Induced incoherency for joint transmission

摘要

Frequency-selective phase shifts are applied to signals transmitted from multiple transmission points involved in a coordinated (joint) transmission to a given UE. An eNodeB or other network node controlling the joint transmission artificially induces frequency selectivity between signals received by the UE in joint transmission from different transmission points, so as to ensure an even balance between constructive and destructive combination over frequency. By applying frequency-selective phase shifts (e.g., pseudo-random phase shifts) to the different transmission points that perform joint transmission, the signals from the different transmission points are forced to combine at the UE in a non-coherent manner. As a result, uncertainty in how the signals combine is drastically reduced, since it can be expected that the signals will always combine incoherently. The reduced uncertainty translates to reduced back-off offset in the link adaptation, and thus in an increased throughput.

主权项

1. A method, in a user equipment, for reporting channel state information (CSI), the method comprising:
measuring a separate channel response for each of two or more reference signals or groups of reference signals; and reporting at least one aggregated channel quality indicator (CQI), based on the measured channel responses and based on an assumption that jointly transmitted signals corresponding to the measured channel responses will, on a per-channel response basis, combine in a non-coherent fashion at the user equipment (UE), wherein, the UE is configured to base the CQI reporting on a predetermined shared understanding between the UE and an evolved Node B (eNB) that a predefined pattern of frequency selective relative phase shifts are applied to transmissions from two or more transmission points for which the UE is performing CSI reporting, wherein the two or more transmission points perform joint transmission and wherein the frequency selective relative phase shifts force the signals from two or more transmission points to combine in a non-coherent fashion at the UE.