Interference suppression

Abstract

Various communication systems may benefit from improved reduction of cross-link interference. For example, certain embodiments may benefit from cross-link interference suppression. In certain embodiments, a method may include receiving, by a first network entity, at least one downlink precoder mapping from a second network entity via at least one interface (401). The method may also include estimating, by the first network entity, at least one basis of at least one common spatial subspace associated with at least one or all identified BS‑BS CLI sources (407). In addition, the method may include, for each reception associated with the first network entity, spatially projecting, by the first network entity, at least one interference covariance matrix estimated by interference rejection combining into at least one orthogonal projection subspace (411).

Description

Technical Field

[0001] Various communication systems may benefit from improved cross-link interference reduction.For example, certain embodiments may benefit from cross-link interference suppression. Background Art

[0002] The 5th generation (5G) mobile communication network supports both frequency division duplex (FDD) and time division duplex (TDD) modes, wherein TDD provides improved availability of unpaired spectrum for new radio (NR) deployment. In addition, due to channel reciprocity, TDD can be a key component in supporting features in massive multi-antenna communications on 5G NR, such as massive multiple-input multiple-output (MIMO), beamforming, and adaptive antenna systems. Summary of the invention

[0003] According to some embodiments, a method may include receiving, by a first network entity, at least one downlink precoder mapping from a second network entity via at least one interface. The method may also include estimating, by the first network entity, at least one basis of at least one common spatial subspace associated with at least one identified CLI source. The method may also include, for each reception associated with the first network entity, spatially projecting, by the first network entity, at least one interference rejection combining (IRC) estimated interference covariance matrix into at least one orthogonal projection subspace.

[0004] According to some embodiments, the apparatus may include means for receiving at least one downlink precoder mapping from a network entity via at least one interface. The apparatus may also include means for estimating at least one basis of at least one common spatial subspace associated with at least one identified CLI source. The apparatus may also include means for spatially projecting at least one interference rejection combining (IRC) estimated interference covariance matrix into at least one orthogonal projection subspace for each reception associated with the apparatus.

[0005] According to some embodiments, the apparatus may include at least one processor and at least one memory including computer program code. The at least one memory and the computer program code may be configured to, together with the at least one processor, cause the apparatus to at least receive at least one downlink precoder mapping from a network entity via at least one interface. The at least one memory and the computer program code may also be configured to, together with the at least one processor, cause the apparatus to at least estimate at least one basis of at least one common spatial subspace associated with at least one identified CLI source. The at least one memory and the computer program code may also be configured to, together with the at least one processor, cause the apparatus to at least spatially project at least one interference covariance matrix estimated by interference rejection combining (IRC) into at least one orthogonal projection subspace for each reception associated with the apparatus.

[0006] According to some embodiments, a non-transitory computer readable medium may be encoded with instructions that, when executed in hardware, may perform a method. The method may receive at least one downlink precoder mapping from a network entity via at least one interface. The method may also estimate at least one basis of at least one common spatial subspace associated with at least one identified CLI source. The method may also spatially project at least one interference rejection combining (IRC) estimated interference covariance matrix into at least one orthogonal projection subspace for each reception associated with the device.

[0007] According to some embodiments, a computer program product may perform a method. The method may receive at least one downlink precoder mapping from a network entity via at least one interface. The method may also estimate at least one basis of at least one common spatial subspace associated with at least one identified CLI source. The method may also spatially project at least one interference rejection combining (IRC) estimated interference covariance matrix into at least one orthogonal projection subspace for each reception associated with the device.

[0008] According to some embodiments, the apparatus may include circuitry configured to receive at least one downlink precoder mapping from a network entity via at least one interface. The circuitry may also estimate at least one basis of at least one common spatial subspace associated with at least one identified CLI source. The circuitry may also spatially project at least one interference rejection combining (IRC) estimated interference covariance matrix into at least one orthogonal projection subspace for each reception associated with the apparatus. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] For a correct understanding of the present invention, reference should be made to the accompanying drawings, in which:

[0010] Figure 1 An example of DL to UL CLI occurrence in dynamic TDD according to certain embodiments is illustrated.

[0011] Figure 2 Examples of URLLC outage delays for static and dynamic TDD in accordance with certain embodiments are illustrated.

[0012] Figure 3 An example of a buffered traffic ratio for dynamic TDD according to some embodiments is illustrated.

[0013] Figure 4 An example of a signal flow graph in accordance with some embodiments is illustrated.

[0014] Figure 5 An example of a method according to some embodiments is illustrated.

[0015] Figure 6 Illustrated are examples of BS-BS CLI suppression and precoder mapping feedback in accordance with certain embodiments.

[0016] Figure 7 An example of three-step BS-BS CLI suppression is illustrated in accordance with certain embodiments.

[0017] Figure 8 An example of an RFC book and a hybrid frame design for TTI=7 OFDM symbols in accordance with certain embodiments is illustrated.

[0018] Fig. 9 Examples of simulation parameters according to some embodiments are illustrated.

[0019] Fig.10 An example of a timing diagram of signaling in a CU / DU structure according to certain embodiments is illustrated.

[0020] 11(a) and 11(b) illustrate examples of UL and DL URLLC outage latency performance in accordance with certain embodiments.

[0021] Fig.12 The diagram shows a method of using 10 according to some embodiments. -5 Table of probabilistic URLLC outage delays.

[0022] Fig.13 An example of carrier-to-interference ratio performance in dB is illustrated in accordance with certain embodiments.

[0023] Fig.14 An example of per-packet throughput performance in Mbps is illustrated in accordance with certain embodiments.

[0024] Fig.15 An example of buffered traffic ratio performance according to certain embodiments is illustrated.

[0025] Fig.16 An example of a system according to some embodiments is illustrated.

[0026] Fig.17 An architecture according to some embodiments is illustrated.

[0027] Fig.18 Another architecture in accordance with some embodiments is illustrated. DETAILED DESCRIPTION

[0028] Among other requirements, 5G NR should support a large number of applications with different Quality of Service (QoS) requirements, giving rise to a wide variety of asymmetric downlink (DL) and uplink (UL) traffic demands. The TDD operation mode is a key factor in achieving it, because the radio frame configuration (RFC) of each base station (BS) can change over time to adapt to the instantaneous traffic demand. For example, each BS can independently change its DL to UL time slot / symbol ratio within a radio frame based on its traffic ratio. However, such operation can introduce additional types of inter-cell cross-link interference (CLI), such as UL to DL or DL ​​to UL. This can include CLI between user equipment (UE-UE) and / or between base stations (BS-BS). In addition, ultra-reliable and low-latency communication (URLLC) is a major component of 5G NR, providing 10 -5 The interruption delay of one or several milliseconds with the highest interruption probability is 100%. Due to the UL / DL switching time and CLI, it is very challenging to achieve such URLLC latency and reliability in the case of dynamic TDD. Although the UL / DL switching time can be maximized by mini-time slot transmission of 5G NR, CLI remains an open challenge.

[0029] In macro deployments, CLI is a critical issue that needs to be mitigated on a pre-receiver or post-receiver basis. For example, due to the power imbalance between DL and UL transmissions in a macro setting, a DL-heavy BS may interfere with a neighboring UL-heavy BS, resulting in significant UL performance degradation. Therefore, CLI, especially BS-BS CLI, is considered a major obstacle to the performance of 5G dynamic TDD macro systems. Coordination schemes between BSs have been developed to counteract CLI; however, these are typically only effective within a certain CLI range and fail to mitigate CLI otherwise. In addition, these coordination schemes can require a large number of CLI user measurements, highly complex implementations, and / or significant signaling overhead.

[0030] Some techniques have been proposed to coordinate the scheme of the fully dynamic TDD system. For example, one technique configures the periodicity and the digital scheme, such as the subcarrier spacing and the cyclic prefix length. The list may contain multiple entities indicating the information that the time slots within the periodicity are configured, and the UL area indication configured for each time slot, such as all DL, all UL, multiple DL symbols in the time slot, and / or multiple UL symbols.

[0031] Another example includes a DL to UL CLI cancellation method using full packet switching. A DL heavy BS signals DL data payload, precoding information, timing information, modulation and coding information, and scheduling decisions to neighboring UL heavy BSs. These UL heavy BSs can cancel DL to UL CLI, improving UL and DL capacity, but X n There is significant control signaling overhead on the interface.

[0032] Other techniques have proposed X-based n A coordination scheme is proposed to avoid UE-UE CLI by preemptively cancelling more critical BS-BS CLI on a best-effort basis. This can lead to significantly enhanced capacity and latency performance, but only within a limited BS-BS CLI range (such as under a DL heavy traffic assumption). Therefore, in the case of strong BS-BS CLI, URLLC latency and capacity performance can degrade exponentially due to excessive UL retransmissions.

[0033] Some proposals may involve network-based UL-DL coordination schemes. Here, a base station may be associated with a common RFC across the entire cluster, such as static TDD. When a base station requires an RFC change, it may signal all base stations within the cluster via an RFC change request. If all base stations agree, the request is accepted and all base stations may switch to the updated RFC, which may still be in static TDD mode. If at least one base station rejects such a request, the requesting base station only changes to the required RFC, and all base stations in the cluster may start monitoring CLI measurements periodically. If the detected CLI level exceeds a predefined threshold, all base stations fall back to static TDD with a common RFC. Therefore, the CLI level should always be limited. However, with the significant reduction in RFC flexibility, cross-X n The interface incurs a large amount of signaling overhead, as well as the need for regular CLI user measurements on the radio control channel.

[0034] Additional proposals may involve hybrid TDD coordination schemes, where the BS dynamically switches between static and dynamic TDD modes based on the detected CLI level. If the CLI level exceeds a threshold, all BSs switch back to the same static TDD RFC. Thus, CLI is always minimized, but the flexibility of the RFC is extremely limited, except for the requirement for high-quality CLI user measurements.

[0035] Some techniques may include coordinated cell muting and rate allocation between all BSs in a cluster to eliminate the dominant CLI offender BS / PRB, but at the expense of capacity area. For example, some BSs may be muted for several subframes, requiring significant control overhead to globally expose individual BS scheduling decisions across clusters.

[0036] Finally, a coordinated reverse frame structure has been proposed, in which BSs are grouped in pairs. Each BS can select the RFC that needs to be completely reversed with the other BS in the pair, thereby biasing the dynamic TDD system towards more DL to UL CLI occurrences than UL to DL CLI occurrences. Coordinated DL to UL CLI elimination can then be adopted at all BSs using advanced non-linear receivers and complex coordination. However, the requirement of a completely reverse frame structure for every two neighboring BSs can place key limitations on TDD RFC flexibility, for example, two neighboring BSs may not initially select exactly the same RFC, but in reverse order.

[0037] With the standard dynamic TDD system model on 5G NR, each BS can independently select its RFC based on its current traffic needs. An RFC can consist of 10 subframes, where each subframe has a duration of 1 millisecond. Each RFC can be divided into two equally sized half-frames of five subframes, each of which is half-frame 0 including subframes 0-4, and half-frame 1 including subframes 5–9. For the case with a normal cyclic prefix, one subframe includes 14 OFDM symbols, while for the case with an extended cyclic prefix and 60kHz subcarrier spacing, it is only equal to 12 OFDM symbols. The number of slots per subframe / radio frame can depend on the subcarrier spacing. For a 15kHz subcarrier spacing, there can be one slot per subframe; for 30kHz, there may be two slots per subframe; for 60kHz, there may be four slots per subframe, and so on. A large number of possible slot formats can be defined in 3GPP TS 38.213, where "D" indicates downlink symbols, "U" indicates uplink symbols, and "F" is flexible. Thus, "F" may refer to muting or being used for downlink or uplink transmissions. As an example, slot formats 0 and 1 may correspond to downlink-only and uplink-only slots, respectively. Slot format 36 may contain the first three downlink transmission symbols, followed by "F" (which may be set to muting during the guard period), and ten uplink transmission symbols. According to 3GPP TS 38.213, the gNB may dynamically inform the UE of the slot format used.

[0038] The flexible frame structure of 5G NR can allow both short transmission time intervals (TTIs) and long transmission time intervals. Therefore, it is suitable for both enhanced mobile broadband (eMBB) and ultra-reliable low latency communication (URLLC) QoS levels. eMBB is enhanced by allowing both mini-slot transmissions (e.g., 2 or 4 symbols) and full-slot transmissions or TTIs of aggregated slots to / from specific users.

[0039] If the base stations do not use exactly the same RFC, neighboring base stations may experience different transmission directions over several symbols / time slots, causing potentially severe CLI, such as Figure 1 As shown in the example in . Therefore, the lower power UL transmissions can be severely degraded due to the strong CLI generated by the neighboring higher power DL transmissions. As a result, the achievable UL capacity can show a significant loss, resulting in more buffered UL traffic in these victim BSs. Therefore, these base stations can be dominated by new and buffered UL traffic, resulting in limited DL capacity and highly reduced overall spectral efficiency.

[0040] Figure 2 The complementary cumulative density function (CCDF) of the URLLC one-way delay for a DL:UL offered traffic ratio of 2:1 (DL heavy) and an offered load of 4 Mbps / cell in total is shown in static and fully dynamic (uncoordinated) TDD settings. -5 The static TDD setting provides improved URLLC latency compared to the dynamic TDD case, i.e. 16.2 ms compared to 105.4 ms for dynamic TDD, at URLLC outage probability of 100 ms. This may be due to critical DL to UL (i.e. BS-BS) CLI, which significantly degrades the adjacent UL decoding capability through higher power DL interfering transmissions. Therefore, the transmitted UL traffic may be accumulated in the scheduling buffer for further retransmissions. As a result, the system may be dominated by new and buffered UL traffic, resulting in suboptimal UL and DL latency and capacity performance.

[0041] To further highlight this UL buffering issue, Figure 3 The average buffer queue ratio for the fully dynamic TDD setup in both cases is presented, which represents the ratio of DL buffered traffic to the total UL and DL buffered traffic. a) uncoordinated and without CLI suppression, and b) coordinated with theoretically perfect CLI suppression, i.e. CLI = 0. For the uncoordinated case, the queue ratio is quite small, such as at the 50th percentile it is 0.248, which means that on average the amount of buffered UL traffic is 3 times the buffered DL traffic, although the offered DL traffic is 2 times the offered UL traffic. This is because the UL traffic is almost successfully decoded after several retransmissions due to the strong BS-BS CLI. This behavior disappears when the CLI is theoretically assumed to be completely cancelled (i.e. no CLI).

[0042] Certain embodiments described herein may have various benefits and / or advantages to overcome the above-mentioned shortcomings by managing CLI by implementing coordination between base stations. For example, certain embodiments may provide a near-optimal TDD coordination scheme to suppress critical BS-BS CLI, resulting in significantly improved UL capacity and latency performance. As a result, the URLLC interruption delay is reduced by 143.0% and the throughput gain per packet is reduced by 139.3% compared to an uncoordinated TDD deployment. In addition, consistent and reliable CLI suppression capabilities can be provided, respectively, regardless of the amount of load provided and the DL to UL service ratio, without the need for regular CLI user measurements.

[0043] Certain embodiments may result in improved reliable BS-BS CLI suppression capabilities independent of the provided load level and DL. Some embodiments may also provide robust and reliable capacity performance in both UL and DL directions, regardless of the provided traffic load and potential CLI levels in both directions. Furthermore, various embodiments require low coordination complexity, limited signaling overhead on the Xn / F1 interface in the absence of periodic user CLI measurements, resulting in improvements in computer-related techniques.

[0044] Figure 4 FIG. 4 illustrates a signaling diagram according to some embodiments. In step 401, it is possible to Fig.16 NE 420 of NE 1610 in the embodiment may send at least one downlink precoder mapping to NE 430, and NE 430 may also be similar to Fig.16 16. The downlink precoder mapping may be at least one wideband or subband precoder index configured to be employed by at least one scheduled downlink user during at least one upcoming mini-time slot / time slot transmission. At least one user-specific precoding matrix index (PMI) may be relayed between at least one base station. In addition, NE 420 and / or NE 430 may communicate with UE 440, which may be similar to Fig.16 1620 in the UE. NE 420 and / or NE 430 may be associated with at least one BS-BS CLI symbol / time slot within at least one current RFC and / or may be a neighboring base station. Additionally, NE 420 may be in DL mode and / or NE 430 may be in uplink mode. At least one DL precoder mapping may be performed by at least one X n In some embodiments, at least one DL precoder mapping may include at least one bit vector configured to indicate at least one selected subband / wideband precoding matrix index (PMI) associated with at least one scheduled DL on an associated time slot. Figure 6As shown in (a), at least one selected subband / wideband PMI may be configured to be used by at least one scheduled user during the next DL symbol of the DL base station.

[0045] In some embodiments, NE 420 may be similar to a centralized unit (CU) and / or NE 430 may be similar to a distributed unit (DU). n -C interface and / or NG interface towards at least one 5G core network (5GC) to send at least one downlink precoder mapping to NE 430, the X n -C interface is configured to coordinate at least one X n AP procedures as defined in 3GPP TS 38.423, the entire contents of which are incorporated herein.

[0046] In some embodiments, the 5G NR architecture may be configured to allow C-RAN implementation associated with at least one CU and / or at least one DU. As described in 3GPP TS 38.460 and / or TS 38.463, the CU-DU configuration may be associated with at least one E1 interface between at least one control plane and at least one user plane in the CU. Additionally or alternatively, the CU-DU configuration may be associated with at least one F1 interface between at least one CU and at least one DU, as described in 3GPP TS 38.470 and / or TS 38.473, the entire contents of which are incorporated herein.

[0047] In some embodiments, when NE 430 is UE 440 or similar to UE 440, NE 430 can directly communicate with at least one other user equipment (such as Fig.16 1620) in the network, and / or with the help of the network with at least one other user equipment (such as Fig.16 For example, NE 430 may act as a relay UE, acting as a UL BS for at least one neighboring UE. In some embodiments, such as Figure 6 As shown in (b), at least one neighboring UE may be affected by a neighboring DL transmission from a neighboring base station. Therefore, downlink precoder signaling may be performed on at least one radio interface from NE 420 to NE 430.

[0048] In various embodiments, such as Fig.10As shown, at least one CU may be configured to act as a master unit and / or at least one DU may be configured to act as a slave unit. At least one downlink precoder mapping may be sent according to at least one F1 control plane signaling path, such as F1-C. In response, at least one CU may determine at least one RFC associated with at least one DU and send at least one determined RCC to at least one DU. The CU may be configured to identify at least one time slot / symbol associated with the DU-DUCLI.

[0049] For each instance of DU-DU CLI, the CU may send at least one request to at least one interfering DU to report at least one used precoder mapping. In response, the CU may forward at least one reported used precoder mapping to at least one interfered DU. At least one interfered DU may adjust at least one parameter to reduce DU-DU CLI interference based on the received at least one used precoder mapping.

[0050] In some embodiments, the CU may coordinate with at least one DU to perform at least one DU-DU radio channel measurement associated with low offered service and / or conditions exceeding at least one interference threshold associated with at least one channel estimation task.

[0051] In response to receiving at least one DL precoder mapping, NE 430 may identify at least one BS-BS CLI source associated with CLI exceeding at least one predefined CLI source threshold in step 403. The at least one identified BS-BS CLI source may be regulated via at least one channel between at least one DL and at least one UL NE. In some embodiments, at least one channel may be estimated based on at least one periodicity, which may be associated with at least one static attribute exceeding at least one predefined static attribute threshold.

[0052] In step 405, NE 430 may sort at least one identified BS-BS CLI source in an order such as descending or ascending according to the CLI associated with each BS-BS CLI source. r -1 BS-BS CLI source, where M r is the number of multiple UE antennas.

[0053] In step 407, NE 430 may estimate the N t - At least one basis of at least one common spatial subspace associated with 1 BS-BS CLI source. For example, NE 430 may perform the estimation according to:

[0054]

[0055]

[0056] where β k is the kth BS-BS CLI source J k =Q k v k The basis vectors of k is the wireless channel between NE 420 and NE 430, and v k is the precoder for the DL user transmitted on the corresponding subband.

[0057] In step 409, NE 430 may estimate at least one orthogonal projection span of a basis for the strongest BS-BS CLI interference according to:

[0058] A=[β1,β2,...,β k ] T

[0059] A ⊥ =A(A ⊥ A) -1 A T

[0060] like Figure 7 As shown, A and A ⊥ represents the BS-BS CLI subspace and its orthogonal projection span.

[0061] In step 411, for each reception associated with NE 430, NE 430 may spatially project at least one interference rejection combining (IRC) estimated interference covariance matrix into at least one orthogonal projection subspace according to:

[0062]

[0063] Where W and are the interference covariance matrix estimated by IRC and the corresponding covariance matrix projected onto the estimated projection subspace.

[0064] In step 413, NE 430 may calculate at least one standard IRC decoding matrix u based on at least one IRC estimated interference covariance matrix as follows:

[0065]

[0066] where H is the expected wireless channel and v is the expected precoder for the corresponding user.

[0067] Figure 5The diagram illustrates a method according to some embodiments of the present invention. Fig.16 An example of a method performed by a NE of NE 1610 illustrated in FIG. 10. In step 501, the NE may receive at least one downlink precoder mapping from a neighboring NE, which may also be similar to Fig.16 NE 1610 in the present RFC. The NE and / or the neighboring NE may be associated with at least one BS-BS CLI symbol / time slot in at least one current RFC and / or may be a neighboring base station. Additionally, the NE may be in DL mode and / or the neighboring NE may be in uplink mode. At least one DL precoder mapping may be performed by at least one X n In some embodiments, at least one DL precoder mapping may include at least one bit vector configured to indicate at least one selected subband / wideband precoding matrix index (PMI) associated with at least one scheduled DL user on an associated time slot. Figure 6 As shown in (a), at least one selected subband / wideband PMI may be configured to be used by at least one scheduled user during the next DL symbol of the DL base station.

[0068] In some embodiments, a NE may be similar to a centralized unit (CU) and / or an adjacent NE may be similar to a distributed unit (DU). n -C interface and / or NG interface towards at least one 5G core network (5GC) to send at least one downlink precoder mapping to a neighboring NE, the X n -C interface is configured to coordinate at least one X n AP processes, as defined in 3GPP TS 38.423, the entire contents of which are incorporated herein. The 5GNR architecture may be configured to allow C-RAN implementations associated with at least one CU and / or at least one DU. As described in 3GPP TS 38.460 and / or TS 38.463, the CU-DU configuration may be associated with at least one E1 interface between at least one control plane and at least one user plane in the CU. Additionally or alternatively, the CU-DU configuration may be associated with at least one F1 interface between at least one CU and at least one DU, as described in 3GPP TS 38.470 and / or TS 38.473, the entire contents of which are incorporated herein.

[0069] In some embodiments, when the NE is a UE or a UE-like device (such as Fig.16 1620), the NE may directly communicate with at least one other user equipment (such as Fig.16 1620) in the network, and / or with the help of the network with at least one other user equipment (such as Fig.16For example, the NE may act as a relay UE, acting as a UL BS for at least one neighboring UE. In some embodiments, such as Figure 6 As shown in (b), at least one neighboring UE may be affected by a neighboring DL transmission from a neighboring base station. Thus, downlink precoder signaling may be performed over at least one radio interface from NE to NE.

[0070] In various embodiments, such as Fig.10 As shown, at least one CU may be configured to act as a master unit and / or at least one DU may be configured to act as a slave unit. At least one downlink precoder mapping may be sent according to at least one F1 control plane signaling path, such as F1-C. In response, at least one CU may determine at least one RFC associated with at least one DU and send at least one determined RCC to at least one DU. The CU may be configured to identify at least one time slot / symbol associated with the DU-DU CLI.

[0071] For each instance of DU-DU CLI, the CU may send at least one request to at least one interfering DU to report at least one used precoder mapping. In response, the CU may forward at least one reported used precoder mapping to at least one interfered DU. At least one interfered DU may adjust at least one parameter to reduce DU-DU CLI interference based on the received at least one used precoder mapping.

[0072] In some embodiments, the CU may coordinate with at least one DU to perform at least one DU-DU radio channel measurement associated with low offered service and / or conditions exceeding at least one interference threshold associated with at least one channel estimation task.

[0073] In response to receiving at least one DL precoder mapping, NE 430 may identify at least one BS-BS CLI source associated with CLI exceeding at least one predefined CLI source threshold in step 503. The at least one identified BS-BS CLI source may be regulated via at least one channel between at least one DL and at least one UL NE. In some embodiments, at least one channel may be estimated based on at least one periodicity, which may be associated with at least one static attribute exceeding at least one predefined static attribute threshold.

[0074] In step 505, the NE may sort the at least one identified BS-BS CLI source in an order such as descending or ascending according to the CLI associated with each BS-BS CLI source. r-1 BS-BS CLI source, where M r is the number of UE antennas

[0075] In step 507, the NE may estimate the number of nodes associated with at least one or all of the identified N t - At least one basis of at least one common spatial subspace associated with 1 BS-BS CLI source. For example, the NE may perform the estimation according to:

[0076]

[0077]

[0078] where β k (is the kth BS-BS CLI source J k =Q k v k The basis vectors of k is the wireless channel between NE and its neighboring NE, and v k is the precoder for the DL user transmitted on the corresponding subband.

[0079] In step 509, the NE may estimate at least one orthogonal projection span of the basis for the strongest BS-BS CLI interference according to:

[0080] A=[β1,β2,...,β k ] T

[0081] A ⊥ =A(A ⊥ A) -1 A T

[0082] Where A and A ⊥ represents the BS-BS CLI subspace and its orthogonal projection span, such as Figure 7 shown.

[0083] In step 511, for each reception associated with the NE, the NE may spatially project at least one interference rejection combining (IRC) estimated interference covariance matrix into at least one orthogonal projection subspace according to:

[0084]

[0085] Where W and are the interference covariance matrix estimated by IRC and the corresponding covariance matrix projected onto the estimated projection subspace.

[0086] In step 513, the NE may calculate at least one standard IRC decoding matrix u according to at least one IRC estimated interference covariance matrix as follows:

[0087]

[0088] where H is the expected wireless channel and v is the expected precoder for the corresponding user.

[0089] Some embodiments described herein may be associated with a specific signaling overhead. For example, in a system with 10 MHz bandwidth, 50 physical resource blocks (PRBs), subband feedback, each of the 8 PRBs, and 4-bit PMI feedback based on 4 antenna port transmissions may be associated with 3 BS-BS CLI slots. The overall signaling overhead for DL ​​precoder mapping associated with each radio frame duration (such as 10 ms) may be determined as:

[0090] bits per 10 ms (i.e. radio frame duration).

[0091] Such signaling may not be required between each DL and UL BS pair because some DL NEs may not cause severe BS-BS CLI to neighboring UL BSs due to weak channels between them, which may be due to long distance, obstacles, advanced beamforming, etc., and may lead to further reduction of signaling overhead.

[0092] As mentioned above, various embodiments described herein may use Fig. 9 At least one of the parameters shown in the table of provides certain advantages. For example, in each cell, there may be K average number of active users. The URLLC service may be characterized by at least one FTP3 service model, a finite Z bit packet size per user, and / or a Poisson point arrival process λ. Therefore, the aggregate of the DL and UL load per cell in bits / second may be given as K×λ {DL，UL} × Z. The system bandwidth may be 10 MHz with 8 antennas at the BS and 2 antennas at the user equipment. The various coordination schemes described herein may be tested at various offered traffic loads of DL heavy traffic ratios, which may correspond to strong DL to UL CLI.

[0093] FIG. 11( a ) and FIG. 11( b ) depict the complementary cumulative distribution functions (CCDFs) (in milliseconds) of UL and DL URLLC delays for different offered load levels of DL:UL=2:1 in various embodiments under the optimal CLI-free scenario. Various embodiments may be used for 10 -5The best outage probability of URLLC outage probability is provided without CLI. Under this outage probability, for an extreme offer load of 7Mbps, various embodiments can only provide +4ms over the case without CLI, but with significantly lower coordination overhead and only through X n interface.

[0094] Fig.12 Provided are 10 various embodiments described herein. -5 Full numerical results of URLLC delay with interruption probability. Specifically, due to strong BS-BS CLI, NC and H-RFC schemes may be affected by extreme interruption delay degradation. Various embodiments may cause UL packets to reach the maximum allowed number of retransmissions before being discarded, which may result in a significant loss of URLLC reliability. Due to the absolute absence of BS-BS and UE-UE CLI, various embodiments may provide an optimal CLI-free case with consistent URLLC delay. However, certain embodiments may provide interruption delay performance similar to the optimal CLI-free case, but with reduced signaling overhead space. As a result, various embodiments provide support for more provided loads to achieve the same interruption delay, such as from 4Mbps to 7Mbps.

[0095] Fig.13 An empirical CDF (ECDF) of the carrier-to-interference ratio (CIR) in dB is presented. Due to effective BS-BS CLI suppression, various embodiments can provide a 3.5 dB increase in CIR compared to NC and H-RFC, close to the optimal no-CLI case. Fig.14 The average throughput per packet in Mbps is similarly illustrated, where certain embodiments may provide an average of 3 times the throughput per URLLC packet compared to H-RFC and NC.

[0096] Fig.15 The queue traffic ratio is shown as above. Fig.14 As shown, some embodiments may provide a queue ratio where approximately twice as much DL traffic may be buffered compared to UL traffic, where the DL traffic provided may be twice as much UL traffic. As a result, UL traffic may be successfully and quickly decoded without being buffered for multiple retransmission attempts. Various embodiments may also provide an optimal CLI-free situation.

[0097] Fig.16 An example of a system according to some embodiments is illustrated.In one embodiment, the system may include a plurality of devices, such as, for example, a network entity 1610 and / or a user equipment 1620 .

[0098] The network entity 1610 may be one or more of the following: a base station, such as an evolved Node B (eNB) or a 5G or new radio Node B (gNB), a serving gateway, a server, and / or any other access node or a combination thereof. The network entity 1610 may also be a UE 1620 or be similar to a UE 1620.

[0099] User device 1620 may include one or more of a mobile device, such as a mobile phone, a smart phone, a personal digital assistant (PDA), a tablet computer or portable media player, a digital camera, a pocket camcorder, a video game console, a navigation unit, such as a global positioning system (GPS) device, a desktop or laptop computer, a single location device, such as a sensor or smart meter, or any combination thereof.

[0100] In addition, in some embodiments, the functions of the network entity 1610 and / or the UE 1620 may be implemented by other network nodes (such as wireless relay nodes). For example, the functions of the NE 1610 may be performed by a mobile terminal (MT) component of an IAB node. In addition, the network entity 1610 and / or the user equipment 1620 may be one or more citizen broadband radio service devices in a citizen broadband radio service device (CBSD).

[0101] One or more of these devices may include at least one processor, indicated as 1611 and 1621, respectively. Processors 1611 and 1621 may be implemented as any computing or data processing device, such as a central processing unit (CPU), an application specific integrated circuit (ASIC), or an equivalent device. The processor may be implemented as a single controller, or multiple controllers or processors.

[0102] At least one memory may be provided in one or more devices indicated by 1612 and 1622. The memory may be fixed or removable. The memory may include computer program instructions or computer codes contained therein. The memories 1612 and 1622 may independently be any suitable storage device, such as a non-transient computer readable medium. A hard disk drive (HDD), a random access memory (RAM), a flash memory or other suitable memory may be used. The memory may be combined on a single integrated circuit as a processor, or may be separated from one or more processors. In addition, the computer program instructions stored in the memory and that may be processed by the processor may be computer program codes in any suitable form, for example, a compiled or interpreted computer program written in any suitable programming language. The memory may be removable or non-removable.

[0103] Processors 1611 and 1621 and memories 1612 and 1622 or a subset thereof may be configured to provide Figures 1 to 15 Components corresponding to the various blocks. Although not shown, the device may also include positioning hardware, such as GPS or micro-electromechanical system (MEMS) hardware, which can be used to determine the location of the device. Other sensors are also allowed and can be included to determine location, altitude, direction, etc., such as a barometer, compass, etc.

[0104] like Fig.16 As shown, transceivers 1613 and 1623 may be provided, and one or more devices may also include at least one antenna, which is shown as 1614 and 1624, respectively. The device may have many antennas, such as an antenna array configured for multiple input multiple output (MIMO) communication, or multiple antennas for multiple radio access technologies. For example, other configurations of these devices may be provided. Transceivers 1613 and 1623 may be transmitters, receivers, or both transmitters and receivers, or may be configured for both sending and receiving units or devices.

[0105] The memory and the computer program instructions may be configured to, together with a processor for a particular device, cause a hardware device such as a user device to perform any of the processes described below (see, for example, Figures 1 to 15 ). Thus, in some embodiments, a non-transitory computer-readable medium may be encoded with computer instructions that, when executed in hardware, perform a process such as one of the processes described herein. Alternatively, some embodiments may be implemented entirely in hardware.

[0106] In some embodiments, the apparatus may include a Figures 1 to 15 The circuit system may be a hardware circuit implementation of any process or function shown. For example, the circuit system may be a hardware circuit implementation only, such as an analog and / or digital circuit system. In another example, the circuit system may be a combination of hardware circuits and software, such as a combination of analog and / or (multiple) digital hardware circuits with software or firmware, and / or any portion of (multiple) hardware processors with software (including (multiple) digital signal processors), software and at least one memory, which work together to enable the device to perform various processes or functions. In yet another example, the circuit system may be a hardware circuit (multiple) and / or (multiple) processor (s), such as (multiple) microprocessors or a portion of (multiple) microprocessors, which includes software, such as firmware for operation. When the operation of the hardware is not required, the software in the circuit system may not be present.

[0107] Fig.17 An architecture according to some embodiments is illustrated. Fig.18 Another architecture in accordance with some embodiments is illustrated.

[0108] The features, structures, or characteristics of certain embodiments described throughout this specification may be combined in any suitable manner in one or more embodiments. For example, the use of the phrases "certain embodiments," "some embodiments," "other embodiments," or other similar language throughout this specification refers to the fact that a particular feature, structure, or characteristic described in conjunction with an embodiment may be included in at least one embodiment of the present invention. Thus, the appearance of the phrases "in certain embodiments," "in some embodiments," "in other embodiments," or other similar language throughout this specification does not necessarily refer to the same set of embodiments, and the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0109] Those skilled in the art will readily appreciate that the invention as discussed above may be practiced in steps of a different order and / or with hardware elements in configurations different from those disclosed. Therefore, although the invention has been described based on these preferred embodiments, certain modifications, variations will be apparent to those skilled in the art while remaining within the spirit and scope of the invention, and alternative configurations will be apparent.

[0110] Partial Glossary

[0111] 3GPP Third Generation Partnership Project

[0112] 5G 5th Generation

[0113] BS Base Station

[0114] CLI Cross Link Interference

[0115] CLI-free Dynamic TDD without CLI

[0116] CQI Channel Quality Indicator

[0117] CU Centralized Unit

[0118] DL Downlink

[0119] DSS Dynamic Slot Set

[0120] DU Distributed Unit

[0121] ECDF Empirical Cumulative Distribution Function

[0122] eMBB Enhanced Mobile Broadband

[0123] eNB Evolved Node B

[0124] EPC Evolved Packet Core

[0125] FDD Frequency Division Duplex

[0126] gNB New Radio Node B

[0127] GPS Global Positioning System

[0128] H-RFC Hybrid RFC Dynamic TDD

[0129] IRC interference refused to merge

[0130] LTE Long Term Evolution

[0131] MAC Media Access Control

[0132] MCS Modulation and Coding Scheme

[0133] MME Mobility Management Entity

[0134] MTC Machine Type Communication

[0135] NC Non-coordinated dynamic TDD

[0136] NG-eNB Next Generation Evolved Node-B

[0137] NR New Radio

[0138] OAM Operations, Administration and Management

[0139] OFDM Orthogonal Frequency Division Multiplexing

[0140] PDU Protocol Data Unit

[0141] PRB Physical Resource Block

[0142] QoS Quality of Service

[0143] RAN Radio Access Network

[0144] RFC Radio Frame Configuration

[0145] RFCB Radio Frame Configuration Book

[0146] RLC Radio Link Control

[0147] SB Subband

[0148] SN Serial Number

[0149] SSS Static Slot Set

[0150] TCP Transmission Control Protocol

[0151] TDD Time Division Duplex

[0152] TTI Transmission Time Interval

[0153] UE User Equipment

[0154] UL Uplink

[0155] URLLC Ultra-Reliable Low Latency Communications

Claims

1. A method of communication, comprising: receiving, by the first network entity from the second network entity via at least one interface, at least one downlink precoder mapping; In response to receiving the at least one downlink precoder mapping, identifying, by the first network entity, at least one CLI source associated with a CLI exceeding at least one predefined cross-link interference CLI source threshold; estimating, by the first network entity, at least one basis of at least one common spatial subspace based on the identified at least one CLI source; estimating, by the first network entity, the at least one common spatial subspace based on the at least one basis of the at least one common spatial subspace; estimating, by the first network entity, at least one orthogonal projection subspace based on the at least one common spatial subspace; For each reception associated with the first network entity, the first network entity spatially projects at least one interference rejection combined (IRC) estimated interference covariance matrix into the at least one orthogonal projection subspace to obtain a spatially projected IRC estimated interference covariance matrix; as well as At least one standard IRC decoding matrix is ​​calculated by the first network entity based on the spatially projected IRC estimated interference covariance matrix.

2. The method according to claim 1, further comprising: The at least one identified BS-BS CLI source is ordered, by the first network entity, according to a CLI associated with each BS-BS CLI source.

3. The method according to claim 1, wherein the interface is X n Interface, X n -C interface, F1 interface, F1-C interface or radio interface.

4. The method of claim 1, wherein the at least one common space subspace is associated with at least one identified BS-BS CLI source. The method according to claim 1 , wherein the first network entity is a user equipment or a base station.

6. The method of claim 1, wherein the first network entity is in a downlink mode and the second network entity is in an uplink mode.

7. The method of claim 1, wherein the first network entity is a centralized unit and the second network entity is a distributed unit.

8. The method of claim 7, wherein the at least one centralized unit is configured to act as a master unit and the at least one distributed unit is configured to act as a slave unit.

9. The method of claim 1, wherein the at least one common space subspace is associated with at least one identified DU-DU CLI source.

10. The method of claim 1, wherein the at least one downlink precoder mapping comprises at least one bit vector configured to indicate at least one selected subband / wideband precoding matrix index (PMI) associated with at least one scheduled downlink user on an associated time slot.

11. The method of claim 1, wherein at least one selected sub-band / wideband PMI is configured to be used by at least one scheduled user during a next downlink symbol of a downlink base station.

12. The method of claim 1, wherein the at least one identified BS-BS CLI source is regulated by at least one channel between at least one DL and at least one UL NE.

13. The method of claim 1, wherein the estimation is based on M r -1 BS-BS CLI source, where M r is the number of UE antennas.

14. An apparatus for communication, comprising: at least one processor; as well as at least one memory including computer program code, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to: receiving at least one downlink precoder mapping from a network entity via at least one interface; In response to receiving the at least one downlink precoder map, identifying at least one CLI source associated with a CLI exceeding at least one predefined cross-link interference CLI source threshold; estimating at least one basis of at least one common spatial subspace based on the identified at least one CLI source; estimating the at least one common spatial subspace based on the at least one basis of the at least one common spatial subspace; estimating at least one orthogonal projection subspace based on the at least one common spatial subspace; spatially projecting, for each reception associated with the apparatus, at least one interference rejection combined (IRC) estimated interference covariance matrix into the at least one orthogonal projection subspace to obtain a spatially projected IRC estimated interference covariance matrix; as well as At least one standard IRC decoding matrix is ​​calculated based on the spatially projected IRC estimated interference covariance matrix.

15. The apparatus according to claim 14, wherein the apparatus is further configured to: The at least one identified BS-BS CLI source is ordered according to the CLI associated with each BS-BS CLI source.

16. The apparatus of claim 14, wherein the interface is X n Interface, X n -C interface, F1 interface, F1-C interface or radio interface.

17. The apparatus of claim 14, wherein the at least one common spatial subspace is associated with at least one identified BS-BS CLI source. The apparatus according to claim 14 , wherein the apparatus is a user equipment or a base station.

19. The apparatus of claim 14, wherein the apparatus is in a downlink mode and the network entity is in an uplink mode.

20. The apparatus of claim 14, wherein the apparatus is a centralized unit and the network entity is a distributed unit.

21. The apparatus of claim 20, wherein the at least one centralized unit is configured to act as a master unit and the at least one distributed unit is configured to act as a slave unit.

22. The apparatus of claim 14, wherein the at least one common space subspace is associated with at least one identified DU-DU CLI source.

23. The apparatus of claim 14, wherein the at least one downlink precoder mapping comprises at least one bit vector configured to indicate at least one selected subband / wideband precoding matrix index (PMI) associated with at least one scheduled downlink user on an associated time slot.

24. The apparatus of claim 14, wherein the at least one selected sub-band / wideband PMI is configured to be used by at least one scheduled user during a next downlink symbol of a downlink base station.

25. The apparatus of claim 14, wherein the at least one identified BS-BS CLI source is regulated by at least one channel between at least one DL and at least one UL NE.

26. The apparatus of claim 14, wherein the estimation is based on M r -1 BS-BS CLI source, where M r is the number of UE antennas.

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