Analyzing Power Beacon Assisted Multi-Source Transmission Using Markov Chain

Wireless power transmission (WPT) is envisioned to be a promising technology for prolonging the lifetime of wireless devices in energy-constrained networks. This paper presents a general power beacon (PB) assisted multi-source transmission, where a practical source selection scheme with information transmission (IT) mode or non-IT mode is developed to maximize the transmission reliability. In the IT mode, a zero-forcing (ZF) beamformed signal with no interference to the destination is transmitted at the multi-antenna PB to supply wireless energy for the sources, and bring non-negative effect to the destination. Among multiple sources, the energy-sufficient source with the best channel quality is selected for wireless information transmission (WIT), while the other sources remain for energy harvesting. In the non-IT mode, the equal power transmission is adopted at PB to focus on energy delivery. Using Markov chain theory, the energy arrival and departure of each finite-capacity storage at the source is characterized mathematically, and the comprehensive analytical expressions of the energy outage probability (EOP), the connection outage probability (COP), and the average transmission delay (ATD) are formulated and derived. Our results reveal that the EOP, COP, and ATD can be significantly improved via increasing the number of sources deployed in the proposed network with finite transmit power of PB. We also prove that the multi-source network will never experience energy outage with infinite transmit power of PB

Design and analysis of a beacon-less routing protocol for large volume content dissemination in vehicular ad hoc networks

Largevolumecontentdisseminationispursuedbythegrowingnumberofhighquality applications for Vehicular Ad hoc NETworks(VANETs), e.g., the live road surveillance service and the video-based overtaking assistant service. For the highly dynamical vehicular network topology, beacon-less routing protocols have been proven to be efficient in achieving a balance between the system performance and the control overhead. However, to the authors’ best knowledge, the routing design for large volume content has not been well considered in the previous work, which will introduce new challenges, e.g., the enhanced connectivity requirement for a radio link. In this paper, a link Lifetime-aware Beacon-less Routing Protocol (LBRP) is designed for large volume content delivery in VANETs. Each vehicle makes the forwarding decision based on the message header information and its current state, including the speed and position information. A semi-Markov process analytical model is proposed to evaluate the expected delay in constructing one routing path for LBRP. Simulations show that the proposed LBRP scheme outperforms the traditional dissemination protocols in providing a low end-to-end delay. The analytical model is shown to exhibit a good match on the delay estimation with Monte Carlo simulations, as well

Enhancing infotainment applications quality of service in vehicular ad hoc networks

Les réseaux ad hoc de véhicules accueillent une multitude d’applications intéressantes. Parmi celles-ci, les applications d’info-divertissement visent à améliorer l’expérience des passagers. Ces applications ont des exigences rigides en termes de délai de livraison et de débit. De nombreuses approches ont été proposées pour assurer la qualité du service des dites applications. Elles sont réparties en deux couches : réseau et contrôle d’accès. Toutefois, ces méthodes présentent plusieurs lacunes. Cette thèse a trois volets. Le premier aborde la question du routage dans le milieu urbain. A cet égard, un nouveau protocole, appelé SCRP, a été proposé. Il exploite l’information sur la circulation des véhicules en temps réel pour créer des épines dorsales sur les routes et les connecter aux intersections à l’aide des nœuds de pont. Ces derniers collectent des informations concernant la connectivité et le délai, utilisées pour choisir les chemins de routage ayant un délai de bout-en-bout faible. Le deuxième s’attaque au problème d’affectation des canaux de services afin d’augmenter le débit. A cet effet, un nouveau mécanisme, appelé ASSCH, a été conçu. ASSCH collecte des informations sur les canaux en temps réel et les donne à un modèle stochastique afin de prédire leurs états dans l’avenir. Les canaux les moins encombrés sont sélectionnés pour être utilisés. Le dernier volet vise à proposer un modèle analytique pour examiner la performance du mécanisme EDCA de la norme IEEE 802.11p. Ce modèle tient en compte plusieurs facteurs, dont l’opportunité de transmission, non exploitée dans IEEE 802.11p.The fact that vehicular ad hoc network accommodates two types of communications, Vehicle-to-Vehicle and Vehicle-to-Infrastructure, has opened the door for a plethora of interesting applications to thrive. Some of these applications, known as infotainment applications, focus on enhancing the passengers' experience. They have rigid requirements in terms of delivery delay and throughput. Numerous approaches have been proposed, at medium access control and routing layers, to enhance the quality of service of such applications. However, existing schemes have several shortcomings. Subsequently, the design of new and efficient approaches is vital for the proper functioning of infotainment applications. This work proposes three schemes. The first is a novel routing protocol, labeled SCRP. It leverages real-time vehicular traffic information to create backbones over road segments and connect them at intersections using bridge nodes. These nodes are responsible for collecting connectivity and delay information, which are used to select routing paths with low end-to-end delay. The second is an altruistic service channel selection scheme, labeled ASSCH. It first collects real-time service channels information and feeds it to a stochastic model that predicts the state of these channels in the near future. The least congested channels are then selected to be used. The third is an analytical model for the performance of the IEEE 802.11p Enhanced Distributed Channel Access mechanism that considers various factors, including the transmission opportunity (TXOP), unexploited by IEEE 802.11p

Infrastructure-Assisted Message Dissemination for Supporting Heterogeneous Driving Patterns

With the advances of Internet of Things technologies, individual vehicles can now exchange information to improve traffic safety, and some vehicles can further improve safety and efficiency by coordinating their mobility via cooperative driving. To facilitate these applications, many studies have been focused on the design of inter-vehicle message dissemination protocols. However, most existing designs either assume individual driving pattern or consider cooperative driving only. Moreover, few of them fully exploit infrastructures, such as cameras, sensors, and road-side units. In this paper, we address the design of message dissemination that supports heterogeneous driving patterns. Specifically, we first propose an infrastructure-assisted message dissemination framework that can utilize the capability of infrastructures. We then present a novel beacon scheduling algorithm that aims at guaranteeing the timely and reliable delivery of both periodic beacon messages for cooperative driving and event-triggered safety messages for individual driving. To evaluate the performance of the protocol, we develop both theoretical analysis and simulation experiments. Extensive numerical results confirm the effectiveness of the proposed protocol

비면허대역 셀룰라 통신의 성능 분석 및 성능 향상 기법 연구

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

On a Joint Physical Layer and Medium Access Control Sublayer Design for Efficient Wireless Sensor Networks and Applications

Wireless sensor networks (WSNs) are distributed networks comprising small sensing devices equipped with a processor, memory, power source, and often with the capability for short range wireless communication. These networks are used in various applications, and have created interest in WSN research and commercial uses, including industrial, scientific, household, military, medical and environmental domains. These initiatives have also been stimulated by the finalisation of the IEEE 802.15.4 standard, which defines the medium access control (MAC) and physical layer (PHY) for low-rate wireless personal area networks (LR-WPAN). Future applications may require large WSNs consisting of huge numbers of inexpensive wireless sensor nodes with limited resources (energy, bandwidth), operating in harsh environmental conditions. WSNs must perform reliably despite novel resource constraints including limited bandwidth, channel errors, and nodes that have limited operating energy. Improving resource utilisation and quality-of-service (QoS), in terms of reliable connectivity and energy efficiency, are major challenges in WSNs. Hence, the development of new WSN applications with severe resource constraints will require innovative solutions to overcome the above issues as well as improving the robustness of network components, and developing sustainable and cost effective implementation models. The main purpose of this research is to investigate methods for improving the performance of WSNs to maintain reliable network connectivity, scalability and energy efficiency. The study focuses on the IEEE 802.15.4 MAC/PHY layers and the carrier sense multiple access with collision avoidance (CSMA/CA) based networks. First, transmission power control (TPC) is investigated in multi and single-hop WSNs using typical hardware platform parameters via simulation and numerical analysis. A novel approach to testing TPC at the physical layer is developed, and results show that contrary to what has been reported from previous studies, in multi-hop networks TPC does not save energy. Next, the network initialization/self-configuration phase is addressed through investigation of the 802.15.4 MAC beacon interval setting and the number of associating nodes, in terms of association delay with the coordinator. The results raise doubt whether that the association energy consumption will outweigh the benefit of duty cycle power management for larger beacon intervals as the number of associating nodes increases. The third main contribution of this thesis is a new cross layer (PHY-MAC) design to improve network energy efficiency, reliability and scalability by minimising packet collisions due to hidden nodes. This is undertaken in response to findings in this thesis on the IEEE 802.15.4 MAC performance in the presence of hidden nodes. Specifically, simulation results show that it is the random backoff exponent that is of paramount importance for resolving collisions and not the number of times the channel is sensed before transmitting. However, the random backoff is ineffective in the presence of hidden nodes. The proposed design uses a new algorithm to increase the sensing coverage area, and therefore greatly reduces the chance of packet collisions due to hidden nodes. Moreover, the design uses a new dynamic transmission power control (TPC) to further reduce energy consumption and interference. The above proposed changes can smoothly coexist with the legacy 802.15.4 CSMA/CA. Finally, an improved two dimensional discrete time Markov chain model is proposed to capture the performance of the slotted 802.15.4 CSMA/CA. This model rectifies minor issues apparent in previous studies. The relationship derived for the successful transmission probability, throughput and average energy consumption, will provide better performance predictions. It will also offer greater insight into the strengths and weaknesses of the MAC operation, and possible enhancement opportunities. Overall, the work presented in this thesis provides several significant insights into WSN performance improvements with both existing protocols and newly designed protocols. Finally, some of the numerous challenges for future research are described

Machine Learning in Wireless Sensor Networks: Algorithms, Strategies, and Applications

Wireless sensor networks monitor dynamic environments that change rapidly over time. This dynamic behavior is either caused by external factors or initiated by the system designers themselves. To adapt to such conditions, sensor networks often adopt machine learning techniques to eliminate the need for unnecessary redesign. Machine learning also inspires many practical solutions that maximize resource utilization and prolong the lifespan of the network. In this paper, we present an extensive literature review over the period 2002-2013 of machine learning methods that were used to address common issues in wireless sensor networks (WSNs). The advantages and disadvantages of each proposed algorithm are evaluated against the corresponding problem. We also provide a comparative guide to aid WSN designers in developing suitable machine learning solutions for their specific application challenges.Comment: Accepted for publication in IEEE Communications Surveys and Tutorial

A Comprehensive Analysis of Literature Reported Mac and Phy Enhancements of Zigbee and its Alliances

Wireless communication is one of the most required technologies by the common man. The strength of this technology is rigorously progressing towards several novel directions in establishing personal wireless networks mounted over on low power consuming systems. The cutting-edge communication technologies like bluetooth, WIFI and ZigBee significantly play a prime role to cater the basic needs of any individual. ZigBee is one such evolutionary technology steadily getting its popularity in establishing personal wireless networks which is built on small and low-power digital radios. Zigbee defines the physical and MAC layers built on IEEE standard. This paper presents a comprehensive survey of literature reported MAC and PHY enhancements of ZigBee and its contemporary technologies with respect to performance, power consumption, scheduling, resource management and timing and address binding. The work also discusses on the areas of ZigBee MAC and PHY towards their design for specific applications