SYSTEMS AND METHODS FOR IMPLEMENTING ABR WITH GUARANTEED MCR

Systems and methods for maintaining cell transmissions at or above the minimum cell transfer rate for ABR-category VCs. An ABR schedule table (AST) in a memory stores ABR VCs scheduled for transmissions. A pointer to the AST indicates that the ABR VC currently addresses is ready to transmit a cell. The schedule pointer is incremented every cell transmission time. When a cell of a particular VC is sent, the VC is rescheduled in another time slot in the AST such that the next cell for that VC is transmitted at close to or equal to that VC's allowed cell transfer rate (ACR) while maintaining its minimum cell transfer rate (MCR). To determine the next time slot in which to reschedule the VC, the system uses an ACR bitmap that compresses the AST and which identifies entries that are not occupied by a VC scheduled for a transmission. The system determines the time slot in the AST that would allow the VC to be transmitted at its ACR. The system then checks the ACR bitmap to determine whether that ACR slot is unoccupied. If occupied, the system searches the ACR bitmap to locate the next empty slot in the AST. If all slots between the ACR slot and the slot which provides for an MCR transmission for that VC are occupied, the system searches an MCR bitmap, which compresses the AST, to determine which VC occupying the AST between the ACR slot and the MCR slot is to be replaced by the VC being rescheduled. The VC that is replaced is itself rescheduled. In this manner MCR is guaranteed for a VC being rescheduled. L'invention concerne des systèmes et procédés permettant de maintenir des transmissions de cellules à la vitesse ou au-dessus de la vitesse de transfert de cellules minimale pour des canaux virtuels de type à débit binaire disponible. Une table de programmation de débit binaire disponible se trouvant dans une mémoire mémorise les canaux virtuels à débit binaire disponible programmés pour des transmissions. Un pointeur vers la table de programmation de débit binaire disponible indique que le débit binaire disponible auquel s'adresse le canal virtuel à ce moment est prêt à transmettre une cellule. Le pointeur de programmation est incrémenté à chaque temps de transmission de cellule. Lorsqu'une cellule d'un canal virtuel particulier est envoyée, le canal virtuel est reprogrammé dans un autre créneau temporel dans la table de programmation de débit binaire disponible de sorte que ce canal virtuel transmette la cellule suivante à la vitesse ou presque à la vitesse d