## 4 DMRF Protocol
### Network Congestion Detection Method
Figure 9: Relationship between Void region and control packets. simulation experiments. Simulation results show that DMRF can not only efficiently reduce the effects of failure nodes, congestion and void area, but also increase the ratio of successful transmission, lower the transmission delay, and reduce the number of the control packets. The primary contributions of this paper are summarized as follows. 1. The jumping transmission mode is explored to guarantee real-time and fault-tolerant characteristics. 2. Feedback mechanism is used to enhance the successful transmission ratio. 3. The average energy cost of each node in the network is balanced and the life time of the whole network is prolonged by the selection method of next hop in which the node in FCS with the minimum times of transmission is selected as the next hop. 4. The feasibility proof and performance analysis are presented to testify the superiority of DMRF. As part of our future work, we would like to extend DMRF for dynamic WSN environments, where fault tolerance characteristic is one of the most desirable features that should be provided. It is also valuable to revise the DMRF protocol for cluster-based real-time routing in order to achieve much lower energy consumption. ## Acknowledgements

This work was partially supported by the National Natural Science Foundation of China under Grant No. 60703101 and No. 60903153. ## References and Notes

* (1) [PERSON]; [PERSON]; [PERSON] A survey on wireless multimedia sensor networks. _Comput. Netw._**2007**, \(5\), 921-960. * (2) [PERSON]; [PERSON]; [PERSON]; [PERSON] Detection and diagnosis of data inconsistency failures in wireless sensor networks. _Comput. Netw._**2006**, _50_, 1247-1260. * (3) [PERSON]; [PERSON]; [PERSON]; [PERSON] SPEED: A stateless protocol for real-time communication in sensor networks. In _Proceedings of the 23 rd International Conference on Distributed Computing Systems_, Washington, DC, USA, October 27-31, 2003; pp. 46-55. * (4) [PERSON]; [PERSON]; [PERSON] MMSPEED: multipath Multi-SPEED protocol for QoS guarantee of reliability and Timeliness in wireless sensor networks. _IEEE Trans. Mob. Comput._**2006**, \(5\), 738-754. * (5) [PERSON]; [PERSON]; [PERSON]; [PERSON] FT-SPEED: A fault-tolerant, real-time routing protocol for wireless sensor networks. In _Proceedings of 2007 International Conference on Wireless Communications, Networking and Mobile Computing_, Shanghai, China, September 21-23, 2007; pp. 2531-2534. * (6) [PERSON]; [PERSON] On scheduling and real-time capacity of hexagonal wireless sensor networks. In _Proceedings of the 19 th Euromicro Conference on Real-Time Systems_, Washington, DC, USA, July 4-6, 2007; pp. 136-145. * [7] [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Real-time power-aware routing in sensor networks. In _Proceedings of the 14 th IEEE International Workshop on Quality of Service_, New Haven, CT, USA, June 19-21, 2006; pp. 83-92. * [8] [PERSON]; [PERSON] An energy-aware qos routing protocol for wireless sensor networks. In _Proceedings of the 23 rd IEEE International Conference on Distributed Computing Systems_, Washington, DC, USA, May 19-22, 2003; pp. 710-715. * [9] [PERSON]; [PERSON]; [PERSON] An energy-efficient real-time routing protocol for sensor networks. _Comp. Commun._**2007**, _30_, 2274-2283. * [10] [PERSON]; [PERSON]; [PERSON] Delay-constrained, energy-efficient routing in wireless sensor networks through topology control. In _Proceedings of the 2006 IEEE International Conference on Networking, Sensing and Control_, Lauderdale, FL, USA, April 23-25, 2006; pp. 35-41. * [11] [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Real-time data delivery in wireless sensor networks: a data-aggregated, cluster-based adaptive approach. In _Proceedings of the 4 th International Conference on Ubiquitous Intelligence and Computing_, Hong Kong, China, July 11-13, 2007; pp. 514-523. * [12] [PERSON]; [PERSON]; [PERSON] A two-hop based real-time routing protocol for wireless sensor networks.