Advanced Wireless LAN

The past two decades have witnessed starling advances in wireless LAN technologies that were stimulated by its increasing popularity in the home due to ease of installation, and in commercial complexes offering wireless access to their customers. This book presents some of the latest development status of wireless LAN, covering the topics on physical layer, MAC layer, QoS and systems. It provides an opportunity for both practitioners and researchers to explore the problems that arise in the rapidly developed technologies in wireless LAN

PERFORMANCE EVALUATION OF CROSS-LAYER DESIGN WITH DISTRIBUTED AND SEQUENTIAL MAPPING SCHEME FOR VIDEO APPLICATION OVER IEEE 802.11E

The rapid development of wireless communication imposes several challenges to support QoS for real-time multimedia applications such as video stream applications. Researchers tackled these challenges from different points of view including the semantics of the video to achieve better QoS requirements. The main goal of this research is to design a UDP protocol to realize a distributed sequential mapping scheme (DSM) with a cross-layer design and evaluate its accuracy under different network conditions. In DSM, the perceived quality of a multi-layer video is addressed by mapping each video layer into channel resources represented as queues or access categories (ACs) existing in IEEE 802.11e MAC layer. This research work further investigates the efficiency of this scheme with actual implementation and thorough simulation experiments. The experiments reported the efficiency of this scheme with the presence of different composite traffic models covering most known traffic scenarios using Expected Reconstructed Video Layers (ERVL) and packet loss rate as accuracy measures. This research work also investigates the accuracy of calculating the ERVL compared to its value using actual readings of layers drop rate. The effect of changing the ACs queue size on the ERVL is studied. The use of this scheme shows zero-drop in the base layer in almost all scenarios where no ongoing traffic is presented except that the testing video sessions between nodes. In these experiments, the ERVL continuously reported high values for the number of expected reconstructed video layers. While these values dramatically vary when introducing ongoing different composite traffic models together with the testing video sessions between nodes. Finally, a 40% increase in the ACs queue size shows significant improvement on ERVL while an increase of the queue size beyond this value has very little significance on ERVL

A fuzzy-based QoS Maximization protocol for WiFi Multimedia (IEEE 802.11e) Ad hoc Networks

The Quality of Service (QoS) management within a multiple-traffic Wi-Fi MultiMedia (WMM) ad hoc network is a tedious task, since each traffic type requires a well determined QoS-level. For this reason, the IEEE Working Group has proposed the IEEE 802.11e Enhanced Distributed Channel Access (EDCA) protocol at the MAC layer of WMM ad hoc networks. However, several studies have shown that EDCA must be further improved for three main reasons. The first reason is the poor performance of EDCA under high traffic conditions due to the high collision rate. The second reason is the need to maximize the traffic performance (delay, throughput, etc.) guaranteed by EDCA, seen the rapid evolution of the applications (multimedia, real time, etc.). The third reason is the need to maximize the energy efficiency of the EDCA, seen its use in battery constrained devices (e.g. Laptop, Smart phone, Tablet computers, etc.). For these three reasons, we propose in this paper a Three-in-One solution MAC protocol called QoS Maximization of EDCA (QM-EDCA), which is an enhanced version of EDCA. Based on the fuzzy logic mathematic theory, QM-EDCA incorporates a dynamic MAC parameters fuzzy logic system, in order to adapt dynamically the Arbitration inter frame Spaces according to the network state and remaining energy. Simulation results show that QM-EDCA outperforms EDCA by reducing significantly the collision rate, and maximizing traffic performance and energy-efficiency. In addition our solution is fully distributed

A fair access mechanism based on TXOP in IEEE 802.11e wireless networks

IEEE 802.11e is an extension of IEEE 802.11 that provides Quality of Service (QoS) for the applications with different service requirements. This standard makes use of several parameters such as contention window; inter frame space time and transmission opportunity to create service differentiation in the network. Transmission opportunity (TXOP), that is the focus point of this paper, is the time interval, during which a station is allowed to transmit packets without any contention. As the fixed amounts of TXOPs are allocated to different stations, unfairness appears in the network. And when users with different data rates exist, IEEE 802.11e WLANs face the lack of fairness in the network. Because the higher data rate stations transfer more data than the lower rate ones. Several mechanisms have been proposed to solve this problem by generating new TXOPs adaptive to the network's traffic condition. In this paper, some proposed mechanisms are evaluated and according to their evaluated strengths and weaknesses, a new mechanism is proposed for TXOP determination in IEEE 802.11e wireless networks. Our new algorithm considers data rate, channel error rate and data packet lengths to calculate adaptive TXOPs for the stations. The simulation results show that the proposed algorithm leads to better fairness and also higher throughput and lower delays in the network.

Frame-based mapping mechanism for energy-efficient MPEG-4 video transmission over IEEE 802.11e networks with better quality of delivery

Recent developments in hardware, software and communication technologies have resulted in increasing interest in the use of wireless local area networks (WLANs). Mobile devices with embedded WLAN functionality are becoming increasingly popular. Such devices must be designed to support applications that require high quality of service (QoS) and have favorable to maximize battery capacity. The resources of queues in IEEE 802.11e networks may be wasted by the transmission of information that is useless to the receiver. This work develops a frame-based mapping mechanism (FBM) that exploits different methods to process I/P/B (Intra/Predictive/Bipredictive) video frame packets. FBM refers to the dropping of arriving packets if the preceding packets in the same video frame have been dropped. When fragmented packets of a single frame are allocated to different access categories (AC) queues, out-of order delivery may occur. Hence, FBM tries to treat all fragmented packets of each video frame equally and allocates them to the same AC queue if possible. The simulation results demonstrate that transmission by the FBM is more efficient than that by other mechanisms, such as EDCA (Enhanced Distributed Channel Access), static mapping and adaptive mapping, suggesting that the energy of a device is not wasted in the transmission of useless video data in WLANs. (C) 2015 Elsevier Ltd. All rights reserved.Foundation item: The National Project of Taiwan (No.: MOST 103-2221-E507-001). Authors are grateful to Ministry of Science and Technology Grant no. (MOST 103-2221-E507-001), Government of Taiwan for financial support to carry out this work.Ke, C.; Yang, C.; Chen, J.; Ghafoor, KZ.; Lloret, J. (2015). Frame-based mapping mechanism for energy-efficient MPEG-4 video transmission over IEEE 802.11e networks with better quality of delivery. Journal of Network and Computer Applications. 58:280-286. https://doi.org/10.1016/j.jnca.2015.08.005S2802865

Throughput quantitative analysis of EDCA 802.11e in different scenarios

This document presents a quantitative analysis of the direct and relative throughput of IEEE 802.11e. The global throughput of an 802.11e WLAN is determined by EDCA (Enhanced Distributed Channel Access) parameters, among other aspects, that are usually configured with predetermined and static values. This study carefully evaluates the Quality of Service (QoS) of Wi-Fi with EDCA in several realistic scenarios with noise and a blend of wireless traffic (e.g., voice, video, and best effort, with Pareto distribution). The metrics of the benefits obtained in each case are compared, and the differentiated impact of network dynamics on each case is quantified. The results obtained show that the default settings are not optimal, and that with an appropriate selection, can be achieved improvements of the order of 25 %, according to the type of traffic. In addition, it could be shown the quantitative impact of each parameter EDCA on the overall performance. This study proposes a new experimental scenario based on the relative proportion of traffic present in the network. Stations have been simulated using the Möbius tool, which supports an extension of SPN (Stochastic Petri Networks), known as HSAN (Hierarchical Stochastic Activity Networks).Facultad de Informátic

TDMAとDCFの組み合わせによるアドホックネットワーク上でのQoS通信の実現方式

　An ad hoc network does not rely on the fixed network infrastructure; it uses a distributed network management method. With the popularity of the smart devices, ad hoc network has received more and more attention, supporting QoS in ad hoc network has become inevitable. Many researches have been done for provision of QoS in ad hoc networks. These researches can be divided into three types.　The first type is contention-based approach which is the most widely used. IEEE 802.11e MAC (media access control) protocol belongs to this type which is an extension of IEEE 802.11 DCF(Distributed Coordination Function). It specifies a procedure to guarantee QoS by providing more transmission opportunities for high priority data. However, since IEEE 802.11eis designed based on the premise that access points are used, when the number of QoS flows increases, packet collisions could occur in multi-hop ad hoc network.　The second type is using TDMA-based approach. The TDMA approach can provide contention-free access for QoS traffics through the appropriate time slot reservation. The current TDMA approaches reserve time slots for both QoS traffics and best-effort traffics. However, it is difficult for TDMA as the only approach to allocating channel access time for best-effort traffics sincet he required bandwidth of the best-effort traffics changes frequently.　We propose a QoS scheme, which takes advantage of both contention-based approach and TDMA-based approach. In the proposed scheme, contention-based approach DCF provides easy and fair channel time for best-effort traffics, and TDMA approach serves the QoS traffics. A time frame structure is designed to manage the bandwidth allocation. A time frame is divided into two periods, specifically the TDMA periods and the DCF periods. The proportion of two periods is decided by QoS traffics. Therefore the QoS traffics are given absolutely higher priority than best-effort traffics. In order to guarantee the transmission of each QoS packet in TDMA period, a time slot assignment algorithm based on QoS data rate has been proposed. The proposed scheme also employs an admission control scheme, which rejects the new QoS user when the channel capacity is reached. In addition, we provide the configuration of the proposed scheme in the mobile environment. The procedures are designed for route changes and new-adding users. 　The proposed scheme is simulated in the QualNet simulator. In the static environment, the performance of the proposed scheme is evaluated in the case of a gradual increase in the number TCP flows and in the case of gradual increase in QoS data rate. Simulation results show that in the static environment the proposed scheme can not only provide effective QoS performance, but also can provide good support for best-effort flows. In the mobile environment, we simulated the performance of the proposed scheme at different moving speed (maximum is 5 Km/h) when the ARF (Auto Rate Fallback) is available. From the simulation results, in a specific mobile environment, the proposed scheme can support the QoS transmission well.電気通信大学201