Patent Description:
In other examples (e.g., in a next generation, a new radio (NR), or <NUM> network), a wireless multiple access communication system may include a number of distributed units (DUs) (e.g., edge units (EUs), edge nodes (ENs), radio heads (RHs), smart radio heads (SRHs), transmission reception points (TRPs), etc.) in communication with a number of central units (CUs) (e.g., central nodes (CNs), access node controllers (ANCs), etc.), where a set of one or more DUs, in communication with a CU, may define an access node (e.g., which may be referred to as a BS, next generation NodeB (gNB or gNodeB), TRP, etc.). A BS or DU may communicate with a set of UEs on downlink channels (e.g., for transmissions from a BS or DU to a UE) and uplink channels (e.g., for transmissions from a UE to a BS or DU).

<NPL>, describes methods for LTE-NR coexistence in overlapping and adjacent spectrum and signaling to support this.

<NPL>, describes NR frequency and time resource allocation granularity, for coordination signalling required in LTE-NR coexistence on adjacent or co-channel spectrum scenarios. <NPL>, describes an EN-DC X2 setup procedure.

Certain aspects provide a method for wireless communication performed by a first base station that uses a first radio access technology (RAT). The method generally includes generating a first resource coordination information comprising one or more resource coordination bitmaps, each of the one or more resource coordination bitmaps indicating one or more shortened transmission time intervals (sTTIs) of a transmission time interval (TTI) assigned to the first RAT for communication, wherein the TTI comprises a plurality of sTTIs. The method also includes transmitting a message including the first resource coordination information to a second base station that uses a second RAT. The method further includes receiving an acknowledgement of the message from the second base station, the acknowledgment including a second resource coordination information comprising one or more modified resource coordination bitmaps, each of the one or more modified resource coordination bitmaps indicating the one or more sTTIs of the TTI assigned to the first RAT for communication and one or more additional sTTIs of the TTI assigned to the second RAT for communication.

Aspects of the present disclosure also provide a processor and a memory, wherein the memory includes a program executable in the processor to cause the first apparatus which uses a first radio access technology (RAT) to perform operations comprising generating a first resource coordination information comprising one or more resource coordination bitmaps, each of the one or more resource coordination bitmaps indicating one or more shortened transmission time intervals (sTTIs) of a transmission time interval (TTI) assigned to the first RAT for communication, wherein the TTI comprises a plurality of sTTIs. The operations further comprise transmitting a message including the first resource coordination information to a second apparatus that uses a second RAT. The operations further comprise receiving an acknowledgement of the message from the second apparatus, the acknowledgment including a second resource coordination information comprising one or more modified resource coordination bitmaps, each of the one or more modified resource coordination bitmaps indicating the one or more sTTIs of the TTI assigned to the first RAT for communication and one or more additional sTTIs of the TTI assigned to the second RAT for communication.

Aspects of the present disclosure also provide a first apparatus comprising means for generating a first resource coordination information comprising one or more resource coordination bitmaps, each of the one or more resource coordination bitmaps indicating one or more shortened transmission time intervals (sTTIs) of a transmission time interval (TTI) assigned to the first RAT for communication, wherein the TTI comprises a plurality of sTTIs. The first apparatus further comprises means for transmitting a message including the first resource coordination information to a second apparatus that uses a second RAT. The first apparatus further comprises means for receiving an acknowledgement of the message from the second apparatus, the acknowledgment including a second resource coordination information comprising one or more modified resource coordination bitmaps, each of the one or more modified resource coordination bitmaps indicating the one or more sTTIs of the TTI assigned to the first RAT for communication and one or more additional sTTIs of the TTI assigned to the second RAT for communication.

Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for enabling a base station (BS), which uses one RAT (e.g., LTE) to coordinate resource utilization with another BS, which uses another RAT (e.g., NR), for communication with a user equipment (UE).

In certain cases, a BS may transmit and/or receive signals to a UE on multiple carriers, which may be referred to as component carriers (CCs), using carrier aggregation (CA). In some cases, the concurrent communication of the UE with LTE and NR base stations, however, may create interference, even when separate CCs are used for each RAT. Certain techniques may be used to reduce this interference by allowing BSs using different RATs to coordinate their resource utilizations in the time and frequency domains for communication with a UE. To coordinate resource utilization among each other, two BSs using different RATs may be configured to utilize resource coordination information that the two BSs may exchange.

For example, a main BS, such as a main eNB (MeNB) using LTE, may generate a "MeNB Resource Coordination Information," including a UL bitmap and a DL bitmap that show MeNB's resource utilization in the time and frequency domains when communicating with a UE. The MeNB then transmits the MeNB Resource Coordination Information to a secondary BS, such as a secondary gNB (SgNB), which uses NR. The SgNB then determines its resource utilization and maps the utilization to the bitmaps received from MeNB by modifying the bitmaps, etc. In certain cases, the MeNB and SgNB are configured to coordinate their resource utilization on a subframe level. However, in LTE Release <NUM> time resources may be structured differently. More specifically, time resources may be structured as shortened TTIs (sTTIs), which may comprise two types. The first type of sTTI is defined as a slot (also referred to as a slot sTTI), which corresponds to a half-subframe. The second type of sTTI is defined as a sub-slot (also referred to as a sub-slot sTTI). With the use of sTTIs, there is a need for configuring the resource coordination information (e.g., LTE-NR coordination information) for two BSs, which use different RATs, at the sTTI level. Accordingly, certain aspects described herein relate to configuring the resource coordination information at the sTTI level. At the sTTI level, subframe structures, such as LTE-FDD sTTI DL subframe structures, are based on different Control Format Indicator (CFI) values. As such, certain aspects described herein also relate to configuring the resource coordination information such that the resource coordination information is independent of what CFI value is used.

The techniques described herein may be used for various wireless communication technologies, such as 3GPP Long Term Evolution (LTE), LTE-Advanced (LTE-A), code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), single-carrier frequency division multiple access (SC-FDMA), time division synchronous code division multiple access (TD-SCDMA), and other networks.

NR access (e.g., <NUM> NR) may support various wireless communication services, such as enhanced mobile broadband (eMBB) targeting wide bandwidth (e.g., <NUM> or beyond), millimeter wave (mmW) targeting high carrier frequency (e.g., <NUM> or beyond), massive machine type communications MTC (mMTC) targeting non-backward compatible MTC techniques, and/or mission critical targeting ultra-reliable low-latency communications (URLLC).

For example, as shown in <FIG>, the BS 110a, which uses one RAT, has a module for coordinating resource utilization with another BS, such as BS 110b, which uses another RAT, for communication with UE 120a.

As illustrated in <FIG>, the wireless communication network <NUM> may include a number of base stations (BSs) <NUM> and other network entities. A BS may be a station that communicates with user equipments (UEs). Each BS <NUM> may provide communication coverage for a particular geographic area. In some examples, the BSs may be interconnected to one another and/or to one or more other BSs or network nodes (not shown) in wireless communication network <NUM> through various types of backhaul interfaces, such as a direct physical connection, a wireless connection, a virtual network, or the like using any suitable transport network.

A finely dashed line with double arrows indicates potentially interfering transmissions between a UE and a BS.

<FIG> illustrates example components of BS <NUM> and UE <NUM> (e.g., in the wireless communication network <NUM> of <FIG>), which may be used to implement aspects of the present disclosure. For example, antennas <NUM>, processors <NUM>, <NUM>, <NUM>, and/or controller/processor <NUM> of the UE <NUM> and/or antennas <NUM>, processors <NUM>, <NUM>, <NUM>, and/or controller/processor <NUM> of the BS <NUM> may be used to perform the various techniques and methods described herein. For example, as shown in <FIG>, the controller/processor <NUM> of BS <NUM>, which uses one RAT, has a module for coordinating resource utilization with another BS, which uses another RAT, for communication with UE <NUM>.

The transmit processor <NUM> may also generate reference symbols, such as for the primary synchronization signal (PSS), secondary synchronization signal (SSS), and cell-specific reference signal (CRS). 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. Downlink signals from modulators 232a-232t may be transmitted via the antennas 234a-234t, respectively.

At the UE <NUM>, the antennas 252a-252r may receive the downlink signals from the BS <NUM> and may provide received signals to the demodulators (DEMODs) in transceivers 254a-254r, respectively. 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.

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 base station <NUM>.

The controllers/processors <NUM> and <NUM> may direct the operation at the BS <NUM> and the UE <NUM>, respectively. The controller/processor <NUM> and/or other processors and modules at the BS <NUM> may perform or direct the execution of processes for the techniques described herein.

Wireless communications technologies may enable networks to support wider transmission bandwidths by using carrier aggregation. For example, in certain aspects, a BS (e.g., BS <NUM>) may transmit and/or receive signals on multiple carriers, which may be referred to as component carriers (CCs) using carrier aggregation (CA). Each component carrier used for communication by BSs and UEs (e.g., UE <NUM>) may have a different associated frequency (e.g., center frequency of the component carrier).

In CA, two or more CCs are aggregated in order to increase the transmission bandwidth. A CA-capable UE may, therefore, simultaneously receive or transmit on one or multiple CCs depending on its capabilities. In some cases, CA allows two separate radio access technologies (RATs) to simultaneously communicate with a UE using two different component carriers. For example, a UE may be configured with dual connectivity (e.g., dual transmitter and dual receiver) to simultaneously communicate with a LTE base station as well an NR base station on different carrier frequencies (e.g., CCs).

In some cases, the concurrent communication of the UE with LTE and NR base stations, however, may create interference, even when separate CCs are used for each RAT. For example, with certain frequency band configurations there may be a harmonic relationship between the bands used to aggregate carriers. This harmonic or intermodulation issue may cause sensitivity degradation in the UE, when the UE communicates with both the LTE and the NR base stations concurrently, even when separate CCs are used by each of the RATs.

In some cases, certain techniques can be used for reducing the interference by coordinating the LTE and NR base stations in the time and the frequency domains for communication with a UE. For example, a UE, which is capable of communicating on multiple UL carriers on different frequencies, may be configured to operate on only one of the LTE or NR CCs at any given time. This is a time division multiplex (TDM) solution used for resolving the harmonic issue by allowing only one of the LTE or NR base stations to communicate with the UE at any given time.

In such an example, for the LTE carrier, the UE may be configured with different configurations. The first configuration comprises a DL-reference UL/DL configuration defined for LTE-FDD (frequency division duplex)-SCell (secondary cell) in LTE-TDD (time division duplex)-FDD CA with LTE-TDD-PCell (primary cell). More specifically, for scheduling or HARQ (hybrid automatic repeat request) timing of the LTE FDD carrier, DL-reference UL/DL configuration defined for LTE-FDD-SCell in LTE/TDD-FDD CA with LTE-TDD-PCell is applied. In addition, using the first configuration, the UE is allowed to transmit NR UL signals at least in the subframe(s) where LTE UL transmission is not allowed according to the DL-reference UL/DL configuration. A second configuration, such as described in 3GPP Release <NUM> based on the LTE-FDD HARQ timing, may also be used. Such configurations, however, are only focused on UL transmission, not DL transmission.

In certain cases, two BSs, such as a MeNB (main eNB, such as the LTE BS) and a SgNB (secondary gNB, such as the NR BS), may use an Addition/Modification Request message of the SgNB to coordinate their resource utilization for communication with a UE. In such cases, if an Addition/Modification Request message of the SgNB contains the MeNB Resource Coordination Information IE (information element), the SgNB may forward it to lower layers for the purpose of resource coordination with the MeNB. Using the Resource Coordination Information IEs, the resource coordination between MeNB and SgNB is performed per UE. In such an example, the MeNB-SgNB coordination may take place in both DL and UL directions.

<FIG> illustrates an example sequence diagram for resource coordination for a UE <NUM> between a MeNB <NUM> and a SgNB <NUM> using the Addition/Modification Request message. As shown, at step <NUM> (i.e., <NUM>. EN-DC (E-UTRAN New Radio Dual Connectivity) X2 setup), MeNB <NUM> and SgNB <NUM> first exchange configuration information, including carrier frequency, bandwidth and TDD UL/DL configuration. At step <NUM>, the MeNB <NUM> determines the HARQ timeline and resource allocation on DL and UL for the UE <NUM> based on the UE <NUM>'s radio capability, the configuration of MeNB <NUM> and/or the configuration of SgNB <NUM>, and network traffic. At least for the harmonic issue described above, the MeNB <NUM> may be able to determine which PRBs (physical resource blocks) may generate interference to the SgNB <NUM> DL if used by the UE <NUM> for transmission. In certain other aspects, only the LTE PCell may be taken into consideration in determining the resource allocation bitmap.

At step <NUM>, the MeNB <NUM> sends the "MeNB Resource Coordination Information," including a UL bitmap and a DL bitmap to the SgNB <NUM>. The UL/DL resource allocation may take HARQ timeline into consideration. In certain aspects, the SgNB <NUM> may consider the received UL Coordination Information IE value until reception of a new update of the IE for the same UE <NUM>. In certain aspects, the SgNB <NUM> considers the received DL Coordination Information IE value until reception of a new update of the IE for the same UE <NUM>.

At step <NUM>, the SgNB <NUM> determines the SgNB <NUM> resource allocation and maps the allocation into the MeNB <NUM> time/frequency bitmap. The SgNB <NUM> then replies with the SgNB <NUM> Addition/Modification Request Acknowledge containing SgNB <NUM> Resource Coordination Information IE to the MeNB <NUM> for the SgNB <NUM> resource allocation. At step <NUM>, MeNB <NUM> sends the HARQ timeline information to the UE <NUM>.

In addition, some aspects relate to adopting a <NUM>-bit TDM coordination pattern bitmap with a <NUM> millisecond periodicity and <NUM> millisecond subframe granularity. The <NUM> millisecond periodicity allows for one transmission and four retransmissions, each with a round-trip time (RTT) of <NUM> milliseconds (<NUM>*<NUM> = <NUM>). Considering each LTE carrier has up to <NUM> PRBs in the frequency domain, such a LTE-NR coordination pattern comprises: <NUM>*<NUM> = <NUM> bits. The <NUM>-bit bitmap may be applicable to certain UE configurations described previously. More specifically, for the second UE configuration described above, a <NUM>-bit message or bitmap may be sufficient to allow for four HARQ transmissions (i.e., <NUM> milliseconds of RTT multiplied by <NUM>). However, a <NUM>-bit bitmap may not be sufficient for some other UE configurations, including the first UE configuration described above, because the TDM pattern periodicity may be more than <NUM>. Note that the first configuration comprises a DL-reference UL/DL configuration defined for LTE-FDD (frequency division duplex)-SCell (secondary cell) in LTE-TDD (time division duplex)-FDD CA with LTE-TDD-PCell (primary cell).

<FIG> illustrates an example table <NUM> including a number of DL-reference UL/DL UE configurations <NUM>-<NUM>, for some of which the <NUM>-bit bitmap may not be sufficient. For example, in order to allow four HARQ transmissions over an FDD SCell, in some cases, more than <NUM> may be required for DL-reference UL/DL configuration '<NUM>' of table <NUM>.

As described above, MeNB <NUM> may generate and include a <NUM>-bit UL bitmap and a <NUM>-bit DL bitmap in the MeNB Resource Coordination Information IE, which may be used to coordinate resource utilization between MeNB <NUM> and SgNB <NUM>. For example, a UL Coordination Information bitmap may comprise a bit string where each position in the string represents a PRB in a subframe. Also value "<NUM>" in a bit string of a UL Coordination Information bitmap indicates "resource not intended to be used for transmission," while value '<NUM>' indicates "resource intended to be used for transmission. " Each position is applicable only in positions corresponding to UL subframes. The bit string may span across multiple contiguous subframes (e.g., maximum <NUM> bits). As described above, because each LTE carrier has up to <NUM> PRBs in the frequency domain, each LTE-NR coordination bit map (e.g., UL or DL) may comprise <NUM> bits (<NUM>*<NUM>).

In certain aspects, the first position of the UL Coordination Information bitmap corresponds to subframe <NUM> in a radio frame where system frame number (SFN) = <NUM>. In certain aspects, the length of the bit string is an integer multiple of <MAT> (e.g., as defined in TS <NUM> [<NUM>]). The UL Coordination Information bitmap is continuously repeated. Also a DL Coordination Information bitmap may comprise a bit string where each bit position in the string represents a PRB in a subframe. Also value '<NUM>' in the bit string indicates "resource not intended to be used for transmission," while value '<NUM>' indicates "resource intended to be used for transmission. " Each position is applicable only in positions corresponding to DL subframes. The bit string may span across multiple contiguous subframes (maximum <NUM>). The first position of the DL Coordination Information bitmap corresponds to the receiving node's subframe <NUM> in a receiving node's radio frame where SFN = <NUM>. The length of the bit string is an integer multiple of <MAT> (e.g., defined in TS <NUM> [<NUM>]). The DL Coordination Information is continuously repeated.

Certain aspects herein relate to the use of a shortened TTI (sTTI) (e.g., as defined in LTE Release <NUM>). In certain aspects, there are two types of sTTIs. The first type of a sTTI is defined as a slot (also referred to as a slot sTTI), which corresponds to a half-subframe. <FIG> illustrates an example LTE-TDD sTTI subframe structure <NUM> comprising two slots <NUM> and <NUM>. Each slot of the subframe corresponds to a sTTI and comprises seven blocks, each block indicating a time symbol.

The second type of sTTI is defined as a sub-slot (also referred to as a sub-slot sTTI). <FIG> illustrates an example LTE-FDD sTTI UL subframe structure <NUM> comprising multiple sub-slots (sTTI <NUM>, sTTI <NUM>, sTTI <NUM>, sTTI <NUM>, sTTI <NUM>, and sTTI <NUM>) where each sub-slot comprises a number of time symbols.

In certain aspects, an LTE-FDD sTTI UL subframe structure may have three different configurations depending on the Control Format Indicator (CFI) value. In LTE, a CFI value defines the time span, in OFDM symbols, of the Physical Downlink Control Channel (PDCCH) transmission (i.e., the control region) for a particular downlink subframe. The CFI is transmitted using the Physical Control Format Indicator Channel (PCFICH). The CFI is limited to the value <NUM>, <NUM>, or <NUM>. For bandwidths greater than ten resource blocks, the number of OFDM symbols used to contain the downlink control information is the same as the actual CFI value. Otherwise, the span of the downlink control information (DCI) is equal to CFI+<NUM> symbols.

<FIG> illustrate three different LTE-FDD sTTI DL subframe structures <NUM>-<NUM>, each configured based on a different CFI value. Each block <NUM> in each one of structures <NUM>-<NUM> indicates a time symbol. <FIG> illustrates LTE-FDD sTTI DL subframe structure <NUM> when the CFI value is <NUM>. <FIG> illustrates LTE-FDD sTTI DL subframe structure <NUM> when the CFI value is <NUM>. <FIG> illustrates LTE-FDD sTTI DL subframe structure <NUM> when the CFI value is <NUM>.

As described above, the LTE-NR coordination information comprises UL and DL bitmaps for coordinating UL and DL resource utilization between the MeNB (e.g., MeNB <NUM>) and the SgNB (e.g., SgNB <NUM>) at the subframe level. With the use of sTTIs, however, there is a need for configuring the LTE-NR coordination information at the sTTI level. Accordingly, certain aspects described below relate to configuring the LTE-NR coordination information at the sTTI level.

<FIG> illustrates example operations <NUM> performed by a first base station that uses a first radio access technology (RAT), according to aspects of the present disclosure. Operations <NUM> begin, at <NUM>, by generating a first resource coordination information comprising one or more resource coordination bitmaps, each of the one or more resource coordination bitmaps indicating one or more shortened transmission time intervals (sTTIs) of a transmission time interval (TTI) assigned to the first RAT for communication, wherein the TTI comprises a plurality of sTTIs.

At <NUM>, operations <NUM> continue by transmitting a message including the first resource coordination information to a second base station that uses a second RAT.

At <NUM>, operations <NUM> receiving an acknowledgement of the message from the second base station, the acknowledgment including a second resource coordination information comprising one or more modified resource coordination bitmaps, each of the one or more modified resource coordination bitmaps indicating the one or more sTTIs of the TTI assigned to the first RAT for communication and one or more additional sTTIs of the TTI assigned to the second RAT for communication.

For a slot sTTI, the timeline may be n+<NUM>, where n stands for the number of transmissions and '<NUM>' stands of the number of retransmissions for each transmission. Accordingly, for example, a <NUM>-bit (<NUM>*<NUM>) message may be used to account for up to four retransmissions for each LTE HARQ process. In such an example, the number '<NUM>' indicates <NUM> of RTT and the number '<NUM>' indicates the number of transmissions (i.e., one transmission and four retransmissions). In some embodiments, assuming a <NUM>-bit IE is sufficient for a <NUM> "TTI + NR coordination," the same number of bits may be sufficient for a slot sTTI and NR coordination. In NR, each radio frame has <NUM> slots, but the timeline is half of that of the legacy LTE. Therefore, a <NUM>-bit coordination message with the periodicity of <NUM> may be used for subframe structures having slot sTTIs (e.g., shown in <FIG>).

For a sub-slot sTTI, however, the DL subframe structure, as described above, may be a function of the CFI value. Therefore, at the sTTI level, TDM coordination may be challenging because the DL subframe structure may change dynamically based on the CFI value, while the LTE-NR coordination information is exchanged semi-statically. As a result, certain embodiments described herein relate to configuring the LTE-NR coordination information such that it is independent of what CFI value is used for DL subframes. In some embodiments, in order to configure an LTE-NR coordination information that is independent of CFI values, a common TDM coordination pattern may be used for all types of DL subframe structures, regardless of the CFI value. For example, in some embodiments, the LTE and NR base stations may be configured such that the first three symbols of the DL subframe structure may be used for LTE transmissions. In such embodiments, no bit indication may be needed in the DL LTE-NR coordination information bitmap to indicate that the first three symbols of each DL subframe shall be used for LTE transmissions. In addition, in some embodiments, when the CFI value is <NUM> or <NUM>, all the "sTTI <NUM>" symbols of each DL subframe, may be used for NR DL transmissions, and when the CFI value is <NUM>, only the last <NUM> symbols of "sTTI <NUM>" may be used for NR DL transmissions. As shown in <FIG>, starting from "sTTI <NUM>," the TDM patterns of all the DL subframe structures are aligned. Accordingly, for each of sTTI2, sTTI3, sTTI4, and sTTI5, a bit in a LTE-NR coordination information bitmap may be used to indicate the time domain resource allocation.

In some embodiments, in one cell, sTTI users (e.g., UEs) may be configured with an n+<NUM>, n+<NUM>, or n+<NUM> timeline. Therefore, in order to make the TDM pattern generally applicable to both types of sTTI (i.e., slot sTTI and sub-slot sTTI), an <NUM>-bit TDM pattern ('<NUM>' ms (i.e., RTT) multiplied by '<NUM>' (i.e., one transmission plus four retransmissions)) = <NUM> bits) may be used for sub-slot TTI+NR coordination. In some embodiments, in the DL LTE-NR coordination information bitmap, <NUM> bits may be used per subframe (<NUM> bit per usable sTTI for NR). Accordingly, in order to make the TDM pattern radio frame-aligned, <NUM> bits (<NUM>*<NUM>) may be used in the time domain. In some embodiments, in each cell, the UE uses only one TTI type. This is because the coordination periodicity is common in Case <NUM> and <NUM> (e.g., Case <NUM> and <NUM> are RAN1 terminology). In addition, the sTTI type is determined by the PUCCH group. Accordingly, as each cell belongs to only one PUCCH group for a UE, in each cell, the UE uses only one TTI type.

In some embodiments, several different techniques may be used to enable the exchange of the sTTI-level LTE-NR coordination information between the MeNB and SgNB.

One technique, in some embodiments, may comprise adding an optional "TTI type" to the Resource Coordination Information IEs comprising the LTE-NR coordination information. For example, a TTI type may be added to the MeNB Resource Coordination Information IE and the SgNB Resource Coordination Information exchanged between the MeNB and SgNB for EN-DC. In some embodiments, equivalent IEs may be used for F1AP (F1- Application Protocol) and XnAP (Xn Application Protocol). In some embodiments, a time domain length of <NUM> bits may be used for the Resource Coordination IEs. In some embodiments, the time domain length of the Resource Coordination IEs may be extended to <NUM> bits. In some embodiments, if a UE is not configured with sTTI (including slot TTI) in the cell, the NR BS (e.g., SgNB, gNB, etc.) and the LTE BS (e.g., MeNB, eNB, etc.) may assume that the TTI type is subframe. If the TTI type is not included, in some embodiments, the SgNB and the MeNB may assume that the TTI type is the type that the RRC has configured for the 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 relating to performing TDM coordination for LTE-NR CA. In certain aspects, computer-readable medium/memory <NUM> stores code <NUM> that, when executed by processor <NUM>, causes communications device <NUM> to perform block <NUM> of operation <NUM>. In certain aspects, computer-readable medium/memory <NUM> stores code <NUM> that, when executed by processor <NUM>, causes communications device <NUM> to perform block <NUM> of operation <NUM>. In certain aspects, computer-readable medium/memory <NUM> stores code <NUM> that, when executed by processor <NUM>, causes communications device <NUM> to perform block <NUM> of operation <NUM>.

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 performing code <NUM>, circuitry <NUM> for performing code <NUM>, and circuitry <NUM> for performing code <NUM>.

<FIG> illustrates an example table <NUM> comprising a number of fields representative of the type of information included in a Resource Coordination IE that comprises a TTI type. The fields of the table include IE/Group Name <NUM>, Presence <NUM>, Range <NUM>, IE Type and Reference <NUM>, and Semantics Description <NUM> (e.g., information used to coordinate resource utilization between the MeNB and the SgNB). As shown, the TTI type may be added as an "IE/Group Name" under field <NUM>. In the IE Type and Reference field <NUM>, the specific TTI type of the subframe structure may be indicated. For example, the TTI type may be either one of five types of TTIs including sTTI CFI <NUM>, sTTI CFI <NUM>, sTTI CFI <NUM>, a slot TTI, or a subframe TTI. Considering each LTE carrier has up to <NUM> PRBs in the frequency domain, each LTE-NR coordination information bitmap (e.g., UL or DL) may comprise <NUM> bits (<NUM> bits*<NUM> PRBs) when the bitmap is extended to <NUM> bits.

Relating to the UL Coordination Information under the IE/Group Name field <NUM>, which is added as another "IE/Group Name," each position in the bitmap represents a PRB in a TTI as indicated by TTI type. The UL Coordination Information may further state that value '<NUM>' indicates a resource not intended to be used for transmission while value '<NUM>' indicates a resource intended to be used for transmission. Each position is applicable only in positions corresponding to UL TTIs. The bit string may span across multiple contiguous TTIs (maximum <NUM>). In certain aspects, the first position of the UL Coordination Information corresponds to subframe <NUM> in a radio frame where SFN = <NUM>. In certain aspects, the length of the bit string is an integer multiple of <MAT>. In certain aspects, the UL Coordination Information is continuously repeated.

Relating to the DL Coordination Information, under the IE/Group Name field <NUM>, which is added as another "IE/Group Name," each position in the bitmap represents a PRB in a TTI as indicated by TTI type. Value '<NUM>' indicates a "resource not intended to be used for transmission" while value '<NUM>' indicates a "resource intended to be used for transmission. " Each position is applicable only in positions corresponding to DL TTIs. The bit string may span across multiple contiguous TTIs (maximum <NUM> bits). In certain aspects, the first position of the DL Coordination Information corresponds to the receiving node's subframe '<NUM>' in a receiving node's radio frame where SFN = <NUM>. In certain aspects, the length of the bit string is an integer multiple of <MAT>. <MAT>, such as defined in TS <NUM> [<NUM>]. In certain aspects, the DL Coordination Information is continuously repeated.

Instead of using the same IE for both TDM and FDM coordination, another technique, in some embodiments, may comprise generating or adding separate TDM and FDM IEs for the resource coordination. The eNB and the gNB may exchange the sub-slot level TDM coordination bitmap, e.g., a sub-slot pattern. In some embodiments, the LTE PRBs reserved for sTTIs are indicated to the gNB. In some cases, the UE may be configured for using sTTIs and also regular TTIs (e.g., subframes) in parallel. In such cases, the existing subframe-level (e.g., subframe*PRB) bitmap may be used for regular TTIs. In some embodiments, a sub-slot pattern as well as sTTI PRBs may be added into the MeNB Resource Coordination Information and the SgNB Resource Coordination Information.

<FIG> illustrates separate TDM and FDM IEs that may be included in, for example, the Resource Coordination Information <NUM>. More specifically, <FIG> shows MeNB Resource Coordination Information <NUM>, comprising a TDM IE <NUM> and an FDM IE <NUM>. Similar information (e.g., information included in Resource Coordination Information <NUM>) may also be added to the SgNB Resource Coordination Information. In TDM IE <NUM>, a bit string (e.g., <NUM> bits) may be added to indicate the UL sTTI structure pattern and another bit string may be added to indicate the DL sTTI structure pattern. In FDM IE <NUM>, another bit string may be added to indicate the LTE sTTI PRB pattern.

In some embodiments, another technique may comprise extending the MeNB Resource Coordination Information and the SgNB Resource Coordination Information to the sub-slot level. In such embodiments, the same IE may be used for TDM (time domain) and the FDM (frequency domain) resource allocation. In such embodiments, instead of using a <NUM>~<NUM>*<NUM> bitmap, a <NUM>~<NUM>*<NUM>*<NUM> UL bitmap and a <NUM>~<NUM>*<NUM>*<NUM> DL bitmap may be used for coordinating UL and DL resource utilization between the MeNB and the SgNB at the sTTI/slot level. In such embodiments, the bit string may comprise <NUM> bits (<NUM>*<NUM>*<NUM>). As described above, each bitmap may allocate <NUM> bits to each subframe for indicating the sTTI resource allocation. As also described above, the first sub-slot may be used by LTE.

In some embodiments, sTTI may not be used in the UL and DL subframe structures. In such embodiments, as described above, the TDM time granularity is in the subframe level. In such embodiments, if the LTE-NR frame boundaries are not aligned, part of a subframe may be wasted in each LTE-NR switching point.

<FIG> illustrates an example LTE frame <NUM> and an example NR frame <NUM> that are not aligned. In the example of <FIG>, area <NUM> of the LTE frame <NUM> or area <NUM> of the NR frame <NUM> may be wasted in each LTE-NR switching point. Accordingly, certain embodiments described herein relate to handling the partial overlapping of LTE-NR subframes. In some embodiments, the MeNB and the SgNB may coordinate which RAT has a high priority in the partially overlapped subframe. For example, the MeNB and the SgNB may exchange the RAT priority over X2/Xn.

By default (e.g., without explicit indication), in some embodiments, the LTE BS may have the higher priority, at least in MR-DC cases where LTE eNB is the master node. In some embodiments, without any explicit indication, the master node may be the high priority RAT. In some embodiments, the low priority RAT may not use the overlapped partial subframe. The LTE-NR timing may be carried in SCG-ConfigInfo as measResultSSTD.

Unless specifically stated otherwise, the term "some" refers to one or more.

Claim 1:
A method of wireless communications performed by a first base station that uses a first radio access technology, RAT, the method comprising:
generating (<NUM>) a first resource coordination information comprising one or more resource coordination bitmaps, each of the one or more resource coordination bitmaps indicating one or more shortened transmission time intervals, sTTIs, of a transmission time interval, TTI, assigned to the first RAT for communication, wherein the TTI comprises a plurality of sTTIs;
transmitting (<NUM>) a message including the first resource coordination information to a second base station that uses a second RAT; and
receiving (<NUM>) an acknowledgement of the message from the second base station, the acknowledgment including a second resource coordination information comprising one or more modified resource coordination bitmaps, each of the one or more modified resource coordination bitmaps indicating the one or more sTTIs of the TTI assigned to the first RAT for communication and one or more additional sTTIs of the TTI assigned to the second RAT for communication.