The Real-time Routing Protocol For Supporting Real-time Query In Wireless Sensor Networks

Many wireless sensor network applications require real-time communication.But it is very hard for real-time routing design when considering the unreliabilityand variant of the sensor network, which making the End-to-End delay uncertain.Even worse, when the interference and noise in the environment is very serious, thequality of the wireless channel may fluctuate very intensive. However, there is nodistributed routing protocol to consider the retransmission number affecting thesingle-hop delay and packet deliver ratio significantly and then leading to theuncertainty in end-to-end delay, which affects the routing protocol’s performance inreal-time and reliability in the end, due to the unreliability of the link.In this paper, we firstly propose the forwarding reliability by considering theunreliability and the delay of a link, and with which, we design a novel real-timerouting protocol(RSPEED). The forwarding reliability denotes the probability todeliver the data successfully to the neighbor node under a given deadline, which weuse to achieve probabilistic QoS guarantee in timeliness and reliability. Ourprotocol can also make trade-off between the transmission delay and the probabilityof successful transmission, to improve the reliability of the transmission when theenvironment and link quality is very poor. The experimental results show that ourapproach can significantly improve the reliability of transmission and reduces thenumber of deadline missed, even when the channel is very poor, our protocol canachieves20%higher performance than SPEED.Secondly, taking into account the limitations of energy in the wireless sensornetworks, we proposes a centralized greedy algorithm by setting the retransmissiontimes to achieve the energy efficiency in real-time routing in this paper. Thealgorithm is able to, when given a path, maximize the probability of successfultransmission of the path while not exceeding the deadline, by determining thenumber of retransmissions of each hop. Even more, through the theoretical analysis,we prove the algorithm can achieve the optimal solution in the polynomial time. Atlength, the experimental results show that the proposed algorithm has excellentperformance, which can optimize the probability of successful transmission under agiven deadline to further improve the performance of real-time routing in an energyefficient way.Finally, according to the real-time routing protocol(RSPEED) proposed in thispaper, we design a real-time query system to meet the user’s real-time queries for special nodes. The real-time query system can ensure that the result is returned tothe user under the deadline and reliability requirements given by the user. Theexperimental results prove the efficient performance of our system in real-timeperformance and reliability.