CN101800725B - Mobile multimedia broadcast transmission system - Google Patents

Abstract

The invention provides a mobile multimedia broadcast transmission system, which comprises a RS encoding and byte interleaving device, an LDPC encoder, a bit interleaver, a constellation mapper, a frequency domain symbol generator, a scrambler, an IFFT converter, a time domain framing device and a transmitter. The system can provide high-quality mobile multimedia services for users within the 5MHz working bandwidth according to the technical scheme of the invention. In addition, a RS code can be optimally selected according to the working bandwidth of the system, a proper encoding mode can be selected according to different channel conditions and accordingly the byte interleaver can be optimized to adopt reasonable interleaving parameters for byte interleaving. The invention with the technical scheme can reasonably set and allocate the continuous pilot frequency, discrete pilot frequency and digital sub-carrier of the system according to the actual bandwidth of the system. Therefore, the mobile multimedia broadcast transmission system can reasonably set the system overhead and effectively utilize spectrum resources for data transmission.

Description

Mobile multimedia broadcast transmission system

Technical field

The present invention relates to digital information transmission technical field, particularly mobile multimedia broadcast transmission system.

Background technology

No matter be wired or the communication service of wireless domain at present, multimedia service has all become the main business that operator provides for the client.Wherein, in wireless communication field, wireless broadcast communication has broad covered area, program characteristics capacious, and its sharpest edges that have have broadcasting property exactly, realizes that any to multiple spot, has the higher transmission bandwidth under low-cost condition.Therefore, radio communication broadcasting has critical role as an important component part of ICT industry in national information infrastructure construction, realization universal service and national information security strategy.

In various multimedia services, wherein mobile multi-media broadcasting service is regarded as a kind of important application that has very much promotion prospect by industry at present.Receiving equipments such as CMMB is seven cun following the small screen of confession under directions, small size, move portable handheld terminal such as mobile phone, PDA, MP3, MP4, digital camera, notebook computer receive the system of business such as broadcast TV program and information service whenever and wherever possible.

At present all be based on existing mobile communication network and Streaming Media at the CMMB that the part service is provided; Yet; Because the technical characterstics such as bandwidth of existing mobile communication network have determined above-mentioned communication mode not do further to promote to existing CMMB performance, being difficult to provides satisfied rating to experience to the user.Consider the advantage of broadcast technology and radio network; Once transmit unlimited the reception; And low-cost, high bandwidth, therefore utilize the cooperative work of radio network and communication network to provide a kind of high-quality broadcast multimedia business to become the main basis that mobile many matchmakers broadcast research and development to handheld terminal.

Special vast in territory to China, transmission environment is complicated; Urban compact western part, eastern region is sparse; Numerous and the diversified national conditions of business demand of user; The applicant has proposed that a kind of to adopt satellite extensively to be covered as main, ground supplement network be the SNA of assisting, and utilizes that satellite broad covered area, construction period are short, the characteristics of instant effect, realize low-cost, realize the technical scheme of mobile multimedia broadcast signal apace in the covering in the whole nation; And relevant technical scheme has been submitted to the application documents of applying for patent of invention, see that specifically application number is 200610113915.9,200610113916.3 application documents.In above-mentioned disclosed application documents, the concrete technical scheme to the CMMB employing has been proposed, comprise the technical schemes such as structure, chnnel coding and modulation of CMMB physical layer channel frame.

Yet the technical scheme that above-mentioned application documents propose is generally the CMMB communication that is operated in 8M or the 2M bandwidth, and along with the fast development of global radio telecommunications, the imbalance between supply and demand of radio frequency resource becomes increasingly conspicuous.Frequency resource is as requisite special resource in a kind of radio communication, and frequency resource has exclusiveness and durability, and promptly in regular hour, area and frequency domain, in a single day frequency resource is used, and other equipment can not re-use; But under regular hour, area, frequency domain and encoding condition, radio frequency is can be multiplexing and shared.Therefore, under the situation that global various countries frequency resource allocation has nothing in common with each other, be necessary to propose a kind of communication system that is adapted to the different operating bandwidth.

Summary of the invention

The object of the invention is intended to solve at least one of above-mentioned technological deficiency, particularly solves the transmission problem of CMMB in the different working bandwidth.Aspect that the present invention adds and advantage part in the following description provide, and part will become obviously from the following description, or recognize through practice of the present invention.

For achieving the above object, the present invention proposes a kind of mobile multimedia broadcast transmission system, comprising:

RS coding and byte interleaver device are used for through the physical logic channel upper layer data stream being carried out RS coding and byte-interleaved; The LDPC encoder is used for the said RS coding and the data of byte interleaver device output are carried out the LDPC coding, obtains Bit data; Bit interleaver is used for the Bit data of said LDPC encoder output is carried out Bit Interleave; Constellation mapper is used for the data of said bit interleaver output are carried out constellation mapping; The frequency domain symbol maker is used for scattered pilot, includes the CP continuous pilot of system information and form the OFDM frequency domain symbol through the data symbol multiple connection of constellation mapping together; Scrambler is used to use pseudo random sequence that said OFDM frequency domain symbol is carried out scrambler; The IFFT converter is used for producing the OFDM time-domain symbol after the frequency domain symbol process IFFT conversion with said scrambler output; The time domain framer is used for connecting to form the physical layer signal frame with behind the said OFDM time-domain symbol composition time slot; Reflector is used for said physical layer signal frame is launched after baseband signal is converted into radio frequency, and wherein said reflector uses the interior 5MHz bandwidth arbitrarily of wireless channel to transmit.

According to embodiments of the invention; Said physical layer signal frame length is 1 second; Comprise that 40 length are 25 milliseconds time slot; Said time slot comprises 1 beacon and 53 OFDM symbols, and said beacon comprises 1 identification signal of transmitter and 2 identical synchronizing signals, and said identification signal of transmitter is carried out obtaining through periodic extension after BPSK mapping and the IFFT conversion by the frequency domain random sequence successively again; Said synchronizing signal through intercepting frequency domain random sequence after, carry out BPSK and IFFT conversion successively and obtain.

According to embodiments of the invention, said identification signal of transmitter carries the sub-carrier number N of said identification signal of transmitter through 117 bit informations sign _ID=128, through BPSK modulation, said identification signal of transmitter X _ID(i) produced by sender unit identification sequence TxID (k) mapping, mapping mode is:

According to embodiments of the invention, said synchronizing signal S _b(t) be the pseudo-random signal of band, length T _bBe 204.8 μ s,

0≤t≤T _b, N wherein _bFor carrying the sub-carrier number of said synchronizing signal, X _b(i) for carrying binary pseudo-random sequence PN _b(k) BPSK modulation signal, (Δ f) _bBe the subcarrier spacing of synchronizing signal, sub-carrier number N _b=1024, and PN _b(k) BPSK modulation signal X _b(i) by PN _b(k) mapping produces, and mapping mode is:

According to embodiments of the invention, said binary pseudo-random sequence is produced by linear feedback shift register, and the initial value of shift register is 01110101101, and generator polynomial is: x ¹¹+ x ⁹+ 1.

According to embodiments of the invention, said identification signal of transmitter, synchronizing signal and OFDM intersymbol adopt the protection of band window function to overlap mutually at interval, and the expression formula of said window function is:

$w\left(t\right)=\left\{\begin{array}{cc}0.5+0.5\mathrm{Cos}(\mathrm{\&pi;}+\mathrm{\&pi;\; t}/T_{\mathrm{GD}}),& 0\&le;t\&le;{\mathrm{<figure-callout\; id="1"\; label="T\; GD"\; filenames="H200910078052XE00012.png,H200910078052XE00031.png"\; state="\{\{state\}\}">T</figure-callout>}}_{\mathrm{GD}}\\ 1,& T_{\mathrm{GD}}<t<T+T_{\mathrm{GD}}\\ 0.5+0.5\mathrm{Cos}(\mathrm{\&pi;}+\mathrm{\&pi;}(T-t)/T_{\mathrm{GD}}),& T+T_{\mathrm{GD}}\&le;t\&le;T+2T_{\mathrm{GD}}\end{array}\right.,$ Wherein, t is a time variable, and T is a constant, T _GDBe said protection length at interval.

According to embodiments of the invention, said RS coding be by original RS (255, the M) RS (192 that produces after through brachymemma of systematic code; K) shortened code; M=K+63 wherein, K is the byte number of information sequence in the code word, said RS (255; M) each code element of systematic code is taken from territory GF (256), and the generator polynomial in this territory is p (x)=x ⁸+ x ⁴+ x ³+ x ²+ 1.

According to embodiments of the invention, (192, K) sign indicating number comprises 4 kinds of patterns to said RS, and the value of K is respectively K=192, K=168, K=160 and K=144 in these 4 kinds of patterns.

According to embodiments of the invention, (192, K) expression formula of the generator polynomial of sign indicating number does said RS $g\left(x\right)=\underset{i=0}{\overset{192-K}{\mathrm{\&Sigma;}}}{g}_i{x}^i;$

When K=192, the coefficient g of the generator polynomial expression formula of RS (192,192) _iFor:

i gi

0 1

When K=168, the coefficient g of the generator polynomial expression formula of RS (192,168) _iFor:

When K=160, the coefficient g of the generator polynomial expression formula of RS (192,160) _iFor:

When K=144, the coefficient g of the generator polynomial expression formula of RS (192,144) _iFor:

According to embodiments of the invention, said upper layer data stream is unit with the byte, and from left to right by row input RS coding and byte interleaver device, wherein, the RS coding is encoded by row, and the start byte of byte interleaver device is mapped in the starting point of certain time slot and sends.

According to embodiments of the invention, the output block length behind the said LDPC coding is 9216 bits, and code check is respectively 1/2 and 3/4, corresponding different code rate, and the corresponding interlace mode of said byte interleaver device is respectively:

Wherein, MI is the line number of byte interleaver device, and the whole bytes in the byte interleaver device are MI * 192 bytes.

According to embodiments of the invention, said bit interleaver adopts 384 * 216 block interleaver; Write each row of said block interleaver from the Bit data of LDPC encoder output successively according to order from top to bottom, until filling up whole block interleaver, reading from left to right again by leu, wherein the output of bit interleaver is alignd with time slot.

According to embodiments of the invention, said frequency domain symbol maker with 234 scattered pilots, 76 CP continuous pilots, the multiple connection of 1566 data subcarriers together, becomes 1876 effective subcarriers in each OFDM symbol.

According to embodiments of the invention, said 76 CP continuous pilots use in said 1876 effective subcarriers the 0th, 6,66,76,92,132,150,170,206,228,260,294,296,328; 338,382,392,406,462,474,480,494,552,562,582,624,630,664,668; 738,744,760,790,806,834,850,922,937,938,952,1024,1040,1068; 1084,1114,1130,1172,1206,1210,1244,1250,1292,1312,1322,1380,1394,1400; 1412,1468,1482,1492,1536,1546,1578,1580,1614,1646,1668,1704,1724,1742; 1782,1798,1808,1868,1875 number of sub-carrier, and therein the 6th, 406,1084,1482,66,462,1114,1492,76; 474,1130,1536,92,480,1172,1546,132,494,1206,1578,150,552,1210; 1580,170,562,1244,1614,206,582,1250,1646,228,624,1292,1668,260; 630,1312,1704,294,664,1322,1724,296,668,1380,1742,328,738,1394; 1782,338,744,1400,1798,382,760,1412,1808,392,790,1468,1868 carry 16 bit system information totally in 64 number of sub-carrier, and said system information comprises that length is that the timeslot number of 6 bits, the byte interleaver device sync id that length is 1 bit, control logic channel change indication and the length that length is 1 bit are the reserved word of 8 bits; Said CP continuous pilot is mapped on the subcarrier with the mode of

; Wherein, the symbol that the identical continuous subcarrier point of different OFDM symbols upward transmits in the same time slot is identical.

According to embodiments of the invention, when OFDM symbol in each time slot be numbered n the time, the subcarrier number m value that scattered pilot is corresponding in the OFDM symbol is:

When mod (n, 2)=0

$m=\left\{\begin{array}{cc}8p+1,& p=\mathrm{0,1,2},\&CenterDot;\&CenterDot;\&CenterDot;,116\\ 8p+3,& p=\mathrm{117,118,119},\&CenterDot;\&CenterDot;\&CenterDot;,233\end{array}\right.$

When mod (n, 2)=1

$m=\left\{\begin{array}{cc}8p+5,& p=\mathrm{0,1,2},\&CenterDot;\&CenterDot;\&CenterDot;,116\\ 8p+7,& p=\mathrm{117,118,119},\&CenterDot;\&CenterDot;\&CenterDot;,233\end{array}\right.,$

The whole values of scattered pilot are 1+0j.

According to embodiments of the invention, the generator polynomial of the pseudo random sequence that said scrambler uses is: x ¹²+ x ¹¹+ x ⁸+ x ⁶+ 1; Said scrambler is divided into 8 kinds of patterns, and corresponding register initial value is respectively:

1) the scrambler pattern 0: initial value 000000000001,

2) the scrambler pattern 1: initial value 000010010011,

3) the scrambler pattern 2: initial value 000001001100,

4) scrambler mode 3: initial value 001010110011,

5) the scrambler pattern 4: initial value 011101000100,

6) the scrambler pattern 5: initial value 010001001100,

7) the scrambler pattern 6: initial value 000101101101,

8) scrambler mode 7: initial value 101010110011;

Said pseudo random sequence is reset in the beginning of each time slot, and all time slots are all by identical pattern scrambler.

According to embodiments of the invention, said IFFT converter carries out 2048 IFFT conversion after 1876 effective subcarriers being placed on the 1st～938 and the 1110th～2047 subcarrier of 2048 number of sub-carrier.

According to embodiments of the invention, the OFDM symbol after said time domain framer will be modulated is formed time slot after adding protection interval, synchronizing signal, transmitter identification signal successively, again 40 time slots is connected to form the physical layer signal frame.

For make mobile multimedia broadcast transmission system can be in different frequency bandwidths operate as normal; Especially can high-quality mobile multi-media service be provided for the user in the 5MHz bandwidth of operation; The present invention is according to the technical characterictic of system; System transmitter id signal, synchronizing signal rationally are provided with, make it stable system information is provided for system.In addition, RS coding is optimized selection according to the bandwidth of operation of system, selects proper encoding mode, correspondingly, byte interleaver device is optimized, use rational interleave parameter to carry out byte-interleaved according to different channel conditions.The technical scheme that the present invention proposes; Actual bandwidth according to system; Setting rationally, the CP continuous pilot of distribution system, scattered pilot, digital subcarrier make mobile multimedia broadcast transmission system that overhead rationally is set, and effectively utilize frequency spectrum resource transmission data.

Description of drawings

Above-mentioned and/or additional aspect of the present invention and advantage are from obviously with easily understanding becoming the description of embodiment below in conjunction with accompanying drawing, wherein:

Fig. 1 is the structural representation of mobile multimedia broadcast transmission system of the present invention;

Fig. 2 is the broadcast channel physical layer logic channel architecture sketch map of mobile multimedia broadcast transmission system of the present invention

Fig. 3 is the logic channel coding and the modulation flow chart of mobile multimedia broadcast transmission system physical layer of the present invention;

Fig. 4 is divided and the frame structure sketch map by the time slot of the formed physical layer signal frame of time slot framing;

Fig. 5 is the structural representation of beacon;

Fig. 6 is the pseudo random sequence generator structural representation of synchronizing signal;

Fig. 7 is the structural representation of OFDM symbol;

The sketch map of Fig. 8 for overlapping between the protection at interval;

Fig. 9 is an OFDM symbolic construction sketch map;

Figure 10 be byte interleaver device and RS (192, the K) sketch map of coding;

Figure 11 is for carrying out the sketch map of Bit Interleave to process LDPC bit stream coded;

Figure 12 is a pilot tone multiple connection mode sketch map of the subcarrier allocation of OFDM symbol being given data symbol, scattered pilot and CP continuous pilot;

Figure 13 is the sketch map of PRBS generation method;

Figure 14 is an OFDM symbol sub-carrier structure sketch map.

Embodiment

Describe embodiments of the invention below in detail, the example of said embodiment is shown in the drawings, and wherein identical from start to finish or similar label is represented identical or similar elements or the element with identical or similar functions.Be exemplary through the embodiment that is described with reference to the drawings below, only be used to explain the present invention, and can not be interpreted as limitation of the present invention.

As shown in Figure 1; Mobile multimedia broadcast transmission system for the present invention proposes comprises: RS coding and byte interleaver device LDPC encoder, bit interleaver, constellation mapper, frequency domain symbol maker, scrambler, IFFT converter, time domain framer, reflector.

Wherein, the RS coding is used for through the physical logic channel upper layer data stream being carried out RS coding and byte-interleaved with byte interleaver device; The LDPC encoder is used for the RS coding and the data of byte interleaver device output are carried out the LDPC coding, obtains Bit data; Bit interleaver is used for the Bit data of LDPC encoder output is carried out Bit Interleave; Constellation mapper is used for the data of bit interleaver output and carries out constellation mapping; The frequency domain symbol maker is used for scattered pilot, includes the CP continuous pilot of system information and form the OFDM frequency domain symbol through the data symbol multiple connection of constellation mapping together; Scrambler is used to use pseudo random sequence that said OFDM frequency domain symbol is carried out scrambler; The IFFT converter is used for producing the OFDM time-domain symbol after the frequency domain symbol process IFFT conversion with scrambler output; The time domain framer is used for connecting to form the physical layer signal frame with behind the OFDM time-domain symbol composition time slot; Reflector is used for said physical layer signal frame is launched after baseband signal is converted into radio frequency, and wherein reflector uses the interior 5MHz bandwidth arbitrarily of wireless channel to transmit.

The mobile multimedia broadcast transmission system that utilizes the present invention to propose can provide the multimedia programming that comprises high-quality digital audio broadcasting, DVB to the user.

The present invention has defined in every 5MHz frequency band; Can broadcast each functional module of physical layer that upper layer data stream carries out adaptation processing to mobile multimedia broadcast transmission system, provide frame structure, chnnel coding, the modulation technique of mobile multimedia broadcasting channel physical layer transmission signal.

The broadcast channel physical layer of the present invention's definition is come the demands of different of adaptive upper strata types of applications to transmission rate through the physical layer logic channel.The physical layer logic channel supports multiple coding and modulation system in order to satisfy different application, the different transmission environment demands of different to signal quality.

The broadcast channel physical layer of the present invention's definition is supported SFN and two kinds of networking models of multiple frequency network, MFN, can select different transmission modes and parameter according to the characteristic and the network environment of practical application.Support the mixed mode of multiple application, reach the coupling of application characteristic and transmission mode, realized application flexibility and economy.

As shown in Figure 2, be the broadcast channel physical layer logic channel architecture sketch map of mobile multimedia broadcast transmission system of the present invention.

Physical layer provides (comprising control logic channel CLCH and service logical channels SLCH) broadcast channel of upper layer application through physical layer logic channel (Physical Logical Channel, i.e. PLCH).Each physical layer logic channel can use the one or more time slots in the 5MHz DTV bandwidth to send.Physical layer is carried out separate encoding and modulation to each physical layer logic channel.Different with modulation parameter according to coding, the physical layer logic channel can provide different transmission capacities.

Fig. 3 is the logic channel coding and the modulation flow chart of mobile multimedia broadcast transmission system physical layer of the present invention.

As shown in the figure, the input traffic of physical layer logic channel through forward error correction coding, interweave and constellation mapping after, carry out the OFDM modulation with scattered pilot and CP continuous pilot multiple connection together.Signal after the modulation forms the physical layer signal frame after inserting frame head.Launch through behind base band to the rf conversion again.

The physical layer logic channel is divided into control logic channel (CLCH) and service logical channels (SLCH).The control logic channel is used for the bearing system configuration information, adopts fixing chnnel coding and modulation pattern to send at system's the 0th time slot.

Fig. 4 is divided and the frame structure sketch map by the time slot of the formed physical layer signal frame of time slot framing.

As shown in the figure, the system physical layer signal was 1 frame in per 1 second, and every frame is divided into 40 time slots (Timeslot, i.e. TS), and the length of each time slot is 25MHzs.Each time slot comprises 1 beacon and 53 OFDM modulated data blocks.

Fig. 5 is the structural representation of beacon.As shown in the figure, beacon comprises 2 identical synchronizing signals and identification signal of transmitter (ID).

Synchronizing signal is the pseudo random sequence of band, and length is designated as T _b, value is 204.8 μ s.The formula that synchronizing signal produces is:

0≤t≤T _b, wherein, N _bBe the sub-carrier number of synchronizing signal, X _b(i) for carrying binary pseudo-random sequence PN _b(k) BPSK modulation signal, (Δ f) _bBe the subcarrier spacing of synchronizing signal, value is 4.8828125kHz, the sub-carrier number N of synchronizing signal _b=1024.

Carry binary sequence pseudorandom PN _b(k) BPSK modulation signal X _b(i) by PN _b(k) mapping produces, and mapping mode is:

Binary pseudo-random sequence PN _b(k) produced by linear feedback shift register as shown in Figure 6, generator polynomial is: x ¹¹+ x ⁹+ 1.The shift register initial value is all identical to each synchronizing signal, is 01110101101.

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 Y _ID, value is 36.0 μ s.Identification signal of transmitter is:

$S_{\mathrm{ID}}\left(t\right)=\frac{1}{\sqrt{N_{\mathrm{ID}}}}\underset{i=0}{\overset{N_{\mathrm{ID}}-1}{\mathrm{\&Sigma;}}}{X}_{\mathrm{ID}}\left(i\right)e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="H200910078052XE00012.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;\; i}{\left(\mathrm{\&Delta;\; f}\right)}_{\mathrm{ID}}(t-T_{\mathrm{IDCP}})},$ 0≤t≤T _ID, wherein, N _IDBe the sub-carrier number of identification signal of transmitter, X _ID(i) for carrying the BPSK modulation signal of sender unit identification sequence, (Δ f) _IDBe the subcarrier spacing of identification signal of transmitter, value is 39.0625kHz, T _IDCPBe the circulating prefix-length of identification signal of transmitter, value is 10.4 μ s, the sub-carrier number N of identification signal of transmitter _ID=128.

Carry the BPSK modulation signal X of sender unit identification sequence _ID(i) produced by sender unit identification sequence TxID (k) mapping, mapping mode is:

Above-mentioned sender unit identification sequence TxID (k) is that length is the pseudo random sequence of 117 bits.The sender unit identification sequence comprises 256 sequences altogether, and wherein sequence 0～sequence 127 is the area sign, is used for the area at marking emitter place, and its even number time slot that inserts in the signal frame sends: the 0th time slot, and the 2nd time slot ...; Sequence 128～255 is a sender unit identification, is used to identify the different transmitters in the areal, and its odd number time slot that inserts in the signal frame sends: the 1st time slot, and the 3rd time slot ....The sender unit identification sequence is defined by hexadecimal sequence, and this hexadecimal sequence is mapped as binary system sender unit identification sequence according to the highest significant bit order formerly.

For make mobile multimedia broadcast transmission system can be in different frequency bandwidths operate as normal; Especially can high-quality mobile multi-media service be provided for the user in the 5MHz bandwidth of operation; Technique scheme is according to the technical characterictic of system; System transmitter id signal, synchronizing signal rationally are provided with, make it stable system information is provided for system.

As shown in Figure 7, be the structural representation of OFDM symbol.The OFDM symbol constitutes circulating prefix-length T by Cyclic Prefix (CP) and OFDM symbol body _CPBe 51.2us, i.e. 256 sampled points behind the IFFT, OFDM symbol lengths TS is 409.6us, i.e. 2048 sampled points behind the IFFT.

Overlap each other through protection interval (GD) between identification signal of transmitter, synchronizing signal and the adjacent OFDM symbol, protection is the length T of GD at interval _GDBe 2.4us, i.e. 12 sampled points behind the IFFT.Between the adjacent-symbol, superpose after the afterbody GD of previous symbol and the weighting of the head GD of back symbol process window function, as shown in Figure 8.

Described window function expression formula is:

$w\left(t\right)=\left\{\begin{array}{cc}0.5+0.5\mathrm{Cos}(\mathrm{\&pi;}+\mathrm{\&pi;\; t}/T_{\mathrm{GD}}),& 0\&le;t\&le;{\mathrm{<figure-callout\; id="1"\; label="T\; GD"\; filenames="H200910078052XE00012.png,H200910078052XE00031.png"\; state="\{\{state\}\}">T</figure-callout>}}_{\mathrm{GD}}\\ 1,& T_{\mathrm{GD}}<t<T+T_{\mathrm{GD}}\\ 0.5+0.5\mathrm{Cos}(\mathrm{\&pi;}+\mathrm{\&pi;}(T-t)/T_{\mathrm{GD}}),& T+T_{\mathrm{GD}}\&le;t\&le;T+2T_{\mathrm{GD}}\end{array}\right.,$ Wherein, t is a time variable, and T is a constant, T _GDBe said protection length at interval.

Choosing of protection blank signal is as shown in Figure 9.For identification signal of transmitter, synchronizing signal and OFDM symbol, the value of T0 and T1 part is seen table 1, T=T0+T1.

Table 1, protection blank signal list of values

Shown in figure 10, for byte interleaver device and RS (192, the K) sketch map of coding.

Byte interleaver device is that MI is capable, the block interleaver of 192 row.The line number MI of byte interleaver device is by byte-interleaved pattern and the decision of LDPC code check, and is as shown in table 2:

Interlace mode 1 interlace mode 2 interlace modes 3

1/2LDPC sign indicating number MI=54 MI=108 MI=216

3/4LDPC sign indicating number MI=81 MI=162 MI=324

The list of values of table 2, byte interleaver device parameter MI

The RS sign indicating number adopt code length be 192 bytes RS (192, K) shortened code.(255, M) systematic code produces through brachymemma this yard, wherein M=K+63 by original RS.K is the byte number of information sequence in the code word, and the check word joint number is (192-K).(192, K) sign indicating number provides 4 kinds of patterns to RS, is respectively K=192, K=168, K=160, K=144.

Each code element of RS sign indicating number is taken from territory GF (256), and its territory generator polynomial is p (x)=x ⁸+ x ⁴+ x ³+ x ²+ 1.

Shortened code RS (192, K) adopt following mode to encode: at K input information byte (m ₀, m ₁..., m _K-1) 63 complete " 0 " bytes of preceding interpolation, be configured to original RS (255, M) list entries of systematic code (0,0 ..., 0, m ₀, m ₁..., m _K-1), coding back generation code word (0,0 ..., 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, the code word that promptly obtains the brachymemma RS sign indicating number of 192 bytes is (m ₀, m ₁..., m _K-1, p ₀, p ₁..., p _255-M-1).

RS (192, K) generator polynomial of sign indicating number is expressed as:

$g\left(x\right)=\underset{i=0}{\overset{192-K}{\mathrm{\&Sigma;}}}{g}_i{x}^i;$

The input message sequence multinomial is:

$m\left(x\right)=\underset{i=0}{\overset{K-1}{\mathrm{\&Sigma;}}}{m}_i{x}^i;$

The systematic code multinomial of output is:

$C\left(x\right)=\underset{i=0}{\overset{191}{\mathrm{\&Sigma;}}}{c}_i{x}^i=x^{192-K}m\left(x\right)+r\left(x\right);$ Wherein, $r\left(x\right)=\frac{x^{192-K}m\left(x\right)}{g\left(x\right)}.$

When K=192, the coefficient g of the generator polynomial expression formula of RS (192,192) _iFor:

i gi

0 1

When K=168, the coefficient g of the generator polynomial expression formula of RS (192,168) _iFor:

When K=160, the coefficient g of the generator polynomial expression formula of RS (192,160) _iFor:

When K=144, the coefficient g of the generator polynomial expression formula of RS (192,144) _iFor:

Coding is following with the method for byte-interleaved: transmission data block is unit with the byte, and from left to right by row input block interleaver, every row MI byte is accomplished up to the K row.The RS coding is encoded by row, the 192-K row after check byte is filled to.Data behind the coding are exported by row according to the order of input more from left to right, all accomplish up to 192 row.

Above-mentioned RS coding is that unit carries out with byte-interleaved with the physical logic channel, and the upper layer data bag of same physical logic channel is imported byte interleaver device successively and carried out byte-interleaved and RS coding.First byte of byte interleaver device the 0th row is defined as the start byte of byte interleaver device.Each output MI * 192 bytes of byte interleaver device always are mapped on the integer time slot sends, and wherein the start byte of byte interleaver device is mapped in the starting point transmission of certain time slot.

Through technique scheme, RS coding is optimized selection according to the bandwidth of operation of system, select proper encoding mode according to different channel conditions, correspondingly, byte interleaver device is optimized, use rational interleave parameter to carry out byte-interleaved.

According to the preferential principle of sending of high order bit, every byte is mapped as 8 bit streams through the transmission data after above-mentioned RS coding and the byte-interleaved, sends into the LDPC encoder.First byte of byte interleaver device the 0th row is defined as the start byte of byte interleaver device, and its highest order always is mapped in first bit of LDPC input bit piece.The LDPC code allocation is as shown in table 3:

Code check input block length IOB is long

1/2 4608 bits, 9216 bits

3/4 6912 bits, 9216 bits

Table 3, LDPC code allocation

The LDPC coding is provided by check matrix H, and the generation method of H matrix is following:

1)

LDPC code check matrix generation method

Below for generating the cyclic program section of

LDPC code check matrix:

2)

LDPC code check matrix generation method

Below for generating the cyclic program section of

LDPC code check matrix:

Shown in figure 11, for process LDPC bit stream coded being carried out the sketch map of Bit Interleave.

Bit interleaver adopts 384 * 216 block interleaver.Binary sequence behind the LDPC coding is according to from top to bottom order each row of write-in block interleaver successively, until filling up whole interleaver, and reading from left to right again by leu.The output of bit interleaver is alignd with time slot, that is, first bit that transmits in each time slot always is defined as first bit of bit interleaver output.

Figure 12 is a pilot tone multiple connection mode sketch map of the subcarrier allocation of OFDM symbol being given data symbol, scattered pilot and CP continuous pilot.Wherein, oblique line is a continuous pilot signal partly, and black part is divided into discrete guide-frequency signal, the data symbol of white portion for obtaining through constellation mapping.Illustrated pilot tone multiple connection with data symbol, scattered pilot with CP continuous pilot multiple connection be in the same place, form the OFDM frequency domain symbol.Each OFDM symbol comprises 1876 number of sub-carrier (0-1875), is designated as X (i), i=0, and 1 ... 1875, comprising 234 scattered pilots, 76 CP continuous pilots, 1566 data subcarriers.

Among Figure 12, CP continuous pilot uses the 0th, 6, and 66,76,92,132,150,170,206,228,260,294,296,328,338; 382,392,406,462,474,480,494,552,562,582,624,630,664,668,738,744; 760,790,806,834,850,922,937,938,952,1024,1040,1068,1084,1114,1130,1172; 1206,1210,1244,1250,1292,1312,1322,1380,1394,1400,1412,1468,1482,1492,1536; 1546,1578,1580,1614,1646,1668,1704,1724,1742,1782,1798,1808,1868,1875 number of sub-carrier, totally 76.

Wherein the 6th, 406,1084,1482,66,462,1114,1492,76,474,1130,1536,92; 480,1172,1546,132,494,1206,1578,150,552,1210,1580,170,562; 1244,1614,206,582,1250,1646,228,624,1292,1668,260,630,1312; 1704,294,664,1322,1724,296,668,1380,1742,328,738,1394,1782; 338,744,1400,1798,382,760,1412,1808,392,790,1468,1868 totally 64 carriers carry 16 bit system information.Information bits adopts 4 times of repeated encodings to be mapped on 4 CP continuous pilots and transmits, and mapping relations are as shown in table 4, and system information is specifically explained as shown in table 4.All the other CP continuous pilot transmission " 0 ".

Repeated encoding mode on table 5, the CP continuous pilot

Table 6, CP continuous pilot system for transmitting information

In the table 6 the concrete institute of each bit to comprise the information content following:

1) bit0～bit5 is a current time slots number, span 0～39;

2) bit6 is the byte interleaver device sync id, and this bit value is that to identify this time slot at 1 o'clock be the initial time slot of byte interleaver device;

3) bit7 is control logic channel change indication, and it adopts the mode indicating terminal control logic channel configuration information change of differential modulation.Said differential mode is following: that suppose that previous frame bit7 transmits is a, 0 or 1, and system's control channel configuration information will change at next frame, and then in this frame, transmit a and keep, change up to take place next time.

4) bit8～bit15 keeps.

Continuous pilot to

is mapped onto the subcarriers.The symbol that the identical continuous subcarrier point of different OFDM symbols upward transmits in the same time slot is identical.

Note n is the numbering of OFDM symbol in each time slot, 0≤n≤52; M is the corresponding subcarrier number of scattered pilot in each OFDM symbol, and then the m value is following:

When mod (n, 2)=0

$m=\left\{\begin{array}{cc}8p+1,& p=\mathrm{0,1,2},\&CenterDot;\&CenterDot;\&CenterDot;,116\\ 8p+3,& p=\mathrm{117,118,119},\&CenterDot;\&CenterDot;\&CenterDot;,233\end{array}\right.$

When mod (n, 2)=1

$m=\left\{\begin{array}{cc}8p+5,& p=\mathrm{0,1,2},\&CenterDot;\&CenterDot;\&CenterDot;,116\\ 8p+7,& p=\mathrm{117,118,119},\&CenterDot;\&CenterDot;\&CenterDot;,233\end{array}\right.,$

The whole values of scattered pilot are 1+0j.

Among Figure 12, press the front and back order mapping (enum) data signal of subcarrier, OFDM symbol.Subcarrier in effective subcarrier of each OFDM symbol except that scattered pilot and CP continuous pilot is a data subcarrier.Have 82998 data subcarriers in each time slot, wherein preceding 82944 data subcarriers are used to carry the data symbol after the constellation mapping, and last 54 data subcarriers are filled 0+0j.

The technique scheme that the present invention proposes; Actual bandwidth according to system; Setting rationally, the CP continuous pilot of distribution system, scattered pilot, digital subcarrier make mobile multimedia broadcast transmission system that overhead rationally is set, and effectively utilize frequency spectrum resource transmission data.

All symbols on the time-frequency grid shown in Figure 12 (effectively subcarrier) comprise data subcarrier, scattered pilot and CP continuous pilot etc., all by a multiple pseudo random sequence P _c(i) scrambler.Said 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 binary pseudo-random sequence (PRBS).

Figure 13 is the sketch map of PRBS generation method.

As shown in the figure, the generator polynomial of PRBS is: x ¹²+ x ¹¹+ x ⁸+ x ⁶+ 1, corresponding with illustrated shift register structure.The initial value of shift register confirms that by the scrambler pattern its corresponding relation is following:

1) the scrambler pattern 0: initial value 000000000001;

2) the scrambler pattern 1: initial value 000010010011;

3) the scrambler pattern 2: initial value 000001001100;

4) scrambler mode 3: initial value 001010110011;

5) the scrambler pattern 4: initial value 011101000100;

6) the scrambler pattern 5: initial value 010001001100;

7) the scrambler pattern 6: initial value 000101101101;

8) scrambler mode 7: initial value 101010110011.

PRBS resets in each time slot beginning, and all time slots are all by identical pattern scrambler.

This scrambler passes through complex symbol on effective subcarrier and multiple pseudo random sequence P _c(i) carry out complex multiplication and realize that the expression formula of said scrambler is:

Y _n(i)＝X _n(i)×P _c(n×1876+i)，0≤i≤1875，0≤n≤52

Wherein, X _n(i) be the i on n OFDM symbol of each time slot effective subcarrier before the scrambler, Y _n(i) be effective subcarrier behind the scrambler.

Figure 14 is an OFDM symbol sub-carrier structure sketch map.

The effective subcarrier Y of OFDM after above-mentioned insertion pilot tone and the scrambling _n(i), 0≤i≤N _S-1 is mapped as the OFDM symbol through IFT, and mapping mode is:

$S_n\left(t\right)=\frac{1}{\sqrt{N_S}}\underset{i=0}{\overset{N_S-1}{\mathrm{\&Sigma;}}}{Z}_n\left(i\right)e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="H200910078052XE00012.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;\; i}{\left(\mathrm{\&Delta;\; f}\right)}_S(t-T_{\mathrm{CP}})},$ 0≤t≤T _S, 0≤n≤52, wherein, S _n(t) be h OFDM symbol in the time slot, N _SBe OFDM symbol sub-carrier number, Z _n(i) be the IFT input signal of n OFDM symbol, (Δ f) _SBe the subcarrier spacing of OFDM symbol, value is 2.44140625kHz, T _CPBe OFDM symbol cyclic prefix length, value is 51.2 μ s, T _SBe the OFDM symbol lengths, value is 460.8 μ s.

OFDM symbol sub-carrier number N _S=2048, IFT input signal Z _n(i) with the effective subcarrier Y of OFDM frequency domain _n(i) mapping relations are:

OFDM symbol through the IFFT conversion is said according to Fig. 7, adds Cyclic Prefix (CP), forms the time domain OFDM symbol.

OFDM symbol after the modulation according to the described frame structure of Fig. 4, is formed time slot after adding protection interval, synchronizing signal, the transmitter identification signal successively.Again 40 time slots are connected to form the physical layer signal frame.

The upper layer data of native system stream can adopt comprise H.264, video flowings such as AVS, MPEG-2, MPEG-4, the data format of audio stream such as AC-3, AAC and other numerous types of data.Various types of broadcast datas that can comprise single medium (for example video frequency source coding, text) and multimedia (mixing of audio frequency, video, text and data) to the data coding.

The above only is a preferred implementation of the present invention; Should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the principle of the invention; Can also make some improvement and retouching, these improvement and retouching also should be regarded as protection scope of the present invention.

Claims (15)

1. a mobile multimedia broadcast transmission system is characterized in that, comprising:

RS coding and byte interleaver device are used for through the physical logic channel upper layer data stream being carried out RS coding and byte-interleaved;

The LDPC encoder is used for the said RS coding and the data of byte interleaver device output are carried out the LDPC coding, obtains Bit data;

Bit interleaver is used for the Bit data of said LDPC encoder output is carried out Bit Interleave;

Constellation mapper is used for the data of said bit interleaver output are carried out constellation mapping;

The frequency domain symbol maker is used for scattered pilot, includes the CP continuous pilot of system information and form the OFDM frequency domain symbol through the data symbol multiple connection of constellation mapping together;

Scrambler is used to use pseudo random sequence that said OFDM frequency domain symbol is carried out scrambler;

The IFFT converter is used for producing the OFDM time-domain symbol after the frequency domain symbol process IFFT conversion with said scrambler output;

The time domain framer is used for connecting to form the physical layer signal frame with behind the said OFDM time-domain symbol composition time slot;

Reflector is used for said physical layer signal frame is launched after baseband signal is converted into radio frequency, and wherein said reflector uses the interior 5MHz bandwidth arbitrarily of wireless channel to transmit;

Wherein, the output block length behind the said LDPC coding is 9216 bits, and code check is respectively 1/2 and 3/4, corresponding different code rate, and said RS coding is respectively with the corresponding interlace mode of byte interleaver device:

Wherein, MI is the line number of byte interleaver device, and the whole bytes in the byte interleaver device are MI * 192 bytes;

Said bit interleaver adopts 384 * 216 block interleaver; Write each row of said block interleaver from the Bit data of LDPC encoder output successively according to order from top to bottom, until filling up whole block interleaver, reading from left to right again by leu, wherein the output of bit interleaver is alignd with time slot;

Said frequency domain symbol maker with 234 scattered pilots, 76 CP continuous pilots, the multiple connection of 1566 data subcarriers together, becomes 1876 effective subcarriers in each OFDM symbol.

2. mobile multimedia broadcast transmission system as claimed in claim 1; It is characterized in that; Said physical layer signal frame length is 1 second, comprises that 40 length are 25 milliseconds time slot, and said time slot comprises 1 beacon and 53 OFDM symbols; Said beacon comprises 1 identification signal of transmitter and 2 identical synchronizing signals; Said identification signal of transmitter is carried out successively passing through periodic extension again after BPSK mapping and the IFFT conversion by the frequency domain random sequence and obtains, said synchronizing signal through intercepting frequency domain random sequence after, carry out BPSK and IFFT conversion successively and obtain.

3. mobile multimedia broadcast transmission system as claimed in claim 2 is characterized in that, said identification signal of transmitter carries the sub-carrier number N of said identification signal of transmitter through 117 bit informations sign _ID=128, through BPSK modulation, said identification signal of transmitter X _ID(i) produced by sender unit identification sequence TxID (k) mapping, mapping mode is:

4. mobile multimedia broadcast transmission system as claimed in claim 2 is characterized in that, said synchronizing signal S _b(t) be the pseudo-random signal of band, length T _bBe 204.8 μ s,

0≤t≤T _b, N wherein _bFor carrying the sub-carrier number of said synchronizing signal, X _b(i) for carrying binary pseudo-random sequence PN _b(k) BPSK modulation signal, (Δ f) _bBe the subcarrier spacing of synchronizing signal, sub-carrier number N _b=1024, and PN _b(k) BPSK modulation signal X _b(i) by PN _b(k) mapping produces, and mapping mode is:

5. mobile multimedia broadcast transmission system as claimed in claim 4 is characterized in that said binary pseudo-random sequence is produced by linear feedback shift register, and the initial value of shift register is 01110101101, and generator polynomial is: x ¹¹+ x ⁹+ 1.

6. mobile multimedia broadcast transmission system as claimed in claim 2 is characterized in that, said identification signal of transmitter, synchronizing signal and OFDM intersymbol adopt the protection of band window function to overlap mutually at interval, and the expression formula of said window function is:

Wherein, t is a time variable, and T is a constant, T _GDBe said protection length at interval.

7. mobile multimedia broadcast transmission system as claimed in claim 1 is characterized in that, said RS coding is by original RS (255; M) RS that produces after through brachymemma of systematic code (192, K) shortened code, wherein M=K+63; K is the byte number of information sequence in the code word; (255, M) each code element of systematic code is taken from territory GF (256) to said RS, and the generator polynomial in this territory is p (x)=x ⁸+ x ⁴+ x ³+ x ²+ 1.

8. mobile multimedia broadcast transmission system as claimed in claim 7 is characterized in that, (192, K) sign indicating number comprises 4 kinds of patterns to said RS, and the value of K is respectively K=192, K=168, K=160 and K=144 in these 4 kinds of patterns.

9. mobile multimedia broadcast transmission system as claimed in claim 8; It is characterized in that; (192, K) expression formula of the generator polynomial of sign indicating number is to said RS

When K=192, the coefficient g of the generator polynomial expression formula of RS (192,192) _iFor:

i g _i

0 1

When K=168, the coefficient g of the generator polynomial expression formula of RS (192,168) _iFor:

When K=160, the coefficient g of the generator polynomial expression formula of RS (192,160) _iFor:

When K=144, the coefficient g of the generator polynomial expression formula of RS (192,144) _iFor:

10. mobile multimedia broadcast transmission system as claimed in claim 9; It is characterized in that; Said upper layer data stream is unit with the byte, from left to right by row input RS coding and byte interleaver device, wherein; The RS coding is encoded by row, and the start byte of byte interleaver device is mapped in the starting point of certain time slot and sends.

11. mobile multimedia broadcast transmission system as claimed in claim 1 is characterized in that, said 76 CP continuous pilots use in said 1876 effective subcarriers the 0th, 6,66,76,92,132,150,170,206,228,260,294,296; 328,338,382,392,406,462,474,480,494,552,562,582,624,630,664; 668,738,744,760,790,806,834,850,922,937,938,952,1024,1040,1068; 1084,1114,1130,1172,1206,1210,1244,1250,1292,1312,1322,1380,1394,1400; 1412,1468,1482,1492,1536,1546,1578,1580,1614,1646,1668,1704,1724,1742; 1782,1798,1808,1868,1875 number of sub-carrier, and therein the 6th, 406,1084,1482,66,462,1114,1492,76; 474,1130,1536,92,480,1172,1546,132,494,1206,1578,150,552,1210; 1580,170,562,1244,1614,206,582,1250,1646,228,624,1292,1668,260; 630,1312,1704,294,664,1322,1724,296,668,1380,1742,328,738,1394; 1782,338,744,1400,1798,382,760,1412,1808,392,790,1468,1868 carry 16 bit system information totally in 64 number of sub-carrier, and said system information comprises that length is that the timeslot number of 6 bits, the byte interleaver device sync id that length is 1 bit, control logic channel change indication and the length that length is 1 bit are the reserved word of 8 bits; Said CP continuous pilot is mapped on the subcarrier with the mode of ; Wherein, the symbol that the identical continuous subcarrier point of different OFDM symbols upward transmits in the same time slot is identical.

12. mobile multimedia broadcast transmission system as claimed in claim 11 is characterized in that, when OFDM symbol in each time slot be numbered n the time, the subcarrier number m value that scattered pilot is corresponding in the OFDM symbol is:

When mod (n, 2)=0

When mod (n, 2)=1

The whole values of scattered pilot are 1+0j.

13. mobile multimedia broadcast transmission system as claimed in claim 1 is characterized in that, the generator polynomial of the pseudo random sequence that said scrambler uses is: x ¹²+ x ¹¹+ x ⁸+ x ⁶+ 1; Said scrambler is divided into 8 kinds of patterns, and corresponding register initial value is respectively:

1) the scrambler pattern 0: initial value 000000000001,

2) the scrambler pattern 1: initial value 000010010011,

3) the scrambler pattern 2: initial value 000001001100,

4) scrambler mode 3: initial value 001010110011,

5) the scrambler pattern 4: initial value 011101000100,

6) the scrambler pattern 5: initial value 010001001100,

7) the scrambler pattern 6: initial value 000101101101,

8) scrambler mode 7: initial value 101010110011;

Said pseudo random sequence is reset in the beginning of each time slot, and all time slots are all by identical pattern scrambler.

14. mobile multimedia broadcast transmission system as claimed in claim 1 is characterized in that, said IFFT converter carries out 2048 IFFT conversion after 1876 effective subcarriers being placed on the 1st～938 and the 110th～2047 subcarrier of 2048 number of sub-carrier.

15. like the described mobile multimedia broadcast transmission system of one of claim 1 to 14; It is characterized in that; OFDM symbol after said time domain framer will be modulated is formed time slot after adding protection interval, synchronizing signal, transmitter identification signal successively, again 40 time slots is connected to form the physical layer signal frame.

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