Email Delivery

Receive new posts as email.

Email address

Syndicate this site

RSS | Atom

Contact

About This Site
Contact Us
Privacy Policy

Search


November 2010
Sun Mon Tues Wed Thurs Fri Sat
  1 2 3 4 5 6
7 8 9 10 11 12 13
14 15 16 17 18 19 20
21 22 23 24 25 26 27
28 29 30        

Stories by Category

Basics :: Basics
Casting :: Casting Listen In Podcasts Videocasts
Culture :: Culture Hacking
Deals :: Deals
FAQ :: FAQ
Future :: Future
Hardware :: Hardware Adapters Appliances Chips Consumer Electronics Gaming Home Entertainment Music Photography Video Gadgets Mesh Monitoring and Testing PDAs Phones Smartphones
Industry :: Industry Conferences Financial Free Health Legal Research Vendor analysis
International :: International
Media :: Media Locally cached Streaming
Metro-Scale Networks :: Metro-Scale Networks Community Networking Municipal
Network Types :: Network Types Broadband Wireless Cellular 2.5G and 3G 4G Power Line Satellite
News :: News Mainstream Media
Politics :: Politics Regulation Sock Puppets
Schedules :: Schedules
Security :: Security 802.1X
Site Specific :: Site Specific Administrative Detail April Fool's Blogging Book review Cluelessness Guest Commentary History Humor Self-Promotion Unique Wee-Fi Who's Hot Today?
Software :: Software Open Source
Spectrum :: Spectrum 60 GHz
Standards :: Standards 802.11a 802.11ac 802.11ad 802.11e 802.11g 802.11n 802.20 Bluetooth MIMO UWB WiGig WiMAX ZigBee
Transportation and Lodging :: Transportation and Lodging Air Travel Aquatic Commuting Hotels Rails
Unclassified :: Unclassified
Vertical Markets :: Vertical Markets Academia Enterprise WLAN Switches Home Hot Spot Aggregators Hot Spot Advertising Road Warrior Roaming Libraries Location Medical Public Safety Residential Rural SOHO Small-Medium Sized Business Universities Utilities wISP
Voice :: Voice

Archives

November 2010 | October 2010 | September 2010 | August 2010 | July 2010 | June 2010 | May 2010 | April 2010 | March 2010 | February 2010 | January 2010 | December 2009 | November 2009 | October 2009 | September 2009 | August 2009 | July 2009 | June 2009 | May 2009 | April 2009 | March 2009 | February 2009 | January 2009 | December 2008 | November 2008 | October 2008 | September 2008 | August 2008 | July 2008 | June 2008 | May 2008 | April 2008 | March 2008 | February 2008 | January 2008 | December 2007 | November 2007 | October 2007 | September 2007 | August 2007 | July 2007 | June 2007 | May 2007 | April 2007 | March 2007 | February 2007 | January 2007 | December 2006 | November 2006 | October 2006 | September 2006 | August 2006 | July 2006 | June 2006 | May 2006 | April 2006 | March 2006 | February 2006 | January 2006 | December 2005 | November 2005 | October 2005 | September 2005 | August 2005 | July 2005 | June 2005 | May 2005 | April 2005 | March 2005 | February 2005 | January 2005 | December 2004 | November 2004 | October 2004 | September 2004 | August 2004 | July 2004 | June 2004 | May 2004 | April 2004 | March 2004 | February 2004 | January 2004 | December 2003 | November 2003 | October 2003 | September 2003 | August 2003 | July 2003 | June 2003 | May 2003 | April 2003 | March 2003 | February 2003 | January 2003 | December 2002 | November 2002 | October 2002 | September 2002 | August 2002 | July 2002 | June 2002 | May 2002 | April 2002 | March 2002 | February 2002 | January 2002 | December 2001 | November 2001 | October 2001 | September 2001 | August 2001 | July 2001 | June 2001 | May 2001 | April 2001 |

Recent Entries

In-Flight Wi-Fi and In-Flight Bombs
Can WPA Protect against Firesheep on Same Network?
Southwest Sets In-Flight Wi-Fi at $5
Eye-Fi Adds a View for Web Access
Firesheep Makes Sidejacking Easy
Wi-Fi Direct Certification Starts
Decaf on the Starbucks Digital Network
Google Did Snag Passwords
WiMax and LTE Not Technically 4G by ITU Standards
AT&T Wi-Fi Connections Keep High Growth with Free Service

Site Philosophy

This site operates as an independent editorial operation. Advertising, sponsorships, and other non-editorial materials represent the opinions and messages of their respective origins, and not of the site operator. Part of the FM Tech advertising network.

Copyright

Entire site and all contents except otherwise noted © Copyright 2001-2010 by Glenn Fleishman. Some images ©2006 Jupiterimages Corporation. All rights reserved. Please contact us for reprint rights. Linking is, of course, free and encouraged.

Powered by
Movable Type

« Time Warner Wi-Fi Routers Have 1990s Style Security Hole | Main | Longmont, Colo., Battle Reminder of Old Muni-Fi War »

October 20, 2009

Apple Slipstreams 3x3 into Wi-Fi Base Stations

Apple offered a quiet update note to its two main base station models today with a big boost in speed and coverage: The company put in a note on the data page (see "Even faster performance") and mentioned in passing to media who were briefed that its AirPort Extreme and Time Capsule base stations would see a boost of up to 50 percent in data throughput and an increase in range of up to 25 percent over the immediately preceding models.

How? 3x3. Engadget found the FCC documents that supports that statement before the announcement today, although the writer didn't explain what this means.

In the MIMO (multiple in, multiple out) antenna system that's used in 802.11n, designers have lots of choices in how to build in range and resiliency, and those choices have increased as silicon and antennas have become cheaper.

Most consumer 802.11n access points use a 2x2 MIMO array, which is two receiving and two transmitting antennas. Each antenna pair is typically handled by a separate radio chain. Each radio chain can transmit unique data for higher data rates, or the same data as other radio chains to increase redundancy, and thus provide better reception at lower rates.

These radio chains use spatial multiplexing, which allows a kind of "body english" in which varying power fed through antennas steers a beam so that it travels a unique path through space, using reflection of objects as one of the characteristics that forms the beam. Multiple receiving antennas decode these individual chains and reassemble data into what was sent in the first place.

In 802.11n, each spatial stream in the highest-rate mode can act like a separate full-speed connection. Since roughly 75 Mbps is the raw rate for 20 MHz channels and 150 Mbps for "wide" 40 MHz channels, a two-stream device maxes out at 300 Mbps of raw throughput.

Nearly all 802.11n base stations sold to date use 2x2 arrays coupled with two spatial streams; some also offer 2x3 arrays for redundancy with just two streams. However, chipmakers have been planning for some time on getting 3x3 arrays with three spatial streams into the market with a raw 450 Mbps rate. Apple may be the first consumer access point maker to bite, although there are definitely other 450 Mbps APs on the market. (See next paragraph for update.)

[Update! An informed commenter--see below--notes that there's only a single AP that does three streams. So Apple isn't slipping in higher bandwidth here, just better signal diversity and performance.]

The additional transmit and receive antennas improve how far signals can travel to a client, and how sensitively an access point can pick up distant transmissions. This accounts for Apple's statement on improved range. It also provides improved bandwidth further from the base station; the data rate doesn't drop off nearly as fast as with 2x2. The "up to 50 percent" figure relates to a range of distances, not close up to the base station.

The Wi-Fi Alliance just approved a testing regime for devices with three spatial streams, and all the major Wi-Fi chipmakers were involved in that testing. Our informed commenter says it'll be until late 2010 before we see a large number of 3-stream devices; other opinions?

No TrackBacks

TrackBack URL: https://db.isbn.nu/mt4/mt-tb.pl/11004

6 Comments

Wow, nice bit of digging & sleuthing, Glenn. Really interesting stuff!

Actually, most enterprise APs are 3x3, however, NONE of the AP Wi-Fi chipsets support 3 streams, and I don't expect Apple to be an exception. The existing 3x3 chipsets support only 2 streams, or in other words, 300Mbps. The 3x3 only provides better rate over range and better reception. The only chipset to offer 3 streams is Intel 5300, but it's available only for clients - and has been shipping for a while. Some vendors plan on having 3x3 AP chipsets late 2010, but this is just a plan for now.

Thank you so much. I have revised the article to include this. I'll be following up on this by interviewing chipmakers about the 3-stream roadmap, since it's awfully confusing even to this reporter, who has been following 802.11n since before it was called 802.11n.

It would be nice to see open ended streams that are software selectable. Hopefully, one day, wireless routers will each have a range of 1 km. or more and will overlap with a redundancy that will prevent failures like we have seen with the Telco's during 9/11 and Katrina. Add a waterproof case, an internal cell phone battery and you've got people surfing the web from their roof tops after a hurricane!

This is really confusing. I have 19 of the 'newer' style Airport Extreme 802.11n models, ranging from the originals with only 100BT ethernet up to the first simultaneous dual-band models, four of which I just got a month ago (damn!).
I was under the impression that these all had three antennas and did MIMO, but now it seems they only did 2x2. Very confusing. Do I understand that a firmware update will not be possible to upgrade the early '09 AEn models to the new 3x3?
On a related note, I have searched without success for anyone who has mapped the radiation pattern of Airport Extremes. Yes, they're supposed to be omnidirectional, but I am guessing there are certain directions that the signal is stronger. Are there any sites which post these patterns anymore? I recall there were a few in the "old" days of wifi.
Thanks...

2x2 is MIMO. It's two receive and two transmit antennas. You can't update the older units to 3x3, because that's a hardware change.

Leave a comment