cient Global Allocation of Synchronous Bandwidths for HardReal - Time Communication with the Timed Token MAC

This paper presents an eecient global synchronous band-width allocation (SBA) scheme for guaranteeing synchronous message deadlines in a timed token network (such as FDDI) where the timed token medium access control (MAC) protocol is used. A local SBA scheme allocates synchronous band-width to a node using only information available locally to that node while a global scheme uses network wide information from all nodes. A local SBA scheme may be preferred for practical use to a global one due to its lower network management overhead. However, a global SBA scheme can greatly outperform a local scheme due to a more appropriate allocation resulted from the more complete global information. That is, use of a global SBA scheme may largely enhance the network ability of guaranteeing synchronous traac. The global scheme proposed in this paper outperforms all existing SBA schemes for guaranteeing synchronous messages with deadlines equal to periods. Numerical examples are given to demonstrate the superiority of the proposed scheme to previously-proposed SBA schemes.