Patent Description:
3GPP contribution "<NPL> discusses CLI measurements and the timing of offset measurement. It discloses a new type of CLI-TA time measurement parameters and cross-link time offset (CL-TO) to measure the timing offset between gNBs or between inter-cell UEs. <CIT> relates to propagation delay difference reporting for multiple component carriers.

Dynamic time division duplex (TDD) may enhance spectrum efficiency of wireless communication networks. However, dynamic TDD may result in interference between User Equipment (UE), such as UE-to-UE cross link interference (CLI) when an uplink (UL) symbol of one cell collides with a downlink (DL) symbol of a nearby cell. A UE that measures CLI may attempt to determine the reception timing of the CLI signal transmitted from a UE in the other cell so that there is no inter-carrier interference in the measurement signal. Otherwise the UE may not properly measure the CLI signal. Aspects presented herein provide a solution to the problem of measuring CLI signals by improving the manner in which a wireless device determines the reception timing of a transmitted CLI signal. In some aspects, the techniques to determine the reception timing of the transmitted CLI signal may be optimized to allow a UE to accurately measure the CLI signal. The techniques to determine the reception timing of the transmitted CLI signal, as presented herein, may utilize information obtained in existing mobility control procedures without affecting the complexity of the UE implementation.

In an aspect of the disclosure, a method, a computer program and an apparatus as claimed in the independent claims are provided for measuring CLI in wireless communications at a first UE. The apparatus receives a first downlink signal from a first base station. The apparatus receives a second downlink signal from a second base station. The apparatus determines a CLI signal measurement from a second UE received at the first UE based on a propagation delay difference. In some aspects, the propagation delay different may be based on the first downlink signal and the second downlink signal.

The base stations <NUM> configured for <NUM> LTE (collectively referred to as Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN)) may interface with the EPC <NUM> through backhaul links <NUM> (e.g., S1 interface). The base stations <NUM> configured for <NUM> NR (collectively referred to as Next Generation RAN (NG-RAN)) may interface with core network <NUM> through backhaul links <NUM>. The base stations <NUM> may communicate directly or indirectly (e.g., through the EPC <NUM> or core network <NUM>) with each other over backhaul links <NUM> (e.g., X2 interface).

The base stations <NUM> / UEs <NUM> may use spectrum up to YMHz (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, etc. MHz) bandwidth per carrier allocated in a carrier aggregation of up to a total of Yx MHz (x component carriers) used for transmission in each direction.

Referring again to <FIG>, in certain aspects, the UE <NUM> may be configured to manage interference from UEs in other cells by measuring the interference signal from other UEs. For example, the UE <NUM> of <FIG> includes a CLI signal measurement component <NUM> configured to receive a first downlink signal from a first base station, receive a second downlink signal from a second base station, and determine a CLI signal measurement from a second UE received by the first UE <NUM> based on a propagation delay difference, in which the propagation delay difference is based on the first downlink signal and the second downlink signal.

Although the following description may be focused on implementations in which the UE manages interference from other UEs in other cells to effectively configure dynamic TDD, the concepts described herein may be applicable to other similar areas, such as instances when the base station is configured to manage interference from other UEs and/or other base stations and is configured to provide interference management instructions to the UE. Furthermore, it should be appreciated that although the following description is focused on <NUM>/NR, the concepts described herein may be applicable to other similar areas, such as LTE, LTE-A, CDMA, GSM, and/or other wireless technologies in which interference management is coordinated by the UE and/or the base station.

The subcarrier spacing may be equal to <NUM>µ = <NUM>, where µ is the numerology <NUM> to <NUM>. <FIG> provide an example of slot configuration <NUM> with <NUM> symbols per slot and numerology µ=<NUM> with <NUM> slots per subframe. The slot duration is <NUM>, the subcarrier spacing is <NUM>, and the symbol duration is approximately <NUM>.

<FIG> is a diagram illustrating a wireless network <NUM> operating in a dynamic TDD configuration in accordance with certain aspects of the disclosure. Dynamic TDD may enhance spectrum efficiency of wireless communication networks and provide a higher throughput by dynamically altering UL or DL transmission direction. However, dynamic TDD may result in UE-to-UE cross link interference. CLI occurs when a UL symbol (e.g., an interfering symbol) of a cell (e.g., an aggressor) collides with a DL symbol (e.g., an interfered symbol) of a nearby cell (e.g., a victim). The configuration of dynamic TDD is able to change dynamically in response to a change of traffic pattern. For example, in instances where the traffic pattern is UL heavy, dynamic TDD may recognize the change in the traffic pattern and adapt by providing more UL symbols to meet the demand. Alternatively, in instances where the traffic pattern is DL heavy, dynamic TDD may provide more DL symbols to meet the demand.

In <FIG>, UE1 <NUM> is within Cell1 <NUM> and is being served by base station <NUM>, while UE2 <NUM> is within Cell2 <NUM> and is being served by base station <NUM>. CLI may occur between UEs at the cell edges of nearby cells, as UEs at cell edges of nearby cells may be in close proximity to each other. As shown in <FIG>, UE1 <NUM> and UE2 <NUM> are at their respective cell edges, and may be communicating with their respective base stations. UE1 <NUM> may send an UL transmission <NUM> to base station <NUM>, while UE2 <NUM> is receiving a DL transmission <NUM> from base station <NUM>. However, in certain instances, the UL transmission <NUM> sent by UE1 <NUM> to base station <NUM> may also be received by UE2 <NUM> while receiving the DL transmission <NUM> from base station <NUM>. The UL transmission <NUM> from UE1 <NUM> received by UE2 <NUM> causes CLI and may interfere with the DL transmission <NUM> UE2 <NUM> from base station <NUM>. As such, one or more UL symbols of the UL signal <NUM> causing the CLI may collide with one or more DL symbols of the DL transmission <NUM>. As used herein, the term CLI signal is defined to be a signal that causes CLI. As further used herein, the terms CLI signal and CLI may be used interchangeably.

In the example of <FIG>, two UL symbols of the UL signal <NUM> causing CLI overlap or collide with two DL symbols of the DL transmission <NUM>, such that CLI occurs at the overlap <NUM>. In order to manage CLI and also effectively configure dynamic TDD configuration for a higher throughput, a measurement mechanism and an interference management mechanism could be helpful. However, CLI may not be effectively measured if the UL transmissions of UE1 are not properly time synchronized with the DL transmission intended for UE2. A UE (e.g., UE2 of <FIG>) that measures CLI may determine the reception timing of the UL signal <NUM> causing the CLI that is transmitted from a UE (e.g., UE1 of <FIG>) in another cell so that there is no inter-carrier or inter-symbol interference in the measurement signal.

If timing synchronization is not done properly, then the energy measurement signal of the CLI power may be incorrect. Also, interference may occur among measurement signals in instances where multiple measurement signals are multiplexed in the frequency domain. As such, strong CLI from one UE may hide a weaker CLI from another UE. CLI measurements may be based on the reference signal received power (RSRP) from the interfering SRS transmitted by UE1 <NUM>, or on the received signal strength indication (RSSI) from any UL transmission from UE1 <NUM>. In order for a UE to measure a CLI based on RSRP, a dedicated time tracking loop may be used for the interfering SRS, which may increase the UE complexity. UEs measuring the CLI based on RSSI do so upon detection of the initial energy detection from a transmission causing CLI. However, this is a non-coherent detection and is vulnerable to noise and interference from other concurrent signals.

One approach to synchronize the timing is to assume that two cells are small cells. Under this approach, the propagation delay between each UE and the respective serving base station can be ignored, on the basis that a transmission from a small cell is immediately received by a UE due in part to the small coverage footprint of small cells. Under this assumption, the timing difference between the CLI signal received at UE2 <NUM> and the DL symbol boundary for UE2 <NUM> is equal to NTA,offset, which is a constant offset which allows the base station to switch between UL and DL. Another approach to synchronize the timing is to assume that the two cells have the same radius, such that the distance between the UEs and the respective base stations are the same. Under this assumption, the propagation delay for both UEs would be the same, such that the CLI from one UE (e.g., UE1 <NUM>) is time aligned with the UL symbol boundary of the other UE (e.g., UE2 <NUM>). These two approaches rely on assumptions that may not always be accurate. For example, the first approach relies on the assumption that both cells are small cells, while the second approach relies on the assumption that both cells have the same coverage radius. These approaches may work in certain settings, but may not be viable in other situations, such that the reception timing of the CLI signal may not be set accurately. Aspects presented herein help a wireless device to accurately determine the reception timing of CLI signals to allow a UE to properly measure CLI signals.

The present disclosure relates to improving the manner in which a wireless device determines the reception timing of a transmitted CLI signal. Optimizing the manner in which a wireless device determines the reception timing of a transmitted CLI signal may allow a network to manage CLI and efficiently configure dynamic TDD for higher throughput. For example, a UE in the network could minimize or eliminate inter-carrier interference in the measurement of the CLI signal due to accurately determining the reception timing of the CLI signal transmitted from another UE. In some aspects, the UE may utilize information obtained in received DL signals in order to determine a CLI signal measurement, and does not have to rely on assumptions that may not be applicable to real-world applications.

<FIG> is a diagram <NUM> illustrating timing relationships of UEs in a wireless network in accordance with certain aspects of the disclosure. The diagram <NUM> of <FIG> includes a UE1 <NUM> within a Cell1 <NUM> and is being served by base station <NUM> via a communication link <NUM>. The diagram <NUM> further includes a UE2 <NUM> within a Cell2 <NUM> and is being served by base station <NUM> via a communication link <NUM>. Cell1 <NUM> and Cell2 <NUM> are neighbor cells, while UE1 <NUM> and UE2 <NUM> are near the edge of their respective cells. UE1 <NUM> is able to transmit UL signals to base station <NUM> and receive DL signals from base station <NUM> via link <NUM>. UE2 <NUM> is able to transmit UL signals to base station <NUM> and receive DL signals from base station <NUM> via link <NUM>. However, since UE1 and UE2 are near the respective cell edges, both may be susceptible to CLI. In some aspects, when UE1 <NUM> is transmitting UL signals <NUM> to base station <NUM>, the UL signals <NUM> may be received by UE2 <NUM> as CLI. The UL signals <NUM>, transmitted by UE1, are received by UE2 as CLI signals (e.g., UL signals <NUM> causing CLI) that may cause interference with the DL signals transmitted to UE2 <NUM> from base station <NUM>. As discussed above, a UE may attempt to determine the timing of the interference to align and/or synchronize the measurement of the interfering signal. A UE (e.g., UE2 <NUM>) that measures CLI may attempt to determine the reception timing of the CLI signal <NUM> transmitted from a UE (e.g., UE1 <NUM>) within another cell.

In the aspect of <FIG>, UE1 and UE2 are in different cells (e.g., Cell1 <NUM> and Cell2 <NUM>, respectively). However, in some aspects, UE1 and UE2 may be within the same cell and served by the same base station. In such aspects, if UE1 <NUM> and UE2 <NUM> are near each other, UE1 <NUM> may transmit UL signals <NUM> to the base station (e.g., base station <NUM> or <NUM>), the UL signals <NUM> may be received by UE2 <NUM> as CLI, as discussed above. The UL signals <NUM>, transmitted by UE1, may be received by UE2 as UL signals <NUM> causing CLI that may cause interference with DL signals transmitted to UE2 <NUM> from the base station (e.g., base station <NUM> or <NUM>). In such instances, a UE may attempt to determine the timing of the interference to align and/or synchronize the measurement of the interfering signal, similarly as discussed above.

In some aspects, a UE (e.g., UE2 <NUM>) may be configured to utilize the DL transmissions received from neighboring cells to determine a CLI signal measurement from another UE (e.g., UE1 <NUM>) received at the UE (e.g., UE2 <NUM>). For example, with reference to diagrams <NUM> and <NUM> <FIG>, respectively, UE2 <NUM> may receive a first DL signal (e.g., DL signal <NUM>, SSB2 <NUM>) from a first base station (e.g., base station <NUM>), and further configured to receive a second DL signal (e.g., DL signal <NUM>, SSB1 <NUM>) from a second base station (e.g., base station <NUM>). <FIG> is a diagram <NUM> illustrating timing relationship of UEs in a wireless network in accordance with certain aspects of the disclosure, while <FIG> is a diagram <NUM> illustrating the comparison of propagation delay and channel delay of UL and DL transmissions in accordance with certain aspects of the disclosure. UE2 <NUM> is within Cell2 and is being served by base station <NUM> but is close to the edge of Cell2 such that UE2 is in a position to receive the second DL signal from a neighbor cell (e.g., Cell1) as part of its mobility protocol, while the base station <NUM> is within a neighboring cell (e.g., Cell1). The UE2 may be configured to determine the timing difference of DL signal <NUM> and DL signal <NUM> to determine the propagation delay difference of DL signal <NUM> and DL signal <NUM>. In some aspects, the first DL signal (e.g., DL signal <NUM>) may comprise a first synchronization signal (e.g., SSB2 <NUM>) from the first base station (e.g., base station <NUM>). In some aspects, the second DL signal (e.g., DL signal <NUM>) may comprise a second synchronization signal (e.g., SSB1 <NUM>) from the second base station (e.g., base station <NUM>). The propagation delay difference <NUM> may be based on the DL signal <NUM> and DL signal <NUM>. In some aspects, the propagation delay difference may be determined based on a difference between a propagation time of DL signal <NUM> and a propagation time of DL signal <NUM>. In some aspects, the propagation delay difference between the first DL signal (e.g., <NUM>, <NUM>) and the second DL signal (e.g., <NUM>, <NUM>) may be similar to a symbol timing difference between the first DL signal (e.g., <NUM>) from the first base station (e.g., <NUM>) and the second DL signal (e.g., <NUM>) from the second base station (e.g., <NUM>).

The UE (e.g., UE2 <NUM>) may determine the CLI signal measurement of the CLI signal (e.g., UL signal <NUM>) based on the propagation delay difference. In some aspects, the UE (e.g., UE2 <NUM>) may determine a reception timing of the CLI signal (e.g., UL signal <NUM>) based on the propagation delay difference between the first DL signal (e.g., <NUM>) and the second DL signal (e.g., <NUM>). The UE may utilize the reception timing of the CLI signal to determine the CLI signal measurement. In some aspects, to determine the CLI signal measurement, the UE (e.g., <NUM>) may determine a symbol timing estimate between the CLI signal (e.g., UL signal <NUM>) received at the first UE (e.g., UE2 <NUM>) and a signal between the first UE (e.g., <NUM>) and the first base station (e.g., <NUM>) that is interfered by the CLI signal (e.g., UL signal <NUM>). The symbol timing estimate may be based on the symbol timing difference between the first DL signal (e.g., <NUM>) and the second DL signal (e.g., <NUM>).

At least one advantage is that the UE may utilize the timing relationship in neighboring cells to determine the CLI signal measurement based on DL signals that the UE already receives. For example, the UE2 may determine the symbol timing of the CLI signal (e.g., UL signal <NUM>) at UE2 by determining the channel delay difference from the first base station (e.g., <NUM>) to the first UE (e.g., UE2 <NUM>) and from the second base station (e.g., <NUM>) to the second UE (e.g., UE1 <NUM>). The UE2 may determine its channel delay based on the synchronization signal (e.g., Synchronization Signal Block (SSB)) received in the DL signal from the first base station (e.g., <NUM>). Although UE2 does not know the channel delay between UE1 and the second base station, UE2 may determine the channel delay between UE1 and the second base station based on the propagation delay of the second DL signal (e.g., <NUM>) from the second base (e.g., <NUM>) station received by UE2. The acquisition of synchronization signals (e.g., SSB) from neighboring cells may already be a part of a UE mobility control procedure, such that acquisition of the SSB does not increase the complexity of UE implementation.

A UE may utilize the timing relationship of two neighboring cells in order for the UE to align or synchronize the measurement with the transmitted symbols. For example, the DL symbol timing at the first base station (e.g., <NUM>) and the second base station (e.g., <NUM>) is T<NUM>. The DL symbols at both base stations are timing synchronized in dynamic TDD systems, which results in both base stations having the same symbol timing. The DL symbol timing for UE1 (e.g., <NUM>) is T<NUM> + Td<NUM>, with Td<NUM> being the channel delay between UE1 (e.g., <NUM>) and its corresponding base station (e.g., <NUM>). The DL symbol timing for UE2 (e.g., <NUM>) is T<NUM> + Td<NUM>, with Td<NUM> being the channel delay between UE2 (e.g., <NUM>) and its serving base station (e.g., <NUM>). The UL symbol timing (e.g., CLI signal transmission timing) at UE1 (e.g., <NUM>) is
TUL<NUM> = T<NUM> + Td<NUM> - TTA<NUM>, = T<NUM> - Td<NUM> - NTA,offsetTs where TTA1 is the UL timing advance of UE1 (e.g., <NUM>), and TTA<NUM> ≈ 2Td<NUM> + NTA,offsetTs, where NTA,offsetTs is a constant value, and Ts is the nominal sample duration. The symbol timing of the CLI signal (e.g., <NUM>) at UE2 (e.g., <NUM>) is
TCLI = TUL<NUM> + T<NUM> = T<NUM> - Td<NUM> - NTA,offsetTs + T<NUM> where T<NUM> is the delay between UE1 (e.g., <NUM>) and UE2 (<NUM>).

The UL symbol timing at UE2 (e.g., <NUM>) is
TUL<NUM> = T<NUM> + Td<NUM> - TTA<NUM> = T<NUM> - Td<NUM> - NTA,offsetTs.

Taking the difference of the symbol timing of the CLI signal at UE2 and the UL symbol timing at UE2 results with
TCLI - TUL<NUM> = -Td<NUM> + T<NUM> + Td<NUM>. In the above equation, it is reasonable to assume that T<NUM> is zero, due in part to the UEs (e.g., UE1 and UE2) being in close proximity to each other. Under such assumption, the symbol timing of the CLI signal at UE2 may be determined by the difference of the channel delays from the base stations to the respective UEs. For example, the symbol timing of the CLI signal at UE2 may be determined by
Td<NUM> - Td<NUM>. UE2 may determine Td<NUM>, but UE2 may not be configured to determine Td<NUM>.

In order for UE2 to determine Td2 - Td<NUM>, UE2 may utilize the downlink signals from the corresponding base stations to determine Td<NUM>. In some aspects, UE2 or the UE configured to measure the CLI signal, may determine Td<NUM> - T<NUM> (e.g., <NUM>) based on the synchronization signals (e.g., SSB, <NUM>, <NUM>) received from the corresponding base stations. Acquisition of the synchronization signal from neighbor cells may be a part of mobility control procedures for UEs. Thus, acquisition of the synchronization signal might not increase the complexity of the UE implementation.

In instances where UE1 and UE2 are in close proximity to each other, the propagation delay Ts<NUM> <NUM> of the synchronization signal (e.g., SSB1 <NUM> or SSB1 <NUM>) from the base station (e.g., <NUM>) serving UE1 received at UE2 (e.g., UE2 <NUM>) is approximately the same as the channel delay Td<NUM> from base station <NUM> to UE1, such that Ts<NUM> ≈ Td<NUM>. UE2 may not know the transmit time of SSB1 <NUM>, and as such, does not know Ts<NUM>, However, UE2 may be configured to measure the delay difference between SSB1 <NUM> and the synchronization signal (e.g., SSB2 <NUM>) transmitted by base station <NUM> to UE2 <NUM>. This delay difference is
ΔTs = (Ts<NUM>,tx + Ts<NUM>) - (Ts<NUM>,tx + Ts<NUM>), where Ts<NUM>,tx is the transmission time of SSB1 <NUM>, Ts<NUM>,tx is the transmission time of SSB2 <NUM>. The difference of Ts<NUM>,tx- Ts<NUM>,tx is a known value, based on the configuration of the synchronization signals (e.g., SSB1 and SSB2) of the respective base stations (e.g., <NUM>, <NUM>).

Removing the contribution of Ts2,tx- Ts<NUM>,tx from ΔTs results in Ts<NUM> - Ts<NUM> = ΔTs - (Ts<NUM>,tx - Ts<NUM>,tx), and replacing Td<NUM> - Td<NUM> with Ts<NUM>, - Ts<NUM> to get TCLI - TUL2 which is the difference between symbol timing of the CLI signal when it arrives at UE2 and the UL symbol timing of UE2, TCLI - TUL2 = T<NUM> + TS2 - Ts1.

As indicated above, T<NUM> may be ignored due to the UEs being in close proximity, results in TCLI - TUL<NUM> = Ts<NUM> - Ts1 = ΔTs - (Ts<NUM>,tx - Ts<NUM>,tx). To get TCLI - TDL<NUM>, which is the timing difference between the CLI signal (e.g., UL signal <NUM>) when it arrives at UE2 and the DL symbol timing of UE2, by using TDL2 = TTA2 + TUL2, which results in
TCLI - TDL<NUM> = Ts<NUM> - Ts<NUM> + TTA<NUM> = ΔTs - (Ts<NUM>,tx - Ts<NUM>,tx) + TTA<NUM>. Both TCLI - TUL<NUM> and TCLI - TDL2 may be utilized to determine the timing of the CLI signal TCLI. As a result, UE2 may determine the CLI signal measurement based on TCLI.

<FIG> is an example communication flow <NUM> between base stations and UEs in accordance with certain aspects of the disclosure. The aspect of <FIG> includes a first base station <NUM> (e.g., base station <NUM>), a first UE <NUM> (e.g., UE2 <NUM>), a second base station <NUM> (e.g., base station <NUM>), and a second UE <NUM> (e.g., UE1 <NUM>). The first UE <NUM> is being served by the first base station <NUM>, while the second UE <NUM> is being served by the second base station <NUM>.

In the illustrated example of <FIG>, at <NUM>, the first UE <NUM> may receive a first downlink signal from the first base station. In some aspects, the first downlink signal may include a synchronization signal (e.g., SSB) for the first base station. As discussed above, the first UE <NUM> may utilize the first downlink signal to determine the propagation delay between the first UE <NUM> and the first base station <NUM>. In some aspects, the first UE <NUM> may determine the symbol timing of the first downlink signal from the first base station <NUM>.

At <NUM>, the second UE <NUM> may receive a second downlink signal from the second base station <NUM>. In some aspects, the second downlink signal may include a synchronization signal (e.g., SSB) for the second base station.

At <NUM>, the first UE <NUM> may receive the second downlink signal from the second base station <NUM>. As discussed above, the first UE <NUM> may utilize the second downlink signal from the second base station <NUM> to determine the propagation delay between the second UE <NUM> and the second base station <NUM>. In some aspects, the first UE <NUM> may determine the symbol timing of the second downlink signal from the second base station <NUM>.

At <NUM>, the first UE <NUM> may determine the propagation delay difference between the first downlink signal and the second downlink signal. In some aspects, a symbol timing difference between the first downlink signal from the first base station and the second downlink signal from the second base station may be similar to the propagation delay difference between the first downlink signal and the second downlink signal.

At 818a, the second UE <NUM> may transmit a second uplink signal to the second base station <NUM>. At 818b, the second UE <NUM> may receive the second uplink signal from the second UE <NUM> in the form of a CLI signal.

At <NUM>, the first UE <NUM> may determine a CLI signal measurement from the second UE received at the first UE. In some aspects, the CLI signal measurement may be based on the propagation delay difference, which may be based on the first downlink signal and the second downlink signal. The propagation delay difference may be based on the difference between the propagation time of the first and second downlink signals.

In some aspects, the first UE <NUM>, at <NUM>, may determine a reception timing of the CLI signal based on the propagation delay difference between the first downlink signal and the second downlink signal, in order to determine the CLI signal measurement. In some aspects, the first UE <NUM>, at <NUM>, may determine a symbol timing estimate between the CLI signal received at the first UE <NUM> and a signal between the first UE <NUM> and the first base station <NUM> that is interfered by the CLI signal, in order to determine the CLI signal measurement. In some aspects, the symbol timing estimate may be based on the symbol timing difference between the first downlink signal and the second downlink signal.

At <NUM>, the first UE <NUM> may transmit a first uplink signal to the first base station <NUM>.

<FIG> is a flowchart <NUM> of a method of wireless communication. The method may be performed by a UE (e.g., the UE <NUM>, <NUM>, <NUM>, <NUM>; the apparatus <NUM>/<NUM>'; the processing system <NUM>, which may include the memory <NUM> and which may be the entire UE or a component of the UE, such as the TX processor <NUM>, the RX processor <NUM>, and/or the controller/processor <NUM>). Aspects of the method may assist a UE to efficiently determine the reception timing of the transmitted CLI signal in order to accurately measure the CLI signal.

At <NUM>, the UE may receive a first downlink signal (e.g., <NUM>, <NUM>, <NUM>) from a first base station (e.g., <NUM>, <NUM>) as shown in connection with <FIG>. For example, <NUM> may be performed by reception component <NUM>, such that the reception component <NUM> receives the downlink signal from base station <NUM>. In some aspects, the first downlink signal may include a first synchronization signal (e.g., <NUM>, <NUM>) as shown in connection with <FIG>. In some aspects, as shown in <FIG>, the downlink signal from base station <NUM> may include sync signals that are received by the reception component <NUM>. At <NUM>, the UE may receive a second downlink signal (e.g., <NUM>, <NUM>, <NUM>) from a second base station (e.g., <NUM>, <NUM>) as shown in connection with <FIG>. For example, <NUM> may be performed by reception component <NUM>, such that the reception component <NUM> receives the downlink signal from base station <NUM>. In some aspects, the second downlink signal may include a second synchronization signal (e.g., <NUM>, <NUM>) as shown in connection with <FIG>.

At <NUM>, the UE may determine a propagation delay difference based on a difference between a propagation time <NUM> of the first downlink signal and a propagation time <NUM> of the second downlink signal as shown in connection with <FIG>. For example, <NUM> may be performed by propagation delay component <NUM>, such that the propagation delay component <NUM> determines a difference between the propagation time of the downlink signal from base station <NUM> and the propagation time of the downlink signal from base station <NUM>. In some aspects, the propagation delay difference <NUM> between the first downlink signal (e.g., <NUM>, <NUM>, <NUM>) and the second downlink signal (e.g., <NUM>, <NUM>, <NUM>) may be similar to a symbol timing difference <NUM> between the first downlink signal (e.g., <NUM>, <NUM>, <NUM>) from the first base station (e.g., <NUM>, <NUM>, <NUM>) and the second downlink signal (e.g., <NUM>, <NUM>, <NUM>) from the second base station (e.g., <NUM>, <NUM>, <NUM>).

At <NUM>, the UE may determine a CLI signal (e.g., <NUM>, <NUM>, <NUM>) measurement from a second UE (e.g., <NUM>, <NUM>, <NUM>, <NUM>) received at the first UE (e.g., <NUM>, <NUM>, <NUM>, <NUM>; the apparatus <NUM>/<NUM>'; the processing system <NUM>) based on a propagation delay difference. In some aspects, the propagation delay difference may be based on the first downlink signal (e.g., <NUM>, <NUM>, <NUM>) and the second downlink signal (e.g., <NUM>, <NUM>, <NUM>). For example, <NUM> may be performed by CLI signal measurement component <NUM>. The CLI signal measurement component <NUM> may receive, as input, the results of the propagation delay component <NUM> to perform <NUM>. In some aspects, for example at <NUM>, to determine the CLI signal measurement, the UE (e.g., <NUM>, <NUM>, <NUM>, <NUM>; the apparatus <NUM>/<NUM>'; the processing system <NUM>) may determine a reception timing of the CLI signal (e.g., <NUM>, <NUM>, <NUM>) based on the propagation delay difference between the first downlink signal (e.g., <NUM>, <NUM>, <NUM>) and the second downlink signal (e.g., <NUM>, <NUM>, <NUM>). For example, <NUM> may be performed by reception timing component <NUM>. The reception timing component <NUM> may receive as input the results of the propagation delay component <NUM>.

At <NUM>, the UE (e.g., <NUM>, <NUM>, <NUM>, <NUM>; the apparatus <NUM>/<NUM>'; the processing system <NUM>) may determine a symbol timing estimate between the CLI signal (e.g., <NUM>, <NUM>, <NUM>) received at the first UE (e.g., <NUM>, <NUM>, <NUM>, <NUM>; the apparatus <NUM>/<NUM>'; the processing system <NUM>) and a signal (e.g., <NUM>, <NUM>) between the first UE and the first base station that is interfered by the CLI signal (e.g., <NUM>, <NUM>, <NUM>). In some aspects, the symbol timing estimate may be based on the symbol timing difference between the first downlink signal (e.g., <NUM>, <NUM>, <NUM>) and the second downlink signal (e.g., <NUM>, <NUM>, <NUM>). For example, <NUM> may be performed by the symbol timing component <NUM>. In some aspects, the propagation delay difference between the first downlink signal (e.g., <NUM>, <NUM>, <NUM>) and the second downlink signal (e.g., <NUM>, <NUM>, <NUM>) may be similar to the symbol timing difference between the first downlink signal (e.g., <NUM>, <NUM>, <NUM>) from the first base station (e.g., <NUM>, <NUM>) and the second downlink signal (e.g., <NUM>, <NUM>, <NUM>) from the second base station (e.g., <NUM>, <NUM>). As discussed above, the propagation delay difference may be used interchangeably with the symbol timing difference, in accordance with the aspects of the disclosure. Thus, the symbol timing component <NUM> may receive as input the results of the propagation delay component <NUM> to determine the symbol timing difference.

<FIG> is a conceptual data flow diagram <NUM> illustrating the data flow between different means/components in an example apparatus <NUM>. The apparatus may be a UE. The apparatus includes a reception component <NUM> that may receive a first downlink signal from the first base station <NUM>, e.g., as described in connection with <NUM> of <FIG>. The reception component <NUM> may receive a second downlink signal from the second base station <NUM>, as described in connection with <NUM> of <FIG>. The reception component <NUM> may receive a CLI signal from the second UE <NUM>, e.g., as described in connection with <NUM> of <FIG>. The apparatus includes a propagation delay component <NUM> that determines the propagation delay difference based on the difference between the propagation time of the first downlink signal and the propagation time of the second downlink signal, e.g., as described in connection with <NUM> of <FIG>. The apparatus includes a CLI signal measurement component <NUM> that determines CLI signal measurement from the second UE received at the first UE based on the propagation delay difference, e.g., as described in connection with <NUM> of <FIG>. In some aspects, the apparatus may include a reception timing component <NUM> that determines the reception timing of the CLI signal based on the propagation delay difference between the first downlink signal and the second downlink signal, e.g., as described in connection with <NUM> of <FIG>. In some aspects, the apparatus may include a symbol timing component <NUM> that determines the symbol timing estimate between the CLI signal received at the first UE and a signal between the first UE and the first base station that is interfered by the CLI signal, e.g., as described in connection with <NUM> of <FIG>. The apparatus may include a transmission component <NUM> that transmits uplink signals to the first base station <NUM>.

<FIG> is a diagram <NUM> illustrating an example of a hardware implementation for an apparatus <NUM>' employing a processing system <NUM>. The processing system <NUM> may be implemented with a bus architecture, represented generally by the bus <NUM>. The bus <NUM> may include any number of interconnecting buses and bridges depending on the specific application of the processing system <NUM> and the overall design constraints. The bus <NUM> links together various circuits including one or more processors and/or hardware components, represented by the processor <NUM>, the components <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and the computer-readable medium / memory <NUM>. The bus <NUM> may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further.

The processing system <NUM> may be coupled to a transceiver <NUM>. The transceiver <NUM> is coupled to one or more antennas <NUM>. The transceiver <NUM> provides a means for communicating with various other apparatus over a transmission medium. The transceiver <NUM> receives a signal from the one or more antennas <NUM>, extracts information from the received signal, and provides the extracted information to the processing system <NUM>, specifically the reception component <NUM>. In addition, the transceiver <NUM> receives information from the processing system <NUM>, specifically the transmission component <NUM>, and based on the received information, generates a signal to be applied to the one or more antennas <NUM>. The processing system <NUM> includes a processor <NUM> coupled to a computer-readable medium / memory <NUM>. The processor <NUM> is responsible for general processing, including the execution of software stored on the computer-readable medium / memory <NUM>. The software, when executed by the processor <NUM>, causes the processing system <NUM> to perform the various functions described supra for any particular apparatus. The computer-readable medium / memory <NUM> may also be used for storing data that is manipulated by the processor <NUM> when executing software. The processing system <NUM> further includes at least one of the components <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. The components may be software components running in the processor <NUM>, resident/stored in the computer readable medium / memory <NUM>, one or more hardware components coupled to the processor <NUM>, or some combination thereof. The processing system <NUM> may be a component of the UE <NUM> and may include the memory <NUM> and/or at least one of the TX processor <NUM>, the RX processor <NUM>, and the controller/processor <NUM>. Alternatively, the processing system <NUM> may be the entire UE (e.g., see <NUM> of <FIG>).

In one configuration, the apparatus <NUM>/<NUM>' for wireless communication includes means for receiving a first downlink signal from a first base station. The apparatus includes means for receiving a second downlink signal from a second base station. The apparatus includes means for determining a cross-link interference (CLI) signal measurement from a second UE received at the first UE based on a propagation delay difference. In some aspects, the propagation delay difference may be based on the first downlink signal and the second downlink signal. The apparatus may further include means for determining the propagation delay difference based on a difference between a propagation time of the first downlink signal and a propagation time of the second downlink signal. The apparatus may further include means for determining a reception timing of the CLI signal based on the propagation delay difference between the first downlink signal and the second downlink signal. The apparatus may further include means for determining a symbol timing estimate between the CLI signal received at the first UE and a signal between the first UE and the first base station that is interfered by the CLI signal. In some aspects, the symbol timing estimate may be based on the symbol timing difference between the first downlink signal and the second downlink signal.

The disclosure provides an optimized technique for UEs to determine the reception timing of a transmitted CLI signal, which in turn allows UEs to accurately measure CLI signals. At least one advantage of the disclosure is that UEs may determine the timing difference between neighbor cell and its serving cell based on the received synchronization signal received from the respective cells. The UE may use the timing difference of the synchronization signal as the difference between the channel delay from the UE that transmits the CLI signal to the corresponding base station and the channel delay from itself to its serving base station. The acquisition of synchronization signals of serving cells and neighbor cells is already part of the UE implementation, such that the complexity of the UE implementation is not increased. As such, the disclosure may be applicable to any CLI scenario and does not impact the complexity of the UE implementation.

Claim 1:
A method for measuring cross-link interference in wireless communications at a first User Equipment, UE, comprising:
receiving (<NUM>) a first downlink signal from a first base station, wherein the first UE is served by the first base station;
receiving (<NUM>) a second downlink signal from a second base station serving a second UE; and
determining (<NUM>) a cross-link interference, CLI, signal measurement from the second UE received at the first UE based on a propagation delay difference, the propagation delay difference being based on a timing difference between the first downlink signal and the second downlink signal.