Information about Cable modem technology

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In addition to the fixed network, there is also the TV cable network, which also consists of fixed lines. It takes its name from "cable TV coverage". Therefore, a technology is meant to be transferred to the TV signals to the TV via a cable network. Before that was the reception of broadcast signals (TV and radio) over a usual home antenna. However, only the reception was so possible from 3 stations. An alternative is satellite. The liberalization of the telecommunications market have for cable operators new possibilities. The cable operators have a wide-area network on which they transmit TV and radio programs. Since it is obvious to extend this network for the transmission of data and use them to additional services, such as offering telephony and Internet access. The cable networks have been built in 80's. They were originally intended only for the transmission of television and radio. For an Internet access or telephony lacked the required feedback channel.

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Network operators / cable operators / cable TV network operator

The operators of cable television networks are cable companies, which are usually for local businesses. Via an extensive cable network, they offer their customers a TV cable connection. Additionally, you can receive television and radio stations. Nationwide, the cable networks reach only three-quarters of all households. In addition, the cables are not in commercial areas because there is no television connections are needed. The construction of the cable network were taken into account only residential areas. The cable network was originally split into four planes. Only the first three planes were among the cable companies. Which was then forced to sell the TV-cable networks. The level-4 was originally awarded to small and medium-sized enterprises. Even today, the level-4 in the possession of about 1,000 individual independent companies. Among these are a few of millions or hundreds of thousands of connections. Most of you use only a few thousand customers. The modernization and reconstruction of the cable network operators also need to level 4 are active. But not all are keen to offer Internet via TV cable. Whether the individual networks may be suitable for return path depends on the particular network configuration, the user profile, the resulting sales potential and marketing strategy. Each operator must consider its cable network to profitability. Normally, all cable networks will eventually be rebuilt.

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Frequency allocation and frequency usage

The laid coaxial cables can cover a frequency range from 5 to 862 MHz. But the frequency range up to 862 MHz is not fully available for data connections. Over 30 TV channels show most of the available spectrum. In addition there are about 200 digital channels. More channels are occupied by the analog FM radio. The TV channels 108-300 MHz has a bandwidth of 7 MHz. The channels of 300 MHz have a bandwidth of 8 MHz (30 Mbit / s). Theoretically there are 100 channels with 8 MHz. Using a 256-QAM modulation can be transported per channel 50 Mbps. This creates a total bandwidth of 5 Gbit / s. However, it is unlikely that this bandwidth will eventually be used exclusively for Internet access. The core business of cable operator is still the distribution of television programs. Therefore, the total bandwidth for Internet access at 1 Gbit / s per head station. After the radio (RStV), each cable operator one-third of its offer reservation for specified channel. Another third, he can either impose stations. This applies to all analog channels used to air programs with nationally established rights. Under these conditions, the frequency spectrum remains only a fraction of broadband Internet and telephony. Much of the will of 65 MHz to 450 MHz used for the transmission of radio and TV. Each analog TV channel occupies a bandwidth of 50 Mbit / s, would fit in the approximately 10 digital programs by a simple resolution or to use for internet access allows. The range of 450 MHz can be up to 862 MHz make fullest. There is the practical limit. The frequency range between 450 and 862 MHz can be freely assigned, depending on the configuration. If the cable length to allow customers to use long instead of 862 only 640 or even 470 MHz. Even with a coaxial cable, the attenuation increases with frequency and cable length. In practice, many networks to 520 or 570 MHz are limited. Only by reducing the size of each segment, ie the subdivision of a hub in several hubs, the frequency spectrum is fully utilized. But in the short and medium term there will be no bottleneck in the frequency spectrum of the tower.