channel operation margin (802.3bj) (COM)

In the case of backplane Ethernet, 100GBase-KR4 is an interface via which four differential signals are transmitted at 25 Gbit/s each via copper lines.

To evaluate the channel properties, the IEEE 802.3bjworking group, which specifies this technology, has developed an evaluation criterion for channel performance in the form of the channel operation margin( COM). This performance assessment involves estimating the losses of the lanes, the reflections, the insertion loss deviation( ILD), the insertion loss, and the crosstalk, crosstalk, and near-crosstalk, and using these to determine the transmission performance, which is ultimately expressed in the received signal level and the signal-to- noise ratio. The channel operation margin is used to evaluate the entire transmission path with transmitter, receiver, cable and HV connector.