Dynamic modulation and transport block size selection based on retransmission frequency
Disclosed is a method and system for dynamically adjusting modulation and encoding scheme (MCS) and transport block size (TBS) used for downlink transmissions from a base station (BS) to a user equipment device (UE) based on a frequency of retransmission requests from the UE. The BS may identify the UE as belonging to a first class of UEs designated as being capable of receiving data at a first data rate that is higher than a second data rate designated for UEs of a second class, for the same downlink channel quality reported by the UE. Based on the identification, the BS may select a MCS and TBS for the UE corresponding to the first data rate. Upon receiving more than a threshold number of retransmission requests from the UE, the BS may switch to using the second, lower data rate. The first and second classes could correspond to later and earlier technology generations, for example.
1. A method operable in a base station of a wireless communication network, the method comprising:
receiving a message from a user equipment device (UE) reporting a particular channel quality measurement by the UE of an air-interface downlink channel from the base station;
making a determination that the UE belongs to a first class of UEs designated as being capable of receiving downlink transmissions at a data rate based on a given reported channel quality measurement that is higher than a data rate for a second class of UEs based on the same given reported channel quality measurement;
transmitting a unit of data to the UE on the air-interface downlink channel at a first data rate specified for the first class of UEs in accordance with the reported particular channel quality measurement, wherein the base station is configured to transmit the unit of data in up to N incremental transmissions, each conveying at least a portion of the unit of data; and
in response to receiving M retransmission requests from the UE during the transmitting, wherein M<N, switching to transmitting the unit of data to the UE on the air-interface downlink channel at a lower, second data rate specified for the second class of UEs in accordance with a current channel quality measurement, the current channel quality measurement being one of the reported particular channel quality measurement or a subsequently reported channel quality measurement.
2. The method of claim 1 , wherein making the determination that the UE belongs to the first class of UEs comprises identifying the UE as a member of the first class of UEs according to an identifier provided by the UE.
3. The method of claim 1 , wherein transmitting the unit of data to the UE on the air-interface downlink channel at the first data rate specified for the first class of UEs in accordance with the reported particular channel quality measurement comprises:
modulating and encoding the data unit using a modulating and encoding scheme (MCS) selected from a first plurality of MCSs based on the reported particular channel quality measurement;
assembling the modulated and encoded data unit into one or more transport blocks, each of a transport block size (TBS) selected from a first plurality of TBSs based on the reported particular channel quality measurement; and
transmitting the one or more transport blocks to the UE on the air-interface downlink channel.
4. The method of claim 3 , wherein transmitting the unit of data to the UE on the air-interface downlink channel at the lower, second data rate specified for the second class of UEs in accordance with the current channel quality measurement comprises:
modulating and encoding at least a portion of the data unit using a MCS selected from a second plurality of MCSs based on the current channel quality measurement, the at least a portion of the data unit being at least that which the UE has failed to receive in M of N transmissions corresponding to the M received retransmission requests;
assembling the modulated and encoded at least a portion of the data unit into one or more alternatively-sized transport blocks, each of a TBS selected from a second plurality of TBSs based on the current channel quality measurement; and
transmitting the one or more alternatively-sized transport blocks to the UE on the air-interface downlink channel in up to N−M incremental retransmissions.
5. The method of claim 1 , wherein transmitting the unit of data to the UE on the air-interface downlink channel at the first data rate specified for the first class of UEs in accordance with the reported particular channel quality measurement comprises making at least M of N incremental transmissions and up to M incremental retransmissions according to a hybrid automatic repeat request (HARQ) protocol, using the first data rate.
6. The method of claim 5 , wherein transmitting the unit of data to the UE on the air-interface downlink channel at the lower, second data rate specified for the second class of UEs in accordance with the current channel quality measurement comprises making up to N−M incremental retransmissions according to the HARQ protocol, using the second data rate.
7. The method of claim 1 , wherein the wireless communication network operates according to Release Version 12 (Rel 12) of LTE or a later release version of LTE,
wherein receiving the message from the UE comprises receiving a particular Channel Quality Indicator (CQI) reported from the UE, and the current channel quality measurement is a current CQI, the current CQI being one of the particular CQI or a subsequently reported CQI,
wherein making the determination that the UE belongs to a first class of UEs comprises identifying the UE as one compliant with Rel 12 or a later release version of LTE,
wherein transmitting the unit of data to the UE on the air-interface downlink channel at the first data rate specified for the first class of UEs in accordance with the reported particular channel quality measurement comprises making at least M of N incremental transmissions and up to M incremental retransmissions according to a hybrid automatic repeat request (HARQ) protocol, using a modulating and encoding scheme (MCS) and transport block size (TBS) selected, based on the particular CQI, from a table specified for Rel 12 or later release version of LTE,
and wherein transmitting the unit of data to the UE on the air-interface downlink channel at the lower, second data rate specified for the second class of UEs in accordance with the current channel quality measurement comprises making up to N−M incremental retransmissions according to the HARQ protocol, using a MCS and TBS selected, based on the current CQI, from a table specified for a release version of LTE earlier than Rel 12.
8. The method of claim 7 , wherein N=8 and M=4.
9. A base station of a wireless communication network, the base station comprising:
a first transceiver;
one or more processors; and
memory accessible to the one or more processors, and storing machine language instructions that, upon execution by the one or more processors, cause the base station to carry out operations including:
receiving a message from a user equipment device (UE) reporting a particular channel quality measurement by the UE of an air-interface downlink channel from the base station;
making a determination that the UE belongs to a first class of UEs designated as being capable of receiving downlink transmissions at a data rate based on a given reported channel quality measurement that is higher than a data rate for a second class of UEs based on the same given reported channel quality measurement;
transmitting a unit of data to the UE on the air-interface downlink channel at a first data rate specified for the first class of UEs in accordance with the reported particular channel quality measurement, wherein the base station is configured to transmit the unit of data in up to N incremental transmissions, each conveying at least a portion of the unit of data; and
in response to receiving M retransmission requests from the UE during the transmitting, wherein M<1V, switching to transmitting the unit of data to the UE on the air-interface downlink channel at a lower, second data rate specified for the second class of UEs in accordance with a current channel quality measurement, the current channel quality measurement being one of the reported particular channel quality measurement or a subsequently reported channel quality measurement.
10. The base station of claim 9 , wherein making the determination that the UE belongs to the first class of UEs comprises identifying the UE as a member of the first class of UEs according to an identifier provided by the UE.
11. The base station of claim 9 , wherein transmitting the unit of data to the UE on the air-interface downlink channel at the first data rate specified for the first class of UEs in accordance with the reported particular channel quality measurement comprises:
modulating and encoding the data unit using a modulating and encoding scheme (MCS) selected from a first plurality of MCSs based on the reported particular channel quality measurement;
assembling the modulated and encoded data unit into one or more transport blocks, each of a transport block size (TBS) selected from a first plurality of TBSs based on the reported particular channel quality measurement; and
transmitting the one or more transport blocks to the UE on the air-interface downlink channel.
12. The base station of claim 11 , wherein transmitting the unit of data to the UE on the air-interface downlink channel at the lower, second data rate specified for the second class of UEs in accordance with the current channel quality measurement comprises:
modulating and encoding at least a portion of the data unit using a MCS selected from a second plurality of MCSs based on the current channel quality measurement, the at least a portion of the data unit being at least that which the UE has failed to receive in M of N transmissions corresponding to the M received retransmission requests;
assembling the modulated and encoded at least a portion of the data unit into one or more alternatively-sized transport blocks, each of a TBS selected from a second plurality of TBSs based on the current channel quality measurement; and
transmitting the one or more alternatively-sized transport blocks to the UE on the air-interface downlink channel in up to N−M incremental retransmissions.
13. The base station of claim 9 , wherein transmitting the unit of data to the UE on the air-interface downlink channel at the first data rate specified for the first class of UEs in accordance with the reported particular channel quality measurement comprises making at least M of N incremental transmissions and up to M incremental retransmissions according to a hybrid automatic repeat request (HARQ) protocol, using the first data rate,
and wherein transmitting the unit of data to the UE on the air-interface downlink channel at the lower, second data rate specified for the second class of UEs in accordance with the current channel quality measurement comprises making up to N−M incremental retransmissions according to the HARQ protocol, using the second data rate.
14. The base station of claim 9 , wherein the wireless communication network operates according to Release Version 12 (Rel 12) of LTE or a later release version of LTE,
wherein receiving the message from the UE comprises receiving a particular Channel Quality Indicator (CQI) reported from the UE, and the current channel quality measurement is a current CQI, the current CQI being one of the particular CQI or a subsequently reported CQI,
wherein making the determination that the UE belongs to a first class of UEs comprises identifying the UE as one compliant with Rel 12 or a later release version of LTE,
wherein transmitting the unit of data to the UE on the air-interface downlink channel at the first data rate specified for the first class of UEs in accordance with the reported particular channel quality measurement comprises making at least M of N incremental transmissions and up to M incremental retransmissions according to a hybrid automatic repeat request (HARQ) protocol, using a modulating and encoding scheme (MCS) and transport block size (TBS) selected, based on the particular CQI, from a table specified for Rel 12 or later release version of LTE,
and wherein transmitting the unit of data to the UE on the air-interface downlink channel at the lower, second data rate specified for the second class of UEs in accordance with the current channel quality measurement comprises making up to N−M incremental retransmissions according to the HARQ protocol, using a MCS and TBS selected, based on the current CQI, from a table specified for a release version of LTE earlier than Rel 12.
15. A non-transitory computer-readable medium having instructions stored there on that, when executed by one or more processors of a base station of a wireless communication network, cause the base station to carry out operations including:
receiving a message from a user equipment device (UE) reporting a particular channel quality measurement by the UE of an air-interface downlink channel from the base station;
making a determination that the UE belongs to a first class of UEs designated as being capable of receiving downlink transmissions at a data rate based on a given reported channel quality measurement that is higher than a data rate for a second class of UEs based on the same given reported channel quality measurement;
transmitting a unit of data to the UE on the air-interface downlink channel at a first data rate specified for the first class of UEs in accordance with the reported particular channel quality measurement, wherein the base station is configured to transmit the unit of data in up to N incremental transmissions, each conveying at least a portion of the unit of data; and
in response to receiving M retransmission requests from the UE during the transmitting, wherein M<N, switching to transmitting the unit of data to the UE on the air-interface downlink channel at a lower, second data rate specified for the second class of UEs in accordance with a current channel quality measurement, the current channel quality measurement being one of the reported particular channel quality measurement or a subsequently reported channel quality measurement.
16. The non-transitory computer-readable of claim 15 , wherein making the determination that the UE belongs to the first class of UEs comprises identifying the UE as a member of the first class of UEs according to an identifier provided by the UE.
17. The non-transitory computer-readable of claim 15 , wherein transmitting the unit of data to the UE on the air-interface downlink channel at the first data rate specified for the first class of UEs in accordance with the reported particular channel quality measurement comprises:
modulating and encoding the data unit using a modulating and encoding scheme (MCS) selected from a first plurality of MCSs based on the reported particular channel quality measurement;
assembling the modulated and encoded data unit into one or more transport blocks, each of a transport block size (TBS) selected from a first plurality of TBSs based on the reported particular channel quality measurement; and
transmitting the one or more transport blocks to the UE on the air-interface downlink channel.
18. The non-transitory computer-readable of claim 17 , wherein transmitting the unit of data to the UE on the air-interface downlink channel at the lower, second data rate specified for the second class of UEs in accordance with the current channel quality measurement comprises:
modulating and encoding at least a portion of the data unit using a MCS selected from a second plurality of MCSs based on the current channel quality measurement, the at least a portion of the data unit being at least that which the UE has failed to receive in M of N transmissions corresponding to the M received retransmission requests;
assembling the modulated and encoded at least a portion of the data unit into one or more alternatively-sized transport blocks, each of a TBS selected from a second plurality of TBSs based on the current channel quality measurement; and
transmitting the one or more alternatively-sized transport blocks to the UE on the air-interface downlink channel in up to N−M incremental retransmissions.
19. The non-transitory computer-readable of claim 15 , wherein transmitting the unit of data to the UE on the air-interface downlink channel at the first data rate specified for the first class of UEs in accordance with the reported particular channel quality measurement comprises making at least M of N incremental transmissions and up to M incremental retransmissions according to a hybrid automatic repeat request (HARQ) protocol, using the first data rate,
and wherein transmitting the unit of data to the UE on the air-interface downlink channel at the lower, second data rate specified for the second class of UEs in accordance with the current channel quality measurement comprises making up to N−M incremental retransmissions according to the HARQ protocol, using the second data rate.
20. The non-transitory computer-readable of claim 15 , wherein the wireless communication network operates according to Release Version 12 (Rel 12) of LTE or a later release version of LTE,
wherein receiving the message from the UE comprises receiving a particular Channel Quality Indicator (CQI) reported from the UE, and the current channel quality measurement is a current CQI, the current CQI being one of the particular CQI or a subsequently reported CQI,
wherein making the determination that the UE belongs to a first class of UEs comprises identifying the UE as one compliant with Rel 12 or a later release version of LTE,
wherein transmitting the unit of data to the UE on the air-interface downlink channel at the first data rate specified for the first class of UEs in accordance with the reported particular channel quality measurement comprises making at least M of N incremental transmissions and up to M incremental retransmissions according to a hybrid automatic repeat request (HARQ) protocol, using a modulating and encoding scheme (MCS) and transport block size (TBS) selected, based on the particular CQI, from a table specified for Rel 12 or later release version of LTE,
and wherein transmitting the unit of data to the UE on the air-interface downlink channel at the lower, second data rate specified for the second class of UEs in accordance with the current channel quality measurement comprises making up to N−M incremental retransmissions according to the HARQ protocol, using a MCS and TBS selected, based on the current CQI, from a table specified for a release version of LTE earlier than Rel 12.