Adaptive Priority Oriented Token Bus

The Token-Passing Bus specified in IEEE Standard 802.4 has two disadvantages. It requires idle stations to handle the token on each token cycle reducing throughput of data frames. Second, the token passing order is basically static. Stations with high priority frames cannot acquire bus control at the beginning of a token cycle. To overcome these disadvantages a new bus access method, Adaptive Priority Oriented Token Bus (APOTB), was developed. APOTB uses a token table concept to control access to the bus. Each station maintains its own token table, in a distributed manner. The token table allows APOTB to overcome the disadvantages of the standard method. It automatically removes idle stations from the token cycle, allowing an increase in data packet throughput. The token passing order is updated on each token cycle, allowing stations with high priority packets to access the bus early in the next token cycle. The APOTB concept is developed in this paper. It´s basic structure, similarities to, and differences from the IEEE 802.4 standard are treated.