Constrained Application Protocol Profile for Robust Header Compression Framework

Due to the extensive growth of Internet of Things (IoT), the number of wireless devices connected to the Internet is increasing and will continue to increase remarkably in the near future. In wireless networks, the available bandwidth is always restricted. Much of the bandwidth is consumed by protocol overheads, while the actual data payload may be only couple of bytes. In this paper, we propose to use header compression to minimize the protocol overhead, especially for IoT-based communication using the new lightweight Constrained Application Protocol (CoAP). We define a CoAP compression profile for Robust Header Compression (ROHC) framework and evaluate its performance in the name of compressed packet size, delay caused by the compression and decompression, behavior in (wireless) lossy links, and energy efficiency. In our tests, the packet size could be reduced by 91.2% at best by using the proposed header compression. The round-trip delay increased slightly due to the extra processing needed for compression and decompression; however in lossy links with bit error rates ≥ 10−3 the smaller packet size due to the header compression turned out to be extremely beneficial due to the smaller need for packet retransmissions. In single packet transaction in our test bed, the header compression increased the energy consumption by 2.5%. However, in lossy links energy may be saved due to the smaller need for packet retransmissions. Other possible scenarios for energy savings were also identified as future work items. Keywords–Constrained Application Protocol (CoAP); Robust Header Compression (ROHC); delay; energy efficiency.