An IS-OFDM system for point-to-point wireless communications that suppresses narrow-band interference comprises an IS-OFDM transmitter and an IS-OFDM receiver, wherein a transmitted signal comprises a plurality of subcarriers, and further wherein each subcarrier contains more than one and potentially all symbols transmitted in a given frame. The circuit protects against load dumps or positive transients applied to any electronic unit. One embodiment of the implant methods starts with inserting the pointed-tip lead assembly directly into tissue. The system also reduces the influence of top and bottom horizons of geological layers by applying data driven techniques that estimate the velocity function in a way that reduces dependence on the boundary conditions.