10 Gbps Physical Layer for Single Twisted Pair

September 10, 2015 //By Norbert Weber, Conrad Zerna, Fraunhofer IIS
10 Gbps Physical Layer for Single Twisted Pair
Applications like advanced driver assistance systems (ADAS) and passenger infotainment drive data rates in automotive vehicles. To realize the lightweight and fuel efficient cars of the future, it is mandatory to increase the data rate, to get more bits over the same channel in the same time. This article introduces an elegant method to increase the data bandwidth in a single twisted pair (STP) cabling.

High data rates in vehicle networks could be achieved through multiple technical approaches. On the one hand this goal could be achieved by investing effort in the channel/transmission medium (see [1]). However, there is always the conflict between electrical requirements, like transfer function and electro-magnetic radiance/ susceptibility, and mechanical requirements, like weight, diameter, stiffness and used materials. The mechanical requirements indirectly stand for usability and costs of the cables. On the other hand, the goal of a higher data rate through the same channel can be achieved by investing in the signal processing at the end points. The development effort takes place up front and the only material costs are increased silicon area. Operating costs will rise by only the (unavoidable) power consumption in the network node; however, the goal of a new physical layer will be not to raise the power consumption per transmitted bit/s. The second option is the main focus of the presented work and technology.

The challenge

Major use cases for high-speed data transmission in vehicles are low-latency uncompressed video transmission and a network backbone of consolidated connections and busses. For the next generation of networks, data rates in the range of 10 Gbps - even up to the 12.5 Gbps required for high-resolution video distribution – are targeted. As a reference, application-proven lightweight cables like the star-quad are taken as a possible candidate for the transmission medium. Achievable lengths should be 10-15 m. At the targeted speeds, the transfer function of common cables becomes more problematic. Higher attenuation at higher frequencies surpasses practically compensable insertion loss in almost every cable type. Moreover, in certain cable types there is a notch present in the signal band in the frequency range from 2 GHz to 3,5 GHz. [2]

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