Priority/Distance based Call Admission Control for High Speed Downlink Packet Access

摘要

HSDPA defines a new High Speed Shared Channel (HS-DSCH) that can achieve peak data rates of up to 14.4 Mbps. Fast link adaptation, fast scheduling and fast HARQ (Hybrid ARQ) are some new features introduced in HS-DSCH to enhance system performance. Radio Network Controller (RNC) is still responsible for admitting new users; however the scheduling function has been shifted to the base station (Node-B) for fast adaptability to the channel conditions. HSDPA cell throughput increase over previous UTRA-FDD releases has been evaluated to be in the order of 50-100% or even more, highly dependent on factors such QoS provisions and the radio environment. Mostly adopted call admission control algorithms uses cell power as limiting factor with static ‘Guard Power Offset’. We propose CAC based on distance/priority to maximize the system throughput. We also introduce the concept of ‘variable’ guard power offset based on past experience. Since users near to the node-B consumer less power, giving higher priority to such users at the time of admission leads to increase in admitted user and number of satisfied users. But cell capacity gain is at the expense of increase in number of unsatisfied users. Our results show that increase in satisfied users is higher than increase in unsatisfied users.