CN101212392B - Mobile multimedia broadcast satellite distribution data encapsulation and synchronization method - Google Patents
Mobile multimedia broadcast satellite distribution data encapsulation and synchronization method Download PDFInfo
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Abstract
The invention discloses a method of encapsulation and synchronization for distribution data in a mobile multimedia broadcast satellite. The invention comprises the following processes: the date quantity of a transmission frame is determined; the number of symbol bytes in a timeslot of a single frequency point under the modulation of narrowest bandwidth and the symbol number with least transmission are taken as a frame; the data in the frame is encapsulated into a packet with a reservation format. The data of each frame is encapsulated into an initial packet and a plurality of data transmission packets; wherein, the initial packet comprises controlling information and the controlling information comprises the transmission characteristics and synchronization information of the frame; according to a selected bandwidth, the transited data of different frequency points in the identical timeslot is encapsulated into a series of transmission packets in the frame unit in frequency, wherein, the different frequency points in the identical timeslot can use different modulation and have different quantity of transmission frames; the obtained series of data packets carries out a scrambling code, an RS coding, a convolution interweaving, a convolution coding, a QPSK mapping, a synchronization information insertion and a pilot signal insertion.
Description
Technical Field
The invention relates to a mobile multimedia broadcasting satellite distribution system, in particular to a mobile multimedia broadcasting satellite distribution data packaging and synchronizing method.
Background
The mobile multimedia broadcasting system provides the multimedia digital video, audio and data service broadcasting service which covers a large range and supports high-quality fixed or mobile reception for users in the frequency range of 30MHz to 3000 MHz. Wherein, the program information can be transmitted by two paths of signals: 1) after OFDM modulation is carried out on a program information source by a mobile multimedia modulator, large-area broadcast coverage is directly provided for users through a satellite S waveband broadcast channel. 2) The program information source simultaneously distributes programs to each ground transponder through a data distribution network, and after OFDM modulation is carried out again by the ground transponders, broadcasting is carried out on S wave bands under specific synchronous conditions, and supplementary coverage is carried out on satellite S wave band direct broadcast signals.
Because the breadth of the members in China is large, and the transmission delay of satellite signals reaching various places is greatly different (for example, the satellite signals reaching Beijing and Shanghai have the transmission delay with the difference of millisecond level), the delay can seriously affect the performance of the whole mobile multimedia broadcasting system, so how to overcome the transmission delay and achieve the transmission synchronization is a very concerned problem.
Disclosure of Invention
The invention aims to provide a mobile multimedia broadcast satellite distribution data encapsulation and synchronization method, which can combine channel coding and interlaced mobile multimedia broadcast symbol data with certain control information to form a transmission packet with a specific format so as to be orderly and unambiguously issued to each ground forwarding modulator by a central modulator.
According to the present invention, a method for encapsulating and synchronizing distribution data of a mobile multimedia broadcasting satellite is provided, wherein a system of the mobile multimedia broadcasting specifies that a signal of 1 second is divided into a predetermined number of time slots, different modulation modes can be adopted in each time slot, symbol data transmitted in one time slot is used as a transmission unit, and the mobile multimedia broadcasting is transmitted in different bandwidths, and the different bandwidths correspond to different numbers of frequency points, the method comprises: encapsulating data in a frame into a transmission packet with a predetermined format, encapsulating the data of each frame into an initial packet and a plurality of data transmission packets, wherein the initial packet comprises control information, and the control information comprises transmission characteristics and synchronization information of the frame; according to the selected bandwidth, sequentially encapsulating data transmitted by different frequency points in the same time slot into a series of transmission packets by taking the frame as a unit, wherein the different frequency points in the same time slot can adopt different modulation modes and have different numbers of transmission frames; dividing the obtained series of transmission packets into a plurality of groups, wherein each group has a predetermined number of transmission packets, performing negation operation on a first byte of a first transmission packet of each group, and inserting synchronization information; scrambling the transmission packet subjected to the negation operation, and performing exclusive or processing on the transmission packet and the local scrambling sequence; RS encoding is carried out on the transmission packet which is processed by the scrambling; carrying out byte convolution interleaving on the data subjected to RS coding; performing convolutional encoding on the output of the convolutional interleaving; performing QPSK mapping on the bit stream output by the convolutional coding; inserting synchronous information into the data after QPSK mapping, wherein the synchronous information comprises two paths of binary pseudorandom sequences, time coding information is modulated on the first path of binary pseudorandom sequences, and modulation information of the second path of binary pseudorandom sequences is reserved; a pilot signal is inserted.
According to an embodiment of the present invention, the system of the mobile multimedia broadcasting specifies that a signal of 1 second is divided into 40 time slots, each time slot is 25 ms; the mobile multimedia broadcast includes two signal bandwidths: 2MHz for 12 frequency points and 8MHz for 3 frequency points; the modulation mode adopted by the system of the mobile multimedia broadcast in each time slot comprises the following steps: BPSK, QPSK, 16 QAM.
According to an embodiment of the present invention, for a 2MHz bandwidth, the number of symbols in a single time slot of each frequency point is 27648 bits, wherein, using a BPSK modulation method, the number of information bits in a single time slot is 27648 bits, and the number of symbol bytes in a single time slot is 3456 bytes; using QPSK modulation mode, the information bit number of single time slot is 55296 bits, the symbol byte number of single time slot is 6912 bytes; using a 16QAM modulation mode, wherein the information bit number of a single time slot is 110592 bits, and the symbol byte number of the single time slot is 13824 bytes;
for the bandwidth of 8MHz, the symbol number of a single time slot of each frequency point is 138240 bits, wherein, a BPSK modulation mode is used, the information bit number of the single time slot is 138240 bits, and the symbol byte number of the single time slot is 17280 bytes; using QPSK modulation mode, the information bit number of single time slot is 276480 bits, the symbol byte number of single time slot is 34560 bytes; using a 16QAM modulation mode, wherein the information bit number of a single time slot is 552960 bits, and the symbol byte number of the single time slot is 69120 bytes;
the data size of one frame is 3456 bytes, so when a 2MHz bandwidth is adopted, the number of transmission frames corresponding to each frequency point is: the BPSK modulation mode is 1 frame; the QPSK modulation mode is 2 frames; the 16QAM modulation mode is 4 frames; when a 2MHz bandwidth is adopted, the number of transmission frames corresponding to each frequency point is respectively as follows: the BPSK modulation mode is 5 frames; the QPSK modulation mode is 10 frames; the 16QAM modulation scheme is 20 frames.
According to an embodiment of the present invention, the transport packets conform to the GB/T17975.1 standard, and each transport packet includes 188 bytes, including a transport packet header of 4 bytes and a data field of 184 bytes; wherein,
the method forms an initial packet having the following fields, including: 32 bits of transmission packet header, wherein the definition of the transmission packet header conforms to GB/T17975.1 specification; wherein, the PID value is 0x05a0, the load unit start indication is 1, the combination of PID value and load unit start indication indicates that the transmission packet is an initial packet, the transmission priority value is 1, the transmission scrambling control value is 00, and the adaptation segment control value is 01; control field, 40 bytes, 320 bits, including: symbol transmission frame initial packet mark, 16 bits; reserved field, 8 bits; configuration change indication, 1bit, in accordance with GY/T220.1-2006 standard; the byte interleaver synchronization mark is 1bit and conforms to GY/T220.1-2006 standard; the time slot number is 6 bits and accords with the standard of GY/T220.1-2006; frequency point number, 8 bits, indicating which frequency point the data in the symbol transmission frame belongs to for transmission; the channel bandwidth indication is 1bit and indicates the signal bandwidth of the current data attribution frequency point, wherein 0 represents 2MHz, and 1 represents 8 MHz; the extension control information mark is 1bit, when the extension control information mark is set to be 1, the extension control information mark indicates that the initial packet of the current symbol transmission frame contains the ground forwarding station identification number, the transmission power, the output frequency point mask and the delay fine adjustment, and when the extension control information mark is set to be 0, the extension control information mark indicates that the corresponding field is meaningless; mapping mode, 6 bits, indicating in which way the data within the current transmission frame is mapped; a distribution mode, 6 bits, indicating in which distribution mode the current symbol data is delivered to each ground forwarding station; the transmission packet number is 10 bits, and indicates that the first data transmission packet in the current symbol transmission frame belongs to the transmission packets in the whole time slot; a synchronization timestamp, 32 bits, indicating the transmission time of the time slot to which the current symbol transmission frame belongs at the ground repeater; the ground forwarding station identification number is 32 bits and is used for uniquely identifying each ground forwarding station; the transmission power is 8 bits and is used for controlling the output power of each ground repeater station, wherein 0x00-0xff represents 0% to 100% of relative power; outputting a frequency point mask, 16 bits, and controlling whether each ground forwarding station sends information of a specific frequency point, wherein the high 4 bits are reserved for definition, the low 12 bits can be used for indicating whether the number of frequency points are transmitted, 1 indicates transmission, and 0 indicates no transmission; delay fine adjustment, 16 bits, for informing a specific ground forwarding station to fine-adjust data buffer time, the adjustment unit is a time slice of 100ns, wherein, a bit for indicating the adjustment direction is also included, 0 represents advance, and 1 represents delay; reserved field, 152 bits; symbol data, 1152 bits, transmitting the channel-coded and interleaved mobile multimedia broadcast data;
the method also forms a data transmission packet having a structure comprising: 32 bits of transmission packet header, wherein the definition of the transmission packet header conforms to GB/T17975.1 specification; wherein, the PID value is 0x054, the load unit initial indication is 0, the transmission priority value is 1, the transmission scrambling control value is 00, and the adaptation segment control value is 01; symbol data, 1472 bits, transmits the mobile multimedia broadcast data which is channel-coded and interleaved.
According to an embodiment of the present invention, the inverting operation is performed on the first byte of the first transport packet of each group, the first byte of the first transport packet of each group is a synchronization byte, and the synchronization byte is inverted to insert the synchronization information.
According to an embodiment of the present invention, the steps of scrambling the transmission packet after the negation operation, RS encoding the transmission packet after the scrambling process, performing byte convolutional interleaving on the data after RS encoding, and performing convolutional encoding on the output of the convolutional interleaving conform to the GS/T17700 standard, where: in the scrambling operation, the locally generated scrambling sequence is a 15-order shift register pseudo-random binary sequence, and the generated polynomial is: g (x) ═ x15+x14+1, the initial value of the register from high to low is: 000000010101001, wherein the sync byte in the transport packet does not participate in the scrambling operation, but the pseudo-random binary sequence generation is uninterrupted during the sync byte phase; in the operation of RS encoding, RS (204, 188) encoding is adopted to perform RS encoding on the transmission packet after scrambling; in the byte convolution interleaving, the interleaving depth is 12, the interleaving shift register depth is 17, and the delay of the whole interleaving-de-interleaving is 2224 bytes; in the convolutional coding, the convolutional coding with the constraint length of 7 is firstly carried out on the output of the convolutional interleaving, the code rate of the coding is 1/2, and then the puncturing operation is carried out on the output of the convolutional coding, which can be supportedThe convolutional coding rate is: 1/2, 2/3, 3/4, 5/6, 7/8.
According to an embodiment of the present invention, said QPSK mapping the bit stream output by the convolutional encoding comprises QPSK mapping based on Gray code; the modulated QPSK symbol rate is 20M, the QPSK transmission rate is higher than the actual service data rate, therefore, the null packet insertion processing is carried out, and the defined format of the null packet conforms to the GB/T17975.1 standard.
According to an embodiment of the present invention, the synchronization information is two binary pseudorandom sequences driven by a 20M system clock, wherein time coding information is modulated on a first binary pseudorandom sequence, and modulation information on a second binary pseudorandom sequence is reserved; the first path of binary pseudo-random sequence is generated by a linear feedback shift register, and the generating polynomial is as follows: x is the number of13+x4+x3+ x +1, shift register initial value 0110101010010; the second path of binary pseudo-random sequence is generated by a linear feedback shift register, and the generating polynomial is as follows: x is the number of18+x17+x16+x13+x12+x10+x8+x6+x3+ x +1, the shift register initial value is 011010101001010101.
According to an embodiment of the present invention, each pseudo code period on the first path of binary pseudo random sequence modulates one bit of time coding data, and the time information is coded into 256 bits of fixed frame length, and the method forms the following time information codes: frame flag, 16 bits, indicating the start of the frame, consisting of 1110101110010000; time period count, 32 bits, indicates the first bit 1 of the frame relative to the system zero time T0The counting value of (2) is used for assisting the ground supplementary forwarding system to realize synchronous capture; satellite frequency difference, 32 bits, representing the frequency deviation value of the satellite forwarding signal at the current moment, the unit is 0.001Hz, and the satellite frequency difference is used for correcting the carrier frequency of the same-frequency forwarding signal of the ground supplementary forwarding system; PN reset period indication, 6 bits, representing the reset periods of the first path of binary pseudorandom sequence and the second path of binary pseudorandom sequence, wherein the reset period indication field takes values from 0x00-0x 3F, and corresponds to each other1 second to 64 seconds; the reset mark is 1bit, and when the value is 1, the reset mark indicates that the initial position of a first path binary system pseudorandom sequence of the current time coding frame is a reset position; pilot frequency insertion mark, 1bit, with 0 value to indicate that no pilot frequency is inserted in the signal; a value of 1 indicates that a pilot is inserted into the signal, and in this step, the pilot is defined as follows: way I: a, 0, -a, 0,... Q way: 0, a, 0, -a.. the pilot level a on each branch is 1/20 of the data level; information type and data segment, 152 bits, reserved for subsequent service and carrying other system information; CRC, 16 bits, used for coding cyclic redundancy check of information of the frame except the frame mark, and the CRC generator polynomial is: x is the number of16+x12+x5+1；
Resetting according to the content in the PN reset period mark at zero time according to a second period, wherein the content of the first path of binary pseudorandom sequence and the second path of binary pseudorandom sequence shift register are initial values during resetting; the rate of each branch of the data QPSK symbol stream is the same as the rate of a system clock and is synchronous with the system clock, the signal composition of data and a time binary pseudorandom sequence code adopts a superposition mode, the signal level of the binary pseudorandom sequence code of each branch is I, Q equal to 1/20 of the data signal level, the first path of binary pseudorandom sequence is superposed with an I path of signal, and the second path of binary pseudorandom sequence is superposed with a Q path of signal.
By adopting the technical scheme of the invention, the mobile multimedia broadcast symbol data which is subjected to channel coding and interweaving can be combined with certain control information to form a transmission packet with a specific format, so that the transmission packet is orderly and unambiguously distributed to each ground forwarding modulator by the central modulator.
Drawings
In the present invention, like reference numerals refer to like features throughout, wherein,
fig. 1 is a block diagram of a mobile multimedia broadcasting satellite distribution system for implementing a mobile multimedia broadcasting satellite distribution data encapsulation and synchronization method of the present invention;
FIG. 2 is a flow chart of a mobile multimedia broadcast satellite distribution data encapsulation and synchronization method according to an embodiment of the invention;
fig. 3 is a frame structure diagram of a transmission frame according to an embodiment of the present invention;
FIG. 4 is a flow diagram illustrating synchronization information insertion in a method according to an embodiment of the invention;
fig. 5 is a constellation diagram for QPSK mapping a convolutionally encoded output bit stream in a method according to an embodiment of the invention;
FIG. 6a is a block diagram of a sequence generator of a first way binary pseudo-random sequence according to an embodiment of the present invention;
FIG. 6b is a block diagram of a sequence generator for the second way binary pseudo-random sequence according to an embodiment of the present invention.
Detailed Description
The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.
Mobile multimedia broadcast data distribution system
When the data distribution network adopts a satellite transmission mode, the structure of the mobile multimedia broadcast data distribution system is shown in fig. 1, and the multimedia broadcast data distribution system 100 shown in fig. 1 can implement the mobile multimedia broadcast satellite distribution data encapsulation and synchronization method of the present invention.
The mobile multimedia modulator 102 performs OFDM modulation on the channel-coded data, directly transmits the channel-coded data to the geostationary satellite 104 through a Ku band after frequency conversion and amplification, and then transmits an OFDM signal to an S band by the satellite to perform large-area broadcast coverage on the ground, wherein the satellite signal is received by the ground user receiver 108. Referring to fig. 1, the mobile multimedia modulator 102 includes: a Stimi channel coding device 120 for performing channel coding; an OFDM exciter 122 for OFDM-modulating the channel-coded data; the first Ku band variable frequency amplifier 124 directly transmits the OFDM-modulated signal to the geostationary satellite 104 via the Ku band after performing variable frequency amplification.
With continued reference to fig. 1, the channel encoded data is synchronously transmitted to the TDM exciter 126, converted to the Ku band by the second Ku band converter amplifier 128, and transmitted to the sync satellite 104 after data packing format conversion and QPSK modulation (strictly compliant with the GS/T17700 standard) and with the insertion of time synchronization information. Satellite 104 transmits the TDM modulated signal directly in the Ku band to terrestrial repeater 106. The terrestrial repeater 106 demodulates the received TDM-modulated signal, performs OFDM modulation again, broadcasts on the S-band under a specific synchronization condition, and performs supplementary coverage on the satellite direct S-band broadcast signal. Terrestrial user receivers 108 receive the signals retransmitted by terrestrial repeaters 106 as a supplement to the S-band signals transmitted by satellites 104.
In the OFDM exciter 122 of the mobile multimedia modulator 102 of fig. 1, a delay block is added. The addition of the module ensures that service information source information at the same time is respectively modulated into an OFDM signal and a QPSK signal, a fixed time delay is met at the space transmission time, and the delay is used by the ground transponder for signal synchronization between a satellite S-band broadcast signal and a transponder S-band broadcast signal.
Mobile multimedia broadcasting satellite distribution data encapsulation and synchronization method
The invention provides a mobile multimedia broadcasting satellite distribution data encapsulation and synchronization method, refer to fig. 2, which shows a flow chart thereof, in the method 200, a mobile multimedia broadcasting system stipulates that 1 second signals are divided into a predetermined number of time slots, each time slot can adopt different modulation modes, symbol data transmitted in one time slot is taken as a transmission unit, and multimedia broadcasting is transmitted in different bandwidths, and the different bandwidths correspond to different numbers of frequency points, the method 200 comprises:
202. determining the data volume of a transmission frame, taking the number of symbol bytes in a time slot of a single frequency point in a modulation mode with the narrowest bandwidth and the least number of transmitted symbols as a frame, and taking the number of symbol bytes in a time slot of a single frequency point in other bandwidths or modulation modes as an integral multiple of the frame;
204. encapsulating data in a frame into a transmission packet with a preset format, encapsulating the data of each frame into an initial packet and a plurality of data transmission packets, wherein the initial packet comprises control information, and the control information comprises transmission characteristics and synchronization information of the frame;
206. according to the selected bandwidth, sequentially encapsulating data transmitted by different frequency points in the same time slot into a series of transmission packets by taking a frame as a unit, wherein the different frequency points in the same time slot can adopt different modulation modes and have different numbers of transmission frames;
208. dividing the obtained series of transmission packets into a plurality of groups, wherein each group has a predetermined number of transmission packets, performing negation operation on a first byte of a first transmission packet of each group, and inserting synchronization information;
210. scrambling the transmission packet subjected to the negation operation, and performing exclusive or processing on the transmission packet and the local scrambling sequence;
212. RS encoding is carried out on the transmission packet which is processed by the scrambling;
214. carrying out byte convolution interleaving on the data subjected to RS coding;
216. performing convolutional encoding on the output of the convolutional interleaving;
218. performing QPSK mapping on the bit stream output by the convolutional coding;
220. inserting synchronous information into the data after QPSK mapping, wherein the synchronous information comprises two paths of binary pseudorandom sequences, time coding information is modulated on the first path of binary pseudorandom sequences, and modulation information of the second path of binary pseudorandom sequences is reserved;
222. a pilot signal is inserted.
The steps of the present invention are described in detail below.
Encapsulation of distributed data
According to the mobile multimedia broadcasting system, a signal within 1 second is specified to be divided into 40 slots, each of which is 25 ms. Different modulation modes can be adopted in each time slot, including: BPSK, QPSK, 16 QAM. When interleaving bytes and bits, the time slots are also used as cyclic units. The receiver may select only signals in a particular time slot for reception in order to operate with low power consumption. Based on the characteristics of the whole mobile multimedia broadcasting satellite distribution system, the symbol data of one time slot is taken as a transmission unit.
For mobile multimedia broadcasting, the total bandwidth that can be used is 25 MHz. According to the invention. In a mobile multimedia broadcasting system, two signal bandwidths are specified: 2MHz and 8 MHz. Taking into account the total bandwidth of 25MHz, different signal bandwidths will have different numbers of frequency points, the number of frequency points being 12 when the bandwidth is 2MHz, and 3 when the bandwidth is 8 MHz. The system simultaneously stipulates 3 modulation modes: BPSK, QPSK and 16 QAM. Thus, the amount of data that can be transmitted by the various modulation configurations within a slot is shown in the following table:
table 1: symbol data amount in single time slot of mobile multimedia broadcasting system
For the convenience of transmission, the invention defines a transmission frame, called as a TDM frame, and the data amount in one transmission frame is determined as follows, the number of symbol bytes in a time slot of a single frequency point in a modulation mode with the narrowest bandwidth and the least number of transmitted symbols is taken as one frame, and the number of symbol bytes in a time slot of a single frequency point in other bandwidths or modulation modes is an integral multiple of one frame.
Referring to table 1 above, the number of bytes of symbols transmitted in a single time slot at a single frequency point in a 2MHz bandwidth and BPSK modulation mode is selected as the data transmission amount of one frame, that is, one frame is 3456 bytes. Accordingly, it is possible to obtain: when the bandwidth is 2MHz, various modulation modes are adopted, and the data volume of each frequency point in a time slot is as follows: BPSK is 1 frame, QPSK is 2 frames, 16QAM is 4 frames. When the bandwidth is 8MHz, the data volume of each frequency point in a time slot is as follows: BPSK is 5 frames, QPSK is 10 frames, 16QAM is 20 frames.
For each transport frame, 3456 bytes are packed into transport packets for transmission, and according to the present invention, the format of the symbolic data transport package is compatible with the GB/T17975.1 standard, and according to the GB/T17975.1 standard, the size of each transport packet is 188 bytes. For 3456 bytes in a frame, 19 transport packets are required. Thus, the present invention encapsulates every 3456 bytes of information data in 19 data transport packets: each data transmission packet is 188 bytes, wherein the first 4 bytes are transmission packet headers, and the remaining 184 bytes are data fields.
Fig. 3 is a frame structure diagram of a transmission frame according to an embodiment of the present invention, and as shown in fig. 3, 19 data transmission packets constitute a symbol transmission frame, wherein the 184-byte data field portion of the first data transmission packet with number 0 contains 40 bytes of control information, which is called a symbol transmission frame initial packet. The data field portion of the remaining 18 transport packets carry only symbol data, referred to as symbol data transport packets. Thus, the data of one frame is decomposed into 3456 ═ 144+18 × 184, i.e., in the initial packet, 144 bytes of symbol data are included, and in the subsequent data transmission packets, 184 bytes of symbol data are each included. The remaining 40 bytes of the data field portion of the initial packet are used to transmit the control word.
Transmission packet structure
The transport packet of symbolic data is compatible with the GB/T17975.1 transport packet format and consists of a 4-byte header and 184-byte data fields. According to the definition of the symbol transmission frame, the symbol data transmission packets are divided into two types, one type is a symbol transmission frame initial packet which comprises control information and symbol data; the other type is a symbol data transmission packet, which contains only symbol data.
The structure of the data transmission packet in the present invention is as follows, and is shown with reference to table 2:
table 2: symbolic data transmission packet
| Grammar for grammar | Number of bits | Mnemonic symbol |
| symbol_data_transport_packet(){ | ||
| transport_packet_header | 32 | bslbf |
| symbol_data | 1472 | bslbf |
Transmitting packet header Transport _ packet _ header: the transport header is defined to comply with the GB/T17975.1 specification, section 2.4.3.2 table 3 and table 4.
The PID value of the symbol data transport packet is set to 0 × 54.
The load cell start indicator is set to 0.
The transmission priority value is set to 1, which has no meaning for a symbol data transmission packet.
The transport scrambling control value is set to 00 (not scrambled).
The adaptation segment control value is 01 (only payload is transmitted).
The remaining values for each parameter can be referred to GB/T17975.1, section 2.4.3.2.
Symbol data: channel-coded and interleaved mobile multimedia broadcast data. Each byte may contain 8 BPSK symbols, or 4 QPSK symbols, or 216 QAM symbols. The LSB of the symbol data is transmitted first within the byte.
The structure of the transmission initial packet in the present invention is as follows, as shown in reference to table 3:
table 3: initial packet of symbol transmission frame
Transmitting packet header Transport _ packet _ header: the transport header is defined to comply with the GB/T17975.1 specification, section 2.4.3.2 table 3 and table 4.
The payload unit start indicator is set to 1 and the remaining definitions are the same as for the symbolic data transport packet.
Symbol transmission frame identification: defined as 0X05A 0. And in combination with the load unit start indication, the current packet is described as the initial packet of the symbol transmission frame.
Configuration change indication configuration _ change _ indicator: see table 7 for GY/T220.1-2006.
Byte interleaver synchronization flag Byte _ interleaver _ sync _ indicator: see table 7 for GY/T220.1-2006.
Slot number time _ slot _ number: see table 7 for GY/T220.1-2006.
Bin number channel _ number: and indicating the frequency point to which the data in the symbol transmission frame belongs to transmit.
Channel bandwidth indication channel _ bandwidth _ indicator: and marking the signal bandwidth of the current data attribution frequency point, wherein 0 is 2MHz, and 1 is 8 MHz.
Extension control information flag e × extended _ control _ info _ indicator: when the value is set to 1, it indicates that the current symbol transmission frame start packet includes extended control information such as a ground forwarding station identification number group _ station _ id, transmission power transmission _ power, an output frequency point mask output _ channel _ mask, and a delay fine _ tune. When set to 0, the corresponding field is meaningless.
Mapping mode mapping _ mode: which represents the way in which data in the current transmission frame is mapped, is defined in detail in table 4 below:
table 4: mapping schema definition table
| Field | Mapping schema | |
| 0×00 | |
|
| 0×01 | |
|
| 0×02 | |
|
| 0×03-0×3f | Retention |
Distribution mode distribution _ mode: which represents the distribution mode in which the current symbol data is delivered to each ground forwarding station, is defined in detail in table 5 below:
table 5: distribution mode definition table
| Field | Mapping schema | |
| 0×00 | Satellite DVB- |
|
| 0×01 | Satellite DVB- |
|
| 0×02 | Ground national standard | |
| 0×03 | Terrestrial DVB-T/ |
|
| 0×04 | Terrestrial T- |
|
| 0×05 | |
|
| 0×06-0×3f | Retention |
Transport packet number TS _ packet _ number: indicating that the first data transmission packet in the current symbol transmission frame belongs to the second transmission packet in the whole time slot. The detailed value ranges are shown in table 6 below:
table 6: transmission packet number value-taking table
| Bandwidth of signal | Mapping schema | Transport packet number dereferencing | |
| | BPSK | 0 | |
| | QPSK | 0、19 | |
| | 16QAM | 0、19、38、57 | |
| | BPSK | 0、19、38、57、76 | |
| | QPSK | 0、19、38、57、76、95、114、133、152、 171 | |
| | 16QAM | 0、19、38、57、76、95、114、133、152、 171 190、209、228、247、266、285、304、 323、342、361 |
Synchronization timestamp synchronization _ time _ stamp: indicating that the time slot to which the current symbol transmission frame belongs is at the transmitting moment of the terrestrial repeater. Each ground transponder can insert synchronous information according to the TDM modulator to recover a 10MHz reference frequency and second period signal. The time synchronization stamp stores a counter value that is the sum of the system time counter value and the total delay of the system transmission. The time synchronization stamp is matched with the second period signal contained in the synchronization information, and the absolute time of the time slot forwarded by the ground repeater is marked.
Ground _ station _ id: can be used to uniquely identify each ground forwarding station.
Transmission power transmission _ power: may be used to control the output power of each terrestrial re-radiation station. 0x00-0x ff represents a relative power of 0% to 100%.
Outputting a frequency point mask output _ channel _ mask: and controlling whether each ground forwarding station sends the information of the specific frequency point. The upper 4 bits of the 16 bits are reserved to define that the lower 12 bits can be used to indicate whether the frequency bin number is transmitted, a '1' indicates transmission, and a '0' indicates no transmission. For example: '0 x 0003' indicates that the frequency points No. 0 and No. 1 are transmitted, and the rest frequency points are closed; '0 × 0 fff' represents opening all frequency points; '0 x 0000' indicates that all frequency bins are closed.
Fine delay _ fine _ tune: for informing a specific ground forwarding station to fine-tune the data buffering time, the adjustment unit is still a time slice of 100 ns. Msb among 16 bits indicates an adjustment direction, '0' indicates advance, '1' indicates retard, and the remaining bits indicate an adjusted value.
Symbol data: the same as the symbol data definition portion of the symbol data transmission packet.
Data encapsulation of same time slot
As already mentioned, according to the present invention, the transmission unit is in units of slots. One time slot is 25ms, and according to the difference of the selected bandwidths, different numbers of frequency points exist in one time slot, for example, a 2MHz bandwidth is selected, the number of frequency points is 12 after rounding, and correspondingly, if an 8MHz bandwidth is selected, the number of frequency points is 3 after rounding, the total bandwidth is (25MHz)/8 MHz. Because the transmission unit is a time slot, the data of all frequency points in the same time slot need to be encapsulated together into continuous transmission packets for transmission. Furthermore, according to the present invention, different modulation methods can be used in different frequency points of the same timeslot, so that the data amount of different frequency points is different, for example, as mentioned above, 2MHz bandwidth BPSK is used as 1 frame data amount, and 8MHz bandwidth 16QAM is used as 20 frames data amount.
Thus, the present invention provides the following way to pack the data of different frequency points in a time slot into continuous and ordered transmission packets, refer to table 7:
TABLE 7 encapsulation sequence of different frequency points in the same time slot
| TS0 Freq0 | …… | TSn Freq0 | TS0 Freq1 | …… | TSn Freq1 | …… | TS0 Freqn | …… | TSn Freqn |
Firstly, packaging data of a first frequency Freq0, starting from a first frame TS0 of the frequency to a last frame TSn;
and then, sequentially packaging the subsequent frequency points, the second frequency point Freq1 and the like until the last frequency point Freqn.
By way of example, example 1: 8MHz bandwidth, 3 frequency points, the modulation mode is BPSK, QPSK and 16QAM in turn, the encapsulation order is as follows:
first, the first frequency Freq0, the modulation scheme is BPSK, the data amount is 5 frames, and the first frame is first encapsulated, where the above-mentioned contents may be referred to for the encapsulation scheme of each frame. After the first frequency point is packaged, the second frequency point Freq1 is packaged, the modulation mode is QPSK, and the data volume is 10 frames. Finally, the third frequency Freq2, the modulation mode is 16qAM, and the data size is 20 frames. Thus, the slot contains a total of 35 frames of data, which are packed together into a total of 665 consecutive transmission packets.
Example 2, 2MHz bandwidth, 12 frequency points, the modulation mode is QPSK, and the encapsulation order is as follows:
first, the first bin Freq0 has a QPSK modulation scheme and a data amount of 2 frames. And then, sequentially packaging the second frequency point Freq1, the third frequency point Freq2. The data amount of each frequency point is 2 frames. Thus, the slot contains a total of 24 frames of data, which is packed into a total of 456 consecutive transport packets.
At this point, the step 202 and the step 206 in the method 200 are completed, and the data of all the frequency points in one time slot are sequentially encapsulated into a certain number of continuous transmission packets.
Insertion of synchronization information
For a certain number of consecutive transmission packets (i.e. data in a series of TDM frames) obtained in the above step, RS (204, 188) coding and convolutional coding are performed according to the definition in the GS/T17700 standard, and then QPSK modulation is performed, the modulated QPSK symbol rate is 20M, the QPSK transmission rate is higher than the actual traffic data rate, and therefore null-packet insertion processing is required, the defined format of the null packet conforms to the GB/T17975.1 standard, these processing corresponds to step 208 and step 222 in the method 200, and the flow of this part can also be referred to as shown in fig. 4, and includes:
insertion of synchronization information (synchronization head reverse)：
For the series of transport packets obtained above, every 8 transport packets are divided into a group, wherein the first byte (sync byte 47H) of the first transport packet of each group is inverted.
Scrambling operations：
And carrying out exclusive OR processing on the transmission packet subjected to the inversion of the synchronization head and the locally generated scrambling code sequence. The local scrambling code is a Pseudo Random Binary Sequence (PRBS) of a shift register of 15 orders, and the generating polynomial is as follows:
G(x)＝x15+x14+1
the initial value of the register from high to low is: 000000010101001. the sync byte does not participate in the scrambling operation, but the PRBS sequence generation is uninterrupted during the sync byte phase. The scrambling code generation circuit is reset at the first bit after the reverse sync byte B8H, so the PRBS generation cycle is 1503 bytes.
RS encoding：
The scrambled transport stream (TS stream) is protected using RS (204, 188) encoding. The RS (204, 188) is the stage code of the original RS (255, 239). The symbols of the RS code are taken from GF (255), and the field generator polynomial is:
p(x)＝x8+x4+x3+x2+1
the RS code generator polynomial is:
G(x)＝(x+λ0)(x+λ1)(x+λ2)....(x+λ15) Wherein λ 02HEX
Byte convolutional interleaving：
And carrying out byte convolution interleaving on the RS coded data. The interleaving depth is 12, and the interleaving shift register depth is 17. The delay of the entire interleaving-deinterleaving is 2224 bytes (11 transport packets).
Convolutional coding：
The output of the convolutional interleaving is first convolutional encoded with a constraint length of 7, and the code rate of the encoding is 1/2. And then, performing puncturing operation on the output of the convolutional coding, wherein the supported convolutional coding code rate is as follows: 1/2, 2/3, 3/4, 5/6, 7/8.
QPSK mapping：
The convolutionally encoded output bit stream is QPSK mapped based on Gray codes, the mapping constellation being shown in fig. 5.
Synchronization information insertion：
The inter-synchronization signal is two paths of binary pseudo-random sequences driven by a 20M system clock, namely a first path of binary pseudo-random sequence PN1 and a second path of binary pseudo-random sequence PN2, wherein time coding information is modulated on PN1, and modulation information on PN2 is reserved.
PN1 is generated by the linear feedback shift register shown in fig. 6a, generating a polynomial of: x is the number of13+x4+x3+ x +1, the shift register initial value is 0110101010010.
PN2 is generated by the linear feedback shift register shown in fig. 6b, generating a polynomial of: x is the number of18+x17+x16+x13+x12+x10+x8+x6+x3+ x +1, the shift register initial value is 011010101001010101.
Each pseudo code period on the PN1 modulates one bit of time-coded data, the time information is coded into a fixed frame length of 256 bits, and the frame format is defined as shown in table 8:
table 8 time code definition format on PN1
| Frame flag 16bit | Time period count 32bit | Satellite frequency difference 32bit | PN reset period indication 6bit | Reset flag 1bit | Pilot insertion flag 1bit | Information type and data segment 152bit | CRC 16bit |
The information of each segment in table 8 is illustrated as follows:
frame flag 16bit, indicating the start of the frame, consisting of "1110101110010000";
the time period count is 32 bits, which represents that the first bit '1' of the frame is relative to the zero time T of the system0The counting value of (2) is used for assisting the ground supplementary forwarding system to realize synchronous capture;
satellite frequency difference 32bit, which represents the frequency deviation value of the satellite forwarding signal at the current moment, has the unit of 0.001Hz, and is used for correcting the carrier frequency of the same-frequency forwarding signal of the ground supplementary forwarding system;
the PN reset period indication 6bit represents the reset periods of PN1 and PN2, and the reset period indication field takes values from 0 multiplied by 00 to 0 multiplied by 3F and respectively corresponds to 1 second to 64 seconds (the default value is 0 multiplied by 00).
And when the value of the reset mark 1bit is 1, marking the initial position of the first PN1 of the current time coding frame as a reset position.
Pilot frequency insertion mark 1bit, 0 mark signal has no pilot frequency inserted; a 1 indicates that a pilot is inserted into the signal (default value is 1).
152 bits of information type and data segment, reserved (taking value as '01010101' according to bytes) for subsequent service and carrying other system information;
CRC16bit, which is used for the cyclic redundancy check of the information coding of the frame except the frame mark, and the CRC generator polynomial is: x is the number of16+x12+x5+1。
The system is reset according to the content in the PN reset period control word in the second period at the zero moment, and the content of the PN1 and the PN2 shift register is an initial value during the reset.
The system time counter is counted up by the system clock by taking the time as the starting time
After a reset second period, the PN1 and the PN2 return to the initial values at the same time, at the moment, the system time counter is cleared, the system time returns to zero, and the accumulation counting is restarted.
The rate of each branch of the data QPSK symbol stream is the same as the system clock rate and is synchronized to the system clock. The signal composition of the data and the time PN code adopts a superposition mode, and the PN code signal level of each branch of I, Q is 1/20 of the data signal level. PN1 is superposed with the I path signal, and PN2 is superposed with the Q path signal.
Pilot signal insertion：
In order to facilitate the transponder to correctly recover the carrier information, a pilot signal is added to the QPSK baseband signal according to the symbol rate, and the pilot signal is defined as follows:
way I: a, 0, -a, 0.
And a path Q: 0, a, 0, -a.
The pilot level a on each branch is 1/20 of the data level.
By adopting the technical scheme of the invention, the mobile multimedia broadcast symbol data which is subjected to channel coding and interweaving can be combined with certain control information to form a transmission packet with a specific format, so that the transmission packet is orderly and unambiguously distributed to each ground forwarding modulator by the central modulator.
Claims (9)
1. A mobile multimedia broadcasting satellite distribution data encapsulation and synchronization method is characterized in that a mobile multimedia broadcasting system stipulates that 1 second signals are divided into a preset number of time slots, different modulation modes can be adopted in each time slot, symbol data transmitted in one time slot is used as a transmission unit, the mobile multimedia broadcasting is transmitted in different bandwidths, and the different bandwidths correspond to different numbers of frequency points, and the method comprises the following steps:
determining the data volume of a transmission frame, taking the number of symbol bytes in a time slot of a single frequency point in a modulation mode with the narrowest bandwidth and the least number of transmitted symbols as a frame, and taking the number of symbol bytes in a time slot of a single frequency point in other bandwidths or modulation modes as an integral multiple of the frame;
encapsulating data in a frame into a transmission packet with a predetermined format, encapsulating the data of each frame into an initial packet and a plurality of data transmission packets, wherein the initial packet comprises control information, and the control information comprises transmission characteristics and synchronization information of the frame;
according to the selected bandwidth, sequentially encapsulating data transmitted by different frequency points in the same time slot into a series of transmission packets by taking the frame as a unit, wherein the different frequency points in the same time slot can adopt different modulation modes and have different numbers of transmission frames;
dividing the obtained series of transmission packets into a plurality of groups, wherein each group has a predetermined number of transmission packets, performing negation operation on a first byte of a first transmission packet of each group, and inserting synchronization information;
scrambling the transmission packet subjected to the negation operation, and performing exclusive or processing on the transmission packet and the local scrambling sequence;
RS encoding is carried out on the transmission packet which is processed by the scrambling;
carrying out byte convolution interleaving on the data subjected to RS coding;
performing convolutional encoding on the output of the convolutional interleaving;
performing QPSK mapping on the bit stream output by the convolutional coding;
inserting synchronous information into the data after QPSK mapping, wherein the synchronous information comprises two paths of binary pseudorandom sequences, time coding information is modulated on the first path of binary pseudorandom sequences, and modulation information of the second path of binary pseudorandom sequences is reserved;
a pilot signal is inserted.
2. The mobile multimedia broadcast satellite distribution data encapsulation and synchronization method of claim 1,
the system of the mobile multimedia broadcasting stipulates that 1 second signals are divided into 40 time slots, and each time slot is 25 ms;
the mobile multimedia broadcast includes two signal bandwidths: 2MHz for 12 frequency points and 8MHz for 3 frequency points;
the modulation mode adopted by the system of the mobile multimedia broadcast in each time slot comprises the following steps: BPSK, QPSK, 16 QAM.
3. The mobile multimedia broadcast satellite distribution data encapsulation and synchronization method of claim 2,
for a 2MHz bandwidth, the number of symbols per frequency bin for a single time slot is 27648 bits, wherein,
using BPSK modulation mode, the information bit number of single time slot is 27648 bits, the symbol byte number of single time slot is 3456 bytes;
using QPSK modulation mode, the information bit number of single time slot is 55296 bits, the symbol byte number of single time slot is 6912 bytes;
using a 16QAM modulation mode, wherein the information bit number of a single time slot is 110592 bits, and the symbol byte number of the single time slot is 13824 bytes;
for an 8MHz bandwidth, the number of symbols per frequency bin for a single time slot is 138240 bits, wherein,
using BPSK modulation mode, the information bit number of single time slot is 138240 bits, the symbol byte number of single time slot is 17280 bytes;
using QPSK modulation mode, the information bit number of single time slot is 276480 bits, the symbol byte number of single time slot is 34560 bytes;
using a 16QAM modulation mode, wherein the information bit number of a single time slot is 552960 bits, and the symbol byte number of the single time slot is 69120 bytes;
wherein, the data amount of one frame is 3456 bytes,
therefore, when a 2MHz bandwidth is adopted, the number of transmission frames corresponding to each frequency point is:
the BPSK modulation mode is 1 frame;
the QPSK modulation mode is 2 frames;
the 16QAM modulation mode is 4 frames;
when a 2MHz bandwidth is adopted, the number of transmission frames corresponding to each frequency point is respectively as follows:
the BPSK modulation mode is 5 frames;
the QPSK modulation mode is 10 frames;
the 16QAM modulation scheme is 20 frames.
4. The mobile multimedia broadcast satellite distribution data encapsulation and synchronization method of claim 3,
the transmission packets conform to the GB/T17975.1 standard, and each transmission packet comprises 188 bytes, a transmission packet header of 4 bytes and a data field of 184 bytes; wherein,
the method forms an initial packet having the following fields, including:
32 bits of transmission packet header, wherein the definition of the transmission packet header conforms to GB/T17975.1 specification; wherein, the PID value is 0x05a0, the load unit start indication is 1, the combination of PID value and load unit start indication indicates that the transmission packet is an initial packet, the transmission priority value is 1, the transmission scrambling control value is 00, and the adaptation segment control value is 01;
control field, 40 bytes, 320 bits, including:
symbol transmission frame initial packet mark, 16 bits;
reserved field, 8 bits;
configuration change indication, 1bit, in accordance with GY/T220.1-2006 standard;
the byte interleaver synchronization mark is 1bit and conforms to GY/T220.1-2006 standard;
the time slot number is 6 bits and accords with the standard of GY/T220.1-2006;
frequency point number, 8 bits, indicating which frequency point the data in the symbol transmission frame belongs to for transmission;
the channel bandwidth indication is 1bit and indicates the signal bandwidth of the current data attribution frequency point, wherein 0 represents 2MHz, and 1 represents 8 MHz;
the extension control information mark is 1bit, when the extension control information mark is set to be 1, the extension control information mark indicates that the initial packet of the current symbol transmission frame contains the ground forwarding station identification number, the transmission power, the output frequency point mask and the delay fine adjustment, and when the extension control information mark is set to be 0, the extension control information mark indicates that the corresponding field is meaningless;
mapping mode, 6 bits, indicating in which way the data within the current transmission frame is mapped;
a distribution mode, 6 bits, indicating in which distribution mode the current symbol data is delivered to each ground forwarding station;
the transmission packet number is 10 bits, and indicates that the first data transmission packet in the current symbol transmission frame belongs to the transmission packets in the whole time slot;
a synchronization timestamp, 32 bits, indicating the transmission time of the time slot to which the current symbol transmission frame belongs at the ground repeater;
the ground forwarding station identification number is 32 bits and is used for uniquely identifying each ground forwarding station;
the transmission power is 8 bits and is used for controlling the output power of each ground repeater station, wherein 0x00-0xff represents 0% to 100% of relative power;
outputting a frequency point mask, 16 bits, and controlling whether each ground forwarding station sends information of a specific frequency point, wherein the high 4 bits are reserved for definition, the low 12 bits can be used for indicating whether the number of frequency points are transmitted, 1 indicates transmission, and 0 indicates no transmission;
delay fine adjustment, 16 bits, for informing a specific ground forwarding station to fine-adjust data buffer time, the adjustment unit is a time slice of 100ns, wherein, a bit for indicating the adjustment direction is also included, 0 represents advance, and 1 represents delay;
reserved field, 152 bits;
symbol data, 1152 bits, transmitting the channel-coded and interleaved mobile multimedia broadcast data;
the method also forms a data transmission packet having a structure comprising:
32 bits of transmission packet header, wherein the definition of the transmission packet header conforms to GB/T17975.1 specification; wherein, the PID value is 0x054, the load unit initial indication is 0, the transmission priority value is 1, the transmission scrambling control value is 00, and the adaptation segment control value is 01;
symbol data, 1472 bits, transmits the mobile multimedia broadcast data which is channel-coded and interleaved.
5. The mobile multimedia broadcast satellite distribution data encapsulation and synchronization method of claim 4,
and performing an inversion operation on the first byte of the first transmission packet of each group, wherein the first byte of the first transmission packet of each group is a synchronization byte, and inverting the synchronization byte to insert the synchronization information.
6. The mobile multimedia broadcast satellite distribution data encapsulation and synchronization method of claim 5,
the steps of scrambling the transmission packet subjected to the negation operation, RS encoding the transmission packet subjected to the scrambling processing, byte convolution interleaving of the data subjected to the RS encoding, and convolution encoding of the output of the convolution interleaving conform to the GS/T17700 standard, wherein:
in the scrambling operation, the locally generated scrambling sequence is a 15-order shift register pseudo-random binary sequence, and the generated polynomial is: g (x) ═ x15+x14+1, the initial value of the register from high to low is: 000000010101001, wherein the sync byte in the transport packet does not participate in the scrambling operation, but the pseudo-random binary sequence generation is uninterrupted during the sync byte phase;
in the operation of RS encoding, RS (204, 188) encoding is adopted to perform RS encoding on the transmission packet after scrambling;
in the byte convolution interleaving, the interleaving depth is 12, the interleaving shift register depth is 17, and the delay of the whole interleaving-de-interleaving is 2224 bytes;
in the convolutional coding, firstly, convolutional coding with the constraint length of 7 is performed on the output of the convolutional interleaving, the coding rate is 1/2, and then, a puncturing operation is performed on the output of the convolutional coding, and the supportable convolutional coding rate is as follows: 1/2, 2/3, 3/4, 5/6, 7/8.
7. The mobile multimedia broadcast satellite distribution data encapsulation and synchronization method of claim 6,
said QPSK mapping the bit stream output by the convolutional encoding comprises QPSK mapping based on a Gray code;
the modulated QPSK symbol rate is 20M, the QPSK transmission rate is higher than the actual service data rate, therefore, the null packet insertion processing is carried out, and the defined format of the null packet conforms to the GB/T17975.1 standard.
8. The mobile multimedia broadcast satellite distribution data encapsulation and synchronization method of claim 7,
the synchronous information is two paths of binary pseudorandom sequences driven by a 20M system clock, wherein time coding information is modulated on a first path of binary pseudorandom sequence, and modulation information on a second path of binary pseudorandom sequence is reserved;
the first path of binary pseudo-random sequence is generated by a linear feedback shift register, and the generating polynomial is as follows: x is the number of13+x4+x3+ x +1, shift register initial value 0110101010010;
the second path of binary pseudo-random sequence is generated by a linear feedback shift register, and the generating polynomial is as follows: x is the number of18+x17+x16+x13+x12+x10+x8+x6+x3+ x +1, the shift register initial value is 011010101001010101.
9. The mobile multimedia broadcast satellite distribution data encapsulation and synchronization method of claim 8,
modulating one bit time coding data in each pseudo code period on the first path of binary pseudo-random sequence, and coding time information into 256 bits of a fixed frame length, wherein the method forms the following time information codes:
frame flag, 16 bits, indicating the start of the frame, consisting of 1110101110010000;
time period count, 32 bits, indicates the first bit 1 of the frame relative to the system zero time T0For assisting in terrestrial supplementary forwardingThe system realizes synchronous capture;
satellite frequency difference, 32 bits, representing the frequency deviation value of the satellite forwarding signal at the current moment, the unit is 0.001Hz, and the satellite frequency difference is used for correcting the carrier frequency of the same-frequency forwarding signal of the ground supplementary forwarding system;
a PN reset period mark, 6 bits, which represents the reset periods of the first path of binary system pseudorandom sequence and the second path of binary system pseudorandom sequence, wherein the reset period mark field takes values from 0x00-0x 3F, and corresponds to 1 second to 64 seconds respectively;
the reset mark is 1bit, and when the value is 1, the reset mark indicates that the initial position of a first path binary system pseudorandom sequence of the current time coding frame is a reset position;
pilot frequency insertion mark, 1bit, with 0 value to indicate that no pilot frequency is inserted in the signal; a value of 1 indicates that a pilot is inserted into the signal, and in this step, the pilot is defined as follows:
way I: a, 0, -a, 0.
And a path Q: 0, a, 0, -a.
Pilot level a on each branch is 1/20 of the data level;
information type and data segment, 152 bits, reserved for subsequent service and carrying other system information;
CRC, 16 bits, used for coding cyclic redundancy check of information of the frame except the frame mark, and the CRC generator polynomial is: x is the number of16+x12+x5+1；
Resetting according to the content in the PN reset period mark at zero time according to a second period, wherein the content of the first path of binary pseudorandom sequence and the second path of binary pseudorandom sequence shift register are initial values during resetting;
the rate of each branch of the data QPSK symbol stream is the same as the rate of a system clock and is synchronous with the system clock, the signal composition of data and a time binary pseudorandom sequence code adopts a superposition mode, the signal level of the binary pseudorandom sequence code of each branch is I, Q equal to 1/20 of the data signal level, the first path of binary pseudorandom sequence is superposed with an I path of signal, and the second path of binary pseudorandom sequence is superposed with a Q path of signal.
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| CN102474481B (en) * | 2009-07-10 | 2014-09-24 | 日本电气株式会社 | Scrambling method and communication apparatus |
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| CN102511154B (en) * | 2010-05-06 | 2014-12-03 | 华为技术有限公司 | Method, device and communication system for modulation transmission |
| CN102468918A (en) * | 2010-11-01 | 2012-05-23 | 华为技术有限公司 | Wireless transmitting and receiving method and device |
| CN102625089B (en) * | 2012-04-05 | 2014-11-19 | 安徽华东光电技术研究所 | Video wireless transmission system based on ultra wideband technology |
| CN102710386A (en) * | 2012-06-18 | 2012-10-03 | 南京信息工程大学 | Channel coding system for meteorological early warning information processing and working method thereof |
| FR2993369B1 (en) * | 2012-07-11 | 2017-10-13 | Centre Nat D'etudes Spatiales | GNSS RADIO SIGNAL FOR IMPROVED SYNCHRONIZATION |
| CN106165300B (en) * | 2014-04-23 | 2019-11-05 | 三菱电机株式会社 | Communication device, communication system and error correction frame generating method |
| CN107864423A (en) * | 2017-10-19 | 2018-03-30 | 电子科技大学 | A kind of visible light communication wireless sound box based on OFDM |
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| CN111953441B (en) * | 2019-05-15 | 2021-09-10 | 大唐移动通信设备有限公司 | Synchronization method and device |
| CN111786718A (en) * | 2020-06-11 | 2020-10-16 | 中国人民解放军63921部队 | Satellite optical network management and control plane signaling transmission method based on AoS insertion service |
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