IEEE 802.3 -- Standardizing the Next Generation of Ethernet PHYs

I attended the IEEE 802.3 standards meeting in York, England recently. Over 200 people came from all over the world to work on standards for the next generation of Ethernet products.

Work is ongoing to standardize new Ethernet PHYs (physical layer devices) for speeds of 1Gbps, 40Gbps, 100Gbps and 400Gbps. The 1Gbps work is focused on the automotive and industrial market segments, a field that Cadence is particularly committed to supporting with its Ethernet IP.

Ethernet is expected to be widely adopted in cars -- it meets all the speed, cost, reliability and inter-operability requirements. The IEEE working group is working to standardize a gigabit PHY optimized for automotive environments that will operate over a single twisted pair of copper. This is a speed upgrade to the existing 100M automotive PHY available from Broadcom. There is also consideration being given to start a project to standardize a method of pre-emption to allow time critical traffic to be sent for closed loop control. Pre-emption is something that manufacturers of industrial control systems are asking for, and is also of interest to the automotive market.

For 40Gbps, work is ongoing to standardize a PHY for operation over 30 meters of four-pair, balanced twisted-pair copper cabling (802.3bq project). The target application for this is data centers.

For 100Gbps, work is ongoing to standardize chip-to-chip and chip-to-module interfaces, backplane PHYs, a twin-ax PHY and a new lower cost multi-mode optical fibre PHY (802.3bj and 802.3bm projects). All these use four lanes operating at 25 Gbps per lane.

There is agreement on the specification for the chip-to-module interface but there is still a discussion over what the CAUI4 chip-to-chip specification will be. Implementers want to limit the loss budget of this to 15dB so the receiver's DFE can be eliminated to save power and reduce burst errors which affect CRC performance. However, some system providers would like a higher loss budget to allow a longer reach.

For 400Gbps, a study group is looking at what the objective should be for the yet to be formed 802.3bs task force. There seems to be agreement that the initial deployments will be sixteen lanes of 25 Gbps per lane and that the 802.3bs project will develop standards for a chip-to-module, a PHY for single-mode optical fibre and a PHY for multi-mode optical fiber.

Arthur Marris, September 2013.