1、 Rec. ITU-R BO.1408-1 1 RECOMMENDATION ITU-R BO.1408-1 Transmission system for advanced multimedia services provided by integrated services digital broadcasting in a broadcasting-satellite channel (Question ITU-R 3/6) (1999-2002) The ITU Radiocommunication Assembly, considering a) that various kinds
2、 of information such as video, including high-definition television (HDTV) as well as limited-definition television (LDTV), audio, text, graphics, and data are provided to the public via the broadcasting channels; b) that information and services can be integrated efficiently and flexibly by using d
3、igital techniques; c) that integrated services digital broadcasting (ISDB) techniques can be used to implement services exploiting the full advantages of digital broadcasting; d) that the MPEG transport stream (MPEG-TS) is widely applied as a container of digitally coded information; e) that a great
4、 benefit is obtained if the integration of data/services can be achieved on a TS basis, which requires the transmission system to deal with multiple MPEG-TSs; f) that the recent progress in digital technology allows a highly bandwidth efficient modulation scheme such as 8-PSK in addition to the conv
5、olutionally-encoded QPSK and BPSK; g) that the required service quality and service availability differ according to applications; h) that rain attenuation, which differs by climatic zones, needs to be taken into account in satellite broadcasting systems; j) that a common ISDB transmission system th
6、at provides a high flexibility of use as well as high spectrum efficiency while covering all the requirements for application, quality and rain attenuation is desirable, rather than introducing multiple systems specifically developed for particular applications; k) that Recommendation ITU-R BO.1516
7、recommends common functional requirements for the integrated receiver-decoder (IRD) of digital multi-programme broadcasting by satellite, noting a) that advanced multimedia systems for ISDB type services are characterised by highest flexibility with respect to: handling several MPEG-TSs; allowing ti
8、me multiplex of appropriate modulation schemes suitable for applications of various transmission robustness, e.g. 8-PSK, QPSK and BPSK; informing the demodulator about the transmission and multiplexing configuration by means of specially robust control signals; 2 Rec. ITU-R BO.1408-1 that the integr
9、ated circuits for satellite (ISDB-S) receivers could potentially be used for the system defined in Recommendation ITU-R BO.1516, because each of the components used in ISDB-S is also used in the systems defined in this Recommendation, recommends 1 that the transmission system described in Annex 1 sh
10、ould be used for ISDB-S system applications. ANNEX 1 General specifications for a generic satellite ISDB-S transmission system Introduction ISDB is a new type of broadcasting for multimedia services. It integrates, systematically, various kinds of digital content, each of which may include multi-pro
11、gramme video from LDTV to HDTV, multi-programme audio, graphics, texts, etc. Most digital content are nowadays encoded into the form of MPEG-TS and delivered worldwide. It is highly desired to integrate the digital content on an MPEG-TS basis. Since the ISDB contains a variety of services, the syste
12、m has to cover a wide range of requirements that may differ from one service to another. For example, a large transmission capacity is required for HDTV services, while a high service availability (or transmission reliability) is required for data services such as delivery of conditional access keys
13、, downloading of software, etc. To integrate these signals of different service requirements, it is desired for the transmission systems to provide a series of modulation and/or error protection schemes which can be selected and combined flexibly in order to meet each requirement of the services int
14、egrated. This is especially true of the ISDB-S systems operating in the 11-12 GHz broadcasting-satellite service (BSS) band in countries that belong to the climate zones with high rain attenuation. ISDB-S transmission systems are characterised by: MPEG interfacing: the input signals to the encoder a
15、nd the output signals from the decoder conform to the MPEG-TS specifications; capability of signal integration on MPEG-TS basis: digital contents can be multiplexed without decoding/re-encoding of the input streams; flexible use of modulation schemes: digital content can be simultaneously transmitte
16、d with the appropriate modulation schemes for each integrated content in the ISDB stream; provision of a control signal that informs the receiver of the multiplexing and modulation configuration. The generic system for ISDB-S is described below. Rec. ITU-R BO.1408-1 3 1 Block definition A general co
17、nfiguration of the system is shown in Fig. 1. The system shall handle three kinds of signals in order to transmit multiple MPEG-TSs with various kinds of modulation schemes and in order to achieve stable and easy reception. The three signals shall be: main signal which consists of multiple MPEG-TSs
18、and carries the programme content; transmission and multiplexing configuration control (TMCC) signal which informs the receiver of the modulation schemes applied, the identification of MPEG-TSs, etc.; and burst signal which ensures stable carrier recovery at the receiver under any reception conditio
19、n (especially under low carrier-to-noise (C/N) ratio conditions). 1408-01RS (204,188)OutercoderFrameconstructionEnergydispersalInterleaverTMCC dataencoderOutercoderEnergydispersalInterleaverEnergydispersalTDMInnercoderBurstinsertionModulationMPEG-TS No. AMPEG-TS No. BControl data No. AControl data N
20、o. BTMCC signalMain signalBurst signalFIGURE 1General configuration of systemconvolutionalcodeTo handle multiple MPEG-TSs and to allow several modulation schemes to be used simultaneously, a frame structure is introduced to the main signal. The input MPEG-TSs shall be combined into a single stream,
21、to which ordinary signal processes for satellite systems are applied (i.e., energy dispersal, interleaving and inner coding). The control data which designates the modulation schemes, etc. for each TS packet shall be encoded into the TMCC signal, to which a series of channel coding is applied. In mo
22、st cases, some parts of the channel coding can be shared with the main signal. The burst signal shall be energy-dispersed to avoid line spectra in the transmission signal. This is done by modulating the burst with a random sequence. Therefore, the burst signal can carry information by modulating it
23、with information data instead of modulating it with a random sequence. In this case, an additional channel coding may be necessary. These three signals shall be time-division multiplexed (time division multiplex (TDM) and modulated by the designated modulation schemes. 2 Outer code for main signal R
24、eed-Solomon (RS) (204,188) shortened code, from the original RS (255,239) code, shall be applied to each input MPEG-TS packet (188 bytes) to generate the error protected packet (204 bytes). The RS coding shall also be applied to the first byte of the packet (MPEG sync word). 4 Rec. ITU-R BO.1408-1 C
25、ode generator polynomial: g(x) = (x + 0) (x + 1) (x + 2) (x + 15), where = 02h Field generator polynomial: p(x) = x8+ x4+ x3+ x2+ 1. The shortened RS code may be implemented by adding 51 bytes, all set to zero, before the information bytes at the input of an RS (255,239) encoder. After the RS coding
26、 procedure, these null bytes shall be discarded. 3 Transport combiner 3.1 Framing structure To combine the TSs, the error-protected 204-byte packets shall be assigned to the “slots” in a “data frame”, as shown in Fig. 2. The slot indicates the absolute position in the data frame and is used as the u
27、nit that designates the modulation scheme and MPEG-TS identification. The size of slot (the number of bytes in a slot) shall be 204 bytes to keep one-to-one correspondence between slots and error-protected packets. The data frame shall be composed of N slots. 1408-02FIGURE 2Frame structure16 bytes18
28、8 bytesMPEG-TS No. Awith paritySlot No. 1Slot No. 2Slot No. 3Slot No. 4Slot No. PSlot No. P + 1Slot No. N 1Slot No. NData frame204 bytes204 bytesMPEG-TS No. Bwith parityMPEG-TS No. Xwith parityA super-frame is introduced to perform interleaving easily. Figure 3 shows the super-frame structure. The s
29、uper-frame shall be composed of M frames, where M corresponds to the depth of interleaving. Rec. ITU-R BO.1408-1 5 1408-03Super-frame188 bytes 16 bytesSlot No. 1Slot No. 3Slot No. 4Slot No. NInterleavedirectionFrame No. MFrame No. 3Frame No. 2Frame No. 1Slot No. 2Slot No. 5PARITYATDAFIGURE 3Super-fr
30、ame structure3.2 Slot assignment As the spectrum efficiency or the transmissible bits per symbol varies with the combination of modulation and inner code rate, the number of packets being transmitted depends on the combination. Since the number of symbols to be modulated by a particular modulation s
31、cheme must be an integer value, the relationship between the number of packets transmitted and the number of symbols for the modulation is given by equation (1). kkkEPBI8= (1) where: Ik, Pk : integers k : number of symbols transmitted with the k-th combination of the modulation scheme and inner code
32、 rate Pk: number of packets transmitted with the k-th combination of the modulation scheme and inner code rate Ek: spectrum efficiency of the k-th combination of the modulation scheme and inner code rate B : number of bytes per packet (= 204). The number of symbols per data frame, ID, is expressed b
33、y equation (2). =kkDII (2) The number of packets transmitted during a frame duration becomes maximum when all the packets are modulated by the modulation-code combination having the highest spectrum efficiency among the possible combinations in the system. Therefore, the number of slots provided by
34、the system is given by substituting the ID and Emaxfor equation (1). BEINmaxD8= (3) 6 Rec. ITU-R BO.1408-1 where N denotes the number of slots that the system provides, and Emaxdenotes the highest spectrum efficiency of the modulation-coded combinations that the system provides. When modulation-code
35、 combinations that do not have the highest spectrum efficiency are used, the number of packets being transmitted becomes lower than the number of the slots provided by the system. In this case, some of the slots shall be filled by dummy data to keep the frame size (the number of slots in a frame) co
36、nstant. These slots are called “dummy slots”. The number of dummy slots Sdin a frame is obtained by the following equation (4). =kkdPNS (4) In the case where multiple modulation schemes are used simultaneously, that is, part of the slots in a frame are modulated by a particular modulation-code combi
37、nation while the rest of slots are modulated by the other combinations, the data shall be modulated from the highest spectrum efficient scheme to the lowest spectrum efficient scheme among the combinations being actually used. In other words, the packets transmitted with higher efficient combination
38、s are assigned to the lower numbered slots in a frame. This modulation order gives the minimum value in the bit error ratio (BER) after decoding the convolutional code in a low C/N reception. Figure 4 shows some examples of slot assignment when QPSK (r = 1/2, r denotes code rate), BPSK (r = 1/2), an
39、d QPSK (r = 3/4) are used, respectively with trellis coded (TC) 8-PSK (r = 2/3). In the examples, TC 8-PSK (r = 2/3) is assumed as the highest spectrum efficient combination of the system. Since the spectrum efficiency of QPSK (r = 1/2) is half that of the TC 8-PSK, one dummy slot is inserted (Fig.
40、4a); since the spectrum efficiency of BPSK (r = 1/2) is a quarter that of the TC 8-PSK, three dummy slots are inserted (Fig. 4b); and since the spectrum efficiency of QPSK (r = 3/4) is 3/4 that of the TC 8-PSK, one dummy slot is inserted for three active slots (Fig. 4c). 1408-04Dummy slot Dummy slot
41、Dummy slotDummy slotDummy slotTC 8-PSKTC 8-PSKa) TC 8-PSK + QPSK (r = 1/2)TC 8-PSKc) TC 8-PSK + QPSK (r = 3/4)QPSK (r = 1/2)BPSK (r = 1/2)b) TC 8-PSK + BPSK (r = 1/2)QPSK (r = 3/4)QPSK (r = 3/4)FIGURE 4Example of slot assignmentQPSK (r = 3/4)TC 8-PSKTC 8-PSKTC 8-PSKTC 8-PSK TC 8-PSKTC 8-PSKNo. 1No.
42、N 3No. N 2No. N 1No. NNo. 1No. N 3No. N 2No. N 1No. NSlot No. 1Slot No. N 1Slot No. NRec. ITU-R BO.1408-1 7 4 Randomization for energy dispersal for main signal In order to comply with ITU Radio Regulations and to ensure adequate binary transitions, the data of the frame shall be randomized in accor
43、dance with the configuration depicted in Fig. 5. 1408-05100101010000000X1 X2 X3 X4 X5 X6 X7 X8 X9 X10 X11 X12 X13 X14 X151 super-frameError-protected packetsRandomizinggateon onFIGURE 5Randomizer schematic diagramInitializationPRBSdataoff offSlot No. 1 inframe No. 1Slot No. 2 inframe No. 1Slot No. 3
44、 inframe No. 1Slot No. 4 inframe No. 1Slot No. N inframe No. M204 bytes1 byteEX-ORThe polynomial for the pseudo random binary sequence (PRBS) generator shall be: 1 + x14+ x15Loading of the sequence “100101010000000” into the PRBS registers, as indicated in Fig. 5, shall be initiated at the second by
45、te of every super-frame. The first bit of the output of the PRBS generator shall be applied to the first bit (i.e., most significant bit (MSB) of the second byte of slot No. 1 in frame No. 1. The PRBS shall be added to the data except to the first byte (MPEG sync byte) of every slot. 5 Interleaving
46、for main signal Inter-frame block interleaving with a depth of M shall be applied to the randomized data, as shown in Fig. 6. Slot assignment for every frame shall be identical throughout a super-frame, resulting in the data being interleaved only between those transmitted with the same modulation-c
47、ode combination. Interleaving shall be applied except to the first byte (MPEG sync byte) of every slot. Figure 6 illustrates an example of interleaving when the depth of interleaving is 8 (i.e., super-frame consists of 8 frames) and two kinds of modulation-code combinations are being used. The data
48、in the original frame is read out in the inter-frame direction, i.e., in the order of A1,1; A2,1; A3,1; ., where Ai,j represents the byte data at j-th slot in i-th frame, to form the interleaved frame. The data in the interleaved frame is read out in the byte direction (horizontally) and fed to the
49、TDM multiplexer. 8 Rec. ITU-R BO.1408-1 It is not necessary to transmit the first byte of each packet (the MPEG sync word of 47h) because the timing references (frame sync words) are sent by the TMCC signal. The omitted MPEG sync words have to be recovered at the receiver to perform outer decoding properly. Note that in this case, B in the equations (1) and (3) should take the value 203 in order for the equation to hold true. 1408-06MPA8,1 A8,2 A8,3 A8,203MPEGA7,1 A7,2 A7,3 A7,203MPEA3,1 A3,2 A3,3 A3,203Modulation AMPEA2,1 A2,2 A2,3 A2,203
