HSPA+ Evolution to Release 12: Performance and Optimization

5 HSDPA Multiflow

Thomas Höhne, Karri Ranta-aho, Alexander Sayenko, and Antti Toskala

5.1 Introduction

This chapter presents the Release 11 HSDPA Multiflow, which was introduced to address and improve the cell edge performance of the HSDPA system. As described in Chapter 2, the Release 5 based HSDPA connection is provided from a single cell only, even though the active set may contain more cells. With HSDPA Multiflow, there is the possibility of obtaining additional diversity and boosting the cell edge data rate by receiving several data streams from neighboring cells. In the following, we first describe the Multiflow principles, before highlighting specific architectural and implementation aspects. The chapter is then concluded with a Multiflow performance evaluation.

5.2 Multiflow Overview

Multiflow is designed to improve the throughput of cell edge users and network-wide capacity by RRM load balancing. It belongs to the category of cell-aggregation features, a number of which were studied and presented in [1] as part of the study item that led to the Multiflow work item effort [2]. Multiflow is very similar to multicarrier HSDPA, with the generalization that cells do not need to have the same timing and can be on the same frequency. Multiflow also has a similarity with the LTE-Advanced dual connectivity, which at the point of writing is being studied as a feature for Release 12 [3]. A comparison to other multipoint and aggregation techniques is provided at the end of this ...