LAN performance Chapter 10 (original) (raw)

Performance analysis of the IEEE 802.11 MAC protocol for wireless LANs

Wireless local area networks (WLANs) are extremely popular being almost everywhere including business, office and home deployments. The IEEE 802.11 protocol is the dominating standard for WLANs. The essential medium access control (MAC) mechanism of 802.11 is called distributed co-ordination function (DCF). This paper provides a simple and accurate analysis using Markov chain modelling to compute IEEE 802.11 DCF performance, in the absence of hidden stations and transmission errors. This mathematical analysis calculates in addition to the throughput efficiency, the average packet delay, the packet drop probability and the average time to drop a packet for both basic access and RTS/CTS medium access schemes. The derived analysis, which takes into account packet retry limits, is validated by comparison with OPNET simulation results. We demonstrate that a Markov chain model presented in the literature, which also calculates throughput and packet delay by introducing an additional transition state to the Markov chain model, does not appear to model IEEE 802.11 correctly, leading to ambiguous conclusions for its performance. We also carry out an extensive and detailed study on the influence on performance of the initial contention window size (CW), maximum CW size and data rate. Performance results are presented to identify the dependence on the backoff procedure parameters and to give insights on the issues affecting IEEE 802.11 DCF performance. network connectivity, being a mouse-click away from key information and applications. Moreover, recent advances in wireless technology and mobile communications have equipped wireless capability portable devices including palmtop computers, laptops and personal digital assistants (PDAs) .

Wireless medium access control protocols

IEEE Communications Surveys & Tutorials, 2000

WIRELESS MEDIUM ACCESS CONTROL PROTOCOLS he ability to communicate with anyone on the planet from anywhere on the planet has been mankind's dream for a long time. Wireless is the only medium that can enable such untethered communication. With the recent advances in VLSI and wireless technologies, it is now possible to build high-speed wireless systems that are cheap as well as easy to install and operate. However, the wireless medium is a broadcast medium, and therefore multiple devices can access the medium at the same time. Multiple simultaneous transmissions can result in garbled data, making communication impossible. A medium access control (MAC) protocol moderates access to the shared medium by defining rules that allow these devices to communicate with each other in an orderly and efficient manner. MAC protocols therefore play a crucial role in enabling this paradigm by ensuring efficient and fair sharing of the scare wireless bandwidth. Wireless MAC protocols have been studied extensively since the 1970s. The initial protocols were developed for data and satellite communications. We are now witnessing a convergence of the telephone, cable and data networks into a single unified network that supports multimedia and real-time applications like voice and video in addition to data. The multimedia applications require delay and jitter guarantees from the network. This demand of the network is known as the Quality of Service (QoS) guarantee. These requirements have led to novel and complex MAC protocols that can support multimedia traffic. This article surveys the various MAC protocols that have been proposed in the literature and compares them based on architecture (MAC coordination , duplexing), performance (throughput, delay, stability, contention resolution algorithms and fairness) and multimedia support (scheduling, access priorities). We confine our study to systems that span relatively small areas. The article is organized as follows. First we contrast different wireless network architectures. We then bring out the issues unique to wireless MAC protocols. The performance metrics used to compare different MAC protocols are discussed later. We then present a classification of the protocols. We will present the different classes of proposed MAC protocols and compare the pros and cons of the proposed protocols. GENERAL NETWORK CONCEPTS A wireless network is comprised of devices with wireless adapters communicating with each other using radio waves. These wireless devices are called nodes in this dissertation. The signal transmitted can be received only within a certain distance from the sender, which is called the range of the node. A base station (BS) is a special node in the network that is not mobile and is located in a central location. Wireless networks differ in the duplexing mechanism and the network architecture.

An adaptive MAC protocol for wireless LANs

Journal of Communications and Networks, 2014

This paper focuses on contention-based Medium Access Control (MAC) protocols used in Wireless Local Area Networks (WLANs). We propose a novel MAC protocol called Adaptive Backoff Tuning MAC (ABTMAC) based on IEEE 802.11 DCF. In our proposed MAC protocol, we utilize a fixed transmission attempt rate and each node dynamically adjusts its backoff window size considering the current network status. We determined the appropriate transmission attempt rate for both cases where the Request-To-Send/Clear-To-Send (RTS/CTS) mechanism was and was not employed. Robustness against performance degradation caused by the difference between desired and actual values of the attempt rate parameter is considered when setting it. The performance of the protocol is evaluated analytically and through simulations. These results indicate that a wireless network utilizing ABTMAC performs better than one using IEEE 802.11 DCF.

Investigation of the IEEE 802.11 medium access control (MAC) sublayer functions

1997

Analysis of the drafi IEEE 802.11 wireless local area network (WLAN) standard is needed to characterize the expected performance of the standard's ad hoc and infrastructure networks. The performance of the medium access control (MAC) sublayer, which consists of Distributed Coordtnatton Function (DCF) and Point Coordination Function (PCF), is determined by simulating asynchronous data trajjic in a 1 Mbps ad hoc network, and asynchronous data and packetized voice trafic in a 1 Mbps infrastructure network. The simulation models incorporate the effect of burst errors, packet size, RTS threshold and fragmentation threshold on network throughput and delay. The results show that the IEEE 802.11 WLAN can achieve a reasonably high eficaency when the medium is almost error-free, but may degrade appreciably under harsh fadtng. The results also show that times ensttive traffic such as packet voice can be supported together with other zntenstve trafic such as packet data. However, an echo canceler is required for packet voice systems.

A new approach to MAC protocol optimization

Globecom '00 - IEEE. Global Telecommunications Conference. Conference Record (Cat. No.00CH37137), 2000

4 systematic and automatic method for dynamically optimizing medium access control (MAC) protocol parameters is presented. Our meta-protocol approach is capable of performing on-line optimization of critical MAC parameters without knowing in advance what network conditions will arise or how they may fluctuate over time. Furthermore, this dynamic optimization is achieved without any centralized control or exchange of control messages between nodes. The power of the new technique is demonstrated by two examples. In a LAN environment, it outperforms traditional contention based MAC protocols that adjust retransmission probabilities, e.g., employing binary exponential backoff. In a synchronous multi-hop environment, it automatically converges to the proper transmission schedule assignments for the actual node density.

Performance analysis of contention based medium access control protocols

We study the performance of contention based medium access control (MAC) protocols. In particular, we provide a simple and accurate method for estimating the throughput of IEEE 802.11 DCF and IEEE 802.11e EDCA. Our method is based on a rigorous analysis of the Markov chain associated with the back-off process at the contending nodes. Our results provide new insights into the operation of the IEEE 802.11 DCF and IEEE 802.11e EDCA. Although we focus on the IEEE 802.11 MAC protocol in this paper, the techniques developed are applicable to a wide variety of contention based MAC protocols. † In order to avoid confusion arising from the superficially similar terminology, we emphasize that the fixed points we talk of in this work are different from the fixed points in [3], [7], . Their fixed points are for the 1dimensional coupling parameter p; our fixed points are for the n-dimensional state descriptor in a joint Markovian representation of the back-off stages at all n stations. The details are provided in the next section.

Performance Evaluation of Priority based Contention- MAC in Mobile Ad-Hoc Networks

2013

The communication through wireless media is in very much demand because of high mobility of the users and establishing ad hoc network in emergency situations, which requires the designing of an efficient and priority based MAC (Medium Access Protocol) to support quality of service in MANET (Mobile Ad hoc Networks) adequately. MAC is the base layer, which is required to catch up the system performance especially in mobile ad hoc wireless network. There are various MAC standards used in MANET. The IEEE 802.11 is one of them and most frequently applied to such networks presently. We found that the IEEE 802.11 MAC standard is not very much suitable into wireless network scenario because its poor performance and not satisfactorily addressing the critical issues of networking like priority based transmission across the nodes results in lower throughput, higher delay and poor fair access of cannels. In this paper, we propose a dynamic PBC-MAC protocol for wireless ad hoc networks- named as...

Modeling Methodology for Wireless LANs Performance

2006

Performance evaluation of wireless LAN is a key point which allows to compute both quantitative parameters (e.g.throughput) and qualitative one (e.g. fairness). Classically, authors use simulation tools or Markovian process in order to model the nodes, the MAC protocol and the network topology. But, each time a new MAC protocol or a new network topology needs to be evaluated, a new model should be described and investigated. So, such approaches are not extensible and reusable. In this work, we show how to take benefit from the compositional approach of stochastic process algebra to propose efficient and extensible models. We provide a generic modeling methodology based on the use of three different components to model i) the node behavior, ii) the MAC protocol used and iii) the nodes interactions (i.e., the network topology). Thanks to our model, it is possible to investigate a new MAC protocol or a new network topology through the use of a new component and without any change in the other components.

Performance comparison of medium access control schemes for IEEE 802.11

2012 18th Asia-Pacific Conference on Communications (APCC), 2012

IEEE 802.11 specifies a set of protocols for a wireless LAN defined by IEEE which covers the physical and data link layer. Nowadays, IEEE 802.11 based WLAN has a widespread and ubiquitous use in providing wireless connectivity to several electronic devices like cell phones, laptops, gaming devices and so on. All these devices operate on the same medium and contend with each other in order to access the medium. All devices using the IEEE 802.11 Standard adopt a basic MAC scheme called the distributed coordination function (DCF) whose key function is contention resolution. The Binary Exponential Backoff (BEB) scheme is used to access the medium and deliver packets over a wireless network. However, the performance and efficiency of IEEE 802.11 DCF scheme is a matter of question as the number of contending stations are increasing everyday. In this paper we make a detailed study of the performance comparison between DCF, CONTI, k-EC and PREMA, which are various contention resolution schemes proposed in various independent researches. The criteria for performance comparison that we will use are collision rate, throughput and average delay between successful transmissions. Also, in this paper we are going to propose an unsaturated model for the contention schemes whose implementation and performance is consistent with the saturated mode used in the above contention schemes. Furthermore, we compare the performance for each of the contention resolution schemes in the unsaturated mode.