Ethernet over copper for broadband

The IEEE 802.3ah subcommittee is developing a standard for Ethernet over voice-grade copper. Dubbed the Ethernet in the First Mile subcommittee, it has made great advances toward its goal of securing a standard for 10M bit/sec service over at least 2,500 feet of copper wire. The group expects to publish a final standard in 2004.

Long-Reach Ethernet (LRE) is an early example of this technology. LRE extends Ethernet by utilizing unconditioned, twisted-pair copper telephone wiring.

LRE uses frequency-division duplexing to separate the downstream channel, the upstream channel, and plain old telephone service (POTS), ISDN or PBX signaling services. This enables the overlay of LRE on existing POTS, ISDN or PBX signaling services without disruption. LRE and POTS/ISDN/PBX services may then be transmitted over the same line without interfering with each other.

LRE provides full-duplex transmission at tremendous speeds and distances:

15M bit/sec symmetric rate (up to 3,200 feet).

10M bit/sec symmetric rate (up to 4,000 feet).

5M bit/sec symmetric rate (up to 5,000 feet).

Because of these advances in speed and distance, a host of new value-added broadband services can be offered, including:

Broadband Internet connectivity for business travelers, office workers and home users.

IP telephony, which lets remote users interact and collaborate in real time.

Converged video/voice/data applications, such as video-on-demand, videoconferencing and e-learning.

Secure, high-speed network access through the addition of VPNs.

For most implementations, three devices are required to effectively deliver LRE to users - an LRE switch, LRE customer premises equipment (CPE) and a POTS splitter.

LRE switches condition incoming and outgoing Ethernet packets so they can run over standard copper wiring. Otherwise, they act much as traditional Ethernet switches - directing, storing and forwarding packets, as well as matching destination and source addresses together into virtual channels. LRE switching units simply need to be installed in a building basement, along with the telephone equipment, using 10/100M bit/sec or 1000Base-T to uplink to the Internet router and/or local servers. 10/100 switch ports also can be used to daisy-chain multiple LRE switches.

How it works
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Each LRE port is terminated in the room with a CPE device. The device splits LRE and POTS traffic, converting the LRE traffic into Ethernet traffic - and vice versa. This provides Ethernet access to the LRE signals that are on the telephone wire, without interfering with the service already in place.

A POTS splitter lets LRE and POTS co-exist on the same telephone line. It is necessary for deployments in which the PBX system is on-site and POTS traffic must coexist over the same copper wiring as LRE traffic.

Together, these components of LRE provide a robust broadband solution that is:

Low-cost - Building owners do not need to rewire their buildings to achieve remarkable increases in available bandwidth.

High-speed - LRE delivers bandwidth of up to 15M bit/sec.

Extremely functional - LRE supports a range of broadband capabilities.

LRE changes the economics of broadband provisioning by providing a cost-effective solution that preserves the existing communications infrastructure of multiunit buildings and enterprise campus customers.

Ethernet over copper for broadband

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