what is wireless lan

Wireless LAN
In the last two decades the wired version of LAN has gained wide popularity and large-scale deployment. The IEEE 802.3 standard has been revised and extended every few years. High-speed versions with transmission rate as high as 1000 Mbps are currently available. Until recently wireless version of LANs were not popular because of the following reasons:
  • High cost: Previously the equipments cost more.
  • Low data rate: Initially, the data rate supported by the WLAN is too less, so
  • it supports only a few applications.
  • Occupational safety concerns
  • Licensing requirements
In the last couple of years the situation has changed significantly. Cheaper, smaller and powerful notebook computers and other mobile computing equipment have proliferated in homes and offices. These devices share various resources such as printers, files and Broadband Internet connections. This has opened up the need for wireless LAN. Wireless LANs also offer a number of other advantages compared to their wired counterpart. Before going into the technical details of Wireless LAN let us first look at various reasons which have led to the development of WLANs. Some of the advantages are mentioned below:

  • Availability of low-cost portable equipments: Due to the technology enhancements, the equipment cost that are required for WLAN set-up have reduced a lot.
  • Mobility: An increasing number of LAN users are becoming mobile. These mobile users require that they are connected to the network regardless of where they are because they want simultaneous access to the network. This makes the use of cables, or wired LANs, impractical if not impossible. Wireless LAN can provide users mobility, which is likely to increase productivity, user convenience and various service opportunities.
  • Installation speed and simplicity: Wireless LANs are very easy to install. There is no requirement for wiring every workstation and every room. This ease ofinstallation makes wireless LANs inherently flexible. If a workstation must be moved, it can be done easily and without additional wiring, cable drops or reconfiguration of the network.
  • Installation flexibility: If a company moves to a new location, the wireless system is much easier to move than ripping up all of the cables that a wired system would have snaked throughout the building. This also provides portability. Wireless technology allows network to go anywhere wire cannot reach.
  • Reduced cost of ownership: While the initial cost of wireless LAN can be higherthan the cost of wired LAN hardware, it is envisaged that the overall installationexpenses and life cycle costs can be significantly lower. Long-term cost-benefitsare greater in dynamic environment requiring frequent moves and changes.
  • Scalability: Wireless LAN can be configured in a variety of topologies to meetthe users need and can be easily scaled to cover a large area with thousands ofusers roaming within it.
However, wireless LAN technology needs to overcome a number of inherent limitations and challenges. Some of the limitations and challenges are mentioned below:

  • Lower reliability due to susceptibility of radio transmission to noise and interference.
  • Fluctuation of the strength of the received signal through multiple paths causing fading.
  • Vulnerable to eavesdropping leading to security problem.
  • Limited data rate because of the use of spread spectrum transmission techniques enforced to ISM band users.

In this lesson we shall introduce the wireless LAN technology based on IEEE 802.11 standard. Its predecessor the IEEE 802.3, commonly referred to as the Ethernet, is the most widely deployed member of the family. IEEE 802.11 is commonly referred to as wireless Ethernet because of its close similarity with the IEEE 802.3. Like IEEE 802.3, it also defines only two bottom levels of ISO’s open system Interconnection (OSI) , As it shares the upper layers with other LAN standards, it is relatively easy to bridge the IEEE 802.11 wireless LANs to other IEEE 802.11 wired LANs to form an extended interconnected wired and wireless LAN network. Although initially wireless LANs were perceived to be as a substitute to wired LANs, now it is recognized as an indispensable adjunct to wired LANs.