Constrained Application Protocol (CoAP) is a new lightweight application-layer protocol under standardization. It can be thought of as a "lightweight" Hypertext Transfer Protocol (HTTP) that can connect for example low power sensor devices to each other through the Internet. For the sensors using CoAP, a very common behaviour is to send the sensor data to the server periodically, or vice versa, the server (or user) periodically asks for the data value from the sensor. The header part of the packet remains almost constant all the time while only the data part changes. In sensor networks the bandwidth for transmission is very limited, so this is not optimal bandwidth usage. Robust Header Compression (ROHC) is a standardized method to compress IP, UDP, RTP headers of Internet packets. It consists of a compressor and a decompressor located on the ends of a link with limited capacity. Redundant information in packet headers is transmitted only in the first packets; in the next packets, only dynamic header parts are transmitted. Packets are classified into flows to take advantage of inter-packet redundancy. A compression profile defines the rules on how the packet headers are compressed. In this work, we first discuss different compression techniques, and then describe the developed CoAP profile for ROHC. In the tests we studied the compression ability of the developed CoAP profile. The achieved savings for the whole packet were up to 86.5%.
|Number of pages||4|
|Journal||Internet of Things|
|Publication status||Published - 2014|
|MoE publication type||D1 Article in a trade journal|