9 research outputs found

    Performance Evaluation of Power Efficient Mechanisms on Multimedia over LTE-A Networks

    Get PDF
    Power optimization is a critical challenge in multimedia services over cellular communication systems. Long Term Evolution-Advanced (LTE-A) has been developed for higher bandwidth access for accommodating today’s heavy data applications to provide better performance. Idle mode permits cellularstations to manipulate power and sources with the aid of limiting its activity for discrete periods and this eliminates the lively requirement for handover and other ordinary operations. Also, provides a periodical method for the cell station for pending downlink traffic directed to the cellularstation and as a result gets rid network handover traffic from basically inactive cellular stations. Discontinuous Reception (DRX) has been carried out to decrease the power intake of the consumer device, and transmission of big quantity of data. At data transfer, mobile device and the network phases negotiation occur. During other times, the device turns its receiver off and enters a low power state. Thereby similarly assisting numerous services and big quantities of information transmissions. This study prepossession of a massive quantity of data. Also proposes the two-power optimization modes idle mode and DRX mode parameters to achieve maximum possible power saving with the higher quality of multimedia services. Furthermore, the effectiveness of using DRX short cycles and DRX long cycles on multimedia services and the overall performance. Using OPNET Simulator 17.5, it concluded that DRX mechanism is preferred to operate compared with the Idle mechanism, also resulted that the DRX long cycles are a very good choice for all multimedia services and the overall network performance

    Towards More Efficient 5G Networks via Dynamic Traffic Scheduling

    Get PDF
    Department of Electrical EngineeringThe 5G communications adopt various advanced technologies such as mobile edge computing and unlicensed band operations, to meet the goal of 5G services such as enhanced Mobile Broadband (eMBB) and Ultra Reliable Low Latency Communications (URLLC). Specifically, by placing the cloud resources at the edge of the radio access network, so-called mobile edge cloud, mobile devices can be served with lower latency compared to traditional remote-cloud based services. In addition, by utilizing unlicensed spectrum, 5G can mitigate the scarce spectrum resources problem thus leading to realize higher throughput services. To enhance user-experienced service quality, however, aforementioned approaches should be more fine-tuned by considering various network performance metrics altogether. For instance, the mechanisms for mobile edge computing, e.g., computation offloading to the edge cloud, should not be optimized in a specific metric's perspective like latency, since actual user satisfaction comes from multi-domain factors including latency, throughput, monetary cost, etc. Moreover, blindly combining unlicensed spectrum resources with licensed ones does not always guarantee the performance enhancement, since it is crucial for unlicensed band operations to achieve peaceful but efficient coexistence with other competing technologies (e.g., Wi-Fi). This dissertation proposes a focused resource management framework for more efficient 5G network operations as follows. First, Quality-of-Experience is adopted to quantify user satisfaction in mobile edge computing, and the optimal transmission scheduling algorithm is derived to maximize user QoE in computation offloading scenarios. Next, regarding unlicensed band operations, two efficient mechanisms are introduced to improve the coexistence performance between LTE-LAA and Wi-Fi networks. In particular, we develop a dynamic energy-detection thresholding algorithm for LTE-LAA so that LTE-LAA devices can detect Wi-Fi frames in a lightweight way. In addition, we propose AI-based network configuration for an LTE-LAA network with which an LTE-LAA operator can fine-tune its coexistence parameters (e.g., CAA threshold) to better protect coexisting Wi-Fi while achieving enhanced performance than the legacy LTE-LAA in the standards. Via extensive evaluations using computer simulations and a USRP-based testbed, we have verified that the proposed framework can enhance the efficiency of 5G.clos

    비면허대역 셀룰라 통신의 성능 분석 및 성능 향상 기법 연구

    Get PDF
    학위논문 (박사) -- 서울대학교 대학원 : 공과대학 전기·정보공학부, 2021. 2. 박세웅.3GPP는 LAA (licensed-assisted access)라고하는 5GHz 비면허 대역 LTE를 개발했습니다. LAA는 충돌 방지 기능을 사용하기 위해 Wi-Fi의 CSMA / CA (Carrier Sense Multiple Access with Collision avoidance)와 유사한 LBT (Listen Before Talk) 작업을 채택하여 각 LAA 다운 링크 버스트의 프레임 구조 오버 헤드는 각각의 종료 시간에 따라 달라집니다. 이전 LBT 작업. 이 논문에서는 비면허 대역 셀룰러 통신을 분석하기위한 수치 모델을 제안한다. 다음으로, 비면허 대역 셀룰러 통신의 다음 두 가지 향상된 기능을 고려합니다. 대역 독립형 셀룰러 통신. 기존 WiFi 분석 모델로는 LAA의 성능을 평가할 수 없다는 점을 감안하여 본 서신에서는 여러 경합 진화 된 NodeB로 구성된 LAA 네트워크의 성능을 분석하기위한 새로운 Markov 체인 기반 분석 모델을 제안합니다. LAA 프레임 구조 오버 헤드의 변형. LTE-LAA는 LTE에서 상속 된 속도 적응 알고리즘을 위해 적응 변조 및 코딩 (AMC) 을 채택합니다. AMC는 진화 된 nodeB (eNB)가 현재 전송의 채널 품질 표시기 피드 백을 사용하여 다음 전송을위한 변조 및 코딩 방식 (MCS)을 선택하도록 돕습니다. 라이선스 대역에서 동작하는 기존 LTE의 경우 노드 경합 문제가 없으며 AMC 성능 에 대한 연구가 잘 진행되고 있습니다. 그러나 비면허 대역에서 동작하는 LTE-LAA 의 경우 충돌 문제로 인해 AMC 성능이 제대로 처리되지 않았습니다. 이 편지에서는 AMC 운영을 고려한 현실적인 채널 모델에서 LTELAA 성능을 분석하기위한 새로 운 Markov 체인 기반 분석 모델을 제안합니다. 무선 네트워크 분석에 널리 사용되는 Rayleigh 페이딩 채널 모델을 채택하고 분석 결과를 ns-3 시뮬레이터에서 얻은 결과 와 비교합니다. 비교 결과는 평균 정확도가 99.5%로 분석 모델의 정확도를 보여줍니다. 높은 데이터 속도에 대한 요구 사항으로 인해 3GPP는 LTE-LAA를위한 다중 반송파 운영을 제공했습니다. 그러나 다중 반송파 동작은 OOBE에 취약하고 제한된 전송 전력을 사용하여 비효율적 인 채널 사용을 초래합니다. 본 논문은 채널 효율을 높이기위한 새로운 다중 반송파 접근 방식을 제안한다. 우리가 제안한 방식은 전송 버스트를 여러 개로 분할하고 전송 전력 제한을 충족하면서 짧은 서브 프레임 전송 을 사용합니다. 또한 채널 상태를 정확하게 판단하여 OOBE 문제를 극복 할 수있는 에너지 감지 알고리즘을 제안합니다. 소프트웨어 정의 라디오를 사용하는 프로토 타입은 99% 이상의 정확도로 채널 상태를 결정하는 에너지 감지 알고리즘의 실행 가능성과 성능을 보여줍니다. ns-3 시뮬레이션을 통해 제안 된 다중 반송파 액세스 방식이 기존 LBT 유형 A 및 유형 B에 비해 사용자인지 처리량에서 각각 최대 59% 및 21.5%의 성능 향상을 달성 함을 확인했습니다. 레거시 LAA에는 배포 문제가 있기 때문에 3GPP와 MulteFire 얼라이언스는 비면허 대역 독립형 셀룰러 통신 시스 템을 제안했습니다. 그러나, 종래의 비면허 대역 독립형 셀룰러 통신 시스템은 상향 링크 제어 메시지의 전송 확률이 낮다. 이 논문은 Wi-Fi 블록 ACK 프레임에 업 링크 제어 메시지를 넣는 W ARQ : Wi-Fi 지원 HARQ를 제안합니다. 또한 W-ARQ의 처 리 성능을 향상시키기 위해 병렬 HARQ 및 클러스터링 된 Minstrel을 제안합니다. 우리가 제안한 알고리즘은 기존 MulteFire가 거의 제로 처리량 성능을 보이는 경우 높은 처리량 성능을 보여줍니다. 요약하면 비면허 대역 셀룰러 통신의 성능을 분석 합니다. 제안 된 모델을 사용함으로써 우리는 레거시 다중 반송파 동작을 주장하며 비면허 셀룰러 통신의 HARQ는 효율적이지 않다. 이러한 이유로, 우리는 최첨단 기 술에 비해 UPT 및 처리량과 같은 네트워크 성능 향상을 달성하는 OOBE 인식 추가 액세스 및 W-ARQ를 제안합니다.3GPP has developed 5 GHz unlicensed band LTE, referred to as licensed-assisted access (LAA). LAA adopts listen before talk (LBT) operation, resembling Wi-Fis carrier sense multiple access with collision avoidance (CSMA/CA), to enable collision avoidance capability, while the frame structure overhead of each LAA downlink burst varies with the ending time of each preceding LBT operation. In this dissertation, we propose numerical model to analyze unlicensed band cellular communication. Next, we consider the following two enhancements of unlicensed band cellular communication: (i) out-of-band emission (OOBE) aware additional carrier access, and (ii) Wi-Fi assisted hybrid automatic repeat request (H-ARQ) for unlicensed-band stand-alone cellular communication. Given that, existing analytic models of Wi-Fi cannot be used to evaluate the performance of LAA, in this letter, we propose a novel Markov chain-based analytic model to analyze the performance of LAA network composed of multiple contending evolved NodeBs by considering the variation of the LAA frame structure overhead. LTE-LAA adopts adaptive modulation and coding (AMC) for the rate adaptation algorithm inherited from LTE. AMC helps the evolved nodeB (eNB) to select a modulation and coding scheme (MCS) for the next transmission using the channel quality indicator feedback of the current transmission. For the conventional LTE operating in the licensed band, there is no node contention problem and AMC performance has been well studied. However, in the case of LTE-LAA operating in the unlicensed band, AMC performance has not been properly addressed due to the collision problem. In this letter, we propose a novel Markov chain-based analysis model for analyzing LTELAA performance under a realistic channel model considering AMC operation. We adopt Rayleigh fading channel model widely used in wireless network analysis, and compare our analysis results with the results obtained from ns-3 simulator. Comparison results show an average accuracy of 99.5%, which demonstrates the accuracy of our analysis model. Due to the requirement for a high data rate, the 3GPP has provided multi-carrier operation for LTE-LAA. However, multi-carrier operation is susceptible to OOBE and uses limited transmission power, resulting in inefficient channel usage. This paper proposes a novel multi-carrier access scheme to enhance channel efficiency. Our proposed scheme divides a transmission burst into multiple ones and uses short subframe transmission while meeting the transmission power limitation. In addition, we propose an energy detection algorithm to overcome the OOBE problem by deciding the channel status accurately. Our prototype using software-defined radio shows the feasibility and performance of the energy detection algorithm that determines the channel status with over 99% accuracy. Through ns-3 simulation, we confirm that the proposed multi-carrier access scheme achieves up to 59% and 21.5% performance gain in userperceived throughput compared with the conventional LBT type A and type B, respectively. Since the legacy LAA has deployment problem, 3GPP and MulteFire alliance proposed unlicensed band stand-alone cellular communication system. However, conventional unlicensed band stand-alone cellular communication system has low transmission probability of uplink control messages. This disertation proposes W-ARQ: Wi-Fi assisted HARQ which put uplink control messages into Wi-Fi block ACK frame. In addition we propose parallel HARQ and clustered Minstrel to enhance throughput performance of W-ARQ. Our proposed algorithm shows high throughput performance where conventional MulteFire shows almost zero throughput performance. In summary, we analyze the performance of unlicensed-band cellular communication. By using the proposed model, we insist the legacy multi-carrier operation and HARQ of unlicensed cellular communication is not efficient. By this reason, we propose OOBE aware additional access and W-ARQ which achievee enhancements of network performance such as UPT and throughput compared with state-of-the-art techniques.Abstract i Contents iv List of Tables vii List of Figures viii 1 Introduction 1 1.1 Unlicensed Band Communication System . . . . . . . . . . . . . . . 1 1.2 Overview of Existing Approaches . . . . . . . . . . . . . . . . . . . 2 1.2.1 License-assisted access . . . . . . . . . . . . . . . . . . . . . 2 1.2.2 Further LAA . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2.3 Non-3GPP Unlicensed Band Cellular Communication . . . . 6 1.3 Main Contribution . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.3.1 Performance Analysis of LTE-LAA . . . . . . . . . . . . . . 6 1.3.2 Out-of-Band Emission Aware Additional Carrier Access for LTE-LAA Network . . . . . . . . . . . . . . . . . . . . . . . 7 1.3.3 W-ARQ: Wi-Fi Assisted HARQ for Unlicensed Band StandAlone Cellular Communication System . . . . . . . . . . . . 8 1.4 Organization of the Dissertation . . . . . . . . . . . . . . . . . . . . 8 2 Performance Analysis of LTE-LAA network 10 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.2 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.3 Proposed Markov-Chain Model . . . . . . . . . . . . . . . . . . . . . 14 2.3.1 Markov Property . . . . . . . . . . . . . . . . . . . . . . . . 14 2.3.2 Markov Chain Model for EPS Type Variation . . . . . . . . . 16 2.3.3 LAA Network Throughput Estimation . . . . . . . . . . . . . 18 2.4 Model Validation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 2.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 3 Out-of-Band Emission Aware Additional Carrier Access for LTE-LAA Network 35 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 3.2 Related work and Background . . . . . . . . . . . . . . . . . . . . . 37 3.2.1 Related work . . . . . . . . . . . . . . . . . . . . . . . . . . 37 3.2.2 Listen Before Talk . . . . . . . . . . . . . . . . . . . . . . . 38 3.2.3 Out-of-Band Emission . . . . . . . . . . . . . . . . . . . . . 39 3.3 Multi-carrier Operation of LTE-LAA . . . . . . . . . . . . . . . . . . 39 3.4 Carrier Sensing considering Out-of-Band Emission . . . . . . . . . . 47 3.4.1 Energy Detection Algorithm . . . . . . . . . . . . . . . . . . 49 3.4.2 Nominal Band Energy Detection . . . . . . . . . . . . . . . . 50 3.4.3 OOBE-Free Region Energy Detection . . . . . . . . . . . . . 51 3.5 Additional Carrier Access Scheme . . . . . . . . . . . . . . . . . . . 52 3.5.1 Basic Operation . . . . . . . . . . . . . . . . . . . . . . . . . 52 3.5.2 Transmission Power Limitation . . . . . . . . . . . . . . . . 53 3.5.3 Dividing Transmission Burst . . . . . . . . . . . . . . . . . . 54 3.5.4 Short Subframe Decision . . . . . . . . . . . . . . . . . . . . 54 3.6 Performance Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . 57 3.6.1 Performance of Energy Detection considering OOBE . . . . . 57 3.6.2 Simulation Environments . . . . . . . . . . . . . . . . . . . . 57 3.6.3 Performance of Proposed Carrier Access Scheme . . . . . . . 58 3.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4 W-ARQ: Wi-Fi Assisted HARQ for Unlicensed Band Stand-Alone Cellular Communication System 66 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 4.2 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 4.3 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 4.4 W-ARQ: Wi-Fi assisted HARQ for Unlicensed Band Stand-Alone Cellular Communication System . . . . . . . . . . . . . . . . . . . . . . 69 4.4.1 Parallel HARQ . . . . . . . . . . . . . . . . . . . . . . . . . 71 4.4.2 Clustered Minstrel . . . . . . . . . . . . . . . . . . . . . . . 72 4.5 Performance Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . 75 4.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 5 Concluding Remarks 80 5.1 Research Contributions . . . . . . . . . . . . . . . . . . . . . . . . . 80 5.2 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 Abstract (In Korean) 90 감사의 글 93Docto

    Enabling Technologies for Ultra-Reliable and Low Latency Communications: From PHY and MAC Layer Perspectives

    Full text link
    © 1998-2012 IEEE. Future 5th generation networks are expected to enable three key services-enhanced mobile broadband, massive machine type communications and ultra-reliable and low latency communications (URLLC). As per the 3rd generation partnership project URLLC requirements, it is expected that the reliability of one transmission of a 32 byte packet will be at least 99.999% and the latency will be at most 1 ms. This unprecedented level of reliability and latency will yield various new applications, such as smart grids, industrial automation and intelligent transport systems. In this survey we present potential future URLLC applications, and summarize the corresponding reliability and latency requirements. We provide a comprehensive discussion on physical (PHY) and medium access control (MAC) layer techniques that enable URLLC, addressing both licensed and unlicensed bands. This paper evaluates the relevant PHY and MAC techniques for their ability to improve the reliability and reduce the latency. We identify that enabling long-term evolution to coexist in the unlicensed spectrum is also a potential enabler of URLLC in the unlicensed band, and provide numerical evaluations. Lastly, this paper discusses the potential future research directions and challenges in achieving the URLLC requirements

    Future Wireless Networks: Towards Learning-driven Sixth-generation Wireless Communications

    Get PDF
    The evolution of wireless communication networks, from present to the emerging fifth-generation (5G) new radio (NR), and sixth-generation (6G) is inevitable, yet propitious. The thesis evolves around application of machine learning and optimization techniques to problems in spectrum management, internet-of-things (IoT), physical layer security, and intelligent reflecting surface (IRS). The first problem explores License Assisted Access (LAA), which leverages unlicensed resource sharing with the Wi-Fi network as a promising technique to address the spectrum scarcity issue in wireless networks. An optimal communication policy is devised which maximizes the throughput performance of LAA network while guaranteeing a proportionally fair performance among LAA stations and a fair share for Wi-Fi stations. The numerical results demonstrate more than 75 % improvement in the LAA throughput and a notable gain of 8-9 % in the fairness index. Next, we investigate the unlicensed spectrum sharing for bandwidth hungry diverse IoT networks in 5G NR. An efficient coexistence mechanism based on the idea of adaptive initial sensing duration (ISD) is proposed to enhance the diverse IoT-NR network performance while keeping the primary Wi-Fi network's performance to a bearable threshold. A Q-learning (QL) based algorithm is devised to maximize the normalized sum throughput of the coexistence Wi-Fi/IoT-NR network. The results confirm a maximum throughput gain of 51 % and ensure that the Wi-Fi network's performance remains intact. Finally, advanced levels of network security are critical to maintain due to severe signal attenuation at higher frequencies of 6G wireless communication. Thus, an IRS-based model is proposed to address the issue of network security under trusted-untrusted device diversity, where the untrusted devices may potentially eavesdrop on the trusted devices. A deep deterministic policy gradient (DDPG) algorithm is devised to jointly optimize the active and passive beamforming matrices. The results confirm a maximum gain of 2-2.5 times in the sum secrecy rate of trusted devices and ensure Quality-of-Service (QoS) for all the devices. In conclusion, the thesis has led towards efficient, secure, and smart communication and build foundation to address similar complex wireless networks

    Gestion dynamique de ressources appliquée aux réseaux cellulaires avec interférence

    Get PDF
    The aim of this thesis is to design, implement and evaluate practical cross-layer algorithms. We focus on LTE and post-LTE uncoordinated networks where interference is a key issue given the new traffic patterns. The goal is to allocate the radio resources in an efficient way. We develop mathematical and computational interference models that allow us to understand the behavior of such networks and we apply an information-theoretic approach to different interference scenarios and traffic characteristics. We have tried to remain as close as possible to practical systems to be able to test the feasibility of the proposed techniques. The thesis deals with performance evaluation of interference scenarios in 4G networks, in particular those arising from small-cell deployments. The work in this thesis also deals with analysis of resource-allocation and incremental-redundancy based hybrid automatic repeat request (HARQ) for bursty interference (or more general time-varying channels) which allows for only partial channel state information at the transmitter. The work is then applied to practical scheduler design for LTE base stations and includes performance analysis for real LTE modems.L'objectif de cette thèse est de concevoir, implémenter et évaluer les algorithmes cross-layer pratiques. Nous nous concentrons sur la technologie LTE et les réseaux non coordonnés post-LTE où l'interférence est un enjeu majeur compte tenu des nouvelles tendances du trafic. L'objectif est d'allouer les ressources radio d'une manière efficace. Nous développons des modèles d'interférence mathématiques et informatiques qui nous permettent de comprendre le comportement de ces réseaux et nous appliquons une approche basée sur la théorie de l'information à différents scénarios d'interférence et caractéristiques du trafic. Nous avons essayé de s'approcher le plus possible de systèmes réels pour être en mesure de tester la faisabilité des techniques proposées. La thèse porte sur l'évaluation de la performance des scénarios d'interférence dans les réseaux 4G, en particulier celles qui découlent du déploiements de cellules de petite taille ("small cells"). Le travail dans cette thèse s'adresse également à l'analyse de l'allocation des ressources et la requête de répétition automatique hybride (HARQ) à redondance incrémentale pour les interférences sporadiques (de façon plus générale les canaux variables dans le temps) qui permet uniquement des informations partielles de l'état du canal à l'émetteur. Ce travail est ensuite appliquée à la conception d'ordonnanceur pour les stations de base LTE et inclut une analyse de performance pour les modems LTE réels

    Optimizations in Heterogeneous Mobile Networks

    Get PDF

    DRX over LAA-LTE-A New Design and Analysis Based on Semi-Markov Model

    No full text
    corecore