Methods and devices for receipt of imbalanced transmission signal

1. A method, comprising:

receiving a multiple-input multiple-output system communication signal comprising at least one primary signal at a first power level from a first antenna and a secondary signal at a second power level different from the first power level from a second antenna;

estimating the first power level of the communication signal from a receive sample covariance matrix by taking into account the difference between the first power level and the second power level;

applying the first power level as estimated to calculate linear minimum mean square error coefficients; and

applying the linear minimum mean square error coefficients to process the communication signal.

2. The method of claim 1 , wherein the estimating comprises calculating the first power level based on higher layer signaling.

3. The method of claim 1 , further comprising:

estimating the noise variance from the received sample covariance matrix by taking into account the difference between the first power level and the second power level.

4. The method of claim 1 , wherein the estimating the first power level comprises estimating pilot power.

5. A method, comprising:

receiving a multiple-input multiple-output system communication signal comprising at least one primary signal at a first power level from a first antenna and a secondary signal at a second power level different from the first power level from a second antenna;

estimating at least one parameter of the communication signal;

applying the at least one parameter as estimated to calculate linear minimum mean square error coefficients; and

applying the linear minimum mean square error coefficients to process the communication signal,

wherein the estimating comprises estimating the linear minimum mean square error as

w LMMSE,1 =( {circumflex over ( H 1 {circumflex over ( H 1 H +{circumflex over ( H 2 {circumflex over ( H 2 H +σ η 2 I 2F ) −1 {circumflex over ( H 1 δ D

and

w LMMSE,2 =( {circumflex over ( H 1 {circumflex over ( H 1 H +{circumflex over ( H 2 {circumflex over ( H 2 H +σ η 2 I 2F ) −1 {circumflex over ( H 2 δ D √{square root over (p)}

where δ D εR F+L−2 ,

δ D stands for unit vector, R stand for real value

F is the length of the receiver equalizer filter operating at a sampling rate of two times chip rate,

L is the length of the channel impulse response (CIR) at the resolution of half chip,

H j,i is the channel matrix with respect to the channel between i th transmit antenna and j th receive antenna,

p is the transmit power of the second transmit antenna,

σ η 2 expresses a noise variance, and

I 2F is an identity matrix.

6. An apparatus, comprising:

at least one processor; and

at least one memory including computer program instructions,

wherein the at least one memory and computer program instructions are configured to, with the at least one processor, cause the apparatus at least to

estimate a first power level of a received multiple-input multiple-output system communication signal comprising at least one primary signal at the first power level from a first antenna and a secondary signal at a second power level different from the first power level from a second antenna, wherein the estimate is obtained from a receive sample covariance matrix by taking into account the difference between the first power level and the second power level;

apply the first power level as estimated to calculate linear minimum mean square error coefficients; and

apply the linear minimum mean square error coefficients to process the communication signal.

7. The apparatus of claim 6 , wherein the estimating comprises calculating the first power level based on higher layer signaling.

8. The apparatus of claim 6 , wherein the at least one memory and computer program instructions are configured to, with the at least one processor, cause the apparatus at least to estimate the noise variance from the received sample covariance matrix by taking into account the difference between the first power level and the second power level.

9. The apparatus of claim 6 , wherein the estimating the first power level comprises estimating pilot power.

10. An apparatus, comprising:

at least one processor; and

at least one memory including computer program instructions,

wherein the at least one memory and computer program instructions are configured to, with the at least one processor, cause the apparatus at least to

estimate at least one parameter of a received multiple-input multiple-output system communication signal comprising at least one primary signal at a first power level from a first antenna and a secondary signal at a second power level different from the first power level from a second antenna;

apply the at least one parameter as estimated to calculate linear minimum mean square error coefficients; and

apply the linear minimum mean square error coefficients to process the communication signal,

wherein the estimating comprises estimating the linear minimum mean square error as

w LMMSE,1 =( {circumflex over ( H 1 {circumflex over ( H 1 H +{circumflex over ( H 2 {circumflex over ( H 2 H +σ η 2 I 2F ) −1 {circumflex over ( H 1 δ D

and

w LMMSE,2 =( {circumflex over ( H 1 {circumflex over ( H 1 H +{circumflex over ( H 2 {circumflex over ( H 2 H +σ η 2 I 2F ) −1 {circumflex over ( H 2 δ D √{square root over (p)}

where δ D εR F+L−2 ,

δ D stands for unit vector, R stand for real value

F is the length of the receiver equalizer filter operating at a sampling rate of two times chip rate,

L is the length of the channel impulse response (CIR) at the resolution of half chip,

H j,i is the channel matrix with respect to the channel between i th transmit antenna and j th receive antenna,

p is the transmit power of the second transmit antenna,

σ η 2 expresses a variance, and

I 2F is an identity matrix.

11. A non-transitory computer readable medium encoded with instructions that, when executed in hardware, perform a process, the process comprising:

receiving a multiple-input multiple-output system communication signal comprising at least one primary signal at a first power level from a first antenna and a secondary signal at a second power level different from the first power level from a second antenna;

estimating the first power level of the communication signal from a receive sample covariance matrix by taking into account the difference between the first power level and the second power level;

applying the first power level as estimated to calculate linear minimum mean square error coefficients; and

applying the linear minimum mean square error coefficients to process the communication signal.

12. The non-transitory computer readable medium of claim 11 , wherein the estimating comprises calculating the first power level based on higher layer signaling.

13. A non-transitory computer readable medium encoded with instructions that, when executed in hardware, perform a process, the process comprising:

receiving a multiple-input multiple-output system communication signal comprising at least one primary signal at a first power level from a first antenna and a secondary signal at a second power level different from the first power level from a second antenna;

estimating at least one parameter of the communication signal;

applying the at least one parameter as estimated to calculate linear minimum mean square error coefficients; and

applying the linear minimum mean square error coefficients to process the communication signal,

wherein the estimating comprises estimating the linear minimum mean square error as

w LMMSE,1 =( {circumflex over ( H 1 {circumflex over ( H 1 H +{circumflex over ( H 2 {circumflex over ( H 2 H +σ η 2 I 2F ) −1 {circumflex over ( H 1 δ D

and

w LMMSE,2 =( {circumflex over ( H 1 {circumflex over ( H 1 H +{circumflex over ( H 2 {circumflex over ( H 2 H +σ η 2 I 2F ) −1 {circumflex over ( H 2 δ D √{square root over (p)}

where δ D εR F+L−2 ,

δ D stands for unit vector, R stand for real value

F is the length of the receiver equalizer filter operating at a sampling rate of two times chip rate,

L is the length of the channel impulse response (CIR) at the resolution of half chip,

H j,i is the channel matrix with respect to the channel between i th transmit antenna and j th receive antenna,

p is the transmit power of the second transmit antenna,

σ η 2 expresses the noise variance, and

I 2F is an identity matrix.