IEEE 802.15.4 Air Interface and Frequency Bands
- the frequency bands and frequencies used as well as details of the radio or air interface for IEEE 802.15.4.
The IEEE 802.15.4 standard offers many advantages to developers of low power, low cost wireless applications in that it provides a reliable physical layer radio air interface and has defined frequencies and frequency bands which it uses.
The physical layer / air or radio interface allow for data rates that are not high by the standards of other wireless and cellular systems, but the key requirements for most low power, low cost systems are for reliable transfer of small amounts of data. To accommodate these requirements, the radio interface has been kept simple.
IEEE 802.15.4 frequencies and frequency bands
The IEEE 802.15.4 frequency bands align with the licence free radio bands that are available around the globe. Of the bands available, the 2.4 GHz (2 400 MHz) band is the most widely used in view of the fact that it is available globally and this brings many economies of scale.
|Frequency band (MHz)||Channels available||Throughput available (kbps)||Region use allowable|
|868 - 868.6||1||20||Europe|
|902 - 928||10 (2003 rel)
30 (2006 rel)
With new allocations arising as a result of issues such as the digital dividend and other countries adopting and using IEEE 802.15.4, other frequencies and bands are being considered. These include: 314-316 MHz, 430-434 MHz, and 779-787 MHz frequency bands in China and the 950 MHz-956 MHz band in Japan. Other frequencies are also being considered for UWB variants of IEEE 802.15.4.
IEEE 802.15.4 modulation formats
There were two different modulation schemes defined for IEEE 802.15.4 in the original standard released in 2003. Both these air interface or radio interface configurations are based on direct sequence spread spectrum, DSSS techniques. The one for the lower frequency bands provides a lower data rate in view if the smaller channel width, whereas the format used at 2.4 GHz enables data to be transferred at rates up to 250 kbps.
The 2006 release of the 802.15.4 standard upgraded an number of areas of the air interface and the modulation schemes. There were four different physical layers that were defined. Three used the DSS approach using either binary or offset quadrature phase shift keying, BPSK and OQPSK. An optional physical layer approach was defined using amplitude sift keying, ASK.
By Ian Poole
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