CN101964677A - Method for positioning physical layer uplink signal in TDD-LTE terminal test - Google Patents

Abstract

The invention discloses a method for positioning a physical layer uplink signal in a TDD-LTE terminal test, which comprises the following steps of: 1) acquiring data of a time slot; 2) performing correlation calculation on a baseband signal of a demodulation reference symbol and the acquired data to determine an initial position of the baseband signal of the demodulation reference symbol; and 3) determining an initial position of a complete time slot according to the initial position of the baseband signal of the demodulation reference symbol. In the method, accurate signal positioning is achieved by performing correlation calculation on the baseband signal of the DMRS and the acquired signals and a foundation is laid for a terminal test item of the TDD-LTE system.

Description

Method for positioning physical layer uplink signal in TDD-LTE terminal test

Technical Field

The invention relates to the technical field of wireless communication, in particular to a method for positioning an uplink signal in a Time Division Duplex (TDD) LTE (Long Term Evolution) terminal test.

Background

Signal positioning, i.e. finding the exact starting position of the signal burst, is very important in TDD-LTE terminal test projects, because it directly determines the real-time and accuracy of the acquired data. The signal burst refers to data of one slot when a transmitter transmits data or a receiver receives data. In the terminal test, the power generally calculated is the power on the burst, and if the positioning has a deviation, the test on the time domain, the frequency domain and the modulation domain in the test item is greatly influenced, and even all the tests are failed. Specifically, if the signal is inaccurately located, the impact on the time domain test is: the calculated power of the time domain is not the power of the subframe or the time slot required to be measured, and the switch time template is not measured aiming at the current time slot; the impact on the frequency domain test was: the sampling points for FFT are not time domain signals needing to be processed, which directly results in incorrect calculated spectral power; the impact on the modulation domain test is: the calculated values of the constellation diagram, the demodulation result and the final index have large deviations. Therefore, accurate positioning of signals in the conventional time slot is a precondition for development of a test project and is also a key and important step in the test project, and the positioning accuracy directly influences the accuracy of time domain, frequency domain and modulation domain tests in the terminal test project.

Signal positioning may also be referred to as signal synchronization, and in CDMA (Code Division multiple access) communication systems, signal synchronization is performed using midamble, also referred to as midamble correlation, on the signal in the regular time slot. The midamble is located in the middle of the time slot and is an m sequence used for channel estimation, power control and synchronization adjustment. For a user, although the content of the data part is uncertain, the intermediate code is fixed, the intermediate code has good autocorrelation, and the start position of the intermediate code in the burst can be found by a correlation method, so that the start point of the burst part can be found. However, in the LTE system, a form of frequency division multiple access is adopted, and in a regular time slot of a baseband signal, without such a fixed midamble, reference signals of all time slots are related to a time slot, and the reference signals are different from time slot to time slot. That is, for the LTE test system, there is no such fixed and unchangeable signal like the midamble of the CDMA system, so it is difficult to find the exact starting position of the burst of the conventional timeslot signal. Therefore, it is desirable to provide a method for positioning uplink signals of a physical layer in a TDD-LTE terminal test to overcome the above-mentioned drawbacks.

Disclosure of Invention

The technical problem to be solved by the present invention is to provide a method for positioning Physical layer Uplink signals in a TDD-LTE terminal test, which can realize accurate positioning of PUSCH (Physical Uplink Shared Channel) and PUCCH (Physical Uplink Control Channel) signals in the TDD-LTE terminal test, and is suitable for performance index tests in the design, development, manufacturing, service and maintenance processes of the TDD-LTE terminal.

In order to solve the above technical problem, the present invention provides a method for positioning physical layer channel signals in a TDD-LTE terminal test, which comprises the following steps:

1) collecting a signal of a time slot;

2) performing correlation operation on the baseband signal of the demodulation reference symbol and the acquired data to determine the initial position of the baseband signal of the demodulation reference symbol; and

3) and determining the starting position of a complete time slot according to the starting position of the baseband signal of the demodulation reference symbol.

The method for positioning the physical layer uplink signal in the TDD-LTE terminal test adopts the baseband signal of the demodulation reference symbol and the acquired signal to perform the correlation operation to position the signal, has accurate positioning and lays a foundation for the terminal test project of the TDD-LTE system.

The invention will become more apparent from the following description when taken in conjunction with the accompanying drawings, which illustrate embodiments of the invention.

Drawings

Fig. 1 is a flowchart illustrating a method for positioning uplink signals of a physical layer in a TDD-LTE terminal test according to an embodiment of the present invention.

Fig. 2 is a schematic diagram of a subframe structure of a radio frame in a TDD-LTE system.

Fig. 3 is an effect diagram of signal positioning by using the method for physical layer uplink signal positioning in TDD-LTE terminal testing of the present invention.

Detailed Description

Embodiments of the present invention will now be described with reference to the drawings, wherein like element numerals represent like elements. As described above, the present invention provides a method for positioning uplink signals of a physical layer in a TDD-LTE terminal test, which can realize accurate positioning of uplink signals in the TDD-LTE terminal test, and is suitable for performance index tests in the design, development, manufacture, service, and maintenance processes of the TDD-LTE terminal.

The technical solutions of the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. As shown in fig. 1, the method for positioning uplink signals of the physical layer in the TDD-LTE terminal test according to this embodiment includes the following steps.

Step S101: data for one time slot is collected. Generally, data in the LTE-TDD system is in units of radio frames, one radio frame includes 10 subframes, and one subframe is 2 slots, as shown in fig. 2.

Step S102: and performing correlation operation on the baseband signal of the demodulation reference symbol and the acquired data to determine the initial position of the baseband signal of the demodulation reference symbol.

The reference signal is a known signal provided by the transmitting end to the receiving end for channel estimation or channel sounding. Because the TDD-LTE uplink uses a single carrier frequency division multiple access technology, Reference signals and data are multiplexed together in a time division manner, and the Reference signals are divided into DMRS (demodulation Reference Signal) and SRS (Sounding Reference Signal), where the DMRS is used for coherent detection and demodulation at the base station end in channel estimation and the SRS is used for channel detection in channel quality measurement. Herein, for ease of understanding, the demodulation reference signal is referred to as a demodulation reference symbol to distinguish from the baseband signal. The DMRS is located in the fourth symbol of each uplink slot, as shown in fig. 2, where R denotes the DMRS.

DMRS is a CAZAC sequence (constant amplitude Zero Auto-correlation) with good autocorrelation and cross-correlation, and once the number of resource blocks is selected, the length of the CAZAC sequence is also selected, and the mapping position in the frequency domain is also fixed. Because only one DMRS is present in the signal of each time slot, a correlation operation is performed on the acquired data and the demodulation reference signal, so that a correlation peak is generated, and the position of the correlation peak is the starting position of the DMRS.

Step S103: and determining the starting position of a complete time slot according to the starting position of the demodulation reference signal. Under the condition of determining the sampling rate, the length of a signal of one time slot is fixed, so that under the condition of determining the starting position of the DMRS, the starting position of one complete time slot can be calculated.

Before step S102, a step of pre-generating a baseband signal of the demodulation reference symbol may be further included.

Further, the process of generating the baseband signal of the demodulation reference symbol is as follows:

and (I) generating a base sequence according to the number of occupied resource blocks and system configuration parameters.

Specifically, the steps are divided into the following aspects:

(1) bandwidth when user occupies

I.e. the length of the base sequence is

Or longer, base sequence

Is obtained by the following formula:

<math><mrow><msub><mover><mi>r</mi><mo>&OverBar;</mo></mover><mrow><mi>u</mi><mo>,</mo><mi>v</mi></mrow></msub><mrow><mo>(</mo><mi>n</mi><mo>)</mo></mrow><mo>=</mo><msub><mi>x</mi><mi>q</mi></msub><mrow><mo>(</mo><mi>n </mi><mi>mod</mi><msubsup><mi>N</mi><mi>ZC</mi><mi>RS</mi></msubsup><mo>)</mo></mrow><mo>,</mo></mrow></math> <math><mrow><mn>0</mn><mo>&le;</mo><mi>n</mi><mo>&lt;</mo><msubsup><mi>M</mi><mi>sc</mi><mi>RS</mi></msubsup><mo>-</mo><mo>-</mo><mo>-</mo><mrow><mo>(</mo><mn>1</mn><mo>)</mo></mrow></mrow></math>

wherein,

indicating the bandwidth occupied by one resource block.

In formula (1), the qth root ZC sequence is defined as:

<math><mrow><msub><mi>x</mi><mi>q</mi></msub><mrow><mo>(</mo><mi>m</mi><mo>)</mo></mrow><mo>=</mo><msup><mi>e</mi><mrow><mo>-</mo><mi>j</mi><mfrac><mrow><mi>&pi;qm</mi><mrow><mo>(</mo><mi>m</mi><mo>+</mo><mn>1</mn><mo>)</mo></mrow></mrow><msubsup><mi>N</mi><mi>ZC</mi><mi>RS</mi></msubsup></mfrac></mrow></msup><mo>,</mo></mrow></math> <math><mrow><mn>0</mn><mo>&le;</mo><mi>m</mi><mo>&le;</mo><msubsup><mi>N</mi><mi>ZC</mi><mi>RS</mi></msubsup><mo>-</mo><mn>1</mn><mo>-</mo><mo>-</mo><mo>-</mo><mrow><mo>(</mo><mn>2</mn><mo>)</mo></mrow></mrow></math>

in formula (2), q is derived from the following formula:

<math><mrow><mover><mi>q</mi><mo>&OverBar;</mo></mover><mo>=</mo><msubsup><mi>N</mi><mi>ZC</mi><mi>RS</mi></msubsup><mo>&CenterDot;</mo><mrow><mo>(</mo><mi>u</mi><mo>+</mo><mn>1</mn><mo>)</mo></mrow><mo>/</mo><mn>31</mn></mrow></math>

length of ZC sequence

Take values to satisfyWherein u and v are the group jump and sequence jump parameters respectively, whether sequence jump is activated is determined by setting the high-level parameters, and the generation process of group jump and sequence jump is described below.

(a) Group hopping

Time slot n_sSequence group number u within a sequence group by group hopping pattern f_gh(n_s) And sequence shift pattern f_ssDefining:

$u=(f_{\mathrm{gh}}\left(n_s\right)+f_{\mathrm{ss}}^{\mathrm{PUSCH}})\mathrm{mod}30---\left(3\right)$

<math><mrow><msubsup><mi>f</mi><mi>ss</mi><mi>PUCCH</mi></msubsup><mo>=</mo><msubsup><mi>N</mi><mi>ID</mi><mi>cell</mi></msubsup><mi>mod</mi><mn>30</mn><mo>,</mo><msubsup><mi>f</mi><mi>ss</mi><mi>PUSCH</mi></msubsup><mo>=</mo><mrow><mo>(</mo><msubsup><mi>f</mi><mi>ss</mi><mi>PUCCH</mi></msubsup><mo>+</mo><msub><mi>&Delta;</mi><mi>ss</mi></msub><mo>)</mo></mrow><mi>mod</mi><mn>30</mn><mo>-</mo><mo>-</mo><mo>-</mo><mrow><mo>(</mo><mn>5</mn><mo>)</mo></mrow></mrow></math>

in equation (4), c is a Gold sequence in the pseudo-random sequence, which is generated according to the following formula:

x₁(n+31)＝(x₁(n+3)+x₁(n))mod2

x₂(n+31)＝(x₂(n+3)+x₂(n+2)+x₂(n+1)+x₂(n))mod2

c(n)＝(x₁(n+N_C)+x₂(n+N_C))mod2 (6)

wherein N is_C1600, the first Gold sequence x₁(n) initialization to x₁(0)＝1，x₁(n) ═ 0, n ═ 1, 2, ·, 30; second Gold sequence x₂(n) is represented by the formula

Initialization is performed with values that depend on the specific application of the sequence.

For f_gh(n_s) In other words, in case of group hop turn on, the second Gold sequence x in equation (5)₂(n) is selected from

Carry out initialization in which

(b) Sequence hopping

In the above formula, c is a pseudo-random sequence if v ═ c (n)_s) Then, the second Gold sequence x₂(n) is selected from

Initialization is performed.

(2) When the length of the base sequence is less than

When, i.e. whenAnd

the base sequence is given by:

<math><mrow><mn>0</mn><mo>&le;</mo><mi>n</mi><mo>&le;</mo><msubsup><mi>M</mi><mi>sc</mi><mi>RS</mi></msubsup><mo>-</mo><mn>1</mn></mrow></math>

whereinThe values are taken from tables 5.5.1.2-1 and 5.5.1.2-2 of the protocol, tables 5.5.1.2-1 and 5.5.1.2-2 corresponding to, respectively

And

(II) frequency shifting the base sequence according to the following formula to generate a reference sequence:

<math><mrow><msubsup><mi>r</mi><mrow><mi>u</mi><mo>,</mo><mi>v</mi></mrow><mrow><mo>(</mo><mi>&alpha;</mi><mo>)</mo></mrow></msubsup><mrow><mo>(</mo><mi>n</mi><mo>)</mo></mrow><mo>=</mo><msup><mi>e</mi><mi>j&alpha;n</mi></msup><msub><mover><mi>r</mi><mo>&OverBar;</mo></mover><mrow><mi>u</mi><mo>,</mo><mi>v</mi></mrow></msub><mrow><mo>(</mo><mi>n</mi><mo>)</mo></mrow><mo>,</mo></mrow></math> <math><mrow><mn>0</mn><mo>&le;</mo><mi>n</mi><mo>&lt;</mo><msubsup><mi>M</mi><mi>sc</mi><mi>RS</mi></msubsup><mo>-</mo><mo>-</mo><mo>-</mo><mrow><mo>(</mo><mn>8</mn><mo>)</mo></mrow></mrow></math>

$M_{\mathrm{sc}}^{\mathrm{RS}}=m{N}_{\mathrm{sc}}^{\mathrm{RB}}$ <math><mrow><mn>1</mn><mo>&le;</mo><mi>m</mi><mo>&le;</mo><msubsup><mi>N</mi><mi>RB</mi><mrow><mi>max</mi><mo>,</mo><mi>UL</mi></mrow></msubsup></mrow></math>

α＝2πn_cs/12 (9)

in the formula (9), n_csIs composed of$n_{\mathrm{cs}}=(n_{\mathrm{DMRS}}^{\left(1\right)}+n_{\mathrm{DMRS}}^{\left(2\right)}+n_{\mathrm{PRS}}\left(n_s\right))\mathrm{mod}12---\left(10\right)$

In the formula (10), n_PRS(n_s) Comprises the following steps:

<math><mrow><msub><mi>n</mi><mi>PRS</mi></msub><mrow><mo>(</mo><msub><mi>n</mi><mi>s</mi></msub><mo>)</mo></mrow><mo>=</mo><msubsup><mi>&Sigma;</mi><mrow><mi>i</mi><mo>=</mo><mn>0</mn></mrow><mn>7</mn></msubsup><mi>c</mi><mrow><mo>(</mo><mn>8</mn><msubsup><mi>N</mi><mi>symb</mi><mi>UL</mi></msubsup><mo>&CenterDot;</mo><msub><mi>n</mi><mi>s</mi></msub><mo>+</mo><mi>i</mi><mo>)</mo></mrow><mo>&CenterDot;</mo><msup><mn>2</mn><mi>i</mi></msup><mo>-</mo><mo>-</mo><mo>-</mo><mrow><mo>(</mo><mn>11</mn><mo>)</mo></mrow></mrow></math>

c is a pseudo-random sequence, a second Gold sequence x₂(n) is represented by the formula

Initialization is performed.

(III) mapping the reference sequence in the resource block to obtain demodulation reference symbols

The reference sequence generated is called resource particles, and is uniformly mapped into a resource block of a frequency domain by taking the central frequency point of a channel bandwidth as a symmetry axis according to parameters configured by an upper layer and a system, wherein the mapped value is r^PUSCHThe specific implementation process is as follows:

<math><mrow><msup><mi>r</mi><mi>PUSCH</mi></msup><mrow><mo>(</mo><mi>n</mi><mo>&CenterDot;</mo><msubsup><mi>M</mi><mi>sc</mi><mi>RS</mi></msubsup><mo>+</mo><mi>k</mi><mo>)</mo></mrow><mo>=</mo><msubsup><mi>r</mi><mrow><mi>u</mi><mo>,</mo><mi>v</mi></mrow><mrow><mo>(</mo><mi>&alpha;</mi><mo>)</mo></mrow></msubsup><mrow><mo>(</mo><mi>n</mi><mo>)</mo></mrow></mrow></math>

n＝0，1

$k=0,...,M_{\mathrm{sc}}^{\mathrm{RS}}-1---\left(12\right)$

where n-0 is the first slot of a subframe, and n-1 is the second slot of a subframe. k is the distribution of resource elements in the frequency domain, starting from the first resource block until all resource blocks are filled.

Generation of baseband signals of (IV) demodulation reference symbols

Since the bandwidth given by the channel is generally larger than the bandwidth required by the resource element, after the resource element mapping, many resource blocks are not used, and the unused resource blocks are all filled to 0, that is, r is^PUSCHMapping the data in the (-) to the frequency domain to fill the resource blocks used by the users and add 0 to the unused resource blocks, thus forming a sequence

Time-continuous signal s in the l-th SC-FDMA symbol in one uplink slot_l(t) is that, since the demodulation reference symbol is located at the fourth symbol, l is 3

Wherein t is 0-t (N)_CP，l+N)×T_s，

2048, 15kHz and a_k，lRepresents the information transmitted on the resource units (k, l).

In communication systems, the devices receive and transmit generally digital signals, so that it is necessary to convert the analog signals into digital signals

The sampling frequency is f-1/T_sChanging t to nT_sSubstituting into s (t), then:

protocol^[1]N shown in Table 5.6-1_CP，lValue (take normal CP). Note that different SC-FDMA symbols within one slot may have different cyclic prefix lengths.

Based on the above analysis, a specific example is now given to illustrate the effects of the present invention.

(1)

Protocol see^[1]Table 5.5.2.1.1-2 sets up the parameters provided by the upper cycloShift.

(2)

Protocol see^[1]Table 5.5.2.1.1-1 sets the value of the DMRS cyclic shift field in DCI format 0 most recently used for PUSCH transmission.

(3) The number of transmission resource blocks is 50 and all resource blocks are occupied.

(4)

Get the normal CP as 12, see protocol^[1]In Table 5.2.3-1,

satisfy the requirement of

Maximum prime number of see protocol^[1]Middle 5.5.1.1

(5)N_CP，l144, see protocol^[1]Medium 5.6-1 normal CP.

(6)

Selecting the occupied bandwidth as 10M, see protocol^[2]Table 5.4.2-1.

(7) Both group hopping and sequence hopping open, see protocol^[1]5.5.1.3。

(8) Parameter Δ of sequence shift pattern in group hopping_ssSee protocol 3^[1]5.5.1.3。

(9)n_PRS(n_s) Set to not 0, see protocol^[1]The formula is calculated at 5.5.2.1.1.

(10)n_sFor the first slot in the 2 nd sub-frame in a radio frame, see protocol^[1]Middle 5.5.2.1.1

Data of one time slot is acquired according to the configuration, and correlation operation is performed on the data and the baseband signal of the demodulation reference symbol, so that the result of fig. 3 is obtained.

As shown in fig. 3, a very ideal correlation result is shown under randomly given parameters. The prominent peak is the starting position of the DMRS, from which the starting point of the complete slot can be accurately calculated. The present solution is not limited to this set of parameters, but it is still applicable in case of flexible configuration of all parameters. The related results strongly prove the reasonability and the accuracy of the scheme and lay a solid foundation for the development of test items.

It should be noted that the above protocol^[1]3GPP TS 36.211: "Evolved Universal Radio Access (E-UTRA); physical channels and modulation ". Protocol^[2]For 3GPP TS 36.512: "Evolved Universal Radio Access (E-UTRA); user Equipment (UE) compatibility transmission and reception; part 1: conformance Testing ".

Claims (3)

1. A method for positioning uplink signals of a physical layer in a TDD-LTE terminal test is characterized by comprising the following steps:

1) collecting data of a time slot;

2) performing correlation operation on the baseband signal of the demodulation reference symbol and the acquired data to determine the initial position of the baseband signal of the demodulation reference symbol; and

3) and determining the starting position of a complete time slot according to the starting position of the baseband signal of the demodulation reference symbol.

2. The method of signal positioning according to claim 1, further comprising: pre-generating a baseband signal of the demodulation reference symbol.

3. The method according to claim 2, wherein the step of pre-generating the baseband signal of the demodulation reference symbol specifically comprises:

generating a base sequence according to the number of the resource blocks and the system configuration parameters;

frequency shifting the base sequence to generate a reference sequence; and

mapping the reference sequence in a resource block to obtain demodulation reference symbols;

performing an inverse Fourier transform on the demodulation reference symbols to generate baseband signals of the demodulation reference symbols.

Images