Showing papers on "IEEE 802.11e-2005 published in 2007"

IEEE Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems Draft Amendment: Management Information Base Extensions

Abstract: This document provides updates to IEEE Std 802.16's MIB for the MAC, PHY and asso- ciated management procedures in order to accommodate recent extensions to the standard.

Performance Evaluation of the IEEE 802.11p WAVE Communication Standard

Abstract: In order to provide Dedicated Short Range Communication (DSRC) for future vehicle-to-vehicle (V2V) communication the IEEE is currently working on the IEEE 802.11p Wireless Access in Vehicular Environments (WAVE) standard. The standard shall provide a multi-channel DSRC solution with high performance for multiple application types to be used in future Vehicular Ad Hoc Networks (VANETs). We provide a performance evaluation of the standard, considering collision probability, throughput and delay, using simulations and analytical means. WAVE can prioritize messages, however, in dense and high load scenarios the the troughput is decreases while the delay is increasing significantly.

Overhaul of ieee 802.11 modeling and simulation in ns-2

Abstract: NS-2, with its IEEE 802.11 support, is a widely utilized simulation tool for wireless communications researchers. However, the current NS-2 distribution code has some significant shortcomings both in the overall architecture and the modeling details of the IEEE 802.11 MAC and PHY modules. This paper presents a completely revised architecture and design for these two modules. The resulting PHY is a full featured generic module able to support any single channel frame-based communications (i.e. it is also able to support non-IEEE 802.11 based MAC). The key features include cumulative SINR computation, preamble and PLCP header processing and capture, and frame body capture. The MAC accurately models the basic IEEE 802.11 CSMA/CA mechanism, as required for credible simulation studies. The newly designed MAC models transmission and reception coordination, backoff management and channel state monitoring in a structured and modular manner. In turn, the contributions of this paper make extending the MAC for protocol researches much easier and provide for a significantly higher level of simulation accuracy.

Performance Evaluation of the IEEE 802.16 MAC for QoS Support

Abstract: The IEEE 802.16 is a standard for broadband wireless communication in metropolitan area networks (MAN). To meet the QoS requirements of multimedia applications, the IEEE 802.16 standard provides four different scheduling services: unsolicited grant service (UGS), real-time polling service (rtPS), non-real-time polling service (nrtPS), and Best Effort (BE). The paper is aimed at verifying, via simulation, the effectiveness of rtPS, nrtPS, and BE (but UGS) in managing traffic generated by data and multimedia sources. Performance is assessed for an IEEE 802.16 wireless system working in point-to-multipoint (PMP) mode, with frequency division duplex (FDD), and with full-duplex subscriber stations (SSs). Our results show that the performance of the system, in terms of throughput and delay, depends on several factors. These include the frame duration, the mechanisms for requesting uplink bandwidth, and the offered load partitioning, i.e., the way traffic is distributed among SSs, connections within each SS, and traffic sources within each connection. The results also highlight that the rtPS scheduling service is a very robust scheduling service for meeting the delay requirements of multimedia applications

Analysis of the contention access period of IEEE 802.15.4 MAC

Abstract: The recent ratification of IEEE 802.15.4 PHY-MAC specifications for low-rate wireless personal area networks represents a significant milestone in promoting deployment of wireless sensor networks (WSNs) for a variety of commercial uses. The 15.4 specifications specifically target wireless networking among low-rate, low-power and low-cost devices that is expected to be a key market segment for a large number of WSN applications. In this article, we first analyze the performance of the contention access period specified in the IEEE 802.15.4 standard in terms of throughput and energy consumption. This analysis is facilitated by a modeling of the contention access period as nonpersistent CSMA with backoff. We show that, in certain applications in which having an inactive period in the superframe may not be desirable due to delay constraints, shutting down the radio between transmissions provides significant savings in power without significantly compromising the throughput. We also propose and analyze the performance of a modification to the specification which could be used for applications in which MAC-level acknowledgements are not used. Extensive ns-2 simulations are used to verify the analysis.

An Implementation of IEEE 1588 Over IEEE 802.11b for Synchronization of Wireless Local Area Network Nodes

Abstract: IEEE 1588 is a new standard to synchronize independent clocks running on separate nodes of a distributed measurement and control system. It is intended for high-accuracy implementations on compact systems such as a single subnet. This paper examines potential accuracy limitations introduced by the physical layer of the IEEE 802.11b wireless local area network. Experimental results are presented that show that these limitations do not preclude clock-synchronization accuracy of several hundred nanoseconds.

IEEE 802.16/WiMAX-based broadband wireless access and its application for telemedicine/e-health services

Abstract: In this article we investigate the application of IEEE 802.16-based broadband wireless access (BWA) technology to telemedicine services and the related protocol engineering issues. An overview of the different evolutions of the IEEE 802.16 standard is presented and some open research issues are identified. A survey on radio resource management, traffic scheduling, and admission control mechanisms proposed for IEEE 802.16/WiMAX systems is also provided. A qualitative comparison between third-generation wireless systems and the IEEE 802.16/WiMAX technology is given. A survey on telemedicine services using traditional wireless systems is presented. The advantages of using IEEE 802.16/WiMAX technology over traditional wireless systems, as well as the related design issues and approaches are discussed. To this end, we present a bandwidth allocation and admission control algorithm for IEEE 802.16-based BWA designed specifically for wireless telemedicine/e-health services. This algorithm aims at maximizing the utilization of the radio resources while considering the quality of service requirements for telemedicine traffic. Some performance evaluation results for this scheme are obtained by simulations

Interference Measurements on Performance Degradation between Colocated IEEE 802.11g/n and IEEE 802.15.4 Networks

Abstract: We have made detailed measurements, on the impact of modern Wireless LAN technologies on the IEEE 802.15.4 in the 2.4 GHz ISM band. We have specifically focused on IEEE 802.11g and pre-standard IEEE 802.11n products as potential interferers. Our measurements show that high levels of network traffic interference from either of these technologies has disastrous impact on the performance of IEEE 802.15.4. Our results also indicate that these interference effects are especially difficult to avoid in the (pre-standard) 802.11n case due to the significantly increased channel bandwidth compared to previous Wireless LAN technologies. Widespread adoption of IEEE 802.11n especially in applications involving high data rates (such as backbones for wireless mesh networks) could thus have serious impact on the usability of IEEE 802.15.4 as well as other low-power 2.4 GHz ISM band technologies. This indicates that low-power building automation, consumer electronics and sensor networks may be vulnerable to the interference from the future IEEE 802.11n high-data rate WLAN deployments.

Establishing Wireless Robust Security Networks: A Guide to IEEE 802.11i

Abstract: This report provides readers with a detailed explanation of next generation 802.11 wireless security. It describes the inherently flawed Wired Equivalent Privacy (WEP) and explains 802.11i's two-step approach (interim and long-term)to providing effective wireless security. It describes secure methods used to authenticate users in a wireless environment, and presents several sample case studies of wireless deployment. It also includes guidance on best practices for establishing secure wireless networks using the emerging Wi-Fi technology.

Feedback-based control for providing real-time services with the 802.11e MAC

Abstract: The 802.11e working group has recently proposed the hybrid coordination function (HCF) to provide service differentiation for supporting real-time transmissions over 802.11 WLANs. The HCF is made of a contention-based channel access, known as enhanced distributed coordination access, and of a HCF controlled channel access (HCCA), which requires a Hybrid Coordinator for bandwidth allocation to nodes hosting applications with QoS requirements. The 802.11e proposal includes a simple scheduler providing a Constant Bit Rate service, which is not well suited for bursty media flows. This paper proposes two feedback-based bandwidth allocation algorithms to be used within the HCCA, which have been referred to as feedback based dynamic scheduler (FBDS) and proportional-integral (PI)-FBDS. These algorithms have been designed with the objective of providing services with bounded delays. Given that the 802.11e standard allows queue lengths to be fed back, a control theoretic approach has been employed to design the FBDS, which exploits a simple proportional controller, and the PI-FBDS, which implements a proportional-integral controller. Proposed algorithms can be easily implemented since their computational complexities scale linearly with the number of traffic streams. Moreover, a call admission control scheme has been proposed as an extension of the one described in the 802.11e draft. Performance of the proposed algorithms have been theoretically analyzed and computer simulations, using the ns-2 simulator, have been carried out to compare their behaviors in realistic scenarios where video, voice, and FTP flows, coexist at various network loads. Simulation results have shown that, unlike the simple scheduler of the 802.11e draft, both FBDS and PI-FBDS are able to provide services with real-time constraints. However, while the FBDS admits a smaller quota of traffic streams than the simple scheduler, PI-FBDS allows the same quota of traffic that would be admitted using the simple scheduler, but still providing delay bound guarantees.

Proportional fair throughput allocation in multirate IEEE 802.11e wireless LANs

Abstract: Under heterogeneous radio conditions, Wireless LAN stations may use different modulation schemes, leading to a heterogeneity of bit rates. In such a situation, 802.11 DCF allocates the same throughput to all stations independently of their transmitting bit rate; as a result, the channel is used by low bit rate stations most of the time, and efficiency is low. In this paper, we propose a more efficient throughput allocation criterion based on proportional fairness. We find out that, in a proportional fair allocation, the same share of channel time is given to high and low bit rate stations, and, as a result, high bit rate stations obtain more throughput. We propose two schemes of the upcoming 802.11e standard to achieve this allocation, and compare their delay and throughput performance.

Priority Based Inter-Vehicle Communication in Vehicular Ad-Hoc Networks using IEEE 802.11e

Abstract: In this paper, we study the use of IEEE 802.11e for priority based safety messaging for inter-vehicle communications (IVC) in vehicular ad-hoc networks (VANET). The message priorities, which are assigned based on message urgency, are associated with different quality of service in terms of average delay and normalized throughput. We investigate the use of IEEE 802.11e to provide priority based service differentiation. To increase the communication reliability we also apply a repetitive transmission mechanism that provides proportional reliability differentiation for each prioritized message. We evaluate the performance of our proposed protocol using OPNET Modeler, in terms of average delay and normalized throughput as a function of the number of repetitions, number of vehicles, bit error rates, data rates, percentage of priority 1 vehicles and packet size. The results show that using proper parameter setting for IEEE 802.11e and appropriate number of repetitions per priority class will result in an efficient solution for IVC that supports different priority safety messaging.

Enhancements to Cognitive Radio Based IEEE 802.22 Air-Interface

Abstract: The IEEE 802.22 standard for wireless regional area network is the first standard for cognitive radio that tries to harness the idle or under-utilized spectrum allocated for TV bands. Two major challenges that are faced by IEEE 802.22 are (i) the issue of self co-existence and (ii) the hidden incumbent problem. In this paper, we discuss these two challenges and provide enhancements to the existing IEEE 802.22 air-interface. We use a graph theoretic technique and propose utility graph coloring for allocating spectrum to different IEEE 802.22 base stations so that they can co-exist. The allocation is done such that objectives such as throughput maximization, proportional fairness, and complete fairness are met. We also propose the use of dynamic multiple broadcast messages that resolves the contention among various consumer premise equipments and alleviates the hidden incumbent problem. Through simulation results, we show that the proposed techniques increase the system spectrum utilization and reduce connection set-up delay.

Performance Analysis of Video Transmission Over IEEE 802.11a/e WLANs

Abstract: This paper presents efficient mechanisms for delay- sensitive transmission of video over IEEE 802.11a/e wireless local area networks (WLANs). Transmitting video over WLANs in real time is very challenging due to the time-varying wireless channel and video content characteristics. This paper provides a comprehensive view of how to adapt the quality of service signaling, IEEE 802.11e parameters and cross-layer design to optimize the video quality at the receiver. We propose an integrated system view of admission control and scheduling for both contention and poll-based access of IEEE 802.11e medium access control (MAC) protocol and outline the merits of each approach for video transmission. We also show the benefits of using a cross-layer optimization by sharing the application, MAC, and physical layer parameters of the open systems interconnection stack to enhance the video quality. We will show through analysis and simulation that controlling the contention-based access in IEEE 802.11e is simple to realize in real products and how different cross-layer strategies used in poll-based access lead to a larger number of stations being simultaneously admitted and/or a higher video quality for the admitted stations. Finally, we introduce a new concept called time fairness, which is critical in enhancing the video performance when different transmitter-receiver pairs deploy different cross-layer strategies.

IEEE 802.20: mobile broadband wireless access

Abstract: This article provides a survey of the emerging IEEE 802.20 standard, also known as mobile broadband wireless access. It provides an introduction to the activities with regard to this standard, including purpose and scope that the specification defines. The relationship with other similar standards such as IEEE 802.16e and 3G are discussed as well. Various technical details of the standard are presented, including quality of service parameters, data rates available to end users, application support, and security. Characteristics that the air interface should provide, specifically in regard to the physical and medium access control layers, are detailed as well

Performance Analysis of 802.15.4 and 802.11e for Body Sensor Network Applications

Abstract: This paper studies the energy efficiency and QoS performance of 802.15.4 and 802.11e MAC protocols for body sensor network applications. We simulated a stand-alone body sensor network, as well as co-existence scenarios where the body sensors operate in the presence of voice, video and IT traffic. Our results indicate that although 802.15.4 and 802.11e can provide an acceptable compromise between power consumption and QoS in some scenarios, there are situations (e.g. co-existence with video and heavy data traffic) in which both performance criteria can not be met simultaneously. This highlights the need for improving existing MAC protocols or designing new solutions that can provide both extremely low power and QoS for body sensor networks (BSNs).

Low-Rate Personal Area Networks: Enabling Wireless Sensors with IEEE 802.15.4

Abstract: This SECOND EDITION of Low-Rate Wireless Personal Area Networks: Enabling Wireless Sensors with IEEE 802154 is the newest handbook in the IEEE Standards Wireless Networks Series This updated book now includes detailed information from the revised IEEE Std 802154-2006, which includes the amendment IEEE 802154b IEEE Std 802154 was developed to address low-cost and low-power design to enable applications in the fields of industrial, agricultural, vehicular, residential, and medical sensors and actuators This book offers the reader an insider's view of the standard Features include an overview of the standard, the motivation and vision behind it, background on the technology, technical features and components, application scenarios, and material not covered in the standard related to the network layer functionality for applications The book also focuses on implementation and system design considerations, including an analysis of system-level, real-world issues that will be important for prospective implementers to consider Presented in a concise and easy to read format by experts intimately involved in the development and writing of the standard, this guide is an invaluable resource to the standard for those interested in the field of "simple" wireless connectivity Low-Rate Wireless Personal Area Networks, 2nd Edition, is a MUST READ for anyone who wants to fully understand the inner-workings and possibilities of the IEEE 802154 standard

Scanning Delays in 802.11 Networks

Abstract: The proliferation of Wireless LANs and the increasing integration of voice into data networks has created the potential for VoWLANs (Voice over Wireless Local Area Networks). This technology has immense cost saving potential and the ability to provide better service and functionality. However, before the integration of VoWLAN is possible, handoff delays must be reduced. Currently, the connectivity transition that occurs from moving between APs (Access Points) is too long, causing poor voice quality and call dropouts. An experimental approach is used to investigate a particular handoff delay known as the scanning delay. The study concludes that the primary source of delay in the scanning process is caused by overlapping channels in the 2.4GHz band.

IEEE 802.21 enabled mobile terminals for optimized WLAN/3G handovers: a case study

Abstract: Wireless LAN hotspots are becoming widely spread. This, combined with the availability of new multi-mode terminals integrating heterogeneous technologies, opens new business opportunities for Mobile Operators. Scenarios in which 3G coverage is complemented by Wireless LAN deployments are becoming available. Therefore all IP based networks are ready to offer a new variety of services across heterogeneous access. However, to achieve this, some aspects still need to be analyzed. In particular, how and when to execute handovers in order to minimize service interruptions and maximize the use of the most appropriate technologies according to user's preferences (for example, a user may prefer to use a lower cost technology if available). This paper presents a simulation study of handover performance between 3G and Wireless LAN access networks. The mobile devices are based on the IEEE 802.21 cross layer architecture and use Wireless LAN signal level thresholds as handover criteria.

A Cross-Layering Design for IPv6 Fast Handover Support in an IEEE 802.16e Wireless MAN

Abstract: Broadband wireless access networks, such as the IEEE 802.16 standard for wireless metropolitan area networks (WMANs), aim to provide high bandwidth, low-cost, scalable solutions that extend multimedia services from backbone networks to wireless users. Because of a larger coverage area, portability and mobility have become significant issues for providing high quality mobile services, as it is crucial to minimize handover latency and maintain IP session continuity. As a result, such issues were addressed by the IEEE 802.16e task group on the mobile WMAN. However, the scope of the IEEE 802.16e standard did not include cross-layering approaches for the enhancement of upper layer handover performance. This article proposes a new cross-layering design for fast IPv6 handover support over IEEE 802.16e. First, we describe the IEEE 802.16 deployment architectures, as well as the link layer, handover procedures in IEEE 802.16e. Next, we describe the operation of fast IPv6 handover and point out the need for interaction between the network layer and the link layer for proper performance. Then, we propose a new cross-layering design to achieve a proper behavior of the fast IPv6 handover over IEEE 802.16e. Finally, we present handover scenarios for the proposed techniques and discuss the major factors that contribute to the handover latency.

SoftMAC: Layer 2.5 Collaborative MAC for Multimedia Support in Multihop Wireless Networks

Abstract: In this paper, we present the challenges in supporting multimedia, in particular, VoIP services over multihop wireless networks using commercial IEEE 802.11 MAC DCF hardware, and propose a novel software solution, called Layer 2.5 SoftMAC. Our proposed SoftMAC resides between the IEEE 802.11 MAC layer and the IP layer to coordinate the real-time (RT) multimedia and best-effort (BE) data packet transmission among neighboring nodes in a multihop wireless network. To effectively ensure acceptable VoIP services, channel busy time and collision rate need to be well controlled below appropriate levels. Targeted at this, our SoftMAC architecture employs three key mechanisms: 1) distributed admission control for regulating the load of RT traffic, 2) rate control for minimizing the impact of BT traffic on RT one, and 3) nonpreemptive priority queuing for providing high priority service to VoIP traffic. To evaluate the efficacy of these mechanisms, extensive simulations are conducted using the network simulator NS2. We also implement our proposed SoftMAC as a Windows network driver interlace specification (NDIS) driver and build a multihop wireless network testbed with 32 wireless nodes equipped with IEEE 802.11 a/b/g combo cards. Our evaluation and testing results demonstrate the effectiveness of our proposed software solution. Our proposed collaborative SoftMAC framework can also provide good support for A/V streaming in home networks where the network consists of hybrid WLAN (wireless LAN) and Ethernet

Analysis and improvement of contention access protocol in IEEE 802.15.4 star network

Abstract: The wireless standard IEEE 802.15.4 is emerging as a key enabling technology for different wireless sensor network applications. IEEE802.15.4 supports a low data rate wireless sensor network with low power requirement. In this paper, we discuss the performance analysis of IEEE 802.15.4 MAC assuming star topology in the beacon enabled mode. We obtain analytical expressions for channel sensing probabilities and saturation throughput during the contention access period. We have included the packet discard analysis and validated the analytical expressions for these parameters using ns-2 simulation. Further, we also discuss the performance analysis of the MAC when the contention access mechanism of IEEE 802.15.4 is modified to have only one channel sensing. Finally, we discuss adaptation of the frame length for the case with one channel sensing.

A Ranging Method with IEEE 802.11 Data Frames for Indoor Localization

Abstract: IEEE 802.11 networks constitute a suitable infrastructure for accurate indoor positioning. However, existing approaches based on fingerprinting present drawbacks that make them not suitable for most of applications. This paper presents an innovative TOA-based ranging technique over IEEE 802.11 networks intended to be the essential step of an indoor location system. This approach is based on round trip time measurements using standard IEEE 802.11 link layer frames and a statistical post-processing to mitigate the noise of the measurements. A prototype has been implemented in order to assess the validity and evaluate the performance of the proposed technique. First results show ranging accuracies of less than one meter of error in LOS situations.

A Novel Performance Model for Distributed Prioritized MAC Protocols

Abstract: Distributed prioritized channel access mechanisms have been adopted by the IEEE 802.11e enhanced distributed channel access (EDCA) and the Multiband OFDM Alliance prioritized channel access (PCA) to support service differentiation. In this paper, we propose a novel analytical model for performance study of such mechanisms. The proposed model gives the average frame service time first and then the per station and network normalized throughput, which makes it applicable to both saturated and unsaturated stations. Furthermore, the model is especially helpful in understanding the different effects of the same prioritizing mechanisms in saturated and unsaturated conditions. To the best of our knowledge, there is no similar work reported in the open literature. The accuracy of the analytical model is demonstrated by extensive simulation.

Uplink Scheduling with Quality of Service in IEEE 802.16 Networks

Abstract: In order to support real-time and bandwidth demanding applications the IEEE 802.16 standard is expected to provide quality of service (QoS). Although the standard defines a QoS signaling framework and four service levels, scheduling mechanisms for this network are unspecified. In this paper, we propose a scheduling discipline for uplink traffic. Simulation results show that our scheme is capable to provide QoS. Moreover it shares fairly the resources among connections of the same service type.