802.15.4 vs ZigBee

As it was mentioned before ZigBee standard is the most direct competition for currently developed WBAN standard. It is even more direct as ZigBee is based on previous version of 802.15.4 (from 2003). Since that time a lot has changed thus a new standard is developed.

In this post I will try to answer a question if we should be afraid that success of new implementation will be crippled by ZigBee older brother.

At first it’s important to show how ZigBee is related to its root 802.15.4. As the old 802.15.4 is focused only on mac layer and physical media specification, ZigBee was developed to build on top of that a fully operational network system with necessary functions e.x. security and encryption. This relation can be described in few points:

  • 802.15.4 (2006) was designed to allow point to point energy sufficient communication
  • ZigBee adds on top of that more services: star topology routing, encryption, application services
  • ZigBee creates semi-centralized network. It allows only end devices to sleep (to reduce power but keep the main node waiting for communication)

In case of new version of 802.15.4 the focus was broadened to include this parts as well in the basic standard. Also the additional options for physical layer were defined to allow even better adaptation of final solution to the application.

A table and short description is shown to illustrate differences between both standards.

ZigBee New 802.15.4
Physical medium Narrow band Narrow band, UWB, HBC
Bands ~900MHz ~900Mhz, 3-10Ghz, 16Mhz, 27MHz
Range 10-100m 10m
Bitrate 20,40,250kbps Upto 100mbps (with UWB)
Power consumption Low Low
Typical application Mostly industrial, building monitoring Sensor nodes in WBAN applications
Complexity Low Very low (with HBC)
Security 128AES 128AES

We can see that a new standard has a lot of advantages over ZigBee –mostly it’s better suited for short distance communication on the body surface. It can’t be forgotten that with use of UWB, as it was already shown, new standard is more suited for medical applications:

  • Low interference with medical equipment
  • Lowest possible effect on living tissue

Thus even with so many common roots, these both standards are quite different. It’s possible that with introduction of new 802.15.4 standard, ZigBee will be adapted to be compatible with new version, or the new version finally will add some way of interoperability with ZigBee. That would help to answer the question of who will win in this confrontation. Unfortunately at this stage of standard development it’s hard to determine how it will end.

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8 Responses to 802.15.4 vs ZigBee

  1. vass says:

    hello..
    i have a quenstion to make ..

    is it possible for a node that uses 802.15.4 communication to communicate with a zigbee node? if i send on the channel that the zigbee node hears is it possible to respond??

    thanks..

    • mikuslaw says:

      Hello Vass,
      At the start I have to tell you that the blog was a part of my course at the university, so I’m not the expert in Zigbee. On the other hand I work in the field of embedded systems, so I may have some info for you. As the Zigbee is just the additional layer built on top of 802.15.4, they use the same physical communication – the same frequencies, the same modulation and so on. That means the 802.15.4 would hear Zigbee radio. It could be hard to use the data gathered this way, as Zigbee has a bit more complicated structure of packets. It seems to me that it’s similar to connectivity in the internet- ehternet packet has a data field that is used to keep the IP packet, which has data field that is used to keep for example ICMP packet and so on. Zigbee has more knowledge what data inside a packet that is inside of another packet means. So, if you would like to use a 802.15.4 radio to talk to Zigbee in a standard Zigbee way, you would have to implement the higher layers yourself (it could be hard to do it in software and keep some of the timings if there are any Zigbee requirements in this topic).
      The good news is that some of the Zigbee radios are built in a way that they can operate in two modes – with Zigbee mode and in 802.15.4 mode (at least is looks this way in case of cc2520 from TI http://www.ti.com/product/cc2520 ). In the list of features you can find:
      “APPLICATIONS
      IEEE 802.15.4 systems
      ZigBee® systems”

      The same with Xbee (thus it has to be turned on): http://www.digi.com/support/kbase/kbaseresultdetl?id=2158
      “XBee radios are 802.15.4 and ZigBee network compatible”

      I would assume that the cost of making the new chip for the Zigbee communication is so high that it would be stupid to limit it’s compatibility with existing 802.15.4 networks as it already would contain all the necessary features. Of course the best way would be to check the datasheet of the Zigbee chip you have, or the one that you are planning to use and make sure.
      What do you want to use, and what for?

      • vass says:

        Thanks for the quick reply Mikuslaw..

        the reason i made the quenstion is beacause i am practising on a project that requires the communication between an arduino and a plogg device(what is plogg device: http://www.plogginternational.com/ ) .. this device creates a zigbee network and sends the results to a usb stick on the pc..my job is to replace the stick with an arduino and get the results there.. the problem is that i use Xbee xb24 that creates a 802.15.4 network not a zigbee one so i am not sure if i am able to get them communicate each other..the good thing is that i configured the xbee to operate on the same channel as plogg(channel 11)..

        i tried also with another Xbee model(Xbee xb24-b) that creates a zigbee network but the default channel that can operate is different from the channel that plogg transmits and receives and is assigned as read only..

        sorry for my english i hope i made u understand what i am talking about.. 🙂

  2. mikuslaw says:

    I would assume that you need a Xbee that can operate in mesh network, but I’m rather limited in this scope. According to http://forums.digi.com/support/forum/viewthread_thread,9385 and http://stackoverflow.com/questions/5382666/how-do-you-set-the-channel-on-a-xbee-pro-series-2 you don’t have to set channels to the same value – the clients should connect to the one that the coordinator will find and use. Sorry that I can’t help you to much, but I have no practical experience with Xbee modules.
    Good luck!

  3. pikachufahd says:

    Hi..
    am making my graduation project it’s a wireless medical body area network ,, am gonna use xbee 802.15.2 ,but i didn’t use it before ,, so could u tell me how to program it with a PIC plz..

    • mikuslaw says:

      It is hard to tell you anything when you are so unspecific. I assume that each radio chip will have it’s own way of communicating/it’s own register’s set etc. The only way you are going to know how to “program” a given radio chip is to study (and study hard) the datasheet of that device. You can also find some examples of use for the chips of major companies.
      I can’t help you too much when you don’t give any specific information and even if you did, I wouldn’t have time to do the job for you.
      The first google search: http://hades.mech.northwestern.edu/index.php/XBee_radio_communication_between_PICs
      Btw is there any difference between 802.15.4 and 802.15.2 other then range? It was ages age when I read about this.

  4. snehal says:

    HI
    I want what is the diffrence in between zigbee & 802.15.4.which one is the best used for the patient monitoring system/

    • mikuslaw says:

      Hi,
      you ask the question that has no easy answer. If you wish to decide on the best radio for you application you should first define your requirements (range, cost, size, the environment in which it will work, the bandwidth, power consumption and many more factors). To get the good answer, try to approach the problem as an engineer and based on information that you will gather make an informed decision.
      I would first read this: http://pages.cs.wisc.edu/~suman/courses/838/papers/zigbee.pdf

      The biggest difference between 802.15.4 and ZigBee is that ZigBee adds routing layer to the 802.15.4 MAC and LLC (so basically it is the same radio, but with mesh network realized in software stack). If you wish to make the monitoring work in mesh then probably go with ZigBee, if mesh is not what you are looking for (or you want to realize it yourself) go with 802.15.4 (if the other factors like price works in favor of this choice). As I said – this choice requires some work on your side.

      Cheers.

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