By John Maxwell Hobbs
The radio standard Zigbee allows a chip to be powered by a battery for a couple of years. The short range and the small amount of data, combined with the long battery life, provide an ideal solution for locks and security systems. But all systems have flaws, and it is important not to be the one to makes all the mistakes. We take a look at Zigbee to see if it is ready for the security market.
ZigBee is a narrowband radio standard being designed for low power building control devices that require unitnerupted battery operation for many years. ZigBee uses radio technology very similar to WiFi or Bluetooth but operation of the network, controlled by software called the “ZigBee stack”, is much different. One distinguishing benefit is that a ZigBee device continues to be a member of its network even if it is in sleep mode. Devices may sleep in an extremely low-power state for long periods waking to transmit a message only when necessary. The wake up and message transmission occur very quickly and use tiny amounts of energy.
WiFi and Bluetooth networks are limited to a small number of nodes. Bluetooth supports a maximum of seven nodes per network and WiFi supports 32 per base station. Both have relativly small operating ranges as well. ZigBee, however, is designed to support thousands of nodes across large distances. ZigBee provides for a type of device called a “router” that can pass a message on to other routers to reach its destination. Routing extends the range of a device beyond that of a single radio pair by allowing the message to “hop” along a path of several routers. Additional routers can be added to provide alternate paths. If a router has failed or cannot reach the next “hop”, the system provides failure detection and can reroute the message along other paths. This allows a ZigBee network to function as a “mesh,” preventing the blocking of message delivery by a single failure, resulting in much more reliable network.
Current Situation
The building-scale range and small amount of data, combined with long battery life, makes ZigBee an ideal solution for locks and security systems. ZigBee technology could enable communication to a secure door, requiring only batteries for power, by using an ultra-low-power card reader and low energy lock. But ZigBee technology is still relatively immature. The radio and microcontroller hardware is mature and advancing, but the stacks, support tools and profiles are still under development.
"Currently, ZigBee is mature enough for sensor networks," says Michel Noxfeld, an R&D Manager of Interconnectivity Platforms at ASSA ABLOY. "Right now it's not ready for the security market. The hardware and radio system are good because security is built in to the standard, but the stack protocols are not there yet," he says.
Noxfeld points out hat a developers are free to use their own applications on top of ZigBee, "it's up to the application developer to use the proper level of encryption just as with any other communication system, so if a security solution uses only the IEEE part of the ZigBee standard, it can be used today."
Open Standards
The ZigBee standard is being developed by the ZigBee Alliance an association of companies working together to enable reliable, cost-effective, low-power, wirelessly networked, monitoring and control products based on an open global standard. ASSA ABLOY has a corporate membership in the alliance. Despite the relative immaturity of ZigBee, product developments are underway. Several companies within ASSA ABLOY are looking at the possibility of developing wireless products using all or part of ZigBee technology.
"It's an interesting paradox: open standards versus high security," says Noxfeld. "Many people think that open standards can't be secure because they are published, but I don't believe this. Many people do their banking securely on the internet today," he says.
ASSA ABLOY has a policy of working with open standards rather than relying on proprietary solutions. "Because ZigBee is being developed by such a large community it can progress faster than competing technologies," says Noxfeld. "A large community will support a large number of stack implementations and profiles, so it makes the technology more competitive."
"Large companies may soon be using ZigBee for building automation, handling machine control, lights, climate, windows, etc. If they want to integrate that with locks, ZigBee may not be appropriate at this time," explains Noxfeld. "The standard is not mature enough to be integrated with other systems. ASSA ABLOY is not rushing into this yet. Right now, we are doing R&D work looking at ZigBee for access control. Mainly, hands on experiments to learn." Research activities include prototyping a simple access control network to study ZigBee technology in detail, creating development guidelines and assisting companies that are considering or executing ZigBee developments.
"We are definitely going to be part of specifying a profile for commercial building automation as a member of the ZigBee Alliance. It is still possibly one to one and a half years away, but we plan to be part of that activity," he says.