In this paper, we present a real-time communication protocol, called SPEED, for sensor networks. The protocol provides three types of real-time communication services, namely, real-time unicast, real-time area-multicast and real-time area-anycast. SPEED is specifically tailored to be a stateless, localized algorithm with minimal control overhead. End-to-end real-time communication guarantees are achieved using a novel combination of feedback control and non-deterministic QoS-aware geographic forwarding with a bounded hop count. SPEED is a highly efficient and scalable protocol for the sensor networks where node density is high while the resources of each node are scarce. Theoretical analysis and simulation experiments are provided to validate our claims.

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Efficient data delivery in vehicular sensor networks is still a challenging research issue. Position-based routing protocols have been proven to be more suitable for dynamic vehicular networks or large-scale mobile sensor networks than traditional ad hoc routing protocols. However, position-based routing assumes that intermediate nodes can always be found to set up an end-to-end connection between the source and the destination; otherwise, it suffers from network partitions which are very common in vehicular networks and leads to poor performances. This paper addresses data delivery challenge in the possible intermittently connected vehicular sensor networks by combining position-based forwarding strategy with store-carry-forward routing scheme from delay tolerant networks. The proposed routing method makes use of vehicle driving direction to determine whether holding or forwarding the packet. Experimental results show that the proposed mechanism outperforms existing position-based solutions in terms of packet delivery ratio.

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Wireless sensor networks are energy constrained. Clustering algorithm is a key technology used to reduce power consumption in WSNs. The LEACH protocol is a typical adaptive clustering routing algorithm with low power consumption. Unfortunately, it has some disadvantages such as uneven distribution of cluster heads and unbalanced energy cost. In each round of communication, if a node moves away from a cluster or towards another cluster after cluster construction, LEACH protocol can't manage the route and process data effectively. An improved algorithm LEACH-M (LEACH-mobile) is presented in this paper to manage such routing problem in mobile network, which can make energy consumption more balanced. Cluster election mode is changed in LEACH-M by considering current energy level of each node and transmission power calculated by relative distance, then adjusting the probability of a node becoming cluster head. Mobile nodes can join new clusters in time and time slots of original and new cluster heads should be re-allocated, so that useless power consumption can be reduced. Simulation result shows that LEACH-M is effective in prolonging network lifetime and improving data transmission efficiency.