Bøger af Darshan Lal Meena

The two largest attractions of wireless communication have been mobility and ease of deployment - laying cables is not only laborious and time consuming, but their maintenance is equally bothersome. Wireless communication today surrounds us in many colors and flavors, each with its unique frequency band, coverage, and range of applications. It has matured to a large extent, and standards have evolved for Personal Area Networks, Local Area Networks as well as Broadband Wireless Access. In any but the most trivial networks, some mechanism is required for routing the packets from the source to the final destinations. This includes the discovery and maintenance of routes along with associated costs. In what is called an 'infrastructure based' wireless network, the job of routing is assigned to dedicated nodes called access points (AP). Configurations of the APs are much less dynamic than their, possibly mobile, endpoint nodes. APs are like base stations which keep track of nodes' associations/disassociations, authentication, etc. and control the traffic flow between their clients as well as between fellow APs. The AP may also be connected to the Internet, thereby providing Internet connectivity to its clients. A promising and very attractive class of wireless networks that has emerged is based on an Ad Hoc topology; these networks are known as Wireless Ad Hoc Networks. The term wireless network implies a computer network in which the links of the communication are wireless. The term Ad Hoc comes from the fact that there is no stable infrastructure for packets forwarding/ routing. The entire life-cycle of Ad Hoc networks is categorized into first, second, and third generation Ad Hoc network systems. Here systems of ad-hoc networks are considered the third generation. Wireless Ad Hoc network first generation emerged in 1972. At that time, they were known as Packet Radio Networks (PRNET). In grouping with ALOHA and CSMA (Carrier Sense Multiple Access), advance for medium access control and a type of distance-vector routing, PRNET were used as a demo purpose for different networking capabilities in a contest environment. Second generation of Ad hoc networks emerged in 1980s, the existing network was then new implemented and improved as the part of a Survivable Adaptive Radio Networks (SURAN) program. Without infrastructure this provided a packet-switched network in the mobile battlefield in the network. This program is beneficial in enhancing the radio performance by manufacturing them cheaper, smaller, and resilient to electronic attacks. Then, as a notebook concept of commercial ad-hoc network has emerged in the 1990s with notebook computers as main communications equipment. The subcommittee of IEEE 802.11 had adopted the term "ad-hoc networks" and the research community had started working on the probability of organizing ad-hoc networks in other areas of application. At the same time, work has been done on the enhancement of ad-hoc networks. There are two systems, then developed on the basis of this concept first is Global Mobile Information Systems) and another one is NTDR (Near-term Digital Radio). The idea behind GloMo was to design a distributed office network with Ethernet-type compact disk connectivity everywhere and every time in handheld devices.