WO2013141307A1

WO2013141307A1 - Reception device and reception power measurement method

Info

Publication number: WO2013141307A1
Application number: PCT/JP2013/058109
Authority: WO
Inventors: 石田　一博
Original assignee: Ｎｅｃカシオモバイルコミュニケーションズ株式会社
Priority date: 2012-03-22
Filing date: 2013-03-21
Publication date: 2013-09-26

Abstract

To enable a reception device provided to a mobile terminal to measure reception power in a highly accurate manner in a high-speed fading environment. A reception device is provided with: a first reference signal reception power (RSRP) measurement unit for measuring a first signal reception power using a value obtained by averaging, over a first period, a channel estimation value estimated on the basis of a known reference signal in an OFDM wireless communication system; a second RSRP measurement unit for measuring a second signal reception power using a value obtained by averaging, over a second period, the channel estimation value; and an RSRP selection unit for comparing the first signal reception power and the second signal reception power and selecting the reception power having a larger value as the result of measuring the signal reception power.

Description

Receiving apparatus and received power measuring method

[Description of related applications]
The present invention is based on a Japanese patent application: Japanese Patent Application No. 2012-0665261 (filed on Mar. 22, 2012), and the entire contents of this application are incorporated herein by reference.
The present invention relates to a receiving apparatus and a received power measuring method, and more particularly to a receiving apparatus provided in a mobile terminal in an OFDM (Orthogonal Frequency Division Multiplexing) wireless communication system, and a received power measuring method by the receiving apparatus.

As a next generation communication method, LTE (Long Term Evolution) standardized by 3GPP (3rd Generation Partnership Project) has attracted attention. In a radio communication system such as LTE, whether or not to perform handover between base stations based on reception quality information such as signal reception power reported from a mobile terminal (also referred to as user equipment, UE (User Equipment)). It is determined. Therefore, in order to carry out a handover to an appropriate base station, it is important to improve the power estimation accuracy in the receiving apparatus provided in the mobile terminal.

A method for measuring channel quality in an OFDM communication system is described in Patent Document 1 as an example.

International Publication No. 2006/107037

The disclosure of the above patent document is incorporated herein by reference. The following analysis was made by the present inventors.

When calculating the signal reception power, the receiving device provided in the mobile terminal performs a voltage averaging process on the channel estimation value in the time direction, and further averages in the frequency direction, and then between adjacent reference signals (RS: Reference Signal) Then, conjugate multiplication is performed, and the received signal power is calculated using a value obtained by in-phase averaging the results.

According to this received power calculation method, even in an environment where the SNR (Signal-to-Noise Ratio) is low, the accuracy of the signal received power can be improved by taking a long voltage average period in the time axis direction. However, in a fast fading environment, when the voltage average time in the time axis direction is increased, there is a problem that the estimated power is reduced due to an error due to a rotation component.

Therefore, in a high-speed fading environment, it becomes an issue to enable a receiving device provided in a mobile terminal to measure received power with high accuracy. An object of the present invention is to provide a receiving apparatus and a received power measuring method for solving such a problem.

The receiving apparatus according to the first aspect of the present invention is:
In an OFDM (Orthogonal Frequency Division Multiplexing) wireless communication system, a first signal reception power is measured using a value obtained by averaging a channel estimation value estimated based on a known reference signal over a first period. A first reference signal received power (RSRP) measurement unit;
A second RSRP measurement unit that measures a second received signal power using a value obtained by averaging the channel estimation value over a second period;
An RSRP selection unit that compares the first signal reception power with the second signal reception power and selects a value not smaller as a measurement result of the signal reception power;

The received power measuring method according to the second aspect of the present invention is:
A signal reception power measurement method by a mobile terminal in an OFDM (Orthogonal Frequency Division Multiplexing) wireless communication system,
Calculating a first signal reception power using a value obtained by averaging a channel estimation value estimated based on a known reference signal over a first period;
Calculating a second signal reception power using a value obtained by averaging the channel estimation value over a second period;
Comparing the first signal reception power and the second signal reception power and selecting the one having a smaller value as the measurement result of the signal reception power.

The receiving apparatus according to the third aspect of the present invention is:
In an OFDM (Orthogonal Frequency Division Multiplexing) wireless communication system, a first signal reception power is measured using a value obtained by averaging a channel estimation value estimated based on a known reference signal over a first period. And a reference signal received power (RSRP) measuring unit for measuring the second signal received power using a value averaged over the second period;
An RSRP selection unit that compares the first signal reception power with the second signal reception power and selects a value not smaller as a measurement result of the signal reception power;

According to the receiving apparatus and received power measuring method of the present invention, received power can be measured with high accuracy in a high-speed fading environment.

It is a block diagram which shows the structure of the receiver which concerns on embodiment as an example. It is a block diagram which shows the structure of the RSRP measurement part in the receiver which concerns on embodiment as an example.

First, the outline of the present invention will be described. Note that the reference numerals of the drawings attached to this summary are merely examples for facilitating understanding, and are not intended to limit the present invention to the illustrated embodiment.

In a high-speed fading environment, if the averaging period of the voltage averaging process is lengthened, the power is measured as a low value due to phase rotation. In such an environment, the power is measured with higher accuracy when the averaging period of the voltage averaging process is shortened.

Therefore, in the present invention, as an example, the result of measuring the power by dividing the period for calculating the voltage average in the entire measurement period into _MH and the result of dividing the measurement into M _L (M _H > M _L ). The results of measuring the power are compared and the higher power is selected as the measurement result. Thereby, the power measurement accuracy in a high-speed fading environment can be improved.

That is, in the present invention, the result of measuring the power with the voltage average calculation period shortened is compared with the result of measuring the power with the voltage average calculation period lengthened, and the higher power is selected. Sometimes it is possible to estimate the received signal power with high accuracy.

Referring to FIG. 1, a receiving apparatus (10) is a value obtained by averaging channel estimation values estimated based on known reference signals in an OFDM (Orthogonal Frequency Division Multiplexing) wireless communication system over a first period. The first reference signal received power (RSRP: Reference Signal Received Power) measuring unit (20H) that measures the first signal received power and the channel estimation value are averaged over a second period Using the value, the second RSRP measurement unit (20L) that measures the second signal reception power is compared with the first signal reception power and the second signal reception power, And an RSRP selection unit (30) that selects as a measurement result of the signal reception power. When the first signal reception power and the second signal reception power are equal, the RSRP selection unit (30) may use either the first signal reception power or the second signal reception power as a measurement result. .

In addition, the first RSRP measurement unit (20H) performs the first based on a value obtained by performing frequency direction averaging and conjugate multiplication on a value obtained by averaging the channel estimation value over a first period. The second RSRP measurement unit (20L) calculates a signal reception power of the signal, and a value obtained by performing frequency direction averaging and conjugate multiplication on a value obtained by averaging the channel estimation value over a second period. Based on the above, the second received signal power may be calculated.

Further, referring to FIG. 2, the first RSRP measurement unit (20H) and the second RSRP measurement unit (20L) each include a measurement period division unit (21) that divides the measurement period of the reference signal, A time direction voltage averaging unit (22) that averages the channel estimation values over each of the divided periods, and a frequency direction averaging unit (23) that averages the values obtained by the averaging in the frequency direction. A conjugate multiplier (24) that performs conjugate multiplication on the value obtained by averaging in the frequency direction, and a power calculator that calculates received signal power based on the value obtained by the conjugate multiplication (25).

(Embodiment)
The receiving apparatus according to the embodiment will be described using LTE standardized in 3GPP as an example. Further, the estimated signal received power is referred to as RSRP (Reference Signal Received Power) following LTE. However, the application destination of this embodiment is not limited to LTE.

FIG. 1 is a block diagram illustrating an example of a configuration of a receiving device provided in an LTE mobile terminal according to the present embodiment. Referring to FIG. 1, the receiving apparatus 10 includes an RF (Radio Frequency) unit 11, an FFT (Fast Fourier Transform) unit 12, a channel estimation unit 13, RSRP measurement units 20 </ b> H and 20 </ b> L, and an RSRP selection unit 30. .

The signal received by the receiving antenna of the mobile terminal (UE) is A / D converted in the RF unit 11 and then converted into frequency component data by Fourier transform in the FFT unit 12. The channel estimation unit 13 estimates a channel estimation matrix representing a channel state using a known reference signal (RS: Reference Signal) that is mapped in advance on a frequency resource.

FIG. 2 is a block diagram showing an example of the configuration of the RSRP measurement unit 20 (

RSRP measurement units

20H and 20L in FIG. 1). Referring to FIG. 2, the RSRP measurement unit 20 includes a measurement period division unit 21, a time direction voltage averaging unit 22, a frequency direction averaging unit 23, a conjugate multiplication unit 24, and a power calculation unit 25.

The division number M of the measurement period is different between the

RSRP measurement units

20H and 20L. RSRP measurement unit 20H, the division number of the measurement period in 20L, respectively _M H, and _{M L.} _Here, M H, _{M L} is a predetermined _constant, satisfying the relation of _M H> M _L. As an example, values such as M _H = 2 and M _L = 1 can be used.

The measurement period dividing unit 21 assumes that the total number of measurement subframes is N and the periods obtained by dividing the measurement period are m = 0, 1,..., M−1, the number of subframes L _m in each period _m , The start subframe number ST _m and the end subframe number ED _m are calculated based on the following equations (1) to (3), respectively.

For example, when N = 4 and M = 2, the number of subframes L _m , start subframe number ST _m , end subframe number ED _m (m = m = 0,1) are respectively the following values:

Similarly, when N = 11, M = 3, the number of subframes L _m , the start subframe number ST _m , and the end subframe number ED _m (for each period m are obtained from equations (1) to (3). m = 0, 1, 2) takes the following values.

Next, the time direction voltage averaging unit 22 performs time axis direction voltage averaging processing of the channel estimation value based on the equation (4) for each measurement period m divided by the measurement period dividing unit 21.

In Equation (4), a is a receiving antenna, b is a transmitting antenna, n is an index of a subframe in a measurement period, t is an index in the time direction of a reference signal (RS) in the subframe, and i is a reference signal (RS ), The frequency direction index N _RST (m) represents the number of symbols including the reference signal (RS) within the measurement period m.

Next, the frequency direction averaging unit 23 performs frequency direction averaging processing on the result after the time direction in-phase averaging based on the following equation (5).

In Equation (5), N _RS represents the number of reference signals (RS) included in the band.

Next, the conjugate multiplier 24 performs conjugate multiplication processing between adjacent reference signals (RS) based on the following equation (6).

Next, the power calculator 25 calculates RSRP based on the following equation (7).

Next, the RSRP selection unit 30 refers to the RSRP _H and RSRP _L measured by the

RSRP measurement units

20H and 20L, and reports RSRP _L as RSRP if RSRP _H <RSRP _L , otherwise Reports RSRP _H as RSRP.

At this time, when RSRP _L becomes small in the high-speed fading environment, RSRP _H having a small influence of the rotation component is selected, and the RSRP can be prevented from being lowered. Therefore, according to the receiving apparatus of this embodiment, power can be measured with high accuracy in a high-speed fading environment.

In the present embodiment, the receiving device 10 includes two

RSRP measurement units

20H and 20L having different measurement period division numbers M. However, the receiving apparatus may include only one RSRP measuring unit that measures the signal reception power for each of the two voltage average calculation periods instead of the

RSRP measuring units

20H and 20L.

In addition, according to this invention, the form described as an appendix below is provided.
[Appendix 1]
This is as the receiving apparatus according to the first aspect.
[Appendix 2]
The first RSRP measurement unit is configured to calculate the first signal based on a value obtained by performing frequency direction averaging and conjugate multiplication on a value obtained by averaging the channel estimation value over the first period. Calculate received power,
The second RSRP measurement unit is configured to generate the second signal based on a value obtained by performing frequency direction averaging and conjugate multiplication on a value obtained by averaging the channel estimation value over the second period. Received power may be calculated.
[Appendix 3]
The first RSRP measurement unit and the second RSRP measurement unit are respectively
A measurement period dividing unit for dividing the measurement period of the reference signal;
A time direction voltage averaging unit that averages the channel estimation value over each of the divided periods;
A frequency direction averaging unit that averages values obtained by the averaging in the frequency direction;
A conjugate multiplier that performs conjugate multiplication on the value obtained by averaging in the frequency direction;
A power calculator that calculates signal reception power based on the value obtained by the conjugate multiplication process.
[Appendix 4]
The measurement period division unit is assumed that N is the total number of subframes in the measurement period and M is the number of divisions of the measurement period, and m (m = 0, 1,...) Of the M periods after the division. , M−1), subframe number L _m , start subframe number ST _m and end subframe number ED _m are respectively

It is good.
[Appendix 5]
The mobile terminal may include the receiving device.
[Appendix 6]
The received power measurement method according to the second aspect is as described above.
[Appendix 7]
In the received power measurement method,
The mobile terminal calculates the first signal reception power based on a value obtained by performing frequency direction averaging and conjugate multiplication on a value obtained by averaging the channel estimation value over the first period. And
The second received signal power may be calculated based on a value obtained by performing frequency direction averaging and conjugate multiplication on a value obtained by averaging the channel estimation value over the second period.
[Appendix 8]
This is as the receiving apparatus according to the third aspect.
[Appendix 9]
The RSRP measurement unit calculates the first signal reception power based on a value obtained by performing frequency direction averaging and conjugate multiplication on a value obtained by averaging the channel estimation value over the first period. And calculating the second signal reception power based on a value obtained by performing frequency direction averaging and conjugate multiplication on a value obtained by averaging the channel estimation value over the second period. Also good.
[Appendix 10]
The RSRP measurement unit
A measurement period dividing unit for dividing the measurement period of the reference signal;
A time direction voltage averaging unit that averages the channel estimation value over each of the divided periods;
A frequency direction averaging unit that averages values obtained by the averaging in the frequency direction;
A conjugate multiplier that performs conjugate multiplication on the value obtained by averaging in the frequency direction;
A power calculator that calculates signal reception power based on the value obtained by the conjugate multiplication process;
May be provided.
[Appendix 11]
When the total number of subframes in the measurement period is N and the number of divisions of the measurement period is M, the measurement period division unit is m-th (M = 0, 1,...) Of the M periods after the division. , M−1), subframe number L _m , start subframe number ST _m and end subframe number ED _m are respectively

It is good.
The disclosure of the above patent document is incorporated herein by reference. Within the scope of the entire disclosure (including claims) of the present invention, the embodiment can be changed and adjusted based on the basic technical concept. Various combinations or selections of various disclosed elements (including each element of each claim, each element of each embodiment, each element of each drawing, etc.) are possible within the scope of the claims of the present invention. It is. That is, the present invention of course includes various variations and modifications that could be made by those skilled in the art according to the entire disclosure including the claims and the technical idea. In particular, with respect to the numerical ranges described in this document, any numerical value or small range included in the range should be construed as being specifically described even if there is no specific description.

DESCRIPTION OF SYMBOLS 10 Receiver 11 RF (Radio Frequency) part 12 FFT (Fast Fourier Transform) part 13

Channel estimation part

20, 20H, 20L RSRP (Reference Signal Received Power) measurement part 21 Measurement period division part 22 Time direction voltage average part 23 Frequency direction Averager 24 Conjugate multiplier 25 Power calculator 30 RSRP (Reference Signal Received Power) selector

Claims

In an OFDM (Orthogonal Frequency Division Multiplexing) wireless communication system, a first signal reception power is measured using a value obtained by averaging a channel estimation value estimated based on a known reference signal over a first period. A first reference signal received power (RSRP) measurement unit;
A second RSRP measurement unit that measures a second received signal power using a value obtained by averaging the channel estimation value over a second period;
An RSRP selection unit that compares the first signal reception power and the second signal reception power and selects a value not smaller as a measurement result of the signal reception power;
A receiving device.
The first RSRP measurement unit is configured to calculate the first signal based on a value obtained by performing frequency direction averaging and conjugate multiplication on a value obtained by averaging the channel estimation value over the first period. Calculate received power,
The second RSRP measurement unit is configured to generate the second signal based on a value obtained by performing frequency direction averaging and conjugate multiplication on a value obtained by averaging the channel estimation value over the second period. Calculate received power,
The receiving device according to claim 1.
The first RSRP measurement unit and the second RSRP measurement unit are respectively
A measurement period dividing unit for dividing the measurement period of the reference signal;
A time direction voltage averaging unit that averages the channel estimation value over each of the divided periods;
A frequency direction averaging unit that averages values obtained by the averaging in the frequency direction;
A conjugate multiplier that performs conjugate multiplication on the value obtained by averaging in the frequency direction;
A power calculator that calculates signal reception power based on the value obtained by the conjugate multiplication process;
Comprising
The receiving device according to claim 2.
The measurement period division unit is assumed that N is the total number of subframes in the measurement period and M is the number of divisions of the measurement period, and m (m = 0, 1,...) Of the M periods after the division. , M−1), subframe number L m , start subframe number ST m and end subframe number ED m are respectively

And
The receiving device according to claim 3.
A mobile terminal comprising the receiving device according to any one of claims 1 to 4.
A signal reception power measurement method by a mobile terminal in an OFDM (Orthogonal Frequency Division Multiplexing) wireless communication system,
Calculating a first signal received power using a value obtained by averaging the channel estimation value estimated based on a known reference signal over a first period by the mobile terminal;
Calculating a second signal reception power using a value obtained by averaging the channel estimation value over a second period;
Comparing the first signal received power and the second signal received power, and selecting the smaller one as the measurement result of the signal received power;
A received power measuring method including:
The mobile terminal calculates the first signal reception power based on a value obtained by performing frequency direction averaging and conjugate multiplication on a value obtained by averaging the channel estimation value over the first period. And
Calculating the second signal reception power based on a value obtained by performing frequency direction averaging and conjugate multiplication on a value obtained by averaging the channel estimation value over the second period;
The received power measuring method according to claim 6.
In an OFDM (Orthogonal Frequency Division Multiplexing) wireless communication system, a first signal reception power is measured using a value obtained by averaging a channel estimation value estimated based on a known reference signal over a first period. And a reference signal received power (RSRP) measuring unit for measuring the second signal received power using a value averaged over the second period;
An RSRP selection unit that compares the first signal reception power and the second signal reception power and selects a value not smaller as a measurement result of the signal reception power;
A receiving device.
The RSRP measurement unit calculates the first signal reception power based on a value obtained by performing frequency direction averaging and conjugate multiplication on a value obtained by averaging the channel estimation value over the first period. Calculating the second signal received power based on a value obtained by performing frequency direction averaging and conjugate multiplication on a value obtained by calculating and averaging the channel estimation value over the second period;
The receiving device according to claim 8.
The RSRP measurement unit
A measurement period dividing unit for dividing the measurement period of the reference signal;
A time direction voltage averaging unit that averages the channel estimation value over each of the divided periods;
A frequency direction averaging unit that averages values obtained by the averaging in the frequency direction;
A conjugate multiplier that performs conjugate multiplication on the value obtained by averaging in the frequency direction;
A power calculator that calculates signal reception power based on the value obtained by the conjugate multiplication process;
Comprising
The receiving device according to claim 9.
The measurement period division unit is assumed that N is the total number of subframes in the measurement period and M is the number of divisions of the measurement period, and m (m = 0, 1,...) Of the M periods after the division. , M−1), subframe number L m , start subframe number ST m and end subframe number ED m are respectively

And
The receiving device according to claim 10.