Ethernet over Coax is a family of technologies that supports the transmission of Ethernet frames over coaxial cable.
History
The first Ethernet standard, known as 10BASE5 in the family of IEEE 802.3, specified baseband operation over 50 ohm coaxial cable, which remained the principal medium into the 1980s, when 10BASE2 coax replaced it in deployments in the 1980s; both being replaced in the 1990s when thinner, cheaper twisted pair cabling came to dominate the market. The use of coaxial cable for Ethernet has been deprecated by 2011. Research in Ethernet transmission over coaxial cable continued, as both consumers and telecommunications operators strive to use existing 75 ohm coaxial cable installations, to carry broadband data into and through the home, and into multiple dwelling unit installations. Most EoC technologies are being developed for in home or on premises networking and are expected to be operated within the domain of a single operator.
as well as its later extension, HomePlug AV2 both operate in a portions of the RF spectrum directly below what is commonly used for terrestrial FM radio broadcasting. HomePlug AV uses BPSK, QPSK, 16 QAM, 64 QAM, 256 QAM, and 1024 QAM modulation strategies between 2 MHz and 30 MHz while the more recent HomePlug AV2 standard extends the upper bound of its spectral use to 86 MHz.
The ITU-T G.hn standard provides high-speed local area networking over existing home wires, including coaxial cable, power lines and phone lines. It defines an Application Protocol Convergence layer for encapsulation standard 802.3 Ethernet frames into G.hn MAC Service Data Units. Other ITU-T standards for home networking over coaxial cable include G.9954, also known as HomePNA 3.1
SLOC
The Intersil SLOC standard simultaneously transmits analog CVBS video and 2-way Ethernet over a single coax cable.
BroadR-Reach
is a Broadcom point-to-point Ethernet PHY technology, adopted by the OPEN Alliance as the OPEN Alliance BroadR-Reach PHY, that specifies a PHY operating full-duplex over one pair of unshielded twisted pair cable at 100 Mb/s.Broadcom developed this as 100BASE-T1, which in turn has been adopted under IEEE 803.2bw. This has been adapted for transmission on other cable formats including Coax. As part of the BroadR-Reach standard the digital signal processor uses a highly optimized scrambler when compared to the scrambler used in 100BASE-TX. This limits the bandwidth of the Ethernet signal to 33.3 MHz, which is about half the bandwidth of 100BASE-TX. A lower signal bandwidth improves return loss and reduces crosstalk. This allows for transmission distance to far exceed the standard 100m.
Other standards
There are also proprietary EoC implementations using WiFi-like OFDM transmission.
CATV compatibility
EoC research is focused on the use of existing cable television infrastructure for Internet access or broadband data transmission for the purpose of being compatible with the existing CATV broadcast signals simultaneously transmitted on the same cable. The EoC technologies must operate outside the frequency domain currently used for CATV or for satellite receiver to set-top box transmissions. Most EoC technologies are designed to operate in frequency bands above 1 GHz, which is the upper bound of television signals and for systems designed to operate in North America using the SCTE 55-1 and SCTE 55-2 CATV transmission systems, as well as in most of Europe and portions of Asia. In many localities CATV systems operate only up to 550 MHz or 750 MHz, wherein some EoC technologies focus on using spectrum between 550 MHz or 750 MHz and 1 GHz. Though less costly, they could potentially conflict with future spectrum expansion up to 1 GHz. Some markets focus on using this 750 MHz to 1 GHz spectrum for EoC, specifically avoiding EoC bands above 1 GHz due to potential ingress noise from over-the-air transmissions and cellular systems.
