The document summarizes the development of the IEEE 802.11n standard for wireless LAN technology. It describes how the standard was developed through a working group process that included initial discussions, the formation of study groups to determine scope, and a task group that evaluated proposals and drafted the standard. Key technologies included in the 802.11n standard are MIMO and 40MHz bandwidth to increase data rates to over 100Mbps and the use of frame aggregation to enhance MAC throughput. Lessons learned from the development process included the need to limit new features and narrow the scope of amendments to speed up time to market.

1. IEEE 802.11n DEVELOPMENT
HISTORY, PROCESS AND
TECHNOLOGY.

2. The slides summarizes the content
presented in paper IEEE 802.11n
Development by Eldad Perahia,
Intel Corporation.

3. ABSTRACT
• This article gives a general overview of IEEE
802.11n process.
• An overview of physical layer used to achieve
600 Mb/s data rate and medium access layer
features employed to enhance throughput to
over 400 Mb/s.
• The added robustness afforded by the
techniques in the standard and issues with
backward compatibility are also addressed.

4. INTRODUCTION
• IEEE 802.11n Working Group began
discussions to extend the data rates of the
physical layer to address higher throughput.
• The high throughput study group(HTSG) was
formed and introduced new antenna
technology such as MIMO.
• Subsequently IEEE 802.11n Task Group began
to develop amendment to the IEEE 802.11n.

5. 802.11 PROCESS TO AMEND THE
STANDARD
The 802.11 WG follows 5 steps to amend the
standard.
• Initial discussions of new ideas in the Wireless Next
Generation Standing Committee (WNG SC).
• Formation of an SG to formulate the purpose and scope of
the amendment.
• Creation of a TG to develop a draft of the amendment that
addresses the purpose and scope.
• Approval of the draft by WG and opening of a Sponsor Ballot
pool for review of the draft by IEEE Standards Association.
• Ratification of the draft by the IEEE-SA Standards Board.

6. 802.11 PROCESS TO AMEND THE
STANDARD (Contd)
• The SG must address five criteria
demonstrating the need for new amendment.
• Broad market potential.
• Compatibility with the family of IEEE 802 standards.
• Distinct identity from other IEEE 802 standards.
• Technical feasibility.
• Economic feasibility.

7. WNG SC
• In 2002, a presentation was made based on increasing
data rates in wired Ethernet and wireless products.
• Subsequently other presentations were calling for
greater than 100 Mb/s data rate by spatial multiplexing
and/or doubling the bandwidth in addition to
improving MAC efficiency.
• The goal of the standard development is to foster new
commercially successful markets by interoperable
products, not to perform research.
• For market success, the goal should be that by the time
standard development is complete, manufacturers are
capable of low-cost silicon implementation of the
system.

8. HT SG
• Work began in HTSG on
– Usage model development.
– Channel model development.
– Selection procedures.
• Components of usage model included
– Applications.
– Environments.
– Use cases.
• The applications include
– Various forms of video and audio.
– Internet and local file transfer.
– VoIP.

9. HT SG(Contd)
• The main environments included home, office
and hotspots.
• Use cases were collected that gave a
description of how someone uses the
application in a particular environment.
• Various use cases were merged to create a
small number of realistic usage models.
• Each usage model contained an AP and
defined number of stations running a mix of
applications based on use cases.

10. TGN PROPOSAL PROCESS
• TGn decided to proceed with the call for
proposals rather than design by committee
approach.
• The first order of business is to complete the
selection procedure and as a first step
functional requirements and comparison
criteria was defined.
• Functional requirement document was created
containing a list of mandatory features,
performance and behavior.

11. TGN PROPOSAL PROCESS(contd)
• Comparison criteria document defined the
simulation results that were required for
complete proposal.
• Totally five proposals were made, out of which
three were submitted by individual companies
and two by a team of companies(TGn and
WWiSE).
• After some years because of the stagnation of
proposals, some of the silicon providers came
out of IEEE and formed Enhanced Wireless
Consortium to craft a basic interoperable
specification.

12. TGN PROPOSAL PROCESS(contd)
• The final EWC specification was adopted as a
joint proposal and submitted for confirmation
with TGn where it passed unanimously in Jan
2006.

13. MARKET EXPECTATIONS
• As the silicon and system providers were
looking for new technology, in 2004 Atheros
developed a proprietary 40Mhz mode built on
802.11g.
• In 2005,2006 the market saw first wave of
proprietary MIMO based wireless LAN
products. These were typically called “pre-n”.

14. MARKET EXPECTATIONS AND
TIMESCALE.
• With down selection process of TGn, the issue
with incorporating so many “pet features” as a
part of compromise is the time it takes to
check, edit, review and test each feature.
• Having realized the market demand for
standards-based interoperable products, the
WiFi Alliance considered certifying devices
based on 802.11n draft.

15. OVERVIEW OF 11N ENHANCEMENTS
• The key requirement that drove most of the
development in 802.11n is the capability of at
least 100 Mb/s MAC throughput.
• Two concepts were employed in 802.11n to
increase the PHY data rates: MIMO and 40
MHz bandwidth channels.
• Increasing the spatial stream and transmit
antenna can increase the data rate but with
the cost associated with antennas, it becomes
optional.

16. OVERVIEW OF 11N
ENHANCEMENTS(contd)
• 40 MHz bandwidth channel mode has become
a core feature due to the low cost of doubling
the data rate from doubling the bandwidth.
• By adding two extra subcarriers into the guard
band on each side of the spectral waveform,
data rate can be increased by 8%.
• Mandatory operation in 802.11n contains an
800ns guard interval between each OFDM
symbol but an optional mode with 400ns
guard channel can increase the data rate by
11%.

17. OVERVIEW OF 11N
ENHANCEMENTS(contd)
• To break the 100Mb/s throughput barrier,
frame aggregation was added to the 802.11n
MAC as the key method of increasing
efficiency.
• Frame aggregation increases length of the
data portion of packet to increase efficiency.
• Types of aggregation
– MAC protocol data unit aggregation(A-MPDU).
– MAC service data unit aggregation(A-MSDU)

18. SUMMARY AND LESSONS LEARNED
• Over 10 wireless devices were certified in the first
few months.
• Just 10 years ago data rates were on the order of
few Mb/s to hundreds of Mb/s and able to
support wireless devices.
• These devices include latest technology such as
MIMO, frame aggregation, and 20/40 MHz
bandwidth channels.
• With a call for proposals and down selection
approach, changes need to be made to guarantee
conclusion and disallow endless loops.

19. SUMMARY AND LESSONS
LEARNED(contd)
• As described, a possible approach to speeding
up the process is to reduce the number of
down selection votes and eliminate the
confirmation vote.
• For the time to develop a standards
amendment to meet market needs, the scope
of an amendment should be narrowed.
• The number of new features in an amendment
should be limited within a narrow scope to
shorten the time to market.