Dynamic rate control in WiFi systems
A wireless device is configured to switch data rates to account for temporary channel conditions or device configuration errors. Pre-selected data rates, more likely to achieve maximum goodput, are stored in a data rate table. The data rate table contains candidate data rates for each pre-selected data rate in the data rate table. When probe transmissions using the preselected data rates fail, dynamic rate probing is utilized to determine a possible cause and extent of the problem. The dynamic rate probing scheme transmits probe transmissions using the candidate data rates and tracks success or failure of these probe transmissions. An analysis of the probe transmissions is used to indicate a possible cause and/or extent of the problematic condition and to determine whether there is a need to reconfigure the data rates in the data rate table.
1. A method for dynamic rate adaption in a wireless network, the method comprising:
storing a plurality of pre-selected data rates for use in transmitting data in the wireless network, each pre-selected data rate associated with a number of spatial streams (Nss) and a modulating and coding (MCS) type, the pre-selected data rates being a subset of all data rates supported by the wireless network;
performing one or more probe transmissions to detect a maximum achievable data rate using the plurality of pre-selected data rates;
determining that the maximum achievable data rate does not meet a threshold criterion based at least in part on the one or more probe transmissions; wherein the threshold criterion is based at least in part on a member of the group consisting of: a packet error rate associated with the maximum achievable data rate and an acknowledgment status of the one or more probe transmissions;
performing a probe transmission using a candidate data rate, the candidate data rate associated with a Nss and MCS type, wherein the MCS type associated with the candidate data rate is different from a set of MCS types associated with members of the plurality of pre-selected data rates assigned to a same Nss as the Nss associated with the candidate data rate; and
adding the candidate data rate to the plurality of pre-selected data rates based at least in part on whether the candidate data rate meets the threshold criterion during the probe transmission.
2. The method of claim 1 , wherein performing the probe transmission using the candidate data rate comprises performing a plurality of probe transmissions using a plurality of candidate data rates, the method further comprising:
if all candidate data rates fail to meet the threshold criterion during the plurality of probe transmissions, maintaining the set of pre-selected data rates unmodified.
3. The method of claim 2 , further comprising:
after waiting a time interval, performing one or more additional probe transmissions from the plurality of candidate data rates.
4. The method of claim 1 , further comprising:
after waiting a time interval, performing additional probe transmissions using the pre-selected data rates; and
if at least one of the pre-selected data rates meets the threshold criterion, returning to performing probe transmissions using the pre-selected data rates.
5. The method of claim 1 , wherein performing the probe transmission using the candidate data rate further comprises:
associating a probe probability vector with each pre-selected data rate, the probe probability vector including one or more candidate data rates, each candidate data rate including a probability of success; and
selecting the candidate data rate based, at least in part, on a highest probability of success.
6. The method of claim 5 , further comprising:
updating the probe probability vector based, at least in part, on a success or failure of the candidate data rate meeting the threshold criterion in the probe transmission.
7. The method of claim 1 , wherein the pre-selected data rates are based, at least in part, on offline simulations.
8. A non-transitory machine-readable storage medium storing code for wireless communication at a wireless device, the code comprising instructions executable to cause the wireless device to:
store a plurality of pre-selected data rates for use in transmitting data in a wireless network, the pre-selected data rates being a subset of data rates supported by the wireless network, each pre-selected data rate associated with a number of spatial streams (Nss) and a modulation and coding scheme (MCS) type; and
perform one or more probe transmissions to detect a maximum achievable data rate from the pre-selected data rates;
determine that the maximum achievable data rate does not meet a threshold criterion based at least in part on the one or more probe transmissions; wherein the threshold criterion is based at least in part on a member of the group consisting of: a packet error rate associated with the maximum achievable data rate and an acknowledgment status of the one or more probe transmissions;
perform a probe transmission using a candidate data rate associated with a Nss and MCS type, wherein the MCS type associated with the candidate data rate is different from a set of MCS types associated with members of the plurality of pre-selected data rates assigned to a same Nss as the Nss associated with the candidate data rate; and
add the candidate data rate to the plurality of pre-selected data rates based at least in part on whether the candidate data rate meets the threshold criterion during the probe transmission.
9. The non-transitory machine-readable storage medium of claim 8 , wherein performing the probe transmission using the candidate data rate comprises performing a plurality of probe transmissions using a plurality of candidate data rates, and wherein the instructions are further executed to cause the wireless device to:
if all candidate data rates fail to meet the threshold criterion during the plurality of probe transmissions, wait a time period before performing one or more additional probe transmissions using one or more of the plurality of candidate data rates.
10. The non-transitory machine-readable storage medium of claim 8 , wherein the instructions are further executable to cause the wireless device to:
if at least one of the pre-selected data rates meets the threshold criterion, returning to performing probe transmissions with the pre-selected data rates.
11. The non-transitory machine-readable storage medium of claim 8 , wherein the instructions are further executable to cause the wireless device to:
associate each pre-selected data rate with a probe probability vector (PPV), the PPV including one or more candidate data rates, each candidate data rate including a probability of success, the probability of success based at least in part on a success or failure of candidate data rates meeting the threshold criterion during probe transmissions.
12. The non-transitory machine-readable storage medium of claim 11 , wherein the instructions are further executable to cause the wireless device to:
select the candidate data rate based at least in part on the probability of success associated with the candidate data rate.
13. The non-transitory machine-readable storage medium of claim 8 , wherein each candidate data rate is configured to increase a select one of the Nss or MCS type associated with the pre-selected data rate.
14. A wireless device, comprising:
a radio transceiver to receive and transmit data via a wireless network; and a rate controller to determine a maximum achievable data rate for transmission of the data, the rate controller configured to:
store a plurality of pre-selected data rates for use in transmitting data in the wireless network, each pre-selected data rate associated with a number of spatial streams (Nss) and a modulation and coding (MCS) type, the pre-selected data rates being a subset of all data rates supported by the wireless network;
perform one or more probe transmissions to detect a maximum achievable data rate from the plurality of pre-selected data rates;
determine that the maximum achievable data rate does not meet a threshold criterion based at least in part on the one or more probe transmissions; wherein the threshold criterion is based at least in part on a member of the group consisting of: a packet error rate associated with the maximum achievable data rate and an acknowledgment status of the one or more probe transmissions;
perform a probe transmission using a candidate data rate associated with a Nss and MCS type, wherein the MCS type associated with the data rate is different from a set of MCS types assigned to a same Nss as the Nss associated with the candidate data rate; and
add the candidate data rate to the plurality of pre-selected data rates based at least in part on whether the candidate data rate meets the threshold criterion during the probe transmission.
15. The wireless device of claim 14 , wherein performing the probe transmission using the candidate data rate comprises performing a plurality of probe transmissions using a plurality of candidate data rates, and wherein the rate controller is further configured to:
if the candidate data rates fail the threshold criterion, wait a time period before performing one or more additional probe transmissions using one or more of the candidate data rates.
16. The wireless device of claim 14 , wherein the rate controller is further configured to:
if a pre-selected data rate meets the threshold criterion, return to performing probe transmissions with the pre-selected data rates.
17. The wireless device of claim 14 , wherein the rate controller is further configured to:
associate each pre-selected data rate with a probe probability vector (PPV), the PPV including one or more candidate data rates, each candidate data rate including a probability of success, the probability of success based at least in part on a success or failure of candidate data rates meeting the threshold criterion during probe transmissions.
18. The wireless device of claim 14 , wherein the rate controller is further configured to:
select the candidate data rate based on a highest probability of success associated with the candidate data rate.