CN1398119A - Structure of up-link/down-link signals for interactive diugital information transmission and synchronous access method - Google Patents
Structure of up-link/down-link signals for interactive diugital information transmission and synchronous access method Download PDFInfo
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Abstract
Interactive digit information transmission characterizes up/down stream signals are in the synchronous step structure. Down-stream signals modulated by TDS-OFDM in down-stream channel in which its frame is PN synchronous signals or mixed synchronous signal frame and in up-line channels, up-line signals modulated by multi-user by burst TDMA, in which its frame synchronous code is PN in 6 step m sequence. The up-line signal frame is made up of multi-user signals shared by multiple user composed of cut-in request and data signals, numbered according to the signal frame structure. The up-line channel cut-in is controlled by the down-stream channel after synchronization via random synchronous cut-in code. Up-link/down stream signals frame structures are synchronized with natural time to support bipolar transmission.
Description
Technical field
The interactive digital message transmission uses/and the structure and the synchronous access method of downstream signal belong to digital information transmission technical field, relate in particular to a kind of interactive digital multimedia television broadcasting (Interactive Cable Digital Multimedia/TVBroadcasting, DMB-IC) usefulness on/structure technology of downstream signal.
Background technology
Information sequence again in the transmission course because multipath disturbs and distortion, the signal that produces through linear convolution is with generation time diffusion and intersymbol interference (ISI).
The technology of effectively eliminating intersymbol interference at present has two: time domain equalization and OFDM (OFDM).Time-domain equalizer technology comparative maturity is widely used in the various communications fields, but its complex structure, the cost height; And it is only relatively good to the short ISI effect of time delay.When the cycle of the time delay of intersymbol interference and transmission signals was in the same order of magnitude, the influence of intersymbol interference just became seriously.Therefore, the cycle that prolongs transmission signals can overcome the influence of intersymbol interference effectively, and this is the principle of OFDM elimination intersymbol interference just.It by in a large number on frequency equally spaced subcarrier (establish total N) constitute.The symbol sebolic addressing of serial transmission also is divided into length for being the group of N.N symbol in every group sends then together respectively by N subcarrier-modulated.So OFDM essence is a kind of parallel modulation technique, it prolongs N to symbol period doubly, thereby has improved the resistance to intersymbol interference.
But when having intersymbol interference in the channel, the orthogonality between the OFDM subcarrier can be destroyed, makes receiver can't correctly extract the modulation symbol on each subcarrier.For this reason, when practical application, need to insert a protection interval delta before the cycle at each ofdm signal.The ability of OFDM opposing ISI depends on the length of Δ, and Δ is long more, and the time delay scope that can eliminate ISI is big more.But the band resource of waste is also many more.The OFDM COFDM transmission of the coding that the DVB-T system in Europe adopts.Inserted some " pilot tone " signals in the OFDM frequency spectrum at random, it has synchronously, channel estimating, transmission mode identification and follow the tracks of the effect of phase noise.The data of modulated pilots are the pseudo random sequences that generates from a pseudo-random sequence generator of stipulating in advance.Also stipulate the kinds of protect interval delta in the DVB-T system, the user is taken all factors into consideration at opposing intersymbol interference ability, saving band resource etc. according to actual conditions, improved the flexibility of system.But among the COFDM, pilot tone is inserted after FFT, and FFT calculating needs (pilot tone) at first synchronously, could calculate FFT then.Therefore, COFDM just adopts the iterative approach algorithm, has convergence error and convergence time problem
It does not insert the COFDM pilot signal TDS-OFDM technology, but has utilized spread spectrum, inserts the PN spread-spectrum signal as Domain Synchronous, be used for frame synchronization,, Frequency Synchronization, time synchronized, channel transfer characteristic is estimated and follow the tracks of phase noise etc.It had both had the advantage of OFDM, had avoided the shortcoming of COFDM again.See application number for details and be 01115520.5, publication number is CN1317903A, " time-domain synchronous orthogonal frequency division multiplex modulation method " by name, and application number is 01124144.6, publication number is two Chinese invention patents of CN1334655A, " protection fill method at interval in the orthogonal FDM modulation system " by name.
At present, OFDM has obtained application in the digital video broadcast-terrestrial that has existed (DVB-T) standard and floor synthetic service digital broadcasting (ISDB-T) standard.The TDS-OFDM technology has then only obtained application in ground digital multimedia TV broad cast system, and has applied for Chinese invention patent (application number: 00123597.4) in 2000.It has used synchronous stagewise frame structure in the structure of channel data bag.
The trend that cable digital TV is low owing to its error rate, capacity big, strong security becomes the Digital Television development then has huge prospect as for the TDS-OFDM technology is used in the interactive digital multimedia cable TV system of leading transmission of audio, video, data message.
The signal structure of up-downgoing channel has all adopted synchronous stagewise frame structure in interactive digital multimedia cable TV system, has more the huge superiority with Absolute Time Synchronization.
Summary of the invention
The objective of the invention is to propose a kind of and natural time simple and clear relation is arranged, be convenient to timing system synchronously, and the interactive digital message transmission that can transmit in digital video broadcasting (DVB-C) system is simultaneously used/structure and the synchronous access method of downstream signal.
The invention is characterized in:
With the downstream signal of time-domain synchronization OFDM (TDS-OFDM) modulation, its frame structure is PN sign indicating number synchronizing signal frame or mixes the synchronizing signal frame in the described down channel; The upward signal of modulating with the multi-user's time division multiple access TDS-OFDM that happens suddenly in the described up channel.
The PN sign indicating number synchronizing signal frame of described downstream signal, its frame swynchronization code is a pseudorandom PN sequence, it is that a kind of its initial phase realizes 2 at least
N7 rank n sequences of the frame of the individual mutual difference of-1 (N is the positive integer of selecting), its proper polynomial is defined as x
7+ x
3+ 1, x is a Boolean variable.
The mixing synchronizing signal frame of described downstream signal, its first MPEG-TS bag are the frame swynchronization code bags by PID sign specific in the MPEG-TS packet header, and first byte (sync byte) in the 8th, 16,24 MPEG-TS packet header is that the B8H after being reversed transmits.
The frame swynchronization code of described upward signal is a pseudorandom PN sequence, and it is that a kind of its initial phase realizes 2 at least
M6 rank m sequences of the frame of the individual mutual difference of-1 (M is the positive integer of selecting), its proper polynomial is defined as x
6+ x+1, x are Boolean variable; Its frame is the multiple user signals that a plurality of users share, and it is made of the data-signal that inserts request signal, and quantity separately is different with the signal frame structure.
After described downstream signal was synchronous, inserting at random of up channel controlled by down channel synchronously.
When the structure of descending signal was PN synchronization code signal frame, the synchronous at random access code of up channel was made of the PN sequence on 36 rank.
When the structure of descending signal was hybrid synchronous signal frame, the synchronous code that inserts at random of up channel was made of a PN sequential coding of isolating empty sequence and 46 rank.
It can accomplish the end in view to use proof.
Description of drawings
Fig. 1 is the frame structure according to DMB-IC transmission channel of the present invention.
Fig. 2 is according to x of the present invention
7The Fibonacci molded lines feedback shift register of+x+1.
Fig. 3 is the frame swynchronization code bag according to hybrid synchronous signal frame of the present invention.
Fig. 4 is the data multiplex according to IDFT piece of the present invention.
Fig. 5 is x among the present invention
6The Fibonacci molded lines feedback shift register of+x+1.
Fig. 6 is the signal element of the signal frame body pattern two of up channel among the present invention.
Fig. 7 is x among the present invention
5The LFSR block diagram of+x+1.
Fig. 8 adopts channel RF modulation function block diagram of the present invention.
Embodiment
The present invention proposes a kind of frame structure of interactive digital multimedia cable TV transmission system.Adopt signal frame, frame group, superframe and day frame hierarchy, has unique frame addressing, with Absolute Time Synchronization, have periodically, be consecutive days circulation timei, with natural time simple and clear relation is arranged, be convenient to be convenient to support the uplink synchronous of transmitted in both directions, receive in the timing of supporting low-power dissipation system with timing system (as the GPS) alignment time, be suitable for continuous and bursty data mixed transport, the industry standard of the existing digital cable TV of the compatible China of the down channel of DMB-IC system.If the present invention is used for wireless transmission channel, it is synchronous to carry out the multi-transmitter of single frequency network at physical transport layer.
The present invention is directed to mainly to as if digital television broadcasting, be elaborated below in conjunction with the frame structure of accompanying drawing to interactive digital multimedia cable TV transmission system of the present invention.1. frame structure is described
The frame structure of physical channel as shown in Figure 1.It is synchronous stagewise frame structure.A basic frame is called signal frame.Signal frame is made up of two parts, i.e. frame synchronization and frame.The frame group is defined as a group signal frame, and its first frame definition is a frame group head (control frame).Superframe is defined as a framing group.The top layer of frame structure be called a day frame (Calendar Day Frame, CDF).Physical channel is the cycle, and and Absolute Time Synchronization.1.1 signal frame
In the DMB-IC system/frame structure of down channel is consistent, and determine by down channel.Signal frame is the elementary cell of DMB-IC system frame structure.The baseband signalling of downlink channel signals frame adopts 16QAM, 64QAM and three kinds of modulation systems of 256QAM, and the baseband signalling of uplink channel signals frame adopts QPSK and two kinds of modulation systems of 16QAM.Each signal frame is formed (see figure 1) by frame synchronization and frame two parts.
Two kinds of signal frame supplies of DMB-IC system definition are with selecting.1.1.1 PN sign indicating number synchronizing signal frame
The frame head of PN sign indicating number synchronizing signal frame is the PN sequence.Signal frame is made up of 4000 symbols, and the duration is 529.1us.
The frame synchronization of down channel adopts no inclined to one side QPSK modulation, and is stable synchronous to obtain.It is made up of the PN sequence of 220 symbols, and the duration is 29.1us.The frame of down channel is that 3780 DFT piece is formed by a length, and the duration is 500us.
The frame synchronization of up channel adopts the spread spectrum coding modulation to support the multi-user synchronous.It is made up of the coding PN sequence of 189 symbols.The frame of up channel is that 3780 multi-user DFT piece is formed by a length.1.1.2 hybrid synchronous signal frame
The frame synchronization of down channel and frame wrap as elementary cell with MPEG-TS.The frame synchronization of down channel adopts a MPEG-TS bag with specific PID, is called the frame swynchronization code bag.According to different modulation systems, the frame of down channel is made up of 15,23 or 31 MPEG-TS bags.The maximum length of hybrid synchronous signal frame is 6528 symbols.
The frame synchronization of up channel adopts the spread spectrum coding modulation to support the multi-user synchronous.It is made up of the coding PN sequence of 272 symbols.The frame length of up channel is 6256 symbols.1.2 frame group
A frame group is made of a control frame (frame group head) and 188 signal frames subsequently, and length is 100 milliseconds.10 frame groups are 1 second, are convenient to like this and timing system (for example GPS) alignment time.Each signal frame among the frame group has unique frame number, and it is coded in the frame synchronizing signal.The frame number of control frame (frame group head) is 0, and the frame number of signal frame is 1-188.
An integer MPEG2 TS bag is just in time transmitted each second in system like this, for no priority mode per second 16920 MPEG2TS bags is arranged; For every layer of per second of multimedia multipriority pattern 7520 MPEG2 TS bags are arranged, the highest have 22560 MPEG2TS to wrap.1.3 superframe
A superframe comprises 600 frame groups, and time span is 1 minute.Each frame group in the superframe is by its frame group number unique identification, and it is encoded in each signal frame.As shown in Figure 1, first frame group number of superframe is 0, and last frame group number is 599.1.4 day frame or superframe group
The superframe group is to carry out periodicity the cycle to repeat with a consecutive days, is made up of 1440 superframes, and time span is 24 hours.In Greenwich Mean Time (GST) 0:0:0 AM or other selected reference time, physical channel frame structure is reset and begins a new day frame.2. the frame synchronization PN sequence of the signal frame structure 2.1 PN sign indicating number synchronizing signal frames of down channel
Each signal frame among the downlink frame group has unique frame synchronization sequence.So frame synchronization can be used for identification as the frame synchronization feature of signal specific frame.
The PN sequence definition is one 7 rank m sequence, realizes that with Fibonacci molded lines feedback shift register (LFSR) its proper polynomial is defined as x
7+ x
3+ 1, the LFSR block diagram is shown in Fig. 2.For a specific signal frame, its signal frame number is decided by the initial phase of PN sequence.
After " 0 " was arrived "+1 " value and " 1 " and arrive the mapping that " 1 " be worth, the PN sequence transformation was the binary signal of non-return-to-zero.2.2 the frame swynchronization code bag of hybrid synchronous signal frame and frame identifier
In the frame group of down channel, the frame synchronizing signal of each signal frame is made of synchronous code bag and identifier.First MPEG-TS package definition of each signal frame is the frame swynchronization code bag, though the frame swynchronization code bag is the MPEG-TS form, it inserts in physical layer, as the signaling channel of DMB-IC, as shown in Figure 3.The frame swynchronization code bag of DMB-IC is by the specific PID sign in the MPEG-TS packet header, and first byte (sync byte) in this packet header is reversed back (B8H) transmission.
The signal frame identifier of down channel is made up of 16 symbols, the signal frame number of coded representation 0-252.The modulating mode of down channel is depended in the position of signal frame identifier symbol, and is as shown in table 1.The position of first symbol in table 1 assumes synchronization packet header is 0.
The position of the frame identifier of the hybrid synchronous signal frame of table 2
| Sign bit character position/pattern | ??16QAM | ?64QAM | ??256QAM |
| ??????1 | ????24 | ????16 | ????12 |
| ??????2 | ????48 | ????32 | ????24 |
| ??????3 | ????72 | ????48 | ????36 |
| ??????4 | ????96 | ????64 | ????48 |
| ??????5 | ????120 | ????80 | ????60 |
| ??????6 | ????144 | ????96 | ????72 |
| ??????7 | ????168 | ????112 | ????84 |
| ??????8 | ????192 | ????128 | ????96 |
| ??????9 | ????216 | ????144 | ????108 |
| ??????10 | ????240 | ????160 | ????120 |
| ??????11 | ????264 | ????176 | ????132 |
| ??????12 | ????288 | ????192 | ????144 |
| ??????13 | ????312 | ????208 | ????156 |
| ??????14 | ????336 | ????224 | ????168 |
| ??????15 | ????360 | ????240 | ????180 |
| ??????16 | ????384 | ????256 | ????192 |
Signal frame identifier sign bit represents that with bpsk signal its 16 constitute two octets, and two octets are identical, are used for representing signal frame number.2.3 the signal frame body of PN sign indicating number synchronizing signal frame
In down channel, the baseband signal of a frame is a DFT (discrete fourier transform) piece.This DFT piece has 3780 sample values in its time domain, they are contrary discrete fourier transforms of 3780 subcarriers in the frequency domain.DFT piece time-domain signal continues 500us, and it is spaced apart 2KHz corresponding to adjacent sub-carrier in the frequency domain.
In a frame, 3780 symbols (carrier wave) are arranged, preceding 9 symbols (symbol 0-8) and back 9 symbols (symbol 3771-3779) are used to carry transmission parameter signaling, and (Transmission Parameter Signaling, TPS), remaining 3762 symbols are used for the payload user data transmission.2.4 the signal frame body of hybrid synchronous signal frame
In down channel,, can there be 15,23 or 31 MPEG-TS bags to be used for transmitting multi-medium data in the frame according to the selection of modulation system.First byte (sync byte) in the 8th, 16,24 MPEG-TS packet header in the frame is reversed back (B8H) transmission.2.5 frame group number
Number (Frame Group Number FGN) has 9 bits to the frame group.To PN sign indicating number synchronizing signal frame, the frame group number is coded among the transmission parameter signaling TPS.To hybrid synchronous signal frame, the frame group number is coded in the frame swynchronization code bag.2.6 the transmission parameter signaling (TPS) of PN sign indicating number synchronizing signal frame
Transmission parameter signaling TPS is embedded in the frame of signal frame, in order to the transfer system configuration information.It is made up of 36 bits, and is mapped as 18 symbols with QPSK.
18 TPS symbols and 3762 data symbols form the frame of signal frame, and give the frequency diversity device, are mapped as corresponding subcarrier.
TPS repeats in each signal frame in the frame group.Transmission mode only could change when new frame group begins.
The definition of TPS sees Table 2.
Table 2 transmission parameter signaling (TPS) table
2.7 the symbol in the PN sign indicating number synchronizing signal frame DFT piece is multiplexing
| Bit Allocation in Discrete | Bit number | Purpose/content |
| Bit0-Bit8 | ????9 | Frame group number |
| Bit9-Bit10 | ????2 | Modulation system |
| Bit11-Bit21 | ????11 | Hyper Frame Number |
| Bit22-Bit35 | ????14 | Keep |
Complex symbol in DFT piece by shown in Figure 4 carry out multiplexing.It is the symbol sebolic addressing before the frequency diversity.3. the frame synchronization PN sequence of signal frame structure 3.1 up channels of up channel
Being used for the synchronous PN sequence definition of up channel is the m sequence on 6 rank, realizes that with Fibonacci molded lines feedback shift register (LFSR) its proper polynomial is defined as x
6+ x+1, the LFSR block diagram is shown in Fig. 5.Initial condition will be determined the phase place of the m sequence that generates, and be defined as 111111.
After " 0 " was arrived "+1 " value and " 1 " and arrive the mapping that " 1 " be worth, the PN sequence transformation was the binary signal of non-return-to-zero.3.2 the access synchronous code at random of up channel
Controlling by down channel synchronously of up channel.According to the signal frame mode that down channel adopts, the access synchronous code at random of up channel is defined as follows.
For down channel is the situation of PN synchronization code signal frame, and the synchronous code that inserts at random of up channel is made up of the PN sequential coding on 36 rank.In this case, the access synchronous code at random that to have 8 different length be 189 symbols.
For down channel is the situation of hybrid synchronous signal frame, and the synchronous code that inserts at random of up channel is made up of a PN sequential coding of isolating empty sequence and 46 rank.In this case, the access synchronous code at random that to have 16 different length be 272 symbols.Isolating empty sequence is made up of 20 null symbols.
The synchronizing sequence of up channel control frame (frame group head) adopts and is encoded to 000 or 0000 PN sequence, by user's use of DMB-IC system front end appointment.The signal frame body of the up channel when 3.3 down channel is PN sign indicating number synchronizing signal frame
In up channel, the baseband signal of a frame is shared by the multi-user.Multiple user signals divides two kinds, and a kind of is to insert request signal; Another kind is a data-signal.The frame of up channel is made of signal element, and each signal element is made up of 378 symbols.Inserting request signal is made of a signal element.Data-signal is made of a plurality of signal elements.The signal frame frame of up channel can be made up of 10 signal elements at most.
At least to there be one and can only have seven to insert request signals at most in the frame of up channel.First signal element of the frame of up channel always inserts request signal.Access request signal number in the frame of up channel is by the decision of the control signal of down channel.It may be empty inserting request signal, also may be the mixing of a plurality of users' access request signal.
Seven data-signals can only be arranged at most in the frame of up channel, and with insert request signal and count sum and can not surpass 8.Data-signal number in the frame of up channel and structure thereof are by the decision of the control signal of down channel.Data-signal is distributed to the sole user, can not share with other users.
The frame of up channel control frame (frame group head) is made up of empty sequence, PN sequence, registering signal and the empty sequence of coding.The PN sequence of coding is represented 52 binary codes, is that length that the m sequence by 52 6 rank constitutes is 3276 sequence.The length of registering signal unit is 384 symbols.The length of former and later two empty sequences all is 60 symbols.The signal frame body of the up channel when 3.4 down channel is hybrid synchronous signal frame
In up channel, the baseband signal of a frame is shared by the multi-user.Multiple user signals divides two kinds, and a kind of is to insert request signal; Another kind is a data-signal.The frame of up channel is made of 16 signal elements.Each signal element has 391 symbols, and as shown in Figure 6, (the m sequence on 5 rank, its proper polynomial is defined as x by the PN sequence of 12 null symbols, 31 symbols for it
5+ x+1, initial condition is 11111, the LFSR block diagram is shown in Fig. 7) and 348 coded data symbols compositions.Inserting request signal is made of a signal element.Data-signal is made of a plurality of signal elements.
At least to there be one and can only have 15 to insert request signals at most in the frame of up channel.First signal element of the frame of up channel always inserts request signal.Access request signal number in the frame of up channel is by the decision of the control signal of down channel.It may be empty inserting request signal, also may be the mixing of a plurality of users' access request signal collision.
15 data-signals can only be arranged at most in the frame of up channel, and with insert request signal count sum can not be above 16.Data-signal number in the frame of up channel and structure thereof are by the decision of the control signal of down channel.Data-signal is distributed to the sole user, can not share with other users.
The frame of up channel control frame (frame group head) is made up of PN sequence, registering signal and the empty sequence of empty sequence, coding.The PN sequence of coding is represented 96 binary codes, is that length that the m sequence by 96 6 rank constitutes is 6048 sequence.The length of registering signal unit is 348 data symbols.The length of former and later two empty sequences all is 104 symbols.4. physical channel is synchronous
The DMB-IC physical channel mainly be meant synchronously down channel synchronously.4.1 the addressing in the channel frame structure
The signal frame of down channel can be discerned with its frame synchronization sequence or frame synchronization identifier.
In the superframe frame group to compile be 0 to No. 599, can number discern by the frame group in identification of the TPS in the signal frame DFT piece or the frame swynchronization code bag.
Superframe in day frame is compiled maximum number since 0, and it can be discerned by the related data of GST time or signal frame.4.2 the signal frame of channel is synchronous
In synchronizing process, it is synchronous that the frame synchronization PN sequence of down channel is used to signal frame, or first byte (sync byte) 47H in the MPEG-TS packet header or its reverse B8H at first be used as bag synchronously, and it is synchronous that the frame synchronization identifier will be used to signal frame then.4.3 signal frame group synchronization
In synchronizing process, the frame synchronizing signal in the control frame of down channel (frame group head) is used to the signal frame group synchronization.4.4 the superframe-synchronized of physical channel
In synchronizing process, the downlink frame group energy in the superframe is discerned by its frame group head.4.5 up channel is synchronous in the physical channel
Up channel be synchronously on the synchronous basis of down channel, undertaken by bidirectional protocol.5. insert at random
It is to carry out on the synchronous basis of down channel that the upward signal of DMB-IC physical channel inserts.5.1 user's registration
The user of DMB-IC system is carrying out must being in enrollment status when upward signal inserts.The user need with system registry and more two kinds of means of new record register.5.1.1 system registry
System registry is undertaken by the user is spontaneous, has randomness.When having the DMB-IC user terminal startup work of up channel function, obtain down channel synchronously after, carry out system registry at once.The frame group head of up channel is used for carrying out system registry.Because the randomness of system registry may exist a plurality of users to carry out the situation of system registry simultaneously.Thereby cause the system registry failure.Therefore, system registry will be carried out repeatedly repeatedly sometimes, until the system registry success.5.1.2 new record more
More new record is to carry out under the control of system, has periodically.5.2 insert request
The user of DMB-IC system is carrying out must inserting request when upward signal inserts.The request of access is divided into initial request and repetitive requests.5.2.1 initial request
To be that the user is spontaneous carry out initial request, has randomness.5.2.2 request again
Again request is carried out under being not reply the situation of initial request in system.5.3 upward signal transmits
After up transmission request was accepted by system, user terminal sent the mode of upward signal according to the system front end appointment.5.3.1 normal termination
Receive user's upward signal when system front end after, if, then notify user's normal termination through the no error of transmission of check.5.3.2 retransmit
Receive user's upward signal when system front end after,, then notify the user to retransmit by specified scheme if find error of transmission through check.
Told about basic composition of the present invention above, realized the function model machine of native system at present with FPGA.The uplink and downlink signals of DMB-IC system is to adopt Domain Synchronous TDS-OFDM (Time-Domain Synchronous Orthogonal FrequencyDivision Multiplexing) modulation system, and the frame synchronization sequence of time domain orthogonal coding as the OFDM protection at interval.The frame synchronization PN sequence of these codings is used for channel estimating and system synchronization, and Frame addressing and location positioning.At receiving terminal, after the PN sequence was removed, the ofdm signal that the PN sequence is filled just was equivalent to the ofdm signal of zero padding.
The system that the present invention realizes follows these steps to carry out:
1) will be carried out the FEC coding by the number of delivering a letter, be mapped as symbol (QPSK or mQAM) stream then;
2), symbols streams is mapped to the relevant position of DFT data block according to the regulation of system;
A DFT piece is become by 3780 sub carrier group, and subcarrier spacing is 2kHz.Therefore, the RF bandwidth that takies is 7.56MHz.Then the DFT data block is carried out frequency diversity and handle, by 7560 point, inverse fast Fourier transform (IFFT) frequency-region signal is transformed to time domain at last.Time domain DFT piece is represented (2 times to the Nyquist sampling) by 7560 sample values.
3) the DFT data block being carried out frequency diversity handles;
4) adopt IDFT the DFT data block to be transformed to the discrete sample value of time domain;
5) with the frame synchronization PN sequence and the time domain DFT data block combinations of coding, constitute the TDS-OFDM signal frame;
6) adopt square root raised cosine (SRRC) filter to carry out pulse-shaping, rolloff-factor α gets 0.15;
7) the baseband signal frame is up-converted on the RF carrier wave;
The TDS-OFDM modulated RF signal is described by following formula:
S(t)＝Re[exp(2πF
ct)U(t)]
Wherein, S (t)-RF signal
F
c-carrier frequency
U (t)-pulse-shaping baseband signal is defined by following formula:
U(t)＝P(t)*[FS(i)+IDFT(k)]
Wherein, the pulse-shaping function of P (t)-SRRC filter
FS (i)-frame synchronization sequence
IDFT (k)-the above step of IDFT piece sample value as shown in Figure 8.
Thereby, the present invention has unique frame addressing, with Absolute Time Synchronization, have periodically (be consecutive days circulation timei), simple and clear relation is arranged, be convenient to timing system (as the GPS) alignment time with natural time, be convenient to support the uplink synchronous of transmitted in both directions, be convenient to support that low-power dissipation system regularly receives, be suitable for continuously and the bursty data mixed transport, the industry standard of the existing digital cable TV of the compatible China of the down channel of DMB-IC system.If the present invention is used for wireless transmission channel, it is synchronous to carry out the multi-transmitter of single frequency network at physical transport layer.
Claims (7)
1, the interactive digital message transmission is used/structure of downstream signal, its signal is synchronous stagewise frame structure, it is characterized in that: with the downstream signal of time-domain synchronization OFDM (TDS-OFDM) modulation, its frame structure is PN sign indicating number synchronizing signal frame or mixes the synchronizing signal frame in the described down channel; The upward signal of modulating with the multi-user's time division multiple access TDS-OFDM that happens suddenly in the described up channel.
2, interactive digital message transmission according to claim 1 is used/structure of downstream signal, it is characterized in that: the PN sign indicating number synchronizing signal frame of described downstream signal, and its frame swynchronization code is a pseudorandom PN sequence, it is that a kind of its initial phase realizes 2 at least
N7 rank n sequences of the frame of the individual mutual difference of-1 (N is the positive integer of selecting), its proper polynomial is defined as x
7+ x
3+ 1, x is a Boolean variable.
3, interactive digital message transmission according to claim 1 is used/structure of downstream signal, it is characterized in that: the mixing synchronizing signal frame of described downstream signal, its first MPEG-TS bag is the frame swynchronization code bag by PID sign specific in the MPEG-TS packet header, and first byte (sync byte) in the 8th, 16,24 MPEG-TS packet header is that the B8H after being reversed transmits.
4, interactive digital message transmission according to claim 1 is used/structure of downstream signal, and it is characterized in that: the frame swynchronization code of described upward signal is a pseudorandom PN sequence, and it is that a kind of its initial phase realizes 2 at least
M6 rank m sequences of the frame of the individual mutual difference of-1 (M is the positive integer of selecting), its proper polynomial is defined as x
6+ x+1, x are that its frame of Boolean variable is the multiple user signals that a plurality of users share, and it is made of the data-signal that inserts request signal, and quantity separately is different with the signal frame structure.
5, interactive digital message transmission according to claim 1 is used/structure of downstream signal and the synchronous cut-in method that proposes is characterized in that: described downstream signal synchronously after, inserting at random of up channel controlled by down channel synchronously.
6, interactive digital message transmission according to claim 5 is used/structure of downstream signal and the synchronous cut-in method that proposes, it is characterized in that: when the structure of descending signal was PN synchronization code signal frame, the synchronous at random access code of up channel was made of the PN sequence on 36 rank.
7, interactive digital message transmission according to claim 5 is used/structure of downstream signal and the synchronous cut-in method that proposes, it is characterized in that: when the structure of descending signal was hybrid synchronous signal frame, the synchronous code that inserts at random of up channel was made of a PN sequential coding of isolating empty sequence and 46 rank.
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| CN 02129309 CN1190051C (en) | 2002-08-30 | 2002-08-30 | Structure of up-link/down-link signals for interactive diugital information transmission and synchronous access method |
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| CN1190051C CN1190051C (en) | 2005-02-16 |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7619964B2 (en) | 2004-07-08 | 2009-11-17 | Nokia Corporation | High doppler channel estimation for OFD multiple antenna systems |
| CN102025479A (en) * | 2009-09-21 | 2011-04-20 | 西安英诺视通信息技术有限公司 | Sample point interweaving multi-path discrete signal time division multiplexing method |
| CN102075236A (en) * | 2010-12-08 | 2011-05-25 | 北京交通大学 | TDD WMNs-based equipment experimental prototype |
| CN108282891A (en) * | 2017-01-05 | 2018-07-13 | 华为技术有限公司 | Method, the network equipment and the terminal device of transmission data |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100405752C (en) * | 2006-01-12 | 2008-07-23 | 北京飞利信电子技术有限公司 | Radio vote system using frequency hopping communication |
-
2002
- 2002-08-30 CN CN 02129309 patent/CN1190051C/en not_active Expired - Fee Related
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7619964B2 (en) | 2004-07-08 | 2009-11-17 | Nokia Corporation | High doppler channel estimation for OFD multiple antenna systems |
| CN102025479A (en) * | 2009-09-21 | 2011-04-20 | 西安英诺视通信息技术有限公司 | Sample point interweaving multi-path discrete signal time division multiplexing method |
| CN102025479B (en) * | 2009-09-21 | 2013-09-18 | 西安英诺视通信息技术有限公司 | Sample point interweaving multi-path discrete signal time division multiplexing method |
| CN102075236A (en) * | 2010-12-08 | 2011-05-25 | 北京交通大学 | TDD WMNs-based equipment experimental prototype |
| CN102075236B (en) * | 2010-12-08 | 2013-11-13 | 北京交通大学 | TDD WMNs-based equipment experimental prototype |
| CN108282891A (en) * | 2017-01-05 | 2018-07-13 | 华为技术有限公司 | Method, the network equipment and the terminal device of transmission data |
| CN108282891B (en) * | 2017-01-05 | 2020-12-22 | 华为技术有限公司 | Data transmission method, network equipment and terminal equipment |
| US10931416B2 (en) | 2017-01-05 | 2021-02-23 | Huawei Technologies Co., Ltd. | Data transmission method, network device, and terminal device |
| US11683134B2 (en) | 2017-01-05 | 2023-06-20 | Huawei Technologies Co., Ltd. | Data transmission method, network device, and terminal device |
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| Publication number | Publication date |
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| CN1190051C (en) | 2005-02-16 |
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