Aspects of the subject disclosure may include, for example, receiving a plurality of orthogonal sounding reference signals (SRS) from a plurality of user equipment (UEs), wherein each SRS of the plurality of orthogonal SRS is provided by a respective UE of the plurality of UEs, determining a downlink (DL) channel, in frequency division duplex (FDD), using spatial correlations relating to the plurality of UEs, wherein the spatial correlations are based on the plurality of orthogonal SRS, calculating a plurality of DL precoding weights for a plurality of coherent modular antenna panels responsive to the determining the DL channel, and applying the plurality of DL precoding weights to the plurality of coherent modular antenna panels to enable multi-user (Mu)-multiple-input-multiple-output (MIMO) for the plurality of UEs. Other embodiments are disclosed.

Aspects of the subject disclosure may include, for example, causing a reference antenna element of a first set of antenna elements of a first antenna array to transmit a first signal, determining for each antenna element of a second set of antenna elements of a second antenna array, a receive-related offset, relative to the reference element, based on inter-element propagation delays between the first and second sets of elements, causing each antenna element of the second set of elements to transmit a respective second signal, based on the reference antenna element receiving the respective second signals, calculating a respective transmit-related offset for each antenna element of the second set of antenna elements relative to the reference antenna element based on the inter-element propagation delays, and performing calibration between the first antenna array and the second antenna array based on the respective receive-related and transmit-related offsets. Other embodiments are disclosed.

Aspects of the subject disclosure may include, for example, obtaining, over an uplink (UL) using an aggregation of modular antenna arrays, a modulated signal that includes feedback transmitted by a user equipment (UE), wherein the aggregation of modular antenna arrays comprises multiple groups of antenna elements, after the obtaining the modulated signal, performing a demodulation of the modulated signal, determining demodulator constellation errors from the demodulation of the modulated signal, performing an error gradient weight adaptation responsive to the determining the demodulator constellation errors to derive revised weights for various antenna elements of the multiple groups of antenna elements, and applying the revised weights to the various antenna elements of the multiple groups of antenna elements to adjust signals received over the UL. Other embodiments are disclosed.

Embodiments of the present disclosure provide a method of processing received signal using a massive MIMO base station (BS). The BS comprises a radio unit (RU), a distributed unit (DU) and an interface. The method comprises receiving a plurality of signals corresponding to the plurality of antennas, said signals comprises at least one of data signals, demodulation reference signals (DMRS) and sounding reference signals (SRS). The RU or DU performs a grouping operation on a subset of the plurality of signals corresponding to a subset of antennas to generate signal groups. The RU performs a first stage filtering on the signals associated with each group using group specific filters to obtain group specific filtered signals. The DU performs a second stage filtering on the group specific filtered signals to obtain second stage filtered signals.

Aspects of the subject disclosure may include, for example, receiving a plurality of orthogonal sounding reference signals (SRS) from a plurality of user equipment (UEs), wherein each SRS of the plurality of orthogonal SRS is provided by a respective UE of the plurality of UEs, determining a downlink (DL) channel, in frequency division duplex (FDD), using spatial correlations relating to the plurality of UEs, wherein the spatial correlations are based on the plurality of orthogonal SRS, calculating a plurality of DL precoding weights for a plurality of coherent modular antenna panels responsive to the determining the DL channel, and applying the plurality of DL precoding weights to the plurality of coherent modular antenna panels to enable multi-user (Mu)-multiple-input-multiple-output (MIMO) for the plurality of UEs. Other embodiments are disclosed.

Methods, apparatus, and systems for wireless communications are disclosed. A first base station may receive one or more message from a second base station. The messages may include downlink beamforming information elements for a downlink cell. Each downlink beamforming information element may be associated with a respective group of resource blocks of a plurality of groups of resource blocks in the downlink cell. The first base station may select a first beamforming codeword for at least one group of resource blocks of the plurality of groups of resource blocks based on the downlink beamforming information associated with the at least one group of resource blocks. The first base station may transmit, to a wireless device, signals on the at least one group of resource blocks employing the first beamforming codeword.

A method for transmitting channel state information performed by a User Equipment (UE) may include receiving, from a base station, a bitmap for configuring codebook subset restriction (CSR) and reporting, to the base station, Channel State Information (CSI), when a number of antenna ports is configured as 16 or more and a number of layers associated with a rank indicator (RI) in the CSI is 3 or 4, a unit of multiple bits in a bitmap for configuring the CSR is associated with each precoder, and a reporting of precoding matrix indicator (PMI) corresponding to the precoder associated with the multiple bits is restricted in the CSI, when the CSR is indicated in any one of the multiple bits, and each bit in the bitmap for configuring the CSR is associated with each precoder.

Transmission quality is improved in an environment in which direct waves dominate in a transmission method for transmitting a plurality of modulated signals from a plurality of antennas at the same time. All data symbols used in data transmission of a modulated signal are precoded by hopping between precoding matrices so that the precoding matrix used to precode each data symbol and the precoding matrices used to precode data symbols that are adjacent to the data symbol in the frequency domain and the time domain all differ. A modulated signal with such data symbols arranged therein is transmitted.

Aspects of the subject disclosure may include, for example, causing a reference antenna element of a first set of antenna elements of a first antenna array to transmit a first signal, determining for each antenna element of a second set of antenna elements of a second antenna array, a receive-related offset, relative to the reference element, based on inter-element propagation delays between the first and second sets of elements, causing each antenna element of the second set of elements to transmit a respective second signal, based on the reference antenna element receiving the respective second signals, calculating a respective transmit-related offset for each antenna element of the second set of antenna elements relative to the reference antenna element based on the inter-element propagation delays, and performing calibration between the first antenna array and the second antenna array based on the respective receive-related and transmit-related offsets. Other embodiments are disclosed.

Aspects of the subject disclosure may include, for example, obtaining information regarding an external source that might be affected by downlink (DL) transmissions emitted by an aggregation of modular antenna arrays, wherein each modular antenna array of the aggregation of modular antenna arrays comprises a set of antenna elements, resulting in multiple sets of antenna elements, and wherein the aggregation of modular antenna arrays is operated in multi-user (Mu)-multiple-input-multiple-output (MIMO) mode in which parallel transmissions are facilitated for a plurality of user equipment (UEs), determining adjustments for particular antenna elements of the multiple sets of antenna elements based on the obtaining the information, wherein the determining the adjustments is based on a probability that interference of the parallel transmissions with the external source will be mitigated, and causing the particular antenna elements to be operated based on the adjustments. Other embodiments are disclosed.