Advanced Packet Scheduling and QoS differentiation in Uplink Packet Access

Most of the research activity is addressed at investigating new ways of enhancing the performances of Uplink Packet Access in Wideband Code Division Multiple Access (WCDMA) systems. The overall scope is to accomplish possible solutions that can dynamically and efficiently allocate uplink resources for packet data in a WCDMA system. The main focus is given to packet scheduling issues on dedicated and common channels, and in the transition between them. Current research activity is mainly directed at dedicated channels. For uplink packet access on dedicated channels, where the traffic generated by a source is typically bursty in time, optimal scheduling solutions must be found when allocating a specific data rate to a certain UE. The main goal is to make the bit rate modifications in uplink packet transmission more dynamic so as to adapt the allocated UE data transmission rate to the typically bursty nature of traffic in data applications. This should make higher utilisation of the allocated rate, which is of particular importance for high load situations dominated by high bit rate users. A subordinate goal could be to momentarily allow users to apply very high data rates, without compromising UL spectral efficiency, and thereby reduce packet transmission delay. The final purpose is to analyse Uplink Packet Access performances when both common and dedicated channels are available for data transmission. With this aim some research activity is being carried out also on WCDMA uplink common channels, particularly on the Random Access Channel (RACH). More specifically, some work is addressed at assessing the potential impact of Hybrid (H-) ARQ techniques on RACH performances. H-ARQ schemes are of great interest for transmission systems that use time-varying channels due to their intrinsic capability to adapt to different channels conditions. Consequently, their potential is fully exploited when Fast Power Control is not applied and therefore they might represent a valuable solution to be proposed and investigated for data transmission over RACH. Transmission of multiple RACH data messages by a single user is also being considered to extend the traffic classes that can be served on RACH. The benefit lies with the smaller packet access delay and possibly lower interference generated at Node-B compared to transmission over dedicated channels. This will possibly lead to further investigations on QoS differentiation on RACH. (Claudio Rosa, Troels B. Sørensen, Preben E. Mogensen; Jeroen Wigard, Klaus I. Pedersen, Nokia)