Packet Scheduling Strategies for IP Services WCDMA

Accurate traffic models are required to evaluate the impact of the new packet data services to the network performance (Quality of Service provision, Radio Resource Management algorithms, channel type selection, etc). A generic way of modelling packet data traffic for non-real time and real time services has been developed. This generic approach allows a single implementation for different packet services within the same traffic type (non-real time and real time) and has been applied to Web Browsing, WAP, e-mail, video telephony and SMS. In order to analyse the performance of the non-real time service, a study about the performance of the Transport Control Protocol over WCDMA networks has been made. The TCP flow control adjusts the transmission rate to the network and receiver's capacity. Due to this protocol self-adaptation to the transmission conditions of the links involved in the TCP connection, the protocol performance cannot be disconnected from the underlying network. In WCDMA networks, the RRM assigns the radio resources to the UE's in the cell, which directly impacts the TCP throughput performance. The results of the study show that the allocation of high bit rate dedicated channels (DCH) to small file downloads (such as web pages) produce poor channelisation code efficiency compared to allocating low bit rate channels. Under certain conditions, for large file downloads (such as ftp) the code efficiency and throughput performance improve significantly due to the protocol nature to fully utilize the bottleneck capacity. This protocol performance suggests a radio resource allocation strategy for DCH channels, which increases the bit rate stepwise as the file transmission evolves starting from a low bit rate. (Pablo Ameigeiras, Preben E. Mogensen; Jeroen Wigard, Nokia)