UNIT IV SATELLITE ACCESS
4.1 Modulation and Multiplexing: Voice, Data, Video :
Communications satellites are used to carry telephone, video, and data
signals, and can use both analog and digital modulation techniques.
Modulation:
Modification of a carrier’s parameters (amplitude, frequency, phase, or a
combination of them) in dependence on the symbol to be sent.
Multiplexing:
Task of multiplexing is to assign space, time, frequency, and code to each
communication channel with a minimum of interference and a maximum of
medium utilization Communication channel refers to an association of sender(s)
and receiver(s) that want to exchange data One of several constellations of a
carrier’s parameters defined by the used modulation scheme.
3.1.1 Voice, Data, Video :
The modulation and multiplexing techniques that were used at this time
were analog, adapted from the technology developed for The change to digital
voice signals made it easier for long-distance.
Figure 3.1 Modulation and Multiplexing: Voice/Data/Video
SCE 51 Dept of ECE
,EC 2045 SATELLITE COMMUNICATION
Communication carriers to mix digital data and telephone Fiber-optic
Cable Transmission Standards System Bit rate (Mbps) 64- kbps Voice channel
capacity Stuffing bits and words are added to the satellite data stream as needed
to fill empty bit and word spaces.
Primarily for video provided that a satellite link's overall carrier-to-noise
but in to older receiving equipment at System and Satellite Specification Ku-
band satellite parameters.
3.1.2 Modulation And Multiplexing:
In analog television (TV) transmission by satellite, the baseband video
signal and one or two audio subcarriers constitute a composite video signal.
Digital modulation is obviously the modulation of choice for transmitting
digital data are digitized analog signals may conveniently share a channel with
digital data, allowing a link to carry a varying mix of voice and data traffic.
Digital signals from different channels are interleaved for transmission
through time division multiplexing TDM carry any type of traffic — the bent
pipe transponder that can carry voice, video, or data as the marketplace
demands.
Hybrid multiple access schemes can use time division multiplexing of
baseband channels which are then modulate.
3.2 Analog – digital transmission system :
3.2.1 Analog vs. Digital Transmission:
Compare at two levels:
1. Data—continuous (audio) vs. discrete (text)
2. Signaling—continuously varying electromagnetic wave vs. sequence of
voltage pulses.
Also Transmission—transmit without regard to signal content vs. being
concerned with signal content. Difference in how attenuation is handled, but not
focus on this.Seeing a shift towards digital transmission despite large analog
base. Why?
SCE 52 Dept of ECE
, EC 2045 SATELLITE COMMUNICATION
Figure 3.2 basic communication systems
• Improving digital technology
• Data integrity. Repeaters take out cumulative problems in transmission.
Can thus transmit longer distances.
• Easier to multiplex large channel capacities with digital
• Easy to apply encryption to digital data
• Better integration if all signals are in one form. Can integrate voice, video
and digital data.
3.2.2 Digital Data/Analog Signals:
Must convert digital data to analog signal such device is a modem to
translate between bit-serial and modulated carrier signals?
To send digital data using analog technology, the sender generates a
carrier signal at some continuous tone (e.g. 1-2 kHz in phone circuits) that looks
like a sine wave. The following techniques are used to encode digital data into
analog signals.
Figure 3.3 Digital /Analog Transmitter & receiver
SCE 53 Dept of ECE
4.1 Modulation and Multiplexing: Voice, Data, Video :
Communications satellites are used to carry telephone, video, and data
signals, and can use both analog and digital modulation techniques.
Modulation:
Modification of a carrier’s parameters (amplitude, frequency, phase, or a
combination of them) in dependence on the symbol to be sent.
Multiplexing:
Task of multiplexing is to assign space, time, frequency, and code to each
communication channel with a minimum of interference and a maximum of
medium utilization Communication channel refers to an association of sender(s)
and receiver(s) that want to exchange data One of several constellations of a
carrier’s parameters defined by the used modulation scheme.
3.1.1 Voice, Data, Video :
The modulation and multiplexing techniques that were used at this time
were analog, adapted from the technology developed for The change to digital
voice signals made it easier for long-distance.
Figure 3.1 Modulation and Multiplexing: Voice/Data/Video
SCE 51 Dept of ECE
,EC 2045 SATELLITE COMMUNICATION
Communication carriers to mix digital data and telephone Fiber-optic
Cable Transmission Standards System Bit rate (Mbps) 64- kbps Voice channel
capacity Stuffing bits and words are added to the satellite data stream as needed
to fill empty bit and word spaces.
Primarily for video provided that a satellite link's overall carrier-to-noise
but in to older receiving equipment at System and Satellite Specification Ku-
band satellite parameters.
3.1.2 Modulation And Multiplexing:
In analog television (TV) transmission by satellite, the baseband video
signal and one or two audio subcarriers constitute a composite video signal.
Digital modulation is obviously the modulation of choice for transmitting
digital data are digitized analog signals may conveniently share a channel with
digital data, allowing a link to carry a varying mix of voice and data traffic.
Digital signals from different channels are interleaved for transmission
through time division multiplexing TDM carry any type of traffic — the bent
pipe transponder that can carry voice, video, or data as the marketplace
demands.
Hybrid multiple access schemes can use time division multiplexing of
baseband channels which are then modulate.
3.2 Analog – digital transmission system :
3.2.1 Analog vs. Digital Transmission:
Compare at two levels:
1. Data—continuous (audio) vs. discrete (text)
2. Signaling—continuously varying electromagnetic wave vs. sequence of
voltage pulses.
Also Transmission—transmit without regard to signal content vs. being
concerned with signal content. Difference in how attenuation is handled, but not
focus on this.Seeing a shift towards digital transmission despite large analog
base. Why?
SCE 52 Dept of ECE
, EC 2045 SATELLITE COMMUNICATION
Figure 3.2 basic communication systems
• Improving digital technology
• Data integrity. Repeaters take out cumulative problems in transmission.
Can thus transmit longer distances.
• Easier to multiplex large channel capacities with digital
• Easy to apply encryption to digital data
• Better integration if all signals are in one form. Can integrate voice, video
and digital data.
3.2.2 Digital Data/Analog Signals:
Must convert digital data to analog signal such device is a modem to
translate between bit-serial and modulated carrier signals?
To send digital data using analog technology, the sender generates a
carrier signal at some continuous tone (e.g. 1-2 kHz in phone circuits) that looks
like a sine wave. The following techniques are used to encode digital data into
analog signals.
Figure 3.3 Digital /Analog Transmitter & receiver
SCE 53 Dept of ECE
