Realistic Topic-Based Data Transmission Protocol in a Mobile Fog Computing Model

Abstract

In the fog computing (FC) models, a fog node supports not only routing functions but also application processes. By the application processes, output data is calculated on input data from sensors and other fog nodes and sent to target fog nodes which can calculate on the output data. In this paper, we consider the MPSFC (Mobile topic-based PS (publish/subscribe) FC) model where mobile fog nodes communicate with one another by publishing and subscribing messages of data in wireless networks. Subscription topics of a fog node denote input data on which the fog node can calculate. Publication topics of a message show data carried by the message. In the TBDT (Topic-Based Data Transmission) and ETBDT (Epidemic and TBDT) protocols proposed in our previous studies, a fog node only publishes a message of the output data to a target fog node in the communication range. Here, while a fewer number of messages are transmitted, the delivery ratio of messages is smaller than the epidemic routing protocol. In this paper, we newly propose PTBDT (Probability and TBDT) and TTLBDT (Time-To-Live Based Data Transmission) protocols in order to increase the delivery ratio. If another node is found in the communication range, a fog node forwards messages to the node. Even if the node is not a target node, the node receives the message with some probability. In the evaluation, we show the delivery ratio in the PTBDT protocol is larger than the TTLBDT protocol.