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After many months of development and testing, the ZigBee Alliance announced last month the formal approval of comprehensive new features for the ZigBee specification. Developers now have the choice of two “Feature Sets” within the specification: the original features published in 2006, now known as the ZigBee Feature Set, and a set of new enhanced features aimed at greater scalability, ease-of-use, and robustness, known as the ZigBee PRO Feature Set. The finalization of the ZigBee PRO Feature Set had been widely anticipated by many in the industry, and is the culmination of a rigorous process that leveraged the collective multi-vendor experience gained by successful wide-spread ZigBee deployments.  This represents a significant milestone for all those leveraging ZigBee technology.

The ZigBee PRO Feature Set enables improved scalability and robustness through many new capabilities, some of which include:

• Stochastic Address Assignment with automatic conflict detection and resolution, eliminating the tree-based address assignment algorithms that required readdressing of nodes when joining a new parent. This delivers simpler network formation and operation, and improved stability in larger networks (>30-50 nodes).
• Asymmetric Link Handling, which takes into account that the RF connectivity between two devices may be better in one direction than the other. By intelligently avoiding very asymmetric links, more reliable routing and less route re-discovery occurs in the network.
• “Many-to-One” route aggregation and source routing, which enables a single route discovery for all nodes feeding data to a central aggregation point, which is a common ZigBee usage scenario. By using common routes to the aggregation point, and allowing that point to use source routing techniques back to the end nodes, overall route table density discovery broadcasts are greatly reduced, offering greater network scalability and robustness. Frequency Agility, which allows the network to monitor and detect interference and move the network to a different channel if desired.

Other enhancements include new security capabilities, multicast options, and fragmentation (allowing larger messages to automatically be divided up among the smaller 15.4 packets). These new ZigBee PRO features solidify ZigBee’s place as the most proven, complete, capable, and robust standard for wireless sensing and control networks.  With these enhancements, the major work on the ZigBee specification is considered complete. The ZigBee Alliance is now shifting it’s attention to expanding the public application profiles in areas where ZigBee is experiencing it’s greatest growth, including Home Automation, Advanced Metering Infrastructure (AMI), Commercial Building Automation, and other segments.

One thing to keep in mind about high RAM concentrators is that nodes communicating with it will continue to send in the route record packet with every inbound message until they receive their first source-routed packet from the concentrator that uses that recorded route. This source routed packet is what tells the node that the source route worked. The APS acknowledgement, if these are turned on, will count as this source routed packet. Also, this route-record suppression is even true for messages routed through this node. Thus, if outlier A sends to concentrator C via many-to-one route A-B-C, the first source routed message from C to B to A will cause B (and A) to stop sending route records up to the concentrator. Please note, that if the concentrator is also the trust center, communication with the trust center will always be as if it were a low ram concentrator, so route records will always be sent in this case.