ZigBee: Untethered and Unlicensed 173
Chapter 12
Table 12-1. Incidentally, task group 1 has undertaken effort to produce a WPAN stand-
ard based upon Bluetooth (v1.1) and in a similar manner to ZigBee the specification
merely covers the PHY and MAC layers.
In our earlier introduction we mentioned that the new revision of the ZigBee
specification (v1.1) will take advantage of the modifications that were made to the
original 802.15.4 specification. You may often see this specification being referred to
as 802.15.4-2003, which represents the year in which the specification was released.
It may be evident that task group 4 is involved in defining the future of this standard.
Within this task group there are further modifications that have been made to the
original 802.15.4 specification. ZigBee v1.1 will take advantage of the 802.15.4b set
of revisions which were specifically commissioned to clarify ambiguities within the
802.15.4-2003 specification. It is expected that the release of the 802.15.4b will coin-
cide with the new release of the ZigBee (v1.1) specification.
The ZigBee Protocol Stack
The ZigBee Alliance has generated several profile specifications that afford the generic
foundation upon which you can create ZigBee-specific applications. In a similar
manner to Bluetooth wireless technology, ZigBee profiles prescribe core use cases or
applications that utilize the ZigBee protocol stack. The core profiles extend to common
functionality, that is, marketed for home, commercial and plant use, but uniquely the
stack provides scalability in that developers can create their own profiles to suit their
particular application. The application will fall into one of the basic profiles as defined
in Table 12.2, which encourage interoperability between ZigBee-enabled devices, very
similar to the Bluetooth strategy. More specifically, a ZigBee network may comprise
several profile types, which collectively form the basis of a distributed application.
Group WPAN Domain
1 Bluetooth
2 Coexistence
3 High data rate
4 Low data rate
5 Mesh networking
Table 12.1 The five task groups within the 802.15 working group that specializes in a
particular wireless personal-area network domain
174 Developing Practical Wireless Applications
For example, a switch on one node will communicate with a light on another node,
in turn, they collectively form a simple light switch (on/off) application. Additionally,
the manufacturer of the switch may differ to that of the manufacturer of the light and,
as such, the profiles assure us of successful interoperation. In creating your own pro-
files, you must inform the ZigBee Alliance who will issue you a profile identifier where
the developer must further define the device descriptions, cluster identifiers and service
types. The profiles for home, commercial and plant have already been defined along
with their respective device descriptions, cluster identifiers and service types.
Understanding the application context
A device descriptor is used to describe the types of devices that a ZigBee-enabled
device is capable of supporting in addition to defining specific data attributes, which
may relate to input/output streams and how such data should be formatted. These
specific attributes can be grouped into clusters which too have their own unique iden-
tifies. It is the characterization of these device descriptors and clusters which uniquely
creates the behavior of a profile. The ability to communicate data between nodes is
achieved using service types; the Key Value Pair (KVP) service is used to provide a basic
command/control mechanism between nodes. The Message (MSG) service type is a
little more dynamic in that it uses the underlying KVP service as the transport mech-
anism to transfer data between nodes, but the payload can be application-specific and
left to the discretion of the developer.
The ZigBee protocol stack, as illustrated in Figure 12.4 comprises several layers,
which conform to the OSI model as we illustrated earlier in Figure 12.3. The stack is
an eclectic number of layers, which are provided by a number of suppliers. For exam-
ple, the PHY and MAC layers are defined by IEEE 802.15.4, whereas the NWK layer,
Application Support Sub-layer (APS), the ZigBee Device Object (ZDO) and Application
Identifier Profile
0 × 00 Network related
0 × 01 Home control
0 × 02 Commercial
0 × 03 Plant control
Table 12.2 A number of stack profile identifiers that may be used within a payload to
specifically identify the profile in operation

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