Throughput Performance of the Distributed and Point Coordination Funtions of an IEEE 802.11 Wireless LANs (original) (raw)

Performance behaviour of IEEE 802.11 distributed coordination function

IET Circuits, Devices & Systems, 2008

The authors present an extensive investigation of the performance of the IEEE 802.11 medium access control (MAC) protocol, with respect to throughput and delay. For the protocol analysis, a new model, which describes the protocol's behaviour to a great extent by incorporating and extending the existing models, is proposed. The authors also present a detailed analysis of the end-to-end delay through the study of the MAC delay and the queueing delay. The authors use the Z-transform of backoff duration to obtain the mean value, the variance and the probability distribution of the MAC delay. For the queueing analysis, first the authors consider an M/G/1 queue in order to provide a first look at the queueing delay. Second, the authors modify the input process of the queue so that the packet arrival process is described by an ON -OFF model, which expresses the bursty nature of traffic. In the investigations, data rates of 1, 5.5 and 11 Mbps are assumed to highlight the effect of the bit rate on network performance for both Basic and request-to-send/ clear-to-send access mechanisms. The throughput and delay analyses are validated by simulating the distributed coordination function, whereas the models are compared with the existing models based on their results. The accuracy of the analyses was found to be quite satisfactory.

Throughput Performance of the Distributed and Point Coordination Functions

We study the throughput and delay as a function of load, of data traffic in an IEEE 802.11 Wireless LAN using the public domain network simulator ns-2. We evaluate the Distributed Coordination Function (DCF) as well as the Point Coordination Function (PCF) modes of operation of IEEE 802.11 in detail. Although the PCF gives consistently higher throughput in the ranges of load studied, it has higher delay in the relatively lighter ranges of load. So it is optimal to use DCF at light loads and switch to PCF when the load increases.

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.

A novel performance analysis model for an IEEE 802.11 wireless LAN

IEEE Communications Letters, 2006

This letter presents a novel analytic model that accurately evaluates the performance of a single-hop IEEE 802.11 wireless LAN (WLAN). By using a closed queuing network, we model an IEEE 802.11 WLAN system that consists of a fixed number of stations and derive the saturated throughput of the IEEE 802.11 distributed coordination function (DCF). The ns-2 simulation results show that our new analysis model is very accurate in evaluating the performance of the IEEE 802.11 DCF.

Performance Analysis of the 802.11 Distributed Coordination Function under Sporadic Traffic

We analyze the performance of the Dis- tributed Coordination Function (DCF) for 802.11 WLANs. We consider a fixed number of contending stations within radio proximity, and we investigate the important case in which stations operate under non-saturated conditions. We assume that the MAC queues of wireless stations receive from the upper layers a stationary arrival process of packets. We identify the fundamental problems that arise in building an analytical model of the system, and we propose different approaches to overcome these difficulties. Finally, we apply our modelling technique to study several important issues in 802.11 networks, such as the impact of bursty traffic and the system performance in a multirate environment. The accuracy of the analytical results is verified by simulation with ns-2.

Comments on Comprehensive Analysis of IEEE 802.11 Distributed Coordination Function

International Journal of Wireless Information Networks, 2009

In this paper, an improved analytical model for IEEE 802.11 distributed coordination function (DCF) under finite load is proposed by closely following the specifications given in IEEE 802.11 standard. The model is investigated in terms of channel throughput assuming perfect channels. It is shown that the proposed model gives better insight into the operation of DCF compared with the existing analytical models.

Throughput and delay analysis of IEEE 802.11 protocol

2002

Wireless technologies in the LAN environment are becoming increasingly important. The IEEE 802.11 standard is the most mature technology for wireless local area networks (WLANs). The performance of the medium access control (MAC) layer, which consists of distributed coordination function (DCF) and point coordination function (PCF), has been examined over the past years. We present an analytical model to compute the saturated throughput of 802.11 protocol in the absence of hidden stations and transmission errors. A throughput analysis is carried out in order to study the performance of 802.11 DCF. Using the analytical model, we develop a frame delay analysis under traffic conditions that correspond to the maximum load that the network can support in stable conditions. The behaviour of the exponential backoff algorithm used in 802.11 is also examined.

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.

A modified point coordination function in IEEE 802.11 wireless LAN

The 11th IEEE International Conference on Networks, 2003. ICON2003.

With recent advances in wireless technologies, wireless LANs are becoming increasingly widespread as an alternative to fixed access technologies. The IEEE 802.11 standard has gained the most popularity among the different standards and is currently being deployed both within enterprises as well as being used for public access. One of the weaknesses of the basic medium access in the 802.11 standard is its relatively poor support for real-time traffic. In order to provide this support, the MAC layer implements a Point Coordination Function (PCF). However, since the PCF is based on a centralized polling protocol, some bandwidth is wasted due to the polling overheads and null packets in case the polled stations do not have any data to transmit. In order to reduce the waste and increase the channel utilization this paper presents a modified version of the standard PCF. The modified PCF uses a distributed polling protocol (DPP) as an access mechanism for the uplink transmission. The transmission period in the modified PCF consists of a distributed polling protocol period (DPPP) which is controlled by the DPP and the real-time traffic downlink period (RTDP). The paper further introduces a technique for dealing with the hidden station problem for use together with the proposed modification. This problem occurs when one or more stations misinterpret the status of the medium leading to unforeseen collisions. Using simulation we compare the performance of the modified PCF with the standard PCF when they are used to support voice transmissions. The results show that the modified PCF significantly improves the channel utilization since it can support a higher number of stations than the standard PCF.