1. Komunikasi Satelit, Sukiswo, ST, MT 1 Baseband Signal & QoS Sukiswo sukiswok@yahoo.com

2. Komunikasi Satelit, Sukiswo, ST, MT2 Outline  Sinyal Baseband  Kinerja / Performansi  Availability  Delay

3. Komunikasi Satelit, Sukiswo, ST, MT3 Sinyal Baseband  The following baseband signals are considered: –telephone signal; –sound programme; –television; –data.

4. Komunikasi Satelit, Sukiswo, ST, MT4 Digital telephone signal  Digital telephony is achieved using voice encoders. Various techniques are used which can be categorised into waveform encoding and vocoders [FRE-91].  Waveform encoding entails three processes: –sampling; –quantisation; –source encoding.  The most popular encoding techniques are: –pulse code modulation (PCM); (Rb=64 kbits.) –delta modulation (DM); (Rb=16 kbits.) –adaptive differential PCM (ADPCM) ; (Rb=16-64 kbits.)

5. Komunikasi Satelit, Sukiswo, ST, MT5 Digital telephone signal Vocoders  Vocoders assume a given speech production mechanism and transmit the parameters of the mechanism.  The linear predictive coding (LPC) technique assumes that the speech production mechanism can be modelled by a filter.  The coefficients of the filter are periodically updated by statistical optimisation over a given number of samples.  The period conditions the duration of the frame (10–50ms) within which the coefficients are transmitted at a data rate Rb as low as 2.4– 4.8 kbit/s.

6. Komunikasi Satelit, Sukiswo, ST, MT6 Digital telephone signal Digital telephony multiplex

7. Komunikasi Satelit, Sukiswo, ST, MT7 Digital telephone signal Characteristics of these multiplexing techniques : –The CEPT hierarchy –The T-carrier hierarchy

8. Komunikasi Satelit, Sukiswo, ST, MT8 Digital telephone signal Digital speech interpolation  Techniques for digital speech concentration such as digital speech interpolation (DSI) take account of the activity factor of telephone channels in order to reduce the number of satellite channels (called ‘bearer channels’) required to transmit a given number of terrestrial telephone channels.  Figure 3.2 shows this principle. The gain of the digital concentrator is given by the ratio m/n. In the INTELSAT/ EUTELSAT system, 240 terrestrial telephone channels require only 127 bearer channels plus one assignment channel and the gain is 240/127 = 1:9.

9. Komunikasi Satelit, Sukiswo, ST, MT9 Digital telephone signal Digital speech interpolation

10. Komunikasi Satelit, Sukiswo, ST, MT10 Sound signals  A high-quality radio sound programme occupies a band from 40Hz to 15 kHz.  For the emission of digitally encoded audio signals, the analogue sound programme must go through an analogue-to-digital converter.  This implies sampling, quantisation and source encoding.  Two encoding techniques, pulse code modulation (PCM) and adaptive delta modulation (ADM) are considered. Some formats have been defined using sampling rates of 32 kHz, 44.1 kHz or 48 kHz(S/PDIF, AES/EBU,MUSICAM,etc.).  In particular, MUSICAM is a popular standard for digital audio compression based on the division of the audio-frequency band into 30 subbands.  MUSICAM proposes various compression ratios (from 4 to 12) starting from a 48 kHz sampling rate and a 16-bit quantisation.

11. Komunikasi Satelit, Sukiswo, ST, MT11 Television signals  Transmission of colour television started using analogue techniques in the mid 1900s.  Various non compatible standards were available: NTSC (Japan, USA, Canada, Mexico, some South American countries and Asia), PAL (Europe, except France, Australia, some South American countries and some African countries) and SECAM (France, countries of the former USSR, Eastern countries and some African countries).  The multiplexed analogue components (MAC) standard was proposed in the 1980s for satellite broadcasting (direct broadcast television) but was never developed into a successful commercial service.

12. Komunikasi Satelit, Sukiswo, ST, MT12 Television signals  Fully digital techniques based on video compression were developed in the 1990s resulting in the widely recognised MPEG standards.  The TV signal has a baseband signal of a few Mbit/s, hence the transmission of digital television is possible without requiring a huge amount of radio-frequency spectrum (see Chapter 4).  At the same time, standards for digital video broadcasting (DVB), and in particular the satellite version (DVB-S), have been adopted, making satellite broadcasting (direct broadcast television) a successful commercial service.

13. Komunikasi Satelit, Sukiswo, ST, MT13 Television signals  Television signals contain three components: the luminance signal, which represents the image in black and white, the chrominance signal, which represents the colour, and the sound.

14. Komunikasi Satelit, Sukiswo, ST, MT14 Television signals The spectrum of the composite television signal

15. Komunikasi Satelit, Sukiswo, ST, MT15 Television signals Generation of television signals.

16. Komunikasi Satelit, Sukiswo, ST, MT16 Television signals Compressed digital television signal  Digital Video Broadcasting (DVB) uses MPEG-2 compression for video and either MP2 (MPEG-1 audio layer 2) or AC3 (Dolby Digital 2.0 or 5.1) for audio.  Audio bitrates used are usually in the 192–256 kbit/s range for MP2 and 192–448 kbit/s for AC3.  An MPEG-2 encoder has two output options: elementary streams and programme (system) streams.  Elementary streams display one audio (.mp2) and one video (.m2v or.mpv) file.  Programme streams comprise a single file containing both audio and video (usually an.mpg file).

17. Komunikasi Satelit, Sukiswo, ST, MT17 Television signals  Digital broadcasting has different distribution and transmission requirements, as shown in Figure

18. Data and multimedia signals  Data is becoming the most common vehicle for information transfer related to a large variety of services, including voice telephony, video and computer-generated information exchange.  One of the most appealing aspects of data transmission is the ability to combine, onto a single transmission, support data generated by a number of individual sources, resulting in a single data stream called aggregate traffic.  This is paramount for transfer of multimedia traffic integrating voice, video and application data. Komunikasi Satelit, Sukiswo, ST, MT18

19. Data and multimedia signals  Traffic like this often displays a reduced bit rate variance compared to the traffic generated by the individual sources, due to the embedded statistical multiplexing.  A network operator uses this opportunity to dimension its links (and particularly satellite links) with a capacity that is less than the sum of the peak bit rate of the individual sources.  This dimensioning considers both the burstiness of the traffic and the multiplexing techniques in use. Komunikasi Satelit, Sukiswo, ST, MT19

20. Data and multimedia signals  The traffic is typically transported by packets. The data structure (transport stream) developed for conveying TV programme components could be used to carry any type of data, taking advantage of the well-recognised standard and mass-market production of equipment.  For example, MPEG-2 transport stream (MPEG-TS) packets are used with DVB-S data transmission.  As for video programmes, MPEG-2 transport stream (MPEG-TS) packet have a fixed size of 188 bytes of which 4 bytes are used for the packet header and 144 bytes for the payload.  The header consists of a synchronisation (sync) byte, a packet identifier (PID), transport error indication and a field of adaptation options. Komunikasi Satelit, Sukiswo, ST, MT20

21. Data and multimedia signals  The asynchronous transfer mode (ATM) data format is used in high data rate, terrestrial networks.  The ATM packet, called an ‘ATM cell’, is a fixed size—53 bytes, of which 5 bytes are used for the header and 48 bytes for the payload.  The header consists of a virtual channel identifier (VCI), a virtual path identifier (VPI), a payload type, and priority and header error check (HEC) fields.  As an MPEG-TS option, ATM cells are used in the DVB return channel via satellite (DVB-RCS). Komunikasi Satelit, Sukiswo, ST, MT21

22. Performance Objectives  The performance objectives have been established by ITU recommendations.  The quality of the baseband signal is defined depending on the considered service at the user–terminal interface or at the interface between a satellite network and a terrestrial network.  The baseband signal-to-baseband noise power ratio (S/N) is the basic parameter for analogue signals.  The bit error rate (BER) is the basic parameter for digital signals.  This book considers only digital signals and techniques. For digital signals, the BER conditions other types of objective, such as errored seconds or error-free seconds, used to give a better appreciation of the quality of the delivered service (ITU-R Rec. S.614; ITU-R Rec. X.140). Komunikasi Satelit, Sukiswo, ST, MT22

23. Performance Objectives Telephone (ITU-R Rec. S.522) stipulates that the bit error rate (BER) must not exceed:  one part in 106, 10-minute mean value for more than 20% of any month;  one part in 104, 1-minute mean value for more than 0.3% of any month;  one part in 103, 1-second mean value for more than 0.05% of any month. Komunikasi Satelit, Sukiswo, ST, MT23

24. Performance Objectives Sound  When a sound programme is transmitted by satellite in digital form, the performance objective is stipulated in terms of bit error rate (BER). Errors have the effect of generating audible ‘clicks’.  To limit their frequency to about one per hour, a bit error rate of the order of 10 -9 is required (CCIR Rep 648). Komunikasi Satelit, Sukiswo, ST, MT24

25. Performance Objectives Television  In the DVB-S standard, the performance objectives are to achieve (QEF) transmission of BER from 10 10 to 10 11 after the Reed- Solomon inner code and BER of 210 4 after the Viterbi outer code [EN-300-421].  This imposes the ratio of energy per information bit to power spectral density of noise, Eb/N0, to be equal to or less than 4.5 dB for the inner code rate of 1/2, less than 5.0 dB for 2/3, 5.5 dB for 3/4, 6.0 dB for 5/6 and 6.4 for 7/8.  Margins of 0.8 dB for modem implementation and 0.36 dB for the noise bandwidth may be added.one part in 106, 10-minute mean value for more than 20% of any month; one part in 104, 1-minute mean value for more than 0.3% of any month; one part in 103, 1-second mean value for more than 0.05% of any month. Komunikasi Satelit, Sukiswo, ST, MT25

26. Performance Objectives Data (ITU-R Rec. S.614) stipulates that the bit error rate for satellite transmission of data at 64 kbit/s at a frequency below 15 GHz on a link which is part of an integrated services digital network (ISDN) must not exceed:  10 -7 during more than 10% of any month;  10 -6 during more than 2% of any month;  10 -3 during more than 0.03% of any month. Komunikasi Satelit, Sukiswo, ST, MT26