Proportional Resource Partitioning over Shared Wireless Links Kamal D. Singh ∗ , David Ros † , Laurent Toutain † and C´ esar Viho ∗ ∗ IRISA / Universit´ e de Rennes 1, Campus Universitaire de Beaulieu, 35042 Rennes cedex, France Email: {Kamal.Singh, Cesar.Viho}@irisa.fr † GET / ENST Bretagne, Rue de la Chˆ ataigneraie, CS 17607, 35576 Cesson S´ evign´ e cedex, France Email: {David.Ros, Laurent.Toutain}@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 data applications ranging from file transfer to multimedia streaming. In spite of the fairly high data rates that HSDPA offers, the shared downlink radio channel used in HSDPA is a challenging environment for delay- and loss-sensitive applications. It is relatively easy to partition resources over wired links with known link capacity. Nevertheless, such partitioning is complex for wireless links with variable capacity; due to the dynamic nature of the link, it is difficult to effectively allocate the resources (i.e., time slots) between users who may be paying different prices for different services. In this paper we study the general problem of resource partitioning for shared wireless links like HSDPA. We consider different QoS classes or user groups, and the use of MAC-layer scheduling for resource partitioning between groups and between individual users. We propose a variant of an existing HSDPA scheduler called Required Activity Detection (RAD) scheduler. The proposal is studied using a detailed UMTS/HSDPA simulator. I. I NTRODUCTION Universal Mobile Telecommunications System (UMTS) cel- lular networks is a 3rd generation of wireless networks that offers higher data rates with respect to older 2G and 2.5G networks. 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) which controls several base stations (BS, or Node B). A mobile user connects her User Equipment (UE) to the UTRAN which in turn may be connected to the Internet through the core network. In the UMTS network, all the links in the core network are usually 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 the 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 resource partitioning. The problem remains to partition the resources effectively between different QoS classes or different users who may be paying different prices for different services. c j c 1 Per User Queues Scheduler QoS Class 1 QoS Class j Fig. 1. Resource partitioning among different user groups. In this paper we study the general problem of resource partitioning for shared wireless links like HSDPA. We consider different QoS classes or user groups as shown in Figure 1, and study how resource allocation among those groups may be done using HSDPA MAC-layer scheduling. We focus on the case in which one of the classes consists in best-effort users. In order to perform hierarchical link sharing (i.e., between QoS classes and then between users in each class), a variant of an existing scheduler, the so-called Required Activity Detection scheduler [2], is proposed, as well as a way of sharing link capacity while trying to avoid starvation of best-effort users. The remainder of this paper is organized as follows. Sec- tion II discusses the related work. Some key concepts of HSDPA and some details of our simulation platform are given in section III. Section IV discusses HSDPA MAC scheduling. Resource partitioning is studied in sections V and VI. Finally, section VII concludes the paper. II. RELATED WORK Some studies have been done that implicitly allocate re- sources either equally or by giving more resources to the QoS users not getting their guarantees. A basic channel-adaptive Proportionally Fair (PF) scheduler that allocates resources among all users is discussed by Jalali et al. in [3]. Channel- adaptive schedulers are reported to take advantage of the multi- user diversity that is inherent of wireless systems. Borst [4] studied the user-level performance of the PF scheduler and gave analytical results by considering scheduling strategies 1-4244-0264-6/07/$25.00 ©2007 IEEE