## 3 Basic System Operation
### SBD Routing
These experiments were executed for 50 s with the querying frequency varied from 0.1 to 100 queries/s. Figure 18a,b show the total hop count and latency as the function of the querying frequency. Figure 18a demonstrates that the total number of hops for all approaches increases linearly. However, the performance of DD is lower because its broadcasting technique leads to vast traffic. It is also noted that the total number of hops for DCSMSS + SBD, DCSMSS + LEACH and SDS schemes is less than that of GHT. GHT always sends a query to ten different nodes for every attribute. SDS always sends queries to five sectors and DCSMSS sends to \(i\) sectors depending on the range \(r\). That's why DCSMSS based schemes show lower hops while SDS is slightly higher. As shown in Figure 18b, the latency of each approach increases with an increase in the querying frequency. The latency of all approaches grows slightly with the increase in querying frequency from 0.1 to ten and then grows sharply when the frequency increases to 100 queries/s. It is also noted that DD has the highest latency. Since DD broadcasts queries to all sectors it gener

Figure 17: (**a**) Total number of events and (**b**) discovery rate. Figure 18: (**a**) Total number of events and (**b**) discovery rate. loss excessive retransmission. Despite having lower collision and subsequent packet loss and retransmission, DCSMSS + SBD's latency is higher than SDS and DCSMSS + LEACH due to the reasoning explained in Section 5.1.2. However, it is interesting to note that the latency of GHT is lower than other approaches when the querying frequency is 100 queries/s. This happens because the number of sectors is lower than the number of nodes and under heavy traffic routing relying on SH became more congested than routing relying on nodes. Moreover, the routing, referred to GPSR, used in GHT uses the greedy forwarding technique which eventually selects the shortest path to route packets. ## 6 Conclusions and Future Work

In this paper a highly scalable distributed information service, DCSMSS, is presented that provides improved performance over comparative schemes. The scheme is an efficient similarity search mechanism for WSN. DCSMSS was applied to a range of WSN scenarios utilizing modeling, simulation and a statistical analysis and found to provide lower latency and improved search accuracy when compared to relatively recent alternate approaches. Discussion has been provided surrounding the alternate approaches and the improvements found when DCSMSS is applied. The research is continuing with future work considering methods to reduce complexity and improve processing at the nodes and SH to reduce energy utilization. DCSMSS has been simulated with a static, non-mobile network. Problems are expected when applying virtual sector formation or synchronization to groups of mobile nodes. Virtual sector or cluster formation in the dynamic WSN is an interesting area for future research. Furthermore, in current model, SH is the only gateway to the sector and hence it could create hotspot around the SH. This issue can be resolved in future work by outsourcing some of the responsibility to MNs, which will act as Secondary SH (SSH). A prototype implementation of DCSMSS is under development using the Texas Instruments' (TI) CC2530 Evolution Module (CC2530 EM) [17], which is ZigBee/IEEE 802.15.4 compliant System-on-Chip with an optimized 8051 MCU core and radio for the 2.4 GHz unlicensed ISM/SRD band. ## Acknowledgments

This work was supported by Victorian International Research Scholarship (VIRS) and RMIT School of Electrical and Computer Engineering (SECE). ## Author Contributions

[PERSON] has done this work during his PhD (July 2011-September 2014). This paper is one of the major outcomes of his PhD thesis. He has recently completed his PhD from SECE, RMIT University. [PERSON] was [PERSON]'s supervisor. ## Conflicts of Interest

The authors declare no conflict of interest.