FREQUENTLY ASKED QUESTIONS
If you don't see an answer to a question you may have or if you have a question you feel we should add to this list, please let us know.
If you don't see an answer to a question you may have or if you have a question you feel we should add to this list, please let us know.
What is the difference between analog vs. digital video transmission?
The main difference is image quality, especially while the transmitter is in motion.
Whereas analog video transmission tends to break up periodically from multipath or interference, digital systems provide you with high quality images right until the edge of reception.
What is OFDM?
Orthogonal Frequency Division Multiplexing (OFDM), is a digital radio modulation method commonly used for data transmission. OFDM uses a large number of closely spaced orthogonal sub carriers to carry information.
Why if OFDM better than FM/AM?
The primary advantage of OFDM over a single-carrier scheme (AM/FM) is its ability to overcome severe channel condition (Multipath, fading, attenuation) without equalization filters. Channel equalization is achieved by using many slowly-modulated narrow-band signals rather than a single rapidly modulated wide-band signal.
What is C-OFDM?
Coded Orthogonal Frequency Division Multiplexing (COFDM) is virtually identical to OFDM, except FEC (Forward Error Correction) is applied to the signal before transmission.
Why is FEC important?
The purpose of FEC is to overcome errors (lost bits) in transmission due to lost carriers from fading, noise, interference (mechanical or harmonic) and other environmental variables. Most digital transmission systems employ FEC.
How do you choose channel bandwidth?
The size of channel bandwidth depends on the amount of data to be carried. The higher the video resolution/quality, the more bandwidth is required. A typical MPEG-2, 720x480 video stream at 30FPS in high quality requires about 8MHZ of “space” in the spectrum. By compressing video more effectively, you reduce the amount of bandwidth required for the same quality video. Rotoconcept's systems use, MPEG4 compression which significantly reduces the required bandwidth in comparison to MPEG-2.
Why reduce channel bandwidth?
By reducing channel bandwidth the transmission becomes cleaner, thus easier to understand for the receiver.
What frequency should I get?
That depends on a lot of variables. Generally speaking,
the lower the frequency, the better the signal will penetrate
objects. As a result, lower frequencies are more suitable
for NLOS (Non Line Of Sight) applications.
For LOS (Line Of Sight) applications, high frequencies are
better suited due to the availability of more channels and
reduced Fresnel zone.
The Fresnel zone is the diameter of the transmission wave
between the transmitter and receiver antennas. Higher
frequencies penetrate objects (man made or naturally occurring)
less effectively but have smaller Fresnel zones. To achieve
perfect LOS, the Fresnel zone should be clear of all obstacles.
As a result, for LOS applications, higher frequencies are
recommended.
The main difference is image quality, especially while the transmitter is in motion.
Whereas analog video transmission tends to break up periodically from multipath or interference, digital systems provide you with high quality images right until the edge of reception.
What is OFDM?
Orthogonal Frequency Division Multiplexing (OFDM), is a digital radio modulation method commonly used for data transmission. OFDM uses a large number of closely spaced orthogonal sub carriers to carry information.
Why if OFDM better than FM/AM?
The primary advantage of OFDM over a single-carrier scheme (AM/FM) is its ability to overcome severe channel condition (Multipath, fading, attenuation) without equalization filters. Channel equalization is achieved by using many slowly-modulated narrow-band signals rather than a single rapidly modulated wide-band signal.
What is C-OFDM?
Coded Orthogonal Frequency Division Multiplexing (COFDM) is virtually identical to OFDM, except FEC (Forward Error Correction) is applied to the signal before transmission.
Why is FEC important?
The purpose of FEC is to overcome errors (lost bits) in transmission due to lost carriers from fading, noise, interference (mechanical or harmonic) and other environmental variables. Most digital transmission systems employ FEC.
How do you choose channel bandwidth?
The size of channel bandwidth depends on the amount of data to be carried. The higher the video resolution/quality, the more bandwidth is required. A typical MPEG-2, 720x480 video stream at 30FPS in high quality requires about 8MHZ of “space” in the spectrum. By compressing video more effectively, you reduce the amount of bandwidth required for the same quality video. Rotoconcept's systems use, MPEG4 compression which significantly reduces the required bandwidth in comparison to MPEG-2.
Why reduce channel bandwidth?
By reducing channel bandwidth the transmission becomes cleaner, thus easier to understand for the receiver.
What frequency should I get?
That depends on a lot of variables. Generally speaking,
the lower the frequency, the better the signal will penetrate
objects. As a result, lower frequencies are more suitable
for NLOS (Non Line Of Sight) applications.
For LOS (Line Of Sight) applications, high frequencies are
better suited due to the availability of more channels and
reduced Fresnel zone.
The Fresnel zone is the diameter of the transmission wave
between the transmitter and receiver antennas. Higher
frequencies penetrate objects (man made or naturally occurring)
less effectively but have smaller Fresnel zones. To achieve
perfect LOS, the Fresnel zone should be clear of all obstacles.
As a result, for LOS applications, higher frequencies are
recommended.
