Patent Description:
After considering this discussion, and particularly after reading the section entitled "Detailed Description" one will understand how the features of this disclosure provide advantages that include improved sidelink communications among user equipments when one UE is outside of coverage of a network.

US patent application <CIT>A relates to a radio terminal that comprises a controller configured to be capable of relaying traffic between another radio terminal and a network by a proximity service. The controller performs a control for transmitting first information and second information, in a sidelink. The first information is used for identifying a location of a radio resource in which the second information is arranged. The second information is used to identify a location of a radio resource for requesting the relay by the proximity.

Aspect of the present invention are set out in the appended claims.

Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for transmitting system information on sidelinks for sidelink operations by user equipments (UEs). In previously known wireless communications systems, most of the necessary configurations for sidelink (e.g., vehicle-to-anything (V2X) or device-to-device (D2D)) communications may be configured on UEs by a next generation NodeB (gNB) or pre-configured in the UEs. These configurations may include subcarrier spacing (SCS), bandwidth, channelization, and/or a time-division duplex (TDD) configuration. If a UE does not receive the configurations from the gNB, then the UE may receive some of the configurations in a physical sidelink broadcast channel (PSBCH) transmitted by another UE, which carries a sidelink master information block (MIB) that may also convey, for example, a frame number of the communication system. Still, the information in a sidelink MIB (S-MIB) may not be sufficient for a UE to start transmitting or receiving on sidelink in certain scenarios. For example, when sidelink transmissions are configured to share licensed spectrum with cellular links (e.g., downlink transmissions from a base station or uplink transmissions to a base station), the resources (e.g., time slots and/or frequency bands) available to sidelink transmissions need to be known to UEs, so UEs know when and on what frequencies to receive or transmit on sidelink(s), and sidelink communications will not interfere with cellular communications. Such resource configurations can be done by a gNB; but in some cases a UE is unable to get the sidelink configuration directly from gNB. In one example, a first UE out of coverage (OoC) of a gNB that desires to communicate with a second UE that is in coverage (InC) of the gNB can't receive sidelink resource configurations from the gNB because the first UE is OoC. In another example, a first UE that is InC of a first gNB, gNB <NUM>. desires to communicate with a second UE that is InC of a second gNB, gNB2, and the two gNBs may have different sidelink configurations, so the first UE cannot communicate with the second UE via a sidelink without the first UE obtaining the sidelink configuration from gNB2.

According to aspects of the present disclosure, techniques for conveying configuration information for sidelink (SL) communications via a sidelink are provided. The configurations may include, for example, TDD uplink/downlink configuration, SL resource pool configuration, and sidelink bandwidth part (BWP) configuration.

The following description provides examples of conveying system information (SI) in sidelink communications in communication systems, and is not limiting of the scope, applicability, or examples set forth in the claims.

In aspects of the present disclosure, LTE 120a, which is in coverage of BS 110a in cell 102a, may transmit system information on a sidelink to UE 120b, which is out of coverage of the cell 102a. UE 120a may use a system information (SI) on sidelink module to determine whether to transmit SI on a sidelink to UE 120b and to transmit the SI on the sidelink to UE 120b. Similarly, UE 120b may use an SI on sidelink module to determine whether to attempt to receive SI on a sidelink from UE 120a and to attempt to receive the SI on the sidelink from 120b.

According to certain aspects, the UEs <NUM> may be configured for transmitting and receiving SI on sidelink. As shown in <FIG>, the UE 120a includes a transmit SI on sidelink manager 122a. The transmit SI on sidelink manager 122a may be configured to transmit first system information to a second UE (e.g., UE 120b); to determine, based on one or more first parameters, to transmit second system information to the second UE; to transmit the second system information in a sidelink system information block (S-SIB) to the second UE; and to communicate with the second UE via sidelink resources determined based on the first system information and the second system information, in accordance with aspects of the present disclosure. Also as shown in <FIG>, the UE 120b includes a receive SI on sidelink manager 122b. The receive SI on sidelink manager 122b may be configured to receive first system information from a second UE; to determine, based on one or more first parameters, to receive second system information from the second UE; to receive the second system information in a sidelink system information block (S-SIB) from the second UE; and to communicate with the second UE via sidelink resources determined based on the first system information and the second system information, in accordance with aspects of the present disclosure.

Wireless communication network <NUM> may also include relay stations (e.g., relay station <NUM>10r), also referred to as relays or the like, that receive a transmission of data and/or other information from an upstream station (e.g., a BS 110a or a UE 120r) and sends a transmission of the data and/or other information to a downstream station (e.g., a UE <NUM> or a BS <NUM>), or that relays transmissions between UEs <NUM>, to facilitate communication between devices.

<FIG> illustrates example components of UE 120a and UE 120b (e.g., in the wireless communication network <NUM> of <FIG>), which may be used to implement aspects of the present disclosure.

At the UE 110a, a transmit processor <NUM> may receive data from a data source <NUM> and control information from a controller/processor <NUM>. The control information may be for the physical sidelink broadcast channel (PSBCH) or physical sidelink control channel (PSCCH), physical uplink control channel (PUCCH), etc. The data may be for the physical sidelink shared channel (PSSCH), physical uplink shared channel (PUSCH), etc. The processor <NUM> may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. A transmit (TX) multiple-input multiple-output (MIMO) processor <NUM> may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to the modulators (MODs) 232a-232t. Each modulator <NUM> may process a respective output symbol stream to obtain an output sample stream. Each modulator may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain an uplink or sidelink signal. Uplink or sidelink signals from modulators 232a-232t may be transmitted via the antennas 234a-234t, respectively.

At the UE 120b, the antennas 252a-252r may receive the sidelink signals from the UE 120a and may provide received signals to the demodulators (DEMODs) in transceivers 254a-254r, respectively. Each demodulator may further process the input samples to obtain received symbols. A MIMO detector <NUM> may obtain received symbols from all the demodulators 254a-254r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor <NUM> may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for the UE 120b to a data sink <NUM>, and provide decoded control information to a controller/processor <NUM>.

On the uplink, at UE 120b, a transmit processor <NUM> may receive and process data (e.g., for the physical uplink shared channel (PUSCH) or the physical sidelink shared channel (PSSCH)) from a data source <NUM> and control information (e.g., for the physical uplink control channel (PUCCH) or the physical sidelink control channel (PSCCH)) from the controller/processor <NUM>. The symbols from the transmit processor <NUM> may be precoded by a TX MIMO processor <NUM> if applicable, further processed by the demodulators in transceivers 254a-254r (e.g., for SC-FDM, etc.), and transmitted to the UE 120a. At the UE 120a, the sidelink signals from the UE 120a may be received by the antennas <NUM>, processed by the modulators <NUM>, detected by a MIMO detector <NUM> if applicable, and further processed by a receive processor <NUM> to obtain decoded data and control information sent by the UE 120b.

The memories <NUM> and <NUM> may store data and program codes for UE 120a and UE 120b, respectively.

The controller/processor <NUM> and/or other processors and modules at the UE 120b may perform or direct the execution of processes for the techniques described herein. For example, as shown in <FIG>, the controller/processor <NUM> of the UE 120a has a transmit SI on sidelink manager <NUM> that may be configured for transmitting first system information to a second UE (e.g., UE 120b); for determining, based on one or more first parameters, to transmit second system information to the second UE; for transmitting the second system information in a sidelink system information block (S-SIB) to the second UE; and for communicating with the second UE via sidelink resources determined based on the first system information and the second system information, according to aspects described herein. As shown in <FIG>, the controller/processor <NUM> of the UE 120b has a receive SI on sidelink manager <NUM> that may be configured for receiving first system information from a second UE; for determining, based on one or more first parameters, to receive second system information from the second UE; for receiving the second system information in a sidelink system information block (S-SIB) from the second UE; and for communicating with the second UE via sidelink resources determined based on the first system information and the second system information, according to aspects described herein. Although shown at the Controller/Processor, other components of the UE 120a and UE 120b may be used performing the operations described herein.

<FIG> shows an exemplary communication system <NUM> illustrating partial coverage in sidelink communication, according to aspects of the present disclosure. In the exemplary communication system, a UE <NUM> is in coverage (InC) of a cell <NUM> served by a base station <NUM> (e.g., a gNB). A UE <NUM> is out of coverage (OoC) of the cell <NUM>, but the UE <NUM> is synchronized to the BS <NUM>, because UE <NUM> is indirectly synchronized to BS <NUM> via the UE <NUM>. In the exemplary communication system, the UE <NUM> may not be allowed to use an arbitrary resource although it is OoC, in order to avoid potential interference of transmissions by UE <NUM> to cellular reception by UE <NUM>. Therefore, TDD UL/DL configuration or other information (e.g., sidelink resource pool) may be needed by UE <NUM>. UE <NUM> can send that information and/or configuration to UE <NUM>, according to aspects of the present disclosure. Thus, if the communications system uses TDD and allocates a portion <NUM> of uplink resources <NUM> to sidelink transmissions, then it would be desirable for the UE <NUM> to obtain information on that allocation, but the UE <NUM> cannot receive it from the BS <NUM> because the UE <NUM> is OoC of the BS <NUM>.

Accordingly, techniques and apparatus for transmitting system information on sidelink are desirable.

Aspects of the present disclosure provide techniques for transmission of system information from a first UE to a second UE via a sidelink transmission. The SI transmission via a sidelink may occur as a two-step transmission (i.e., two separate transmissions and receptions).

In aspects of the present disclosure, the first transmission contains the first system information (e.g., a sidelink master information block (S-MIB)), and the second transmission contains the second system information (e.g., a sidelink system information block (S-SIB)).

<FIG> is an exemplary call flow <NUM> of transmitting system information on sidelink, according to aspects of the present disclosure. In the exemplary call flow, a first UE <NUM> receives first system information (e.g., in a sidelink master information block (S-MIB)) from a second UE <NUM> at <NUM>. At <NUM>, the first UE determines to receive second system information. The first UE then determines time and frequency resources to receive the second system information at <NUM>. Meanwhile, the second UE determines to transmit the second system information at <NUM>, and at <NUM>, the second UE determines time and frequency resources to transmit the second system information. At <NUM>, the second UE transmits the second system information via the resources determined at <NUM>, and the first UE receives the second system information on the resources determined at <NUM>. At <NUM>, the first UE determines time and frequency resources for sidelink communications, based on the first and second system information. The second UE determines time and frequency resource for sidelink communications, based on the first and second system information, at <NUM>. At <NUM>, the first UE and the second UE communicate via sidelink on the determined time and frequency resources.

According to aspects of the present disclosure, the S-SIB carries one or more of a TDD UL/DL configuration, a sidelink resource pool (i.e., time and/or frequency resources allocated for sidelink communications), and a bandwidth part (BWP) for sidelink communication.

In aspects of the present disclosure, the first transmission implies or indicates a set of resources for the second transmission.

According to aspects of the present disclosure, the second transmission may be optional, i.e., not all UEs communicating on sidelink are required to transmit and/or receive second system information (e.g., an S-SIB).

In aspects of the present disclosure, a UE receiving system information on a sidelink receives a first system information (e.g., in an S-MIB), then the UE determines whether to receive second system information (e.g., in an S-SIB). The UE receives the second system information, if the determination is to receive the second system information, based on the first system information.

According to aspects of the present disclosure, the UE communicates with other UEs on sidelink based at least on the first and second system information. For example, the UE may determine a sidelink resource configuration(s) based on the first and second system information.

In aspects of the present disclosure, the first system information may indicate or imply the presence of the second system information. That is, an indicator in the first system information may directly indicate that another UE has or will transmit the second system information, or a parameter in the first system information may imply that another UE has or will transmit the second system information.

In aspects of the present disclosure, a UE receives the second system information when presence of the second system information is indicated or implied by first system information. For example, an S-MIB includes a parameter that indicates the presence of an S-SIB, or an S-MIB includes a parameter that implies the presence of an S-SIB. In another example, an S-MIB includes a parameter indicating the system is TDD, and then a UE determines to receive S-SIB based on the system being TDD, i.e., the UE will not receive the S-SIB if the system is not TDD (for instance, the system is FDD, or, sidelink communication is deployed on unlicensed spectrum or spectrum for Intelligent Transportation Systems, etc.). In yet another example, an S-MIB includes a parameter indicating or implying the synchronization source on sidelink is a gNB, then the UE determines to receive the S-SIB, i.e., the UE will not receive the S-SIB if the synchronization source is not a gNB but some other synchronization source, such as a global navigation satellite system (GNSS) or a UE. In still another example, the first system information may be conveyed by a sidelink synchronization signal block (S-SSB) that conveys an S-MIB, and information in the S-SSB that is not in the S-MIB implies the presence of S-SIB. For example, an S-SSB transmitted by a UE implies or indicates that the synchronization source on sidelink is a gNB (i.e., not GNSS or the UE), but the coverage status of a UE receiving the S-SSB is out of coverage, so the receiving UE receives the S-SIB to communicate via sidelink with the transmitting UE. This is similar to the partial coverage scenario described above with reference to <FIG>.

According to aspects of the present disclosure, a UE may determine whether to receive second system information based on one or more of the following factors (i.e., the UE determines whether to receive based on information at the UE's and not the indication of an S-MIB):.

In aspects of the present disclosure, the UE determines to receive second system information when the UE successfully decodes the first system information, i.e., receiving of the second system information is mandatary for the UE when the UE successfully decodes the first system information. For example, a network standard requires the two types of system information to always be transmitted together, so a UE decoding the first system information determines to attempt to receive the second system information.

According to aspects of the present disclosure, a UE that has determined to receive second system information may determine a time resource (e.g., a slot) to receive the second system information.

In aspects of the present disclosure, a UE that has determined to receive second system information may determine that there is a window (e.g., a set of consecutive slots) to receive the second system information and then attempt to receive the second system information using a time resource occurring during the window. The size of the window may, for example, be pre-configured or be determined based on a received configuration (e.g., received in first system information), subcarrier spacing, or some other parameter.

According to aspects of the present disclosure, the first system information may include one or more parameter(s) indicating a time resource (e.g., a slot) to receive the second system information, and a UE that has determined to receive the second system information determines when to receive the second system information based on the indication in the first system information. For example, first system information indicates a specific slot to receive the second system information, and a UE receiving the first system information determines the specific slot to receive the second system information based on the indication in the first system information.

In aspects of the present disclosure, there is a configured, pre-configured, pre-defined, and/or pre-determined parameter indicating the time resource (e.g., a slot) to receive the second system information, and a UE that has determined to receive the second system information determines a time resource to receive the second system information based on the parameter.

<FIG> is an exemplary timeline <NUM> illustrating use of a window to receive second system information and use of a parameter, k, indicating a time resource for receiving second system information, according to aspects of the present disclosure. First system information is received in an S-MIB by a UE at <NUM>. In one example, the UE attempts to receive second system information in an S-SIB during a time resource occurring during an exemplary window <NUM>. The length of the window may be determined by a parameter. In another example, a parameter, k, indicates that the second system information comes in an S-SIB in a slot (n+k) at <NUM>, when the first system information comes in slot n. In the example, the parameter k ≥ <NUM>.

In aspects of the present disclosure, a UE that has determined to receive second system information determines frequency resources (e.g., resource blocks (RBs)) on which to receive the second system information.

According to aspects of the present disclosure, first system information may have one or more parameters indicating the frequency resources to receive the second system information, and the UE that has determined to receive the second system information may determine the frequency resources to receive the second system information based on the one or more parameters.

In aspects of the present disclosure, the frequency resources used to receive first system information implies the frequency resources to receive the second system information.

According to aspects of the present disclosure, the frequency resources used to receive first system information implies a number of frequency resources may be used to receive the second system information, and the UE that has determined to receive the second system information receives in the implied frequency resources, e.g., by blind decoding signals received in each of the implied frequency resources.

<FIG> illustrate exemplary frequency allocations <NUM> and <NUM> for transmission of an S-SIB via a physical sidelink shared channel (PSSCH), according to aspects of the present disclosure. In the frequency allocation <NUM>, a sidelink bandwidth <NUM> is divided into four sub-channels, <NUM>, <NUM>, <NUM>, and <NUM>, each of which contains multiple RBs. During a first period (e.g., a slot), a UE receives a PSBCH <NUM> containing an S-MIB. In one example, in a later period, the receiving UE blindly decodes PSCCH <NUM> (i.e., tries a few offsets with respect to the S-MIB starting RB) to receive the PSCCH containing the sidelink control information (SCI) that indicates the frequency resources allocated for the PSSCH conveying the S-SIB. In a second example, in the later period, the S-MIB indicates an offset of the PSCCH <NUM> starting RB with respect to the S-MIB starting RB, and the PSCCH contains SCI indicating the frequency resources allocated for the PSSCH conveying the S-SIB. In the frequency allocation <NUM>, an SCI <NUM> in a second period has a same starting position as an S-MIB in a first period. The SCI indicates a starting position of a PSSCH conveying S-SIB in the second period as an offset from the starting position of the S-MIB <NUM>.

<FIG> illustrates exemplary frequency allocations <NUM> and <NUM> for transmission of an S-SIB via a PSSCH, according to aspects of the present disclosure. In the frequency allocation <NUM>, a sidelink bandwidth <NUM> is divided into four sub-channels, <NUM>, <NUM>, <NUM>, and <NUM>, each of which contains multiple RBs. In the frequency allocations <NUM> and <NUM>, the S-SIB is sent in a same period (e.g., a same slot) as the S-MIB. In the frequency allocation <NUM>, the PSCCH conveying the SCI <NUM> indicating the frequency allocation of the PSSCH conveying the S-SIB <NUM> is adjacent to the frequency allocation for the S-MIB <NUM>. A UE receiving the S-MIB <NUM> may determine the frequency location of the PSCCH conveying the SCI <NUM> as being adjacent to the frequency location of the PSBCH conveying the S-MIB <NUM>. In the frequency allocation <NUM>, the PSCCH conveying the SCI <NUM> indicating the frequency allocation of the PSSCH conveying the S-SIB <NUM> is located at an offset <NUM> from the frequency location of the PSBCH conveying the S-MIB <NUM>. The MIB <NUM> may convey an indication of that offset <NUM>. Alternatively, a receiving UE may determine the offset by blindly decoding to find the PSCCH conveying the SCI <NUM>.

According to aspects of the present disclosure, transmitting the S-MIB and S-SIB in a same period (e.g., a same slot) may conserve transmission resources as compared to transmitting the S-MIB and the S-SIB in different periods, as portions of a period conveying an S-MIB may not be available for any other transmissions (e.g., sidelink transmissions cannot be made because system information in the S-SIB has not been transmitted).

In aspects of the present disclosure, the slot (e.g., a time resource) used for transmission of an S-MIB may be included in an S-SIB window. Thus, an offset of k = <NUM> may indicate that the S-MIB and S-SIB are transmitted in a same slot, as illustrated in <FIG>.

According to aspects of the present disclosure, it may be mandatory (e.g., defined in a network communications standard) that S-MIB and S-SIB be transmitted in a same slot.

In aspects of the present disclosure, an S-MIB may indicate a slot for S-SIB transmission, e.g., by including a time offset that indicates the slot of the S-SIB transmission, counting from and including the slot for the S-MIB transmission. That is, the S-MIB may indicate time offset of zero, which indicates the S-SIB is transmitted in the same slot as the S-MIB.

According to aspects of the present disclosure, a frequency location of a PSCCH conveying an allocation (e.g., an SCI) for an S-SIB may be adjacent to a frequency location of a PSBCH conveying an S-MIB, and a receiving UE determines a frequency location to decode the PSCCH conveying the allocation of the S-SIB based on the frequency location of the PSBCH conveying the S-MIB.

In aspects of the present disclosure, an offset to a frequency location of a PSCCH conveying an allocation (e.g., an SCI) for an S-SIB may be indicated by an S-MIB (e.g., as shown in frequency allocation <NUM> in <FIG>).

According to aspects of the present disclosure, an offset to a frequency location of a PSCCH conveying an allocation (e.g., an SCI) for an S-SIB may be determined by a UE receiving an S-MIB and blindly decoding the PSCCH conveying the allocation for the S-SIB. The UE may start from a location indicated by the S-MIB.

In aspects of the present disclosure, the first system information is carried by an S-MIB transmitted on a physical sidelink broadcast channel (PSBCH), and the second system information is carried by an S-SIB transmitted on a physical sidelink shared channel (PSSCH).

According to aspects of the present disclosure, the second system information may have parameters indicating one or more of:.

In aspects of the present disclosure, the first and second system information may be transmitted periodically.

According to aspects of the present disclosure, the first and second system information may be transmitted with a same periodicity, however, repetition within a period may be different. For example, the second system information may be repeated less often than the first system information. In this example, the periodicity is <NUM>, a number of transmission occasions of first system information within a period is L<NUM>, and a number of transmission occasions of second system information within a period is L<NUM>. In this example, L<NUM> is configurable (e.g., based on carrier frequency range), but L<NUM> is fixed. That is, L<NUM> may be configured to any of <NUM>, <NUM>, <NUM>, <NUM>, etc., but L<NUM> is fixed at <NUM>. In another example, both L<NUM> and L<NUM> are fixed for a given carrier frequency range, e.g., L<NUM>=L<NUM>=<NUM> if carrier frequency of the communications system is less than <NUM>.

In aspects of the present disclosure, both L<NUM> and L<NUM> are configurable. They may be determined based on carrier frequency range, whether a communications system uses TDD or FDD, or other parameters.

<FIG> is an exemplary timeline <NUM> showing periodic transmissions of first system information and second system information when L<NUM> ≠ L<NUM>, according to aspects of the present disclosure. In the exemplary timeline, transmission of first system information and second system information are both done periodically, with the period shown at <NUM>. Also in the exemplary timeline L<NUM> = <NUM>, and thus first system information is transmitted at <NUM>, <NUM>, <NUM>, and <NUM>. In the exemplary timeline, L<NUM> = <NUM>, and thus second system information is transmitted at <NUM> and <NUM>.

<FIG> is a flow diagram illustrating example operations <NUM> for wireless communication, in accordance with certain aspects of the present disclosure. The operations <NUM> may be performed, for example, by a first UE (e.g., such as a UE 120b in the wireless communication network <NUM>). Operations <NUM> may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor <NUM> of <FIG>). Further, the transmission and reception of signals by the first UE in operations <NUM> may be enabled, for example, by one or more antennas (e.g., antennas <NUM> of <FIG>). In certain aspects, the transmission and/or reception of signals by the first UE may be implemented via a bus interface of one or more processors (e.g., controller/processor <NUM>) obtaining and/or outputting signals.

The operations <NUM> may begin, at block <NUM>, by a first UE receiving first system information from a second UE. For example, the UE <NUM> of <FIG> receives first system information from the UE <NUM>. In the example, the UE <NUM> (i.e., the first UE) may be out of coverage (OoC) and thus may rely on obtaining the first system information (e.g., for configuration) from UE <NUM> (i.e., the second UE). The configuration may include a TDD UL/DL configuration, or other information such as a sidelink resource pool. The configuration may enable the first UE to avoid potential interference of its own transmission even though the first UE may be OoC. In some aspects, the first system information may include a sidelink master information block (S-MIB).

At block <NUM>, operations <NUM> may continue with the first UE determining, based on one or more first parameters, to receive second system information from the second UE. Continuing the example, as further discussed below, UE <NUM> determines, based on one or more first parameters, to receive second system information from UE <NUM>. In the example, the one or more first parameters may indicate or imply a presence of a sidelink secondary information block (S-SIB).

Operations <NUM> may continue at block <NUM> with the first UE receiving the second system information in a sidelink system information block (S-SIB) from the second UE. Continuing the example, UE <NUM> receives the second system information in an S-SIB from the second UE. In some instances, the first UE may receive the second system information based on the one or more first parameters of the first system information. In other instances, the first UE may determine whether to receive the second system information based on the frequency band deploying the sidelink between the first UE and the second UE, or based on a timer operating in accordance to a previously received second system information. In some other instances, the first UE may determine to receive the second system information upon successfully decoding the first system information (e.g., when S-MIB and S-SIB are transmitted together).

At block <NUM>, operations <NUM> may continue with the first UE communicating with the second UE via sidelink resources determined based on the first system information and the second system information. Continuing the example, UE <NUM> communicating with UE <NUM> via sidelink resources determined based on the first system information (received in block <NUM>) and the second system information (received in block <NUM>). In an example, the sidelink resources may include one or more sub-channels (frequency resources) and one or more time slots (e.g., time resources). In some aspects, the first UE may determine one or more time slots to receive the second system information. As further discussed below, the UE may determine the time slots (e.g., time resources) based on a time window or a parameter indicating a time resource for receiving the second system information. The parameter may be a configured or pre-defined parameter.

In aspects of the present disclosure, a UE (e.g., UE 120a in <FIG>) may transmit first system information (e.g., in an S-MIB), determine whether to transmit second system information (e.g., in an S-SIB), transmit the second system information if the determination is to transmit it, and then communicate with one or more other UEs on sidelink based at least on the first and second system information (e.g., the UE determines sidelink resource configurations based on the first and second system information).

According to aspects of the present disclosure, before transmitting the first and/or second system information, the UE may receive third system information, where the third system information is sent by a gNB or another UE; and the third system information indicates or implies at least one of the following:.

In aspects of the present disclosure, a UE may determine to transmit second system information based on a synchronization priority on sidelink of the UE. That is, the UE has information regarding its own synchronization priority and determines to transmit second system information based on that synchronization priority. The UE's synchronization priority may be associated to its S-SSB or S-MIB transmission. When performing sidelink synchronization, a UE determines its synchronization priority, and the UE transmits second system information only if the UE has higher synchronization priority than a threshold synchronization priority to transmit second system information. For example, a base station has the highest synchronization priority (priority level <NUM>), a UE directly synchronized to a base station has the second highest synchronization priority (priority level <NUM>), a UE directly synchronized to a UE that is directly synchronized to a base station has the next highest synchronization priority (priority level <NUM>), etc..

A UE may be configured to transmit second system information only if its synchronization priority is equal to or higher than level <NUM>. In another example, a synchronization priority of a UE may be indicated by a hop counter from an original synchronization source as follows: if the UE is directly synchronized to a base station, then the UE has hop counter equal to <NUM>; if the UE is synchronized to another UE which has hop counter <NUM> (i.e., the other UE directly synchronized to a base station), then the UE has hop counter equal to <NUM>, etc. In this example, the smaller the hop counter a UE has, the higher the synchronization priority that UE has. In yet another example, a UE transmits second system information only if the UE has a synchronization hop counter equal to <NUM> (i.e., only UEs directly synchronized to base station(s) transmit second system information). In still another example, a UE transmits second system information if the UE has a synchronization hop counter that is smaller than a threshold nhop, which has a (pre-)configured or pre-determined value.

According to aspects of the present disclosure, a UE performing operations <NUM> may receive the first system information (i.e., in block <NUM>) via a sidelink master information block (S-MIB). In aspects of the present disclosure, the S-MIB may be conveyed via a physical sidelink broadcast channel (PSBCH).

In aspects of the present disclosure, the first system information received by a UE performing operations <NUM> may include a first parameter of the one or more first parameters that implicitly indicates the second UE will transmit or has transmitted the S-SIB. According to aspects of the present disclosure, the first parameter may indicate the second UE uses a time-division duplex (TDD) communication system. Additionally or alternatively the first parameter may indicate that a synchronization source for the second UE is a base station (BS).

In aspects of the present disclosure, the first system information received by a UE performing operations <NUM> may be conveyed in a sidelink synchronization signal block (S-SSB).

According to aspects of the present disclosure, the one or more first parameters of block <NUM> in operations <NUM> may include a frequency band used by the second UE for transmitting the first system information.

In aspects of the present disclosure, the one or more first parameters of block <NUM> in operations <NUM> may include an elapsed time since the first UE previously received another second system information. According to aspects of the present disclosure, the other second system information may have been received from a base station (BS). Alternatively, the other second system information may have been received from the second UE.

In aspects of the present disclosure, the one or more first parameters of block <NUM> in operations <NUM> may include an indication that the first UE decoded the first system information.

According to aspects of the present disclosure, a UE performing operations <NUM> may determine a time resource (e.g., a slot) to receive the S-SIB and receive the S-SIB at the determined time. In aspects of the present disclosure, the time resource may occur during a window (e.g., as illustrated in <FIG>), and the UE may determine a size of the window. According to aspects of the present disclosure, determining the size of the window may include determining the size of the window based on subcarrier spacing used by the second UE to transmit the first system information. In aspects of the present disclosure, the first system information may include one or more second parameters and the UE may determine the time based on the one or more second parameters. According to aspects of the present disclosure, the time may occur a predetermined period after the UE receives the first system information.

In aspects of the present disclosure, a UE performing operations <NUM> may determine a frequency resource to receive the S-SIB (i.e., the S-SIB received in block <NUM>). According to aspects of the present disclosure, the first system information may include one or more second parameters and the UE may determine the frequency resource to receive the S-SIB based on the one or more second parameters. In aspects of the present disclosure, a UE performing operations <NUM> may determine the frequency resource to receive the S-SIB based on a frequency used to transmit the first system information. Alternatively or additionally, a UE performing operations <NUM> may determine the frequency resource to receive the S-SIB by determining a plurality of frequency resources and performing blind decoding to receive the second system information in the plurality of frequency resources.

According to aspects of the present disclosure, a UE performing operations <NUM> may receive the S-SIB in a physical sidelink shared channel (PSSCH).

In aspects of the present disclosure, the second system information received in block <NUM> may include a time-division duplex (TDD) uplink/downlink (UL/DL) configuration for sidelink communications, a sidelink slots configuration indicating slots allocated for sidelink communications, a sidelink bandwidth part indicating a frequency band allocated for sidelink communication, and/or a sidelink resource pool indicating a set of time and frequency resources allocated for sidelink communication.

According to aspects of the present disclosure, the first system information in block <NUM> may be transmitted by the second UE at a first periodicity, and the second system information may be transmitted by the second UE at a second periodicity (e.g., as illustrated in <FIG>).

<FIG> is a flow diagram illustrating example operations <NUM> for wireless communication, in accordance with certain aspects of the present disclosure. The operations <NUM> may be performed, for example, by a first UE (e.g., such as the UE 120a in the wireless communication network <NUM>). The operations <NUM> may be complimentary operations by the first UE to the operations <NUM> performed by the UE described with reference to <FIG>, above. For example, the operations <NUM> may be performed by a UE transmitting system information (SI) via a sidelink, and a UE performing operations <NUM> may receive the SI via the sidelink from the UE performing operations <NUM>.

Operations <NUM> may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor <NUM> of <FIG>). Further, the transmission and reception of signals by the first UE in operations <NUM> may be enabled, for example, by one or more antennas (e.g., antennas <NUM> of <FIG>). In certain aspects, the transmission and/or reception of signals by the first UE may be implemented via a bus interface of one or more processors (e.g., controller/processor <NUM>) obtaining and/or outputting signals.

The operations <NUM> may begin, at block <NUM>, with the first UE transmitting first system information to a second UE. For example, the UE <NUM> of <FIG> transmits first system information to UE <NUM>. In the example, the UE <NUM> may be in coverage and able to transmit the first system information for configuration of the UE <NUM>. Like in operations <NUM>, the configuration may include TDD UL/DL configuration or other information such as a sidelink resource pool. In some aspects, the first system information may include a sidelink master information block (S-MIB).

Operations <NUM> may continue, at block <NUM>, with the first UE determining, based on one or more first parameters, to transmit second system information to the second UE. Continuing the example, UE <NUM> determines, based on one or more first parameters, to transmit second system information to UE <NUM>. For example, UE <NUM> may make the determination before transmitting the first system information, or after transmitting the first system information but before transmitting the second system information to UE <NUM>. In another example, UE <NUM> may receive third system information sent by a network device (e.g., a gNB or another UE) indicating specifications regarding transmitting the second system information. The specifications may include (<NUM>) whether to send the second system information, (<NUM>) resources to use for sending second system information, such as any relevant time or frequency resources, and (<NUM>) parameters carried by the second system information, as further described in various aspects below.

At block <NUM>, operations <NUM> may continue with the first UE transmitting the second system information in a sidelink system information block (S-SIB) to the second UE. Continuing the example, UE <NUM> transmits the second system information in an S-SIB to UE <NUM>. In some examples, the first UE may transmit the second system information that uses the one or more first parameters of the first system information. In other examples, the first UE may transmit the second system information in response to requests sent from the second UE, which determines whether to receive the second system information based on the frequency band deploying the sidelink between the first UE and the second UE, or based on a timer operating in accordance to a previously received second system information. In some other examples, the second UE may determine to receive the second system information upon successfully decoding the first system information (e.g., when S-MIB and S-SIB are transmitted together).

Operations <NUM> may continue, at block <NUM>, with the first UE communicating with the second UE via sidelink resources determined based on the first system information and the second system information. Continuing the example, UE <NUM> communicates with UE <NUM> via sidelink resources determined based on the first system information (transmitted at block <NUM>) and the second system information (transmitted at block <NUM>). In the example, UE <NUM> may determine sidelink resource configurations based on the first system information and the second system information.

In aspects of the present disclosure, an S-SIB may be carried by a PSSCH, and an allocation of a set of time and frequency resources for the PSSCH may be indicated by aPSCCH.

According to aspects of the present disclosure, an S-SIB time location may be determined from an S-MIB time location.

In aspects of the present disclosure, an S-SIB may be transmitted in a window of length N (e.g., <NUM>) slots after transmission of an S-MIB. A UE receiving the S-MIB may try to decode an S-SIB during the window.

According to aspects of the present disclosure, an S-MIB may include a parameter indicating a slot (e.g., a time resource) carrying an S-SIB. A UE receiving the S-MIB may then receive the S-SIB in the indicated slot.

In aspects of the present disclosure, an S-MIB may indicate a window or a slot to receive an S-SIB, due to uncertainty of a TDD UL/DL pattern making it impractical to use a predetermined slot for transmission of an S-SIB.

In aspects of the present disclosure, an S-SIB contains system information from a cellular communication system for sidelink communications with a UE operating in that cellular communication system. Thus, a UE may be able to transmit and receive on sidelink after receiving the S-SIB.

According to aspects of the present disclosure, S-SIB transmission and reception may be optional for some sidelink communications. For example, receiving an S-SIB may not be needed for sidelink communications in ITS or unlicensed spectrum.

In aspects of the present disclosure, whether an S-SIB has or will be transmitted may be indicated by an S-MIB.

According to aspects of the present disclosure, other configurations may be contained in an S-SIB.

In aspects of the present disclosure, a BWP configuration for SL communications may be included in an S-SIB. Such a BWP configuration may be used for SL communications when the SL communications share licensed spectrum, and for ITS or unlicensed spectrum, a UE may use a default pre-configuration instead of a BWP configuration included in an S-SIB.

According to aspects of the present disclosure, a wireless communications network may use transmission of system information via sidelink communications (e.g., transmission of SI in an S-MIB and/or an S-SIB) to act as a UE-to-network relay.

In aspects of the present disclosure, a UE performing operations <NUM> may receive third system information from a base station (BS) or a third UE, wherein the third system information includes the one or more first parameters (i.e., the first parameters of block <NUM>). According to aspects of the present disclosure, the third system information may include an indication of time or frequency resources to be used for transmitting the second system information (i.e., block <NUM>). In aspects of the present disclosure, the third system information may include a portion of the second system information.

According to aspects of the present disclosure, a UE performing operations <NUM> may transmit the first system information via a sidelink master information block (S-MIB). In aspects of the present disclosure, the UE may transmit the S-MIB via a physical sidelink broadcast channel (PSBCH).

In aspects of the present disclosure, the first system information may include a first parameter of the one or more first parameters that implicitly indicates the first UE will transmit or has transmitted the S-SIB. According to aspects of the present disclosure, the first parameter may indicate the first UE uses a time-division duplex (TDD) communication system. In aspects of the present disclosure, the first parameter may indicate that a synchronization source for the first UE is a base station (BS).

According to aspects of the present disclosure, a UE performing operations <NUM> may transmit the first system information in a sidelink synchronization signal block (S-SSB).

In aspects of the present disclosure, the one or more first parameters of block <NUM> may include a frequency band used by the first UE for transmitting the first system information.

According to aspects of the present disclosure, the one or more first parameters of block <NUM> may include an elapsed time since the first UE previously transmitted another second system information.

In aspects of the present disclosure, a UE performing operations <NUM> may determine a time resource (e.g., a slot) to transmit the S-SIB and transmit the S-SIB using the determined time resource. According to aspects of the present disclosure, the time resource may occur during a window (e.g., as illustrated in <FIG>), and the UE may determine a size of the window. In aspects of the present disclosure, determining the size of the window may include determining the size of the window based on subcarrier spacing used by the first UE to transmit the first system information. Additionally or alternatively, the first system information may include one or more second parameters and the UE may determine the time resource based on the one or more second parameters. Additionally or alternatively, the UE may determine the time resource as occurring a predetermined period after transmitting the first system information (e.g., as illustrated in <FIG>).

According to aspects of the present disclosure, a UE performing operations <NUM> may determine a frequency resource to transmit the S-SIB (i.e., the S-SIB in block <NUM>). In aspects of the present disclosure, the first system information may include one or more second parameters and the UE may determine the frequency resource based on the one or more second parameters. Additionally or alternatively, the UE may determine the frequency resource based on a frequency used to transmit the first system information.

In aspects of the present disclosure, a UE performing operations <NUM> may transmit the S-SIB in a physical sidelink shared channel (PSSCH).

According to aspects of the present disclosure, the second system information may include a time-division duplex (TDD) uplink/downlink (UL/DL) configuration for sidelink communications, a sidelink slots configuration indicating slots allocated for sidelink communications, a sidelink bandwidth part indicating a frequency band allocated for sidelink communication, and/or a sidelink resource pool indicating a set of time and frequency resources allocated for sidelink communication.

In aspects of the present disclosure, a UE performing operations <NUM> may transmit the first system information at a first periodicity and transmit the second system information at a second periodicity (e.g., as illustrated in <FIG>).

According to aspects of the present disclosure, a UE performing operations <NUM> may determine its own synchronization priority and determine to transmit the second system information (i.e., as described in block <NUM>) based on at least the synchronization priority of the first UE.

The processing system <NUM> includes a processor <NUM> coupled to a computer-readable medium/memory <NUM> via a bus <NUM>. In certain aspects, the computer-readable medium/memory <NUM> is configured to store instructions (e.g., computer-executable code) that when executed by the processor <NUM>, cause the processor <NUM> to perform the operations illustrated in <FIG>, or other operations for performing the various techniques discussed herein for transmitting system information on sidelink. In certain aspects, computer-readable medium/memory <NUM> stores code <NUM> for receiving first system information from a second UE; code <NUM> for determining, based on one or more first parameters, to receive second system information from the second UE, code <NUM> for receiving the second system information in a sidelink system information block (S-SIB) from the second UE, and code <NUM> for communicating with the second UE via sidelink resources determined based on the first system information and the second system information. In certain aspects, the processor <NUM> has circuitry configured to implement the code stored in the computer-readable medium/memory <NUM>. The processor <NUM> includes circuitry <NUM> for receiving first system information from a second UE; circuitry <NUM> for determining, based on one or more first parameters, to receive second system information from the second UE, circuitry <NUM> for receiving the second system information in a sidelink system information block (S-SIB) from the second UE, and circuitry <NUM> for communicating with the second UE via sidelink resources determined based on the first system information and the second system information.

The processing system <NUM> includes a processor <NUM> coupled to a computer-readable medium/memory <NUM> via a bus <NUM>. In certain aspects, the computer-readable medium/memory <NUM> is configured to store instructions (e.g., computer-executable code) that when executed by the processor <NUM>, cause the processor <NUM> to perform the operations illustrated in <FIG>, or other operations for performing the various techniques discussed herein for transmitting system information on sidelink. In certain aspects, computer-readable medium/memory <NUM> stores code <NUM> for transmitting first system information to a second UE; code <NUM> for determining, based on one or more first parameters, to transmit second system information to the second UE, code <NUM> for transmitting the second system information in a sidelink system information block (S-SIB) to the second UE, and code <NUM> for communicating with the second UE via sidelink resources determined based on the first system information and the second system information. In certain aspects, the processor <NUM> has circuitry configured to implement the code stored in the computer-readable medium/memory <NUM>. The processor <NUM> includes circuitry <NUM> for transmitting first system information to a second UE; circuitry <NUM> for determining, based on one or more first parameters, to transmit second system information to the second UE, circuitry <NUM> for transmitting the second system information in a sidelink system information block (S-SIB) to the second UE, and circuitry <NUM> for communicating with the second UE via sidelink resources determined based on the first system information and the second system information.

The terms "first" and "second" (and "third" and so on) are used to describe elements in the order they appear in certain examples, embodiments, or contexts. The terms "first" and "second," and other such language indicating an order of appearance, do not provide specific technical characterization unless particularly designated or classified herein. For example, a first device and a second device may refer to two devices that are mentioned in such order. When described in another context or in another example, the "second device" as initially referred to may be described as a "first device" in the other context or the other example. Such designation allows each context or example to include self-contained description without reliance on other contexts or examples described herein.

For example, such a computer program product may comprise a computer-readable medium having instructions stored (and/or encoded) thereon, the instructions being executable by one or more processors to perform the operations described herein, for example, instructions for performing the operations described herein and illustrated in <FIG> and/or <FIG>.

Claim 1:
A method for wireless communications performed by a first user equipment, UE, comprising:
receiving first system information from a second UE (<NUM>);
determining, based on one or more first parameters, to receive second system information from the second UE (<NUM>);
receiving the second system information in a sidelink system information block, S-SIB, from the second UE, wherein the first system information comprises a first parameter of the one or more first parameters that implicitly indicates the second UE will transmit or has transmitted the S-SIB and wherein the first parameter indicates at least one of:
the second UE uses a time division duplex, IDD, communication system; or
a synchronization source of the second UE is a base station BS; and
communicating with the second UE via sidelink resources determined based on the first system information and the second system information (<NUM>).