| 摘要 |
<p>In order to schedule the transmission onto a link of cells associated with different virtual channels, a transmission schedule is set up associating virtual channels with respective transmission time slots. Each time a cell is sent, the corresponding virtual channel is re-allocated to a time slot that is offset from the current one by an amount dependent on the desired rate of transmission. This desired rate is specified for each virtual channel in a corresponding transmission rate indicator (69) comprising a fixed integer part (70), a fixed fractional part (71), and a variable accumulation part (72). The fixed parts (70,71) of the indicator define the desired rate whilst the accumulation part (72) is used in calculating each successive offset. More particularly, to determine the offset of the time slot next to be allocated to a virtual channel, the three parts (70-72) of the corresponding transmission rate indicator (69) are added up and the integer component (74) of the result is used as the offset, the fractional remainder (75) being stored back to the accumulation part (72) of the transmission rate indicator. This arrangement permits a fine control to be achieved on the average transmission rate. A similar approach can be used to control the rate of credit generation in systems where transmit credits are used to regulate cell transmission. <MATH></p> |
