Two standards are emerging for wireless network topologies that address the International Organization for Standardization’s (ISO) Open Systems Interconnect (OSI) seven-layer network model. The IEEE 802.15.4 specification defines the physical (PHY), media access control (MAC) and data link layers, while the ZigBee specification defines the network, security and application interface layers. Layer seven, the application layer, is defined by the customer. IEEE 802.15.4 offers a choice of three alternate PHY layers, dependent on geographic deployment—915 MHz in the Americas, 868 MHz in Europe, and 2.4 GHz global.
The development of these two standards promotes tight integration of the wireless network hardware and software components to support:
• Acknowledgement-based communications
• Guaranteed time slots with dedicated bandwidth for high-priority nodes
• Data integrity with 16-bit error checking
• Packet freshness timers
• Management of data encryption options (up to 128-bit)
• Multiple topologies, including star, mesh, and hybrid star/mesh
• Application profiles for interoperability.
ZigBee-ready
While 802.15.4 specifies the fundamental RF characteristics of the wireless network, the ZigBee Alliance is defining standards for reliable, cost-effective, low-power applications in wireless monitoring and control. ZigBee Alliance members include five promoter companies—Honeywell, Invensys, Mitsubishi, Motorola and Philips—as well as wireless IP providers, original equipment manufacturers and leading semiconductor manufacturers, such as AMI Semiconductor and Intel.
An early 2003 research report from West Technology Research Solutions (WTRS), based in Mountain View, Calif., estimates the overall ZigBee component market will reach $1.7 billion by 2007. Markets served include home and building automation, utilities, industrial automation and remote control toys. By 2006, according to the research firm, annual shipments for the industrial automation market alone will exceed 90 million units. Says Kirsten West, a principal at WTRS, “ZigBee’s low cost, low power consumption, long range, small form factor and standardization make it exceptionally appealing to remote control and automation applications.”
Helicomm inc .)是第一个市场之一ZigBee-ready wireless solution. Based in Carlsbad, Calif., the company was founded in 2001 to create wireless products built on the IEEE 802.15.4 and ZigBee standards. Says Helicomm president, Jack Sun, “We provide an end-to-end wireless networking solution so our customers can bring the best products to market in the shortest period of time.” The company’s ZigBee-Ready Starter Bundle, priced at $10,000, includes communication modules, network gateways, wireless security, configuration utilities, development tools, services, training and technical support.
See the story that goes with this sidebar: Networks create low-cost sensor links
