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Mar 01 2012

How to improve cell-edge data rates: World’s first HSPA+ Multiflow demo by Nokia Siemens Networks and Qualcomm

Macro sites deliver voice up to the cell edge, but data rates drop off quickly. The further a user moves away from the site center, the weaker the signal. Less signal means less bandwidth and lower data rates by far.

Users are unaware of cell-edges and expect high data rates ‘at their location’ From a network point of view, most users are near the edge of a cell most of the time. Thus, operators must improve cell-edge data rates to match users’ expectations of a good, consistent experience ‘at their location’.

Multiple cells can transmit data to a device at the same time Today, data is transmitted to a device from a single cell called the serving cell The Multiflow feature, a 3GPP release 11 work item, allows two cells to simultaneously transmit data to the same user. Thus the signal from a neighboring assisting cell helps the serving cell. Without Multiflow, it would interfere somewhat with the serving cell and so decrease the bandwidth.

Prerequisites Terminals can receive two flows from two base stations. The terminals must have a minimum of two receive antennas and interference-aware receiver chains to be able to spatially separate and successfully decode the flows.

Existing terminals work as before When a cell acts as a ‘serving cell’ for a first terminal and an ‘assisting cell’ for a second terminal, traffic for the first terminal is prioritized. This rule ensures that existing non Multiflow terminals perform as before.

Multiflow mostly benefits the cell-edge and also offloads highly loaded cells Users at the cell edge gain most from the Multiflow technology, since they are the most likely to receive transmissions from multiple cells with adequate signal quality. Furthermore unused capacity in neighbor cells is utilized to offload traffic from highly loaded cells, thus improving user experience.

Three quarters of all cells have free resources and can thus “help out” other cells When cells do not serve  a user, their radio resources are idle. These cells can assist those cells that are serving  Multiflow users. In today’s networks, only a quarter of all cells are ever fully loaded; so three quarters of the cells can help out other cells.

Network loading conditions are dynamic The more uneven and dynamic the loading conditions, the greater the benefits of HSPA+ Multiflow.

Nokia Siemens Networks and Qualcomm are showing the world’s first Multiflow demo on commercial network hardware

This demonstration is using Nokia Siemens Networks’ commercial Single RAN equipment (Flexi Multiradio Base Station and Multicontroller platform) and Qualcomm Prototype Multi-Flow Mobile Terminal. The demo is being shown at MWC 2012.

Read our whitepaper on Long Term HSPA Evolution: Efficient resource utilization

This post is by Maik Braun from our Mobile Broadband team.

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