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[emmsys]

Hi everyone,

There are lots of press releases going around highlighting the emergence of new wireless technologies, particularly ZigBee. There are some misconceptions going around that might confuse anyone new to wireless technologies. I'm going to try to clarify a few here:

1.0. All wireless technologies are the same, it's just that some are faster than others.
This is false on so many levels. There are lots of different characteristics for each wireless technology out there. A few of those characteristics are also sources of misconceptions as you'll see below. Different wireless technologies suit different applications and markets better. Besides throughput, some technologies are for high power applications, some are for low power applications. Cost and complexity are also distinguishing factors.

1.1. One standard to rule them all
There are quite a few standards out there for wireless communications, each being targeted at different markets and functions. You have ZigBee, 802.11b,g,n, Bluetooth, Z-Wave etc. etc. They are different in many ways: modulating scheme, headers, network topology etc. Some standards are better for large data rates and high power applications, others are better for small data rates and low power. Some are more reliable and flexible than others (depending on range, topology etc.).

1.2. One frequency for everything
Not everyone runs at 2.4 GHz. There are wireless technologies running at 433MHz, 900MHz, 2.4GHz, 868MHz etc. and even those that are running at the same frequency may not be compatible (ex. Bluetooth and ZigBee). Each frequency has advantages and disadvantages, ranging from throughput, interference resistance, penetration through different materials, worldwide or local acceptance, licensing etc. So there is no one frequency that suits every need.

1.3. A power amplifier cures all woes (or range matters)
Longer range seems to be a good marketing tool. However, does someone really need a thermostat that can transmit signals over 1000 meters? There are some applications where long range helps (for example, monitoring moisture in large open fields) and there are others where it is not necessary. Putting on the most powerful power-amp won't help your battery life and it may be overkill if you only need to communicate 10's of meters away. It's also not the best solution to overcoming interference since it just overpowers the other signals (causing interference for the other devices). So there's a lot more to RF design than more power.

1.4. 802.15.4 and ZigBee are one and the same
This is a misconception only because of ZigBee's popularity. It's become synonymous with 2.4GHz and 802.15.4. 802.15.4 is the IEEE standard that ZigBee runs on top of (i.e. the physical layer). As defined by wikipedia: ZigBee is a published specification set of high level communication protocols. The ZigBee Alliance defined what messages are transmitted over the air.

So there's a short list of some of the misconceptions out there. If you have any that you would like cleared up feel free to add to this section and I will try to clarify them for you.

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