The CDMA overlay concept
L.B. Milstein, Donald L. Schilling · 2002
We present an overview of the results which have been obtained on the concept of allowing wideband code division multiple access (CDMA) waveforms to share a common spectrum with conventional, narrowband signals. Such sharing of the frequency spectrum is referred to as a CDMA overlay, and has the potential of enhancing the overall spectral efficiency. The overlay has been demonstrated in both the PCS band and the cellular band. It is also shown that such an overlay could be successfully accomplished either by employing tunable notch filters in the transmitters and receivers of the CDMA units, or by using a multicarrier CDMA waveform.