A study of received signal-level distribution in wideband transmissions in mobile communications

A mobile propagation model, which includes not only indirect arriving waves but also a direct arriving waves and is applicable to picocell, microcell, and macrocell, is proposed in order to clarify fundamental propagation characteristics in instantaneous received signal-level variation through narrowband and wideband transmissions. On the basis of this model, we derive a mathematical expression for the instantaneous received signal-level. Through an analysis of this expression, a new propagation parameter called equivalent received bandwidth 2ΔfΔL_max is proposed. The dependence of the received signal-level distribution on the new parameter is studied by computer simulation. It is shown that the fading depth depends strongly on the 2ΔfΔL_max, as a parameter of the power ratio a. When 2ΔfΔL_max<10 MHz·m, the fading depth depends only on the power ratio a. When 2ΔfΔL_max>10 MHz·m, the fading depth depends not only on the power ratio a but also on the 2ΔfΔL _max and it decreases as 2ΔfΔL_max increases. On the other hand, the number of arriving waves and the minimum effective amplitude of arriving waves are examined quantitatively. According to the results, when the number of arriving waves N is larger than 6, the fading depth is independent of N, and the minimum amplitude of arriving waves should be larger than -20 dB relative to the maximum amplitude in indirect arriving waves