Patent Description:
A wireless multiple-access communications system may include a number of base stations (BSs), each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE).

To meet the growing demands for expanded mobile broadband connectivity, wireless communication technologies are advancing from the LTE technology to a next generation new radio (NR) technology. NR may provision for dynamic medium sharing among network operators in a licensed spectrum, a shared spectrum, and/or an unlicensed spectrum. For example, shared spectrums and/or unlicensed spectrums may include frequency bands at about <NUM> gigahertz (GHz), about <NUM>, and about <NUM>.

In a radio access network such as an NR network, a base station may transmit synchronization signals to allow UEs to search and acquire synchronization to a cell within the radio access network. In some instances, a base station may transmit synchronization signals repeatedly at a predetermined periodicity. When the network operates at high frequencies, for example, at about <NUM> or above <NUM>, the path-loss may be high. To overcome the high path-loss, a base station may perform beamforming, which may include analog and/or digital beamforming, to create narrow beams for transmissions to UEs in the network. For example, the base station may transmit synchronization signals in different beam directions using narrow transmission beams. When the network operates in a shared medium or a shared channel, the synchronization signal transmissions may collide with transmissions from other nodes sharing the channel. One approach to avoiding collisions is to perform listen-before-talk (LBT) to ensure that the shared channel is clear before transmitting a synchronization signal. Since a base station may sweep through multiple narrow beams for synchronization signal transmissions, LBT procedures considering beam sweeping are desirable.

<CIT> discloses a eNB that generates a reservation signal after LBT protocol indicates an idle state, and before start of discovery reference signal transmission.

<CIT> is directed to wireless communication in long term evolution (LTE) in unlicensed spectrum and teaches that if a listen-before-talk (LBT) protocol is applied, there can be an idle period after the end of channel occupancy and that the idle period can include a Clear Channel Assessment (CCA) period towards the end of the idle period, where carrier sensing is performed by the UE. Further, it is assumed that the LAA (licensed assisted access) cell can start to transmit signals immediately after the last CCA slot according to a certain listen-before-talk protocol or channel access protocol is determined to be idle and if the last CCA slot transmission is determined to be idle by a LAA cell, the LAA cell can proceed to transmit a set of signals which shall be referred to as Channel Occupancy Signals (COS). Thereby, the COS contains PSS, SSS, CRS and possibly CSI-RS.

<CIT> refers to channel access of multi-antenna and teaches that interference can be avoided by forming a directional narrow beam through beamforming, since for directions other than the directional beam the signal energy is low. Further, due to the LBT of existing omnidirectional antenna, the advantages of beamforming space division multiplexing cannot be fully utilized, and the spectrum efficiency is reduced.

<CIT> is directed to techniques for implementing listen before talk (LBT) for discovery reference signals (DRS) transmission in unlicensed band operation of a wireless system. Thereby, an eNB can transmit a reservation signal between the duration after the successful LBT and before the start of DRS transmission (at the subframe boundary within the transmissions). Further, the reservation signal can be triggered by a misalignment at an end of an LBT protocol and a start of a DRS transmission, wherein the reservation signal reserves an unlicensed frequency band of the unlicensed spectrum for the DL transmission. Upon the detection of an alignment between the LBT and the DRS, a reservation signal could also not be generated or transmitted, but the DRS transmission could occur as soon as the network device or RF circuitry is able.

The following summarizes some aspects of the present disclosure to provide a basic understanding of the discussed technology. Its sole purpose is to present some concepts of one or more aspects of the disclosure in summary form as a prelude to the more detailed description that is presented later.

The techniques described herein may be used for various wireless communication networks such as code-division multiple access (CDMA), time-division multiple access (TDMA), frequency-division multiple access (FDMA), orthogonal frequency-division multiple access (OFDMA), single-carrier FDMA (SC-FDMA) and other networks. An OFDMA network may implement a radio technology such as Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE <NUM> (Wi-Fi), IEEE <NUM> (WiMAX), IEEE <NUM>, Flash-OFDMA, 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. The techniques described herein may be used for the wireless networks and radio technologies mentioned above as well as other wireless networks and radio technologies, such as a next generation (e.g., <NUM>th Generation (<NUM>) operating in mmWave bands) network.

To facilitate synchronization in a network, a base station (BS) may sweep through multiple narrow beams directing towards different beam directions in a designated time period for transmitting discovery signals. The designated time period may be referred to as a discovery reference signal (DRS) measurement timing configuration (DMTC) period. The DMTC periods may be repeated at a predetermined periodicity. The discovery signals may be referred to as synchronization signal blocks (SSBs). An SSB may include a combination of synchronization signals, broadcast system information signals, and/or discovery reference signals. In some instances, each SSB in a DMTC period may be transmitted in a different beam direction.

The present application describes mechanisms for performing LBT prior to discovery signal transmissions in a frequency spectrum shared by multiple network operating entities. For example, a BS may perform omnidirectional LBT and/or spatial-specific LBTs to determine whether a channel is clear in beam directions where discovery signals are expected to be transmitted in a subsequent time period. When the omnidirectional LBT and/or the spatial-specific LBTs indicate that the channel is idle, the BS may proceed with the discovery signal transmissions. When the omnidirectional LBT and/or the spatial-specific LBTs indicate that the channel is busy, the BS may refrain from proceeding with the discovery signal transmissions.

In an embodiment, the BS may perform omnidirectional LBT prior to a DMTC period. For example, the BS may monitor the channel for a transmission from another node using an omnidirectional reception beam. When the channel is clear, the BS may additionally transmit a channel reservation signal or a preamble signal using an omnidirectional transmission beam to indicate a reservation for the channel in a subsequent DMTC period.

In an embodiment, the BS may perform multiple spatial-specific or directional LBTs, sweeping through a set of narrow directional reception beams, prior to a DMTC period. For example, the BS may monitor the channel in a beam direction covering a group of one or more expected beam transmission directions in a subsequent DMTC period in each directional LBT. When the directional LBT indicates that the channel is clear, the BS may additionally transmit a channel reservation signal in the monitored direction.

In an embodiment, the BS may perform multiple spatial-specific LBTs, sweeping through a set of directional beams, within a DMTC period. For example, the BS may monitor the channel in a beam direction covering a group of one or more expected beam transmission directions in a subsequent sub-period within the DMTC period. When the directional LBT indicates that the channel is clear, the BS may additionally transmit a channel reservation signal in the monitored direction.

In an embodiment, the BS may transmit the discovery signals in a portion of a system frequency band. The BS may transmit a channel reservation signal concurrent with a discovery signal using frequency-division multiplexing (FDM) in the system frequency band. The BS may transmit a data signal on remaining resources in the DMTC period. The BS may transmit the data signal in a beam direction based on monitored beam directions.

Aspects of the present application can provide several benefits. For example, the omnidirectional LBT and the omnidirectional channel reservation can avoid interference from nearby transmitters with a minimal system overhead. The directional LBTs and the directional channel reservations can avoid interference from transmitters that use directional transmission beams and/or directional reception beams. Thus, the directional LBTs and the directional channel reservations can further improve system performance and reduce collisions. Performing the directional LBTs and the directional channel reservations within a DMTC period can reduce the time gap between a directional LBT and transmissions in corresponding monitored beam directions. The reduction in the time gap can further improve system performance. The use of FDM for transmitting channel reservation signals concurrent with discovery signals can reduce system overhead. The use of unused resources within the DMTC period for data transmissions can improve system resource utilization efficiency. The disclosed embodiments may be suitable for use with any wireless communication protocol in any wireless network for spectrum sharing.

<FIG> illustrates a wireless communication network <NUM> according to embodiments of the present disclosure. The network <NUM> includes BSs <NUM>, UEs <NUM>, and a core network <NUM>. In some embodiments, the network <NUM> operates over a shared spectrum. The shared spectrum may be unlicensed or partially licensed to one or more network operators. Access to the spectrum may be limited and may be controlled by a separate coordination entity. In some embodiments, the network <NUM> may be a LTE or LTE-A network. In yet other embodiments, the network <NUM> may be a millimeter wave (mmW) network, a new radio (NR) network, a <NUM> network, or any other successor network to LTE. The network <NUM> may be operated by more than one network operator. Wireless resources may be partitioned and arbitrated among the different network operators for coordinated communication between the network operators over the network <NUM>.

The BSs <NUM> may wirelessly communicate with the UEs <NUM> via one or more BS antennas. Each BS <NUM> may provide communication coverage for a respective geographic coverage area <NUM>. In 3GPP, the term "cell" can refer to this particular geographic coverage area of a BS and/or a BS subsystem serving the coverage area, depending on the context in which the term is used. In this regard, a BS <NUM> may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other types of cell. A pico cell may generally cover a relatively smaller geographic area and may allow unrestricted access by UEs with service subscriptions with the network provider. A femto cell may also generally cover a relatively small geographic area (e.g., a home) and, in addition to unrestricted access, may also provide restricted access by UEs having an association with the femto cell (e.g., UEs in a closed subscriber group (CSG), UEs for users in the home, and the like). In the example shown in <FIG>, the BSs 105a, 105b and 105c are examples of macro BSs for the coverage areas 110a, 110b and 110c, respectively. The BSs 105d is an example of a pico BS or a femto BS for the coverage area 110d. As will be recognized, a BS <NUM> may support one or multiple (e.g., two, three, four, and the like) cells.

Communication links <NUM> shown in the network <NUM> may include uplink (UL) transmissions from a UE <NUM> to a BS <NUM>, or downlink (DL) transmissions, from a BS <NUM> to a UE <NUM>. The UEs <NUM> may be dispersed throughout the network <NUM>, and each UE <NUM> may be stationary or mobile. A UE <NUM> may also be referred to 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 also be a cellular 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 personal electronic device, a handheld device, a personal computer, a wireless local loop (WLL) station, an Internet of things (IoT) device, an Internet of Everything (IoE) device, a machine type communication (MTC) device, an appliance, an automobile, or the like.

The BSs <NUM> may communicate with the core network <NUM> and with one another. At least some of the BSs <NUM> (e.g., which may be an example of an evolved NodeB (eNB), a next generation NodeB (gNB), or an access node controller (ANC)) may interface with the core network <NUM> through backhaul links <NUM> (e.g., S1, S2, etc.) and may perform radio configuration and scheduling for communication with the UEs <NUM>. In various examples, the BSs <NUM> may communicate, either directly or indirectly (e.g., through core network <NUM>), with each other over backhaul links <NUM> (e.g., X1, X2, etc.), which may be wired or wireless communication links.

Each BS <NUM> may also communicate with a number of UEs <NUM> through a number of other BSs <NUM>, where the BS <NUM> may be an example of a smart radio head. In alternative configurations, various functions of each BS <NUM> may be distributed across various BSs <NUM> (e.g., radio heads and access network controllers) or consolidated into a single BS <NUM>.

In some implementations, the network <NUM> utilizes orthogonal frequency division multiplexing (OFDM) on the downlink and single-carrier frequency division multiplexing (SC-FDM) on the UL. OFDM and SC-FDM partition the system bandwidth into multiple (K) orthogonal subcarriers, which are also commonly referred to as tones, bins, or the like. Each subcarrier may be modulated with data.

In an embodiment, the BSs <NUM> can assign or schedule transmission resources (e.g., in the form of time-frequency resource blocks) for DL and UL transmissions in the network <NUM>. DL refers to the transmission direction from a BS <NUM> to a UE <NUM>, whereas UL refers to the transmission direction from a UE <NUM> to a BS <NUM>. The communication can be in the form of radio frames. A radio frame may be divided into a plurality of subframes, for example, about <NUM>. Each subframe can be divided into slots, for example, about <NUM>. Each slot may be further divided into mini-slots. In a frequency-division duplexing (FDD) mode, simultaneous UL and DL transmissions may occur in different frequency bands. For example, each subframe includes a UL subframe in a UL frequency band and a DL subframe in a DL frequency band. In a time-division duplexing (TDD) mode, UL and DL transmissions occur at different time periods using the same frequency band. For example, a subset of the subframes (e.g., DL subframes) in a radio frame may be used for DL transmissions and another subset of the subframes (e.g., UL subframes) in the radio frame may be used for UL transmissions.

The DL subframes and the UL subframes can be further divided into several regions. For example, each DL or UL subframe may have pre-defined regions for transmissions of reference signals, control information, and data. Reference signals are predetermined signals that facilitate the communications between the BSs <NUM> and the UEs <NUM>. For example, a reference signal can have a particular pilot pattern or structure, where pilot tones may span across an operational bandwidth or frequency band, each positioned at a pre-defined time and a pre-defined frequency. For example, a BS <NUM> may transmit cell specific reference signals (CRSs) and/or channel state information -reference signals (CSI-RSs) to enable a UE <NUM> to estimate a DL channel. Similarly, a UE <NUM> may transmit sounding reference signals (SRSs) to enable a BS <NUM> to estimate a UL channel. Control information may include resource assignments and protocol controls. Data may include protocol data and/or operational data. In some embodiments, the BSs <NUM> and the UEs <NUM> may communicate using self-contained subframes. A self-contained subframe may include a portion for DL communication and a portion for UL communication. A self-contained subframe can be DL-centric or UL-centric. A DL-centric subframe may include a longer duration for DL communication than UL communication. A UL-centric subframe may include a longer duration for UL communication than UL communication.

In an embodiment, a UE <NUM> attempting to access the network <NUM> may perform an initial cell search by detecting a primary synchronization signal (PSS) from a BS <NUM>. The PSS may enable synchronization of period timing and may indicate a physical layer identity value. The UE <NUM> may then receive a secondary synchronization signal (SSS). The SSS may enable radio frame synchronization, and may provide a cell identity value, which may be combined with the physical layer identity value to identify the cell. The SSS may also enable detection of a duplexing mode and a cyclic prefix length. Some systems, such as TDD systems, may transmit an SSS but not a PSS. Both the PSS and the SSS may be located in a central portion of a carrier, respectively.

After receiving the PSS and SSS, the UE <NUM> may receive a master information block (MIB), which may be transmitted in the physical broadcast channel (PBCH). The MIB may contain system bandwidth information, a system frame number (SFN), and a Physical Hybrid-ARQ Indicator Channel (PHICH) configuration. After decoding the MIB, the UE <NUM> may receive one or more system information blocks (SIBs). For example, SIB1 may contain cell access parameters and scheduling information for other SIBs. Decoding SIB1 may enable the UE <NUM> to receive SIB2. SIB2 may contain radio resource configuration (RRC) configuration information related to random access channel (RACH) procedures, paging, physical uplink control channel (PUCCH), physical uplink shared channel (PUSCH), power control, SRS, and cell barring. After obtaining the MIB and/or the SIBs, the UE <NUM> can perform random access procedures to establish a connection with the BS <NUM>. After establishing the connection, the UE <NUM> and the BS <NUM> can enter a normal operation stage, where operational data may be exchanged.

In an embodiment, the network <NUM> may operate over a shared channel, which may include a licensed spectrum, a shared spectrum, and/or an unlicensed spectrum, and may support dynamic medium sharing. The BSs <NUM> and the UEs <NUM> may be operated by multiple network operating entities sharing resources in the shared channel. A BS <NUM> or a UE <NUM> may reserve a transmission opportunity (TXOP) in the shared channel by transmitting a reservation signal prior to transmitting data in the TXOP. Other BSs <NUM> and/or other UEs <NUM> may listen to the channel and refrain from accessing the channel during the TXOP upon detection of the reservation signal.

In an embodiment, the shared channel may be located at frequencies of about <NUM> or above <NUM>. When a BS <NUM> operates at a high-frequency range, the BSs <NUM> may communicate with the UEs <NUM> using narrow directional beams to overcome the high path-loss in the high-frequency range. For example, the BS <NUM> may transmit discovery signals, such as PSSs, SSSs, PBCH signals, and/or other discovery reference signals, using narrow directional beams. The BS <NUM> may sweep the narrow directional beams in multiple directions for the discovery signal transmissions to allow UEs <NUM> located in different directions with respect to the BS <NUM> to search and synchronize to the BS <NUM>. In order to avoid collisions with transmissions from other BSs <NUM> and/or other UEs, the BS <NUM> may perform LBT in a spatial domain (e.g., spatial-aware LBT) prior to transmitting the discovery signals. Mechanisms for performing LBT with discovery signal transmissions are described in greater detail herein.

<FIG> and <FIG> illustrate various mechanisms for transmitting discovery signals in units of synchronization signal blocks (SSBs). Each SSB may include a PSS, an SSS, a PBCH signal, and/or any discovery related reference signals. In <FIG> and <FIG>, the x-axes represent time in some constant units, and the y-axes represent frequency in some constant units.

<FIG> illustrates a discovery signal transmission scheme <NUM> according to embodiments of the present disclosure. The scheme <NUM> may be employed by BSs such as the BSs <NUM> in a network such as the network <NUM>. The scheme <NUM> illustrates a plurality of transmission slots <NUM> in a frequency band <NUM> over a duration <NUM>. Each transmission slot <NUM> includes a plurality of symbols <NUM>. The frequency band <NUM> may be located at frequencies of about sub-<NUM> or above <NUM>. In some embodiments, the frequency band <NUM> may be in an unlicensed spectrum or a shared spectrum. A transmission slot <NUM> may correspond to a subframe or a slot within a subframe. A symbol <NUM> may correspond to an OFDM symbol. A BS may communicate with a UE such as the UEs <NUM> in the transmission slots <NUM>. The BS may transmit SSBs <NUM> in one or more of transmission slots <NUM> over the duration <NUM>. The SSBs <NUM> may be transmitted over a frequency band <NUM>. The transmissions are represented by pattern filled boxes. In an embodiment, the frequency band <NUM> may correspond to a system bandwidth of a network and the frequency band <NUM> may have a substantially smaller bandwidth than the system bandwidth and may be located within the frequency band <NUM>. The transmissions of the SSBs <NUM> in the narrower frequency band <NUM> allow a UE to synchronize to the network by operating in a smaller bandwidth than the system bandwidth, thereby reducing UE implementation complexity.

The duration <NUM> may be referred to as a DMTC window, which may include any suitable amount of time. As an example, the duration <NUM> may be about five milliseconds (ms). The number of transmission slots <NUM> within the duration <NUM> may vary depending on the subcarrier spacing (SCS) and the number of symbols <NUM> within a transmission slot <NUM>. In an embodiment, each transmission slot <NUM> may include about fourteen symbols <NUM>. When the SCS is about <NUM> kilohertz (kHz), each transmission slot <NUM> may span about <NUM> and the duration <NUM> may include about five transmission slots <NUM>. When the SCS is about <NUM>, each transmission slot <NUM> may span about <NUM> and the duration <NUM> may include about ten transmission slots <NUM>. When the SCS is about <NUM>, each transmission slot <NUM> may span about <NUM> and the duration <NUM> may include about forty transmission slots <NUM>. When the SCS is about <NUM>, each transmission slot <NUM> may span about <NUM> microseconds (µs) and the duration <NUM> may include about eighty transmission slots <NUM>.

In the scheme <NUM>, a BS may transmit L number of SSBs <NUM> with the duration <NUM>, where L is a positive integer. As an example, each SSB <NUM> may span about four symbols <NUM>. Thus, each transmission slot <NUM> may include a maximum of about two SSBs <NUM>. As shown, a SSB 220a may be transmitted in the third, fourth, fifth, sixth symbols <NUM> of a transmission slot <NUM> and another SSB 220b may transmitted in the ninth, tenth, eleventh, and twelve symbols <NUM> of the transmission slot <NUM>. In some other embodiments, the two SSBs 220a and 220b may be transmitted during other symbols <NUM> within the transmission slot <NUM>. L may have a value of about <NUM>, <NUM>, or <NUM> depending on the SCS and the duration <NUM>. In an embodiment, L may be about <NUM> or <NUM> for a SCS of about <NUM> or about <NUM>. When L is <NUM>, a BS may transmit four SSBs <NUM> in two transmission slots <NUM> within the duration <NUM>. In some instances, the BS may transmit the SSBs <NUM> in consecutive transmission slots <NUM>. When L is <NUM>, a BS may transmit eight SSBs <NUM> in four transmission slots <NUM> (e.g., consecutively) within the duration <NUM>.

In an embodiment, L may be about <NUM> for a SCS of about <NUM> or about <NUM>. Thus, a BS may transmit sixty-four SSBs <NUM> in about thirty-two transmission slots <NUM> within the duration <NUM>. In some instances, the BS may transmit the SSBs <NUM> in groups of eight SSBs <NUM> over four transmission slots <NUM> and the groups may be separated by one transmission slot <NUM>.

In an embodiment, a BS may transmit SSBs <NUM> in different beam directions over the duration <NUM>. For example, the BS may include an array of antenna elements and may configure the array of antenna elements to form a transmission beam <NUM> in a certain direction. As an example, the BS may transmit the SSB 220a over a transmission beam 211a (e.g., shown as pattern-filled) directing towards a direction <NUM> and may transmit the SSB 220b over another transmission beam 211b (e.g., shown as pattern-filled) directing towards a direction <NUM>. In some instances, the duration <NUM> or the DMTC window may be repeated at a predetermined periodicity (e.g., at about <NUM>, about <NUM>, or about <NUM>), where a BS may periodically transmit the SSBs <NUM>.

<FIG> illustrates a discovery signal transmission scheme <NUM> according to embodiments of the present disclosure. The scheme <NUM> may be employed by BSs such as the BSs <NUM> in a network such as the network <NUM>. The scheme <NUM> may have a substantially similar transmission slot configuration as in the scheme <NUM>. However, the scheme <NUM> may employ different SCSs for data transmissions and discovery signal or SSB transmissions. As an example, a network may employ an SCS of about <NUM> for data transmissions and an SCS of about <NUM> for SSB transmissions. Similar to the scheme <NUM>, a transmission slot <NUM> may include about fourteen symbols <NUM>. However, a BS may transmit a maximum of about four SSBs <NUM> similar to the SSBs <NUM> in a transmission slot <NUM>. Each SSB <NUM> may span about two symbols <NUM> instead of four symbols <NUM> due to the larger SCS used for SSB transmissions. Similar to the scheme <NUM>, each SSB <NUM> may be transmitted in a different beam direction. As shown, a BS may sweep through multiple narrow directional transmissions beams 211a, 211b, 211c, and 211d during a transmission slot <NUM> for transmitting the SSBs 320a, 320b, 320c, and 320d, respectively.

<FIG> is a block diagram of an exemplary UE <NUM> according to embodiments of the present disclosure. The UE <NUM> may be a UE <NUM> as discussed above. As shown, the UE <NUM> may include a processor <NUM>, a memory <NUM>, a communication discovery module <NUM>, a transceiver <NUM> including a modem subsystem <NUM> and a radio frequency (RF) unit <NUM>, and one or more antennas <NUM>. These elements may be in direct or indirect communication with each other, for example via one or more buses.

The memory <NUM> may include a cache memory (e.g., a cache memory of the processor <NUM>), random access memory (RAM), magnetoresistive RAM (MRAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), flash memory, solid state memory device, hard disk drives, other forms of volatile and non-volatile memory, or a combination of different types of memory. In an embodiment, the memory <NUM> includes a non-transitory computer-readable medium. The instructions <NUM> may include instructions that, when executed by the processor <NUM>, cause the processor <NUM> to perform the operations described herein with reference to the UEs <NUM> in connection with embodiments of the present disclosure. Instructions <NUM> may also be referred to as code. The terms "instructions" and "code" should be interpreted broadly to include any type of computer-readable statement(s). For example, the terms "instructions" and "code" may refer to one or more programs, routines, subroutines, functions, procedures, etc. "Instructions" and "code" may include a single computer-readable statement or many computer-readable statements.

The communication discovery module <NUM> may be implemented via hardware, software, or combinations thereof. For example, the communication discovery module <NUM> may be implemented as a processor, circuit, and/or instructions <NUM> stored in the memory <NUM> and executed by the processor <NUM>. The communication discovery module <NUM> may be used for various aspects of the present disclosure. For example, the communication discovery module <NUM> is configured to receive discovery signals (e.g., PSS, SSSs, PBCH signals, discovery reference signals, and SSBs <NUM> and <NUM>) from a BS such as the BSs 105a over a shared channel (e.g., the frequency band <NUM>), synchronize to the BS based on the discovery signals, and/or communicate with the BS after synchronization, as described in greater detail herein.

As shown, the transceiver <NUM> may include the modem subsystem <NUM> and the RF unit <NUM>. The transceiver <NUM> can be configured to communicate bi-directionally with other devices, such as the BSs <NUM>. The modem subsystem <NUM> may be configured to modulate and/or encode the data from the memory <NUM>, and/or the communication discovery module <NUM> according to a modulation and coding scheme (MCS), e.g., a low-density parity check (LDPC) coding scheme, a turbo coding scheme, a convolutional coding scheme, a digital beamforming scheme, etc. The RF unit <NUM> may be configured to process (e.g., perform analog to digital conversion or digital to analog conversion, etc.) modulated/encoded data from the modem subsystem <NUM> (on outbound transmissions) or of transmissions originating from another source such as a UE <NUM> or a BS <NUM>. The RF unit <NUM> may be further configured to perform analog beamforming in conjunction with the digital beamforming. Although shown as integrated together in transceiver <NUM>, the modem subsystem <NUM> and the RF unit <NUM> may be separate devices that are coupled together at the UE <NUM> to enable the UE <NUM> to communicate with other devices.

The RF unit <NUM> may provide the modulated and/or processed data, e.g. data packets (or, more generally, data messages that may contain one or more data packets and other information), to the antennas <NUM> for transmission to one or more other devices. This may include, for example, transmission of random access signals for initial network attachment and/or data signals carrying information data according to embodiments of the present disclosure. The antennas <NUM> may further receive data messages transmitted from other devices. This may include, for example, reception of discovery signals such as PSSs, SSSs, PBCH signals, discovery reference signals, and/or SSBs according to embodiments of the present disclosure. The antennas <NUM> may provide the received data messages for processing and/or demodulation at the transceiver <NUM>. The antennas <NUM> may include multiple antennas of similar or different designs in order to sustain multiple transmission links. The RF unit <NUM> may configure the antennas <NUM>.

<FIG> is a block diagram of an exemplary BS <NUM> according to embodiments of the present disclosure. The BS <NUM> may be a BS <NUM> as discussed above. A shown, the BS <NUM> may include a processor <NUM>, a memory <NUM>, a communication discovery module <NUM>, a transceiver <NUM> including a modem subsystem <NUM> and a RF unit <NUM>, and one or more antennas <NUM>. These elements may be in direct or indirect communication with each other, for example via one or more buses.

The communication discovery module <NUM> may be implemented via hardware, software, or combinations thereof. For example, the communication discovery module <NUM> may be implemented as a processor, circuit, and/or instructions <NUM> stored in the memory <NUM> and executed by the processor <NUM>. The communication discovery module <NUM> may be used for various aspects of the present disclosure. For example, the communication discovery module <NUM> is configured to perform spatial-aware or directional LBT in a shared channel (e.g., the frequency band <NUM>), transmit discovery signals (e.g., SSBs <NUM> and <NUM>) based on the results of the LBT, and/or transmit channel reservation signals or preamble signals to silence other nearby transmitters that may interfere with discovery signal transmission, as described in greater detail herein.

As shown, the transceiver <NUM> may include the modem subsystem <NUM> and the RF unit <NUM>. The transceiver <NUM> can be configured to communicate bi-directionally with other devices, such as the UEs <NUM> and/or another core network element. The modem subsystem <NUM> may be configured to modulate and/or encode data according to a MCS, e.g., a LDPC coding scheme, a turbo coding scheme, a convolutional coding scheme, a digital beamforming scheme, etc. The RF unit <NUM> may be configured to process (e.g., perform analog to digital conversion or digital to analog conversion, etc.) modulated/encoded data from the modem subsystem <NUM> (on outbound transmissions) or of transmissions originating from another source such as a UE <NUM> or <NUM>. The RF unit <NUM> may be further configured to perform analog beamforming and/or digital beamforming for directional signal transmissions and/or receptions. In some embodiments, the transceiver <NUM> may include antenna array elements and/or transceiver components (e.g., power amplifiers) that can be switched on or off to form a beam in a particular direction. Alternatively, the transceiver <NUM> may include multiple transmit/receive chains and may switch between the multiple transmit/receive chains to form a beam in a particular direction. Although shown as integrated together in transceiver <NUM>, the modem subsystem <NUM> and the RF unit <NUM> may be separate devices that are coupled together at the BS <NUM> to enable the BS <NUM> to communicate with other devices.

The RF unit <NUM> may provide the modulated and/or processed data, e.g. data packets (or, more generally, data messages that may contain one or more data packets and other information), to the antennas <NUM> for transmission to one or more other devices. This may include, for example, transmission of information to complete attachment to a network and communication with a camped UE <NUM> or <NUM> according to embodiments of the present disclosure. The antennas <NUM> may further receive data messages transmitted from other devices and provide the received data messages for processing and/or demodulation at the transceiver <NUM>. The antennas <NUM> may include multiple antennas of similar or different designs in order to sustain multiple transmission links.

<FIG> illustrate various mechanisms for performing spatial-aware or directional LBTs in a shared channel prior to transmitting discovery signals (e.g., PSSs, SSSs, PBCH signals, discovery reference signals, and/or SSBs <NUM> and <NUM>). In <FIG>, the x-axes represent time in some constant units, and the y-axes represent frequency in some constant units.

<FIG> illustrates a discovery signal transmission scheme <NUM> with omnidirectional LBT according to embodiments of the present disclosure. The scheme <NUM> may be employed by BSs such as the BSs <NUM> and <NUM> in a network such as the network <NUM>. The scheme <NUM> includes a DMTC period <NUM> including a plurality of transmission slots <NUM> in a frequency band <NUM> shared by multiple network operating entities. The transmission slots <NUM> are shown as <NUM>S(<NUM>) to <NUM>S(N). Each transmission slot <NUM> includes a plurality of symbols <NUM>. The DMTC period <NUM>, the transmission slots <NUM>, the symbols <NUM>, and the frequency band <NUM> may be substantially similar to the duration <NUM>, the transmission slots <NUM>, the symbols <NUM>, and the frequency band <NUM>, respectively. The DMTC period <NUM> may be repeated at a sparse frequency rate, for example, at about every <NUM>, every <NUM>, or any suitable rate.

Similar to the schemes <NUM> and <NUM>, a BS may transmit a plurality of SSBs <NUM> in a frequency band <NUM> within the frequency band <NUM> using multiple directional transmission beams <NUM> directing towards different beam directions during the DMTC period <NUM>. The frequency band <NUM> may be substantially similar to the frequency band <NUM>. The direction transmission beams <NUM> may be substantially similar to the direction transmission beams <NUM>. For example, the BS may transmit a subset of the SSBs <NUM> in the transmission slot <NUM>S(<NUM>) and another subset of the SSBs <NUM> in the transmission slot <NUM>S(N). In the transmission slot <NUM>S(<NUM>), the SSBs 620a, 620b, 620c, and 620d may be transmitted over different transmission beams 611a, 611b, 611c, and 611d, respectively, each directing towards a different direction. Similarly, in the transmission slot <NUM>S(N), the SSBs 620e, 620f, <NUM>, and <NUM> may be transmitted over different transmission beams 611e, 611f, <NUM>, and <NUM>, respectively, each directing towards a different direction. The SSBs <NUM> may be substantially similar to the SSBs <NUM> and <NUM>. For example, each SSB <NUM> may include a PSS, a SSS, a PBCH signal, and/or a discovery reference signal, as described in greater detail herein.

To avoid collisions with transmissions from other nodes (e.g., the BSs <NUM> and the UEs <NUM>) in the frequency band <NUM>, the BS may listen to the channel (e.g., the frequency band <NUM>) prior to transmitting the SSBs <NUM>. For example, the BS may perform omnidirectional LBT <NUM> in a period <NUM> prior to the DMTC period <NUM>. The BS may configure antenna array elements (e.g., in the transceiver <NUM>) such that the BS may receive signals in all available directions as shown by the omnidirectional reception beam <NUM>. When the BS detects a transmission from another node (e.g., a BS <NUM> or a UE <NUM>) in the channel from any direction, the BS may refrain from proceeding with the transmissions of the SSBs <NUM> during the DMTC period <NUM>. The detection may be based on energy detection and/or sequence (e.g., a predetermined waveform used for channel reservation) detection and/or preamble (e.g., a predetermined waveform transmitted along with a packet) detection. However, when the BS determines that the channel is idle, the BS may continue to transmit the SSBs <NUM> during the DMTC period <NUM>.

The BS may optionally transmit a channel reservation signal <NUM> after performing the omnidirectional LBT <NUM> to avoid interference from nearby transmitters. The BS may transmit the channel reservation signal <NUM> over an omnidirectional transmission beam in a period <NUM>. The period <NUM> may follow the period <NUM> without a time gap since the BS is not required to switch a beam direction between the omnidirectional LBT <NUM> and the omnidirectional transmission of the channel reservation signal <NUM>. The BS may configure the antenna array elements to transmit in all directions, as shown by the omnidirectional transmission beam <NUM>. The channel reservation signal <NUM> may include a predetermined preamble sequence. When another transmitter detected the channel reservation signal <NUM>, the transmitter may refrain from transmitting in the frequency band <NUM>.

The scheme <NUM> may avoid interferers that are substantially close to the BS. However, the omnidirectional LBT <NUM> may not be effective in detecting energy or a preamble transmission from a specific beam direction and the omnidirectional channel reservation may not be heard by a node listening or sensing the channel in a specific beam direction.

<FIG> illustrates a discovery signal transmission scheme <NUM> with spatial-specific LBT according to embodiments of the present disclosure. The scheme <NUM> may be employed by BSs such as the BSs <NUM> and <NUM> in a network such as the network <NUM>. The scheme <NUM> may be substantially similar to the scheme <NUM>. However, the scheme <NUM> may perform spatial-specific LBT and spatial-specific channel reservation in addition to omnidirectional LBT and omnidirectional channel reservation. As shown, a BS may perform spatial-specific LBT <NUM> by sweeping through a plurality of directional reception beams <NUM> in a period <NUM> prior to the DMTC period <NUM>. For example, the BS may perform K number of spatial-specific LBTs <NUM> as shown by <NUM>B(<NUM>) to 710BB(K). Each reception beam <NUM> may have a coverage over one or more of the transmission beams <NUM> used for transmitting the SSBs <NUM> during the DMTC period <NUM>. In other words, the receive beams <NUM> may have a wider beam width than the transmission beams <NUM>. As an example, a BS may configure antenna array elements to form a reception beam <NUM>B(<NUM>) for sensing the channel (e.g., the frequency band) in the beam directions of the transmission beams 611a, 611b, 611c, and 611d.

When a spatial-specific LBT <NUM> indicates that the channel is clear, the BS may proceed with transmissions of SSBs <NUM> in the beam directions corresponding to the spatial-specific LBT <NUM>. Conversely, when a spatial-specific LBT <NUM> indicates that the channel is occupied, the BS may refrain from transmitting SSBs <NUM> in the beam directions corresponding to the spatial-specific LBT <NUM>.

Similar to the scheme <NUM>, the BS may optionally transmit a channel reservation signal <NUM> after performing each spatial-specific LBT <NUM>. The channel reservation signal <NUM> may be substantially similar to the channel reservation signals <NUM>. But, the channel reservation signal <NUM> may be transmitted using a directional beam <NUM>. As shown, the channel reservation signals <NUM> are transmitted in the same beam direction as a prior spatial-specific LBT <NUM>.

The spatial-specific LBTs and the spatial-specific channel reservations may be effective in avoiding interferers transmitting and/or listening in specific spatial directions. Thus, the scheme <NUM> may further reduce collisions compared to the scheme <NUM>. However, the BS may require a time gap <NUM> for switching from one beam direction to another beam direction between the spatial-specific LBTs <NUM>. The presence of the time gap <NUM> may lead to a collision from an interferer beginning a transmission within the time gap <NUM>.

<FIG> illustrates a discovery signal transmission scheme <NUM> with spatial-specific LBT according to embodiments of the present disclosure. The scheme <NUM> may be employed by BSs such as the BSs <NUM> and <NUM> in a network such as the network <NUM>. The scheme <NUM> may be substantially similar to the scheme <NUM>. However, a BS may sweep spatial-specific LBTs <NUM> in all K directions prior to transmitting spatial-specific channel reservations signals <NUM> in response to the spatial-specific LBTs <NUM>. The spatial-specific LBTs <NUM> and the transmissions of the spatial-specific channel reservations signals <NUM> may be performed within a period <NUM> prior to the DMTC period <NUM>. A time gap similar to the time gap <NUM> may be required between each spatial-specific LBT <NUM> and each spatial-specific channel reservation signal <NUM> transmissions to allow the BS to switch antenna array configurations.

<FIG> illustrates a discovery signal transmission scheme <NUM> with spatial-specific LBT according to embodiments of the present disclosure. The scheme <NUM> may be employed by BSs such as the BSs <NUM> and <NUM> in a network such as the network <NUM>. The scheme <NUM> may be substantially similar to the schemes <NUM> and <NUM>. However, in the scheme <NUM>, a BS may perform spatial-specific LBTs <NUM> and transmit spatial-specific channel reservation signals <NUM> within a DMTC period <NUM> instead of prior to a DMTC period <NUM>.

The BS may perform a spatial-specific LBT <NUM> prior to transmitting a subset of one or more SSBs <NUM>. The spatial-specific LBT <NUM> may be performed based on the expected beam transmission directions used for transmitting the subset of SSBs <NUM>. As an example, the BS may perform a spatial-specific LBT <NUM>B(<NUM>) using a directional reception beam <NUM>B(<NUM>) prior to transmitting the SSBs 620a, 620b, 620c, and 620d. The directional reception beam <NUM>B(<NUM>) may include a coverage over the transmission beams 611a, 611b, 611c, and 611d. The BS may optionally transmit a channel reservation signal <NUM> in response to each spatial-specific LBT <NUM> by using the same beam direction as the spatial-specific LBT <NUM>. The BS may perform the spatial-specific LBT <NUM> and transmit the spatial-specific channel reservation signal <NUM> transmission immediately before the transmission of the first SSB 620a in the subset, for example, in a period of one to two symbols <NUM>.

When a spatial-specific LBT <NUM> (e.g., the spatial-specific LBT <NUM>B(<NUM>)) indicates that the channel is clear, the BS may proceed with transmitting SSBs <NUM> (e.g., the SSBs 620a, 620b, 620c, and 620d) in the beam directions corresponding to the spatial-specific LBT <NUM>. Conversely, when a spatial-specific LBT <NUM> (e.g., the spatial-specific LBT <NUM>B(K)) indicates that the channel is occupied, the BS may refrain from transmitting SSBs <NUM> in the beam directions corresponding to the spatial-specific LBT <NUM> as shown by the dashed box with the cross.

Comparing the scheme <NUM> to the schemes <NUM> and <NUM>, the scheme <NUM> may further reduce collisions. In addition, the scheme <NUM> may allow the channel reservation signals <NUM> to be multiplexed with the SSBs <NUM>, as described in greater detail herein.

While the schemes <NUM>-<NUM> are illustrated with omnidirectional LBT and omnidirectional channel reservation transmissions in conjunctions with spatial-specific LBTs and spatial-specific channel reservations, the omnidirectional LBT and the omnidirectional channel reservation transmissions may be optional.

<FIG> illustrates a discovery signal transmission scheme <NUM> with concurrent channel reservation signal transmission according to embodiments of the present disclosure. The scheme <NUM> may be employed by BSs such as the BSs <NUM> and <NUM> in a network such as the network <NUM>. In particular, the scheme <NUM> may be used in conjunction with the scheme <NUM> to transmit a channel reservation signal <NUM> using FDM in place of the channel reservation signal <NUM> (e.g., using TDM). For example, a BS may transmit an SSB <NUM> including a PSS <NUM>, an SSS <NUM>, and PBCH signals <NUM> in the frequency band <NUM> and may transmit a channel reservation signal <NUM> in the same symbol as the PSS <NUM> using remaining unused resources (e.g., resource elements (REs)) in the frequency portion <NUM>. The channel reservation signal <NUM> may include a predetermined preamble sequence configured based on the number of unused resource elements in the frequency portion <NUM>. In addition, the BS may transmit a demodulation reference signal (DMRS) <NUM> distributed in the frequency portion <NUM> to facilitate decoding of the PBCH signals <NUM>, channel discovery, and/or channel synchronization. Since the channel reservation signal <NUM> is frequency multiplexed with the SSB <NUM>, the scheme <NUM> may reduce system overhead compared to the scheme <NUM>.

As shown in the scheme <NUM> and <NUM>, there are unused resources (e.g., time-frequency resources) in the DMTC period <NUM>. For example, the first, second, third, fourth, thirteen, and fourteen symbols <NUM> in the transmission slot <NUM>S(<NUM>) are unused. Thus, a BS may transmit a data signal in the unused symbols <NUM>. In an embodiment, the BS may transmit the data signal in a beam direction corresponding to a spatial-specific LBT <NUM> performed for the subset of SSBs <NUM> in the transmission slot <NUM>S(<NUM>). For example, the BS may use a directional transmission beam similar to the transmission beam <NUM>B(<NUM>), which may be wider than the transmission beams 611a, 611b, 611c, and 611d, for the data signal transmission. Alternatively, the BS may select a directional transmission beam from any one of the transmission beams 611a, 611b, 611c, and 611d. The BS may also transmit the data signal in the same symbol <NUM> as an SSB <NUM> using remaining unused frequency resources (e.g., in the frequency portion <NUM>) and in the same beam direction as the SSB <NUM>. Thus, the BS may multiplex data signals with the SSBs <NUM> in a transmission slot <NUM> in a time domain and/or frequency domain.

<FIG> is a flow diagram of a communication discovery method <NUM> according to embodiments of the present disclosure. Steps of the method <NUM> can be executed by a computing device (e.g., a processor, processing circuit, and/or other suitable component) of a wireless communication device, such as the BSs <NUM> and <NUM>. The method <NUM> may employ similar mechanisms as in the schemes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> as described with respect to <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, and <FIG>, respectively. As illustrated, the method <NUM> includes a number of enumerated steps, but embodiments of the method <NUM> may include additional steps before, after, and in between the enumerated steps. In some embodiments, one or more of the enumerated steps may be omitted or performed in a different order.

At step <NUM>, the method <NUM> includes sensing, by a wireless communication device, a channel (e.g., the frequency bands <NUM> and <NUM>) in a spatial domain based on a plurality of expected beam transmission directions (e.g., based on the transmission beams <NUM> and <NUM>). The wireless communication device may be associated with a first network operating entity. The channel may be shared by a plurality of network operating entity including the first network operating entity.

At step <NUM>, the method <NUM> includes transmitting, by the wireless communication device, a plurality of discovery signals (e.g., the SSBs <NUM> and <NUM>, the PSS <NUM>, the SSS <NUM>, the PBCH signals <NUM>, and/or any discovery reference signal) in one or more of the plurality of expected beam transmission directions during a discovery period (e.g., the DMTC period <NUM>) to facilitate synchronization in the channel based on the sensing.

In an embodiment, the sensing includes monitoring the channel for a transmission from another wireless communication device using an omnidirectional reception beam (e.g., the omnidirectional reception beam <NUM>) before the discovery period. In response to the sensing, the wireless communication device may transmit a channel reservation signal (e.g., the channel reservation signal <NUM>) over an omnidirectional transmission beam (e.g., the omnidirectional transmission beam <NUM>) before the discovery period.

In an embodiment, the sensing includes sweeping through multiple narrow directional reception beams (e.g., the reception beams <NUM>) and listening to the channel in each of the beam directions. For example, the sensing includes monitoring the channel in a first subset of the plurality of expected beam transmission directions (e.g., the beam directions of the beams 611a, 611b, 611c, and 611d) for a transmission from another wireless communication device. The monitoring includes configuring antenna elements (e.g., in the transceiver <NUM>) of the wireless communication device to direct reception in a beam direction including a coverage over the first subset of the plurality of expected beam transmission directions. In such an embodiment, the transmitting of the plurality of discovery signals may include transmitting a subset of the plurality of discovery signals (e.g., the SSBs 620a, 620b, 620c, and 620d), each in one of the first subset of the plurality of expected beam transmission directions. The sensing can further include monitoring the channel in a second subset of the plurality of expected beam transmission directions (e.g., based on the beams 611e, 611f, <NUM>, and <NUM>) for a transmission from another wireless communication device. The sensing can be repeated in subsets of the expected beam transmission directions until all beam directions are monitored.

In some embodiments, the directional sensing (e.g., using the narrow beams) may be performed prior to the discovery period, for example, as shown in the schemes <NUM> and <NUM>. In response to the sensing, the wireless communication device may transmit a channel reservation signal (e.g., the channel reservation signal <NUM>) after sensing each beam direction before switching to another beam direction. Each channel reservation signal may be transmitted in the same direction as the sensing. Alternatively, the wireless communication device may sweep through all the subset of beam directions for sensing before sweeping through the subset of beam directions for transmitting the channel reservation signals.

In some embodiments, the directional sensing may be performed within the discovery period, for example, as shown in the scheme <NUM>. For example, the channel is monitored in the first subset of the plurality of expected beam transmission directions within the discovery period before transmitting the subset of the plurality of discovery signals. In response to the sensing, the wireless communication device may transmit a channel reservation signal in the same direction as the sensing before transmitting the subset of discovery signals. In some embodiments, the wireless communication device can transmit the channel reservation signal concurrent with at least one of the subset of discovery signals using FDM, for example, as shown in the scheme <NUM>. In some embodiments, the monitoring in the second subset of the plurality of expected beam transmission directions may detect a transmission from another wireless communication device. Upon the detection, the wireless communication device may refrain from transmitting discovery signals in the second subset of the plurality of expected beam transmission directions.

Also, as used herein, including in the claims, "or" as used in a list of items (for example, a list of items prefaced by a phrase such as "at least one of" or "one or more of") indicates an inclusive list such that, for example, a list of [at least one of A, B, or C] means A or B or C or AB or AC or BC or ABC (i.e., A and B and C).

Claim 1:
A method (<NUM>) of wireless communication, comprising:
sensing (<NUM>), by a base station, a channel in a spatial domain based on a plurality of expected beam transmission directions, wherein the base station is associated with a first network operating entity, and wherein the channel is shared by a plurality of network operating entities including the first network operating entity, wherein the sensing includes monitoring the channel for a transmission from a wireless communication device using an omnidirectional reception beam before a discovery period;
transmitting, by the base station, a channel reservation signal using an omnidirectional transmission beam before the discovery period based on the sensing; and
transmitting (<NUM>), by the base station, a plurality of discovery signals in one or more of the plurality of expected beam transmission directions during the discovery period to facilitate synchronization in the channel based on the sensing.