Recent Advances in Cellular D2D Communications

Device-to-device (D2D) communications have attracted a great deal of attention from researchers in recent years. It is a promising technique for offloading local traffic from cellular base stations by allowing local devices, in physical proximity, to communicate directly with each other. Furthermore, through relaying, D2D is also a promising approach to enhancing service coverage at cell edges or in black spots. However, there are many challenges to realizing the full benefits of D2D. For one, minimizing the interference between legacy cellular and D2D users operating in underlay mode is still an active research issue. With the 5th generation (5G) communication systems expected to be the main data carrier for the Internet-of-Things (IoT) paradigm, the potential role of D2D and its scalability to support massive IoT devices and their machine-centric (as opposed to human-centric) communications need to be investigated. New challenges have also arisen from new enabling technologies for D2D communications, such as non-orthogonal multiple access (NOMA) and blockchain technologies, which call for new solutions to be proposed. This edited book presents a collection of ten chapters, including one review and nine original research works on addressing many of the aforementioned challenges and beyond

A fast and reliable broadcast service for LTE-advanced exploiting multihop device-to-device transmissions

Several applications, from the Internet of Things for smart cities to those for vehicular networks, need fast and reliable proximity-based broadcast communications, i.e., the ability to reach all peers in a geographical neighborhood around the originator of a message, as well as ubiquitous connectivity. In this paper, we point out the inherent limitations of the LTE (Long-Term Evolution) cellular network, which make it difficult, if possible at all, to engineer such a service using traditional infrastructure-based communications. We argue, instead, that network-controlled device-to-device (D2D) communications, relayed in a multihop fashion, can efficiently support this service. To substantiate the above claim, we design a proximity-based broadcast service which exploits multihop D2D. We discuss the relevant issues both at the UE (User Equipment), which has to run applications, and within the network (i.e., at the eNodeBs), where suitable resource allocation schemes have to be enforced. We evaluate the performance of a multihop D2D broadcasting using system-level simulations, and demonstrate that it is fast, reliable and economical from a resource consumption standpoint

Distributed Relay Selection for Heterogeneous UAV Communication Networks Using A Many-to-Many Matching Game Without Substitutability

This paper proposes a distributed multiple relay selection scheme to maximize the satisfaction experiences of unmanned aerial vehicles (UAV) communication networks. The multi-radio and multi-channel (MRMC) UAV communication system is considered in this paper. One source UAV can select one or more relay radios, and each relay radio can be shared by multiple source UAVs equally. Without the center controller, source UAVs with heterogeneous requirements compete for channels dominated by relay radios. In order to optimize the global satisfaction performance, we model the UAV communication network as a many-to-many matching market without substitutability. We design a potential matching approach to address the optimization problem, in which the optimizing of local matching process will lead to the improvement of global matching results. Simulation results show that the proposed distributed matching approach yields good matching performance of satisfaction, which is close to the global optimum result. Moreover, the many-to-many potential matching approach outperforms existing schemes sufficiently in terms of global satisfaction within a reasonable convergence time.Comment: 6 pages, 4 figures, conferenc

先進ITSのための中継アシスト車車間通信技術の研究

Wireless vehicular communications for advanced Intelligent Transport Systems (ITS) have the potential to support safety driving, enhance the efficiency of transportation and play an important role in the future automated driving system. The vehicle-to-vehicle(V2V), vehicle-to-infrastructure (V2I) and vehicle-to-pedestrian (V2P) communications in the advanced ITS enable safety support applications that can predict potential traffic accidents, warn drivers and, in some cases, directly control vehicles to prevent collisions. Such applications require highly reliable broadcast communications. However, the reliability of wireless communication in vehicular environments suffers from fast fading due to multipath propagation, shadowing , and distance-dependent path loss. In addition, hidden terminal (HT) problem is a great concern in CSMA/CA based wireless networks due to its distributed access nature. The packet delivery rate (PDR) of V2V communications rapidly decreases especially under non-line-of-sight (NLOS) environments such as intersections. A vehicle-roadside-vehicle relay-assisted V2V communication scheme has been proposed to improve the reliability of V2V communications. In the scheme, packets sent from a vehicle can be directly received by other vehicles or relayed by a relay station (RS) to the other vehicles. Then path diversity effect can be obtained that improves PDR of V2V communications. However, when the V2V traffic becomes higher, the number of packets that RS has to retransmit becomes larger. This leads to a large number of packets waiting in the transmit queue of RS and packet congestion happens. If the normal relay scheme is employed, thepackets may be dropped due to the limited queue size. Then the gain obtained by relay-assist may be decreased. A packet payload combining relay (PCRL) scheme is proposed to deal with the congestion issue. In the scheme, multiple V2V packet payloads are combined into a single packet and the resultant packet is rebroadcasted once the channel becomes idle. Analytical and simulated results show that the proposed PCRL scheme can remarkably alleviate the congestion issue and improve the relaying performance.The PCRL scheme, however, still suffers from HT problem. In the intersection environments where LOS propagation between VSs is often unavailable, the packet collision frequently happens due to HTs when RS receives V2V packets. If RS cannot receive V2V packets, the advantage of relay-assist becomes smaller. Therefore an improved PCRL scheme with sectorized receiving RS (SR-V2VC/PCRL) is proposed to mitigate the effect of HT problem as well as alleviating the congestion issue. An analytical model is then developed to analyze the performance of SR-V2VC/PCRL scheme considering a single intersection scenario. Numerical results show that the reliability of V2V communications is significantly improved by the proposed scheme. Furthermore, performance of the SR-V2VC/PCRL scheme is discussed for an urban environment with multiple intersections. In such environment, RSs at intersections should cooperate with each other to obtain the largest diversity gain. After theoretically analyzing the performance of the sectorized receiving scheme under multiple interference sources, large-scale simulations are conducted to evaluate the performance of SR-V2VC/PCRL scheme. It is shown that the SR-V2VC/PCRL remarkably improves the reliability of V2V communications. SR-V2VC/PCRL scheme even performs better when employing higher data rate modulation for V2V and relay transmissions.The aforementioned proposals can remarkably improve the reliability of V2V communications. In order to improve the performance of relay-assist ed scheme when traffic load becomes even higher, a network coding(NC)based PCRL scheme (PCRL-NC) with a payload sorting and selection algorithm is proposed to adapt multiple node environment in an intersection. It is shown that the scheme can benefit from NC in alleviating the congestion issue while effectively mitigating the disadvantage of NC. As a result, the introduction of PCRL-NC to the proposed SR-V2VC/PCRL scheme can remarkably improve the reliability of V2V communications under various traffic environments.　近年，先進的なITS (Intelligent Transport Systems: 高度道路交通システム)のための通信技術への期待が高まっている．これには，車両がその位置や速度などの情報を交換する車車間通信，路側機が車両へ信号状態や道路規制などの情報を提供する路車間通信，車両と歩行者の間で情報の交換を行う歩車間通信などがある．これらにブロードキャスト通信を活用することで，各車両では潜在的な交通事故を予測して運転手に警告し，さらには制動を行うことにより事故を未然に回避できる．さらにこの情報を利用して車両を自動制御することで，交通流を意識した協調型自動走行を実現することが可能になるものと期待されている． 車車間通信を用いて安全運転支援およびより高度な自動走行システムを実現するためには，高信頼，かつ低遅延の無線通信技術が要求される．しかしながら道路上の移動通信では，多重波伝搬によるフェージングや建物によるシャドウイング，さらに自律分散通信システム特有の問題である隠れ端末問題による干渉などの影響で，通信の信頼度が低下する．特に事故発生確率の高い交差点ではその影響が顕著である．　本論文では車車間通信の品質を改善することを目的として，交差点等に中継局(Relay Station; RS)を設置し，車車間通信パケットを転送中継する中継アシスト車車間通信に関する諸技術が提案されている．中継局は交差点付近の信号機などに併設され，高いアンテナ高を有することと，他の車載局に対して見通し内(Line-of-Sight; LOS)伝搬環境にあるため，中継アシストシステムはシャドウイングやフェージングの問題の軽減に有効であることが既に示されている．しかしながら，トラヒックが増加するにつれて中継局での輻輳問題が発生し，中継効果が低下するという課題があった．そこで本論文では中継によるエアトラヒックの増加を抑える方法として，中継送信時に複数のパケットペイロードをまとめて１つのパケットに再構成して送信するペイロード合成中継法を提案する．本提案法により中継局での輻輳問題が解決でき，中継効果が向上することを解析結果から明らかにした．　交差点における中継アシスト車車間通信のもう1つの課題として，中継局受信時に隠れ端末問題の影響で受信成功率が低下することがある．この課題に対しては中継局受信時にセクタアンテナを用いることが有効であることが示されているが，本研究ではペイロード合成中継法にセクタ化受信を組合せたセクタ化受信ペイロード合成中継法を提案し，その効果を理論解析およびシミュレーションにより示した．セクタ化受信によって中継局での受信成功率を改善すると中継すべきパケット数が増加するが，提案法ではペイロード合成によって中継パケットの送信効率を高めることができるので，結果として中継効果を高めて平均パケット伝送成功率を大幅に向上できることを明らかにした．　さらに，複数交差点からなる市街地環境におけるセクタ化受信ペイロード合成中継法の効果を，大規模ネットワークシミュレーションを用いてブロードキャスト配信成功率として総合的に評価した．他の車両および離れた中継局など干渉源が複数存在する市街地環境においても，提案法を用いることによって隠れ端末問題の影響が有効に回避できること，隣接する中継局間で互いに棲分け中継をすることで非常に高い中継効果が得られることを明らかにした．　以上のように提案法は中継アシスト車車間通信の特性を大幅に改善できるが，通信トラヒックがさらに高い環境に対処するため，中継パケットのエアトラヒックをさらに圧縮できる方法として，複数ノード環境に適したネットワークコーディング法を用いたペイロード合成中継法を提案する．本提案法では，車車間ペイロードのソーティングと合成対象パケットの選択アルゴリズムによって複数ノード環境でのネットワークコーディングの弱点を抑えつつ，輻輳問題に有効に対処できることを示した．結果として本提案法をセクタ化受信と組合せることで，幅広い通信トラヒック条件においてブロードキャスト配信成功率が大きく向上することを明らかにした．電気通信大学201

Multi-Dimensional Resource Orchestration in Vehicular Edge Networks

In the era of autonomous vehicles, the advanced technologies of connected vehicle lead to the development of driving-related applications to meet the stringent safety requirements and the infotainment applications to improve passenger experience. Newly developed vehicular applications require high-volume data transmission, accurate sensing data collection, and reliable interaction, imposing substantial constrains on vehicular networks that solely rely on cellular networks to fetch data from the Internet and on-board processors to make driving decisions. To enhance multifarious vehicular applications, Heterogeneous Vehicular Networks (HVNets) have been proposed, in which edge nodes, including base stations and roadside units, can provide network connections, resulting in significantly reduced vehicular communication cost. In addition, caching servers are equipped at the edge nodes, to further alleviate the communication load for backhaul links and reduce data downloading delay. Hence, we aim to orchestrate the multi-dimensional resources, including communication, caching, and sensing resources, in the complex and dynamic vehicular environment to enhance vehicular edge network performance. The main technical issues are: 1) to accommodate the delivery services for both location-based and popular contents, the scheme of caching contents at edge servers should be devised, considering the cooperation of caching servers at different edge nodes, the mobility of vehicles, and the differential requirements of content downloading services; 2) to support the safety message exchange and collective perception services for vehicles, communication and sensing resources are jointly allocated, the decisions of which are coupled due to the resource sharing among different services and neighboring vehicles; and 3) for interaction-intensive service provisioning, e.g., trajectory design, the forwarding resources in core networks are allocated to achieve delay-sensitive packet transmissions between vehicles and management controllers, ensuring the high-quality interactivity. In this thesis, we design the multi-dimensional resource orchestration schemes in the edge assisted HVNets to address the three technical issues. Firstly, we design a cooperative edge caching scheme to support various vehicular content downloading services, which allows vehicles to fetch one content from multiple caching servers cooperatively. In particular, we consider two types of vehicular content requests, i.e., location-based and popular contents, with different delay requirements. Both types of contents are encoded according to fountain code and cooperatively cached at multiple servers. The proposed scheme can be optimized by finding an optimal cooperative content placement that determines the placing locations and proportions for all contents. To this end, we analyze the upper bound proportion of content caching at a single server and provide the respective theoretical analysis of transmission delay and service cost (including content caching and transmission cost) for both types of contents. We then formulate an optimization problem of cooperative content placement to minimize the overall transmission delay and service cost. As the problem is a multi-objective multi-dimensional multi-choice knapsack one, which is proved to be NP-hard, we devise an ant colony optimization-based scheme to solve the problem and achieve a near-optimal solution. Simulation results are provided to validate the performance of the proposed scheme, including its convergence and optimality of caching, while guaranteeing low transmission delay and service cost. Secondly, to support the vehicular safety message transmissions, we propose a two-level adaptive resource allocation (TARA) framework. In particular, three types of safety message are considered in urban vehicular networks, i.e., the event-triggered message for urgent condition warning, the periodic message for vehicular status notification, and the message for environmental perception. Roadside units are deployed for network management, and thus messages can be transmitted through either vehicle-to-infrastructure or vehicle-to-vehicle connections. To satisfy the requirements of different message transmissions, the proposed TARA framework consists of a group-level resource reservation module and a vehicle-level resource allocation module. Particularly, the resource reservation module is designed to allocate resources to support different types of message transmission for each vehicle group at the first level, and the group is formed by a set of neighboring vehicles. To learn the implicit relation between the resource demand and message transmission requests, a supervised learning model is devised in the resource reservation module, where to obtain the training data we further propose a sequential resource allocation (SRA) scheme. Based on historical network information, the SRA scheme offline optimizes the allocation of sensing resources (i.e., choosing vehicles to provide perception data) and communication resources. With the resource reservation result for each group, the vehicle-level resource allocation module is then devised to distribute specific resources for each vehicle to satisfy the differential requirements in real time. Extensive simulation results are provided to demonstrate the effectiveness of the proposed TARA framework in terms of the high successful reception ratio and low latency for message transmissions, and the high quality of collective environmental perception. Thirdly, we investigate forwarding resource sharing scheme to support interaction intensive services in HVNets, especially for the delay-sensitive packet transmission between vehicles and management controllers. A learning-based proactive resource sharing scheme is proposed for core communication networks, where the available forwarding resources at a switch are proactively allocated to the traffic flows in order to maximize the efficiency of resource utilization with delay satisfaction. The resource sharing scheme consists of two joint modules: estimation of resource demands and allocation of available resources. For service provisioning, resource demand of each traffic flow is estimated based on the predicted packet arrival rate. Considering the distinct features of each traffic flow, a linear regression scheme is developed for resource demand estimation, utilizing the mapping relation between traffic flow status and required resources, upon which a network switch makes decision on allocating available resources for delay satisfaction and efficient resource utilization. To learn the implicit relation between the allocated resources and delay, a multi-armed bandit learning-based resource sharing scheme is proposed, which enables fast resource sharing adjustment to traffic arrival dynamics. The proposed scheme is proved to be asymptotically approaching the optimal strategy, with polynomial time complexity. Extensive simulation results are presented to demonstrate the effectiveness of the proposed resource sharing scheme in terms of delay satisfaction, traffic adaptiveness, and resource sharing gain. In summary, we have investigated the cooperative caching placement for content downloading services, joint communication and sensing resource allocation for safety message transmissions, and forwarding resource sharing scheme in core networks for interaction intensive services. The schemes developed in the thesis should provide practical and efficient solutions to manage the multi-dimensional resources in vehicular networks

Analytical Performance Evaluation of Cooperative and Multi-Radio Concepts in Emerging Wireless Networks

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Development of Energy and Delay Efficient Protocols for WSAN

Wireless sensor-actor network (WSAN) is a collection of resource conservative sensors and few resource-rich actors. It is widely used in various applications such as environmental monitoring, battlefield surveillance, industrial process control, and home applications. In these real-time applications, data should be delivered with minimum delay and energy. In this thesis, delay and energy efficient protocols are designed to achieve these objectives. The first contribution proposes a delay and energy aware coordination protocol (DEACP) to improve the network performance. It consists of two-level hierarchical K-hop clustering and backup cluster head (BCH) selection mechanism to provide coordination among sensors and actors. Further, a priority based event forwarding mechanism has also been proposed to forward the maximum number of packets within the bounded delay. The simulation results demonstrate the effectiveness of DEACP over existing protocols. In the second work, an interference aware multi-channel MAC protocol (IAMMAC) has been suggested to assign channels for the communication among nodes in the DEACP. An actor assigns the static channels to all of its cluster members for sensor-sensor and sensor-actor coordination. Subsequently, a throughput based dynamic channel selection mechanism has been developed for actor-actor coordination. It is inferred from the simulation results that the proposed IAMMAC protocol outperforms its competitive protocols. Even though its performance is superior, it is susceptible to be attacked because it uses a single static channel between two sensors in the entire communication. To overcome this problem, a lightweight dynamic multi-channel MAC protocol (DM-MAC) has been designed for sensor sensor coordination. Each sensor dynamically selects a channel which provides maximum packet reception ratio among the available hannels with the destination. The comparative analysis shows that DM-MAC protocol performs better than the existing MAC protocols in terms of different performance parameters. WSAN is designed to operate in remote and hostile environments and hence, sensors and actors are vulnerable to various attacks. The fourth contribution proposes a secure coordination mechanism (SCM) to handle the data forwarding attacks in DEACP. In the SCM, each sensor computes the trust level of its neighboring sensors based on the experience, recommendation, and knowledge. The actor analyzes the trust values of all its cluster members to identify the malicious node. Secure hash algorithm-3 is used to compute the message authentication code for the data. The sensor selects a neighbor sensor which has the highest trust value among its 1-hop sensors to transfer data to the actor. The SCM approach outperforms the existing security mechanisms

Clustering algorithm for D2D communication in next generation cellular networks : thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering, Massey University, Auckland, New Zealand

Next generation cellular networks will support many complex services for smartphones, vehicles, and other devices. To accommodate such services, cellular networks need to go beyond the capabilities of their previous generations. Device-to-Device communication (D2D) is a key technology that can help fulfil some of the requirements of future networks. The telecommunication industry expects a significant increase in the density of mobile devices which puts more pressure on centralized schemes and poses risk in terms of outages, poor spectral efficiencies, and low data rates. Recent studies have shown that a large part of the cellular traffic pertains to sharing popular contents. This highlights the need for decentralized and distributive approaches to managing multimedia traffic. Content-sharing via D2D clustered networks has emerged as a popular approach for alleviating the burden on the cellular network. Different studies have established that D2D communication in clusters can improve spectral and energy efficiency, achieve low latency while increasing the capacity of the network. To achieve effective content-sharing among users, appropriate clustering strategies are required. Therefore, the aim is to design and compare clustering approaches for D2D communication targeting content-sharing applications. Currently, most of researched and implemented clustering schemes are centralized or predominantly dependent on Evolved Node B (eNB). This thesis proposes a distributed architecture that supports clustering approaches to incorporate multimedia traffic. A content-sharing network is presented where some D2D User Equipment (DUE) function as content distributors for nearby devices. Two promising techniques are utilized, namely, Content-Centric Networking and Network Virtualization, to propose a distributed architecture, that supports efficient content delivery. We propose to use clustering at the user level for content-distribution. A weighted multi-factor clustering algorithm is proposed for grouping the DUEs sharing a common interest. Various performance parameters such as energy consumption, area spectral efficiency, and throughput have been considered for evaluating the proposed algorithm. The effect of number of clusters on the performance parameters is also discussed. The proposed algorithm has been further modified to allow for a trade-off between fairness and other performance parameters. A comprehensive simulation study is presented that demonstrates that the proposed clustering algorithm is more flexible and outperforms several well-known and state-of-the-art algorithms. The clustering process is subsequently evaluated from an individual user’s perspective for further performance improvement. We believe that some users, sharing common interests, are better off with the eNB rather than being in the clusters. We utilize machine learning algorithms namely, Deep Neural Network, Random Forest, and Support Vector Machine, to identify the users that are better served by the eNB and form clusters for the rest of the users. This proposed user segregation scheme can be used in conjunction with most clustering algorithms including the proposed multi-factor scheme. A comprehensive simulation study demonstrates that with such novel user segregation, the performance of individual users, as well as the whole network, can be significantly improved for throughput, energy consumption, and fairness

Optimization and Communication in UAV Networks

UAVs are becoming a reality and attract increasing attention. They can be remotely controlled or completely autonomous and be used alone or as a fleet and in a large set of applications. They are constrained by hardware since they cannot be too heavy and rely on batteries. Their use still raises a large set of exciting new challenges in terms of trajectory optimization and positioning when they are used alone or in cooperation, and communication when they evolve in swarm, to name but a few examples. This book presents some new original contributions regarding UAV or UAV swarm optimization and communication aspects