Patent ID: 6044091
Filing Date: 2000-03-28
Classification: H04L,H04Q

Abstract:
A method for scheduling a plurality of cells of a call via a connection linking a multiplicity of nodes which include a source node and a destination node, each of the nodes of the connection having a frame counter, the method comprising the steps of:(a) determining a frame size for the call, wherein the frame size is composed of an M number of time slots with M being a positive integer, each of the time slots being of a preset time interval;(b) detecting each propagation delay and each delay bound between two nodes of each neighboring node pair, said each neighboring node pair including an upstream node positioned toward the source node and a downstream node located toward the destination node, wherein said each propagation delay represents a number of time slots during which a cell is propagated to the downstream node and said each delay bound represents P number of time slots before which the cell must be served to the downstream node after becoming eligible for transmission at the upstream node, with P being a positive integer;(c) synchronizing the frame counters of all the nodes of the connection based on the propagation delays and the delay bounds, wherein each frame counter counts down the time slots of each frame to be reset to the frame size and an upstream count counted by the frame counter at the upstream node is correlated to a downstream count counted by the frame counter at the downstream node;(d) holding each cell, after the arrival of said each cell at the upstream node, until the upstream count is reset to the frame size of the frame at which said each cell arrives so that said each cell becomes eligible for transmission, wherein the arrival of said each cell is identified with an arrival count read from the frame counter at the upstream node on arriving of said each cell at the upstream node, the arrival count representing a remaining time till an eligible time for the transmission after which said each cell is served as an eligible cell by a predetermined scheduling discipline;(e) transmitting said eligible cell from the upstream node to the downstream node before the upstream count of the frame counter at the upstream node is reset to the frame size of the frame, wherein the transmission of said eligible cell is identified with a departure count read from the frame counter at the upstream node on transmitting of said eligible cell, the departure count representing another remaining time till the delay bound before which said each eligible cell is served; and(f) repeating said steps (d) and (e) for each of the remaining neighboring node pairs until said each cell reaches the destination node;wherein the departure count DC.sub.ij.sup.k and the arrival count AC.sub.i+1,j.sup.k are synchronized with each other as follows:AC.sub.i+1,j.sup.k =DC.sub.ij.sup.k -(T.sub.j -d.sub.ij)wherein the departure count DC.sub.ij.sup.k represents the upstream count counted by the frame counter at an upstream node i on transmitting of a cell k of a connection j from the upstream node i to the downstream node i+1; the arrival count AC.sub.i+1,j.sup.k represents the downstream count counted by the frame counter at a downstream node i+1 on arriving of the cell k of the connection j at the downstream node i+1; T.sub.j a frame size of the connection i; d.sub.ij the delay bound between the upstream node i and the downstream node i+1 of the connection j.