In the Third Generation Partnership (3GPP) Long Term Evolution (LTE) downlink multiple-input multiple-output (MIMO) transmission modes, user equipments (UEs) in the communications system feedback their best channel state information (CSI), such as rank indicator (RI) and/or precoding matrix indicator (PMI), to evolved NodeBs (eNBs), according to the criterion of maximizing the UEs' own throughput. However, determining maximum throughput at every UE individually is generally not the same as maximizing overall system throughput, since different CSI values will generate different levels and types of interference to other UEs in the system. This is particularly true when MIMO vertical tilting (different down tilt beam angles) is used because a higher down tilt beam will generally cause less interference to other devices.
USPTO Backgrounds
USPTO Backgrounds