CN101964991A - Error vector magnitude measurement method and device of TDD-LTF (Time Division Duplex-Laser Terrain Follower) terminal random access channel - Google Patents

Abstract

The invention discloses error vector magnitude measurement method and device of a TDD-LTF (Time Division Duplex-Laser Terrain Follower) terminal random access channel. The method comprises the following steps of: correlating 64 random access preambles with a receiving signal to produce 64 correlation peaks, selecting the preamble with the greatest correlation peak as a required preamble, correlating the preamble with the receiving signal, determining the starting position of the receiving signal, and taking out one random access signal; calculating a frequency error by using the correlation between the cyclic prefix of the signal and the last part of sampling points, eliminating phase error components, removing the cyclic prefix, performing FFT (Fast Fourier Transform), taking a complex value symbol block in allocated physical resource blocks, performing FFT on the required preamble to obtain reference signals, and taking the average magnitude value of the reference signals to obtain the magnitude of a measurement signal; comparing the phase of the complex value symbol block with the phases of the reference signals, taking the average phase difference as a hardware phase deviation, subtracting the hardware phase deviation from the phase of the complex value symbol block to obtain the phase of the measurement signal; and calculating EVM (Error Vector Magnitude) according to the measurement signal and the reference signals.

Description

The vector amplitude error method of measurement and the device of TDD-LTE terminal Random Access Channel

Technical field

The present invention relates to TDD-LTE terminal test field, particularly relate to a kind of vector amplitude error method of measurement and device of TDD-LTE terminal Random Access Channel.

Background technology

PRACH (Packet Random Access Channel, Packet Random Access Channel) preamble pulse sequence quality is the measurement that requires terminal is launched PRACH targeting sequencing ability according to core net, and base station correct demodulation PRACH channel is given security.Important content as transmitting set terminal radio frequency index test, EVM (Error Vector Magnitude, Error Vector Magnitude) the index consistency test is being brought into play irreplaceable effect at aspects such as terminal equipment research and development, production line quality control and radio frequency impairments location, and EVM is as a very important index weighing transmitter performance.

The receiver actual reception to digital modulation signals and ideal signal on amplitude, phase place and frequency, all exist certain difference, these differences are showing as measuring-signal and the deviation of standard constellation point on amplitude and phase place on the I/Q plane.EVM measures the difference vector of measuring-signal and reference signal, is called as error vector.EVM is defined as all square ratio of error vector power and reference vector power, represents that with the percentage form object of test is an accidental access signal.

EVM is the deviation between measuring-signal and the reference signal, and wherein measuring-signal is no frequency deviation and the influence of no initial phase, and the measuring-signal that therefore how to obtain not having frequency deviation and initial phase influence is the key issue that EVM tests.The measurement of the vector amplitude error that is used for TDD-LTE terminal Random Access Channel that proposes at present, the influence of not removing the hardware skew, the vector amplitude error of obtaining like this is not accurate enough.

Summary of the invention

The objective of the invention is in order to overcome the deficiency of above-mentioned background technology, a kind of result of calculation the vector amplitude error method of measurement and the device of TDD-LTE terminal Random Access Channel accurately are provided.

The vector amplitude error method of measurement of TDD-LTE terminal Random Access Channel provided by the invention comprises the following steps:

(1) utilize local 64 random access guidings that produce to carry out relevant with received signal, produce 64 relevant peaks, selecting wherein, the pairing random access guiding of relevant peaks of peak value maximum is required random access guiding, relevant with required random access guiding with received signal, determine the original position of received signal according to the position of the relevant peaks that produces, and extracting an accidental access signal from the original position of received signal, the accidental access signal that extracts is N by length _gCyclic Prefix and comprise the sequence composition of N sampled point, the length of sequence is N;

(2) utilize the correlation of Cyclic Prefix and its last part sampling point of the accidental access signal that extracts in (1), calculate the frequency error Δ f of this accidental access signal,

(3) each sampled point with the accidental access signal that extracts in (1) multiply by exp (jkt _c2 π Δ f), eliminate the phase error that is caused by frequency error, wherein j is the imaginary part unit in the plural number, and k is the constant of sampled point sequence number correspondence, k=1, and 2 ..., N, N are the sequence length in the accidental access signal, t _cBe the time interval, the frequency error of Δ f for obtaining in (2);

(4) will eliminate accidental access signal after the phase error in (3) with N _gPoint is starting point, takes out the signal that N is ordered, and removes Cyclic Prefix, wherein N _gBe the circulating prefix-length of accidental access signal, N is the sequence length in the accidental access signal;

(5) accidental access signal of having removed Cyclic Prefix in (4) is carried out fast fourier transform, and take out the complex value symbolic blocks in the Physical Resource Block that has distributed;

(6) phase place of complex value symbolic blocks every bit in (5) is compared with the phase place of reference signal every bit, the mean value of getting the phase difference of being had a few is as the hardware skew, and the phase place of complex value symbolic blocks deducts this hardware skew, obtains the phase place of measuring-signal; The required random access guiding of selecting in (1) is done fast fourier transform, obtain reference signal, the amplitude of reference signal is averaged, obtain the amplitude of measuring-signal; Phase place and amplitude by measuring-signal obtain measuring-signal, again according to measuring-signal and reference signal error of calculation amplitude of the vector.

Further, the complex value symbolic blocks in (5) is that length is that l, width are the matrix of f, wherein the subcarrier number of f for having distributed.

Further, the formula according to measuring-signal and reference signal error of calculation amplitude of the vector is in (6):

${\mathrm{EVM}}_{\mathrm{PRACH}}=\sqrt{\frac{\underset{f\∈F}{\mathrm{\Σ}}{|Z^{\′}\left(f\right)-I\left(f\right)|}^2}{P_0}}\×100\%$

Wherein: EVM is an Error Vector Magnitude, and Z ' (f) is the measuring-signal of no frequency error and hardware phase effect, and I (f) is a reference signal, and F is the carrier number of distributes resource blocks, P ₀Power for reference signal.

On the basis of above-mentioned method of measurement, the present invention also provides the vector amplitude error measurement mechanism of TDD-LTE terminal Random Access Channel, comprising:

Positioning unit: be used to utilize local 64 random access guidings that produce to carry out relevant with received signal, produce 64 relevant peaks, selecting wherein, the pairing random access guiding of relevant peaks of peak value maximum is required random access guiding, relevant with required random access guiding with received signal, determine the original position of received signal according to the position of the relevant peaks that produces, and extracting an accidental access signal from the original position of received signal, the accidental access signal that extracts is N by length _gCyclic Prefix and comprise the sequence composition of N sampled point, the length of sequence is N;

Frequency error computing unit: be used to utilize the Cyclic Prefix of the accidental access signal that positioning unit extracts and the correlation of its last part sampling point, calculate the frequency error Δ f of this accidental access signal;

Remove the phase error unit: each sampled point that is used for accidental access signal that positioning unit is extracted multiply by exp (jkt _c2 π Δ f), eliminate the phase error that is caused by frequency error, wherein j is the imaginary part unit in the plural number, and k is the constant of sampled point sequence number correspondence, k=1, and 2 ..., N, N are the sequence length in the accidental access signal, t _cBe the time interval, the frequency error that Δ f obtains for the frequency error computing unit;

Remove cyclic prefix unit: be used for the accidental access signal after the elimination phase error with N _gPoint is starting point, takes out the signal that N is ordered, and removes Cyclic Prefix, wherein N _gBe the circulating prefix-length of accidental access signal, N is the sequence length in the accidental access signal;

Fast Fourier transform unit: be used for the accidental access signal of removing Cyclic Prefix is carried out fast fourier transform, and take out complex value symbolic blocks in the Physical Resource Block distributed;

Reference signal acquiring unit: be used for the required random access guiding that positioning unit is selected is done fast fourier transform, obtain reference signal;

Hardware skew acquiring unit: be used for the phase place of complex value symbolic blocks every bit is compared with the phase place of reference signal every bit, the mean value of getting the phase difference of being had a few is as the hardware skew;

Error Vector Magnitude computing unit: be used for the phase place of complex value symbolic blocks is deducted this hardware skew, obtain the phase place of measuring-signal; The amplitude of reference signal is averaged, obtain the amplitude of measuring-signal; Phase place and amplitude by measuring-signal obtain measuring-signal, again according to measuring-signal and reference signal error of calculation amplitude of the vector.

Further, described complex value symbolic blocks is that length is that l, width are the matrix of f, wherein the subcarrier number of f for having distributed.

The influence that the present invention obtains the hardware skew and removes the hardware skew according to the phase place of reference signal and received signal, implementation procedure is simple, calculating is more accurate, thereby can overcome the shortcoming of conventional method.

Description of drawings

Fig. 1 is a method flow diagram of the present invention.

Fig. 2 is that the embodiment of the invention is carried out signal flow graph and the schematic diagram that located in connection is calculated.

Fig. 3 is embodiment of the invention calculated rate error by principle figure.

Embodiment

The present invention is described in further detail below in conjunction with drawings and Examples, but this embodiment should not be construed as limitation of the present invention.

Referring to shown in Figure 1, the vector amplitude error method of measurement of TDD-LTE provided by the invention (Time Division Duplexing-Long Term Evolution, time division duplex-Long Term Evolution) terminal Random Access Channel comprises following 6 steps:

Step (1):

By after receiver (receiving system) received signal, its quadrature demodulation is become I, Q two paths of signals in the TDD-LTE terminal.Referring to shown in Figure 2, utilize available in the local sub-district that produces 64 random access guidings and received signal to carry out located in connection, 64 relevant peaks of relevant generation, selecting wherein, the pairing random access guiding of relevant peaks of peak value maximum is required random access guiding, relevant with required random access guiding with received signal, determine the original position of received signal according to the position of the relevant peaks that produces, and extracting an accidental access signal from the original position of received signal, the accidental access signal that extracts is N by length _gCyclic Prefix and comprise the sequence composition of N sampled point, the length of sequence is N, and 5 kinds of forms are specifically arranged, and is as shown in table 1.The embodiment of the invention is an example with leading format 4, and circulating prefix-length is 448, comprises 4096 sampled points in the sequence.

Table 1: random access guiding parameter

Leading form	N g	N
			0	3168	24576
1	21024	24576
			2	6240	2.24576
3	21024	2.24576
			4	448	4096

Step (2):

Utilize the correlation of Cyclic Prefix He its last part sampling point of the accidental access signal that extracts in the step (1), calculate the frequency error Δ f of this accidental access signal.The process of concrete calculated rate error delta f is referring to shown in Figure 3, because data distortion can be bigger under the situation that multipath disturbs for Cyclic Prefix, so utilize the relevant number of minimizing data to reduce the error of calculating at this, at first take out the part of Cyclic Prefix in the symbol, utilize the Cyclic Prefix that takes out to be correlated with then and obtain frequency error value with a part identical with its corresponding symbol end.Concrete grammar is as follows: accidental access signal is to be N by length _gCyclic Prefix and the length data that are N form, Cyclic Prefix is the last N of signal _gThe repetition of individual sampling point, when frequency deviation influenced, the relation of Cyclic Prefix and signal last part sampling point can be represented by following formula:

$r(m,n+N)=r(m,n)e^{-j2\mathrm{\π\ΔfN}{t}_c}$

Wherein m is signal index (herein being 1 accidental access signal, i.e. m=1), and n is the index of each sampled point, and N is the length of sequence in the accidental access signal, the accidental access signal of r for extracting, and j is the imaginary part unit in the plural number, Δ f is the frequency deviation that estimates, t _cBe the time interval.

Can get thus:

$z=\underset{n=1}{\overset{N_g}{\mathrm{\Σ}}}r(m,n)r^{*}(m,n+N)$

$=\underset{n=1}{\overset{N_g}{\mathrm{\Σ}}}r(m,n){\left(r(m,n)e^{j2\mathrm{\π\ΔfN}{t}_c}\right)}^{*}$

$=e^{-j2\mathrm{\π\Δf}{t}_c}\underset{n=1}{\overset{N_g}{\mathrm{\Σ}}}{\left|r(m,n)\right|}^2$

N _gBe the length of each symbol cyclic prefix, t _cBe the time interval, N is the length of sequence in the accidental access signal, and Δ f is the frequency deviation that estimates, and j is the imaginary part unit in the plural number, and * is a conjugation of asking plural number.

So the frequency deviation Δ f that estimates is: Arg () is for asking angle function.

Step (3): each sampled point of the accidental access signal that extracts in the step (1) be multiply by exp (jkt _c2 π Δ f), eliminate the phase error that is caused by frequency error, wherein j is the imaginary part unit in the plural number, and k is the constant of sampled point sequence number correspondence, k=1, and 2 ..., N, N are the sequence length 4096 in the accidental access signal, t _cBe the time interval, Δ f is the frequency error of obtaining in the step (2).

Step (4): will eliminate accidental access signal after the phase error in the step (3) with N _gPoint is got 4096 points backward for starting point, removes Cyclic Prefix, wherein N _gCirculating prefix-length 448 for accidental access signal.

Step (5):

The accidental access signal of having removed Cyclic Prefix in the step (4) is carried out FFT (Fast Fourier Transformation, fast fourier transform) conversion, and take out complex value symbolic blocks in the Physical Resource Block distributed, the complex value symbolic blocks is that length is that l, width are the matrix of f, wherein the subcarrier number of f for having distributed.

Step (6);

The phase place of complex value symbolic blocks every bit in the step (5) is compared with the phase place of reference signal every bit, and the mean value of getting the phase difference of being had a few is as the hardware skew, and the phase place of complex value symbolic blocks deducts this hardware skew, obtains the phase place of measuring-signal;

The required random access guiding of selecting in the step (1) is done fast fourier transform, obtain reference signal, the amplitude of reference signal is averaged, obtain the amplitude of measuring-signal; Phase place and amplitude by measuring-signal obtain measuring-signal, and according to measuring-signal and reference signal error of calculation amplitude of the vector, the formula of error of calculation amplitude of the vector EVM is again:

${\mathrm{EVM}}_{\mathrm{PRACH}}=\sqrt{\frac{\underset{f\∈F}{\mathrm{\Σ}}{|Z^{\′}\left(f\right)-I\left(f\right)|}^2}{P_0}}\×100\%$

Wherein: EVM is an Error Vector Magnitude, and Z ' (f) is the measuring-signal of no frequency error and hardware phase effect, and I (f) is a reference signal, and F is the carrier number of distributes resource blocks, P ₀Power for reference signal.

On the basis of above-mentioned method of measurement, the present invention also provides the vector amplitude error measurement mechanism of TDD-LTE terminal Random Access Channel, comprising:

Positioning unit: be used to utilize local 64 random access guidings that produce to carry out relevant with received signal, produce 64 relevant peaks, selecting wherein, the pairing random access guiding of relevant peaks of peak value maximum is required random access guiding, relevant with required random access guiding with received signal, determine the original position of received signal according to the position of the relevant peaks that produces, and extracting an accidental access signal from the original position of received signal, the accidental access signal that extracts is N by length _gCyclic Prefix and comprise the sequence composition of N sampled point, the length of sequence is N;

Frequency error computing unit: be used to utilize the Cyclic Prefix of the accidental access signal that positioning unit extracts and the correlation of its last part sampling point, calculate the frequency error Δ f of this accidental access signal;

Remove the phase error unit: each sampled point that is used for accidental access signal that positioning unit is extracted multiply by exp (jkt _c2 π Δ f), eliminate the phase error that is caused by frequency error, wherein j is the imaginary part unit in the plural number, and k is the constant of sampled point sequence number correspondence, k=1, and 2 ..., N, N are the sequence length in the accidental access signal, t _cBe the time interval, the frequency error that Δ f obtains for the frequency error computing unit;

Remove cyclic prefix unit: be used for the accidental access signal after the elimination phase error with N _gPoint is starting point, takes out the signal that N is ordered, and removes Cyclic Prefix, wherein N _gBe the circulating prefix-length of accidental access signal, N is the sequence length in the accidental access signal;

Fast Fourier transform unit: be used for the accidental access signal of removing Cyclic Prefix is carried out fast fourier transform, and take out complex value symbolic blocks in the Physical Resource Block distributed, the complex value symbolic blocks is that length is that l, width are the matrix of f, wherein the subcarrier number of f for having distributed.

Reference signal acquiring unit: be used for the required random access guiding that positioning unit is selected is done fast fourier transform, obtain reference signal;

Hardware skew acquiring unit: be used for the phase place of complex value symbolic blocks every bit is compared with the phase place of reference signal every bit, the mean value of getting the phase difference of being had a few is as the hardware skew;

Error Vector Magnitude computing unit: be used for the phase place of complex value symbolic blocks is deducted this hardware skew, obtain the phase place of measuring-signal; The amplitude of reference signal is averaged, obtain the amplitude of measuring-signal; Phase place and amplitude by measuring-signal obtain measuring-signal, again according to measuring-signal and reference signal error of calculation amplitude of the vector.

In the terminal test of TDD-LTE, the method for measurement of the available embodiment of the invention and device carry out the measurement of the vector amplitude error of PRACH channel, thereby weigh the quality of communication system modulation quality.

Obviously, those skilled in the art can carry out various changes and modification to the present invention and not break away from the spirit and scope of the present invention.Like this, if of the present invention these are revised and modification belongs within the scope of claim of the present invention and equivalent technologies thereof, then the present invention also is intended to comprise these changes and modification interior.

The content that is not described in detail in this specification belongs to this area professional and technical personnel's known prior art.

Claims (5)

1. the vector amplitude error method of measurement of a TDD-LTE terminal Random Access Channel is characterized in that comprising the following steps:

(1) utilize local 64 random access guidings that produce to carry out relevant with received signal, produce 64 relevant peaks, selecting wherein, the pairing random access guiding of relevant peaks of peak value maximum is required random access guiding, relevant with required random access guiding with received signal, determine the original position of received signal according to the position of the relevant peaks that produces, and extracting an accidental access signal from the original position of received signal, the accidental access signal that extracts is N by length _gCyclic Prefix and comprise the sequence composition of N sampled point, the length of sequence is N;

(2) utilize the correlation of Cyclic Prefix and its last part sampling point of the accidental access signal that extracts in (1), calculate the frequency error Δ f of this accidental access signal,

(3) each sampled point with the accidental access signal that extracts in (1) multiply by exp (jkt _c2 π Δ f), eliminate the phase error that is caused by frequency error, wherein j is the imaginary part unit in the plural number, and k is the constant of sampled point sequence number correspondence, k=1, and 2 ..., N, N are the sequence length in the accidental access signal, t _cBe the time interval, the frequency error of Δ f for obtaining in (2);

(4) will eliminate accidental access signal after the phase error in (3) with N _gPoint is starting point, takes out the signal that N is ordered, and removes Cyclic Prefix, wherein N _gBe the circulating prefix-length of accidental access signal, N is the sequence length in the accidental access signal;

(5) accidental access signal of having removed Cyclic Prefix in (4) is carried out fast fourier transform, and take out the complex value symbolic blocks in the Physical Resource Block that has distributed;

(6) the required random access guiding of selecting in (1) is done fast fourier transform, obtain reference signal, the amplitude of reference signal is averaged, obtain the amplitude of measuring-signal; The phase place of complex value symbolic blocks every bit in (5) is compared with the phase place of reference signal every bit, and the mean value of getting the phase difference of being had a few is as the hardware skew, and the phase place of complex value symbolic blocks deducts this hardware skew, obtains the phase place of measuring-signal; Amplitude and phase place by measuring-signal obtain measuring-signal, again according to measuring-signal and reference signal error of calculation amplitude of the vector.

2. the vector amplitude error method of measurement of TDD-LTE terminal Random Access Channel as claimed in claim 1 is characterized in that: the complex value symbolic blocks in (5) is that length is that l, width are the matrix of f, wherein the subcarrier number of f for having distributed.

3. the vector amplitude error method of measurement of TDD-LTE terminal Random Access Channel as claimed in claim 1 is characterized in that: the formula according to measuring-signal and reference signal error of calculation amplitude of the vector in (6) is:

${\mathrm{EVM}}_{\mathrm{PRACH}}=\sqrt{\frac{\underset{f\∈F}{\mathrm{\Σ}}{|Z^{\′}\left(f\right)-I\left(f\right)|}^2}{P_0}}\×100\%$

Wherein: EVM is an Error Vector Magnitude, and Z ' (f) is the measuring-signal of no frequency error and hardware phase effect, and I (f) is a reference signal, and F is the carrier number of distributes resource blocks, P ₀Power for reference signal.

4. the vector amplitude error measurement mechanism of a TDD-LTE terminal Random Access Channel is characterized in that comprising:

Positioning unit: be used to utilize local 64 random access guidings that produce to carry out relevant with received signal, produce 64 relevant peaks, selecting wherein, the pairing random access guiding of relevant peaks of peak value maximum is required random access guiding, relevant with required random access guiding with received signal, determine the original position of received signal according to the position of the relevant peaks that produces, and extracting an accidental access signal from the original position of received signal, the accidental access signal that extracts is N by length _gCyclic Prefix and comprise the sequence composition of N sampled point, the length of sequence is N;

Frequency error computing unit: be used to utilize the Cyclic Prefix of the accidental access signal that positioning unit extracts and the correlation of its last part sampling point, calculate the frequency error Δ f of this accidental access signal;

Remove the phase error unit: each sampled point that is used for accidental access signal that positioning unit is extracted multiply by exp (jkt _c2 π Δ f), eliminate the phase error that is caused by frequency error, wherein j is the imaginary part unit in the plural number, and k is the constant of sampled point sequence number correspondence, k=1, and 2 ..., N, N are the sequence length in the accidental access signal, t _cBe the time interval, the frequency error that Δ f obtains for the frequency error computing unit;

Remove cyclic prefix unit: be used for the accidental access signal after the elimination phase error with N _gPoint is starting point, takes out the signal that N is ordered, and removes Cyclic Prefix, wherein N _gBe the circulating prefix-length of accidental access signal, N is the sequence length in the accidental access signal;

Fast Fourier transform unit: be used for the accidental access signal of removing Cyclic Prefix is carried out fast fourier transform, and take out complex value symbolic blocks in the Physical Resource Block distributed;

Reference signal acquiring unit: be used for the required random access guiding that positioning unit is selected is done fast fourier transform, obtain reference signal;

Hardware skew acquiring unit: be used for the phase place of complex value symbolic blocks every bit is compared with the phase place of reference signal every bit, the mean value of getting the phase difference of being had a few is as the hardware skew;

Error Vector Magnitude computing unit: be used for the phase place of complex value symbolic blocks is deducted this hardware skew, obtain the phase place of measuring-signal; The amplitude of reference signal is averaged, obtain the amplitude of measuring-signal; Phase place and amplitude by measuring-signal obtain measuring-signal, again according to measuring-signal and reference signal error of calculation amplitude of the vector.

5. the vector amplitude error measurement mechanism of TDD-LTE terminal Random Access Channel as claimed in claim 4 is characterized in that: described complex value symbolic blocks is that length is that l, width are the matrix of f, wherein the subcarrier number of f for having distributed.

Images