LTE Multiflow is an extension of LTE Carrier Aggregation that can aggregate carriers across non co-located nodes. By aggregating carriers from Macro with carriers from small cells, it enables tighter integration of small cells with Macros and further improves HetNets performance.
There are two types of LTE Multiflow: packet-level aggregation and bearer-level aggregation. Packet-level aggregation can be used when low-latency high-throughput backhaul is available, which allows choosing a serving cell for each IP packet based on scheduling on each cell. A common RLC across serving nodes is required to reorder packets in a flow. A key benefit of packet-level aggregation is that it improves overall system capacity and user experience, especially for bursty traffic and cell-edge users.
On the otherhand, bearer-level aggregation is used when non co-located cells are connected by a backhaul with median latency and/or median throughput. In this casebearer-level aggregation relies on per bearer decision of where to serve each IP packet. The benefit of bearer-level aggregation is that it increases mobility robustness and reduce signaling load to core network for nomadic UEs. The UE connection is anchored on the macro with control and high QoS data served by macro, while best effort data can be offloaded to small cells.
LTE Multiflow is currently being studied in 3GPP Rel-12, with Qualcomm Research actively contributing to its standardization