CN106973026B - Preamble symbol receiving method - Google Patents

Abstract

The invention provides a method for receiving a leading symbol, which is characterized by comprising the following steps: processing the received physical frame to obtain a baseband signal; judging whether a pilot symbol expected to be received exists in the baseband signal or not; determining the position of the received preamble symbol in a physical frame and decoding the signaling information carried by the preamble symbol when the signaling information exists, wherein when judging whether the preamble symbol expected to be received exists in the baseband signal, the reliability judgment can be carried out by using any one of the following modes or any at least two modes in a free combination mode: the method comprises an initial timing synchronization mode, an integral frequency offset estimation mode, a precise timing synchronization mode, a channel estimation mode and a decoding result analysis mode, and can solve the problems of single-frequency interference and small-offset estimation failure under dangerous delay.

Description

Preamble symbol receiving method

The present application is a divisional application of the original, the application number of the original is 201510064118.5, the application date of the original is 2015/02/06, and the invention of the original is entitled "preamble symbol generating method and receiving method".

Technical Field

The invention belongs to the field of broadcast communication, and particularly relates to a method for generating a preamble symbol, a method for receiving the preamble symbol and a corresponding device.

Background

At present, a method for implementing time synchronization between a transmitting end and a receiving end in an OFDM system is basically implemented based on preamble symbols. The preamble symbol is a symbol sequence known to both the transmitting end and the receiving end of the OFDM system, the preamble symbol marks the beginning of a physical frame (named as P1 symbol), only one P1 symbol or a plurality of P1 symbols occur consecutively in each physical frame, and the uses of the P1 symbol include:

1) enabling a receiving end to quickly detect whether a signal transmitted in a channel is an expected received signal;

2) providing basic transmission parameters (such as FFT point number, frame type information and the like) to enable a receiving end to carry out subsequent receiving processing;

3) detecting initial carrier frequency deviation and timing error for achieving frequency and timing synchronization after compensation;

4) emergency alerts or broadcast system wake-up.

Generally, the preamble symbol includes a physical layer Format Control part (PHY Format Control, or PFC) and a physical layer Content Control part (PHY Content Control, or PCC), and the preamble symbol of the DVB _ T2 system includes P1 and P2, which are used for transmitting signaling information or further for transmitting frame Format parameters. However, the prior art P1 can only transmit 7-bit signaling, which results in inefficient transmission of the system, and is not suitable for coherent decoding system, and does not consider the need for transmitting the signaling by selecting the number of time domain symbols of the preamble symbol to meet the system requirement.

Disclosure of Invention

The problem to be solved by the present invention is that the preamble symbol transmission method in the prior art causes the system transmission efficiency to be insufficient, and is not suitable for the coherent decoding system, and does not consider to transmit the required signaling by selecting the time domain symbol number of the preamble symbol to adapt to the system requirement.

In order to solve the above problem, an embodiment of the present invention provides a method for generating a preamble symbol, where the method for generating a preamble symbol is characterized by including: generating frequency domain subcarriers based on the frequency domain subject sequence; performing inverse Fourier transform on the frequency domain subcarriers to obtain time domain main body signals; and generating the preamble symbol from at least one time domain symbol formed based on the time domain subject signal, wherein the step of generating the frequency domain subcarriers comprises: a predetermined sequence generation rule for generating the frequency domain subject sequence; and/or processing the frequency domain subject sequence to generate a predetermined processing rule of the frequency domain subcarriers, wherein the predetermined sequence generation rule includes any one or two of the following: generating based on different sequence generating formulas; and/or based on the same sequence generating formula, and further performing cyclic shift on the generated sequence, wherein the predetermined processing rule comprises: and carrying out phase modulation on the pre-generated subcarriers obtained by processing based on the frequency domain main body sequence according to the frequency offset value.

Optionally, in the step of performing phase modulation on the frequency offset value based on the pre-generated subcarriers, the frequency domain subcarriers corresponding to the same time domain main signal perform phase modulation on each effective subcarrier in the frequency domain subcarriers by using the same frequency offset value, and the frequency offset values used by the frequency domain subcarriers corresponding to different time domain main signals are different.

Optionally, in the predetermined sequence generation rule, the different sequence generators are obtained by assigning different root values to the same constant-envelope zero-autocorrelation sequence, and the same sequence generator is obtained by assigning the same root value to the constant-envelope zero-autocorrelation sequence.

Optionally, the step of generating the frequency domain subcarriers includes: generating the frequency-domain subject sequence using a different sequence generator in the predetermined sequence generation rule.

Optionally, the step of generating the frequency domain subcarriers includes: and generating the frequency domain main body sequence by using different sequence generation formulas in the predetermined sequence generation rule, and continuing to use the predetermined processing rule for the frequency domain main body sequence to generate frequency domain subcarriers.

Optionally, wherein the frequency-domain body sequence is generated based on one or more of the constant-envelope zero auto-correlation sequences, the frequency-domain body sequence having a predetermined sequence length N_ZC。

Optionally, when generated based on a plurality of said constant-envelope zero-auto-correlation sequences, each respectively has a corresponding subsequence length L_MGenerating rules according to the predetermined sequence for each constant envelope zero auto-correlation sequenceThen generating a sub-sequence of length L_MA plurality of said subsequences are spliced to have said predetermined sequence length N_ZCThe frequency domain subject sequence of (a).

Optionally, the frequency domain subject sequence has a predetermined sequence length N_ZCNot greater than the Fourier transform length N that the time domain subject signal has_FFTThe step of obtaining the pre-generated subcarriers based on the frequency domain subject sequence processing includes a processing and filling step, and the processing and filling step includes: with reference to a predetermined sequence length N_ZCMapping the frequency domain subject sequence into positive frequency subcarriers and negative frequency subcarriers; referring to the Fourier transform length N_FFTFilling a preset number of virtual subcarriers and direct current subcarriers in the outer edges of the positive frequency subcarriers and the negative frequency subcarriers; and circularly left-shifting the resulting subcarriers so that the zero subcarrier corresponds to the first position of the inverse fourier transform.

Optionally, the step of processing the filling further comprises the steps of: and performing PN modulation on the frequency domain main body sequence, thereby performing the mapping again, wherein the PN sequences for performing the PN modulation on the frequency domain main body sequence corresponding to each time domain main body signal are the same or different.

Optionally, the step of performing the cyclic shift in the predetermined sequence generation rule is provided before or after performing the PN modulation.

Optionally, wherein information is transmitted by using the corresponding root value in the first time domain main body signal and/or the initial phase of the PN sequence for performing the PN modulation.

Optionally, wherein, when the frequency domain subcarriers used for signaling transmission are generated using the predetermined sequence generation rule,

if a pre-known frequency domain main body sequence is adopted by a first time domain main body signal in the at least one time domain main body signal, the frequency domain main body sequence and the corresponding frequency offset value are not used for signaling transmission.

Optionally, the preamble symbol is located in a physical frame, and the signaling transmitted through the frequency domain body sequence includes a frame format parameter for indicating the physical frame and/or for indicating emergency broadcast content.

Optionally, wherein the time domain symbol has the following three-segment structure: wherein the first three-stage structure comprises: the time domain main signal, a part of generated prefixes selected from the tail end of the time domain main signal and a part of generated suffixes selected from the prefix range based on the time domain main signal; the second three-stage structure comprises: the time domain main signal, a part of generated prefixes selected from the tail ends of the time domain main signal and a part of generated prefixes selected from the prefix range based on the time domain main signal, wherein the preamble symbols comprise: said time domain symbol having said first three-segment structure; or a time domain symbol having said second three-segment structure; or a plurality of time domain symbols with the first three-segment structure and/or a plurality of time domain symbols with the second three-segment structure which are not arranged in sequence are freely combined.

The embodiment of the invention also provides a generation method of the preamble symbol, which is characterized in that the time domain symbol with the following three-section structure is generated based on the time domain main body signal; and generating the preamble symbol based on at least one of the time domain symbols,

wherein the first three-stage structure comprises: the time domain main signal, a part of generated prefixes selected from the tail end of the time domain main signal and a part of generated suffixes selected from the prefix range based on the time domain main signal; the second three-stage structure comprises: the time domain main signal, a part of generated prefixes selected from the tail ends of the time domain main signal and a part of generated prefixes selected from the prefix range based on the time domain main signal, wherein the preamble symbols comprise: said time domain symbol having said first three-segment structure; or a time domain symbol having said second three-segment structure; or a plurality of time domain symbols with the first three-segment structure and/or a plurality of time domain symbols with the second three-segment structure which are not arranged in sequence are freely combined.

Optionally, the time-domain bulk signal is defined as a first portion, the time-domain bulk signal portion as the suffix or the super-prefix is defined as a second portion, and the time-domain bulk signal portion as the prefix is defined as a third portion, where the third portion is obtained by directly copying a portion of the first portion, and the second portion is obtained by modulating a frequency offset based on a portion of the first portion. .

Optionally, wherein the length of the first portion is set to N_ASetting the length of the second part as Len_BSetting the length of the third portion to Len_CSetting the number of a first sampling point of the first three-segment structure, which is selected to correspond to the start of the second portion, to N1_1, and setting the number of a second sampling point of the second three-segment structure, which is selected to correspond to the start of the second portion, to N1_2, satisfy the following formula: n1_1+ N1_2 ═ 2N_A-(Len_B+Len_c) Performing a modulation frequency offset value f of the modulation frequency offset_SHSelecting a frequency domain subcarrier interval (1/N) corresponding to the time domain symbol_AT or 1/(Len)_B+Len_c) And T, randomly selecting the modulation initial phase, wherein T is a sampling period.

Optionally, wherein for each first and each second of said three-segment structures, N_A2048, let Len_CValue 520 Len_BThe value is 504, the serial number N1_1 of the first sampling point is 1544, the serial number N1_2 of the second sampling point is 1528, and the modulation frequency offset value f is_SHIs 1/(1024T) or 1/(2048T).

Optionally wherein the emergency broadcast is identified by a different starting point from which the second portion was selected from the first portion.

Optionally, the number of at least one time domain symbol included in the preamble symbol is four.

Optionally, the three segments of structures respectively possessed by the four time domain symbols sequentially are: the first three-segment structure, the second three-segment structure, the first three-segment structure, and the second three-segment structure; or the first three-segment structure, the second three-segment structure, and the second three-segment structure; or the second three-segment structure, the first three-segment structure, and the first three-segment structure; or the first three-segment structure, the second three-segment structure, the first three-segment structure, and the first three-segment structure; or the first three-segment structure, and the second three-segment structure; or the first three-segment structure, and the first three-segment structure; or the first three-segment structure, the second three-segment structure, and the second three-segment structure.

Optionally, the time domain subject signal is obtained by performing inverse fourier transform on a frequency domain subcarrier generated based on the frequency domain subject sequence, where the step of generating the frequency domain subcarrier includes: a predetermined sequence generation rule for generating the frequency domain subject sequence; and/or processing the frequency domain subject sequence to generate a predetermined processing rule of the frequency domain subcarriers, wherein the predetermined sequence generation rule includes any one or two of the following: generating based on different sequence generating formulas; and/or based on the same sequence generating formula, and further performing cyclic shift on the generated sequence, wherein the predetermined processing rule comprises: and carrying out phase modulation on the pre-generated subcarriers obtained by processing based on the frequency domain main body sequence according to the frequency offset value.

The embodiment of the invention also provides a method for receiving the preamble symbol, which is characterized in that the received physical frame is processed to obtain a baseband signal; judging whether a pilot symbol expected to be received exists in the baseband signal or not; and determining the position of the received preamble symbol in the physical frame and solving the signaling information carried by the preamble symbol when the signaling information exists.

Optionally, when determining whether the preamble symbol expected to be received exists in the baseband signal, the reliability determination may be performed by using any one of the following manners or any at least two manners in a free combination manner: an initial timing synchronization mode, an integer frequency offset estimation mode, a precise timing synchronization mode, a channel estimation mode and a decoding result analysis mode.

Optionally, the fractional frequency offset estimation is performed on the preliminary result obtained by the initial timing synchronization method.

Optionally, when a first time-domain subject signal in the at least one time-domain subject signal does not transmit signaling as known information, the initial timing synchronization method includes: and carrying out differential operation through the first time domain symbol, carrying out differential operation on a time domain sequence corresponding to the known information, carrying out cross correlation on the two to obtain cross correlation values, and carrying out initial synchronization at least based on the obtained one or more cross correlation values.

Optionally, the integer frequency offset estimation method is performed based on a result obtained by the initial timing synchronization method.

Optionally, the step of performing integer frequency offset estimation includes any one or two combinations of the following two ways: the first integer frequency offset estimation method comprises the following steps: modulating all or part of the intercepted time domain waveforms by different frequency offsets in a frequency sweeping mode to obtain a plurality of frequency sweeping time domain signals, performing sliding correlation on a known time domain signal obtained by performing Fourier inverse transformation on a known frequency domain sequence and each frequency sweeping time domain signal, and then, taking a frequency offset value modulated by the frequency sweeping time domain signal with a maximum correlation peak value as an integral multiple frequency offset estimation value; and/or the second integer frequency offset estimation mode comprises the following steps: and circularly shifting the frequency domain subcarrier obtained by intercepting the main time domain signal according to the position result of initial timing synchronization and performing Fourier transform according to different shift values in a frequency sweep range, intercepting a receiving sequence corresponding to the effective subcarrier, performing predetermined operation on the receiving sequence and a known frequency domain sequence, performing inverse Fourier transform, and obtaining the corresponding relation between the shift value and the integer frequency offset estimation value based on the inverse Fourier transform results of a plurality of groups of shift values, thereby obtaining the integer frequency offset estimation value.

Optionally, after the integer frequency offset estimation is completed, the transmission signaling is analyzed after the frequency offset is compensated.

Optionally, after the integer-time frequency offset estimation is completed, when a first time domain subject signal in the at least one time domain subject signal does not transmit a signaling as known information, the precise timing synchronization mode is performed by using the known signal.

Optionally, the channel estimation method included in the step of parsing the transmission signaling includes: and after the last time domain main signal is decoded, using the obtained decoding information as sending information, performing channel estimation again in the time domain/frequency domain, and performing certain specific operation with the previous channel estimation result to obtain a new channel estimation result for channel estimation of signaling analysis of the next time domain main signal.

The embodiment of the invention also provides a device for generating the preamble symbols corresponding to the generating method and the receiving method respectively.

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

according to the preamble symbol generating method and receiving method, the preamble symbol generating device and receiving device provided by the embodiment of the invention, as any one of the preamble symbols or a plurality of freely combined three-segment structures are generated, the main part of each three-segment symbol can transmit signaling in a time domain structure and a frequency domain structure respectively, in the time domain, coherent demodulation can be realized by adopting the three-segment structure, meanwhile, the problem of single-frequency interference is solved by implementing modulation frequency offset in a suffix or prefix, and the problem of small-offset estimation failure under dangerous delay is solved by two different three-segment structures; in addition, in the frequency domain, the generated sequence is further subjected to cyclic shift to generate frequency domain subcarriers based on different sequence generation formulas and/or based on the same sequence generation formula, and optionally, the phase modulation is further performed on the pre-generated subcarriers obtained by processing according to frequency offset values, so that the transmission efficiency of the system is improved. Further, the time domain main signal in the first time domain symbol may adopt a known symbol for initial synchronization and channel estimation of coherent detection, and the number of time domain symbols in the preamble symbol may be flexibly selected according to system requirements to transmit the required signaling.

Drawings

Fig. 1 is a flowchart illustrating a first embodiment of a preamble symbol generation method according to the present invention;

FIG. 2 is a schematic diagram of a time domain structure of a physical frame in an embodiment of the present invention;

fig. 3 is a schematic diagram of a physical frame structure including a format control part and a content control part in an embodiment of the present invention;

fig. 4 is a schematic frequency domain diagram corresponding to a time domain symbol in a preamble symbol according to an embodiment of the present invention;

FIG. 5 is a schematic illustration of a first three-stage structure in an embodiment of the invention;

FIG. 6 is a schematic illustration of a second three-segment structure in an embodiment of the invention;

FIG. 7 is a flowchart illustrating a second embodiment of a preamble symbol generation method according to the present invention;

fig. 8 is a flowchart illustrating an embodiment of a preamble symbol receiving method according to the present invention;

FIG. 9 is a block diagram of the logic operation of the present invention for obtaining preliminary timing synchronization results using 4 sets of accumulated correlation values for 4 time domain symbols; and

fig. 10 is a block diagram of the logic operation of obtaining the preliminary timing synchronization result by using 2 groups of accumulated correlation values of 2 time domain symbols according to the present invention.

Detailed Description

The inventor finds that the preamble symbol in the prior art has the problems of low transmission efficiency, insufficient transmission flexibility, poor initial timing synchronization performance, and poor decoding performance under low signal-to-noise ratio due to the fact that coherent decoding cannot be implemented.

In view of the above problems, the inventors have studied and provided a method for generating and receiving preamble symbols, which not only improves the timing synchronization performance of preamble symbols, but also can implement coherent decoding by using the characteristic of cyclic prefix, thereby improving the reception performance in most cases. Meanwhile, signaling is transmitted in both time domain and frequency domain, the signaling transmission is implemented in the frequency domain through various methods, and the emergency broadcast identification can be implemented in the time domain. Meanwhile, signaling needing to be transmitted is realized by flexibly using the number of the time domain symbols so as to meet the system requirements and realize the transmission flexibility and expandability. Meanwhile, aiming at the generation method of the preamble symbol, the corresponding receiving algorithms are specifically set forth, and the receiving algorithms can realize very robust performance with lower complexity.

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 flowchart illustrating a method for generating preamble symbols according to an embodiment of the present invention. As shown in fig. 1, the method for generating a preamble symbol in this embodiment includes the following steps:

step S1-1: generating frequency domain subcarriers based on the frequency domain subject sequence;

step S1-2: performing inverse Fourier transform on the frequency domain subcarriers to obtain time domain main body signals; and

step S1-3: a preamble symbol is generated from at least one time domain symbol formed based on the time domain subject signal.

Wherein the step of generating the frequency domain subcarriers comprises: (1) a predetermined sequence generation rule for generating a frequency domain subject sequence; and/or (2) predetermined processing rules for processing the frequency domain subject sequence for generating frequency domain subcarriers,

(1) the predetermined sequence generation rule includes any one or two of the following combinations:

(1a) generating based on different sequence generating formulas; and/or

(1b) Is generated based on the same sequence generating formula, and the generated sequence is further subjected to cyclic shift,

(2) the predetermined processing rule includes: and carrying out phase modulation on the pre-generated subcarriers obtained by processing the main body sequence based on the frequency domain according to the frequency offset value.

Fig. 2 is a schematic time domain structure diagram of a physical frame in an embodiment of the present invention.

As shown in fig. 2, the present embodiment discloses a frame structure, and fig. 2 shows two physical frames, each of which includes a preamble symbol and a data area, wherein the preamble symbol precedes the data area.

The data area is used for transmitting data information such as TS packets or IP packets.

The preamble symbol is used for fast detection to determine whether the signal transmitted in the channel is a signal expected to be received, and provides basic transmission parameters (such as FFT point number, frame type information, etc.), so that the receiving end can perform subsequent receiving processing; detecting initial carrier frequency deviation and timing error for achieving frequency and timing synchronization after compensation; emergency broadcast wakeup, etc.

Fig. 3 is a schematic diagram of a physical frame structure including a format control portion and a content control portion in an embodiment of the present invention.

As shown in fig. 3, the physical frame structure includes a preamble symbol and a data area, wherein the preamble symbol includes: the part PFC and the part PCC are controlled by the physical layer format. Of course, the preamble symbol according to the present invention is not limited to include the PFC part and the PCC part.

The format control part PFC consists of one or more time domain symbols (indicated by a hatched box in the figure), each OFDM time domain symbol being of the same size. In this embodiment, the time domain symbol is an OFDM symbol.

FIG. 5 is a schematic illustration of a first three-stage structure in an embodiment of the invention; and FIG. 6 is a schematic illustration of a second three-stage structure in an embodiment of the present invention.

The format control part PFC of the preamble symbol includes at least one time domain symbol, and since the time domain symbol in this embodiment adopts the following first three-segment structure or second three-segment structure, the time domain symbol included in the preamble symbol may also be referred to as a three-segment structure time domain symbol. However, without limitation, the time domain symbols satisfying the above-mentioned preamble symbol may also adopt other structures other than the three-segment structure.

As can be seen from fig. 5 and fig. 6, in the first embodiment, the time domain symbol has the following three-stage structure: a first three-stage structure as in fig. 5: the method comprises the steps of firstly, generating a time domain main signal (A section), generating a prefix (C section) based on the rear part of the time domain main signal, and selecting a part of generated suffix (B section) in the prefix range based on the time domain main signal; a second three-stage structure as in fig. 6: the method comprises the steps of generating a time domain main signal (A section), generating a prefix (C section) based on the rear part of the time domain main signal, and selecting a part of generated prefix (B section) in a prefix range based on the time domain main signal.

A time domain body signal (denoted by a in the figure) is used as a first part, a part is taken out according to a preset acquisition rule at the tail end of the first part, the first part is processed and copied to the front part of the first part to generate a third part (denoted by C in the figure) to be used as a prefix, meanwhile, a part is taken out according to a preset acquisition rule from the rear part of the first part, the predetermined processing is processed and copied to the rear part of the first part or the predetermined processing is copied to the front part of the prefix to generate a second part (denoted by B in the figure) to be respectively used as a suffix or a super prefix, and therefore, a first three-segment structure (CAB structure) with B as a suffix and a second three-segment structure (BCA structure) with B as a super prefix shown in fig. 5 are respectively generated, and the second three-segment structure (BCA structure) shown.

Based on the time domain symbol having the three-segment structure, the preamble symbol generated in this embodiment may include: a time domain symbol having a first three-segment structure; or a time domain symbol having a second three-segment structure; or a plurality of time domain symbols with the first three-segment structure and/or a plurality of time domain symbols with the second three-segment structure which are not arranged in sequence are freely combined. That is, the preamble symbol may only contain CAB or BCA, or may be several CABs or several BCAs, or may be any arbitrary combination of several CABs and several BCAs without limitation in number. It should be particularly noted that the preamble symbol of the present invention is not limited to a structure containing only C-a-B or B-C-a, but may also contain other time domain structures, such as a conventional CP structure.

The section A is obtained by performing IFFT transform of 2048 points, for example, on the basis of a certain frequency domain main body sequence, and the section C in the three-section structure is a direct copy of a part in the section A, while the section B is a modulation signal section of a part in the section A, and the data range of the section B does not exceed the data range of the section C, namely, the range of the part A selected to the modulation signal section B does not exceed the range of the part A intercepted as the prefix C. Preferably, the sum of the length of B and the length of C is the length of a.

Let N_ALet Len be the length of A_CIs the length of C, Len_BIs the length of the modulation signal segment B. Let the sampling point number of A be 0,1, … N_ALet N1 be the sample point number selected to be copied to the first portion a corresponding to the start of the second portion B of the modulation signal segment, and N2 be the sample point number selected to be copied to the first portion a corresponding to the end of the second portion B of the modulation signal segment. Wherein the content of the first and second substances,

N2＝N1+Len_B-1 (formula 1)

In general, the modulation applied to the second part B segment is modulation frequency offset, modulation M sequence or other sequences, etc., in this implementation, taking modulation frequency offset as an example, if P1_ a (t) is a time domain expression of a, the time domain expression of the first common preamble symbol is

Wherein, the modulation frequency deviation value f_SHCan be selected as the frequency domain subcarrier interval corresponding to the time domain OFDM symbol, namely 1/N_AT, or 1/(Len)_B+Len_c) T where T is the sampling period, N_AIs the length of a time domain OFDM symbol, e.g., N_AIs 1024, take f _SH1/1024T, and the modulation frequency offset may be arbitrarily chosen for the initial phase. To sharpen the correlation peak, f_SHCan also be selected to be 1/(Len)_BT) or a value close to its value.

In the structure of B-C-A, the modulation frequency deviation value is just opposite to that of the structure of C-A-B, and the modulation can be arbitrarily selected as an initial phase.

Setting the serial number of a first sampling point corresponding to the first part (A) and selecting the starting point of the second part (B) in the first three-segment structure (CAB) as N1_1, setting the serial number of a second sampling point corresponding to the first part (A) and selecting the starting point of the second part (B) in the second three-segment structure (BCA) as N1_2, wherein the serial numbers of the first sampling point N1_1 and the second sampling point N1_2 need to satisfy the following formula

N1_1+N1_2＝2N_A-(Len_B+Len_c) (formula 4)

The advantage of satisfying such a relationship is that the delay relationship of the same content from segment C to segment B in the C-A-B structure is the same as the delay relationship of the same content from segment B to segment A in the B-C-A structure, and the delay relationship of the same content from segment A to segment B in the C-A-B structure is the same as the delay relationship of the same content from segment B to segment C in the B-C-A structure, which is beneficial for the receiver implementation. And in the C-A-B structure and the B-C-A structure, if the modulation adopted for the B section is modulation frequency offset, the frequency offset values f of the two structures_SHBut just the opposite, facilitates the receiver implementation.

The symbol of C-A-B structure is represented by the symbol No. 1, and the symbol of B-C-A structure is represented by the symbol No. 2. Then, let P1_ A (t) be the time domain expression of A1, P2_ A (t) be the time domain expression of A2, and then the time domain expression of the C-A-B three-segment structure is

The time domain expression of the three-section structure of B-C-A is as follows

The first three-segment structure and the second three-segment structure which are arranged in sequence are not distinguished, and different leading symbols which are freely combined by a plurality of first three-segment structures and/or a plurality of second three-segment structures can be respectively formed according to different sequences. The time domain expression of a first preamble symbol, which is 1C-a-B and 1B-C-a in order, and the time domain expression of a second preamble symbol, which is 1B-C-a and 1C-a-B in order, are given below by way of example.

Then, the time domain expression of the first preamble symbol is:

the time domain expression of the second preamble symbol is:

other combinations of C-A-B and B-C-A can be deduced according to the time domain expression of the first preamble symbol and the second preamble symbol, and repeated description is omitted here.

As in the above case, when the C-a-B structure and the B-C-a structure are cascaded, the problem of small bias estimation failure under a dangerous delay can be solved. When the critical delays cause the cancellation of the C and a segments, the CB segment of the first structure and the BC segment of the second structure can still be used for timing synchronization and estimation bias.

The number of at least one time domain symbol contained in the preamble symbol is set to transmit four symbols, and several preferred four time domain symbol structures are given below and are arranged in sequence as any one of the following structures:

(1) C-A-B, B-C-A, C-A-B, B-C-A; or

(2) C-A-B, B-C-A, B-C-A, B-C-A; or

(3) B-C-A, C-A-B, C-A-B, C-A-B; or

(4) C-A-B, B-C-A, C-A-B, C-A-B; or

(5) C-A-B, C-A-B, C-A-B, B-C-A; or

(6) C-A-B, C-A-B, C-A-B, C-A-B or

(7)C-A-B，C-A-B，B-C-A，B-C-A。

Among them, the structure of four time domain symbols, such as (1) C-A-B, B-C-A, maximizes the effect of concatenation. For example, (2) the structure of four time domain symbols, C-A-B, B-C-A, B-C-A, B-C-A, lengthens the guard interval of the subsequent symbol A portion, and typically the first symbol is a known signal, so C-A-B is used.

One preferred embodiment of a three-stage structure, N_A2048, let Len_CIs 520, Len_BWhere P1_ a (t) is the temporal body a expression, 504, N1_1 is 1544, N1_2 is 1528, it can be derived that the temporal expressions of C-a-B and B-C-a are the same

And

further, f_SHIt can be selected as 1/(1024T) or 1/(2048T).

Further, the emergency broadcast system may be identified by selecting a different starting point for the second part B from the first part a, i.e. by selecting a different N1, or N1_1 and N1_2, by copying to the starting point of the B segment. A symbol of a three-segment structure such as C-a-B, N1_ 1-1544 identifies a general system, and N1_ 1-1528 identifies an emergency broadcast system. For another example, in the notation of the three-segment structure of B-C-a, N1_2 ═ 1528 identifies a general system, and N1_2 ═ 1544 identifies an emergency broadcast system.

As can be seen from the preamble symbol generation procedure in fig. 1, the time domain main signal a is obtained by generating frequency domain subcarriers based on the frequency domain main sequence and performing inverse fourier transform IFFT. And then a time domain symbol with a three-segment structure of C-A-B or B-C-A is formed by the time domain main signal A, thereby forming a preamble symbol with at least one time domain symbol in the embodiment.

The following describes the generation process in the time domain main body signal a of three-segment structure (CAB or BCA).

Fig. 4 is a schematic frequency domain diagram corresponding to one time domain symbol in the preamble symbol according to the embodiment of the present invention.

As shown in fig. 4, a frequency domain subcarrier of a time domain symbol in PFC for a preamble symbol is generated, and the frequency domain subcarrier is obtained based on a frequency domain main body sequence.

The generation of the frequency domain subcarriers includes a predetermined sequence generation rule for generating a frequency domain subject sequence and/or a predetermined processing rule for processing the frequency domain subject sequence to generate the frequency domain subcarriers.

For a predetermined sequence generation rule, the generation process of the frequency domain subject sequence is flexible, and the predetermined sequence generation rule includes any one or a combination of two of the following: generating based on different sequence generating formulas; and/or based on the same sequence generating formula, and further performing cyclic shift on the generated sequence. In this embodiment, the constant envelope zero autocorrelation sequence (CAZAC sequence) is used, that is, the different sequence generating equations may be obtained by assigning different root values to the same CAZAC sequence, or the same sequence generating equation may be obtained by assigning the same root value to the CAZAC sequence.

The frequency domain subject sequence is generated based on one or more CAZAC sequences, the frequency domain subject sequence having a predetermined sequence length N_ZC. The predetermined sequence length N_ZCNot greater than the Fourier transform length N that the time domain subject signal has_FFT。

The step of processing and filling the frequency domain subject sequence generally comprises: with reference to a predetermined sequence length N_ZCMapping the frequency domain main body sequence into a positive frequency subcarrier and a negative frequency subcarrier; with reference to the Fourier transform length N_FFTFilling a preset number of virtual subcarriers and direct current subcarriers at the outer edges of the positive frequency subcarriers and the negative frequency subcarriers; and circularly left-shifting the resulting subcarriers so that the zero subcarrier corresponds to the first position of the inverse fourier transform.

Here, an example of generation based on one CAZAC sequence is described. First, N is generated_ZCA long frequency domain body sequence (Zadoff-Chu, sequence, ZC), which is one of the CAZAC sequences,

the sequence formula is:

note N_ZCMay be equal to or less than N_rootThe ZC _ M sequence is divided into two parts, the left half part has the length of

Mapped to the negative frequency part, the right half length is

Mapping to a positive frequency part, N_ZCA certain natural number can be selected, and the FFT length of the section A is not exceeded; in addition, at the edge of negative frequency, complement

Number of zeros, and at the edges of positive frequencies, complement

The number of zeros, being virtual subcarriers; thus, the specific sequence is composed of

The number of the zero lines is zero,

a number of PN modulated ZC sequences, 1 dc subcarrier,

a PN modulated ZC sequence and

each zero is composed sequentially; number of effective subcarriers is N_ZC+1

In particular, the generation of frequency domain subject sequences, such as sequence formulas

Several different root values q can be selected, for the sequence generated by each root value q, different cyclic shifts can be performed to obtain more sequences, and the signaling is transmitted by any one or two of the 2 ways.

For example, taking 256 root values q, 256 sequences are obtained, i.e. 8 bits can be transmitted, based on 2^8 ^ 256 and the shift value is set to 1024, each of the 256 sequences can perform 0-1023 shifts again, i.e. each sequence realizes 10-bit signaling transmission through 1024 shifts, based on 2^10 ^ 1024, thus 8+10 ^ 18-bit signaling can be transmitted altogether.

These signallings are mapped to bit fields, and the transmitted signallings can contain frame format parameters for indicating physical frames and/or for indicating emergency broadcast contents, wherein the frame format parameters are as follows: the frame number, the frame length, the bandwidth of the PCC symbol, the bandwidth of the data region, the FFT size and guard interval length of the PCC symbol, and the PCC modulation and coding parameters.

The cyclic shift in the predetermined sequence generation rule may be performed before the PN sequence modulation is performed on the ZC sequence, or may be performed after the PN sequence modulation, and PN sequences used for the PN modulation are the same or different for the frequency domain main body sequences corresponding to the time domain main body signals.

If the first time domain main signal in the at least one time domain main signal adopts a pre-known frequency domain main sequence, the frequency domain main sequence and the corresponding frequency offset value are not used for signaling transmission, and signaling is transmitted by the PFC in a subsequent time domain symbol.

The phase difference between the frequency domain main body sequence (ZC sequence) used by the last OFDM symbol and the frequency domain main body sequence (ZC sequence) used by the first OFDM symbol is 180 degrees, which is used for indicating the last OFDM symbol of PFC; the ZC sequence used for the first OFDM symbol in the PFC is generally a root sequence with a certain length and without cyclic shift, and at this length, the ZC sequence has a set, so that the ZC sequence in the set is selected by the present invention, which may indicate certain information, such as a version number or indicate a type or mode of a service transmitted in a data frame; in addition, information is transmitted by using the corresponding root value in the first time domain main body signal and/or the initial phase of the PN sequence for PN modulation, and the initial phase of the PN also has a certain signaling capability, such as indicating a version number.

Here, an example of generation based on a plurality of CAZAC sequences is described. Each CAZAC sequence has a corresponding sub-sequence length L_MGenerating a sequence having a subsequence length L for each CAZAC sequence according to the predetermined sequence generation rule_MA plurality of subsequences are spliced to have a predetermined sequence length N_ZCThe frequency domain body sequence of (1).

Specifically, the frequency domain effective subcarriers are generated by M CAZAC sequences each having a length L₁,L₂,...L_MAnd satisfy

The generation method of each CAZAC sequence is the same as the above method, only one step is added, and after M CAZAC sequences are generated, the M CAZAC sequences are spliced into a sequence with the length of N_ZCThe selected ZC _ M is modulated by PN sequence to form new ZC _ I, which is then interleaved in frequency domain to fill in the same sub-carrier position and has the length of the left half part

Mapped to the negative frequency part, the right half length is

Mapping to a positive frequency part, N_ZCA certain natural number can be selected, and the FFT length of the section A is not exceeded; in addition, at the edge of negative frequency, complement

Number of zeros, and at the edges of positive frequencies, complement

The number of zeros, being virtual subcarriers; thus, the specific sequence is composed of

The number of the zero lines is zero,

a number of PN modulated ZC sequences, 1 dc subcarrier,

a PN modulated ZC sequence and

zero sequence, wherein the step of modulating PN may also be performed after frequency domain interleaving.

The subcarrier position padding may also take other processing padding steps, which are not limited herein.

The sub-carriers obtained by the processing and filling are circularly moved to the left, and after the first half and the second half of the frequency spectrum are exchanged, the zero sub-carrier is corresponding to the first position of the discrete inverse Fourier transform to obtain the preset length N similar to the ftshift in Matlab_FFTThe pre-generated subcarriers of the frequency domain OFDM symbol of (1).

Further, in the frequency domain subcarrier generation process of the present embodiment, in addition to the above-described predetermined sequence generation rule, a predetermined processing rule for processing the frequency domain subject sequence to generate the frequency domain subcarriers may be more preferably adopted. The present invention is not limited to forming the frequency domain subcarriers using either or both of the predetermined processing rule and the predetermined sequence generation rule.

The predetermined processing rule includes: and performing phase modulation on the pre-generated subcarrier according to the frequency offset value S, wherein the pre-generated subcarrier is obtained by processing, filling, circulating, left shifting and the like on the frequency domain main body sequence. In the predetermined processing rule, the frequency domain subcarriers corresponding to the same time domain main signal a perform phase modulation on each effective subcarrier in the frequency domain subcarriers by using the same frequency offset value S, and the frequency offset values used by the frequency domain subcarriers corresponding to different time domain main signals a are different from each other by S.

For a predetermined processing rule, specifically, the subcarrier expression of the original OFDM symbol is

a₀(k) k＝0,1,2,...N_FFT-1，

(formula 12)

The expression for phase modulating each subcarrier by a certain frequency offset value, such as s, is as follows:

the zero carrier multiplication operation is actually not required to be carried out, and only the effective subcarriers are required to be operated. The frequency offset value s may be selected within a range [ - (N)_FFT-1),+(N_FFT-1)]Based on the fourier transform length N that the time domain subject signal has_FFTAnd determining that different values can be used for transmitting signaling.

It should be noted that the above-mentioned method for performing phase modulation on each pre-generated subcarrier according to the frequency offset value S can also be implemented in the time domain. Equivalent to: the original frequency domain OFDM symbol without the modulation phase is subjected to IFFT conversion to obtain a time domain ODFM symbol, the time domain OFDM symbol can be subjected to cyclic shift to generate a time domain main signal A, and signaling is transmitted through different cyclic shift values. In the present invention, each effective subcarrier is phase-modulated at a certain frequency offset value in the frequency domain, and the obvious time domain equivalent operation method is also within the present invention.

In summary, in the generation process of the frequency domain subcarriers, the present embodiment may select and freely combine any one or at least two of the predetermined sequence generation rule (1a), the predetermined sequence generation rule (1b) and the predetermined processing rule (2) based on the frequency domain subject sequence.

For example, the preamble symbol generation method of rule (1a) is adopted to transmit signaling.

Taking 256 root values q and 0-1023 cyclic shift values for each root value q as described in the above example, 8+ 10-18 bit signaling may be transmitted.

For another example, the generation method of the preamble symbol of rule (1a) and rule (2) is used to transmit signaling.

The root value q takes 2 types, the time domain OFDM symbol length is 2048, 1024 types of shift values are taken, and 1+10 ═ 11 bit signaling is transmitted at intervals of 2, such as 0, 2, 4, 6, …, 2046 and the like.

For another example, only the preamble symbol generation method of rule (2) is used.

The root value q is fixed, and the phase modulation is carried out on the frequency domain subcarrier according to different frequency offset values S, such as the N_FFTIn the range of 2048 (parts by weight),

k＝0,1,2,...N_FFTthe s value of-1 is 0, 8, 16, … 2032, etc., which is equivalent to a time domain OFDM symbol after IFFT is performed on a frequency domain OFDM symbol without phase modulation, cyclic shift is performed on 256 different shift values, and 8-bit signaling is transmitted at 8 intervals, such as 0, 8, 16, … 2032, etc. Here, the present invention does not limit the left shift or the right shift of the cyclic shift, and when s is a positive number, the left shift corresponds to the time domain cyclic shift, for example, the value is 8, and the left shift corresponds to the time domain cyclic shift 8; when s is a negative number, the corresponding time domain cycle is shifted to the right, for example, the value is-8, and the corresponding time domain cycle is shifted to the right by 8.

The invention also provides a receiving method of the leading symbol embodiment II. Fig. 7 is a flowchart illustrating a second embodiment of a preamble symbol generation method according to the present invention.

As shown in fig. 7, the method for generating a preamble symbol in this embodiment includes the following steps:

step S2-1: generating a time domain symbol having the following three-segment structure based on the time domain subject signal; and

step S2-2: a preamble symbol is generated based on the at least one time domain symbol.

Wherein a first of the three-stage structures comprises: the time domain main signal, a part of generated prefixes selected from the tail end of the time domain main signal and a part of generated suffixes selected from the prefix range based on the time domain main signal; a second three-stage structure of the three-stage structures comprises: the time domain main signal, a part of generated prefix selected from the tail end of the time domain main signal and a part of generated prefix selected from the prefix range based on the time domain main signal,

the preamble symbol includes: said time domain symbol having said first three-segment structure; or a time domain symbol having said second three-segment structure; or a plurality of time domain symbols with the first three-segment structure and/or a plurality of time domain symbols with the second three-segment structure which are not arranged in sequence are freely combined.

In the second embodiment, the technical elements corresponding to the first embodiment, such as the first three-stage structure and the second three-stage structure, have specific structures, and the same description is omitted here.

The embodiment of the invention also provides a method for receiving the preamble symbol. Fig. 8 is a flowchart illustrating an embodiment of a preamble symbol receiving method according to the present invention.

As shown in fig. 8, the preamble symbol receiving method in this embodiment includes the following steps:

step S3-1: processing the received physical frame to obtain a baseband signal;

step S3-2: judging whether the baseband signal has the pilot symbol expected to be received and generated by the generation method;

step S3-3: and determining the position of the received preamble symbol in the physical frame and solving the signaling information carried by the preamble symbol.

When determining whether the preamble symbol expected to be received exists in the baseband signal at step S3-2, the reliability determination may be performed by using any one of the following manners or any combination of at least two manners: an initial timing synchronization mode, an integer frequency offset estimation mode, a precise timing synchronization mode, a channel estimation mode and a decoding result analysis mode.

This step S3-2 includes an initial timing synchronization mode for preliminarily determining the position of the preamble symbol in the physical frame. Further, after the initial synchronization, a small deviation estimation can be performed based on the result of the initial timing synchronization. In addition, after the initial synchronization, the integer frequency offset estimation method may be performed based on a result obtained by the initial timing synchronization method.

When the preamble symbol generation method of the transmitting end adopts the way that the first time domain main signal is not transmitted with signaling as known information, the (①) initial timing synchronization mode comprises the steps of carrying out differential operation through the first time domain symbol, carrying out differential operation on a time domain sequence corresponding to the known information, carrying out cross correlation on the time domain sequence and the time domain sequence to obtain a cross correlation value, and carrying out initial synchronization at least based on the obtained one or more cross correlation values.

Next, a method of estimating integer frequency offset based on the initial timing synchronization result will be described, where the step of estimating integer frequency offset includes any one or a combination of two methods: .

The first integer frequency offset estimation method comprises the following steps: modulating all or part of the intercepted time domain waveforms by different frequency offsets in a frequency sweeping mode to obtain a plurality of frequency sweeping time domain signals, performing sliding correlation on a known time domain signal obtained by performing Fourier inverse transformation on a known frequency domain sequence and each frequency sweeping time domain signal, and then, taking a frequency offset value modulated by the frequency sweeping time domain signal with the maximum correlation peak value as an integral multiple frequency offset estimation value; and/or

The second integer frequency offset estimation method comprises the following steps: and performing cyclic shift on frequency domain subcarriers obtained by performing Fourier transform on the main time domain signals intercepted according to the position result of initial timing synchronization according to different shift values in a frequency sweep range, intercepting a receiving sequence corresponding to the effective subcarriers, performing predetermined operation on the receiving sequence and a known frequency domain sequence, performing inverse Fourier transform, and obtaining a corresponding relation between the shift values and the integer frequency offset estimation value based on inverse Fourier transform results of a plurality of groups of shift values, thereby obtaining the integer frequency offset estimation value.

The following example specifically describes the offset estimation manner, and the offset estimation and the initial channel estimation can be performed by using the known information of the first symbol of the PFC, which must be referred to the known information of the first symbol.

A first integer frequency offset estimation mode, which intercepts all or part of the received time domain waveform of the preamble symbol according to the position of the preamble symbol detected by the initial timing synchronization, and modulates the part of the time domain waveform with different frequency offsets by adopting a frequency sweep mode, i.e. with a fixed frequency change step diameter, such as corresponding integer frequency offset interval, to obtain a plurality of time domain signals

Where T is the sampling period, f_sIs the sampling frequency. The known frequency domain sequence is subjected to inverse Fourier transform according to a predetermined subcarrier filling mode to obtain a time domain signal A2, and A2 is used as a known signal and is associated with each A1_yPerforming sliding correlation, and selecting the A1 with the largest correlation peak_yThen the frequency offset value y modulated by the frequency offset is the estimated integer frequency offset value.

Wherein, the sweep frequency range corresponds to the frequency deviation range that the system needs to resist, for example, the frequency deviation of plus or minus 500K needs to resist, the sampling rate of the system is 9.14M, the preamble symbol main body is 2K long, and the sweep frequency range is

I.e., [ -114,114 [ -114]。

The second integral multiple frequency offset estimation mode: intercepting a main time domain signal A according to the position where the preamble symbol synchronously detected by the initial timing appears, performing FFT, performing cyclic shift of different shift values in a frequency sweep range on the frequency domain subcarrier after the FFT, then intercepting a receiving sequence corresponding to an effective subcarrier, performing certain operation (usually conjugate multiplication or division) by using the receiving sequence and a known frequency domain sequence, performing IFFT on the result, and performing specific operation on the result of the IFFT, such as taking the maximum path energy or taking a plurality of large path energies for accumulation. Then, after several IFFT operations, several groups of operation results are obtained each time after several IFFT operations. And judging which shift value corresponds to the integer frequency offset estimation based on the plurality of groups of results, thereby obtaining an integer frequency offset estimation value.

The general judgment method is to select the group of corresponding shift values with the largest energy as the integer frequency offset estimation value based on several groups of results.

There are many specific algorithms for estimating the integer frequency offset, and the detailed description is omitted.

In addition, channel estimation is completed by using the received first symbol containing the known information and the known frequency domain sequence in the first symbol and/or the time domain signal corresponding to the inverse fourier transform performed on the first symbol, and the channel estimation can also be performed in the time domain and/or in the frequency domain, including time-frequency joint operation, which is not expanded here.

Further, after the integral multiple frequency offset estimation is completed, the frequency offset is compensated and then the transmission signaling is analyzed.

Further optionally, after the integer-times frequency offset estimation is completed, when a first time domain subject signal in the at least one time domain subject signal does not transmit signaling as known information, a precise timing synchronization mode is performed by using the known signal.

The step of analyzing the transmission signaling includes a channel estimation mode, and the channel estimation mode includes: and after the last time domain main signal is decoded, using the obtained decoding information as sending information, performing channel estimation again in the time domain/frequency domain, and performing certain specific operation with the previous channel estimation result to obtain a new channel estimation result for channel estimation of signaling analysis of the next time domain main signal.

Further, after the frame format parameter and/or the emergency broadcast content are solved, the position of the PCC symbol or the position of the data symbol may be obtained according to the parameter content and the determined position of the PFC symbol, and the PCC symbol or the data symbol may be subsequently parsed based on the obtained position.

More specifically, for the preamble symbol having a three-segment structure defined from a time domain perspective as the CAB or BCA having an unlimited number of arbitrary combinations in embodiment two:

in a receiving end for receiving such preamble symbols, the (②) th initial timing synchronization method includes, when it is detected that the time domain symbol has a three-segment structure, performing a delay-sliding auto-correlation using a unique processing relationship and/or a modulation relationship of each CAB and/or BCA to obtain one or more sets of accumulated correlation values, performing a specific mathematical operation based on the one or more sets of correlation values, and performing at least a preliminary timing synchronization based on the operation result values.

Continuing with such preamble symbols, when the transmitting end uses a different starting point mark of the first part to select the second part for the emergency broadcast, the initial timing synchronization resolves the emergency broadcast by any one or any two of the following free combinations: different delay relationships of the same content between the third portion and the second portion; and different delay relationships of the same content between the first part and the second part to distinguish between transmitting the emergency broadcast and the normal broadcast.

Further, when the PFC in the transmitted preamble symbol includes both of the following two cases (a) and (b),

(a) a first one of the at least one time domain body signal is not used for signaling as known information;

(b) and detecting that the time domain subject signal has the three-segment structure,

when the two methods are completed, a first preliminary synchronization operation value obtained by the (①) th initial timing synchronization method and a second preliminary synchronization operation value obtained by the (②) th initial timing synchronization method are weighted, and the initial timing synchronization is completed based on the weighted operation values.

The method for preliminarily determining the position of the preamble symbol in the physical frame is described below with reference to specific method data and an operation formula.

[ initial timing synchronization method (①) ]

When the first symbol of the PFC does not transmit signaling and is a known signal, the (①) th initial timing synchronization mode may perform a difference operation on the first symbol of the PFC, perform a difference operation on a time domain signal corresponding to the known information, perform a cross-correlation on the time domain signal and the time domain signal, perform an initial synchronization on the basis of one or more sets of results of the difference correlation, and preliminarily determine a position of the preamble symbol in the physical frame.

Next, a specific procedure of the differential correlation in the (①) th initial timing synchronization mode is described, and first, a procedure of the single set of differential correlations is described.

Determining a differential value, carrying out differential operation according to the differential value on received baseband data, carrying out differential operation according to the differential value on a local time domain sequence corresponding to known information, and then carrying out cross correlation on the two differential operation results to obtain a differential correlation result corresponding to the differential value. The operation of this single set of differential correlation results is prior art. Let the difference value be D and the received baseband data be r_nThe specific formula of each step is described as follows;

first, the received baseband data is subjected to a difference operation in accordance with the difference value

After differential operation, the phase rotation caused by the carrier frequency offset becomes a fixed carrier phase e^j2πDΔfWhere Δ f denotes a carrier frequency deviation.

Simultaneously, the local time domain sequence is also subjected to differential operation

Then, the received data after difference and the local difference sequence are mutually correlated to obtain

In the case of a system without multipath, and without noise,

the correlation peak can be given well and the peak is not affected by the carrier deviation. The frame sync/timing sync position is obtained by using the following formula

It can be known from the single-set differential correlation operation process that the differential correlation algorithm can resist the influence of any large carrier frequency offset, but the signal noise is enhanced because the differential operation is performed on the receiving sequence first, and the noise enhancement is very serious under the condition of low signal-to-noise ratio, which causes the signal-to-noise ratio to be obviously deteriorated.

To avoid the above problem, therefore, more than one set of differential correlation operations may be performed, such as performing 64 sets of differential correlations, with N being equal to 64, to obtain

Where D (0), D (1), …, D (N-1) are selected N different differential values.

And carrying out specific mathematical operation on the N results to obtain a final correlation result.

In this embodiment, for the process in which multiple sets of differential correlations (64 sets) are selected according to the predetermined differential selection rule, any one of the following two types may be adopted based on the performance requirement of the transmission system:

(1) first predetermined differential selection rule: and D (i) randomly selecting N different values and satisfying that D (i) < L, wherein L is the length of a local time domain sequence corresponding to the known information.

(2) A second predetermined differential selection rule: the difference value D (i) selects N different values as the arithmetic sequence and satisfies D (i) < L, that is

K is to satisfy

Where L is the local time domain sequence corresponding to the known informationThe length of the column.

The N results (64 results) are subjected to predetermined processing operations to obtain final correlation results, and two preferred embodiments of the predetermined processing operations are described herein.

First predetermined processing operation:

the difference value D (i) can be arbitrarily selected from N different values, and D (i) < L is satisfied. Because of the arbitrarily selected differential value D (i), each set of differentially correlated phases e^j2πD(i)ΔfN-1 is different from each other and cannot be directly vector-added, so that only absolute value addition or averaging can be weighted. And carrying out preset processing operation on the N different differential correlation results through the following formula to obtain a final differential result. The following equation is an example of adding absolute values to obtain a final difference result.

Second type of predetermined processing operation:

the difference value D (i) may be N different values, D (i) < L, and D (i) is an arithmetic progression, i.e., D (i +1) -D (i) ═ K, K is a value satisfying D (i) < L

Is a constant integer of (a).

The difference value selected according to the rule is obtained as

After the differential correlation value is obtained, conjugate multiplication is carried out on the adjacent 2 groups of differential correlation values, and the value obtained after the conjugate multiplication of the N-1 groups is obtained through the following formula.

Because, originally each set of different phases e will be multiplied by this conjugate^j2πD(i)ΔfBecome the same e^j2πKΔfTherefore, N-1 group RM obtained by the following equation 8_i,mCan be weighted vector added or averaged to obtain the bestThe result is finally differenced to obtain a better performance than the first predetermined processing operation. The following is an example of vector addition to obtain the final difference result.

It should be noted that, when the difference value d (i) is obtained by using the second predetermined difference selection rule, the final correlation result may be obtained by not only matching the conjugate multiplication values obtained in the second predetermined processing operation and then performing weighted vector addition or averaging, but also matching at least two differential correlation results directly obtained in the first predetermined processing operation and performing weighted absolute value addition or averaging.

Thereby based on the operation R_dc,mThe position of the preamble symbol in the physical frame is preliminarily determined.

[ initial timing synchronization method (②) ]

When the preamble symbol has a time domain structure of C-A-B or B-C-A, the baseband signal is subjected to necessary inverse processing and/or signal demodulation and then is subjected to delay sliding autocorrelation by utilizing the processing relation and/or modulation relation specific to C-A-B and/or B-C-A to obtain 1 or more groups of accumulated correlation values, delay relation matching and/or specific mathematical operation are carried out on the basis of the one or more groups of accumulated correlation values, and then the operation value is used for initial timing synchronization, so that the position of the preamble symbol in a physical frame is preliminarily determined. For example, the formula of obtaining the accumulated correlation value by the delayed sliding autocorrelation is as follows:

U₁(n)＝r(n)r^*(n-N_A)

can select the U pair₁' (n) normalizing the energy to obtain U_1s'(n)。

Namely, it is

Energy normalizationOther methods can also be adopted, U₁The conjugation in (N) can also be performed by r (N), and r (N-N)_A) Conjugation is not taken.

In the structure of each C-A-B or B-C-A, three accumulated correlation values of CA, AB and CB based on the same content can be obtained respectively.

For example, the structure of C-A-B is only used as an example, and B-C-A can be correspondingly derived.

The same part of the section C and the section a is used for the sliding delay correlation, and it is noted that the above energy normalization step can be added, and is not described here again. Three correlation values were obtained for each 1C-A-B or B-C-A structure: u shape_ca'(n)，U_cb'(n)，U_cb'(n)

And performing sliding delay correlation by using the same part of the B section and the C section, which only modulates the frequency offset:

and B, performing sliding delay correlation by using the same part of the B section and the A section, which only modulates the frequency offset:

wherein corr _ len can take 1/f_SHT to avoid continuous wave interference, or Len_BSo that the peak is sharp.

When the preamble symbol comprises a plurality of three-segment structures, a plurality of groups of three accumulated correlation values of CA, AB and CB, i.e. a plurality of groups of U_ca'(n)，U_cb'(n)，U_ab' (n) performing delay relationship matching and/or mathematical operations based on one or more of the plurality of sets of values to obtain a final operation value, and using the operation value for initial synchronization.

For example, for the preferred 4 time domain symbols with three-segment structure, the arrangement is C-A-B, B-C-A, C-A-B, B-C-A, which results in

Then can be combined with

One or more of them is subjected to delay relation matching and/or phase adjustment and then added or averaged to obtain the final U_ca(n) of (a). Because they have the same phase value. Delay matching is exemplified as follows:

and

can be combined with

One or more of them is subjected to delay relation matching and/or phase adjustment and then added or averaged to obtain the final U_cb-ab(n) of (a). Because they have the same phase value. Delay matching is exemplified as follows:

and

can be combined with

One or more of them is subjected to delay relation matching and/or phase adjustment and then added or averaged to obtain the final U_ab-cb(n) of (a). Delay matching is exemplified as follows:

and

finally, based on U_ca(n) and U_cb-ab(n) and U_ab-cbAnd (n) performing delay matching and performing specific operation, wherein the delay matching is as follows:

U_ca(n)，U_cb-ab(n),U_ab-cb(n-A)

the initial timing synchronization is completed based on the operation result, and the specific digital operation may be absolute value addition. Such as taking the maximum position to complete initial timing synchronization.

It should be noted that, in the above embodiment, in consideration of the influence of the system sample clock offset, the delay numbers of some of the delay correlators may be added or subtracted by one to form themselves and three delay numbers after adding or subtracting one, the sliding delay autocorrelation is performed according to the three delay numbers, and the most significant one of the correlation results is selected, and the timing offset may be estimated.

Fig. 9 is a block diagram of the logic operation for obtaining the preliminary timing synchronization result by using 4 groups of accumulated correlation values of 4 time domain symbols in the present embodiment; fig. 10 is a block diagram of the logic operation of obtaining the preliminary timing synchronization result by using 2 groups of accumulated correlation values of 2 time domain symbols in the present embodiment.

Not in general, when the preamble symbol includes other time domain characteristics besides the structure of C-a-B or B-C-a, other timing synchronization methods implemented for other time domain structural characteristics are superimposed on the timing synchronization method using the structural characteristics of C-a-B or B-C-a, without departing from the spirit of the present invention.

Further, after the initial timing synchronization is initially completed, fractional frequency offset estimation can be performed by using the initial timing synchronization result of the (①) th mode and/or the (②) th mode.

The algorithm for fractional frequency offset estimation, specifically, for example, when the (①) th preliminary timing synchronization mode is adopted,

take its maximum value, corresponding to a phase e^j2πKΔfΔ f can be calculated and converted to the corresponding 1 st fractional value.

As another specific example, when the (②) th primary timing synchronization mode is used, U is selected_ca(n) the angle of the maximum value can be calculated as the 2 nd small deviation value, and then U is calculated_cb-ab(n) and U_ab-cbAfter conjugate multiplication, (n) the angle corresponding to the maximum value is also taken, and the 3 rd small deviation value can be calculated. As discussed above in the illustrative portion of the logical block diagram where angles are used to find the bias, the bias estimation can be based on either or both of the 2 nd and 3 rd bias values.

When the PFC in the transmitted preamble symbol contains the characteristics required for the implementation of the (①) th and (②) th preliminary timing synchronization modes, the small bias estimation value is obtained based on any one of the 1 st, 2 nd and 3 rd small bias values or the combination of at least two of the values.

In the step of resolving the signaling information carried by the preamble symbol in step S3-3, the step of analyzing the signaling information includes: and solving signaling information carried by the preamble symbol by using all or part of the time domain waveform of the preamble symbol and/or a frequency domain signal obtained by performing Fourier transform on all or part of the time domain waveform of the preamble symbol.

For example, the length N of the A segment position corresponding to each received symbol of the PFC part_FFTAfter FFT operation of corresponding length is carried out on the time domain received data, zero carrier is removed, the received frequency domain sub-carrier is taken out according to the effective sub-carrier position, and signaling analysis is carried out by utilizing the frequency domain sub-carrier.

If the transmitting sequence is modulated by PN, the receiving end can firstly demodulate PN operation on the received frequency domain subcarrier and then analyze ZC sequence signaling. And the received frequency domain subcarriers of the non-demodulated PN can be directly used for signaling analysis. The two differ only in the way the set of known sequences takes, as will be explained below.

Further, in the step of analyzing the signaling information, a set of known signaling sequences generated by all possible different root values and/or different frequency domain shift values of the frequency domain subject sequence sent by the sending end and all possible frequency domain modulation frequency offset values are utilized to analyze the signaling. The set of known sequences here, includes the following meanings:

if the PN is modulated at the transmitting end, the known sequence set may refer to a sequence set after the PN is modulated or a sequence set before the PN is modulated. If the receiving end carries out PN demodulation operation in the frequency domain, the known sequence set adopts a sequence set before PN modulation, and if the receiving end does not adopt PN demodulation in the frequency domain, the known sequence set adopts a sequence set after PN modulation. If the time domain waveform corresponding to the known sequence set is used, the sequence set after PN modulation is necessarily adopted by the CAZAC sequence.

Further, if the transmitting end performs an interleaving operation after generating the CAZAC sequence, the known sequence set may refer to a sequence set after frequency domain interleaving after the CAZAC sequence/or the PN modulation, or a sequence set before frequency domain interleaving. If the receiving end carries out de-interleaving operation in the frequency domain, the known sequence set adopts a sequence set before frequency domain interleaving, and if the receiving end does not adopt de-interleaving operation in the frequency domain, the known sequence set adopts a sequence set after frequency domain interleaving. If the time domain waveform corresponding to the known sequence set is used, a CAZAC sequence and/or a sequence set for modulating PN and de-interleaving is necessarily adopted, that is, a set composed of sequences mapped onto subcarriers at last.

The following description will be made of a specific procedure of signaling analysis from two transmission cases adopted in the following generation method of the transmitting end.

< first transmission case > when the generated sequence is further cyclically shifted using generation based on a different sequence generation equation and/or generation based on the same sequence generation equation in the generation of the frequency domain subcarriers.

And performing specific mathematical operation on the frequency domain signaling subcarrier, the channel estimation value and all possible frequency domain main body sequences for signaling analysis, wherein the specific mathematical operation comprises any one of the following operations:

(1) maximum likelihood correlation operation combined with channel estimation; or

(2) And after the channel estimation value is used for carrying out channel equalization on the frequency domain signaling subcarrier, carrying out correlation operation on the frequency domain signaling subcarrier and all possible frequency domain main body sequences, and selecting the maximum correlation value as a decoding result of signaling analysis.

The following describes the signaling resolution procedure in the first transmission case.

For example, let i equal to 0: M-1, M be the number of signaling subcarriers, and j equal to 0:2^P-1, P is the number of signalling bits transmitted in the frequency domain, i.e. the corresponding set of signalling subcarriers has a total of 2^PEach element corresponding to a sequence of length M_iFor each channel estimation value corresponding to a signaling subcarrier, SC _ rec_iFor the received frequency domain signaling subcarrier values,

for the ith in the jth element in the set of signalling subcarriersAnd (4) taking values.

Then

Take max (corr)_j) And obtaining the frequency domain transmission signaling corresponding to j.

If the transmitting end modulates PN, SC _ rec_iWithout PN demodulation, then

Correspondingly adopting a sequence set after PN modulation; if SC _ rec_iAfter PN demodulation, then

The sequence set before PN modulation is correspondingly adopted.

For the operation of the transmitting end including frequency domain interleaving, it can be simply deduced that the operation is not specifically described here.

Optionally, the decoding process of the frequency domain transmission signaling may also be performed in the time domain, a time domain signaling waveform set corresponding to a known signaling subcarrier set after IFFT transformation is directly and synchronously correlated with a time domain received signal at an accurate multipath position, and the frequency domain transmission signaling may also be solved by taking the one with the largest absolute value of the correlation value, which is not described herein again.

If the signaling subcarrier of each symbol of the PFC is formed by modulating PN by more than one ZC sequence and interleaving in the frequency domain, after the receiving end obtains the effective subcarrier in the frequency domain, corresponding frequency domain de-interleaving operation is carried out, PN demodulation operation is carried out, and then ZC sequence signaling analysis is carried out. If the modulated PN is before the frequency domain interleaving, the frequency domain de-interleaving is firstly carried out, and then the PN is demodulated. If the modulated PN is interleaved in the frequency domain, the PN is demodulated firstly and then the frequency domain de-interleaving is carried out, or the frequency domain de-interleaving is carried out firstly and then the PN is demodulated. But the demodulated PN sequence is now the original PN deinterleaved PN sequence.

< second transmission case > when the phase modulation of the pre-generated subcarrier with the frequency offset value is employed in the generation process of the frequency domain subcarrier.

The signaling analysis is carried out by utilizing any one or at least two combinations of the following three signaling analysis modes:

a first analysis signaling mode: after effective subcarriers are taken out from the frequency domain signals for channel equalization, matching/division operation is carried out on the frequency domain signals and each known sequence of a known signaling set, and frequency domain frequency offset values are directly obtained or inverse Fourier operation is carried out; and/or

The second analysis signaling mode: when the frequency domain signaling set of each time domain symbol is determined to have only one known sequence and the known sequences of the front and rear symbols are also the same, analyzing signaling only by time domain cyclic shift values solved by delay correlation between the front and rear time domain symbols; and/or

The third analysis signaling mode: and correspondingly cross-correlating the time domain receiving signal of each time domain symbol with the time domain known sequences corresponding to the known frequency domain sequences before all possible modulation frequency offsets, performing preset processing on the cross-correlation values, further performing delay correlation on the cross-correlation values of the pre-processed front and rear symbols according to the preset symbol length relation of the time domain symbols, solving a time domain cyclic shift value, and analyzing the transmission signaling based on the time domain cyclic shift value.

Specifically, in the step of decoding the signaling information carried by the preamble symbol by using the frequency domain signal, if the originating frequency domain sequence generates a signal obtained by phase modulating each effective subcarrier according to the frequency offset value S, the following 3 analysis receiving algorithms can be implemented:

analytic reception algorithm No. 1:

and taking the value of the effective subcarrier from the frequency domain signal, performing channel equalization, performing matching/division operation on each subcarrier and the subcarrier corresponding to each frequency domain known sequence of the known frequency domain signaling set, performing IFFT operation, and solving the transmitted signaling (including a frequency domain main body sequence and the signaling transmitted by a time domain cyclic shift value) based on the IFFT result.

For example, the expression of the transmitted frequency domain subcarrier before being phase-modulated is known as A_kAfter phase modulation, the expression is

After passing through the channel, the received frequency domain data is expressed as

Wherein A is_kIs a known value of the kth carrier in the known signaling set. Then, proceed to

Or E_k＝R_k·(A_k·H_k)^*Or

Wherein sigma²To estimate the noise variance, E is added_kIFFT operation is performed, and the position where the absolute value of the operation result is the largest is used for analysis signaling, that is, the frequency domain modulation frequency offset value S (time domain cyclic shift value).

For example, given that the frequency domain signaling set has only 1 known sequence, i.e. signaling is transmitted only by means of frequency domain modulation frequency offset value S (time domain cyclic shift value), the signaling of time domain cyclic shift transmission is resolved based on the result of one IFFT, where its maximum absolute value occurs.

For example, a known frequency domain signaling set has 2 known sequences, which are generated by CAZAC sequences with different root values root and are PN-modulated to transmit 1 signaling, and 8 signaling is transmitted by means of a domain modulation frequency offset value (time domain cyclic shift value), then 2 of the above-mentioned processes are respectively performed to obtain 2 IFFT results, based on the 2 IFFT results, the one with the largest absolute value is selected to resolve the 1-bit signaling transmitted by the frequency domain, and the 8-bit signaling transmitted by the time domain cyclic shift is resolved according to the position where the large peak occurs.

Analytic reception algorithm No. 2:

and solving signaling transmitted by the time domain cyclic shift value, namely a frequency domain modulation frequency offset value, based on the delay correlation between the front symbol and the rear symbol. The method can be used for the known frequency domain signaling set corresponding to each time domain main signal only has one known sequence, the known sequences corresponding to the time domain main signals of the front and rear time domain symbols are the same, and the signaling is transmitted only by depending on the frequency domain modulation frequency offset value (time domain cyclic shift value).

In particular, for example, time domain shift transmission N-bit signaling, respectively corresponding to 2^NA shift value,. then 2^NAdding the inherent delay number between 2 symbols to each shift value to obtain 2^NA delay value, receiver tries 2^NDelay correlation of delay values D, the delay correlation expression being as above

Wherein L can be selected as the length of the time domain subject A, n₀The starting point of the time domain main body A is represented after timing initial synchronization or accurate timing synchronization.

In total obtain 2^NAnd E (D), taking out the D corresponding to the maximum value, and obtaining the transmitted signaling by reverse deduction.

Analytic reception algorithm No. 3:

based on the time domain received signal, the time domain known sequences corresponding to the known frequency domain sequence set before all possible modulation frequency offsets corresponding to the time domain main signal of each time domain symbol are subjected to cross correlation, specific operation is carried out based on the cross correlation value, and the processed cross correlation value is further subjected to delay correlation of the interval length of front and back 2 symbols, such as the 2 nd analytic receiving algorithm, so as to solve the signaling transmitted by the time domain cyclic shift value.

The specific operations performed on the cross-correlation values here are, in general, extracting the large path and filtering out noise. Specifically, the larger peak portion of the cross-correlation value is retained, while the noise floor is set to 0. And then, based on the processed cross-correlation value, further performing delay correlation of front and back 2 symbols, wherein the method and the judgment are the same as those of the 2 nd analysis receiving algorithm, and are not repeated here.

To explain further, if more than one time domain known sequence is corresponding to the known frequency domain sequence set corresponding to the time domain main signal of each time domain symbol, that is, the transmitting end includes a method of generating different root values of the CAZAC sequence by using the frequency domain and/or generating cyclic shift of the same root value of the CAZAC sequence by using the frequency domain to transmit the signaling, and also transmits the signaling by using the method of performing phase modulation on each effective subcarrier by the frequency domain according to the frequency offset value, the time domain known sequences are all cross-correlated with the time domain received signal, then each time domain symbol selects the one with the largest cross-correlation value for subsequent processing, and the element in the known frequency domain sequence set corresponding to the one with the largest cross-correlation value is used to resolve the signaling transmitted by using different root values of the CAZAC sequence generated by the frequency domain and/or generating cyclic shift of the same root value of the CAZAC sequence by using the frequency domain. And simultaneously, further performing delay correlation of the interval lengths of the front and the back 2 symbols by using the subsequent cross-correlation value to solve the signaling transmitted by the method for performing phase modulation on each effective subcarrier by the frequency domain according to the frequency offset value.

Further, no matter which signaling analysis method is adopted, after the previous time domain main signal of the PFC is decoded, assuming that the decoding is correct, the previous decoding information is used as the transmission information, channel estimation is performed again in the time domain/frequency domain, and a certain specific operation is performed with the previous channel estimation result to obtain a new channel estimation result for channel estimation of signaling analysis of the next time domain main signal.

Further, after the signaling parsing is completed, that is, the frame format parameters and/or the emergency broadcast content are solved, the position of the PCC symbol or the position of the data symbol may be obtained according to the parameter content and the determined position of the PFC symbol, and the PCC symbol or the data symbol may be subsequently parsed based on the position of the PCC symbol or the data symbol.

Finally, it is specifically noted that there are various methods for determining whether there is a preamble symbol expected to be received at the receiving end, for example, the determination is made according to the operation result after correlation in the ① th initial timing synchronization, and the determination can also be made according to the reliability of the subsequent integer frequency offset estimation, accurate timing synchronization, channel estimation or decoding result.

The ① initial timing synchronization is judged by the related operation result, a fixed threshold method can be adopted, that is, if the operation result exceeds the fixed threshold, the preamble symbol part expected to be received is considered to exist, and the position where the corresponding three-segment structure time domain symbol appears can be deduced based on the position corresponding to the operation result.

Not shown in the figure, an embodiment of the present invention further provides a device for generating a preamble symbol, where the device includes: a subcarrier generation unit that generates a frequency domain subcarrier based on the frequency domain subject sequence; the frequency domain transformation unit is used for performing inverse Fourier transformation on the frequency domain subcarriers to obtain time domain main body signals; and a time domain processing unit generating a preamble symbol from at least one time domain symbol formed based on the time domain subject signal.

Wherein, the subcarrier generating unit comprises: a sequence generation module for generating a predetermined sequence generation rule of the frequency domain subject sequence; and/or a carrier processing module for processing the frequency domain subject sequence for generating predetermined processing rules for the frequency domain subcarriers.

The predetermined sequence generation rule in the sequence generation module comprises any one or two of the following combinations: generating based on different sequence generating formulas; and/or based on the same sequence generating formula, further performing cyclic shift on the generated sequence, wherein the predetermined processing rule in the carrier processing module comprises: and carrying out phase modulation on the pre-generated subcarriers obtained by processing the main body sequence based on the frequency domain according to the frequency offset value.

Not shown in the figure, an embodiment of the present invention further provides a device for generating a preamble symbol, where the device includes: a time domain generating unit which generates a time domain symbol having the following three-segment structure based on the time domain subject signal; and a preamble generating unit generating a preamble symbol based on the at least one time domain symbol.

Wherein the first three-stage structure comprises: selecting a part of generated prefixes at the tail ends of the time domain main signal and the time domain main signal, and selecting a part of generated suffixes in the prefix range based on the time domain main signal; the second three-stage structure comprises: the method comprises the steps of selecting a part of generated prefixes at the tail ends of a time domain main signal and a time domain main signal, and selecting a part of generated prefixes in a prefix range based on the time domain main signal.

The preamble symbol generated by the preamble generation unit includes: a time domain symbol having a first three-segment structure; or a time domain symbol having a second three-segment structure; or a plurality of time domain symbols with the first three-segment structure and/or a plurality of time domain symbols with the second three-segment structure which are not arranged in sequence are freely combined.

Not shown in the figure, an embodiment of the present invention further provides a receiving apparatus for a preamble symbol, where the receiving apparatus includes: the baseband processing unit is used for processing the received physical frame to obtain a baseband signal; the judging unit judges whether the pilot symbol expected to be received exists in the baseband signal; and the signaling analysis unit is used for determining the position of the received preamble symbol in the physical frame and solving the signaling information carried by the preamble symbol when the signaling information exists.

The preamble symbol generating device and the receiving device provided in this embodiment correspond to the preamble symbol generating method and the receiving method in the foregoing embodiments, respectively, so that the structure and technical elements of the device can be formed by corresponding conversion of the generating method, and are omitted for description.

Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention by using the methods and technical contents disclosed above.

Claims (9)

1. A preamble symbol receiving method, comprising the steps of:

processing the received physical frame to obtain a baseband signal;

judging whether a pilot symbol expected to be received exists in the baseband signal or not;

determining the position of the received preamble symbol in the physical frame and solving the signaling information carried by the preamble symbol when the signaling information exists,

when determining whether the preamble symbol expected to be received exists in the baseband signal, the reliability determination may be performed by using any one of the following manners or any at least two manners in a free combination manner:

an initial timing synchronization mode, an integer frequency offset estimation mode, a precise timing synchronization mode, a channel estimation mode and a decoding result analysis mode,

generating a preamble symbol based on a time domain signal, wherein the time domain symbol has the following three-segment structure: wherein the first three-stage structure comprises: the time domain main signal, a part of generated prefixes selected from the tail end of the time domain main signal and a part of generated suffixes selected from the prefix range based on the time domain main signal; the second three-stage structure comprises: the time domain main signal, a part of generated prefixes selected from the tail ends of the time domain main signal and a part of generated prefixes selected from the prefix range based on the time domain main signal, wherein the preamble symbols comprise: said time domain symbol having said first three-segment structure; or a time domain symbol having said second three-segment structure; or a plurality of time domain symbols with the first three-segment structure and/or a plurality of time domain symbols with the second three-segment structure which are not arranged in sequence are freely combined,

performing correlation operation by using the processing relationship between any two segments in the three-segment time domain structure of the time domain signal with the first three-segment structure and/or the time domain signal with the second three-segment structure to obtain an accumulated correlation value; after the accumulated correlation value is used for operation, the initial timing synchronization is carried out.

2. A method of receiving preamble symbols according to claim 1,

wherein, when the first time domain subject signal in the at least one time domain subject signal does not transmit signaling as known information, the initial timing synchronization mode includes:

and carrying out differential operation through the first time domain symbol, carrying out differential operation on a time domain sequence corresponding to the known information, carrying out cross correlation on the two to obtain cross correlation values, and carrying out initial synchronization at least based on the obtained one or more cross correlation values.

3. A method of receiving preamble symbols according to claim 1,

in the step of performing integer frequency offset estimation, any one or two combinations of the following two ways are included: .

The first integer frequency offset estimation method comprises the following steps: modulating all or part of the intercepted time domain waveforms by different frequency offsets in a frequency sweeping mode to obtain a plurality of frequency sweeping time domain signals, performing sliding correlation on a known time domain signal obtained by performing Fourier inverse transformation on a known frequency domain sequence and each frequency sweeping time domain signal, and then, taking a frequency offset value modulated by the frequency sweeping time domain signal with a maximum correlation peak value as an integral multiple frequency offset estimation value; and/or

The second integer frequency offset estimation method comprises the following steps: and circularly shifting the frequency domain subcarrier obtained by intercepting the main time domain signal according to the position result of initial timing synchronization and performing Fourier transform according to different shift values in a frequency sweep range, intercepting a receiving sequence corresponding to the effective subcarrier, performing predetermined operation on the receiving sequence and a known frequency domain sequence, performing inverse Fourier transform, and obtaining the corresponding relation between the shift value and the integer frequency offset estimation value based on the inverse Fourier transform results of a plurality of groups of shift values, thereby obtaining the integer frequency offset estimation value.

4. A method of receiving preamble symbols according to claim 1,

and after finishing the integral frequency offset estimation, when the first time domain main signal in the at least one time domain main signal does not transmit a signaling as known information, the known signal is utilized to carry out the accurate timing synchronization mode.

5. A method of receiving preamble symbols according to claim 1,

the channel estimation method, included in the step of analyzing the transmission signaling, includes:

and after the last time domain main signal is decoded, using the obtained decoding information as sending information, performing channel estimation again in the time domain/frequency domain, and performing certain specific operation with the previous channel estimation result to obtain a new channel estimation result for channel estimation of signaling analysis of the next time domain main signal.

6. A method of receiving preamble symbols according to claim 1,

when the sending end selects different starting point marks of the suffix or the super prefix from the time domain main body signal in the initial timing synchronization mode, the emergency broadcast is analyzed through free combination of any one or two of the following phases:

different delay relationships of the same content between the prefix and the suffix or prefix; and

different delay relationships of the same content between the time domain body signal and the suffix or prefix.

7. A method of receiving preamble symbols according to claim 1,

when the preamble symbols transmitted include the following two cases:

a first one of the at least one time domain body signal is not used for signaling as known information; and detecting that the time domain subject signal has the three-segment structure,

the initial timing synchronization is accomplished based on either one or a combination of the following two,

the first initial timing synchronization method: carrying out differential operation through the first time domain symbol, carrying out differential operation on a time domain sequence corresponding to the known information, carrying out cross correlation on the two to obtain a cross correlation value, and obtaining a first operation value based on one or more obtained cross correlation values to complete initial synchronization; and

the second initial timing synchronization method: utilizing the specific processing relationship and/or modulation relationship of each first three-segment structure and/or second three-segment structure to make delay sliding self-correlation to obtain one group or several groups of accumulated correlation values, then making specific mathematical operation on the basis of one group or several groups of correlation values to obtain second operation value to implement preliminary timing synchronization,

and when the initial timing synchronization mode is completed based on the two modes, performing weighted operation on the obtained first operation value and the second operation value, and completing the initial timing synchronization based on the weighted operation value.

8. A method of receiving preamble symbols according to claim 1,

in the step of parsing the signaling information,

and analyzing the signaling by utilizing a known signaling sequence set and/or all possible frequency domain modulation frequency offset values generated by all possible different root values and/or different frequency domain shift values of the frequency domain main body sequence transmitted by a transmitting end.

9. A method of receiving preamble symbols according to claim 1,

when the generated sequence is further circularly shifted by using generation based on different sequence generation formulas and/or generation based on the same sequence generation formula in the generation process of the frequency domain sub-carriers,

performing specific mathematical operation on the frequency domain signaling subcarrier, the channel estimation value and all possible frequency domain main body sequences to perform signaling analysis,

wherein the specific mathematical operation comprises any one of:

maximum likelihood correlation operation combined with channel estimation; or

And after the channel estimation value is used for carrying out channel equalization on the frequency domain signaling subcarrier, carrying out correlation operation on the frequency domain signaling subcarrier and all possible frequency domain main body sequences, and selecting the maximum correlation value as a decoding result of signaling analysis.

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