802.11n - Next Generation Wireless Technology (Came in CES 2012)

This technology description has been taken from a draft. Now this technology has been release in CES 2012.

IEEE 802.11n, the  newest draft specification for  Wi-Fi®. It is designed to provide an overview of the  technology, describe new techniques used to  achieve greater speed  and  range, and  identify applications, products, and environments that will  benefit from the  technology.

The growing pervasiveness of Wi-Fi  is helping to  extend the  technology beyond the PC  and   into   consumer  electronics  applications  like   Internet   telephony,  music streaming,  gaming,  and   even   photo  viewing  and   in-home  video   transmission. Personal  video  recorders and  other A/V  storage appliances that collect  content in one spot  for  enjoyment around the  home  are accelerating this  trend.

These  new   uses,   as  well   as  the   growing  number  of  conventional  WLAN  users, increasingly combine to  strain existing Wi-Fi  networks. Fortunately, a  solution  is close at  hand. The industry has come  to  an agreement on the  components that will make  up  802.11n, a new  WLAN standard that promises both  higher data  rates  and increased reliability,  and  the  IEEE standards-setting body  is  ironing out  the  final details. Though the  specification is  not  expected to  be  finalized before 2007, the draft is  proving to  be  reasonably stable   as  it progresses through the  formal IEEE review process.

In   the   meantime,  hardware  that  conforms  to   the   802.11n draft  is  becoming available,  so   consumers  can   begin    building  high-speed  wireless  networks  in anticipation of  the  standard while  ensuring interoperability at  high  speeds  and  still supporting their existing WLAN hardware.

The purpose of  this  white paper  is to  explain the  impending 802.11n standard and how  it will  enable  WLANs  to  support emerging media-rich applications. The  paper will   also  detail how   802.11n  compares with   existing  WLAN  standards and  offer strategies for  users  considering higher-bandwidth alternatives.

Wi-Fi® Standards Comparison

The  first WLAN  standard to  become accepted  in  the  market was  802.11b, which specifies encoding techniques that provide for  raw data  rates up to 11 Mbps using  a modulation  technique  called   Complementary  Code   Keying,  or   CCK,   and   also supports Direct-Sequence Spread  Spectrum, or DSSS, from the  original 802.11 specification. The  802.11a standard, defined at  about the  same  time  as 802.11b, uses a more  efficient transmission method called  Orthogonal Frequency Division Multiplexing, or  OFDM. OFDM, as implemented in 802.11a, enabled raw  data  rates up  to  54  Mbps.   Despite its  higher data   rates, 802.11a never   caught on  as  the successor to 802.11b because  it resides  on an incompatible radio  frequency band: 5

GHz versus  2.4  GHz for  802.11b.

Note:  All  of  the  WLAN  standards provide  for  multiple  transmission options,  so  that  the   network  can   drop  to  lower  (albeit  easier   to maintain) data  rates as environmental interference challenges communications. In  the  most   favorable circumstances, 802.11a and 802.11b support data  rates up to 54 Mbps and 11 Mbps respectively.)

In  June  2003, the  IEEE ratified 802.11g, which   applied OFDM modulation to  the

2.4-GHz band. This  combined the  best  of  both   worlds:  raw data   rates   up  to  54

Mbps on the  same  radio frequency as the  already popular 802.11b. WLAN hardware built  around 802.11g was  quickly embraced by  consumers and  businesses seeking higher  bandwidth.  In   fact,  consumers were   so  eager   for   a  higher-performing alternative  to   802.11b  that  they   began   buying  WLAN  client   and   access-point hardware nearly a year  before the  standard was finalized.

Today, the  vast  majority of computer network hardware shipping supports 802.11g. Increasingly,  as  technology  improves  and  it  becomes easier   and   less  costly   to support  both   2.4   GHz  and   5  GHz  in  the   same   chipset,  dual-band  hardware  is becoming more  commonplace. Much  of  the  WLAN client  hardware available today, in fact, supports both  802.11a and 802.11g.

A similar scenario to the  draft 802.11g phenomenon is now  unfolding with 802.11n. The  industry came  to a substantive agreement with regard to  the  features to  be included in the  high-speed 802.11n standard in early  2006. And though it will  likely be 2007  before the  standard is ratified, the  specification is stable  enough for  draft-n Wi-Fi cards  and routers to already be making their way  to store  shelves.

Major Components of 802.11n

Feature	Definition	Specification Status
Better OFDM	Supports wider bandwidth & higher code rate to bring maximum data rate to 65 Mbps	Mandatory
Space- Division Multiplexing	Improves performance by parsing data into multiple streams transmitted through multiple antennas	Optional for up to four spatial streams
Diversity	Exploits the existence of multiple antennas to improve range and reliability. Typically employed when the number of antennas on the receiving end is higher than the number of streams being transmitted.	Optional for up to four antennas
MIMO  Power Save	Limits power consumption penalty of MIMO by utilizing multiple antennas only on as-needed basis	Required
40 MHz Channels	Effectively doubles data rates by doubling channel width from 20 MHz to 40 MHz	Optional
Aggregation	Improves efficiency by allowing transmission bursts of multiple data packets between overhead communication	Required
Reduced Inter-frame Spacing (RIFS)	One of several draft-n features designed to improve efficiency. Provides a shorter delay between OFDM transmissions than in 802.11a or g.	Required
Greenfield Mode	Improves efficiency by eliminating support for 802.11a/b/g devices in an all draft-n network	Currently optional

Primary IEEE 802.11 Specifications

	802.11a	802.11b	802.11g	802.11n
Standard Approved	July 1999	July 1999	June 2003	Not yet ratified
Maximum Data Rate	54 Mbps	11 Mbps	54 Mbps	600  Mbps
Modulation	OFDM	DSSS or CCK	DSSS or CCK or OFDM	DSSS or CCK or OFDM
RF Band	5 GHz	2.4  GHz	2.4  GHz	2.4  GHz or 5 GHz
Number of Spatial Streams	1	1	1	1, 2, 3, or 4
Channel Width	20 MHz	20 MHz	20 MHz	20 MHz or 40 MHz

One  of  the  most  important features in  the  draft-n specification to  improve mixed- mode  performance is aggregation. Rather  than  sending a single  data  frame, the transmitting client  bundles several frames together. Thus,  aggregation improves efficiency by  restoring the  percentage of  time that data  is being  transmitted over the  network, as

It is much  easier  for  draft-n devices  to  coexist with 802.11g and  802.11a hardware because  they  all  use  OFDM.  Even  so,  there are  features in  the  specification that increase  efficiency  in  OFDM-only networks.  One  such  feature is  Reduced   Inter- Frame  Spacing, or RIFS, which  shortens the  delay  between transmissions.

For  the  best  possible performance,  the  draft-n  specification provides for  what  is called   greenfield  mode,  in  which   the   network  can   be  set   to   ignore  all  earlier standards. It is not  clear  at this  stage  whether greenfield mode  will  be a mandatory or an optional feature in the  final  802.11n draft, but  it is likely  to be an option.

Realistically, battery-powered  WLAN  hardware  will   continue  to   be  built  around

802.11g and even  802.11b for some  time. Despite the  improved efficiency built  into the  draft-n specification, however, it is difficult to  eliminate all  of  the  obstacles of

802.11b. This  means   that  consumers looking for  the  best  possible network performance  may   want to  consider replacing  802.11b  WLAN  hardware  on  their networks.

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Considerations of WLAN Hardware

Source: BroadCom's White Paper on Draft 802.11n - The Next Generation Wireless Technology.

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