40 Years with the Ungerboeck Model: A Look at its Potentialities [Lecture Notes]

It has been about 40 years since Gottfried Ungerboeck published his paper [1] on an alternative maximum-likelihood (ML) detector for intersymbol interference (ISI) channels. The ISI model used by Ungerboeck is commonly referred to as the Ungerboeck model. Ungerboeck?s ML detector has equivalent performance compared to Forney?s detector, which was published two years earlier in [2], but received lesser considerations. Perhaps the best example of this is the fact that a BCJR algorithm [3] operating on the Ungerboeck model was derived as late as 2005 [4]. However, the Ungerboeck model has many strong aspects and has therefore been rediscovered over the last few decades.