WO2022235448A1

WO2022235448A1 - Front-loaded fast beam tracking pilots

Info

Publication number: WO2022235448A1
Application number: PCT/US2022/026254
Authority: WO
Inventors: Jibing Wang; Erik Stauffer
Original assignee: Google Llc
Priority date: 2021-05-07
Filing date: 2022-04-26
Publication date: 2022-11-10

Abstract

A base station for allocating communication resources for a user equipment (UE), determines (402) a configuration that allocates (i) a first set of radio resources in a subframe for transmitting N UE-specific downlink (DE) reference signals to the UE via respective beams having different beam directions when the UE is in a connected state with the base station, where N is greater than one, and (ii) a second set of radio resources in the subframe for communicating data with the UE, with an earliest time resource of the first set of radio resources beginning no later in the subframe than an earliest time resource of the second set of radio resources; and transmits (404) one or more signals collectively indicating the determined configuration to the UE.

Description

FRONT-LOADED FAST BEAM TRACKING PILOTS

FIELD OF THE DISCLOSURE

[0001] This disclosure relates to wireless communications and, more particularly, to fast beam tracking techniques for reliable transmission and/or reception of data via high-precision beams.

BACKGROUND

[0002] The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

[0003] To increase channel bandwidths, modem wireless communication systems can utilize high frequencies, such as gigahertz (GHz) range frequencies for fifth-generation (5G) radio access (“NR”) and terahertz (THz) range frequencies for sixth-generation (6G) systems. While these high frequencies generally offer high data throughput, high-frequency signals exchanged between a base station (e.g., a gNB) and user equipment (“UE”) of such systems are often blocked or attenuated by obstacles (e.g., buildings, environmental factors such as rain, etc.). For a UE that is moving relative to the base station (i.e., a mobile UE), this phenomenon is dynamic, and therefore poses an even greater challenge to maintaining consistent, high quality communication with a base station.

[0004] To mitigate this problem, the base station and UE can use beam tracking procedures to identify and use a beam pair link for high-frequency signal transmission and reception. Particularly, the base station transmits tracking pilot signals via different base station beams (“BS beams”) to the UE, which can receive the tracking pilot signals via one or more UE beams. In turn, the UE can perform measurements on the different BS beams to select a BS beam and a UE beam (i.e., the beam pair link). The UE reports the selected BS beam back to the base station, so that the base station can transmit a high-frequency signal via the selected BS beam, and the UE can receive the high-frequency signal via the selected UE beam.

[0005] However, using beam tracking techniques to identify and utilize the beam pair link for optimal communication takes time, which can degrade network efficiency. Delays in identifying the appropriate beams to use for downlink and/or uplink communications can result in poor quality communication between the UE and the base station with quickly changing channel conditions, particularly when the UE and/or base station exhibit high mobility.

SUMMARY

[0006] Generally speaking, a base station and/or UE can implement the fast beam tracking techniques of this disclosure to robustly and consistently send and/or receive data via high- precision beams ( e.g ., using a PDSCH and/or PUSCH). Particularly, the base station can send tracking pilot signals via different high-precision BS beams in different directions prior to communicating data with the UE. To facilitate faster tracking by the UE, the base station “front loads” the pilot signals by sending the pilot signals before, or at least no later than, an uplink or downlink data communication. The UE can determine which one of the BS beams exhibits better signal conditions (e.g., higher signal strength, lower noise or interference, etc.), and provide feedback to the base station indicating the selected BS beam. The pilot signals and the feedback may be exchanged between the base station and the UE over the same frequency (e.g., if using time domain duplex, or TDD) or different frequencies (e.g., if using frequency domain duplex, or FDD). Based on the feedback, the base station and the UE can then communicate uplink and/or downlink data using the selected BS beam.

[0007] One example embodiment of these techniques is a method in a base station for allocating communication resources for a UE. The method can be executed by processing hardware and includes determining a configuration that allocates (i) a first set of radio resources in a subframe for transmitting N UE-specific downlink (DL) reference signals to the UE via respective beams having different beam directions when the UE is in a connected state with the base station, where N is greater than one, and (ii) a second set of radio resources in the subframe for communicating data with the UE, with an earliest time resource of the first set of radio resources beginning no later in the subframe than an earliest time resource of the second set of radio resources, and transmitting to the UE signal(s) collectively indicating the determined configuration. Another embodiment of these techniques is a base station including processing hardware configured to execute the method above.

[0008] Yet another example embodiment of these techniques is a method implemented in a UE. The method can be executed by processing hardware and includes receiving from a base station signal(s) collectively indicating a configuration that allocates (i) a first set of radio resources in a subframe for transmitting N UE-specific downlink (DL) reference signals to the UE via respective beams having different beam directions when the UE is in a connected state with the base station, where N is greater than one, and (ii) a second set of radio resources in the subframe for communicating data with the EGE, with an earliest time resource of the first set of radio resources beginning no later in the subframe than an earliest time resource of the second set of radio resources, and communicating with the base station in accordance with the configuration. Still another example embodiment of these techniques is a UE including processing hardware configured to execute the method above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Fig. 1A is a block diagram of an example communication system in which fast beam tracking techniques of this disclosure can be implemented;

[0010] Fig. IB is a block diagram of a base station of Fig. 1A transmitting downlink (DL) reference signals via respective BS beams, and a UE of Fig. 1 A receiving one or more of the DL reference signals via UE beam(s);

[0011] Fig. 2 is a messaging diagram of an example scenario in which a UE of Fig. 1 A transmits channel state information (CSI) feedback to a base station of Fig. 1 A based on front-loaded DL reference signals the UE receives from the base station;

[0012] Figs. 3A and 3B illustrate example subframes, arranged according to front-loaded CSI configurations that a base station of Fig. 1A may indicate to a UE of Fig. 1 A in the example scenario of Fig. 2 (for downlink and uplink data transmissions, respectively);

[0013] Fig. 4 is a flow diagram of an example method for allocating communication resources according to a front-loaded CSI configuration, from the perspective of a base station of Fig. 1A; and

[0014] Fig. 5 is a flow diagram of an example method for allocating communication resources according to a front-loaded CSI configuration, from the perspective of a UE of Fig. 1A.

DETAILED DESCRIPTION OF THE DRAWINGS

[0015] Fig. 1A illustrates an example communication system 100 in which fast beam tracking techniques of this disclosure can be implemented. The communication system 100 includes a user equipment (UE) 102 and a base station 104. The UE 102 can be any suitable device capable of wireless communication ( e.g ., any of the exemplary user devices discussed below after the description of the figures). While Fig. 1A depicts a single UE 102, the communication system 100 may include any number ( e.g ., greater than one) of UEs. The base station 104 can coordinate downlink (DL) and uplink (UL) transmissions to and from the UE 102, using techniques described in further detail below.

[0016] The base station 104 may be communicatively connected to a core network (CN)

110 via an NG interface, for example. In some implementations, the base station 104 is a 5G New Radio (NR) base station operating as a 5G Node B (gNB), and the CN 110 is a 5G core network (5GC). In other implementations, however, the communication system 100 can include one or more base stations that operate according to radio access technologies (RATs) of types other than NR, and these base stations can be connected to CNs of other types. The CN 110 can be, for example, a 5GC, a less advanced core network (e.g., an evolved packet core (EPC)), or, conversely, a more advanced core network.

[0017] The base station 104 is associated with a radio access network (RAN) and provides coverage to a cell 124. While Fig. 1A depicts the base station 104 as associated with only one cell 124, it is understood that the base station 104 may also cover one or more additional cells not shown in Fig. 1A. Although a fixed terrestrial base station is shown, the base station 104 can be implemented as part of a satellite, drone, high altitude platform (HAP) station, or other suitable moving base station. Further, the RAN can include any suitable number of base stations that collectively support one or more RATs. The UE 102 can communicatively connect with the RAN via the base station 104 when operating within the cell 124, and in turn can communicatively connect with the CN 110 via the RAN.

[0018] The UE 102 is equipped with at least one antenna 140 to communicate signals with the base station 104 via UE beams, and processing hardware 130. In some implementations, the UE 102 is equipped with multiple antennas 140 to support multiple-input, multiple-output (MIMO) communications. MIMO communications can improve data rates (with spatial multiplexing, i.e., transmitting different data from different antennas) and/or error rates (with spatial diversity, i.e., transmitting redundant data on different antennas), for both DL and UL transmissions. The UE 102 may have transmit-receive antennas to support simultaneous transmission/reception paths, or separate transmit and receive antennas. MIMO communication between the base station 104 and the UE 102 is discussed further below.

[0019] The processing hardware 130 can include one or more general-purpose processors (e.g., CPUs) and at least one non-transitory computer-readable memory storing instructions executable on the one or more general processors and/or special-purpose processing units, such as a wireless communication chipset. The processing hardware 130 includes a physical (PHY) layer controller 132. The PHY layer controller 132 is responsible for internal procedures at a PHY layer 182 of a wireless communication protocol stack 180, such as demodulating and decoding DL control and data signals received from a base station (e.g., the base station 104), encoding and modulating UL control and data signals, and so on. Additionally, the PHY layer controller 132 includes a channel state information (CSI) feedback controller 133 and, in some implementations, a sounding reference signal (SRS) controller 135. The CSI feedback controller 133 supports functions related to transmitting CSI feedback to the base station 104 via a UE beam, as described further below. The SRS controller 135 can send a SRS to the base station 104 on the same UE beam that carries the CSI feedback. In turn, the base station 104 can detect the SRS on the UE beam and consequently acquire the CSI feedback.

[0020] The processing hardware 130 also includes an upper layers controller 134. The upper layers controller 134 is responsible for internal procedures at corresponding upper layers 184 above the PHY layer 182 of the protocol stack 180, such as aggregating UL data and disaggregating DL data for the UE 102. The upper layers 184 may include, for example, a medium access control (MAC) layer 185, a radio link control (RLC) layer 186, a packet data convergence protocol (PDCP) layer 187, and a radio resource control (RRC) layer 188. Generally, the upper layers controller 134 may support channel access, user plane data transfer, control plane data transfer, measurement reporting, system configuration, mobility management, and/or other upper-layer procedures.

[0021] In addition, the processing hardware 130 includes a beam switching controller 142. The beam switching controller 142 is responsible for switching between or among UE beams generated by antenna 140.

[0022] The base station 104 includes multiple antennas 170 capable of beamforming to communicate signals with the UE 102 via BS beams. Similar to the UE 102, the base station 104 may be equipped with multiple antennas 170 to support MIMO communications. Fig.

1A depicts an example implementation in which the base station 104 includes four transmit- receive antennas each having its own transmit/receive circuitry in the radio frequency (RF) front end, and the UE 102 includes two transmit-receive antennas each having its own transmit/receive circuitry in the RF front end. Accordingly, the depicted UE 102 can support two DL and two UL streams, corresponding to two MIMO layers (2x2 MIMO communication). The depicted base station 104, using its four transmit-receive antennas, can support four MIMO layers. It is understood that the UE 102 and the base station 104 may instead have more or fewer antennas than are depicted in Fig. 1A, thereby supporting more or fewer MIMO layers.

[0023] The base station 104 also includes processing hardware 160, which can include one or more general-purpose processors (e.g., CPUs) and at least one non-transitory computer- readable memory storing instructions executable on the one or more general processors and/or special-purpose processing units, such as a wireless communication chipset. Similar to the processing hardware 130 of the UE 102, the processing hardware 160 can include a PHY layer controller 162 and an upper layers controller 164 corresponding to the PHY layer 182 and upper layers 184, respectively, of the protocol stack 180. Controllers 162 and 164 may perform similar or corresponding functions as controllers 132 and 134, but from the perspective of the base station 104 rather than the UE 102. For example, the PHY layer controller 162 may encode and modulate DL control and data signals transmitted to the UE 102 and demodulate and decode UL control and data signals received from the UE 102, and the upper layers controller 164 may aggregate DL data for the UE 102 and disaggregate UL data received from the UE 102.

[0024] In addition, the PHY layer controller 162 includes a CSI configuration controller 163. The CSI configuration controller 163 can determine a front-loaded CSI configuration that the base station 104 will transmit to the UE 102, as described below with reference to Figs. 3 A and 3B. Generally speaking, for either DL or UL communications, the base station 104 determines a front-loaded CSI configuration that defines/indicates time and frequency resources that the base station 104 will allocate to transmit one or more tracking pilot signals for channel information acquisition, such as CSI reference signals (CSI-RSs). The UE 102 and possibly other UEs can use (e.g., perform measurements on) the tracking pilot signal(s) to estimate various parameters (e.g., a channel quality indicator (CQI), a rank indicator (RI), and a precoding matrix indicator (PMI)) relating to channel quality or conditions currently experienced by the UE 102. Stated differently, the UE 102 can determine the state of the communication link or channel between the UE 102 and the base station 104. The UE 102 then transmits this channel information to the base station 104 in the form of CSI feedback. Using the CSI feedback (possibly in conjunction with other information, in some implementations), the base station 104 can determine a best beam to use to communicate data with the UE 102. [0025] Particularly, pursuant to the front-loaded CSI configuration, the base station 104 (e.g., CSI configuration controller 163) can transmit CSI-RSs via different BS beams, each having a respective different beam direction, prior to communicating data with the UE 102.

In some implementations, pursuant to the front-loaded CSI configuration, the UE 102 is configured to scan for the CSI-RSs via the different BS beams, assess signal quality and generate respective CSI feedback for each BS beam on which the UE 102 was able to receive/detect a CSI-RS, and report the CSI feedback for each of those BS beams to the base station 104. The CSI feedback for each BS beam can include a beam identifier (e.g., a CSI- RS Resource Indicator (CRI)) to identify the corresponding BS beam. In some implementations, after assessing signal quality for each BS beam, the UE 102 may report to the base station 104 the CSI feedback (including the beam identifier) for a BS beam that the UE 102 selected (e.g., based in whole or in part on the assessed signal quality for that BS beam and possibly other BS beams). The selected BS beam may exhibit signals conditions that are better than the other unselected BS beams. For example, the selected BS beam may have a higher signal strength, higher signal-to-noise ratio (SNR), lower noise or interference, and/or other suitable signal characteristics relative to other BS beams. In these various implementations, the UE 102 provides UE-specific CSI feedback to the base station 104.

That is, if the communication system 100 includes one or more other UEs in addition to UE 102, each UE processes any one or more of the CSI-RSs received by that UE and provides its own, UE-specific feedback of a selected BS beam to the base station 104. In turn, the base station 104 can communicate data with that particular UE using the BS beam indicated by the UE-specific feedback.

[0026] In some implementations, the PHY layer controller 162 also includes an SRS processor 165. The SRS processor 165 can receive and measure the quality of an SRS transmission from the UE 102 (e.g., an SRS generated by the SRS controller 135) to quickly acquire the UE beam carrying CSI feedback indicating the selected BS beam. When DL and UL transmissions share the same frequency or frequencies using time division multiplexing (e.g., TDD), the SRS processor 165 can exploit channel reciprocity and estimate channel information for a DL MIMO channel between the base station 104 and the UE 102 based on the estimated state of the corresponding UL counterpart of the DL MIMO channel (i.e., the measured quality of the SRS transmission). [0027] Further, similar to the beam switching controller 142 of the UE 102, the processing hardware 160 can include a beam switching controller 172 responsible for switching between or among BS beams formed by antenna 170.

[0028] The upper layers controllers 134 and 164, PHY layer controllers 132 and 162, CSI feedback controller 133, CSI configuration controller 163, SRS controller 135, SRS processor 165, and beam switching controllers 142 and 172 can each be implemented using any suitable combination of hardware, software, and/or firmware. In one example implementation, the controllers or processors 132, 133, 134, 142, 162, 163, 164, 165, and 172 are respective sets of instructions that the respective processing hardware 130 or 160 executes to perform the various functions described herein.

[0029] Fig. IB illustrates the wireless communication network 100 when the base station 104 ( e.g ., CSI configuration controller 163) transmits beamformed CSI-RSs, or other suitable DL reference signals, that the UE 102 can use to estimate a MIMO channel between the base station 104 and the UE 102. The base station 104 in this scenario transmits one or more CSI- RSs via a BS beam 151 with a first beam direction, one or more CSI-RSs via a BS beam 152 with a second beam direction, one or more CSI-RSs via a BS beam 153 with a third beam direction, one or more CSI-RSs via a BS beam 154 with a fourth beam direction, and one or more CSI-RSs via a BS beam 155 with a fifth beam direction. The base station 104 in general can generate any suitable number of BS beams using antennas 170 (e.g., over a plurality of antenna ports), depending on the implementation.

[0030] The UE 102 (e.g., CSI feedback controller 133) can receive some or all of the CSI- RSs from the base station 104, depending on factors such as the position of the UE 102 relative to the base station 104, the position and type of any intervening formations or structures, the strength of multipath reflections, and so on. In some implementations, the UE 102 receives the one or more CSI-RSs via one or more UE beams formed by antenna 140.

The UE 102 in this scenario receives the one or more CSI-RSs via UE beams 156, 157, and 158 with respective first, second, and third beam directions. The UE 102 in general can generate any suitable number of UE beams using antenna 140 (e.g., over a plurality of antenna ports), depending on the implementation.

[0031] The UE 102 can perform reference signal measurements on the different BS beams. In some implementations, the UE 102 can determine and select one of the BS beams 151-155 that exhibits better signal conditions (e.g., higher signal strength, higher SNR, lower noise or interference, etc.) relative to the other of the BS beams 151-155, and provide CSI feedback to the base station 104 indicating the selected BS beam. The selected BS beam ( e.g ., BS beam 153) may be a beam that directly reaches the UE 102 from the base station 104, or a beam that reflects off of an obstacle (e.g., intervening building, hill, etc.) before reaching the UE 102, for example. In some implementations of the reference signal measurement procedure, the UE 102 can sweep a plurality of UE beams formed by the antennas 140, and for each formed UE beam 156-158, assess the signal quality for each of the BS beams 151-155. The UE 102 can then identify a beam pair link, consisting of one of the UE beams and one of the BS beams, that collectively exhibits good (e.g., optimum) signal conditions. As illustrated in the scenario of Fig. IB, the UE 102 identifies BS beam 153 and UE beam 157 as the optimal beam pair link 159 (e.g., due to unobstructed alignment of the directions of BS beam 153 and UE beam 157), and consequently selects the BS beam 153 as the BS beam that exhibits better signal conditions than those of the other BS beams 151, 152, 154, and 155. In turn, the UE 102 provides CSI feedback to the base station 104 indicating that the BS beam 153 is the selected BS beam. In other implementations and/or scenarios, rather than selecting BS beam 153, the UE 102 can determine respective CSI feedback for more than one of the BS beams 151-155, and provide the determined CSI feedback to the base station 104. Using the CSI feedback, the base station 104 can determine that the BS beam 153 is the best beam for communicating with the UE 102. In these various implementations, the base station 104 can proceed to transmit and/or receive data streams to and/or from the UE 102 via the BS beam 153 (or a beam oriented similar to the beam BS 153, such as UE beam 157).

[0032] It is understood that, in some implementations, the base station 104 may also consider other factors (e.g., interference with other UEs), beyond the CSI feedback from the UE 102, when determining which of BS beams 151-155 to use for communications with the UE 102. It should also be understood that any beam pair link identified by the UE 102 (e.g., beam pair link 159) may be valid for a short time duration because of mobility of the UE 102 (e.g., due to steering or tilting of antennas 140, translational motion from being inside a moving vehicle), mobility of the base station 104 (e.g., a satellite, drone, HAP station), and/or even interference of any obstacles (e.g., a building, vehicle, precipitation) between the UE 102 and the base station 104. For example, due to interference from a building between the UE 102 and the base station 104 while the UE 102 is identifying an optimum beam pair link, BS beam 155 may reflect off the building and consequently align with UE beam 158. Accordingly, the UE 102 may identify BS beam 155 and UE beam 158 as a candidate beam pair link, and if the link exhibits better signal conditions than beam pair link 159, the UE 102 may identify the link as the optimum beam pair link.

[0033] Fig. 2 illustrates a messaging diagram of an example scenario 200 in which the UE 102 selects a BS beam based on front-loaded DL reference signals, and provides CSI feedback indicating the selected BS beam to the base station 104.

[0034] In the beginning of example scenario 200, the UE 102 is in a connected state of a RAT protocol for controlling radio resources (e.g., NR-RRC CONNECTED) with the base station 104. That is, the UE 102 has already scanned and accessed a cell (e.g., cell 124) of the RAN that includes the base station 104, e.g., by performing a cell search procedure. In some scenarios, during the cell search procedure, the UE 102 can detect or decode various cell-specific signals (e.g., Primary Sync Signal (PSS), Secondary Sync Signal (SSS), Physical Broadcast Channel (PBCH)) via Synchronization Signal Block (SSB) beams from the base station 104.

[0035] In some implementations, the base station 104 receives 202 capability information from the UE 102. In other implementations, the base station 104 may receive the capability information of the UE 102 from another base station (not shown) of the RAN, or from the CN 110. The capability information may indicate, for example, how many MIMO layers the UE 102 can process, or can currently process under current channel conditions. For example, the UE 102 with two antennas can report a 2-layer, 2x2 MIMO processing capability. More generally, the capability information may indicate a number of antennas of the UE 102, or include an indication of a number of antenna ports the base station 104 can determine for the UE 102. Further, the capability information reported by the UE 102 may be specific to each of one or more carrier frequency bands. In yet other implementations, steps 202 and 204 may be omitted entirely.

[0036] The base station 104 then determines 206 a front- loaded CSI configuration for the UE 102. In some implementations in which the base station 104 receives the capability information of the UE 102, the base station 104 can determine 206 the front-loaded CSI based on the capability information of the UE 102. Generally, a configuration specifies radio resources that include time resources and possibly frequency resources. To determine the “front-loaded” CSI configuration as described herein, the base station 104 front loads time- frequency radio resources in a subframe for A reference signals (e.g., for ACSTRSs) that the base station 104 will transmit specifically to the UE 102 before UL and/or DL data communication with the UE 102. More specifically, the front-loaded CSI configuration allocates time resources of a subframe such that the base station 104 transmits A UE-specific reference signals to the UE 102 at a time beginning no later than any DL or UL data communication within the subframe (e.g., beginning no later than any PDSCH or PUSCH within the subframe, depending on the implementation). As such, the base station 104 has an opportunity to consider CSI feedback provided by the UE 102 based on the A reference signals before communicating most (or all) data with the UE 102 within a given subframe. The front-loaded CSI configuration can also allocate time resources for the base station 104 to receive the CSI feedback from the UE 102, with those time resources following all time resources allocated for transmitting the A reference signals to the UE 102, but preceding all time resources for communicating data with the UE 102. In some implementations, the allocated time resources can also include guard periods (GPs), as described in more detail below.

[0037] In some implementations, the base station 104 can determine the value of A and the width of each BS beam used to collectively carry the A reference signals for the front-loaded CSI configuration based on a mobility estimate that the base station 104 forms for the UE 102. For example, the more mobile the UE 102, the higher the value of A set by the base station 104, in order to utilize a more refined set of reference signals to reach the UE 102. As another example, the less mobile the UE 102, the wider the BS beams used to collectively carry the A reference signals. In some implementations, if the base station 104 is mobile (e.g., a satellite, drone, HAP station), the base station 104 can determine A and the width of each BS beam based on its own mobility estimate. The base station 104 can also (or instead) consider other factors when defining A and the width of each BS beam, such as a time elapsed since allocating radio resources for the UE 102, a time elapsed since receiving signaling from the UE 102 (e.g., CSI feedback, an SRS, an indication of a selected BS beam) during an earlier subframe (i.e., prior to the subframe that occupies the front- loaded CSI configuration), and/or circumstances of other UEs served by the base station 104.

[0038] After determining 206 the front-loaded CSI configuration for the UE 102, the base station 104 generates and transmits 208 a control signal including the front- loaded CSI configuration to the UE 102. The base station 104 can transmit 208 the control signal to the UE 102 via a wide beam that is wider than any BS beam (e.g., any of BS beams 151-155 of Fig. IB), or via a BS beam (e.g., one of BS beams 151-155) that the base station 104 selected based on signaling received from the UE 102 during an earlier subframe. In some implementations, the base station 104 transmits 208 the control signal to the UE 102 via a control channel ( e.g ., PDCCH) signal that is specific to the UE 102. The control channel signal including the front-loaded CSI configuration may be an upper-layer message, such as a MAC message, RLC message, PDCP message, or RRC message. In some implementations, the base station 104 includes the front-loaded CSI configuration within a DL Control Information (DCI) included in the control signal. In some implementations, the base station 104 transmits the front-loaded CSI configuration to the UE 102 via a plurality of control signals.

[0039] After receiving the front-loaded CSI configuration via the control signal, the UE 102 applies 210 the front-loaded CSI configuration, in order to prepare to receive the A reference signals from the base station 104. That is, when the base station 104 at some later time transmits 212 the A reference signals to the UE 102 via A different BS beams, the UE 102 can search the radio resources associated with those A reference signals in accordance with the front-loaded CSI configuration. Consequently, the UE 102 can receive the A reference signals and perform signal measurements on those A reference signals. In some implementations, the UE 102 can sweep 214 through each of its UE beams (e.g., each of UE beams 156-158) when receiving each of the A reference signals. As described above in Fig. IB, the UE 102 can select one of the UE beams and one of the BS beam (i.e., the optimal beam pair link) having better signal conditions for establishing a highly directional link between the UE 102 and the base station 104 based on the measurements of the A reference signals. In some implementations or scenarios, the UE 102 may identify a plurality of beam pair links due to an obstacle between the UE 102 and the base station 104, or mobility of the UE 102 and/or base station 104 as described above, and determine which of the plurality of beam pair links is the optimum beam pair link.

[0040] In turn, the UE 102 can generate 216 CSI feedback indicating the selected BS beam based on the reference signal measurements. In some implementations, the CSI feedback can include an identifier of the selected BS beam. The CSI feedback may also include a variety of information estimated by the UE 102 based on how well the UE 102 was able to receive the reference signal of the selected BS beam. For example, the CSI feedback may include a CQI, PMI, and/or RI as determined by the UE 102 based on its measurement for the selected BS beam. [0041] In some implementations, the UE 102 can exploit channel reciprocity in a TDD system to use the same UE beam that was selected to receive at least one of the N reference signals to also transmit 224 the CSI feedback to the base station 104. That is, to transmit 224 the CSI feedback to the base station 104, the UE 102 can switch 218 to the selected UE beam (if not already using that UE beam), and subsequently transmit 224 the CSI feedback to the base station 104 via the selected UE beam. In some implementations, the UE 102 can send 220 a UL reference signal, such as an SRS, to the base station 104 via the selected UE beam, so that the base station 104 can quickly acquire 222 the selected UE beam based on the SRS.

[0042] After receiving the CSI feedback, the base station 104 can switch 226 to the selected BS beam as indicated by the CSI feedback (if not already using that BS beam), to prepare to send or receive data to or from the UE 102 via the selected BS beam. The UE 102 and base station 104 can then communicate 230 UL data and/or DL data via the selected UE beam and BS beam.

[0043] In some implementations, the sequence of events shown in Fig. 2 (possibly omitting events 202 and/or 204) is repeated whenever the base station 104 determines a new front- loaded CSI configuration for the UE 102. For example, the sequence of events may be repeated because the base station 104 has received a new indication of capability information of the UE 102, or possibly because the base station 104 has received CSI feedback from the UE 102 that triggers an updated channel configuration.

[0044] Next, Figs. 3 A and 3B illustrate subframes arranged according to example implementations of front-loaded CSI configurations for transmissions between a UE ( e.g ., the UE 102) and a base station (e.g., the base station 104) in accordance with the techniques of this disclosure. Generally speaking, pursuant to a front-loaded CSI configuration, the base station can transmit N > 2 fast beam tracking pilots on certain frequency and time radio resources that occupy part of a subframe, before, or at least no later than, any UL or DL data communication (i.e., PUSCH or PDSCH communication) within the subframe. The front- loaded CSI configuration can define the value of N and a duration of each of the N fast beam tracking pilots, as well as the subframe. For example, the subframe can have a defined duration (e.g., 1 ms) partitioned into a defined number of time resources, or slots (e.g., 1 slot, 2 slots, 4 slots, 8 slots, 16 slots, etc.), where the slot length varies based on subcarrier spacing and number of slots per subframe. Each slot can be defined to occupy a certain number of sequential symbols (e.g., 14 Orthogonal Frequency Division Multiplexing (OFDM) symbols, 12 OFDM symbols, etc.), and each symbol can occupy a span of subcarriers. In some implementations, the base station 104 can transmit a plurality of subframes to the UE 102.

[0045] Fig. 3A illustrates a subframe 300A arranged according to an example front-loaded CSI configuration that the base station 104 can provide to the UE 102 ( e.g ., in event 208 of Fig. 2) for transmitting DL data to the UE 102 via a highly directional link. As illustrated, the example subframe 300A is partitioned into 8 time slots, i.e., slots 301-308. Each slot can have a certain duration (e.g., 0.0625 ms, 0.125 ms, 0.25 ms, 0.5 ms, 1 ms), and contain a certain number of sequential symbols (e.g., 12 symbols, 14 symbols). However, generally speaking, the subframe 300A may occupy any suitable number of time slots or symbols.

[0046] At slot 301, the UE 102 receives a DL control signal on a PDCCH from the base station 104. In some implementations, the DL control signal on the PDCCH carries a DCI or other suitable field or information element (IE) for scheduling a first set of radio resources corresponding to respective slots 302-306 in the subframe 300A for transmitting N tracking pilot signals (i.e., in this implementation, N CSI-RSs), and a second set of radio resources (e.g., PDSCH) corresponding to slot 308 in the subframe 300A for communicating DL data with the UE 102. Thus, the N tracking pilot signals are “front-loaded” relative to DL data communication within the subframe 300A. The DCI can define this front-loaded configuration by defining/specifying N, the duration of each of the N tracking pilot signals (e.g., 1 slot), and the CSI-RS positions, for example. Generally, the DCI (or other field or IE) defines/specifies a front-loaded CSI configuration that results in an earliest time resource for transmitting the N tracking pilot signals beginning no later in the subframe 300A than an earliest time resource for communicating DL data with the UE 102.

[0047] By front-loading the N tracking pilot signals relative to the PDSCH, the base station 104 can send the A tracking pilot signals before, or at least concurrently with, the earliest DL data communications of subframe 300A with the UE 102. As illustrated in Fig. 3A, the example subframe 300A schedules five (i.e., N= 5) tracking pilot signals on the same frequency resources in the subframe 300A as are occupied by the PDSCH, but on earlier time slots. As noted above, each of the five tracking pilot signals can correspond to a different BS beam. For example, and with reference to Fig. IB, slot 302 can correspond to BS beam 151 carrying CSI-RS 1, slot 303 can correspond to BS beam 152 carrying CSI-RS 2, slot 304 can correspond to BS beam 153 carrying CSI-RS 3, slot 305 can correspond to BS beam 154 carrying CSI-RS 4, and slot 306 can correspond to BS beam 155 carrying CSI-RS 5. [0048] The frequency resources assigned to the N tracking pilot signals and the frequency resources assigned to the PDSCH can be, but need not be, coextensive. Fig. 3A shows an implementation of subframe 300A in which the respective frequency resources assigned to the five tracking pilot signals and PDSCH are coextensive, and in which all five tracking pilot signals occur entirely before the PDSCH. Although not illustrated in Fig. 3A, in other implementations of subframe 300A, the respective frequency resources assigned to the N tracking pilot signals and PDSCH are not coextensive, but one or more of the N tracking pilot signals still occur before the PDSCH. In yet other implementations of subframe 300A, the respective frequency resources assigned to the N tracking pilot signals and PDSCH are not coextensive, and the earliest scheduled tracking pilot signal ( e.g ., CSI-RS 1) begins at the same time as at least some frequency resources assigned to the PDSCH.

[0049] Similarly, the frequency resources assigned to the N tracking pilot signals and the frequency resources assigned to the PDCCH can be, but need not be, coextensive. Fig. 3A shows an implementation of subframe 300A in which the respective frequency resources assigned to the five tracking pilot signals and PDCCH are coextensive. Although not illustrated in Fig. 3A, in other implementations of subframe 300A, the respective frequency resources assigned to the N tracking pilot signals and PDCCH are not coextensive. For example, the base station 104 can transmit the PDCCH to the UE 102 in a low frequency band via a wide beam that is wider than any of the BS beams carrying the N tracking pilot signals transmitted in a high frequency band. In some cases, the base station 104 can utilize cross-carrier scheduling or carrier aggregation techniques to schedule the PDCCH on one component carrier (e.g., in a low frequency band) and the N tracking pilot signals on other component carriers (e.g., in the same high frequency band as the PDSCH).

[0050] Further, the PDCCH can carry a DCI (e.g., the same DCI that schedules the N tracking pilot signals and the PDSCH) scheduling a third set of radio resources (e.g.,

PUCCH) corresponding to a slot 307 (i.e., after slots 301-306 and prior to slot 308) at which the UE 102 is to send UL CSI feedback to the base station 104. As such, the DCI can allocate all time resources of the third set of radio resources to precede all the time resources of the second set of radio resources (e.g., for the PDSCH) in the configuration. By front- loading the CSI feedback relative to the PDSCH, the base station 104 can select and use a good (e.g., optimum) BS beam for sending the DL data via a highly directional link. For example, and again with reference to Fig. IB, the UE 102 can provide UL CSI feedback during slot 307 to indicate that BS beam 153 exhibits better signal conditions than those of BS beams 151, 152, 154 and 155. The UL CSI feedback need not be scheduled on the same frequency resources as the N tracking pilot signals. In some implementations, the frequency resources of the UL CSI feedback are the same as the frequency resources of the N tracking pilot signals, as illustrated in FIG. 3A ( e.g ., if using TDD). In other implementations, the frequency resources of the UL CSI feedback are at least partially different than the frequency resources of the /V tracking pilot signals (e.g., if using FDD).

[0051] Although not illustrated in Fig. 3A, in some implementations, the PDCCH can carry a DCI (e.g., the same DCI that schedules the A tracking pilot signals and the PDSCH) scheduling a fourth set of radio resources corresponding to a time (e.g., slot), before the slot 307, at which the UE 102 is to transmit an UL reference signal (e.g., SRS) to the base station 104 to facilitate acquisition of the UL CSI feedback by the base station 104, as described above.

[0052] Referring now to Fig. 3B, the base station 104 can provide a subframe 300B to the UE 102 (e.g., in event 208 of Fig. 2) for receiving UL data from the UE 102 via a highly directional link. Similar to the various implementations of subframe 300A described above, the depicted subframe 300B occupies a single subframe, which is partitioned into 8 slots. Slots 301-307 may be identical or similar to those described above with respect to Fig. 3A. However, in contrast to slot 308 of subframe 300A (which back-loads a PDSCH for communicating DL data with the UE 102), slot 309 of subframe 300B back-loads a PUSCH for communicating UL data with the UE 102.

[0053] In some implementations, the base station 104 may provide, in each of subframes 300A or 300B, sufficiently large guard periods (GPs), also known as guard times, in which neither DL nor UL transmissions occur between the UE 102 and base station 104. In this way, the UE 102 can avoid transmitting and/or receiving signals before the UE 102 is ready (e.g., while the UE 102 is busy switching from UL transmission to DL reception, switching beams, generating CSI feedback information or UL data for transmission, etc.). Generally, GPs may be used for both TDD and FDD communications. However, GPs may be reduced or eliminated for some FDD implementations that do not require switching between DL and UL transmissions.

[0054] In some implementations, the PDCCH at slot 301 can carry a DCI (e.g., the same DCI that schedules the N tracking pilot signals and the PDSCH) scheduling the GPs in the subframe. With reference to Figs. 3A and 3B, GP 310 of subframes 300A and 300B may occupy slot 306, to ensure that CSI-RS 5 ends sufficiently early relative to the start of the UL CSI feedback at slot 307. In the subframe 300A, GP 312 may occupy slot 308, to ensure that the PDSCH at slot 308 begins sufficiently late relative to the end of the UL CSI feedback at slot 307. Similarly, in the subframe 300B, GP 313 may occupy slot 309, such that the PUSCH at slot 309 begins sufficiently late relative to the end of the UL CSI feedback at slot 307.

[0055] In some implementations, the base station 104 may determine GPs 310 and 312 (or GPs 310 and 313) based on capability information the base station 104 received from the UE 102 (e.g., in event 202 of Fig. 2) and/or its own capabilities. For example, the base station 104 can determine/set GP 310 based on UE capability information that corresponds to one or more factors that might cause a time delay, such as the processing time required for the UE 102 to select an optimum BS beam (e.g., in event 214 of Fig. 2), time required for the UE 102 to generate CSI feedback (e.g., in event 216 of Fig. 2), and/or time required for the UE 102 to switch to a selected UE beam (e.g., in event 218 of Fig. 2). The base station 104 can determine/set GP 312 based on UE capability information that corresponds to time required for the UE 102 to switch from transmission mode (e.g., to send CSI feedback to the base station 104) to reception mode (e.g., to receive data from the base station 104). In some implementations, to determine GP 312 or GP 313, the base station 104 can consider its own capability corresponding to time required for the base station 104 to acquire the selected UE beam (e.g., in event 222 of Fig. 2), and hence CSI feedback via the UE beam, and/or time required for the base station 104 to switch to the BS beam indicated by the UE 102 to send DL data or receive UL data (e.g., in event 226 of Fig. 2).

[0056] Fig. 4 is a flow diagram of an example method 400 for allocating communication resources for a UE (e.g., the UE 102), which can be implemented in a base station (e.g., the base station 104 of Fig. 1A). The method 400 begins at block 402, where the base station determines a configuration for the UE (e.g., event 206 of Fig. 2). The configuration can be a front-loaded CSI configuration (e.g., as in the subframe 300A or 300B described above with reference to Fig. 3A or Fig. 3B, respectively) that allocates (i) a first set of radio resources in a subframe for transmitting N UE-specific DL reference signals to the UE via respective beams having different beam directions when the UE is in a connected state with the base station, where N is greater than one, and (ii) a second set of radio resources in the subframe for communicating data with the UE, with an earliest time resource of the first set of radio resources beginning no later in the subframe than an earliest time resource of the second set of radio resources. In some implementations, the base station determines at least a portion of the configuration based on UE capability information, which may be received from the UE ( e.g ., event 202 of Fig. 2). For example, the base station may determine one or more guard periods in the configuration based on UE capability information (e.g., in event 214 of Fig. 2), such as UE capability information indicative of the processing time required for the UE to select an optimum beam, or indicative of the time required for the UE to switch from transmission mode to reception mode (e.g., to receive data from the base station). At block 404, the base station transmits one or more signals collectively indicating the determined configuration to the UE (e.g., event 208 of Fig. 2).

[0057] Fig. 5 is a flow diagram of an example method 500 for communicating with a base station (e.g., the base station 104 of Fig. 1A) in accordance with a configuration provided by the base station. The method 500 can be implemented in a UE such as the UE 102 of Fig.

1A. The method 500 begins at block 502, where the UE receives, from the base station, one or more signals collectively indicating a configuration, such as the front- loaded CSI configuration described above in Fig. 3A or Fig. 3B (e.g., event 208 of Fig. 2). In some implementations, prior to block 502, the UE can transmit capability information to the base station, so that the base station can determine at least a portion of the configuration based on the capability information (e.g., event 202 of Fig. 2). For example, the capability information can indicate a minimum time period for the UE to transition between receiving at least one of the N tracking pilot signals and transmitting the CSI feedback, and/or a minimum time period for the UE to transition between transmitting the CSI feedback and receiving data with the base station. At block 504, the UE communicates with the base station in accordance with the configuration (e.g., event 230 of Fig. 2).

[0058] The following additional considerations apply to the foregoing discussion.

[0059] A user device in which the techniques of this disclosure can be implemented (e.g., the UE 102) can be any suitable device capable of wireless communications such as a smartphone, a tablet computer, a laptop computer, a mobile gaming console, a point-of-sale (POS) terminal, a health monitoring device, a drone, a camera, a media- streaming dongle or another personal media device, a wearable device such as a smartwatch, a wireless hotspot, a femtocell, or a broadband router. Further, the user device in some cases may be embedded in an electronic system such as the head unit of a vehicle or an advanced driver assistance system (ADAS). Still further, the user device can operate as an internet-of-things (IoT) device or a mobile-internet device (MID). Depending on the type, the user device can include one or more general-purpose processors, a computer-readable memory, a user interface, one or more network interfaces, one or more sensors, etc.

[0060] Certain embodiments are described in this disclosure as including logic or a number of components or modules. Modules may can be software modules ( e.g ., code stored on non- transitory machine-readable medium) or hardware modules. A hardware module is a tangible unit capable of performing certain operations and may be configured or arranged in a certain manner. A hardware module can comprise dedicated circuitry or logic that is permanently configured (e.g., as a special-purpose processor, such as a field programmable gate array (FPGA) or an application- specific integrated circuit (ASIC)) to perform certain operations. A hardware module may also comprise programmable logic or circuitry (e.g., as encompassed within a general-purpose processor or other programmable processor) that is temporarily configured by software to perform certain operations. The decision to implement a hardware module in dedicated and permanently configured circuitry, or in temporarily configured circuitry (e.g., configured by software) may be driven by cost and time considerations.

[0061] When implemented in software, the techniques can be provided as part of the operating system, a library used by multiple applications, a particular software application, etc. The software can be executed by one or more general-purpose processors or one or more special-purpose processors.

[0062] Upon reading this disclosure, those of skill in the art will appreciate still additional alternative structural and functional designs for fast beam tracking techniques through the disclosed principles herein. Thus, while particular embodiments and applications have been illustrated and described, it is to be understood that the disclosed embodiments are not limited to the precise construction and components disclosed herein. Various modifications, changes and variations, which will be apparent to those of ordinary skill in the art, may be made in the arrangement, operation and details of the method and apparatus disclosed herein without departing from the spirit and scope defined in the appended claims.

[0063] Example 1. A method in a base station for allocating communication resources for a user equipment (UE), the method comprising: determining, by processing hardware, a configuration that allocates (i) a first set of radio resources in a subframe for transmitting N UE- specific downlink (DL) reference signals to the UE via respective beams having different beam directions when the UE is in a connected state with the base station, where N is greater than one, and (ii) a second set of radio resources in the subframe for communicating data with the UE, with an earliest time resource of the first set of radio resources beginning no later in the subframe than an earliest time resource of the second set of radio resources; and transmitting to the UE, by the processing hardware, one or more signals collectively indicating the determined configuration.

[0064] Example 2. The method of example 1, wherein each of the N DL reference signals is a Channel State Information Reference Signal (CSI-RS).

[0065] Example 3. The method of example 1 or 2, wherein the configuration defines N and a duration of each of the N DL reference signals.

[0066] Example 4. The method of any one of examples 1-3, wherein the configuration further allocates a third set of radio resources in the subframe for receiving uplink (UL) channel state information (CSI) feedback from the UE.

[0067] Example 5. The method of example 4, wherein all time resources of the third set of radio resources precede all the time resources of the second set of radio resources in the configuration.

[0068] Example 6. The method of example 4 or 5, wherein all the time resources of the first set of radio resources precede all the time resources of the third set of radio resources.

[0069] Example 7. The method of any one of examples 4-6, wherein frequency resources of the first set of radio resources are different than frequency resources of the third set of radio resources.

[0070] Example 8. The method of any one of examples 4-7, wherein the configuration further indicates a first guard period preceding all the time resources of the third set of radio resources and following all the time resources of the first set of radio resources.

[0071] Example 9. The method of example 8, wherein the configuration further indicates a second guard period preceding all the time resources of the second set of radio resources and following all the time resources of the third set of radio resources.

[0072] Example 10. The method of example 9, further comprising: receiving capability information of the UE, wherein the base station determines the second guard period based on the capability information. [0073] Example 11. The method of example 8, further comprising: receiving capability information of the UE, wherein the base station determines the first guard period based on the capability information.

[0074] Example 12. The method of any one of examples 4-11, wherein the configuration further allocates a fourth set of radio resources in the subframe for receiving one or more UL reference signals from the UE to facilitate acquisition of the UL CSI feedback.

[0075] Example 13. The method of example 12, wherein the fourth set of radio resources precedes the third set of radio resources in the configuration.

[0076] Example 14. The method of examples 12 or 13, wherein each of the one or more UL reference signals includes a Sounding Reference Signal (SRS).

[0077] Example 15. The method of any one of the preceding examples, wherein transmitting the one or more signals collectively indicating the determined configuration includes transmitting the one or more signals via a Physical Downlink Control Channel (PDCCH).

[0078] Example 16. The method of example 15, wherein frequency resources of the PDCCH differ from frequency resources of the first set of radio resources.

[0079] Example 17. The method of example 15, wherein transmitting the one or more signals collectively indicating the determined configuration includes transmitting the one or more signals via a wide beam that is wider than any of the beams for transmitting N UE- specific downlink (DL) reference signals.

[0080] Example 18. The method of example 15, wherein transmitting the one or more signals collectively indicating the determined configuration includes transmitting the one or more signals via one of the beams based on signaling received from the UE during an earlier subframe.

[0081] Example 19. The method of any one of the preceding examples, wherein the second set of radio resources is part of a Physical Downlink Shared Channel (PDSCH) or a physical uplink shared channel (PUSCH).

[0082] Example 20. The method of any one of examples 4-19, wherein the third set of radio resources is part of a physical uplink control channel (PUCCH). [0083] Example 21. The method of example 20, wherein frequency resources of the third set of radio resources differ from frequency resources of the first set of radio resources.

[0084] Example 22. The method of example 20, wherein frequency resources of the third set of radio resources are the same as frequency resources of the first set of radio resources.

[0085] Example 23. The method of any one of the preceding examples, wherein the one or more signals include a Downlink Control Information (DCI).

[0086] Example 24. The method of any one of examples 1-22, wherein the one or more signals include a radio resource control (RRC) message.

[0087] Example 25. The method of any one of the preceding examples, wherein the base station determines N and a width of each of the beams based on at least one of: a mobility estimate of the UE; a time elapsed since the base station allocated radio resources for the UE; a time elapsed since the base station received previous signaling from the UE; or circumstances of other UEs served by the base station.

[0088] Example 26. A base station comprising hardware and configured to perform the method of any one of examples 1-25.

[0089] Example 27. A method in a user equipment (UE), the method comprising: receiving from a base station, by processing hardware, one or more signals collectively indicating a configuration that allocates (i) a first set of radio resources in a subframe for transmitting N UE- specific downlink (DL) reference signals to the UE via respective beams having different beam directions when the UE is in a connected state with the base station, where N is greater than one, and (ii) a second set of radio resources in the subframe for communicating data with the UE, with an earliest time resource of the first set of radio resources beginning no later in the subframe than an earliest time resource of the second set of radio resources; and communicating with the base station, by the processing hardware, in accordance with the configuration.

[0090] Example 28. The method of example 27, wherein each of the N DL reference signals is a Channel State Information Reference Signal (CSI-RS).

[0091] Example 29. The method of example 27 or 28, wherein the configuration defines N and a duration of each of the N DL reference signals. [0092] Example 30. The method of any one of examples 27-29, wherein the configuration further allocates a third set of radio resources in the subframe for transmitting uplink (UL) channel state information (CSI) feedback to the base station.

[0093] Example 31. The method of example 30, wherein all time resources of the third set of radio resources precede all the time resources of the second set of radio resources in the configuration.

[0094] Example 32. The method of example 30 or 31, wherein all the time resources of the first set of radio resources precede all the time resources of the third set of radio resources.

[0095] Example 33. The method of any one of examples 30-32, wherein frequency resources of the first set of radio resources are different than frequency resources of the third set of radio resources.

[0096] Example 34. The method of any one of examples 30-33, wherein the configuration further indicates a first guard period preceding all the time resources of the third set of radio resources and following all the time resources of the first set of radio resources.

[0097] Example 35. The method of example 34, wherein the configuration further indicates a second guard period preceding all the time resources of the second set of radio resources and following all the time resources of the third set of radio resources.

[0098] Example 36. The method of example 34 or 35, further comprising: transmitting capability information to the base station prior to receiving the one or more signals collectively indicating the configuration, wherein the capability information indicates one or both of (i) a first minimum time period for the UE to transition between receiving at least one of the N DL reference signals and transmitting the UL CSI feedback, and (ii) a second minimum time period for the UE to transition between transmitting the UL CSI feedback and receiving data with the base station.

[0099] Example 37. The method of any one of examples 30-36, wherein the configuration further allocates a fourth set of radio resources in the subframe for transmitting one or more UL reference signals to the base station to facilitate acquisition of the UL CSI feedback.

[0100] Example 38. The method of example 37, wherein the fourth set of radio resources precedes the third set of radio resources in the configuration.

[0101] Example 39. The method of example 37 or 38, wherein each of the one or more UL reference signals includes a Sounding Reference Signal (SRS). [0102] Example 40. The method of any one of examples 27-39, wherein receiving the one or more signals collectively indicating the configuration includes receiving the one or more signals via a Physical Downlink Control Channel (PDCCH).

[0103] Example 41. The method of example 40, wherein frequency resources of the PDCCH differ from frequency resources of the first set of radio resources.

[0104] Example 42. The method of example 40, wherein receiving the one or more signals collectively indicating the configuration includes receiving the one or more signals via a wide beam that is wider than any of the beams.

[0105] Example 43. The method of example 40, wherein receiving the one or more signals collectively indicating the configuration includes receiving the one or more signals via one of the beams based on signaling transmitted to the base station during an earlier subframe.

[0106] Example 44. The method of any one examples 27-43, wherein the second set of radio resources is part of a Physical Downlink Shared Channel (PDSCH) or a physical uplink shared channel (PUSCH).

[0107] Example 45. The method of any one of examples 30-44, wherein the third set of radio resources is part of a physical uplink control channel (PUCCH).

[0108] Example 46. The method of example 45, wherein frequency resources of the third set of radio resources differ from frequency resources of the first set of radio resources.

[0109] Example 47. The method of example 45, wherein frequency resources of the third set of radio resources are the same as frequency resources of the first set of radio resources.

[0110] Example 48. The method of any one of examples 27-47, wherein the one or more signals include a Downlink Control Information (DCI).

[0111] Example 49. The method of any one of examples 27-47, wherein the one or more signals include a radio resource control (RRC) message.

[0112] Example 50. A user equipment (UE) comprising hardware and configured to perform the method of any one of examples 27-49.

Claims

What is claimed is:

1. A method in a base station for allocating communication resources for a user equipment (UE), the method comprising: determining, by processing hardware, a configuration that allocates (i) a first set of radio resources in a subframe for transmitting N UE- specific downlink (DL) reference signals to the UE via respective beams having different beam directions when the UE is in a connected state with the base station, where N is greater than one, and (ii) a second set of radio resources in the subframe for communicating data with the UE, with an earliest time resource of the first set of radio resources beginning no later in the subframe than an earliest time resource of the second set of radio resources; and transmitting to the UE, by the processing hardware, one or more signals collectively indicating the determined configuration.

2. The method of claim 1, wherein each of the N UE- specific DL reference signals is a Channel State Information Reference Signal (CSI-RS).

3. The method of claim 1 or 2, wherein the configuration further allocates a third set of radio resources in the subframe for receiving uplink (UL) channel state information (CSI) feedback from the UE.

4. The method of claim 3, wherein the configuration further indicates at least one of (i) a first guard period preceding all the time resources of the third set of radio resources and following all the time resources of the first set of radio resources and (ii) a second guard period preceding all the time resources of the second set of radio resources and following all the time resources of the third set of radio resources.

5. The method of claim 4, further comprising: receiving capability information of the UE, wherein the base station determines at least one of the first guard period and the second guard period based on the capability information.

6. The method of any one of claims 3, 4, and 5, wherein the configuration further allocates a fourth set of radio resources in the subframe for receiving one or more UL reference signals from the UE to facilitate acquisition of the UL CSI feedback, each of the one or more UL reference signals including a Sounding Reference Signal (SRS).

7. The method of any one of the preceding claims, wherein the second set of radio resources is part of a Physical Downlink Shared Channel (PDSCH) or a physical uplink shared channel (PUSCH).

8. A base station comprising hardware and configured to perform the method of any one of claims 1-7.

9. A method in a user equipment (UE), the method comprising: receiving from a base station, by processing hardware, one or more signals collectively indicating a configuration that allocates (i) a first set of radio resources in a subframe for transmitting N UE-specific downlink (DL) reference signals to the UE via respective beams having different beam directions when the UE is in a connected state with the base station, where N is greater than one, and (ii) a second set of radio resources in the subframe for communicating data with the UE, with an earliest time resource of the first set of radio resources beginning no later in the subframe than an earliest time resource of the second set of radio resources; and communicating with the base station, by the processing hardware, in accordance with the configuration.

10. The method of claim 9, wherein each of the N UE-specific DL reference signals is a Channel State Information Reference Signal (CSI-RS).

11. The method of claim 9 or 10, wherein the configuration further allocates a third set of radio resources in the subframe for transmitting uplink (UL) channel state information (CSI) feedback to the base station.

12. The method of claim 11, wherein the configuration further indicates at least one of (i) a first guard period preceding all the time resources of the third set of radio resources and following all the time resources of the first set of radio resources and (ii) a second guard period preceding all the time resources of the second set of radio resources and following all the time resources of the third set of radio resources.

13. The method of claim 12, further comprising: transmitting capability information to the base station prior to receiving the one or more signals collectively indicating the configuration, wherein the capability information indicates one or both of (i) a first minimum time period for the UE to transition between receiving at least one of the N DL reference signals and transmitting the UL CSI feedback, and (ii) a second minimum time period for the UE to transition between transmitting the UL CSI feedback and receiving data with the base station.

14. The method of any one of claims 11-13, wherein the configuration further allocates a fourth set of radio resources in the subframe for transmitting one or more UL reference signals to the base station to facilitate acquisition of the UL CSI feedback, each of the one or more UL reference signals including a Sounding Reference Signal (SRS).

15. The method of any one claims 9-14, wherein the second set of radio resources is part of a Physical Downlink Shared Channel (PDSCH) or a physical uplink shared channel (PUSCH).

16. A user equipment (UE) comprising hardware and configured to perform the method of any one of claims 9-15.