On the efficiency of wireless networks with partially overlapping channels

This paper presents a theoretical investigation of the spectral efficiency of a shared wireless channel. A large number of narrow bandlimited users share a common wideband channel with no cooperation between them. We derive an exact expression for the spectral efficiency of the shared spectrum when each user treats the interference from other signals as an additive noise. These new expressions are used to investigate the effects of non-orthogonal channel spacing on the overall spectral and area-spectral efficiencies of shared wireless channels. As far as the spectral efficiency in bits per second per Hertz is concerned, our results reveal that there is actually no gain that can be achieved with the channelization of the shared wideband channel. In contrast, when raised-cosine spectra are used, it shown that channelization results in a more than 21% loss in the spectral efficiency, and that it is more efficient to let users transmit arbitrarily at the shared wideband channel without channelization.