Performance Enhancement due to the TNL Congestion Control on the Simultaneous Deployment of both HSDPA and HSUPA

the main focus of the work presented in this paper is to analyze the effect of the Transport Network Layer (TNL) congestion control on the High Speed Packet Access (HSPA) performance. The TNL and in particular the Iub link needs to be carefully dimensioned. Firstly because it has significant impact on the end-to-end and network performance and secondly due to the high number of required links in the network, the Iub is a major cost factor for the network operators. The congestion control function works together with the air interface scheduler and Hybrid Automatic Repeat Request (HARQ) in order to control the offered load to the TNL network. In this manner, the data flow over the TNL is adequately adapted to the user’s air interface data rate and to the available TNL capacity avoiding congestion in the transport network. In addition, the paper focuses as well on the effects of the simultaneous deployment of both High Speed Downlink and Uplink Packet Access (HSDPA & HSUPA). This is done by comparing the results from deploying HSDPA or HSUPA separately in the system against the simultaneous deployment of both (To the best of our knowledge, there are only few publications in which this has been investigated, especially in combination with the Congestion Control). The reason for such a comparison is to highlight the effects that appear when both are deployed together, since most of the previous studies were focusing only on either HSDPA or HSUPA, whereas the final goal is to use both together in one system. The simulation results presented in this paper confirm that the congestion in the transport network can be controlled in such a way that the available TNL capacity can be effectively utilized and hence the performance of HSPA network can be significantly improved in all aspects. In the ComNets TZI working group at the university of Bremen, a number of projects focusing on the TNL dimensioning and TNL features development for the HSPA network are being worked on [14, 15, 16, 17, 18, 19 and 20].