Providing Congestion Control in the Iub Transport Network for HSDPA

The introduction of High Speed Downlink Packet Access (HSDPA) presents new challenges to be solved in the UMTS Terrestrial Radio Access Network. Bandwidth reservation for HSDPA is not efficient and TCP cannot efficiently resolve a congestion situation because lower layer retransmissions hide the congestion situations from TCP. An HSDPA Flow Control algorithm was introduced by 3GPP to control congestion. This HSDPA Flow Control algorithm was originally intended to control radio scheduler queues in Node B. In this paper we propose an algorithm that also provides congestion control in the transport network. The performance analysis concentrates on transport network limited scenarios and shows that the algorithm can achieve high end-user perceived throughput, while maintaining low delay and loss in the transport network. The analysis also shows the advantages of the newly introduced congestion detection functionality.