Patent ID: 9225403
Filing Date: 2015-12-29
Classification: H04B

Abstract:
1. A method of operating a transmission system of a base station in a mobile communication network, the method comprising the steps of: determining, by the base station, a signal quality received by a Multiple Input Multiple Output (MIMO) functionality user equipments (UEs), said base station serving a first group of mobile communication network UEs, the transmission system comprising a first transmission branch for transmitting a first radio signal by a first physical antenna and a second transmission branch for transmitting a second radio signal by a second physical antenna, where an additional phase offset is added to one of the transmission branches, said phase offset being calculated by taking into account the signal quality received by a sub-group of the UEs served by the base station; where for the UEs served by the base station using the MIMO functionality, said transmission system applies MIMO precoding weights before transmission, to the first and second radio signals, the value of said MIMO precoding weights being updated for each MIMO user equipment, every certain period of time, based on information reported by said MIMO UEs; when the signal quality received by one of said MIMO UEs is below a certain first threshold, switching from MIMO functionality to a Virtual Antenna Mapping technique by assigning a fixed value to the MIMO precoding weights for said MIMO UE such that the additional phase offset has an effect on said MIMO UE without changing the MIMO configuration of said MIMO UE; and maintaining the MIMO precoding weights in said fixed value until a certain first criteria is fulfilled such that for said MIMO UE the precoding weights are not updated every said certain period of time.