Pick the right wireless sensor/controller for your connected MCU-based design
Different protocols offer different capabilities. Consider various options for radios conforming to IEEE 802.15.4 and how the selection of the protocol stack can influence the overall system. The protocol options are:
* 6loWPAN
* TI SimpliciTI
* Microchip MIWI
* Zigbee
The 6loWPAN/IPv6 solution offers adhoc network configuration and the best long term prospects while SimpliciTI and MiWi are fully operational today but proprietary. Zigbee has a large following and specialized subsets have been completed for specific applications. Only time will tell which protocol dominates for a given application; however, by understanding the needs of users for your particular application, a wise protocol selection is possible.
All these protocols can do the job for most applications but which protocol will dominate for which specific application? 6loWPAN will become the most widely used with IPv6 compatibility and lower cost. The other protocols will be around for many years and may dominate specific applications or segments.
A further protocol consideration is making sure that you have the right end of the protocol selected. Often protocols come in separate client and server versions: for example a web browser (http requests) and a web server (http responses). This may seem like an obvious observation, but with the myriad of protocols in use it is difficult to keep all the aspects of all protocols in a coherent picture and it should always be double checked.
If you consider a wireless web server design, what would the best underlying transport protocol be? Clearly, IP is required for a web service; however, the wireless connection could be provided by Bluetooth, WiFi or 6loWPAN with an 802.15.4 radio. A simple application of the second rule shows that data rate would be poor with 802.15.4 and that WiFi would provide the best data rate. In comparison Bluetooth offers lower power consumption with good bandwidth. The decision gets more complex though because the radio module becomes important as a part of the design decision.
Most designers choose to include a wireless module in their design. This eliminates the need for telecommunications certifications and also eliminates the need for antenna design in most cases. Unless volumes exceed 50K units, this is generally the lowest cost approach. Given that most designers will use a module, certain restrictions exist depending on the module selection that limit flexibility, increase module costs and may lead to unexpected development costs. Again, careful attention to the protocols and the application are required.
Migrating your wireless protocol implementation onto wireless chips and modules you lock your application to the vendor’s module or chip. The perception is that implementation time and cost will be reduced because the protocol implementation is already done; however, this is often not the case in the longer term. The apparent short term benefit often turns into a medium or longer term limitation, or worse still, a near term system limitation that can endanger the entire design.
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