It's usually a straight dead shot. With optical fiber and any land based radio, there is always obstructions to bend around, physical loses, ground clutter. Bas

It's usually a straight dead shot. With optical fiber and any land based radio, there is always obstructions to bend around, physical loses, ground clutter. Basically signal to noise is way higher with line of sight. Higher SNR means lower bit error rate means deeper modulation (cutting edge is like 65536-QAM and maybe higher). Noisy channel coding theorem and all that.