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A ZigBee Network
Wireless Attributes:
ZigBee 1.0 networks typically operate in 1 or 2 frequency
ranges depending on the device and location. Table 1 describes
the available frequencies.
|
|
Frequency Band (MHz) |
|
|
868.3 |
902-928 |
2400-2483.5 |
|
# of Channels |
1 |
10 |
16 |
|
Bandwidth (kHz) |
600 |
2000 |
5000 |
|
Data rate (kbps) |
20 |
40 |
250 |
|
Symbol rate (ksps) |
20 |
40 |
62.5 |
|
Unlicensed
Geographic Usage |
Europe |
America (approx) |
Worldwide |
|
Frequency
Stability |
40ppm |
|
|
Table 1 - Frequencies used by ZigBee
Table Source:
http://www.rtcmagazine.com/home/article.php?id=100656&pg=1 (Used without
permission)
In either location (Europe or America) a
ZigBee node may use either or both frequencies. The lower frequencies are
typically referred to as Industrial, Scientific, and Medical (ISM) frequencies.
Network Layout:
Figure 1 - ZigBee Layers
Image Source:
http://ines.zhwin.ch/uploads/pics/zigbee_layer_01.png (Used without
Permission)
The ZigBee networking (NWK) layer, Figure 1 is on top of the IEEE MAC/PHY 802.15.4 implementation. The required functionality to create and
manage mesh networks is provided by the Zigbee network standard. Self-forming
and self-healing networks are possible, especially for remote environments;
alternatively, networks can be completely (or mostly) manually configured for
managed environments.
Many sub-networks can be formed by breaking up networks
physically larger than 2^16 nodes. This process of breaking the physically
larger networks increases ease of use, robustness, and network capacity.
The IEEE 802.15.4 standard specifies two physical types of
devices and three logical types. The Full Function Device (FFD) and the Reduced
Function Device (RFD) are the two physical types. Either of the two devices may
act as a: sensor node, control node or composite device (logical types); but
only an FFD can perform routing tasks for a network. Depending on the location
in a network the FFDs may have child devices for which the router performs
routing functions. Figure 2 below shows a graphical representation of
the connectivity practical in a ZigBee network using 802.15.4 devices.
Figure 2 - A ZigBee Network Layout
Image Source:
http://www.korwin.net/eng/infor/img/images_zb1.gif (Used without Permission)
Related links for this page:
ZigBee via
Wikipedia
ZigBee Alliance
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