Setting the parameters right for two-hop IEEE 802.11e ad hoc networks (original) (raw)

Throughput Analysis and Admission Control for IEEE 802.11a

Mobile Networks and Applications, 2005

We propose a new Markov model for the distributed coordination function (DCF) of IEEE 802.11. The model incorporates carrier sense, non-saturated traffic and SNR, for both basic and RTS/CTS access mechanisms. Analysis of the model shows that the throughput first increases, and then decreases with the number of active stations, suggesting the need for an admission control mechanism. We introduce such a mechanism, which tries to maximize the throughput while maintaining a fair allocation. The maximum achievable throughput is tracked by the mechanism as the number of active stations increases. An extensive performance analysis shows that the mechanism provides significant improvements.

The IEEE 802.11 Distributed Coordination Function in Small

International Journal of wireless …, 2003

The IEEE 802.11 standards for wireless local area networks define how the stations of an ad-hoc wireless network coordinate in order to share the medium efficiently. This work investigates the performance of such a network by considering the two different access mechanisms proposed in these standards. The IEEE 802.11 access mechanisms are based on the carrier sense multiple access with collision avoidance (CSMA/CA) protocol using a binary slotted exponential backoff mechanism. The basic CSMA/CA mechanism uses an acknowledgment message at the end of each transmitted packet, whereas the request to send/clear to send (RTS/CTS) CSMA/CA mechanism also uses a RTS/CTS message exchange before transmitting a packet. In this work, we analyze these two access mechanisms in terms of throughput and delay. Extensive numerical results are presented to highlight the characteristics of each access mechanism and to define the dependence of each mechanism on the backoff procedure parameters.

Performance Analysis of IEEE 802.11 in Multi-hop Wireless Networks

Lecture Notes in Computer Science, 2007

Multi-hop wireless networks provide a quick and easy way for networking when we need a temporary network or when cabling is difficult. The 802.11 Medium Access Control (MAC) plays an important role in the achievable system performance. There have been many studies on analytic modeling of single-hop 802.11 wireless networks but only a few on the analysis of multihop wireless networks. Furthermore, the object of these researches is an homogeneous ad-hoc wireless networks; therefore they are not appropriate for a network with structure such as wireless mesh networks. This paper introduces an analytic model of throughput performance for the IEEE 802.11 multi-hop networks, which allows us to compute the achievable throughput on a given path in multi-hop wireless networks. The model shows that there is an optimal point at which throughput is maximized. Using this model and a Markov model for modeling the operation of the IEEE 802.11 DCF we can determine the amount of data that each node should inject to the network to get the best throughput performance.

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) .

A Capacity Analysis for the IEEE 802.11 MAC Protocol

Wireless Networks, 2001

The IEEE 802.11 MAC protocol provides shared access to a wireless channel. This paper uses an analytic model to study the channel capacity -i.e., maximum throughput -when using the basic access (two-way handshaking) method in this protocol. It provides closed-form approximations for the probability of collision p, the maximum throughput S and the limit on the number of stations in a wireless cell.

Dynamic tuning of the IEEE 802.11 protocol to achieve a theoretical throughput limit

Networking, IEEE/ACM …, 2000

In wireless LANs (WLANs), the medium access control (MAC) protocol is the main element that determines the efficiency in sharing the limited communication bandwidth of the wireless channel. In this paper we focus on the efficiency of the IEEE 802.11 standard for WLANs. Specifically, we analytically derive the average size of the contention window that maximizes the throughput, hereafter theoretical throughput limit, and we show that: 1) depending on the network configuration, the standard can operate very far from the theoretical throughput limit; and 2) an appropriate tuning of the backoff algorithm can drive the IEEE 802.11 protocol close to the theoretical throughput limit. Hence we propose a distributed algorithm that enables each station to tune its backoff algorithm at run-time. The performances of the IEEE 802.11 protocol, enhanced with our algorithm, are extensively investigated by simulation. Specifically, we investigate the sensitiveness of our algorithm to some network configuration parameters (number of active stations, presence of hidden terminals). Our results indicate that the capacity of the enhanced protocol is very close to the theoretical upper bound in all the configurations analyzed.

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.

Performance Analysis of the IEEE 802.11 Wireless LAN Standard1

1999

IEEE 802.11 is a relatively new standard for communication in a wireless LAN. Its need arose from the many differences between traditional wired and wireless LANs and the increased need for interoperability among different vendors. To date, detailed performance measures for this CSMA/CA protocol are not known. We describe the results of our Discrete-Event Simulation of the Distributed Coordination Function (DCF) within the MAC sublayer. We model an ideal LAN and describe the best case performance. Our results show the relationship between the protocol options and total system throughput.

Runtime optimization of IEEE 802.11 wireless lans performance

IEEE Transactions on Parallel and Distributed Systems, 2004

IEEE 802.11 is the standard for Wireless Local Area Networks (WLANs) promoted by the Institute of Electrical and Electronics Engineers. Wireless technologies in the LAN environment are becoming increasingly important, and the IEEE 802.11 is the most mature technology to date . Previous works have pointed out that the standard protocol can be very inefficient, and that an appropriate tuning of its congestion control mechanism (i.e., the backoff algorithm) can drive the IEEE 802.11 protocol close to its optimal behavior. To perform this tuning a station must have exact knowledge of the network contention level; unfortunately, in a real case, a station cannot have exact knowledge of the network contention level (i.e. number of active stations and length of the message transmitted on the channel) but it, at most, can estimate it. This paper presents and evaluates a distributed mechanism for the contention control in IEEE 802.11 Wireless LANs. Our mechanism, named Asymptotically Optimal Backoff (AOB), dynamically adapts the backoff window size to the current network contention level, and guarantees that an IEEE 802.11 WLAN asymptotically achieves its optimal channel utilization. The AOB mechanism measures the network contention level by using two simple estimates: the slot utilization, and the average size of transmitted frames. These estimates are simple and can be obtained by exploiting information that is already available in the standard protocol. AOB can be used to extend the standard 802.11 access mechanism without requiring any additional hardware. The performance of the IEEE 802.11 protocol, with and without the AOB mechanism, is investigated in the paper via simulation. Simulation results indicate that our mechanism is very effective, robust and has traffic differentiation potentialities. Keywords: Wireless LAN (WLAN), IEEE 802.11, multiple access protocol (MAC), protocol capacity, performance analysis 2 access at a competitive price. A major factor in achieving this goal is the availability of appropriate networking standards. IEEE Std 802.11 defines a Medium Access Control (MAC) and Physical Layer (PHY) specification for a Wireless Local Area (WLAN) network to provide wireless connectivity for fixed, portable, and moving stations within a local area [IEE97].

IEEE 802.11 distributed coordination function (DCF): analysis and enhancement

2002

Being a part of IEEE project 802, the 802.11 medium access control (MAC) is used to support asynchronous and time bounded delivery of radio data packets. It is proposed that a distributed coordination function (DCF), which uses carrier sense multiple access with collision avoidance (CSMA/CA) and binary slotted exponential backoff, be the basis of the IEEE 802.11 WLAN MAC protocols. This paper proposes a throughput enhancement mechanism for DCF by adjusting the contention window (CW) resetting scheme. Moreover, an analytical model based on Markov chain is introduced to compute the enhanced throughput of 802.11 DCF. The accuracy of the model and the enhancement of the proposed scheme are verified by elaborate simulations