Stale data removal using latency count in a WiMAX scheduler
View Patent ↗A system and method of removing items from a transmission scheduler queue includes assigning a latency count to each item indicating latency, i.e. time the item has remained in the system before being transmitted, adding a number of frames that have elapsed since a previous scheduler run to the latency count at each scheduler run to obtain a current latency count, comparing the current latency count to a removal period, which may be predetermined once or recalculated in each scheduler run, and removing the item if the comparison indicates that the current latency count exceeds the removal period before the item has been output from the queue.
1. A scheduler of a station in a wireless network, the scheduler having a queue of items and a removal period, each of the items having a latency count that is updated on each run of the scheduler, an item being removed from the queue when a current latency count associated with the item exceeds the removal period,
wherein the latency count is a count of frames, and
wherein the removal period is equal to a ratio of a remaining length of the queue and a current traffic rate, or the removal period is equal to a ratio of a remaining length of the queue and a maximum sustained traffic rate.
2. The scheduler according to claim 1 , wherein a latency count of an item entering the queue is set to a negative number having a magnitude equal to an allowed latency value of the item.
3. The scheduler according to claim 1 , wherein a latency count of an item entering the queue is calculated from a quality of service latency parameter or a jitter parameter.
4. The scheduler according to claim 1 , wherein a latency count of an item entering the queue is set to zero.
5. The scheduler according to claim 1 , wherein the latency count of the item is updated at the beginning of a run of the scheduler by adding a number of frames that have elapsed since a previous run of the scheduler to the latency count.
6. A method of removing items from a scheduler queue on a scheduler, comprising:
assigning a latency count to an item equal to a negative number having a magnitude equal to an allowed latency value of the item;
adding a number of frames that have elapsed since a previous scheduler run of the scheduler to the latency count at each scheduler run to obtain a current latency count;
comparing the current latency count to a removal period;
removing the item when the comparison indicates that the current latency count exceeds the removal period before the item has been output from the queue, and
setting the removal period equal to a ratio of a remaining length of the queue and a current traffic rate, or setting the removal period equal to a ratio of a remaining length of the queue and a maximum sustained traffic rate.
7. The method of removing items from a scheduler queue according to claim 6 , in which the latency count is calculated from a quality of service latency parameter or a jitter parameter.
8. The method of removing items from a scheduler queue according to claim 6 , further comprising setting a latency count of an item entering the queue to a negative number having a magnitude equal to an allowed latency value of the item.
9. The method of removing items from a scheduler queue according to claim 6 , further comprising calculating a latency count of an item entering the queue from a quality of service latency parameter or a jitter parameter.
10. The method of removing items from a scheduler queue according to claim 6 , further comprising setting a latency count of an item entering the queue to zero.
11. The method of removing items from a scheduler queue according to claim 6 , further comprising updating the latency count of the item at the beginning of a run of the scheduler by adding a number of frames that have elapsed since the previous run of the scheduler to the latency count.
12. A system of removing items from a scheduler queue, comprising:
means for assigning a latency count to a negative number having a magnitude equal to an allowed latency value of the item;
means for adding a number of frames that have elapsed since a previous scheduler run to the latency count at each scheduler run to obtain a current latency count;
means for comparing the current latency count to a removal period;
means for removing the item when the comparison indicates that the current latency count exceeds the removal period as before the item has been output from the queue; and
means for setting the removal period equal to a ratio of a remaining length of the queue and a current traffic rate, or means for setting the removal period equal to a ratio of a remaining length of the queue and a maximum sustained traffic rate.
13. A scheduling system for a station, the system comprising:
a scheduler processing a plurality of items of user data and management messages in one or more input queues, each of the items having a latency count;
the input queues having a predetermined size and a calculated or predetermined rate at which items arrive at the queues;
wherein the latency count is incremented on each run of the scheduler by a number of frames that have passed the scheduler since the item was put in the input queue;
wherein an item is removed from the input queue when the latency count exceeds a ratio of the predetermined size and the predetermined rate,
wherein the predetermined size is equal to a remaining length of the queue, and
wherein the predetermined rate is equal to a current traffic rate or a maximum sustained traffic rate.