A Modified DPWS Protocol Stack for 6LoWPAN-Based Wireless Sensor Networks

In this paper, a modification of the protocol stack of the device profile for web services (DPWS) is proposed which can be applied in wireless sensor networks (WSNs) that comply with the IPv6 over low-power wireless personal area networks (6LoWPAN) architecture. The modification is based on a new format for the DPWS message exchanges without prohibiting the usage of the web services (WS) and the extensible markup language (XML) set of rules. The modified DPWS was implemented on the SunSPOT wireless sensor mote (WSM) and it was observed that it processes XML documents with a mean computation time less by 53% than the respective computation time of the DPWS while it consumes less EEPROM and RAM by 84% and 85%, respectively. Furthermore, its network performance was assessed by testing it over a real 6LoWPAN-based WSN with its maximum number of WSMs being 12. In order to validate these results and extend them to larger-scale 6LoWPAN-based WSNs, the network simulator 2 (NS-2) was used by enhancing it with a developed 6LoWPAN object. The NS-2 was also utilized for comparing the modified DPWS, the DPWS and a binary-based DPWS in terms of packet delivery ratio and maximum transmission delay. Simulation results have shown that the modified DPWS presents better performance than the DPWS and offers inferior results only when it is compared with the binary-based DPWS which, however, does not retain the WSs interoperability feature as it does not use XML documents.