ZigBee: Untethered and Unlicensed 177
Chapter 12
at the NWK layer the application-specific data needs to move up and down the stack
and there are service entities that ensure the NWK layer interfaces appropriately with
the APL. In a similar manner to the APS, the NWK layer data entity (NLDE) sup-
ports a data service through a service access point (NLDE-SAP) and, of course, the ME
integrally manages the intercommunication mechanism (NLME) and its associated
service access point (NLME-SAP). Again, the whole data exchange is managed by a
database and in this instance the managed objects are located in a network information
base (NIB). More specifically, the NLDE transports application-specific PDUs
(APDUs) between connected devices on the same network and provides services for
the generation of a NWK layer PDU (referred to as an NPDU).
In light of the numerous technologies that are already competing with ZigBee it is
hard to imagine that ZigBee will establish successful and fruitful market dominance.
Likewise, its longevity is in doubt, as the initial pioneers seem to be moving on to ful-
fill other objectives. Although fatalistically, ZigBee has suffered a similar destination
to that of Bluetooth, it has found a niche market, a unique application. Bluetooth has
found a marriage between cell phones and headsets and ZigBee seems to have had
moderate success within the lighting arena. It really is a niche and with ZigBee being
implemented within this domain we can easily forget that its there. We are reminded
of that elusive killer application, but perhaps sadly, the only killing spree that will be
endured here is the demise of ZigBee itself. It is hard to imagine where exactly ZigBee
will fit in to the existing genre of wireless technologies, as we have already highlighted,
other wireless technologies have succeeded. From a Developing Practical Wireless
Applications perspective, it is really difficult to gauge where ZigBee will succeed: small
toys and such, no-one really knows; lighting, home control, automation: still not sure,
as everyone has had an opportunity at developing the smart home. Should we play
devil’s advocate here: does anyone care?
The ZigBee Alliance ratified its standard wireless technology (v1.0) in December
2004 and made it public in June 2005.
The Alliance is now finalizing v1.1, which takes advantage of the enhancements
that were made to the original 802.15.4 specification.
The new revision of the specification will be available at the end of 2006, start of
2007, but it is unclear as to who will be watching this damp squib.
ZigBee seems to lack a basic feature set that so many other wireless technologies
offer as a founding step forward.
It seems that a significant number of the initial promoter companies are already
abandoning ship; it really doesnt bode well for the future of ZigBee.
The technology itself received an ambivalent response from manufacturers and
the press alike, and its acceptance still remains somewhat muted.
Many have argued that the need for the technology is futile, in the wake of other
well-established technologies such as Bluetooth, Z-Wave and WiFi.
Bluetooth Lite, a would-be derivative of the original specification, with its prom-
ised optimized Media Access Controller (MAC) should have naturally made ZigBee
a regrettable mistake.
The momentum behind Bluetooth Lite wavered and disinterest dominated the
rigmarole of enduring yet another spat at defining a new technology.
With more cost effective solutions for WiFi and a decrease in power consumption,
WiFi at first glance appears to be a more obvious choice.
Alas, WiFi is quite simply overkill for these types of applications such as toys,
monitoring, control and so on; not just in terms of its data throughput, but more-
over its application (software) base.
There is a considerable overlap between ZigBee and Z-Wave (ZenSys).
Zensys withdrew its support from the Alliance and essentially formed their own
Z-Wave Alliance group.
There isnt a great difference between the two technology solutions.
Zensys has a clear advantage, as it has already established within the market a large
consumer base of home control and automation products.
ZigBee has yet to do this.
Z-Wave is increasingly being seen as the de facto standard for wireless home
control and automation solutions.
The ZigBee Alliance has persevered and released their initial specification for the
technology world to see and it continues to evolve the technology.
ZigBees inception is derived from a notion of simplicity.
When we compare other standards-based wireless technologies, they tend to be
larger, in software and hardware implementation terms, and consume more
The foundation on which ZigBee is derived is a cost effective wireless model that
the ZigBee Alliance hopes will become a de facto standard.
ZigBees topology, Z-Wave is essentially a simple one to understand.
178 Developing Practical Wireless Applications

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