Performance of fast Node B scheduling and L1 HARQ schemes in WCDMA uplink packet access

The performance of WCDMA uplink systems deploying Node B based scheduling and fast hybrid ARQ (HARQ) retransmission protocols is studied. With fast Node B scheduling and fast L1 HARQ schemes, both the uplink packet scheduling functionality and the entity controlling the retransmission mechanism are moved from the radio network controller (RNC) to the Node B. A Node B scheduling algorithm is proposed to increase the utilisation of the allocated uplink resources; this is achieved by making use of already existing information about the transmitted data rate of the UEs. Moreover, fast L1 HARQ schemes make retransmissions less costly from a delay perspective compared to an equivalent RNC controlled ARQ mechanism. Therefore, the physical channel can be operated with somewhat higher error probability, which converts directly into enhanced system capacity. The potential capacity gain from fast L1 Node B controlled HARQ strategies and fast Node B scheduling operation is estimated by means of an analytical study, as well as system level simulations. The combined gain obtained by jointly deploying fast Node B scheduling and fast L1 HARQ retransmission schemes is estimated in the range from 25% to 60%, depending on the mobility scenario. Fast Node B scheduling and L1-based HARQ protocols are included in 3GPP's "Feasibility Study for Enhanced Uplink for UTRA FDD" (TR 25.896 V1.1.2, 2003).