Microwave Engineering Europe - January/February 2008 - (Page 22)

22 WIRELESS SENSOR NETWORKS — ZigBee of application-level communications between node pairs through the use of individual “link keys”. While this is also optional in the ZigBee Feature Set as well the earlier 2006 ZigBee speciﬁcation, it is expected to be more widely deployed going forward. This allows speciﬁc node-to-node application level data to be protected from other nodes in the network. This is important for the collection of potentially sensitive private data or the validation of potentially disruptive commands. The security enhancements in ZigBee PRO are also important to providing secure basic network operation. For example, certain types of ZigBee nodes can “sleep” (power down for a period of time to conserve power use), and hence miss a “change network key” message from the security Trust Center. When a sleeping device wakes up, it will try to communicate with the network using its old network key, and will be unable to participate in the network. ZigBee PRO provides the ability for the newly awoken node to use a speciﬁc link key to encrypt a message that validates itself with the Trust Center and gets the new network key in a similarly encrypted message. Otherwise, the validation message and network key would need to be sent “in the clear”, potentially compromising the security of the overall network. These same mechanisms can be used to wirelessly commission (i.e. conﬁgure for use) individual devices securely, never requiring important data to be transmitted without some level of encrypted protection. The High Security mode provided in ZigBee PRO adds some further protections for device authentication and key management and distribution, including the use of the SKKE. This mode also provides some additional protections against security replay attacks. The additional security capabilities inherent in ZigBee PRO are critical as ZigBee is used in increasingly important applications. The control of critical systems infrastructure, whether in a commercial building, utility grid, industrial plant, or a home security system must not be compromised. Improved ease-of-use and operation The ZigBee PRO Feature Set also provides some additional features that simplify the use and deployment of ZigBee applications. One feature (also available optionally in the base ZigBee Feature Set), is Fragmentation. The IEEE 802.15.4 deﬁnes a maximum packet size of 128 bytes, which is optimum for short, efﬁcient control and sensor data messaging. However, there may be times where an application desires to send a larger message. ZigBee now provides a means for the stack to automatically fragment a larger message into smaller ZigBee packets and reassemble the message at the receiving node, relieving the application of this task. Commissioning a ZigBee network (like any control network), refers to the task of conﬁguring the individual control or sensor devices with the information they need to perform the desired function. This information may include: what network to join, what ZigBee Feature Set is in use, provision of security keys, and establishing command/ control binding relationships (i.e. what lights a given switch turns on or off). Commissioning typically takes place using a dedicated tool (laptop, PDA, etc.) or through a physical interface on the device (perhaps a simple button). The updated ZigBee speciﬁcation provides a new “Commissioning Cluster” that standardizes command sets for usual conﬁguration parameters. ZigBee PRO, with its additional security capabilities, allows this commissioning to be performed in a secure manner. When to use the ZigBee PRO Feature Set? The additional capabilities provided by the ZigBee PRO Feature Set are useful in ZigBee networks of any size, but are especially useful in relatively large networks (30-50 nodes or more) that will especially beneﬁt from the new scalability features. The use of security with sleeping devices should also drive the use of ZigBee PRO, as the new security functions allow devices to easily rejoin the network if a network key update is missed during sleep. Developers should also consider the stack functions required by the relevant standard Application Proﬁle for their design. The newly released Home Automation proﬁle can be used with either the ZigBee or ZigBee PRO feature sets, however most applications will likely desire the scalability offered by ZigBee PRO. Future Application Proﬁles may require or strongly desire the use of functions only available in the ZigBee PRO feature set, so developers in other application areas, such as advanced metering or building automation, should be watching these developments. The ZigBee PRO Feature Set: More of a good thing The ZigBee PRO Feature Set incorporates the learning of several years of ZigBee success. The improved scalability, resiliency, security, and ease-of-use of the ZigBee PRO Feature Set add to the foundation of a very capable, robust, and stable multi-vendor standard for even the most demanding wireless control networks. About the author Bob Gohn has over 20 years experience working in both semiconductor and networking equipment companies. Bob has held a number of marketing and engineering positions at companies including Freescale, C-Port, 3Com, Standard Microsystems Corporation, Raycom Systems, Netways, and Hazeltine. Company Information Ember Corporation www.ember.com MICROWAVE ENGINEERING EUROPE Free subscription at: www.mwee.com/subscribe Microwave Engineering Europe ● January/February 2008 ● www.mwee.com 019_020_021_022_MWEE.indd 22 24/01/08 11:14:43 http://www.ember.com http://www.mwee.com/subscribe http://www.mwee.com

Table of Contents Feed for the Digital Edition of Microwave Engineering Europe - January/February 2008

Microwave Engineering Europe - January/February 2008 Contents News Comment Radio: Raising the Bar for the Radio: Making 802.11n Work Cover Feature: The RF-System-In-Package Trend - Efficient Design with Advanced Design System 2008 Wireless Sensor Networks: The Zigbee PRO Feature Set: More of a Good Thing Very Fast Measurements of Wireless Devices with Small Antennas in Reverberation Chambers WiMAX Update 2008 Bridging the Gap from the CMOS DSP to the Antenna in OFDM Systems Products Calendar

Microwave Engineering Europe - January/February 2008

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