Power Allocation for Downlink Shared Channel in UMTS
Original Publication Date: 2002-Jul-18
Included in the Prior Art Database: 2002-Jul-18
In UMTS, the Downlink Shared Channel (DSCH) is used to transmit data packets from the Node B to the User Equipment (UE) using the fat pipe multiplexing concept. Each DSCH is associated with a Dedicated Channel (DCH) which is used for power control, channel estimation and transmission of associated control information for the DSCH. In this paper, we propose a method to determine the power allocation of the DSCH and its associated DCH such that any Service Frame Error Rate (SFER) target can be met for both the DSCH and the associated DCH subject to power availability. The proposed algorithm relies on a two-step process to accomplish this goal. First, the required Ec/Iors (based on given target SFERs) for the DSCH and DCH are determined from a reference curve plus offset factors that are based solely on the requested data rates. From these two power requirements, the gain factor of the DSCH is set relative to the associated DCH. Next, outer-loop power control is used to drive the operating SFER of the DCH to its target range regardless of channel conditions. Since power control in the DSCH is coupled with that on the DCH, its operating SFER will also converge to the target range. From simulation results, it is shown that the proposed algorithm is able to accommodate the required SFER targets with high accuracy under various fading channel conditions and service rates.