Zigbee as a Wireless Interface

Maco Lighting has chosen a wireless interface based on the Zigbee standard. Zigbee offers a number of advantages over other wireless technologies. In particular Zigbee is superior in terms of cost, robustness and power usage.

Self Forming and Self Healing Network

The Zigbee standard allows nodes in a network to adjust their communication paths on the fly to increase robustness. As new nodes are installed they automatically connect to existing networks. This reduces the effort required to set up a new network or add extra nodes to a new network.

This also means that if a node becomes damaged or otherwise unable to communicate, links to that node can be rerouted so that other nodes on the network do not lose connectivity. This happens automatically without the network needing to be reconfigured.

Non-Interfering

Zigbee adheres to the IEE 802.15.4 standard and uses the recognised 2.4GHz industrial, scientific and medical (ISM) band. ISM bands are reserved and used for license-free communications. Because the bands are expected to have other signals in nearby channels any communications protocols using them, including Zigbee, are designed to be tolerant of interference. Some other bands are only reserved for general use in certain countries and can be used elsewhere for more regulated use.

While the 2.4GHz band is commonly used for other applications, such as wireless networking, Zigbee networks can operate within the upper channels that are not used by WiFi network devices. Only channels 1-13 are available to wireless networks. Often these are further restricted to only channels 1,6 and 11. Because Zigbee is a low bandwidth protocol, the 802.15.4 standard allows the use of the higher frequency channels 14 - 16 as well as the normal 1 - 13.

Maco Lighting decided to use 2.4GHz as it poses less risk of interference with expensive medical and scientific equipment that mainly use the 900mhz range, which is a high concern for some university and medical institutions.

Standard Signal Equipment

Because Zigbee operates within the standard 2.4GHz band it uses easily available boosters and antennas. This reduces the final cost of the product and also increases the overall performance of the entire network.

Security

While neither IEEE 802.15.4 or the Zigbee standard specifies a particular encryption method they both support implementation specific encryption. Maco Lighting has chosen 128-bit AES encryption to secure the wireless communication. 128-bit AES encryption has been approved by the NSA for protection of SECRET level information.