Serially connected bi-directional DFE suitable for 8-VSB modulation

A serially connected bi-directional decision feedback equalizer (SB-DFE) is proposed to improve the performance of channel equalization by exploiting implicit multipath diversity. The SB-DFE improves equalization performance by cascading normal and time-reversed DFEs. Conventional bi-directional DFEs obtain improved performance by combining the two DFEs in parallel. They, however, need accurate channel estimation and the performance is not guaranteed for multi-level modulation because they utilize each DFEs hard decided output symbols. On the other hand, the SB-DFE utilizes the soft output of the normal DFE at the first DFE as the input to the following time-reversed DFE without channel estimation. The performance of the SB-DFE is compared with that of the normal DFE and the bi-directional arbitrated DFE (BAD) in the 8-level vestigial sideband (8-VSB) modulation system with Brazilian digital high-definition television (HDTV) test channels. The SB-DFE has 1 ∼ 1.8 dB signal-to-noise ratio (SNR) gains over the others.