## 8 Conclusions and Ongoing Work  
In this article, a real-time, memory-efficient, energy-efficient, user-friendly and fault-tolerant WSN OS MIROS is designed and implemented. MIROS achieves the real-time scheduling with less RAM cost. With this feature, the real-time WSN applications are feasible to be executed on the low-end high memory-constraint WSN nodes, e.g., after the MIROS is applied, the memory-constrained iLive nodes can be used to run the time-critical industrial engine control tasks. Besides this feature, MIROS also shows the advantages in having a long lifetime, being fault-tolerant and supporting efficient remote reprogramming. Consequently, the WSN nodes become practicable to be deployed in the harsh environments where the human-labor maintenances (e.g., the effort to bring the nodes back after the deployment for the power recharging, the application reprogramming and the fault reparation) are difficult. Furthermore, MIROS provides a user-friendly application development environment. In this manner, the WSN proliferation can be promoted to more application domains. Typically, MIROS can be applied in the contexts with the following rigorous conditions: (1) nodes are equipped with the low-end microcontrollers, and are constrained in the memory and energy resources; (2) a real-time guarantee is required by some tasks; (3) the deployment environment is harsh so that it is difficult to re-collect the nodes after they are deployed. As for the ongoing work, MIROS will focus on the following topics:  
_Finite-state-machine MIROS:_ To improve the software reliability further, all the system services in MIROS will be developed by using the finite-state-machine programming style. Every time the code related to a state is executed, the execution result will be checked. If the result is incorrect, the roll-back recovery will be performed. Only when the result is validated, can the execution transit into the next state. An execution error can thus be limited to spread widely, and the run-time failure probability can be decreased. _Establishment of the intra-communication network among the multiple cores:_ To simplify the management of the multi-core WSN platform, the communication among the multiple cores on the multi-core platform will be operated as the communication among the nodes in a network. For example, the communication among the cores on the multi-core node can be achieved in the networking modes: P2P (point to point), P2M (point to multi-point) and M2P (multi-point to point). Moreover, the \"channel/pipes\" concept (similar to the \"socket/ports\" concept in the TCP/IP protocol) will be applied in the MIROS IPC to abstract the low-level hardware communication details. _System on Chip (SoC) technology:_ Currently, different multi-core WSN nodes (EMWSN, MiLive, liveT, _etc._) have been developed to meet the different application contexts. This development method is complicated in the manufacture process and high in the maintenance cost. In the next generation of the multi-core hardware development, the SoC technology will be used. With the SoC, the working modes of the multi-core nodes can be reconfigured by uploading different firmware. Once reconfigured, a node can change the modes and adapt to the new application context. In so doing, one integrated multi-core node can be used to support different kinds of WSN applications. As a result, the manufacture cost can be reduced and the software development cycle can be minimized. _Parallel computing to improve the real-time performance:_ The multi-core technology is presently used to reduce energy consumption, to improve system reliability and to realize the new debugging approach. In future work, this technology will also be used to improve the system real-timeperformance. In the case that two or more hard real-time tasks are triggered simultaneously, these tasks will be distributed onto different cores and be processed concurrently. The deadlines of the real-time tasks can therefore be better guaranteed.