CATV and HFC Network Design: Technical Specifications
Definitions and Bandwidth
We’re going to use the premises for the design and installation of an ELN US CATV system. The first thing to note is the frequency at which it will work, or rather, the services that we offer. This step is simply a business decision.
Calculating the Headend
One can choose the team, but now we have to specify the programming we want. Then, we venture to select the right equipment to get the satellite signal.
Technical Characteristics of the Earth Station
- For the choice of the number of antennas, it is good to specify in advance that what matters is the type of service provided.
- Thinking we want only one satellite dish, and from there we get 24 channels, is an error.
- Now we know that the lower the number of antennas, and the more channels we want to get, we will be forced to put more outputs (splitters), which means a very poor signal.
Communication of the Equipment in the Header
The recommended equipment should be fairly close to the group of satellite dishes to prevent high losses due to the effect of the cables.
CATV Network Design Stages
- Terrain survey of the area to serve.
- Determination of the architecture.
- Definition of use.
- Determination.
- Definition of quality parameters.
- Consideration of operating conditions for the final design.
- Preliminary design.
Terrain Survey
Make travel surveys of the land for accurate information:
a. Different support points between points of support.
b. Distances.
c. Number of customers in every customer category.
d. Type.
Determination of the Area to Serve
It is recommended that the location of the header be in a place populated enough to succeed in order to support starting and that first investment where there will definitely not be profit.
Signal to Noise Ratio (SNR)
SNR is the ratio of the average power of the baseband signal and the average power of noise.
Carrier to Noise Ratio (CNR)
CNR is the ratio between the power of the RF carrier and noise present in that portion of the spectrum.
Output level rises 1 dB = CNR = 1 dB improvement.
Second-Order Beat (CSO)
This type of distortion is caused roughly by the mixture of carriers.
Output level = low 1 dB, CSO improvement = 1 dB.
Composite Triple Beat (CTB)
This kind of distortion is caused by the mixture of three carriers.
Output level low 1 dB = 2 dB improvement CTB.
Cross-Modulation (XMOD)
Such cross-modulation of distortion is the quasar mixed signals created when multiple signals are amplified.
Hum Modulation
Hum modulation is unwanted by the video carrier frequency signals of the feed line or harmonics thereof. It is usually caused by problems or failures in power supplies or problems with thin diagonal lines.
CSO = CTB = moving horizontal lines or bands.
XMOD = diagonal stripes and/or superimposed images.
HUM = horizontal strip that runs the screen from top to bottom.
Direct Return vs. Return
The return level will define the value of the tap on the devices closest to the amplifier.
Express Line
Express lines look to reach distant points without exceeding the maximum cascade. We use lossless cable so that power can go as far as possible without exceeding the limits of the waterfall.
Link Design
- Consider the losses experienced by the signal as it travels down the fiber.
- Determine the type of bond based on the location of populations.
- Based on the total attenuation, calculate the optimal TX power or obtain it in an optical link.
1. The number of connectors or splices fusion.
2. The optical couplers or splitters needed to distribute the signal value of the routes.
3. Optical transmitter power.
Design Stages for HFC
Designing for HFC is like putting together a puzzle. The procedure to follow is the reverse of a tree-and-branch network. In HFC network design, small cells group together. The first step is wiring the area in nodes. The quantity is chosen, the location of the node is determined, and it is linked to the amplifier. An explicit fiber trace is defined, linking the node to the hub.