## 6 Conclusions  
Environment monitoring is important for the safety of coal mine production. As the traditional cable monitoring system (CMS) cannot collect all the required environmental parameters and is difficult to deploy in complex areas such as the mining areas and the mined-out areas of mines, WSN is investigated to monitor the environment in underground coal mines. An integrated environment monitoring system for underground coal mines using CMS as the backbone network and the WSN as the supplementary network is proposed. In detail, the following aspects were studied:  
1. The architecture of the system was designed; the deployment scheme and the working modes of WSN were put forward in detail.
2. To ensure the stable and effective operation of the WSN, a set of key supporting technologies were discussed, including a routing mechanism with minimum hops and multiple paths based on LQI, a collision avoidance mechanism in combination of CSMA/CA and time division multiple access, a data aggregation strategy, a unified parameter gathering scheme and a relative synchronization scheme to make the network work synchronously. Finally, the method of interconnecting the WSN and the CMS was proposed so as to transmit the underground data of WSN to the GMDC.
3. As the WSN nodes have limited energy, calculation and processing power, an integrated network management scheme was designed in four aspects, _i.e._, topology management, location management, energy management and fault management, so as to monitor the network continuously and ensure the stable operation of the WSN.  
Experiments were performed both in the laboratory and in an underground coal mine, to test the performance of the designed WSN, the proposed management scheme and the interconnection method between the WSN and CMS. The results showed that the WSN and the management scheme worked well as expected, and the interconnection between the WSN and the CMS could ensure the reliable transmission of monitoring data from the WSN to the GMDC.  
The technologies used in the proposed system are all designed based on their suitability for the underground coal mine surveillance application, therefore some of them may not be so advanced  
Figure 8: Test results displayed on the KJF16B.  
in theory, but they were selected because they could make the system working smoothly as a whole. The proposed system has some good features such as universality and expansibility, and we anticipate it can be used for environment monitoring for other relevant fields.  
This work was supported by the National Science& Technology Pillar Program (2013 BAK06B03), Korea Research Council for Industrial Science and Technology under B551179-12-07-00, and two Natural Science Foundations of China (Grant No. 51274018 and Grant No. 61302106).  
The work was carried out in collaboration between all the authors. [PERSON], [PERSON] and [PERSON] defined the research theme. [PERSON] and [PERSON] designed methods and experiments, carried out the experiments, analyzed the data, interpreted the results and wrote the paper. [PERSON] co-designed experiments, discussed analyses, interpretation, and presentation. All authors have contributed to, seen and approved the manuscript.  
The authors declare no conflict of interest.