Generalized maximum likelihood sequence detection and estimation (GMLSDE) was developed using the EM algorithm. This method combines channel parameter estimation and data detection under the maximum likelihood criterion, bringing together various receivers for different channel models. The GMLSDE helps to understand the relationship between channel models, receiver structures, and optimization levels. Per-survivor processing (PSP) and per-branch processing (PBP) methods naturally arise from the EM aspect of GMLSDE.