How does ZigBee fit into a home network?
Taking a look at the type of data that circulates within a PAN, we find that most of it is small packets that control devices or obtain their status. Wireless sensor applications, such as wireless smoke and CO2 detectors, or wireless home security systems, stay in deep-sleep mode and only send short bursts of information if a trigger event occurs. The main requirements for devices in these networks are extremely low power consumption, the ability to sleep for a long time, simplicity, and low cost.

ZigBee offers all of these. Its low power consumption means ZigBee can run for years on inexpensive, off-the-shelf batteries. ZigBee devices offer a great potential for energy conservation, as there's no need for them to be plugged into electrical power.

A home network should support different topologies, such as a star or mesh network, to effectively cover a household and its appliances. Another major advantage of ZigBee is its ability to form a mesh network so a garage door opener, sprinkler system, security system, and television can all join the same ad hoc network and be controlled by one device. A ZigBee network is capable of supporting up to 254 client nodes, plus one master device. The standard operates in sub-1Ghz and 2.45Ghz bands with a range of up to 75 meters.

A typical ZigBee-enabled device includes an RFIC (Radio Frequency Integrated Circuit) with a partially implemented PHY (physical layer) connected to a low-power, low-voltage 8-bit microcontroller. This connects peripherals to an application sensor or actuators.

The protocol stack and application firmware reside on flash memory integrated into the chip. The stack requires about 4 kilobytes of the memory. Full implementation of the protocol stack takes less than 32 kilobytes of memory. The network coordinator may require extra RAM for a node device's database and for transaction and pairing tables.

The 802.15.4 standard defines 26 primitives, or system instructions, for the PHY and MAC (Mandatory Access Control) layers, and dozens of others can be added. Those numbers are still modest compared to 131 primitives defined for Bluetooth, but such a compact footprint enables you to run ZigBee on a simple 8-bit microcontroller, such as an HC08- or 8051-based processor core for efficient signal conversion.

How is the market responding?
With ZigBee's integrated chipsets and radios dramatically dropping in price over the next few years, leading electronic manufacturers, such as Samsung and Motorola, are quickly integrating the technology into their home electronics products. The rapid integration means ZigBee could easily become a common household name. Manufacturers such as C-guys, Chipcon and Freescale already offer ZigBee-complaint platforms, with C-guys leading the way with the first ZigBee SDIO card for PDAs and handhelds. It's important for these manufacturers to provide consumers with devices that allow for universal connectivity amongst machines from various OEMs (Original Equipment Manufacturers).

It's ultimately up to the consumer to decide the fate of this new wireless technology. Being able to turn on your indoor lights, television, close your curtains and pre-heat your oven from your car on the way home from work is pretty cool.

Dr. Hiroshi Ide is Director of Product Research and Development for C-guys and has 15 years of experience in the technology industry. Dr. Ide graduated from Iowa State University with a doctorate degree in mechanical engineering.