In order to comply with emission regulation, reach their profitability targets and minimise the in-use cost of their vehicles, OEMs are seeking solutions to optimise their aftertreatment systems. For SCR system engineers, one of the most important challenges is to reduce the system's cost, while keeping its high level of NOx emission reduction performance. Ways to achieve this cost reduction include 1. using an engine out NOx estimation model instead of a NOx sensor upstream of the SDPF catalyst and 2. eliminating the Ammonia Slip Catalyst downstream of the SDPF catalyst. Achieving these challenging targets requires actions on the complete SCR system, from the optimisation of mixing and uniformity in the SDPF catalyst to the development of robust controls. To face these challenges, DENSO has developed a novel exhaust reverse flow concept, combined with a blade mixer, increasing mixing length and total mixing performance. The SDPF catalyst uniformity during transient and not only steady state operation of the engine has been investigated. On the controls side, robust engine out NOx, advanced Ammonia storage modelling and robust system adaption controls were developed. Finally, the robustness of the whole SCR system against tolerances and errors through extended sensitivity analysis has been evaluated.