Dynamic Context for Static Context Header Compression in LPWANs

Header compression is the key to adapting long header protocols like IPv6 for transmission using short frame size network protocols such as are used in Low Power Wide Area Networks (LPWANs). In LPWANs only one or two octets may be available to transmit upper layer protocol headers, which makes known header compression mechanisms unsuitable. Static Context Header Compression (SCHC) has recently been proposed to address the LPWANs limitations. SCHC works under the assumption that LPWANs are preprogrammed with known data flows, thus uses a static context. However, this assumption is not always valid in an Internet of Things (IoT) context, where devices should be accessible from any IPv6 address. Therefore, in this paper we propose a dummy mapping technique that can effectively compress/decompress some header fields of unknown flows. The dummy mapping creates a fixed size list of dummy values that are dynamically mapped at the gateway compressor to the values of headers fields. The mappings stay alive to compress/decompress these fields until their flow ends, and then the same dummy values can be remapped to different header fields of different flows. The Dummy mapping exploits the SCHC framework and does not require resynchronization to meet the limitations of LPWANs. Here, we explore the impact of the dummy mapping size, the request arrival rate and the LPWAN link layer parameters on the compression efficiency.