Methods of controlling data rate in wireless communications systems
View Patent ↗In an aspect of the method, a received data packet is decoded in order to determine a packet error rate value, and an average package error value for N received data packets is updated based on the determined packet error rate value. The updated average packet error rate value is then compared against a threshold value and a data rate request is issued based on this comparison. In another aspect, a response to a transmitted data packet is received, the response being related to an average packet error rate value. The average packet error rate value is compared against a threshold and a data rate is modified based on the comparison. In each of the above aspects, a data rate control margin that is used to overcome channel estimate errors resulting from transmission delays may be dynamically adjusted, e.g., in real time, in order to optimize system resources.
1. A method of data rate control in a wireless system, comprising:
decoding a received data packet to determine a packet error rate value;
updating an average packet error rate value for N received data packets based on said determined packet error rate value;
comparing said updated average packet error rate value against at least one threshold packet error rate value based on a requested transmission rate;
issuing a data rate request based on said comparison;
measuring a signal to noise ratio value (SNR MEAS ) associated with the decoded data packet;
adjusting a data rate control margin parameter (DRC MARGIN ) that is used to overcome channel estimate errors resulting from transmission delays based on said comparison; and
estimating a signal to noise ratio value (SNR EST ) that accounts for transmission delays based on said SNR MEAS and said adjusted DRC MARGIN , wherein said issued data rate request is based on said SNR EST .
2. The method of claim 1 , wherein said updating includes calculating an average encoded packet error rate (EPER AVG ) on a per-packet basis over a sliding window, said EPER AVG changing with time.
3. The method of claim 1 , wherein said adjusting is performed in real time.
4. The method of claim 1 , wherein
said at least one threshold value is selected from one of a first threshold and a second threshold,
said adjusting further includes increasing said DRC MARGIN if the average packet error rate value is equal to or exceeds the first threshold, and
said SNR EST being reduced as defined by an expression
SNR EST =SNR MEAS −DRC MARGIN.
5. The method of claim 4 , wherein said issuing a data rate request further includes:
determining a DRC value using said SNR EST , and
sending said DRC value to specify the requested data rate.
6. The method of claim 1 , wherein said issuing a data rate request further includes sending a data rate control, DRC, value that specifies the requested transmission rate based on said SNR EST .
7. The method of claim 1 , wherein said comparing is defined by an expression
EPER AVG ( k )≧ TPER ( k )+ Hys 1( k ),
where k represents a data rate control DRC value specifying the requested transmission rate, EPER AVG (k) is an average encoded packet error rate, TPER(k)+Hys 1(k) representing said at least one threshold value, TPER(k) is the target packet error rate, and Hys 1(k) is a specified constant rate.
8. The method of claim 7 , said adjusting further defined by an expression:
DRC MARGIN(new) =DRC MARGIN +UpStep, if EPER AVG ( k )≧ TPER ( k )+ Hys 1( k ),
where UpStep is a specified increase adjustment to said DRC MARGIN .
9. The method of claim 1 , wherein
said at least one threshold value is selected from one of a first threshold and a second threshold,
said adjusting further including decreasing DRC MARGIN if the average packet error rate value is less than a second threshold value, and
said SNR EST being increased as defined by an expression
SNR EST =SNR MEAS −DRC MARGIN.
10. The method of claim 9 , wherein said issuing a data rate request further includes:
determining a DRC value using said SNR EST , and
sending said DRC value to specify the requested data rate.
11. The method of claim 1 , wherein said comparing is defined by an expression
EPER AVG ( k )< TPER ( k )− Hys 2( k ),
where k represents a data rate control (DRC) value specifying the requested transmission rate, EPER AVG (k) is an average encoded packet error rate, TPER(k) is the target packet error rate, and Hys(2) is a specffied constant rate.
12. The method of claim 11 , said adjusting further defined by an expression:
DRC MARGIN(new) =DRC MARGIN −DownStep, if EPER AVG (k)<TPER(k)−Hys2(k), where DownStep is a specified decrease adjustment to DRC MARGIN .
13. A method of data rate control in a wireless system, comprising:
receiving a response to a transmitted data packet, the response indicative of a change in calculated average packet error rate;
comparing an updated average packet error rate value against a threshold packet error rate value based on a requested transmission rate; and
modifying a data rate based on said comparison;
measuring a signal to noise ratio value (SNR MEAS ) associated with the transmitted data packet;
estimating a signal to noise ratio value (SNR EST ) that accounts for transmission delays based on said SNR MEAS and said modified data rate.
14. The method of claim 13 , further comprising:
adjusting a data rate control margin parameter (DRC MARGIN ) that is used to overcome channel estimate errors resulting from transmission delays based on said comparison.
15. The method of claim 13 , wherein said adjusting is performed in real time.
16. The method of claim 13 , wherein said receiving further includes receiving an acknowledgment (ACK) message, said ACK message indicating a decrease in calculated average packet error rate.
17. The method of claim 13 , wherein said receiving further includes receiving a negative acknowledgment (NAK) message, said NAK message indicating an increase in calculated average packet error rate.
18. A method of determining a data rate control margin (DRC MARGIN ) for data rate control in a wireless system, the DRC MARGIN used to overcome channel estimate errors resulting from transmission delay, comprising:
decoding a received data packet to determine a packet error rate value;
updating an average packet error rate value for N received data packets based on said determined packet error rate value;
comparing said updated packet error rate value against a threshold packet error rate value based on a requested transmission rate;
determining an adjustment to DRC MARGIN based on said comparison;
measuring a signal to noise ratio value (SNR MEAS ) associated with the decoded data packet;
estimating a signal to noise ratio value (SNR EST ) that accounts for transmission delays based on said SNR MEAS and said adjusted DRC MARGIN .
19. The method of claim 18 , further comprising issuing a data rate request based on said determined adjustment to DRC MARGIN .
20. The method of claim 18 , wherein said determining is performed in real time.
21. A method of determining a data rate control margin (DRC MARGIN ) for data rate control in a wireless system, the DRC MARGIN used to overcome channel estimate errors resulting from transmission delay, comprising:
receiving a response to a transmitted data packet;
updating an average packet error rate value based on said received response;
comparing said updated packet error rate value against a threshold packet error rate value based on a requested transmission rate;
determining an adjustment to said DRC MARGIN based on said comparison;
measuring a signal to noise ratio value (SNR MEAS ) associated with the transmitted data packet; and
estimating a signal to noise ratio value (SNR MEAS ) that accounts for transmission delays based on said SNR MEAS and said adjusted DRC MARGIN .
22. The method of claim 21 , further comprising adjusting a data rate based on said determined adjustment to DRC MARGIN .
23. The method of claim 21 , wherein said determining is performed in real time.