluation 19 2.3.1 Schedulers for Multiple Traffic Classes 20 2.3.2 Impact of Scheduler Selection Rule 25 2.3.3 Frame Based Schedulers 27 2.3.4 Impact of Partial Feedback 30 2.3.5 Adaptive Threshold Version Schedulers 33 2.4 Conclusion 36 Chapter 3 Frequency Reuse Policies for Fixed Relays in Cellular Networks 40 3.1 System Model 40 3.1.1 Frame Transmission and Frequency Reuse Patterns among RSs 42 3.1.2 Positioning of RSs and Channel Capacity 44 3.1.3 Area Spectral Efficiency 45 3.2 Radio Resource Management Policies Based on Frequency Reuse 46 3.2.1 Path Selection Rule 46 3.2.2 Frequency Reuse and Frame Transmission Pattern Matchings among Cells 52 3.3 Monte Carlo Simulation and Results 53 3.4 Consideration of Practical Issues 80 3.5 Conclusion 81 Chapter 4 Surveys of Further Works 83 4.1 Further Works on QoS Schedulers 83 4.1.1 WiMAX Schedulers 85 4.1.2 LTE Schedulers 92 4.2 Further Works on Radio Resource Management in Relay Systems 98 4.3 Future Challenges 100 Chapter 5 Conclusion 104 Bibliography 107 초록 127Docto

보장 서비스 구현을 위한 차별 서비스의 파라미터에 관한 연구

Thesis (master`s)--서울대학교 대학원 :전기공학부,2000.Maste

Flexible and Bendable Vibrotactile Actuator Using Electro-conductive Polyurethane

1

APPARATUS AND METHOD FOR DISTANCE ADAPTIVE CONTENTION WINDOW ADJUSTMENT IN WIRELESS SENSOR NETWORKS

본 발명은 무선 센서네트워크 환경에서 MAC(Medium Access Control) 계층의 효율적인 경쟁 윈도우를 선택하여 싱크노드로 향하는 데이터 패킷의 전송시간을 줄이고, 높은 처리량을 얻기 위한 무선 센서 네트워크에서 거리 적응적 경쟁 윈도우 조절 장치 및 방법을 제공하기 위한 것으로서, 거리 적응적 경쟁 윈도우 조절 장치는 센서 노드에서 라우팅 프로토콜을 통해 라우팅을 담당하는 센서 라우팅 프로토콜부와, 데이터 링크 계층과 상호 작용할 수 있는 센서-MAC 기반의 MAC(Media Access Control)부와, 상기 MAC부에서 인터페이스 버퍼에 쌓여있는 프레임 개수를 모니터링하여 혼잡상태여부를 결정하는 모니터링부와, 상기 모니터링부를 통해 혼잡상태가 인식되면 경쟁 윈도우의 슬롯(slot) 수를 동적으로 조절하여 채널 경쟁에 참여하도록 하는 윈도우 조절부를 포함하는데 있다.거리 적응적 경쟁 윈도우 조절 장치는 센서 노드에서 라우팅 프로토콜을 통해 라우팅을 담당하는 센서 라우팅 프로토콜부와, 데이터 링크 계층과 상호 작용할 수 있는 센서-MAC 기반의 MAC(Media Access Control)부와, 상기 MAC부에서 인터페이스 버퍼에 쌓여있는 패킷 개수를 모니터링하여 혼잡상태여부를 결정하는 모니터링부와, 상기 모니터링부를 통해 혼잡상태가 인식되면 경쟁 윈도우의 슬롯(slot) 수를 동적으로 조절하여 채널 경쟁에 참여하도록 하는 윈도우 조절부를 포함하며; 상기 센서 라우팅 프로토콜부는 플루딩(flooding)하는 관심(interest) 패킷에 경유한 거리 정보를 나타내는 홉 카운트 정보를 포함하는 것을 특징으로 하는 무선 센서 네트워크에서 거리 적응적 경쟁 윈도우 조절 장치