Performance study for a microcell hot spot embedded in CDMA macrocell systems

The code-division multiple-access (CDMA) system can provide more capacity than other systems, and the hierarchical layer of cells is required for system design. However, the problem is whether the same radio frequency (RF) channels used in a CDMA overlayed/underlayed macrocell and microcell structure also obtain a high capacity as in the homogeneous structure. In this study, we investigate the interference of uplink and downlink from both the microcell and macrocell under a hierarchical structure. Downlink power control scheme and two power control methods for uplink are also considered. Performance measures such as blocking probability, C/I, capacity, and service hole area are also obtained by computer simulation. Besides, some extra efforts for microcell are also noted, such as more power transmitted by a microcell base station (BS) should be paid if the same RF channels are used in the hierarchical structure. The capacities of macrocell and microcell in the overlaying/underlaying structure are limited by uplink and downlink, respectively. With downlink power control, microcellular capacity can be increased. However, combining of downlink power control for microcell and C/I uplink power control for macrocell causes the overall system capacity to significantly increase.