CN109861935A - The generation method of frequency-domain OFDM symbol and the generation method of leading symbol - Google Patents
The generation method of frequency-domain OFDM symbol and the generation method of leading symbol Download PDFInfo
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- H—ELECTRICITY
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- 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
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- 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
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- H—ELECTRICITY
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- 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
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- 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
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Abstract
The invention discloses a kind of generation methods of leading symbol, wherein the generation method of leading symbol in physical frame, which comprises the steps of: makees inverse discrete fourier transform to the frequency-domain OFDM symbol of predetermined length to obtain time-domain OFDM symbol；Determine circulating prefix-length；From the time-domain OFDM symbol of the rear portion intercepts circulating prefix-length of time-domain OFDM symbol as cyclic prefix；A part of the time-domain OFDM symbol of circulating prefix-length based on above-mentioned interception generates modulated signal multiplied by frequency displacement sequence；Leading symbol is generated based on cyclic prefix, time-domain OFDM symbol and modulated signal; wherein; modulated signal is generated using single times of subcarrier spacing frequency modulation; it ensure that and utilize the related peak value that may be significantly of delay in receiving end; it is avoided that receiving end by continuous wave CO_2 laser or mono-tone interference; perhaps occur and error detection peak value occur when the length of protection interval length and modulated signal is identical in the isometric multipath channel of modulated signal length or reception signal.
Description
Technical Field
The invention relates to the technical field of wireless broadcast communication, in particular to a method for generating frequency domain OFDM symbols and a method for generating preamble symbols in physical frames.
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, and serves as the start of a physical frame (named P1 symbol), and the P1 symbol appears only once in each physical frame, and marks the start of the physical frame. The P1 symbols have the following uses:
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) so that a receiving end can perform subsequent receiving processing;
3) and detecting initial carrier frequency offset and timing error, and compensating to achieve frequency and timing synchronization.
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 occurs in timing coarse synchronization using the CAB structure, which results in an error in estimating the carrier integer multiple frequency offset in the frequency domain.
In addition, in the process of generating the frequency domain OFDM symbol, a fixed sequence and a signaling sequence need to be generated in the frequency domain. However, the signaling sequence generated by the prior art has a relatively high peak-to-average power, and the signaling sequence is cyclically shifted in the time domain or cyclically shifted plus shifted, which may cause a failure in the multipath channel when the transmitted sequence is detected by correlating the received signal with the set of known sequences in the time domain.
Disclosure of Invention
The invention solves the problems that the signaling sequence generated by the prior art has higher peak average power and the signaling sequence is circularly shifted or circularly shifted and phase shifted on a time domain. Moreover, the DVB _ T2 standard proposes the problem that the performance of frequency domain channel estimation is reduced due to the design of P1 symbols based on the CAB time domain structure.
In order to solve the above problem, an embodiment of the present invention provides a method for generating a frequency domain OFDM symbol, including the following steps: respectively generating a fixed sequence and a signaling sequence on a frequency domain; the fixed sequence and the signaling sequence are constant modulus sequences, and the modulus of each complex number in the fixed sequence and the signaling sequence is equal; filling a fixed sequence and a signaling sequence onto effective subcarriers, wherein the fixed sequence and the signaling sequence are arranged in a parity staggered manner; and filling zero sequence subcarriers on two sides of the effective subcarriers respectively to form frequency domain OFDM symbols with preset length.
Optionally, generating the signaling sequence in the frequency domain includes:
determining the length and the number of the signaling sequences;
determining root values in a CAZAC sequence generation formula based on the length and the number of the signaling sequences; the length of the signaling sequence is less than or equal to a root value, and the root value is more than or equal to twice of the number of the signaling sequences; the root value is preferably chosen as the length of the signaling sequence.
Selecting different q values to generate a CAZAC sequence, wherein the number of the q values is equal to the number of the signaling sequences, and the sum of any two q values is not equal to a root value;
and selecting the signaling sequence from each CAZAC sequence according to the determined length of the signaling sequence.
Optionally, generating the signaling sequence in the frequency domain includes:
determining the length and the number of the signaling sequences;
determining a plurality of root values in a CAZAC sequence generation formula based on the length and the number of the signaling sequences; the length of the signaling sequence is smaller than or equal to the minimum value of the selected plurality of root values, and the sum of the selected plurality of root values is larger than or equal to twice the number of the signaling sequence;
selecting different q values to generate a CAZAC sequence aiming at each root value, wherein the number of the q values is less than or equal to 1/2 of the corresponding root value, and the sum of any two q values is not equal to the corresponding root value;
and selecting the signaling sequence from each CAZAC sequence according to the determined length of the signaling sequence.
Optionally, the number of q values is selected to be different for each root value, and the sum of the number of q values is equal to the number of signaling sequences.
Optionally, one root value of the plurality of root values is selected as the length of the signaling sequence.
Optionally, the selecting the signaling sequence from each CAZAC sequence obtained according to the determined length of the signaling sequence includes: and determining the signaling sequence according to the CAZAC sequence generated by the root value selected as the length of the signaling sequence.
Optionally, the root value is a prime number.
Optionally, the length of the fixed sequence is equal to the length of the signaling sequence, and the length is smaller than 1/2 of the predetermined length.
Optionally, the filling zero sequence subcarriers at two sides of the effective subcarrier to form a frequency domain OFDM symbol with a predetermined length respectively includes: and filling zero sequence subcarriers with equal length on two sides of the effective subcarriers respectively to form frequency domain OFDM symbols with preset length.
Optionally, the length of the zero sequence subcarrier filled on each side is greater than a critical length value, and the critical length value is determined by the system sampling rate, the symbol rate and the predetermined length.
Optionally, the predetermined length is 1024.
The embodiment of the invention also provides a method for generating the preamble symbol in the physical frame, which comprises the following steps: obtaining a frequency domain OFDM symbol with a preset length according to the generation method of the frequency domain OFDM symbol; performing inverse discrete Fourier transform on the frequency domain OFDM symbol with the preset length to obtain a time domain OFDM symbol; determining a cyclic prefix length; intercepting the time domain OFDM symbol with the cyclic prefix length from the time domain OFDM symbol as a cyclic prefix; generating a modulation signal based on the intercepted time domain OFDM symbol with the cyclic prefix length; generating a preamble symbol based on the cyclic prefix, the time domain OFDM symbol, and the modulation signal.
Optionally, after the generating a modulation signal based on the truncated time domain OFDM symbol with the cyclic prefix length further includes: according to the length of the modulation signal; and selecting different starting points for intercepting the cyclic prefix part in the time domain OFDM symbol, and intercepting the part with the length of the modulation signal from the starting points for transmitting signaling information.
Optionally, the signaling information includes hook information, transmitter flag information, or other transmission parameters.
Optionally, the predetermined length is 1024, the cyclic prefix length and the length of the modulation signal are 512.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
according to the method for generating the frequency domain OFDM symbol provided by the embodiment of the invention, the fixed sequence and the signaling sequence are filled on the effective subcarriers in a parity interleaving mode, and through the specific frequency domain structure design, the fixed sequence can be used as the pilot frequency in the physical frame, so that a receiving end can conveniently decode and demodulate the preamble symbol in the received physical frame.
Moreover, the signaling sequence and the fixed sequence both adopt constant modulus sequences, have smaller Peak to average Power Ratio (PAPR), and avoid the characteristic that the generated signaling sequence has cyclic shift or cyclic shift plus phase shift in the time domain, which can cause the problem of failure in the multipath channel when the transmitted sequence is detected by correlating the time domain known sequence set with the received signal.
According to the method for generating the preamble symbol in the physical frame provided by the embodiment of the invention, the cyclic prefix length is determined according to different channel environments, and the time domain OFDM symbol with the cyclic prefix length is intercepted from the time domain OFDM symbol to be used as the cyclic prefix, so that the problem of the reduction of the frequency domain channel estimation performance is solved. And generating a modulation signal based on the intercepted time domain OFDM symbol with the cyclic prefix length, so that the generated preamble symbol has good decimal frequency offset estimation performance and timing synchronization performance.
Furthermore, a part of or all data segments copied to the cyclic prefix in the time domain OFDM symbol can be taken from the modulation signal, and the signaling parameters are transmitted by selecting different starting positions.
Furthermore, the structure of the modulation signal using the time domain OFDM symbol and the time domain OFDM symbol (as a preamble symbol) ensures that a distinct peak can be obtained at the receiving end using delay correlation. In addition, in the process of generating the preamble symbol, the modulation signal of the time domain OFDM symbol is designed to avoid that the receiving end is subjected to continuous wave interference or single frequency interference, or that a multipath channel with the same length as the modulation signal occurs, or that a false detection peak occurs when the guard interval length in the received signal is the same as the length of the modulation signal.
Drawings
Fig. 1 is a flowchart illustrating a method for generating a frequency domain OFDM symbol according to an embodiment of the present invention;
fig. 2 is a flowchart illustrating a method for generating preamble symbols in a physical frame according to an embodiment of the present invention.
Detailed Description
The inventor finds that the signaling sequence generated by the prior art has higher peak average power and the signaling sequence is cyclically shifted or cyclically shifted plus phase shifted in the time domain.
In view of the above problems, the inventors have studied and provided a method for generating a frequency domain OFDM symbol and a method for generating a preamble symbol in a physical frame. The generated signaling sequence is prevented from having the characteristic of cyclic shift or cyclic shift plus phase shift in the time domain. And the problem of the performance reduction of frequency domain channel estimation is solved, and the time domain OFDM symbol is utilized to generate a modulation signal, so that the generated preamble symbol has good decimal frequency offset estimation and timing synchronization performance. Further, the receiving end can still process the received signal within the range of-500 kHz to 500kHz by ensuring the carrier frequency deviation.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
Fig. 1 is a schematic flow chart of a specific embodiment of a method for generating a frequency domain OFDM symbol according to the present invention. Referring to fig. 1, the method for generating a frequency domain OFDM symbol includes the steps of:
step S11: respectively generating a fixed sequence and a signaling sequence on a frequency domain; the fixed sequence and the signaling sequence are constant modulus sequences, and the modulus of each complex number in the fixed sequence and the signaling sequence is equal;
step S12: filling a fixed sequence and a signaling sequence onto effective subcarriers, wherein the fixed sequence and the signaling sequence are arranged in a parity staggered manner;
step S13: and filling zero sequence subcarriers on two sides of the effective subcarriers respectively to form frequency domain OFDM symbols with preset length.
Specifically, as described in step S11, the fixed sequence and the signaling sequence are generated in the frequency domain, respectively. The fixed sequence includes the relevant information that the receiving end can use to do carrier frequency synchronization and timing synchronization, and the signaling sequence includes each basic transmission parameter.
In this embodiment, the fixed sequence and the signaling sequence are constant modulus sequences, and the modulus of each complex number in the fixed sequence and the signaling sequence is equal. It should be noted that the complex number includes a real number (i.e., the imaginary part of the complex number is zero).
In this embodiment, the signaling sequence may be generated in the frequency domain in any one of the following two ways, and the two ways of generating the signaling sequence are described in detail below.
Mode 1:
1.1, determining the length and the number of signaling sequences;
1.2 determining root values in a CAZAC sequence generation formula based on the length and the number of the signaling sequences; the length of the signaling sequence is smaller than or equal to the root value, and the root value is larger than or equal to twice of the number of the signaling sequences. Preferably, the root value is chosen as the length of the signaling sequence.
For example, the sequence length L and the number of signalings are determined. For example, if N bits are to be transmitted, the number of signaling num is 2NAnd selects the root value of exp (j pi qn (n +1)/root) in the CAZAC sequence generation formula. Wherein, the sequence length L is less than or equal to the root value, and the root value is more than or equal to 2 x num. Root values are typically prime numbers.
1.3 choosing different q values to generate CAZAC sequences, where the number of q values is equal to the number of signaling sequences and the sum of any two q values is not equal to the root value.
For example, num different q's are selected0、q1、......、qnum-1Generating a CAZAC sequence:
exp(jπqn(n+1)/root)，n＝0，...root-1。
in this embodiment, q is selectedi(0. ltoreq. i. ltoreq. num-1) must satisfy the following conditions: any 2 qi、qj(0. ltoreq. i, j. ltoreq. num-1) satisfies qi+qj≠root.
Under the above conditions, a sequence that makes the PAPR of the entire frequency domain OFDM symbol low is preferentially selected. And if L is equal to or greater than 2 × num, root is preferably selected to be L.
1.4 selecting the signaling sequence from each CAZAC sequence obtained according to the determined length of the signaling sequence. Note that, if L is root, truncation is not necessary, and the obtained CAZAC sequence can be used as a signaling sequence.
For example, each of the num sequences is truncated into a continuous partial sequence or a complete sequence with a length of L as a signaling sequence.
For example, inL350 and num 256. Root is selected to 751, then q is selected to 0, 1.. 255, satisfying qi+qj≠751，(0≤i，j≤256-1)。
Alternatively, L353 and num 128. Root is chosen to be 353, then q is chosen to be 0, 1i+qj≠353，(0≤i，j≤128-1)。
Mode 2:
2.1 determining the length and the number of the signaling sequences;
2.2 determining a plurality of root values in a CAZAC sequence generation formula based on the length and the number of the signaling sequences; the length of the signaling sequence is smaller than or equal to the minimum value of the selected plurality of root values, and the sum of the selected plurality of root values is larger than or equal to twice the number of the signaling sequences. Preferably, the root value is chosen as the length of the signaling sequence.
For example, the sequence length L and the number of signalings are determined. For example, if N bits are to be transmitted, the number of signaling num is 2NAnd selecting a plurality of K roots of exp (j pi qn (n +1)/root) in the CAZAC sequence generation formulak(K is more than or equal to 0 and less than or equal to K-1). Wherein the length L of the signaling sequence is less than or equal to all rootskMinimum value of, and a number of rootskIs greater than or equal to 2 x num, i.e.Root in generalkThe values are prime numbers.
2.3 for each root value, selecting a different q value results in a CAZAC sequence, where the number of q values is less than or equal to 1/2 for the corresponding root value, and the sum of any two q values is not equal to the corresponding root value.
For example, for each rootk(K is more than or equal to 0 and less than or equal to K-1), num is selectedkA different q0、q1、Generating a CAZAC sequence exp (j)πqn(n+1)/rootk)，n＝0，...rootk-1. Wherein,
and is
In this embodiment, q is selectedi(0≤i≤numk-1) the following conditions must be satisfied: any 2 qi、qj(0≤i，j≤numk-1) satisfies qi+qj≠rootk。
Under the above conditions, a sequence that makes the PAPR of the entire frequency domain OFDM symbol low is preferentially selected. And one of the root ═ L may be preferentially selected. So that the autocorrelation value of the sequence generated by the root is zero.
2.4 selecting the signaling sequence from each CAZAC sequence obtained according to the determined length of the signaling sequence. It is emphasized that if a root is L, the signaling sequence is determined from the CAZAC sequence generated from the root value selected as the length of the signaling sequence.
For example, each of the num sequences is truncated into a continuous partial sequence or a complete sequence with a length of L as a signaling sequence.
For example, L353 and num 128, for example. Root is preferentially selected to be 353 in mode 1. Then, q is selected to be 0, 1. Satisfy qi+qjNot equal to 353, (i is more than or equal to 0, and j is more than or equal to 128-1). Finally, each sequence is truncated to a length of 353.
For another example, L is 350 and num is 256. In mode 2, root1 is selected as 353, root2 as 359, and then for root1 as 353, a total of 128 sequences q 0, 1, 2,. 127 are selected, qi+qjNot equal to 353. Then for root2 359, 128 sequences of q 100, 101, 102.. 227 were selected, for a total of 256 sequences. At last every one willThe sequences are truncated to a length of 350.
The fixed sequence and the signaling sequence are padded on the active subcarriers and are arranged in a parity staggered manner as described in step S12.
In a preferred embodiment, the length of the fixed sequence is equal to the length of the signaling sequence, and the length is less than 1/2 of the predetermined length. The predetermined length is 1024, but it can be changed according to the system requirement in practical application.
Taking the predetermined length as 1024 as an example, let the length of the fixed sequence be N (that is, the number of the effective subcarriers carrying the fixed sequence be N), and the length of the signaling sequence be M (that is, the number of the effective subcarriers carrying the signaling sequence be M), where M is equal to N in this embodiment. In other embodiments, N may also be slightly larger than M.
The fixed sequence and the signaling sequence are arranged in a parity staggered manner, namely the fixed sequence is filled to the position of even subcarrier (or odd subcarrier), correspondingly, the signaling sequence is filled to the position of odd subcarrier (or even subcarrier), thereby the distribution state of the parity staggered arrangement of the fixed sequence and the signaling sequence is presented on the effective subcarrier of the frequency domain. It should be noted that, when the lengths of the fixed sequence and the signaling sequence are not consistent (for example, M > N), the parity interleaving of the fixed sequence and the signaling sequence may be implemented by means of zero padding sequence subcarriers.
Zero sequence subcarriers are padded on both sides of the effective subcarrier to form frequency domain OFDM symbols of a predetermined length, respectively, as described in step S13.
In a preferred embodiment, this step comprises: and filling zero sequence subcarriers with equal length on two sides of the effective subcarriers 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-M-N, and (1024-M-N)/2 zero-sequence subcarriers are padded on both sides.
Further, in order to ensure that the receiving end can still process the received signal within the carrier frequency deviation range of-500 kHz to 500kHz, the value of (1024-M-N)/2 is usually larger than the critical length value (set to TH), which is determined by the systematic symbol rate and the predetermined length. E.g. a systematic symbol rate of 1024, 7.61M, and a sampling rate of 9.14M, the predetermined length is then 1024For example, when M is 350, G is 324, and each side is padded with 162 zero-sequence subcarriers.
Accordingly, subcarriers (i.e., frequency domain OFDM symbols) P1_ X of a predetermined length (1024) are provided0，P1_X1，L，P1_X1023Generated by filling in the following way:
wherein,the parity positions may be interchanged.
Fig. 2 is a flowchart illustrating a method for generating preamble symbols in a physical frame according to an embodiment of the present invention. Referring to fig. 2, the method for generating preamble symbols in a physical frame includes the following steps:
step S21: generating a frequency domain OFDM symbol with a preset length according to the generation method of the frequency domain OFDM symbol;
step S22: performing inverse discrete Fourier transform on the frequency domain OFDM symbol with the preset length to obtain a time domain OFDM symbol;
step S23: determining a cyclic prefix length;
step S24: intercepting the time domain OFDM symbol with the cyclic prefix length from the time domain OFDM symbol as a cyclic prefix;
step S25: generating a modulation signal based on the intercepted time domain OFDM symbol with the cyclic prefix length;
step S26: generating a preamble symbol based on the cyclic prefix, the time domain OFDM symbol, and the modulation signal.
In this embodiment, reference may be made to the description of the above embodiment for implementation of the step S21, and details are not repeated here.
As shown in step S22, the frequency domain OFDM symbol with the predetermined length is inverse discrete fourier transformed to obtain a time domain OFDM symbol.
The inverse discrete fourier transform described in this step is a common way of converting a frequency domain signal into a time domain signal, and is not described herein again.
P1_XiObtaining a time domain OFDM symbol after performing inverse discrete Fourier transform:
the cyclic prefix length is determined as described in step S23.
Unlike the prior art, in the embodiment, a Cyclic Prefix (CP) needs to be added before the time domain OFDM symbol, and the wireless broadcast communication system can determine the length of the CP (set to N) according to different channel environmentscp). For example, the cyclic prefix length may be determined based on the length of the multipath against which the wireless broadcast communication system needs to contend. That is, when generating the preamble symbol, the wireless broadcast communication system can determine the multipath length that the preamble symbol needs to contend with, and thus determine the cyclic prefix.
The time domain OFDM symbol of the cyclic prefix length is truncated from the time domain OFDM symbol as a cyclic prefix as stated in step S24.
In this embodiment, the cyclic prefix length is equal to or less than the predetermined length. Taking the predetermined length as 1024 as an example, the cyclic prefix length may be 1024 or less than 1024. Preferably, the cyclic prefix length is 512, that is, in this step, the second half (length is 512) of the time domain OFDM symbol is truncated as the cyclic prefix, so as to solve the problem of performance degradation of frequency domain channel estimation.
And as indicated by step S25, generating a modulated signal based on the truncated time domain OFDM symbol with the cyclic prefix length. In practice, the length of the modulated signal cannot exceed the length of the cyclic prefix portion.
Specifically, the method comprises the following steps:
1) setting a frequency shift sequence;
2) multiplying the time domain OFDM symbol or a part of the time domain OFDM symbol by the frequency shift sequence to obtain the modulation signal.
For example, let NcpFor a determined cyclic prefix length, LenBIs the length of the modulated signal. N1 is the sampling point number of the time domain OFDM symbol corresponding to the start point selected to be copied to the modulation signal segment, N2 is the sampling point number of the time domain OFDM symbol corresponding to the end point selected to be copied to the modulation signal segment, N2 is N1+ LenB-1. Preferably, the length of the time domain OFDM symbol is 1024, NcpIs 512, LenBAlso 512.
The frequency shift sequence isWherein f isSHThe sub-carrier spacing corresponding to the A symbol is selected as 1/NAT, wherein NAIs the length of a. To sharpen the correlation peak, fSHCan also be selected to be 1/(Len)BT). When LenB＝NCPWhen f is presentSH＝1/NCPT。
M (t) can also be designed into other sequences, such as m-sequence or some simplified window sequence.
The modulation signal of the partial time domain OFDM symbol is P1_ b (t), P1_ b (t) is obtained by multiplying the partial time domain OFDM symbol by the frequency shift sequence m (t), i.e., P1_ b (t) is:
where N1 is the sample point number of the ofdm symbol of a segment that is selected to be copied to the start of the B segment.
A preamble symbol is generated based on the cyclic prefix, the time domain OFDM symbol and the modulation signal as described in step S26.
Specifically, the cyclic prefix is spliced at the front part of the time domain OFDM symbol as a guard interval, and the modulation signal is spliced at the rear part of the OFDM symbol as a modulation frequency offset sequence to generate a preamble symbol.
For example, the preamble symbol may be based on employing the time domain expression:
in other embodiments, if the predetermined length takes on another value (i.e., not 1024), then 1024 in the above equation P1(t) will be changed to the corresponding value (i.e., consistent with the predetermined length), and N will be the same as NcpIt may also be changed to other values, preferably NcpIs half of said predetermined length.
Further, the following steps are also included after the step S14:
1) according to the length of the modulation signal;
2) and selecting different starting points for intercepting the cyclic prefix part in the time domain OFDM symbol, and intercepting the part with the length of the modulation signal from the starting points for transmitting signaling information.
For example, the predetermined length is 1024, NCPIs 512, LenBIs 256.
Wherein, N1 can be 512+ i 160 ≦ i < 16, which can represent 16 different access methods for transmitting 4-bit signaling parameters. Different transmitters may transmit their corresponding identities by taking a different N1, the same transmitter may also transmit the transmission parameters by changing N1 in time.
In other embodiments, based on the method for generating the frequency domain OFDM symbol described above, a person skilled in the art may use other embodiments (not limited to the generation of the preamble symbol in the physical frame provided in this embodiment) to process the frequency domain OFDM symbol to generate the preamble symbol in the time domain.
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 (5)
1. A method for generating preamble symbols in a physical frame, comprising the steps of:
performing inverse discrete Fourier transform on the frequency domain OFDM symbol with the preset length to obtain a time domain OFDM symbol;
determining a cyclic prefix length;
intercepting the time domain OFDM symbol with the length of the cyclic prefix from the rear part of the time domain OFDM symbol as the cyclic prefix;
generating a modulation signal based on the intercepted part of the time domain OFDM symbol with the cyclic prefix length multiplied by a frequency shift sequence;
and generating a preamble symbol based on the cyclic prefix, the time domain OFDM symbol and the modulation signal, wherein the modulation signal is generated by adopting single subcarrier interval modulation frequency offset.
2. The method of generating preamble symbols in a physical frame according to claim 1,
the frequency shift sequence isWherein f isSHCan be selected as the subcarrier interval corresponding to the time domain OFDM symbol, namely 1/NAT, wherein NAIs the length of the time domain OFDM symbol.
3. The method as claimed in claim 1, wherein the method for generating preamble symbols in a physical frame further comprises, after the generating a modulation signal based on the truncated time domain OFDM symbols with cyclic prefix length:
according to the length of the modulation signal;
and selecting different starting points for intercepting the cyclic prefix part in the time domain OFDM symbol, and intercepting the part with the length of the modulation signal from the starting points for transmitting signaling information.
4. The method of claim 3, wherein the signaling information comprises hook information, transmitter flag information, or other transmission parameters.
5. The method of generating preamble symbols in a physical frame according to claim 1,
concatenating the cyclic prefix at a front portion of the time-domain OFDM symbol and the modulated signal at a rear portion of the OFDM symbol, and the time-domain OFDM symbol to generate a preamble symbol,
the predetermined length is 1024, the cyclic prefix length is 512, and the length of the modulated signal is 512; or
The predetermined length is 1024, the cyclic prefix length is 512, and the length of the modulated signal is 256.
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| 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 |
| CN112039810B (en) * | 2014-04-30 | 2024-01-26 | 上海数字电视国家工程研究中心有限公司 | Method for generating frequency domain OFDM symbol and method for generating preamble symbol |
| KR102444038B1 (en) | 2014-08-07 | 2022-09-19 | 원 미디어, 엘엘씨 | Flexible Orthogonal Frequency Division Multiplexed Physical Transmission Data Frame Dynamic Composition Method |
| MX2017001613A (en) | 2014-08-07 | 2018-01-24 | Coherent Logix Inc | Multi-partition radio frames. |
| CA3194847A1 (en) | 2014-08-25 | 2016-03-03 | ONE Media, LLC | Dynamic configuration of a flexible orthogonal frequency division multiplexing phy transport data frame preamble |
| KR102541395B1 (en) | 2015-03-09 | 2023-06-07 | 원 미디어, 엘엘씨 | System discovery and signaling |
| TWI770632B (en) | 2015-04-08 | 2022-07-11 | 美商第一媒體有限責任公司 | Advanced data cell resource mapping |
| EP3440787A1 (en) | 2016-04-07 | 2019-02-13 | Sinclair Broadcast Group, Inc. | Next generation terrestrial broadcasting platform aligned internet and towards emerging 5g network architectures |
| CN108347399B (en) * | 2017-01-22 | 2021-05-07 | 上海矽久微电子有限公司 | Method and device for generating and receiving preamble signal |
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