June 15th, 2006
How to jam your neighbor's Wi-Fi legally
Do you ever get frustrated with your neighbor hogging all the Internet bandwidth on the block? Tired of your neighbor using his Wi-Fi gear on channel 1, 6, or 11 (that’s all the possible choices) on the 2.4 GHz spectrum? Well now’s your chance to get even! Introducing Draft N and Pre-N Wi-Fi! They might not interoperate at high speeds with each other but they’re FCC legal and they’re guaranteed to shut your neighbor down or your money back!
While Airgo’s third generation product achieves record breaking throughput, it annihilates any legacy 802.11 b/g product in the vicinity and effectively shuts them down. Ok that’s not an actual advertisement, but it might as well be one. Our friend Tim Higgins has been at it again testing so called "Draft N" and "Pre N" Wi-Fi gear (implied compatibility with 802.11n) and he has some very interesting results about the interoperability and interference characteristics of these products. Earlier this month, Tim ran a battery of tests on these wannabe 802.11n Wi-Fi products to see if they lived up to the kind of throughput and range being promised by the Wi-Fi vendors.
What the first set of tests reveals is that Airgo’s product still beats the "Draft N" competition from Broadcom and Marvell hands down with their third generation MIMO product in range and throughput. Note: The results showing the Cisco business-grade 802.11g gear performing so well on range may not be a good test of chipset efficiency since it can use 100 mW of transmit power which may be higher than the consumer gear tested. One could also easily quadruple the range on a Cisco Access Point with the right kind of high-powered antenna but that wouldn’t be a fair measurement on how good the radio and chipset design is.
In the second set of tests examining interoperability and interference characteristics on neighboring 802.11g Access Points, the results are alarming. While the Draft N and Pre N products technically work with each other, it would seem that most of them don’t interoperate at the higher speeds. Broadcom announced that their Draft N products will interoperate at high speeds with Atheros Draft N products, but the Atheros based products weren’t available for testing yet at the time of the review. Broadcom and Atheros feeling the heat from relative newcomer Airgo have put their fiercely competitive past behind them though I’m not sure if this will help if they can’t post good throughput versus range numbers against Airgo. When I asked Broadcom’s representative if they were guaranteeing future compatibility with 802.11n in writing, I couldn’t really get a straight answer and was told that their Draft G product was eventually compatible with 802.11g and that they are using a flexible design that can change if the 802.11n draft standard changes. I finally got them to admit that there are no such guarantees for actual 802.11n compatibility.
Airgo is a very interesting story by itself. I’ve praised them in the past for having the cleanest design in terms of staying in a single 20 MHz channel while retaining the speed crown. Airgo’s competitors eventually pushed past the performance of Airgo’s first and second generation products by hogging two radio channels and Airgo quickly answered with their third generation product that also used a 40 MHz wide signal and regained a massive lead in throughput which holds today. The problem is that Airgo when from being the nicest single-channel neighbor in town to being the absolute worst Wi-Fi neighbor in town.
While Airgo’s third generation product achieves record breaking throughput, it annihilates any legacy 802.11 b/g product in the vicinity and effectively shuts them down. The other products from Broadcom and Marvel weren’t quite as devastating to the neighbors, but the damage is still severe. What’s crazy is that these products are FCC legal and are being sold on store shelves today. This is a serious problem in the city where town homes and condominiums are right next to each other and it’s even a problem for businesses which primarily uses 802.11 b/g. While these products are aimed at the home market, they’re also sometimes used in a small office environment and these radio jamming characteristics are intermittent (when data is being sent) and difficult to track down.
So who is to blame for all of this? Airgo to its credit pushed for spectrum efficiency among the 802.11n standards body as long as it could and tried to lead by example while everyone else was spectrum hogging. Once it was clear that the 802.11n draft standard wasn’t going to be swayed on spectrum efficiency, Airgo turned to the dark side and became the biggest spectrum hog of all. The industry was moving the right direction with dual band 2.4/5 GHz products which mitigate interference issues until the arrival of the 802.11n MIMO type products because customers are easily seduced by higher speeds when what’s really needed is less interference and better range.
The range issues could have been easily solved with higher gain antennas which ironically are frowned upon by the FCC but don’t do nearly as much damage to the neighbors. Since larger antennas are optional, people won’t resort to them unless they really needed the longer range in which case no one’s nearby to begin with. With these N based products, they come off the factory floor ready to jam everything within its operating radius and this seems to be what the 802.11n standards body is encouraging with its decision to allow for wider channels. The fact that almost none of these new "N" products interoperate with each other and none of them guarantee future compatibility with 802.11n is sad. The best solution for anyone wishing to avoid the radio jam is to move to 802.11a and the 5 GHz band as soon as possible.
George Ou is Technical Director of ZDNet. See his full profile and disclosure of his industry affiliations.
LOL
