ZigBee

ZigBee is an industry standard for wireless networks. PHY and MAC layer based on IEEE 802.15.4, which allows household appliances, sensors and many more. short distances to connect (10 to 100 meters). The standard was developed by the ZigBee Alliance, which was founded in late 2002. It is an association of currently more than 230 companies that are driving the global development of this technology. First ZigBee products came on the market in early 2005.

Introduction

ZigBee represents a protocol stack (stack ), based on resources imported in December 2004 standard ( Standard) IEEE 802.15.4 specified OSI PHY and MAC sublayers touches according to the OSI model.

It is (eg battery) provided in hard to reach areas where the replacement of batteries only with great expense for the use of maintenance-free wireless switches and sensors with limited energy supply. The standard features also include a coarse level measurement ( RSSI), which supports the construction of networks.

The ZigBee and IEEE 802.15.4 Standard provide the developer with three different types of devices ( ZigBee devices ) are available. With these devices, the ZigBee Wireless Personal Area Network ( WPAN) is being established. There are three roles that can fulfill a ZigBee device:

Addressing

There is both direct and indirect addressing possible.

In direct addressing nodes and end points of the other side is given. A node ( = a ZigBee module ) can serve multiple endpoints. ( Can operate similar to each computer on the Internet on multiple ports TCP connections ). However, no fixed association between the service and endpoint is provided. ( So do not: Thermostats usually listen on end point 26). Each node represents a maximum of 255 endpoints available, many of which are reserved for special purposes. For application logic the endpoints 1 to 240 are provided. Endpoint 255 is reserved for broadcasts to all endpoints. The end points 241-254 are reserved for future special tasks, endpoint 0 for administrative tasks. There may, for example, query other modules on which are end points to address, for example, thermostats.

In the indirect addressing of the coordinator short addresses (English short address ) awards with a length of 16 bits. When connecting a node to a network he logs in to the coordinator and gets assigned an address. The coordinator sets the short address with the corresponding MAC address in a table in its memory. Want a node to communicate with another, a request is first sent to the coordinator, who forwards it to the recipient node. This information about the logical connection of nodes is called binding. A switch can control in this way, for example, several lamps. The coordinator creates an entry for each logical connection in the binding table. To manage the network is greatly simplified and made more flexible. Functions of new devices to existing devices are replaced by a single Binding quickly added or.

Y2K

The default data types for time values ​​in ZigBee packets are for absolute time stamps to the second and cover the years 2000 to 2187th periods are accurately reflected in milliseconds (0 milliseconds to 49 days).

ZigBee IP

ZigBee IP is the extension of the ZigBee stack for IPv6. The ZigBee Alliance is based in the development of existing protocols from standards bodies such as IETF, IEEE, W3C, ISO and IEC.

The stack uses the network layer ( OSI model network layer), among others, developed by the IETF 6LoWPAN and RPL protocols. The 6LoWPAN protocol allows the connection of devices or sensor networks to the Internet via IPv6 (Internet of Things ).

ZigBee RF4CE

RF4CE is an acronym for radio frequency for consumer electronics.

ZigBee RF4CE is to establish a standard for wireless networking of consumer-friendly devices.

Areas of application

• Industry and automation technology plant control
• Goods monitoring
• Transmitting sensor data

• Patient data transmission

• Consumer electronics (eg, 3D shutter glasses )
• Computer peripherals
• Wireless detectors

In the area of ​​Home Automation and M2M ZigBee is in direct competition with Z -Wave. For both protocols, there are a number OSGi -based framework solutions that involve going beyond the pure log home automation functions, such as a device abstraction layer.

In the area of ​​medical technology is worth mentioning as a rival standard Bluetooth or the specification of the Continua Alliance.

Risks associated with ZigBee

Since the ZigBee standard 2003, only one coordinator is possible, when using Indirect Addressing the failure of the coordinator can compromise the entire network, as it keeps all the routing and device information in volatile memory. The ZigBee network is hierarchically structured and thus has a single point of failure ( SPOF ). However, routers can be configured so that they take over the role of the coordinator in case of error.

Field tests showed greater problem of coexistence of IEEE 802.15.4 with Wi-Fi and Bluetooth in the 2.45 GHz band. With Bluetooth, the introduced since version 1.2 adaptive frequency hopping method proves (English frequency hopping ), which evades Fi, but the remaining frequencies is more common than interferers. Wi-Fi makes by the strong growth in traffic problems. The significance of these results is questioned by the ZigBee Alliance and started by a compatibility study a rebuttal. To avoid the problem of interference, ZigBee offers the possibility to use, instead of the 2.4 GHz band, the 868 MHz band in which the maximum allowed low occupancy times ( less than one percent transmission activity per channel ) for the minimization of potential interference worry.

As a threat, attack possibilities could emerge similar to the WLAN. This ZigBee has many errors that were included in the outdated WEP standard. Decryption of ZigBee Keys is very fast and is already firmly implemented in tools such as Wireshark.