CN109617846B - Transmitter, receiver, preamble symbol generation method and reception method - Google Patents

Transmitter, receiver, preamble symbol generation method and reception method Download PDF

Info

Publication number
CN109617846B
CN109617846B CN201811344671.4A CN201811344671A CN109617846B CN 109617846 B CN109617846 B CN 109617846B CN 201811344671 A CN201811344671 A CN 201811344671A CN 109617846 B CN109617846 B CN 109617846B
Authority
CN
China
Prior art keywords
time domain
symbol
preamble symbol
signal
preamble
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201811344671.4A
Other languages
Chinese (zh)
Other versions
CN109617846A (en
Inventor
张文军
邢观斌
黄戈
徐洪亮
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Shanghai National Engineering Research Center of Digital Television Co Ltd
Original Assignee
Shanghai National Engineering Research Center of Digital Television Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Shanghai National Engineering Research Center of Digital Television Co Ltd filed Critical Shanghai National Engineering Research Center of Digital Television Co Ltd
Priority to CN201811344671.4A priority Critical patent/CN109617846B/en
Publication of CN109617846A publication Critical patent/CN109617846A/en
Application granted granted Critical
Publication of CN109617846B publication Critical patent/CN109617846B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2689—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation
    • H04L27/2692—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation with preamble design, i.e. with negotiation of the synchronisation sequence with transmitter or sequence linked to the algorithm used at the receiver
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H04L27/2605—Symbol extensions, e.g. Zero Tail, Unique Word [UW]
    • H04L27/2607—Cyclic extensions
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H04L27/261—Details of reference signals
    • H04L27/2613—Structure of the reference signals

Abstract

The invention provides a transmitter, a receiver and a method for generating a preamble symbol to receive, which is characterized in that: generating a time domain symbol with any one of the following three-segment structures based on the obtained time domain main body signal; and generating preamble symbols based on time domain symbols, wherein the first is a main body, a prefix generated based on all or part of the main body and a suffix generated based on all or part of the prefix through modulation, the second is a main body, a prefix generated based on all or part of the main body and a hyper-prefix generated based on all or part of the prefix through modulation, when the main body, the prefix generated based on all or part of the main body and the hyper-prefix generated based on all or part of the prefix through modulation, a common preamble symbol is generated based on one, and when the main body, the hyper-preamble symbol is generated based on a plurality of time slots through splicing, and the receiving method of the receiving end comprises the following steps: processing the physical frame to obtain a baseband signal; judging whether the baseband signal has an expected common or reinforced preamble symbol; and if so, determining the position of the preamble symbol in the physical frame and solving the carried signaling information.

Description

Transmitter, receiver, preamble symbol generation method and reception method
The scheme is a divisional application with application number 201410753506.X, a generation method and a receiving method of a preamble symbol and application date 2014, 12, month and 10.
Technical Field
The present invention relates to the field of wireless broadcast communication technologies, and in particular, to a method for generating a preamble symbol and a method for receiving the preamble symbol.
Background
Generally, in order for a receiving end of an OFDM system to correctly demodulate data transmitted by a transmitting end, the OFDM system must implement accurate and reliable time synchronization between the transmitting end and the receiving end. Meanwhile, since the OFDM system is very sensitive to the carrier frequency offset, the receiving end of the OFDM system needs to provide an accurate and efficient carrier frequency spectrum estimation method to accurately estimate and correct the carrier frequency offset.
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.
The DVB _ T2 standard provides a P1 symbol design based on a CAB time domain structure, and the functions are well realized. However, there are still some limitations on low complexity reception algorithms. For example, in a long multipath channel with 1024, 542, or 482 symbols, a large deviation may occur when the timing coarse synchronization is performed by using a three-segment structure such as CAB, which results in an error in estimating the carrier integer frequency offset in the frequency domain. Additionally, DBPSK differential decoding may also fail in complex frequency selective fading channels, such as long multipath. Moreover, since the DVB _ T2 has no cyclic prefix in the time domain structure, if the DVB _ T2 is combined with a frequency domain structure that needs to perform channel estimation, the performance of the frequency domain channel estimation is seriously degraded.
Disclosure of Invention
The invention solves the problems that in the current DVB _ T2 standard and other standards, a DVB _ T2 time domain structure has no cyclic prefix, so that the DVB _ T2 standard and other standards cannot be applied to coherent detection, and the detection of preamble symbols in a complex frequency selective fading channel by a low-complexity receiving algorithm has failure probability.
In order to solve the above problem, an embodiment of the present invention provides a method for generating a preamble symbol, which is characterized by including the following steps: generating a time domain symbol having any one of three-segment structures based on the obtained time domain main signal; and generating a preamble symbol based on one or two time domain symbols, wherein the first three-segment structure is as follows: the second three-segment structure includes a time domain main signal, a prefix generated based on a rear part of the time domain main signal, and a suffix generated based on a rear part of the time domain main signal by modulation: the time domain main body signal, the prefix generated based on the rear part of the time domain main body signal and the prefix generated based on the rear part of the time domain main body signal are modulated, a common preamble symbol is generated when one time domain symbol is based, and a reinforced preamble symbol is generated by splicing when two time domain symbols with different three-segment structures are based.
Optionally, the time domain main signal is a time domain OFDM symbol obtained by performing inverse discrete fourier transform on a frequency domain OFDM symbol of a predetermined length.
Optionally, the frequency domain OFDM symbol includes a virtual subcarrier, a signaling sequence subcarrier, and a fixed sequence subcarrier, and after the signaling sequence subcarrier and the fixed sequence subcarrier are arranged according to a predetermined staggered arrangement rule, the virtual subcarrier is distributed on both sides thereof, and the predetermined staggered arrangement rule includes any one of the following two rules: first predetermined staggering rule: arranged in even-odd staggered or even-odd staggered manner; and a second predetermined staggering rule: a part of the signalling sequence is placed on odd subcarriers and another part on even subcarriers, and a part of the fixed sequence is placed on odd subcarriers and another part on even subcarriers.
Optionally, the step of generating a prefix, a suffix, or a super-prefix includes the steps of: the time domain main body signal is taken as a first part, a part is taken out from the tail end of the first part according to a preset acquisition rule, the first part is processed according to a first preset processing rule and copied to the front part of the first part to generate a third part as a prefix, meanwhile, a part is taken out from the rear part of the first part according to a preset acquisition rule, the second part is processed according to a second preset processing rule and copied to the rear part of the first part or processed and copied to the front part of the prefix to generate a second part as a suffix or a super prefix respectively.
Optionally, wherein the predetermined obtaining rule includes: let LenBIs the length of the second part, LenCLength of the third part, LenB≤LenCIf N1 is the sample point number of the first portion corresponding to the start point of the selected copy to the second portion, and N2 is the sample point number of the first portion corresponding to the end point of the selected copy to the second portion, the following equations are satisfied: n2 ═ N1+ LenB-1。
Optionally, wherein the first predetermined processing rule includes: directly copying; or multiplying each sampled signal in the extracted portion by a same fixed coefficient or a predetermined different coefficient, the second predetermined processing rule comprising: performing modulation processing when the first predetermined processing rule is direct copy; or when the first predetermined processing rule multiplies each sample signal in the extracted part by a same fixed coefficient or a predetermined different coefficient, the corresponding coefficient is multiplied, and then the modulation processing is performed.
Optionally, the common preamble symbol is used for identifying the emergency broadcast through any one of the first three-segment structure and the second three-segment structure based on the same time domain main signal.
Optionally, in two different time domain symbols of the enhanced pilot symbol, two time domain main signals thereof are different, and three segments of structures adopted are also different, and the first enhanced pilot symbol and the second enhanced pilot symbol are respectively formed by different sequencing of the two time domain symbols and are used for identifying the emergency broadcast.
The embodiment of the invention also provides a method for receiving the preamble symbol, which is characterized by comprising the following steps: step S2-1: processing the received physical frame to obtain a baseband signal; step S2-2: judging whether the baseband signal has an expected received common preamble symbol or an enhanced preamble symbol; step S2-3: and if so, determining the position of the preamble symbol in the physical frame and solving the signaling information carried by the preamble symbol.
Optionally, the processing the physical frame to obtain the baseband signal includes the following steps: and when the received signal is an intermediate frequency signal, the frequency spectrum is shifted after the analog-to-digital conversion, and the baseband signal is obtained after the filtering and the down-sampling processing.
Optionally, in a case that it is known that the transmitting end is only possible to transmit the normal preamble symbol, determining whether the normal preamble symbol expected to be received exists in the baseband signal includes the following steps: step S2-21A: according to a preset acquisition rule and/or a preset processing rule between every two of a third part, a first part and a second part of the common preamble symbols expected to be received, performing corresponding reverse processing on the baseband signals, performing signal demodulation, and then performing delay sliding autocorrelation to obtain three delay correlation accumulated values; step S2-21B: performing mathematical operation based on at least one of the three delay correlation accumulated values, and performing peak detection on the mathematical operation result; and step S2-21C: and if the peak value detection result meets a preset condition, determining that the common preamble signal expected to be received exists in the baseband signal.
Alternatively, in the case that it is known that the transmitting end is only possible to transmit the enhanced preamble symbol, the determining whether the enhanced preamble symbol expected to be received exists in the baseband signal comprises the following steps: step S2-22A: according to a preset acquisition rule and/or a preset processing rule between every two of a third part, a first part and a second part of a first three-section structure and a second three-section structure in the reinforced pilot symbols expected to be received, correspondingly performing reverse processing and signal demodulation on baseband signals, and then performing delay sliding autocorrelation to obtain six delay correlation accumulated values, wherein the six values are actually acquired by 3 delay correlators, and when the fixed sequences of two symbols of the reinforced pilot symbols are the same, the delay correlation accumulated values of the third part of the two symbols before and after and the combined splicing part of the first part can be obtained; step S2-22B: adding the six delay correlation accumulated values of the step S2-22A with the same delay relation or adding after phase adjustment to obtain three delay correlation accumulated values, carrying out mathematical operation on the three delay correlation accumulated values and at least one of the delay correlation accumulated values of the third part and the first part of the front and back two symbols, and carrying out peak value detection on the mathematical operation result; step S2-22C: and if the peak detection result meets a preset condition, determining that the enhanced preamble signal expected to be received exists in the baseband signal.
Optionally, determining the position of the preamble symbol in the physical frame includes: and determining the position of the preamble symbol in the physical frame based on the result of peak detection meeting a preset condition, and if the preamble symbol expected to be received exists, determining the position of the preamble symbol in the physical frame according to the part value or the maximum value where the peak value is large or performing decimal frequency offset estimation.
Optionally, the step of solving the signaling information carried by the preamble symbol by using all or part of the time domain waveform of the preamble symbol and/or the frequency domain signal obtained by performing fourier transform on all or part of the time domain waveform of the preamble symbol comprises the step of performing operation on a signal containing a signaling sequence subcarrier and a signaling sequence subcarrier set or a time domain signal corresponding to the signaling sequence subcarrier set to solve the signaling information carried by the signaling sequence subcarrier in the preamble symbol, wherein the signaling sequence subcarrier set is generated based on a known signaling sequence set.
Optionally, the method for receiving a preamble symbol in the embodiment of the present invention is further characterized by further including the following steps: 1) intercepting a signal containing a fixed subcarrier according to the determined position of the preamble symbol in the physical frame; 2) and carrying out operation on the signal containing the fixed subcarrier and a frequency domain fixed subcarrier sequence or a time domain signal corresponding to the frequency domain fixed subcarrier sequence to obtain integral multiple frequency offset estimation or channel estimation.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
according to the method for generating the preamble symbol and the receiving method provided by the embodiment of the invention, coherent detection can be realized when a signal with a certain length is intercepted from the rear part of a time domain main body signal as a cyclic prefix or a hyper-prefix, the problem of performance reduction of incoherent detection is solved, and a modulation signal is generated based on the intercepted signal with the length of the cyclic prefix, so that the generated preamble symbol has good fractional frequency offset estimation performance and timing synchronization performance, furthermore, one or two symbols can be selected and sent as a common preamble symbol or a reinforced preamble symbol respectively according to the requirements of transmission efficiency and robustness, and when a symbol with a three-segment structure is transmitted as a preamble symbol, emergency broadcasting is identified by designing two different three-segment structures based on the same OFDM symbol main body; when transmitting two symbols with three-segment structure as preamble symbols, the two OFDM symbols have different main bodies and the three-segment structure is different, on the basis, the emergency broadcast is identified by the sequential arrangement of two three-segment structures, and by the three-segment structures with different symbols, the problem of small bias estimation failure under certain multipath channels with special length can be avoided, furthermore, the preamble symbol of the invention utilizes a structure that three sections have part of the same content, thereby ensuring that an obvious peak value can be obtained by utilizing delay correlation at a receiving end, and, in the process of generating the preamble symbol, the modulation signal of the time domain main body number is designed to avoid the receiving end from continuous wave interference or single frequency interference, or a multipath channel having the same length as the modulation signal length occurs, or a situation occurs in which a peak is erroneously detected when the guard interval length and the modulation signal length in the received signal are the same.
Drawings
Fig. 1 is a flowchart illustrating an embodiment of a preamble symbol generation method according to the present invention;
FIG. 2 is a diagram illustrating a three-segment structure in a first generic preamble symbol according to an embodiment of the present invention;
FIG. 3 is a diagram illustrating a three-segment structure in a second generic preamble symbol according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a first generic preamble symbol acquisition process according to an embodiment of the present invention;
fig. 5 is a schematic diagram of an acquisition process based on a second generic preamble symbol in an embodiment of the present invention;
FIG. 6 is a diagram illustrating a structure of two three sections in a first enhanced preamble symbol according to an embodiment of the present invention;
FIG. 7 is a diagram illustrating the structure of two three sections in a second enhanced preamble symbol according to an embodiment of the present invention;
FIG. 8 is a diagram illustrating a first enhanced preamble symbol acquisition based process according to an embodiment of the present invention;
FIG. 9 is a diagram illustrating a second enhanced preamble symbol acquisition based process in an embodiment of the present invention;
FIG. 10 is a schematic diagram of the arrangement of signaling sequence sub-carriers, fixed sequence sub-carriers, and virtual sub-carriers according to a first predetermined staggering rule in an embodiment of the present invention;
FIG. 11 is a diagram illustrating the arrangement of signaling sequence sub-carriers, fixed sequence sub-carriers, and virtual sub-carriers according to a second predetermined staggering rule in an embodiment of the present invention;
fig. 12 is a schematic diagram illustrating an arrangement of two time domain main signals in an enhanced preamble symbol shifted with a shift value of 1 in a predetermined association rule relatively as a whole in an embodiment of the present invention;
fig. 13 is a schematic diagram illustrating an arrangement of two time domain main signals in the enhanced preamble symbol shifted with a shift value of 2 in a predetermined association rule relatively as a whole in an embodiment of the present invention;
fig. 14 is a flowchart illustrating an embodiment of a preamble symbol receiving method according to the present invention;
fig. 15 is a logic diagram of peak value acquisition of the first generic preamble symbol corresponding to the three-segment structure CAB in the embodiment of the present invention;
FIG. 16 is a logic diagram illustrating the peak acquisition of the second generic preamble symbol corresponding to the BCA with three-segment structure in an embodiment of the present invention;
fig. 17 is a logic diagram illustrating peak acquisition of a first enhanced preamble symbol according to an embodiment of the present invention; and
fig. 18 is a logic diagram illustrating peak acquisition of a second enhanced preamble symbol according to an embodiment of the present invention.
Detailed Description
The inventor finds that in the current DVB _ T2 standard and other standards, the DVB _ T2 time domain structure has no cyclic prefix, and is not suitable for coherent detection, and the preamble symbol has a problem of a probability of failure in detection by a low-complexity receiving algorithm under a complex frequency selective fading channel.
In view of the above problems, the inventors have studied and provided a preamble symbol generation method and a preamble symbol reception method, which solve the problem of performance degradation of incoherent detection, have good fractional frequency offset estimation performance and timing synchronization performance, and can avoid the problem of small offset estimation failure occurring in certain multipath channels with special lengths, ensure that an obvious peak can be obtained at a receiving end by using delay correlation, and avoid the situation of the above false detection peak.
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: obtaining a time domain main signal;
step S1-2: generating a time domain symbol having any one of a first three-segment structure and a second three-segment structure based on the obtained time domain body signal; and
step S1-3: a preamble symbol is generated based on one or two time domain symbols,
wherein, the first three-stage structure is: the second three-segment structure includes a time domain main signal, a prefix generated based on a rear part of the time domain main signal, and a suffix generated based on a rear part of the time domain main signal by modulation: the apparatus includes a time domain body signal, a prefix generated based on a rear portion of the time domain body signal, and a prefix generated based on a rear portion of the time domain body signal.
When a preamble symbol is generated based on a time domain symbol, the preamble symbol is a common preamble symbol; when the preamble symbol is generated by splicing two time domain symbols based on different three-segment structures, the preamble symbol is a reinforced preamble symbol.
Fig. 2 is a schematic diagram of a three-segment structure in a first general preamble symbol according to an embodiment of the present invention. Fig. 3 is a schematic diagram of a three-segment structure in a second generic preamble symbol according to an embodiment of the present invention.
A time domain main signal (denoted by a in the figure) is used as a first part, a part is taken out from the tail end of the first part according to a preset acquisition rule, the first part is processed according to a first preset processing rule and copied to the front part of the first part to generate a third part (denoted by C in the figure) as a prefix, meanwhile, a part is taken out from the rear part of the first part according to a preset acquisition rule, the second part is processed according to a second preset processing rule and copied to the rear part of the first part or processed and copied to the front part of the prefix to generate a second part (denoted by B in the figure) as a suffix or a super prefix respectively, and thus, a first common preamble symbol (CAB structure) with B as a suffix as shown in fig. 2 and a second common preamble symbol (BCA structure) with B as a super prefix are respectively generated, as shown in fig. 3.
In this embodiment, when the first generic preamble symbol is transmitted, it indicates that the system is transmitting a generic broadcast service; when the second generic preamble symbol is transmitted, it indicates that the system is transmitting emergency broadcast service. The invention may also indicate that the system is transmitting emergency broadcast service when transmitting the first type of normal preamble symbol, and indicate that the system is transmitting general broadcast service when transmitting the second type of normal preamble symbol. The common preamble symbol is used for identifying the emergency broadcast through any one of a first three-segment structure (CAB structure) and a second three-segment structure (BCA structure) based on the same time domain main signal.
For a specific rule of processing after acquiring the third part and the second part from the first part, the first predetermined processing rule includes: directly copying; or multiplying each sampled signal in the extracted portion by a same fixed coefficient or a predetermined different coefficient. The second predetermined processing rule includes: performing modulation processing when the first predetermined processing rule is direct copy; or when the first predetermined processing rule multiplies each sampled signal in the fetched portion by a same fixed coefficient or a predetermined different coefficient. That is, when the third portion is directly copied as a prefix, the second portion is modulated and then used as a suffix or a superprecision, and when the third portion is multiplied by a corresponding coefficient, the second portion is also multiplied by the coefficient and modulated and then used as a suffix or a superprecision.
Fig. 4 is a schematic diagram of a first generic preamble symbol acquisition process according to an embodiment of the present invention.
In this embodiment, the segment C is a direct copy of the segment a, and the segment B is a modulated signal segment of the segment a, as shown in fig. 4, for example, the length of a is 1024, the length of C is truncated to 520, and the length of B is 504, where each sample of the signal may be multiplied by a fixed coefficient or each sample may be multiplied by a different coefficient when C and B are subjected to certain processing.
The data range of B does not exceed the data range of C, i.e., the portion a selected for the modulated signal segment B does not extend beyond the portion a truncated as the prefix C. Preferably, the sum of the length of B and the length of C is the length of a.
Let NALet Len be the length of ACIs the length of C, LenBIs the length of the modulation signal segment B. Let the sampling point number of A be 0,1, … NALet 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+LenB-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
Figure BDA0001863457090000111
Wherein, the modulation frequency deviation value fSHCan be selected as the frequency domain subcarrier interval corresponding to the time domain OFDM symbol, namely 1/NAT，Where T is the sampling period, NAIs the length of the time domain OFDM symbol, in this example, NAIs 1024, take fSH1/1024T. And the modulation frequency offset can be arbitrarily selected to be an initial phase, in order to make the correlation peak sharp, fSHCan also be selected to be 1/(Len)BT)。
As shown in FIG. 4, NA＝1024；LenC＝520，LenB504, 520 for N1. When the CA segment contains the same content, the autocorrelation delay is NAThe CB section contains the same content and has an autocorrelation delay of NA+LenBAnd the segment AB contains the same content with autocorrelation delay LenB。
Fig. 5 is a schematic diagram of an acquisition process based on a second generic preamble symbol in an embodiment of the present invention.
Similarly, the time domain expression of the second generic preamble symbol is that, in order to make the receiving end processing methods as consistent as possible, the modulation frequency offset value is exactly opposite to the C-a-B structure in the B-C-a structure, and the modulation may be arbitrarily selected as the initial phase.
Figure BDA0001863457090000121
As shown in FIG. 5, NA＝1024；LenC＝520，LenB504, N1, 504, when the CA segment contains the same content with an autocorrelation delay of NAThe BC segment contains the same content with an autocorrelation delay of LenBAnd the BA segment contains the same content with an autocorrelation delay of NA+LenB。
FIG. 6 is a diagram illustrating the structure of two three sections in the first enhanced preamble symbol according to the embodiment. FIG. 7 is a diagram showing the structure of two three sections in the second enhanced preamble symbol according to the embodiment.
As shown in fig. 6 and 7, two different time domain symbols of the enhanced preamble symbol have different time domain main body signals and different three-segment structures, and the first enhanced preamble symbol shown in fig. 6 and the second enhanced preamble symbol shown in fig. 7 are formed by different sequencing of the two time domain symbols, respectively, and are used for identifying emergency broadcasting.
On the basis of the existing two common leading symbols, 2 symbols can be connected to form two reinforced leading symbols. When the type 1 enhanced preamble symbol is transmitted, it indicates that the system is transmitting a general broadcast service; when the second enhanced preamble symbol is transmitted, it indicates that the system is transmitting emergency broadcast services. It is also possible that the first enhanced preamble symbol indicates that the system is transmitting the emergency broadcast service, and the second enhanced preamble symbol indicates that the system is transmitting the general broadcast service.
The enhanced preamble symbol is composed of two general symbols, and the main parts (i.e., a) of the two general symbols may be different, so that the enhanced preamble symbol can transmit twice or nearly twice as much signaling as the general preamble symbol.
In order to add autocorrelation values of 2 symbols and obtain more robust performance when using enhanced preamble symbols, the parameter N1 of each 2 symbols (i.e., N1 is the sampling point number of a corresponding to the start point selected to be copied to the modulation signal segment B) needs to satisfy a certain relationship, where N1 of the first symbol is N1_1, N1 of the second symbol is N1_2, and N1_1+ N1_2 needs to satisfy N1_1+ N1_2A. And if the modulation applied to the B segment is a modulation frequency offset, the frequency offset value is the opposite.
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, assuming that P1_ A (t) is the time domain expression of A1 and P2_ A (t) is the time domain expression of A2, the time domain expression of the first three-segment structure is
Figure BDA0001863457090000131
The time domain expression of the second three-segment structure is
Figure BDA0001863457090000132
Then, the time domain expression of the first enhanced preamble symbol is, here, 2N since the sum of the length of B and the length of C is the length of AAI.e., the sum of the lengths of B, C, A.
Figure BDA0001863457090000141
Then, the time domain expression of the second enhanced preamble symbol is
Figure BDA0001863457090000142
Fig. 8 is a schematic diagram of a first enhanced preamble symbol acquisition process according to an embodiment of the present invention.
As shown in FIG. 8, a preferred embodiment is that the C, A and B segments of 2 general symbols are the same in length, and N isA＝1024；Ncp＝520，LenB504, only N1 differs, N1_1 is 520, and N1_2 is 504. As shown in the following figures, the first enhanced preamble symbol and the second enhanced preamble symbol are provided separately.
Take fSHWhen 1/1024T, the time domain expression for the first three-segment structure is as follows
Figure BDA0001863457090000143
Fig. 9 is a schematic diagram of a second enhanced preamble symbol acquisition process according to an embodiment of the present invention.
As shown in FIG. 9, the time domain expression of the second three-segment structure is
Figure BDA0001863457090000144
In step S1-1, the time domain main signal a is obtained by performing inverse fourier transform on the frequency domain OFDM symbol to obtain a time domain OFDM symbol, as a source of the time domain main signal.
Let P1_ X be the corresponding frequency domain OFDM symbol, P1_ XiObtaining a time domain OFDM symbol after performing inverse discrete Fourier transform:
Figure BDA0001863457090000151
where M is the power sum of the active non-zero subcarriers.
The P1_ X frequency domain structure, i.e., frequency domain OFDM symbol, includes three parts, a virtual subcarrier, a signaling sequence (referred to as SC) subcarrier, and a fixed sequence (referred to as FC) subcarrier, respectively.
After the signaling sequence subcarriers and the fixed sequence subcarriers are arranged according to a preset staggered arrangement rule, distributing the virtual subcarriers on two sides of the signaling sequence subcarriers, wherein the preset staggered arrangement rule comprises any one of the following two rules:
first predetermined staggering rule: arranged in even-odd staggered or even-odd staggered manner; and
second predetermined staggering rule: a part of the signalling sequence is placed on odd subcarriers and another part on even subcarriers, and a part of the fixed sequence is placed on odd subcarriers and another part on even subcarriers.
The first preset staggered arrangement rule is that SC and FC are staggered in odd-even mode or staggered in even-odd mode, so that FC is used as a pilot frequency rule to be arranged, the second preset staggered arrangement rule is convenient to realize channel estimation, a part of SC sequences need to be placed on odd subcarriers, and the rest SC sequences need to be placed on even subcarriers; meanwhile, partial FC sequences are required to be placed on odd subcarriers, and the rest FC sequences are required to be placed on even subcarriers, so that the condition that FC or SC are placed on odd or even subcarriers and are faded completely under some special multipath is avoided, and the emission improves the complexity of neglecting channel estimation, so that the method is a better choice.
Let L be the length of the fixed sequence (i.e. L be the number of active subcarriers carrying the fixed sequence), and P be the length of the signaling sequence (i.e. P be the number of active subcarriers carrying the signaling sequence). It should be noted that, when the lengths of the fixed sequence and the signaling sequence are not consistent (for example, P > L), the fixed sequence and the signaling sequence may be staggered according to the above rule by way of zero padding sequence subcarriers.
Fig. 10 is a schematic diagram illustrating an arrangement of signaling sequence subcarriers, fixed sequence subcarriers, and virtual subcarriers according to a first predetermined staggering rule in an embodiment of the present invention.
As shown in fig. 10, in the present preferred embodiment, the present step includes: and filling certain zero sequence subcarriers on two sides of the effective subcarrier respectively to form frequency domain OFDM symbols with preset length.
Following the example of a predetermined length of 1024, the length G of the zero-sequence subcarrier is 1024-L-P, and (1024-L-P)/2 zero-sequence subcarriers are padded on both sides. For example, if L is P353, G is 318, and each side is padded with 159 zero-sequence subcarriers.
The frequency domain OFDM symbols generated according to the first predetermined staggering rule include the steps of:
the (11) fixed sequence generating step: the fixed sequence consists of 353 complex numbers, the modulus of which is constant, and the nth value of the fixed sequence subcarrier is expressed as:
Figure BDA0001863457090000161
wherein R is the power ratio of FC to SC, SCiModulus constant is 1
Figure BDA0001863457090000171
The fixed sequence subcarrier camber value omeganDetermined by a first predetermined fixed subcarrier radian value table of table 1 below;
TABLE 1 fixed subcarrier radian measurement table (optimized according to a first predetermined staggering rule)
Figure BDA0001863457090000172
Figure BDA0001863457090000181
A (12) signaling sequence generating step of: generating 512 signaling sequences in total, i.e. Seq0，Seq1，…Seq511Each signalling sequence Seq0～Seq511Taking the inverse numbers, i.e. -Seq0～-Seq511The receiving end uses the positive and negative of the correlation value to distinguish the positive sequence or the reverse sequence, i.e. 10bit signaling information is transmitted, 512 signaling sequences can be further divided into 4 groups, each group has 128 signaling sequences, and the sub-steps of generating each group of 128 signaling sequences are as follows:
the first substep: generating a reference sequence zci(N) which is a length N Zadoff-Chu sequence zc (N):
Figure BDA0001863457090000182
substep 2-by copying twice zci(N) generating of length 2N
Figure BDA0001863457090000183
Figure BDA0001863457090000184
3 rd substep from
Figure BDA0001863457090000185
At a particular starting position kiTruncating the length 353 sequence to generate SCi(n)：
SCi(n)＝zci *(ki-1+n),n＝0～352
Each set of signalling sequences Seq0～Seq127N value of (u)iAnd the shift value kiAre respectively formed byTable 2 through table 5 below correspond to the predetermined signaling sequence parameter table determination.
First set of sequences Seq0～Seq127N value of (u)iAnd the shift value kiAs shown in table 2 below.
Table 2: first set of signaling sequence parameters
Figure BDA0001863457090000186
Figure BDA0001863457090000191
Second set of sequences Seq128～Seq255Is the same as the first set of sequences, and has the value of N, uiAnd the shift value kiAs shown in table 3 below.
Table 3: second set of signaling sequence parameters
Figure BDA0001863457090000192
Third group sequence Seq256～Seq383Is the same as the first set of sequences, and has the value of N, uiAnd the shift value kiAs shown in table 4 below.
Table 4: third set of signaling sequence parameters
Figure BDA0001863457090000193
Figure BDA0001863457090000201
Fourth group sequence Seq384～Seq511Is the same as the first set of sequences, and has the value of N, uiAnd the shift value kiTable 5 below shows.
Table 5: fourth set of signaling sequence parameters
Figure BDA0001863457090000202
A (13) permutation and padding step of forming the frequency domain OFDM symbol according to the following formula after padding the virtual subcarriers by arranging the fixed sequences and the signaling sequences obtained in the (11) and (12) in a parity interleaving manner,
Figure BDA0001863457090000203
fig. 11 is a schematic diagram illustrating an arrangement of signaling sequence subcarriers, fixed sequence subcarriers, and virtual subcarriers according to a second predetermined staggering rule in an embodiment of the present invention.
As shown in fig. 11, the first half of the signaling sequence on the left side of the dotted line in the figure is placed on the odd subcarriers, the other half of the signaling sequence on the right side of the dotted line in the figure is placed on the even subcarriers, the first half of the fixed sequence on the left side of the dotted line is placed on the even subcarriers, and the rear half of the fixed sequence on the right side of the dotted line is placed on the odd subcarriers. Namely P1_ X0,P1_X1,L,P1_X1023And generating according to a second preset staggered arrangement rule, placing odd carriers and FC even carriers in the first half section of SC, placing even carriers in the second half section of SC, placing odd carriers in the FC, and exchanging the odd and even positions of the signaling sequence and the fixed sequence in the first half section and the second half section. Such a fixed sequence of sub-carriers
Figure BDA0001863457090000212
Sub-carriers of a signalling sequence
Figure BDA0001863457090000213
The positions of the parity can be interchanged without any influence on the transmission performance.
When filling the virtual carrier, the lengths of the zero sequence subcarriers filled on the left and right sides may be different, but the difference is not too large.
The following continues with a specific embodiment of the frequency domain symbols generated by the optimization according to the second predetermined staggering rule. The frequency domain OFDM symbols generated according to the second predetermined staggered arrangement rule include the steps of:
a (21) fixed sequence generation step of generating only the fixed sequence subcarrier radian value ω, which is the same as the step of generating the (11) fixed sequencenThe value of (a) is determined by a second predetermined fixed subcarrier radian value table; wherein the second predetermined fixed subcarrier radian measure table is represented by the following table 6:
TABLE 6 fixed subcarrier radian measurement table (optimized according to a second predetermined staggering rule)
Figure BDA0001863457090000211
Figure BDA0001863457090000221
A (22) th signaling sequence generation step that is the same as the (12) th signaling sequence generation step,
a (23) permutation and filling step, after the signaling sequence and the fixed sequence obtained in the (21) step and the (22) step are arranged according to even, even and odd interleaving and zero carriers are filled at the left and the right sides, a frequency domain OFDM symbol is formed according to the following formula,
Figure BDA0001863457090000231
for the enhanced preamble symbol, the structure of the time domain OFDM symbols of the two time domain main signals may further satisfy at least one of the following three predetermined association rules, in addition to the frequency domain OFDM symbol generation step described above:
first predetermined association rule: the respective signaling sequence sets of the two time domain OFDM symbols assume the same. For example, 10 bits are transmitted in a single symbol as described above, so that the total transmission capacity is 20 bits.
Second predetermined association rule: the fixed sequence of the second time domain OFDM symbol remains the same as the fixed sequence of the first time domain OFDM symbol.
A third predetermined association rule: the effective subcarrier position of the second time domain OFDM symbol containing the fixed sequence and the signaling sequence is a left shift or a right shift of the whole of the effective subcarrier position in the first time domain OFDM symbol, and the shift value is usually controlled in the range of 0-5.
Fig. 12 and 13 are schematic diagrams of relative global shifting of two time domain subject signals having shift values 1 and 2 by a predetermined association rule.
The preferred embodiment of the generation of the frequency domain symbols of a1 and a2 in the enhanced preamble symbols is as follows:
the body of the first symbol a1 is identical to the frequency domain symbol of the normal preamble symbol generated according to the second predetermined interleaving rule described above, and the FC and SC sequences, the frequency domain placement position, and the zero padding carriers are identical.
The body of the second symbol a2 is the same as the FC and SC sequences of the normal preamble symbol generated according to the second predetermined interleaving rule described above, and the effective subcarrier position of a2 is shifted left by one bit for a1 as a whole. Namely, it is
Figure BDA0001863457090000241
Fig. 14 is a flowchart illustrating a specific embodiment of a preamble symbol receiving method according to the present invention.
As shown in fig. 14, the preamble symbol receiving method in this embodiment includes the following steps:
step S2-1: processing the received physical frame to obtain a baseband signal;
step S2-2: judging whether the common pilot symbols or the reinforced pilot symbols expected to be received exist in the baseband signals;
step S2-3: and if the judgment result is yes, determining the position of the preamble symbol in the physical frame and solving the signaling information carried by the preamble symbol.
Specifically, as described in step S2-1, the received physical frame is processed to obtain a baseband signal. Generally, a signal received by a receiving end is a zero intermediate frequency signal, and therefore, it is necessary to perform analog-to-digital conversion on the signal to obtain a digital signal, and then perform processing such as filtering and down-sampling to obtain a baseband signal. If the receiving end receives the intermediate frequency signal, the receiving end needs to perform spectrum shifting after performing analog-to-digital conversion on the intermediate frequency signal, and then performs processing such as filtering and down-sampling to obtain a baseband signal.
As described in step S2-2, the method for determining whether the normal preamble symbol or the enhanced preamble symbol expected to be received exists in the baseband signal includes the following specific cases.
In this embodiment, if it is known that the transmitting end is only able to transmit the normal preamble symbol but is not able to transmit the enhanced preamble symbol, the determining whether there is the normal preamble symbol expected to be received in the baseband signal includes the following steps:
step S2-21A: according to the processing relation and/or modulation relation between the section C, the section A and the section B in the expected received common preamble symbol, the baseband signal is subjected to necessary reverse processing and signal demodulation and then is subjected to delay sliding autocorrelation so as to obtain three delay correlation accumulated values;
step S2-21B: performing mathematical operation based on one, two or three of the three delay correlation accumulated values, and performing peak value detection on the mathematical operation result;
step S2-21C: and if the peak detection result meets a preset condition, determining that the common preamble signal expected to be received exists in the baseband signal.
Further, the steps S2-21A may obtain 2 groups of accumulated delay correlation values according to a predetermined obtaining rule and/or a predetermined processing rule between two of the sections C, a, and B of the first generic preamble symbol and the second generic preamble symbol, where each group has 3 values, and the steps S2-21B include performing a mathematical operation on one, two, or three of the three accumulated delay correlation values in each of the 2 groups, and performing peak detection on a result of the mathematical operation. If the first group of peak value detection meets a preset condition, determining that a first type of common preamble signal expected to be received exists in the baseband signal; if the second group of peak value detection meets the preset condition, determining that a second common preamble signal expected to be received exists in the baseband signal; if both groups are satisfied, a separate determination is required, for example, the determination may be made based on the dominance of the peak-to-noise ratios of the two groups.
On this basis, if it is known that the transmitting end is only possible to transmit the enhanced preamble symbol but is not possible to transmit the normal preamble symbol, the determining whether the enhanced preamble symbol expected to be received exists in the baseband signal comprises the following steps:
step S2-22A: according to a preset acquisition rule and/or a preset processing rule between each two of a C section, an A section and a B section of a C-A-B structure and a B-C-A structure in an expected received common preamble symbol, performing necessary corresponding reverse processing and signal demodulation on a baseband signal, and then performing delay sliding autocorrelation to obtain six delay correlation accumulated values which can be actually completed by only 3 delay autocorrelators; in addition, when the FC sequences of 2 symbols for reinforcing the leading symbols are the same, delay correlation accumulated values of the combined splicing part of the C + A sections of the front and rear 2 symbols can be obtained;
step S2-22B: adding the six delay correlation accumulated values of the step S2-22A with the same delay relation or adding after phase adjustment; obtaining three related accumulated values with different delays, carrying out mathematical operation on one, two, three or four of the three related accumulated values and the related accumulated values of the delay of the combined splicing part of the C section and the A section of the front and the back 2 symbols, and carrying out peak value detection on the mathematical operation result;
step S2-22C: and if the peak detection result meets a preset condition, determining that the enhanced preamble signal expected to be received exists in the baseband signal.
Further, step S2-22A may obtain 2 groups of delay correlation accumulation values, each group having 6 values, according to different delay relationships within and between symbols of the first enhanced pilot symbol and the second enhanced pilot symbol, and when the FC sequences of 2 symbols of the enhanced pilot symbol are the same, obtain C + a delay correlation accumulation values of 2 symbols before and after the 2 groups; and step S2-22B includes adding the same delay to the 6 delay-related accumulated values of each of the 2 groups; obtaining 2 groups of related accumulated values each containing 3 different delays; and performing mathematical operation on one, two, three or four of the three delay correlation accumulated values of each group in the 2 groups and the delay correlation accumulated values of the combined splicing part of the C sections and the A sections of the front and the back 2 symbols, and performing peak value detection on the mathematical operation result. If the first group of peak value detections meets a preset condition, determining that a first enhanced preamble signal expected to be received exists in the baseband signal; if the second group of peak value detection meets the preset condition, determining that a second enhanced preamble signal expected to be received exists in the baseband signal; if both groups are satisfied, a separate determination is required, for example, the determination may be made based on the dominance of the peak-to-noise ratios of the two groups.
If the transmitting end may send the enhanced preamble symbol, or may send the normal preamble symbol, the enhanced preamble symbol detection of S2-22 is also performed even if the normal preamble symbol detection of S2-21 is performed, which is not repeated herein, because the enhanced preamble symbol necessarily includes the structure of the normal preamble symbol, when both satisfy the preset condition, if the peak value of the enhanced preamble symbol is better than the peak value of the normal preamble symbol by a certain threshold, it is determined as the enhanced preamble symbol, otherwise, it is determined as the normal preamble symbol.
For the aforementioned embodiment, the peak value obtaining block diagram of the normal preamble symbol can be shown in fig. 15 and fig. 16. Fig. 15 is a logic diagram of peak value acquisition of the first generic preamble symbol corresponding to the three-segment structure CAB in the embodiment of the present invention. Fig. 16 is a logic diagram of peak acquisition of the second generic preamble symbol corresponding to the three-segment structure BCA in the embodiment of the present invention.
The same parts in fig. 15 and 16 require only one set of receiving resources, which are separated for clarity. Wherein C, a, B in the figure represent the length of the C-segment, a-segment and B-segment signals, respectively, and the moving average filter may be a power normalization filter. In this figure, C + B ═ a is satisfied.
The peak acquisition block diagram of the enhanced pilot symbols can be seen in fig. 17 and 18. Fig. 17 is a logic diagram illustrating peak acquisition of a first enhanced preamble symbol according to an embodiment of the present invention. Fig. 18 is a logic diagram illustrating peak acquisition of a second enhanced preamble symbol according to an embodiment of the present invention.
Specifically, as described in step S2-3, when the determination result is yes, the following steps are included to determine the position of the preamble symbol in the physical frame and solve the signaling information carried by the preamble symbol.
Determining the position of the preamble symbol in the physical frame comprises: the position of the preamble symbol in the physical frame is determined based on the result of peak detection satisfying a preset condition.
If the preamble symbol expected to be received exists, the position of the preamble symbol in the physical frame is determined according to the part of the value with the large peak value or the maximum value. Fractional frequency offset estimation can also be performed by using the result of peak detection.
The decoding of the signaling information carried by the preamble symbol in the step S2-3 includes the following steps: 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.
And performing operation on the signal containing the signaling sequence subcarrier and the signaling sequence subcarrier set or a time domain signal corresponding to the signaling sequence subcarrier set to solve the signaling information carried by the signaling sequence subcarrier in the preamble symbol. Wherein the set of signaling sequence subcarriers is generated based on a known set of signaling sequences.
The signal containing the signaling sequence subcarrier comprises the following components: all or part of the time domain waveform of the received preamble symbol, or 1 or 2 frequency domain OFDM symbols obtained by cutting 1 or 2 main OFDM symbols from the preamble symbol and performing Fourier transform. The signaling sequence subcarrier set is a set formed by filling each signaling sequence in the signaling sequence set onto an effective subcarrier.
In particular, the sectionTaking 1 or 2N corresponding to ODFM symbol main bodyACarrying out Fourier transformation on the time domain signals with the length to obtain 1 or 2 frequency domain OFDM symbols; then, removing zero carrier, and taking out 1 or 2 frequency domain signaling sub-carriers according to the signaling sub-carrier position. And performing specific mathematical operation on the channel estimation value and the known signaling sequence subcarrier set to complete the frequency domain decoding function.
For example, let i equal to 0: M-1, M be the number of signaling subcarriers, and j equal to 0:2P-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 2PEach element corresponding to a sequence of length M, HiFor each channel estimation value corresponding to a signaling subcarrier, SC _ reciFor the received frequency domain signaling subcarrier values,
Figure BDA0001863457090000291
and taking the ith value of the jth element in the signaling sequence subcarrier set. Then
Figure BDA0001863457090000292
Take max (corr)j) And corresponding j, obtaining the signaling information transmitted by the frequency domain.
In other embodiments, the above process may also be performed in the time domain, a time domain signaling waveform set corresponding to a frequency domain symbol of a corresponding length generated by zero padding at a proper position by using a known signaling sequence subcarrier set is subjected to inverse fourier transform is directly subjected to synchronous correlation with a time domain received signal at an accurate multipath position, and the signal information transmitted in the frequency domain may also be solved by taking the one with the largest absolute value of the correlation value, which is not described herein again.
Further, the receiving end may also use the fixed sequence to perform integer frequency offset estimation or channel estimation, that is, the preamble symbol receiving method of the present invention may further include the following steps:
1) intercepting a signal containing a fixed subcarrier according to the determined position of the preamble symbol in the physical frame;
2) and carrying out operation on the signal containing the fixed subcarrier and a frequency domain fixed subcarrier sequence or a time domain signal corresponding to the frequency domain fixed subcarrier sequence to obtain integral multiple frequency offset estimation or channel estimation.
Specifically, the present embodiment includes the following steps: 1) intercepting a signal containing a fixed subcarrier according to the determined position of the preamble symbol in the physical frame; 2) and carrying out operation on the signal containing the fixed subcarrier and a frequency domain fixed subcarrier sequence or a time domain signal corresponding to the frequency domain fixed subcarrier sequence to obtain integral multiple frequency offset estimation or channel estimation.
Wherein the signal containing the fixed subcarriers comprises: all or part of the time domain waveform of the received preamble symbol, or a frequency domain OFDM symbol obtained by intercepting the time domain OFDM symbol from the preamble symbol and performing Fourier transform.
Two methods for performing integer frequency offset estimation at the receiving end are described in detail below.
The method comprises the following steps:
and intercepting all or part of the time domain waveform of the received preamble symbol according to the position of the detected preamble symbol in the physical frame. A frequency sweeping manner is adopted, that is, the partial time domain waveform is modulated with different frequency offsets by a fixed frequency change step diameter (for example, corresponding to an integral multiple frequency offset interval), so that a plurality of time domain signals are obtained:
Figure BDA0001863457090000301
t is the sampling period, fsIs the sampling frequency. The time domain signal corresponding to the inverse fourier transform of the known frequency domain fixed sequence subcarrier is a2, a2 is used as a known signal, and a1 is assigned to each of the known signalsyPerforming sliding correlation, and selecting the A1 with the largest correlation peakyThen 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 length of the preamble symbol main body is 1K, and the sweep frequency range is
Figure BDA0001863457090000302
I.e., -57,57]。
The correlation used in the frequency sweep can be equivalently realized by FFT and IFFT, and the description is omitted here.
The method 2 comprises the following steps:
and intercepting a time domain signal corresponding to the ODFM symbol main body in the preamble symbol, performing Fourier transform to obtain a frequency domain OFDM symbol, performing cyclic shift of the sweep frequency range on the frequency domain OFDM symbol obtained by transform, performing point-separation differential multiplication according to the position of FC on a subcarrier and the interval of front and back 2 fixed sequence subcarriers, performing correlation operation on the result and a point-separation differential multiplication value of a known fixed sequence subcarrier to obtain a series of correlation values, and selecting the cyclic shift corresponding to the maximum correlation value to correspondingly obtain an integer frequency offset estimation value.
Further, when it is determined that there is an enhanced pilot symbol expected to be received in the baseband signal, if the shift value of the position of the effective subcarrier of the enhanced pilot symbol is an even number, 2 frequency domain OFDM symbols obtained by performing fourier transform on 2 time domain signals corresponding to the OFDM symbol main body may be subjected to the same cyclic shift in the frequency sweep range at the same time for the 2 frequency domain OFDM symbols obtained by the transform, each shifted symbol reception value is subjected to conjugate multiplication with the known fixed sequence subcarrier value of the symbol, and after the product values of the same subcarrier position of the 2 symbols are subjected to conjugate multiplication again, the conjugate multiplication values of all effective FC subcarriers at the common position of the 2 symbols are accumulated, that is, the present invention provides a method for accumulating the conjugate multiplication values of all effective FC subcarriers at the common position of the 2 symbols, and a method for accumulating the conjugate multiplication values of the known fixed sequence subcarrier values of the symbol
Figure BDA0001863457090000311
j is an element of the sweep range, Ri,1,jFor the received value, R, at the FC position after shifting j in the frequency domain of the first symboli,2,jCorresponding to the received value at the FC position shifted by j in the frequency domain of the second symbol,
Figure BDA0001863457090000312
and
Figure BDA0001863457090000313
the known values of FC on a certain sub-carrier of the first symbol and the second symbol respectively, M is the total number of known FC, thus obtaining a series of correspondencesAnd selecting the cyclic shift corresponding to the maximum accumulated value from the accumulated values of all cyclic shift values to correspondingly obtain an integral multiple frequency offset estimation value.
The received signal containing the fixed sequence subcarrier and the known frequency domain fixed sequence subcarrier and/or the time domain signal corresponding to the inverse fourier transform are used to complete channel estimation, and may be performed in the time domain and/or in the frequency domain, which is not described herein again.

Claims (17)

1. A method for generating a preamble symbol, comprising:
generating a time domain symbol having any one of the following two and/or two three-segment structures based on the time domain body signal for generating a preamble symbol,
wherein, the first three-segment structure is: the time domain subject signal, a prefix generated based on a rear portion of the time domain subject signal, and a suffix modulated and generated based on the rear portion of the time domain subject signal,
the second three-stage structure is: the time domain body signal, a prefix generated based on a rear part of the time domain body signal, and a prefix generated based on a rear part of the time domain body signal;
the generated enhanced preamble symbol has a time domain symbol with a first three-segment structure and a time domain symbol with a second three-segment structure;
in the first three-segment structure, the length of the suffix is smaller than that of the prefix;
in a second of the three-segment structures, the length of the super-prefix is smaller than the length of the prefix.
2. A method for generating preamble symbols according to claim 1, wherein:
the time domain main signal is a time domain OFDM symbol obtained by performing inverse discrete Fourier transform on a frequency domain OFDM symbol with a predetermined length.
3. A method for generating preamble symbols according to claim 1, wherein:
the step of generating the prefix, the suffix, or the super-prefix includes:
taking the time domain main signal as a first part, taking a part from the tail end of the first part according to a preset acquisition rule, processing according to a first preset processing rule and copying the part to the front part of the first part to generate a third part as the prefix,
and taking a part from the rear part of the first part according to a preset acquisition rule, processing and copying the part to the rear part of the first part according to a second preset processing rule or processing and copying the part to the front part of the prefix to generate a second part so as to be used as the suffix or the hyper prefix respectively.
4. A preamble symbol generation method as claimed in claim 3,
wherein the predetermined acquisition rule comprises:
let LenBLength of said second portion, LenCLength of said third portion, LenB<LenCIf N1 is the number of sampling points selected to be copied to the first portion corresponding to the start point of the second portion, and N2 is the number of sampling points selected to be copied to the first portion corresponding to the end point of the second portion, the following equations are satisfied: n2 ═ N1+ LenB-1。
5. A preamble symbol generation method according to claim 3, characterized in that:
wherein the first predetermined processing rule includes: the copy is made directly on the recording medium,
the second predetermined processing rule includes: and performing modulation processing when the first predetermined processing rule is direct copy.
6. A preamble symbol generation method as claimed in claim 3,
the third part is obtained based on direct copying of the first part, the second part is obtained based on modulation frequency offset of the first part,
with the following setting P1_ a (t) being the time domain expression of the first part, the time domain expression of the first three-segment structure satisfies the following relationship:
Figure FDA0003273936570000021
wherein, the modulation frequency deviation value fSHCan be selected as the frequency domain subcarrier interval corresponding to the time domain OFDM symbol, namely 1/NAT, and the modulation initial phase is arbitrarily selected, T is the sampling period, NAFor the length of the time domain OFDM symbol, LenBLength of said second portion, LenCFor the length of the third portion, N1 is the sample point number of the first portion selected to be copied to the beginning of the second portion.
7. A preamble symbol generation method as claimed in claim 3,
with the following setting P1_ a (t) being the time domain expression of the first part, the time domain expression of the second three-segment structure satisfies the following relationship:
Figure FDA0003273936570000031
wherein the modulation frequency offset value in the second three-segment structure is opposite to the modulation frequency offset value in the first three-segment structure and is-fSHAnd the modulation can select the initial phase arbitrarily.
8. A preamble symbol generation method as claimed in claim 1,
with reference to the symbol with the first three-segment structure represented by reference numeral 1 and the symbol with the second three-segment structure represented by reference numeral 2, let P1_ a (t) be the time domain expression of the time domain main signal in the first three-segment structure, and P2_ a (t) be the time domain expression of the time domain main signal in the second three-segment structure,
wherein f isSHCan be selected as the frequency domain subcarrier interval corresponding to the time domain OFDM symbol, namely 1/NAT, T is sampling period, NAFor the length of the time domain OFDM symbol, LenBIs the length of the second part, LenCN1_1 and N1_2 are sample point numbers selected to be copied to the first part corresponding to the start of the second part,
then, the time domain expression of the symbol of the first three-segment structure is:
Figure FDA0003273936570000032
then, the time domain expression of the symbol of the second three-segment structure is:
Figure FDA0003273936570000041
9. a preamble symbol receiving method, comprising the steps of:
step S2-1: processing the received physical frame to obtain a baseband signal;
step S2-2: determining whether the preamble symbol of claim 1 expected to be received is present in the baseband signal;
step S2-3: and if so, determining the position of the preamble symbol in the physical frame and solving the signaling information carried by the preamble symbol.
10. A method of receiving preamble symbols according to claim 9,
the processing the physical frame to obtain a baseband signal comprises the following steps:
when the received signal is a zero intermediate frequency signal, after analog-to-digital conversion, filtering and down-sampling processing are carried out to obtain the baseband signal,
and when the received signal is an intermediate frequency signal, the frequency spectrum is shifted after analog-to-digital conversion, and the baseband signal is obtained through filtering and down-sampling processing.
11. A preamble symbol receiving method as claimed in claim 9, wherein:
in the case that it is known that a transmitting end is only possible to transmit a pilot symbol with a plurality of three-segment structures, i.e. a reinforced pilot symbol, the step of determining whether the reinforced pilot symbol expected to be received exists in the baseband signal comprises the following steps:
step S2-22A: according to a preset acquisition rule and/or a preset processing rule between the first part, the first part and the second part of the first three-segment structure and the second three-segment structure in the reinforced pilot symbols expected to be received, respectively performing reverse processing and signal demodulation on the baseband signals, and then performing delay sliding autocorrelation to obtain a delay correlation accumulated value;
step S2-22B: adding the delay correlation accumulated values with the same delay relation or adding the delay correlation accumulated values after phase adjustment to obtain correlation accumulated values with different delays, performing mathematical operation based on the delay correlation accumulated values, and performing peak value detection on the mathematical operation result;
step S2-22C: and if the result of the peak value detection meets a preset condition, determining that the preamble signal expected to be received exists.
12. A method of receiving preamble symbols according to claim 9,
the determining the position of the preamble symbol in the physical frame includes: determining a position of the preamble symbol in the physical frame based on a result of peak detection satisfying a preset condition,
and if the pilot symbol expected to be received exists, determining the position of the pilot symbol in the physical frame according to the part of the value or the maximum value with the large peak value or performing decimal frequency offset estimation.
13. A method of receiving preamble symbols according to claim 9,
the method for solving the signaling information carried by the preamble symbol by using the frequency domain signal obtained by performing Fourier transform on all or part of the time domain waveform of the preamble symbol and/or all or part of the time domain waveform of the preamble symbol comprises the following steps:
and performing operation on a signal containing a signaling sequence subcarrier and a signaling sequence subcarrier set or a time domain signal corresponding to the signaling sequence subcarrier set to solve signaling information carried by the signaling sequence subcarrier in the preamble symbol, wherein the signaling sequence subcarrier set is generated based on a known signaling sequence set.
14. A preamble symbol receiving method as claimed in claim 9, further comprising the steps of:
1) intercepting a signal containing a fixed subcarrier according to the determined position of the preamble symbol in the physical frame;
2) and carrying out operation on the signal containing the fixed subcarrier and a frequency domain fixed subcarrier sequence or a time domain signal corresponding to the frequency domain fixed subcarrier sequence to obtain integral multiple frequency offset estimation or channel estimation.
15. A method of receiving preamble symbols according to claim 14,
obtaining the integer-times frequency offset estimate comprises:
intercepting all or part of the time domain waveform of the received preamble symbol according to the position of the detected preamble symbol in the physical frame;
modulating the partial time domain waveform with different frequency offsets in a frequency sweeping mode to obtain a plurality of time domain signals; and
the known frequency domain fixed sequence subcarrier is subjected to inverse Fourier transform to obtain corresponding time domain signals, the time domain signals are taken as known signals to be subjected to sliding correlation with each time domain signal, the maximum correlation peak value is selected to appear, the frequency offset value modulated by the maximum correlation peak value is the integral multiple frequency offset estimation value,
the frequency sweep range corresponds to the frequency offset range against which the system needs to cope.
16. A method of receiving preamble symbols according to claim 14,
obtaining the integer-times frequency offset estimate comprises:
intercepting corresponding time domain main signals in the preamble symbol, performing Fourier transform to obtain frequency domain OFDM symbols, performing cyclic shift in sweep frequency range, performing point-spaced differential multiplication, performing correlation operation with the point-spaced differential multiplication value of known fixed sequence subcarrier to obtain a series of correlation values, selecting the cyclic shift corresponding to the maximum correlation value to obtain an integer multiple frequency offset estimation value,
the frequency sweep range corresponds to the frequency offset range against which the system needs to cope.
17. A method of receiving preamble symbols according to claim 14,
the channel estimation is completed by utilizing the received signal containing the fixed sequence subcarrier and the known frequency domain fixed sequence subcarrier and/or the time domain signal corresponding to the Fourier inverse transformation of the known frequency domain fixed sequence subcarrier, and the channel estimation is completed in the time domain and/or the frequency domain.
CN201811344671.4A 2014-12-10 2014-12-10 Transmitter, receiver, preamble symbol generation method and reception method Active CN109617846B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201811344671.4A CN109617846B (en) 2014-12-10 2014-12-10 Transmitter, receiver, preamble symbol generation method and reception method

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CN201410753506.XA CN105743624B (en) 2014-12-10 2014-12-10 The generation method and method of reseptance of leading symbol
CN201811344671.4A CN109617846B (en) 2014-12-10 2014-12-10 Transmitter, receiver, preamble symbol generation method and reception method

Related Parent Applications (1)

Application Number Title Priority Date Filing Date
CN201410753506.XA Division CN105743624B (en) 2014-04-05 2014-12-10 The generation method and method of reseptance of leading symbol

Publications (2)

Publication Number Publication Date
CN109617846A CN109617846A (en) 2019-04-12
CN109617846B true CN109617846B (en) 2022-01-28

Family

ID=56239961

Family Applications (7)

Application Number Title Priority Date Filing Date
CN201410753506.XA Active CN105743624B (en) 2014-04-05 2014-12-10 The generation method and method of reseptance of leading symbol
CN201611191913.1A Withdrawn CN106685626A (en) 2014-12-10 2014-12-10 Preamble receiving method
CN201611191893.8A Pending CN106685882A (en) 2014-12-10 2014-12-10 Method for generating frequency domain OFDM symbols
CN201611189364.4A Pending CN106603459A (en) 2014-12-10 2014-12-10 Generating method and receiving method for preamble symbol
CN201811344671.4A Active CN109617846B (en) 2014-12-10 2014-12-10 Transmitter, receiver, preamble symbol generation method and reception method
CN201611190318.6A Withdrawn CN106685881A (en) 2014-12-10 2014-12-10 Precursor symbol generating method and receiving method
CN201611190980.1A Pending CN106850487A (en) 2014-12-10 2014-12-10 The method of reseptance of leading symbol

Family Applications Before (4)

Application Number Title Priority Date Filing Date
CN201410753506.XA Active CN105743624B (en) 2014-04-05 2014-12-10 The generation method and method of reseptance of leading symbol
CN201611191913.1A Withdrawn CN106685626A (en) 2014-12-10 2014-12-10 Preamble receiving method
CN201611191893.8A Pending CN106685882A (en) 2014-12-10 2014-12-10 Method for generating frequency domain OFDM symbols
CN201611189364.4A Pending CN106603459A (en) 2014-12-10 2014-12-10 Generating method and receiving method for preamble symbol

Family Applications After (2)

Application Number Title Priority Date Filing Date
CN201611190318.6A Withdrawn CN106685881A (en) 2014-12-10 2014-12-10 Precursor symbol generating method and receiving method
CN201611190980.1A Pending CN106850487A (en) 2014-12-10 2014-12-10 The method of reseptance of leading symbol

Country Status (1)

Country Link
CN (7) CN105743624B (en)

Families Citing this family (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9843845B2 (en) 2012-11-28 2017-12-12 Sinclair Broadcast Group, Inc. Terrestrial broadcast market exchange network platform and broadcast augmentation channels for hybrid broadcasting in the internet age
WO2016022287A1 (en) 2014-08-07 2016-02-11 Coherent Logix, Incorporated Multi-partition radio frames
CA2956957C (en) 2014-08-07 2019-02-12 ONE Media, LLC Dynamic configuration of a flexible orthogonal frequency division multiplexing phy transport data frame
BR122018067680B1 (en) 2014-08-25 2023-10-17 ONE Media, LLC METHOD FOR ENCODING DATA, TRANSMITTER FROM A BASE STATION OR A BROADCAST PORT IN A BROADCAST NETWORK, METHOD FOR SIGNALING TERMINATION OF A CONTROL FRAME FROM A PREAMBLE OF A BROADCAST COMMUNICATION FRAME IN A BROADCAST NETWORK, AND CONFIGURED TRANSMITTER TO BE USED IN A BROADCAST NETWORK
CN110798421A (en) * 2015-02-12 2020-02-14 上海数字电视国家工程研究中心有限公司 Method and device for receiving preamble symbol
KR102342727B1 (en) 2015-03-09 2021-12-24 원 미디어, 엘엘씨 System discovery and signaling
KR20230170776A (en) 2015-04-08 2023-12-19 원 미디어, 엘엘씨 Advanced data cell resource mapping
WO2017177010A1 (en) 2016-04-07 2017-10-12 ONE Media, LLC Next generation terrestrial broadcasting platform aligned internet and towards emerging 5g network architectures
WO2019018149A1 (en) * 2017-07-18 2019-01-24 Marvell World Trade Ltd. Wakeup packet modulation and demodulation
KR20190035391A (en) * 2017-09-26 2019-04-03 삼성전자주식회사 Apparatus and method for generating and detecting preamble symbol
CN109660266B (en) * 2017-10-11 2020-11-13 大唐移动通信设备有限公司 Signal processing method and device
CN109041253B (en) * 2018-09-06 2020-11-20 北京遥测技术研究所 Diversity access method and system based on iterative detection in unmanned aerial vehicle cluster measurement and control
CN109842430B (en) * 2019-04-10 2020-09-08 西安电子科技大学 LoRa modulation signal demodulation method under multipath channel
CN111711594B (en) * 2020-07-20 2023-06-13 浙江大华技术股份有限公司 Single-frequency interference processing method and device
CN113973036B (en) * 2021-12-22 2022-03-15 元智科技集团有限公司 Orthogonal frequency division multiplexing frequency synchronization method for video communication
CN114844793B (en) * 2022-05-16 2023-09-26 重庆邮电大学 System and method for improving preamble detection success rate of frame structure of Internet of things
CN117278178A (en) * 2022-06-15 2023-12-22 中兴通讯股份有限公司 Data transmission method, device and storage medium

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101960810A (en) * 2008-03-07 2011-01-26 诺基亚公司 System and methods for receiving OFDM symbols having timing and frequency offsets
CN102075480A (en) * 2009-11-20 2011-05-25 清华大学 Method and system for generating frame synchronization sequences for digital information transmission
CN103078825A (en) * 2013-01-30 2013-05-01 清华大学 Method and device for generating frame synchronizing sequence in digital communication system
CN103532899A (en) * 2013-07-31 2014-01-22 上海数字电视国家工程研究中心有限公司 Time domain OFDM synchronization symbol generation and demodulation method, and data frame transmission method

Family Cites Families (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1937604B (en) * 2005-09-20 2013-01-16 中兴通讯股份有限公司 Initial access frame synchronizing method and device for orthogonal frequency division multiplexing system
CN101034970B (en) * 2006-03-08 2010-10-20 北京中电华大电子设计有限责任公司 Valve value self-adaptive selection synchronization signal detection method and device
US8243634B2 (en) * 2007-03-07 2012-08-14 Telefonaktiebolaget L M Ericsson (Publ) Random access in time division duplex communication systems
CN101374131B (en) * 2007-08-20 2013-01-30 株式会社Ntt都科摩 Method and apparatus of timing synchronization, leading symbol as well as method and apparatus for generating the same
KR101000794B1 (en) * 2008-08-29 2010-12-13 전자부품연구원 Method for synchronizing in wireless communication system
JP5446725B2 (en) * 2009-10-28 2014-03-19 ソニー株式会社 Receiving device, receiving method, receiving system
CN102055705A (en) * 2009-11-10 2011-05-11 中兴通讯股份有限公司 Uplink synchronization method and system for terminals
JP2012191565A (en) * 2011-03-14 2012-10-04 Sony Corp Receiver, reception method, and program
GB2489283A (en) * 2011-03-24 2012-09-26 Sony Corp OFDM frequency domain channel estimation with virtual scattered pilots created in frequency notches to restore pattern before interpolation
CN102752859B (en) * 2011-04-19 2017-05-03 中兴通讯股份有限公司 Method for sending uplink synchronizing channel and device
CN102158459B (en) * 2011-05-13 2013-08-07 清华大学 OFDM (Orthogonal Frequency Division Multiplexing) block transmission method based on time-frequency two-dimension training information
CN102664850B (en) * 2012-04-13 2014-10-22 豪威科技(上海)有限公司 Multi-carrier mode low-complexity channel noise-reducing method and device thereof in wireless local area network (WLAN)
CN102891814B (en) * 2012-09-06 2015-02-25 天津市德力电子仪器有限公司 Method for implementing channel multi-path detection based on P1 sign
JP5942732B2 (en) * 2012-09-20 2016-06-29 アイコム株式会社 COMMUNICATION DEVICE AND COMMUNICATION METHOD
CN102891811B (en) * 2012-09-21 2015-06-17 杭州华三通信技术有限公司 Name service database locking method and exchange
US9088455B2 (en) * 2012-12-20 2015-07-21 Broadcom Corporation OFDM or OFDMA signaling for ranging and data
CN103532898B (en) * 2013-04-22 2017-03-22 上海数字电视国家工程研究中心有限公司 OFDM training symbol synchronization method based on CAZAC sequence
CN103546416B (en) * 2013-07-12 2016-12-28 上海数字电视国家工程研究中心有限公司 Ofdm symbol synchronization method

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101960810A (en) * 2008-03-07 2011-01-26 诺基亚公司 System and methods for receiving OFDM symbols having timing and frequency offsets
CN102075480A (en) * 2009-11-20 2011-05-25 清华大学 Method and system for generating frame synchronization sequences for digital information transmission
CN103078825A (en) * 2013-01-30 2013-05-01 清华大学 Method and device for generating frame synchronizing sequence in digital communication system
CN103532899A (en) * 2013-07-31 2014-01-22 上海数字电视国家工程研究中心有限公司 Time domain OFDM synchronization symbol generation and demodulation method, and data frame transmission method

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
地面数字电视广播系统中前导符号的设计;张超等;《2011国际传输与覆盖研讨会》;20111018;全文 *

Also Published As

Publication number Publication date
CN106603459A (en) 2017-04-26
CN106685881A (en) 2017-05-17
CN106850487A (en) 2017-06-13
CN105743624A (en) 2016-07-06
CN109617846A (en) 2019-04-12
CN105743624B (en) 2019-02-26
CN106685626A (en) 2017-05-17
CN106685882A (en) 2017-05-17

Similar Documents

Publication Publication Date Title
CN109617846B (en) Transmitter, receiver, preamble symbol generation method and reception method
US20200374167A1 (en) Preamble symbol generation and receiving method, and frequency-domain symbol generation method and device
CN107248968B (en) Method for generating preamble symbol
US11071072B2 (en) Preamble symbol receiving method and device
CN107222444B (en) Method for receiving and processing preamble symbol in physical frame
CN110190938B (en) Method for generating preamble symbol in physical frame
CN106685885B (en) Preamble symbol receiving apparatus
US8509104B2 (en) Identifying a sequence of received signals
CN106685883B (en) Preamble symbol receiving apparatus
CN112039810B (en) Method for generating frequency domain OFDM symbol and method for generating preamble symbol
CN105262710B (en) Receiving and processing method of frequency domain OFDM symbol

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant