Group demos power-saving PON protocol
Representatives of Alcatel-Lucent, IMEC and Orange participated in the demo of the Bi-PON technology defined by AlcaLu’s Bell Labs division. It is one of 25 research projects at GreenTouch, a group of systems companies, carriers, research institutes and universities defining technologies to cut power consumption in communications as much as thousand-fold over the next decade.
“Normal power consumption improvements are in the range of about 25 percent a year, so these are major breakthroughs we are seeking,” said Gee Rittenhouse, chairman of the group.
Currently 2.5 Gbit/second PONs are widely deployed as last mile links to homes and offices. So-called XG PON, 10 Gbit/s versions, are now in development that will sport a new sleep mode capability to lower power consumption.
However, even with the new sleep mode, current PON technologies generate a significant amount of overhead traffic—almost 99 percent of its content. The Bi-PON protocol uses bit-interleaving to slash the amount of packet-data overhead and thus reduce power consumption.
The Bi-PON protocol arranges data in a bit-interleaved formats in clock periodicity matching the subscriber rate. Thus unneeded data can be dropped before hitting clock and data recovery circuits. The group adapted existing bit-interleaving technology by adding a flexible capability to change subscriber rates to match the needs of customers as they shifted among voice, video or data services.
“We implemented it in an FPGA to show dynamic power consumption,” said Peter Vetter, chairman of GreenTouch’s wireline group and a Bell Labs researcher. “The FPGA uses a lot of static power, but shows the type of dynamic power we can achieve in an ASIC,” he said.
The protocol was developed by a Bell Labs researcher. It opens the door to other power savings using voltage scaling in PON circuits, Vetter said.
The demo uses new clock and data circuits developed by Belgium’s Imec research institute. The group has also designed a Bi-PON ASIC it aims to demo in June. The new chips will consume a total of about 100 milliwatts compared to as much as 3 W for today’s 10G PON chips, Vetter said.
Using the technology, system designers could decrease power consumption on PON systems from about 10 W per subscriber today to about 5 W in the medium term and as little as 1 W in the long term, he said. The technology could be a requirement to keep power levels down in the 40G PON generation, he added.
Bi-PON is the second research demo from the consortium. Previously it showed advanced work in antenna design. Among its other projects, it is working on comms circuits operating at near threshold supply voltage and new forms of logic
Bell Labs has applied for four patents on Bi-PON. The GreenTouch group shares intellectual property on a royalty-free basis members, but IP owners can charge non-members royalty fees.
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