Method and System for Link Adaptation Using Metric Feedback

• US 20120057585A1
• Filed: 11/14/2011
• Published: 03/08/2012
• Est. Priority Date: 05/04/2007
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola Mobility, Inc. (Lenovo Group Ltd.)
• Inventors: Sayana, Krishna Kamal, Zhuang, Xiangyang
• Granted Patent: US 8,374,197 B2
• Time in Patent Office: Days
• US Class Current: 370/338
• 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 a plurality of mutual information per coded bit metrics for a plurality of candidate modulation types per coding layer. 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, including a modulation type selected from one of the plurality of candidate modulation types per coding layer, 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 a plurality of mutual information per coded bit metrics for a plurality of candidate modulation types per coding layer, wherein the mutual information per coded bit metrics are based on channel state knowledge of the sub-channels;

based on the received plurality of mutual information per coded bit metrics, 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, including a modulation type selected from one of the plurality of candidate modulation types per coding layer, based on transmission condition of the communication link.

2. The method according to claim 1, wherein the transmission parameters further include open-loop multiple-input multiple-output (MIMO) transmission mode information or closed-loop MIMO transmission mode information, and 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 the plurality of mutual information per coded bit metrics for the plurality of candidate modulation types per coding layer is an index transmitted from the mobile station.

5. The method according to claim 4, wherein the index is mapped into a bit field.

6. The method according to claim 4, wherein the index is based on a predetermined table known to both the base station and the mobile station.

7. The method according to claim 6, wherein the predetermined table is defined based on different quantization ranges for mutual information per coded bit metrics of each candidate modulation type per coding layer.

8. The method according to claim 6, 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 per coding layer.

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 and a coding layer 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. The method according to claim 9, wherein the parameterized relationship is defined as:

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

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

generating feedback information, wherein the feedback information includes the plurality of mutual information per coded bit metrics for the plurality of candidate modulation types per coding layer 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.

12. The method according to claim 11, wherein computing the plurality of mutual information per coded bit metrics for the plurality of candidate modulation types per coding layer comprises:

for each candidate modulation type, 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.

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

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

mapping the one or more variables to the mutual information per coded bit metric.

14. The method according to claim 13, 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 11, 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 a plurality of mutual information per coded bit metrics for a plurality of candidate modulation types per coding layer, 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 plurality of mutual information per coded bit metrics, 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, including a modulation type selected from one of the plurality of candidate modulation types per coding layer, 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 for storing a predetermined table, wherein the plurality of mutual information per coded bit metrics for the plurality of candidate modulation types per coding layer references an index in the predetermined table.

18. The base station according to claim 17, wherein the predetermined table is known to both the base station and the mobile station and 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 per coding layer.

19. 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.

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

generates feedback information, wherein the feedback information includes the plurality of mutual information per coded bit metrics for the candidate modulation types per coding layer according to a request from the base station,

wherein the transceiver transmits the generated feedback information to the base station.

21. The mobile station according to claim 20, wherein the processor computes the plurality of mutual information per coded bit metrics 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.

22. The mobile station according to claim 20, further comprising:

a memory, coupled to the processor, for storing a predetermined table known to the base station and the mobile station, wherein the feedback information has an index to the predetermined table indicating the plurality of mutual information per coded bit metrics for the plurality of candidate modulation types per coding layer.