The WAN or interbox connection has long limited the overall performance of networking systems. Technical advances have increased the bandwidth of connections between communications equipment to a point where the system itself cannot process the torrent of data rushing in. Intrabox communication is the bottleneck, and at its heart is the backplane transceiver.

A solution architected specifically for the backplane environment would satisfy the three features that communications-system designers seek when evaluating backplane I/O solutions: speed, ease of design and reliability.

The speed of existing solutions and density of traces through the connector already limit intrabox communications. The optimal solution would provide higher bandwidths through the backplane while limiting crosstalk that restricts the number of signals routable through a connector.

Backplane implementations are difficult to design and are unreliable because existing parts are not specific to the

environment. A backplane transceiver should adapt itself to its environment (channel distance, crosstalk and so on) and automatically work at any distance and in any environment.

Total reliability is needed from the backplane transceiver because it lies at the heart of communications systems that sit at critical junctures in the network. It should be possible to look inside the transceiver to determine the status of any link and modify internal parameters to adjust for channel deficiencies.

At the moment, generic parts or those designed for other markets, such as Ethernet, are all that's available. Overall system performance is limited by the bandwidth achievable through the backplane connector. System introduction is delayed by the multiple revisions of a backplane required to achieve reliable operation, or by late changes required to solve electromagnetic-interference problems.

The problems occur at the relatively modest speeds of 1 to 3 Gbits/second. The designer faces increased challenges as the speed of backplane communications rises beyond 2 Gbits/s, since the backplane channel degrades significantly as the frequency increases. The system designer is also confronted by increasing dispersion and EMI at higher frequencies.

At higher speeds, backplane design demands a new and directed approach, one that would incorporate continuous adaptive signal processing to alleviate reflections and crosstalk without user adjustments. It would also include integrated dynamic channel-matching and multilevel-signaling techniques. A backplane communications system is the way to avoid intrabox bottlenecks and delayed product rollouts.

Paul Nahi is the Chief Executive Officer at Accelerant Networks Inc., based in Portland, Ore.<.I>