This paper presents a simplified SpaceWire network architecture to overcome a challenging high-speed and real time packet switching process required in a baseband processing unit of a regenerative satellite payload as a part of the “On-Board Processing EHF (Extremely High Frequency) Satellite Transponder and Testbed Development Project”. This is an R&D Project supported by the Scientific and Technological Research Council of Turkey (TUBITAK). With this project, an on-board processing geo-satellite transponder serving two spot beams will provide communications between satcom terminals. The baseband processing subsystem in this project takes part as the central unit by providing on-board processing power by using the state of the art space qualified FPGAs and Leon-3FT based processors. This subsystem, of which the internal network structure is discussed here, is currently being developed by Communications and Information Technologies Group of Aselsan A.Ş., Turkey.