# US 10,122,517 B2 · Methods for estimating reference signal received power of cellular communication signals

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- Number: US 10,122,517 B2
- Document ID: US10122517B2
- Status: Granted
- Kind: B2
- Application number: 14/982,526
- Filed: 2015-12-29
- Published: 2017-06-29
- Granted: 2018-11-06
- Earliest claimed: 2015-12-29
- Assignees: Ceva D.S.P. Ltd.
- Applicants: Ceva D.S.P. Ltd.
- Inventors: Gideon Kutz; Noam Zach; Guy Keshet; Kfir Bezalel
- Web page: https://patentgrep.com/patent/US10122517B2

## CPC

- H04L 5/006: {Quality of the received signal, e.g. BER, SNR, water filling}
- H04B 17/327: Received signal code power [RSCP]
- H04B 17/328: {Reference signal received power [RSRP]; Reference signal received quality [RSRQ]}
- H04L 5/0007: {the frequencies being orthogonal, e.g. OFDM(A) or DMT}
- H04L 5/0048: {Allocation of pilot signals, i.e. of signals known to the receiver (allocation of control signalling H04L5/0053; use of control signalling H04L5/0091)}
- H04W 24/10: Scheduling measurement reports {; Arrangements for measurement reports}
- H04W 52/244: {Interferences in heterogeneous networks, e.g. among macro and femto or pico cells or other sector / system interference [OSI]}
- H04W 72/542: using measured or perceived quality
- H04B 17/345: Interference values ({signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR]} H04B17/336)
- H04J 11/005: {of intercell interference}
- H04L 25/0204: {of multiple channels}
- H04W 52/40: during macro-diversity or soft handoff
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H04B: TRANSMISSION
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)
- H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S)

## Abstract

Methods for RSRP estimation in LTE networks that perform interference cancellation are provided. In particular, a bias that is present during interference cancellation is account for in the RSRP estimation of a target cell.

## Claims

### Claim 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 yi from the first base station and at least one interference base station transmitted over the LTE network, wherein yi=[y0,i, . . . , yN-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 yi=C0,iF0h0,i+C1,iF1h1,i+ni,
wherein C0,i is a Cell specific Reference Signal for the target first base station, F0 is a modified version of the FFT for the first base station, and h0,i is a channel domain impulse response sampled at a bandwidth sample rate of the cellular communications signal for the first base station, C1,i is a Cell specific Reference Signal for a second base station of the LTE network, F1 is a modified version of the FFT for the second base station, and h1,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=F1†C1,iHyi,
wherein F1†=(F1HF1)−1F1H,
wherein C1,iH 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=yi−C1,iF1{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=F0†C0,iH(Ic);
determining a bias matrix Bi based on the second channel estimation, wherein {tilde over (h)}0,i=h0,i−F0†C0,iHF1F1\C1,iHC0,iF0h0,i+{dot over (n)}i,
wherein F0† is the F0†=(F0HF0)−1F0H,
wherein C0,iH 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 ĥ0,i is expressed as, ĥ0,i=(I−Bi)−1ĥ0,i=h0,i+(I−Bi)−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/MΣi=0M-1|F0ĥ0,i|2−gσ2,
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, σ2 is noise power,
wherein RSRP is expressed as
RSRP=1/MΣi=0M-1{tilde over (h)}0,1−H(I−Bi)−HF0hF0(I−Bi)−1{tilde over (h)}0,i−gσ2;
reporting the RSRP of the first base station; and
managing cell handover based on the RSRP.

### Claim 2 (depends on 1)

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.

### Claim 3 (depends on 1)

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

### Claim 4 (depends on 1)

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

### Claim 5 (depends on 4)

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

### Claim 6 (depends on 1)

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

### Claim 7 (depends on 6)

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

### Claim 8 (depends on 7)

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

### Claim 9 (depends on 1)

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

### Claim 10 (depends on 1)

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

### Claim 11 (depends on 1)

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

### Claim 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 yi transmitted over the LTE network,
wherein yi=[y0,i, . . . , yN-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 yi=C0,iF0h0,i+C1,iF1h1,i+ni,
wherein C0,i is a Cell specific Reference Signal for the target cell, F0 is a modified version of the FFT for the first base station, and h0,i is a channel domain impulse response sampled at a bandwidth sample rate of the cellular communications signal for the first base station, C1,i is a Cell specific Reference Signal for a second base station of the LTE network, F1 is a modified version of the FFT for the second base station, and h1,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=F1†C1,iHyi,
wherein F1†=(F1HF1)−1F1H,
wherein C1,iH 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=yi−C1,iF1{tilde over (h)}1,i;
determining a second channel estimation {tilde over (h)}0,i the interference cell,
wherein {tilde over (h)}0,i=F0†C0,iH(Ic);
determining a bias matrix Bi,
wherein {tilde over (h)}0,i=h0,i−F0†C0,iHF1F1\C1,iHC0,iF0h0,i+{dot over (n)}i,
wherein F0† is the F0†=(F0HF0)−1F0H,
wherein C0,iH 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 ĥ0,i is expressed as, ĥ0,i=(I−Bi)−1=h0,i+(I−Bi)−1{dot over (n)}i;
determining RSRP estimation of the target cell,
wherein
RSRP
=
1
M
⁢
∑
i
=
0
M
-
1
⁢

F
0
⁢
h
^
0
,
i

2
-
g
⁢
⁢
σ
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, σ2 is noise power,
wherein RSRP is expressed as
RSRP
=
1
M
⁢
∑
i
=
0
M
-
1
⁢
h
~
0
,
1
H
⁡
(
I
-
B
i
)
-
H
⁢
F
0
h
⁢
F
0
⁡
(
I
-
B
i
)
-
1
⁢
h
~
0
,
i
-
g
⁢
⁢
σ
2
;
reporting the RSRP of the first base station.

### Claim 13 (depends on 12)

The method of claim 12 further comprising:
approximating (I−Bi)−H to (I+Bi)H based on a first and second element of a Neumann series approximation of Bi.

### Claim 14 (depends on 13)

The method of claim 13 wherein determining the RSRP further comprises:
determining an expectation value of Bi
wherein B=E(Bi)=F0†diag(F1F1†)F0; and
replacing Bi with the expectation value such that,
RSRP
=
1
M
⁢
∑
i
=
0
M
-
1
⁢
(
F
0
H
⁢
F
0
+
2
⁢
⁢
Re
⁡
(
B
_
H
⁢
F
0
H
⁢
F
0
)
)
⁢
h
~
0
,
i
-
g
⁢
⁢
σ
2
.

### Claim 15 (depends on 12)

The method of claim 12 further comprising ignoring BiHF0HF0Bi.

### Claim 16 (depends on 12)

The method of claim 12 wherein determining the expectation value of the filtered noise term further comprises:
g=M·Tr(F0†HGF0†−2Re(F0†HGF0†diag(F1F1†))+M·Tr((F1F1†)Hdiag(F0†HGF0†)F1F1†) wherein G=F0HF0+2Re(BHF0HF0).