779 research outputs found
Unified clustering and communication protocol for wireless sensor networks
In this paper we present an energy-efficient cross layer protocol for providing application specific reservations in wireless senor networks called the “Unified Clustering and Communication Protocol ” (UCCP). Our modular cross layered framework satisfies three wireless sensor network requirements, namely, the QoS requirement of heterogeneous applications, energy aware clustering and data forwarding by relay sensor nodes. Our unified design approach is motivated by providing an integrated and viable solution for self organization and end-to-end communication is wireless sensor networks. Dynamic QoS based reservation guarantees are provided using a reservation-based TDMA approach. Our novel energy-efficient clustering approach employs a multi-objective optimization technique based on OR (operations research) practices. We adopt a simple hierarchy in which relay nodes forward data messages from cluster head to the sink, thus eliminating the overheads needed to maintain a routing protocol. Simulation results demonstrate that UCCP provides an energy-efficient and scalable solution to meet the application specific QoS demands in resource constrained sensor nodes. Index Terms — wireless sensor networks, unified communication, optimization, clustering and quality of service
Performance Analysis for Bandwidth Allocation in IEEE 802.16 Broadband Wireless Networks using BMAP Queueing
This paper presents a performance analysis for the bandwidth allocation in
IEEE 802.16 broadband wireless access (BWA) networks considering the
packet-level quality-of-service (QoS) constraints. Adaptive Modulation and
Coding (AMC) rate based on IEEE 802.16 standard is used to adjust the
transmission rate adaptively in each frame time according to channel quality in
order to obtain multiuser diversity gain. To model the arrival process and the
traffic source we use the Batch Markov Arrival Process (BMAP), which enables
more realistic and more accurate traffic modelling. We determine analytically
different performance parameters, such as average queue length, packet dropping
probability, queue throughput and average packet delay. Finally, the analytical
results are validated numerically.Comment: 16 page
Final report on the evaluation of RRM/CRRM algorithms
Deliverable public del projecte EVERESTThis deliverable provides a definition and a complete evaluation of the RRM/CRRM algorithms selected in D11 and D15, and evolved and refined on an iterative process. The evaluation will be carried out by means of simulations using the simulators provided at D07, and D14.Preprin
Energy-efficient wireless communication
In this chapter we present an energy-efficient highly adaptive network interface architecture and a novel data link layer protocol for wireless networks that provides Quality of Service (QoS) support for diverse traffic types. Due to the dynamic nature of wireless networks, adaptations in bandwidth scheduling and error control are necessary to achieve energy efficiency and an acceptable quality of service. In our approach we apply adaptability through all layers of the protocol stack, and provide feedback to the applications. In this way the applications can adapt the data streams, and the network protocols can adapt the communication parameters
Adaptive reservation TDMA protocol for wireless multimedia traffic
An Adaptive Reservation Time Division Multiple Access (AR-TDMA) control protocol for Wireless Asynchronous
Transfer Mode (WATM) networks is proposed in this paper. AR-TDMA combines the advantages of distributed
access and centralised control for transporting Constant Bit Rate (CBR), Variable Bit Rate (VBR) and Available Bit
Rate (ABR) traffic efficiently over a wireless channel. The contention slots access for reservation requests is
governed by two protocols, the Adaptive Framed Pseudo-Bayesian Aloha with Adaptive Slot Assignment (AFPBAASA)
protocol and the Framed Pseudo-Bayesian Aloha with Adaptively Prioritised Controlled Capture (FPBAAPCC)
protocol. Both protocols provide different access priorities to the control packets in order to improve the
Quality-of-Service (QoS) offered to time sensitive connections. AR-TDMA also features a novel integrated resource
allocation algorithm that efficiently schedules terminals’ reserved access to the wireless ATM channel by
considering their requested bandwidth and QoS. Integration of CBR, voice, VBR, data and control traffic over the
wireless ATM channel using the proposed AR-TDMA protocol is considered in the paper. The performance of the
AR-TDMA in conjunction with the AFPBA-ASA protocol and FPBA-APCC protocol has been investigated and the
simulation results are presented showing that the protocol satisfies the required QoS of each traffic category while
providing a highly efficient utilisation of approximately 96% for the wireless ATM channel
Cross layer optimization in 4G Wireless mesh networks
Wireless networks have been rapidly evolving over the past two decades. It is foreseen that Fourth generation (4G) wireless systems will involve the integration of wireless mesh networks and the 3G wireless systems such as WCDMA. Moreover their wireless mesh routers will provide service to wireless local networks (WLANs) and possibly incorporate MIMO system and smart admission control policies among others. This integration will not only help the service providers cost effectiveness and users connectivities but will also improve and guarantee the QoS criteria. On the other hand, cross layer design has emerged as a new and major thrust in improving the quality of service (QoS) of wireless networks. Cross layer design involves the interaction of various layers of the network hierarchy which could further improve the QoS of the 4G integrated networks. In this work we seek new techniques for improving the overall QoS of integrated 4G systems. Towards this objective we start with the local low tier WLAN access. We then investigate CDMA alternatives to the TDMA access for wireless mesh networks. Cross layer design in wireless mesh networks is then pursued. In the first phase of this thesis a new access mechanism for WLANs is developed, in which users use an optimum transmission probability obtained by estimating the number of stations from the traffic conditions in a sliding window fashion, thereby increasing the throughput compared to the standard DCF and RTS/CTS mechanism while maintaining the same fairness and the delay performance. In the second phase we introduce a code division multiple access/Time division duplex technique CDMA/TDD for wireless mesh networks, we outline the transmitter and receiver for the relay nodes and evaluate the efficiency, delay and delay jitter performances. This CDMA based technique is more amenable to integrating the two systems (Mesh networks and WCDMA or CDMA 2000 of3G). We compare these results with the TDMA operation and through analysis we prove that the CDMA system outperforms the TDMA counterparts. In the third phase we proceed to an instance of cross layer optimized networks, where we develop an overall optimization routine that finds simultaneously the best route and the best capacity allocation to various nodes. This optimization routine minimizes the average end to end packet delay over all calls subject to various contraints. In the process we use a new adaptive version of Spatial TDMA as a platform for comparison purposes of the MAC techniques involved in the cross layer design. In this phase we also combine CDMA/TDD and optimum routing for cross layer design in wireless mesh networks. We compare the results of the CDMA/TDD system with results obtained from the STDMA system. In our analysis we consider the parallel transmissions of mesh nodes in a mesh topology. These parallel transmissions will increase the capacity resulting in a higher throughput with a lower delay. This will allow the service providers to accommodate more users in their system which will obviously reduce the colt and the end users will enjoy a better service paying a lower amount
Controlo de acesso ao meio em comunicações veiculares de tempo-real
Despite several preventive measures, the number of roadway accidents is still very high, being considered even a problem of public health by some entities. This thesis has as global purpose of contributing to the reduction of that number of accidents, and consequent fatalities, by using safety-related applications that use communication among vehicles. In particular, the primary goal is guaranteeing that communication between users in vehicular environments is done with appropriate time bounds to transfer safety-critical information. In detail, it is studied how to manage the scheduling of message’s transmissions (medium access control - MAC), in order to define precisely who will communicate and when is the appropriate instant. The preferable situation where a communication infrastructure is present with full coverage (RSUs) is also studied, from which medium access control is defined precisely, and vehicles (OBUs) become aware of medium utilization. Also, sporadic situations (e.g., absence of RSUs) are studied in which the communication network is “ad hoc” and solely formed by the current vehicles. It is used the recently WAVE / IEEE 802.11p standard, specific for vehicular communications, and it is proposed a TDMA based solution, with appropriate coordination between RSUs in order to effectively disseminate a critical safety event. It is taken into account two different ways of choosing the instant for the initial broadcast, and both cases are compared. In case there is no infrastructure available, methods are derived to minimize communication medium access collisions, and to maximize the available bandwidth. The results reflect the total end-to-end delay, and show that adequate times are attained, and meet with the requisites for the type of applications being considered. Also, enhancements are obtained when using the alternate choice for the initial broadcast instant.Apesar de diversas medidas preventivas, o nĂşmero de acidentes rodoviários continua a ser muito elevado, sendo mesmo considerado uma questĂŁo de saĂşde pĂşblica por algumas entidades. Esta tese tem como objetivo geral contribuir para a redução desse nĂşmero de acidentes, e consequentes fatalidades, atravĂ©s da utilização de aplicações de segurança que envolvem comunicação entre veĂculos. Em particular, o objetivo principal Ă© garantir que a comunicação entre utentes, em ambientes veiculares, seja efetuada com limites temporais apropriados Ă transferĂŞncia de informações crĂticas. De forma mais detalhada, Ă© estudada a gestĂŁo do escalonamento das transmissões (controlo de acesso ao meio – MAC) que irá definir quem vai comunicar e quando o pode fazer. SĂŁo estudadas situações (desejadas) onde há uma infra-estrutura de comunicações com cobertura integral (RSUs), a partir da qual se faz a coordenação do acesso ao meio pelos veĂculos (OBUs), e situações (esporádicas, por ausĂŞncia de RSU) em que a rede de comunicação Ă© “ad hoc” e apenas constituĂda pelos veĂculos presentes. Utiliza-se a recente norma WAVE / IEEE 802.11p, especĂfica para comunicações veiculares, e propõe-se uma solução baseada em TDMA, com coordenação apropriada entre RSUs para disseminação efetiva de um evento crĂtico de segurança. A escolha do instante para o broadcast inicial do evento de segurança tambĂ©m Ă© tida em conta, e sĂŁo comparados dois casos distintos. No caso da ausĂŞncia de infraestrutura, derivam-se mĂ©todos para minimizar colisões no acesso ao meio de comunicação, e maximizar a largura de banda disponĂvel. Os resultados refletem o atraso total end-to-end, mostrando tempos apropriados para os requisitos das aplicações em causa, e evidenciando melhorias aquando da escolha alternativa para o instante do broadcast inicial.Programa Doutoral em Engenharia EletrotĂ©cnic
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