CN109981512B

CN109981512B - Time offset estimation method and device of OFDM system, storage medium and terminal

Info

Publication number: CN109981512B
Application number: CN201711459594.2A
Authority: CN
Inventors: 申建平; 赵况平; 张家辉; 柳柏明
Original assignee: Spreadtrum Communications Shanghai Co Ltd
Current assignee: Spreadtrum Communications Shanghai Co Ltd
Priority date: 2017-12-28
Filing date: 2017-12-28
Publication date: 2021-11-26
Anticipated expiration: 2037-12-28
Also published as: CN109981512A

Abstract

A time offset estimation method and device, storage medium and terminal of OFDM system are disclosed, the time offset estimation method includes: in OFDM systemsAdvancing the timing by N.T_intThe time length begins to receive data, and the total receiving time length is 1 subframe plus 2 N.T_intTo obtain received data, T_intIs a preset unit offset duration, and N is the maximum number of the preset unit offset durations supported; data of length 1 sub-frame is taken out from received data, and decimal time offset T is calculated based on the data_f(ii) a By T_intReceiving data for step traversal, taking out data of 1 subframe each time and calculating CFI; determining the offset number N according to the CFI obtained in the traversal process, wherein N is an integer and-N<n<N; calculating a total time offset Δ T, wherein Δ T is n.T_int+T_f. By the scheme of the invention, the time offset estimation with low complexity and high reliability can be realized, and the timing synchronization requirement of the OFDM system is met.

Description

Time offset estimation method and device of OFDM system, storage medium and terminal

Technical Field

The present invention relates to the field of wireless communication technologies, and in particular, to a method and an apparatus for estimating a time offset of an OFDM system, a storage medium, and a terminal.

Background

Orthogonal Frequency division Multiplexing (OFDM for short) technology has high spectrum utilization rate and excellent inter-symbol interference resistance, is very suitable for broadband high-speed communication scenarios, and is widely applied to wireless mobile communication systems.

The OFDM technology divides a channel into a plurality of parallel orthogonal subcarriers to transmit data, and the timing synchronization problem is a key problem influencing the transmission accuracy of the OFDM channel and is one of important factors determining the performance of an OFDM system. Since a large time offset may cause inter-symbol interference and even destroy the orthogonality of subcarriers, a low-complexity and high-reliability timing offset (i.e., time offset) estimation method is particularly important for an OFDM system.

The existing time offset estimation techniques mainly include two types: one is blind detection and blind estimation based on the cyclic prefix of the OFDM, and has the disadvantage that the detection timing offset range is limited, and the other is high in complexity and poor in anti-noise capability because the timing offset estimation is completed based on the training sequences of the primary synchronization signal and the secondary synchronization signal in a Long Term Evolution (LTE) OFDM system.

Therefore, it is very important to realize low-complexity and high-reliability time offset estimation for the OFDM system.

Disclosure of Invention

The invention solves the technical problem of how to realize time offset estimation with low complexity and high reliability so as to meet the requirement of an OFDM system on timing synchronization.

In order to solve the above technical problem, an embodiment of the present invention provides a method for estimating a time offset of an OFDM system, where the method for estimating a time offset of an OFDM system includes: advancing N.T. based on OFDM system timing_intThe time length begins to receive data, and the total receiving time length is 1 subframe plus 2 N.T_intTo obtain received data, wherein T_intIs a preset unit offset duration, and N is the maximum number of the preset unit offset durations supported; taking out data with the length of 1 subframe from the received data, and calculating decimal time offset T based on the data with the length of 1 subframe_f(ii) a By T_intTraversing the received data for step length, taking out data with the length of 1 subframe each time and calculating a CFI code sequence; determining the offset number N according to the CFI code sequence obtained in the traversal process, wherein N is an integer and-N<n<N; calculating a total time offset Δ T, wherein Δ T is n.T_int+T_f。

Optionally, the determining the offset number n according to the CFI code sequence obtained in the traversal process includes: in the traversing process, after data with the length of 1 subframe is taken out each time and a CFI code sequence is calculated, DCI is detected according to the CFI code sequence obtained through calculation; if the DCI detection is successful, calculating the offset number n by using the position of the data with the length of 1 subframe taken out at this time relative to the reference, wherein the value of n is equal to the offset duration between the position and the reference and T_intN is determined by the sign ofWhether the position is ahead or behind the reference.

Optionally, the determining the offset number n according to the CFI code sequence obtained in the traversal process further includes: after each CFI code sequence is calculated, mutual information between the CFI code sequence and a known CFI code sequence is calculated to obtain CFI mutual information; and if the DCI detection fails after traversing the received data, calculating the offset number n by using the position of the data of the subframe with the length of 1 corresponding to the maximum value of the CFI mutual information relative to a reference.

Optionally, the formula for calculating the CFI mutual information is I (a, B) ═ h (a) + h (B) -h (ab); wherein, a represents the CFI sequence obtained by calculation, B represents the known CFI code sequence, I (a, B) represents the CFI mutual information, h (a), h (B) represent the information entropy of A, B, respectively, and h (ab) represents the uncertainty of the CFI information remaining in the OFDM system after communication.

Optionally, the DCI detection success may refer to: and receiving the DCI from the data with the length of 1 subframe, and correctly decoding the DCI.

Optionally, after obtaining the received data, the method for estimating time offset further includes: and storing the received data into a cache.

In order to solve the above technical problem, an embodiment of the present invention further provides a time offset estimation device for an OFDM system, where the time offset estimation device for the OFDM system includes: a receiving module adapted to advance N.T based on the timing of the OFDM system_intThe time length begins to receive data, and the total receiving time length is 1 subframe plus 2 N.T_intTo obtain received data, wherein T_intIs a preset unit offset duration, and N is the maximum number of the preset unit offset durations supported; a first calculating module, adapted to take out data with length of 1 sub-frame from the received data, and calculate decimal time offset T based on the data with length of 1 sub-frame_f(ii) a A second calculation module adapted to calculate T_intTraversing the received data for step length, taking out data with the length of 1 subframe each time and calculating a CFI code sequence; a determining module adapted to determine the CFI code sequence obtained in the traversal processThe number of fixed offsets N, N being an integer and-N<n<N; a third calculation module adapted to calculate a total time offset Δ T, wherein Δ T is n.T_int+T_f。

Optionally, the determining module includes: the first calculation submodule is suitable for detecting the DCI according to the CFI code sequence obtained by calculation after data with the length of 1 subframe is taken out and the CFI code sequence is calculated each time in the traversal process; a first determining submodule adapted to calculate the offset number n using the position of the data of length 1 subframe fetched this time with respect to a reference if the DCI detection is successful, wherein the value of n is equal to the quotient of the offset duration between the position with respect to the reference and Tint, the sign of n depending on whether the position is ahead or behind the reference.

Optionally, the determining module further includes: the second calculation sub-module is suitable for calculating mutual information between the CFI code sequence and a known CFI code sequence after calculating the CFI code sequence each time so as to obtain CFI mutual information; and if the DCI detection fails after the data reception is finished, the second determining submodule is adapted to calculate the offset number n by using the position, relative to a reference, of the data of the subframe with the length of 1 corresponding to the maximum value of the CFI mutual information.

Optionally, the time offset estimation apparatus further includes: and the storage module is suitable for storing the received data into a cache after the received data is obtained.

To solve the above technical problem, an embodiment of the present invention further provides a storage medium, on which computer instructions are stored, and when the computer instructions are executed, the steps of the time offset estimation method of the OFDM system are executed.

In order to solve the above technical problem, an embodiment of the present invention further provides a terminal, including a memory and a processor, where the memory stores computer instructions executable on the processor, and the processor executes the steps of the time offset estimation method for the OFDM system when executing the computer instructions.

Compared with the prior art, the technical scheme of the embodiment of the invention has the following beneficial effects:

the embodiment of the invention provides a time offset estimation method of an OFDM system, which comprises the following steps: advancing N.T. based on OFDM system timing_intThe time length begins to receive data, and the total receiving time length is 1 subframe plus 2 N.T_intTo obtain received data, wherein T_intIs a preset unit offset duration, and N is the maximum number of the preset unit offset durations supported; taking out data with the length of 1 subframe from the received data, and calculating decimal time offset T based on the data with the length of 1 subframe_f(ii) a By T_intTraversing the received data for step length, taking out data with the length of 1 subframe each time and calculating a CFI code sequence; determining the offset number N according to the CFI code sequence obtained in the traversal process, wherein N is an integer and-N<n<N, further obtaining integral multiple timing offset; calculating a total time offset Δ T, wherein Δ T is n.T_int+T_fThat is, the total timing offset can be determined by using the sum of the calculation result of the integer multiple timing offset and the calculation result of the decimal multiple timing offset, and the total timing offset of the OFDM system can be obtained without modifying the existing OFDM frame structure. The technical scheme provided by the embodiment of the invention has low complexity of calculating the time offset of integral multiple based on the CFI code sequence, can cover a larger range of timing offset and reduces the requirement on the clock precision of the system. Moreover, since the parameter (e.g., the maximum number of supported preset unit offset durations) is adjustable, the processing duration of the time offset estimation and the maximum time offset supported by the system can be compromised, further shortening the time offsetAnd (4) processing time.

Further, the determining the offset number n according to the CFI code sequence obtained in the traversal process includes: in the traversing process, after data with the length of 1 subframe is taken out each time and a CFI code sequence is calculated, DCI is detected according to the CFI code sequence obtained through calculation; if the DCI detection is successful, the position of the currently taken out subframe is kept synchronous with the OFDM system timing reference, and the offset number n can be calculated by utilizing the position of the data which is taken out at this time and has the length of 1 subframe relative to the reference, wherein the value of n is equal to the offset duration between the position and the reference and T_intThe sign of n depends on whether the position is ahead or behind the reference.

Further, the determining the offset number n according to the CFI code sequence obtained in the traversal process further includes: after each CFI code sequence is calculated, mutual information between the CFI code sequence and a known CFI code sequence is calculated to obtain CFI mutual information; if the DCI detection fails after traversing the received data, it means that the network does not send DCI information to the user, and at this time, it may be determined according to information theory that a subframe position corresponding to the maximum value of the CFI mutual information maintains synchronization with the OFDM system timing reference, and the offset number n may be determined and calculated by using a position of the data of the 1 subframe length corresponding to the maximum value of the CFI mutual information with respect to the reference, so as to obtain the total time offset Δ T.

Drawings

Fig. 1 is a flowchart illustrating a method for estimating a time offset of an OFDM system according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a received data duration of a time offset estimation method of an OFDM system according to an embodiment of the present invention;

fig. 3 is a flowchart illustrating a method for estimating a time offset of an OFDM system according to another embodiment of the present invention;

fig. 4 is a schematic structural diagram of a time offset estimation apparatus of an OFDM system according to an embodiment of the present invention.

Detailed Description

As will be appreciated by those skilled in the art, as background art, existing time offset estimation techniques have either a small timing offset range or a time offset estimation algorithm with high complexity and poor noise immunity.

The embodiment of the invention provides a time offset estimation method of an OFDM system, which comprises the following steps: advancing N.T. based on OFDM system timing_intThe time length begins to receive data, and the total receiving time length is 1 subframe plus 2 N.T_intTo obtain received data, wherein T_intIs a preset unit offset duration, and N is the maximum number of the preset unit offset durations supported; taking out data with the length of 1 subframe from the received data, and calculating decimal time offset T based on the data with the length of 1 subframe_f(ii) a By T_intTraversing the received data for step length, taking out data with the length of 1 subframe each time and calculating a CFI code sequence; determining the offset number N according to the CFI code sequence obtained in the traversal process, wherein N is an integer and-N<n<N, further obtaining integral multiple timing offset; calculating a total time offset Δ T, wherein Δ T is n.T_int+T_fThat is, the total timing offset can be determined by using the sum of the calculation result of the integer multiple timing offset and the calculation result of the decimal multiple timing offset, and the total timing offset of the OFDM system can be obtained without modifying the existing OFDM frame structure. The technical scheme provided by the embodiment of the invention has low complexity of calculating the time offset of integral multiple based on the CFI code sequence, can cover a larger range of timing offset and reduces the requirement on the clock precision of the system. Moreover, since parameters (e.g., the maximum number of supported preset unit offset durations) are adjustable, a trade-off between the processing duration of the time offset estimation and the maximum time offset supported by the system can be made, further reducing the processing time.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

Fig. 1 is a schematic flow chart of a time offset estimation method of an OFDM system according to an embodiment of the present invention, where the time offset estimation method can be applied to a User Equipment (UE) side. Taking LTE OFDM system as an example, the time offset estimation method may specifically include the following steps:

step S101: advancing N.T. based on OFDM system timing_intThe time length begins to receive data, and the total receiving time length is 1 subframe plus 2 N.T_intTo obtain received data, wherein T_intIs a preset unit offset duration, and N is the maximum number of the preset unit offset durations supported;

step S102: taking out data with the length of 1 subframe from the received data, and calculating decimal time offset T based on the data with the length of 1 subframe_f；

Step S103: by T_intTraversing the received data for step length, taking out data with the length of 1 subframe each time and calculating a CFI code sequence;

step S104: determining the offset number N according to the CFI code sequence obtained in the traversal process, wherein N is an integer and-N < N < N;

step S105: calculating a total time offset Δ T, wherein Δ T is n.T_int+T_f。

Specifically, in step S101, the UE may determine the maximum supported timing offset range according to the characteristics of the actual LTE OFDM communication system before receiving data, with the OFDM system timing as a reference. The maximum number N of unit offset durations is preset. Since the local reception and the OFDM system may be advanced or delayed in time offset, in order to accurately estimate the time offset, a preset time may be set to receive a part of data more than 1 subframe so as to estimate the time offset. The UE may receive data in advance of the preset time before a subframe to be received (i.e., a subframe synchronized with the timing of the OFDM system), and continue to receive data for the preset time after the subframe to be received is received. Those skilled in the art will understand that the preset time may be the maximum timing deviation range that the LTE OFDM system can support. The sampling rate of the LTEOFDM system is 30.72MHz, the time slot Ts is (30.72 multiplied by 1e +6)^-1Second, in a typical scenario, a maximum time offset estimate of 1023Ts may be supported. If the preset unit offset time length T is set_int341Ts, thenThe maximum number of preset unit offset durations N may be 3, and the maximum timing offset may be N.T_int＝3×341T_S＝1023T_S。

Further, to calculate the time offset estimate of the LTE OFDM system, a total time offset Δ T may be defined, where Δ T may be defined as the sum of an integer multiple of the time offset and a fractional multiple of the time offset, i.e., Δ T ═ n · T_int+T_fwherein-N is<n<And N is added. It should be noted that the UE may adjust the maximum timing offset according to its processing capability, for example, N may be 2, N may be 1, or N may be 0, so as to shorten the processing time, or N may be 4, 5, or another value, so as to increase the timing offset supported by the UE.

Further, after the UE determines the maximum N value, to calculate the timing offset, the UE may advance N · T with the OFDM system timing as a reference_intThe time length begins to receive data, and the receiving time length is 1 subframe plus 2 N.T_intTo obtain received data. After obtaining the received data, the UE may store the received data in a buffer (also referred to as a buffer).

Further, step S102 is executed, the UE may optionally extract time domain data with a length of 1 subframe from the received data, perform Fast Fourier Transform (FFT) on the data of 1 subframe to obtain frequency domain data, extract a Reference Signal (RS) from the frequency domain data, and obtain a Power Delay Profile (PDP) of a wireless channel by using the received RS and the local RS. After obtaining the PDP, the UE may determine the fractional time offset T according to an error relationship between the PDP and the timing reference of the OFDM system_f. For example, under the conventional cyclic prefix, RS can be selected from OFMD symbols, such as selecting symbol 0, symbol 4, symbol 7 and symbol 11 to calculate PDP, and finally T is obtained_f。

Preferably, the UE may extract data with a length of 1 subframe from a start time of the received data, or extract data with a length of 1 subframe from the received data based on a timing reference of the OFDM system. Preferably, 1 subframe corresponding to the reference timing can be taken out(i.e. the 3 rd sub-frame) duration corresponding data calculation T_f。

As a non-limiting example, referring to fig. 2, N is 3, and the total duration of the received data is 1 subframe plus 2N · T_intTotal 1 subframe plus 6T_intTime length data. When N is 3, with T_intFor the step size, 2(N-1) +1 ═ 5 subframes may be taken out, that is, the received data (-N +1+ T) that may be buffered for the first time_f) The position starts to fetch data of 1 sub-frame duration (i.e. the 1 st sub-frame in fig. 2), and then the second time T can be shifted_intThe duration of the subframe is 1, and the data (i.e. the 2 nd subframe in fig. 2) of the subframe duration is taken out again; and so on until 2(N-1) +1 equals 5 subframes. It should be noted that, in practical application, the value of N may be set according to the processing capability of the UE and the variation of the network timing offset, and is not described herein again.

Further, in step S103, the UE may associate T with_intTraversing the received data as a step size. In the traversal process, data with the duration of 1 subframe can be sequentially taken out from the received data in the buffer, and a CFI code sequence is calculated based on the data. The CFI code sequence may be obtained after the UE demodulates and decodes the data. Obviously, if N is 3, the UE will calculate the CFI code sequence 2(N-1) +1 ═ 5 times, and similarly, if N is 2, the UE will calculate the CFI code sequence 3 times, and further description of other values of N will be omitted.

Preferably, the UE performs traversal on the data, and may first remove the influence of the decimal time offset, for example, the UE may traverse from (-N +1) T_int+T_fAnd starting to take out data with the duration of 1 subframe, thereby eliminating the influence of decimal time offset.

Further, in step S104, the UE may determine an integer time offset according to the CFI code sequence obtained in the traversal process. Specifically, after the CFI code sequence is calculated, DCI may be detected based on the CFI code sequence. If the network sends DCI information to the UE, and the UE receives the DCI and obtains the DCI information after demodulation and decoding, that is, the UE successfully detects the DCI, then the DCI information means that the UE successfully detects the DCIThe data with the length of 1 subframe taken out this time is the actual received data corresponding to the subframe sent by the OFDM system, in other words, the UE can determine the time corresponding to the currently taken out 1 subframe as the actual receiving time. Comparing the timing reference of the OFDM system with the actual reception time, the offset number n may be obtained. For example, n may be represented by the offset duration T between the position of the data of length 1 subframe taken this time relative to the reference and the reference_intIs determined. The sign of n may take a negative sign if the actual reception time is earlier than the reference, whereas the sign of n may take a positive sign if the actual reception time is later than the reference.

As a variation, after the CFI code sequence is obtained by calculation, the UE may further calculate mutual information between the CFI code sequence and a known CFI code sequence to obtain CFI mutual information. Specifically, the CFI mutual information may be represented as I (a, B), where a represents a calculated CFI sequence and B is a known CFI code sequence, and as is known from information theory, I (a, B) ═ h (a) + h (B) -h (ab); h (a), h (b) indicate information entropies of A, B, i.e., h (a) ═ Σ p_A(a)logp_A(a)，H(B)＝-∑p_B(b)logp_B(b) In that respect H (A) + H (B) represents the uncertainty of the prior CFI information of the OFDM system before communication, H (AB) represents the uncertainty of the residual CFI information of the OFDM system after communication, namely

H(A,B)＝-∑p_AB(a,b)logp_AB(a,b)。

Further, a joint probability distribution p of A, B is calculated_AB(a, b) can be represented by a normalized joint histogram:

wherein the edge probability p_A(i) Can be expressed as:

edge probability p_B(j) Can be expressed as:

further, according to the specification of the LTE protocol, the known CFI code sequence contains four code words, as shown in table 1.

TABLE 1

1	<0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1>
		2	<1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0>
3	<1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1,0,1,1>
		4 (Retention)	<0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0>

Further, the theoretical calculation results of the CFI mutual information are shown in table 2. As can be seen from table 2, when the calculated CFI code sequence is combined with the known CFI code sequence, the value of CFI mutual information is larger. That is, the larger the value of the CFI mutual information is, the higher the probability that the data of the length 1 subframe extracted this time is the actually received subframe is.

TABLE 2

I(A,B)	1	2	3
				1	0.6435	0.1894	0.1670
2	0.1894	0.6435	0.1670
				3	0.1670	0.1670	0.6211

Further, after the UE calculates the CFI mutual information, the CFI mutual information may be stored in a pre-established array. For example, the array name is CFI _ INFO, and its element storage location can be represented as CFI _ INFO [ N + N ], and the offset number N can be known from the storage location of the CFI mutual information.

Further, after traversing all the received data, if the UE does not detect DCI yet, the UE may calculate the offset number n by using a position of the data of 1 subframe in length corresponding to the maximum value of the CFI mutual information with respect to a reference. That is, the UE may find the maximum CFI mutual information value according to the CFI mutual information stored in the array, and obtain the offset number n according to the storage location of the maximum CFI mutual information.

Fig. 3 is a flowchart illustrating a method for estimating a time offset of an OFDM system according to another embodiment of the present invention. Specifically, the time offset estimation method may be performed as follows:

firstly, step S201 is executed, that is, the UE determines the maximum value range of N, where the value of the offset number N is-N < N;

next, step S202 is performed, i.e., the UE receives 1 subframe plus 2 N.T_intReceiving data of the duration and storing the data into a cache; in consideration of the possibility of an advance or a delay of the timing offset, the received data is advanced by N · T compared to the reference timing of the OFDM system_intAnd time length, starting to receive data.

Step S203 is executed again, that is, data of 1 subframe duration is extracted from the received data, and the decimal time offset T is calculated_f. The UE can perform FFT (fast Fourier transform) on the taken data with the duration of 1 subframe to obtain frequency domain data, then determine an RS (Reed-Solomon) symbol from the frequency domain data, and compare the PDP with a local RS symbol according to the RS symbol, thereby calculating the decimal time offset T_f。

Further, step S204 is executed, namely T_intAnd traversing the received data for the step size. During traversal, can be from (-N +1) · T_int+T_fAnd starting to take data of one sub-frame duration so as to remove the influence of decimal time offset on actually received data. In the process of traversing the received data, data with the duration of 1 subframe is taken out each time until all subframes are taken out, for example, when traversing starts, N is a value of-N +1, and then the received data is moved by T_intThe duration, in which N takes the value of-N +2, and so on, N takes the values of-N +2, … …, N-1.

Further, step S205 is executed to determine a CFI code sequence, calculate and store CFI mutual information, and then detect DCI. Specifically, the UE may demodulate and decode the CFI according to the extracted data of 1 subframe duration to determine a CFI code sequence, calculate and store CFI mutual information by using a CFI mutual information calculation formula, and detect the DCI according to the CFI obtained by the calculation.

Further, step S206 is performed, i.e. it is determined whether the UE detects DCI, and if DCI is detected, step S2071 is performed, and the offset number n is determined, i.e. integer multiple of time offset n · T can be obtained_intAnd jumping to execute step S208; if the detection of the DCI fails, executing step S2072, determining whether the traversal of n is finished, and if the traversal of n is not finished, jumping to step S204; if the detection of the DCI fails after traversing the received data, step S2073 is executed, i.e. n corresponding to the maximum value of the CFI mutual information is determined, and then integer multiple time offset n.T can be obtained_intAnd jumping to step S208;

finally, step S208 is executed to determine the total timing deviation Δ T as n · T_int+T_f。

Therefore, the time offset estimation method of the OFDM system provided by the embodiment of the invention can support a flexible and adjustable timing offset range, is simple to calculate, and can reduce the requirement on the clock precision of the system.

Fig. 4 is a schematic structural diagram of a time offset estimation apparatus of an OFDM system according to an embodiment of the present invention, which can be used to implement the technical solution of the time offset estimation method of the OFDM system. Specifically, the time offset estimation apparatus 4 may include: a receiving module 41, a first calculating module 43, a second calculating module 44, a determining module 45 and a third calculating module 46.

Specifically, the receiving module 41 is adapted to advance by N · T with reference to the OFDM system timing_intThe time length begins to receive data, and the total receiving time length is 1 subframe plus 2 N.T_intTo obtain received data, wherein T_intIs a preset unit offset duration, and N is the maximum number of the preset unit offset durations supported; the first calculating module 43 is adapted to extract data with a length of 1 sub-frame from the received data, and calculate a fractional time offset T based on the data with the length of 1 sub-frame_f(ii) a The second calculation module 44 is adapted to calculate T_intTraversing the received data for step length, taking out data with the length of 1 subframe each time and calculating a CFI code sequence; the determining module 45 is adapted to determine an offset number N, N being an integer and-N, from the CFI code sequence obtained in the traversal process<n<N; the third calculationThe module 46 is adapted to calculate the total time offset Δ T, where Δ T ═ n · T_int+T_f。

Further, the determining module 45 may include: a first calculation sub-module 451 and a first determination sub-module 452. Specifically, the first calculating sub-module 451 is adapted to detect DCI according to a CFI code sequence obtained by calculation after data with a length of 1 subframe is taken out and the CFI code sequence is calculated each time in a traversal process; if the DCI detection is successful, the first determining submodule 452 is adapted to calculate the offset number n using the position of the data of length 1 subframe fetched this time relative to a reference, where the value of n is equal to the quotient of the offset duration between the position relative to the reference and Tint, and the sign of n depends on whether the position is ahead or behind the reference. Further, the DCI detection success refers to: and receiving the DCI from the data with the length of 1 subframe, and correctly decoding the DCI.

Further, the determination module 45 may further include a second calculation submodule 453 and a second determination submodule 454. In particular, the second computation submodule 453 is adapted to compute each time after the CFI code sequence is computed, further compute mutual information between the CFI code sequence and a known CFI code sequence to obtain CFI mutual information; if the DCI detection fails after the data reception is finished, the second determining submodule 454 is adapted to calculate the offset number n by using the position of the data of the subframe with the length of 1 corresponding to the maximum CFI mutual information with respect to the reference.

Further, the formula for calculating the CFI mutual information is I (a, B) ═ h (a) + h (B) -h (ab); wherein, a represents the CFI sequence obtained by calculation, B represents the known CFI code sequence, I (a, B) represents the CFI mutual information, h (a), h (B) represent the information entropy of A, B, respectively, and h (ab) represents the uncertainty of the CFI information remaining in the OFDM system after communication.

Further, the time offset estimation apparatus 4 may further include a storage module 42. In particular, the storage module 42 is adapted to store the received data in a buffer after obtaining the received data.

For more details of the operation principle and the operation mode of the time offset estimation device 4, reference may be made to the related description in fig. 1 and fig. 2, and details are not repeated here.

Further, although The LTE OFDM system is taken as an example in The embodiment of The present invention, if a future next-Generation wireless communication system, for example, The Fifth-Generation mobile communication (5G) system, still uses OFDM technology as a physical layer technology, The embodiment of The present invention can still be used in a next-Generation wireless communication network.

Further, the embodiment of the present invention further discloses a storage medium, on which a computer instruction is stored, and when the computer instruction runs, the technical solution of the time offset estimation method of the OFDM system in the embodiments shown in fig. 1 and fig. 2 is executed. Preferably, the storage medium may include a computer-readable storage medium such as a non-volatile (non-volatile) memory or a non-transitory (non-transient) memory. The computer readable storage medium may include ROM, RAM, magnetic or optical disks, and the like.

Further, an embodiment of the present invention further discloses a terminal, which includes a memory and a processor, where the memory stores a computer instruction capable of being executed on the processor, and when the processor executes the computer instruction, the technical solution of the time offset estimation method for the OFDM system in the embodiments shown in fig. 1 and fig. 2 is executed. In particular, the terminal may be a user equipment.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A method for estimating time offset of an OFDM system, comprising:

advancing N.T. based on OFDM system timing_intThe time length begins to receive data, and the total receiving time length is 1 subframe plus 2 N.T_intTo obtain a data ofReceive data, wherein T_intIs a preset unit offset duration, and N is the maximum number of the preset unit offset durations supported;

taking out data with the length of 1 subframe from the received data, and calculating decimal time offset T based on the data with the length of 1 subframe_f；

By T_intTraversing the received data for step length, taking out data with the length of 1 subframe each time and calculating a CFI code sequence;

determining the offset number N according to the CFI code sequence obtained in the traversal process, wherein N is an integer and-N<n<N; the determining an offset number n according to the CFI code sequence obtained in the traversal process includes: in the traversing process, after data with the length of 1 subframe is taken out each time and a CFI code sequence is calculated, DCI is detected according to the CFI code sequence obtained through calculation; if the DCI detection is successful, calculating the offset number n by using the position of the data with the length of 1 subframe taken out at this time relative to the reference, wherein the value of n is equal to the offset duration between the position and the reference and T_intThe sign of n depends on whether the position is ahead or behind the reference; the determining the offset number n according to the CFI code sequence obtained in the traversal process further includes: after each CFI code sequence is calculated, mutual information between the CFI code sequence and a known CFI code sequence is calculated to obtain CFI mutual information; if the DCI detection fails after traversing the received data, calculating the offset number n by using the position of the data of the subframe with the length of 1 corresponding to the maximum value of the CFI mutual information relative to a reference;

calculating a total time offset Δ T, wherein Δ T is n.T_int+T_f。

2. The method according to claim 1, wherein the CFI mutual information is calculated as I (a, B) ═ h (a) + h (B) -h (ab); wherein, a represents the CFI sequence obtained by calculation, B represents the known CFI code sequence, I (a, B) represents the CFI mutual information, h (a), h (B) represent the information entropy of A, B, respectively, and h (ab) represents the uncertainty of the CFI information remaining in the OFDM system after communication.

3. The method of claim 1, wherein the DCI detection success is: and receiving the DCI from the data with the length of 1 subframe, and correctly decoding the DCI.

4. The method of claim 1, further comprising, after obtaining the received data: and storing the received data into a cache.

5. An apparatus for estimating a time offset of an OFDM system, comprising:

a receiving module adapted to advance N.T based on the timing of the OFDM system_intThe time length begins to receive data, and the total receiving time length is 1 subframe plus 2 N.T_intTo obtain received data, wherein T_intIs a preset unit offset duration, and N is the maximum number of the preset unit offset durations supported;

a first calculating module, adapted to take out data with length of 1 sub-frame from the received data, and calculate decimal time offset T based on the data with length of 1 sub-frame_f；

A second calculation module adapted to calculate T_intTraversing the received data for step length, taking out data with the length of 1 subframe each time and calculating a CFI code sequence;

a determining module adapted to determine an offset number N, N being an integer and-N, from the CFI code sequence obtained in the traversal process<n<N; the determining module comprises: the first calculation submodule is suitable for detecting the DCI according to the CFI code sequence obtained by calculation after data with the length of 1 subframe is taken out and the CFI code sequence is calculated each time in the traversal process; a first determining submodule adapted to calculate the offset number n using a position of the data of length 1 subframe fetched this time with respect to a reference if the DCI detection is successful, wherein a value of n is equal to an offset duration between the position with respect to the reference and T_intThe sign of n depends on whether the position is ahead or behind the reference; the second calculation sub-module is suitable for calculating mutual information between the CFI code sequence and a known CFI code sequence after calculating the CFI code sequence each time so as to obtain CFI mutual information; a second determining submodule, configured to calculate the offset number n by using a position, relative to a reference, of the data of 1 subframe in length corresponding to the maximum CFI mutual information if the DCI detection fails after traversing the received data;

a third calculation module adapted to calculate a total time offset Δ T, wherein Δ T is n.T_int+T_f。

6. The apparatus according to claim 5, wherein the formula for calculating the CFI mutual information is I (A, B) ═ H (A) + H (B) -H (AB); wherein, a represents the CFI sequence obtained by calculation, B represents the known CFI code sequence, I (a, B) represents the CFI mutual information, h (a), h (B) represent the information entropy of A, B, respectively, and h (ab) represents the uncertainty of the CFI information remaining in the OFDM system after communication.

7. The apparatus according to claim 5, wherein the DCI detection success means: and receiving the DCI from the data with the length of 1 subframe, and correctly decoding the DCI.

8. The apparatus according to claim 5, further comprising:

and the storage module is suitable for storing the received data into a cache after the received data is obtained.

9. A storage medium having stored thereon computer instructions, which when executed by a processor, perform the steps of the method for time offset estimation of an OFDM system according to any of claims 1 to 4.

10. A terminal comprising a memory and a processor, the memory having stored thereon computer instructions executable on the processor, wherein the processor, when executing the computer instructions, performs the steps of the method for estimating time offset for an OFDM system according to any of claims 1 to 4.