UE specific beamforming for narrowband communications

Methods, systems, and devices for wireless communications are described in which beamforming may be configured at a user equipment (UE) for narrowband communications. The UE may be a narrowband UE that may provide an indication to a base station that the UE is capable of performing beamforming communication for a unicast channel transmission. Such an indication may be provided in response to the UE receiving a non-beamformed broadcast channel transmission from the base station via a first carrier. The base station may receive the indication and configure the UE with a beamformed narrowband communications scheme. Such a beamformed formed narrowband communications scheme may be used for narrowband downlink shared channel communications, narrowband downlink control channel communications, or combinations thereof. In some cases, beamformed communications may be configured on a different carrier than the first carrier. The base station and UE may then communicate using beamformed transmissions.

CROSS REFERENCES

The present application for patent claims priority to International Patent Application No. PCT/CN2019/086997 by Wei et. al., entitled “UE SPECIFIC BEAMFORMING FOR NARROWBAND COMMUNICATIONS,” filed May 15, 2019; and to International Patent Application No. PCT/CN2018/087267 by Wei et. al., entitled “UE SPECIFIC BEAMFORMING FOR NARROWBAND COMMUNICATIONS,” filed May 17, 2018, each of which is assigned to the assignee hereof and each of which is hereby incorporated by reference in its entirety.

BACKGROUND

The following relates generally to wireless communications, and more specifically to UE specific beamforming for narrowband communications.

Some wireless communications systems may provide for narrowband communication between wireless devices, such as narrowband Internet of Things (NB-IoT) devices, or devices implementing Machine-to-Machine (M2M) communication or Machine Type Communication (MTC). In some examples, NB-IoT devices may operate using a bandwidth of one resource block (RB) or 180 kHz, as compared to 1.4 MHz to 20 MHz or higher system bandwidths that may be used in some LTE or NR devices. In some cases, NB-IoT devices or other narrowband communications devices may have reduced complexity or reduced performance metrics and may be associated with narrowband communication, low cost operation, low power consumption, or the like.

In some cases, wireless devices (e.g., base stations, UEs, etc.) may also use beamformed or precoded signals for transmission and/or reception of wireless communications. For example, a base station may utilize beamformed or precoded transmissions to provide more directional transmissions that may mitigate path losses that may be experienced by non-beamformed or non-precoded transmissions which may have a relatively wide beam or omnidirectional transmission pattern. Such beamforming or precoding may present challenges for narrowband devices

SUMMARY

The described techniques relate to improved methods, systems, devices, and apparatuses that support user equipment (UE) specific beamforming for narrowband communications. In various aspects, techniques are described in which beamforming may be configured at a UE for narrowband communications. In some cases, the UE may be a narrowband UE that may provide an indication to a base station that the UE is capable of performing beamforming. Such an indication may be provided in response to the UE receiving a non-beamformed broadcast channel transmission from the base station via a first carrier (e.g., an anchor carrier). The base station may receive the indication and configure the UE with a beamformed narrowband communications scheme. Such a beamformed narrowband communications scheme may be used for narrowband downlink shared channel communications, narrowband downlink control channel communications, or combinations thereof. In some cases, beamformed communications may be configured on a different carrier than the first carrier. The base station and UE may then communicate using beamformed transmissions, which may provide more efficient and more reliable communications than non-beamformed transmissions.

A method of wireless communication at a UE is described. The method may include receiving, via a first carrier, a non-beamformed narrowband physical broadcast channel (NPBCH) transmission from a base station according to an NPBCH communications scheme, transmitting, responsive to the NPBCH transmission, an indication to the base station of a UE capability to support beamformed transmissions for narrowband downlink communications from the base station, receiving, from the base station, configuration information indicating a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the first carrier, and receiving the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications based on the beamformed narrowband communications scheme.

An apparatus for wireless communication at a UE is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to receive, via a first carrier, an NPBCH transmission from a base station according to an NPBCH communications scheme, transmit, responsive to the NPBCH transmission, an indication to the base station of a UE capability to support beamformed transmissions for narrowband downlink communications from the base station, receive, from the base station, configuration information indicating a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the first carrier, and receive the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications based on the beamformed narrowband communications scheme.

Another apparatus for wireless communication at a UE is described. The apparatus may include means for receiving, via a first carrier, an NPBCH transmission from a base station according to an NPBCH communications scheme, transmitting, responsive to the NPBCH transmission, an indication to the base station of a UE capability to support beamformed transmissions for narrowband downlink communications from the base station, receiving, from the base station, configuration information indicating a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the first carrier, and receiving the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications based on the beamformed narrowband communications scheme.

A non-transitory computer-readable medium storing code for wireless communication at a UE is described. The code may include instructions executable by a processor to receive, via a first carrier, an NPBCH transmission from a base station according to an NPBCH communications scheme, transmit, responsive to the NPBCH transmission, an indication to the base station of a UE capability to support beamformed transmissions for narrowband downlink communications from the base station, receive, from the base station, configuration information indicating a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the first carrier, and receive the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications based on the beamformed narrowband communications scheme.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the beamformed narrowband communications scheme may be based on a precoded narrowband reference signal (NRS), and the NPBCH communications scheme uses a non-precoded NRS. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the configuration information includes a default precoding cycling granularity for the precoded NRS that indicates a number of subframes between precoding changes for the precoded NRS. Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for measuring one or more precoded NRS transmissions based on the default precoding cycling granularity, and where cross-subframe channel estimation may be restricted.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the one or more precoded NRS transmissions may be received via a single antenna port. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the one or more precoded NRS transmissions may be received via two antenna ports, and where the receiving may include operations, features, means, or instructions for combining received signals from each of the two antenna ports and decoding the beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications based on the combined received signals. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the decoding may be based on space frequency block coding (SFBC) or per-resource element (RE) level co-phase cycling. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the precoded NRS transmission of a single antenna port or two antenna ports may be independently configured for the narrowband downlink control channel and the narrowband downlink shared channel.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving downlink control information (DCI) that indicates a change of precoding cycling granularity for a scheduled narrowband downlink shared channel, and where a precoding matrix for a subframe may be based on one or more of a subframe number, the default precoding cycling granularity, a configured number of beams, or a total number of transmission subframes scheduled for the narrowband downlink shared channel. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the change of precoding cycling granularity indicates that a non-precoded NRS may be used for the scheduled narrowband downlink shared channel.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving downlink control information (DCI) that indicates a change of precoding cycling granularity for a scheduled narrowband downlink shared channel, where the change of precoding cycling granularity may be based on a configured number of precoders for the scheduled narrowband downlink shared channel. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the change of precoding cycling granularity indicates that a non-precoded NRS may be used for the scheduled narrowband downlink shared channel.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein the configuration information includes a first number of antenna ports for the beamformed narrowband communications scheme different than a second number of antenna ports for the NPBCH communications scheme, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications are received via the first number of antenna ports.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein the narrowband communications scheme may be independently configured for the narrowband downlink control channel and the narrowband downlink shared channel.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the configuration information further indicates whether a multi-user multiple input multiple output (MU-MIMO) or a single-user multiple input multiple output (SU-MIMO) communications scheme may be used for downlink communications to the UE. Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining a reference signal pattern based on the indication of MU-MIMO or SU-MIMO.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving second configuration information indicating the narrowband downlink control channel may be on the first carrier, and where the beamformed narrowband communications scheme may be used only for the narrowband downlink shared channel communications.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the configuration information includes information for an aperiodic sounding reference signal (SRS). Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving a trigger to perform an aperiodic SRS transmission and transmitting the SRS to the base station responsive to the trigger.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving a trigger to perform an aperiodic channel state information (CSI) measurement, measuring one or more reference signal transmissions from the base station responsive to the trigger and transmitting a CSI measurement report to the base station based on the measuring. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, a set of precoded NRSs or a set of precoded aperiodic CSI reference signals may be transmitted. In some cases, the measuring includes determining which of the set of precoded reference signals may be preferred. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the trigger may be received in a downlink grant and an indication of which of the set of precoded reference signals may be preferred may be transmitted in an acknowledgment/negative-acknowledgment (ACK/NACK) resource configured by the base station. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the set of precoded reference signals may be transmitted using the null resource elements of the narrowband downlink shared channel.

A method of wireless communication at a base station is described. The method may include transmitting, via a first carrier, an NPBCH communication according to an NPBCH communications scheme, receiving, responsive to the NPBCH communication, an indication from a UE that indicates a UE capability to support beamformed communications for narrowband downlink communications from the base station, and determining, based on the indication of the UE capability, a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications to the UE. The method may further include transmitting, to the UE, configuration information indicating the beamformed narrowband communications scheme, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the NPBCH, and communicating with the UE based on the beamformed narrowband communications scheme.

An apparatus for wireless communication at a base station is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to transmit, via a first carrier, an NPBCH communication according to an NPBCH communications scheme, receive, responsive to the NPBCH communication, an indication from a UE that indicates a UE capability to support beamformed communications for narrowband downlink communications from the base station, and determine, based on the indication of the UE capability, a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications to the UE. The instructions may be further executable by the processor to cause the apparatus to transmit, to the UE, configuration information indicating the beamformed narrowband communications scheme, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the NPBCH, and communicate with the UE based on the beamformed narrowband communications scheme.

Another apparatus for wireless communication at a base station is described. The apparatus may include means for transmitting, via a first carrier, an NPBCH communication according to an NPBCH communications scheme, receiving, responsive to the NPBCH communication, an indication from a UE that indicates a UE capability to support beamformed communications for narrowband downlink communications from the base station, and determining, based on the indication of the UE capability, a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications to the UE. The apparatus may further include means for transmitting, to the UE, configuration information indicating the beamformed narrowband communications scheme, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the NPBCH, and communicating with the UE based on the beamformed narrowband communications scheme.

A non-transitory computer-readable medium storing code for wireless communication at a base station is described. The code may include instructions executable by a processor to transmit, via a first carrier, an NPBCH communication according to an NPBCH communications scheme, receive, responsive to the NPBCH communication, an indication from a UE that indicates a UE capability to support beamformed communications for narrowband downlink communications from the base station, and determine, based on the indication of the UE capability, a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications to the UE. The code may further include instructions executable by a processor to transmit, to the UE, configuration information indicating the beamformed narrowband communications scheme, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the NPBCH, and communicate with the UE based on the beamformed narrowband communications scheme.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the beamformed narrowband communications scheme may be based on a precoded NRS, and the NPBCH communications scheme uses a non-precoded NRS. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the configuration information includes a default precoding cycling granularity for the precoded NRS that indicates a number of subframes between precoding changes for the precoded NRS. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the precoded NRS may be transmitted via a single antenna port.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting one or more precoded NRSs based on at least in part on the default precoding cycling granularity, and where cross-subframe channel estimation may be restricted. Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving a measurement report from the UE based on the one or more precoded NRS transmissions and determining beamforming parameters for the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications to the UE based on the measurement report. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may include data that may be coded based on SFBC or per-RE level co-phase cycling. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the precoded NRS transmission of a single antenna port or two antenna ports may be independently configured for the narrowband downlink control channel and the narrowband downlink shared channel.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting DCI that indicates a change of precoding cycling granularity for a scheduled narrowband downlink shared channel, and where a precoding matrix for a subframe may be based on one or more of a subframe number, the default precoding cycling granularity, a configured number of precoders, or a total number of transmission subframes scheduled for the narrowband downlink shared channel. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the change of precoding cycling granularity indicates that a non-precoded NRS may be used for the scheduled narrowband downlink shared channel.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the configuration information further indicates whether a MU-MIMO or a SU-MIMO communications scheme may be used for downlink transmissions to the UE. Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining a reference signal pattern based on the indication of MU-MIMO or SU-MIMO.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting a second configuration to the UE indicating that the narrowband downlink control channel may be on the first carrier, and where the beamformed narrowband communications scheme may be used only for the narrowband downlink shared channel communications.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the configuration information includes information for an aperiodic SRS. Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting a trigger to the UE to perform an aperiodic SRS transmission and receiving an SRS from the UE responsive to the trigger. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the trigger is transmitted in a downlink grant. Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting a trigger to the UE to perform an aperiodic CSI measurement and receiving a CSI measurement report from the UE responsive to the trigger.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting one of: a set of precoded NRSs or a set of precoded aperiodic CSI reference signals using the null resource elements of the narrowband downlink shared channel. Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving an indication of which of the set of precoded reference signals may be preferred at the UE. Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for configuring an uplink ACK/NACK resource for providing the indication of which of the set of precoded reference signals may be preferred and providing the uplink ACK/NACK resource to the UE with the configuration information, and where the indication of which of the set of precoded reference signals may be preferred at the UE may be received via the uplink ACK/NACK resource.

DETAILED DESCRIPTION

Various aspects of the present disclosure relate to methods, systems, devices, and apparatuses that support configuration of user equipment (UE) specific beamforming for narrowband communications. In some cases, a base station may configure beamforming at a UE for narrowband communications, such as narrowband physical downlink control channel (NPDCCH) communications, narrowband physical downlink shared channel (NPDSCH), or both. In some cases, the UE may provide an indication to a base station that the UE is capable of performing beamforming. Such an indication may be provided in response to the UE receiving a non-beamformed narrowband physical broadcast channel (NPBCH) transmission from the base station via a first carrier (e.g., an anchor carrier). The base station may receive the indication and configure the UE with a beamformed narrowband communications scheme for NPDCCH communications, NPDSCH communications, or combinations thereof. In some cases, beamformed NPDSCH communications may be configured independently of beamformed or non-beamformed NPDCCH communications. In some cases, beamformed communications may be configured on a different carrier than the first carrier. The base station and UE may then communicate using beamformed transmissions, which may provide more efficient and more reliable communications than non-beamformed transmissions.

In some cases, such UEs may be narrowband Internet of Things (NB-IoT) devices that may utilize a narrowband region of a system operating frequency bandwidth. In some cases, the UEs may use Machine-to-Machine (M2M) communication or Machine Type Communication (MTC) data communication technologies that allow automated devices to communicate with one another with little or no human intervention. For example, M2M and/or MTC may refer to communications from a device that integrate sensors or meters to measure or capture information and relay that information to a central server or application program that may make use of the information or present the information to humans interacting with the program or application. Such a device may be called an NB-IoT device, a M2M device, an MTC device, or an MTC UE, to provide a few examples, and may be referred to simply as a UE herein. In some examples, the narrowband communications may occupy one resource block (RB) of system bandwidth, which may correspond to 180 kHz of bandwidth, as compared to 1.4 MHz to 20 MHz or higher system bandwidth that may be used in non-narrowband wireless devices. When referring to narrowband transmissions, reference may be made to transmissions having a bandwidth that may be narrower than a bandwidth associated with one or more wideband channels in a wireless communications system. For example, in a 5G or NR system, wideband channel bandwidth may be between 20 MHz and 80 MHz, and a narrowband device may use a bandwidth that may be lower than a lowest wideband channel bandwidth, such as 180 kHz (corresponding to a bandwidth of one RB), for example.

As indicated above, in some cases beamforming may be used in narrowband communications, which may enhance reliability and efficiency of a wireless communications system through more directional transmissions. Beamforming may be achieved by adjusting the signals communicated via antenna elements of an antenna array such that signals propagating at particular orientations with respect to an antenna array experience constructive interference while others experience destructive interference. A transmitting device or a receiving device may apply certain amplitude and phase offsets to signals carried via two or more antenna elements in the antenna array associated with the device. The adjustments associated with each of the antenna elements may be defined by a beamforming weight set, which may also be referred to as a precoding vector or precoding parameters, associated with a particular orientation (e.g., with respect to the antenna array of the transmitting device or receiving device, or with respect to some other orientation). In some cases, different sets of beamforming parameters may be provided in a precoding matrix, and a particular set or vector of beamforming parameters may be indicated by a precoding matrix indicator (PMI). When precoding is applied at a transmitter, the resultant signal that is transmitted may be referred to as a precoded signal or a beamformed signal. When referring to beamformed communications herein, reference is made to communications in which at least some degree of directionality may be achieved through adjustments associated with two or more antenna elements, such as through the selection of a PMI to be used for the beamformed communication.

In some cases, a base station may communicate with a relatively large number of narrowband UEs, such as in an NB-IoT network. Certain of the UEs may have different capabilities than other of the UEs, which may include beamforming capabilities. For example, a first subset of UEs in such a network may be relatively low-complexity devices that may not be capable of beamforming, while a second subset of UEs may have relatively higher complexity and may be capable of beamforming. A base station may thus transmit signals in a non-beamformed communications scheme for all communications with the first subset of UEs, and may use beamforming for at least some communications with the second subset of UEs. In some cases, UEs may transmit an indication of UE capability to the base station, and the base station may configure beamforming based on the UE capability. In some cases, UEs may transmit an explicit indication of capability (e.g., in an information element (IE) within a capability indication message) to the base station. In other cases, the UE capability may be inferred from a UE category or UE class that may be transmitted to the base station. In some cases, multiple carriers may be configured in a network, and a first carrier, or anchor carrier, may be configured for non-beamformed transmissions that may be used by all of the narrowband UEs, and a second carrier may be configured for beamformed transmissions that may be used by the second subset of UEs.

In some cases, beamforming parameters for beamformed transmissions may be determined based on one or more reference signal transmissions. For example, a narrowband reference signal (NRS) may be transmitted using two or more different sets of precoding parameters which a UE may measure to identify a preferred beam (e.g., based on which set of precoding parameters provided a highest signal strength at the UE). In some cases, the base station may configure the UE with a reference signal pattern that indicates reference signal resources that may be measured at the UE. The UE may measure the received reference signals and provide a measurement report to the base station to identify a preferred beam. In some cases, precoder cycling may be used in which scheduled narrowband transmissions may use precoding values for a number of subframes, and then switch to different precoding for a second number of subframes. In such cases, a precoding matrix for a subframe may be determined based on one or more of a subframe number, a default precoding cycling granularity, a configured number of precoders or beams, a total number of transmission subframes scheduled for the narrowband downlink transmissions, or any combination thereof. In some cases, downlink control information (DCI) may indicate a change in precoding cycling granularity for a scheduled narrowband downlink shared channel.

In some cases, the UE may provide an indication of a preferred precoding matrix. Such an indication of the preferred precoding matrix may be provided, in some cases, via an acknowledgment/negative-acknowledgment (ACK/NACK) resource that may be configured by the base station for indicating the preferred precoding matrix. In such a case, the UE may select one of the configured ACK/NACK resources based on an index of a preferred precoding matrix. For example, the resource of the ACK/NACK transmission may be selected from a number of available subcarrier offsets (e.g., offset values are {0, −1, −2, −3, −4, −5, −6, −7} in the case of 8 precoding matrix beams). Such a technique may provide the indication of the preferred precoding matrix while not increasing the uplink feedback overhead for providing the indication.

Aspects of the disclosure are initially described in the context of a wireless communications system. Various examples of beamforming configurations are then discussed. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to UE specific beamforming for narrowband communications.

FIG.1illustrates an example of a wireless communications system100that supports UE specific beamforming for narrowband communications in accordance with aspects of the present disclosure. The wireless communications system100includes base stations105, UEs115, and a core network130. In some examples, the wireless communications system100may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, or a New Radio (NR) network. In some cases, wireless communications system100may support NB-IoT devices. One or more UEs115may be such narrowband devices that may utilize relatively narrow transmission bandwidths for communications, and may be low-cost and low-complexity devices.

In some examples, base station105or UE115may be equipped with multiple antennas, which may be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communications, or beamforming. For example, wireless communications system100may use a transmission scheme between a transmitting device (e.g., a base station105) and a receiving device (e.g., a UE115), where the transmitting device may be equipped with multiple antennas and the receiving devices are equipped with one or more antennas.

MIMO communications may employ multipath signal propagation to increase the spectral efficiency by transmitting or receiving multiple signals via different spatial layers, which may be referred to as spatial multiplexing. The multiple signals may, for example, be transmitted by the transmitting device via different antennas or different combinations of antennas. Likewise, the multiple signals may be received by the receiving device via different antennas or different combinations of antennas. Each of the multiple signals may be referred to as a separate spatial stream, and may carry bits associated with the same data stream (e.g., the same codeword) or different data streams. Different spatial layers may be associated with different antenna ports used for channel measurement and reporting. MIMO techniques include single-user MIMO (SU-MIMO) where multiple spatial layers are transmitted to the same receiving device, and multiple-user MIMO (MU-MIMO) where multiple spatial layers are transmitted to multiple devices.

In one example, a base station105may use multiple antennas or antenna arrays to conduct beamforming operations for directional communications with a UE115. For instance, some signals (e.g. synchronization signals, reference signals, beam selection signals, or other control signals) may be transmitted by a base station105multiple times in different directions, which may include a signal being transmitted according to different beamforming or precoding weight sets associated with different directions of transmission. Transmissions in different beam directions may be used to identify (e.g., by the base station105or a receiving device, such as a UE115) a beam direction for subsequent transmission and/or reception by the base station105. Some signals, such as data signals associated with a particular receiving device, may be transmitted by a base station105in a single beam direction (e.g., a direction associated with the receiving device, such as a UE115).

In some examples, the beam direction associated with transmissions along a single beam direction may be determined based at least in in part on a signal that was transmitted in different beam directions. For example, a UE115may receive one or more of the signals transmitted by the base station105in different directions, and the UE115may report to the base station105an indication of the signal it received with a highest signal quality, or an otherwise acceptable signal quality. Although these techniques are described with reference to signals transmitted in one or more directions by a base station105, a UE115may employ similar techniques for transmitting signals multiple times in different directions (e.g., for identifying a beam direction for subsequent transmission or reception by the UE115), or transmitting a signal in a single direction (e.g., for transmitting data to a receiving device).

A carrier may be associated with a particular bandwidth of the radio frequency spectrum, and in some examples the carrier bandwidth may be referred to as a “system bandwidth” of the carrier or the wireless communications system100. For example, the carrier bandwidth for non-narrowband devices may be one of a number of predetermined bandwidths for carriers of a particular radio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 MHz). In some examples, one or more UEs115may be narrowband devices and may be configured for operating over portions of the wideband carrier bandwidth. Such a device, for example, may be configured for operation using a narrowband protocol type that is associated with a predefined portion or range (e.g., set of subcarriers or RBs) within a carrier (e.g., “in-band” deployment of a narrowband protocol type).

As indicated above, one or more UEs115may be narrowband devices that may be configured for beamforming of narrowband communications. In some cases, a UE115may provide an indication to a base station105that the UE115is a narrowband device that is capable of performing beamforming. Such an indication may be provided in response to the UE115receiving a non-beamformed NPBCH transmission from a base station105on a first carrier. The base station105may receive the indication and configure the UE115with a beamformed narrowband communications scheme. Such a beamformed narrowband communications scheme may be used for NPDCSH communications, NPDCCH communications, or combinations thereof. In some cases, beamformed communications may be configured on a different carrier than the first carrier. The base station105and UE115may then communicate using beamformed transmissions, which may provide more efficient and more reliable communications than non-beamformed transmissions.

FIG.2illustrates an example of a wireless communications system200that supports UE specific beamforming for narrowband communications in accordance with aspects of the present disclosure. In some examples, wireless communications system200may implement aspects of wireless communications system100. The wireless communications system200may include base station105-aand UE115-a, which may be examples of a base station105and a UE115, as described with reference toFIG.1.

Base station105-amay provide network coverage for geographic area110-a. Base station105-aand UE115-amay communicate using beamformed or directional transmissions, and non-beamformed transmissions. For example, in downlink communications, base station105-amay transmit downlink transmissions to UE115-ausing non-beamformed downlink transmissions205(e.g., using non-precoded transmissions over an antenna array that may provide coverage to a portion of geographic area110-a. In such cases, the antenna ports of such NB-IoT devices are tied up to the same ports used for NPBCH. The number of NRS ports may be either one or two, and in the case of two ports, space frequency block coding (SFBC) based transmission diversity may be used for NPDCCH/NPDSCH transmissions. Further, NPDCCH and NPDSCH may have the same antenna ports and transmission scheme. The base station105-amay also transmit beamformed downlink transmissions to UE115-ausing beamformed downlink transmissions beams215, and UE115-amay receive the downlink transmissions using downlink reception beam210.

In the example ofFIG.2, the UE115-amay be a narrowband device that may be capable of beamforming. In cases where TDD is used for communications, uplink transmissions and downlink transmissions may be on the same carrier and channel reciprocity may be applicable and beamforming/precoding parameters may be determined by the base station105-athat may be used for both uplink and downlink transmissions. In some cases, frequency division duplexing may be used for communications, and the UE115-amay provide to feedback CSI, such as PMI, to indicate preferred precoding vectors. In some cases, base station105-aand UE115-amay also use one or more coverage enhancement techniques (e.g., based on repetitions, TTI bundling, power boosting, or combinations thereof), and beamforming may also be used in conjunction therewith to further enhance coverage.

In some cases, when base station105-ais serving devices that are not capable of beamforming, NRS transmissions may not be precoded in order to allow these devices to perform downlink measurements on the NRS. In some cases, an anchor carrier, or a first carrier, may use non-beamformed transmissions, and a second carrier may use beamformed transmissions. In such a manner, a device that is capable of beamforming, such as UE115-a, may use beamforming on the second carrier (e.g., for NPDSCH transmissions) while using non-beamformed transmissions on the first carrier. In such cases, a precoded NRS may be transmitted on the second carrier that may be used for measurements related to beamforming/precoding. In some cases, the precoded NRS may also be provided in transmissions of the first carrier that are invalid subframes (e.g., the base station105-amay advertise certain NB-IoT downlink subframes as invalid subframes where NRS does not exist). A device that is not capable of beamforming may ignore such subframes, while a device that is capable of beamforming may receive NPDSCH/NPDCCH transmissions and a precoded NRS in such subframes. Transmission and measurements of precoded NRS transmissions will be discussed in more detail below.

In some cases, the base station105-amay configure NPDCCH and NPDSCH independently. For example, a non-beamformed NRS-based scheme may be used for NPDCCH, and precoded NRS based beamforming may be used for NPDSCH. Further, in some cases, beamforming may be configured for both NPDCCH and NPDSCH, but the transmission scheme may be different (e.g., single port precoded NRS for NPDCCH and two ports diversity transmission for NPDSCH). In some cases, for NPDSCH, configuration information provided by the base station105-amay configure beamformed communications, and DCI may enable or disable UE specific beamforming for the scheduled NPDSCH transmissions. In cases where precoded NRS is used for beamforming, such a reference signal may act as a UE-specific reference signal (UERS). In such cases, the precoded NRS has a same structure as non-precoded NRS, and the base station105-amay also configure a restriction on cross-subframe channel estimation for NRS, due to potential phase jumps occurring across subframes. In cases where beamforming is configured for NPDSCH, NPDCCH can be configured on a different carrier with the non-precoded NRS based transmission scheme for NPDCCH, and performance degradation due to the limitation on cross-subframe channel estimation for precoded NRS or UERS can be avoided for NPDCCH. In cases where NPDCCH and NPDSCH are configured on the same carrier when using the non-precoded NRS based transmission scheme for NPDCCH, beamforming can be used for the scheduled NPDSCH only when not overlapping with an NPDCCH search space. In some cases, a beamformed narrowband communications scheme (e.g., a beamforming configuration for narrowband communications) may be independently configured for NPDCCH and NPDSCH.

When transmitting a UERS, such as a precoded NRS that is transmitted to the UE115-a, a single port transmission scheme may be configured, or a two-port transmission scheme may be configured. For single port transmission schemes, the UE115-ais only required to receive one UERS/precoded NRS port for channel estimation. In cases where two port diversity transmission is used, the UE115-amay perform channel estimation for two UERS/precoded NRS ports and then combine the signals from both UERS/precoded NRS ports for decoding NPDSCH. In some cases, for two port diversity transmission, the combining and decoding may be SFBC or per-RE level co-phase cycling. In cases where SFBC is used, an SFBC precoding matrix may be provided that may be the same as that of non-beamformed 2-port NRS. In cases where per-RE level co-phase cycling is used, the UE115-amay assume the precoding operation for precoded NRS and data defined by:

W2(i)={[1ej⁢π2⁢i]},i=0,1,2,3
and i is RE index.
Therefore the UE115-amay combine the signals from both precoded NRS ports by multiplying per-RE level transforming matrix W2(i) for decoding NPDSCH. In some cases, the transmission scheme, including using single port or two ports, for UE-specific beamforming may be semi-statically configured by RRC or dynamically configured by DCI. In some cases, the configuration information includes a first number of antenna ports for the beamformed narrowband communication scheme that may be different than a second number of antenna ports for the NPBCH communications scheme. The beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be received via the first number of antenna ports.

FIGS.3A and3Billustrate examples of reference signal resources300and350that support UE specific beamforming for narrowband communications in accordance with aspects of the present disclosure. In some examples, reference signal resources300may be implemented in aspects of wireless communications system100or200. In some cases, if MU-MIMO is supported for beamforming, additional reference signal ports (e.g., UERS or precoded NRS ports) may be configured for the co-scheduling UE. The reference signal ports of different UEs may be orthogonally multiplexed using either frequency division multiplexing (FDM) or code division multiplexing (CDM).

FIG.3Aillustrates reference signal resources300for FDM, with resources305configured for precoded NRS port 0, and resources310configured for precoded NRS port 1. In cases where FDM is used for MU-MIMO, DCI may be used to signal also whether another precoded NRS port is presented in the subframe for RE mapping of NPDSCH.FIG.3Billustrates reference signal resources350for CDM, with resources355configured for precoded NRS port 0, and resources360configured for precoded NRS port 1. In some cases, to reduce the DCI overhead, FDM may be used for SU-MIMO and CDM for MU-MIMO. In some cases, a base station may include an indication in configuration information of UE specific beamforming that indicates whether SU-MIMO or MU-MIMO is configured for narrowband transmissions, which the UE may use to determine the precoded NRS pattern. As illustrated inFIGS.3A and3B, resources305,310,355, or360used for NRS may be transmitted as part of an NPDSCH transmission, with NPDSCH mapped to other resources320of the illustrated resources. That is, the NPDSCH may be rate matched around resources305,310,355, or360(e.g., the NPDSCH may have null resources corresponding to resources305,310,355, or360).

Reference signals transmitted in the reference signal resources may be measured by a UE and the measurements, and in some cases a preferred beam or PMI, may be transmitted to the base station. In some cases, in order to reduce a number of measurements associated with reference signal transmissions, aperiodic reference signal processes may be configured, as discussed in more detail with respect toFIGS.4and5.

FIG.4illustrates an example of aperiodic SRS based on CSI feedback400that supports UE specific beamforming for narrowband communications in accordance with aspects of the present disclosure. In some examples, aperiodic SRS based on CSI feedback400may be implemented in aspects of wireless communications system100or200. In some cases, UE power consumption associated with periodic reference signal measurements may be relatively high, and aperiodic measurements may be implemented.

In the example ofFIG.4, the base station may transmit an NPDCCH transmission with a downlink grant for a first NPDSCH transmission, as indicated at405. In some cases, the downlink grant (or uplink grant) may be provided in DCI, which may also trigger aperiodic SRS. Then, from SRS measurements the NB-IoT base station may determine one or multiple precoding vectors. If a precoded NRS (or UERS) is precoded by cycling over multiple precoding vectors, the UE may further provide feedback for the preferred beam to refine precoding for subsequent NPDSCH transmissions.

In this example, the UE may receive a first NPDSCH transmission via a non-precoded NRS-based transmission, as indicated at410. The UE may transmit an aperiodic SRS transmission, as indicated at415. In some cases, iterating uplink and downlink TDD transmissions may include a number of NPDSCH transmissions and SRS transmissions, as indicated at420. The base station may identify a precoding vector, which may be indicated in an NPDCCH downlink grant for a second NPDSCH transmission, as indicated at425. The precoded NRS based transmission of the second NPDSCH transmission may be transmitted by the base station, as indicated at430, which the UE may receive using precoding indicated in the second grant information. The UE may decode the received transmission in accordance with the transmission scheme used for the transmission (e.g., based on SFBC or per-RE level phase co-cycling). The UE may determine HARQ ACK/NACK feedback, which may be provided to the base station as indicated at435. In some cases, a number of different precoding vectors may be used for precoded NRS transmissions, which may be measured at the UE to identify a preferred beam, which may be provided as feedback to the base station to further refine NRS precoding for subsequent NPDSCH transmissions, as also indicated at435.

In some cases, the base station may configure a set of the resources for ACK/NACK transmissions, and the UE may select one resource based on a preferred beam index. In such cases, the base station may configure certain ACK/NACK resources to correspond to a particular beam index associated with a particular precoded NRS. The UE may then select the ACK/NACK resource that corresponds to the preferred beam at the UE. In some cases, the resource of ACK/NACK transmission may be a subcarrier offset (e.g., offset values are {0, −1, −2, −3, −4, −5, −6, −7} in the case of 8 precoded NRS beams). Such techniques may allow the UE to provide feedback of a preferred beam index without an increase in the uplink feedback overhead.

FIG.5illustrates an example of aperiodic CSI reference signal (CSI-RS) based feedback500that supports UE specific beamforming for narrowband communications in accordance with aspects of the present disclosure. In some examples, aperiodic CSI-RS feedback500may implement aspects of wireless communications system100or200. Similarly as discussed above, in some cases UE power consumption associated with periodic reference signal measurements may be relatively high, and aperiodic CSI-RS measurements may be implemented.

In the example ofFIG.5, the base station may transmit an NPDCCH transmission with a downlink grant for a first NPDSCH transmission, as indicated at505. In some cases, the downlink grant (or uplink grant) may be provided in DCI, which may also trigger aperiodic CSI-RS transmission. The UE may receive a first NPDSCH transmission via a non-precoded NRS-based transmission, as indicated at510. The UE may measure a number of aperiodic CSI-RS transmissions, as indicated at515. The RE locations/subframes for the precoded CSI-RS and the total number of CSI-RS beams, in some cases, are configured by the base station. The precoded CSI-RS may be transmitted with the scheduled NPDSCH using the null NPDSCH tones or resource elements. In some cases, null tones or resource elements may refer to tones or resource elements that may not be used for transmissions. For example, null PDSCH tones may refer to tones not used for PDSCH transmission; e.g., tones that may be used for puncturing or rate matching PDSCH for CSI-RS transmission. In some cases, the precoded CSI-RS may be repeated over a block of consecutive N subframes for improving measurement accuracy. Each precoded CSI-RS may be 1-port. In some cases, a scheduled NPDSCH communication may include a number of subframes with multiple NPDSCH transmissions and CSI-RS transmissions, as indicated at520. The UE may determine HARQ ACK/NACK feedback, and in some cases, may identify a preferred beam/precoding vector, which may be transmitted to the base station, as indicated at525. Similarly as discussed above, in some cases the base station may configure a set of the resources for ACK/NACK transmissions, and the UE may select one resource based on a preferred beam index.

An NPDCCH with a second downlink grant may be provided by the base station at530. The second downlink grant may indicate a precoding vector that is used for the corresponding downlink NPDSCH transmission. The UE may receive the second NPDSCH transmission based on a precoded NRS based transmission, as indicated at535. The UE may decode the received transmission in accordance with the transmission scheme used for the transmission (e.g., based on SFBC or per-RE level phase co-cycling). The UE may again determine HARQ ACK/NACK feedback, which may be provided to the base station.

FIG.6illustrates an example of a precoder cycling600that supports UE specific beamforming for narrowband communications in accordance with aspects of the present disclosure. In some examples, precoder cycling600may be implemented in aspects of wireless communications system100or200. As discussed above, precoded NRS transmissions may be provided by a base station, in which different precoding may be used for different transmission subframes. Such beam cycling over subframes may be applied for precoded NRS based transmissions to achieve both channel estimation accuracy and precoder diversity gain. In some cases, for non-precoded NRS based transmissions, a UE may assume NRS is not changed over subframes, such that there is not a phase jump. However, for precoded NRS based transmissions, there is potential for phase jumps due to precoding changes. In such cases, a UE needs to know the location of the phase jump to reset channel estimation.

In the example ofFIG.6, an NPDCCH transmission605may provide information for precoder cycling and for an NPDSCH transmission duration615. In some cases, a default precoding cycling granularity610may be configured to be X subframes. In such cases, X is the number of consecutive subframes (e.g., based on absolute SFN) that a same precoding is used for precoded NRS transmissions, and a same precoding matrix is assumed per antenna port for X consecutive subframes. The precoding matrix may vary from one set of X subframes to another set of X subframes. In some cases, without further indication by DCI, UE may use X subframes for UERS/precoded NRS channel estimation with no assumption whether the precoding is changed from one set of X subframes to another set of X subframes. The DCI may also indicate the change of precoding cycling granularity for the scheduled NPDSCH by signaling the number of precoders or beams for precoder cycling. The UE may then determine the precoding cycling based on absolute SFN, subframe number, X, the configured number of precoders or beams, the total number of transmission subframes for the scheduled NPDSCH, or a combination of these parameters. For example, the granularity may change to an integer multiple of X subframes. In this example, an initial beam620(beam #0) may use a first precoding from a start of NPDSCH transmissions and for a subsequent set of X subframes. A second beam625(beam #1) may be used for two sets of X subframes, followed by a third beam630(beam #2) and a fourth beam635(beam #3) that are each used for one set of X subframes. In some cases, the DCI may provide an indication of the change of precoding cycling granularity that indicates that the UE is to use non-precoded NRS for a scheduled narrowband downlink shared channel, and thus such DCI may indicate a fallback to the non-beamformed transmissions. In some cases, the UE will assume the fallback to the non-beamformed transmission for the scheduled NPDSCH when transmission is overlapping with an NPDCCH search space which may be a periodical block of subframes configured by a higher layer. In such cases, the non-beamformed transmission is used for NPDCCH.

FIG.7illustrates an example of a process flow700that supports UE specific beamforming for narrowband communications in accordance with aspects of the present disclosure. In some examples, process flow700may implement aspects of wireless communications system100or200. In some examples, process flow700may be implemented by a UE, such as a UE115ofFIG.1or2.

At705, the UE may receive a broadcast transmission with system information. For example, the UE may receive an NPBCH transmission that provides synchronization and timing information that may be used for establishing a connection with a base station. The broadcast transmission may be received via a first carrier according to a non-precoded transmission scheme.

At710, the UE may transmit a capability indication to the base station. In some cases, the capability indication may be provided to the base station as part of a connection establishment procedure when the UE is establishing a connection with the base station. In some cases, such a connection establishment may be an initial connection establishment with the base station. In other cases, such a connection establishment may be a reestablishment of a prior connection or a reconfiguration of an existing connection between the UE and the base station. In some cases, the indication of the UE capability may be an explicit indication of capability (e.g., in an IE within a capability indication message) to the base station. In other cases, the UE capability may be inferred from a UE category or UE class that may be transmitted to the base station.

At715, the UE may determine whether a received configuration from the base station initiates beamforming. In some cases, the base station may provide configuration information via RRC signaling to the UE, which may configure beamformed transmissions. If the UE determines that such configuration information does not include beamforming configuration information, the UE may use a non-beamformed communications scheme, as indicated at720.

If the UE determines at715that the configuration information does indicate a beamformed communications scheme the UE may, at725, transmit or receive precoded reference signals using different precoding. In some cases, TDD communications may be implemented, and the UE may transmit SRS transmissions to the base station for determining different precoding. In cases that use FDD communication, the UE may receive precoded CSI-RS transmission and preform CSI measurements on the transmissions. The UE may provide CSI measurement reports to the base station, and in some cases may also indicate a preferred beam or precoding to the base station. In some cases, the preferred beam may be indicated based on an ACK/NACK resource used for a HARQ ACK/NACK transmission that is transmitted to the base station. In some cases, as discussed above, precoding cycling may be used, and the UE may determine a change of precoding matrix for a subframe is based at least in part on a subframe number, the default precoding cycling granularity, a configured number of precoders or beams, or a total number of transmission subframes for the scheduled narrowband downlink shared channel. The UE may use the determined precoding granularity to receive a precoded NRS.

At730, the UE may determine precoding for NPDSCH transmissions, NPDCCH transmissions, or both. In some cases, the precoded NRS may be transmitted via a single port. In some cases, the precoded NRS may be transmitted via two antenna ports. In the case of two antenna ports, UE may combine the signals from both antenna ports for decoding NPDCCH/NPDSCH.

At735, the UE may use a beamformed communications scheme for NPDSCH transmission, NPDCCH transmissions, or combinations thereof. As indicated above, in some cases, the precoding used for subsequent downlink transmissions may be indicated in the DCI with a downlink grant. In some cases, the beamformed downlink transmissions may be received on a second carrier that is different than a first carrier that is used to transmit NPBCH.

FIG.8illustrates an example of a process flow800that supports UE specific beamforming for narrowband communications in accordance with aspects of the present disclosure. In some examples, process flow800may implement aspects of wireless communications system100or200. In some examples, process flow800may be implemented by a base station, such as a base station105ofFIG.1or2.

At805, the base station may transmit a broadcast communication with system information. For example, the base station may transmit an NPBCH that provides synchronization and timing information that may be used for establishing a connection with a base station. The NPBCH may be transmitted via a first carrier according to a non-precoded transmission scheme.

At810, the base station may receive a connection establishment request from a UE. In some cases, the request may be part of a connection establishment procedure when the base station is establishing a connection with the UE. In some cases, such a connection establishment may be an initial connection establishment with the UE. In other cases, such a connection establishment may be a reestablishment of a prior connection or a reconfiguration of an existing connection between the base station and the UE.

At815, the base station may determine whether the UE has a capability of beamforming. As indicated above, such a determination may be made based on the received UE capability indication. In some cases, the capability indication may be provided to the base station as part of the connection establishment procedure. In some cases, the indication of the UE capability may be an explicit indication of capability (e.g., in an IE within a capability indication message) to the base station. In other cases, the UE capability may be inferred from a UE category or UE class that may be transmitted to the base station. If the base station determines that the UE does not indicate a beamforming capability, the base station may configure a non-beamformed communications scheme, as indicated at820.

If the base station determines at815that the configuration information does indicate a beamformed communications capability, the base station, at825, may configure a beamformed communications scheme. In some cases, the beamformed communications scheme may be configured by RRC signaling, and the base station may, in some cases, provide precoding information for precoded transmissions, that may be used by the UE and the base station for beamformed communications. In some cases, the base station may configure the UE to provide aperiodic measurement reports from which beam or precoding parameters may be selected. In some cases, the base station may configure ACK/NACK resources such that different ACK/NACK resources are associated with different beams, and an indication ACK/NACK via a particular resource may indicate which beam is preferred at the UE.

At830, the base station may trigger aperiodic SRS transmissions or measurements for different precoded reference signals. In some cases, TDD communications may be implemented, and the UE may transmit SRS transmissions to the base station for determining precoding vectors. In cases that use FDD communication, the base station may transmit precoded CSI-RSs and the UE may preform CSI measurements on the transmissions. The UE may provide CSI measurement reports to the base station, and in some cases may also indicate a preferred beam or precoding to the base station (e.g., via selection of a configured ACK/NACK resources as discussed above). In some cases, as discussed above, precoding cycling may be used, and the base station may determine a change of precoding matrix for a subframe may be based at least in part on a subframe number, the default precoding cycling granularity, a configured number of precoders or beams, or a total number of transmission subframes for the scheduled narrowband downlink shared channel. The base station may use the determined precoding granularity to transmit a precoded NRS.

At835, the base station may determine precoding for NPDSCH transmissions, NPDCCH transmissions, or both. In some cases, the precoding for NPDSCH and NPDCCH may be the same or different (i.e., using different number of NRS ports). In some cases, the DCI may also indicate the number of NRS ports for one or more subsequent NPDSCH transmissions, which may be the same precoding as NPDCCH transmissions, or may be different than NPDCCH precoding.

At840, the base station may use a beamformed communications scheme for NPDSCH transmission, NPDCCH transmissions, or combinations thereof. As indicated above, in some cases, the beamforming downlink transmission used for NPDSCH may be indicated in the DCI with a downlink grant. In some cases, the beamformed downlink transmissions may be transmitted on a second carrier that is different than a first carrier that may be used to transmit NPBCH.

The communications manager915may receive, via a first carrier, an NPBCH transmission from a base station according to an NPBCH communications scheme, transmit, responsive to the NPBCH transmission, an indication to the base station of a UE capability to support beamformed transmissions for narrowband downlink communications from the base station, receive, from the base station, configuration information indicating a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the first carrier, and receive the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications based on the beamformed narrowband communications scheme. The communications manager915may be an example of aspects of the communications manager1210described herein.

FIG.10shows a block diagram1000of a device1005that supports UE specific beamforming for narrowband communications in accordance with aspects of the present disclosure. The device1005may be an example of aspects of a device905or a UE115as described herein. The device1005may include a receiver1010, a communications manager1015, and a transmitter1040. The device1005may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

The receiver1010may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to UE specific beamforming for narrowband communications). Information may be passed on to other components of the device1005. The receiver1010may be an example of aspects of the transceiver1220described with reference toFIG.12. The receiver1010may utilize a single antenna or a set of antennas.

The communications manager1015may be an example of aspects of the communications manager915as described herein. The communications manager1015may include a connection establishment manager1020, a capability indication component1025, a beamforming configuration manager1030, and a receive beam manager1035. The communications manager1015may be an example of aspects of the communications manager1210described herein.

The connection establishment manager1020may receive, via a first carrier, an NPBCH transmission from a base station according to an NPBCH communications scheme. In some cases, the NPBCH communications scheme may be a non-beamformed communications scheme, and a first carrier may carry NPBCH communications.

The capability indication component1025may transmit, responsive to the NPBCH transmission, an indication to the base station of a UE capability to support beamformed transmissions for narrowband downlink communications from the base station. In some cases, UEs may transmit an explicit indication of capability (e.g., in an IE within a capability indication message) to the base station. In other cases, the UE capability may be inferred from a UE category or UE class that may be transmitted to the base station.

The beamforming configuration manager1030may receive, from the base station, configuration information indicating a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the first carrier.

The receive beam manager1035may receive one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications based on the beamformed narrowband communications scheme. In some cases, the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may include beamformed communications via a second carrier that is different than the first carrier of the NPBCH transmission.

The transmitter1040may transmit signals generated by other components of the device1005. In some examples, the transmitter1040may be collocated with a receiver1010in a transceiver module. For example, the transmitter1040may be an example of aspects of the transceiver1220described with reference toFIG.12. The transmitter1040may utilize a single antenna or a set of antennas.

FIG.11shows a block diagram1100of a communications manager1105that supports UE specific beamforming for narrowband communications in accordance with aspects of the present disclosure. The communications manager1105may be an example of aspects of a communications manager915, a communications manager1015, or a communications manager1210as described herein. The communications manager1105may include a connection establishment manager1110, a capability indication component1115, a beamforming configuration manager1120, a decoder1125, a reference signal manager1130, a DCI component1135, and a CSI feedback component1140. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses).

The connection establishment manager1110may receive, via a first carrier, an NPBCH transmission1150from a base station according to an NPBCH communications scheme. In some cases, connection establishment manager1110may provide an indication1155of the NPBCH transmission (or the NPBCH transmission1150) to a capability indication component1115.

The capability indication component1115may transmit, responsive to the NPBCH transmission, an indication1160to the base station of a UE capability to support beamformed transmissions for narrowband downlink communications from the base station.

The beamforming configuration manager1120may receive, from the base station, configuration information1165indicating a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the first carrier. In some examples, the beamforming configuration manager1120may determine a reference signal pattern based on the indication of MU-MIMO or SU-MIMO. In some examples, the beamforming configuration manager1120may receive second configuration information1165indicating the narrowband downlink control channel may be on the first carrier, and where the beamformed narrowband communications scheme may be used only for the narrowband downlink shared channel communications.

In some cases, the configuration information1165includes a default precoding cycling granularity for the precoded NRS that indicates a number of subframes between precoding changes for the precoded NRS. In some cases, the precoded NRS transmission of a single antenna port or two antenna ports may be independently configured for the narrowband downlink control channel and the narrowband downlink shared channel. In some cases, the configuration information1165includes a first number of antenna ports for the beamformed narrowband communications scheme that is different than a second number of antenna ports for the NPBCH communications scheme.

In some cases, beamforming configuration manager1120may provide some or all of the configuration information1165(e.g., via beamforming parameters1166) to a decoder1125. In some cases, beamforming configuration manager1120may configure (e.g., via beamforming parameters1166) decoder1125to receive beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications based on the beamformed narrowband communications scheme.

Decoder1125may receive one or more beamformed narrowband downlink shared channel communications1170or narrowband downlink control channel communications1170based on the beamformed narrowband communications scheme. In some cases, the one or more beamformed narrowband downlink shared channel communications1170or narrowband downlink control channel communications1170are received via one or two antenna ports. In some cases, the one or more beamformed narrowband downlink shared channel communications1170or narrowband downlink control channel communications1170are received via the first number of antenna ports.

Decoder1125may receive one or more precoded NRS transmissions1185. The decoder1125may measure the one or more precoded NRS transmissions1185based on the default precoding cycling granularity (e.g., included in configuration information1165), and where cross-subframe channel estimation may be restricted. In some cases, the one or more precoded NRS transmissions are received via a single antenna port. In some cases, the one or more precoded NRS transmissions are received via two antenna ports. In some cases, the beamformed narrowband communications scheme may be based on a precoded NRS, and the NPBCH communications scheme uses a non-precoded NRS.

Decoder1125may combine received signals (e.g., beamformed narrowband downlink shared channel communications1170, narrowband downlink control channel communications1170, or precoded NRS transmissions1185) from each of the two antenna ports. In some examples, the decoder1125may decode the beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications based on the combined received signals. For example, the decoder1125may combine the one or more precoded NRS transmissions received via two antenna ports and use channel estimation of the combined one or more precoded NRS transmissions for decoding the beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications. In some cases, the decoding may be based on SFBC or per-RE level co-phase cycling. In some cases, decoder1125may output decoded beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications1199.

The reference signal manager1130may receive a trigger1175to perform an aperiodic SRS transmission. In some examples, the reference signal manager1130may transmit the SRS1180to the base station responsive to the trigger.

The DCI component1135may receive DCI1190that indicates a change of precoding cycling granularity for a scheduled narrowband downlink shared channel, and where a change of precoding matrix for a subframe may be based on one or more of a subframe number, the default precoding cycling granularity, a configured number of precoders or beams, or a total number of transmission subframes scheduled for the narrowband downlink shared channel. In some cases, the change of precoding cycling granularity indicates that a non-precoded NRS may be used for the scheduled narrowband downlink shared channel. In some cases, DCI component1135may provide control information1191(e.g., an indication of a change of precoding cycling granularity) to beamforming configuration manager1120and/or to decoder1125.

The CSI feedback component1140may receive a trigger1195to perform an aperiodic CSI measurement. In some examples, the CSI feedback component1140may measure one or more reference signal transmissions (e.g., one or more precoded NRS transmissions) from the base station responsive to the trigger. In some examples, the CSI feedback component1140may transmit a CSI measurement report1197to the base station based on the measuring. In some cases, the measuring includes determining which of the set of precoded reference signals is preferred. In some cases, the set of precoded reference signals may be transmitted using the null resource elements of the narrowband downlink shared channel.

FIG.12shows a diagram of a system1200including a device1205that supports UE specific beamforming for narrowband communications in accordance with aspects of the present disclosure. The device1205may be an example of or include the components of device905, device1005, or a UE115as described herein. The device1205may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communications manager1210, an I/O controller1215, a transceiver1220, an antenna1225, memory1230, and a processor1240. These components may be in electronic communication via one or more buses (e.g., bus1245).

The communications manager1210may receive, via a first carrier, an NPBCH transmission from a base station according to an NPBCH communications scheme, transmit, responsive to the NPBCH transmission, an indication to the base station of a UE capability to support beamformed transmissions for narrowband downlink communications from the base station, receive, from the base station, configuration information indicating a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the first carrier, and receive the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications based on the beamformed narrowband communications scheme.

The I/O controller1215may manage input and output signals for the device1205. The I/O controller1215may also manage peripherals not integrated into the device1205. In some cases, the I/O controller1215may represent a physical connection or port to an external peripheral. In some cases, the I/O controller1215may utilize an operating system such as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, or another known operating system. In other cases, the I/O controller1215may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, the I/O controller1215may be implemented as part of a processor. In some cases, a user may interact with the device1205via the I/O controller1215or via hardware components controlled by the I/O controller1215.

The memory1230may include random access memory (RAM) and read only memory ROM. The memory1230may store computer-readable, computer-executable code1235including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory1230may contain, among other things, a basic input/output system (BIOS) which may control basic hardware or software operation such as the interaction with peripheral components or devices.

FIG.13shows a block diagram1300of a device1305that supports UE specific beamforming for narrowband communications in accordance with aspects of the present disclosure. The device1305may be an example of aspects of a base station105as described herein. The device1305may include a receiver1310, a communications manager1315, and a transmitter1320. The device1305may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

The receiver1310may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to UE specific beamforming for narrowband communications, etc.). Information may be passed on to other components of the device1305. The receiver1310may be an example of aspects of the transceiver1620described with reference toFIG.16. The receiver1310may utilize a single antenna or a set of antennas.

The communications manager1315may transmit, via a first carrier, an NPBCH communication according to an NPBCH communications scheme, receive, responsive to the NPBCH communication, an indication from a UE that indicates a UE capability to support beamformed communications for narrowband downlink communications from the base station, determine, based on the indication of the UE capability, a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications to the UE, transmit, to the UE, configuration information indicating the beamformed narrowband communications scheme, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the NPBCH, and communicate with the UE based on the beamformed narrowband communications scheme. The communications manager1315may be an example of aspects of the communications manager1610described herein.

The transmitter1320may transmit signals generated by other components of the device1305. In some examples, the transmitter1320may be collocated with a receiver1310in a transceiver module. For example, the transmitter1320may be an example of aspects of the transceiver1620described with reference toFIG.16. The transmitter1320may utilize a single antenna or a set of antennas.

FIG.14shows a block diagram1400of a device1405that supports UE specific beamforming for narrowband communications in accordance with aspects of the present disclosure. The device1405may be an example of aspects of a device1305or a base station105as described herein. The device1405may include a receiver1410, a communications manager1415, and a transmitter1440. The device1405may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

The receiver1410may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to UE specific beamforming for narrowband communications). Information may be passed on to other components of the device1405. The receiver1410may be an example of aspects of the transceiver1620described with reference toFIG.16. The receiver1410may utilize a single antenna or a set of antennas.

The communications manager1415may be an example of aspects of the communications manager1315as described herein. The communications manager1415may include a connection establishment manager1420, a capability indication component1425, a beamforming configuration manager1430, and a transmission beam manager1435. The communications manager1415may be an example of aspects of the communications manager1610described herein.

The connection establishment manager1420may transmit, via a first carrier, an NPBCH communication according to an NPBCH communications scheme. In some cases, the NPBCH communications scheme may be a non-beamformed communications scheme, and a first carrier may carry NPBCH communications.

The capability indication component1425may receive, responsive to the NPBCH communication, an indication from a UE that indicates a UE capability to support beamformed communications for narrowband downlink communications from the base station. In some cases, UEs may transmit an explicit indication of capability (e.g., in an IE within a capability indication message) to the base station. In other cases, the UE capability may be inferred from a UE category or UE class that may be transmitted to the base station.

The beamforming configuration manager1430may determine, based on the indication of the UE capability, a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications to the UE and transmit, to the UE, configuration information indicating the beamformed narrowband communications scheme, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the NPBCH.

The transmission beam manager1435may communicate with the UE based on the beamformed narrowband communications scheme.

The transmitter1440may transmit signals generated by other components of the device1405. In some examples, the transmitter1440may be collocated with a receiver1410in a transceiver module. For example, the transmitter1440may be an example of aspects of the transceiver1620described with reference toFIG.16. The transmitter1440may utilize a single antenna or a set of antennas.

FIG.15shows a block diagram1500of a communications manager1505that supports UE specific beamforming for narrowband communications in accordance with aspects of the present disclosure. The communications manager1505may be an example of aspects of a communications manager1315, a communications manager1415, or a communications manager1610described herein. The communications manager1505may include a connection establishment manager1510, a capability indication component1515, a beamforming configuration manager1520, a transmission beam manager1525, a reference signal manager1530, a DCI component1535, and a CSI feedback component1540. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses).

The connection establishment manager1510may transmit, via a first carrier, an NPBCH communication1545according to an NPBCH communications scheme. In some cases, the NPBCH communications scheme may be a non-beamformed communications scheme, and a first carrier may carry NPBCH communications.

The capability indication component1515may receive, responsive to the NPBCH communication, an indication1550from a UE that indicates a UE capability to support beamformed communications for narrowband downlink communications from the base station. In some cases, capability indication component1515may provide beamforming capability information1551associated with the capability to a beamforming configuration manager1520.

The beamforming configuration manager1520may determine, based on the beamforming capability information1551, a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications to the UE. In some examples, the beamforming configuration manager1520may transmit, to the UE, configuration information1555indicating the beamformed narrowband communications scheme, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the NPBCH. In some examples, the beamforming configuration manager1520may determine beamforming parameters for the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications to the UE based on a measurement report. In some examples, beamforming configuration manager1520may provide an indication1560of the beamformed narrowband communications scheme to a transmission beam manager1525.

In some examples, the beamforming configuration manager1520may determine a reference signal pattern based on the indication of MU-MIMO or SU-MIMO. In some examples, the beamforming configuration manager1520may transmit a second configuration1555to the UE indicating the narrowband downlink control channel is on the first carrier, and where the beamformed narrowband communications scheme is used only for the narrowband downlink shared channel communications. In some examples, the beamforming configuration manager1520may configure an uplink ACK/NACK resource for providing the indication of which of the set of precoded reference signals is preferred. In some examples, the beamforming configuration manager1520may provide the uplink ACK/NACK resource to the UE with the configuration information, and where the indication of which of the set of precoded reference signals is preferred at the UE may be received via the uplink ACK/NACK resource.

In some cases, the beamformed narrowband communications scheme may be based on a precoded NRS, and the NPBCH communications scheme uses a non-precoded NRS. In some cases, the configuration information1555includes a default precoding cycling granularity for the precoded NRS that indicates a number of subframes between precoding changes for the precoded NRS. In some cases, the precoded NRS may be transmitted via a single antenna port. In some cases, the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications include data that may be coded based on SFBC or per-RE level co-phase cycling. In some cases, the precoded NRS transmission of a single antenna port or two antenna ports may be independently configured for the narrowband downlink control channel and the narrowband downlink shared channel.

The transmission beam manager1525may communicate (e.g., via signals1565) with the UE based on the beamformed narrowband communications scheme.

The reference signal manager1530may transmit one or more precoded NRSs1570based on at least in part on the default precoding cycling granularity, and where cross-subframe channel estimation may be restricted. In some examples, the reference signal manager1530may receive a measurement report1575from the UE based on the one or more precoded reference signal transmissions. In some examples, the reference signal manager1530may transmit a trigger1580to the UE to perform an aperiodic SRS transmission. In some examples, the reference signal manager1530may receive an SRS1585from the UE responsive to the trigger.

The DCI component1535may transmit DCI1590that indicates a change of precoding cycling granularity for a scheduled narrowband downlink shared channel, and where a change of precoding matrix for a subframe may be based on one or more of a subframe number, the default precoding cycling granularity, a configured number of precoders or beams, or a total number of transmission subframes scheduled for the narrowband downlink shared channel. In some cases, the change of precoding cycling granularity indicates that a non-precoded NRS may be used for the scheduled narrowband downlink shared channel.

The CSI feedback component1540may transmit a trigger1595to the UE to perform an aperiodic CSI measurement. In some examples, the CSI feedback component1540may receive a CSI measurement report1597from the UE responsive to the trigger. In some examples, the CSI feedback component1540may transmit one of: a set of precoded NRSs1599or a set of precoded aperiodic CSI reference signals1599. In some examples, the CSI feedback component1540may transmit the trigger1595in a downlink grant and receive an indication1593of which of the set of precoded reference signals is preferred at the UE.

FIG.16shows a diagram of a system1600including a device1605that supports UE specific beamforming for narrowband communications in accordance with aspects of the present disclosure. The device1605may be an example of or include the components of device1305, device1405, or a base station105as described herein. The device1605may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communications manager1610, a network communications manager1615, a transceiver1620, an antenna1625, memory1630, a processor1640, and an inter-station communications manager1645. These components may be in electronic communication via one or more buses (e.g., bus1650).

The communications manager1610may transmit, via a first carrier, an NPBCH) communication according to an NPBCH communications scheme, receive, responsive to the NPBCH communication, an indication from a UE that indicates a UE capability to support beamformed communications for narrowband downlink communications from the base station, determine, based on the indication of the UE capability, a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications to the UE, transmit, to the UE, configuration information indicating the beamformed narrowband communications scheme, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the NPBCH, and communicate with the UE based on the beamformed narrowband communications scheme.

In some cases, the wireless device may include a single antenna1625. However, in some cases the device may have more than one antenna1625, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

The memory1630may include RAM, ROM, or a combination thereof. The memory1630may store computer-readable code1635including instructions that, when executed by a processor (e.g., the processor1640) cause the device to perform various functions described herein. In some cases, the memory1630may contain, among other things, a BIOS which may control basic hardware or software operation such as the interaction with peripheral components or devices.

The processor1640may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, the processor1640may be configured to operate a memory array using a memory controller. In some cases, a memory controller may be integrated into processor1640. The processor1640may be configured to execute computer-readable instructions stored in a memory (e.g., the memory1630) to cause the device to perform various functions (e.g., functions or tasks supporting UE specific beamforming for narrowband communications).

The code1635may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code1635may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code1635may not be directly executable by the processor1640but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

At1705, the UE may receive, via a first carrier, an NPBCH transmission from a base station according to an NPBCH communications scheme. The operations of1705may be performed according to the methods described herein. In some examples, aspects of the operations of1705may be performed by a connection establishment manager as described with reference toFIGS.9through12. In some cases, the NPBCH communications scheme may be a non-beamformed communications scheme, and a first carrier may carry NPBCH communications.

At1710, the UE may transmit, responsive to the NPBCH transmission, an indication to the base station of a UE capability to support beamformed transmissions for narrowband downlink communications from the base station. The operations of1710may be performed according to the methods described herein. In some examples, aspects of the operations of1710may be performed by a capability indication component as described with reference toFIGS.9through12. In some cases, the UE may transmit an explicit indication of capability (e.g., in an IE within a capability indication message) to the base station. In other cases, the UE capability may be inferred from a UE category or UE class that may be transmitted to the base station. In some cases, the UE capability indication may be provided in RRC signaling during a connection establishment, connection reestablishment, or connection reconfiguration.

At1715, the UE may receive, from the base station, configuration information indicating a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications is configured on a different carrier than the first carrier. The operations of1715may be performed according to the methods described herein. In some examples, aspects of the operations of1715may be performed by a beamforming configuration manager as described with reference toFIGS.9through12. In some cases, the beamformed narrowband communications scheme is based on a precoded NRS, and the NPBCH communications scheme is based on a non-precoded NRS. In some cases, the configuration information includes a default precoding cycling granularity for the precoded NRS that indicates a number of subframes between precoding changes for the precoded NRS.

At1720, the UE may receive one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications based on the beamformed narrowband communications scheme. The operations of1720may be performed according to the methods described herein. In some examples, aspects of the operations of1720may be performed by a receive beam manager as described with reference toFIGS.9through12. In some cases, the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may include beamformed communications via a second carrier that is different than the first carrier of the NPBCH transmission.

At1805, the UE may receive, via a first carrier, an NPBCH transmission from a base station according to an NPBCH communications scheme. The operations of1805may be performed according to the methods described herein. In some examples, aspects of the operations of1805may be performed by a connection establishment manager as described with reference toFIGS.9through12. In some cases, the NPBCH communications scheme may be a non-beamformed communications scheme, and a first carrier may carry NPBCH communications.

At1810, the UE may transmit, responsive to the NPBCH transmission, an indication to the base station of a UE capability to support beamformed transmissions for narrowband downlink communications from the base station. The operations of1810may be performed according to the methods described herein. In some examples, aspects of the operations of1810may be performed by a capability indication component as described with reference toFIGS.9through12. In some cases, the UE may transmit an explicit indication of capability (e.g., in an IE within a capability indication message) to the base station. In other cases, the UE capability may be inferred from a UE category or UE class that may be transmitted to the base station. In some cases, the UE capability indication may be provided in RRC signaling during a connection establishment, connection reestablishment, or connection reconfiguration.

At1815, the UE may receive, from the base station, configuration information indicating a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications is configured on a different carrier than the first carrier. The operations of1815may be performed according to the methods described herein. In some examples, aspects of the operations of1815may be performed by a beamforming configuration manager as described with reference toFIGS.9through12. In some cases, the beamformed narrowband communications scheme may be based on a precoded NRS, and the NPBCH communications scheme uses a non-precoded NRS. In some cases, the configuration information includes a default precoding cycling granularity for the precoded NRS that indicates a number of subframes between precoding changes for the precoded NRS.

At1820, the UE may receive one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications based on the beamformed narrowband communications scheme. The operations of1820may be performed according to the methods described herein. In some examples, aspects of the operations of1820may be performed by a receive beam manager as described with reference toFIGS.9through12. In some cases, the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may include beamformed communications via a second carrier that is different than the first carrier of the NPBCH transmission.

At1825, the UE may combine received signals from each of the two antenna ports. The operations of1825may be performed according to the methods described herein. In some examples, aspects of the operations of1825may be performed by a decoder as described with reference toFIGS.9through12.

At1830, the UE may decode the beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications based on the combined received signals. The operations of1830may be performed according to the methods described herein. In some examples, aspects of the operations of1830may be performed by a decoder as described with reference toFIGS.9through12. In some cases, the decoding may be based on SFBC or per-RE level co-phase cycling.

At1905, the UE may receive, via a first carrier, an NPBCH transmission from a base station according to an NPBCH communications scheme. The operations of1905may be performed according to the methods described herein. In some examples, aspects of the operations of1905may be performed by a connection establishment manager as described with reference toFIGS.9through12. In some cases, the NPBCH communications scheme may be a non-beamformed communications scheme, and a first carrier may carry NPBCH communications.

At1910, the UE may transmit, responsive to the NPBCH transmission, an indication to the base station of a UE capability to support beamformed transmissions for narrowband downlink communications from the base station. The operations of1910may be performed according to the methods described herein. In some examples, aspects of the operations of1910may be performed by a capability indication component as described with reference toFIGS.9through12. In some cases, the UE may transmit an explicit indication of capability (e.g., in an IE within a capability indication message) to the base station. In other cases, the UE capability may be inferred from a UE category or UE class that may be transmitted to the base station. In some cases, the UE capability indication may be provided in RRC signaling during a connection establishment, connection reestablishment, or connection reconfiguration.

At1915, the UE may receive, from the base station, configuration information indicating a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the first carrier. The operations of1915may be performed according to the methods described herein. In some examples, aspects of the operations of1915may be performed by a beamforming configuration manager as described with reference toFIGS.9through12. In some cases, the beamformed narrowband communications scheme may be based on a precoded NRS, and the NPBCH communications scheme uses a non-precoded NRS. In some cases, the configuration information includes a default precoding cycling granularity for the precoded NRS that indicates a number of subframes between precoding changes for the precoded NRS.

At1920, the UE may receive one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications based on the beamformed narrowband communications scheme. The operations of1920may be performed according to the methods described herein. In some examples, aspects of the operations of1920may be performed by a receive beam manager as described with reference toFIGS.9through12. In some cases, the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may include beamformed communications via a second carrier that is different than the first carrier of the NPBCH transmission.

At1925, the UE may receive a trigger to perform an aperiodic SRS transmission. The operations of1925may be performed according to the methods described herein. In some examples, aspects of the operations of1925may be performed by a reference signal manager as described with reference toFIGS.9through12.

At1930, the UE may transmit the SRS to the base station responsive to the trigger. The operations of1930may be performed according to the methods described herein. In some examples, aspects of the operations of1930may be performed by a reference signal manager as described with reference toFIGS.9through12.

At2005, the UE may receive, via a first carrier, an NPBCH transmission from a base station according to an NPBCH communications scheme. The operations of2005may be performed according to the methods described herein. In some examples, aspects of the operations of2005may be performed by a connection establishment manager as described with reference toFIGS.9through12. In some cases, the NPBCH communications scheme may be a non-beamformed communications scheme, and a first carrier may carry NPBCH communications.

At2010, the UE may transmit, responsive to the NPBCH transmission, an indication to the base station of a UE capability to support beamformed transmissions for narrowband downlink communications from the base station. The operations of2010may be performed according to the methods described herein. In some examples, aspects of the operations of2010may be performed by a capability indication component as described with reference toFIGS.9through12. In some cases, the UE may transmit an explicit indication of capability (e.g., in an IE within a capability indication message) to the base station. In other cases, the UE capability may be inferred from a UE category or UE class that may be transmitted to the base station. In some cases, the UE capability indication may be provided in RRC signaling during a connection establishment, connection reestablishment, or connection reconfiguration.

At2015, the UE may receive, from the base station, configuration information indicating a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the first carrier. The operations of2015may be performed according to the methods described herein. In some examples, aspects of the operations of2015may be performed by a beamforming configuration manager as described with reference toFIGS.9through12. In some cases, the beamformed narrowband communications scheme may be based on a precoded NRS, and the NPBCH communications scheme uses a non-precoded NRS. In some cases, the configuration information includes a default precoding cycling granularity for the precoded NRS that indicates a number of subframes between precoding changes for the precoded NRS.

At2020, the UE may receive one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications based on the beamformed narrowband communications scheme. The operations of2020may be performed according to the methods described herein. In some examples, aspects of the operations of2020may be performed by a receive beam manager as described with reference toFIGS.9through12. In some cases, the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may include beamformed communications via a second carrier that is different than the first carrier of the NPBCH transmission.

At2025, the UE may receive a trigger to perform an aperiodic CSI measurement. The operations of2025may be performed according to the methods described herein. In some examples, aspects of the operations of2025may be performed by a CSI feedback component as described with reference toFIGS.9through12.

At2030, the UE may measure one or more reference signal transmissions from the base station responsive to the trigger. The operations of2030may be performed according to the methods described herein. In some examples, aspects of the operations of2030may be performed by a CSI feedback component as described with reference toFIGS.9through12.

At2035, the UE may transmit a CSI measurement report to the base station based on the measuring. The operations of2035may be performed according to the methods described herein. In some examples, aspects of the operations of2035may be performed by a CSI feedback component as described with reference toFIGS.9through12.

At2105, the base station may transmit, via a first carrier, an NPBCH communication according to an NPBCH communications scheme. The operations of2105may be performed according to the methods described herein. In some examples, aspects of the operations of2105may be performed by a connection establishment manager as described with reference toFIGS.13through16. In some cases, the NPBCH communications scheme may be a non-beamformed communications scheme, and a first carrier may carry NPBCH communications.

At2110, the base station may receive, responsive to the NPBCH communication, an indication from a UE that indicates a UE capability to support beamformed communications for narrowband downlink communications from the base station. The operations of2110may be performed according to the methods described herein. In some examples, aspects of the operations of2110may be performed by a capability indication component as described with reference toFIGS.13through16. In some cases, UEs may transmit an explicit indication of capability (e.g., in an IE within a capability indication message) to the base station. In other cases, the UE capability may be inferred from a UE category or UE class that may be transmitted to the base station.

At2115, the base station may determine, based on the indication of the UE capability, a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications to the UE. The operations of2115may be performed according to the methods described herein. In some examples, aspects of the operations of2115may be performed by a beamforming configuration manager as described with reference toFIGS.13through16. In some cases, the beamformed narrowband communications scheme may be based on a precoded NRS, and the NPBCH communications scheme uses a non-precoded NRS. In some cases, the configuration information includes a default precoding cycling granularity for the precoded NRS that indicates a number of subframes between precoding changes for the precoded NRS.

At2120, the base station may transmit, to the UE, configuration information indicating the beamformed narrowband communications scheme, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the NPBCH. The operations of2120may be performed according to the methods described herein. In some examples, aspects of the operations of2120may be performed by a beamforming configuration manager as described with reference toFIGS.13through16.

At2125, the base station may communicate with the UE based on the beamformed narrowband communications scheme. The operations of2125may be performed according to the methods described herein. In some examples, aspects of the operations of2125may be performed by a transmission beam manager as described with reference toFIGS.13through16.

At2205, the base station may transmit, via a first carrier, an NPBCH communication according to an NPBCH communications scheme. The operations of2205may be performed according to the methods described herein. In some examples, aspects of the operations of2205may be performed by a connection establishment manager as described with reference toFIGS.13through16. In some cases, the NPBCH communications scheme may be a non-beamformed communications scheme, and a first carrier may carry NPBCH communications.

At2210, the base station may receive, responsive to the NPBCH communication, an indication from a UE that indicates a UE capability to support beamformed communications for narrowband downlink communications from the base station. The operations of2210may be performed according to the methods described herein. In some examples, aspects of the operations of2210may be performed by a capability indication component as described with reference toFIGS.13through16. In some cases, UEs may transmit an explicit indication of capability (e.g., in an IE within a capability indication message) to the base station. In other cases, the UE capability may be inferred from a UE category or UE class that may be transmitted to the base station.

At2215, the base station may determine, based on the indication of the UE capability, a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications to the UE. The operations of2215may be performed according to the methods described herein. In some examples, aspects of the operations of2215may be performed by a beamforming configuration manager as described with reference toFIGS.13through16.

At2220, the base station may transmit, to the UE, configuration information indicating the beamformed narrowband communications scheme, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the NPBCH. The operations of2220may be performed according to the methods described herein. In some examples, aspects of the operations of2220may be performed by a beamforming configuration manager as described with reference toFIGS.13through16. In some cases, the beamformed narrowband communications scheme may be based on a precoded NRS), and the NPBCH communications scheme uses a non-precoded NRS, and where the configuration information includes a default precoding cycling granularity for the precoded NRS that indicates a number of subframes between precoding changes for the precoded NRS. In some cases, the configuration information includes a default precoding cycling granularity for the precoded NRS that indicates a number of subframes between precoding changes for the precoded NRS.

At2225, the base station may transmit one or more precoded NRSs based on at least in part on the default precoding cycling granularity, and where cross-subframe channel estimation may be restricted. The operations of2225may be performed according to the methods described herein. In some examples, aspects of the operations of2225may be performed by a reference signal manager as described with reference toFIGS.13through16.

At2230, the base station may receive a measurement report from the UE based on the one more precoded NRS transmissions. The operations of2230may be performed according to the methods described herein. In some examples, aspects of the operations of2230may be performed by a reference signal manager as described with reference toFIGS.13through16.

At2235, the base station may determine beamforming parameters for the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications to the UE based on the measurement report. The operations of2235may be performed according to the methods described herein. In some examples, aspects of the operations of2235may be performed by a beamforming configuration manager as described with reference toFIGS.13through16.

At2305, the base station may transmit, via a first carrier, an NPBCH communication according to an NPBCH communications scheme. The operations of2305may be performed according to the methods described herein. In some examples, aspects of the operations of2305may be performed by a connection establishment manager as described with reference toFIGS.13through16. In some cases, the NPBCH communications scheme may be a non-beamformed communications scheme, and a first carrier may carry NPBCH communications.

At2310, the base station may receive, responsive to the NPBCH communication, an indication from a UE that indicates a UE capability to support beamformed communications for narrowband downlink communications from the base station. The operations of2310may be performed according to the methods described herein. In some examples, aspects of the operations of2310may be performed by a capability indication component as described with reference toFIGS.13through16. In some cases, UEs may transmit an explicit indication of capability (e.g., in an IE within a capability indication message) to the base station. In other cases, the UE capability may be inferred from a UE category or UE class that may be transmitted to the base station.

At2315, the base station may determine, based on the indication of the UE capability, a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications to the UE. The operations of2315may be performed according to the methods described herein. In some examples, aspects of the operations of2315may be performed by a beamforming configuration manager as described with reference toFIGS.13through16.

At2320, the base station may transmit, to the UE, configuration information indicating the beamformed narrowband communications scheme, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the NPBCH. The operations of2320may be performed according to the methods described herein. In some examples, aspects of the operations of2320may be performed by a beamforming configuration manager as described with reference toFIGS.13through16.

At2325, the base station may communicate with the UE based on the beamformed narrowband communications scheme. The operations of2325may be performed according to the methods described herein. In some examples, aspects of the operations of2325may be performed by a transmission beam manager as described with reference toFIGS.13through16. In some cases, the beamformed narrowband communications scheme may be based on a precoded NRS), and the NPBCH communications scheme uses a non-precoded NRS, and where the configuration information includes a default precoding cycling granularity for the precoded NRS that indicates a number of subframes between precoding changes for the precoded NRS. In some cases, the configuration information includes a default precoding cycling granularity for the precoded NRS that indicates a number of subframes between precoding changes for the precoded NRS.

At2330, the base station may transmit DCI that indicates a change of precoding cycling granularity for a scheduled narrowband downlink shared channel, and where a precoding matrix for a subframe may be based on one or more of a subframe number, the default precoding cycling granularity, a configured number of precoders or beams, or a total number of transmission subframes scheduled for the narrowband downlink shared channel. The operations of2343may be performed according to the methods described herein. In some examples, aspects of the operations of2330may be performed by a DCI component as described with reference toFIGS.13through16.

At2405, the base station may transmit, via a first carrier, an NPBCH communication according to an NPBCH communications scheme. The operations of2405may be performed according to the methods described herein. In some examples, aspects of the operations of2405may be performed by a connection establishment manager as described with reference toFIGS.13through16. In some cases, the NPBCH communications scheme may be a non-beamformed communications scheme, and a first carrier may carry NPBCH communications.

At2410, the base station may receive, responsive to the NPBCH communication, an indication from a UE that indicates a UE capability to support beamformed communications for narrowband downlink communications from the base station. The operations of2410may be performed according to the methods described herein. In some examples, aspects of the operations of2410may be performed by a capability indication component as described with reference toFIGS.13through16. In some cases, UEs may transmit an explicit indication of capability (e.g., in an IE within a capability indication message) to the base station. In other cases, the UE capability may be inferred from a UE category or UE class that may be transmitted to the base station.

At2415, the base station may determine, based on the indication of the UE capability, a beamformed narrowband communications scheme for one or more of narrowband downlink shared channel communications or narrowband downlink control channel communications to the UE. The operations of2415may be performed according to the methods described herein. In some examples, aspects of the operations of2415may be performed by a beamforming configuration manager as described with reference toFIGS.13through16.

At2420, the base station may transmit, to the UE, configuration information indicating the beamformed narrowband communications scheme, where the one or more beamformed narrowband downlink shared channel communications or narrowband downlink control channel communications may be configured on a different carrier than the NPBCH. The operations of2420may be performed according to the methods described herein. In some examples, aspects of the operations of2420may be performed by a beamforming configuration manager as described with reference toFIGS.13through16.

At2425, the base station may transmit a trigger to the UE to perform an aperiodic SRS transmission. The operations of2425may be performed according to the methods described herein. In some examples, aspects of the operations of2425may be performed by a reference signal manager as described with reference toFIGS.13through16.

At2430, the base station may receive an SRS from the UE responsive to the trigger. The operations of2430may be performed according to the methods described herein. In some examples, aspects of the operations of2430may be performed by a reference signal manager as described with reference toFIGS.13through16.

At2435, the base station may transmit a trigger to the UE to perform an aperiodic CSI measurement. The operations of2435may be performed according to the methods described herein. In some examples, aspects of the operations of2435may be performed by a CSI feedback component as described with reference toFIGS.13through16.

At2440, the base station may transmit one of: a set of precoded NRSs or a set of precoded aperiodic CSI reference signals. The operations of2440may be performed according to the methods described herein. In some examples, aspects of the operations of2440may be performed by a CSI feedback component as described with reference toFIGS.13through16.

At2445, the base station may receive a CSI measurement report from the UE responsive to the trigger. The operations of2445may be performed according to the methods described herein. In some examples, aspects of the operations of2445may be performed by a CSI feedback component as described with reference toFIGS.13through16.

At2450, the base station may transmit the trigger in a downlink grant and receive an indication of which of the set of precoded reference signals is preferred at the UE. The operations of2450may be performed according to the methods described herein. In some examples, aspects of the operations of2450may be performed by a CSI feedback component as described with reference toFIGS.13through16. In some cases, the base station may configure an uplink ACK/NACK resource for providing the indication of which of the set of precoded reference signals is preferred. In such cases, the base station may provide the uplink ACK/NACK resource to the UE with the configuration information, and where the indication of which of the set of precoded reference signals is preferred at the UE is received via the uplink ACK/NACK resource.