Patent Description:
For example, a fifth generation (<NUM>) wireless communications technology (which can be referred to as new radio (NR)) is envisaged to expand and support diverse usage scenarios and applications with respect to current mobile network generations. In an aspect, <NUM> communications technology can include: enhanced mobile broadband addressing human-centric use cases for access to multimedia content, services and data; ultra-reliable-low latency communications (URLLC) with certain specifications for latency and reliability; and massive machine type communications, which can allow a very large number of connected devices and transmission of a relatively low volume of non-delay-sensitive information. As the demand for mobile broadband access continues to increase, however, further improvements in NR communications technology and beyond may be desired.

For example, for NR communications technology and beyond, current synchronization signal identification solutions may not provide a desired level of speed or customization for efficient operation. Thus, improvements in wireless communication operations may be desired. <NPL> discusses details of Synchronization Signal Design. <NPL> discusses issues on SS block design and indication method.

In an aspect, the present disclosure includes a method of wireless communications. according to appended claim <NUM>.

In another aspect, the present disclosure includes an apparatus for wireless communication. according to claim <NUM>.

In another aspect, the disclosure provides a computer-readable medium storing computer-executable code. according to claim <NUM>.

Additionally, the term "component" as used herein may be one of the parts that make up a system, may be hardware, firmware, and/or software stored on a computer-readable medium and executable by a hardware processor, and may be divided into other components.

The present disclosure generally relates to synchronization signal blocks (SSBs) transmitted in new radio (NR) procedures that may be executed by a UE and a base station, resulting in communications that may be more efficient than conventional SSB procedures. For example, NR communications may include an SSB-Index information element (IE) that identifies an SS-Block within an SS-Burst. The SSB-Index IE may be defined as an integer between <NUM> and <NUM> (representing a maximum of <NUM> SSBs), which requires a minimum of six bits to transmit. In some cases, a number of relevant SSBs is significantly less than the maximum number of SSBs, but the same SSB-Index IE may be used, resulting in a fixed length to indicate the SSB index.

In an aspect, the present disclosure provides for a compressed SSB index that may have an index length less than the defined SSB-Index IE. The compressed SSB index length may be based on a number of relevant SSBs and determined by both a UE and a base station either separately, or based on communicated rules. The compressed SSB index length may be dynamic and may adjust to a current configuration, communication context, or UE state. As such, in some cases, the compressed SSB index may reduce the number of bits transmitted over the air for communicating information regarding SSBs. That is, the compressed SSB index may reduce overhead associated with SSBs and/or improve reliability of communications. For example, a control channel carrying measurements of SSBs may utilize fewer resources or utilize a lower coding rate.

Additional features of the present aspects are described in more detail below with respect to <FIG>.

It should be noted that the techniques described herein may be used for various wireless communication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and other systems. The terms "system" and "network" are often used interchangeably. IS-<NUM> Releases <NUM> and A are commonly referred to as CDMA2000 1X, 1X, etc. IS-<NUM> (TIA-<NUM>) is commonly referred to as CDMA2000 1xEV-DO, High Rate Packet Data (HRPD), etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. An OFDMA system may implement a radio technology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA), IEEE <NUM> (Wi-Fi), IEEE <NUM> (WiMAX), IEEE <NUM>, Flash-OFDM™, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are new releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and GSM are described in documents from an organization named "3rd Generation Partnership Project" (3GPP). The techniques described herein may be used for the systems and radio technologies mentioned above as well as other systems and radio technologies, including cellular (e.g., LTE) communications over a shared radio frequency spectrum band. The description below, however, describes an NR/<NUM> system for purposes of example, and NR/<NUM> terminology is used in much of the description below, although the techniques are applicable beyond NR/<NUM> applications (e.g., to legacy networks or other next generation communication systems).

Referring to <FIG>, in accordance with various aspects of the present disclosure, an example wireless communication network <NUM> includes at least one UE <NUM> with a modem <NUM> having an SSB index component <NUM> that manages communication of new radio (NR; also referred to as <NUM>) SSB indices, in communication with base station <NUM>, resulting in communication of a compressed SSB index <NUM>. For example, SSB index component <NUM> may include a context component <NUM> configured to determine a number of relevant SSBs based on a context of the UE <NUM> and/or the base station <NUM>. In an aspect, the SSB index component <NUM> may determine an SSB index <NUM> of an SSB to be identified in a communication. The SSB index component <NUM> may map the selected SSB index to the compressed SSB index <NUM> using a mapping rule <NUM> selected based on the context and/or a number of relevant SSBs. For example, the context may refer to a connection status or configuration of the UE <NUM>. The number of relevant SSBs may be a value signaled by the base station <NUM> or determined based on the context. Further, wireless communication network <NUM> includes at least one base station <NUM> with a modem <NUM> having a SSB component <NUM> that performs complementary operations with respect to the SSB index component <NUM>, in communication with UE <NUM>. The SSB component <NUM>, independently or in combination with SSB index component <NUM> of UE <NUM>, may transmit a synchronization signal <NUM> including a number of the SS-blocks <NUM> (each of which may correspond to an SSB index <NUM>). For example, the synchronization signal <NUM> may be based, at least in part, on feedback from the SSB index component <NUM>. The SSB component <NUM> may transmit a remaining minimum system information (RMSI), which may be carried in a SIB1 message, <NUM>, which may be used by the SSB index component <NUM> of the UE <NUM> to obtain information about the SS-blocks <NUM>, such as a number of transmitted SSBs. The SSB component <NUM> may also determine a mapping rule <NUM>, which in turn may be used to determine a compressed SSB index <NUM>. Conversely, when either the SSB component <NUM> or the SSB index component <NUM> receives a communication including a compressed SSB index <NUM>, the SSB component <NUM> or the SSB index component <NUM> may map the compressed SSB index <NUM> to an SSB index <NUM> and/or an SS-block <NUM>. Thus, according to the present disclosure, compressed SSB index <NUM> may be included in over the air communications in a manner that improves an efficiency of UE <NUM> and base station <NUM> in identifying SS-blocks <NUM>.

The wireless communication network <NUM> may include one or more base stations <NUM>, one or more UEs <NUM>, and a core network <NUM>. The core network <NUM> may provide user authentication, access authorization, tracking, internet protocol (IP) connectivity, and other access, routing, or mobility functions. The core network <NUM> may include one or both of an Evolved Packet Core (EPC) and a <NUM> Core (5GC). The base stations <NUM> may interface with the core network <NUM> through backhaul links <NUM> (e.g., S1, etc.), which may be wired or wireless communication links. The base stations <NUM> may perform radio configuration and scheduling for communication with the UEs <NUM>, or may operate under the control of a base station controller (not shown). In various examples, the base stations <NUM> may communicate, either directly or indirectly (e.g., through core network <NUM>), with one another over backhaul links <NUM> (e.g., X1, etc.), which may be wired or wireless communication links.

The base stations <NUM> may wirelessly communicate with the UEs <NUM> via one or more base station antennas. In some examples, base stations <NUM> may be referred to as a base transceiver station, a radio base station, an access point, an access node, a radio transceiver, a NodeB, eNodeB (eNB), gNodeB (gNB), Home NodeB, a Home eNodeB, a relay, or some other suitable terminology. The geographic coverage area <NUM> for a base station <NUM> may be divided into sectors or cells making up only a portion of the coverage area (not shown). The wireless communication network <NUM> may include base stations <NUM> of different types (e.g., macro base stations or small cell base stations, described below). Additionally, the plurality of base stations <NUM> may operate according to different ones of a plurality of communication technologies (e.g., <NUM> (New Radio or "NR"), fourth generation (<NUM>)/LTE, <NUM>, Wi-Fi, Bluetooth, etc.), and thus there may be overlapping geographic coverage areas <NUM> for different communication technologies.

In some examples, the wireless communication network <NUM> may be or include one or any combination of communication technologies, including a NR or <NUM> technology, a Long Term Evolution (LTE) or LTE-Advanced (LTE-A) or MuLTEfire technology, a Wi-Fi technology, a Bluetooth technology, or any other long or short range wireless communication technology. In LTE/LTE-A/MuLTEfire networks, the term eNB may be generally used to describe the base stations <NUM>, while the term UE may be generally used to describe the UEs <NUM>. The wireless communication network <NUM> may be a heterogeneous technology network in which different types of eNBs provide coverage for various geographical regions. For example, each eNB or base station <NUM> may provide communication coverage for a macro cell, a small cell, or other types of cell. The term "cell" is a 3GPP term that can be used to describe a base station, a carrier or component carrier associated with a base station, or a coverage area (e.g., sector, etc.) of a carrier or base station, depending on context.

A macro cell may generally cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs <NUM> with service subscriptions with the network provider.

A small cell may include a relative lower transmit-powered base station, as compared with a macro cell, that may operate in the same or different frequency bands (e.g., licensed, unlicensed, etc.) as macro cells. A femto cell may also cover a small geographic area (e.g., a home) and may provide restricted access and/or unrestricted access by UEs <NUM> having an association with the femto cell (e.g., in the restricted access case, UEs <NUM> in a closed subscriber group (CSG) of the base station <NUM>, which may include UEs <NUM> for users in the home, and the like).

The communication networks that may accommodate some of the various disclosed examples may be packet-based networks that operate according to a layered protocol stack and data in the user plane may be based on the IP. A user plane protocol stack (e.g., packet data convergence protocol (PDCP), radio link control (RLC), MAC, etc.), may perform packet segmentation and reassembly to communicate over logical channels. For example, a MAC layer may perform priority handling and multiplexing of logical channels into transport channels. The MAC layer may also use hybrid automatic repeat/request (HARQ) to provide retransmission at the MAC layer to improve link efficiency. In the control plane, the radio resource control (RRC) protocol layer may provide establishment, configuration, and maintenance of an RRC connection between a UE <NUM> and the base stations <NUM>. The RRC protocol layer may also be used for core network <NUM> support of radio bearers for the user plane data. At the physical (PHY) layer, the transport channels may be mapped to physical channels.

The UEs <NUM> may be dispersed throughout the wireless communication network <NUM>, and each UE <NUM> may be stationary or mobile. A UE <NUM> may also include or be referred to by those skilled in the art as a mobile station, 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, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology. A UE <NUM> may be a cellular phone, a smart phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a tablet computer, a laptop computer, a cordless phone, a smart watch, a wireless local loop (WLL) station, an entertainment device, a vehicular component, a customer premises equipment (CPE), or any device capable of communicating in wireless communication network <NUM>. Additionally, a UE <NUM> may be Internet of Things (IoT) and/or machine-to-machine (M2M) type of device, e.g., a low power, low data rate (relative to a wireless phone, for example) type of device, that may in some aspects communicate infrequently with wireless communication network <NUM> or other UEs. A UE <NUM> may be able to communicate with various types of base stations <NUM> and network equipment including macro eNBs, small cell eNBs, macro gNBs, small cell gNBs, relay base stations, and the like.

The UE <NUM> may be configured to establish one or more wireless communication links <NUM> with one or more base stations <NUM>. The wireless communication links <NUM> shown in wireless communication network <NUM> may carry uplink (UL) transmissions from a UE <NUM> to a base station <NUM>, or downlink (DL) transmissions, from a base station <NUM> to a UE <NUM>. The downlink transmissions may also be called forward link transmissions while the uplink transmissions may also be called reverse link transmissions. Each wireless communication link <NUM> may include one or more carriers, where each carrier may be a signal made up of multiple sub-carriers (e.g., waveform signals of different frequencies) modulated according to the various radio technologies described above. Each modulated signal may be sent on a different subcarrier and may carry control information (e.g., reference signals, control channels, etc.), overhead information, user data, etc. In an aspect, the wireless communication links <NUM> may transmit bidirectional communications using frequency division duplex (FDD) (e.g., using paired spectrum resources) or time division duplex (TDD) operation (e.g., using unpaired spectrum resources). Frame structures may be defined for FDD (e.g., frame structure type <NUM>) and TDD (e.g., frame structure type <NUM>). Moreover, in some aspects, the wireless communication links <NUM> may represent one or more broadcast channels.

In some aspects of the wireless communication network <NUM>, base stations <NUM> or UEs <NUM> may include multiple antennas for employing antenna diversity schemes to improve communication quality and reliability between base stations <NUM> and UEs <NUM>. Additionally or alternatively, base stations <NUM> or UEs <NUM> may employ multiple input multiple output (MIMO) techniques that may take advantage of multi-path environments to transmit multiple spatial layers carrying the same or different coded data.

Wireless communication network <NUM> may support operation on multiple cells or carriers, a feature which may be referred to as carrier aggregation (CA) or multicarrier operation. A carrier may also be referred to as a component carrier (CC), a layer, a channel, etc. The terms "carrier," "component carrier," "cell," and "channel" may be used interchangeably herein. A UE <NUM> may be configured with multiple downlink CCs and one or more uplink CCs for carrier aggregation. The base stations <NUM> and UEs <NUM> may use spectrum up to Y MHz (e.g., Y = <NUM>, <NUM>, <NUM>, or <NUM>) bandwidth per carrier allocated in a carrier aggregation of up to a total of Yx MHz (x = number of component carriers) used for transmission in each direction. Allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or less carriers may be allocated for DL than for UL).

The wireless communication network <NUM> may further include base stations <NUM> operating according to Wi-Fi technology, e.g., Wi-Fi access points, in communication with UEs <NUM> operating according to Wi-Fi technology, e.g., Wi-Fi stations (STAs) via communication links in an unlicensed frequency spectrum (e.g., <NUM>). When communicating in an unlicensed frequency spectrum, the STAs and AP may perform a clear channel assessment (CCA) or listen before talk (LBT) procedure prior to communicating in order to determine whether the channel is available.

Additionally, one or more of base stations <NUM> and/or UEs <NUM> may operate according to a NR or <NUM> technology referred to as millimeter wave (mmW or mmwave) technology. For example, mmW technology includes transmissions in mmW frequencies and/or near mmW frequencies. Extremely high frequency (EHF) is part of the radio frequency (RF) in the electromagnetic spectrum. For example, the super high frequency (SHF) band extends between <NUM> and <NUM>, and may also be referred to as centimeter wave. Communications using the mmW and/or near mmW radio frequency band has extremely high path loss and a short range. As such, base stations <NUM> and/or UEs <NUM> operating according to the mmW technology may utilize beamforming in their transmissions to compensate for the extremely high path loss and short range.

Referring to <FIG>, a diagram <NUM> includes a synchronization signal <NUM> (or synchronization signal burst series) that a base station <NUM> may transmit for UEs to perform cell detection and measurement. For certain frequency bands (e.g., > <NUM> or mmWave), the synchronization signal <NUM> may be transmitted in the form of a sweeping beam. The sweeping beam may include a periodic synchronization signal bursts <NUM> of synchronization signal blocks (SS-blocks) <NUM>, which may correspond to SS-block <NUM>. For example, the SS-burst <NUM> may include L SS-blocks <NUM>. In an example, the number of SS-blocks L may be <NUM>, for example, in spectrum > <NUM>. Fewer SS-blocks may be supported in lower frequency spectrum. For example, a maximum of L = <NUM> SS-blocks may be used for frequency bands less than or equal to <NUM> and a maximum of L = <NUM> SS-blocks may be used for frequency bands between <NUM> and <NUM>. The SS-burst <NUM> may have a duration <NUM> and a periodicity <NUM>. The SS-blocks <NUM> may include an NR primary synchronization signal (NR-PSS), an NR secondary synchronization signal (NR-SSS), and an NR Physical broadcast channel (NR-PBCH). The SS-burst <NUM> composes multiple SS-blocks <NUM> to enable repetitive transmissions of SS-blocks in different directions for multi-beam configurations. A SS-burst set includes multiple SS-bursts to complete the beam sweeping of a coverage area. For multi-beam configuration, SS-blocks may be transmitted from the same beam multiple times within one SS-burst. The number of SS-bursts within a SS-burst set and the number of SS-blocks within a SS-burst may be determined based on the deployment scenario and operating frequency band. For example, the number of SS-blocks within a SS-burst in the deployment scenario of beam sweeping in a multi-beam configuration may be determined by the number of beams and the downlink (DL)/guard period(GP)/uplink (UL) configuration. In order to complete beamsweeping the coverage area, each beam may have at least one SS-block transmission over the sweeping interval of the SS-burst. The number of SS-bursts within a SS-burst set and SS-blocks within a SS-burst may be flexibly determined in the deployment.

Referring additionally to <FIG> and Table <NUM> (below), during operation, UE <NUM> may execute an implementation of an NR RACH procedure, according to a <NUM>-step NR RACH message flow <NUM>, due to the occurrence of one or more RACH trigger events <NUM>. Suitable examples of RACH trigger event <NUM> may include, but are not limited to: (i) an initial access from RRC_IDLE to RRC_CONNECTED ACTIVE; (ii) downlink (DL) data arrival during RRC_IDLE or RRC_CONNECTED INACTIVE; (iii) UL data arrival during RRC_IDLE or RRC_CONNECTED INACTIVE; (iv) a handover during the connected mode of operation; and (v) a connection re-establishment (e.g., a beam failure recovery procedure).

The NR RACH procedure may be associated with a contention based random access procedure, or with a contention free random access procedure. In an implementation, a contention based NR RACH procedure corresponds to the following RACH trigger events <NUM>: an initial access from RRC_IDLE to RRC_CONNECTED ACTIVE; UL data arrival during RRC_IDLE or RRC_CONNECTED INACTIVE; and, a connection re-establishment. In an implementation, a contention-free NR RACH procedure corresponds to the following RACH trigger events <NUM>: downlink (DL) data arrival during RRC_IDLE or RRC_CONNECTED INACTIVE; and, a handover during the connected mode of operation.

On the occurrence of any of the above RACH trigger events <NUM>, the execution of NR RACH procedure may include <NUM>-step NR RACH message flow <NUM> (see <FIG> and Table <NUM>), where UE <NUM> exchanges messages with one or more base stations <NUM> to gain access to a wireless network and establish a communication connection.

At <NUM>, for example, UE <NUM> may transmit a first message (Msg <NUM>), which may be referred to as a random access request message, to one or more base stations <NUM> via a physical channel, such as a physical random access channel (PRACH). For example, Msg <NUM> may include one or more of a RACH preamble and a resource requirement.

At <NUM>, one of more of the base stations <NUM> may respond to Msg <NUM> by transmitting a second message (Msg <NUM>), which may be referred to as a random access response (RAR) message, over a physical downlink control channel (e.g., PDCCH) and/or a physical downlink shared channel (e.g., PDSCH). For example, Msg <NUM> may include one or more of a detected preamble identifier (ID), a timing advance (TA) value, a temporary cell radio network temporary identifier (TC-RNTI), a backoff indicator, an UL grant, and a DL grant.

At <NUM>, in response to receiving Msg <NUM>, UE <NUM> may transmit a third message (Msg <NUM>), which may be an RRC connection request or a scheduling request, via a physical uplink channel (e.g., PUSCH) based on the UL grant provided in Msg <NUM> of a selected serving base station <NUM>-a. The UE <NUM> may ignore the Msg <NUM> of a non-selected base station <NUM>-b. In an aspect, Msg <NUM> may include a tracking area update (TAU), such as on a periodic basis or if UE <NUM> moves outside of one or more tracking areas (TAs) initially provided to UE <NUM> in a tracking area identifier (TAI) list. Also, in some cases, Msg <NUM> may include a connection establishment cause indicator, which identifies a reason why UE <NUM> is requesting to connect to the network. In an aspect, Msg <NUM> may include an indication of a preferred SS-block <NUM>. The UE <NUM> may execute the SSB index component <NUM> to transmit a compressed SSB index <NUM> in Msg <NUM> based on a number of actually transmitted beams indicated by the RMSI <NUM>.

At <NUM>, in response to receiving Msg <NUM>, base station <NUM> may transmit a fourth message (Msg <NUM>), which may be referred to as a contention resolution message, to UE <NUM> via a physical downlink control channel (e.g., PDCCH) and/or a physical downlink shared channel (e.g., PDSCH). For example, Msg <NUM> may include a cell radio network temporary identifier (C-RNTI) for UE <NUM> to use in subsequent communications.

In the above description, a collision scenario was not discussed but a collision between two or more UEs <NUM> requesting access can occur. For instance, two or more UEs <NUM> may send Msg <NUM> having a same RACH preamble, since the number of RACH preambles may be limited and may be randomly selected by each UE <NUM> in a contention-based NR RACH procedure. As such, each UE <NUM> will receive the same temporary C-RNTI and the same UL grant, and thus each UE <NUM> may send a similar Msg <NUM>. In this case, base station <NUM>-a may resolve the collision in one or more ways: (i) both Msg <NUM> may interfere with each other, and so base station <NUM>-a may not send Msg <NUM>, thus each UE <NUM> will retransmit Msg <NUM>; (ii) base station <NUM>-a may successfully decode only one Msg <NUM> and send an ACK message to that UE; and (iii) base station <NUM>-a may successfully decode both Msg <NUM>, and then send a Msg <NUM> having a contention resolution identifier (e.g., an identifier tied to one of the UEs) to both UEs, and each UE <NUM> receives the Msg <NUM>, decodes the Msg <NUM>, and determines if the UE <NUM> is the correct UE by successfully matching or identifying the contention resolution identifier. It should be noted that such a problem may not occur in a contention-free NR RACH procedure, as in that case, base station <NUM>-a may inform UE <NUM> of which RACH preamble to use.

The UE <NUM> may select physical random access channel (PRACH) resources for the Msg1 transmission based on the best received SS-block <NUM>. The selection of the best SS-block <NUM> during Msg1 transmission allows the base station <NUM> to find the set of appropriate directions to transmit a channel state information reference signal (CSI-RS) for the UE <NUM>. However, network <NUM> can also obtain the strongest SS-block index of the UE by configuring the UE <NUM> to convey this information explicitly through Msg3 of contention based random access and implicitly through Msg1 of contention free random access in dedicated time/frequency regions. Additionally, network <NUM> can configure UE <NUM> to report the strongest SS-block in Msg3 of contention based random access and Msg1 of contention free random access that occurs in dedicated time/frequency region. The network <NUM> may use this information to find appropriate CSI-RS directions for the UE <NUM>.

A base station <NUM> may not transmit a maximum number of SS-blocks during an SS burst set. Since the UE <NUM> receives only a subset of the SS-blocks <NUM>, the UE <NUM> may be unaware of which SS-blocks <NUM> were actually transmitted. The base station <NUM> may signal the actually transmitted SS-blocks in the remaining minimum system information (RMSI) <NUM>. The RMSI <NUM> may carry a compressed indication of which SS-blocks <NUM> were transmitted. In an implementation, for example, the RMSI <NUM> may include a first bitmap indicating which groups of SS-blocks <NUM> are transmitted and a second bitmap indicating which SS-blocks <NUM> are actually transmitted within the group. A group may be defined as consecutive SS/PBCH blocks. Each group may have the same pattern of SS/PBSCH block transmission.

In an aspect, the number of bits used to convey the compressed SSB index <NUM> depends on a network configuration and a UE context or state. The configuration and state may determine the relevant SSBs among which one SSB is to be identified by an SSB index <NUM>. Not all SSBs may be relevant; for example, some SSBs may not be transmitted or monitored. A parameter, M, may be defined as the number of relevant SSBs. The compressed SSB index <NUM> may be based on the parameter M. For example, the length of the compressed SSB index <NUM> may be the ceiling of log<NUM>(M). That is, the length may be the minimum number of bits required to uniquely represent M SSBs. The compressed SSB index <NUM> may be mapped to the SSB index <NUM> when the relevant SSBs or indices thereof are known. Note that if M is not a power of <NUM>, then certain possible values of the compressed SSB index of ceiling(log<NUM>(M)) bits may be invalid. This may be avoided by enforcing M to be a power of <NUM>, or by discarding messages with the index set to invalid values, or by assigning alternative interpretations to those invalid values. For example, an alternative interpretation may be to re-map the invalid values to a subset of the valid indices, but perform a different operation on the indices thus identified (e.g., a different type of measurement, etc.).

As mentioned above, the maximum number of SSBs, L, may depend on a frequency band used for communication. In an aspect, the number of relevant SSBs, M, may be the maximum number of SSBs, L. For example, in NR, L = <NUM> for <= <NUM>, L=<NUM> for <NUM> - <NUM>, and L = <NUM> for <NUM> - <NUM>. By setting M = L, the compressed SSB index <NUM> may reduce the length of the index for frequency bands less than <NUM>.

In another aspect, the UE state may be defined with respect to the RACH procedure (e.g., the NR RACH procedure described with respect to <FIG>). Prior to the RACH procedure, the UE <NUM> has little information about the relevant SSBs. For example, the UE <NUM> may know only the frequency band being searched. Accordingly, the UE may initially set M = L. After the UE <NUM> acquires initial synchronization (by receiving an SSB) and reads RMSI <NUM>, the UE <NUM> may have some information on which of the L SSBs are actually transmitted (e.g., based on the bit maps in the RMSI). Accordingly, the UE <NUM> may set M equal to the indicated number of SSBs transmitted during the RACH procedure. For example, if the UE <NUM> includes beam information such as identifying a preferred SSB in message <NUM> of the RACH procedure, the SSB index component <NUM> may transmit a compressed SSB index <NUM> with a length based on the indicated number of SSBs transmitted. Once the RACH procedure is completed and the UE <NUM> establishes an RRC connection with the base station <NUM>, the UE <NUM> may receive updated or more detailed information on which of the L SSBs are actually transmitted. For example, an RRC configuration message may indicate exactly which SSBs are actually transmitted via a bitmap. Accordingly, the SSB index component <NUM> may set M equal to the number of transmitted SSBs indicated by the RRC configuration message, which may be different than the number of transmitted SSBs indicated by the RMSI <NUM>.

In an aspect, the SSB index component <NUM> and the context component <NUM> may determine the number of relevant SSBs based on a combination of network configuration and UE state. A mapping rule <NUM> may determine how the SSB index component <NUM> maps between the SSB index <NUM> and the compressed SSB index <NUM>. For example, for frequency bands with low L (e.g., frequency less than <NUM> and L less than or equal to <NUM>), the SSB index component <NUM> may set M = L, even if the base station <NUM> does not actually transmit the maximum number of L SSBs. Setting M = L may provide a simple reduction of index length (e.g., <NUM> bits reduced to <NUM> or <NUM> bits). Although further reductions based on actual number of SSBs transmitted may further reduce the index length, tracking the number of actually transmitted SSBs may also add complexity. In an aspect, however, if only one SSB is configured (e.g., M = <NUM> when no beamsweeping), transmitting an SSB index <NUM> may not be necessary and the length of the compressed SSB index <NUM> may be zero. For cases where L is relatively large (e.g., L = <NUM> for frequency bands greater than <NUM>), setting M based on an indicated number of transmitted SSBs may provide significant reduction in the length of the compressed SSB index <NUM>. For example, if a base station <NUM> is permitted to use L=<NUM> SSBs, but only transmits <NUM> SSBs, the length of the compressed SSB index <NUM> may be reduced from <NUM> to <NUM>. If the base station <NUM> further provides a UE with a specific set of SSBs to monitor (e.g., <NUM> SSBs), the compressed SSB index <NUM> may be reduced to <NUM>.

The number of relevant SSBs and/or the length of the compressed SSB index <NUM> may also be based on a particular type of communication. For example, the UE <NUM> may report signal quality as either a layer <NUM> (PHY) RSRP report or a layer <NUM> (RRC) measurement report. A layer <NUM> RSRP may be transmitted on a control channel (e.g., PUCCH) with limited resources that is not protected by RLC retransmission or HARQ. Accordingly, a layer <NUM> RSRP transmission may benefit from a shorter compressed SSB index <NUM> that allows higher reliability. Therefore, M (or the index length) may be set based on the smallest number of relevant SSBs (e.g., a monitoring set). In contrast, a layer <NUM> measurement report may be transmitted on a higher capacity data channel protected by RLC and/or HARQ. Accordingly, the benefit of a shorter compressed SSB index <NUM> may be minimal and M may be set to L.

In another example, the UE <NUM> may transmit information regarding an SSB transmitted by a base station <NUM>-b (e.g., a neighbor cell) other than a serving base station <NUM>-a. For the serving base station <NUM>-a, the UE <NUM> may have access to the RMSI <NUM> or RRC configuration messages and therefore know how many SS-blocks <NUM> are actually transmitted. When performing inter-cell measurements, the UE <NUM> may not have access to the RMSI <NUM> or RRC configuration messages associated with the other base station <NUM>-b. Accordingly, when reporting inter-cell measurements, the SSB index component <NUM> may set M equal to L of the other base station <NUM>-b, even if a lower value of M is used for measurement of the serving base station <NUM>-a.

In an aspect, the UE <NUM> and the base station <NUM> may use the same mapping rule <NUM> to determine the length of the compressed SSB index <NUM> and the value corresponding to the respective SS-block <NUM>. The UE <NUM> and the base station <NUM> may determine a current mapping rule <NUM> based on the same factors of network configuration and UE state. In another aspect, the base station <NUM> may provide a configuration parameter that indicates which mapping rule <NUM> to use. The base station <NUM> may transmit the configuration parameter via a management information block (MIB), system information block (SIB), RRC message, MAC control element (MAC-CE), or downlink control information (DCI).

In an aspect, the compressed SSB index <NUM> may be utilized in either uplink or downlink messages. The compressed SSB index <NUM> may replace a SSB-Index IE. For example, downlink messages may include signals identifying a set of one or more SSB indices to monitor or report, or identifying an index of a SSB that has a quasi-co-location (QCL) relationship to a signal of interest. Such messages may be carried in RRC signaling or in a MAC-CE, for example, a MAC-CE carrying an SP SRS activation or deactivation may indicate a QCL relationship between the SRS and an SSB. Example uplink messages may include a RACH message <NUM> or a <NUM>-step RACH message-A that indicates a preferred SSB and layer <NUM> measurement reports indicating which SSB is measured.

Referring to <FIG>, for example, a method <NUM> of wireless communication according to the above-described aspects for utilizing a compressed SSB index includes one or more of the below-defined actions. The method <NUM> may be performed by a UE <NUM> or a base station <NUM>. The blocks of the method <NUM> may be performed in an order other than that illustrated and described. In particular, the block <NUM> may occur earlier (e.g., before block <NUM>) when the UE <NUM> or the base station <NUM> is receiving a communication, and may occur later (e.g., after block <NUM>) when the UE <NUM> or the base station <NUM> is transmitting a communication.

At block <NUM>, method <NUM> includes determining a number of relevant SSBs with respect to a communication. In an aspect, for example, the SSB index component <NUM> of UE <NUM> may execute the context component <NUM> or the base station <NUM> may execute the SSB component <NUM> to determine the number of relevant SS-blocks <NUM>, M, with respect to a communication. The determination may be based on one or more of: a maximum number of SSBs for a frequency band of the communication, a state of a UE, or whether the SSBs are for a serving cell or neighbor cell In one aspect, at block <NUM>, determining the number of relevant SSBs may include the context component <NUM> or the SSB component <NUM> determining the number of relevant SSBs based at least in part on a maximum number of SSBs for a frequency band of the communication. In another aspect (which may be performed by UE <NUM>), at block <NUM>, determining the number of relevant SSBs may include the context component <NUM> or the SSB component <NUM> determining a number of SSBs configured for a base station <NUM> based on an indication from the base station <NUM>, such as the RMSI <NUM> or an RRC configuration message. In an aspect, the state of the UE may be defined with respect to the RACH procedure. For example, prior to the RACH procedure, the UE may be in an idle mode or an inactive mode, and after the RACH procedure, the UE may be in a connected mode. In another aspect, when reporting inter-cell measurements (e.g., of neighbor cells), the number of relevant SSBs may be maximum number of SSBs for a carrier frequency, whereas a lower number of relevant SSBs may be used for measurement of the serving cell (e.g., based on RMSI).

At block <NUM>, method <NUM> includes determining a compressed index length based on the number of relevant SSBs. In an aspect, for example, the SSB index component <NUM> or the SSB component <NUM> may determine the compressed index length based on the number of relevant SSBs. For instance, at block <NUM>, determining the compressed index length based on the number of relevant SSBs may include the SSB index component <NUM> or the SSB component <NUM> determining a minimum number of bits to uniquely identify each relevant SSB. In another aspect, at block <NUM>, the determining the compressed index length based on the number of relevant SSBs may include the SSB index component <NUM> receiving a configuration parameter indicating a rule (e.g., mapping rule <NUM>) for determining the compressed index length based on the number of relevant SSBs. The SSB index component <NUM> may determine the compressed index length based on the indicated rule.

At <NUM>, method <NUM> includes transmitting or receiving the communication including a compressed index value of the compressed index length. In an aspect, for example, the SSB index component <NUM> or the SSB component <NUM> may transmit or receive the communication including a compressed index value (e.g., compressed SSB index <NUM>) of the compressed index length. That is, the compressed SSB index <NUM> may include a number of bits equal to the determined compressed index length.

At <NUM>, method <NUM> includes mapping between the compressed index value and an SSB index value based on the compressed index length and the number of relevant SSBs. In an aspect, for example, the SSB index component <NUM> or the SSB component <NUM> may map between the compressed index value (e.g., compressed SSB index <NUM>) and an SSB index value (e.g., SSB index <NUM>) based on the compressed index length and the number of relevant SSBs. For example, when receiving the communication, the SSB index component <NUM> or the SSB component <NUM> may convert the received value of the compressed SSB index <NUM> to a value of the SSB index <NUM>. Conversely, when transmitting the communication, the SSB index component <NUM> or the SSB component <NUM> may convert the value of the SSB index <NUM> to the value of the compressed SSB index <NUM>.

Although the above description is focused on SSB indexing, it may be noted that the concepts described herein apply more generally to indexing of any set of resources or signals, such as CSI-RS or SRS. For example, when multiple CSI-RS resources may be configured, the CSI-RS resource indexing may be based on the maximum possible number of CSI-RS resources, the actual number of configured CSI-RS resources, or the actual number of configured CSI-RS resources that are relevant to the operation (e.g., a measurement report) requiring identification of a CSI-RS resource by an index.

Referring to <FIG>, one example of an implementation of UE <NUM> may include a variety of components, some of which have already been described above, but including components such as one or more processors <NUM> and memory <NUM> and transceiver <NUM> in communication via one or more buses <NUM>, which may operate in conjunction with modem <NUM> and SSB index component <NUM> to enable one or more of the functions described herein related to communicating using a compressed SSB index. Further, the one or more processors <NUM>, modem <NUM>, memory <NUM>, transceiver <NUM>, RF front end <NUM> and one or more antennas <NUM>, may be configured to support voice and/or data calls (simultaneously or non-simultaneously) in one or more radio access technologies. The antennas <NUM> may include one or more antennas, antenna elements, and/or antenna arrays.

In an aspect, the one or more processors <NUM> can include a modem <NUM> that uses one or more modem processors. The various functions related to SSB index component <NUM> may be included in modem <NUM> and/or processors <NUM> and, in an aspect, can be executed by a single processor, while in other aspects, different ones of the functions may be executed by a combination of two or more different processors. For example, in an aspect, the one or more processors <NUM> may include any one or any combination of a modem processor, or a baseband processor, or a digital signal processor, or a transmit processor, or a receiver processor, or a transceiver processor associated with transceiver <NUM>. In other aspects, some of the features of the one or more processors <NUM> and/or modem <NUM> associated with SSB index component <NUM> may be performed by transceiver <NUM>.

Also, memory <NUM> may be configured to store data used herein and/or local versions of applications <NUM> or SSB index component <NUM> and/or one or more of the subcomponents thereof being executed by at least one processor <NUM>. Memory <NUM> can include any type of computer-readable medium usable by a computer or at least one processor <NUM>, such as random access memory (RAM), read only memory (ROM), tapes, magnetic discs, optical discs, volatile memory, non-volatile memory, and any combination thereof. In an aspect, for example, memory <NUM> may be a non-transitory computer-readable storage medium that stores one or more computer-executable codes defining SSB index component <NUM> and/or one or more of the subcomponents thereof, and/or data associated therewith, when UE <NUM> is operating at least one processor <NUM> to execute SSB index component <NUM> and/or one or more of the subcomponents thereof.

Receiver <NUM> may include hardware, firmware, and/or software code executable by a processor for receiving data, the code comprising instructions and being stored in a memory (e.g., computer-readable medium). Additionally, receiver <NUM> may process such received signals, and also may obtain measurements of the signals, such as, but not limited to, Ec/Io, SNR, RSRP, RSSI, etc. Transmitter <NUM> may include hardware, firmware, and/or software code executable by a processor for transmitting data, the code comprising instructions and being stored in a memory (e.g., computer-readable medium).

In an aspect, RF front end <NUM> may use one or more switches <NUM> to select a particular LNA <NUM> and a corresponding specified gain value based on a desired gain value for a particular application.

In an aspect, RF front end <NUM> may use one or more switches <NUM> to select a particular PA <NUM> and a corresponding specified gain value based on a desired gain value for a particular application.

Referring to <FIG>, one example of an implementation of base station <NUM> may include a variety of components, some of which have already been described above, but including components such as one or more processors <NUM> and memory <NUM> and transceiver <NUM> in communication via one or more buses <NUM>, which may operate in conjunction with modem <NUM> and SSB component <NUM> to enable one or more of the functions described herein related to utilizing a compressed SSB index.

Claim 1:
A method of wireless communications, comprising:
determining (<NUM>) a number of relevant synchronization signal blocks, SSBs with respect to a communication based on one or more of: a maximum number of SSBs for a frequency band of the communication, a state of a user equipment, UE, or whether the SSBs are for a serving cell or neighbor cell;
determining (<NUM>) a compressed index length based on the number of relevant SSBs;
transmitting (<NUM>) or receiving the communication including a compressed index value of the compressed index length; and
mapping (<NUM>) between the compressed index value and an SSB index value based on the compressed index length and the number of relevant SSBs, characterized in that the communication is a radio resource control layer measurement report associating a signal quality with the SSB index value.