CN108989259B - Time offset estimation method and system for narrow-band physical uplink shared channel of wireless comprehensive measurement instrument - Google Patents

Time offset estimation method and system for narrow-band physical uplink shared channel of wireless comprehensive measurement instrument Download PDF

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CN108989259B
CN108989259B CN201810797513.8A CN201810797513A CN108989259B CN 108989259 B CN108989259 B CN 108989259B CN 201810797513 A CN201810797513 A CN 201810797513A CN 108989259 B CN108989259 B CN 108989259B
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吴帅
周英
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Shenzhen Itest Technology Co ltd
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Abstract

The invention provides a time offset estimation method and a system for a narrow-band physical uplink shared channel of a wireless comprehensive measurement instrument, wherein the time offset estimation method comprises the following steps: step S1, performing a first time offset estimation on the received data of the narrowband physical uplink shared channel to obtain a first start position of the data; step S2, extracting the narrowband demodulation reference signal time domain data of the front part and the back part to obtain first time domain data and second time domain data; step S3, calculating the correlation value of the first time domain data and the second time domain data at the current moment; step S4, determining whether the maximum correlation value is greater than a preset threshold value according to the correlation value, and re-confirming the second start position of the data until the maximum correlation value is greater than the preset threshold value. The invention can effectively reduce the calculation time length of time offset estimation, can ensure good work under the condition of large frequency offset, can further obtain better symbol timing estimation performance, and has certain frequency offset resistance effect.

Description

Time offset estimation method and system for narrow-band physical uplink shared channel of wireless comprehensive measurement instrument
Technical Field
The invention relates to a time offset estimation method, in particular to a time offset estimation method of a narrow-band physical uplink shared channel of a wireless comprehensive tester, and a time offset estimation system adopting the time offset estimation method of the narrow-band physical uplink shared channel of the wireless comprehensive tester.
Background
The OFDM technology has become the most competitive transmission technology in the mobile communication system due to its characteristics of high spectrum utilization, strong resistance to multipath fading, reliable transmission, and the like. The OFDM adopts orthogonal subcarriers for modulation, is sensitive to the orthogonality of the carriers, and can form self-interference once the orthogonality is damaged, thereby seriously reducing the performance. Symbol synchronization errors cause intersymbol interference, destroy the orthogonality of subcarriers, and have a large influence on a system, so that accurate symbol synchronization is very important.
The symbol timing synchronization algorithms that exist today can be roughly classified into two categories, namely data-aided (DA) algorithms or non-data-aided (NDA) algorithms (i.e., blind estimation). The DA algorithm can be further divided into two methods, one is a method based on a training symbol sequence, and the other is a method based on inserting a pilot symbol, but these methods all reduce the data rate, resulting in a decrease in the spectrum utilization of the system. The NDA algorithm utilizes the structure of the OFDM symbol, such as estimation based on virtual subcarriers and cyclic prefixes. Based on the blind estimation of the virtual subcarrier, the characteristic value diversity is needed when a subspace algorithm is adopted, the calculation amount is large, and the realization is complex; the Maximum Likelihood (ML) algorithm based on the cyclic prefix is susceptible to data, noise and channel, and the accuracy of the algorithm is not high.
NB-IOT (NarrowBand Internet of Things) is a NarrowBand IOT (Internet of Things) technology based on honeycomb, and supports the honeycomb data connection of low-power consumption equipment in a wide area network. The NB-IOT is mainly applied to scenes with low throughput, large time delay tolerance and low mobility, such as intelligent electric meters, remote sensors, intelligent buildings and the like. The NB-IOT can be directly deployed in the existing GSM or LTE network, namely, the existing base station can be reused to reduce the deployment cost and realize smooth upgrade.
The NB-IOT uplink defines a narrowband physical layer uplink shared channel (NPUSCH) and a narrowband physical layer random access channel (NPRACH). The present patent application is primarily concerned with symbol timing synchronization of the NPUSCH channel. In the NB-IOT system, a Narrowband Physical Uplink Shared Channel (NPUSCH) is mainly used to transmit data information and control information of a terminal. The uplink transmission bandwidth of the NB-IOT system is 180kHz, the uplink simultaneously supports 3.75kHz and 15kHz subcarrier intervals, and the multiple access mode is single carrier frequency division multiple access (SC-FDMA); the use of 3.75kHz subcarrier spacing only supports single subcarrier scheduling, while the 15kHz subcarrier spacing supports both single and multiple subcarrier scheduling. To better fit the 3.75kHz subcarrier spacing, the protocol defines a new narrowband slot structure of length 2 ms. As shown in fig. 2 and 3 below, one radio frame includes 5 narrowband slots, each of which includes 7 Orthogonal Frequency Division Multiplexing (OFDM) symbols.
Wherein the time-frequency resource grid (including one time slot) in fig. 2 and 3
Figure BDA0001736296710000021
Sub-carriers and
Figure BDA0001736296710000022
one SC-FDMA symbol). For Δ f 15kHz, the slot number of a radio frame is ns∈{0,1,…,19}，
Figure BDA0001736296710000023
Figure BDA0001736296710000024
For Δ f ═ 3.75kHz, ns∈{0,1,…,4}，，
Figure BDA0001736296710000025
The NB-IOT uplink introduces the concept of resource units, and the scheduling of uplink data and the transmission of HARQ-ACK information are both in units of resource units. One resource unit is defined as being in the time domain
Figure BDA0001736296710000026
One continuous SC-FDMA symbol and frequency domain
Figure BDA0001736296710000027
A plurality of continuous sub-carriers, wherein
Figure BDA0001736296710000028
And
Figure BDA0001736296710000029
as shown in the following table:
the different formats of NPUSCH include resource units and time slot numbers
Figure BDA00017362967100000210
From the above table, it can be seen that: for a single tone NPUSCH, if one 3.75kHz subcarrier spacing is used, its RU spans 32ms in the time domain; if a single 15kHz subcarrier is used, its RU spans 8ms in the time domain.
For the multi-tone NPUSCH, when 3 subcarriers are used, the RU spans 4ms in the time domain; when 6 subcarriers are used, the RU spans 2ms in the time domain; when 12 subcarriers are used, the RU spans 1ms in the time domain.
For NPUSCH format 2, the RU spans 8ms in the time domain if a single 3.75kHz subcarrier is used, and 2ms in the time domain if a single 15kHz subcarrier is used.
In the NB-IOT system, for NPUSCH Format1, the physical uplink shared channel also has a pilot sequence, i.e. a Narrow-band Demodulation Reference Signal (ndsmrs) per timeslot. Where each two adjacent ndsmrs have the same transmission time interval (7 OFDM symbols apart). The reference signal NDMRS is mainly used for channel estimation and time and frequency synchronization of a physical uplink shared channel.
During production testing, a DUT is usually connected to a wireless integrated tester by a wired connection. The DUT and the wireless comprehensive tester are two independent systems, so the transmission delay of signals and the processing time of the ADC cause the time offset of symbols, and if the signals are directly demodulated, the inter-symbol interference is caused, and the orthogonality of subcarriers is influenced. Accurate symbol timing synchronization is necessary prior to signal processing.
Considering an OFDM communication system, a transmitter up-converts a baseband signal by carrier modulation and then down-converts the signal to baseband at a receiver by using the same local carrier. The IFFT and FFT are the basic functions of transmitter modulation and receiver demodulation, respectively. In order to perform an N-point FFT at the receiver, accurate samples of the transmitted signal need to be obtained within an OFDM symbol period. In other words, in order to detect the start point of each (CP-removed) OFDM symbol, symbol timing synchronization must be performed, which helps to obtain accurate sampling. Assuming a time offset of delta magnitude in the time domain, then at a sample rate of FsIn the case of (1), τ sample point shifts τ δ · F may exists。
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a time offset estimation method for a narrowband physical uplink shared channel of a wireless integrated tester, which can obtain better symbol timing estimation performance and has a certain frequency offset resistant effect, and further provide a time offset estimation system using the time offset estimation method for the narrowband physical uplink shared channel of the wireless integrated tester.
To this end, the invention provides a time offset estimation method for a narrow-band physical uplink shared channel of a wireless comprehensive tester, which comprises the following steps:
step S1, performing a first time offset estimation on the received data of the narrowband physical uplink shared channel to obtain a first start position of the data;
step S2, extracting the narrowband demodulation reference signal time domain data of the front part and the back part to obtain first time domain data and second time domain data;
step S3, calculating the correlation value of the first time domain data and the second time domain data at the current moment;
step S4, determining whether the maximum correlation value is greater than a preset threshold value according to the correlation value, and re-confirming the second start position of the data until the maximum correlation value is greater than the preset threshold value.
In a further improvement of the present invention, the step S1 includes the following sub-steps:
step S101, obtaining the received data of the narrow-band physical uplink shared channel;
step S102, a first time offset estimation is carried out through double sliding window power detection, and then a first initial position of data is obtained.
A further refinement of the invention is that said step S2 comprises the following sub-steps:
step S201, locally generating frequency domain modulation data of a narrowband demodulation reference signal, and calculating and recording the sign of the frequency domain modulation data of the narrowband demodulation reference signal;
step S202, extracting the time domain data of the narrowband demodulation reference signal of the front part to obtain first time domain data;
step S203, extracting the narrowband demodulation reference signal time domain data of the latter part to obtain second time domain data.
In a further improvement of the present invention, in the step S201, whether the frequency domain modulation data of the narrowband demodulation reference signal is a single tone signal is determined, and if so, the sign is calculated according to the frequency domain complex symbol data of the narrowband demodulation reference signal; and if not, the rotation mark position 1 of the sign of the frequency domain modulation data of the narrowband demodulation reference signal is used.
The invention is further improved in that in the step S201, the formula is used
Figure BDA0001736296710000041
Figure BDA0001736296710000042
Calculating sign of frequency domain modulation data of the narrowband demodulation reference signal in single-tone signal modeNDMRS(k1) Or, setting signNDMRS(k1) 1 is ═ 1; wherein the content of the first and second substances,
Figure BDA0001736296710000043
k1for the subscript index of the narrowband demodulation reference signal, real () denotes the real part of the complex signal, imag () denotes the imaginary part of the complex signal, SNDMRS(k) K is more than or equal to 0 and less than or equal to N for the frequency domain complex symbol data of the narrow-band demodulation reference signalNDMRS-1，NNDMRSThe number of single carrier frequency division multiple access symbols of the narrow-band demodulation reference signal.
The invention is further improved in that in the step S202, the formula is used
Figure BDA0001736296710000044
Figure BDA0001736296710000045
Extracting first time domain data
Figure BDA0001736296710000046
Wherein n is1The index is a time slot number index, m is a time domain sampling point index of a current time slot number, τ is a length index of shift correlation operation, totalSymLen is a time domain total length of a single carrier frequency division multiple access symbol containing a cyclic prefix, and r is received time domain data.
The invention is further improved in that in the step S203, the formula is used
Figure BDA0001736296710000047
Figure BDA0001736296710000051
Extracting second time domain data
Figure BDA0001736296710000052
Wherein n is2Is the index of the time slot number, m is the index of the time domain sampling point of the current time slot number, tau is the index of the length of the shift correlation operation, totalSymLen is the total time domain length of a single carrier frequency division multiple access symbol containing the cyclic prefix,
Figure BDA0001736296710000053
is the sign of the local NDMRS data, and r is the received time domain data.
In a further improvement of the present invention, in the step S3, the formula is used
Figure BDA0001736296710000054
Calculating a correlation value between the first time domain data and the second time domain data at the current time
Figure BDA0001736296710000055
Wherein pndrsdata 1 and pndrsdata 2 are the values of the first time domain data and the second time domain data at the current time, respectively.
A further refinement of the invention is that said step S4 comprises the following sub-steps:
step S401, calculating τ ═ τ + 1;
step S402, judging whether tau is larger than Nstart+N corrLen1, if not, returning to step S2, if yes, jumping to step S403;
step S403, using formula
Figure BDA0001736296710000056
Searching to obtain a maximum correlation value, comparing the maximum correlation value with a preset threshold value, and if the maximum correlation value is larger than the threshold value, determining that the maximum correlation value is larger than the threshold value
Figure BDA0001736296710000057
Is a time bias estimated value; otherwise, an error is returned.
The invention also provides a time bias estimation system of the narrow-band physical uplink shared channel of the wireless comprehensive tester, which adopts the time bias estimation method of the narrow-band physical uplink shared channel of the wireless comprehensive tester.
Compared with the prior art, the invention has the beneficial effects that: carrying out double sliding window power detection on the received data of the narrow-band physical uplink shared channel to obtain a rough initial position, so that the calculation time length of the time offset estimation subdivided later can be reduced; then extracting the time domain data of the narrowband demodulation reference signals of the front part and the rear part, and finding a peak value through a correlation value of the first time domain data and the second time domain data to determine subdivided time offset estimation, wherein the fine time offset estimation can be ensured to work well under the condition of large frequency offset, so that better symbol timing estimation performance can be obtained, and a certain frequency offset resistant effect is achieved; finally, the wireless comprehensive tester can more accurately estimate the time offset of DUT (tested device) data under the condition of smaller complexity, and can well meet the requirements of production test.
Drawings
FIG. 1 is a schematic workflow diagram of one embodiment of the present invention;
fig. 2 is a schematic diagram of a timeslot structure at a subcarrier interval of a narrowband internet of things;
fig. 3 is a schematic diagram of a time slot structure at another subcarrier interval of a narrowband internet of things;
FIG. 4 is a schematic diagram illustrating the principle of symbol timing estimation based on cyclic prefix according to an embodiment of the present invention;
FIG. 5 is a diagram of a time domain structure of a narrowband physical uplink shared channel in an embodiment of the present invention, where a carrier spacing is 15 kHz;
FIG. 6 is a flowchart illustrating the operation of one embodiment of the present invention to generate the rotation flag for the local sign;
fig. 7 is a detailed workflow diagram of one embodiment of the present invention.
Detailed Description
Preferred embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.
This example explains the terms first: NB-IOT (narrow Band Internet of things) is a narrow-Band Internet of things; npusch (narrow band Physical Uplink Shared channel) is a narrow-band Physical Uplink Shared channel; OFDM (orthogonal Frequency Division multiplexing) is orthogonal Frequency Division multiplexing; DA (data aid) as data assistance; NDA (non Data aid) is non-Data-assisted; ml (maximum likelihood) is the maximum likelihood estimate; GSM (Global System for Mobile communication) is a Global System for Mobile communications; lte (long Term evolution) is long Term evolution; SC-FDMA (Single-Carrier Frequency-Division Multiple Access) is Single carrier Frequency Division Multiple Access.
It is assumed that there is only a timing error of magnitude τ between the transmitter and receiver, without any phase noise. The time domain received signal can be expressed as:
Figure BDA0001736296710000061
where N is 1,2, … N is the sequence number of the time domain sample point, k is 1,2, …, N is the sequence number of the frequency domain subcarrier, N is the number of samples, H [ k [ k ] ]]For each sub-carrier's frequency domain channel parameter, X k]For transmitted frequency domain data, z [ n ]]Channel gaussian noise in the time domain. Generally used time offset estimation techniques are Cyclic Prefix (CP) based time offset estimation and training sequence based time offset estimation based on the NPUSCH channel format of the NB-IOT system.
Analysis of the cyclic prefix based time domain STO estimation technique as shown in fig. 4, a CP (cyclic prefix) is a copy of a portion of data in an OFDM symbol. This means that the CP (cyclic prefix) and the corresponding data part are the same. And this same can be used for the estimation of STO. As shown in FIG. 4, B and B' represent N of CP, respectivelyGN of sample and data portionsGAnd (4) sampling. Note that the two sample blocks in B and B' are identical and that the two sample blocks are separated by NsubAnd (4) sampling. Consider two sliding windows W1 and W2. Spaced apart by a distance NsubAnd (4) sampling. The direct similarity of samples in two windows can be searched by sliding windows W1 and W2. N within two windows when CP of OFDM symbol falls within W1GThe direct similarity of the sample blocks is maximized. Using this maximum point, STO can be identified. The similarity of two blocks of samples W1 and W2 is maximized when the difference between the two blocks is minimized. Therefore, in two windows, the search results (from N)GOne sample) at the point where the difference between the two blocks takes the minimum value, STO can be estimated:
Figure BDA0001736296710000071
although this technique is simple, its performance may be degraded when there is a CFO in the receiving system.
Another symbol timing estimation based on the training sequence is to use the baseband received signal after down conversion to perform sliding cross-correlation operation with the locally stored NDMRS sequence, and the position of the correlation peak is used to determine the timing synchronization position of the system.
The estimation accuracy based on the cyclic prefix algorithm is related to the length of the cyclic prefix CP, and the longer the length of the cyclic prefix CP, the higher the estimation accuracy. The symbol timing estimation based on the cyclic prefix can adapt to the change of the channel well, but the cyclic prefix is easily affected by intersymbol interference, so that the estimation accuracy is reduced. Since the cyclic prefix of the SC-FDMA symbol of the NPUSCH channel is relatively short, and the length that cannot be used due to the influence of windowing or the like needs to be excluded, the accuracy of symbol timing estimation using the cyclic prefix is not high. In actual cellular communication, generally, delay estimation of the whole system is already performed when the UE randomly accesses, and then the UE adjusts the transmission time when transmitting a signal, so as to ensure that an NPUSCH signal received by the base station is within the CP. However, in the non-signaling test mode of the integrated tester, the procedures of UE synchronization and random access are not performed, but the time offset synchronization needs to be performed accurately.
In this case, for a wireless integrated measurement mode, this example can obtain a complete packet of NPUSCH (narrowband physical uplink shared channel) data at one time, extract a sequence of the NDMRS signals (narrowband demodulation reference signals) in the data, then perform grouping, and perform symbol timing estimation on two sets of the NDMRS signals (narrowband demodulation reference signals), so as to obtain better symbol timing estimation performance and have a certain anti-frequency offset effect.
Therefore, as shown in fig. 1 and fig. 7, this example provides a method for estimating a time offset of a narrowband physical uplink shared channel of a wireless comprehensive measuring instrument, including the following steps:
step S1, performing a first time offset estimation on the received data of the narrowband physical uplink shared channel to obtain a first start position of the data;
step S2, extracting the narrowband demodulation reference signal time domain data of the front part and the back part to obtain first time domain data and second time domain data;
step S3, calculating the correlation value of the first time domain data and the second time domain data at the current moment;
step S4, determining whether the maximum correlation value is greater than a preset threshold value according to the correlation value, and re-confirming the second start position of the data until the maximum correlation value is greater than the preset threshold value.
Step S1 in this example includes the following substeps:
step S101, obtaining the received data of the narrow-band physical uplink shared channel;
step S102, carrying out first time offset estimation through double sliding window power detection to obtain a first initial position of data. The first start position is a coarse start position and the second start position is a fine start position.
More specifically, the NPUSCH channel includes an ndsmrs sequence, in this example, a power window is first used to detect and obtain coarse timing synchronization of a signal, that is, the first time offset estimation of step S102, to obtain a coarse starting position, and this step can be implemented by using existing dual sliding window power detection; all the NDMRS sequences of the NPUSCH signal are then extracted for fine timing synchronization (more accurate time offset estimation) of the subsequent steps.
Suppose that the received NPUSCH signal of a burst is r (t),0 ≦ t<TpWherein T ispThe total duration of this packet signal. The received signal is down-converted and,the digital baseband signal after ADC sampling and other processing is r (n),0 is more than or equal to n<NpIn which N ispThe total number of points of the baseband digital signal to be processed is counted.
Firstly, coarse time offset estimation is carried out by using double sliding window power detection to obtain a coarse initial position N of a useful signalstartThe coarse starting position NstartThe start position obtained in step S1.
Next, the fine time offset estimation is performed by using the received NDMRS signal, and for the NPUSCH Format1 Format, it is assumed that the subcarrier spacing is Δ f and the number of time slots is NslotThen, according to the time domain structure diagram shown in fig. 5, the number of SC-FDMA symbols of the ndsmrs is NDMRS＝Nslot. For the single tone mode of NPUSCH, the frequency domain data of the ndsmrs are only equal in absolute value, and there may be a case of an opposite sign, so that there is no strong correlation for each of the ndsmrs symbols after the conversion to the time domain.
Therefore, for a single tone (single tone refers to a single tone signal, in a single tone mode, one ndsmrs frequency domain symbol data corresponds to one ndsmrs SC-FDMA symbol of a time domain), first, the ndsmrs frequency domain modulation data is locally generated, and the sign of each frequency domain ndsmrs data is recorded. Assuming that the frequency domain complex symbol data of the generated local NDMRS is SNDMRS(k),0≤k≤N NDMRS1, then according to the formula
Figure BDA0001736296710000081
Obtaining the sign of NDMRS frequency domain data, wherein
Figure BDA0001736296710000082
That is, step S2 described in this example preferably includes the following sub-steps:
step S201, locally generating frequency domain modulation data of a narrowband demodulation reference signal, and calculating and recording the sign of the frequency domain modulation data of the narrowband demodulation reference signal;
step S202, extracting the time domain data of the narrowband demodulation reference signal of the front part to obtain first time domain data;
step S203, extracting the narrowband demodulation reference signal time domain data of the latter part to obtain second time domain data.
As shown in fig. 6, in the step S201 of this embodiment, if the frequency domain modulation data of the narrowband demodulation reference signal is a single-tone signal, the sign is calculated according to the frequency domain complex symbol data of the narrowband demodulation reference signal; and if not, the rotation mark position 1 of the sign of the frequency domain modulation data of the narrowband demodulation reference signal is used.
More specifically, in step S201 in this example, the formula is used
Figure BDA0001736296710000091
Calculating sign of frequency domain modulation data of the narrowband demodulation reference signal in single-tone signal modeNDMRS(k1) Wherein, in the step (A),
Figure BDA0001736296710000092
for multi-tone mode (multitone mode)
Figure BDA0001736296710000093
Figure BDA0001736296710000094
k1For the subscript index of the narrowband demodulation reference signal, real () denotes the real part of the complex signal, imag () denotes the imaginary part of the complex signal, SNDMRS(k) K is more than or equal to 0 and less than or equal to N for the frequency domain complex symbol data of the narrow-band demodulation reference signalNDMRS-1，NNDMRSThe number of single carrier frequency division multiple access symbols of the narrow-band demodulation reference signal.
In step S202 in this example, the formula is shown
Figure BDA0001736296710000095
Figure BDA0001736296710000096
Extracting first time domain data
Figure BDA0001736296710000097
Wherein n is1The index is a time slot number index, m is a time domain sampling point index of a current time slot number, τ is a length index of shift correlation operation, totalSymLen is a time domain total length of a single carrier frequency division multiple access symbol containing a cyclic prefix, and r is received time domain data.
In step S203 described in this example, the formula is used
Figure BDA0001736296710000098
Extracting second time domain data
Figure BDA0001736296710000099
Wherein n is2Is the index of the time slot number, m is the index of the time domain sampling point of the current time slot number, tau is the index of the length of the shift correlation operation, totalSymLen is the total time domain length of a single carrier frequency division multiple access symbol containing the cyclic prefix,
Figure BDA00017362967100000910
and the sign of the local NDMRS data is represented, and r is the received time domain data.
More specifically, this example defines two variables for extracting the NDMRS time domain data of the front and rear portions of the received signal, respectively, and it is assumed that the two variables are pndmsdata 1 and pndmsdata 2, respectively. The pNDmrsData1 data can be represented as
Figure BDA00017362967100000911
Wherein N isstart≤τ≤Nstart+NcorrLen-1，
Figure BDA00017362967100000912
0≤m≤totalSymLen-1。n1Is the index of the time slot number, m is the index of the time domain sampling point of the current time slot number, τ is the length index of the shift correlation operation, totalSymLen is the total time domain length of one SC-FDMA symbol containing the cyclic prefix.
The pNDmrsData2 data can be represented as
Figure BDA0001736296710000101
Wherein N isstart≤τ≤Nstart+NcorrLen-1，
Figure BDA0001736296710000102
0≤m≤totalSymLen-1。n2Is the index of the time slot number, m is the index of the time domain sampling point of the current time slot number, τ is the index of the timing offset, totalSymLen is the total time domain length of one SC-FDMA symbol containing the cyclic prefix.
It is worth mentioning that, as can be seen from the above equation, for the data of pNDmrsData2, the sign needs to be rotated according to the locally stored ndsmrs sign flag. Therefore, for different τ, one symbol rotation is required for each time domain data point in each slot of pNDmrsData2, which is computationally time consuming.
Through practical analysis, the method can find that N is satisfiedcorrLen<In the case of totanSymLen, it is only necessary to be N at τstartThe totalSymLen time domain samples of each slot of pndmsdata 2 are symbol rotated for τ>Nstart(not satisfying τ ═ N)startJust adopt tau>NstartOf (d) only one point needs to be phase rotated, as shown in fig. 7, NcorrLenThe maximum number of time offset synchronization points, therefore, the above equation can be modified as follows:
Figure BDA0001736296710000103
wherein τ is Nstart，
Figure BDA0001736296710000104
0≤m≤totalSymLen-1。
Figure BDA0001736296710000105
Wherein N isstart+1≤τ≤Nstart+NcorrLen-1，
Figure BDA0001736296710000106
m＝totalSymLen-1。
That is, comparing the two methods under the condition that the values of τ and m are different, the first method needs the following cycle times: n is a radical ofcorrLen*NNDMRStotalSymLen/2, the second method requires only a total number of cycles
Figure BDA0001736296710000107
Therefore, the values of τ and m are chosen to be τ ═ Nstart，
Figure BDA0001736296710000108
M is more than or equal to 0 and less than or equal to totalSymLen-1 or Nstart+1≤τ≤Nstart+NcorrLen-1，
Figure BDA0001736296710000109
When m is totalSymLen-1, the time consumption of the algorithm can be saved. τ is the length index of the shift correlation operation, and m is the time domain sampling point index of the current time slot number.
Next, the acquired pndmrsta 1 data and pndrsdata 2 data at the current τ time are subjected to correlation calculation. That is, in step S3 described in this example, the formula is used
Figure BDA0001736296710000111
Calculating a correlation value between the first time domain data and the second time domain data at the current time
Figure BDA0001736296710000112
Wherein pndrsdata 1 and pndrsdata 2 are the values of the first time domain data and the second time domain data at the current time, respectively.
It can be seen that by using the method of performing time domain correlation using the ndsmrs, the time offset estimation can be more accurate step by step, and the initial position of the coarse effective signal can be obtained through the first step of the double sliding window power detection, so that the calculation time length of the following fine time offset estimation can be reduced. And then, the fine time offset estimation method is determined by extracting the NDMRS data of the received data, dividing the extracted NDMRS data into two halves and carrying out correlation peak value finding, and the fine time offset estimation method can work well under the condition of large frequency offset. And under the condition of fine time offset estimation, aiming at the condition that the NDMRS data has an abnormal sign in the single tone mode, firstly, frequency domain NDMRS complex symbol data is locally generated, and then whether the time domain data needs to be subjected to sign rotation is determined according to the sign of the generated data. And finally, the comprehensive tester can more accurately estimate the time offset of the DUT data under the condition of smaller complexity, and can well meet the production test. In summary, the flow of the timing offset estimation algorithm based on the NDMRS in the comprehensive tester system is shown in FIG. 6.
As shown in fig. 7, step S4 in this example includes the following sub-steps:
step S401, calculating τ ═ τ + 1;
step S402, judging whether tau is larger than Nstart+N corrLen1, if not, returning to step S2, if yes, jumping to step S403;
step S403, using formula
Figure BDA0001736296710000113
Searching to obtain a maximum correlation value, comparing the maximum correlation value with a preset threshold value, and if the maximum correlation value is larger than the threshold value, determining that the maximum correlation value is larger than the threshold value
Figure BDA0001736296710000114
The time offset estimation value is obtained, so that more accurate time offset estimation can be calculated; otherwise, returning an error, and failing to estimate the timing of the current signal symbol.
The invention also provides a time bias estimation system of the narrow-band physical uplink shared channel of the wireless comprehensive tester, which adopts the time bias estimation method of the narrow-band physical uplink shared channel of the wireless comprehensive tester.
In summary, in this embodiment, the received data of the narrowband physical uplink shared channel is subjected to the power detection with the double sliding windows to obtain a rough initial position, so that the calculation time length of the time offset estimation subdivided later can be reduced; then extracting the time domain data of the narrowband demodulation reference signals of the front part and the rear part, and finding a peak value through a correlation value of the first time domain data and the second time domain data to determine subdivided time offset estimation, wherein the fine time offset estimation can be ensured to work well under the condition of large frequency offset, so that better symbol timing estimation performance can be obtained, and a certain frequency offset resistant effect is achieved; finally, the wireless comprehensive tester can more accurately estimate the time offset of DUT (tested device) data under the condition of smaller complexity, and can well meet the requirements of production test.
More specifically, in the present embodiment, in the wireless comprehensive measurement instrument, the NDMRS data of each time slot is extracted, then the NDMRS data is divided into two pieces, namely, a first half and a second half, and then correlation calculation is performed on the two pieces of data, so that the influence of frequency offset on time offset estimation can be resisted by the method.
Aiming at the condition that the correlation of SC-FDMA symbols of a time domain is poor due to the fact that the NDMRS modulation sequence of the frequency domain is different in sign under a single tone mode (single tone mode), the method comprises the steps of firstly generating the NDMRS modulation sequence locally, then obtaining a sign rotation flag bit, and carrying out sign compensation on received NDMRS data. And the NPUSCH uses the extracted NDMRS to carry out time bias estimation.
That is, the present example proposes, for the time offset estimation problem of NPUSCH demodulation in NB-IOT, to perform coarse time offset estimation by using dual sliding window power detection; then, the NDMRS data of each time slot is extracted, the NDMRS data is partitioned and then subjected to fine time offset estimation, and only the frequency domain modulation symbol of the NDMRS is locally generated, so that the problem of poor SC-FDMA time domain data correlation of each NDMRS in a single tone mode (single tone mode) can be solved. Through software design, the calculation complexity of sign rotation in a single tone mode (single tone mode) is reduced. By the method, high time offset estimation precision can be brought to the wireless comprehensive measurement instrument, the wireless comprehensive measurement instrument can work well under the condition of large frequency offset, time domain NDMRS data does not need to be generated locally, and the calculation complexity is reduced.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.

Claims (6)

1. A time offset estimation method for a narrow-band physical uplink shared channel of a wireless comprehensive measurement instrument is characterized by comprising the following steps:
step S1, performing a first time offset estimation on the received data of the narrowband physical uplink shared channel to obtain a first start position of the data;
step S2, extracting the narrowband demodulation reference signal time domain data of the front part and the back part to obtain first time domain data and second time domain data;
step S3, calculating the correlation value of the first time domain data and the second time domain data at the current moment;
step S4, judging whether the maximum correlation value is larger than the preset threshold value according to the correlation value, and reconfirming the second initial position of the data until the maximum correlation value is larger than the preset threshold value;
the step S2 includes the following sub-steps:
step S201, locally generating frequency domain modulation data of a narrowband demodulation reference signal, and calculating and recording the sign of the frequency domain modulation data of the narrowband demodulation reference signal;
step S202, extracting the time domain data of the narrowband demodulation reference signal of the front part to obtain first time domain data;
step S203, extracting the narrowband demodulation reference signal time domain data of the latter part to obtain second time domain data;
in the step S202, the formula is passed
Figure FDA0003031094100000011
Extracting first time domain data
Figure FDA0003031094100000012
Wherein n is1The index is a time slot number index, m is a time domain sampling point index of a current time slot number, tau is a length index of shift correlation operation, totalSymLen is a time domain total length of a single carrier frequency division multiple access symbol containing a cyclic prefix, and r is received time domain data;
in the step S203, the formula is passed
Figure FDA0003031094100000013
Extracting second time domain data
Figure FDA0003031094100000014
Wherein n is2Is the index of the time slot number, m is the index of the time domain sampling point of the current time slot number, tau is the index of the length of the shift correlation operation, totalSymLen is the total time domain length of a single carrier frequency division multiple access symbol containing the cyclic prefix,
Figure FDA0003031094100000015
and representing the sign of the local NDMRS mapping data, and r is the received time domain data.
2. The method for estimating the time offset of the narrowband physical uplink shared channel of the integrated wireless measuring instrument according to claim 1, wherein the step S1 comprises the following substeps:
step S101, obtaining the received data of the narrow-band physical uplink shared channel;
step S102, a first time offset estimation is carried out through double sliding window power detection, and then a first initial position of data is obtained.
3. The method for estimating the time offset of the narrowband physical uplink shared channel of the integrated wireless measuring instrument according to claim 1 or 2, wherein in the step S201, whether the frequency domain modulation data of the narrowband demodulation reference signal is a single tone signal or not, if yes, the sign is calculated according to the frequency domain complex symbol data of the narrowband demodulation reference signal; and if not, the rotation mark position 1 of the sign of the frequency domain modulation data of the narrowband demodulation reference signal is used.
4. The method for estimating the time offset of the narrowband physical uplink shared channel of the integrated wireless measuring instrument according to claim 3, wherein in the step S201, the time offset is estimated according to a formula
Figure FDA0003031094100000021
Calculating sign of frequency domain modulation data of the narrowband demodulation reference signal in single-tone signal modeNDMRS(k1) Or, setting signNDMRS(k1) 1 is ═ 1; wherein the content of the first and second substances,
Figure FDA0003031094100000022
k1for the subscript index of the narrowband demodulation reference signal, real () denotes the real part of the complex signal, imag () denotes the imaginary part of the complex signal, SNDMRS(k) K is more than or equal to 0 and less than or equal to N for the frequency domain complex symbol data of the narrow-band demodulation reference signalNDMRS-1，NNDMRSThe number of single carrier frequency division multiple access symbols of the narrow-band demodulation reference signal.
5. The method for estimating the time offset of the narrowband physical uplink shared channel of the integrated wireless measuring instrument according to claim 4, wherein in the step S3, the time offset is estimated according to a formula
Figure FDA0003031094100000023
Calculating a correlation value between the first time domain data and the second time domain data at the current time
Figure FDA0003031094100000024
Wherein pndrsdata 1 and pndrsdata 2 are the values of the first time domain data and the second time domain data at the current time, respectively.
6. The method for estimating the time offset of the narrowband physical uplink shared channel of the integrated wireless measuring instrument according to claim 5, wherein the step S4 comprises the following substeps:
step S401, calculating τ ═ τ + 1;
step S402, judging whether tau is larger than Nstart+NcorrLen-1, if not returning to step S2, if so, jumping to step S403, NstartFor coarse starting positions of the useful signal, NcorrLenThe maximum number of time offset synchronization points;
step S403, using formula
Figure FDA0003031094100000025
Searching to obtain a maximum correlation value, comparing the maximum correlation value with a preset threshold value, and if the maximum correlation value is larger than the threshold value, determining that the maximum correlation value is larger than the threshold value
Figure FDA0003031094100000031
Is a time bias estimated value; otherwise, an error is returned.
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