Normalized Rate Guarantee Scheduler for High Speed Downlink Packet Access Kamal Deep Singh IRISA/INRIA Campus de Beaulieu 35042 Rennes Cedex, France ksingh@irisa.fr David Ros GET/ENST Bretagne Rue de la Chˆ ataigneraie, CS 17607 35512 Cesson S´ evign´ e Cedex, France david.ros@enst-bretagne.fr Abstract—High Speed Downlink Packet Access (HSDPA) is a packet-based data service in UMTS networks that supports data rates of several Mbit/s, making it suitable for applications ranging from file transfer to multimedia streaming. One of the salient points of HSDPA is the use of MAC-layer scheduling to per- form resource management (i.e., bandwidth allocation between terminals), taking into account the radio channel conditions of all users. Usually, additional factors like fairness between users, cell throughput or quality-of-service (QoS) parameters are also considered in the scheduling mechanism. In this paper we consider different QoS classes or user groups and study resource allocation among those user groups using HSDPA MAC-layer scheduling. We propose a Normalized Rate Guarantee (NRG) scheduler, which is an extension of a previous QoS scheduler by Hosein (2002). When allocating the available bandwidth, the NRG scheduler takes into account the fact that QoS requirements (in terms of minimum bandwidth) may vary from one flow to the other. It tries to apportion loss rates in a fairer way during congestion. Another goal of NRG is to avoid the deterioration of QoS when best-effort load is increased. I. I NTRODUCTION Universal Mobile Telecommunications System (UMTS) cel- lular networks offer higher data rates with respect to older 2G and 2.5G networks and, with the Release 5 version, is evolving into an all-IP, packet network. Moreover, recent enhancements have made it possible for UMTS networks to support data rates of several Mbit/s, making them suitable for applications ranging from file transfer to multimedia streaming. A typical UMTS network consists of a core network and the UMTS Terrestrial Radio Access Network (UTRAN). The UTRAN consists of Radio Network Controllers (RNC) each controlling several base stations (BS, or Node B). A mobile user connects her User Equipment (UE) to the UTRAN, which in turn is connected to the Internet through the Serving GPRS Support Node (SGSN) and the Gateway GPRS Support Node (GGSN) present in the core network. In general, the links in the core UMTS network are over-provisioned. Such over-provisioning of the core network, together with the fluctuations in radio channel quality that are inherent of wireless links, will often make the UTRAN act as a bottleneck. Therefore, resource management will be required in UTRAN to provide good Quality of Service (QoS) to the users. High Speed Downlink Packet Access (HSDPA) [1] is an enhancement to UMTS networks and it supports data rates of several Mbit/s. In spite of the fairly high data rates that HSDPA offers, the shared downlink radio channel used in HSDPA is a challenging environment for effective data scheduling by taking into account the different QoS requirements. In this paper we propose a new scheduler called Normalized Rate Guarantee (NRG). NRG improves upon the existing HSDPA QoS schedulers because, unlike those schedulers, it is not sensitive to the best-effort (BE) load and during congestion it apportions the loss rates, among different QoS users, in a fair way. The performance of NRG is evaluated using traces of real video encoded using the H.264 format. The remainder of this paper is organized as follows. Section II discusses the related work. Some key concepts of HSDPA and some details of our simulation platform are given in sections III and IV. We describe the NRG scheduler in section V and its performance is evaluated in section VI. Section VII concludes the paper. II. RELATED WORK Basic channel-adaptive Proportionally Fair (PF) scheduling that allocates resources among all users is discussed by Jalali et al. in [2]. Channel-adaptive schedulers are reported to take advantage of the multi-user diversity that is inherent of wireless systems. Borst [3] studied the user-level performance of the PF scheduler and gave analytical results by considering scheduling strategies for the QoS users. A dynamic setting with a random nature of service demands is considered in [3], in comparison to many previous works assuming static user population. Bonald et al. [4] extended the results of [3] by using some general scheduling and admission control schemes. Andrews et al. proposed a scheduler based on providing delay and rate guarantees in [5]. Barriac et al. [6] extended the PF scheduler to equalize the user throughputs for QoS users. Hosein showed in [7] that “good” schedulers can be designed based upon user utility functions. Kolding [8] proposed a new scheduler, based on a better estimation of the required scheduling activity for a given user. Pedersen et al. [9] discussed the mapping of the schedulers to the QoS parameters specified by the 3GPP project. III. HIGH SPEED DOWNLINK PACKET ACCESS (HSDPA) A new transport channel called High Speed Downlink Shared Channel (HS-DSCH) has been introduced for HSDPA 1930-529X/07/$25.00 © 2007 IEEE This full text paper was peer reviewed at the direction of IEEE Communications Society subject matter experts for publication in the IEEE GLOBECOM 2007 proceedings.