Performance of high-speed downlink packet access in coexistence with dedicated channels

The joint third-generation system performance of high-speed downlink packet access (HSDPA) and Release 99 (Rel'99) dedicated channels (DCH) is studied. Given such a scenario, the optimal sharing of the cell carrier transmit power between HSDPA and DCH, which is conditioned on a certain number of channelization codes that are reserved for HSDPA transmission, is addressed. Detailed network-performance results are shown from a comprehensive dynamic system-level simulator, which includes a simulation of many cells and users, and a detailed modeling of layer 1 to layer 3. Compared to a scenario without HSDPA, the total cell throughput can be increased by 69% by allocating five high-speed physical downlink shared channel codes and 35% of the maximum cell transmit power to HSDPA transmission. These results are obtained for a macrocellular scenario with best effort packet data services. Furthermore, it is demonstrated that part of this capacity gain comes from better utilization of the available cell transmit power since less power control headroom must be reserved for HSDPA. The presented performance results reflect the expected performance improvement from gradually introducing HSDPA in an existing Rel'99 wideband code-division multiple-access network.