Improved Uplink Macro Diversity Combining in Evolved HSPA Systems

The need to improve the performance and the efficiency of the existing HSPA systems resulted in the 3 GPP study item HSPA Evolution. The proposed system architecture for Evolved HSPA is a flat one, where network nodes are interconnected with packet based transport. As a result of the flat architecture, mobility control and handover decisions are done by the Evolved HSPA Node B that incorporates the RNC functionalities as well. During handovers the uplink traffic is forwarded through the Iur interface to the serving Evolved HSPA Node B that is combining the received flows and forwards the combined flow towards the core network. The system performance and efficiency can be improved by reducing the amount of the forwarded traffic. This paper discusses the available option and proposes an alternative solution that has minimal impact on the delay sensitive real time traffic. The improvement options are evaluated with simulations. The results are showing that the alternative forwarding strategies are improving the efficiency of the system.