Load sharing in hierarchical cell structure for high speed downlink packet transmission

We investigate the load sharing problem between the umbrella microcell and the overlaid picocells in a hierarchical cell structure. A load sharing strategy is proposed and its performance is evaluated by simulation when it is used for transmission of mobile Internet traffic. The results show that, with the proposed strategy, the microcell backs up the picocell well, especially when a specific picocell cluster suffers an unusually heavy load condition. By using the strategy, we can reduce the installation cost otherwise needed for the system capacity of every picocell cluster to cope with the unusually heavy load.