Patent Description:
Reference signals are commonly used in wireless communication to facilitate various communication functions, for example, channel estimation and measurement, signal demodulation, synchronization, beam management and selection, interference estimation, cell search and selection, etc. Hence, reference signals can be generally categorized into two types, including reference signals for the purpose of channel measurement and reference signals for demodulation of data. One example of reference signals is the Channel State Information Reference Signal (CSI-RS) that may be used by a user equipment (UE) to estimate a wireless channel and report channel quality information (CQI) back to a base station. Channel estimation determines the characteristic of a wireless channel so that a receiver can remove the noise and/or distortion introduced by the channel from the received signal. For example, the base station or network can transmit a CSI-RS, and the UE evaluates the received signal quality based on the CSI-RS and reports the measurement results to the network.

Beamforming is a technique for improving the performance (e.g., throughput, signal quality) of wireless communications using multiple antennas. Beamforming applies different weightings of amplitude and phase to the signal on each antenna in order to transmit the signal in one or more beams. In beamforming applications, the base station can generate a beamforming matrix based on a specific channel report from a UE, for example, based on the CSI-RS. The beamforming matrix may include the magnitude and phase information for configuring the antennas.

<CIT> relates to a terminal, base station, base station controller and millimeter-wave cellular communication method. International Patent Application Publication No. <CIT> relates to a low-power carrier type and related methods and apparatus. <NPL>summarizes discussion points regarding SRS design. <NPL>, discusses enhancement of SCell coverage with massive beamforming in a carrier aggregation scenario.

One aspect of the present disclosure provides an apparatus for wireless communication using carrier aggregation in a wireless communication network that includes a primary cell (PCell) and a secondary cell (SCell). The apparatus includes a communication interface configured for wireless communication, a memory, and a processor operatively coupled to the communication interface and the memory. The apparatus transmits a first reference signal of the PCell and receives a first measurement report from a user equipment (UE). The first measurement report indicates a quality of the first reference signal. The apparatus determines that the UE is potentially located in a coverage area of the SCell based on the quality of a first reference signal. The apparatus transmits an SCell measurement configuration message for configuring the UE that is potentially located in the coverage area of the SCell to measure a second reference signal transmitted by the SCell for initial beam selection using one or more first beams. The apparatus transmits a signal boost message for triggering the SCell to extend a range of the second reference signal from a first range to a second range, in response to determining that a quality of the second reference signal is less than a predetermined quality.

Another aspect of the present disclosure provides a method of carrier aggregation in a wireless communication network that includes a PCell and an SCell. A scheduling entity of the PCell transmits a first reference signal of the PCell and receives a first measurement report from a user equipment (UE). The first measurement report indicates a quality of the first reference signal. The scheduling entity determines that the UE is potentially located in a coverage area of the SCell based on the quality of the first reference signal. The scheduling entity transmits an SCell measurement configuration message for configuring the UE that is potentially located in the coverage area of the SCell to measure a second reference signal transmitted by the SCell for initial beam selection using one or more first beams. The scheduling entity transmits a signal boost message for triggering the SCell to extend a range of the second reference signal from a first range to a second range, in response to determining that a quality of the second reference signal is less than a predetermined quality.

While aspects and embodiments are described in this application by illustration to some examples, those skilled in the art will understand that additional implementations and use cases may come about in many different arrangements and scenarios. Innovations described herein may be implemented across many differing platform types, devices, systems, shapes, sizes, packaging arrangements. For example, embodiments and/or uses may come about via integrated chip embodiments and other non-module-component based devices (e.g., end-user devices, vehicles, communication devices, computing devices, industrial equipment, retail/purchasing devices, medical devices, AI-enabled devices, etc.). While some examples may or may not be specifically directed to use cases or applications, a wide assortment of applicability of described innovations may occur. Implementations may range a spectrum from chip-level or modular components to non-modular, non-chip-level implementations and further to aggregate, distributed, or OEM devices or systems incorporating one or more aspects of the described innovations. In some practical settings, devices incorporating described aspects and features may also necessarily include additional components and features for implementation and practice of claimed and described embodiments. For example, transmission and reception of wireless signals necessarily include a number of components for analog and digital purposes (e.g., hardware components including antenna, RF-chains, power amplifiers, modulators, buffer, processor(s), interleaver, adders/summers, etc.). It is intended that innovations described herein may be practiced in a wide variety of devices, chip-level components, systems, distributed arrangements, end-user devices, etc. of varying sizes, shapes and constitution.

Aspects of the present disclosure provide various apparatuses and methods for extending the range of a reference signal to facilitate carrier aggregation (CA) in wireless communications. In some examples, a network includes a primary cell (PCell) and one or more secondary cells (SCells). The PCell and SCells may use carriers in different frequency bands. For example, the PCell may use a carrier with a frequency below <NUM>, and the SCells may use a millimeter wave (mmW) carrier. In some aspects of the disclosure, when a UE is beyond the range of a reference signal from the secondary cell (SCell), the primary cell may trigger the secondary cell to increase the range of its reference signal using a higher gain beam and/or reference signal repetition.

In a hybrid RAN, an LTE cell may act as a primary cell (PCell), and one or more <NUM> NR cells may be secondary cells associated with the PCell.

The radio access network <NUM> is further illustrated supporting wireless communication for multiple mobile apparatuses. A mobile apparatus may be referred to as user equipment (UE) in 3GPP standards, but may also be referred to by those skilled in the art as a mobile station (MS), a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal (AT), a mobile terminal, a wireless terminal, a remote terminal, a handset, a terminal, a user agent, a mobile client, a client, or some other suitable terminology. A UE may be an apparatus that provides a user with access to network services.

Within the present document, a "mobile" apparatus need not necessarily have a capability to move, and may be stationary. The term mobile apparatus or mobile device broadly refers to a diverse array of devices and technologies. UEs may include a number of hardware structural components sized, shaped, and arranged to help in communication; such components can include antennas, antenna arrays, RF chains, amplifiers, one or more processors, etc. electrically coupled to each other. For example, some non-limiting examples of a mobile apparatus include a mobile, a cellular (cell) phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal computer (PC), a notebook, a netbook, a smartbook, a tablet, a personal digital assistant (PDA), and a broad array of embedded systems, e.g., corresponding to an "Internet of things" (IoT). A mobile apparatus may additionally be an automotive or other transportation vehicle, a remote sensor or actuator, a robot or robotics device, a satellite radio, a global positioning system (GPS) device, an object tracking device, a drone, a multi-copter, a quad-copter, a remote control device, a consumer and/or wearable device, such as eyewear, a wearable camera, a virtual reality device, a smart watch, a health or fitness tracker, a digital audio player (e.g., MP3 player), a camera, a game console, etc. A mobile apparatus may additionally be a digital home or smart home device such as a home audio, video, and/or multimedia device, an appliance, a vending machine, intelligent lighting, a home security system, a smart meter, etc. A mobile apparatus may additionally be a smart energy device, a security device, a solar panel or solar array, a municipal infrastructure device controlling electric power (e.g., a smart grid), lighting, water, etc.; an industrial automation and enterprise device; a logistics controller; agricultural equipment; military defense equipment, vehicles, aircraft, ships, and weaponry, etc. Still further, a mobile apparatus may provide for connected medicine or telemedicine support, i.e., health care at a distance. Telehealth devices may include telehealth monitoring devices and telehealth administration devices, whose communication may be given preferential treatment or prioritized access over other types of information, e.g., in terms of prioritized access for transport of critical service data, and/or relevant QoS for transport of critical service data.

Transmissions from a UE (e.g., UE <NUM>) to a base station (e.g., base station <NUM>) may be referred to as uplink (UE) transmissions.

A primary cell may communicate with a secondary cell using a backhaul connection.

<FIG> is a diagram illustrating an example of a radio access network (RAN) <NUM>. In some examples, the RAN <NUM> may be the same as the RAN <NUM> described above and illustrated in <FIG>. The geographic area covered by the RAN <NUM> may be divided into cellular regions (cells) that can be uniquely identified by a user equipment (UE) based on an identification broadcasted from one access point or base station. <FIG> illustrates macrocells <NUM>, <NUM>, and <NUM>, and a small cell <NUM>, each of which may include one or more sectors (not shown). A sector is a sub-area of a cell. All sectors within one cell are served by the same base station. A radio link within a sector can be identified by a single logical identification belonging to that sector. In a cell that is divided into sectors, the multiple sectors within a cell can be formed by groups of antennas with each antenna responsible for communication with UEs in a portion of the cell.

Within the RAN <NUM>, the cells may include UEs that may be in communication with one or more sectors of each cell. Further, each base station <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> may be configured to provide an access point to a core network <NUM> (see <FIG>) for all the UEs in the respective cells. For example, UEs <NUM> and <NUM> may be in communication with base station <NUM>; UEs <NUM> and <NUM> may be in communication with base station <NUM>; UEs <NUM> and <NUM> may be in communication with base station <NUM> by way of RRH <NUM>; UE <NUM> may be in communication with base station <NUM>; and UE <NUM> may be in communication with mobile base station <NUM>. In some examples, the UEs <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and/or <NUM> may be the same as the UE/scheduled entity <NUM> described above and illustrated in <FIG>.

In a further aspect of the RAN <NUM>, sideline signals may be used between UEs without necessarily relying on scheduling or control information from a base station. For example, two or more UEs (e.g., UEs <NUM> and <NUM>) may communicate with each other using peer to peer (P2P) or sidelink signals <NUM> without relaying that communication through a base station (e.g., base station <NUM>). In a further example, UE <NUM> is illustrated communicating with UEs <NUM> and <NUM>. Here, the UE <NUM> may function as a scheduling entity or a primary sidelink device, and UEs <NUM> and <NUM> may function as a scheduled entity or a non-primary (e.g., secondary) sidelink device. In still another example, a UE. may function as a scheduling entity in a device-to-device (D2D), peer-to-peer (P2P), or vehicle-to-vehicle (V2V) network, and/or in a mesh network. In a mesh network example, UEs <NUM> and <NUM> may optionally communicate directly with one another in addition to communicating with the scheduling entity <NUM>. Thus, in a wireless communication system with scheduled access to time-frequency resources and having a cellular configuration, a P2P configuration, or a mesh configuration, a scheduling entity and one or more scheduled entities may communicate utilizing the scheduled resources.

In the radio access network <NUM>, the ability for a UE to communicate while moving, independent of its location, is referred to as mobility. The various physical channels between the UE and the radio access network are generally set up, maintained, and released under the control of an access and mobility management function (AMF, not illustrated, part of the core network <NUM> in <FIG>), which may include a security context management function (SCMF) that manages the security context for both the control plane and the user plane functionality, and a security anchor function (SEAF) that performs authentication.

In various aspects of the disclosure, a radio access network <NUM> may utilize DL-based mobility or DL-based mobility to enable mobility and handovers (i.e., the transfer of a UE's connection from one radio channel to another). In a network configured for DL-based mobility, during a call with a scheduling entity, or at any other time, a UE may monitor various parameters of the signal (e.g., a reference signal) from its serving cell as well as various parameters of neighboring cells. Depending on the quality of these parameters, the UE may maintain communication with one or more of the neighboring cells. During this time, if the UE moves from one cell to another, or if signal quality from a neighboring cell exceeds that from the serving cell for a given amount of time, the UE may undertake a handoff or handover from the serving cell to the neighboring (target) cell. For example, UE <NUM> (illustrated as a vehicle, although any suitable form of UE may be used) may move from the geographic area corresponding to its serving cell <NUM> to the geographic area corresponding to a neighbor cell <NUM>. When the signal strength or quality from the neighbor cell <NUM> exceeds that of its serving cell <NUM> for a given amount of time, the UE <NUM> may transmit a reporting message to its serving base station <NUM> indicating this condition. In response, the UE <NUM> may receive a handover command, and the UE may undergo a handover to the cell <NUM>.

In a network configured for UL-based mobility, UL reference signals from each UE may be utilized by the network to select a serving cell for each UE. In some examples, the base stations <NUM>, <NUM>, and <NUM>/<NUM> may broadcast unified synchronization signals (e.g., unified Primary Synchronization Signals (PSSs), unified Secondary Synchronization Signals (SSSs) and unified Physical Broadcast Channels (PBCH)). In some examples, the PSS, SSS and PBCH may be included in a synchronization signal block (SSB).

The UEs <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> may receive the unified synchronization signals or SS blocks, derive the carrier frequency and slot timing from the synchronization signals, and in response to deriving timing, transmit an uplink pilot or reference signal. The uplink pilot signal transmitted by a UE (e.g., UE <NUM>) may be concurrently received by two or more cells (e.g., base stations <NUM> and <NUM>/<NUM>) within the radio access network <NUM>. Each of the cells may measure a strength of the pilot signal, and the radio access network (e.g., one or more of the base stations <NUM> and <NUM>/<NUM> and/or a central node within the core network) may determine a serving cell for the UE <NUM>. As the UE <NUM> moves through the radio access network <NUM>, the network may continue to monitor the uplink pilot signal transmitted by the UE <NUM>. When the signal strength or quality of the pilot signal measured by a neighboring cell exceeds that of the signal strength or quality measured by the serving cell, the network <NUM> may handover the UE <NUM> from the serving cell to the neighboring cell, with or without informing the UE <NUM>.

The use of zones in <NUM> networks or other next-generation communication networks enables the uplink-based mobility framework and improves the efficiency of both the UE and the network, since the number of mobility messages that need to be exchanged between the UE and the network may be reduced.

In various implementations, the air interface in the radio access network <NUM> may utilize licensed spectrum, unlicensed spectrum, or shared spectrum. Licensed spectrum provides for exclusive use of a portion of the spectrum, generally by virtue of a mobile network operator purchasing a license from a government regulatory body. Unlicensed spectrum provides for shared use of a portion of the spectrum without need for a government-granted license. While compliance with some technical rules is generally still required to access unlicensed spectrum, generally, any operator or device may gain access. Shared spectrum may fall between licensed and unlicensed spectrum, wherein technical rules or limitations may be required to access the spectrum, but the spectrum may still be shared by multiple operators and/or multiple RATs. For example, the holder of a license for a portion of licensed spectrum may provide licensed shared access (LSA) to share that spectrum with other parties, e.g., with suitable licensee-determined conditions to gain access.

The air interface in the radio access network <NUM> may utilize one or more duplexing algorithms. Duplex refers to a point-to-point communication link where both endpoints can communicate with one another in both directions. Full duplex means both endpoints can simultaneously communicate with one another. Half duplex means only one endpoint can send information to the other at a time. In a wireless link, a full duplex channel generally relies on physical isolation of a transmitter and receiver, and suitable interference cancellation technologies. Full duplex emulation is frequently implemented for wireless links by utilizing frequency division duplex (FDD) or time division duplex (TDD). In FDD, transmissions in different directions operate at different carrier frequencies. In TDD, transmissions in different directions on a given channel are separated from one another using time division multiplexing. That is, at some times the channel is dedicated for transmissions in one direction, while at other times the channel is dedicated for transmissions in the other direction, where the direction may change very rapidly, e.g., several times per slot.

In some aspects of the disclosure, the scheduling entity and/or scheduled entity may be configured for beamforming and/or multiple-input multiple-output (MIMO) technology. For example, the scheduling entity may be a base station, eNB. <FIG> illustrates an example of a wireless communication system <NUM> supporting MIMO. In a MIMO system, a transmitter <NUM> includes multiple transmit antennas <NUM> (e.g., N transmit antennas) and a receiver <NUM> includes multiple receive antennas <NUM> (e.g., M receive antennas). Thus, there are N × M signal paths <NUM> from the transmit antennas <NUM> to the receive antennas <NUM>. Each of the transmitter <NUM> and the receiver <NUM> may be implemented, for example, within a scheduling entity <NUM>, a scheduled entity <NUM>, or any other suitable wireless communication device.

The use of such multiple antenna technology enables the wireless communication system to exploit the spatial domain to support spatial multiplexing, beamforming, and transmit diversity. Spatial multiplexing may be used to transmit different streams of data, also referred to as layers, simultaneously on the same time-frequency resource. The data streams may be transmitted to a single UE to increase the data rate or to multiple UEs to increase the overall system capacity, the latter being referred to as multi-user MIMO (MU-MIMO). This is achieved by spatially precoding each data stream (i.e., multiplying the data streams with different weighting and phase shifting) and then transmitting each spatially precoded stream through multiple transmit, antennas on the downlink. The spatially precoded data streams arrive at the UE(s) with different spatial signatures, which enables each of the UE(s) to recover the one or more data streams destined for that UE. On the uplink, each UE transmits a spatially precoded data stream, which enables the base station to identify the source of each spatially precoded data stream.

In Time Division Duplex (TDD) systems, the UL and DL are reciprocal, in that each uses different time slots of the same frequency bandwidth. Therefore, in TDD systems, the base station may transmit the Channel State Information Reference Signal (CSI-RS) with separate C-RS sequences for each layer to provide for multi-layer channel estimation. From the CSI-RS, the UE may measure the channel quality across layers and resource blocks.

In order for transmissions over the radio access network <NUM> to obtain a low block error rate (BLER) while still achieving very high data rates, channel coding may be used. That is, wireless communication may generally utilize a suitable error correcting block code. In a typical block code, an information message or sequence is split up into code blocks (CBs), and an encoder (e.g., a CODEC) at the transmitting device then mathematically adds redundancy to the information message. Exploitation of this redundancy in the encoded information message can improve the reliability of the message, enabling correction for any bit errors that may occur due to the noise.

In the developing <NUM> NR specifications, user data may be coded using quasicyclic low-density parity check (LDPC) with two different base graphs: one base graph is used for large code blocks and/or high code rates, while the other base graph is used otherwise. Control information and the physical broadcast channel (PBCH) are coded using Polar coding, based on nested sequences. For these channels, puncturing, shortening, and repetition are used for rate matching.

However, those of ordinary skill in the art will understand that aspects of the present disclosure may be implemented utilizing any suitable channel code. Various implementations of scheduling entities <NUM> and scheduled entities <NUM> may include suitable hardware and capabilities (e.g., an encoder, a decoder, and/or a CODEC) to utilize one or more of these channel codes for wireless communication.

Referring back to <FIG>, the air interface in the radio access network <NUM> may utilize one or more multiplexing and multiple access algorithms to enable simultaneous communication of the various devices. For example, <NUM> NR specifications provide multiple access for UL transmissions from UEs <NUM> and <NUM> to base station <NUM>, and for multiplexing for DL transmissions from base station <NUM> to one or more UEs <NUM> and <NUM>, utilizing orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP). In addition, for UL transmissions, <NUM> NR specifications provide support for discrete Fourier transform-spread-OFDM (DFT-s-OFDM) with a CP (also referred to as single-carrier FDMA (SC-FDMA)). However, within the scope of the present disclosure, multiplexing and multiple access are not limited to the above schemes, and may be provided utilizing time division multiple access (TDMA), code division multiple access (CDMA), frequency division multiple access (FDMA), sparse code multiple access (SCMA), resource spread multiple access (RSMA), or other suitable multiple access schemes. Further, multiplexing DL transmissions from the base station <NUM> to UEs <NUM> and <NUM> may be provided utilizing time division multiplexing (TDM), code division multiplexing (CDM), frequency division multiplexing (FDM), orthogonal frequency division multiplexing (OFDM), sparse code multiplexing (SCM), or other suitable multiplexing schemes.

In some aspects of the disclosure, <NUM> networks may support carrier aggregation of a primary cell (PCell) and one or more secondary cells (SCells). In some examples, the PCell may use sub-<NUM> carriers, and the SCells may use above-<NUM> carriers (e.g., mmW carriers). In one example, the PCell may be an LTE cell, and the SCells may be <NUM> cells. The PCell and SCells may be implemented using the RAN <NUM>.

Various aspects of the present disclosure will be described with reference to an OFDM waveform, schematically illustrated in <FIG>. It should be understood by those of ordinary skill in the art that the various aspects of the present disclosure may be applied to a DFT-s-OFDMA waveform in substantially the same way as described hereinbelow. That is, while some examples of the present disclosure may focus on an OFDM link for clarity, it should be understood that the same principles may be applied as well to DFT-s-OFDMA waveforms and other types of OFDMA waveforms.

Within the present disclosure, a frame refers to a predetermined duration (e.g., <NUM>) for wireless transmissions, with each frame consisting of a predetermined number of subframes (e.g., <NUM> subframes of <NUM> each). On a given carrier, there may be one set of frames in the UL, and another set of frames in the DL. Referring now to <FIG>, an expanded view of an exemplary DL subframe <NUM> is illustrated, showing an OFDM resource grid <NUM>. However, as those skilled in the art will readily appreciate, the PHY transmission structure for any particular application may vary from the example described here, depending on any number of factors. Here, time is in the horizontal direction with units of OFDM symbols; and frequency is in the vertical direction with units of subcarriers or tones.

The resource grid <NUM> may be used to schematically represent time-frequency resources for a given antenna port. That is, in a MIMO and/or beamforming implementation with multiple antenna ports available, a corresponding multiple number of resource grids <NUM> may be available for communication. The resource grid <NUM> is divided into multiple resource elements (REs) <NUM>. An RE, which is <NUM> subcarrier × <NUM> symbol, is the smallest discrete part of the time-frequency grid, and contains a single complex value representing data from a physical channel or signal. Depending on the modulation utilized in a particular implementation, each RE may represent one or more bits of information. In some examples, a block of REs may be referred to as a physical resource block (PRB) or more simply a resource block (RB) <NUM>, which contains any suitable number of consecutive subcarriers in the frequency domain. In one example, an RB may include <NUM> subcarriers, a number independent of the numerology used. In some examples, depending on the numerology, an RB may include any suitable number of consecutive OFDM symbols in the time domain. Within the present disclosure, it is assumed that a single RB such as the RB <NUM> entirely corresponds to a single direction of communication (either transmission or reception for a given device).

A UE generally utilizes only a subset of the resource grid <NUM>. An RB may be the smallest unit of resources that can be allocated to a UE. Thus, the more resource blocks (RBs) scheduled for a UE, and the higher the modulation scheme chosen for the air interface, the higher the data rate for the UE.

Each subframe <NUM> (e.g., <NUM> subframe) may consist of one or multiple adjacent slots. In the example shown in <FIG>, one subframe <NUM> includes four slots <NUM>, as an illustrative example. In some examples, a slot may be defined according to a specified number of OFDM symbols with a given cyclic prefix (CP) length. For example, a slot may include <NUM> or <NUM> OFDM symbols with a nominal CP. Additional examples may include mini-slots having a shorter duration (e.g., <NUM>, <NUM>, <NUM>, or <NUM> OFDM symbols). These mini-slots may in some cases be transmitted occupying resources scheduled for ongoing slot transmissions for the same or for different UEs.

An expanded view of one of the slots <NUM> illustrates the slot <NUM> including a control region <NUM> and a data region <NUM>. In general, the control region <NUM> may carry control channels (e.g., PDCCH), and the data region <NUM> may carry data channels (e.g., PDSCH or PUSCH). Of course, a slot may contain all DL, all UL, or at least one DL portion and at least one UL. The simple structure illustrated in <FIG> is merely exemplary in nature, and different slot structures may be utilized, and may include one or more of each of the control region(s) and data region(s).

Although not illustrated in <FIG>, the various REs <NUM> within an RB <NUM> may be scheduled to cany one or more physical channels, including control channels, shared channels, data channels, etc. Other REs <NUM> within the RB <NUM> may also carry pilots or reference signals. These pilots or reference signals may provide for a receiving device to perform channel estimation of the corresponding channel, which may enable coherent demodulation/detection of the control and/or data channels within the RB <NUM>.

In a DL transmission, the transmitting device (e.g., the scheduling entity <NUM>) may allocate one or more REs <NUM> (e.g., within a control region <NUM>) to carry DL control information <NUM> including one or more DL control channels that generally carry information originating from higher layers, such as a physical broadcast channel (PBCH), a physical downlink control channel (PDCCH), etc., to one or more scheduled entities <NUM>. In addition, DL REs may be allocated to carry DL physical signals that generally do not carry information originating from higher layers. These DL physical signals may include a primary synchronization signal (PSS); a secondary synchronization signal (SSS); demodulation reference signals (DM-RS); phase-tracking reference signals (PT-RS); channel-state information reference signals (CSI-RS); etc..

The synchronization signals PSS and SSS (collectively referred to as SS), and in some examples, the PBCH, may be transmitted in an SSB that includes <NUM> consecutive OFDM symbols, numbered via a time index in increasing order from <NUM> to <NUM>. In the frequency domain, the SSB may extend over <NUM> contiguous subcarriers, with the subcarriers being numbered via a frequency index in increasing order from <NUM> to <NUM>. Of course, the present disclosure is not limited to this specific SSB configuration. Other nonlimiting examples may utilize greater or fewer than two synchronization signals: may include one or more supplemental channels in addition to the PBCH; may omit a PBCH; and/or may utilize nonconsecutive symbols for an SSB, within the scope of the present disclosure.

The PDCCH may carry downlink control information (DCI) for one or more UEs in a cell. This can include, but is not limited to, power control commands, scheduling information, a grant, and/or an assignment of REs for DL and UL transmissions.

In an UL transmission, a transmitting device (e.g., a scheduled entity <NUM>) may utilize one or more REs <NUM> to cany UL control information <NUM> (UCI). The UCI can originate from higher layers via one or more UL control channels, such as a physical uplink control channel (PUCCH), a physical random access channel (PRACH), etc., to the scheduling entity <NUM>. Further, UL REs may carry UL physical signals that generally do not carry information originating from higher layers, such as demodulation reference signals (DM-RS), phase-tracking reference signals (PT-RS), sounding reference signals (SRS), etc. In some examples, the control information <NUM> may include a scheduling request (SR), i.e., a request for the scheduling entity <NUM> to schedule uplink transmissions. Here, in response to the SR transmitted on the control channel <NUM>, the scheduling entity <NUM> may transmit downlink control information <NUM> that may schedule resources for uplink packet transmissions.

UL control information may also include hybrid automatic repeat request (HARQ) feedback such as an acknowledgment (ACK) or negative acknowledgment (NACK), channel state information (CSI), or any other suitable UL control information. HARQ is a technique well-known to those of ordinary skill in the art, wherein the integrity of packet transmissions may be checked at the receiving side for accuracy, e.g., utilizing any suitable integrity checking mechanism, such as a checksum or a cyclic redundancy check (CRC). If the integrity of the transmission confirmed, an ACK may be transmitted, whereas if not confirmed, a NACK may be transmitted. In response to a NACK, the transmitting device may send a HARQ retransmission, which may implement chase combining, incremental redundancy, etc..

In addition to control information, one or more REs <NUM> (e.g., within the data region <NUM>) may be allocated for user data or traffic data. Such traffic may be carried on one or more traffic channels, such as, for a DL transmission, a physical downlink shared channel (PDSCH); or for a UL transmission, a physical uplink shared channel (PUSCH).

In order for a UE to gain initial access to a cell, the RAN may provide system information (SI) characterizing the cell. This system information may be provided utilizing minimum system information (MSI), and other system information (OSI). The MSI may be periodically broadcast over the cell to provide the most basic information required for initial cell access, and for acquiring any OSI that may be broadcast periodically or sent on-demand. In some examples, the MSI may be provided over two different downlink channels. For example, the PBCH may carry a master information block (MIB), and the PDSCH may carry a system information block type <NUM> (SIB1). In the art, SIB1 may be referred to as the remaining minimum system information (RMSI).

OSI may include any SI that is not broadcast in the MSI. In some examples, the PDSCH may carry a plurality of SIBs, not limited to SIB1, discussed above. Here, the OSI may be provided in these SIBs, e.g., SIB2 and above.

The channels or carriers described above and illustrated in <FIG> and <FIG> are not necessarily all the channels or carriers that may be utilized between a scheduling entity <NUM> and scheduled entities <NUM>, and those of ordinary skill in the art will recognize that other channels or carriers may be utilized in addition to those illustrated, such as other traffic, control, and feedback channels.

<FIG> is a block diagram illustrating an example of a hardware implementation for a scheduling entity <NUM> employing a processing system <NUM>. For example, the scheduling entity <NUM> may be a user equipment (UE) as illustrated in any one or more of <FIG>, <FIG>, <FIG>, and/or <NUM>. In another example, the scheduling entity <NUM> may be a base station as illustrated in any one or more of <FIG>, <FIG>, <FIG> and/or <NUM>.

The scheduling entity <NUM> may be implemented with a processing system <NUM> that includes one or more processors <NUM>. Examples of processors <NUM> include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. In various examples, the scheduling entity <NUM> may be configured to perform any one or more of the functions described herein. That is, the processor <NUM>, as utilized in a scheduling entity <NUM>, may be used to implement any one or more of the processes and procedures described below and illustrated in <FIG>.

In this example, the processing system <NUM> may be implemented with a bus architecture, represented generally by the bus <NUM>. The bus <NUM> may include any number of interconnecting buses and bridges depending on the specific application of the processing system <NUM> and the overall design constraints. The bus <NUM> communicatively couples together various circuits including one or more processors (represented generally by the processor <NUM>), a memory <NUM>, and computer-readable media (represented generally by the computer-readable medium <NUM>). The bus <NUM> may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further. A bus interface <NUM> provides an interface between the bus <NUM> and a transceiver <NUM>. The transceiver <NUM> provides a communication interface or means for communicating with various other apparatus over a transmission medium. Depending upon the nature of the apparatus, a user interface <NUM> (e.g., keypad, display, speaker, microphone, joystick) may also be provided. Of course, such a user interface <NUM> is optional, and may be omitted in some examples, such as a base station.

In some aspects of the disclosure, the processor <NUM> may include circuitry, for example, UE communication circuit <NUM>, inter-cell communication circuit <NUM>, SCell configuration circuit <NUM>, and reference signal (RS) measurement circuit <NUM>, configured to implement one or more of the functions described below in relation to <FIG>. The UE communication circuit <NUM> may be configured to perform various communication-related functions (e.g., UL communication and DL communication) between the scheduling entity <NUM> and one or more UEs or scheduled entities. The inter-cell communication circuit <NUM> may be configured to perform various communication-related functions (e.g., backhaul communication) between a PCell and an SCell. The SCell configuration circuit <NUM> may be configured to perform various SCell configuration functions, for example, reference signal configuration of an SCell. The RS measurement circuit <NUM> may be configured to control and configure RS measurement configuration of a reference signal of an SCell.

One or more processors <NUM> in the processing system may execute software. The software may reside on a computer-readable medium <NUM>. The computer-readable medium <NUM> may be a non-transitory computer-readable medium. A non-transitory computer-readable medium includes, by way of example, a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip), an optical disk (e.g., a compact disc (CD) or a digital versatile disc (DVD)), a smart card, a flash memory device (e.g., a card, a stick, or a key drive), a random access memory (RAM), a read-only memory (ROM), a programmable ROM (PROM), an erasable PROM (EPROM), an electrically erasable PROM (EEPROM), a register, a removable disk, and any other suitable medium for storing software and/or instructions that may be accessed and read by a computer. The computer-readable medium <NUM> may reside in the processing system <NUM>, external to the processing system <NUM>, or distributed across multiple entities including the processing system <NUM>. The computer-readable medium <NUM> may be embodied in a computer program product. By way of example, a computer program product may include a computer-readable medium in packaging materials. Those skilled in the art will recognize how best to implement the described functionality presented throughout this disclosure depending on the particular application and the overall design constraints imposed on the overall system.

In one or more examples, the computer-readable storage medium <NUM> may include software (e.g., UE communication instructions <NUM>, inter-cell communication instructions <NUM>, SCell configuration instructions <NUM>, and RS measurement configuration instructions <NUM>) configured to implement one or more of the functions described above in relation to <FIG>. The UE communication instructions <NUM> may configure the processor <NUM> to perform various communication-related functions (e.g., UL communication and DL communication) between the scheduling entity <NUM> and one or more scheduled entities (e.g., UEs). The inter-cell communication instructions <NUM> may configure the processor <NUM> to perform various communication-related functions (e.g., backhaul communication) between a PCell and an SCell. The SCell configuration instructions <NUM> may configure the processor <NUM> to perform various SCell configuration functions, for example, reference signal configuration of an SCell. The RS measurement configuration instructions <NUM> may configure the processor <NUM> to control and configure RS measurement configuration of a reference signal of an SCell.

<FIG> is a conceptual diagram illustrating an example of a hardware implementation for an exemplary scheduled entity <NUM> employing a processing system <NUM>. In accordance with various aspects of the disclosure, an element, or any portion of an element, or any combination of elements may be implemented with a processing system <NUM> that includes one or more processors <NUM>. For example, the scheduled entity <NUM> may be a UE as illustrated in any one or more of <FIG>, <FIG>, <FIG> and/or <NUM>.

The processing system <NUM> may be substantially the same as the processing system <NUM> illustrated in <FIG>, including a bus interface <NUM>, a bus <NUM>, memory <NUM>, a processor <NUM>, and a computer-readable medium <NUM>. Furthermore, the scheduled entity <NUM> may include a user interface <NUM> and a transceiver <NUM> substantially similar to those described above in <FIG>. That is, the processor <NUM>, as utilized in a scheduled entity <NUM>, may be used to implement any one or more of the processes described below and illustrated in relation to <FIG>.

In some aspects of the disclosure, the processor <NUM> may include circuitry, for example, communication circuit <NUM>, reference signal (RS) measurement circuit <NUM>, and carrier aggregation circuit <NUM>, configured to implement one or more of the functions described below in relation to <FIG>. The communication circuit <NUM> may be configured to perform various communication-related functions (e.g., UL communication and DL communication) between the scheduled entity <NUM> and a scheduling entity (e.g., PCell or SCell). The RS measurement circuit <NUM> may be configured to perform various reference signal measurement functions, for example, measuring and reporting reference signals of a PCell and an SCell. The carrier aggregation circuit <NUM> may be configured to perform various carrier aggregation related functions, for example, aggregating carriers from a PCell and an SCell.

In one or more examples, the computer-readable storage medium <NUM> may include software (e.g., communication instructions <NUM>, RS measurement instructions <NUM>, and carrier aggregation instructions <NUM>) configured to implement one or more of the functions described above in relation to <FIG>. The communication instructions <NUM> may configure the processor <NUM> to perform various communication-related functions (e.g., UL communication and DL communication) between the scheduled entity <NUM> and a scheduling entity (e.g., PCell or SCell). The RS measurement instructions <NUM> may configure the processor <NUM> to perform various reference signal measurement functions, for example, measuring and reporting reference signals of a PCell and an SCell. The carrier aggregation instructions <NUM> may configure the processor <NUM> to perform various carrier aggregation related functions, for example, aggregating carriers from a PCell and an SCell.

<FIG> is a diagram illustrating a carrier aggregation (CA) scenario in accordance with some aspects of the present disclosure. A UE <NUM> is located in a primary cell (PCell) <NUM> controlled by a first base station <NUM>. The first base station <NUM> is associated with a second base station <NUM> that controls a secondary cell (SCell) <NUM>. The UE <NUM> may be any of the UEs illustrated in <FIG>, <FIG>, and/or <NUM>. The first base station <NUM> and second base station <NUM> may be any of the base stations or scheduling entities illustrated in <FIG>, <FIG>, and/or <NUM>. In some examples, the PCell <NUM> and SCell <NUM> form a <NUM> hybrid RAN. The first base station <NUM> may communicate with the UE <NUM> using one or more sub-<NUM> carriers, and the second base station <NUM> may communicate with the UE <NUM> using one or more carriers above <NUM> (e.g., millimeter wave (mmW) carriers). When using above-<NUM> frequency (e.g., mmW) carriers, the second base station <NUM> may use beamforming to transmit and receive signals. In some examples, the first base station <NUM> and the second base station <NUM> may be co-located.

Using carrier aggregation (CA) can increase per user and system throughput in a network. In a hybrid <NUM> network example, CA may involve the aggregation of a carrier from the PCell and a mmW carrier from the SCell. Initially, the UE <NUM> is connected with the first base station <NUM>, and search for a potential SCell that uses a mmW carrier. To facilitate CA, the second base station <NUM> periodically transmits reference signals via different beams <NUM> for initial beam selection. In one aspect of the disclosure, the reference signal (RS) <NUM> may be a Channel State Information Reference Signal (CSI-RS) or synchronization signal block (SSB). If the UE <NUM> is located near the edge of the SCell <NUM> and/or unable to receive the RS <NUM> due to various reasons (e.g., interference, insufficient signal strength, etc.), the UE <NUM> cannot detect the RS and select the best beam transmitted by the SCell <NUM> based on the RS.

Aspects of the present disclosure provide various procedures, apparatuses, and methods for extending the coverage of a reference signal (RS) transmitted by an SCell. In some examples, a PCell may trigger an SCell to boost the RS range by using higher gain beams and/or RS repetitions. The RS range refers to the range or distance that an RS may reach and be detected by a receiver (e.g., UE).

<FIG> is a diagram illustrating an example of RS coverage extension procedure using higher gain beams in accordance with some aspects of the present disclosure. A UE <NUM> is located in a primary (PCell) <NUM> controlled by a first base station <NUM>. The first base station <NUM> is associated with a second base station <NUM> that controls a secondary cell (SCell) <NUM>. The UE <NUM> may be any of the UEs illustrated in <FIG>, <FIG>, and/or <NUM>. The first base station <NUM> and second base station <NUM> may be any of the base stations and scheduling entities illustrated in <FIG>, <FIG>, and/or <NUM>. In some examples, the first base station <NUM> and the second base station <NUM> may be co-located. The second base station <NUM> may transmit an RS in a plurality of beams using beamforming like that shown in <FIG>.

The PCell <NUM> configures the UE <NUM> to detect a beam from the SCell <NUM> for potential CA. For example, the PCell <NUM> transmits a measurement request <NUM> to the UE <NUM> to measure a reference signal (RS) from the SCell <NUM>. In beamforming applications, the PCell <NUM> may configure the UE to measure one or more beams including the reference signal. The UE <NUM> performs the measurements and reports that to the base station <NUM> of the PCell. Based on the UE's measurement report <NUM>, the PCell (e.g., base station <NUM>) can determine whether or not the UE can receive the reference signal from the SCell <NUM> with sufficient quality to support CA. If needed, the PCell (i.e., first base station <NUM>) may trigger the SCell (e.g., second base station <NUM>) via a wired or wireless backhaul connection to boost or extend the range of its RS by using higher gain beams. For example, the SCell may transmit its RS <NUM> using beams <NUM> that are narrower than the beams <NUM> (see <FIG>) to provide a higher peak gain. The SCell may transmit its RS <NUM> using the beams <NUM> in turn to sweep the beams in multiple directions. In some examples, the SCell may transmit the RS <NUM> on multiple beams <NUM> simultaneously. Using higher gain beams, the SCell can extend the RS range such that it is more likely that the UE <NUM> can detect a beam from the SCell <NUM>.

<FIG> is a diagram illustrating an example of RS coverage extension procedure using repetition in accordance with some aspects of the present disclosure. A UE <NUM> is be located in a primary cell (PCell) <NUM> controlled by a first base station <NUM>. The first base station <NUM> is associated with a second base station <NUM> that controls a secondary cell (SCell) <NUM>. The UE <NUM> may be any of the UEs illustrated in <FIG>, <FIG>, and/or <NUM>. The first base station <NUM> and second base station <NUM> may be any of the base stations and scheduling entities illustrated in <FIG>, <FIG>, and/or <NUM>. The second base station <NUM> may transmit an RS in one or more beams using beamforming. In some examples, the first base station <NUM> and second base station <NUM> may be co-located.

The PCell <NUM> configures the UE <NUM> to detect a beam from the SCell <NUM> for potential CA. For example, the PCell <NUM> transmits a measurement request <NUM> to the UE <NUM> to measure a reference signal from the SCell <NUM>. In beamforming applications, the PCell <NUM> may configure the UE to measure one or more beams carrying the reference signal. The UE <NUM> performs the measurements and reports that to the base station <NUM> of the PCell. Based on the UE's measurement report <NUM>, the PCell (e.g., base station <NUM>) can determine whether or not the UE can receive the reference signal from the SCell <NUM> with sufficient quality to support CA. If needed, the PCell (e.g., first base station <NUM>) may trigger the SCell (e.g., second base station <NUM>) to boost or extend the range of its RS by using repetition. For example, the PCell may instruct the SCell to transmit its RS in one or more beams with a predetermined repetition (e.g., <NUM> or more RS repetition in each beam). To that end, the PCell informs the UE <NUM> the repetition pattern, repetition number, and time-frequency resources assigned to the repeated RS so that the UE can receive and combine the repeated RS transmissions to increase the likelihood that the UE can detect the best beam carrying the RS. For example, the first base station <NUM> may provide the repetition information to the UE using an RRC message and/or downlink control information (DCI).

In addition to repeating the RS using a same beam, the RS repetition can also use different beams that are quasi-collocated with a reference beam <NUM>. In an example illustrated in <FIG>, each quasi-collocated beam <NUM> for the repetition has a narrower beam width than the corresponding reference beam <NUM>, and different beams for the repetition are pointed to different directions within the beam width of the reference beam. Therefore, the RS is repeated across different narrower beams <NUM> within the angular range of the wider reference beam <NUM>. Due to the higher gain of each narrow beam, the UE may detect the RS from one of the narrow beams before the end of RS repetition.

<FIG> is a diagram illustrating a procedure <NUM> for extending a reference signal coverage of a cell in accordance with some aspects of the disclosure. In some examples, the process <NUM> may be used to extend the RS coverage of a secondary cell. In some examples, the process <NUM> may be carried out by any suitable apparatus or means for carrying out the functions or algorithm described below.

At block <NUM>, a primary cell (PCell) configures a UE to measure a reference signal of the PCell. Referring to <FIG>, for example, a PCell transmits a PCell measurement configuration message <NUM> to configure the UE to measure the channel quality of the PCell. In some examples, the PCell may communicate with the UE using a carrier frequency below <NUM> (sub-<NUM>), and the SCell may communicate with the UE using a carrier frequency above <NUM> (e.g., mmW carrier). Based on the PCell measurement configuration message <NUM>, the UE measures, for example at <NUM>, PCell's reference signal (e.g., CSI-RS or SSB). After measuring the PCell, the UE transmits a PCell measurement report <NUM> back to the PCell. In some examples, the PCell measurement report <NUM> may include a reference signal received power (RSRP) or reference signal received quality (RSRQ) of the reference signal (e.g., CSI-RS or SSB), and/or other channel state information (CSI).

In some aspects of the disclosure, the UE may transmit the PCell measurement report <NUM> using a layer <NUM> report or layer <NUM> report. Layer <NUM> and layer <NUM> refer to the protocol stack layers used in communication. Layer <NUM> may include the physical layer, and layer <NUM> may include the RRC layer. In one example, a layer <NUM> report may be a periodic, semiperiodic, or aperiodic physical layer report. In one example, a layer <NUM> report may be an event triggered report (e.g., an event A1) that is triggered when the serving cell's channel quality becomes better than a certain threshold.

Referring back to <FIG>, at decision block <NUM>, the PCell uses the reported PCell measurements (e.g., CSI-RSRP or SS-RSRP) to determine whether or not the UE is potentially in the SCell's coverage area. If the base stations of the PCell and SCell are co-located or in close proximity to each other, the PCell uses the reported PCell measurements to determine the potential that the UE is in the SCell's coverage area. In one example, if the reported CSI-RSRP or SS-RSRP is above a predetermined threshold value, the PCell may determine that the UE is in the SCell's coverage area. When the UE is in the SCell's coverage area, the UE can communicate with the SCell's scheduling entity or base station.

If the PCell determined that the UE is potentially in the SCell's coverage area, at block <NUM>, the PCell configures the UE to measure the SCell's reference signals to confirm that the UE is in the SCell's coverage. Referring to <FIG>, for example, the PCell transmits an SCell measurement configuration message <NUM> to configure the UE to measure the channel quality of the SCell. Based on the SCell measurement configuration message <NUM>, at block <NUM>, the UE detects and measures, for example, the SCell's reference signal <NUM> (e.g., CSI-RS or SSB). Then, the UE transmits an SCell measurement report <NUM> back to the PCell such that the PCell can determine whether the SCell can be used for CA by the UE. For example, the SCell measurement report <NUM> may include the RSRP and/or RSRQ of the SCell's reference signal (e.g., CSI-RS or SSB), and/or other CSI. The UE may transmit the SCell measurement report <NUM> using a layer <NUM> (L1) or layer <NUM> (L3) report.

Referring back to <FIG>, at decision block <NUM>, the PCell decides whether or not to extend the SCell's RS range. For example, if the reported SCell reference signal quality (e.g., CSI-RSRP or SS-RSRP) is below a threshold value, or the UE transmitted no SCell measurement report at all for event triggered measurements, the PCell transmits an RS range boost message <NUM> (see <FIG>) to trigger the SCell to extend or boost its RS range from a nominal range to an extended range. In some aspects of the disclosure, the PCell may configure the SCell, via a wireless or wired backhaul connection, to extend its RS range using a higher gain beam as described above in relation to <FIG> and/or using RS repetition as described above in relation to <FIG>.

If the PCell extended SCell RS range, at block <NUM>, the PCell configures the UE to measure the SCell's range extended RS. Referring to <FIG>, for example, the PCell transmits an extended RS measurement configuration <NUM> to configure the UE to measure (block <NUM>) the range extended RS from the SCell. The extended RS measurement configuration <NUM> may include RS repetition pattern and/or RS measurement metric. Then, the UE may report the measurements to the PCell using an L1 or L3 report (e.g., Extended RS measurement report <NUM>). In one example, if the quality of the extended RS (e.g., CSI-RSRP or SS-RSRP) measured by the UE is still below a threshold value, or the UE reports no SCell measurement report for event triggered measurements, the PCell may instruct the SCell to further boost the RS range and request the UE to measure the boosted RS again. In another example, the PCell may request the UE to measure the SCell's RS again when the UE reports higher PCell signal quality (e.g., higher CSI-RSRP or SS-RSRP).

<FIG> is a diagram illustrating an exemplary reference signal (RS) repetition pattern in accordance with some aspects of the disclosure. In some examples, this RS repetition pattern may be used to extend a reference signal of the SCell as described in relation to <FIG> above. In one particular example, the reference signal may be a CSI-RS or SSB. Four exemplary centralized CSI-RS resource sets <NUM>, <NUM>, <NUM>, and <NUM> are shown in <FIG>. Each centralized CSI-RS resource set includes certain time-frequency resources similar to the resource elements (REs) <NUM> described above in relation to <FIG>.

A CSI-RS <NUM> may be repeated one or more times in each CSI-RS resource set. Two exemplary REs allocated to CSI-RS <NUM> are illustrated in <FIG>. In other examples, two or more REs may be allocated to CSI-RS repetition in each CSI-RS resource set. In one aspect of the disclosure, an SCell may use a fixed transmit (Tx) beam for all CSI-RS resources within a CSI-RS resource set. In some examples, all resources in the resource set may have the same time-frequency allocation size and may be configured with the same periodicity. In one aspect of the disclosure, all four CSI-RS resource sets <NUM>, <NUM>, <NUM>, and <NUM> correspond to the same TX beam. For example, an SCell may transmit the CSI-RS in all four CSI-RS resource sets using the same TX beam.

In one aspect of the disclosure, a PCell may define a measurement metric for the RS per CSI-RS resource set instead of per resource (e.g., RE). The PCell may inform the UE the CSI-RS repetition pattern and measurement metric, for example, in an extended RS measurement configuration <NUM> (see <FIG>). With the knowledge of the RS repetition and measurement metric, the UE can measure and report the CSI-RS back to the PCell. For example, the RS repetition pattern may indicate the specific REs allocated to repeat CSI-RS per CSI-RS resource set.

In one example, the measurement metric of a repeated CSI-RS may include the reference signal received power (RSRP) of a CSI-RS resource set that is determined as the RSRP over all resources in the same resource set. In another example, the measurement metric of a repeated CSI-RS may include the signal-to-interference-plusnoise ratio (SINR) of a CSI-RS resource set that is determined as the linearly summed RSRP over all resources in the resource set divided by the linearly averaged noise plus interference power over all resources in the same CSI-RS resource set.

In another example, the measurement metric of a repeated CSI-RS may include the relative received signal strength indication (RSSI) of a CSI-RS resource set that is determined as the linearly averaged RSSI over all resources in the same CSI-RS resource set.

In another example, the measurement metric of a repeated CSI-RS may include the reference signal received quality (RSRQ) of a CSI-RS resource set that is determined as:
<MAT> where N is the number of RBs in the RSSI measurement bandwidth.

The UE may report the CSI-RS measurements using a layer (L1) or layer <NUM> (L3) report (e.g., an extended RS measurement report <NUM> of <FIG>). If the UE transmits an L3 report, the UE may apply L3 filtering to each metric per CSI-RS resource set. For example, L3 filtering may apply a rolling average to the measurements. L3 filtering averages raw measurements in a certain time window, to reflect long-term cell quality by smoothing short-term variations, e.g., due to fading. Averaged CSI-RS measurements may be more suitable for cell selection purpose.

In another example, the measurement metric of a repeated CSI-RS may include a rank indicator, preceding matrix indicator (PMI), and/or channel quality indicator (CQI) per layer (e.g., MIMO layer) that can be determined based on a channel matrix linearly averaged over all resources in a CSI-RS resource set.

In another example, the measurement metric of a repeated CSI-RS may include a rank indicator, PMI, and/or CQI per layer that can be determined based on a channel matrix per resource, and then further linearly averaged over all resources in a CSI-RS resource set.

In the above measurement metric examples, a "linearly averaged" operation may be replaced with a linearly summed operation, or choosing a maximum or minimum of the measured values.

<FIG> is a diagram illustrating another exemplary reference signal repetition pattern <NUM> in accordance with some aspects of the disclosure. In some examples, an SCell may use this repetition pattern <NUM> to extend the range of a reference signal as described above in relation to <FIG>. In one particular example, the repeated reference signal may be a CSI-RS or SSB. Eight exemplary CSI-RS resource sets <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are shown in <FIG>. Each resource set includes certain time-frequency resources similar to the resource elements (REs) <NUM> shown in <FIG>.

In one aspect of the disclosure, an SCell may repeat a reference signal (e.g., CSI-RS) using a fixed Tx beam that is distributed across multiple resource sets. That is, CSI-RS repetition may be performed per fixed Tx beam that corresponds to a subset of resources per CSI-RS resource set, and is distributed across multiple resource sets. For example, referring to <FIG>, Tx beam <NUM> is repeated over a subset <NUM> in a first set of CSI-RS resource set and a subset <NUM> of a second set of CSI-RS resource set. The subsets <NUM> and <NUM> are not adjacent to each other. Similarly, Tx beam <NUM> is repeated over a subset <NUM> in the first set of CSI-RS resource set and a subset <NUM> of the second set of CSI-RS resource set. Tx beam <NUM> and Tx beam <NUM> may be repeated in a similar fashion. In some examples, all resources (e.g., REs) per beam and across beams may have the same time-frequency allocation size.

In one example, a UE located near an SCell may not need CSI-RS repetition, and hence may only wake up in one resource set periodically to get a full beam sweep measurement. For example, the UE can wake up only in the first set <NUM> or second set <NUM> of CSI-RS resource set.

In one aspect of the disclosure, a PCell may define a measurement metric per Tx beam index, instead of per resource (e.g., RE). The PCell may inform the UE the CSI-RS repetition pattern and measurement metric, for example, in an extended RS measurement configuration <NUM> (see <FIG>).

In one example, the measurement metric of a repeated CSI-RS may include the RSRP of resources corresponding to a Tx beam index (e.g., Tx beam <NUM>, Tx beam <NUM>, Tx beam <NUM>, and Tx beam <NUM>) that is determined as the linearly summed RSRP over all resources of the same beam.

In another example, the measurement metric of a repeated CSI-RS may include the SINR of resources corresponding to a Tx beam index that is determined as the linearly summed RSRP over all resources of a Tx beam index divided by the linearly averaged noise plus interference power over all resources for the same beam index. For example, the CSI-RS resources of Tx beam <NUM> (see <FIG>) include resource sets <NUM> and <NUM>, the CSI-RS resources of Tx beam <NUM> include resource sets <NUM> and <NUM>, the CSI-RS resources of Tx beam <NUM> include resource sets <NUM> and <NUM>, and the CSI-RS resources of Tx beam <NUM> include resource sets <NUM> and <NUM>.

In another example, the measurement metric of a repeated CSI-RS may include the RSSI of resources corresponding to a Tx beam index that is determined as the linearly averaged RSSI over all resources for the same Tx beam index.

In another example, the measurement metric of a repeated CSI-RS may include the RSRQ of resources corresponding to a Tx beam index that is determined as:
<MAT> where N is the number of RBs in the RSSI measurement bandwidth.

The UE may report the above described CSI-RS measurements using an L1 or L3 report (e.g., an extended RS measurement report <NUM> of <FIG>). If the UE transmits the measurements in an L3 report, the UE may apply L3 filtering to each metric per beam index. For example, L3 filtering may apply a rolling average to the measurements.

In another example, the measurement metric of a repeated CSI-RS may include a rank indicator, PMI, and CQI per layer (e.g., MIMO layer) that can be determined based on a channel matrix linearly averaged over all resources for a same Tx beam index. In another example, the measurement metric of a repeated CSI-RS may include a rank indicator, PMI, and CQI per layer that can be determined based on a channel matrix per resource, and then further linearly averaged over all resources for the same Tx beam index. In the above-described measurement metric examples, a "linearly averaged" operation may be replaced with a linearly summed operation, or choosing a maximum or minimum of the measured values.

<FIG> is a flow chart illustrating an exemplary process <NUM> operable by a primary cell for carrier aggregation in accordance with some aspects of the present disclosure. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all embodiments. In some examples, the process <NUM> may be carried out by the scheduling entity <NUM> illustrated in <FIG>. In some examples, the process <NUM> may be carried out by any suitable apparatus or means for carrying out the functions or algorithm described below.

In one particular example, the process <NUM> may be performed by a base station or scheduling entity of a PCell like a base station <NUM> of <FIG> or a base station <NUM> of <FIG>. At block <NUM>, the base station of the PCell transmits a first reference signal of the PCell. For example, the base station may use a UE communication circuit <NUM> (see <FIG>) to transmit the first reference signal via a transceiver <NUM>. In some examples, the base station of the PCell may transmit a CSI-RS or SSB as the reference signal using a sub-<NUM> carrier. In other aspects of the disclosure, the first reference signal may be a reference signal that allows a UE to estimate a wireless channel and report channel quality information back to a base station.

At block <NUM>, the base station receives a first measurement report from a UE, indicating a quality of the first reference signal. For example, the base station of the PCell may use the UE communication circuit <NUM> and transceiver <NUM> to receive the first measurement report <NUM>. The first measurement report may include a reference signal received power (RSRP) and/or reference signal received quality (RSRQ) of the first reference signal (e.g., CSI-RS or SSB), and/or other channel state information (CSI).

At block <NUM>, the base station of the PCell determines that a UE is potentially located in a coverage area of an SCell based on the quality of a first reference signal of the PCell. The base station may determine or estimate the location of the UE based on the first measurement report. For example, the base station of the PCell may use the RS measurement circuit <NUM> to process the first measurement report (e.g., measurement report <NUM> described in relation to <FIG> and <FIG>) to determine whether or not the UE is potentially located in a coverage area of the SCell. The base station of the PCell has knowledge of the SCell coverage. Therefore, the base station of the PCell can also determine whether the UE is potentially located in the coverage area of the SCell based on the first measurement report. In some examples, the base stations of the PCell and SCell are co-located.

At block <NUM>, the base station of the PCell transmits an SCell measurement configuration message for configuring the UE that is potentially located in the coverage area of the SCell, to measure a second reference signal transmitted by the SCell for initial beam selection using one or more first beams. The SCell measurement configuration message may indicate the configuration or information (e.g., allocated time-frequency resources, sequences, port, layer, etc.) of a reference signal transmitted by the SCell. For example, the base station of the SCell may transmit a reference signal (e.g., CSI-RS or SSB) on one or more mmW beams or other high frequency beams (e.g., above <NUM> beams). The base station of the PCell may use the UE communication circuit <NUM> and transceiver <NUM> to transmit an SCell measurement configuration <NUM> (see <FIG>) to configure the UE to measure the SCell's reference signal.

At block <NUM>, the base station of the PCell transmits a signal boost message for triggering the SCell to extend a range of the second reference signal from a first range to a second range, in response to determining that a quality of the second reference signal is less than a predetermined quality. In one example, the base station of the PCell may request or trigger the SCell to transmit the reference signal using a higher gain beam as described above in relation to <FIG>. In another example, the base station may request or trigger the SCell to transmit the reference signal using RS repetition as described above in relation to <FIG>. The base station of the PCell may use the SCell configuration circuit <NUM> and transceiver <NUM> to transmit a signal boost message (e.g., RS range boost message <NUM> in <FIG>) to the SCell through a wireless or wired backhaul connection. To that end, the base station of the PCell may use the UE communication circuit <NUM> to inform (e.g., transmitting an extended RS measurement configuration message <NUM>) the UE a repetition pattern of the range-extended reference signal for at least one fixed beam and a measurement metric of the range-extended reference signal. The measurement metric may be one or more of the RSSI, SINR, RSRQ, rank indicator, PMI, and/or CQI, as described above in relation to <FIG> and <FIG>.

<FIG> is a flow chart illustrating an exemplary process <NUM> for carrier aggregation (CA). As described below, some or all illustrated features may be omitted in a particular implementation, and some illustrated features may not be required. In some examples, the process <NUM> may be carried out by the scheduled entity <NUM> illustrated in <FIG>. In some examples, the process <NUM> may be carried out by any suitable apparatus or means for carrying out the functions or algorithm described below.

In one particular example, the process <NUM> may be performed by the UE <NUM> of <FIG> or UE <NUM> of <FIG> to facilitate CA across a PCell and an SCell. At block <NUM>, the UE measures a first reference signal from the PCell. For example, the first reference signal may be a CSI-RS or SSB transmitted by the PCell <NUM> or <NUM> using a sub-<NUM> carrier. The UE may use the RS measurement circuit <NUM> and/or transceiver <NUM> to receive and measure the first reference signal. In other aspects of the disclosure, the first reference signal may be a reference signal that allows the UE to estimate a wireless channel and determine the corresponding channel quality information.

At block <NUM>, the UE transmits a first measurement report of the first reference signal to the PCell. The first measurement report facilitates the PCell in determining that the UE is potentially in a coverage area of the SCell. In some examples, the first measurement report may include one or more of the RSSI, SINR, RSRQ, rank indicator, PMI, and/or CQI of time-frequency resources used to transmit the first reference signal. The UE may use the communication circuit <NUM> and transceiver <NUM> to transmit the first measurement report as an L1 report or L3 report.

At block <NUM>, the UE measures a second reference signal received from the SCell. For example, the UE may use the RS measurement circuit <NUM> and transceiver <NUM> to measure the second reference signal. In other aspects of the disclosure, the second reference signal may be a reference signal that allows the UE to estimate a wireless channel and determine the corresponding channel quality information. In one example, the second reference signal may be CSI-RS or SSB (e.g., SCell RS <NUM> of <FIG>).

At block <NUM>, the UE may transmit a second measurement report indicating the quality of the second reference signal to the PCell. In some examples, the UE may use the communication circuit <NUM> and transceiver <NUM> to transmit the second measurement report (e.g., SCell measurement report <NUM> in <FIG>) in an L1 report or L3 report. The second measurement report may include a reference signal received power (RSRP) of the second reference signal, a reference signal received quality (RSRQ) of the second reference signal, and/or other signal quality indicators.

At block <NUM>, the UE may use a carrier aggregation circuit <NUM> to search for a range-extended second reference signal for initial beam selection for carrier aggregation of the PCell and SCell. In one example, the SCell may transmit the range-extended second reference signal using a higher gain beam as described above in relation to <FIG>. In another example, the SCell may transmit the range-extended second reference signal using RS repetition as described above in relation to <FIG>. To that end, the PCell may inform the UE on the repetition pattern of the range-extended reference signal and the measurement metric for the range-extended reference signal. For example, the base station of the PCell may transmit an extended RS measurement configuration <NUM> (see <FIG>) to inform the UE on the repetition pattern of the range-extended reference signal and the measurement metric for the range-extended reference signal.

In one configuration, the apparatus <NUM> and/or <NUM> for wireless communication includes means for performing the operations and procedures described above in relation to <FIG>. In one aspect, the aforementioned means may be the processor(s) <NUM> and/or <NUM> shown in <FIG> and <FIG> configured to perform the functions recited by the aforementioned means. In another aspect, the aforementioned means may be a circuit or any apparatus configured to perform the functions recited by the aforementioned means.

Of course, in the above examples, the circuitry included in the processor <NUM> or <NUM> is merely provided as an example, and other means for carrying out the described functions may be included within various aspects of the present disclosure, including but not limited to the instructions stored in the computer-readable storage medium <NUM>/<NUM>, or any other suitable apparatus or means described in any one of the <FIG>, <FIG>, and/or <NUM>, and utilizing, for example, the processes and/or algorithms described herein in relation to <FIG>.

Claim 1:
An apparatus for wireless communication using carrier aggregation in a wireless communication network comprising a primary cell, PCell, and a secondary cell, SCell, the apparatus comprising:
a communication interface configured for wireless communication;
a memory; and
a processor operatively coupled to the communication interface and the memory,
wherein the processor and the memory are configured to:
transmit, via the communication interface, a first reference signal of the PCell;
receive, via the communication interface, a first measurement report from a user equipment, UE, indicating a quality of the first reference signal;
determine that the UE is potentially located in a coverage area of the SCell based on the quality of the first reference signal;
transmit, via the communication interface, an SCell measurement configuration message for configuring the UE that is potentially located in the coverage area of the SCell to measure a second reference signal transmitted by the SCell for initial beam selection using one or more first beams; and
transmit, to the SCell, a signal boost message for triggering the SCell to extend a range of the second reference signal from a first range to a second range, in response to determining that a quality of the second reference signal is less than a predetermined quality.