An arrangement for minimizing cell-delay variations in a communications system that supports multiple constant-bit-rate connections

摘要

An ATM cell constructor (100) limits transmission-delay variations between successive cells of traffic of individual narrowband and wideband channels in a multi-channel environment. Whenever an ATM AAL1 layer (112) of processing completes assembling (606) an ATM cell payload for a narrowband channel (611), it increments (612) a count that anticipates the number of ATM cells that will mature for transmission during the next cell construction period. For wideband channels, a function checks (1010) whether traffic from the number of narrowband channels that form the wideband channel will result in completion of assembly of that channel's cell payload during the next cell construction period; if so, the function increments (1012) the abovementioned count. The count is reset (302) at the beginning of each cell construction period. Upon receipt (700) of a command to add (start processing) a new channel, a TSI controller (132) compares (704) the count against a threshold that equals the total number of presently-active channels divided by the number of octets of traffic carried by each cell, plus one. If the threshold exceeds the count, the TSI controller sets up (706) a TSI (108) to start processing the new channel; otherwise the TSI controller delays (712-714) setting up the TSI to process the new channel until occurrence (902) of a cell construction period when the threshold exceeds the count. The net effect is to shift the delay variations from cells of active channels to the start-up of processing of new channels. <IMAGE>