Capacity analysis for closed and open access femto cell networks

We investigate the performance of femto cell networks in both closed and open access regimes. Specifically, we analyse the typical user capacity as well as the sum capacity of all users in a macro cell with a Poisson field of femto base stations. The closed access results demonstrate that while the system sum capacity initially increases with the density of femto cells, this gain comes with a significant performance penalty suffered by an individual macro user. In open access mode, we show via analytical derivations that macro users only benefit from access to the available femto base stations for impractically high densities. Furthermore, we derive limiting sum capacity results showing that while the mean sum capacity initially increases linearly with femto density, sum capacity will eventually decay to zero in the limiting case as the femto density approaches infinity.