DVB-S2：下一代数字卫星广播标准详解

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"DVB-S2标准协议是数字卫星广播的第二代标准，旨在提高信道传输容量并扩大服务范围，受到了广电、电信和计算机行业的广泛关注。该标准由ETSI（欧洲电信标准协会）制定，具体规范可在EN302307-1 V1.4.1(2014-11)文档中找到。关键词包括BSS、数字、DVB、调制、卫星和电视。文档可以从ETSI官网下载。" DVB-S2（Digital Video Broadcasting - Satellite - Second Generation）是欧洲电信标准协会（ETSI）推出的一种数字卫星广播标准，它在DVB-S的基础上进行了重大改进，以应对不断增长的带宽需求和多样化的服务需求。DVB-S2标准主要关注三个方面：帧结构、信道编码和调制系统，这些都对提高广播效率和服务质量至关重要。 1. **帧结构**：DVB-S2引入了更高效的帧结构，允许更灵活的数据分配和更高的传输效率。新的帧结构设计考虑了不同类型的业务需求，如交互式服务、新闻采集和其他宽带卫星应用。 2. **信道编码**：DVB-S2采用了先进的前向纠错编码（FEC），如低密度奇偶校验码（LDPC）和涡轮码，这极大地提高了对抗信道噪声和干扰的能力，同时减少了错误率，确保了服务质量。FEC的选择可以根据信道条件动态调整，以实现最佳性能。 3. **调制系统**：DVB-S2支持多种调制方式，包括QPSK、16QAM、32QAM、64QAM到256QAM，调制阶数的增加可以显著提升频谱效率，但同时也增加了接收端解调的复杂性。调制方式的选择取决于信道条件和需要传输的数据量。 4. **扩展业务范围**：DVB-S2不仅提升了传统电视广播的服务质量，还支持交互式服务、高清视频、数据广播和互联网接入等更多元化的服务。这使得卫星通信能够更好地融入到现代通信网络中，与有线电视、移动通信和固定宽带网络形成互补。 5. **技术兼容性**：DVB-S2设计时考虑了与现有DVB-S系统的兼容性，确保了平滑过渡和设备的升级可能性，同时降低了运营商和用户的成本。 6. **标准化过程**：DVB-S2标准的制定是一个多领域合作的过程，涉及到广电、电信和计算机等多个行业的专家，确保了标准的全面性和前瞻性。 7. **文档获取**：DVB-S2的具体技术细节和规范记录在EN302307-1 V1.4.1(2014-11)文档中，用户可以从ETSI的官方网站免费下载。此文档是DVB-S2实施和设备开发的重要参考。 DVB-S2标准通过技术创新和优化，提升了数字卫星广播的效率和灵活性，为广播行业带来了新的机遇和挑战，推动了卫星通信技术的发展。

ETSI

ETSI EN 302 307

1 V1.4.1 (2014

11)

PLL Phase-Locked Loop

PLS Physical Layer Signalling

PMT Program Map Table

PRBS Pseudo Random Binary Sequence

PS Professional Services

PSK Phase Shift Keying

QEF Quasi-Error-Free

QPSK Quaternary Phase Shift Keying

RCS Return Channel via Satellite

RF Radio Frequency

RO Roll-Off

SA Stream Adaptation

SDTV Standard Definition TeleVision

SI Service Information

SIS Single Input Stream

SMATV Satellite Master Antenna TeleVision

SNG Satellite News Gathering

SOF Start Of Frame

SSA Solid State Amplifier

SSB Single SideBand

TDM Time Division Multiplex

TS Transport Stream

TSDT Transport Stream Descriptor Table

TS/GS Transport Stream/Generic Stream

TSN Time Slice Number (See Annex M)

TV TeleVision

TWT Travelling Wave Tube

TWTA Travelling Wave Tube Amplifier

UP User Packet

UPL User Packet Length

VCM Variable Coding and Modulation

4 Transmission system description

4.1 System definition

The System is defined as the functional block of equipment performing the adaptation of the baseband digital signals,

from the output of a single (or multiple) MPEG transport stream multiplexer(s) (ISO/IEC 13818-1 [1]), or from the

output of a single (or multiple) generic data source(s), to the satellite channel characteristics. The System is designed to

support source coding as defined in ISO/IEC 13818 [1], TR 101 154 [i.3] and TS 102 005 [i.1]. Data services may be

transported in Transport Stream format according to EN 301 192 [4] (e.g. using Multi-protocol Encapsulation), or

Generic Stream format.

If the received signal is above the C/N+I threshold, the Forward Error Correction (FEC) technique adopted in the

System is designed to provide a "Quasi Error Free" (QEF) quality target. The definition of QEF adopted for DVB-S2 is

"less than one uncorrected error-event per transmission hour at the level of a 5 Mbit/s single TV service decoder",

approximately corresponding to a Transport Stream Packet Error Ratio PER< 10

-7

before de-multiplexer.

ETSI

ETSI EN 302 307

1 V1.4.1 (2014

11)

4.2 System architecture

According to figure 1, the DVB-S2 System shall be composed of a sequence of functional blocks as described below.

Mode adaptation shall be application dependent. It shall provide input stream interfacing, Input Stream

Synchronization (optional), null-packet deletion (for ACM and Transport Stream input format only), CRC-8 coding for

error detection at packet level in the receiver (for packetized input streams only), merging of input streams (for Multiple

Input Stream modes only) and slicing into DATA FIELDs. For Constant Coding and Modulation (CCM) and single

input Transport Stream, Mode Adaptation shall consist of a "transparent" DVB-ASI (or DVB-parallel) to logical-bit

conversion and CRC-8 coding. For Adaptive Coding and Modulation (ACM), Mode Adaptation shall be according to

annex D.

A Base-Band Header shall be appended in front of the Data Field, to notify the receiver of the input stream format and

Mode Adaptation type. To be noted that the MPEG multiplex transport packets may be asynchronously mapped to the

Base-Band Frames.

For applications requiring sophisticated merging policies, in accordance with specific service requirements (e.g. Quality

of Service), Mode Adaptation may optionally be performed by a separate device, respecting all the rules of the DVB-S2

specification. To allow standard interfacing between Mode and Stream Adaptation functions, an optional modulator

interface (Mode Adaptation input interface) is defined, according to clauses I.1 (separate signalling circuit) or I.2

(in-band signalling).

Stream adaptation shall be applied, to provide padding to complete a Base-Band Frame and Base-Band Scrambling.

Forward Error Correction (FEC) Encoding shall be carried out by the concatenation of BCH outer codes and LDPC

(Low Density Parity Check) inner codes (rates 1/4, 1/3, 2/5, 1/2, 3/5, 2/3, 3/4, 4/5, 5/6, 8/9, 9/10). Depending on the

application area, the FEC coded block shall have length n

ldpc

= 64 800 bits or 16 200 bits. When VCM and ACM is

used, FEC and modulation mode may be changed in different frames, but remains constant within a frame.

Mapping into QPSK, 8PSK, 16APSK and 32APSK constellations shall be applied, depending on the application area.

Gray mapping of constellations shall be used for QPSK and 8PSK.

Physical layer framing shall be applied, synchronous with the FEC frames, to provide Dummy PLFRAME insertion,

Physical Layer (PL) Signalling, pilot symbols insertion (optional) and Physical Layer Scrambling for energy dispersal.

Dummy PLFRAMEs are transmitted when no useful data is ready to be sent on the channel. The System provides a

regular physical layer framing structure, based on SLOTs of M = 90 modulated symbols, allowing reliable receiver

synchronization on the FEC block structure. A slot is devoted to physical layer signalling, including Start-of-Frame

delimitation and transmission mode definition. This mechanism is suitable also for VCM and ACM demodulator

setting. Carrier recovery in the receivers may be facilitated by the introduction of a regular raster of pilot symbols

(P = 36 pilot symbols every 16 SLOTs of 90 symbols), while a pilot-less transmission mode is also available, offering

an additional 2,4 % useful capacity.

Base-Band Filtering and Quadrature Modulation shall be applied, to shape the signal spectrum (squared-root raised

cosine, roll-off factors 0,35 or 0,25 or 0,20) and to generate the RF signal.

ETSI

ETSI EN 302 307

1 V1.4.1 (2014

11)

Table 1: System configurations and application areas

System configurations

Broadcast

services

Interactive

services

DSNG

Professional

services

QPSK 1/4,1/3, 2/5 O N N N

1/2, 3/5, 2/3, 3/4, 4/5, 5/6,

8/9, 9/10

N N N N

8PSK 3/5, 2/3, 3/4, 5/6, 8/9, 9/10 N N N N

16APSK 2/3, 3/4, 4/5, 5/6, 8/9, 9/10 O N N N

32APSK 3/4, 4/5, 5/6, 8/9, 9/10 O N N N

CCM N N (see note 1) N N

VCM O O O O

ACM NA N (see note 2) O O

FECFRAME (normal) 64 800 (bits) N N N N

FECFRAME (short) 16 200 (bits) NA N O N

Single Transport Stream N N (see note 1) N N

Multiple Transport Streams

O O (see note 2) O O

Single Generic Stream NA O (see note 2) NA O

Multiple Generic Streams NA O (see note 2) NA O

Roll-off 0,35, 0,25 and 0,20 N N N N

Input Stream Synchronizer NA except

(see note 3)

O (see note 3) O (see note 3)

O (see note 3)

Null Packet Deletion NA except

(see note 3)

O (see note 3) O (see note 3)

O (see note 3)

Dummy Frame insertion NA except

(see note 3)

N N N

Wide-band mode (see annex M) O O O O

N = normative, O = optional, NA = not applicable.

NOTE 1: Interactive service receivers shall implement CCM and Single Transport Stream.

NOTE 2: Interactive Service Receivers shall implement ACM at least in one of the two options: Multiple Transport

Streams or Generic Stream (single/multiple input).

NOTE 3: Normative for single/multiple TS input stream(s) combined with ACM/VCM or for multiple TS input streams

combined with CCM.

Within the present document, a number of configurations and mechanisms are defined as "Optional". Configurations

and mechanisms explicitly indicated as "optional" within the present document, for a given application area, need not be

implemented in the equipment to comply with the present document. Nevertheless, when an "optional" mode or

mechanism is implemented, it shall comply with the specification as given in the present document.

5 Subsystems specification

The subsystem specification description is organized according to the functional block diagram of figure 1.

5.1 Mode adaptation

This sub-system shall perform Input Interfacing, Input Stream Synchronization (optional), Null-packet deletion (for TS

input streams and ACM only), CRC-8 encoding for error detection (for packetized input streams only), input stream

merging (for multiple input streams only) and input stream slicing in DATA FIELDs. Finally, base-band signalling

shall be inserted, to notify the receiver of the adopted Mode Adaptation format.

According to figure 3, the input sequence(s) is (are):

• Single or multiple Transport Streams (TS).

• Single or multiple Generic Streams (packetized or continuous).

The output sequence is a BBHEADER (80 bits) followed by a DATA FIELD.

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