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Abstract
This report investigates an architecture for interconnecting Internet and Zigbee sensor network which is founded on IEEE802.15.4 standard. It presents a web-sensor gateway to deliver data between Internet protocol and Zigbee/IEEE802.15.4 protocol, transparently. It also introduce the common gateway interface (CGI) technology to satisfy users on the web browser to efficiently manage and query the Zigbee sensor network, ubiquitously. Finally, a simulation prototype is proposed.
1. Introduction to Zigbee
Zigbee is a wireless technology developed as an open global standard to address the unique needs of low cost, low power, wireless sensor networks. The standard takes full advantage of the IEEE 802.15.4 physical radio specification. The Zigbee protocol carries all the benefits of the IEEE802.15.4 protocol with added networking functionality. The low cost allows the technology to be widely deployed in wireless control and monitoring applications. In addition, the low power allows longer life with smaller batteries; hence the Zigbee sensor network can provide higher reliability and larger range.
As the Zigbee sensor network is getting much attention in the wireless communications society, research works on web sensor gateway are also getting popular. Recently, more literatures on the Internet-Zigbee gateway are getting produced. The basic functionalities of the gateway are query distribution, data aggregation, and message conversion. From the literatures, it is widely accepted that web-based management should be used for managing and querying the Zigbee sensor network because the Internet provides flexibility and convenience of access. Our research is also motivated by solving the problem of data communication that happens in a Zigbee sensor network and Internet. This report presents a novel Internet-Zigbee gateway architecture that achieves the functions of protocol translation between two different networks. Most of all, we make use of an embedded CGI technology to set up a web server in the gateway so the users on the web browser can visit the Zigbee sensor network through web-sensor gateway
2. Zigbee Protocol Stack
ZigBee, like other communications networks such as Ethernet, IrDA and Bluetooth, divide up the communications tasks into layers on a stack loosely based on the 7-layer Open Systems Interconnection model. At the top is the application that uses the data; at the bottom is the actual transmission medium such as coax, infrared or microwaves. In the middle is all the glue so that applications on different nodes can communicate securely and reliably without needing to know anything’s going on in between, or how the data got from place to place. The ZigBee standard is mostly concerned with the higher layers of the stack; lower layers adopt the
2.1 Physical Layer (PHY):
The PHY layer consists of a half duplex radio transceiver operating at 868MHz, 915MHz or 2.4GHz. 868MHz is license-free in Europe, whereas 915MHz is license-free in North America and Australia. 2.4GHz may be used practically worldwide, and so is expected to dominate in future. It also has the greatest number of channels available.