25-04-2012, 01:01 PM
WLAN-Wireless LAN full report
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INTRODUCTION
As we know “Computer Net work” is the linking of two or more computers within a well defined area. Of the common networks used today Local area networks(LAN) serve to provide solutions of the most general interest .A wireless Local area network (WLAN ) is a flexible data communication system implemented as an extension to ,or as an alternative for a wired LAN. As the name suggests a wireless LAN is one that makes use of wireless transmission medium, i.e. wireless LAN transmits and receives data over air, and minimizing the need for the wired connection. Thus wireless LAN combines data connectivity with user mobility. WLANs also allow greater flexibility and portability than traditional wired LAN which requires a wire to connect a user computer to the network. The initial cost for WLAN hardware can be higher than the cost of wired LAN hardware. But the overall installation expenses and lifecycle cost can be significantly lower. With WLAN users can access shared information without looking for a place to plug in, and network managers can setup or argument networks without installing or moving wires. There are many reasons people choose to deploy a wireless LAN, Increase the productivity due to increase mobility, Lower infrastructure cost compared to wired networks, Rapid deployment schedules
2. WHAT IS WIRELESS
The term “wireless “reflects any means of communication that occurs without wires. The wireless is also called unguided media, i.e. wireless provide a means for transmitting electromagnetic waves but not guided them. Wireless technology in simplest sense enables one or more devices to communicate with out any physical connection, without requiring network of peripheral cabling.
3. WIRELESS LAN REQUIREMENTS
A wireless LAN must meet some sort of requirements typical of any LAN
• High capability
• Ability to cover short distances
• Full connectivity among attached stations.
• Broadcast Capability
In addition there are no of requirement specific to wireless LAN environment.
Throughput:
The MAC protocol should make as efficient use as possible of the wireless media to maximize capacity.
Number of nodes
The wireless LAN may need to support hundreds of nodes across multiple cells.
Service Area
A typical coverage area for WLAN has a diameter of 100 to 300 meters.
Connection to backbone LAN
For infrastructure WLAN this is easily accomplished through the access points (AP) that connect to both type of LAN
Battery and power consumption
Mobile workers use battery and powered work stations that need to have a long battery life cycle when used with wireless adapters. Typical wireless LAN implementations have features to reduce power consumptions while not using the network, such as sleep mode.
Transmission Robustness And Security
Unless properly design a WLAN may be interference prone and easily eavesdropped. The design of a WLAN must permit reliable transmission even in noisy environment and should provide some level of security from eavesdropping.
4. WLAN COMPONENTS
A wireless LAN comprises two types of components.
Wireless Station
Access point
1. WIRELESS STATION
A wireless station or client is typically a laptop or notebook personal computer (PC) with Wireless Network Interface Card (NIC). A WLAN client may also be a desktop or handheld device within publicly addressed area. Wireless laptops and notebooks-“Wireless enabled”-are identical to laptops and notebooks except that they use Wireless NIC to connect to the access point (AP) in the network.
NETWWORK INTERFACE CARD (NIC)
The wireless (NICs) is commonly inserted in the clients Personal Computer Memory Card International Association (PCMCIA) slot or Universal Serial Bus (USB) port. The NIC use radio signals to establish connection to the WLAN. It is also called wireless adapter or WLAN cards. It consists of the radio transceiver and the logic to interact with the client machine and software. WLAN adapters provide an interface between client network operating system (NOS) and wireless via antenna. The nature of the wireless connection is transparent to the NOS.
They are available in three footprints:
• USB based.
• PCMCIA based (primarily for portable PCs)
• PCI cards for fixed PCs or Desktop PCs.
2. ACCESS POINT (AP)
It acts as a bridge between the wireless and wired network interface such as 802.3 and bridging software .The access point (AP) functions as a base station for the wireless network aggregating multiple wireless stations to the wired network. The access point (AP) is a stationary device that is a part of wired LAN.
Bridging Function
Access Points (AP) may also provide a bridging function. Bridging connects two or more networks together and allows them to communicate –to exchange network traffic. Bridging involves: