197 research outputs found

    Energy-efficient wireless communication

    Get PDF
    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

    Goodbye, ALOHA!

    Get PDF
    ©2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.The vision of the Internet of Things (IoT) to interconnect and Internet-connect everyday people, objects, and machines poses new challenges in the design of wireless communication networks. The design of medium access control (MAC) protocols has been traditionally an intense area of research due to their high impact on the overall performance of wireless communications. The majority of research activities in this field deal with different variations of protocols somehow based on ALOHA, either with or without listen before talk, i.e., carrier sensing multiple access. These protocols operate well under low traffic loads and low number of simultaneous devices. However, they suffer from congestion as the traffic load and the number of devices increase. For this reason, unless revisited, the MAC layer can become a bottleneck for the success of the IoT. In this paper, we provide an overview of the existing MAC solutions for the IoT, describing current limitations and envisioned challenges for the near future. Motivated by those, we identify a family of simple algorithms based on distributed queueing (DQ), which can operate for an infinite number of devices generating any traffic load and pattern. A description of the DQ mechanism is provided and most relevant existing studies of DQ applied in different scenarios are described in this paper. In addition, we provide a novel performance evaluation of DQ when applied for the IoT. Finally, a description of the very first demo of DQ for its use in the IoT is also included in this paper.Peer ReviewedPostprint (author's final draft

    Medium Access Control Protocols for Ad-Hoc Wireless Networks: A Survey

    Get PDF
    Studies of ad hoc wireless networks are a relatively new field gaining more popularity for various new applications. In these networks, the Medium Access Control (MAC) protocols are responsible for coordinating the access from active nodes. These protocols are of significant importance since the wireless communication channel is inherently prone to errors and unique problems such as the hidden-terminal problem, the exposed-terminal problem, and signal fading effects. Although a lot of research has been conducted on MAC protocols, the various issues involved have mostly been presented in isolation of each other. We therefore make an attempt to present a comprehensive survey of major schemes, integrating various related issues and challenges with a view to providing a big-picture outlook to this vast area. We present a classification of MAC protocols and their brief description, based on their operating principles and underlying features. In conclusion, we present a brief summary of key ideas and a general direction for future work

    Overlapped CDMA system in optical packet networks : resource allocation and performance evalutation

    Get PDF
    Dans cette thèse, la performance du système CDMA à chevauchement optique (OVCDMA) au niveau de la couche de contrôle d'accès au support (MAC) et l'allocation des ressources au niveau de la couche physique (PRY) sont étudiées. Notre but est d'apporter des améliorations pour des applications à débits multiples en répondant aux exigences de délai minimum tout en garantissant la qualité de service (QoS). Nous proposons de combiner les couches PRY et MAC par une nouvelle approche d'optimisation de performance qui consolide l'efficacité potentielle des réseaux optiques. Pour atteindre notre objectif, nous réalisons plusieurs étapes d'analyse. Tout d 'abord, nous suggérons le protocole S-ALOHA/OV-CDMA optique pour sa simplicité de contrôler les transmissions optiques au niveau de la couche liaison. Le débit du réseau, la latence de transmission et la stabilité du protocole sont ensuite évalués. L'évaluation prend en considération les caractéristiques physiques du système OY-CDMA, représentées par la probabilité de paquets bien reçus. Le système classique à traitement variable du gain (YPG) du CDMA, ciblé pour les applications à débits multiples, et le protocole MAC ±round-robin¿ récepteur/émetteur (R31), initialement proposé pour les réseaux par paquets en CDMA optique sont également pris en compte. L'objectif est d ' évaluer comparativement la performance du S-ALOHA/OY-CDMA en termes de l'immunité contre l'interférence d'accès lTIultiple (MAI) et les variations des charges du trafic. Les résultats montrent que les performances peuvent varier en ce qui concerne le choix du taux de transmission et la puissance de transmission optique au niveau de la couche PRY. Ainsi, nous proposons un schéma de répartition optimale des ressources pour allouer des taux de transmission à chevauchement optique et de puissance optique de transmission dans le système OY-CDMA comme des ressources devant être optimalement et équitablement réparties entre les utilisateurs qui sont regroupés dans des classes de différentes qualités de service. La condition d'optimalité est basée sur la maximisation de la capacité par utilisateur de la couche PHY. De ce fait, un choix optimal des ressources physiques est maintenant possible, mais il n'est pas équitable entre les classes. Par conséquent, pour améliorer la performance de la couche liaison tout en éliminant le problème d'absence d'équité, nous proposons comme une approche unifiée un schéma équitable et optimal pour l'allocation des ressources fondé sur la qualité de service pour des multiplexages temporels des réseaux par paquets en CDMA à chevauchement optique. Enfin, nous combinons cette dernière approche avec le protocole MAC dans un problème d'optimisation d'allocation équitable des ressources à contrainte de délai afin de mieux améliorer le débit du réseau et le délai au niveau de la couche liaison avec allocation équitable et optimale des ressources au niveau de la couche PHY

    Medium access control design for all-IP and ad hoc wireless network

    Get PDF
    Medium Access Control (MAC) protocol in a wireless network controls the access of wireless medium by mobile terminals, in order to achieve its fair and efficient sharing. It plays an important role in resource management and QoS support for applications. All-IP wireless WAN is fully IP protocol-based and it is a strong candidate beyond 3G (Third Generation Wireless Network). Ad hoc wireless network has recently been the topic of extensive research due to its ability to work properly without fixed infrastructure. This dissertation is composed of two main parts. The first part pursues a Prioritized Parallel Transmission MAC (PPTM) design for All-IP Wireless WAN. Two stages are used and each packet is with a priority level in PPTM. In stage 1, a pretransmission probability is calculated according to the continuous observation of the channel load for a certain period of time. In stage 2, a packet is prioritized and transmitted accordingly. It is modeled and analyzed as a nonpreemptive Head-Of-the-Line prioritized queueing system with Poisson arrival traffic pattern. Its performance is analyzed under three other traffic patterns, which are Constant Bit Rate, Exponential On/Off, and Pareto On/Off, by using a NS-2 simulator, and compared with that of Modified Channel Load Sensing Protocol. PPTM supports dynamic spread code allocation mechanism. A mobile terminal can apply for a spreading code according to the current channel condition. To use the idea of dynamic bandwidth allocation in PPTM for adhoc wireless network, a Dynamic-Rate-with-Collision-Avoidance (DRCA) MAC protocol is proposed in the second part of the dissertation. DRCA is based on spread spectrum technology. In DRCA, a terminal sets the spreading factor for a packet according to the activity level of neighboring nodes. If the total number of usable spreading codes with this spreading factor is less than the total number of mobile terminals in the network, to avoid collision, the spreading code id is broadcast such that other terminals can avoid using it when the packet is being transmitted. The performance of DRCA is theoretically analyzed in a slotted, single-hop, multi-user environment. To evaluate DRCA\u27s performance in an environment closed to a real one, a simulator that supports multi-hop, random mobility pattern is created with OPNET. Both theoretical and simulation results show that DRCA outperforms MACA/CT (Multiple Access with Collision Avoidance with Common Transmitter-based) in case if there are more than one communication pair and the ratio of inactive mobile terminals to active ones is high

    Automatic rate adaptation and energy-saving mechanisms based on cross-layer information for packet-switched data networks

    Get PDF
    A set of novel PHY-MAC mechanisms based on a cross layer dialogue have been proposed, and their performance has been analyzed. System efficiency improvement is achieved by means of automatic transmission rate adaptation, trading off bit rate for power, with resulting energy saving features in a generic packet-switched CDMA access network. The rate adaptation mechanism improves spectrum efficiency while keeping packet delay minimized. On the other hand, power dependent strategies reduce power consumption and intercell interference. Simulation results show that the benefits obtained are very encouraging, so the proposed schemes could be used in future communication systems.Peer Reviewe

    Medium access control protocol design for wireless communications and networks review

    Get PDF
    Medium access control (MAC) protocol design plays a crucial role to increase the performance of wireless communications and networks. The channel access mechanism is provided by MAC layer to share the medium by multiple stations. Different types of wireless networks have different design requirements such as throughput, delay, power consumption, fairness, reliability, and network density, therefore, MAC protocol for these networks must satisfy their requirements. In this work, we proposed two multiplexing methods for modern wireless networks: Massive multiple-input-multiple-output (MIMO) and power domain non-orthogonal multiple access (PD-NOMA). The first research method namely Massive MIMO uses a massive number of antenna elements to improve both spectral efficiency and energy efficiency. On the other hand, the second research method (PD-NOMA) allows multiple non-orthogonal signals to share the same orthogonal resources by allocating different power level for each station. PD-NOMA has a better spectral efficiency over the orthogonal multiple access methods. A review of previous works regarding the MAC design for different wireless networks is classified based on different categories. The main contribution of this research work is to show the importance of the MAC design with added optimal functionalities to improve the spectral and energy efficiencies of the wireless networks
    • …
    corecore