Methods for estimating reference signal received power of cellular communication signals

1. A method for performing cellular communication in a Long Term Evolution (LTE) network, the method comprising:

receiving a request for a reference signal received power (RSRP) estimation from a first base station;

receiving a cellular communication signal y i from the first base station and at least one interference base station transmitted over the LTE network, wherein y i =[y 0,i , . . . , y N-1,i ] T , N is a size of an observation vector of the cellular communication signal, i is the i-th orthogonal frequency-division multiplexing (OFDM) symbol,

wherein the received cellular communication signal after a Fast Fourier Transform (FFT) in the i-th orthogonal frequency-division multiplexing (OFDM symbol) is applied is defined by y i =C 0,i F 0 h 0,i +C 1,i F 1 h 1,i +n i ,

wherein C 0,i is a Cell specific Reference Signal for the target first base station, F 0 is a modified version of the FFT for the first base station, and h 0,i is a channel domain impulse response sampled at a bandwidth sample rate of the cellular communications signal for the first base station, C 1,i is a Cell specific Reference Signal for a second base station of the LTE network, F 1 is a modified version of the FFT for the second base station, and h 1,i is a channel domain impulse response sampled at the bandwidth sample rate of the cellular communications signal for the second base station;

determining a first channel estimation of {tilde over (h)} 1,i the second base station of the LTE network based on the cellular communication signal, wherein {tilde over (h)} 1,i =F 1 † C 1,i H y i ,

wherein F 1 † =(F 1 H F 1 ) −1 F 1 H ,

wherein C 1,i H the Cell specific Reference Signal for the second base station of the LTE network and H is a Hermitian transpose operator;

performing an interference cancellation Ic based on the cellular communication signal and the first channel estimation, wherein Ic=y i −C 1,i F 1 {tilde over (h)} 1,i ;

determining a second channel estimation {tilde over (h)} 0,i the first base station based on the cellular communication signal after interference cancellation, wherein {tilde over (h)} 0,i =F 0 † C 0,i H (I c );

determining a bias matrix B i based on the second channel estimation, wherein {tilde over (h)} 0,i =h 0,i −F 0 † C 0,i H F 1 F 1 \ C 1,i H C 0,i F 0 h 0,i +{dot over (n)} i ,

wherein F 0 † is the F 0 † =(F 0 H F 0 ) −1 F 0 H ,

wherein C 0,i H is the Cell specific Reference Signal for the second base station of the LTE network, and {dot over (n)} i is a filtered noise term,

wherein ĥ 0,i is expressed as, ĥ 0,i =(I−B i ) −1 ĥ 0,i =h 0,i +(I−B i ) −1 {dot over (n)} i ;

determining RSRP estimation of the first base station based on the second channel estimation and the bias, wherein RSRP=1/MΣ i=0 M-1 |F 0 ĥ 0,i | 2 −gσ 2 ,

wherein M is a predefined number of symbols in the cellular communication signal, g is an expectation value of the filtered noise term {dot over (n)} i , σ 2 is noise power,

wherein RSRP is expressed as

RSRP=1/ MΣ i=0 M-1 {tilde over (h)} 0,1 −H ( I−B i ) −H F 0 h F 0 ( I−B i ) −1 {tilde over (h)} 0,i −gσ 2 ;

reporting the RSRP of the first base station; and

managing cell handover based on the RSRP.

2. The method of claim 1 wherein the bias is a bias matrix and determining the bias further comprises determining an expectation value of the bias matrix.

3. The method of claim 1 wherein the bias is a bias matrix and determining the bias further comprises using a Neumann series approximation.

4. The method of claim 1 wherein determining the bias further comprises retrieving the bias from a computer memory.

5. The method of claim 4 wherein determining the bias further comprises modifying the retrieved bias.

6. The method of claim 1 wherein determining the RSRP estimation is further based on a noise factor.

7. The method of claim 6 further comprising retrieving the noise factor from a computer memory.

8. The method of claim 7 further comprising modifying the retrieved noise factor.

9. The method of claim 1 wherein pilot symbols of the target cell and pilot symbols of the interfering cell overlap.

10. The method of claim 1 wherein the target cell and the interfering cell have an overlapping area of cellular coverage.

11. The method of claim 1 wherein the cellular communication signal is an orthogonal frequency-division multiplexing (OFDM) signal.

12. A method for performing cellular communication in a in Long Term Evolution (LTE) network, the method comprising:

receiving a request for a reference signal received power (RSRP) estimation from a target cell;

receiving a cellular communication signal y i transmitted over the LTE network,

wherein y i =[y 0,i , . . . , y N-1,i ] T , N is a size of an observation vector of the cellular communication signal, i is the i-th orthogonal frequency-division multiplexing (OFDM) symbol,

wherein the received cellular communication signal after the Fast Fourier Transform (FFT) in the i-th orthogonal frequency-division multiplexing (OFDM symbol) is applied is defined by y i =C 0,i F 0 h 0,i +C 1,i F 1 h 1,i +n i ,

wherein C 0,i is a Cell specific Reference Signal for the target cell, F 0 is a modified version of the FFT for the first base station, and h 0,i is a channel domain impulse response sampled at a bandwidth sample rate of the cellular communications signal for the first base station, C 1,i is a Cell specific Reference Signal for a second base station of the LTE network, F 1 is a modified version of the FFT for the second base station, and h 1,i is a channel domain impulse response sampled at the bandwidth sample rate of the cellular communications signal for the interference cell;

determining a first channel estimation of {tilde over (h)} 1,i of the interference cell,

wherein {tilde over (h)} 1,i =F 1 † C 1,i H y i ,

wherein F 1 † =(F 1 H F 1 ) −1 F 1 H ,

wherein C 1,i H the Cell specific Reference Signal for the second base station of the LTE network and H is a Hermitian transpose operator;

performing an interference cancellation Ic,

wherein Ic=y i −C 1,i F 1 {tilde over (h)} 1,i ;

determining a second channel estimation {tilde over (h)} 0,i the interference cell,

wherein {tilde over (h)} 0,i =F 0 † C 0,i H (I c );

determining a bias matrix B i ,

wherein {tilde over (h)} 0,i =h 0,i −F 0 † C 0,i H F 1 F 1 \ C 1,i H C 0,i F 0 h 0,i +{dot over (n)} i ,

wherein F 0 † is the F 0 † =(F 0 H F 0 ) −1 F 0 H ,

wherein C 0,i H is the Cell specific Reference Signal for an interference cell of the LTE network, and {dot over (n)} i is a filtered noise term,

wherein ĥ 0,i is expressed as, ĥ 0,i =(I−B i ) −1 =h 0,i +(I−B i ) −1 {dot over (n)} i ;

determining RSRP estimation of the target cell,

wherein

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wherein M is a predefined number of symbols in the cellular communication signal, g is an expectation value of the filtered noise term {dot over (n)} i , σ 2 is noise power,

wherein RSRP is expressed as

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reporting the RSRP of the first base station.

13. The method of claim 12 further comprising:

approximating (I−B i ) −H to (I+B i ) H based on a first and second element of a Neumann series approximation of B i .

14. The method of claim 13 wherein determining the RSRP further comprises:

determining an expectation value of B i

wherein B =E(B i )=F 0 † diag(F 1 F 1 † )F 0 ; and

replacing B i with the expectation value such that,

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15. The method of claim 12 further comprising ignoring B i H F 0 H F 0 B i .

16. The method of claim 12 wherein determining the expectation value of the filtered noise term further comprises:

g=M·Tr ( F 0 †H GF 0 † −2 Re ( F 0 †H GF 0 † diag( F 1 F 1 † ))+ M·Tr (( F 1 F 1 † ) H diag( F 0 †H GF 0 † ) F 1 F 1 † ) wherein G=F 0 H F 0 +2 Re ( B H F 0 H F 0 ).