1、 Rep. ITU-R BO.2101 1 REPORT ITU-R BO.2101*Digital satellite broadcasting system (television, sound and data) with flexible configuration*(2007) 1 Introduction This Report describes studies undertaken by administrations on DVB-S2, the second-generation specification for satellite broadband applicati
2、ons, developed by the DVB (Digital Video Broadcasting) Project in 2003, targeting the following satellite applications: TV and sound broadcasting, interactivity (i.e. Internet Access) and contribution services, such as TV contribution links and DSNG (digital satellite news gathering). DVB-S2 1, 2, 3
3、 is the second-generation system for satellite broadband services, defined by DVB in 2003, in the tenth anniversary of the birth of DVB-S 4, the first DVB system for satellite broadcasting. The system has been designed for different types of applications: Broadcasting of standard definition and high
4、-definition television (SDTV and HDTV); Interactive Services, including Internet Access, for satellite broadcasting applications (for IRDs Integrated receivers decoders and PC personal computers); Contribution applications, such as digital TV contribution and news gathering; Data content distributio
5、n and Internet trunking. The DVB-S2 standard has been specified around three key concepts: best transmission performance, total flexibility and reasonable receiver complexity. To achieve the best performance-complexity trade-off with an appreciable capacity gain over DVB-S, DVB-S2 benefits from more
6、 recent developments in channel coding and modulation. LDPC, low density parity check codes, combined with QPSK (quadrature phase shift keying), 8-PSK(phase shift keying), 16 amplitude phase shift keying (APSK) and 32-APSK modulations allow the system to work properly on the non-linear satellite cha
7、nnel with a performance approaching the Shannon limit, whilst maintaining a reasonable receiver complexity. The framing structure allows for maximum flexibility in a versatile system and also synchronization in worst case configurations (low signal-to-noise ratio, SNR). For interactive point-to-poin
8、t applications such as Intenet Protocol (IP) unicasting, the adoption of the adaptive coding and modulation (ACM) functionality allows optimization of the transmission parameters for each individual user on a frame-by-frame basis, dependent on path conditions, under closed-loop control via a return
9、channel (connecting the IRD/PC to the DVB-S2 up-link station via terrestrial or satellite links, signaling the IRD/PC reception condition). This results in a further increase in the spectrum utilization efficiency of DVB-S2 over DVB-S, allowing the optimization *This Report is intended as a supporti
10、ng information for the use of Recommendation ITU-R BO.1784 Digital satellite broadcasting system with flexible configuration (television, sound and data). Eventually this Report may become a nucleus for a new handbook on satellite digital broadcasting in the BSS bands above 11.7 GHz. * DVB-S2 is cha
11、racterized by a multitude of configuration parameters (modulation and coding, framing structure, pilots signals) allowing the system to be flexibly used in different operating conditions. 2 Rep. ITU-R BO.2101 of the space segment design, thus making possible a drastic reduction in the cost of satell
12、ite-based IP services. DVB-S2 flexibility allows the system to cope with any existing satellite transponder characteristics, with a large variety of spectrum efficiencies and associated SNR requirements. Furthermore it is designed to handle the variety of advanced audio-video formats defined in DVB.
13、 DVB-S2 accommodates any input stream format, including single or multiple Moving Picture Expert Group Transport Streams (MPEG-TS) (characterized by 188-byte packets), IP as well as asynchronous transfer mode (ATM) packets, continuous bit-streams. Two years since the system publication as a European
14、 Telecommunication Standards Institute (ETSI) standard, a variety of DVB-S2 products is offered by the industry, and services are being launched by several broadcasters around the world. To verify the status of the DVB-S2 technology, the DVB-S2 ad-hoc group has launched a laboratory test campaign, w
15、ith the task to verify the compliancy of available equipment to the standard, and the effective gain in performance with respect to the first generation system DVB-S. The Annexes in this Report describe: a) the results of the Laboratory tests carried out by Rai-CRIT1on equipment provided by seven di
16、fferent equipment manufacturers in June 2006. Furthermore, the first operational contribution network adopting DVB-S2 is described, as set up by EBU (European Broadcasting Union) in the Eurovision contribution network for HDTV transmissions during the 2006 FIFA World Cup. Finally, some references ar
17、e provided for further documents giving useful guidelines for the use of the DVB-S2 system; b) the results of studies carried out by Network Ten Australia, Nine Network Australia and Singtel Optus along with Australian agents for equipment suppliers, who loaned modulators and demodulators, and manuf
18、acturers of DVB-S2 equipment to assess the system performance for broadcast contribution with respect to DVB-SNG modem implementation margin and margin to threshold for each modulation mode. References 1 ETSI. EN 302 307 (V1.1.2) Digital Video Broadcasting (DVB). Second generation framing structure,
19、 channel coding and modulation systems for Broadcasting. Interactive Services, News Gathering and other broadband satellite applications. 2 ETSI. TR 102 376 Digital Video Broadcasting (DVB). User guidelines for the second generation system for Broadcasting. Interactive Services. News Gathering and o
20、ther broadband satellite applications (DVB-S2). 3 Internat. J. on Sat. Com. Networks May-June 2004. Vol. 22, 3, Special issue on The DVB-S2 standard for Broadband Satellite Systems. 4 ETSI. EN 300 421 (V1.1.2) Digital Video Broadcasting (DVB). Framing structure, channel coding and modulation for 11/
21、12 GHz satellite services. 1BERTELLA, A., MIGNONE, V., SACCO, B. and TABONE, M. Technology Innovation Centre of Rai, Corso Giambone, 68, 10135, Torino, Italy (e-mail: . rai.it). Rep. ITU-R BO.2101 3 Annex 1 Rai-CRIT laboratory tests 1 Introduction The DVB ad hoc group responsible for the standardisa
22、tion of DVB-S2 has launched a laboratory test campaign to evaluate the performance of the DVB-S2 equipment. Following this request, the European tests had been carried out by Rai in their CRIT laboratories in the second half of June 2006, with DVB-S2 equipment made available by manufacturers, either
23、 in the form of off-the-shelf products or of laboratory prototypes. The tests carried out at Rai-CRIT laboratories include additive white gaussian noise (AWGN) performance, non-linear channel and phase noise degradation. The results clearly indicate that the equipment performance is in line with the
24、 simulation results presented in the DVB-S2 standard. Implementation loss is in the order of 0.2 dB for QPSK, 0.5 dB for 8-PSK, 0.8 dB for 16-APSK and 1.2 dB for 32-APSK. Single carrier and multicarrier configuration have been implemented and compared to DVB-S equivalent configurations, showing that
25、 DVB-S2 can offer excellent gains both in terms of capacity or performance and in terms of flexibility. Furthermore variable coding and modulation (VCM) and ACM configurations have been implemented, and the equipment capability verified. Finally, it is to be noted that the equipment under test showe
26、d optimum interoperability. The Eurovision contribution network for HDTV transmissions during the 2006 FIFA World Cup shows the benefits of the use of DVB-S2 to increase the available system capacity. Thanks to DVB-S2, the EBU reports that it has been able to increase the available bit-rate by about
27、 40%, compared to the usual DVB-S transmission parameters. This allowed transmitting HDTV contribution quality signals in a 36 MHz transponder, which would not otherwise have been possible. 2 Objectives of the Rai-CRIT DVB-S2 test campaign The work has the important twofold objective to verify the s
28、tatus of DVB-S2 equipment, thus demonstrating the excellence of the standard in operation, and to help in the equipment development. The tests that have been performed on the different modems are as follows: a) Constant coding and modulation (CCM) configuration Scope of the analysis of this configur
29、ation is the assessment of the equipment performance in the various modulation and coding rates offered by the standard, independently from the application. The tests include the following measures: Bit error rate (BER) and MPEG-TS packet error rate (PER) performance in the presence of additive whit
30、e gaussian noise (AWGN), both at intermediate frequency (IF) main measures, and at radio frequency (RF). This allows the comparison of the theoretical performance indicated in the DVB-S2 standard 1, Table 13 with that of the real equipment. 4 Rep. ITU-R BO.2101 Bit error rate (BER) and MPEG-TS packe
31、t error rate (PER) performance in the presence of AWGN and satellite channel non-linearity. The scope of this test is the system performance verification on the nonlinear satellite channel, and the estimation of the optimum satellite operating point for each tested configuration. Performance in the
32、presence of phase noise: typical and critical cases of low noise block (LNB) phase noise mask will be considered, representing contribution equipment as well as domestic ones, currently installed in the outdoor unit for DVB-S QPSK reception, which could result critical for higher order modulations.
33、In fact, it is likely that the domestic users will probably not change their outdoor unit, when moving from DVB-S to DVB-S2. b) Variable coding and modulation (VCM) configuration Scope of the analysis of this configuration is to verify the receiver capability to adapt its operations to changes of th
34、e modulation and coding format of the transmitted signal. c) Adaptive coding and modulation (ACM) configuration Scope of the analysis of this configuration is to verify the equipment capability to adapt its operations to the channel variation, the target being interactive point-to-point applications
35、. 3 Methodology used Essentially, the main objective of the laboratory tests was the validation of the hardware equipment performance against the simulation results as reported in EN 302 307 (ETSI standard) and TR 102 376 (User guidelines). The reference test configurations and set-up and the proced
36、ures adopted for each of the performance measurements listed above are described in the following sections. Target performance for DVB-S2 had been established in a PER equal to 107, corresponding to less than one erroneous MPEG-TS packed per hour per program at a bit rate of 5 Mbit/s. This is a very
37、 stringent target, that requires long measures2. Since a large number of modems and configurations have been tested, each measure could not last longer than about 10-15 min. Assuming that the total transmitted stream is analysed and that at least 50 erroneous packets must be computed for each measur
38、e, to guarantee the reliability of the result, PER measurement validity stops at about 105 to 106. Therefore BER/PER curves have been evaluated versus Es/N0with a step in Es/N0of 0.1 dB down to PER of about 105 to 106and the Es/N0value for the target PER of 107has been extrapolated. To confirm the e
39、xtrapolation at PER of 107, Es/N0has then been increased of 0.1 dB and a new 10 min measure started, to verify the absence of errors. Finally for some selected configurations the target PER of 107has been validated by means of longer measures, to confirm the results of the extrapolation. 4 System co
40、nfigurations under test The DVB-S2 system encompasses 28 different modulation and coding options (MODCOD), two different frame sizes, and many other options to choose from, for the maximum flexibility. 2It is not possible to follow the procedure used in the evaluations of first generation modems, wh
41、ere a concatenation of codes was used and performance could be measured after inner Viterbi decoding at a BER of 2 104. Rep. ITU-R BO.2101 5 In order to allow for an effective validation work of the DVB-S2 system performance, a selection of modes was adopted for the lab tests, with the objective to
42、cover all the application areas and profiles targeted by DVB-S2. Main attention was devoted to the CCM configuration, with constant frame size of 64 800 bits (Normal FECFRAME, forward error correction frame). The presence/absence of pilot sequences has been selected as required by the measure. The f
43、ollowing modulations and coding rates have been selected for an in-deep analysis3: QPSK 1/2 8-PSK 2/3 16-APSK 3/4 32-APSK 4/5. Secondly, VCM/ACM configurations have been tested, without any constraints on the MODCOD configurations and frame size to be adopted. 5 Laboratory set-up and basic test proc
44、edure The laboratory performance evaluation of the DVB-S2 system is carried out by changing the parameters of the channel impairments (noise, nonlinearity, phase noise, interference) and measuring the PER at the receiver side. Additional observations on the decoded picture are carried out to verify
45、the results. Figure 1 shows a simplified scheme of the RAI Laboratory set-up, simulating the channel impairments. The detailed set-up for the different tests is given in Annex 1. FIGURE 1 Block diagram of the RAI Laboratory set-up 6 Test results 6.1 AWGN test Figures 2 to 5 show the system performan
46、ce on the AWGN channel respectively for QPSK, 8-PSK, 16-APSK and 32-APSK in the normal FECFRAME configuration. The symbol rate is of 27.5 MBd, 3In some specific cases other modulations and coding rates have been considered, and are indicated in the Report. 6 Rep. ITU-R BO.2101 except for 32-APSK whe
47、re it is 20 MBd4, and the roll-off 35%. The curves are an average of the results obtained in the measurements. Implementation loss, calculated as the Es/N0PER=107with respect to the simulation results indicated in 1, Table 13, are in the range 0.2 to 0.6 dB for QPSK, 0.2 to 0.9 dB for 8-PSK, 0.3 to
48、1.3 dB for 16-APSK, 1.3 to 1.7 dB for 32-APSK. FIGURE 2 QPSK performance on the AWGN channel (IF loop). Normal frame size and no pilots FIGURE 3 8-PSK performance on the AWGN channel (IF loop). Normal frame size and pilots 4Maximum symbol rate available for the 32-APSK configuration. Above 20 MBd, t
49、he equipment performance is for the time being not guaranteed, since the clock speed and/or the FPGA density do not allow to perform the required number of LDPC decoder iterations. It can be expected that improvements of FPGA technology could in the near future allow to cover at full performance extreme baud rates. Rep. ITU-R BO.2101 7 FIGURE 4 16-APSK performance on the AWGN channel (IF loop). Normal frame size and pilots FIGURE 5 32-APSK performance on the AWGN channel (IF loop). Normal frame size and pilots Figures
