A survey of QoS enhancements for IEEE 802.11 wireless LAN
01 Aug 2004-Wireless Communications and Mobile Computing (John Wiley & Sons, Ltd)-Vol. 4, Iss: 5, pp 547-566
TL;DR: The QoS limitations of IEEE 802.11 wireless MAC layers are analyzed and different QoS enhancement techniques proposed for802.11 WLAN are described and classified along with their advantages/drawbacks.
Abstract: *Summary Quality of service (QoS) is a key problem of today’s IP networks. Many frameworks (IntServ, DiffServ, MPLS, etc.) have been proposed to provide service differentiation in the Internet. At the same time, the Internet is becoming more and more heterogeneous due to the recent explosion of wireless networks. In wireless environments, bandwidth is scarce and channel conditions are time-varying and sometimes highly lossy. Many previous research works show that what works well in a wired network cannot be directly applied in the wireless environment. Although IEEE 802.11 wireless LAN (WLAN) is the most widely used WLAN standard today, it cannot provide QoS support for the increasing number of multimedia applications. Thus, a large number of 802.11 QoS enhancement schemes have been proposed, each one focusing on a particular mode. This paper summarizes all these schemes and presents a survey of current research activities. First, we analyze the QoS limitations of IEEE 802.11 wireless MAC layers. Then, different QoS enhancement techniques proposed for 802.11 WLAN are described and classified along with their advantages/drawbacks. Finally, the upcoming IEEE 802.11e QoS enhancement standard is introduced and studied in detail.
Citations
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TL;DR: The new QoS features of 802.
Abstract: The IEEE 802.11 WLAN legacy standard cannot provide QoS support for multimedia applications. Thus, considerable research efforts have been carried out to enhance QoS support for 802.11. Among them, 802.11e is the upcoming QoS-enhanced standard proposed by the IEEE working group. This article describes in detail the new QoS features of 802.11e based on the latest version of the standard draft. We investigate the performance of 802.11e through computer simulations. Using simple examples, we show the effectiveness of adaptive schemes under the 802.11e framework.
196 citations
Additional excerpts
...Based on different criteria, they can be classified into STA-based vs. queue-based, or DCFbased vs. PCF-based enhancements [ 5 ]....
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TL;DR: FHCF is proposed, a simple and efficient scheduling algorithm for 802.11e that aims to be fair for both CBR and VBR flows and provides good fairness while supporting bandwidth and delay requirements for a large range of network loads.
Abstract: The IEEE 802.11e medium access control (MAC) layer protocol is an emerging standard to support quality of service (QoS) in 802.11 wireless networks. Some recent work shows that the 802.11e hybrid coordination function (HCF) can improve significantly the QoS support in 802.11 networks. A simple HCF referenced scheduler has been proposed in the 802.11e which takes into account the QoS requirements of flows and allocates time to stations on the basis of the mean sending rate. As we show in this paper, this HCF referenced scheduling algorithm is only efficient and works well for flows with strict constant bit rate (CBR) characteristics. However, a lot of real-time applications, such as videoconferencing, have some variations in their packet sizes, sending rates or even have variable bit rate (VBR) characteristics. In this paper we propose FHCF, a simple and efficient scheduling algorithm for 802.11e that aims to be fair for both CBR and VBR flows. FHCF uses queue length estimations to tune its time allocation to mobile stations. We present analytical model evaluations and a set of simulations results, and provide performance comparisons with the 802.11e HCF referenced scheduler. Our performance study indicates that FHCF provides good fairness while supporting bandwidth and delay requirements for a large range of network loads.
148 citations
Cites background or methods from "A survey of QoS enhancements for IE..."
...Keywords: IEEE 802.11e, WLAN, medium access control (MAC), quality of service (QoS)...
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...In order to meet the negotiated QoS requirements, the QoS-enhanced AP (QAP) needs to schedule efficiently downlink and uplink frame transmissions....
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...In 802.11e HCF, each QoS-enhanced station (QSTA) that requires a strict QoS support is allowed to send QoS requirement packets to the QAP while QAP can allocate the corresponding channel time for different QSTAs according to the requests....
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20 Jun 2004
TL;DR: A new scheme called adaptive fair EDCF is described that extends EDCF, by increasing the contention window during deferring periods when the channel is busy, and by using an adaptive fast backoff mechanism when the channels are idle.
Abstract: The emerging widespread use of real-time multimedia applications over wireless networks makes the support of quality of service (QoS) a key problem. In this paper, we focus on QoS support mechanisms for IEEE 802.11 wireless ad-hoc networks. First, we review limitations of the upcoming IEEE 802.11e enhanced DCF (EDCF) and other enhanced MAC schemes that have been proposed to support QoS for 802.11 ad-hoc networks. Then, we describe a new scheme called adaptive fair EDCF that extends EDCF, by increasing the contention window during deferring periods when the channel is busy, and by using an adaptive fast backoff mechanism when the channel is idle. Our scheme computes an adaptive backoff threshold for each priority level by taking into account the channel load. The new scheme significantly improves the quality of multimedia applications. Moreover, it increases the overall throughput obtained both in medium and high load cases. Simulution results show that our new scheme outperforms EDCF and other enhanced schemes. Finally, we show that the adaptive fair EDCF scheme achieves a high degree of fairness among applications of the same priority level.
128 citations
Cites background from "A survey of QoS enhancements for IE..."
...PCF is known to perform poorly [3], [4], [10] for many reasons such as the access point is not able to poll all the stations during one cycle when the node’s transmission duration is variable....
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TL;DR: This paper summarizes emerging wireless broadband access technologies, ranging from WLANs to satellite communications, as well as explaining the latest standards in the IEEE 802.11 and 802.16 families in detail.
124 citations
Cites background from "A survey of QoS enhancements for IE..."
...If more than one STA try to access the air interface simultaneously a collision occurs....
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Patent•
13 Sep 2005
TL;DR: In this paper, two new MAC measurements are proposed for WTRU uplink traffic loading measurement, and an AP service loading measurement and are generally applicable at least to layers 1 and 2 as applied to a least 802.11k in the context of OFDM and CDMA 2000 systems.
Abstract: An improved method of network management, particularly in the context of standards IEEE802.11 and IEEE802.11k, through two new MAC measurements, with attendant advantages. The two new measurements include WTRU uplink traffic loading measurement, and an AP service loading measurement and is generally applicable at least to layers 1 and 2 as applied to a least 802.11k in the context of OFDM and CDMA 2000 systems, but is applicable to other scenarios as well. A Method for determining and advertising congestion is also provided for a Wireless Local Area Network (WLAN) system. The present invention also introduces a method for managing congestion when congestion is detected. This aspect of the present invention applies primarily to wireless systems that use the Carrier Sense Multiple Access/ Collision Avoidance (CSMA/CA) mechanism. The methods are advantageously implemented in selectively configured WTRUs of various forms.
124 citations
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TL;DR: An architecture for implementing scalable service differentiation in the Internet achieves scalability by aggregating traffic classification state which is conveyed by means of IP-layer packet marking using the DS field [DSFIELD].
Abstract: This document defines an architecture for implementing scalable service differentiation in the Internet. This architecture achieves scalability by aggregating traffic classification state which is conveyed by means of IP-layer packet marking using the DS field [DSFIELD]. Packets are classified and marked to receive a particular per-hop forwarding behavior on nodes along their path. Sophisticated classification, marking, policing, and shaping operations need only be implemented at network boundaries or hosts. Network resources are allocated to traffic streams by service provisioning policies which govern how traffic is marked and conditioned upon entry to a differentiated services-capable network, and how that traffic is forwarded within that network. A wide variety of services can be implemented on top of these building blocks.
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3,114 citations
TL;DR: In this article, the concept of punctured convolutional codes is extended by punctuating a low-rate 1/N code periodically with period P to obtain a family of codes with rate P/(P+l), where l can be varied between 1 and (N-1)P. This allows transmission of incremental redundancy in ARQ/FEC (automatic repeat request/forward error correction) schemes and continuous rate variation to change from low to high error protection within a data frame.
Abstract: The concept of punctured convolutional codes is extended by punctuating a low-rate 1/N code periodically with period P to obtain a family of codes with rate P/(P+l), where l can be varied between 1 and (N-1)P. A rate-compatibility restriction on the puncturing tables ensures that all code bits of high rate codes are used by the lower-rate codes. This allows transmission of incremental redundancy in ARQ/FEC (automatic repeat request/forward error correction) schemes and continuous rate variation to change from low to high error protection within a data frame. Families of RCPC codes with rates between 8/9 and 1/4 are given for memories M from 3 to 6 (8 to 64 trellis states) together with the relevant distance spectra. These codes are almost as good as the best known general convolutional codes of the respective rates. It is shown that the same Viterbi decoder can be used for all RCPC codes of the same M. the application of RCPC codes to hybrid ARQ/FEC schemes is discussed for Gaussian and Rayleigh fading channels using channel-state information to optimise throughput. >
1,967 citations
Journal Article•
TL;DR: The concept of punctured convolutional codes is extended by punctuating a low-rate 1/N code periodically with period P to obtain a family of codes with rate P/(P+l), where l can be varied between 1 and (N-1)P.
Abstract: The concept of punctured convolutional codes is extended by punctuating a low-rate 1/N code periodically with period P to obtain a family of codes with rate P/(P+l), where l can be varied between 1 and (N-1)P. A rate-compatibility restriction on the puncturing tables ensures that all code bits of high rate codes are used by the lower-rate codes. This allows transmission of incremental redundancy in ARQ/FEC (automatic repeat request/forward error correction) schemes and continuous rate variation to change from low to high error protection within a data frame. Families of RCPC codes with rates between 8/9 and 1/4 are given for memories M from 3 to 6 (8 to 64 trellis states) together with the relevant distance spectra. These codes are almost as good as the best known general convolutional codes of the respective rates. It is shown that the same Viterbi decoder can be used for all RCPC codes of the same M. the application of RCPC codes to hybrid ARQ/FEC schemes is discussed for Gaussian and Rayleigh fading channels using channel-state information to optimise throughput. >
1,877 citations
12 Jun 1994
TL;DR: The author proves that the scheme possesses the desired fairness property and is nearly optimal, in the sense that the maximum permissible disparity among the normalized services offered to the backlogged sessions is never more than two times the corresponding figure in any packet-based queueing system.
Abstract: An efficient fair queueing scheme which is feasible for broadband implementation is proposed and its performance is analyzed. The author defines fairness in a self-contained manner, eliminating the need for the hypothetical fluid-flow reference system used in the present state of art and thereby removing the associated computational complexity. The scheme is based on the adoption of an internally generated virtual time as the index of work progress, hence the name self-clocked fair queueing. The author proves that the scheme possesses the desired fairness property and is nearly optimal, in the sense that the maximum permissible disparity among the normalized services offered to the backlogged sessions is never more than two times the corresponding figure in any packet-based queueing system. >
1,289 citations