Performance Modelling of IEEE 802.11g Wireless LAN (original) (raw)

Performance modelling of fairness in IEEE 802.11 wireless LAN protocols

2019

Wireless communication has become a key technology in the modern world, allowing network services to be delivered in almost any environment, without the need for potentially expensive and invasive fixed cable solutions. However, the level of performance experienced by wireless devices varies tremendously on location and time. Understanding the factors which can cause variability of service is therefore of clear practical and theoretical interest. In this thesis we explore the performance of the IEEE 802.11 family of wireless protocols, which have become the de facto standard for Wireless Local Area Networks (WLANs). The specific performance issue which is investigated is the unfairness which can arise due to the spatial position of nodes in the network. In this work we characterise unfairness in terms of the difference in performance (e.g. throughput) experienced by different pairs of communicating nodes within a network. Models are presented using the Markovian process algebra PEPA...

Formal Performance Modelling and Analysis of IEEE 802.11 Wireless LAN Protocols

2015

The IEEE 802.11 family of protocols for wireless local area networks have been used widely for many years. In this paper we present a PEPA model for 802.11b operating under a number of scenarios which highlight different performance issues, and the channel access in terms of utilisation, throughput with fairness and unfairness are studied in this paper. In particular we study the issue of fairness when there is competition for access to the transmission channel. © 2015 Newcastle University. Printed and published by Newcastle University, Computing Science, Claremont Tower, Claremont Road, Newcastle upon Tyne, NE1 7RU, England. Bibliographical details ABDULLAH, C. O AND THOMAS, N. Formal Performance Modelling and Analysis of IEEE 802.11b Wireless LAN Protocols [By] C. O. Abdullah and N. Thomas Newcastle upon Tyne: Newcastle University: Computing Science, 2015. (Newcastle University, Computing Science, Technical Report Series, No. CS-TR-1484)

A Distributed Fair Scheduling Scheme With a New Analysis Model in IEEE 802.11 Wireless LANs

IEEE Transactions on Vehicular Technology, 2008

In this paper, we study the performance of 802.11 wireless local area networks (WLANs) and propose a distributed packet scheduling scheme that improves the short-term fairness among stations in a WLAN. First, we present a completely different analytical model to analyze the performance of 802.11 distributed coordination function (DCF), which models the channel contention dynamics of an IEEE 802.11 system, rather than the individual user perspective adopted by most previous analytical works based on Markov chains. Our model is much simpler than previous Markov chain models that have been used popularly to model the DCF's binary exponential backoff (BEB) procedure. In our model, the backoff stage and the value of the backoff counter are represented as a queueing system and the residual service time at the queue, respectively. Then, we model an entire 802.11 WLAN as a closed queuing network and derive the performance of the 802.11 DCF based on the queueing theory. Next, by exploiting the analytic results, we develop a simple distributed runtime estimation scheme that effectively calculates the number of contending stations. Finally, we propose a distributed packet scheduling scheme that improves the short-term fairness to the IEEE 802.11 network. The scheme utilizes the token bucket mechanism and controls the packet arrival rate sent down to the medium access control (MAC) layer from the logical link control (LLC) layer by adjusting the token-generation rate according to the measured channel contention level. Performance evaluation results show that our scheduling scheme provides a higher degree of short-term fairness as well as throughput improvement.

Improving Throughput and Fairness in IEEE 802.11e

WLANs have become increasingly popular and widely deployed. The MAC protocol is one of the important technology of the WLAN and affects communication efficiency directly. In this paper, focusing on MAC protocol, we propose a novel protocol that network nodes dynamically optimize their backoff process to achieve high throughput while supporting satisfied QoS. Distributed model MAC protocol has an advantage that no infrastructure such as access point is necessary. On the other hand, total throughput decreases heavily and cannot guarantee QoS under a high traffic load, which needs to be improved. Through theoretical analysis, we find that the average idle interval can represent current network traffic load and can be used together with estimated number of nodes for setting optimal CW. Since necessary indexes can be obtained through direct measurement from channel, our scheme will not increase any added load to networks, which makes our schemes simpler and more effective. Through simulation comparison with conventional method, we show that our scheme can greatly enhance the throughput and the QoS no matter the network is in saturated or nonsaturated case, while maintaining good fairness.

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.

Fairness And Quality Of Service Issues And Analysis Of Ieee 802.11E Wireless Lan

2010

The IEEE 802.11e which is an enhanced version of the 802.11 WLAN standards incorporates the Quality of Service (QoS) which makes it a better choice for multimedia and real time applications. In this paper we study various aspects concerned with 802.11e standard. Further, the analysis results for this standard are compared with the legacy 802.11 standard. Simulation results show that IEEE 802.11e out performs legacy IEEE 802.11 in terms of quality of service due to its flow differentiated channel allocation and better queue management architecture. We also propose a method to improve the unfair allocation of bandwidth for downlink and uplink channels by varying the medium access priority level.

Modeling methodology for wireless lans performance evaluation

4th Hets-Nets Conference, 2006

Fairness Analysis of IEEE 802.11 Multirate Wireless LANs

IEEE Transactions on Vehicular Technology, 2007

This paper investigates the issue of fairness in IEEE 802.11-based multirate wireless local area networks (WLANs). Distributed coordination function, which is the medium-accesscontrol (MAC) protocol used in 802.11 WLANs, provides equal long-term channel access probability to competing stations, irrespective of the time required in sending a frame. When equal-sized frames are used and channel conditions are similar, each station, regardless of its data rate, achieves the same throughput. Furthermore, the aggregate throughput is reduced to a level much closer to what one gets when all stations are of lower rate. This anomaly in the performance is a result of unfair channel time allocation for stations when they use multiple data rates. We consider provisioning of time-based fairness in which each station receives an equal share of the wireless channel occupancy time. We demonstrate that under time-based fairness, the throughput that a tagged node achieves in a multirate WLAN with n nodes is identical to what it would achieve in a single-rate WLAN with n nodes all at the same data rate as the tagged node. Furthermore, we show that under time-based fairness scheme, the ratio of throughputs per station corresponding to two different bit rates is directly proportional to the ratio of their bit rates. We analyze different mechanisms in achieving time-based fairness by using an analytical model. Using Jain's fairness index, optimal MAC parameters required in achieving maximum fairness between slow and fast stations are obtained. The impacts of these mechanisms on throughput of slow and fast stations are explored. We also consider the notion of proportional fairness in a multirate scenario and prove that it is equivalent to fair channel time allocation. Last, our investigation of an alternative fairness criterion also leads us to propose that the IEEE 802.11 MAC protocol should be redesigned with temporal fairness as a design objective in avoiding inefficiencies related to the performance anomaly. Index Terms-Multirate wireless local area networks (WLANs), performance analysis, proportional fairness, throughput-based fairness, time-based fairness.

Performance and fairness enhancement in IEEE 802.11 WLAN networks

AEU - International Journal of Electronics and Communications, 2014

The multi-rate transmission mechanism in IEEE 802.11 can improve its reliability and robustness. However, it causes a performance anomaly. After analyzing the reasons for the performance anomaly in multi-rate mechanism, we propose a new scheme to solve the performance anomaly. By adjusting packet size according to the transmission rate, this scheme guarantees that these nodes with different transmit rates can access wireless channel fairly. Theoretical analysis and performance evaluation show that the proposed scheme can well solve the performance anomaly problem. occupation time for each node is equal, which yields a good trade-off between fairness and efficiency in multi-rate WLAN networks. However, the time spent by higher rate nodes to occupy the wireless channel is less than the one spent by lower rate ones, which results in time unfairness. Obviously, it is unfair for the nodes working at high transmission rate, and meanwhile it further leads to serious decreases of the network performance. Thus, it is necessary to solve this unfair issue for multi-rate IEEE 802.11 WLAN networks. The main contents of this paper are listed as follows: (1) we analyze the performance anomaly while multi-rates coexisting; (2) we propose a TRPSA (Transmission Rate-based Packet Size Adjustment) scheme to solve the unfair issue under the situation of multi-rate and multi-node; (3) a theoretical demonstration and detailed simulation results are given. We prove that TRPSA can realize the fairness under a multi-rate and multi-node situation meanwhile improving the network performance.

Effect of the contention window size on performance and fairness of the IEEE 802.11 standard

Wireless Personal Communications, 2007

IEEE 802.11 is a widely used standard for MAC and PHY layers of WLANs. Unfortunately, the access methods offered in this standard cannot support QoS (Quality of Service) for real-time traffics. Using multimedia applications over WLANs is increasing and, on the other hand, it seems that the access methods employed in this standard causes high variations in delay or jitter and wastes bandwidth due to collisions. There are many methods to enable DCFbasic access method in 802.11-with service differentiation and QoS. The difficulty in majority of these methods is unfair bandwidth allocation among low and high priority traffics at high loads resulting starvation for low priority traffics. In this paper, we modify the way that the CW (Contention Window) size is calculated after a successful transmission and study the effect of the CW size on performance and fairness. Results of our simulations show that the performance of DCF with this modification is better, specially, for traffics in which throughput is the most important parameter.

Performance Modelling of IEEE 802.11g Wireless LAN (original) (raw)

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