802.11n May Stomp on 802.11b/g Networks?

[Jason Dunn]

<div class='os_post_top_link'><a href='http://www.tgdaily.com/2006/03/13/802_11n_backwards_compatibility_issues/' target='_blank'>http://www.tgdaily.com/2006/03/13/8...ibility_issues/</a><br /><br /></div><i>"Airgo Networks took the occasion of last Friday's vote by the IEEE 802.11n Taskgroup to proceed to the "letter ballot" phase of the standardization process, to go public with the developing standard's little secret. The firm claims that the "802.11n Draft 1.0 does not provide for interoperability with nearby legacy 802.11b/g networks". "Specifically, if 'Draft N' or 'N Ready' products are released to market based on Draft 1.0 of the standard, they will severely degrade - or even disable - nearby 802.11b and 802.11g networks," Airgo said. The firm's announcement is the first public acknowledgment by a chipmaker of behavior that TomsNetworking documented two months ago in its review of Netgear's RangeMax 240. The Netgear product is based on Airgo's third-generation chipset that uses a 40 MHz wide band to achieve greater than 100 Mbps of application-level throughput."</i><br /><br />This is not good news at all. 8O I already have a lot of problems with wireless routers in my home because there are eight other networks within range, so I'm shuddering to think what will happen when an 802.11n router gets introduced into the mix. Although, now that I think about it more, I'll probably be the first one getting an 802.11n on my street, so I'll be the guy causing problems for everyone else. :devilboy:

[ricksfiona]

I wouldn't worry about it. The router/AP manufacturers will just include the capability to connect like B/G/N by having the chips to speak in those languages. It would be nice to have the backward compatibility, but I can sometimes see the need if you will see a great increase in performance....

[beq]

Aside from Tim Higgins at Tom's Networking, I've also found helpful articles from the UK's Techworld talking about the convoluted 802.11n development process. First there was the brouhaha with the competing TGnSync (advocating 40MHz channel bonding) vs. WWiSE IEEE task group proposals...

Then while the two camps were supposedly collaborating on a joint proposal, a secret group called the EWC was founded by Intel, Atheros, Broadcom, and Marvell, which attempted to bypass the deadlock by developing their own proposal in private (though some say the real motive was to gain an advantage over Airgo, the one company with several generations of MIMO chipsets on the market).

The EWC proposal became the basis for the IEEE 802.11n draft spec that was approved earlier this month, and it came as no surprise that all three EWC founders sans Intel have immediately announced that they already have working chipsets complying to the draft.


I'd like to find out more info on this draft spec. For example, is the 600 Mbps top speed (symbol rate) only achievable with a 4x4 MIMO antenna array configuration (as opposed to 3x3, 2x2, etc)? How come some articles list the top speed of the spec as 300 Mbps?

The interesting thing is that the 11n draft allows the option to use the 5GHz band (backward compatible with 11a) in addition to the 2.4GHz band (backward compatible with 11b/g). And I hear the 11n draft chipsets from Atheros, Broadcom, and Marvell are all dual-band designs.

In addition to that, I read that the top speeds of the 11n draft requires the wider 40MHz channel, but various articles also mention that this would likely be feasible only with the use of both 2.4GHz and 5GHz bands! What does this mean? For example, does it mean the 11n equipment might only use 20MHz in the 2.4GHz band and 20MHz in the 5GHz band, so there won't really be a lot higher interference with neighboring 11b/g equipment (in 2.4GHz band)??


I'm also curious why Airgo started using 40MHz channel (in the 2.4GHz band) for their current MIMO chipsets, when they had originally opposed channel bonding as causing too much interference. And why would they now go back again and criticize the 11n draft spec, if their own existing MIMO designs also take up 40MHz channel width?


P.S. Some recent Techworld articles in descending chronological order (might require registration, and sometimes slow):

http://www.techworld.com/mobility/news/index.cfm?NewsID=5549

http://www.techworld.com/mobility/features/index.cfm?FeatureID=2303

http://www.techworld.com/mobility/features/index.cfm?FeatureID=2281

http://www.techworld.com/mobility/features/index.cfm?FeatureID=2280

http://www.techworld.com/mobility/features/index.cfm?FeatureID=2216

http://www.techworld.com/mobility/features/index.cfm?FeatureID=2162

http://www.techworld.com/mobility/features/index.cfm?FeatureID=2132

http://www.techworld.com/mobility/features/index.cfm?FeatureID=1915

http://www.techworld.com/mobility/news/index.cfm?NewsID=4550

http://www.techworld.com/mobility/news/index.cfm?NewsID=4421

[Jason Dunn]

I wouldn't worry about it. The router/AP manufacturers will just include the capability to connect like B/G/N by having the chips to speak in those languages.

Um...did you read the article? The real issue is not compatibility, it's the fact that an 802.11n router using the 40mhz side band will cause interference problems with other routers in the area. It's the 802.11n router stomping on everything else within range...that's the problem.

[emuelle1]

I'll probably end up keeping my b router for a while, since it still works great. Hopefully there won't be any n routers in my neighborhood for a long time. My two immediate neighbors are senior citizens, and one is still debating whether or not to replace his first-generation Pentium class Packard Bell. I doubt I have to worry about him getting an n-spec router any time soon.

[martin_ayton]

Laying aside the W?BIC argument, I'm curious as to why a home user would want or need an n-spec router. Given that the fastest ADSL connection that I am aware of (in the UK at least) tops out at 8meg, what is the point of having a router than can go much faster than that? Is it because you want to stream HD video wirelessly within the home? If so, just what sort of bandwidth would that take? Normal app's wouldn't seem to require that sort of grunt run over a home network and I'm not sure I can tell the difference between extremely fast and blindingly fast

I can see why a really high bandwidth device would be useful in an office or cafe environment where possibly tens of users are all taking up their bit of bandwidth, but I just don't get it for the home situation.

I'm not being cynical or sarcastic: I really can't identify what problem this spec is solving (for home use). Can anyone enlighten me?

[Jason Dunn]

Is it because you want to stream HD video wirelessly within the home? If so, just what sort of bandwidth would that take?

For me, I like the speed for file transfers. I use www.foldershare.com to keep all my PCs in sync, and if I'm pushing around 100's of MB of files I want 108mbps not 54mbps. You also never get the rated speed - 108mbps would give you REAL 54-70mbps, whereas 54mbps rarely hits a true 6.75MB/s.

And definitely for anyone that's doing video streaming, especially with multiple devices (Xbox 360, etc.), more bandwidth is better.

Certainly though 802.11n will not make wireless Web browsing for instance be any faster.

[martin_ayton]

Thanks Jason. I can see what you are driving at. However, I suspect that even for a power user, you have an unusual requirement to i) move (large) files around in the home and ii) the desire to see that done very quickly indeed. Beyond 'LAN parties' where the actual PC to PC data transfer isn't all that high, I would guess that most people's home networks are simply a way of sharing one internet connection with two or three PCs. To run a true network at home with data actually flowing around the network as opposed to just into and out of it is probably a feat achieved by vanishingly few people. And so I come back to a variation of my original point - is there actually a (large enough) market need for the 'n' specification?

There again, do people / markets think rationally? Perhaps the 'go-faster stripes' on the WiFi 'n' boxes will be enough to sell them whether people need that speed or not.

On that basis I may have to go and get one myself - just to ensure that I'm not going to suffer interference because my neighbour feels the need, the need for speed :devilboy:

[emuelle1]

A b spec router is fine for web browsing, although the security on a g router is much better. I do second Jason's statement about file transfer speed though. I had to send my wife's laptop in for service a couple of times, and while I was trying to back up some of her important files (the Windows File Settings Transfer Wizard generated a gig and a half sized file) to my desktop for safe keeping, the transfer was taking way too long. I took her laptop to my desk and plugged it directly in to the router, and the transfer took off and finished much faster.

It still doesn't justify to my wife the need for a g router though.

[Jason Dunn]

There again, do people / markets think rationally? Perhaps the 'go-faster stripes' on the WiFi 'n' boxes will be enough to sell them whether people need that speed or not.

I understand what you're saying about the speed issue, but there's much more to 802.11n than speed - greater range, and most important of all, greater resistance to interference. 802.11b/g routers are very fragile and easily lose huge amounts of speed at even the slightest bit of interference. 802.11n is a huge advance in fixing all the problems that b/g routers have.

[beq]

If you check out all the announcements and marketing for 802.11n, you DO see the ability to send multiple audio/video streams around the house (especially high-def) being touted as one of the most important benefits of the greater speed and range.

(Not to be confused with wireless cable-replacement connections such as ultrawideband-based wireless 1394, etc.)

For example, 11n can be compelling with computer-based entertainment/storage sources being distributed to Wi-Fi media players around the house (where the TV/speakers are).

Or a central storage such as a NAS (ex. Infrant ReadyNAS NV), with data accessed wirelessly on desktops and laptops.

Or even if you set up a regular backup of one computer's data to another computer wirelessly...

[ctmagnus]

Or even if you set up a regular backup of one computer's data to another computer wirelessly...

Ugh. B sucks for that.

[PDANEWBIE]

Heres the big question will Wireless N stop being affected by cordless phones? That right there is my BIGGEST complaint about wireless as it stands with B/G.

Second biggest is the security concerns of manufacturers shippng their wireless devices wide open. IMHO they should be locked down and left for the user to open.

[martin_ayton]

there's much more to 802.11n than speed - greater range, and most important of all, greater resistance to interference.

Ok,*that* rings my bells. My b/g router drops out in various parts of my house, particularly when I'm using my Blue Angel with its notoriously poor reception. Now I definitely want one... :D

[k1darkknight]

Heres the big question will Wireless N stop being affected by cordless phones?
Another good, related question...will the 11n spec routers themselves actually CAUSE interference with cordless phones? Or anything else (besides b/g routers), for that matter?