Interference Suppression in Wireless Cellular Networks through Picocells

It is well-known that co-channel interference (CCI) limits the capacity of traditional cellular networks which mainly support voice communications. The problem becomes more prominent when cellular systems evolve to support high bit-rate data applications. It has been demonstrated that base station cooperation can reduce CCI and increase cellular system capacity while maintaining the current network infrastructure, since collaborative base stations essentially form a virtual MIMO system with geographically dispersed multiple antennas. In this work we also consider another approach for interference suppression, i.e. to divide a cellular system into picocells through denser base station deployment. Instead of resorting to complicated cooperation techniques, which is essentially a software approach, denser base station deployment focuses on infrastructure upgrade as a hardware approach. For a 2-dimensional hexagon cellular array and the propagation model under consideration, we observe that the operating regime shifts from interference-limited to noise- limited when the density increases to about 20 bases stations per km2. To compare the performance of both approaches we adopt the criterion to maximize the minimum served spectral efficiency with a certain user outage constraint. Simulations show that denser base station deployment outperforms suboptimal cooperation schemes (zero-forcing) when the density increases beyond 3_12 base stations per km2, the exact value depending on the rules of outage user selection. However, close-to-optimal cooperation schemes (zero-forcing with dirty-papercoding) are always superior to denser base station deployment