METHOD AND SYSTEM FOR LINK ADAPTATION USING METRIC FEEDBACK

• US 20080273490A1
• Filed: 05/04/2007
• Published: 11/06/2008
• Est. Priority Date: 05/04/2007
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Zhuang, Xiangyang, Sayana, Krishna Kamal
• Granted Patent: US 8,687,561 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04B 7/0417 Feedback systems
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 1/0028 Formatting
• CPC Class Codes: H04L 1/0035 evaluation of received explicit signalling
• CPC Class Codes: H04L 1/06 using space diversity
• CPC Class Codes: H04L 1/1812 Hybrid protocols; Hybrid automatic repeat request [HARQ]
• CPC Class Codes: H04W 72/21 in the uplink direction of a wireless link, i.e. towards the network
• CPC Class Codes: H04W 88/02 Terminal devices
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

A method for link adaptation at a base station using metric feedback is disclosed. The method can include the steps of communicating with a mobile station over a communication link having one or more sub-channels and during the communication, receiving from the mobile station information relating to one or more mutual information per coded bit metrics for one or more candidate modulation types. The mutual information per coded bit metrics can be based on channel state knowledge of the sub-channels. Also, based on the received information, the operational performance of the mobile station can be predicted in view of one or more transmission parameters and performance factors and one or more of the transmission parameters can be selected based on a transmission condition of the communication link.

Claims

1. A method for link adaptation at a base station using metric feedback, comprising:

communicating with a mobile station over a communication link having one or more sub-channels;

during the communication, receiving from the mobile station information relating to one or more mutual information per coded bit metrics for one or more candidate modulation types, wherein the mutual information per coded bit metrics are based on channel state knowledge of the sub-channels;

based on the received information, predicting operational performance of the mobile station in view of one or more transmission parameters and one or more performance factors; and

selecting one or more of the transmission parameters based on transmission condition of the communication link.

2. The method according to claim 1, wherein the transmission parameters include open-loop multiple-input multiple-output (MIMO) transmission mode information or closed-loop MIMO transmission mode information and a modulation type, a coding rate or a packet size for the coding layers of the open-loop and closed-loop MIMO transmission modes.

3. The method according to claim 2, wherein the open-loop MIMO transmission mode information and the closed-loop MIMO transmission mode information include a number of symbol streams to be sent or a number of coding layers and the closed-loop MIMO transmission mode information further includes closed-loop antenna beamforming weights of each symbol stream.

4. The method according to claim 1, wherein hybrid automatic repeat request (HARQ) is part of a scheduling at the base station and the transmission parameters correspond to a packet that will be combined with one or more previous transmissions.

5. The method according to claim 4, wherein predicting operational performance of the mobile station in view of one or more transmission parameters and performance factors comprises:

at the base station, computing a new mutual information per coded bit metric based on the mutual information per coded bit metrics received from the mobile station at different time instants corresponding to first and subsequent HARQ transmissions, wherein the mobile station is to combine the first and subsequent HARQ transmissions.

6. The method according to claim 1, wherein the information relating to one or more mutual information per coded bit metrics for one or more candidate modulation types is an index transmitted from the mobile station, wherein the mobile station computes the mutual information per coded bit metric for a single preferred candidate modulation type and further maps the single preferred candidate modulation type and the corresponding mutual information per coded bit metric to the index based on a predetermined table known to both the base station and the mobile station.

7. The method according to claim 1, wherein the information relating to one or more mutual information per coded bit metrics for one or more candidate modulation types is an index transmitted from the mobile station, wherein the mobile station computes the mutual information per coded bit metric for each of a plurality of candidate modulation types and further maps the plurality of mutual information per coded bit metrics to the index based on a predetermined table known to both the base station and the mobile station.

8. The method according to claim 7, wherein the predetermined table known to both the base station and the mobile station is defined based on joint probability distribution of the plurality of mutual information per coded bit metrics and coding rate constraints for each candidate modulation type.

9. The method according to claim 1, wherein predicting operational performance of the mobile station in view of one or more transmission parameters and performance factors comprises mapping the mutual information per coded bit metric corresponding to a candidate modulation type to a packet error rate under potential coding rates and packet sizes according to a numerically determined relationship between the mutual information per coded bit metric and the packet error rate or according to a parameterized relationship.

10. A method for link adaptation at a mobile station, comprising:

computing one or more mutual information per coded bit metrics for one or more candidate modulation types based on a channel state knowledge of one or more sub-channels;

generating feedback information based on the mutual information per coded bit metrics for the candidate modulation types according to a request from a base station with which the mobile station is communicating; and

transmitting the generated feedback information to the base station.

11. The method according to claim 10, wherein computing the mutual information per coded bit metrics for the candidate modulation types comprises:

computing the mutual information per coded bit on at least one of the sub-channels as the mutual information between each coded bit and a log-likelihood ratio of that bit based on a receiver type; and

averaging the mutual information per coded bit over one or more of the subchannels.

12. The method according to claim 11, wherein computing the mutual information per coded bit on the subchannel further comprises:

deriving one or more variables relating to a channel condition based on the channel state knowledge and a receiver type; and

mapping the variables to the mutual information per coded bit.

13. The method according to claim 12, wherein the variables include a signal to noise and interference ratio based on a receiver type and if the receiver type is a multiple-input multiple output (MIMO) receiver, the variables further include eigenvalues, eigen-subspace powers, and a condition number of a channel state matrix.

14. The method according to claim 12, wherein mapping the variables to the mutual information per coded bit is based on a predetermined numerical table or a function parameterized by the variables.

15. The method according to claim 10, wherein the feedback information is an index that the mutual information per coded bit metrics are mapped to based on a predetermined table known to the base station and the mobile station or is a recommended setting for one or more transmission parameters as requested by the base station or is a combination of both.

16. A base station for link adaptation that uses metric feedback, comprising:

a transceiver that communicates with a mobile station over a communication link having a plurality of sub-channels and during the communication, receives from the mobile station information relating to one or more mutual information per coded bit metrics for one or more candidate modulation types, wherein the mutual information per coded bit metrics are based on channel state knowledge of the sub-channels; and

a performance engine coupled to the transceiver, wherein based on the received information, the performance engine predicts operational performance of the mobile station in view of one or more transmission parameters and performance factors and selects one or more of the transmission parameters based on transmission condition of the communication link.

17. The base station according to claim 16, further comprising a memory coupled to the performance engine, wherein the information relating to one or more mutual information per coded bit metrics for one or more candidate modulation types is an index received from the mobile station, wherein the mobile station computes the mutual information per coded bit metric for a single preferred candidate modulation type and further maps the single preferred candidate modulation type and the corresponding mutual information per coded bit metric to the index based on a predetermined table known to the mobile station and also stored in the memory of the base station.

18. The base station according to claim 16, further comprising a memory coupled to the performance engine, wherein the information relating to one or more mutual information per coded bit metrics for one or more candidate modulation types is an index received from the mobile station, wherein the mobile station computes the mutual information per coded bit metric for each of a plurality of candidate modulation types and further maps the plurality of mutual information per coded bit metrics to the index based on a predetermined table known to the mobile station and also stored in the memory of the base station.

19. The base station according to claim 18, wherein the predetermined table known to both the base station and the mobile station is defined based on joint probability distribution of the plurality of mutual information per coded bit metrics and coding rate constraints of each of the candidate modulation types.

20. The base station according to claim 16, wherein the performance engine predicts operational performance of the mobile station in view of one or more transmission parameters and performance factors by mapping the mutual information per coded bit metric corresponding to a candidate modulation type to a packet error rate under potential coding rates and packet sizes according to a numerically determined relationship between the mutual information per coded bit metric and the packet error rate or according to a parameterized relationship.

21. A mobile station for link adaptation using metrics, comprising:

a transceiver for communicating with a base station; and

a processor coupled to the transceiver, wherein the processor;

computes one or more mutual information per coded bit metrics for one or more candidate modulation types based on a channel state knowledge of one or more sub-channels; and

generates feedback information based on the mutual information per coded bit metrics for the candidate modulation types according to a request from the base station, wherein the transceiver transmits the generated feedback information to the base station.

22. The mobile station according to claim 21, wherein the processor computes the mutual information per coded bit metrics for the candidate modulation types by:

computing the mutual information per coded bit on at least one of the sub-channels as the mutual information between each coded bit and a log-likelihood ratio of that bit based on a receiver type; and

averaging the mutual information per coded bit over one or more of the subchannels.

23. The mobile station according to claim 22, wherein the processor computes the mutual information per coded bit on the subchannel further by:

deriving one or more variables relating to channel condition based on the channel state knowledge and a receiver type; and

mapping the variables to the mutual information per coded bit.

24. The mobile station according to claim 23, wherein the processor maps the variables to the mutual information per coded bit based on a predetermined numerical table or a function parameterized by the variables.

25. The mobile station according to claim 21, wherein the feedback information is an index that the mutual information per coded bit metrics are mapped to based on a predetermined table known to the base station and the mobile station or is a recommended setting for one or more transmission parameters as requested by the base station or is a combination of both.