Showing papers on "IEEE 802.11e-2005 published in 2000"

Performance analysis of the IEEE 802.11 distributed coordination function

Abstract: The IEEE has standardized the 802.11 protocol for wireless local area networks. The primary medium access control (MAC) technique of 802.11 is called the distributed coordination function (DCF). The DCF is a carrier sense multiple access with collision avoidance (CSMA/CA) scheme with binary slotted exponential backoff. This paper provides a simple, but nevertheless extremely accurate, analytical model to compute the 802.11 DCF throughput, in the assumption of finite number of terminals and ideal channel conditions. The proposed analysis applies to both the packet transmission schemes employed by DCF, namely, the basic access and the RTS/CTS access mechanisms. In addition, it also applies to a combination of the two schemes, in which packets longer than a given threshold are transmitted according to the RTS/CTS mechanism. By means of the proposed model, we provide an extensive throughput performance evaluation of both access mechanisms of the 802.11 protocol.

Distributed fair scheduling in a wireless LAN

Abstract: Fairness is an important issue when accessing a shared wireless channel. With fair scheduling, it is possible to allocate bandwidth in proportion to weightsof the packet flows sharing the channel. This paper presents a fully distributed algorithm for fair scheduling in a wireless LAN. The algorithm can be implemented without using a centralized coordinator to arbitrate medium access. The proposed protocol is derived from the Distributed Coordination Function in the IEEE 802.11 standard. Simulation results show that the proposed algorithm is able to schedule transmission such that the bandwidth allocated to different flows is proportional to their weights. An attractive feature of the proposed approach is that it can be implemented with simple modifications to the IEEE 802.11 standard.

Net throughput with IEEE 802.11 wireless LANs

Abstract: The throughput for IEEE 802.11 wireless LANs has been evaluated with respect to various kinds of overhead. The impact of several sources of overhead has been modeled. Sources include gap time, preamble, PHY (physical layer), MAC (medium access layer) and TCP/IP header fields, ACK (acknowledgement) and request frames. After measurement of the net throughput and detailed monitoring of actual exchange of frames, this modeling has been refined. A close fit is found between the results for IEEE 802.11b obtained from this model and as measured using currently available 2.4 GHz products. Therefore, it is expected that throughput from 5 GHz IEEE 802.11a products currently in development can be accurately predicted using this model.

QoS provided by the IEEE 802.11 wireless LAN to advanced data applications: a simulation analysis

Abstract: IEEE 802.11 is a Media Access Control lMACr protocol which has been standardized by IEEE for Wireless Local Area Networks lWLANsr. The IEEE 802.11 MAC protocol offers two types of services to its usersc synchronous and asynchronous. This paper presents an inddepth analysis, by simulation, of the asynchronous part alone. The analysis is performed by considering station data traffic patterns lhereafter advanced data trafficr which have a very similar shape to traffic generated by WWW applications. We carried out the simulation by taking into consideration two classes of scenariosc balanced and unbalanced. In the former class each station has the same offered load while in the latter class a specific station is more loaded than the others. Our conclusion is that the IEEE 802.11 MAC protocol performs satisfactorily for both classes of scenarios, although performance measures with advanced traffic are worse than the corresponding performance measures with Poissonian traffic. Furthermore, we broadened our analysis to include higher medium capacities than those planned li.e., 1 and 2 Mbit/secr up to 10 Mbit/sec. This part of the analysis shows that the IEEE 802.11 MAC protocol is not adequate to work at speeds planned for the forthcoming ATM Wireless LAN.

Design and performance evaluation of an asymptotically optimal backoff algorithm for IEEE 802.11 Wireless LANs

Abstract: This paper presents and evaluates a distributed mechanism for the contention control in IEEE 802.11 Wireless LANs. Specifically, our mechanism named Asymptotically Optimal Backoff (AOB), dynamically adapts the backoff window size to the current load. AOB guarantees that an IEEE 802.11 WLAN asymptotically (i.e. for a large number of active stations) achieves its optimal channel utilization. The proposed mechanism merges the ideas on adaptive backoff presented previously with some properties derived from the IEEE 802.11 capacity analysis. AOB can be used on top of the standard 802.11 access mechanism without requiring any modification to the standard or additional hardware. The AOB mechanism adapts the backoff to the network contention level by using two simple load estimates: the slot utilization and the average size of transmitted frames. These estimates are simple and can be obtained with no additional costs or overheads. The performance of the IEEE 802.11 protocol with or without the AOB mechanism is investigated in the paper via simulation. Simulative results indicate that our mechanism is very effective and brings the utilization of the system close to the optimal level for a wide range of load and network configurations.

Throughput performance of wireless LANs operating at 2.4 and 5 GHz

Abstract: The throughput performance of IEEE 802.11 wireless LANs has been evaluated in relation to overhead. Sources of overhead are gap time, preamble, header fields for the PHY (physical) and the MAC (medium access control) layer, ACK (acknowledgement) frames, the TCP (transmission control protocol). The impact of this overhead can be modeled. After measuring the net throughput with 2.4 GHz products and detailed monitoring of actual exchange of frames, this modeling has been refined. The close fit between the results of measuring and of modeling for currently available 2.4 GHz product allows an accurate prediction for enhanced 2.4 GHz versions and new 5 GHz products.

Packet telephony support for the IEEE 802.11 wireless LAN

Abstract: Packet telephony is one of the most promising applications in the Internet. In this paper, we propose a modified MAC protocol supporting voice traffic over the IEEE 802.11 WLAN. The proposed scheme adapts the power-saved mode of the IEEE 802.11 specifications in such a way that it approaches the TDM access mode carrying voice traffic, and is compatible with the IEEE 802.11 standard. Simulation results show that the proposed scheme does not degrade the performance of the IEEE 802.11 WLAN using the DCF and also provides good voice quality.

Integrated Service Mappings on IEEE 802 Networks

Abstract: This document describes mappings of IETF Integrated Services over LANs built from IEEE 802 network segments which may be interconnected by IEEE 802.1D MAC Bridges (switches). It describes parameter mappings for supporting Controlled Load and Guaranteed Service using the inherent capabilities of relevant IEEE 802 technologies and, in particular, 802.1D-1998 queuing features in switches.

IEEE 1451.2: An interpretation and example implementation

Abstract: The IEEE 1451 set of standards define an architecture which allows sensor and actuator nodes to connect into a live distributed control network, in a true 'plug and play' fashion. The standard itself is composed of four parts. IEEE 1451.1 through to IEEE 1451.4. Although the extent of each part is well defined currently only the first two parts (IEEE 1451.1 and IEEE 1451.2) exist as fully released, balloted standards. This paper provides an explanatory oveview of the various parts of the IEEE 1451 standard. A target hardware environment for an IEEE 1451.2 STIM (Standard Transducer Interface Module) is introduced, in the guise of the Analog Devices ADuC812 Microconverter chip, which was designed abinitio to meet the IEEE 1451.2 standard hardware requirements. A software environment has been developed by the authors to realise the full STIM functionality in the ADuC812. This software is designed on a modular basis, and it is mapped to the ADuC812 hardware to realise a fully compliant IEEE 1451.2 STIM. Based on the implementation experience the STIM resource requirements in terms of program and data memory are defined. The software model is composed and presented, so that a functional breakdown of the IEEE 1451.2 implementation can be extracted. The software code described can be easily ported to various proprietary hardware platforms. To provide a meaningful demonstration, this STIM implementation is interfaced to a HP BFOOT-66501 NCAP to demonstrate a remote temperature control application, operating over the World-Wide-Web (via an Ethernet network). The STIM implementation described in this paper is independent of any particular type of host network, as the IEEE 1451 standard is intended to fit around any existing network solution.

Adaptive approaches to enhance throughput of IEEE 802.11 wireless LAN with bursty channel

Abstract: Two simple back-off based fragment adaptive algorithms for improving the throughput of IEEE 802.11 wireless LAN are proposed and studied. The simulation results show major improvement in channel throughput and reduction in system end-to-end delay. The results also indicate that proposed adaptive fragmentation algorithms perform the best when the channel is very noisy.

A Framework for Integrated Services Over Shared and Switched IEEE 802 LAN Technologies

Abstract: This memo describes a framework for supporting IETF Integrated Services on shared and switched LAN infrastructure. It includes background material on the capabilities of IEEE 802 like networks with regard to parameters that affect Integrated Services such as access latency, delay variation and queuing support in LAN switches. It discusses aspects of IETF's Integrated Services model that cannot easily be accommodated in different LAN environments. It outlines a functional model for supporting the Resource Reservation Protocol (RSVP) in such LAN environments. Details of extensions to RSVP for use over LANs are described in an accompanying memo [14]. Mappings of the various Integrated Services onto IEEE 802 LANs are described in another memo [13].

An ATM-Based Indoor Millimeter-Wave Wireless LAN for Multimedia Transmissions

Abstract: Developments in new frequency bands for wireless communications make a broadband channel for new services possible. Great effort has been made researching and developing broadband wireless communication in the 60-GHz millimeterwave band since the early 1990s. In this paper, we design an ATM (asynchronous transfer mode)-based indoor millimeterwave wireless local area network (WLAN) that supports multimedia transmissions and focus on the wireless access topic for implementation of wireless ATM. We propose an integrated multimedia transmission protocol, based on the MAC (medium access control) protocol, called RS-ISMA (reservation-based slotted idle signal multiple access). It supports CBR (constant bit rate), VBR (variable bit rate), ABR (available bit rate) and UBR (unspecified bit rate) transmissions and provides QoS (quality of service)-dependent adaptive retransmissions. An RS-ISMAbased prototype full-duplex indoor high-speed WLAN in the 60GHz band was developed. key words: high-speed wireless LAN, 60-GHz millimeter-wave

A MAC protocol for a wireless LAN based on OFDM-CDMA

Abstract: Local access encompasses requirements of high throughput, transfer performance, flexibility, and ease of user/terminal mobility at a relatively low cost. While some of these targets can often be met satisfactorily with wired infrastructures, it is getting increasingly popular to resort to wireless access (wireless LAN), mainly because of its simpler deployment, continuous coverage, availability of ad hoc connectivity, and user/terminal mobility support. This article outlines the proposal of a broadband quality-oriented WLAN system. The basic system characteristics are described, with details given on a MAC protocol supporting IP and exploiting an OFDM-CDMA technique.

Application aware scheduling for power management on IEEE 802.11

Abstract: Asynchronous medium access protocols, like the MAC of IEEE 802.11, are inherently energy inefficient. Hosts have to continuously listen to the air waiting for packet arrivals. The power management mode of operation of IEEE 802.12 represents a significant improvement, however still has energy inefficiencies due to the one-fits-all policy and the medium access contention. To maximize energy efficiency and user satisfaction, the power management mechanism has to take into account application requirements. Traditional QoS specifications ignore energy consumption, and we argue that all service classes, including best effort, should be subdivided in energy consumption sublevels. We developed an application aware power management mechanism on top of the IEEE 802.12 power management which works on the trade-off between delay and power consumption, and allows per-flow customization.

An introduction to IEEE 802.11 wireless LANs

Abstract: As the capability of wireless LAN systems improves, interest in these systems is soaring. In this paper, an overview of wireless LANs is presented which will include broad, system level topics relating directly to IEEE 802.11 systems.

Implementation options for the distribution system in the 802.11 wireless LAN infrastructure network

Abstract: The IEEE 802.11 wireless LAN standard specifies which messages shall be exchanged between an access point and a station to support mobility. However, the implementation of mobility in the wired part of the network, i.e. the distribution system or inter-access point protocol, is not specified. This paper presents and evaluates different options for the implementation of the distribution system used to forward messages between stations in a wireless LAN infrastructure network. The usage of stations in ad hoc mode as bridges or gateways towards a wired LAN is also discussed.

IEEE 1394: changing the way we do multimedia communications

Abstract: The mark of a good bus design is to be general-purpose enough so that its use expands to applications beyond those for which it was originally intended. Compare the narrowly defined EISA (Extended Industry Standard Architecture) specification and the now-defunct MicroChannel bus to the vibrant IEEE 1394 standard, which has numerous specifications built around it already, and many more under development. This article highlights some of the many applications made possible, or made better, by expanding on the 1394 standard. It also directs you to the key specifications that have developed for each of the application areas.

Emulation of ad-hoc networks on IEEE 802.11

Abstract: This paper reports on the emulation of ad-hoc networks based on the IEEE 802.11 standard using the Berkeley Network Simulator including its CMU Monarch (ad-hoc) extension (NS). We examined the emulation capabilities of the Network Simulator. Performance and verification tests also have been done using the emulator. Requirements of the emulator were tested. Some important attributes of emulation, like real-time requirements and CPU power were shown by the tests.

A Performance Analysis of IEEE 802.11 Networks in the Presence of Hidden Stations

Abstract: IEEE 802.11 is a wireless network standard that was completed in 1997. Unfortunately, the medium access protocol described in the standard meets some problems that arise from the presence of so-called hidden stations. This situation can cause degradation of the network performance. The paper describes a simulation analysis of influence of hidden stations on the IEEE 802.11 network efficiency in four different hidden terminals scenarios. The throughput and the mean packet delay as a function of the offered load has been studied. The presented results allow us to determine the usefulness of RTS/CTS mechanism usage in the presence of hidden stations.

LMDS standards architectural issues

Abstract: The IEEE 802.16.1 Task Group is developing PHY and MAC protocols as part of the LAN/MAN series of standards. Issues related to standards development for LMDS are discussed. Solutions incorporated into the current set of baseline documents are described, along with rationale for their inclusion.

Enhanced medium access control of IP-based high speed wireless LANs

Abstract: We adapt a general form of multiple access multi-layer collision anticipation/resolution (MULCAR) to describe the existing IEEE 802.11 MAC DCF. We further explore the proper way of tailoring the splitting tree to achieve higher throughput and lower delay, primarily for high rate OFDM transmission wireless LAN at 5 GHz.

Title Modulation and Equalization Criteria for 2-11 GHz Fixed Broadband Wireless Systems Date Submitted 2000-08-24

Abstract: We give a brief survey of anti-multipath techniques and associated modulation (OFDM and single-carrier) formats, which are pertinent for 802.16.3 fixed broadband wireless systems. Careful modeling and evaluation of power amplifier nonlinearities and frequency offsets is important for evaluation of proposed PHY modulation formats. Because of the sensitivity of OFDM systems to these impairments, Single-carrier modulation schemes with reduced- complexity adaptive equalization strategies merit serious consideration. Purpose Among the key characteristics of any 802.16.3 air interface standard are modulation and equalization. This document provides guidance and background on these topics for the evaluation of 802.16.3 PHY proposals. Notice This document has been prepared to assist IEEE 802.16. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release The contributor grants a free, irrevocable license to the IEEE to incorporate text contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE's name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE's sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.16.

Priority queue-based IEEE 1394 device driver for supporting real-time characteristics

Abstract: This paper proposes an architecture of IEEE 1394 device driver that support the priority-based queueing of packets for guaranteeing real-time characteristics, and improve the predictability of high priority application. This architecture can accommodate the real-time requirements of various applications and devices that include digital multimedia equipment with QoS guarantee and real-time middleware for implementing the IEEE 1394 based home network.

A forward error recovery technique for real-time MPEG-2 video transport and its performance over wireless IEEE 802.11 LAN

Abstract: Real-time MPEG-2 video transport applications do not usually have the luxury of a reverse channel for recovering from any errors that might occur during communication. Degradation in quality of decoded video frames is immediately apparent in the presence of errors in headers. In this paper, we focus on protecting header information by replicating it in any free space that might be available in the defined MPEG-2 transport stream packets. We also present our implementation experience over wired ATM as well as wireless IEEE 802.11 LAN by incorporating this forward error recovery approach with a real-time MPEG-2 encoder. In our experiments, it is found that the free space available is generally more than adequate for replicating essential header information.

Bridging network traffic between wireless and wired lans in Windows NT

Abstract: This paper presents two different alternatives for interconnecting Local Area Networks (LANs) in the data link layer. The solutions use a Windows NT workstation as a bridge between separate networks. Interconnection is provided by either implementing an intermediate driver or a protocol driver into the Windows NT networking stack. Both alternatives screen traffic according to the address fields of network frames and therefore unnecessary traffic can be avoided. Bridge will be used for interconnections between an Ethernet wired LAN, a standard IEEE 802.11 wireless LAN, and TUTWLAN that is a wireless LAN designed at Tampere University of Technology. The protocol driver is concluded to be a more practical alternative for implementing the bridging functionality in TUTWLAN because of its simpler structure and estimated higher performance.

Near field smart array antenna for IEEE 802.11 wireless LAN II

Abstract: The worldwide availability of the unlicensed 2.4-GHz industrial, scientific and medical (ISM) band has propelled the IEEE to issue the 802.11 standard for wireless LAN II. On the other hand, smart antenna technology is a valuable add-in feature to wireless LAN systems. However, the problem of near-field distortion that upsurges from the indoor channel characteristics at the mentioned band has been overlooked. In this paper we evaluate the performance of the proposed near field distortion-compensated smart antenna for indoor wireless systems under the IEEE 802.11 standard's specifications for the 2.4-GHz band.