Wireless LANs

Different Wireless LAN Standards

• IEEE 802.11a (also called WiFi5)- supports speeds from 6 Mbps up to 54 Mbps - works in unlicensed 5-GHz radio band -  It will use the same MAC layer as 802.11. Products started appearing in 3Q 2001 and 1Q 2002. Standard includes features like priority for certain types of traffic. 
• IEEE 802.11b (also called WiFi)- Slightly older standard that supports speeds up to 11 Mbps in 2.4 GHZ radio band.  Several vendors offer products conforming to this standard.  New generation of 802.11 compatible cards for handhelds like Compaq's iPAQ coming out now (mid 2001).
• IEEE 802.11d - LAN/MAN standard
• IEEE 802.11e - Working on QoS (quality of service) issue in LANs
• IEEE 802.11g - Objective is to increase the speed of 802.11b - Initially it was 22 Mbps in 2.4 GHz band. Now it is 54 Mbps. Initial approval in August 2002 - Final specification expected during the first half of 2003. 
• IEEE 802.16 - A draft Wireless LAN standard for Metro Area Networks based on OFDM and using IEEE 802.11a as a foundation - approved in December 2001.
• IEEE 802.11x - About Wireless LAN security and other class of service specifications. Go here for more
• IEEE 802.11n - New standard for very high-speed WLANs (200-500 Mbps) over short distances. 

What does 802.11 standard address?

IEEE 802.11 standard primarily addresses two separate layers of the ISO networking model:

• Physical network layer - lowest ISO layer that defines the physical transmission characteristics of the signal - in this case, radio signal such as the frequency, power levels, and type of modulation. 
• MAC (The Media Access layer, or MAC, is mostly made up of software-based protocols that enable devices to talk to each other. 

IEEE 802.11e
The IEEE's 802.11e draft specification creates the industry's first true universal wireless standard - one that offers seamless interoperability between business, home and public environments (such as airports and hotels), yet still offers features that meet the unique needs of each. 

Unlike other wireless initiatives, this is the first wireless standard that spans home and business environments. And it adds quality-of-service (QoS) features and multimedia support to the existing 802.11b and 802.11a wireless standards, while maintaining full backward compatibility with these standards. 

QoS and multimedia support are critical to wireless home networks where voice, video and audio will be delivered. Broadband service providers view QoS and multimedia-capable home networks as an essential ingredient to offering residential customers video on demand, audio on demand, voice over IP and high-speed Internet access

IEEE 802.11x
IEEE 802.11 Task Group I of the 802.11 Working Group is working (as of mid 2002) on a draft text to "enhance the current 802.11 MAC to provide improvements in security."  Here is brief description, courtesy ComputerWorld - an IDG company

• IEEE 802.11e -- Quality of Service

  This quality-of-service methodology will prioritize the transport of voice, audio and video traffic over wireless LANs (WLAN) to better support streaming media. The standard, which is still under development, will use a method called hybrid coordination function, or HCF. A final standard is expected in the first half of next year (2003) and will support legacy devices via firmware and device driver updates.

• IEEE 802.11f -- Multi-vendor Access Point Roaming or Interoperability

  Today, a user roaming between access points may lose some packets during the handoff between different vendors' devices. This standard ensures multi-vendor access-point interoperability through the Inter-Access Point Protocol, or IAPP. The final standard, expected by year's end (may be, more likely in early 2003), will arrive as a flash update to legacy access points.

   

• IEEE 802.11h -- Interference

  The 802.11a standard faces interference problems in Europe, where it shares the 5-GHz frequency band with radar and satellite communications. Dynamic Frequency Selection, or DFS, allows devices to detect such transmissions and switch to an alternative channel. The Transmit Power Control protocol will allow users close to an access point to reduce transmission power in order to reduce interference with other users. A final standard, expected early next year, will require client device driver and access-point firmware updates.

   

• IEEE 802.11i -- Security (Expected to be ratified in September 2003)

  The big kahuna of WLAN issues -- the emerging security specification -- will combine improved encryption with authentication. Components include 802.1x, a method for transporting an authentication protocol between the client and access-point devices, and the Transport Layer Security (TLS) protocol, which handles user authentication and key distribution between the end-user device and the TLS authentication service, which will sit on a back-end RADIUS server. Other protocols are also in discussion, including Trivial TLS, a simpler version that should be easier to deploy.

  Two encryption methods replace the discredited Wired Equivalent Privacy (WEP) protocol. Temporal Key Integrity Protocol (TKIP), is an interim method. It will support legacy clients and access points through software updates, but cryptographers say TKIP will be broken eventually. The other scheme, based on the Advanced Encryption Standard, will offer the best security but will likely require new hardware. While the specification won't be final until sometime next year, vendors are collaborating to produce an interoperable version of TKIP that should be available this year.

  Vendors' proprietary fixes, based on partial implementations of the standard or enhanced versions of WEP, aren't acceptable, says Duncan Kitchin, wireless LAN lead architect at Intel Corp. and vice chairman of the IEEE 802.11e working group. "There's an awful lot of snake oil out there," he says. Until the standard is final, he adds, users who need strong security should implement a virtual private network.

For more info about IEEE 802.11 standards, go to the following three sites 

1. IEEE standards web site
2. Jim Geier's website
3. Proxim's website