Complexity reduction of the decoders for interleaved trellis coded modulation schemes for 10 gigabit Ethernet over copper

10GBASE-T (10 gigabit Ethernet over unshielded twisted pairs) will probably use a 10-level pulse amplitude modulation (PAM10) as well as a 4D trellis code similar to the one in 1000BASE-T (1000 megabit Ethernet over copper medium). The trellis code can be used in a conventional way as in 1000BASE-T, but the corresponding decoder with a long critical path needs to operate at 833 MHz. To solve the problem, two interleaved trellis coded modulation schemes were proposed in our previous work. The inherent decoding speed requirements can be relaxed by factors of 4 and 2, respectively. Due to intersymbol interference (ISI), the branch metric units in the decoders corresponding to the two interleaved modulation schemes are much more complicated than those in the conventional decoder. Thus, this paper considers the problem of complexity reduction of the decoders for the two interleaved modulation schemes. Two complexity reduction schemes are proposed. Simulation results show that the performance loss due to complexity reduction is negligible.