`
`802.11 "Decrypted"
`Adrian Stephens
`Intel Corporation
`15 JJ Thompson Ave
`Cambridge CB3 0FD, UK
`+44 1223 763457
`
`
`
`
`
`
`ABSTRACT
`This short paper introduces wireless IEEE 802 standards and
`activities with a focus on explaining the purpose of the many
`802.11 amendments.
`
`Categories and Subject Descriptors
`A.1 [INTRODUCTORY AND SURVEY]
`C.2.5 [Local and Wide-Area Networks]
`
`General Terms
`Standardization
`
`Keywords
`TBD
`
`1. INTRODUCTION
`As wireless technology increasingly pervades our lives, the
`decisions made in wireless standards bodies such as the IEEE
`802.11 have the potential to impact our lives. From the user
`viewpoint, emerging standards will support new applications,
`higher throughput and increasing mobility. From the implementer
`viewpoint, the increasing complexity must be hidden from the
`user. New standards create new challenges and emergent
`behaviors that call for academic scrutiny.
`The question addressed here is: what are 802 and 802.11, and
`what do the various letters after ".11" signify?
`2. IEEE 802
`IEEE 802 is a project of the Institute of Electrical and Electronic
`Engineers (IEEE) LAN/MAN Standards Committee (LMSC). It
`was created in February 1980 – hence the name 802.
`The LMSC is a committee of the IEEE Standards Association
`(IEEE-SA), which is the body that publishes completed standards
`and their amendments.
`Within project 802, are various working groups – each of which
`defines one or more standards or recommended practices.
`The currently active working groups are listed in Table 1.
`Table 1 - IEEE 802 Working Groups
`Working Group Name
`802.1
`Higher Layer LAN protocols
`802.3
`Ethernet
`802.11
`Wireless LAN
`802.15
`Wireless PAN
`
`802.16
`802.17
`802.18
`802.19
`802.20
`802.21
`802.22
`
`Broadband Wireless Access
`Resilient Packet Ring
`Radio Regulatory technical advisory group
`Coexistence technical advisory group
`Mobile Broadband Wireless Access
`Media Independent Handoff
`Wireless Regional Area Networks
`
`
`
`3. 802.11
`The 802.11 working group working held its first meeting in
`September 1990 and issued the first draft of the 802.11 standard
`in early 1995, completed in late 1997. This document included a
`medium access controller (MAC) and physical layer (PHY)
`definitions for three media:
`•
`Infrared
`•
`Frequency Hopping Spread Spectrum (FHSS) in the
`2.4GHz ISM band (1, 2 Mbps)
`• Direct Sequence Spread Spectrum (DSSS) in the 2.4
`GHz ISM band (1, 2 Mbps)
`
`
`Originally the FHSS PHY was the most popular because of its
`lower cost and robustness. The author is not aware of any
`commercial products using the Infrared PHY. The DSSS PHY
`did not become popular until 802.11b increased the PHY rates to
`5.5 and 11 Mbps. 802.11b is the version that has made wireless
`networking a popular commercial product.
`Since the original version, 802.11 spawned task groups to
`produce amendments to the 802.11 standard. The first task group
`(TG) is called "TGa", and its amendment is called 802.11a, and so
`on. Each TG is authorized by the IEEE-SA and has a well-
`defined scope defined in its Project Authorization Request (PAR)
`document. The 802.11 task groups are described in Table 2.
`Those task groups that are currently active are indicated as such.
`
`
`Task
`Group
`TGa
`
`Table 2 - IEEE 802.11 Task Groups
`Description
`
`This group developed a higher speed PHY based on
`orthogonal frequency division multiplexing (OFDM)
`in the 5GHz bands.
`The group cooperated with the European ETSI
`BRAN project and the two produced very similar
`
`ACM SIGCOMM Computer Communication Review
`
`91
`
`Volume 35, Number 2, April 2005
`
`Exhibit 1037
`Panasonic v. UNM
`IPR2024-00364
`Page 1 of 3
`
`

`

`PHY specifications.
`802.11a has the advantage of several hundred of
`MHz of spectrum in the 5GHz band. However, it did
`not have the popular impact that 802.11b had due to
`the increased cost of operating at these frequencies.
`802.11g made 802.11a speeds available in the
`2.4GHz band. As the costs of 5GHz components has
`fallen, 802.11a looks increasingly attractive, and
`802.11 a/b/g combination products are commonly
`available.
`802.11b extended the DSSS PHY to support 5.5 and
`11 Mbps. It has been the most successful version of
`802.11 to date, and is now being replaced by
`802.11g.
`This defines 802.11 MAC procedures to support
`bridge operation. It is a supplement to 802.1D
`developed in cooperation with the 802.1 working
`group.
`regulatory
`to additional
`This extends support
`domains and provides on-the-air signaling and
`control of parameters affected by the regulatory
`domain
`(such as channelization and hopping
`patterns).
`TGe is still active, although it has nearly completed
`the standards process. It defines support for QoS for
`both distributed (EDCA) and centralized (HCCA)
`mechanisms. It supports QoS flows based on a user
`priority, suitable for connectionless data.
`Although the 802.1 MAC interface does not support
`connection-oriented data transfer, the 802.11e traffic
`specification (TSPEC) comes close to defining a
`connection – describing a flow in terms of size, rate,
`period and many other parameters. This makes
`802.11e also suitable for periodic data such as VoIP.
`Additional
`improvements
`include power-saving
`(APSD) and additional efficiency gains through a
`selective acknowledgement (Block Ack).
`This group developed recommended practices for an
`Inter-Access Point Protocol (IAPP) intended to
`provide interoperable management of the distribution
`system between APs from different manufacturers.
`It
`is uncertain what
`impact
`this recommended
`practice has had.
`The 802.11g amendment essentially allows operation
`of the 802.11a OFDM modulation in the 2.4 GHz
`band.
`It provides 802.11a throughput at close to 802.11b
`prices.
`The challenge for 802.11g devices is to coexist with
`the installed base of 802.11b devices. This is
`achieved through various protection mechanisms,
`although there is some penalty in performance for
`operating in such an environment.
`802.11h defined enhancements to 802.11a to support
`operation in the license exempt bands in Europe. It
`supports measurement and reporting of channel
`
`TGb
`
`TGc
`
`TGd
`
`TGe
`
`TGf
`
`TGg
`
`TGh
`
`TGi
`
`TGj
`
`TGk
`Active
`
`TGma
`
`TGn
`Active
`
`TGp
`Active
`
`energy in order to provide dynamic frequency
`selection (DFS).
`It also provides control of transmit power (TPC).
`This group was created to address issues and
`concerns with the original 802.11 WEP security
`mechanism.
`802.11i defines two new mechanisms. TKIP is a
`medium
`strength mechanism
`designed
`for
`compatibility with hardware
`implementing
`the
`original 802.11 WEP security mechanism. WEP has
`proven to be susceptible to various types of attack,
`and TKIP provides a stopgap solution to these. AES
`provides the much stronger 128-bit block encryption,
`which is supported by newer hardware.
`802.11j supports operation in Japan in the 4.9 and
`5GHz bands. It extends the operation of the 802.11a
`PHY to operate in a 10MHz channel (half the
`channel width of 802.11a), and also allows longer
`range communication by increasing the turnaround
`interval to allow for longer propagation delays.
`802.11k defines measurement of the radio channel
`that allows a device (a client device or an access
`point, or management software above) to make
`informed decisions relating to selecting an access
`point and selecting an operating channel.
`TGk is currently active.
`This group provides maintenance changes (editorial
`and technical corrections) to 802.11-1999, 2003
`edition (incorporating 802.11a-1999, 802.11b-1999,
`802.11b-1999 corrigendum 1-2001, and 802.11d-
`2001).
`802.11n will define modifications to both PHY and
`MAC
`layers
`to provide
`substantially higher
`throughput than 802.11 a/g. The project requires
`100Mbps of useful throughput (at the top of the MAC
`interface), which requires about 200Mbps at the
`PHY.
`TGn is currently in its down-selection process to
`select between proposed solutions.
`Current proposals use multiple antenna technology
`and increased channel width to achieve significantly
`higher than the target. A maximum throughput of
`~600Mbps at the PHY has been described, although
`first generation products are unlikely to support the
`optional features that achieve this figure.
`The PHY fixed overheads are not reduced, and
`aggregation and other enhancements are necessary in
`the MAC to restore an acceptable level of efficiency
`(~70%).
`The TGp amendment will support communication
`between vehicles and the roadside and between
`vehicles while operating at speeds up to a minimum
`of 200 km/h for communication ranges up to 1000
`meters.
`It will use the 5.850-5.925 GHz band within North
`
`ACM SIGCOMM Computer Communication Review
`
`92
`
`Volume 35, Number 2, April 2005
`
`Exhibit 1037
`Panasonic v. UNM
`IPR2024-00364
`Page 2 of 3
`
`

`

`TGr
`Active
`
`TGs
`Active
`
`America defined for this purpose.
`TGr is chartered with developing a secure, fast BSS
`transition solution, when a Station (STA) roams from
`one Access Point (AP) to another AP, within an
`Extended Service Set (ESS). High BSS transition
`latencies
`using
`existing
`802.11 mechanisms
`(including 802.11i Security addendum), along with a
`lack of inter-operability between STA and AP
`vendors in harmoniously executing these procedures
`in performing this transition, are technical hurdles for
`widespread deployment of Voice over Internet
`Protocol (VoIP) over 802.11 LANs.
`like
`Delay
`and
`jitter
`sensitive
`applications
`multimedia, video, and voice, which have to co-exist
`with traditional, intermittent data traffic, demand a
`flexible and scalable solution, which maintains the
`security guarantees provided by IEEE 802.11i. It is a
`market-driven requirement that the BSS transitions
`be
`executed with minimal
`latencies, while
`maintaining the same Quality of Service (QoS), and
`confidentiality and integrity protection, that the STA
`was being afforded at the existing AP, when the STA
`moves to the next AP. By some estimates, the
`procedures recommended by TGr should take less
`than 50 milliseconds, in order to be effective for the
`voice/video class of applications.
`TGr is progressing the merger of two proposals that
`were voted in at the January 2005 meeting, through a
`down-select process, from an initial pool of eight.
`TGs is considering how to create a Mesh of APs to
`provide a Wireless Distribution System (WDS) using
`the existing IEEE 802.11 MAC/PHY layers.
`The mesh needs to support broadcast and directed
`transmissions over potentially multiple "hops"
`between APs. It has to be self-configuring.
`TGs are executing their selection process. They have
`
`TGu
`Active
`
`TGv
`Active
`
`TGw
`
`
`a call for proposals out that will results in proposals
`being heard in July 2005.
`TGu will define an amendment to IEEE 802.11 to
`support interworking with external networks.
`The group is currently working on its functional
`requirements.
`This group will provide Wireless Network
`Management enhancements to the 802.11 MAC, and
`PHY, to extend prior work in radio measurement to
`effect a complete and coherent upper layer interface
`for managing 802.11 devices in wireless networks.
`802.11 and later 802.11i established mechanisms to
`protect data frames, but does nothing to protect
`control frames internal to 802.11. For example, it is
`possible to forge disassociation requests. 802.11w is
`being chartered to extend the 802.11i protections to
`data frames. It is expected that 802.11w will begin its
`work in May 2005.
`
`
`4. References
`The most accessible source of information are the IEEE web-sites.
`The
`IEEE
`802
`LMSC
`home
`page
`is:
`http://grouper.ieee.org/groups/802/
`The IEEE 802.11 WG home page is: http://www.ieee802.org/11/.
`This contains more detailed description of the scope and status of
`the individual task groups.
`The IEEE 802.11 WG working documents are available (after free
`registration) from: http://802wirelessworld.com.
`Approved amendments are available
`for download here:
`http://standards.ieee.org/getieee802/.
`
`
`The author speaks for himself. Views expressed by the author are
`not necessarily endorsed by his employer.
`
`
`
`ACM SIGCOMM Computer Communication Review
`
`93
`
`Volume 35, Number 2, April 2005
`
`Exhibit 1037
`Panasonic v. UNM
`IPR2024-00364
`Page 3 of 3
`
`