UL Signals for Mobility Measurements Sample Clauses

UL Signals for Mobility Measurements. Unlike in traditional LTE networks, the system proposed in [GMR+16] is based on the channel quality of uplink (UL) rather than downlink (DL) signals. This has several key benefits. First, the use of UL signals eliminates the need for the UE to send measurement reports back to the network and thereby removes a point of failure in the control signaling path. Second, if digital beamforming or beamforming with multiple analog streams is available at the mmWave node, then the directional scan time can be dramatically reduced when using UL-based measurements. Finally, since the base station is less power constrained than a mobile device, digital or hybrid beamforming will likely be more feasible at the BS side. Therefore, the work in [GMR+16] proposes a novel multi-cell measurement reporting system where each UE directionally broadcasts a sounding reference signal (SRS) in a time-varying direction that continuously sweeps the angular space. Each potential serving node scans all its angular directions and monitors the strength of the received SRS along with its variance, to better capture the dynamics of the channel. A centralized controller obtains complete directional knowledge from all the potential nodes in the network to make the optimal serving node selection and scheduling decision. In the proposed framework, illustrated in Figure 5-1, there is one major node called MCell (Master Cell, in accordance with 3GPP LTE terminology), which is typically a microwave base station. However, functionally, the MCell can be any network entity that performs centralized handover and scheduling decisions. The UE may receive data from a number of nodes, either mmWave or microwave, and we call each such node an SCell (Secondary Cell). In order to communicate and exchange control information, the SCells and the MCell are inter-connected via traditional backhaul X2 interface connections, while each user can be reached by its serving MCell through the legacy 4G-LTE band. 1 D1 D13 D3 D12 D4 Backhaul X2 D11 SCell 2 D5 D2 D13 D3 Designated SCell D10 D6 MCell D9 D8 D7 D12 D4 1 D1 D11 D5 D2 D10 D6 D3 D13 ckhaul X2 D12 D4 D11 SCell 1 D5 d6 d4 d5 D10 D6 SCell 3 d8 d1 d2 D9 D8 D7 D9 D8 D7 UE transmits SRSs Tsig Tper UE d2 time UE d8 SRS UE d3 SRS UE d2 SRS UE d1 SRS D16 The network will monitor the signal strength on each of the directions pairs for each of the possible links. This is done by each SCell building a report table (RT), based on the channel quality of each receiving direct...