The Effects of Multipath Delay Spread on the Performance of High Rate Digital QAM and OFDM Wireless Link Operating in Tunnels

One of the primary limitations in realizing wide band wireless communication links in tunnels and long corridors are caused by multipath interferences and delay spread. Multiple reflections from the walls are expressed as dispersion of the propagating wave, resulting in amplitude and phase distortions in the received signal. The severity of the distortion is affected by the geometrical dimensions of the tunnel, the building materials of its walls, the carrier frequency and the wave polarization, the modulated waveform and its resulted bandwidth. Familiarity with the various phenomena on the wave propagation and accurate modeling of the space-frequency effects are required to design reliable indoor wireless link.