We compare four different approaches to specification and refinement of the software parts in SW/SW communication channels with respect to design productivity. The four approaches are CoWare [12], MakeApp [7], ComSyn [8], and manual refinement. Manual refinement is still predominant in practice for most embedded systems. With this case study we hope to show its deficiencies and how it can be improved with tool support available today. The comparison is done by analysing the impact of different techniques on the design process. The analysis is based on two designs, a channel decoder of a transceiver in a D-AMPS base station and an operation and maintenance block of an ATM network. We compare the design productivity with respect to development effort, validation effort, and library maintenance effort.