Optimal power allocation for heterogeneous network capacity maximization

We investigate the optimal joint power allocation in Heterogeneous Networks (HetNets) to maximise its capacity. Considering frequency reuse in the network, we study two power-constraint cases, i.e., per-cell power constraint case and per-tier power constraint case. We formulate the capacity maximization problem by allowing each subcarrier of Marco eNodeB (MeNB) to be shared by users from multiple Picos. We mathematically demonstrate that the optimal power allocation in the per-cell power constraint case has a remarkably simple nature: each Pico transmits to its user with maximum power, while MeNB either selects only one user to jointly transmit with maximum power or does not transmit to any user. In the per-tier power constraint case, the difference is that the power allocation between two Picos takes the form of water-filling. Numerical results verify that our proposed schemes outperform the conventional interference coordination schemes.