CN101018105B - A classified modulating mobile digital multimedia broadcast signal transmission system and method - Google Patents

Abstract

The invention discloses a mobile digital multimedia broadcast signal transmission system comprising: two groups of channel decoders respectively receiving a first and a second groups of data flows and transforming bit flows after coding and interleaving treatment to the data flows; a constellation mapper used for combining the two groups of bit flows output by the two groups of channel decoders and mapping into QAM mode signal flows, allocating two bits with maximal energy to the first group of data flows, and allocating other bits with low energy to the second group of data flows, and increasing the energy of the two bits with the maximal energy; an OFDM signal forming module used for forming OFDM signals according to the signals formed by the constellation mapper; a framing module used for adding beacon into the OFDM signals and forming transmission frame; an up-conversion module used for up conversing the transmission frame and generating RF signal to be transmitted. The invention can provide data transmission with different quality grades for different service demands.

Description

A kind of classified modulating mobile digital multimedia broadcast signal transmission system and method

Technical field

The present invention relates to the mobile digital multi-media broadcast field, relate in particular to signal transmission system and method in a kind of mobile digital multi-media broadcast.

Technical background

OFDM (OFDM) is a kind of known multi-carrier modulation method, and its main thought is: channel is divided into some orthogonal sub-channels, converts high-speed data signal to parallel low speed sub data flow, be modulated on each subchannel and transmit.Orthogonal signalling can separately can reduce the phase mutual interference ICI between the subchannel like this through adopt correlation technique at receiving terminal.Signal bandwidth on each subchannel is less than the correlation bandwidth of channel, so can regard the flatness decline as on each subchannel, thereby can eliminate intersymbol interference.And because the bandwidth of each subchannel only is the sub-fraction of former channel width, it is relatively easy that channel equalization becomes.OFDM has been used in the several wireless system standards at present, for example European DAB and digital video broadcast system (DAB, DVB-T, DVB-H), 5GHz high data rate WLAN (IEEE802.11a, HiperLan2, MMAC) system etc.

In that some have adopted in the multi-media broadcasting system of OFDM at present, also there are some defectives and unsatisfactory place.CMMB is the mobile transmission system to handheld terminal; Main challenge is that design supports low-power consumption, high dynamic terminal equipment to receive various speed and categorical data stream; And multi-media broadcasting system of the prior art only uses unified code rate and interleaving mode to handle to data flow; So; When receiver ambient signal of living in is bad, can only solve the quality problems of multi-medium data such as image, and the transfer of data of different quality grade can not be provided according to different demands for services through the approach that increases the receiver power consumption; In addition, in the frame structure of some multi-media broadcasting systems, do not have independently synchronization signal designs, increased the lock in time and the synchronization accuracy of receiver; Moreover scrambler design has only a kind ofly in these broadcast systems, also is unfavorable for single frequency network.

For solution comprises many defectives that the problems referred to above are interior again, need a better mobile digital multi-media broadcast transfer scheme.

Summary of the invention

In view of this, the object of the present invention is to provide the transfer system and the method for signal and communication in a kind of mobile digital multimedia broadcast system.

In order to achieve the above object, the present invention provides scheme following:

A kind of mobile digital multimedia broadcast signal transmission system, its characteristics are that it comprises:

Two groups of channel encoders receive first, second group data stream respectively and data flow is converted to bit stream after coding and interleaving treatment;

Constellation mapper; Be mapped as the symbols streams of QAM pattern after two groups of bit streams combinations that are used for said two groups of channel encoders are exported; The dibit that energy wherein is maximum is distributed to first group data stream; Give second group data stream with other low-yield Bit Allocation in Discrete, and increase the energy of the maximum dibit of energy;

The OFDM symbol forms module, and the symbols streams that is used for forming according to said constellation mapper forms the OFDM symbol;

Become frame module, be used for said OFDM symbol is added beacon to form transmission frame;

The up-conversion module is used for said transmission frame is carried out the radiofrequency signal that up-conversion is used to launch with generation.

Further, above-mentioned QAM pattern is 16QAM or 64QAM pattern;

Further, when above-mentioned QAM pattern was the 16QAM pattern, bit-order was b0b1b2b3, and b0b1 is distributed to first group data stream, and b2b3 is distributed to second group data stream;

Further, said each channel encoder all includes outer encoder, external interleaver, inner encoder and interleaver, and first and second group data stream is handled back output through outer encoder, external interleaver, inner encoder and interleaver successively;

Further, said each channel encoder has different coding speed and interleaving mode;

Further, described two-way channel encoder is different, and every path channels encoder includes only the part unit in outer encoder, external interleaver, inner encoder and the interleaver;

Further, said outer encoder adopts binary system BCH code or RS sign indicating number;

Further, said external interleaver only interweaves to the checking symbol of RS sign indicating number, and the information symbol to the RS sign indicating number does not interweave;

Further, said inner encoder adopts LDPC sign indicating number or QC-LDPC sign indicating number;

Further, the subcarrier that said OFDM symbol forms module with the corresponding relation of data and pilot tone is: when (1) was 8MHz when the channel width position, effectively subcarrier number was 0～3075 or when the channel width position was 2MHz, effective subcarrier number was 0～627; (2) insert scattered pilot, in even number OFDM symbol, since 0, effective subcarrier that numbering satisfies the 8*K form is a scattered pilot, and wherein K is an integer; In odd number OFDM symbol, effective subcarrier that numbering satisfies the 8*K+4 form is a scattered pilot, and wherein K is an integer; (3) add CP continuous pilot; (4) modulate effectively-1537～1538 in the corresponding IFFT conversion of subcarrier 0～3075 difference, or-313～314 in the corresponding IFFT conversion of 0～627 difference;

Further, said scattered pilot increases the 2-4dB transmitting power;

Further, said beacon comprises two identical synchronizing signals and identification signal of transmitter.

The present invention is through adopting the mode of dual input hierarchical modulation; In to the QAM modulation that energy is maximum two bits or four bits separate with all the other bits; Modulate different code streams respectively; These two code streams can have different coding speed and interleaving mode; The energy that can also increase simultaneously two maximum bits of energy carries out different modulation to the data code flow of different-energy, makes that receiving function reaches better reception, and can be the transfer of data that different demands for services provides the different quality grade; Moreover the insertion of synchronizing signal has been accelerated synchronizing speed and the precision of receiver and can be used for channel estimating in the beacon infrastructure; Also have, the present invention selectively increases transmitting power and is used to improve the receiver channel estimation performance in scattered pilot, make that the channel estimating of receiving terminal is more accurate, and the demodulation performance of receiving terminal also improves a lot.

Come the present invention with embodiment with reference to the accompanying drawings and include but not limited to that above-mentioned plurality of advantages carries out more detailed explanation.

Description of drawings

Fig. 1 is the block diagram of a kind of execution mode of mobile digital multimedia broadcast signal transmission system of the present invention;

Fig. 2 is the block diagram of the channel coding module of mobile digital multimedia broadcast signal transmission system of the present invention;

Fig. 3 A, 3B are respectively 16QAM and 64QAM pattern constellation mapping sketch map;

Fig. 4 is data subcarrier, scattered pilot and the CP continuous pilot subcarrier allocation figure at the OFDM symbol;

Fig. 5 is the concrete structure that linear feedback shift is deposited;

Fig. 6 is B _fOFDM sub-carrier structure figure during=8MHz;

Fig. 7 is B _fOFDM sub-carrier structure figure during=2MHz;

Fig. 8 is that time slot is divided and frame assumption diagram;

Fig. 9 is a beacon infrastructure;

Figure 10 is the structure chart of OFDM symbol;

Figure 11 is RS coding and single fisherman's knot composition.

Embodiment

According to an aspect of the present invention, the present invention proposes a kind of a kind of execution mode of mobile digital multimedia broadcast signal transmission system, it is said specifically to please refer to Fig. 1.Generally speaking, said mobile digital multimedia broadcast signal transmission system comprises that two groups of channel encoders 10,11, constellation mapper 20, OFDM symbol form module 30, become frame module 40, up-conversion module 50.Said two groups of channel encoders 10,11 receive first, second group data stream respectively and after coding and interleaving treatment, convert data flow into bit stream.Be mapped as the symbols streams of QAM pattern after two groups of bit streams combinations that said constellation mapper 20 is used for said two groups of channel encoders are exported.Said OFDM symbol forms module 30 and is used for forming the OFDM symbol according to the symbols streams of said constellation mapper formation.Said one-tenth frame module 40 is used for said OFDM symbol is added beacon to form transmission frame.Said up-conversion module 50 is used for said transmission frame is carried out the radiofrequency signal that up-conversion is used to launch with generation.

According to another aspect of the present invention; The present invention proposes a kind of a kind of execution mode of mobile digital multi-media broadcast signal transmission method; Said a kind of mobile digital multi-media broadcast signal transfer approach comprises: a) receive first, second group data stream respectively and after coding and interleaving treatment, convert data flow into bit stream; B) after combining, two groups of bit streams said two groups of channel encoders being exported are mapped as the symbols streams of QAM pattern; C) symbols streams that forms according to said constellation mapper forms the OFDM symbol; D) said OFDM symbol is added beacon to form transmission frame; E) said transmission frame is carried out launching after the up-conversion.

Below main pass order according to signal flow successively the embodiment of each functional module is described in detail.

1.1 chnnel coding

Specifically please referring to Fig. 2; Each channel encoder all includes outer encoder 101, external interleaver 102, inner encoder 103 and inner encoder 104, and first and second group data stream is handled back output through outer encoder, external interleaver, inner encoder and inner encoder successively.Said first group data stream and second group data stream can be to be formed by same data distribution, and wherein group data stream is represented the maximum dibit of energy, and second group data stream is represented other low-yield bits.In a concrete embodiment, said data flow can be a video data stream.

1.1.1 outer coding and outer interweaving

Said outer encoder can adopt binary system BCH code or RS sign indicating number.The binary system BCH code can adopt the shortened code (240,216) of (255,231).The RS sign indicating number can adopt code length be 240 bytes RS (240, K) shortened code, (255, M) systematic code produces through brachymemma this yard, wherein M=K+15 by original RS.(240, K) sign indicating number provides 4 kinds of patterns to RS, is respectively K=240, K=224, K=192, K=176.

Shortened code (240, K) can adopt following mode to encode: at K input information byte (m ₀, m ₁..., m _K-1) 15 complete " 0 " bytes of preceding interpolation, be configured to original (255, M) list entries of systematic code (0 ... 0, m ₀, m ₁..., m _K-1), coding back generation code word (0 ... 0, m ₀, m ₁..., m _K-1, p ₀, p ₁..., p _255-M-1), from code word, leave out the byte of interpolation again, promptly obtain the shortened code (m of 240 bytes ₀, m ₁..., m _K-1, p ₀, p ₁..., p _255-M-1).

The external interleaver structure can be block interleaver, and the columns of external interleaver can be fixed as 240, and interleave depth is by line number M _IConfirm.

Work as B _fDuring=8MHz, the line number of external interleaver is by the byte-interleaved pattern of system's appointment and the LDPC code check decision of inner encoder; Work as B _f=2MHz, the line number of external interleaver is by the LDPC code check of constellation mapping pattern and inner encoder, shown in following table one.External interleaver parameter MI, wherein, B _fThe expression baseband bandwidth.

Table one

This shows, increased the shorter option that interweaves when interweaving outside, can lower the memory demand of reception like this, reduce power consumption simultaneously.

1.1.2 in-line coding and interweaving

Inner encoder can adopt LDPC sign indicating number or QC-LDPC sign indicating number, and code allocation is shown in table two.

Table two

Code check	The information bit length K	Code word size N
			1/2	4608 bits	9216 bits
3/4	6912 bits	9216 bits

LDPC output code word C={c ₀, c ₁..., c ₉₂₁₅By input information bits S={s ₀, s ₁..., s _K-1And check bit P={p ₀, p ₁..., p _9215-KForm as follows:

$c_{\mathrm{COL}\_\mathrm{ORDER}\left(i\right)}=\left\{\begin{array}{cc}{p}_i& 0\≤i\≤9215-K\\ s_{i+K-9216}& 9216-K\≤i\≤9215\end{array}\right.$

The information bit of 1/2LDPC piece is corresponding to the TS bag of 3 188 bytes, and the information bit of 3/4LDPC piece is corresponding to the TS bag of 4.5 188 bytes.

Inner encoder can also adopt QC-LDPC coding, because the performance of the performance of QC-LDPC sign indicating number and common LDPC sign indicating number quite or lower slightly, still has very low implementation complexity.The complexity of its realization of decoding has only 1/4 of common LDPC sign indicating number decoding complexity, even lower.And LDPC decoding occupies the proportion about 1/3 in the demodulator circuit of receiving terminal, and simplification LDPC decoding has very large meaning to the cost and the power consumption of receiving terminal.Radio communication and the broadcast system of most of at present employing LDPC all adopt the QC-LDPC sign indicating number basically.

Bit input interleaver behind the LDPC coding interweaves.Interleaver adopts M _b* I _bBlock interleaver, M _bAnd I _bValue shown in table three.

Table three

?	M b	I b
			B f＝8MHz	384	360
B f＝2MHz	192	144

The output of interleaver and slot synchronization, first bit that promptly transmits in the time slot are defined as first bit of bit interleaver output all the time.

Memory requirements when interior interleaving block can adopt the design of squarish can reduce the receiver deinterleaving.

1.2 constellation mapping

Be mapped as the symbols streams of QAM pattern after two groups of bit streams combinations that said constellation mapper is used for said two groups of channel encoders are exported.Said QAM pattern is 16QAM, 64QAM or 256QAM pattern.Utilize hierarchical modulation that the quality of different brackets is provided to different service requests.Because first group data stream is represented the maximum dibit of energy; Second group data stream is represented other low-yield bits; Please specifically referring to shown in Fig. 3 A, when the QAM pattern was the 16QAM pattern, bit-order was b0b1b2b3; Can b0b1 be distributed to first group data stream, b2b3 is distributed to second group data stream; Please specifically referring to shown in Fig. 3 B, when the QAM pattern was the 64QAM pattern, bit-order was b0b1b2b3b4b5, can b0b1 be distributed to first group data stream, and b2b3b4b5 distributes to second group data stream; When the QAM pattern is the 256QAM pattern, b0b1 is distributed to first group data stream, b2b3b4b5b6b7b8b9b10b11b12b13b14b15 is distributed to second group data stream.Constellation mapper can also adopt BPSK, QPSK pattern in addition.

Various sign map add the power normalization factor (normalization factor of QPSK

; The normalization factor of 16QAM

; The normalization factor of 64QAM

), make the average power of various sign map convergent.

So far can find out, in the present invention two maximum bits of energy in 16QAM and the 64QAM modulation separated with all the other bits that modulate different code streams respectively, these two code streams can have different coding speed and interleaving mode.Can increase simultaneously the energy of two bits of energy maximum in 16QAM and the 64QAM modulation.At first carry out 16QAM or 64QAM modulation according to common mode; Then the amplitude of I road signal and Q road signal (seeing also Fig. 2 and Fig. 3) is increased a numerical value 1 or 3 respectively and (suppose that the I of 16QAM or the amplitude of Q are 1,3; The I of 64QAM or the amplitude of Q are 1,3,5,7), sign is constant.The transfer of data of different quality grade can be provided for different demands for services like this.

1.3OFDM symbol forms

Said OFDM symbol is loaded into effective subcarrier and forms the OFDM symbol after forming the symbols streams of module 40 with scattered pilot and the output of CP continuous pilot insertion constellation mapping module.After being loaded into effective subcarrier, the symbols streams of constellation mapping module output forms data subcarrier.

Each OFDM symbol comprises N _VIndividual effective subcarrier, N _VValue is:

$N_V=\left\{\begin{array}{cc}3076,& B_f=8\mathrm{MHz}\\ 628,& B_f=2\mathrm{MHz}\end{array}\right.$

Remember in each time slot on n the OFDM symbol i effectively subcarrier be X _n(i), i=0,1 ... N _V-1; 0≤n≤52.The subcarrier of OFDM symbol is distributed to data subcarrier, scattered pilot and CP continuous pilot according to mode shown in Figure 4.

1.3.1 CP continuous pilot

B _fDuring=8MHz, comprise N1 CP continuous pilot in each OFDM symbol; B _fDuring=2MHz, each OFDM symbol comprises N2 CP continuous pilot.

The partial continuous pilot tone is used to transmit transmission parameter signaling, and modulation system is BPSK, and transmission parameter signaling comprises timeslot number; The byte interleaver device sync id, configuration change indication, front and back protection length option; The external encode and the option that interweaves, the in-line coding and the option that interweaves, scattered pilot option etc.

1.3.2 scattered pilot

Scattered pilot sends known symbol 1+0j.The subcarrier number m value rule that scattered pilot is corresponding in n OFDM symbol in each time slot is as follows:

B _f＝8MHz：

if?mod(n，2)＝＝0 if?mod(n，2)＝＝1

Option one $m=\left\{\begin{array}{c}8P+1,p=\mathrm{0,1},\·\·\·191\\ 8p+3,p=\mathrm{192,193,}\·\·\·383\end{array}\right.$ $m=\left\{\begin{array}{c}8P+5,p=\mathrm{0,1},\·\·\·191\\ 8p+7,p=\mathrm{192,193,}\·\·\·383\end{array}\right.$

if?mod(n，2)＝＝0?if?mod(n，2)＝＝1

Option 2 $m=\left\{\begin{array}{c}8P+1,p=\mathrm{0,1},\·\·\·191\\ 8p+6,p=\mathrm{192,193,}\·\·\·383\end{array}\right.$ $m=\left\{\begin{array}{c}8P+5,p=\mathrm{0,1},\·\·\·191\\ 8p+10,p=\mathrm{192,193,}\·\·\·383\end{array}\right.$

The inserted mode of option 2 can be simplified the design of receiving terminal scattered pilot interpolation filter.

B _f＝2MHz：

if?mod(n，2)＝＝0?if?mod(n，2)＝＝1

$m=\left\{\begin{array}{c}8P+1,p=\mathrm{0,1},\·\·\·38\\ 8p+3,p=\mathrm{39,40},\·\·\·77\end{array}\right.$ $m=\left\{\begin{array}{c}8P+5,p=\mathrm{0,1},\·\·\·38\\ 8p+7,p=\mathrm{39,40},\·\·\·77\end{array}\right.$

Scattered pilot can selectively increase the 2-4dB transmitting power and be used to improve the receiver channel estimation performance, can make the channel estimating of receiving terminal more accurate, and the demodulation performance of receiving terminal is improved more than the 0.5dB.

1.3.3 data subcarrier

Subcarrier in each OFDM symbol except that scattered pilot and CP continuous pilot is a data subcarrier.The data symbol of data subcarrier after according to the front and back sequential delivery constellation mapping of subcarrier, OFDM symbol.Have 138330 (B in each time slot _f=8MHz) or 27666 (B _f=2MHz) individual data subcarrier, wherein preceding 138240 (B _f=8MHz) or 27648 (B _f=2MHz) number of sub-carrier is used to carry the data complex symbol after the constellation mapping, last 90 (B _f=8MHz) or 18 (B _f=2MHz) individual symbol is filled 0+0j.

1.3.4 scrambler

To data subcarrier, scattered pilot and CP continuous pilot etc., all by a multiple pseudo random sequence P _c(i) scrambler.

Multiple pseudo random sequence P _c(i) generating mode is following:

$P_c\left(i\right)=\frac{\sqrt{2}}{2}[(1-2S_i\left(i\right))+j(1-2S_q\left(i\right))]$

Wherein, S _i(i) and S _q(i) be that 12 bit shift register produce pseudo random sequence, produce that corresponding generator polynomial is: x by linear feedback shift register shown in Figure 5 ¹²+ x ¹¹+ x ⁸+ x ⁶+ 1.The initial value of shift register provides 8 kinds of different options, shown in table four:

Scrambler shift register initial value

Table four

Option	Initial value
		0	0000?0000?0001
1	0000?1001?0011
		2	0000?0100?1100
3	0010?1011?0011
		4	0111?0100?0100
5	0000?0100?1100
		6	0001?0110?1101
7	0010?1011?0011

The concrete structure that the linear feedback shift of scrambler is deposited please refer to Fig. 5.Scrambler passes through complex symbol on effective subcarrier and multiple pseudo random sequence P _c(i) carrying out complex multiplication realizes.During single frequency network, the adjacent transmitters in the service area adopts different scrambling codes to the data scrambling, utilizes identification signal of transmitter and scrambling code information to help receiver and selects the signal of " the best " transmitter emission to receive.

1.3.4 OFDM modulated carrier

OFDM subcarrier Y behind insertion pilot tone and the scrambler _n(i), 0≤i≤N _SBe mapped as the OFDM symbol through IFT:

$S_n\left(t\right)=\frac{1}{N_S}\underset{i=0}{\overset{N_S-1}{\mathrm{\&Sigma;}}}{Z}_n\left(i\right)e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="H061D1996520061030E000042.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;i}{\left(\mathrm{\&Delta;f}\right)}_S(t-T_{\mathrm{CP}})},$ 0≤t≤(T _S+T _CP)，0≤n≤52

Wherein:

S _n(t) be n OFDM symbol in the time slot

N _SBe OFDM symbol sub-carrier number, value is:

$N_S=\left\{\begin{array}{cc}4096,& B_f=8\mathrm{MHz}\\ 1024,& B_f=2\mathrm{MHz}\end{array}\right.$

(Δ f) _sBe the subcarrier spacing of OFDM symbol, value is 2.44140625kHz.

Z _n(i) be data carried by data on the i number of sub-carrier in n the OFDM symbol, mapping relations are following

B _f＝8MHz：

$Z_n\left(i\right)=\left\{\begin{array}{cc}{Y}_n(i-1),& 1\&le;i\&le;1538\\ Y_n(i-1020),& 2558\&le;i\&le;4095\\ 0,& i=0\mathrm{or}1539\&le;i\&le;2557\end{array}\right.$

B _f＝2MHz：

$Z_n\left(i\right)=\left\{\begin{array}{cc}{Y}_n(i-1),& 1\&le;i\&le;314\\ Y_n(i-396),& 710\&le;i\&le;1023\\ 0,& i=0\mathrm{or}315\&le;i\&le;709\end{array}\right.$

B _f=8MHz and B _fOFDM sub-carrier structure during=2MHz is respectively like Fig. 6 and shown in Figure 7.

1.4 framing

Said one-tenth frame module 40 is used for said OFDM symbol is added beacon to form transmission frame.

1.4.1 the time domain frame structure of said transmission frame

Physical layer signal was 1 frame in per 1 second, was divided into 40 time slots.The length of each time slot is 25ms, comprises 1 beacon and 53 OFDM symbols.Time slot division and frame structure are as shown in Figure 8.

The reason of dividing slot transmission is to adopt different slot transmission to data flow of different nature (video, audio frequency, control information and emergent broadcasting information etc.), to make things convenient for the flexible configuration of media access layer (MAC).

1.4.2 beacon

Beacon infrastructure is as shown in Figure 8, comprises 2 identical synchronizing signals and identification signal of transmitter (TxID).

A) synchronizing signal

Said synchronizing signal S _b(t) be the pseudo-random signal of band, length is designated as T _b, value is 204.8 μ s.Synchronizing signal is produced by following formula:

$S_b\left(t\right)=\frac{1}{N_b}\underset{i=0}{\overset{N_b-1}{\mathrm{\&Sigma;}}}{X}_b\left(i\right)e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="H061D1996520061030E000042.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;i}{\left(\mathrm{\&Delta;f}\right)}_{b}t},$ 0≤t≤T _b

Wherein: N _bBe the sub-carrier number of synchronizing signal, value is following:

$N_b=\left\{\begin{array}{cc}2048,& B_f=8\mathrm{<figure-callout\; id="512"\; label="MHz"\; filenames="H061D1996520061030E000042.png"\; state="\{\{state\}\}">MHz</figure-callout>}\\ 512,& B_f=2\mathrm{MHz}\end{array}\right..$

(Δ f) _bBe the subcarrier spacing of synchronizing signal, value is 4.8828125kHz.

X _b(i) be the pseudo-random signal of BPSK modulation, pseudo random sequence is produced by ten single place shift registers.

The insertion of synchronizing signal has been accelerated synchronizing speed and the precision of receiver and can be used for channel estimating.

B) identification signal of transmitter

Identification signal of transmitter S _ID(t) be the pseudo-random signal of band, be used to identify different transmitters.S _ID(t) length is designated as T _ID, value is 36.0 μ s.Identification signal of transmitter is produced by following formula:

$S_{\mathrm{ID}}\left(t\right)=\frac{1}{N_{\mathrm{ID}}}\underset{i=0}{\overset{N_{\mathrm{ID}}-1}{\mathrm{\&Sigma;}}}{X}_{\mathrm{ID}}\left(i\right)e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="H061D1996520061030E000042.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;i}{\left(\mathrm{\&Delta;f}\right)}_{\mathrm{ID}}(t-T_{\mathrm{IDCP}})},$ 0≤t≤T _ID

Wherein: N _IDBe the sub-carrier number of identification signal of transmitter, value is following:

$N_b=\left\{\begin{array}{cc}256,& B_f=8\mathrm{MHz}\\ 64,& B_f=2\mathrm{MHz}\end{array}\right.$

(Δ f) _IDBe the subcarrier spacing of identification signal of transmitter, value is 39.0625kHz.

X _IDThe pseudo-random signal of (i) modulating for BPSK.

Sender unit identification sequence TxID (k) length is 191 bit (B _f=8MHz) or 37 bit (B _f=2MHz).

The Cyclic Prefix of sender unit identification (IDCP) length T _IDCP=10.4uS

1.4.3OFDM symbol

The OFDM symbol is by Cyclic Prefix (CP), and OFDM symbol body and selectable protection (GI) at interval constitute.Shown in figure 10.The protection blank signal is overlapped through windowing by the protections of the front and back between adjacent OFDM (GD) and forms, and is as shown in Figure 9.

T ₀Be symbol body length, T ₁Be circulating prefix-length, T _GDBe front and back protection length.T ₀, T ₁And T _GDValue list in table five:

Table five

Option	T0(μs)	T1(μs)	TGD(μs)
				1	409.6	51.2	2.4
2	409.6	53.6	0

1.5 up-conversion

Said up-conversion module 50 is used for said transmission frame is carried out the radiofrequency signal that up-conversion is used to launch with generation.

The baseband signal of framing produces radiofrequency signal through behind the quadrature up-conversion, and radiofrequency signal is described through following formula:

$S\left(t\right)=\mathrm{Re}\{\exp (j\&times;2\mathrm{\&pi;}{f}_{c}t)\&times;[\mathrm{Frame}\left(t\right)\&CircleTimes;F\left(t\right)\left]\right\}$

Wherein, S (t) is a radiofrequency signal

f _cBe carrier frequency

Frame (t) is the baseband signal after the framing

F (t) is the emission filter impulse response.

The above is merely preferred embodiment of the present invention, and is in order to restriction the present invention, not all within spirit of the present invention and principle, any modification of being done, is equal to replacement etc., all should be included within protection scope of the present invention.

Claims (13)

1. a mobile digital multimedia broadcast signal transmission system is characterized in that it comprises

Two groups of channel encoders receive first, second group data stream respectively and data flow is converted to bit stream after coding and interleaving treatment;

Constellation mapper; Be mapped as the symbols streams of QAM pattern after two groups of bit streams combinations that are used for said two groups of channel encoders are exported; The dibit that energy wherein is maximum is distributed to first group data stream; Give second group data stream with other low-yield Bit Allocation in Discrete, and increase the energy of the maximum dibit of energy;

The OFDM symbol forms module, and the symbols streams that is used for forming according to said constellation mapper forms the OFDM symbol;

Become frame module, be used for said OFDM symbol is added beacon to form transmission frame;

The up-conversion module is used for said transmission frame is carried out the radiofrequency signal that up-conversion is used to launch with generation.

2. mobile digital multimedia broadcast signal transmission system according to claim 1 is characterized in that, said QAM pattern is 16QAM or 64QAM pattern.

3. mobile digital multimedia broadcast signal transmission system according to claim 2 is characterized in that, when the QAM pattern was the 16QAM pattern, bit-order was b0b1b2b3, and b0b1 is distributed to first group data stream, and b2b3 is distributed to second group data stream.

4. mobile digital multimedia broadcast signal transmission system according to claim 2; It is characterized in that when the QAM pattern was the 64QAM pattern, bit-order was b0b1b2b3b4b5; B0b1 is distributed to first group data stream, b2b3b4b5 is distributed to second group data stream.

5. mobile digital multimedia broadcast signal transmission system according to claim 1; It is characterized in that; Said each channel encoder includes outer encoder, external interleaver, inner encoder and interleaver, and first and second group data stream is handled back output through outer encoder, external interleaver, inner encoder and interleaver successively.

6. mobile digital multimedia broadcast signal transmission system according to claim 5 is characterized in that, said each channel encoder has different coding speed and interleaving mode.

7. mobile digital multimedia broadcast signal transmission system according to claim 5; It is characterized in that; Described two-way channel encoder is different, and every path channels encoder comprises the part unit in outer encoder, external interleaver, inner encoder and the interleaver.

8. mobile digital multimedia broadcast signal transmission system according to claim 5 is characterized in that, said outer encoder adopts binary system BCH code or RS sign indicating number.

9. mobile digital multimedia broadcast signal transmission system according to claim 8 is characterized in that, said external interleaver only interweaves to the checking symbol of RS sign indicating number, and the information symbol to the RS sign indicating number does not interweave.

10. mobile digital multimedia broadcast signal transmission system according to claim 5 is characterized in that, the inner encoder in the said channel encoder adopts LDPC sign indicating number or QC-LDPC sign indicating number.

11. mobile digital multimedia broadcast signal transmission system according to claim 1; It is characterized in that; Said OFDM symbol forms the subcarrier of module and the corresponding relation of data and pilot tone is: when (1) is 8MHz when the channel width position; Effectively subcarrier number is 0～3075 or when the channel width position is 2MHz, effective subcarrier number is 0～627; (2) insert scattered pilot, in even number OFDM symbol, since 0, effective subcarrier that numbering satisfies the 8*K form is a scattered pilot, and wherein K is an integer; In odd number OFDM symbol, effective subcarrier that numbering satisfies the 8*K+4 form is a scattered pilot, and wherein K is an integer; (3) add CP continuous pilot; (4) modulate effectively-1537～1538 in the corresponding IFFT conversion of subcarrier 0～3075 difference, or-313～314 in the corresponding IFFT conversion of 0～627 difference.

12. mobile multimedia broadcast signal transmission system according to claim 11 is characterized in that, said scattered pilot increases the 2-4dB transmitting power.

13. mobile multimedia broadcast signal transmission method according to claim 1 is characterized in that, said beacon comprises two identical synchronizing signals and identification signal of transmitter.

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