Dynamic Queue Utilization Based MAC for multi-hop Ad Hoc networks

The end-to-end throughput in single flow multi-hop Ad Hoc networks decays rapidly with path length. Along the path, the success rate of delivering packets towards the destination decreases due to higher contention, interference, limited buffer size and limited shared bandwidth constraints. In such environments the queues fill up faster in nodes closer to the source than in the nodes nearer the destination. In order to reduce buffer overflow and improve throughput for a saturated network, this paper introduces a new MAC protocol named Dynamic Queue Utilization Based Medium Access Control (DQUB-MAC). The protocol aims to prioritise access to the channel for queues with higher utilization and helps in achieving higher throughput by rapidly draining packets towards the destination. The proposed MAC enhances the performance of an end-to-end data flow by up to 30% for a six hop transmission in a chain topology and is demonstrated to remain competitive for other network topologies and for a variety of packet sizes

A Spectrum Efficient Self-Admission Framework for Coexisting IEEE 802.15.4 Networks under Heterogeneous Traffics

Due to the limited bandwidth resource and the interference among networks, it is challengeable to coordinate the bandwidth resource of multiple IEEE 802.15.4-based wireless personal area networks (WPANs) with heterogeneous traffics, especially in a distributed mode. In this paper, to handle this problem, we first propose a renewal carrier sense multiple access (CSMA)-based self-admission access mechanism for coexisting WPANs in order to maximize the frequency resource utilization and satisfy the diverse rate requirements of heterogeneous traffics. Secondly, we propose the time-space-hard core point process (TS-HCPP) to abstract the renewal CSMA-based self-admission access process for the IEEE 802.15.4 network with multi-channels. TS-HCPP considers the correlation of time and space, and appropriately judges the strong interference between coexisting WPANs, which can solve the density underestimation problems of traditional HCPP. Finally, relying on the TS-HCPP, we obtain the optimum combination of access parameters, which meets the minimum service rate requirements for heterogeneous traffics and maximizes the frequency resource utilization. The simulation results show that the density of coexisting WPANs evaluated by the TS-HCPP matches the experimental results, and an improvement in spectral efficiency of coexisting WPANs can be achieved in our proposed self-admission framework

Modeling and Analysis of Cellular Networks Using Stochastic Geometry: A Tutorial

This paper presents a tutorial on stochastic geometry (SG)-based analysis for cellular networks. This tutorial is distinguished by its depth with respect to wireless communication details and its focus on cellular networks. This paper starts by modeling and analyzing the baseband interference in a baseline single-tier downlink cellular network with single antenna base stations and universal frequency reuse. Then, it characterizes signal-to-interference-plus-noise-ratio and its related performance metrics. In particular, a unified approach to conduct error probability, outage probability, and transmission rate analysis is presented. Although the main focus of this paper is on cellular networks, the presented unified approach applies for other types of wireless networks that impose interference protection around receivers. This paper then extends the unified approach to capture cellular network characteristics (e.g., frequency reuse, multiple antenna, power control, etc.). It also presents numerical examples associated with demonstrations and discussions. To this end, this paper highlights the state-of-the-art research and points out future research directions

Device-to-device communication : effects of using spatial spectrum sensing and dual band networks

Orientador: Paulo CardieriDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: A técnica comunicação Device-to-Device (D2D) é considerada como uma das tecnologias candidatas para a implementação de sistemas celulares de quinta geração (5G). Basicamente, essa técnica permite a comunicação direta entre dois terminais de usuário que estejam próximos entre si, sem, assim, usar a estação rádio base (BS, Base Station). A técnica D2D tem a capacidade de fornecer altas taxas de dados com menor consumo de energia, devido à menor distância do enlace entre transmissor e receptor. Essas características tornam-se atraentes para os pesquisadores que estão na busca de tecnologias capazes de atender o alto tráfego de dados que atualmente circula nas redes sem fio, e garantir os padrões de qualidade de serviço (QoS, Quality of Service) esperados pelos usuários. Esse presente trabalho estuda a técnica de comunicação D2D em uma rede celular no modo underlay de compartilhamento de canal, isto é, quando um canal uplink da rede celular é compartilhado entre terminais operando no modo convencional, isto é, conectados às BS, e terminais operando no modo D2D. Com essa forma de compartilhamento de canal, a interferência entre os enlaces celulares e D2D pode degradar o desempenho da rede. Para controlar o nível de interferência, assume-se que os terminais operando no modo D2D utilizam a técnica de spectrum sensing (SS) para detectar o estado do canal (livre ou ocupado), antes de iniciar a sua transmissão. São considerados nesse estudo dois cenários de uso do spectrum sensing. No Cenário I, os terminais D2D usam SS para evitar a interferência entre eles e os terminais celulares. Nesse sentido, como consequência do processo de SS, as posições dos transmissores D2D podem ser modeladas pelo processo pontual chamado Poisson Hole Process. No Cenário II, o processo de spectrum sensing empregado pelos terminais D2D é usado para detectar o uso do canal não apenas por algum terminal celular, mas também por algum terminal D2D. O processo pontual resultante que modela os transmissores D2D neste cenário é uma versão do chamado processo Matérn Point Process. Para esses dois cenários são derivadas expressões de probabilidade de outage para os enlaces celulares e enlaces D2D, empregando ferramentas de Geometria Estocástica, usando os processos pontuais mencionados. Com base nessas expressões de probabilidade de outage, é apresentada uma análise do desempenho da rede celular-D2D. Outra tecnologia atraente para sistemas 5G é a comunicação na faixa de ondas milimétricas, uma vez que tal faixa apresenta uma largura de banda maior, permitindo altas taxas de dados. No entanto, a comunicação na banda de ondas milimétricas requer linha de visada, sendo, portanto, altamente susceptível a bloqueio do enlace devido às condições de propagação. Esse trabalho estuda também a comunicação D2D em um cenário em que os terminais podem operar nas bandas de ondas milimétricas e microondas, combinado com um esquema de retransmissão de pacotes. No cenário estudado aqui, os terminais D2D operam prioritariamente na banda de ondas milimétricas, mas quando as condições de propagação nessa banda se deterioram, eles podem mudar para a banda de microondas, como uma tentativa de melhorar o desempenho geral. Também usando elementos de geometria estocástica, são derivadas expressões de probabilidade de outage para a comunicação nas duas bandas, e uma análise do desempenho desse esquema de transmissão é investigadoAbstract: Device-to-Device Communication is deemed as one of the key technologies for the fifth generation of cellular systems (5G). Basically, this strategy of communication allows user terminals to communicate directly with each other, without any assistance from base stations. Device-to-device communication is capable of providing high data rate, coverage extension, and reduced energy consumption. Due to the shorter distance of the link between transmitter and receiver. These features are attractive to researchers who are searching for technologies can handle the high data traffic that currently circulates on wireless networks, and ensures the quality of service standards (QoS), expected by users. This present work investigates the performance of an underlay D2D cellular network, in which D2D terminals and cellular terminals share the same uplink channel. In order to control the level of interference, we assume that D2D terminals employ spectrum sensing (SS) in order to detect the presence of other transmission on the target channel. Two scenarios are considered regarding the use of spectrum sensing. In Scenario I, the D2D terminals employ SS to avoid interference between them and cellular terminals. Therefore, the locations of D2D transmitters can be modeled by a Poisson Hole Process. In Scenario II, spectrum sensing is used to control the interference among D2D terminals and cellular terminals, as in Scenario I, and the interference among D2D terminals. In this scenario, the locations of D2D terminals are better modeled by a version of the Matérn Point Process. Using elements of Stochastic Geometry, expressions for outage probabilities in both scenarios are derived and used in the performance analysis of these two scenarios. Another attractive technology for 5G cellular systems is millimeter-wave communication, due to the availability of large bandwidth at this frequency band, allowing for a high data rate. However, the communication in the millimeter wave band is highly susceptible to link blockage, degrading the communication performance. In this work, we investigate the performance of a D2D network in which terminals can operate either in the millimeter-wave band or in the microwave band, combined with a packet retransmission scheme and beam-forming. The terminals primarily operate in the millimeter-wave band, and when the propagation conditions deteriorate, they can switch to the microwave band as an attempt to improve the overall performance. Using tools from Stochastic Geometry, the performance of this communication strategy is investigatedMestradoTelecomunicações e TelemáticaMestra em Engenharia ElétricaCAPE

OPTIMISING APPLICATION PERFORMANCE WITH QOS SUPPORT IN AD HOC NETWORKS

The popularity of wireless communication has increased substantially over the last decade, due to mobility support, flexibility and ease of deployment. Among next generation of mobile communication technologies, Ad Hoc networking plays an important role, since it can stand alone as private network, become a part of public network, either for general use or as part of disaster management scenarios. The performance of multihop Ad Hoc networks is heavily affected by interference, mobility, limited shared bandwidth, battery life, error rate of wireless media, and the presence of hidden and exposed terminals. The scheduler and the Medium Access Control (MAC) play a vital role in providing Quality of Service (QoS) and policing delay, end-to-end throughput, jitter, and fairness for user application services. This project aims to optimise the usage of the available limited resources in terms of battery life and bandwidth, in order to reduce packet delivery time and interference, enhance fairness, as well as increase the end-to-end throughput, and increase the overall network performance. The end-to-end throughput of an Ad Hoc network decays rapidly as the hop count between the source and destination pair increases and additional flows injected along the path of an existing flow affects the flows arriving from further away; in order to address this problem, the thesis proposes a Hop Based Dynamic Fair Scheduler that prioritises flows subject to the hop count of frames, leading to a 10% increase in fairness when compared to a IEEE 802.11b with single queue. Another mechanism to improve network performance in high congestion scenarios is network-aware queuing that reduces loss and improve the end-to-end throughput of the communicating nodes, using a medium access control method, named Dynamic Queue Utilisation Based Medium Access Control (DQUB-MAC). This MAC provides higher access probability to the nodes with congested queue, so that data generated at a high rate can be forwarded more effectively. Finally, the DQUB-MAC is modified to take account of hop count and a new MAC called Queue Utilisation with Hop Based Enhanced Arbitrary Inter Frame Spacing (QU-EAIFS) is also designed in this thesis. Validation tests in a long chain topology demonstrate that DQUB-MAC and QU-EAIFS increase the performance of the network during saturation by 35% and 40% respectively compared to IEEE 802.11b. High transmission power leads to greater interference and represents a significant challenge for Ad Hoc networks, particularly in the context of shared bandwidth and limited battery life. The thesis proposes two power control mechanisms that also employ a random backoff value directly proportional to the number of the active contending neighbours. The first mechanism, named Location Based Transmission using a Neighbour Aware with Optimised EIFS for Ad Hoc Networks (LBT-NA with Optimised EIFS MAC), controls the transmission power by exchanging location information between the communicating nodes in order to provide better fairness through a dynamic EIFS based on the overheard packet length. In a random topology, with randomly placed source and destination nodes, the performance gain of the proposed MAC over IEEE 802.11b ranges from approximately 3% to above 90% and the fairness index improved significantly. Further, the transmission power is directly proportional to the distance of communication. So, the performance is high and the durability of the nodes increases compared to a fixed transmission power MAC such as IEEE 802.11b when communicating distance is shorter. However, the mechanism requires positional information, therefore, given that location is typically unavailable, a more feasible power control cross layered system called Dynamic Neighbour Aware – Power controlled MAC (Dynamic NA -PMAC)is designed to adjust the transmission power by estimating the communicating distance based on the estimated overheard signal strength. In summary, the thesis proposes a number of mechanisms that improve the fairness amongst the competing flows, increase the end-to-end throughput, decrease the delay, reduce the transmission power in Ad Hoc environments and substantially increase the overall performance of the network