Sharing vs. splitting spectrum in OFDMA femtocell networks

A network comprised of high-density femtocells coexisting with low-density macrocells, in an orthogonal frequency-division multiple access (OFDMA) setting, is considered. Two approaches are investigated: (1) spectrum sharing where macrocells and femtocells can access the same subchannels, and (2) spectrum splitting where macrocells and femtocells access separate portions of the spectrum. In both approaches, the trade-off between the utilized bandwidth and the signal-to-interference ratio (SIR), as femtocells or macrocells access more subchannels, is studied. The number of utilized subchannels that maximizes the average spectral efficiency for femtocells, subject to a minimum average spectral efficiency constraint for macrocells, is analyzed for both approaches, showing that the performance with spectrum splitting is better than spectrum sharing, for the considered model.