Q

VDSL, LRE and deploying a WLAN in a building without CAT5 cabling

I'm deploying a WLAN in buildings that have no CAT5 cabling. I came across LRE and VDSL, I'm not sure what is the difference between them.
In one installation, I need to put four access points in four corners of a building (yes there are better ways); the key question is how do I connect those APs to the main switch/router without running CAT 5 cables, as that might not be possible. In other words, I'd like to know of other products that allow me to reuse the phone wiring already installed.
I want to know my options and then a recommended solution based on quality product, capacity then price.
Very High Bit Rate DSL (VDSL) is an ANSI standard for sending data over twisted pair local loops at speeds up to 55 Mbps. Like other DSL standards, VDSL defines how data and voice can be modulated for transmission over copper wire between a telco's central office (CO) and the subscriber's home or office. To learn more about VDSL and other xDSL standards, commonly referred to as a "last mile" technologies, see the DSL Forum website.

Long Range Ethernet (LRE) is a Cisco solution that uses VDSL modulation to support symmetric Ethernet over unshielded twisted-pair inside wiring -- aka Plain Old Telephone Service (POTS) lines already installed inside your walls. LRE supports full-duplex Ethernet up to 15 Mbps and 5000 feet, and can coexist with analog or digital voice services, including ISDN and ADSL. You'd need an LRE-capable switch (e.g., the Cisco Catalyst 2924...

LRE XL) and a termination device for each Ethernet drop (e.g., the Cisco 575 LRE CPE). You'd connect each AP to a 575 LRE CPE, plug that CPE device into the nearest RJ-11 telephone jack, and haul traffic back to one centrally-located Catalyst switch. A new LRE-capable switch will set you back at least $2500, plus perhaps $120 per CPE device.

Another option is HomePNA, defined by the Home Phoneline Networking Alliance. As the name suggests, this technology is largely designed for use inside the home, allowing broadband Internet traffic, video traffic, and voice all share the same POTS lines. HomePNA 3.0, an extension of version 2.0 (now an ITU standard) can support up to 128 Mbps of traffic. Depending upon your environment, you might be able to use HomePNA in your office -- but HomePNA can't share POTS lines with a PBX system. You'd interconnect your APs using HomePNA bridges. With only four APs, this would cost you less than LRE; for example, the Linksys HPB200 HomePNA-to-10 Mbps Ethernet bridge retails for about $170.

Finally, there's HomePlug, defined by the HomePlug Powerline Alliance. HomePlug competes directly with HomePNA for interconnecting devices within the home, but rides over existing electrical cables instead of twisted-pair telephone lines, reaching speeds up to 14 Mbps. One drawback of HomePlug is the variable interference caused by noisy devices sharing the same powerline -- for example, have you ever seen your household lights dim when using your printer, fax machine, or microwave oven? HomePlug devices are built to detect and adapt to this interference, but noise sources may be greater in an office environment. HomePlug products are even cheaper than HomePNA -- for example, the Linksys PLEBR10 Instant PowerLine Etherfast 10/100 Bridge now retails for around $80.

 

This was first published in January 2004

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