Dynamic Slot Multiplexing Under Operating Modes for TDMA-Based Real-Time Networking Systems

The Time Division Multiple Access (TDMA) scheme has been proposed as the one which assures real-time messaging in a networking system. In the TDMA scheme, a networking system operates based on time slots which are defined as discrete time units. Some messages are periodically and exclusively assigned to their own time slots and are assured to be sent between network nodes by their own deadline. In this paper, we note that an operating situation of a system determines what functions of the system run. More concretely, an operating situation determines what data the system requires and how frequently it requires them. We propose to introduce operating modes, each of which reflects its own operating situation, to the TDMA scheme. An operating mode is specified by a set of communication signals which are active under the operating mode. We propose a dynamic slot multiplexing (DSM) technique which switches operating modes and assignments of communication signals to time slots adaptively with operating situations. System designers are to schedule all messages of communication signals for every operating mode so that the messages are sent by their own deadline. Compared with a single-mode TDMA system, in which a single message schedule is determined for all communication signals, our approach optimally determines a message schedule for each operating mode so that it can avoid wasting networking resources. Our experiment shows that DSM technique achieves about 21%-37% lower operating frequency than static slot multiplexing one.