Downlink Packet Scheduling for IP Packet Services in UMTS

IP packet services will play an important role in 3rd generation wireless networks, so that different and new kind of multimedia services will be provided, such as video-telephony, video retrieval, WWW browsing, e-mail downloading, e-commerce, etc. These services have different characteristics (activity cycle, average bit rate, call duration) and requirements (Eb/No, QoS, delay). On the other hand, the amount of radio resources allocated to each user will strongly depend on his QoS requirements. The available air interface capacity will be shared among packet users by running Packet Scheduling function. The packet scheduler will decide the allocated bit rates every frame. The chosen packet scheduler strategy will also impact the cost function and the offered QoS. Different packet scheduling strategies have been analysed and compared to traditional algorithms (round robin and C/I- based), in terms of delay, throughput and packet call delay. In order to evaluate the radio resource consumption of each service, the cost function "total BS transmitted energy per correct received bit" has been employed. Modified Round Robin algorithm has been proposed as a trade-off between C/I-based throughput and Round Robin scheduling fairness. This algorithm is also extendible to different services and different user profiles, so users belonging to a higher class on the one hand, and more delay-sensitive services on the other hand experience lower delay. In order to design efficient packet scheduler and AC algorithms accurate traffic models of each service have to be taken into account. Traffic models for the following services have been developed: speech, WWW browsing, e-mail, WAP, streaming and SMS. For NRT (Non Real Time) services (WWW, WAP, SMS and e-mail) a generic model that characterises the common properties of them has been developed, while a different model has been applied to model streaming traffic. (Isaías López, Pablo Ameigeiras, Preben E. Mogensen; Jeroen Wigard, Nokia)