This memo discusses the use of the Constrained Application Protocol (CoAP) protocol in building sensors and other devices that employ cellular networks as a communications medium.
Building communicating devices that employ these networks is obviously well known, but this memo focuses specifically on techniques necessary to minimize power consumption. CoAP has many advantages, including being simple to implement; a thousand lines for the entire software above IP layer is plenty for a CoAP-based sensor, for instance.
However, while many of these advantages are obvious and easily obtained, optimizing power consumption remains challenging and requires careful design.
The memo targets primarily 3GPP cellular networks in their 2G, 3G, and LTE variants and their future enhancements, including possible power efficiency improvements at the radio and link layers.
The exact standards or details of the link layer or radios are not relevant for our purposes, however. To be more precise, the material in this memo is suitable for any large-scale, public network that employs point-to-point communications model and radio technology.
Our focus is devices that need to be optimized for power usage, and on devices that employ CoAP. As a general technology, CoAP is similar to HTTP. It can be used in various ways and network entities may take on different roles.
This freedom allows the technology tobe used in efficient and less efficient ways. Some guidance is needed to understand what communication models over CoAP are recommended when low power usage is a critical goal.
The recommendations in this memo should be taken as complementary to device hardware optimization, microelectronics improvements, and further evolution of the underlying link and radio layers.
Further gains in power efficiency can certainly be gained on several fronts; the approach that we take in this memo is to do what can be done at the IP, transport, and application layers to provide the best possible power efficiency.
Application implementors generally have to use the current generation microelectronics, currently available radio networks and standards, and so on. This focus in our memo should by no means be taken as an indication that further evolution in these other areas is unnecessary.
Such evolution is useful, is ongoing, and is generally complementary to the techniques presented in this memo. The evolution of underlying technologies may change what techniques described here are useful for a particular application, however.
To read this external content in full, downlaod the complete memo from the IETF Working Group web page.