Many researchers employ IEEE802.15.4 as communication technology for wireless sensor networks (WSNs). However, medium access control (MAC) layer requirements for communications in wireless sensor networks (WSNs) vary because the network is usually optimized for specific applications. Thus, one particular standard will hardly be suitable for every possible application. Two general categories of MAC techniques exist: contention based and schedule based. This paper explains these two main approaches and includes examples of each one. The paper concludes with a unique performance analysis and comparison of benefits and limitations of each protocol with respect to WSNs.
Wireless sensor networks must measure environmental conditions, such as temperature, over extended periods and therefore require a long system lifetime. The design of long lifetime networks in turn requires efficient sensor node circuits, algorithms, and protocols. Protocols such as GSP (Gossip-based Sleep Protocol) have been shown to mitigate energy consumption in idle listening and receiving, by turning off the receiver circuit. However, previous studies of network lifetime have been based on physical topologies in which nodes were placed on a square grid or randomly distributed throughout the service area. This paper shows that the lifetime of a sensor network depends on the physical topology of the sensor nodes. The lifetime of a sensor network varies as a function of both the size of the network and the transmission range of individual nodes.
Multiple factors are contributing to the surge in the demand for wireless LANs (WLANs): laptop penetration, increased user mobility, ubiquitous access to the Internet and intranets, and newly introduced Voice over IP (VoIP) capabilities. Today almost all popular wireless LAN applications such as web access, email processing, telnet, FTP, and data base access are using client-server architecture. However, the number of supported mobile nodes depends on the type of application the user employs. Thus, evaluation of the number of voice users supported by a Wireless LAN access point is beginning to attract the attention of those involved in deployment of Wireless LANs. Currently, most commercial wireless data networks are arbitrarily installed. The only optimization, if any, is that for the area covered by an access point. However the coverage aspect of the network design is only suitable for the initial installation phases wherein the capacity of users and the channel utilization is low. We investigate QoS parameters necessary to support voice and the implications these parameters have on WLAN design.
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