In recent past, wireless LANs have carved a significant niche in the local area network market. Increasingly, organizations are finding that wireless LANs are an indispensable adjunct to traditional wired LANs to satisfy requirements for mobility, relocation, ad hoc networking, and coverage of locations difficult to wire.
As the name suggests, a wireless LAN is a network that makes use of a wireless transmission medium. Until relatively recently, wireless LANs were used very little. The reasons for this included high prices, low data rates, occupational safety concerns, and licensing requirements. As these problems have been addressed, the popularity of wireless LANs has grown rapidly.
Early wireless LAN products (introduced in the late 1980s) were marketed as substitution for traditional wired LANs. A wireless LAN saves the cost of installation of LAN cabling, and eases the task of relocation and other modifications of network structure. However, this motivation for wireless LANs was overtaken by events. First, as awareness for the need of LANs became greater, architects designed new buildings to include extensive pre-wiring for data application. Second, with advances in data transmission technology, there is an increasing reliance on twisted pair cabling for LANs and, in particular, Category 3 and Category 5 unshielded twisted pairs. Older buildings are already wired with an abundance of Category 3 cable, and many newer buildings are pre-wired with Category 5. Thus the use of wireless LANs to replace wired LANs has not happened to any great extent.

  WLAN APPLICATIONS
Wireless local area networking can be found in almost every industry that has employees who need the mobility and freedom to conduct business without being chained to their desk.
Wireless LAN technology is an ideal application for colleges and schools. Teachers can create classroom presentations on the laptop computer in their office and then carry that computer with them right into the classroom. They need not spend time connecting to the campus LAN using cables; rather their laptop automatically makes the wireless connection as soon as they walk into the room. Teachers can also send class material directly to students in the classroom who have their own wireless laptops. The wireless connections also offer students a degree of freedom that they have not experienced before. Students can access the school/university "wireless LANs" from almost any location on campus.
Almost all manufacturing operations have one thing in common. They take up a large amount of space. Most manufacturing operations are spread out over several different buildings and offices that receive, process and ship products. Wiring between the buildings can be very costly and typically involves a monthly charge for the connectivity. Within each building there can be, likewise, a vast amount of space. Wiring within these large buildings becomes very expensive. If the computers are in fixed locations, performing such jobs as taking inventory would involve making notes and later on entering data into a computer. Wireless LANs can help provide the solutions to these problems.
In a hospital, wireless LANs can be used for carrying out various activities. Wireless LANs in hospitals allow the health care industry to improve in two primary areas: maintaining patient records and documenting the administration of medication. Typically, nurses must write a note on paper regarding a patient's condition or treatment and then take it back to the nurse's station for entering the data into a computer. However, having multiple patients to care for and a single computer at the nurse's station can make it difficult for nurses to perform the clinical documentation on the computer in the timely fashion. As a result, a nurse who administrated treatment in the morning may be forced to wait until the end of the shift to document it in the system. Administering medication could thus become a problem area. Typically, medication printouts are posted at the medican area. As nurses administer medication, they cross off the treatment from the list and initial the changes they made in the list. However, since nurses cannot update the paper record immediately, a patient could get an extra dose of medication, before an order for a new or changed medication was processed. This practice also causes duplicate documentation. Nurses first check the medication printouts to determine the medication to be given. Then they document on paper that the medication was actually given and later enter the data on the computer. Wireless LANs offer a good alternative to this traditional practice.
Wireless LANs can be implemented for warehouse management, investment banking, entertainment etc.

 WIRELESS LAN REQUIREMENTS
A wireless LAN must meet the same sort of requirements typical of any LAN, including high capacity, ability to cover short distances, full connectivity among attached stations and broadcast capability. In addition, there are a number of requirements specific to the wireless LAN environment. The following are among the most important requirements for wireless LANs:
Throughput: The medium access control protocol should make use as efficient as possible of the wireless medium to maximize capacity.
Number of nodes:      Wireless LANs may need to support hundreds of nodes across multiple cells.Connection to backbone LAN: In most cases, interconnections with stations on a
wired backbone LAN are required. For infrastructure wireless LANs, this is easily accomplished through the use of control modules that connect to both types of LANs. There may also be the need to accommodate mobile users and ad hoc wireless networks.
Service area: A typical coverage area for a wireless LAN has a diameter of 100 to 300 m.
Battery power consumption: Mobile wireless uses battery-powered workstations that need to have a long battery life when used with wireless adapters. This suggests,at a MAC protocol that requires mobile nodes to monitor access points constantly or = engage in frequent handshakes with a basic station is inappropriate. Typical wireless LAN implementations have features to reduce power consumptions while not using network, such as a sleep mode.
Transmission robustness and security:         Unless properly designed, a wireless LAN may be interface prone and easily eavesdropped. The design of a wireless LAN must permit reliable transmission even in a noisy environment and should provide a level of security from eavesdropping.
Collected network operation: As wireless LANs become more popular, it is quite likely for two or more wireless LANs to operate in the same area or in some area where the interface between the LANs is possible. Such interference may thwart the normal operation of a MAC algorithm and may allow unauthorized access to a particular LAN.
License-free operation: Users should prefer to buy and operate wireless LAN products without having to secure a license for the frequency band used by the LAN. Handoff/roaming: The MAC protocol used in the wireless LAN should enable mobile stations to move from one cell to another.
Dynamic configuration: The MAC addressing and network management aspects of the LAN should permit dynamic and automated addition, deletion, and relocation of end systems without disruption to other users.

  PLANNING FOR WIRELESS LANs
    If you fail to plan, then you plan to fail." This familiar quotation is especially true in planning network. The steps for planning a wireless LAN are similar to those for planning a wired network:
Accessing needs Determining cost Gathering information Selecting a WLAN.
There are also special wireless concerns that must be considered, such as compatibility and interpretability, which wireless standards to follow, and which wireless technology to use.`Do we really need it?' is a question that organizations often ask too late in the planning process. In fact, it should be the first question that is asked. Sometimes changing a procedure or adding personnel may solve the problem, making investment in a new computer network unnecessary. However, determining the need can sometimes be difficult because the solution may not be just to invest in technology, but to access a combination of several different resources.
Look at the organization as a whole; in fact, the first step in accessing the need is to look at the organization or the business as a whole. Some questions to ask include:
What is the purpose or mission of the organization?
Is the current mission expected to change in the future? What is the size of the organization?
How much growth is anticipated in the organization?
Although these questions may seem very basic, they often reveal a great deal that can help you access needs. For example, a business that is rapidly losing market share and has changed presidents three times in the past six months may not be in a position to invest heavily in new networking technologies. On the other hand, a business that has captured a niche in the market place and currently has no serious competition may be poised for rapid growth, and a new network may become the backbone of that growth. Obtaining a firm conceptual grip on the organization as a whole and its current status will reveal whether an investment today in technology is a wise step.
The next step in assigning the need for a wireless network is to look at how the organization or business uses its current network. For example, answer these questions:
How does the current network support the organization's misson? What applications run on the network?
How many users does it support?
What are the strengths and weaknesses of the current network?
Some organizations, such as banks or brokerage firms, require networks that have a very high degree of security. Other organizations require networks to be completely fault-tolerent and cannot afford any downtime. How the network supports the organization is an important consideration. Examining the current status of the network, especially the application that runs on the network and the number of users, reveals much of this information.
This question regarding the strengths and weaknesses of the network can clarify whether a new network is needed. If the current network can be upgraded or adapted to meet the current needs, then a new network may not be necessary. However, if the current network cannot support the anticipated figure growth of the business or is based on a very old technology, then investing in a new network may be the better option.
Documentation of the current network may include a table that summarizes information about the current network. As an example, summarize the information as in Table 9.1.

After assessing the needs and examining the current status of the network and mechnical documentation, you can decide whether to upgrade the network, replace - it or add a new network to meet the needs.
`Can we afford it?" is the question that should be raised at this point of the process. It is senseless to spend hundreds of hours in planning a network if you have not assessed the costs and have not determined whether the project can be budgeted. T- is important to remember to take into account installation and maintenance expenses as well as the budget support and additional training for the technical staff.

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