Abstract
Vehicles and roadside units can be connected by a vehicular ad hoc network (VANET), which is an important component of future intelligent transport systems that can support various safety and non-safety related services. The network topology changes rapidly in VANET due to the high mobility of vehicles, making it difficult to design a reliable and efficient medium access control (MAC) protocol. Many MAC protocols based on time-division multiple access (TDMA) have been proposed for VANET to optimize network performance, but few of them consider the different requirements of nodes. Nodes may have diverse requirements for spectrum access, and one node may have a diversified strategy for transmitting messages over time, as its motion and network topology change rapidly. The application layer should dynamically adjust the package generation frequency as needed to reduce unnecessary spectrum access. In this paper, we propose a novel application suitable time slot sharing MAC protocol (ASTSMAC) for the broadcasting of the basic safety messages (BSMs) that can adapt to different transmission cycle requirements in the application layer program. In our scheme, one slot can be shared by more than one node, even if they are in each other’s communication range. Simulation results show that ASTSMAC can provide significantly higher packet delivery ratio and lower collision rate. Further, the network can accommodate more nodes when the traffic-density is high.
Highlights
With the rapid development of the automobile industry and continuous improvement of road infrastructure, the road network has become intertwined and complicated, and the number of vehicles running on roads has increased dramatically
We propose a novel application-suitable time slot sharing medium access control (MAC) protocol (ASTSMAC), which mainly focus on the broadcasting of the basic safety messages (BSMs)
Our contributions are summarized as follows: 1. We present an application suitable time-slot sharing MAC protocol that allows more than one node to share the same time slot, even if they are in each other’s communication range
Summary
With the rapid development of the automobile industry and continuous improvement of road infrastructure, the road network has become intertwined and complicated, and the number of vehicles running on roads has increased dramatically. TDMA-based protocols divide time into frames, where each frame contains several time slots and only one node is allowed to access the spectrum in a certain slot within a certain range This provides higher throughput with lower collision ratios compared to contention-based MAC protocols in high traffic-density situations. Adjusting the frame length can accommodate density changes, but each node occupies the same channel resource; the MAC protocol does not satisfy the diversified demand for channel access by different nodes Information such as the type of vehicle, which was defined in the application-layer, should be considered when adjusting the transmission rate. Nodes can transmit using different frequencies, and more than one node can share the same slot, even they are in each other’s communication range This can satisfy the communication needs of more vehicles with fewer time slots, reducing the number of invalid message transmissions and increasing the effective data transmission rate of the network.
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