WLAN is now mainstream in India as more and more enterprises deploy it and discover that it is a productivity tool. Convenient and easy to deploy, WLAN is economical too. And, the same wireless network can be used for voice and video applications.

Though 802.11b-based WLANs are still the most common, 802.11g is the current flavour. Not only does 802.11g offer more throughput and better performance than 802.11b; it is backward compatible with 802.11b.

Technology Options
• 802.11b: The 802.11b offers a throughput of 11 Mbps theoretically (practically it is 5.5 Mbps) and operates in the 2.4 GHz band. The standard has a rated operating range of 100 meters. In the 2.4 GHz ISM band, there is about 80 MHz of useable spectrum. Hence, in a radius of 100 meters, three 22 MHz, 802.11b systems can operate on a non-interfering basis, each offering speeds up to of 11 Mbps.

• 802.11g: The 802.11g standard also uses the 2.4 GHz band, with a data rate comparable to that of 802.11a. Besides offering five times more throughput then 802.11b, 802.11g is backward compatible with 802.11b, enabling an access points built for 802.11g to connect 802.11b.

• 802.11a: The 802.11a standard offers connections at speed of 54 Mbps and runs on the 5 GHz band. It is projected to have an operating range of 50 meters.

With the wide acceptance of competing 802.11g standard supporting similar speeds and backward compatibility with 802.11b, has made 802.11a a not so popular choice for WLAN deployment. With availability of Dual/tri mode AP's supporting the 802.11a/b/g standards user can still weigh the benefits of each standard and deploy combination of products in their network.

• 802.11n: Vendors are working on a new version named 802.11n that would offer a minimum throughput of 100 Mbps (some vendors are trying to for 500 Mbps to 630 Mbps). However, 802.11n-based WLAN is unlikely to reach users until the beginning of 2006 as IEEE has still not finalized the standard and the industry is almost vertically split on the specifics of standardization.

Components of a WLAN
• The 802.11b/g wireless networking consists of stations or hubs, access points, and ports.

• A station (STA) is a network node that is equipped with a wireless network device. A personal computer with a wireless network adapter is known as a wireless client (i.e., laptops using wireless PCI cards or mobile chips).

• Wireless clients can communicate directly with each other or through a wireless access point (AP).

• Wireless AP is a wireless network node that acts as a bridge between STAs and a wired network. Wireless APs are similar to cellular phone networks' base stations. Wireless clients communicate with both the wired network and other wireless clients through the wireless AP. Wireless APs are not mobile. It acts as a peripheral bridge device that extend the wired network.

• A port is a channel of a device that can support a single point-to-point connection. For IEEE 802.11b, a port is an association, a logical entity over which a single wireless connection is made. A typical wireless client with a single wireless network adapter has one port and can support only one wireless connection. A typical wireless AP has multiple ports and can simultaneously support multiple wireless connections.

The logical connection between a port on the wireless client and the port on a wireless AP is a point-to-point bridged LAN segment-similar to an Ethernet-based network client that is connected to an Ethernet switch.

Challenges
• As enterprises expand their WLAN networks and use them for voice and video applications as well, these networks will throw up three key challenges: achieving quality of service (QoS), ensuring security, and interoperability with other wireless networks for hassle-free network management.

• As of today, there is no built-in QoS in 802.11 networks, so quality is only best effort. As far as plain data applications like e-mail or surfing are concerned, best-effort services are enough. However, QoS would be important for multimedia applications on 802.11 networks and other advanced applications like VoIP over WLAN. Because they are delay- and throughput-sensitive, they would require better traffic management and bandwidth assignment. Today, there is no prioritization of traffic on Wi-Fi networks.

• IEEE's 802.11e standard, which is likely to be ratified by early 2005, is expected to take care of these QoS issues.

• Working on the standard, Wi-Fi Alliance has come up with Wi-Fi for Multimedia (WMM) and started a program called Wi-Fi Certified for WMM that will certify Wi-Fi products in terms of their QoS capabilities. According to a Wi-Fi Alliance paper, WMM will add prioritized QoS capabilities to Wi-Fi networks and optimize their performance when multiple, concurring applications (each with different latency and throughput requirements) compete for network resources.

• There would be issues of seamless connectivity between different WLANs and also between WLANs and wired LANs, as wireless networks grow in terms of numbers and types.

• There would be issues relating to management and interoperability between different protocols.

• Security has remained a key concern of enterprises, since the day they began deploying WLANs. The Wi-Fi Alliance had, in September 2004, announced the first round of products that are Wi-Fi Certified for the WPA2 (Wi-Fi Protected Access 2) capability. WPA2 is based upon the IEEE's 802.11i amendment to the 802.11 standard. Wi-Fi Alliance has said that products that are Wi-Fi Certified for WPA will remain technically sound and secure. Products that are certified for WPA2 give IT managers the assurance that the technology meets interoperability standards and in turn, helps them manage support and deployment costs.

Tips
• Regulatory guidelines: Both 802.11b and 802.11g can be deployed without government's permission. The government also plans to de-license the 5 GHz band (for 802.11a) for indoor use. However, an official notification to this effect is awaited.

• Radio survey: How an enterprise architectures the network is very important. Carrying out a radio survey of the area to be covered by WLAN would be the first step towards deploying a WLAN for optimum utilization. A survey is important for two reasons: one, it helps an enterprise design its network better and two, it would ensure that one network's signal does not interfere with other networks in and around the proposed deployment site.

• Site survey: After radio survey, the other important consideration should be the interior design structure of the site. WLAN systems use RF. And the distance over which RF waves can travel is not a function of the product alone. It also depends on the propagation path of RF. Even though RF waves can penetrating most indoor walls and other physical obstacles, their range of coverage surely depends on the indoor architecture of the building. In open spaces, each WLAN access hub can cover up to 300 feet. While, with physical barriers-like walls a hub could be effective in the range of 130 feet only. This would naturally mean that access points are to be placed strategically so as to overcome the physical barriers inside a building. Otherwise, users would not be able to enjoy the advantage of mobility or roam around freely in a building with their connected laptops. The enterprise should get the site survey conducted for verifying the coverage and estimating the number of WLAN APs required at the premise. This would depend on the topology of the location and the amount of throughput required.

• Integrating existing LAN: How an enterprise integrates WLAN with the existing wired LAN is very important. The integration should facilitate seamless movement of a user from WLAN to wired LAN and vice versa. Also, services should be enabled on the WLAN in the same way as the wired LAN. Integration would also mean things like single password access for both wired LAN and Wi-Fi.

• Security: WLAN networks are found prone to unauthorized access, breaking of encryption, and loss of data integrity. And except some of the well-known vendors, most do not use any accepted security standards. So enterprises must ensure to deploy only those products that adhere to the accepted and proven security standards.

• QoS: An enterprise must also ensure that the network should have QoS built in. This should also mean that the WLAN must allow to prioritize voice, data, and video on the network and the network be scalable.

• Manageability: Managing a WLAN could be a challenge as the network grows and adds more users. Enterprises must manage WLAN in the same way as the traditional LAN and both should be managed together from the same platform.