CN101035295A - Frame-synchronization generation method and its device in the ground digital TV system - Google Patents

Abstract

The invention provides a terrestrial digital television broadcasting transmission system in the frame synchronization method for the selection and installation, a digital information processing areas, characterized lies: This invention provides a three length of the header, PN420, PN595 and PN945. PN420 and PN945 from eight bands and nine bands have a linear feedback shift register, and the need for expansion cycle, PN595 and 10 bands have a linear feedback shift register sequence truncated sequence. Depending on the model chosen, it will be a corresponding model PN header inserted into the frame of the sequence data before forming signal frame. When choosing PN420 or PN945 mode, the header of each signal frame required a certain phase of the rotation, and PN595 mode, each signal frames header were the same. PN header which is used to establish synchronization, channel estimation and balanced. Short synchronous time, simple channel estimation, high quality of receiver performance characteristics can be got by using it.

Description

Frame-synchronization generation method in a kind of terrestrial digital television system and device thereof

Technical field

The present invention relates to a kind of digital information transmission field, be specifically related to the frame synchronizing in a kind of terrestrial digital television system.

Background technology

The development of television industries and cause is carried out round the center that rises to of rating quality and service ability always, and Digital Television is as new generation TV tech, and its rating quality increases substantially; Simultaneously, development space has been created in more other service that is adopted as of digitizing technique.The development of Digital Television will be of great importance to the development of whole electronic information industry.

Ground system of digital television broadcast is the important component part in the radio and television system.It is with digital video broadcast-satellite system and cable digital TV broadcast system and other auxiliary system is collaborative mutually provides comprehensive audient to cover, and is part and parcel in the comprehensive nerve of a covering of China's radio and television.China has 2/3rds TV user will lean on wireless coverage; In addition, under situations such as natural calamity, war, than cable TV and satellite television, terrestrial television is the transmission system with fast quick-recovery radio and television covering power.

At present, existing in the world three kinds of ground digital television broadcast transmission standards: the U.S. ATSC of the AS committee standard that 1. adopts the 8VSB modulation; 2. adopt the European digital video broadcasting of Coded Orthogonal Frequency Division Multiplexing (COFDM) (COFDM) to organize the DVB-T standard; 3. adopt the Japanese ISDB-T standard of frequency band segment transmissions OFDM (BST-OFDM).

The ground digital television broadcast wireless transmitting system requires to have good antijamming capability, disturbs as noise jamming, the interference of static multipath, dynamic multi-path, and possesses the fixing ability that receives and move reception, possesses the reliable reception under the complex communication environment of city.Many such as building under urban environment, multipath reflection, scattering, refraction are all compared strongly, cause more intense multipath to disturb, the intersymbol interference that this can be more intense, influence the synchronous and receptivity of terrestrial digital television system, also can cause system to take defeat under the serious situation.Ground digital television receiver must carry out effective channel estimating and channel equalization at receiving terminal for this reason, thus the distortion that compensate for channel is brought.

In order to realize system synchronization and channel estimating, U.S. ATSC has used the training of one section PN sequence as equalizer, and European DVB-T has used time domain cyclic prefix and pilot tone.The ATSC standard pin designs fixing the reception, and for pursuing the high availability of frequency spectrum, the data frame structure piece is bigger, goes up time varying channel thereby channel estimation and equalization is difficult to follow the tracks of, and can not support to move reception, can only support fixing the reception.The DVB-T standard originally also is the fixing design that receives, but owing to used the frequency domain continuous pilot and scattered pilot tone, can support to move to receive, and shortcoming is that signal is longer lock in time of reentrying again, and mobile receptivity is had to a certain degree influence.Because frequency domain scattered pilot and continuous pilot can occupy effective data bandwidth, reduced the data transmission rate of system simultaneously.

Summary of the invention

The object of the present invention is to provide a kind of frame-synchronization generation method and device thereof that can be used in the terrestrial digital television system, synchronous to realize receiving terminal and transmitting terminal, and can carry out channel estimating and channel equalization training.

Frame-synchronization generation method provided by the invention may further comprise the steps:

The 1st step: the base band code stream of input carries out error protection by forward error correction coding, carries out constellation mapping afterwards and interweaves, and forms 3744 data symbols;

The 2nd step: the system information of 36 symbols is placed on before the data of 3744 symbols, and after the frame data processing, forms the time domain frame of 3780 symbols;

The 3rd step: according to the difference of selected frame head mode, the PN sequence that to generate corresponding 420 symbols and be PN420,595 symbols and be PN595 or 945 symbols be PN945 is as the frame synchronization head;

The 4th step: the frame head PN sequence that generates is inserted in before the frame data, forms a complete signal frame;

The 5th step: signal frame obtains baseband signal output after forming filter carries out filtering.

The forward error correction coding of the frame-synchronization generation method in above-mentioned a kind of terrestrial digital television system is a cascaded code, and outer sign indicating number is a Bose-Chaudhuri-Hocquenghem Code, and ISN is the LDPC coding; Constellation mapping is a kind of in 64QAM, 32QAM, 16QAM, 4QAM and the 4QAM-NR mapping, and interweaving is the convolutional interleave based on symbol.

Wherein the frame data processing comprises two kinds of patterns: single carrier mode and multi-carrier mode.

Make the symbol of the frame information of 3780 symbols that the data message of the system information of 36 symbols of X (k) expression and 3744 symbols is combined to form.

A) under the single carrier mode, the time domain frame that the frame data processing forms is:

F _Body(k)＝X(k) k＝0，1，2，……，3779

B) under the multi-carrier mode, at first X (k) is carried out frequency-domain-interleaving, obtains X (n), carry out following computing afterwards:

$F_{\mathrm{Body}}\left(k\right)=\frac{1}{\sqrt{C}}\underset{n=1}{\overset{C}{\mathrm{\&Sigma;}}}X\left(n\right){\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="A20071006555600161.png"\; state="\{\{state\}\}">e</figure-callout>}}^j$ k＝0，1，2，……，3779 C＝3780

Above-mentioned PN420 is that the m sequence of length 255 is the cyclic extensions of PN255.

PN595 is that length is that 1023 m sequence is the shortened code of PN1023.

PN945 is that the m sequence of length 511 is the cyclic extensions of PN511.

The device that frame synchronization in a kind of terrestrial digital television system produces comprises preceding paragraph error correcting encoder, constellation mapping and interleaver, system information insertion device, frame data processor, framing device and forming filter and forms.The framing device will have PN frame head sequence generator to participate in providing frame head for data, and PN frame head sequence generator comprises three parts arranged side by side: a PN420 generating apparatus, a PN595 generating apparatus and a PN945 generating apparatus.The PN420 generating apparatus enables controller, mapping and amplitude adjustment by 225 frame number counters, 8 rank linear feedback shift registers, PN420 initial phase maker, PN420 and forms.The PN595 generating apparatus enables controller, mapping and amplitude adjustment by 10 rank linear feedback shift registers, PN595 and forms.The PN945 generating apparatus enables controller, mapping and amplitude adjustment by 200 frame number counters, 9 rank linear feedback shift registers, PN945 initial phase maker, PN945 and forms.

The generator polynomial of 8 above-mentioned rank linear feedback shift registers is:

G ₂₅₅(x)＝1+x+x ⁵+x ⁶+x ⁸

The generator polynomial of 10 above-mentioned rank linear feedback shift registers is:

G ₁₀₂₃(x)＝1+x ³+x ¹⁰

The initial phase of this 10 rank linear feedback shift register is 0000000001.

The generator polynomial of 9 above-mentioned rank linear feedback shift registers is:

G ₅₁₁(x)＝1+x ²+x ⁷+x ⁸+x ⁹

When being in the PN420 pattern, a superframe contains 225 signal frames; When being in the PN595 pattern, a superframe contains 216 signal frames; When being in the PN945 pattern, a superframe contains 200 signal frames.

In the superframe, the sequence of the frame head PN420 of each signal frame is all inequality, by the initial phase decision of PN420.

In the superframe, the phase place of the frame head PN595 of each signal frame is identical.

In the superframe, the sequence of the frame head PN945 of each signal frame is all inequality, by the initial phase decision of PN945.

The present invention is applied to national digital television terrestrial broadcasting transmission standard, adopts the PN sequence as the frame synchronization head, and its advantage or characteristics show following aspect specifically:

● owing to be used as the PN sequence of frame head, can be used for carrying out synchronously and channel estimating, save pilot tone, compare with the ISDB-T scheme with DVB-T, it is high more than 10% that its availability of frequency spectrum is wanted.

● synchronizing speed is higher than DVB-T.Use the PN sequence to fill protection at interval; utilize the good autocorrelation of PN sequence, can so that system at the synchronization aspects more robust that seems, because of related operation carries out in time domain; lock in time is short to be about 1 millisecond, and be a few tens of milliseconds OFDM lock in time of DVB-T scheme.

● simultaneously, utilize the good autocorrelation and the stochastic behaviour of known PN sequence, can train accurately, the distorted signals that equalizer is optimally produced in the compensate for channel transmission time-domain equalizer.Channel estimating only needs to utilize current demand signal to finish simultaneously, therefore can more change places and satisfy the requirement that fast moving receives.

● because the PN sequence is known,, after treatment promptly, can obtain the frame signal identical with zero padding removing of the influence of PN sequence by related operation synchronously and under the known situation of channel response to frame.Existing theoretical proof, guardtime are spaced apart null value and fill that to be spaced apart the performance that periodic extension is filled under the same channel with guardtime be of equal value.

Description of drawings

The structured flowchart of Fig. 1 emission system of the present invention;

The multistage multi-frame structure figure of Fig. 2 system of the present invention;

Three kinds of signal frame structure figure of Fig. 3 the present invention;

The structure chart of PN420 among Fig. 4 the present invention;

The structure chart of PN945 among Fig. 5 the present invention;

8 rank linear feedback shift register figure among Fig. 6 the present invention;

10 rank linear feedback shift register figure among Fig. 7 the present invention;

9 rank linear feedback shift register figure among Fig. 8 the present invention;

PN frame head sequence generator structure chart among Fig. 9 the present invention;

The generating apparatus structure chart of PN420 among Figure 10 the present invention;

The generating apparatus structure chart of PN595 among Figure 11 the present invention;

The generating apparatus structure chart of PN945 among Figure 12 the present invention.

Embodiment

Below in conjunction with description of drawings a kind of specific implementation of the present invention.

Figure 1 shows that the structured flowchart of a kind of emission system of the present invention.The input signal of this emission system is a base band code stream waiting for transmission, and input code flow obtains the data of 3744 symbols behind forward error correction coder 1, constellation mapping and interleaver 2.System information maker 3 as encoder bit rate, constellation mapping pattern, interlace mode etc., generates the system information of 36 symbols according to different transmission modes, and system information adopts the identical 4QAM modulation mapping mode of I, Q.The system information of the data of 3744 symbols and these 36 symbols is inserted device 4 by system information and is combined, and forms the data X (k) of 3780 symbols, and wherein system information is in the front of data segment.The data X of these 3780 symbols (k) obtains the frame of 3780 symbols behind frame data processor 5.The purpose of frame data processing is in order to obtain the frame data of time domain, according to the difference of single and multi-carrier pattern, need carry out following calculating respectively:

Under single carrier mode, all data processing are all finished in time domain, so X (k) has been a time domain data, so the computing formula of frame data processing is as follows:

F _Body(k)＝X(k) k＝0，1，2，……，3779

Wherein, the speed of frame data symbol is 7.56Ms/s, and bandwidth is 7.56MHz.

Under multi-carrier mode, X (k) is considered to frequency domain data, so at first X (k) is carried out frequency-domain-interleaving, obtains X (n).The purpose of frequency-domain-interleaving is that X (k) is mapped on effective 3780 subcarrier in frequency domain, needs afterwards X (n) is carried out 3780 IDFT computings, thereby obtains the frame data of time domain:

$F_{\mathrm{Body}}\left(k\right)=\frac{1}{\sqrt{C}}\underset{n=1}{\overset{C}{\mathrm{\&Sigma;}}}X\left(n\right){\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="A20071006555600161.png"\; state="\{\{state\}\}">e</figure-callout>}}^j$ k＝0，1，2，……，3779 C＝3780

Have 3780 effective subcarriers under the multi-carrier mode, occupied bandwidth is 7.56MHz, and subcarrier spacing is 2kHz.

PN frame head sequence generator 6 generates the frame head of PN420, PN595 or PN945 according to selected different frame head mode.In framing 7, the frame data of time domain are in the same place with corresponding PN frame head combined sequence, and the PN frame head is before the frame data, and the data after the combination are signal frame.The pairing signal frame length of PN420, PN595 and PN945 is respectively 4200,4375 and 4725 symbols.In three kinds of frame head modes, the length of frame all just as, be 3780 symbols, the duration is 500 μ s.What the modulation system of the PN sequence of frame head adopted is the identical 4QAM mapping of I, Q.

Signal frame behind the framing obtains the data output of base band through behind the forming filter 8.Forming filter adopts the FIR filter of square root raised cosine (SRRC) roll-off characteristic.The rolloff-factor of SRRC is 0.05.The frequency response of this SRRC filter is:

$H\left(f\right)=\left\{\begin{array}{cc}1& \left|f\right|\&le;(1-\mathrm{\&alpha;})/2T_s\\ {\{\frac{1}{2}+\frac{1}{2}\cos \left(\frac{\mathrm{\&pi;}\left[\left({2T}_s\right|f|-1+\mathrm{\&alpha;})\right]}{2\mathrm{\&alpha;}}\right)\}}^{\frac{1}{2}}& (1-\mathrm{\&alpha;})/2T_s<\left|f\right|\&le;(1+\mathrm{\&alpha;})/2T_s\\ 0& \left|f\right|>(1+\mathrm{\&alpha;})/2T_s\end{array}\right.$

T wherein _sBe the symbol period (1/7.56 μ s) of input signal, α is the square root raised cosine filter rolloff-factor.

Figure 2 shows that the multi-frame structure figure of multilevel hierarchy of the present invention.Wherein signal frame is the most basic construction unit, and signal frame is made up of frame head and frame two parts, and wherein frame head has three kinds of patterns, i.e. PN420, PN595 and PN945, respective signal frame length 555.56 μ s, 578.7 μ s and 625 μ s respectively.

Superframe is the set of one group of signal frame, and the time span of superframe is 125ms under the different frame head mode, so under three kinds of patterns of PN420, PN595 and PN945, a superframe contains 225,216 and 200 signal frames respectively.

Dividing frame definition is the set of one group of superframe, and time span is 1 minute, so a branch frame contains 480 superframes.

Day, frame definition was the set of a component frame, and time span is 24 hours, contains 1440 branch frames.

Fig. 3 has shown the composition diagram of three kinds of signal frame structure more specifically.

The purpose that the invention provides three kinds of different frame head modes is in order to adapt to different applied environments and coverage.PN420 can provide the protection interval of 55.6 μ s; be adapted at setting up in the city scope regional single frequency network; PN945 can provide the protection interval of 125 μ s; be fit to set up national single frequency network on a large scale; and PN595 can provide the protection interval of 78.7 μ s; simultaneously because PN595 simple in structure, and do not have the recycling-guard characteristic, can utilize time-domain equalizer to resist the characteristic of channel at receiving terminal.

Figure 4 shows that the structure chart of the cyclic extensions of PN420.The basic sequence of PN420 is that length is that 255 m sequence is PN255, and this PN255 is generated by 8 rank linear feedback shift registers (LFSR), and generator polynomial is:

G ₂₅₅(x)＝1+x+x ⁵+x ⁶+x ⁸

The structure of this LFSR as shown in Figure 6.By G ₂₅₅(x) sequence of Sheng Chenging is a maximal-length sequence, m sequence just, and its cycle is 2 ⁸-1=255.

The PN255 of one-period can be divided into three parts: preceding 83 bits, middle 90 bits, back 82 bits.In order to obtain the PN420 of cyclic extensions, need carry out following operation:,, promptly obtain the PN sequence of 420 bits of cyclic extensions with back 82 bit continued accesses of this PN255 front to PN255 with preceding 83 bit continued accesses of this PN255 afterbody to PN255.

Characteristic according to the m sequence, above-mentioned cyclic extensions equivalence is following process: the PN255 that generates 3 cycles continuously, intercept back 82 bits of first cycle PN255, intercept preceding 83 bits of the 3rd cycle PN255, together with the PN255 of second period, the PN sequence of common 420 bits that constitute is the PN420 of cyclic extensions.So PN420 is exactly by the m sequence of 8 rank LFSR with continuous 420 bits of a certain initial phase generation, this character also just provides easier hardware implementation mode for generating PN420.

Under the PN420 frame head mode, contain 225 signal frames in the superframe, the frame head sequence of the PN420 of these 225 signal frames is inequality simultaneously, has 225 PN420 sequences, each sequence is by the initial phase decision of 8 rank LFSR.When adopting this mode, the frame head of each signal frame uses at the frame number that receiving terminal can be used as signal frame, thereby can bring additional some to make things convenient for function.

Following table is when adopting this variable phase PN420, the initial phase correspondence table of the contained PN420 of each signal frame in superframe.

Sequence number	Initial phase	Sequence number	Initial phase	Sequence number	Initial phase	Sequence number	Initial phase	Sequence number	Initial phase
										0	10110000	45	11111111	90	11010110	135	11100001	180	00010111
1	01100001	46	00001011	91	11000011	136	10101100	181	01111111
										2	11011000	47	11111110	92	01101011	137	11110000	182	00101110
3	11000010	48	00000101	93	10000110	138	01011000	183	00111111
										4	11101100	49	11111101	94	00110101	139	01111000	184	01011101
5	10000101	50	10000010	95	00001101	140	10110001	185	10011111
										6	01110110	51	11111010	96	00011010	141	00111100	186	10111010
7	00001010	52	11000001	97	00011011	142	01100010	187	01001111
										8	10111011	53	11110101	98	10001101	143	10011110	188	01110101

9	00010100	54	01100000	99	00110110	144	11000101	189	10100111
										10	11011101	55	11101010	100	11000110	145	11001111	190	11101011
11	00101001	56	00110000	101	01101100	146	10001010	191	11010011
										12	01101110	57	11010100	102	01100011	147	11100111	192	11010111
13	01010010	58	10011000	103	11011001	148	00010101	193	11101001
										14	10110111	59	10101000	104	00110001	149	01110011	194	10101111
15	10100101	60	01001100	105	10110011	150	00101010	195	11110100
										16	11011011	61	01010000	106	00011000	151	00111001	196	01011111
17	01001011	62	10100110	107	01100110	152	01010101	197	01111010
										18	11101101	63	10100001	108	00001100	153	00011100	198	10111110
19	10010111	64	01010011	109	11001101	154	10101010	199	10111101
										20	11110110	65	01000011	110	00000110	155	00001110	200	01111101
21	00101111	66	10101001	111	10011010	156	01010100	201	01011110
										22	11111011	67	10000111	112	10000011	157	10000111	202	11111011
23	01011110	68	01010100	113	10011010	158	10101001	203	00101111
										24	01111101	69	00001110	114	00000110	159	01000011	204	11110110
25	10111101	70	10101010	115	11001101	160	01010011	205	10010111
										26	10111110	71	00011100	116	00001100	161	10100001	206	11101101
27	01111010	72	01010101	117	01100110	162	10100110	207	01001011
										28	01011111	73	00111001	118	00011000	163	01010000	208	11011011
29	11110100	74	00101010	119	10110011	164	01001100	209	10100101
										30	10101111	75	01110011	120	00110001	165	10101000	210	10110111
31	11101001	76	00010101	121	11011001	166	10011000	211	01010010
										32	11010111	77	11100111	122	01100011	167	11010100	212	01101110
33	11010011	78	10001010	123	01101100	168	00110000	213	00101001
										34	11101011	79	11001111	124	11000110	169	11101010	214	11011101
35	10100111	80	11000101	125	00110110	170	01100000	215	00010100
										36	01110101	81	10011110	126	10001101	171	11110101	216	10111011
37	01001111	82	01100010	127	00011011	172	11000001	217	00001010
										38	10111010	83	00111100	128	00011010	173	11111010	218	01110110

39	10011111	84	10110001	129	00001101	174	10000010	219	10000101
										40	01011101	85	01111000	130	00110101	175	11111101	220	11101100
41	00111111	86	01011000	131	10000110	176	00000101	221	11000010
										42	00101110	87	11110000	132	01101011	177	11111110	222	11011000
43	01111111	88	10101100	133	11000011	178	00001011	223	01100001
										44	00010111	89	11100001	134	11010110	179	11111111	224	10110000

Equally, Figure 5 shows that the structure chart of the cyclic extensions of PN945.The basic sequence of PN945 is that length is that 511 m sequence is PN511, and this PN511 is generated by 9 rank linear feedback shift registers (LFSR), and generator polynomial is:

G ₅₁₁(x)＝1+x ²+x ⁷+x ⁸+x ⁹

The structure of this LFSR as shown in Figure 8.By G ₅₁₁(x) sequence of Sheng Chenging is a maximal-length sequence, m sequence just, and its cycle is 2 ⁹-1=511.

Equally, be similar to the structure of PN420, the PN511 of one-period can be divided into three parts: preceding 217 bits, middle 77 bits, back 217 bits.In order to obtain the PN945 of cyclic extensions, need carry out following operation:,, promptly obtain the PN sequence of 945 bits of cyclic extensions with back 217 bit continued accesses of this PN511 front to PN511 with preceding 217 bit continued accesses of this PN511 afterbody to PN511.In like manner, PN945 is exactly by the m sequence of 9 rank LFSR with continuous 945 bits of a certain initial phase generation.

Under the PN945 frame head mode, contain 200 signal frames in the superframe, the frame head sequence of the PN945 of these 200 signal frames is inequality simultaneously, has 200 PN945 sequences, each sequence is by the initial phase decision of 9 rank LFSR.When adopting this mode, the frame head of each signal frame uses at the frame number that receiving terminal can be used as signal frame, thereby can bring additional some functions easily.

Following table is when adopting this variable phase PN945, the initial phase correspondence table of the contained PN945 of each signal frame in superframe.

Sequence number	Initial phase	Sequence number	Initial phase	Sequence number	Initial phase	Sequence number	Initial phase	Sequence number	Initial phase
										0	111110111	40	001110000	80	011111010	120	011111010	160	001110000
1	111101110	41	101111111	81	101100110	121	010110011	161	110111111
										2	011111011	42	000111000	82	101111101	122	111110101	162	011100001
3	111011100	43	011111111	83	011001101	123	001011001	163	011011111
										4	001111101	44	000011100	84	110111110	124	111101011	164	111000010

5	110111001	45	111111111	85	110011010	125	100101100	165	101101111
										6	000111110	46	100001110	86	111011111	126	111010110	166	110000100
7	101110010	47	111111110	87	100110101	127	010010110	167	110110111
										8	100011111	48	010000111	88	011101111	128	110101100	168	100001000
9	011100101	49	111111100	89	001101011	129	001001011	169	011011011
										10	110001111	50	101000011	90	101110111	130	101011000	170	000010001
11	111001010	51	111111001	91	011010110	131	100100101	171	001101101
										12	011000111	52	010100001	92	110111011	132	010110000	172	000100010
13	110010100	53	111110011	93	110101101	133	110010010	173	000110110
										14	101100011	54	001010000	94	111011101	134	101100001	174	001000101
15	100101000	55	111100110	95	101011010	135	011001001	175	100011011
										16	010110001	56	000101000	96	011101110	136	011000010	176	010001011
17	001010001	57	111001100	97	010110101	137	001100100	177	010001101
										18	001011000	58	000010100	98	001110111	138	110000101	178	100010110
19	010100011	59	110011001	99	101101011	139	100110010	179	101000110
										20	000101100	60	100001010	100	000111011	140	100001010	180	000101100
21	101000110	61	100110010	101	101101011	141	110011001	181	010100011
										22	100010110	62	110000101	102	001110111	142	000010100	182	001011000
23	010001101	63	001100100	103	010110101	143	111001100	183	001010001
										24	010001011	64	011000010	104	011101110	144	000101000	184	010110001
25	100011011	65	011001001	105	101011010	145	111100110	185	100101000
										26	001000101	66	101100001	106	111011101	146	001010000	186	101100011
27	000110110	67	110010010	107	110101101	147	111110011	187	110010100
										28	000100010	68	010110000	108	110111011	148	010100001	188	011000111
29	001101101	69	100100101	109	011010110	149	111111001	189	111001010
										30	000010001	70	101011000	110	101110111	150	101000011	190	110001111
31	011011011	71	001001011	111	001101011	151	111111100	191	011100101
										32	100001000	72	110101100	112	011101111	152	010000111	192	100011111
33	110110111	73	010010110	113	100110101	153	111111110	193	101110010
										34	110000100	74	111010110	114	111011111	154	100001110	194	000111110

35	101101111	75	100101100	115	110011010	155	111111111	195	110111001
										36	111000010	76	111101011	116	110111110	156	000011100	196	001111101
37	011011111	77	001011001	117	011001101	157	011111111	197	111011100
										38	011100001	78	111110101	118	101111101	158	000111000	198	011111011
39	110111111	79	010110011	119	101100110	159	101111111	199	111101110

Figure 7 shows that the structure chart of the LFSR of PN595.Be different from PN420 and PN945, PN595 does not adopt the PN junction structure of cyclic extensions, but has adopted the shortened code of the m sequence of 1023 length, specifically is the mode of preceding 595 chips of PN1023.The generator polynomial of this PN1023 is G ₁₀₂₃(x)=1+x ³+ x ¹⁰, initial phase is 0000000001.

Figure 9 shows that a kind of cut-away view of the PN frame head sequence generator of realizing 6.This PN frame head sequence generator generates the PN frame head sequence of respective length according to the difference of the frame head mode of selecting.Its inside comprises PN420 generating apparatus 9, PN595 generating apparatus 10, PN945 generating apparatus 11, frame head mode controller 12 and PN sequence selection device 13 compositions.

PN420 generating apparatus 9, PN595 generating apparatus 10 and PN945 generating apparatus 11 generate PN420, PN595 and three kinds of PN frame heads of PN945 sequence respectively.Frame head mode controller 12 is according to the difference of choosing the PN frame head mode, and the corresponding control signal of selecting of output is given PN sequence selection device 13.When selecting the PN420 pattern, frame head mode controller 12 outputs 2 bit control signals " 00 ", when selecting the PN595 pattern, frame head mode controller 12 outputs 2 bit control signals " 01 ", when selecting the PN945 pattern, frame head mode controller 12 outputs 2 bit control signals " 10 ".PN sequence selection device 13 is chosen corresponding PN sequence according to 2 bit control signals of frame head mode controller 12 outputs, promptly when control signal is " 00 ", PN sequence selection device 13 is selected the output of PN420 sequence, when control signal is " 01 ", PN sequence selection device 13 is selected the output of PN595 sequence, when control signal was " 10 ", PN sequence selection device 13 was selected the output of PN945 sequence.

Figure 10 shows that the hardware configuration of a kind of PN420 of generation, enable controller 17, mapping and amplitude comprising 225 frame number counters 14, PN420 initial phase maker 15,8 rank linear feedback shift registers 16, PN420 and adjust 18 compositions.According to the narration of front, PN420 is produced by 8 basic rank LFSR.

Under the PN420 pattern, a superframe contains 225 signal frames, and the phase place of the PN420 of each signal frame is different, and the PN sequence of this specific character can be used as the sign of frame number in the superframe, but has also brought certain complexity for the generation of PN420.225 frame number counters 14 are used for calculating the frame number of current demand signal frame in a superframe, and its count range is from 0～224.PN420 initial phase maker 15 by looking into PN420 initial phase bit table, produces the initial phase of correspondence according to the frame number that produces for the PN420 of each signal frame.16 corresponding initial phases of basis of 8 rank linear feedback shift registers produce pairing m sequence.

With first signal frame in the superframe is example, by the initial phase bit table as can be known, the initial phase of first signal frame PN420 is " 10110000 " (sequence number 0 in the corresponding initial phase bit table), and the corresponding order of the unit among this initial phase and the 8 rank LFSR is " D8～D1 ", referring to Fig. 6.

The generation of this m sequence enables controller 17 controls with the time span that produces by PN420 constantly.PN420 enables controller 17 and produces two signals: enable signal and reset signal.Reset signal at each signal frame at first, just moment of beginning of PN420, the initial phase that PN420 initial phase maker 15 is produced is loaded in the 8 rank linear feedback shift registers 16, as the initial phase of LFSR; Enable signal is used for controlling the length that produces the m sequence, and its time width is the time of 420 bits, and the pulse duration of each bit is (1/7.56 μ s).Enable signal is that high level is effective, produces the m sequence between high period, and LFSR is out-of-work between low period.This enable with reset signal control under the m sequence of 420 bits producing be the PN420 sequence of corresponding initial phase.

The PN420 that 8 rank linear feedback shift registers 16 produce is the binary bit stream of a serial, but not the symbols streams of time domain, so need by mapping and amplitude adjustment 18 bit stream to be converted into symbols streams.At first binary PN sequence that LFSR is produced arrive the mapping that " 1 " arrive in "+1 ", " 1 " through " 0 ", is converted into the serial sequence of two level, carry out the identical 4QAM modulation of I, Q afterwards, thereby the time-domain symbol that obtains correspondence flows.Carry out the amplitude adjustment afterwards, so that the power of PN sequence is 2 times of the frame data power.

Figure 11 shows that the hardware structure diagram of a kind of PN595 of generation, comprise that 10 rank linear feedback shift registers 19, PN595 enable controller 20, mapping and amplitude and adjust 21 compositions.Because under the PN595 pattern, the PN595 of each signal frame is all identical in superframe, is preceding 595 bits of PN1023, so no longer need to be similar to the initial phase maker of PN420 in the PN595 maker.PN595 enables controller 20 and produces enable signal and reset signals, and reset signal resets to initial condition " 0000000001 " in initial moment of PN595 just in initial moment of each signal frame with 10 rank linear feedback shift registers 19; Enable signal enables for LFSR provides work, and the width of enable signal is 595 bits, and the pulse duration of each bit is (1/7.56 μ s).In the enable signal valid period, LFSR generates the m sequence, and between dynamic stage, LFSR quits work.So just obtained length and be 595 m sequence, i.e. PN595.

Afterwards, mapping will be carried out " 0 " with amplitude adjustment 21 and arrive the mapping that " 1 " is arrived in "+1 ", " 1 ", carry out the identical 4QAM of I, Q afterwards and modulate, and carry out the amplitude adjustment then.Different with PN420, the signal power of PN595 is identical with the frame data power, so the PN sequence is adjusted to identical with average power signal by the amplitude adjustment.

Figure 12 shows that the hardware generating structure of a kind of PN945, enable controller 25, mapping and amplitude adjustment 18 by 200 frame number counters 22, PN945 initial phase maker 23,9 rank linear feedback shift registers 24, PN945 and form.Operation principle and process that it is concrete are similar to PN420.

Claims (17)

1. the frame-synchronization generation method in the terrestrial digital television system is characterized in that, may further comprise the steps:

The 1st step: the base band code stream of input carries out error protection by forward error correction coding, carries out constellation mapping afterwards and interweaves, and forms 3744 data symbols;

The 2nd step: the system information of 36 symbols is placed on before the data of 3744 symbols, and after the frame data processing, forms the time domain frame of 3780 symbols;

The 3rd step: according to the difference of selected frame head mode, the PN sequence that to generate corresponding 420 symbols and be PN420,595 symbols and be PN595 or 945 symbols be PN945 is as the frame synchronization head;

The 4th step: the frame head PN sequence that generates is inserted in before the frame data, forms a complete signal frame;

The 5th step: signal frame obtains baseband signal output after forming filter carries out filtering.

2. the frame-synchronization generation method in a kind of terrestrial digital television system according to claim 1 is characterized in that: described forward error correction coding is a cascaded code, and outer sign indicating number is a Bose-Chaudhuri-Hocquenghem Code, and ISN is the LDPC coding; Constellation mapping is a kind of in 64QAM, 32QAM, 16QAM, 4QAM and the 4QAM-NR mapping, and interweaving is the convolutional interleave based on symbol.

3. the frame-synchronization generation method in a kind of terrestrial digital television system according to claim 1 is characterized in that: described frame data processing comprises two kinds of patterns: single carrier mode and multi-carrier mode;

Make the symbol of the frame information of 3780 symbols that the data message of the system information of 36 symbols of X (k) expression and 3744 symbols is combined to form;

A) under the single carrier mode, the time domain frame that the frame data processing forms is:

F _Body(k)＝X(k) k＝0，1，2，……，3779

B) under the multi-carrier mode, at first X (k) is carried out frequency-domain-interleaving, obtains X (n), carry out following computing afterwards:

$F_{\mathrm{Body}}\left(k\right)=\frac{1}{\sqrt{C}}\underset{n=1}{\overset{C}{\mathrm{\&Sigma;}}}X\left(n\right)e^{j2\mathrm{\&pi;n}\frac{k}{C}}$ k＝0，1，2，……，3779 C＝3780

4. the frame-synchronization generation method in a kind of terrestrial digital television system according to claim 1 is characterized in that, PN420 is that the m sequence of length 255 is the cyclic extensions of PN255.

5. the frame-synchronization generation method in a kind of terrestrial digital television system according to claim 1 is characterized in that: PN595 is that length is that 1023 m sequence is the shortened code of PN1023.

6. the frame-synchronization generation method in a kind of terrestrial digital television system according to claim 1 is characterized in that: PN945 is that the m sequence of length 511 is the cyclic extensions of PN511.

7. the frame-synchronization generation method in a kind of terrestrial digital television system according to claim 1 is characterized in that: during the PN420 pattern, a superframe contains 225 signal frames; During the PN595 pattern, a superframe contains 216 signal frames; During the PN945 pattern, a superframe contains 200 signal frames.

8. the frame-synchronization generation method in a kind of terrestrial digital television system according to claim 1 is characterized in that: in the superframe, the sequence of the frame head PN420 of each signal frame is all inequality, by the initial phase decision of PN420.

9. the frame-synchronization generation method in a kind of terrestrial digital television system according to claim 1 is characterized in that: in the superframe, the phase place of the frame head PN595 of each signal frame is identical.

10. the frame-synchronization generation method in a kind of terrestrial digital television system according to claim 1 is characterized in that: in the superframe, the sequence of the frame head PN945 of each signal frame is all inequality, by the initial phase decision of PN945.

The device that frame synchronization in 11 1 kinds of terrestrial digital television systems produces, comprise forward error correction coder, constellation mapping and interleaver, system information maker and system information and insert device, frame data processor, framing device and forming filter composition, it is characterized in that, comprise three parts arranged side by side again for the framing device provides the PN frame head sequence generator of frame head part: a PN420 generating apparatus, a PN595 generating apparatus and a PN945 generating apparatus.

12. the device that the frame synchronization in a kind of terrestrial digital television system according to claim 11 produces, it is characterized in that the PN420 generating apparatus enables controller, mapping and amplitude adjustment by 225 frame number counters, 8 rank linear feedback shift registers, PN420 initial phase maker, PN420 and forms.

13. the device that the frame synchronization in a kind of terrestrial digital television system according to claim 11 produces is characterized in that the PN595 generating apparatus enables controller, mapping and amplitude adjustment by 10 rank linear feedback shift registers, PN595 and forms.

14. the device that the frame synchronization in a kind of terrestrial digital television system according to claim 11 produces, it is characterized in that the PN945 generating apparatus enables controller, mapping and amplitude adjustment by 200 frame number counters, 9 rank linear feedback shift registers, PN945 initial phase maker, PN945 and forms.

15. the device that the frame synchronization in a kind of terrestrial digital television system according to claim 12 produces is characterized in that the generator polynomial of described 8 rank linear feedback shift registers is:

G ₂₅₅(x)＝1+x+x ⁵+x ⁶+x ⁸。

16. the device that the frame synchronization in a kind of terrestrial digital television system according to claim 13 produces is characterized in that the generator polynomial of described 10 rank linear feedback shift registers is:

G ₁₀₂₃(x)＝1+x ³+x ¹⁰

The initial phase of this 10 rank linear feedback shift register is 0000000001.

17. the device that the frame synchronization in a kind of terrestrial digital television system according to claim 14 produces is characterized in that the generator polynomial of described 9 rank linear feedback shift registers is:

G ₅₁₁(x)＝1+x ²+x ⁷+x ⁸+x ⁹。

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