C-View
Remote Video Systems
sales@cviewinc.com
Remote Video Systems
sales@cviewinc.com
C-View systems work with either in the 1.2 GHz range or the 2.4 GHz range.
The 1.2 GHz range provides for a longer range then the 2.4 GHz range and
is less populated. (WIFI and Bluetooth work in the 2.4 GHz range and could
cause interference.) The ABTXRX 1.2 A works in the 1.2 GHz range.
The 1.2 GHz range is considered to be ‘Microwave’ (UHF, “L band”)
The Encyclopedia describes Microwaves as electromagnetic waves with
wavelengths ranging from 1 mm to 300 mm, or frequencies between 300 MHz
and 300 GHz
The term microwave generally refers to “alternating current” signals with
frequencies between 300 MHz (3×108 Hz) and 300 GHz (3×1011 Hz).
("Both IEC standard 60050 and IEEE standard 100 define "microwave"
frequencies starting at 1 GHz (30 cm wavelength).
Because of the Frequency range used, the (Transmitter and receiver)
antennas must be ‘seeing each other’ and be “in Line of Sight” for proper
transmission.
Also, due to the longer distances being achieved with the higher power
systems and high efficient antennas, the antennas need to be placed as
high as possible.
This due to the curvature of the globe but also because seawater absorbs
higher frequency transmitting energy.
High Gains, Omni Directional versus Directional:
When transmitting, using a directional antenna, more of the transmitted
power will be sent in the direction of the receiver, increasing the received
signal strength. The disadvantage is that both antennas ( transmitting and
receiving ) must be pointed in each others direction.
C-View developed a High Gain antenna, using a U-shaped iso tropical set up
(Shtrikman/Matzner) resulting in a gain peak of 12 dBi
Both the transmitting antenna and the receiving antenna need to be of the
same construction.
An antenna that makes a transmitted signal 10 times stronger will also
capture 10 times as much energy when used as a receiving antenna. Due to
reciprocity, these two effects are equal.
The 1.2 GHz range provides for a longer range then the 2.4 GHz range and
is less populated. (WIFI and Bluetooth work in the 2.4 GHz range and could
cause interference.) The ABTXRX 1.2 A works in the 1.2 GHz range.
The 1.2 GHz range is considered to be ‘Microwave’ (UHF, “L band”)
The Encyclopedia describes Microwaves as electromagnetic waves with
wavelengths ranging from 1 mm to 300 mm, or frequencies between 300 MHz
and 300 GHz
The term microwave generally refers to “alternating current” signals with
frequencies between 300 MHz (3×108 Hz) and 300 GHz (3×1011 Hz).
("Both IEC standard 60050 and IEEE standard 100 define "microwave"
frequencies starting at 1 GHz (30 cm wavelength).
Because of the Frequency range used, the (Transmitter and receiver)
antennas must be ‘seeing each other’ and be “in Line of Sight” for proper
transmission.
Also, due to the longer distances being achieved with the higher power
systems and high efficient antennas, the antennas need to be placed as
high as possible.
This due to the curvature of the globe but also because seawater absorbs
higher frequency transmitting energy.
High Gains, Omni Directional versus Directional:
When transmitting, using a directional antenna, more of the transmitted
power will be sent in the direction of the receiver, increasing the received
signal strength. The disadvantage is that both antennas ( transmitting and
receiving ) must be pointed in each others direction.
C-View developed a High Gain antenna, using a U-shaped iso tropical set up
(Shtrikman/Matzner) resulting in a gain peak of 12 dBi
Both the transmitting antenna and the receiving antenna need to be of the
same construction.
An antenna that makes a transmitted signal 10 times stronger will also
capture 10 times as much energy when used as a receiving antenna. Due to
reciprocity, these two effects are equal.
Wave length used:
Micro waves
Micro waves
Antennas
Directional versus Omni Directional
Directional versus Omni Directional
High Gain Omni Directional Antenna
In this section we aim to provide information related to the Video Transmission Systems technology.
C-View is curious to hear from you: remarks, suggestions, questions, etc.
Please contact us at : marius@cviewinc.com
C-View is curious to hear from you: remarks, suggestions, questions, etc.
Please contact us at : marius@cviewinc.com
Click here to go to:
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Site lay out page
Contact page
Products page
Site lay out page
Contents:
Wave length used (Micro waves)
Antennas
Multiplexing
Wave length used (Micro waves)
Antennas
Multiplexing
Compression and Multiplexing
Compression makes data "smaller" so more information can be transmitted
over telephone lines. It is a technique to increase the capacity of telephone
lines. With compression, data to be transmitted is made smaller by removing
white spaces and redundant images, as well as by abbreviating the most
frequently appearing letters. For example, with a facsimile, compression
removes white spaces from pictures, and only transmits the images.
Modems use compression to achieve greater throughput, or rates of
transmitted information. When a modem equipped with compression
transmits text, repeated words are abbreviated into smaller codes. For
example, since E, T, O and I appear frequently in a text, compression sends
shortened versions of 3 bits rather than 7 or 8 bits. Therefore, a page would
consist of about 1,600 bits instead of 2,200 bits.
If a word processing file was 10 pages long, compression that removed white
spaces, redundant characters and abbreviated characters might compress
the document to 7 pages, which takes less time to transmit. Thus, a modem
using compression would be able to send greater amounts of computer data
in a smaller amount of time over analog lines. This increases throughput. In
order for compression to work, the two sites transmitting and receiving must
have matching compression.
Video Compression
Video compression works by transmitting only the changed image and not
the same image repeatedly. In video conferencing, nothing is transmitted
until the person being photographed moves or speaks. Fixed objects such
as walls, and background are not repeatedly transmitted.Another method of
video compression is to only transmit part of the image. The coder, or device
doing the compression, knows that discarding minor changes in images
would not distort the viewed image noticeably. Improvements in video
compression in the mid-1980s gave birth to the commercial viability of video
conferencing rooms. These systems made it economical to use video since
they required less bandwidth, which means cheaper telephone lines. Video
conferencing became affordable to a wider range of organizations since they
could lease cheaper phone lines as low as $14 per hour instead of using the
traditional T-1 lines at hundreds of dollars per hour.
In most cases, the cheaper lines still had acceptable video quality. New
compression algorithms meant that slower speed digital lines were an
acceptable choice for video meetings. As such, a new industry was created.
Compression Methods
There are various types of compression methods. Companies such as
AT&T, Motorola, PictureTel and Compression Labs have all designed unique
compression schemes using math algorithms.
A Codec (which is an abbreviation for a coder-decoder) encodes text, audio,
video or image using a compression algorithm. For this compression to work,
both the sending and receiving ends must have the same compression
method. The sending end looks at the data, voice or image, then codes it,
while the receiving end of the transmitter decodes it.
For devices from multiple manufacturers to operate together, compression
standards have been agreed upon for modems, digital television, video
conferencing and other devices. Digital television compression works much
like video compression. It allows pictures to be transmitted in a highly
abbreviated form.
With most video pictures, the image in one frame is similar to that in the
previous frame since the background remains the same while the actors
move only slightly from one frame to the next. Therefore, instead of
transmitting the entire image again, a compression system sends only the
parts of the picture that change. Digital compression makes it possible to
represent continuous color-TV signal. This compression squeezes video and
analog signals into small enough units so that studio-quality television can
be sent on standard digital Television channels. The analog standard for
television is 525 scan lines, or lines of images. High definition television
(HDTV) will enable a television screen to display 1125 scanned lines.
A greater number of scan lines results in clearer, studio-quality pictures.
Additional lines of image are seen as a denser higher resolution of detailed
images on the screen. This is done through computer manipulation of the
video and audio portions of the television signals.
Because of the powerful compression and decompression tool used by
computers, very little of the images are lost to the viewer. The quality of
digital television is high enough so that people watching television will
perceive the quality to be similar to movies in theaters.
Multiplexing
Another method of manipulating data to achieve greater throughput is
through multiplexing. Multiplexing is a technique used in communications and
input/output operations for transmitting a number of separate signals
simultaneously over a single channel or line.
To maintain the integrity of each signal on the channel, multiplexing can
separate the signals by time, space, or frequency. The device used to
combine the signals is a multiplexer, and the separate signals are recovered
at the end by a demultiplexer.
Multiplexing combines traffic from multiple telephones and data devices into
one single stream so that many devices can share a particular
telecommunication path. Multiplexing makes more efficient use of telephone
lines, as does compression. However, unlike compression, multiplexing does
not alter the actual data sent.
Multiplexing equipment is typically located in long distance companies, local
telephone companies and at end-user premises, and is associated with both
analog and digital services. Examples of multiplexing over digital facilities
include T-1, fractional T-1, T-3, ISDN and ATM technologies.
The oldest multiplexing techniques were devised by AT&T for use with
analog voice services. The goal was to make more efficient use of the most
expensive portion of the public telephone network, the outside wires used to
connect homes and telephone offices to each other. This analog technique
is referred to as frequency-division multiplexing, which allows multiple voice
and later data calls to share paths between central offices. Therefore, AT&T
would not need not construct cable connections for each conversation, since
multiple conversations could share the same wire between a telephone
company’s central office.
Digital Multiplexing
Digital multiplexing schemes operate at greater speeds and carry more traffic
than analog multiplexing. For example, T-3 carries 672 conversations over
one line at speeds of 45 megabits per second. With both digital analog
multiplexing, a matching multiplexer is required at both the sending and
receiving ends of the communications channel.
T-3 is used for very large customers, telephone companies and Internet
Service Provider networks.
T-1 is the most common form of multiplexing for end-user organizations. T-1
is lower in both cost and capacity than T-3. T-1 allows more than two voice
and / or data conversations to share a path. T-1 applications include linking
organization sites together for voice calls, email, database access, and links
between end-users and telephone companies for discounted rates on
telephone calls. Like T-3 services, matching multiplexers are required at both
ends of a T-1 link.
Frequency-Division Multiplexing
Frequency-division multiplexing is a scheme in which numerous signals are
combined for transmission on a single communications line or channel. Each
signal is assigned a different frequency (sub-channel) within the main
channel.
With frequency-division multiplexing, each channel has its own base
frequency, and its own carrier frequency. The carrier frequency can be
modulated using several different methods to derive either digital or analog
channels.
The modulation method and the characteristics of the information on the
channel (such as the bit rate) determine the bandwidth needed per channel.
The circuitry to handle a channel in a frequency-division multiplexer is quite
complicated and therefore costly. For analog signals such as television
signals, however, frequency-division multiplexing can still be a good choice.
Frequency-division multiplexing can be used on optical fibers by using a
different frequency and thus a different wavelength of the light beam for
each channel. With optical systems, the term wavelength multiplexing is
used. On radio links not only different frequencies but also different
polarization angles can be used. Suppose a long-distance cable is available
with a bandwidth allotment of 3 Mhz. This is 3,000 kHz, so theoretically, it is
possible to place 1,000 signals, each 3 kHz wide, into the long-distance
channel. The circuit that does this is known as a multiplexer. It accepts the
input from each individual end user, and generates a signal on a different
frequency for each of the inputs. This results in a high-bandwidth, complex
signal containing data from all the end users. At the other end of the long-
distance cable, the individual signals are separated out by means of a circuit
called a demultiplexer, and routed to the proper end users. A two-way
communications circuit requires a multiplexer/demultiplexer at each end of
the long-distance, high-bandwidth cable.
When frequency-division multiplexing is used in a communications network,
each input signal is sent and received at maximum speed at all times. This is
its chief asset. However, if many signals must be sent along a single long-
distance line, the necessary bandwidth is large, and careful engineering is
required to ensure that the system will perform properly.
In some systems, a different scheme, known as time-division multiplexing, is
used instead.
Time-division Multiplexing
Time-division multiplexing has become a cost-effective method that is not
only used on trunk circuits between switching centers but is today even
starting to be used on local circuits to the customer. The basic interface of
the ISDN is an example of this trend.
With time-division multiplexing, the whole bandwidth is assigned to each
particular channel for a fraction of the total transmission time. This fraction
can vary from one bit for bit-interleaved multiplexers, to a few thousand bits
in the newest types of high bit-rate multiplexers; the synchronous time-
division multiplexing (STDM) designed for the synchronous transfer mode.
Time-division can even be used to transfer samples of bits, derived by
scanning the input channels with a frequency at least 3 times higher than the
highest bit rate on these tributary channels. With this method digital signals
from various sources with even unknown or changing bit rates can be
multiplexed and reproduced (with a tolerable distortion) at the other end of
the common channel (CCITT, 1988d).
All these time-division multiplexers are fixed slot time-division multiplexers, in
that they assign a fixed slot to each channel in a cyclic scan of all the
tributary channels. The fixed position of the slot in the cycle for each channel
makes it possible to identify the destination outlet for each portion of the
information received over the common channel.
This process requires synchronization in order to guarantee that the
scanning of the received information at that output side was at the same
speed as the cyclic scan at the input side.
All slots of one cyclic scan are arranged in a frame. In this frame, one
generally finds additional information to ensure correct synchronization and
frame alignment, needed to present the information from the input channels
arriving at the wrong output channels as a result of being out of phase.
The circuit that combines signals at the source (transmitting) end of a
communications link is known as a multiplexer. It accepts the input from each
individual end user, breaks each signal into segments, and assigns the
segments to the composite signal in a rotating, repeating sequence. The
composite signal thus contains data from all the end users.
As with frequency-division multiplexing, at the other end of the long-distance
cable, the individual signals are separated out by means of a circuit called a
demultiplexer, and routed to the proper end users. Again, as in frequency-
division multiplexing, a two-way communications circuit requires a
multiplexer/demultiplexer at each end of the long-distance, high-bandwidth
cable.
As always, if many signals must be sent along a single long-distance line,
careful engineering is required to ensure that the system will perform
properly. An asset of time-division multiplexing is its flexibility. The scheme
allows for variation in the number of signals being sent along the line, and
constantly adjusts the time intervals to make optimum use of the available
bandwidth.
The Internet is a classic example of a communications network in which the
volume of traffic can change drastically from hour to hour.
Compression makes data "smaller" so more information can be transmitted
over telephone lines. It is a technique to increase the capacity of telephone
lines. With compression, data to be transmitted is made smaller by removing
white spaces and redundant images, as well as by abbreviating the most
frequently appearing letters. For example, with a facsimile, compression
removes white spaces from pictures, and only transmits the images.
Modems use compression to achieve greater throughput, or rates of
transmitted information. When a modem equipped with compression
transmits text, repeated words are abbreviated into smaller codes. For
example, since E, T, O and I appear frequently in a text, compression sends
shortened versions of 3 bits rather than 7 or 8 bits. Therefore, a page would
consist of about 1,600 bits instead of 2,200 bits.
If a word processing file was 10 pages long, compression that removed white
spaces, redundant characters and abbreviated characters might compress
the document to 7 pages, which takes less time to transmit. Thus, a modem
using compression would be able to send greater amounts of computer data
in a smaller amount of time over analog lines. This increases throughput. In
order for compression to work, the two sites transmitting and receiving must
have matching compression.
Video Compression
Video compression works by transmitting only the changed image and not
the same image repeatedly. In video conferencing, nothing is transmitted
until the person being photographed moves or speaks. Fixed objects such
as walls, and background are not repeatedly transmitted.Another method of
video compression is to only transmit part of the image. The coder, or device
doing the compression, knows that discarding minor changes in images
would not distort the viewed image noticeably. Improvements in video
compression in the mid-1980s gave birth to the commercial viability of video
conferencing rooms. These systems made it economical to use video since
they required less bandwidth, which means cheaper telephone lines. Video
conferencing became affordable to a wider range of organizations since they
could lease cheaper phone lines as low as $14 per hour instead of using the
traditional T-1 lines at hundreds of dollars per hour.
In most cases, the cheaper lines still had acceptable video quality. New
compression algorithms meant that slower speed digital lines were an
acceptable choice for video meetings. As such, a new industry was created.
Compression Methods
There are various types of compression methods. Companies such as
AT&T, Motorola, PictureTel and Compression Labs have all designed unique
compression schemes using math algorithms.
A Codec (which is an abbreviation for a coder-decoder) encodes text, audio,
video or image using a compression algorithm. For this compression to work,
both the sending and receiving ends must have the same compression
method. The sending end looks at the data, voice or image, then codes it,
while the receiving end of the transmitter decodes it.
For devices from multiple manufacturers to operate together, compression
standards have been agreed upon for modems, digital television, video
conferencing and other devices. Digital television compression works much
like video compression. It allows pictures to be transmitted in a highly
abbreviated form.
With most video pictures, the image in one frame is similar to that in the
previous frame since the background remains the same while the actors
move only slightly from one frame to the next. Therefore, instead of
transmitting the entire image again, a compression system sends only the
parts of the picture that change. Digital compression makes it possible to
represent continuous color-TV signal. This compression squeezes video and
analog signals into small enough units so that studio-quality television can
be sent on standard digital Television channels. The analog standard for
television is 525 scan lines, or lines of images. High definition television
(HDTV) will enable a television screen to display 1125 scanned lines.
A greater number of scan lines results in clearer, studio-quality pictures.
Additional lines of image are seen as a denser higher resolution of detailed
images on the screen. This is done through computer manipulation of the
video and audio portions of the television signals.
Because of the powerful compression and decompression tool used by
computers, very little of the images are lost to the viewer. The quality of
digital television is high enough so that people watching television will
perceive the quality to be similar to movies in theaters.
Multiplexing
Another method of manipulating data to achieve greater throughput is
through multiplexing. Multiplexing is a technique used in communications and
input/output operations for transmitting a number of separate signals
simultaneously over a single channel or line.
To maintain the integrity of each signal on the channel, multiplexing can
separate the signals by time, space, or frequency. The device used to
combine the signals is a multiplexer, and the separate signals are recovered
at the end by a demultiplexer.
Multiplexing combines traffic from multiple telephones and data devices into
one single stream so that many devices can share a particular
telecommunication path. Multiplexing makes more efficient use of telephone
lines, as does compression. However, unlike compression, multiplexing does
not alter the actual data sent.
Multiplexing equipment is typically located in long distance companies, local
telephone companies and at end-user premises, and is associated with both
analog and digital services. Examples of multiplexing over digital facilities
include T-1, fractional T-1, T-3, ISDN and ATM technologies.
The oldest multiplexing techniques were devised by AT&T for use with
analog voice services. The goal was to make more efficient use of the most
expensive portion of the public telephone network, the outside wires used to
connect homes and telephone offices to each other. This analog technique
is referred to as frequency-division multiplexing, which allows multiple voice
and later data calls to share paths between central offices. Therefore, AT&T
would not need not construct cable connections for each conversation, since
multiple conversations could share the same wire between a telephone
company’s central office.
Digital Multiplexing
Digital multiplexing schemes operate at greater speeds and carry more traffic
than analog multiplexing. For example, T-3 carries 672 conversations over
one line at speeds of 45 megabits per second. With both digital analog
multiplexing, a matching multiplexer is required at both the sending and
receiving ends of the communications channel.
T-3 is used for very large customers, telephone companies and Internet
Service Provider networks.
T-1 is the most common form of multiplexing for end-user organizations. T-1
is lower in both cost and capacity than T-3. T-1 allows more than two voice
and / or data conversations to share a path. T-1 applications include linking
organization sites together for voice calls, email, database access, and links
between end-users and telephone companies for discounted rates on
telephone calls. Like T-3 services, matching multiplexers are required at both
ends of a T-1 link.
Frequency-Division Multiplexing
Frequency-division multiplexing is a scheme in which numerous signals are
combined for transmission on a single communications line or channel. Each
signal is assigned a different frequency (sub-channel) within the main
channel.
With frequency-division multiplexing, each channel has its own base
frequency, and its own carrier frequency. The carrier frequency can be
modulated using several different methods to derive either digital or analog
channels.
The modulation method and the characteristics of the information on the
channel (such as the bit rate) determine the bandwidth needed per channel.
The circuitry to handle a channel in a frequency-division multiplexer is quite
complicated and therefore costly. For analog signals such as television
signals, however, frequency-division multiplexing can still be a good choice.
Frequency-division multiplexing can be used on optical fibers by using a
different frequency and thus a different wavelength of the light beam for
each channel. With optical systems, the term wavelength multiplexing is
used. On radio links not only different frequencies but also different
polarization angles can be used. Suppose a long-distance cable is available
with a bandwidth allotment of 3 Mhz. This is 3,000 kHz, so theoretically, it is
possible to place 1,000 signals, each 3 kHz wide, into the long-distance
channel. The circuit that does this is known as a multiplexer. It accepts the
input from each individual end user, and generates a signal on a different
frequency for each of the inputs. This results in a high-bandwidth, complex
signal containing data from all the end users. At the other end of the long-
distance cable, the individual signals are separated out by means of a circuit
called a demultiplexer, and routed to the proper end users. A two-way
communications circuit requires a multiplexer/demultiplexer at each end of
the long-distance, high-bandwidth cable.
When frequency-division multiplexing is used in a communications network,
each input signal is sent and received at maximum speed at all times. This is
its chief asset. However, if many signals must be sent along a single long-
distance line, the necessary bandwidth is large, and careful engineering is
required to ensure that the system will perform properly.
In some systems, a different scheme, known as time-division multiplexing, is
used instead.
Time-division Multiplexing
Time-division multiplexing has become a cost-effective method that is not
only used on trunk circuits between switching centers but is today even
starting to be used on local circuits to the customer. The basic interface of
the ISDN is an example of this trend.
With time-division multiplexing, the whole bandwidth is assigned to each
particular channel for a fraction of the total transmission time. This fraction
can vary from one bit for bit-interleaved multiplexers, to a few thousand bits
in the newest types of high bit-rate multiplexers; the synchronous time-
division multiplexing (STDM) designed for the synchronous transfer mode.
Time-division can even be used to transfer samples of bits, derived by
scanning the input channels with a frequency at least 3 times higher than the
highest bit rate on these tributary channels. With this method digital signals
from various sources with even unknown or changing bit rates can be
multiplexed and reproduced (with a tolerable distortion) at the other end of
the common channel (CCITT, 1988d).
All these time-division multiplexers are fixed slot time-division multiplexers, in
that they assign a fixed slot to each channel in a cyclic scan of all the
tributary channels. The fixed position of the slot in the cycle for each channel
makes it possible to identify the destination outlet for each portion of the
information received over the common channel.
This process requires synchronization in order to guarantee that the
scanning of the received information at that output side was at the same
speed as the cyclic scan at the input side.
All slots of one cyclic scan are arranged in a frame. In this frame, one
generally finds additional information to ensure correct synchronization and
frame alignment, needed to present the information from the input channels
arriving at the wrong output channels as a result of being out of phase.
The circuit that combines signals at the source (transmitting) end of a
communications link is known as a multiplexer. It accepts the input from each
individual end user, breaks each signal into segments, and assigns the
segments to the composite signal in a rotating, repeating sequence. The
composite signal thus contains data from all the end users.
As with frequency-division multiplexing, at the other end of the long-distance
cable, the individual signals are separated out by means of a circuit called a
demultiplexer, and routed to the proper end users. Again, as in frequency-
division multiplexing, a two-way communications circuit requires a
multiplexer/demultiplexer at each end of the long-distance, high-bandwidth
cable.
As always, if many signals must be sent along a single long-distance line,
careful engineering is required to ensure that the system will perform
properly. An asset of time-division multiplexing is its flexibility. The scheme
allows for variation in the number of signals being sent along the line, and
constantly adjusts the time intervals to make optimum use of the available
bandwidth.
The Internet is a classic example of a communications network in which the
volume of traffic can change drastically from hour to hour.
Multiplexing