A Power-Allocation-Combined Scheduling Algorithm for CDMA-Based High-Rate Packet Data Systems Insoo Koo 1 , Jens Zander 2 , and Kiseon Kim 1 1 Dept. of Infor. and Comm., Kwang-Ju Institute of Science and Technology, 1 Oryong-dong, Puk-gu, Kwangju, 500-712, Korea 2 Radio Communication Systems, S3 Isafjordsgatan 30B, KISTA, Stockholm, Sweden. Abstract. In CDMA-based packet data systems such as HDR and HS- DPA which are designed to support high rate services, BSs transmit data packets with a maximum power based on time multiplexing mode such that only one user can be serviced at a time. In this paper, we propose a power-allocation-combined scheduling algorithm for HDR-like systems in which we adopt a code division multiplexing (CDM) transmis- sion method in the downlink common channel in order to utilize channel orthogonality such that we can serve more than one user at a time slot specially when there exist remaining resources after serving the firstly se- lected user by the scheduler. Simulation results show that the proposed scheme outperforms the conventional scheme as the traffic load increases. 1 Introduction CDMA-based high-rate packet data systems, called as the 3.5 th generation CDMA systems beyond IMT-2000, such as HDR and HSDPA adopt common shared channels in the forward link in order to provide a high bit rate packet data service and an improved throughput. For example, HDR systems adopt the forward packet data channel (FPDCH)[1] while HSDPA systems use the high speed downlink shared channel (HS-DSCH)[2]. These common shared channels are capable of supporting high bit rate by employing adaptive modulation and coding with Hybrid ARQ, turbo codes and transmit diversity. One of the most distinct features of these common shared channels however is to adopt rate adaptation and to service multiple packet data users based on time multiplexing mode. In addition, a mix of services with different requirements is expected to be serviced in the context of next generation CDMA systems. In order to support the quality of various services through the common shared channels, efficient MAC protocols are needed. More specially, it is expected that a scheduling al- gorithm among MAC protocols plays an important role in the common shared channels since it controls the allocation of the shared resources among users and to a large extent determines the overall behavior of the system. Recently, many works have been done regarding scheduling algorithm for common shared channels in order to increase total throughput and guarantee P. Langendoerfer et al. (Eds.): WWIC 2004, LNCS 2957, pp. 225–235, 2004. c  Springer-Verlag Berlin Heidelberg 2004