Method and Arrangement for SINR Feedback in MIMO Based Wireless Communication Systems

• US 20100098030A1
• Filed: 11/01/2006
• Published: 04/22/2010
• Est. Priority Date: 11/01/2006
• Status: Active Grant

• Current Assignee: Unwired Planet LLC (JP Morgan Chase & Co)
• Original Assignee: Unwired Planet LLC (JP Morgan Chase & Co)
• Inventors: Cheng, Jung-Fu Thomas, Krasny, Leonid, Molnar, Karl, Wang, Yi-Pin Eric, Grant, Stephen
• Granted Patent: US 8,644,263 B2
• Time in Patent Office: Days
• US Class Current: 370/335
• CPC Class Codes: H04B 2201/709727 GRAKE type RAKE receivers
• CPC Class Codes: H04B 7/0426 Power distribution
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0015 characterised by the adaptation strategy
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/0618 Space-time coding
• CPC Class Codes: H04W 52/262 taking into account adaptive modulation and coding [AMC] scheme AMC per se H04L1/0001
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

The present invention relates to a method and arrangement to enhance the communication performance in wireless communication systems. The method of the invention provides better adjustment of reported SINR in MIMO, and PARC-MIMO based communication systems. According to the method information relating to signal-to-interference-plus-noise ratio is determined by the user equipment and reported to the base station. The base station adjust reported SINRs using a model of the SINR dependences of power and code allocation. The dependences is modeled by a function comprising a first parameter relating only to power allocation and a second parameter relating only to code allocation. The first parameter has a power allocation exponent and the second parameter has a code allocation exponent. Both the power allocation exponent and the code allocation exponent are data stream dependent.

Claims

1. A method of adjusting transmission parameters in a multiple input multiple output, hereinafter referred to as MIMO, based wireless communication system, wherein a base station is in communication with at least one user equipment utilizing a plurality of antenna streams, m, the adjustment based at least partly on reported channel quality indicators, hereinafter referred to as CQI, wherein the CQI comprises information relating to at least one signal-to-interference-plus-noise ratio, hereinafter referred to as SINR, and in that the adjustment of transmission parameters for use in transmissions from the base station, a model of the SINR dependences of power and code allocation is utilized wherein the dependences is modeled by a function comprising a first parameter relating only to power allocation with a power allocation exponent, and a second parameter relating only to code allocation with a code allocation exponent.

2. The method according to claim 1, wherein the said power allocation exponents q_α

(m), are dependent on the antenna stream, m.

3. The method according to claim 2, wherein at least one of the power allocation exponents q_α

(m), is in the range 0<

q_α

(m)<

1.

4. The method according to claim 3, wherein the power allocation exponents have the relations 0<

q_α

(1)<

q_α

(2)<

. . . <

q_α

(M)=1, wherein q_α

(M) represents the power allocation exponent of the last antenna stream.

5. The method according to claim 1, wherein the said code allocation exponents q_k(m), are dependent on the antenna stream, m.

6. The method according to claim 5, wherein at least one of the code allocation exponents q_k(m), is in the range −

1<

q_k(m)<

0.

7. The method according to claim 3, wherein the code allocation exponents have the relations −

1=q_k(M)<

q_K(M−

1)<

. . . <

q_k(1)<

0, wherein q_K(M) represents the power allocation exponent of the last antenna stream.

8. The method according to claim 1, wherein successive interference cancellation, SIC, is utilized for the reception, and at each stage of the successive interference cancellation an output SINR(m) can be related, and a power allocation exponent, q_α

(m), and a code allocation exponent q_k(m), can be estimated utilizing the outputted SINR(m) for each m.

9. The method according to claim 8, wherein the modeling function has essentially the form:

SINR_inst(m)=a<sup>qα

(m)</sup>b^qk(m)SINR_ref(m),

wherein SINR_inst(m) is an adjusted SINR value to be used in the adjustment of transmission parameters, SINR_ref(m) is an estimated value based on previously broadcasted information on reference power and/or code allocation, a is the first parameter relating only to power allocation, and b is the second parameter relating only to code allocation, q_α

(m) is the power allocation exponent associated with the first parameter, and q_k(m) the code allocation exponent associated with the second parameter.

10. The method according to claim 9, wherein at least one of the power allocation exponent, q_α

(m) and the code allocation exponent, q_k(m) is determined by the user equipment and reported to the base station.

11. The method according to claim 1, comprising the steps of:

broadcasting of first representations of power and/or code allocation from the base station;

the user equipment receiving (310) first representations of power and/or code allocation;

the user equipment estimating SINRs, for each m, using the received first representations of power and/or code allocation;

the user equipment reporting information to the base station relating to the estimated SINRs;

the base station adjusting the reported SINR estimates according to the instantaneous power and code allocation using the model of the SINR dependence on the power allocation exponent and the code allocation exponent; and

the base station selecting modulation and coding scheme based on the adjusted SINRs.

12. The method according to claim 11, comprising the steps of:

the BS broadcasting information about reference power allocation α

_ref and/or code allocation K_ref,

the UE receiving power allocation α

_ref and/or code allocation K_ref,

the UE estimating for each m, SINR according to power allocation α

_ref and code allocation K_ref,

the UE estimating for each m, SINR power allocation exponent q_α

(m) for the reference power allocation α

_ref,

the UE estimating for each m, SINR code allocation exponent q_k(m) for the reference code allocation K_ref,

the UE reporting back to the BS power allocation exponents q_α

(m) and code allocation exponents q_k(m),

the BS adjusting the reported SINR estimates according to the instantaneous power and code allocation using the reported power allocation exponents and the code allocation exponents; and

the BS selecting transmission parameters based on the adjusted SINRs.

13. The method according to claim 11, comprising the steps of:

the BS broadcasting information about reference power allocation α

_ref and/or code allocation K_ref,

the UE receiving power allocation α

_ref code allocation K_ref,

the UE estimating for each m, SINR according to power allocation α

_ref and code allocation K_ref,

the UE reporting back to the BS the estimated SINR values;

the BS adjusting the reported SINR estimates according to the instantaneous power and code allocation using pre-determined power allocation and code allocation exponents; and

BS selecting modulation and coding scheme (MCS) based on the adjusted SINR.

14. The method according to claim 11, wherein the base station broadcasts an updated code allocation information, the UE estimates the output SINR based on the updated code allocation information and a nominal power allocation factor and estimates the power allocation exponent q_α

(m) with respect to power allocation, and the BS adjust the SINR estimates using q_α

(m) as the scaling slope to account for difference between instantaneous power allocation and the nominal power allocation factor, and using a predetermined scaling slope to account for any deviation between the instantaneous code allocation and the broadcasted allocation information.

15. The method according to claim 14, wherein the pre-determined code is approximated with code allocation exponent relating to a SISO system.

16. The method according to claim 15, comprising the steps of:

the BS broadcasting information about reference power allocation α

_ref and an updated code allocation K_ref,

the UE receiving power allocation α

_ref and updated code allocation K_ref,

the UE estimating for each m, SINR according to power allocation α

_ref and updated code allocation K_ref,

the UE estimating for each m, SINR power allocation exponent q_α

(m) for the reference power allocation α

_ref and the nominal code allocation K_ref,

the UE reporting back to the BS the estimated SINR for all the m streams and the power allocation exponent q_α

(m) for the first m−

1 streams;

the BS adjusting the reported SINR estimates according to the instantaneous power and code allocation using the reported power allocation exponents; and

the BS selecting modulation and coding scheme (MCS) based on the adjusted SINR.

17. The method according to claim 11, wherein the base station broadcasts first reference power and code allocations at a first time instance and second reference power and code allocations at a second time instance, and the base station derive allocation exponents using reported SINR values relating to the first and second reference power and code allocations.

18. The method according to claim 15, comprising the steps of:

the BS broadcasting information about 1^st reference power allocation α

_ref1 and a code allocation K_ref1;

the UE receiving power allocation α

_ref1 and code allocation K_ref1;

the UE estimating SINR according to power allocation α

_ref1 and code allocation K_ref1;

the UE reporting back to the BS the estimated SINR for all the m streams;

the BS broadcasting information about second reference power allocation α

_ref2 and an code allocation K_ref2;

the UE receiving power allocation α

_ref2 and code allocation K_ref2;

the UE estimating SINR according to power allocation α

_ref2 and code allocation K_ref2

the UE reporting back to the BS the estimated SINR for all the m streams;

the BS deriving the power and code allocation exponents using the reported SINR estimates associated with first reference power and code allocation factors and second reference power and code allocation factors;

the BS adjusting the reported SINR estimates according to the instantaneous power and code allocation;

the BS selecting modulation and coding scheme (MCS) based on the adjusted SINR.

19. A radio base station adapted to be part of a wireless communication system and to utilize a plurality of antenna streams, m, in the wireless communication with user equipments, the radio base station provided with multiple antennas and radio communication means for communicating via the multiple antennas, comprising:

a power and code allocation module comprising;

a broadcasting module adapted to broadcast representations of power and/or code allocation to UEs;

a feedback reception module adapted to receive feedback information relating to estimated SINRs from an UE;

a SINR adjustment module adapted to adjust reported SINR, provided from the feedback reception module, using the assumption that the output SINR of an UE receiver can be modelled as a function with one parameter having an exponential dependence on a power allocation exponent and another parameter having an exponential dependence on a code allocation exponent, and a

a transmission parameter module in connection with the SINR adjustment module and the radio transmission means, and adapted to select transmission parameters based on the adjusted SINR.

20. The radio base station according to claim 19, wherein the feedback reception module is adapted to receive SINR estimates.

21. The radio base station according to claim 20, wherein the SINR adjustment module is adapted to derive allocation exponents from the reported SINRs, prior to adjusting the reported SINRs.

22. The radio base station according to claim 19, wherein the feedback reception module is adapted to receive power allocation exponents and/or code allocation exponents or representations thereof.

23. A user equipment adapted to be used in a wireless communication system and to receive a plurality of antenna streams, m, the user equipment provided with multiple antennas and radio communication means (860) for communicating via the multiple antennas, comprising:

a power/code allocation feedback module adapted to receive broadcasted power and/or code allocations and to feedback CQI relating to power and/or code allocation;

an allocation exponent estimation module wherein the allocation exponent estimation module is adapted to SINR estimates, provided by the SINR estimation module, estimate power and/or code allocation exponents, using the assumption that the SINR can be modelled as a function with a dependence on a power allocation exponent and a code allocation exponent; and

wherein the power/code allocation feedback module is adapted to feed back allocation exponents.