Dedicated Channels Research Articles

Performance of High-Speed Downlink Packet Access in Coexistence With Dedicated Channels

The joint third-generation system performance of high-speed downlink packet access (HSDPA) and Release 99 (Rel'99) dedicated channels (DCH) is studied. Given such a scenario, the optimal sharing of the cell carrier transmit power between HSDPA and DCH, which is conditioned on a certain number of channelization codes that are reserved for HSDPA transmission, is addressed. Detailed network-performance results are shown from a comprehensive dynamic system-level simulator, which includes a simulation of many cells and users, and a detailed modeling of layer 1 to layer 3. Compared to a scenario without HSDPA, the total cell throughput can be increased by 69% by allocating five high-speed physical downlink shared channel codes and 35% of the maximum cell transmit power to HSDPA transmission. These results are obtained for a macrocellular scenario with best effort packet data services. Furthermore, it is demonstrated that part of this capacity gain comes from better utilization of the available cell transmit power since less power control headroom must be reserved for HSDPA. The presented performance results reflect the expected performance improvement from gradually introducing HSDPA in an existing Rel'99 wideband code-division multiple-access network

Mixed traffic in UMTS downlink

The traffic being transferred within 3G mobile networks will be composed by different information flows with various constraints on the required QoS (bit rate, delays, etc.). In this scenario, flexibility will be a key point for the success of 3G systems. UMTS (Universal Mobile Telecommunication System) offers both circuit switched and packet switched transfer mode, and within each transfer mode, different QoS can be achieved by properly setting physical parameters such as the spreading factor of the physical channels, the power control scheme, the rate of the FEC protecting code, etc. In this letter, we give an evaluation of the downlink performance of W-CDMA UMTS radio interface when providing access to multimedia services. In particular, we analyze through simulations a typical scenario where voice calls and Web-browsing sessions share the same frequency carrier, the former using the dedicated channels (DCH), the latter being transferred on the downlink shared channel (DSCH).

Packet service in UMTS: delay-throughput performance of the downlink shared channel

The Universal Mobile Telecommunications System, wide band code-division multiple access (W-CDMA) radio interface is characterized by great flexibility and a variety of different physical and logical channel types: for example, on the downlink the dedicated channels (DCH) offers circuit switching, the downlink shared channel (DSCH) and forward access channel use packet switching, the former with closed loop power control. Furthermore, several user rates and protections are possible, by choosing suitable parameters, such as spreading factors (SFs), code rates and automatic repeat request (ARQ) schemes. In this paper we present the results, obtained by a detailed simulation, about the effect of several parameters and system alternatives on the capacity of the downlink segment of the W-CDMA interface with packet service. In particular, we investigate the effect of the SF, the code rate, the ARQ and the power control on the DSCH capacity and delay-throughput performance.