Wireless Personal Area Networks
A significant number of development projects have a wireless component. There are many different wireless technologies available, including Wi-Fi, GSM, RFID, Bluetooth, 2.4G custom protocols and Personal Area Networks. Personal Area Networks use a high level communication protocols to create area networks built from small, low-power digital radio-enabled devices.
Personal Area Networks in particular have been growing in popularity; this is due to a number of factors:
◦ Small form factor
◦ Flexibility
◦ Low power solutions available
◦ Low complexity improves reliability
Personal Area Network Solutions
Among the many providers of Personal Area Network (Wikipedia) solutions are Microchip, Atmel and Texas Instruments; each of which supports a variety of protocols. Some of the protocols available and some we have worked with include:
◦ Microchip: ZigBee and custom MiWi protocol
◦ Atmel: ZigBee and custom ZigBit modules
◦ Texas Instruments: ZigBee, SimpleLink and custom SimpliciTI protocol
Figure 1 – A small, low-power circuit using a Microchip module and MiWi module
Capability Requirements
These protocols and modules encompass a wide range of capabilities and features. When choosing a protocol and module, the key requirements include:
Node Count
Solutions exist which support everything from two to many thousands of networked devices.
The way in which the devices are linked together affects the complexity, latency and reliability of the network. The simplest topology is a peered network, where each device only communicates directly to its neighbours.
Figure 2: Peered Topology
For a larger network, a cluster-tree topology introduces routing, allowing messages to be sent to non-neighbouring devices through established “branches”.
Figure 3: Cluster-Tree topology
While the cluster-tree topology allows for routing, it does not do so in the most efficient way – some messages will be routed all the way down to the base of the tree before being routed back out to the destination. For a more adaptable, reliable and faster network a mesh topology is more suitable. Mesh networking allows each device to freely route along the most direct path.
Figure 4: Mesh topology