A Few FAQ’s about ZigBee

“There are people and there are technologies, people are the people who actually make those technologies happen. “

Oh well, that is just a quotation , you can disagree with it. For what is more important is this new standard world is calling ZigBee nowadays. I am going to try to break the whole topic up in some questions, do let me know how does it feel like at gopchandani@gmail.com

Anyway, the first one is:

Q. What exactly is ZigBee?

A. ZigBee is the commercial name for IEEE 802.15.4 standard, analogous to Wi-Fi for 802.11. But it is not just the name which has changed. ZigBee brings in a few “additions” on the “top” of IEEE 802.15.4 standard stack. Anyway, both of them are meant to define a Wireless Personal Area Network (W-PANs) for devices that could communicate using a Ad-Hoc wireless network using low-power radios. Now, there comes in another one:

Q. We had Wi-Fi and Bluetooth, Why is ZigBee so important?

A. Wi-Fi is the standard for Wireless Ethernet, Bluetooth is for PANs but what makes ZigBee distinguished is its ability to save precious power on the mobile device which is one of the major engineering challenges. As the technology is getting integrated and mobile, we need more and more facilities on the go, but the science of batteries is unfortunately unable to cope up with the increasing demand of consumption we are having, so we need technologies that have guts to do it all but with little power consumption. Wi-Fi and Bluetooth both consume an enormous power and there are applications where we simply do not need that much of data-rates and that is exactly where ZigBee comes in the game. So:

Q. What are the possible applications of ZigBee?

A. Call this a law or anything, there is a trade-off between the data-rate requirements and power specifications of a system. We have applications like:

Home/Building Automation
Wireless Survillence
Traffic Control and Management
Industrial Control and Monitoring
Environmental Monitoring
Medical Sensing and Monitoring

which can be enormously benefited by ZigBee. For example we could have a ZigBee transceiver embedded in a every electrical device in a building and also a remote control carried by user. All these ZigBee “nodes” can then form a mesh network of their own – on the go – and give the user complete control on every device’s function. This network would be extensible and would require very less deployment time and would simply eliminate the “classic” style of having electrical switches in our building. This network is also completely portable and can “talk” to another ZigBee network because they all understand the same protocols.

The same scenario can be repeated for all the applications presented above. ZigBee can be extensively used in Wireless Sensor Networks and these transceivers can be combined embedded “intelligence” in form of micro-controllers to make these network even more intelligent. And all this is not about future, it is already happening around us.

Q. So, What does it have be engineered?

A. ZigBee works in ISM (Instrumentation Scientific and Medical) band of 2.4 GHz radio frequencies in Pakistan and most of the countries in world (except for Europe and US who use 868 MHz and 915 MHz respectively for ISM). Since it is an unlicensed band, it makes ZigBee both cheap to be used because there are no spectrum charges and prone to interference from other electronic devices like intercoms and even Wi-Fi. But, ZigBee has been designed to cope with these disturbances and can offer maximum data rates of 250 Kbits/s up to a maximum range of 10-75 meters.

ZigBee does it all by using Direct Sequence Spread Spectrum modulation which implies that it makes up CHIPs of data which is usually larger in size for every bit of information and transmits them on a larger band of frequencies. Effectively, it consumes more bandwidth but it tends provide higher throughput by using a variety of techniques like orthogonality and makes ZigBee more interference prone.

For Medium Access Control (MAC) for every node , ZigBee employs CSMA-CA (Carrier Sense Multiple Access, Collision Avoidance) scheme. That is, every ZigBee node first “senses” for the presence of an on-going transmission in the medium, if it finds a transmission going on, it delays its transmission for a pseudo-random interval and transmits otherwise. This technique has proved very efficient and provides somewhat less greedy approach to nodes for spectrum usage.

Q. Where is this all heading towards?

A. The Wireless Sensor Networks are highly researched field around the world. They form the basic blocks of what is called Ubiquitous Computing – the concept of embedding intelligence in “everything” and making everything connected. ZigBee is the stepping stone towards the concept and further enhancements are expected in the time to come. So let’s keep our fingers crossed for enjoying the very best of technology, because that is really what it is all about.

Q. What if I want a better scoop of ZigBee?

A. Visit Wikipedia’s ZigBee page and ZigBee Alliance’ homepage for getting wholesome information of topics relating to ZigBee. These two sites are also a primitive motivation for most of the content presented in this article.