Monday, April 23, 2007

802.11n- making sure everyone forgets about 802.11a

Every meeting I attend I get asked the same question right at the onset- "What about 802.11n?" My first response is usually "What about it?" followed by "What do you know about it?" I would usually dismiss these questions as merely knowledge-gathering questions if it were not for the potential purchasing ramifications.

Many people see 802.11n as the wireless technology that is going to finally make it possible for them to get HD video, VoWLAN calls, and all sorts of multimedia traffic at the same time on their computer. After all, the draft plans call for the technology to offer close to 120Mbps of throughput (of course that is the "in-a-vacuum" spec, much like the 54Mb for 802.11a/g). This fire is further fueled by the fact that every month sees the passing of a draft resolution and companies are starting to release 802.11n APs and client cards. This makes it seem that resolution of the debates and the emergence of a draft standard are right around the corner. Unfortunately, nothing could be further from the truth.

It is pretty clear that 802.11n is going to incorporate something called Multiple In/Multiple Out technology, allowing for "full duplex" via wireless. Remember, wireless is a half-duplex technology. With an association to an AP or radio, you can either transmit or receive at any time, you can't do both. 802.11n has promised to change that- by utilizing more channels at the same time and therefore allowing one to transmit on one channel and receive on the other. I won't deny- it is very exciting and the possibilities are there. However, people tend to overlook that the possibilities are already here now- they exist in the red-headed stepchild known as 802.11a.

802.11a made its debut in the consumer market around the same time as 802.11b and was much more expensive. Then 802.11g came out and everyone thought that they were getting everything they would get with 802.11a plus compatibility with 802.11b. The only difference is that because 802.11a is in the less crowded 5.8Ghz space and has more non-overlapping channels compared to the three for the 2.4Ghz range where 802.11b/g reside, it tends to work much better- there is simply less potential interference from other devices (Quick sidenote: try this experiment- set your 802.11b/g channel to 11 and go into your kitchen with your laptop. Turn on your microwave and look what happens to your wireless signal or your ability to send/receive data). Anyway, because 802.11a received such a tepid response, people still tend to ignore it and believe that 802.11n is going to fix all the problems they have with 802.11b/g.

The key question to ask, is what are you currently doing or wish to do that you cannot do with 802.11a? Given the much more open space in the 802.11a range, one can reach high throughput speeds allowing them to do most of the things they desire with 802.11n. Plus, no one is quite sure how 802.11n is going to work within a mixed environment. On its own, 802.11n will give you great results, but in a mixed environment it will have to drop significantly to give equal time to the other clients (much like 802.11g has to do for 802.11b).

Further complicating the issue, is that 802.11n will not work with the same 802.3af Power over Ethernet that is currently being used by companies everywhere. The radios require too much power to drive the MIMO technology and will need to have power adapters until the new PoE standard is adopted. The infrastructure costs to companies alone will be quite huge, and there will not even be a great benefit because true 802.11n clients are not going to be out until the tail end of 2008. Plus, as I mentioned earlier, unless you are in a n-only environment, you are not going to get all the throughput you desire.

"But what about all those wireless routers at Best Buy?" you ask. Well, those are based on the pre-draft standard, and given the number of changes being made on an almost monthly basis, the purchases you make now might not be a simple firmware upgrade to get to the released draft standard. Also, you are probably not running anything in your house that requires such a speedy wireless connection. I currently run 802.11g-only environment, and I get more than enough throughput to satisfy all my needs. The key is to make sure and select the least congested channel (I suggest channel 1) and making sure that you try and get rid of all the b clients in your environment so that you don't have to lower throughput to accommodate for them. In an office environment, look to 802.11a- you can run it over the existing PoE and can also take advantage of the less crowded bandwidth. The performance limitations that exist for 802.11g are not there for 802.11a because it runs on its own radio.

I know I sound like I am pessimistic on 802.11n, but I assure you I await its arrival like everyone else. The misconception is that one should put off wireless investments today to wait for the 802.11n standard to be release in 1.5 years from now. That is the big mistake- the cost to your company will far outweigh any benefits that you will see from the technology. It is not the hardware that drives the moves to new technology, but consumer need and the applications. Eventually you will need it- there is no doubt, but 802.11a can handle everything presently and into the foreseeable future.

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