KR100839275B1 - Apparatus and Method for estimating power of interference and noise and SIR estimator of mobile terminal using the same in WCDMA system - Google Patents

Abstract

The present invention relates to an apparatus and method for estimating SIR more efficiently by avoiding bias in the signal power in estimating signal to interference ratio (SIR) of a terminal.

The noise power estimation method of a wideband code division multiple access terminal according to the present invention comprises the steps of: dividing a signal input at a symbol level into a real part and an imaginary part to obtain and output power corresponding to an absolute value multiplication for each signal; And converting the power output at the symbol level to be output at a bit level, obtaining and outputting an average value of the total power output of the bit converted to the bit level, and outputting a signal component from the output average bit power. Subtracting and outputting bit level power, and outputting noise power by averaging the subtracted output value for a predetermined period.

According to the configuration of the present invention as described above, it is possible to eliminate the problem of hardware burden to compensate for the bias included in the signal power in the future, and to provide an advantage of more accurate SIR estimation.

SIR estimation, noise power, bit level, symbol level

Description

Apparatus and Method for estimating power of interference and noise and SIR estimator of mobile terminal using the same in WCDMA system

1 is a diagram illustrating an SIR estimating apparatus using signal and noise power estimation according to the related art.

2 is a diagram illustrating an SIR estimation apparatus of a wideband code division multiple access terminal according to an embodiment of the present invention.

3A to 3D are graphs of the performance of the SIR estimating apparatus when the power of noise is expressed in symbol units.

4A to 4 are graphs of the performance of the SIR estimating apparatus when the power of noise is in units of bits.

<Explanation of symbols for the main parts of the drawings>

220: signal power estimation unit 230: noise power estimation unit

231: noise power separation unit 232: absolute value square

233: noise signal converter 234: noise average calculator

235: subtraction unit 236: alpha tracker

240: SIR compensation unit

The present invention relates to a noise power estimator for a wideband code division multiple access terminal, a method thereof, and an SIR estimating apparatus using the same.

The mobile communication terminal estimates a signal-to-interference ratio (SIR) by receiving a signal transmitted from a base station. SIR is a value representing the ratio of the received signal power and the interference power of the channel to which the signal is transmitted, and is measured as one parameter for determining the state of the channel in the terminal. In particular, for downlink power control, the UE estimates the SIR, compares the SIR with a preset threshold SIR _target, and transmits a TPC (Transmit Power Control) value to the base station according to the comparison result. It is a very important task.

The power of the signal in the code division multiple access system uses the combiner output signal of the rake receiver. At the rake finger, the DPCH signal is despreaded to convert the chip unit signal into a symbol unit signal, and at the combiner terminal, the channel value obtained by the channel estimator is conjugated and multiplied. To compensate for the channel.

If the channel passed in the air has L multi-paths, the number of fingers becomes L, and the combiner stage combines the channel-compensated DPCH signals from each of the L fingers to maximize MRC (Maximal- Ratio-Combining). The combiner stage outputs the MRC signal.

SIR estimation requires measuring the power of the signal and the power of the interference and noise.

The power of the signal is generally obtained using coherence using pilot bits of a DPCCH. The pilot bit corresponding to a known training signal is used. That is, after extracting the pilot bit field of the DPCCH from the combiner output signal, the coherent signal power is measured using the pilot bit field.

The power of noise is usually obtained by I / Q separation of the combiner output signal to obtain the power of each path, and then the power of the signal is subtracted from it. The power of the noise thus obtained has a fairly fluctuating value in every slot. However, as is generally known, the power of interference signals and noise does not change significantly. Therefore, the low-pass filtering of the power of the noise obtained for each slot is performed to find an average value over a long period. This can be obtained by passing the power of sequential interference and noise signals through an Alpha Tracker.

1 is a view showing an SIR estimating apparatus through signal and noise power estimation according to the prior art,

Referring to FIG. 1, an SIR estimator for explaining a conventional signal and noise power estimation method includes a signal power measurement unit measuring coherent signal power from a signal output from a combiner 110 terminal of a rake receiver. 120 and a SIR estimator 140 for obtaining an SIR using an output of the noise power measurement unit 130 and the signal power measurement unit 120 and the noise power measurement unit 130 that measure the incoherent noise power. It is configured to include).

In order to measure coherent signal power in the SIR estimating apparatus using the signal and noise power estimation according to the related art configured as described above, first, a pilot bit or a pilot symbol of a DPCCH is extracted from a DPCH.

The real component and the imaginary component are extracted by the signal component extractor 121 of the signal power measurement unit 120 from the extracted pilot signal. The coherent processing unit 122 performs coherent processing on the real part and the imaginary part, respectively, and outputs them. The signal average detector 123 calculates an average of the coherence calculated signals during the pilot bit field from the output of the coherence processor 122.

The signal power calculator 124 obtains the power of each of the real part and the imaginary part of the signal by taking the absolute value of the real part signal average and the imaginary part signal average, which are the outputs of the signal average detector 123, and then square. In this case, noise bias is included in the power of the signal. Detailed analysis of the bias term is described in detail in Korean Patent Application No. 2004-107865 filed earlier.

The signal power adder 125 adds the real part power and the imaginary part power output from the signal power calculator 124 to output to the SIR estimator 140.

On the other hand, in order to obtain the power of the interference and noise signal, first, the real part and the imaginary part are separated and output from the signal component extraction unit 131 of the noise power measurement unit 130.

The absolute value multiplier 132 obtains and outputs a square of the absolute value of each individual signal output from the signal component extractor 131, respectively.

The noise average detector 133 obtains an average value by adding the pilot symbol number to the output of the absolute value multiplier 132 and outputs the average value.

The noise power calculator 134 calculates and outputs the instantaneous value for each slot by subtracting the power of the signal component from each of the real and imaginary part outputs of the noise average detector 133.

The noise component adder 135 sums the real and imaginary power output values of the noise power calculator 134 to obtain the power of the noise and interference signal for each instant symbol of the corresponding slot. The noise and interference signal power obtained as described above are input to an alpha tracker 136.

The alpha tracker 136 calculates and outputs the instantaneous noise and interference signal power over a considerably long period in consideration of the fact that the power of the noise and interference signal does not change significantly with time.

The SIR estimator 140 obtains and outputs an SIR by using the outputs of the signal power measurer 120 and the noise power measurer 130.

When measuring the power of the signal using the SIR estimator according to the prior art as described above, the power of the noise added in the channel acts as a bias to the power of the measured signal as described above.

In addition, 3GPP 24.211 spec. In this case, the number of pilot bits may be 2 in the downlink slot format. This occurs in downlink slot formats 2, 2A, 3, 3A. In such a case, using a conventional method leads to a problem that power of noise and interference signals cannot be obtained. In other words, when Npilot = 2, Np = 1 and in this case, it means to average with one symbol. Therefore, the variance of the combiner output signal, which is a statistical characteristic of the interference and noise signals, cannot be obtained. There is a problem.

It is an object of the present invention to provide a noise power estimator and a method for estimating the power of noise even when the number of pilot bits is small.

Another object of the present invention is to provide an SIR estimator capable of estimating the power of noise even when the number of pilot bits is small in addition to the estimation of signal power without bias.

The noise power estimation method of the wideband code division multiple access terminal according to the present invention for achieving the above object, the signal input at the symbol level is divided into a real part and an imaginary part corresponding to the multiplication of the absolute value for each signal Obtaining and outputting power; converting power output at the symbol level to be output at a bit level; obtaining and outputting an average value of the total power of bits converted to the bit level and outputting the average; And subtracting the bit level power of the signal component from the total power of the bit, and outputting the noise power by averaging the subtracted output value for a predetermined period.

The step of converting the power output at the symbol level to be output at the bit level, characterized in that for converting the parallel output of the power corresponding to the square of the absolute value of the real and imaginary parts to be output to the serial output.

In the calculating and outputting the average value of the power converted into the bit level and outputting, the average value of the power converted into the bit level and output is divided by the total number of bits in the corresponding slot, divided by the total number of bits in the slot. It is characterized by setting it as a value.

In the calculating and outputting the average value of the power converted to the bit level and outputting, the average value of the output power is a value obtained by dividing the power of the noise obtained for each bit by the number of pilot bits and dividing by the corresponding number.

In the subtracting and outputting the bit level power of the signal component from the output average power, the bit level power of the input signal component is characterized in that 0.5 times the signal component symbol level power.

In addition, the noise power estimator of the wideband code division multiple access terminal to achieve the above object, the noise component separation unit for separating and outputting the rake combiner output signal into a real part and an imaginary part signal, An absolute value square unit for obtaining and outputting a square of an absolute value for each individual signal to be output; a noise signal converter for converting a power signal for each symbol output from the absolute value square for a bit power signal; A noise average calculating unit for obtaining and outputting an average value of an output value of the noise signal converting unit, a subtracting unit subtracting and outputting a bit level power value of a signal component from an output of the noise average calculating unit, and outputting the subtracting unit for a predetermined period of time; And an alpha tracker for averaging the output.

The noise average calculation unit may add the signal power output value of each of the corresponding slots output from the noise signal converter and divide the total power into the total number of bits in the corresponding slot.

The bit level power of the signal component input to the subtractor is 0.5 times the signal component symbol level power value.

The SIR estimator of the wideband code division multiple access terminal for achieving the another object, the signal power estimation unit for estimating and outputting the signal power from the received signal, and the present invention for estimating and outputting the noise power from the received signal And a SIR compensator for outputting a transmission power control signal according to the output signal of the signal power estimator and the bit level noise power estimator.

The signal power estimator detects and outputs the signal power from which the bias is removed.
The SIR compensator may include a first multiplier that obtains and outputs a bit level power of a data packet control channel from an output of the signal power estimator, and a second multiplier that outputs a target signal power by multiplying a noise power for each bit by a target SIR. And a subtractor for detecting a difference between the bit level power of the control channel and the target signal power and outputting the difference to the TPC controller, and a TPC controller for outputting an uplink transmission power control (TPC) signal according to the output of the subtractor. It features.

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According to the present invention configured as described above, if there is no bias in the signal power estimated by the signal power estimator to eliminate the problem of the hardware burden of compensating for the bias included in the signal power in the future according to the existing method At the same time, the bit-level noise power estimator makes it possible to estimate the power of the noise even when the number of pilot bits is small, thereby enabling a more accurate SIR estimation.

Hereinafter, a noise power estimator and an estimation method of a wideband code division multiple access terminal and an SIR estimating apparatus using the same will be described in detail with reference to the accompanying drawings.

2 is a diagram illustrating an SIR estimation apparatus of a wideband code division multiple access terminal according to an embodiment of the present invention.

Referring to FIG. 2, a noise power estimator of a wideband code division multiple access terminal according to an embodiment of the present invention estimates and outputs signal power from a signal output from a combiner 110 of a rake receiver. A bit level noise power estimator 230 for estimating and outputting noise power at a bit level from the signal output from the combiner end of the rake receiver 110, the signal power estimator 220, The SIR compensator 240 outputs a transmission power control signal according to the output signal of the bit level noise power estimator 230.

The signal power estimator 220 includes a conjugator 221, a multiplier 222, an average calculator 223, a simple square 224, and a signal power detector 225. do.

The bit level noise power estimator 230 includes a noise power separator 231, an absolute value square unit 232, a noise signal converter 233, a noise average calculator 234, and a subtractor ( 235 and an alpha tracker 236.

The SIR compensator 240 includes a first multiplier 241, a second multiplier 242, a subtractor 243, and a TPC control unit 244.

The operation and noise power estimation method of the SIR estimation apparatus of the wideband code division multiple access terminal including the noise power estimator of the wideband code division multiple access terminal according to the present invention will be described.

In the present invention, a simple square is used instead of the square of the absolute value used in the conventional method to remove the bias that may occur when measuring the signal power. According to the simple square, only the real term is taken from a squared value represented by a complex number and output as a signal power.

As such, the signal power estimator 220 detects and outputs the signal power from which the bias is removed, so that the multiplier 222 of the signal power estimator 220 is conjugated to the output signal of the lake combiner stage 110. Multiplying the conjugate value (conjugate) of the pilot symbol of the data packet control channel output from the gator unit 221,

The average calculator 223 averages and outputs the multiplier 222 output signal during the pilot bit field.

The simple square unit 224 obtains and outputs a simple square of the average value which is the output value of the average calculator 223.

The signal power detector 225 obtains a real part of the square value obtained by the simple square unit 224 and outputs it as a signal power estimation value to obtain a signal power estimation value from which bias is removed from the received total signal power. Will be.

Hereinafter, an operation of obtaining the power of the noise and the interference signal at the bit level from the signal output from the combiner terminal of the rake receiver 110 in the bit level noise power estimator 230 will be described.

On the other hand, in obtaining the power of the noise and interference signal, first, the noise power separation unit 231 first separates the complex-type rake combiner 110 output signal into a real part and an imaginary part. This is the same as the conventional method.

The absolute value squarer 232 obtains the square of the absolute value of each of the real and imaginary signals output from the noise component separator 231 and outputs the squares of the absolute values separately.

When the real part and the imaginary part powers are separately output from the absolute value square part 232, the noise signal converter 233 outputs the real and imaginary part output signal strings in parallel to a parallel output (Parallel to Serial: P /). Switch to S). In this case, the output signal of the noise signal converter 233 alternates the real part and the imaginary part, and this becomes a bit signal instead of a symbol. Here, the difference between symbols and bits may be recalled that downlink modulation is quadrature phase shift keying (QPSK). That is, since the output signal of the rake combiner 110 is modulated and sent in the QPSK form by the transmitting end, a complex signal is output. This means that one symbol is represented by two bits. Thus, dividing a complex signal into a real part and an imaginary part corresponds to converting a symbol into a bit. Therefore, the output signal of the noise signal converter 233 becomes a bit signal.

The noise average calculator 234 calculates and outputs an average value of the bit signals output from the noise signal converter 233. In order to calculate the average value of the output bit signals, the noise average calculator 234 adds the signal power output values of the entire bits of the corresponding slots output from the noise signal converter 233 and divides them by the total number of bits in the corresponding slot. . The average value of the bit signals output from the noise average calculator 234 corresponds to the total power of the output signal of the rake combiner 110.

Accordingly, the subtractor 235 subtracts the signal power (bit level power of the signal component) from the average value of the bit signals to output power of the bit interference and noise signal.

On the other hand, as can be seen in Figure 2, the signal power estimation has no bias, but has a structure for measuring the power in symbol units, in the case of noise power estimation, the total power of the lake combiner output signal is Npilot = In case of 2, it is a structure that estimates the power of a unit of bits rather than a symbol.

Therefore, in order to obtain the power of the interference and noise signal for each bit, the signal power for each symbol obtained from the signal power must be converted into the signal power for each bit. This bit-by-bit signal power is possible by multiplying the signal power per symbol by 0.5.

Therefore, subtracting the signal power of each bit multiplied by 0.5 by the signal power of each symbol from the total power of each bit combiner output, that is, the bit level power of the signal component is made to be half of the signal component symbol level power. Input to 235, the result is a value corresponding to the noise power per bit.

The power of the bit-by-bit interference and noise signal thus obtained is passed through the alpha tracker 236 to achieve a long-term average, and the output of the alpha tracker 236 is used to perform SIR estimation. Used as power for interference and noise signals.

Hereinafter, the output of the signal power estimator 220 for detecting and outputting the signal power from which the bias is removed and the output of the noise power estimator 230 to which the bit-by-bit noise and interference signal estimation method is applied according to the present invention are described. An operation of the SIR estimator 240 for estimating the SIR using the estimated SIR and outputting a transmit power control signal for controlling the transmit power using the estimated SIR will be described.

Schematically speaking, the final SIR generates an uplink transmit power control (UL TPC) signal compared to the target SIR. For this purpose, instead of dividing the signal power into interference and noise power, multiply the target SIR by the estimated interference and noise signal power to obtain the expected target signal power, and compare this value with the estimated signal power to generate a UL TPC.

This will be described for each detailed component of the SIR estimator 240.

First, the first multiplier 241 of the SIR estimator 240 obtains and outputs a bit level power of a data packet control channel from an output of the signal power estimator 220.

In addition, the second multiplier 242 outputs the target signal power by multiplying the target SIR by the bit power noise power output of the noise power estimation unit 230.

The subtractor 243 detects a difference between the bit level power of the data packet control channel that is the output of the first multiplier 241 and the target signal power that is the output of the second multiplier 242, and outputs the difference to the TPC controller 244. .

The TPC control unit 244 outputs the uplink transmission power control (UL TPC) signal according to the output of the subtractor 243. That is, when the target signal power is greater than the bit level power of the data packet control channel, the TPC control unit 244 outputs a control signal to decrease uplink transmission power, and conversely, the target signal power controls the data packet. If it is greater than the bit level power of the channel, the control signal is output to increase the uplink transmission power.

In order to test the effect of the SIR estimation apparatus of the wideband code division multiple access terminal according to the present invention described above, the following simulation was performed.

The overall environmental conditions for the simulation are as follows.

The average length was taken as 120 slots (80ms).

In the coherent sum square calculated by the coherent calculation in the signal power measuring method, the absolute square estimates the biased signal power, and the simple square according to the present invention. Unbiased signal power was estimated.

As a method of measuring interference and noise signal power, symbol noise power is measured using a conventional device configuration configured as shown in FIG. 1, and a bit noise power measurement method is measured using a device configuration configured according to the present invention as shown in FIG. 2. It was.

The channel condition is an additional white Gaussian noise (AWGN) 1 path, and the signal-to-noise ratio (Eb / No) is -15 to 20 dB for DPCH_Eb / No and -10 dB for CPICH_Ec / No. Fixed, 10% of total power).

The conditions for the spreading coefficient SFd and the corresponding pilot bit number set the spreading coefficient SFd for 8, 16, 32, and 128, respectively, and the data rate was 384 kbps, 144 kbps, 64 kbps, 12.2 kbps and the number of pilot bits (Npilot) were eight.

3A to 4D show the results of simulating the performance of the SIR estimating apparatus in the case of the conventional configuration and in the case of the configuration of the present invention under the simulation environment under the above conditions.

3A to 3D are graphs of the performance of the SIR estimator in the case of using the power of noise in symbol units.

3A to 3D are performance graphs of the SIR estimating apparatus when SFd = 128, SFd = 32, SFd = 16, and SFd = 8, respectively.

4A to 4 are graphs of the performance of the SIR estimator in the case where the power of the noise is in units of bits.

4A to 4D are performance graphs of the SIR estimating apparatus when SFd = 128, SFd = 32, SFd = 16, and SFd = 8, respectively.

As can be seen in Figures 3a to 3d, when measuring the power of the noise in symbol units, the signal power has no bias, that is, the case according to the configuration of the present invention there is a bias by the conventional method The overall performance is good compared with that, especially at low SNR.

Observing the results of FIGS. 4A to 4D, it can be seen that when the noise power is estimated in bits, the performance shows a constant value regardless of the bias of the signal power.

In other words, it can be seen that the performance of the SIR estimator varies considerably depending on how the power of the noise is estimated. When measuring the power of a biased signal, bias compensation was performed in the SIR calculation.

As a result of the experiment as described above, it was confirmed that according to the present invention, more accurate SIR can be estimated than that according to the prior art. As a result, when generating the UL TPC, the TPC combining method due to the TPC error can be more accurate, which can reduce the noise rise in the cell.

The SIR estimation apparatus of the wideband code division multiple access terminal according to the present invention has been described in detail above. However, the present invention is not limited thereto, and the present invention is included in the present invention even if the present invention is carried out without change and modification without departing from the spirit of the present invention, and the fact will be apparent to those skilled in the art.

According to the SIR estimation apparatus of the wideband code division multiple access terminal according to the present invention, there is no bias in estimating signal power, and according to the conventional method, there is a problem of hardware burden that must be compensated for in the bias included in the signal power later. It provides an advantage that can be eliminated.

In addition, even when the number of pilot bits is small, a more accurate SIR may be estimated by using a noise power estimator capable of estimating the power of noise.

Claims (11)

Dividing a complex signal input at a symbol level into a real part and an imaginary part to obtain and output power corresponding to a square value of an absolute value for each signal; Converting the power output at the symbol level to be output at a bit level; Obtaining and outputting an average value of the total power of the bits converted to the bit level and output; Subtracting and outputting bit level power of a signal component from the output average bit total power value; And outputting noise power by averaging the subtracted value for a predetermined period. The method of claim 1, wherein the converting the power output at the symbol level to be output at the bit level, A method of estimating noise power of a wideband code division multiple access terminal, comprising converting a parallel output of power corresponding to a square of an absolute value of an output real part and an imaginary part into a serial output. The method of claim 1, wherein in the step of obtaining and outputting an average value of the power converted to the bit level and output, The average value of the power converted to the bit level and output is the noise power estimation of the wideband code division multiple access terminal, characterized in that the output value of the signal power for each bit of the corresponding slot is divided by the total number of bits in the slot. Way. The method of claim 1, wherein in the step of obtaining and outputting an average value of the power converted to the bit level and output, The average value of the output power is a noise power estimation method of a wideband code division multiple access terminal, characterized in that the power of the noise obtained for each bit is added by the number of pilot bits divided by the number. 2. The wide bandwidth as claimed in claim 1, wherein in the subtracting and outputting the bit level power of the signal component from the outputted average power, the bit level power of the input signal component is 0.5 times the signal component symbol level power. Noise power estimation method of code division multiple access terminal. A noise component separator for separating and outputting the rake combiner output signal into a real part and an imaginary part signal; An absolute value square unit which obtains and outputs a square of an absolute value for each individual signal output from the noise component separator; A noise signal converter converting the power signal for each symbol output from the square of the absolute value into a power signal for each bit; A noise average calculator for calculating and outputting an average value of the output values of the noise signal converter; A subtraction unit for subtracting and outputting a bit level power value of a signal component from an output of the noise average calculator; And an alpha tracker for averaging the output of the subtractor for a predetermined period and outputting the noise. The method of claim 6, wherein the noise average calculation unit, The noise power estimator of the wideband code division multiple access terminal characterized in that the signal power output value of each bit of the corresponding slot output from the noise signal converter is divided by the total number of bits in the slot. 7. The noise power estimator of the wideband code division multiple access terminal according to claim 6, wherein the bit level power of the signal component input to the subtractor is 0.5 times the signal component symbol level power. A signal power estimator for estimating and outputting signal power from the received signal; A bit level noise power estimator of claim 6 for estimating and outputting noise power from a received signal; And an SIR compensator for outputting a transmission power control signal according to the output signal of the signal power estimator and the bit level noise power estimator. The method of claim 9, wherein the signal power estimator, SIR estimator of a wideband code division multiple access terminal, characterized in that for detecting and outputting the signal power without the bias. The method of claim 9, wherein the SIR compensator, A first multiplier for obtaining and outputting bit level power of a data packet control channel from an output of the signal power estimator; A second multiplier outputting a target signal power by multiplying the target SIR by the noise power for each bit; A subtractor for detecting a difference between the bit level power of the data packet control channel and the target signal power and outputting the detected signal to a TPC controller; And a TPC control unit for outputting an uplink transmission power control (TPC) signal according to the output of the subtractor.

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