Interleaved trellis coded modulation and decoding for 10 Gigabit Ethernet over copper

It is highly likely that 10 Gigabit Ethernet over copper (10GBASE-T) transceivers will use a 10-level pulse amplitude modulation (PAM 10) as well as a 4D trellis code as in 1000BASE-T. The traditional trellis coded modulation scheme, as in 1000BASE-T, leads to a design where the corresponding decoder with a long critical path needs to operate at 833 MHz. It is difficult to meet the critical path requirements of such a decoder. To solve the problem, two interleaved trellis coded modulation schemes are proposed. The inherent decoding speed requirements are relaxed by factors of 4 and 2, respectively. Parallel decoding of the interleaved codes requires multiple decoders. To reduce the hardware overhead, time-multiplexed or folded decoder structures are proposed where only one decoder is needed and each delay in the decoder is replaced with four delays for scheme 1 and two delays for scheme 2, respectively. These delays can be used to reduce the critical path. Compared with the conventional decoder, the folded decoders for the two proposed schemes can achieve speedups of 4 and 2, respectively. Simulation results show that the error-rate performances of the two schemes are quite close to that of the conventional scheme.