IEEE 802.11 Standard

Before diving in, a few terms related to WLANs need to be covered, ESS, PHY and MAC. My over simplistic definitions are below. Feel free to jump onto Google or Wikipedia to get more info.

PHY - how the bits get into the air
MAC - how devices/users get connected to wireless network/each other
ESS - is a wireless network with multiple access points connected together

Published and In Process Standards, Amendments, and Recommendations

Out of the 20+ 802.11 standards, amendments, and/or proposals that cover almost every letter of the alphabet listed below are 10 that everyone (at least every techie) should know by letter.

802.11b

1. 802.11b - Higher Speed PHY Extension in the 2.4 GHz BandEven though 802.11b is slow compared other standards it is #1 on my list for taking WLANs from a niche technology to mainstream. For many, 802.11b is still fast enough for surfing the web from their couch or network access in conference rooms.A quick history lesson below…In 1999 802.11b was ratified pushing 802.11 speeds to 11Mbps. Around the same time the Wireless Ethernet Compatibility Alliance (WECA) formed.

   In 2000 802.11b adoption took off fueled by low cost consumer grade equipment from vendors like Linksys and WECA’s Wi-Fi certification program for 802.11b interoperability.

802.11n

2. 802.11n = High ThroughputA big problem in wireless communications is multipath propagation. Multipath propagation occurs when signals bounce off buildings, walls, and other objects and arrive at the receiver at different times. If the time difference is large enough the receiver gets confused and can’t interpret the signal causing retransmissions and therefore reducing the speed of the 802.11 network.11n specification puts a technical spin on the saying “When life hands you lemons, make lemonade” by takes advantage of multipath propagation to increase throughput to speeds above 100Mbps. By using multiple input-multiple output (MIMO) or in other words multiple transmitters, antennas and receivers the following techniques are possible:

   Spatial Diversity - use multiple antennas to induce multipath for the purpose of recombining the multiple signals to increase the single gain resulting in higher theoretical speeds.

   Channel Multiplexing - send multiple signals using multiple antennas, therefore multiplying speeds.

   Beam Forming - by using smart antennas to concentrate transmitted power towards receivers, beam forming increases range while not reducing throughput.

   802.11n Draft requires spatial diversity for improved throughput. The other methods are also implemented by some vendors in Pre-N products to increase throughput and range.

802.11i

3. 802.11i = MAC Security EnhancementsInteroperability, speed, and range improvements are great but what about security?This is where 802.11i, aka WPA2 if you like Wi-Fi Alliance terminology, significantly improves WLAN security. 802.11i beefs up encryption by utilizing Advanced Encryption Standard (AES) and has improved key exchange methods. 802.11i is secure enough for the US Department of Defense (see June 2, 2006 supplement to DoD Directive 8100.2)

802.11s

4. 802.11s = ESS mesh networkingIronically, all wireless networks still have wires! To increase coverage or capacity additional access points are added to the network and then connected back to the wired network.What if a new access point added to the network only needed power and used the existing wireless network to get back to the wired network. This will be possible with mesh networking and standardized by IEEE as 802.11s.Mesh networking/802.11s deserves a blog by itself but for now the short description is that 802.11s will allow self forming/self healing WLANs by configuring minimal information (like SSID) and introducing the access point into the network. Mesh products are available from commercial vendors such as Tropos, BelAir, Strix, and many others but they all implement proprietary protocols and are priced much higher than the access points available at the local electronics store.

   A few uses for mesh networks are below
   - add wireless to a historical building where cabling is not possible
   - network an entire neighborhood to share high speed Internet
   - temporary networks for first responders

802.11e

5. 802.11e = MAC Enhancements (QoS)Cool…we have speed, range, security and the ability to build city-wide 802.11 networks, all using standards based low cost 802.11 equipment.But…what happens when you are surfing the web and using your wireless VoIP phone on a congested 802.11 network…your calls may sound garbled. The problem isn’t your Internet connection…it’s 802.11…..it doesn’t know the difference between bits of data and bits of voice trafffic.802.11e fixes this by adding quality of service (QoS) to 802.11.

802.11u

6. 802.11u = InterWorking with External NetworksNow things are getting exciting…surfing the web, downloading files, and making voice calles using your wireless 802.11 phone..but what happens if you are not in near a WLAN and still would like to make a telephone call. Wouldn’t it be cool if your 802.11 phone also worked on cellular networks? 802.11u (and some efforts by IEEE 802.21) will allow handoff from WLANs to cellular networks.

802.11r

7. 802.11r = Fast Roaming802.11 allows you to roam to the access point that has the strongest signal and you would never notice it while surfing the web.Roaming when using real-time communications like VoIP requires faster roaming than current 802.11 can support. Even a split second loss of connectivity can cause problems such as dropped calls. 802.11r will correct this with improvements roaming speeds and reduce impact of lost connectivity during hand offs.

802.11a

8. 802.11a = Higher Speed PHY Extension in the 5GHz Band802.11a, operates in several bands in 5GHz range, uses a signaling method called orthogonal frequency-division multiplexing (OFDM) which is not affected very much by multi-path propagation.In addition to improved signaling method 802.11a also has more channels that are usable compared to 802.11 b/g making it very useful for crowded networks where more channel are needed to provide coverage and capacity.

802.11w

9. 802.11w = Protected Management Frames802.11i significantly boosted security but only for data traffic. 802.11w will most likely extend 802.11i security to management frames and interfact with 802.11r, 11u, 11s and others to secure how devices/users get connected.

802.11g

10. 802.11g = Further Higher Data Rate Extension in the 2.4 GHz Band802.11g added OFDM to 2.4GHz band, improved data rates to 54Mbps, and is backward compatible with 802.11b.Sounds perfect, right? Not really, the 54Mbps speeds are only possible at short ranges and operating in backward compatability mode with 11b causes overall throughput to suffer.

*Title is not exactly correct…not all are standards..yet. Some have been around for a while and others will be finalized in next few years. The IEEE website has a nice 802.11 Official Timelines page with information about the various projects and when the specifications will be finalized.

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Filed under: WLAN Standards