Performance Evaluation of an L-Band Broadcast DAB/DMB System in Simulated Subway Tunnel Environment

This paper examines radio wave propagation in underground and subway environments from the perspective of providing digital radio with multimedia and video enhanced services (DAB/DMB) as a continuity of the same services offered above ground. To this end, a preliminary simulation framework of a DAB/DMB transmission system inside a rectangular subway tunnel is proposed. First, the received power and path-loss along the tunnel are predicted with a reflection ray-based propagation model. Then, the wideband radio characteristics of the DAB/DMB signal (mean delay spread, impulse response and fading behavior) are modeled and simulated based on subway tunnel measurements reported in literature. In addition, the benefits of space diversity techniques such as Maximal Ratio Combining (MRC) and Cyclic Delay Diversity (CDD) on the performance of the DAB/DMB transmission system have been investigated under the flat fading degradation as exhibited by the subway tunnel propagation channel.