Simulated performance evaluation of a hybrid MAC-layer protocol for dependable multi-channel distributed systems with hard real-time requirements

In this paper an efficient hybrid MAC-layer protocol for dependable multi-channel networking structures is presented and evaluated. This new protocol handles C sub-channels totally, that is c physically or frequency divided sub-channels for the information or data packets and one (1) request sub-channel, where the request packets are transmitted and (C=c+1). The proposed mechanism for the accessing of the request sub-channel slots is a TDMA-like scheme. An effective reservation mechanism based on the transmitted requests is used for the deterministic accessing of the slots of the information sub-channels, mainly at high loads. Additionally, the random access ALOHA-like protocol is selected for the dynamic accessing of the Free Information Slots (FISs) for low traffic conditions, when the stations transmit no requests. This combination offers bounded packet delay and high throughput-mean delay performance under mixed (asynchronous/synchronous) traffic. On the other hand, the proposed multi-channel networking structure offers high operational reliability due to the existed channel redundancy.