The Impact of RTS Threshold on IEEE 802.11 MAC Protocol

[[abstract]]Wireless technologies and applications received great attention in recent years. 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 wireless local area networks (WLANs). The request-to-send/clear-to-send (RTS/CTS) mechanism is an optional handshaking procedure used by the IEEE 802.11 wireless network to reduce the possibility of collision. The RTS_Threshold (RT) value which determines when the RTS/CTS handshaking mechanism should be used is an important parameter to investigate; since different RT values will produce different performance characteristics in data transmission. This paper presents an evaluation of the influence of the RT parameter on the IEEE 802.11 wireless network, and gives a guideline to dynamically adjust the RT value. Simulation results of this paper show that, in order to achieve the best performance, the RT should be dynamically adjusted according to the environment. However, we suggest to have the RTS/CTS always activated (RT = 0), saving complex work designing and implementing a dynamic RT mechanism, to obtain a near best performance.[[notice]]補正完

Simulation

In this paper, performance analysis of the Wireless and Wired computer networks through simulation has been attempted using OPNET as simulating tool. For wired networks, the performance parameters like delay and throughput have been investigated with varying transmission links and load balancers. The load-balancing has been analyzed through parameters like analysis of traffic sent and traffic received. While in wireless networks the metrics like delay, retransmission attempts and throughput have been estimated with varying physical characteristic and buffer size. From the obtained results, it is gathered that performance of the wired networks is good if high speed Ethernet links like 1000 Base X and server-load balancing policy are used whereas the performance of Wireless LAN can be improved by fine tuning and properly choosing the WLAN parameters. For the tested simulation scenarios the performance is observed to be better with wireless networks using infra-red type physical characteristics and higher buffer size (1024Kb

Wireless industrial monitoring and control networks: the journey so far and the road ahead

While traditional wired communication technologies have played a crucial role in industrial monitoring and control networks over the past few decades, they are increasingly proving to be inadequate to meet the highly dynamic and stringent demands of today’s industrial applications, primarily due to the very rigid nature of wired infrastructures. Wireless technology, however, through its increased pervasiveness, has the potential to revolutionize the industry, not only by mitigating the problems faced by wired solutions, but also by introducing a completely new class of applications. While present day wireless technologies made some preliminary inroads in the monitoring domain, they still have severe limitations especially when real-time, reliable distributed control operations are concerned. This article provides the reader with an overview of existing wireless technologies commonly used in the monitoring and control industry. It highlights the pros and cons of each technology and assesses the degree to which each technology is able to meet the stringent demands of industrial monitoring and control networks. Additionally, it summarizes mechanisms proposed by academia, especially serving critical applications by addressing the real-time and reliability requirements of industrial process automation. The article also describes certain key research problems from the physical layer communication for sensor networks and the wireless networking perspective that have yet to be addressed to allow the successful use of wireless technologies in industrial monitoring and control networks