This chapter introduces traffic separation technique and presents several traffic separation approaches to transmit HSPA (HSDPA/HSUPA) traffic and UMTS Release 99 (R99) traffic over a shared access transport network. The traffic separation technique enables QoS differentiations of HSPA and R99 traffic, while aiming to achieve a maximum utilization of the transport resources. In this chapter, two transport networks are studied for UMTS access network: ATM (Asynchronous Transfer Mode) based transport network and IP based transport network with DSL (Digital Subscriber Line) technology. In the ATM based transport network, the authors suggest the traffic separation approaches by using separate ATM Virtual Paths (VPs) or Virtual Circuits (VCs) for transmitting R99 and HSPA traffic with different ATM QoS class. With the introduction of IP transport, the authors propose to transport the HSPA traffic over the DSL network while transmitting the R99 traffic with the legacy ATM network. The benefit of applying traffic separation and its impact on the performance of the transport network as well as the end users are studied in this article. The quantitative evaluations are provided by simulations. The results presented are obtained from own developed UMTS R99 and HSPA simulation models, which can generate HSDPA and HSUPA traffic as well as R99 traffic in the same UMTS network and transmit them with different transport technologies and traffic separation approaches. The presented results demonstrate that applying traffic separation between HSPA and R99 traffic can considerably improve the performance of both HSPA and R99 traffic, and as well bring significant gain on efficient bandwidth utilizations.
TopIntroduction
Universal Mobile Telecommunication Systems (UMTS) is a key standard of the third-generation (3G) WCDMA-based cellular network. Since the operation of UMTS Release 99 (named as R99 in this article) which is the first UMTS release, UMTS has been widely deployed all over the world and experiences an intensive growth in recent years following a rapidly increasing number of mobile subscribers and a dramatically growing data traffic. The services offered by UMTS have been extensively expanded from primarily voice telephony service to a variety of appealing data and multimedia-based data services such as web browsing, email, FTP upload/download, video conferencing, video streaming, high resolution video, and IPTV, etc. The growing data service constitutes a dominant traffic share in the mobile networks and the resultant amount of data traffic still continues rising. In order to improve the support for the data services with enhanced resource efficiency and service quality, High Speed Downlink Packet Access (HSDPA) (3GPP TR 25.855, 2001) and High Speed Uplink Packet Access (HSUPA) also named as Enhance Uplink (3GPP TS 25.309, 2006) are introduced by 3GPP Release 5 and Release 6 individually as the evolution of UMTS to enhance the transmission of data packet traffic on the downlink and uplink separately. They offer very high data rate (up to 14.4 Mbps in the downlink with HSDPA and 5.76 Mbps in the uplink with HSUPA), low latency, and increased system capacity for transmitting data services with the use of fast Hybrid Automatic Repeat Request (HARQ), fast Node B scheduling, and short Transmission Time Interval (TTI). To support these new features, HSDPA uses a new downlink transport channel called High-Speed Downlink Shared Channel (HS-DSCH) that is shared by all HSDPA UEs in the cell and HSUPA uses a new uplink transport channel called E-DCH (Enhanced Dedicated Channel) for each HSUPA UE to provide high-speed data traffic transmission. HSDPA and HSUPA are jointly referred to as High Speed Packet Access (HSPA) (Dahlman, Parkvall, Sköld, & Beming, 2007).
In the current deployment of HSPA and R99 in the UMTS Terrestrial Radio Access Network (UTRAN), HSPA can co-exist with existing UMTS R99 technology by sharing the same access transport network, as illustrated in Figure 1. It is seen that one UMTS cell supports (1) normal UMTS R99 users like traditional voice users; (2) HSDPA users who require HSDPA service for high-speed data transfer on the downlink, e.g. Internet access; (3) HSUPA users who only uses HSUPA service for uplink data transmissions, e.g. FTP upload; (4) or HSPA users who use HSUPA on the uplink and HSDPA on the downlink simultaneously. In such network deployments, HSPA technology is integrated directly into the existing UMTS R99 nodes via software or hardware upgrades, i.e. the integrated Node B and RNC support both R99 and HSPA radio technologies. In this case, the Iub interface, which is the logical interface between the RNC and the Node B, carries both HSPA traffic and R99 traffic at the same time.
Figure 1. UMTS network transmitting R99 and HSPA traffic