EC8094 SATELLITE COMMUNICATION UNIT IV SATELLITE ACCESS AND CODING METHODS
V.R.S. College of Engineering and Technology
(Reaccredited by NAAC and an ISO 9001:2008 Recertified Institution)
Subject Name : SATELLITE COMMUNICATION
Subject code : EC8094
Regulation : 2017
Year/Semester : IV/VIII
Branch : ECE
UNIT IV
SATELLITE ACCESS AND CODING METHODS
Modulation and Multiplexing: Voice, Data, Video, Analog – digital transmission system, Digital video
Broadcast, multiple access: FDMA, TDMA, CDMA, DAMA Assignment Methods, compression –
encryption, Coding Schemes.
4.1 Modulation and Multiplexing
4.1.1 Source Signals: Voice, Data, Video
4.1.1.1 Telephone speech signal
4.1.1.2 Data signals
4.1.1.3 Video signals
4.1.2 Analog Transmission System
4.1.2.1 Amplitude Modulation
4.1.2.2 Frequency Division Multiplexing
4.1.2.3 Frequency Modulation
4.1.3 Digital transmission systems
4.1.3.1 PCM System
4.1.3.2 Adaptive Delta Modulation
4.1.3.3 Adaptive differential PCM (ADPCM)
4.1.3.4 Time-Division Multiplexing
4.2 Digital video Broadcast
4.3 Multiple access
4.3.1 FDMA
4.3.1.1 Preassigned FDMA
4.3.1.2 Demand – Assigned FDMA
4.3.2 TDMA
4.3.2.1 Implementation of TDMA
4.3.2.2 Pre assigned TDMA
4.3.2.3 Demand-assigned TDMA
4.3.2.3.1 Speech Interpolation & Prediction
4.3.2.4 Satellite-Switched TDMA
4.3.3 Code Division Multiple Accesses (CDMA)
4.3.3.1 Basic CMDA System
4.3.3.2 Direct Sequence Spread Spectrum
4.3.3.3 The Code signal C(t)
1
Compiled by: Mr. S. Parthiban, M.Tech., Asst. Prof., Dept. of ECE, VRSCET.
,EC8094 SATELLITE COMMUNICATION UNIT IV SATELLITE ACCESS AND CODING METHODS
4.3.3.4 The autocorrelation function for c(t)
4.3.3.5 Acquisition and Tracking
4.3.3.6 Spectrum Spreading And Despreading
4.3.3.7 CDMA throughput
4.3.3.8 Throughout Efficiency
4.3.3.9 Advantages of CDMA
4.3.4 DAMA (Refer : 4.3.1.2, 4.3.2.3)
Assignment Methods
4.4 Compression
4.5 Encryption
4.5.1 Introduction
4.5.2 Satellite Encryption
4.5.3 Procedure
4.5.4 Types Of Encryption
4.5.5 Working Of Encryption
4.5.6 Implementing Encryption In Robots
4.5.7 Advantage
4.5.8 Applications
4.6 Coding Schemes
4.6.1 Linear Block Codes
4.6.2 Cyclic Codes
4.6.2.1 Hamming codes
4.6.2.2 BCH codes
4.6.2.3 Reed-Solomon codes
4.6.3 Convolution Codes
4.6.4 Interleaving
4.6.5 Concatenated Codes
4.6.6 Link Parameters Affected by Coding
4.6.7 Automatic Repeat Request (ARQ)
4.1 Modulation and Multiplexing
4.1.1 Source Signals: Voice, Data, Video
➢ Source signals:-
✓ Voice, Data and video signals are the considered as business signals.
✓ Voice, data video are the three most common signals transmitter over satellite channels.
✓ Telephone speech signal, data signals of various types, and video signals, both broadcast
quality and business teleconferencing quality types of signals transmitted.
4.1.1.1 Telephone speech signal:-
✓ This is one of a class of audio signals occupying bandwidth of up to about 20 kHz.
Characteristics of telephone speech signals
✓ For economized and acceptable quality, the occupied bandwidth is 300 to 3400Hz.
✓ Nominal frequency spacing per channel is 4 kHz.
✓ Signal to noise ratio is 50dB.
2
Compiled by: Mr. S. Parthiban, M.Tech., Asst. Prof., Dept. of ECE, VRSCET.
,EC8094 SATELLITE COMMUNICATION UNIT IV SATELLITE ACCESS AND CODING METHODS
✓ Telephone speech signal exhibit an amplitude distribution increasing both active speech and
silent intervals.
✓ Interference levels must be kept at levels of 60 – 65dB.
✓ The speech activity (average duty cycle) is 30-40%
✓ Increasing the use of digital transport facilities will result in significantly enhanced telephone
speech quality (more bandwidth and less noise).
✓ A useful measure of performance in telephone speech is the signal-to-noise ratio of the
received signal, together with the received power level at the telephone handset or some other
well-defined point in the system.
✓ Telephone speech signals exhibit an amplitude distribution as shown in figure, representing
both active speech and silent intervals, indicated by the jump at values x = 0 .
✓ From this distribution it can be determined that a practical peak-to-average ratio of 19dB
(approximately 3% peak clipping) is acceptable for engineering purposes.
✓ If this is coupled with the log-normal speech power distribution of telephone talkers with an
average of -22dBm and standard deviation of 5.5 dB.
✓ It should be realized that the 3% peak clipping only applies to the loudest talkers and that by
far the majority experiences none at all.
✓ The CCITT specifies the cross-talk interference must be kept at levels of -65dB or less.
✓ This translates to a 43-dB or better speech-to-crosstalk ratio.
✓ Important characteristic is that talkers tend to pause between phrases and sentences, which
results in active speech energy of about 1.33s average duration.
✓ The average activity (or) duty cycle in the speech signal is about 30% to 40% active and thus
70% to 60% idle time.
3
Compiled by: Mr. S. Parthiban, M.Tech., Asst. Prof., Dept. of ECE, VRSCET.
, EC8094 SATELLITE COMMUNICATION UNIT IV SATELLITE ACCESS AND CODING METHODS
✓ In digital transmission, two additional parameters transmission bit rate and bit error rate must
be specified for ultimate quality of the reconstructed analog speech signal.
✓ Typical digital transmission rates for commercial speech telephony, ranges from 4.8 to 64kbs.
✓ Higher rates represent the public dial-up network, quality and lower rate the private business
network quality (or) cellular mobile systems.
4.1.1.2 Data signals:-
✓ Data signals are broadly classified into three ranges, by speed as
(i) Narrow band data (3300b/s)
(ii) Voice band data (3300b/s to 19 Kb/s)
(iii) Wide band data (> 19 kb/s)
✓ Narrow band data begin at telegraphy rates and includes a wide range of communication
applications with terminals and teleprinters usually implemented over with facilities requiring
no special precautions.
✓ Voice band data signals such as facsimile and transactional services supported at rates up to
19 kb/s suing data modems.
✓ Wide band data applications such as diachronic mail, high speed file transfer, computer-aided
design, video and teleconferencing and imaging utilize the efficient high-speed transmission
capabilities offered by satellite.
✓ In digital transmission, the protocols used to control computer communications.
✓ Transmission error rate depends critically on the applications.
✓ The error rate for data is moving several than for voice by order of magnitude.
✓ Thus a complicate system deigns where both voice and data applications must share the same
link
4.1.1.3 Video signals:-
✓ There are two types of video signals transmitted via satellite circuits,
→ Broadcast quality commercial television.
→ Television used for business teleconferencing
✓ Commercial broad cast quality signals are high-resolution high-quality signals and thus require
large bandwidth (or) high rates.
✓ Business video signal employ much laver data rates ( 1.544 Mb/s) and a great deal of signal
processing is usually required to reduce data rate and bandwidth.
✓ Coding algorithms are defined by standard organization such as CCITT and VSTI committee.
✓ Television signals contain information in electrical form from which a picture can be recreated.
✓ To translate a complete picture into an electrical signal the electronic image of that picture is
trace scanned at high speed in a systematic manner.
✓ Such scanning is done horizontally starting at the upper-left corner.
✓ When the bottom of the image is reached, signifying the completion of a field, the process is
restarted from the top again, thus two fields complete a frame.
✓ Frame rate in US is 30 per second and in Europe (or) Japan the frame rate is 25 per second.
✓ The intensity of the light in part of the image is called Luminance and is represented by the
magnitude of the waveform representing each scan line.
4
Compiled by: Mr. S. Parthiban, M.Tech., Asst. Prof., Dept. of ECE, VRSCET.
V.R.S. College of Engineering and Technology
(Reaccredited by NAAC and an ISO 9001:2008 Recertified Institution)
Subject Name : SATELLITE COMMUNICATION
Subject code : EC8094
Regulation : 2017
Year/Semester : IV/VIII
Branch : ECE
UNIT IV
SATELLITE ACCESS AND CODING METHODS
Modulation and Multiplexing: Voice, Data, Video, Analog – digital transmission system, Digital video
Broadcast, multiple access: FDMA, TDMA, CDMA, DAMA Assignment Methods, compression –
encryption, Coding Schemes.
4.1 Modulation and Multiplexing
4.1.1 Source Signals: Voice, Data, Video
4.1.1.1 Telephone speech signal
4.1.1.2 Data signals
4.1.1.3 Video signals
4.1.2 Analog Transmission System
4.1.2.1 Amplitude Modulation
4.1.2.2 Frequency Division Multiplexing
4.1.2.3 Frequency Modulation
4.1.3 Digital transmission systems
4.1.3.1 PCM System
4.1.3.2 Adaptive Delta Modulation
4.1.3.3 Adaptive differential PCM (ADPCM)
4.1.3.4 Time-Division Multiplexing
4.2 Digital video Broadcast
4.3 Multiple access
4.3.1 FDMA
4.3.1.1 Preassigned FDMA
4.3.1.2 Demand – Assigned FDMA
4.3.2 TDMA
4.3.2.1 Implementation of TDMA
4.3.2.2 Pre assigned TDMA
4.3.2.3 Demand-assigned TDMA
4.3.2.3.1 Speech Interpolation & Prediction
4.3.2.4 Satellite-Switched TDMA
4.3.3 Code Division Multiple Accesses (CDMA)
4.3.3.1 Basic CMDA System
4.3.3.2 Direct Sequence Spread Spectrum
4.3.3.3 The Code signal C(t)
1
Compiled by: Mr. S. Parthiban, M.Tech., Asst. Prof., Dept. of ECE, VRSCET.
,EC8094 SATELLITE COMMUNICATION UNIT IV SATELLITE ACCESS AND CODING METHODS
4.3.3.4 The autocorrelation function for c(t)
4.3.3.5 Acquisition and Tracking
4.3.3.6 Spectrum Spreading And Despreading
4.3.3.7 CDMA throughput
4.3.3.8 Throughout Efficiency
4.3.3.9 Advantages of CDMA
4.3.4 DAMA (Refer : 4.3.1.2, 4.3.2.3)
Assignment Methods
4.4 Compression
4.5 Encryption
4.5.1 Introduction
4.5.2 Satellite Encryption
4.5.3 Procedure
4.5.4 Types Of Encryption
4.5.5 Working Of Encryption
4.5.6 Implementing Encryption In Robots
4.5.7 Advantage
4.5.8 Applications
4.6 Coding Schemes
4.6.1 Linear Block Codes
4.6.2 Cyclic Codes
4.6.2.1 Hamming codes
4.6.2.2 BCH codes
4.6.2.3 Reed-Solomon codes
4.6.3 Convolution Codes
4.6.4 Interleaving
4.6.5 Concatenated Codes
4.6.6 Link Parameters Affected by Coding
4.6.7 Automatic Repeat Request (ARQ)
4.1 Modulation and Multiplexing
4.1.1 Source Signals: Voice, Data, Video
➢ Source signals:-
✓ Voice, Data and video signals are the considered as business signals.
✓ Voice, data video are the three most common signals transmitter over satellite channels.
✓ Telephone speech signal, data signals of various types, and video signals, both broadcast
quality and business teleconferencing quality types of signals transmitted.
4.1.1.1 Telephone speech signal:-
✓ This is one of a class of audio signals occupying bandwidth of up to about 20 kHz.
Characteristics of telephone speech signals
✓ For economized and acceptable quality, the occupied bandwidth is 300 to 3400Hz.
✓ Nominal frequency spacing per channel is 4 kHz.
✓ Signal to noise ratio is 50dB.
2
Compiled by: Mr. S. Parthiban, M.Tech., Asst. Prof., Dept. of ECE, VRSCET.
,EC8094 SATELLITE COMMUNICATION UNIT IV SATELLITE ACCESS AND CODING METHODS
✓ Telephone speech signal exhibit an amplitude distribution increasing both active speech and
silent intervals.
✓ Interference levels must be kept at levels of 60 – 65dB.
✓ The speech activity (average duty cycle) is 30-40%
✓ Increasing the use of digital transport facilities will result in significantly enhanced telephone
speech quality (more bandwidth and less noise).
✓ A useful measure of performance in telephone speech is the signal-to-noise ratio of the
received signal, together with the received power level at the telephone handset or some other
well-defined point in the system.
✓ Telephone speech signals exhibit an amplitude distribution as shown in figure, representing
both active speech and silent intervals, indicated by the jump at values x = 0 .
✓ From this distribution it can be determined that a practical peak-to-average ratio of 19dB
(approximately 3% peak clipping) is acceptable for engineering purposes.
✓ If this is coupled with the log-normal speech power distribution of telephone talkers with an
average of -22dBm and standard deviation of 5.5 dB.
✓ It should be realized that the 3% peak clipping only applies to the loudest talkers and that by
far the majority experiences none at all.
✓ The CCITT specifies the cross-talk interference must be kept at levels of -65dB or less.
✓ This translates to a 43-dB or better speech-to-crosstalk ratio.
✓ Important characteristic is that talkers tend to pause between phrases and sentences, which
results in active speech energy of about 1.33s average duration.
✓ The average activity (or) duty cycle in the speech signal is about 30% to 40% active and thus
70% to 60% idle time.
3
Compiled by: Mr. S. Parthiban, M.Tech., Asst. Prof., Dept. of ECE, VRSCET.
, EC8094 SATELLITE COMMUNICATION UNIT IV SATELLITE ACCESS AND CODING METHODS
✓ In digital transmission, two additional parameters transmission bit rate and bit error rate must
be specified for ultimate quality of the reconstructed analog speech signal.
✓ Typical digital transmission rates for commercial speech telephony, ranges from 4.8 to 64kbs.
✓ Higher rates represent the public dial-up network, quality and lower rate the private business
network quality (or) cellular mobile systems.
4.1.1.2 Data signals:-
✓ Data signals are broadly classified into three ranges, by speed as
(i) Narrow band data (3300b/s)
(ii) Voice band data (3300b/s to 19 Kb/s)
(iii) Wide band data (> 19 kb/s)
✓ Narrow band data begin at telegraphy rates and includes a wide range of communication
applications with terminals and teleprinters usually implemented over with facilities requiring
no special precautions.
✓ Voice band data signals such as facsimile and transactional services supported at rates up to
19 kb/s suing data modems.
✓ Wide band data applications such as diachronic mail, high speed file transfer, computer-aided
design, video and teleconferencing and imaging utilize the efficient high-speed transmission
capabilities offered by satellite.
✓ In digital transmission, the protocols used to control computer communications.
✓ Transmission error rate depends critically on the applications.
✓ The error rate for data is moving several than for voice by order of magnitude.
✓ Thus a complicate system deigns where both voice and data applications must share the same
link
4.1.1.3 Video signals:-
✓ There are two types of video signals transmitted via satellite circuits,
→ Broadcast quality commercial television.
→ Television used for business teleconferencing
✓ Commercial broad cast quality signals are high-resolution high-quality signals and thus require
large bandwidth (or) high rates.
✓ Business video signal employ much laver data rates ( 1.544 Mb/s) and a great deal of signal
processing is usually required to reduce data rate and bandwidth.
✓ Coding algorithms are defined by standard organization such as CCITT and VSTI committee.
✓ Television signals contain information in electrical form from which a picture can be recreated.
✓ To translate a complete picture into an electrical signal the electronic image of that picture is
trace scanned at high speed in a systematic manner.
✓ Such scanning is done horizontally starting at the upper-left corner.
✓ When the bottom of the image is reached, signifying the completion of a field, the process is
restarted from the top again, thus two fields complete a frame.
✓ Frame rate in US is 30 per second and in Europe (or) Japan the frame rate is 25 per second.
✓ The intensity of the light in part of the image is called Luminance and is represented by the
magnitude of the waveform representing each scan line.
4
Compiled by: Mr. S. Parthiban, M.Tech., Asst. Prof., Dept. of ECE, VRSCET.
