Chapter 9 - ZigBee Gateways

Abstract

This chapter explains how gateways work in ZigBee, and describes some common pitfalls when deploying them in the field. A ZigBee gateway is a means of transferring data between a ZigBee network and devices on another network. One simple application of a gateway that interacts with ZigBee is the automatic printing of a list each morning of all the battery-operated ZigBee devices with low battery charge. For a large network, with many thousands of nodes, this can be a huge time and cost-saver for the maintenance personnel. The ZigBee Alliance is continuing to improve the technology, but gateways have not yet been standardized. The advantage of Island Controller technique is that very few routes are needed to support very large networks from a single gateway. The disadvantage is that a human must plan the network and determine which nodes will be Island Controllers. Planning of this nature typically takes place in commercial buildings. Another disadvantage is that the receiving node can't tell who sent the packet, as the packet appears to come from the last Island Controller. Commissioning can make sure the data is sent to the proper gateway. 2.4 GHz 802.15.4 radios communicate at 250 kbps (kilobits per second). This is considered the maximum bandwidth of any given radio. For determining average bandwidth available for applications, one needs to consider the interferers, density of the network, ZigBee protocol overhead, and communication patterns.