I just finished reading an article on www.Wirelessnetdesign.com about possible serious interference issues stemming from use of UWB by the proposed High Speed Bluetooth. See the article:
Testing raises concerns over 802.11-based high-speed Bluetooth
The article not only points out some interference concerns of UWB with standard Wifi\WiMax and some IMT-2000 service, it is also a great primer on the technologies involved.
While I will not break down the article here -( you can read it for yourself, it is not overly leaden with unfamiliar terminology and there are a ton of graphs)- the basic premise should be understood. Radio frequency transmissions are an extremely poor way to transfer data as they suffer innumerable sources of signal degradation. The article focuses on the specific effects of UWB's technique of transmitting information in short low energy pulses but over a large bandwidth (typically greater then 500 MHz), but the principals hold true for any RF installation.
We -(and especially consumers) have been influenced to view consumer RF (usually referring to the ISM bands) as a reliable well thought out standard in which every effort has been made to insure the units we use can resist interference or will not cause issue with other consumer systems. Or as the article states
The reality is that consumers expect to be able to use multiple technologies simultaneously, without interference
Unfortunately two things make this concept a bit utopianstic.
- FCC Part 15 - Go ahead read it, very interesting stuff there -(no, really).
- Getting a standard to market often involves trading pure concepts for workable solutions which allows for innovations and relative ease of implementation.
Regardless of the install type, the environment in which the system is put into can have a dramatic effect on the wireless reliability. Environmental factors can be external (Radio, TV, Aeronautic, STL, etc), Internal factors (wireless phone systems, multi-mode, frequency density and transceiver -(gateway)- proximity). As the article states:
...unless they are located approximately 8 meters apart for 2.6 GHz and 16m apart at 2.3GHz. If they are co-located in a single device achieving this level of isolation between radios is unrealistic...
For UWB the answer stated in the article is a method of Time And | OR Phase intervals, which is fine for UWB but is not a current practical method for standard wifi. Note the distances the article states for minimum separation! 8- 16 meters ! The basic concept of providing adequate distances between RF devices and their transceivers is just as important as antenna orientation and frequency allocation.
There are some great resources on the web which can help you get the basics
Air Magnet - www.airmagnet.com - have fantastic webinars on all aspects of wireless systems, if you cannot catch one of the live sessions they archive them all. In fact I just received a notice for a webinar on the 26th entitled: 802.11n Primer: What You Need to Know" -- It looks like a good one.
The fine folks at Infocomm international - www.infocomm.org have a couple of great on-line classes concerning network functionality of which the Audio-Video & control System Networking is full of great information.
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