HFC stands for Hybrid Fiber Coax. Basically HFC is a device used for telecommunication networks and is a combination of fiber optic technology, optoelectronic and traditional coaxial cable technology that is a technology "hybrid". Today the use of HFCs in the telecommunications network gets the most attention because it theoretically allows the delivery of various services at once (multiservice), such as telephony, internet, cable TV and Video-On-Demand (VOD) with the promise of data transmission speed is higher and prices affordable by the user. HFC network can be implemented through the use of cable TV network that has been widely as in the United States or by building new infrastructure, cable TV with HFC technology
In the race to satisfy customer (consumer) will be the Internet service is faster and cheaper, a factor that plays an important role is the bandwidth (bandwidth). In comparison, the telephone cable network has low bandwidth, so having a low-speed cable TV network while providing a very wide bandwidth that offers a higher speed. By leveraging the advantages of this TV cable network, Internet users can get connection speeds 500-1000 times faster than regular dial-up modem and 100-200 times faster than ISDN connections that exist today. The files that usually takes several minutes for download can be done in a much shorter time. This shows great potential for the provision of network-owned multimedia services in real time. In the United States of CATV network (an abbreviation commonly used for cable TV) are spread in more than 60 million homes.With all these advantages some of the obstacles faced in implementation of the CATV network as a multiservice CATV providers are mostly using the full system of coaxial cable with the following weaknesses:• Susceptible to a variety of disorders such as radio station AM / FM, CB radio, etc..• Age and temperature changes continuously (temperature fluxes) causes cracks in the trunk so that the cable insulation turned into a giant antenna.• All of the above noise can be pick up by the amplifier and propagate to the nodes on the network.• If the CATV network in a particular area to serve many customers / home then in the area will arise a strong electromagnetic field that can affect electronic devices on aircraft through the area.
To menangulangi the problems mentioned above is used in the fiber optic trunk network as much as 5% of ingress emerged from the trunk. Desired ideal situation is to use fiber to the curb or neighborhood hub and then use coaxial cable to the customer's point of limiting the ingress and localize.Network Topology
HFC networks typically use a tree and branch network as well as those used by CATV networks.
Figure coaxial cable network with tree structure and branch for cable TVIn the picture above, the headend is a tool for receiving signals from satellites or from the antenna. The signal is processed electronically, in order to obtain quality images and sound good, do "scrambling" (randomization) to prevent access from those who do not need and do ad insertion process. After processing all of the channels transmitted through a single coaxial cable.
On his way, high frequency signal transmitted from the headend are degraded so that the amplifier-amplifier is required along the cable route. Amplifier-amplifier is usually used voltage 60 VAC. Power supply (in the form of ferro conditioner or UPS) are typically installed along the path to provide power to the amplifier-amplifier is used. Additional resources are directly inserted into the coaxial cable and will travel along with the video signal.
Feeder cable is a cable through a neighborhood (a few houses) and the feeder cable is coax branched several taps. At each customer's home, a drop cable connected from the tap, which is located outside the home, to a device that is in the house. Tree and branch network to show the need for UPS compared to the signal conditioner without the battery. If power is lost at one point along the power supply then the customer is located far down the track will also lose their cable service.
When using the HFC network used coaxial cable in the trunk was replaced by lines made of fiber optics. In the HFC network, the amplifier-amplifier still be used along a path that will coax cable but on the HFC network nodes which have fiber optic signals are converted back into the form of electrical signals to be transmitted to customers' homes via coaxial cable. On a network that can be used for two-way communication (downstream and upstream), the fiber node can also perform the conversion from electrical to optical. Each fiber node has its own power supply to provide power to the conversion tool optical / electrical and / or the trunk amplifier. Fiber is often referred to as the Optical node Terminal Node (OTN). In a large HFC network OTN is able to serve 200 to 1200 homes (usually around 500 houses). Fiber part of the HFC network is able to transmit signals as far as 25 miles without reinforcement and usually do not require resources.Tree and branch network is not the only network that may be because there are other network topologies that can be used like a star topology, or FSA (Fiber to Serving Area).
In the topology tree and branch, some branched fiber optic cable from the headend to the nodes that are spread in a star topology. Furthermore, on each node is a signal transmitted via coax cable using a tree topology and branch. For more details, see the following picture:
Image of HFC network with a combination of tree and branch topology with a star
Main Components
1. Headend
Headend is an important part of the HFC system. At the headend, the signal from a variety of sources (such as satellite signals, the signal off-air) is received and converted to the proper signal delivery form. At the time of the signals are ready to be delivered, the signals are combined in a single cable and is ready to be sent over the network. Headend consists of several parts, among others, is the receiver, demodulator / decoder, modulator and combiner.1.1 Receiver
Receiver function here is as a receiver signal derived from the earth station before being forwarded to the modulator. While the function of earth station is to capture the source signals from satellites. In each of these receivers happen sorting signal for selecting a desired channel due to signals received from satellites is still composed of many channels. The signal is then forwarded to the modulator.1.2 Demodulator / Decoder
For signal sources which are off-air signal, prior to broadcast RF signals received by the antenna to the modulator dimasukkkan then the signals are separated first based on the channel. The separation is performed by the demodulator / decoder.1.3 Modulator
Source signals at the headend in the form of baseband signals, before being sent to the combiner must first modulated carrier signal into the RF. Therefore this source signals must be passed to a baseband modulator that places the audio and video components at the RF carrier signal.1.4 Combiner
Combiner refers to the process of placing a variety of RF signals in a single cable for distribution through the network.
Before the signals are combined first, conducted a process of "scrambling" (randomization) signal to prevent access from those who do not need and do ad insertion process.
Penggambungan the most common method used in broadband RF system is a pairing-off sequence in which the groups consisting of two signals are combined at the same time, then the result of merging these groups are combined again. This process continues until all signals are in the same cable. To support the merger process, used a series of mini-called splitter.
1.5 Cable Router
Cable Router serves as an interface between the type of standard network (PSTN) with the HFC headend distribution point, control bandwidth usage and spectrum in data communications on HFC and manages all cable modem connected to it.1.6 Cable Telephony
Cable telephony functions as the interface between the PSTN network with the HFC headend distribution point for delivering telephony services within a two-way communication.1.7 Optoelectronics
The signal is passed through an optical fiber is in the form (the form of light). Light is a form of electromagnetic radiation with a very high frequency with a frequency range in the order of terahertz (THz). As the RF carrier signal, carrier signal light waves can also carry information. Therefore, the signal coming out of the combiner is in the form of electrical signals (RF), then this signal must be converted first into an optical signal (light) by using optoelectronic that converts electrical signals into light signals and vice versa.
Delivery signal through an optical link includes two main components namely:• Optical Transmitter
Optical transmitter on the optoelectronic at the headend is the point where the optoelectronic received RF carrier signal from the combiner. The incoming signal into an optical transmitter of the RF carrier signal in the form of electrical signals, because it can be passed on to fiber optic signal lines should be changed first to a form of light. Transmitter is responsible for changing the input electrical signals into optical signals and transmit the optical signal into an optical fiber channel.
Core
HeadendRF SignalThe electric current changeLaserFocusing LensFiber OpticsOptical ModulatorDC currentOptical OutputFigure Scheme Optical Transmitter• Optical Receiver
Optical receivers at the headend is part Optoelectronic Optoelectronic accept the point where the optical signal from fiber optic line which is the upstream signal received from customers. The signal entering the receiver in the form of light (optical). The function of this receiver is to recover the original RF signal from the carrier wave light (Lightwave carrier). The receiver will convert the received optical signals into electrical output RF.
The main parts of the optical receivers involved in the conversion process is the focusing lens (focusing lens), photodiode (photodiode) and RF amplifier (RF amplifier). Consider the following picture:CoreRF OutputInput OpticsGo to Distribution NetworkCoaxial cablePhoto diode
Fiber OpticsBraceImage Optical Receiver Scheme• RF Amplifier
RF amplifier serves to strengthen the RF signals generated by the receiver.2. Fiber Node
As mentioned above, the fiber node is a node on the network where the signals from the trunk optical fiber is converted into electrical signals to be forwarded to the coax cable or vice versa. Fiber node consists of optoelectronic devices and power Inserter. Optoelectronic tool is a tool that convert light signals into electrical signals or vice versa.2.1 Optoelectronics
Optoelectronic parts on HFC network consists of two parts:• Transmitter• Receiver• RF Amplifier
The three types of devices have been described above.2.2 Power Inserter
Power Inserter is an interface that connects the external power supply to the node. So, power is channeled into the node through the power Inserter. One feature of the Power Inserter is surge suppression to protect the cable from the current rises abruptly (surge) and the excess voltage (overvoltage).3. Terminal3.1 C I U (Customer Interface Unit)
Represents the interface between the customer terminal with HFC coaxial cable network. Based services with the ability of 64 Kbps, the customer may be held at the POTS service, ISDN BRA and data channels flexibly. In its development are available several types of devices in accordance with the level of customer needs. Can be placed with an indoor or outdoor mounting dependent power rationing system.Power rationing system consists of:a. Local power for each terminal Ciu for 100/240V AC with battery backup.b. Ration drop from the coaxial network (the terminal BONU) for 60 or 90V AC at a frequency of 60 Hz.3.2 Cable Modem
Cable modem is a device that allows high-speed access to the Internet via a CATV network. Cable modems typically have two connections, one to an outlet on the wall and the other to a computer (PC).
Cable modem speed varies. In the downstream direction (from network to a computer), speeds can reach 36 Mbps. Only a few computers that are able to be connected with such high speed so that a more realistic value is between 3 to 10 Mbps. In the reverse direction, namely upstream, the speed can reach 10 Mbps, but most modem producers will choose more optimal speeds between 200 kbps and 2 Mbps. At the beginning of the use of cable modems so that asymmetrical setup will be more widely used where the downstream channel has a higher bandwidth allocation than the upstream. This is because Internet applications that exist today tend to be asymmetrical. Activities that are downstream such as the World Wide Web (http) send more data to the computer than to the network.
Actually using the word "modem" for this tool can be misleading because it may cause shadows on the traditional telephone modems. The similarity between the cable modem and regular modem is that both perform modulation and demodulation of the signal. But the cable modem is much more complex than his brother's telephone modem. Cable modems can act as a modem, tuner, tools for encryption / decryption, bridge, router, ethernet hubs and so on in accordance with the service that is served.
Usually the cable modem receives and sends data in a different way. In the downstream direction, digital data is modulated and then superimposed on the 6 MHz television carrier, between 42 Mhz and 750 Mhz. There are many ways of modulation but the two most popular techniques used are QPSK (up to 10 Mbps) and QAM64 (up to 36 Mbps). These signals can be placed in a 6 MHz channel on both sides of the TV signal without disturbing the video signal cable TV. In the cable network that is activated in both directions, upstream transmission (also known as reverse path) is done at a frequency between 5 and 40 MHz. Environmental frequencies tend to have a lot of noise, the disruption of HAM radio, CB radio and impulse noise from home appliances. In addition, noise, other noise coming from the connectors that are not installed in tandem or the ugly wires. Therefore, tree-shaped network used and the branch then all the noise accumulated in the upstream direction. To reduce this problem most producers using QPSK modulation or similar methods that are more robust, but slower than QAM QPSK.3.3 Set Top Box (STB)
Set Top Box is a device installed in the homes of customers to select the channel, record and use the other facilities provided by the provider. STB, among others, the process of unscrambling the signal from channels that have been subscribed by the customer.
In the race to satisfy customer (consumer) will be the Internet service is faster and cheaper, a factor that plays an important role is the bandwidth (bandwidth). In comparison, the telephone cable network has low bandwidth, so having a low-speed cable TV network while providing a very wide bandwidth that offers a higher speed. By leveraging the advantages of this TV cable network, Internet users can get connection speeds 500-1000 times faster than regular dial-up modem and 100-200 times faster than ISDN connections that exist today. The files that usually takes several minutes for download can be done in a much shorter time. This shows great potential for the provision of network-owned multimedia services in real time. In the United States of CATV network (an abbreviation commonly used for cable TV) are spread in more than 60 million homes.With all these advantages some of the obstacles faced in implementation of the CATV network as a multiservice CATV providers are mostly using the full system of coaxial cable with the following weaknesses:• Susceptible to a variety of disorders such as radio station AM / FM, CB radio, etc..• Age and temperature changes continuously (temperature fluxes) causes cracks in the trunk so that the cable insulation turned into a giant antenna.• All of the above noise can be pick up by the amplifier and propagate to the nodes on the network.• If the CATV network in a particular area to serve many customers / home then in the area will arise a strong electromagnetic field that can affect electronic devices on aircraft through the area.
To menangulangi the problems mentioned above is used in the fiber optic trunk network as much as 5% of ingress emerged from the trunk. Desired ideal situation is to use fiber to the curb or neighborhood hub and then use coaxial cable to the customer's point of limiting the ingress and localize.Network Topology
HFC networks typically use a tree and branch network as well as those used by CATV networks.
Figure coaxial cable network with tree structure and branch for cable TVIn the picture above, the headend is a tool for receiving signals from satellites or from the antenna. The signal is processed electronically, in order to obtain quality images and sound good, do "scrambling" (randomization) to prevent access from those who do not need and do ad insertion process. After processing all of the channels transmitted through a single coaxial cable.
On his way, high frequency signal transmitted from the headend are degraded so that the amplifier-amplifier is required along the cable route. Amplifier-amplifier is usually used voltage 60 VAC. Power supply (in the form of ferro conditioner or UPS) are typically installed along the path to provide power to the amplifier-amplifier is used. Additional resources are directly inserted into the coaxial cable and will travel along with the video signal.
Feeder cable is a cable through a neighborhood (a few houses) and the feeder cable is coax branched several taps. At each customer's home, a drop cable connected from the tap, which is located outside the home, to a device that is in the house. Tree and branch network to show the need for UPS compared to the signal conditioner without the battery. If power is lost at one point along the power supply then the customer is located far down the track will also lose their cable service.
When using the HFC network used coaxial cable in the trunk was replaced by lines made of fiber optics. In the HFC network, the amplifier-amplifier still be used along a path that will coax cable but on the HFC network nodes which have fiber optic signals are converted back into the form of electrical signals to be transmitted to customers' homes via coaxial cable. On a network that can be used for two-way communication (downstream and upstream), the fiber node can also perform the conversion from electrical to optical. Each fiber node has its own power supply to provide power to the conversion tool optical / electrical and / or the trunk amplifier. Fiber is often referred to as the Optical node Terminal Node (OTN). In a large HFC network OTN is able to serve 200 to 1200 homes (usually around 500 houses). Fiber part of the HFC network is able to transmit signals as far as 25 miles without reinforcement and usually do not require resources.Tree and branch network is not the only network that may be because there are other network topologies that can be used like a star topology, or FSA (Fiber to Serving Area).
In the topology tree and branch, some branched fiber optic cable from the headend to the nodes that are spread in a star topology. Furthermore, on each node is a signal transmitted via coax cable using a tree topology and branch. For more details, see the following picture:
Image of HFC network with a combination of tree and branch topology with a star
Main Components
1. Headend
Headend is an important part of the HFC system. At the headend, the signal from a variety of sources (such as satellite signals, the signal off-air) is received and converted to the proper signal delivery form. At the time of the signals are ready to be delivered, the signals are combined in a single cable and is ready to be sent over the network. Headend consists of several parts, among others, is the receiver, demodulator / decoder, modulator and combiner.1.1 Receiver
Receiver function here is as a receiver signal derived from the earth station before being forwarded to the modulator. While the function of earth station is to capture the source signals from satellites. In each of these receivers happen sorting signal for selecting a desired channel due to signals received from satellites is still composed of many channels. The signal is then forwarded to the modulator.1.2 Demodulator / Decoder
For signal sources which are off-air signal, prior to broadcast RF signals received by the antenna to the modulator dimasukkkan then the signals are separated first based on the channel. The separation is performed by the demodulator / decoder.1.3 Modulator
Source signals at the headend in the form of baseband signals, before being sent to the combiner must first modulated carrier signal into the RF. Therefore this source signals must be passed to a baseband modulator that places the audio and video components at the RF carrier signal.1.4 Combiner
Combiner refers to the process of placing a variety of RF signals in a single cable for distribution through the network.
Before the signals are combined first, conducted a process of "scrambling" (randomization) signal to prevent access from those who do not need and do ad insertion process.
Penggambungan the most common method used in broadband RF system is a pairing-off sequence in which the groups consisting of two signals are combined at the same time, then the result of merging these groups are combined again. This process continues until all signals are in the same cable. To support the merger process, used a series of mini-called splitter.
1.5 Cable Router
Cable Router serves as an interface between the type of standard network (PSTN) with the HFC headend distribution point, control bandwidth usage and spectrum in data communications on HFC and manages all cable modem connected to it.1.6 Cable Telephony
Cable telephony functions as the interface between the PSTN network with the HFC headend distribution point for delivering telephony services within a two-way communication.1.7 Optoelectronics
The signal is passed through an optical fiber is in the form (the form of light). Light is a form of electromagnetic radiation with a very high frequency with a frequency range in the order of terahertz (THz). As the RF carrier signal, carrier signal light waves can also carry information. Therefore, the signal coming out of the combiner is in the form of electrical signals (RF), then this signal must be converted first into an optical signal (light) by using optoelectronic that converts electrical signals into light signals and vice versa.
Delivery signal through an optical link includes two main components namely:• Optical Transmitter
Optical transmitter on the optoelectronic at the headend is the point where the optoelectronic received RF carrier signal from the combiner. The incoming signal into an optical transmitter of the RF carrier signal in the form of electrical signals, because it can be passed on to fiber optic signal lines should be changed first to a form of light. Transmitter is responsible for changing the input electrical signals into optical signals and transmit the optical signal into an optical fiber channel.
Core
HeadendRF SignalThe electric current changeLaserFocusing LensFiber OpticsOptical ModulatorDC currentOptical OutputFigure Scheme Optical Transmitter• Optical Receiver
Optical receivers at the headend is part Optoelectronic Optoelectronic accept the point where the optical signal from fiber optic line which is the upstream signal received from customers. The signal entering the receiver in the form of light (optical). The function of this receiver is to recover the original RF signal from the carrier wave light (Lightwave carrier). The receiver will convert the received optical signals into electrical output RF.
The main parts of the optical receivers involved in the conversion process is the focusing lens (focusing lens), photodiode (photodiode) and RF amplifier (RF amplifier). Consider the following picture:CoreRF OutputInput OpticsGo to Distribution NetworkCoaxial cablePhoto diode
Fiber OpticsBraceImage Optical Receiver Scheme• RF Amplifier
RF amplifier serves to strengthen the RF signals generated by the receiver.2. Fiber Node
As mentioned above, the fiber node is a node on the network where the signals from the trunk optical fiber is converted into electrical signals to be forwarded to the coax cable or vice versa. Fiber node consists of optoelectronic devices and power Inserter. Optoelectronic tool is a tool that convert light signals into electrical signals or vice versa.2.1 Optoelectronics
Optoelectronic parts on HFC network consists of two parts:• Transmitter• Receiver• RF Amplifier
The three types of devices have been described above.2.2 Power Inserter
Power Inserter is an interface that connects the external power supply to the node. So, power is channeled into the node through the power Inserter. One feature of the Power Inserter is surge suppression to protect the cable from the current rises abruptly (surge) and the excess voltage (overvoltage).3. Terminal3.1 C I U (Customer Interface Unit)
Represents the interface between the customer terminal with HFC coaxial cable network. Based services with the ability of 64 Kbps, the customer may be held at the POTS service, ISDN BRA and data channels flexibly. In its development are available several types of devices in accordance with the level of customer needs. Can be placed with an indoor or outdoor mounting dependent power rationing system.Power rationing system consists of:a. Local power for each terminal Ciu for 100/240V AC with battery backup.b. Ration drop from the coaxial network (the terminal BONU) for 60 or 90V AC at a frequency of 60 Hz.3.2 Cable Modem
Cable modem is a device that allows high-speed access to the Internet via a CATV network. Cable modems typically have two connections, one to an outlet on the wall and the other to a computer (PC).
Cable modem speed varies. In the downstream direction (from network to a computer), speeds can reach 36 Mbps. Only a few computers that are able to be connected with such high speed so that a more realistic value is between 3 to 10 Mbps. In the reverse direction, namely upstream, the speed can reach 10 Mbps, but most modem producers will choose more optimal speeds between 200 kbps and 2 Mbps. At the beginning of the use of cable modems so that asymmetrical setup will be more widely used where the downstream channel has a higher bandwidth allocation than the upstream. This is because Internet applications that exist today tend to be asymmetrical. Activities that are downstream such as the World Wide Web (http) send more data to the computer than to the network.
Actually using the word "modem" for this tool can be misleading because it may cause shadows on the traditional telephone modems. The similarity between the cable modem and regular modem is that both perform modulation and demodulation of the signal. But the cable modem is much more complex than his brother's telephone modem. Cable modems can act as a modem, tuner, tools for encryption / decryption, bridge, router, ethernet hubs and so on in accordance with the service that is served.
Usually the cable modem receives and sends data in a different way. In the downstream direction, digital data is modulated and then superimposed on the 6 MHz television carrier, between 42 Mhz and 750 Mhz. There are many ways of modulation but the two most popular techniques used are QPSK (up to 10 Mbps) and QAM64 (up to 36 Mbps). These signals can be placed in a 6 MHz channel on both sides of the TV signal without disturbing the video signal cable TV. In the cable network that is activated in both directions, upstream transmission (also known as reverse path) is done at a frequency between 5 and 40 MHz. Environmental frequencies tend to have a lot of noise, the disruption of HAM radio, CB radio and impulse noise from home appliances. In addition, noise, other noise coming from the connectors that are not installed in tandem or the ugly wires. Therefore, tree-shaped network used and the branch then all the noise accumulated in the upstream direction. To reduce this problem most producers using QPSK modulation or similar methods that are more robust, but slower than QAM QPSK.3.3 Set Top Box (STB)
Set Top Box is a device installed in the homes of customers to select the channel, record and use the other facilities provided by the provider. STB, among others, the process of unscrambling the signal from channels that have been subscribed by the customer.