| 10 | | This algorithm conducts a per-MAC destination rate control. For each different destination, link statistics are stored separately. |
| | 11 | Description of functions in sample.c: |
| | 12 | |
| | 13 | {{{ |
| | 14 | I. static __inline int best_rate_ndx(struct sample_node *sn, int size_bin, int require_acked_before) |
| | 15 | }}} |
| | 16 | |
| | 17 | The objective of this function is to return the bit-rate with the lowest avg. pkt. tx. time. |
| | 18 | {{{ |
| | 19 | Process information starting from the lowest rate: |
| | 20 | 1. if ((avg. pkt. tx. time for this pkt. size and bit-rate <= 0) or |
| | 21 | ((packets have not been acked for this pkt. size and bit-rate) and |
| | 22 | (multi-rate retry is disabled))) |
| | 23 | process next higher bit-rate; |
| | 24 | 2. if (processing 9Mbps) |
| | 25 | process next higher bit-rate; // 9Mbps is never better than 12Mbps |
| | 26 | 3. if (successive failures at this rate > 3) |
| | 27 | process next higher bit-rate; |
| | 28 | 4. if (avg. pkt. tx. time for this rate is lowest so far) |
| | 29 | set best_rate_index to that of current rate; |
| | 30 | |
| | 31 | if (best rate index found) |
| | 32 | return best_rate_index; |
| | 33 | else |
| | 34 | return -1; |
| | 35 | }}} |
| | 36 | |
| | 37 | {{{ |
| | 38 | II. static __inline int pick_sample_ndx(struct sample_node *sn, int size_bin) |
| | 39 | }}} |
| | 40 | |
| | 41 | The objective of this function is to return the index of a "suitable" bit-rate that can be sampled. |
| | 42 | {{{ |
| | 43 | 1. if (no packets have been sent successfully at any of the higher bit-rates) |
| | 44 | return (index of lowest bit-rate); |
| | 45 | 2. current_tx_time = avg. tx. time for the bit-rate at which the card was operating in the previous interval; |
| | 46 | 3. Process information starting from the index of the lowest rate (for (i = 0); i < max_rate_index; i++)): |
| | 47 | 1. Choose 1 + the index of the last rate that was sampled + i; |
| | 48 | 2. if (i == current_rate_index) |
| | 49 | proceed to next higher bit-rate; |
| | 50 | 3. if (perfect_tx_time(rate(i)) > avg. tx. time (current rate)) |
| | 51 | proceed to next higher bit-rate; |
| | 52 | 4. if ((last tx. at rate(i) was less than 10 seconds ago) and |
| | 53 | (successive failures at rate(i) > 3)) |
| | 54 | proceed to next higher bit-rate; |
| | 55 | 5. if ((rate(i) > 11Mbps) and (rate(i) > current rate + 2)) |
| | 56 | proceed to next higher bit-rate; |
| | 57 | 6. if (rate(i) == 9Mbps) |
| | 58 | process next higher bit-rate; // 9Mbps is never better than 12Mbps |
| | 59 | 7. if ((current rate == 11Mbps) and (rate(i) > 12Mbps)) |
| | 60 | proceed to next higher bit-rate; |
| | 61 | 8. return i; |
| | 62 | }}} |
