A transition radiation detector (TRD) prototype based on a single multiwire proportional chamber coupled with a small drift region was developed for the innermost part of the CBM-TRD subsystem. It preserves the same gas thickness for transition radiation absorption as the double-sided TRD prototype for which a pion misidentification probability of better than 1% for a six layer configuration was obtained. In the same time it fulfills the requirement of a high geometrical efficiency of CBM-TRD stations. The readout electrode geometry with triangular shaped pads gives access to a two-dimensional position information with a single TRD layer. The detector was tested with a mixed electron/pion beam of 1–5GeV/c momentum at the CERN PS accelerator. A pion misidentification probability of 1.18% for a six layer configuration based on this architecture was obtained. The two-dimensional position resolutions (along and across the pads) were measured. The pad signals were processed using a new front-end electronics called Fast Analog Signal Processor (FASP), designed for high-counting-rate environments. CADENCE simulations were used for further optimization of the FASP amplifier for operating this new architecture.