Methods for reducing interference in sub-band full duplex communication

Abstract

A base station beamforming method for reducing cross link interference (CLI) on an uplink (UL) band of a first base station (110) caused by a second base station (120) realized by a system comprising the first base station (110), and the second base station (120) having line of sight with the first base station (110) capable of communicate in sub-band full duplex (SBFD) mode and capable of multiple input multiple output (MIMO) communication; and at least a first user equipment (210) and at least a second user equipment (220) capable of communicate in SBFD mode and capable of MIMO communication.

Description

[0001] METHODS FOR REDUCING INTERFERENCE IN SUB-BAND FULL DUPLEX COMMUNICATION

[0002] TECHNICAL FIELD

[0003] Invention relates to a base station beamforming method for reducing cross link interference (CLI) on an uplink (UL) band of a first base station caused by a second base station and a method and a user equipment beamforming method for reducing cross link interference (CLI) on an uplink (UL) band of a first user equipment caused by a second user equipment.

[0004] PRIOR ART

[0005] The advent of fifth generation (5G) networks is revolutionizing various industries and accommodating an increasing number of users, thus fostering a more interconnected and digitally advanced society. In prior iterations, 5G standards primarily emphasized services with specific requirements. For instance, enhanced mobile broadband (eMBB) services necessitated large bandwidths, while ultra-reliable and low latency communication (URLLC) services prioritized low latency and high reliability enhancements. These services often coexist and demand flexible network scheduling to accommodate diverse needs, necessitating advanced duplex methods.

[0006] Time division duplex (TDD) is designated as the duplex mode for 5G networks operating above approximately 2 GHz. TDD offers the advantage of using a single carrier with adaptable uplink (UL) and downlink (DL) ratios, addressing asymmetric UL and DL requirements. Moreover, channel reciprocity enables efficient acquisition of channel state information (CSI), reducing overhead particularly with a high number of antennas. However, commercial networks predominantly support DL-heavy TDD configurations, which limits UL resources, resulting in diminished UL throughput, coverage, and increased latency.

[0007] To enhance UL performance, various techniques like multiple-input multiple-output (MIMO) and carrier aggregation (CA) have been employed in the initial releases of the 3GPP 5G new radio (NR) standards. Additionally, Releases 16 and 17 introduce solutions to minimize latency for URLLC services, such as mini-slot monitoring and scheduling. Release 17 also enhances UL channels to improve coverage. Addressing the evolving needs of 5G services, three significant challenges arise in conventional TDD systems: ensuring UL throughput and coverage while satisfying latency requirements for both DL and UL simultaneously; ensuring DL throughput while meeting latency requirements for both DL and UL simultaneously; and ensuring DL throughput, UL throughput, and coverage simultaneously to support use cases like extended reality (XR).

[0008] One effective approach to tackle these challenges is full duplex communication, allowing simultaneous transmission and reception of DL and UL signals on overlapping time and frequency resources, potentially doubling spectral efficiency. However, implementing full duplex systems presents architectural and cost challenges for wide-area deployment.

[0009] Several techniques have been proposed to mitigate self-interference in full duplex systems, including in-band and sub-band approaches. While in-band techniques offer fully overlapping resources in the frequency domain, sub-band methods divide signals into sub-bands for interference cancellation. Non-overlapping sub-band full duplex (SBFD) emerges as a feasible alternative, enabling UL reception within DL slots of a TDD period. This facilitates simultaneous UL and DL operations, allowing base stations to accommodate diverse user requirements.

[0010] Despite the benefits of SBFD, detailed designs and interference handling mechanisms remain scarce. In the context of Dynamic TDD (D-TDD), two new types of interference have emerged: gNB-to-gNB co-channel inter-subband CLI and UE-to-UE co-channel inter-subband CLL The former refers to interference at a gNB receiver caused by another gNB transmitting on nonoverlapping frequency resources. The latter involves interference at a UE receiver from another UE connected to a neighboring cell of the serving cell and transmitting on nonoverlapping frequency resources. D-TDD dynamically allocates time resources between uplink (UL) and downlink (DL) links. In addition to D-TDD, SBFD systems have been introduced, which allocate frequency resources separately to uplink (UL) and downlink (DL) systems. SBFD systems introduce two more interference types: Intra-cell UE-to-UE co-channel intersubband CLI, which is interference at a UE receiver from another UE connected to the same cell and transmitting on non-overlapping frequency resources, and gNB self-interference (SI), where the gNB's receive antennas capture interfering signals from its own transmit antennas. The disclosed invention aims to address interference types 2 and 3, as described below:

[0011] 1 ) gNB self-interference (SI): SI refers to the receive antennas of the gNB capturing the interfering signals from its own transmit antennas. 2) gNB-to-gNB co-channel inter-subband CLI: Interference at a gNB receiver from another gNB transmitting on non-overlapping frequency resources.

[0012] 3) Intra-cell UE-to-UE co-channel inter-subband CLI: Interference at a UE receiver from another UE connected to the same cell and transmitting on non-overlapping frequency resources.

[0013] 4) Inter-cell UE-to-UE co-channel inter-subband CLI: Interference at a UE receiver from another UE connected to a neighbor cell of the serving cell and transmitting on non-overlapping frequency resources.

[0014] It is determined that interference levels are increased at the edge sub-bands (where uplink sub-bands and downlink sub-bands of the sub-band full duplex symbol.

[0015] The related works discussed in the 3GPP meeting discussion are referenced as [1 ,2], Regarding the first interference type mentioned in [1 Section 6.1.3], it is stated that this is not considered a problem. However, for the second and fourth interference types, methods described below are proposed in [1 ,2],

[0016] • Spatial domain coordination scheme for gNB Tx-beam nulling

[0017] • UL resource muting-based scheme for measuring the gNB-to-gNB CLI interference covariance matrix.

[0018] For the third interference type, Coordinated Scheduling is also proposed in the same document.

[0019] Prior art documents [1 ,2] focuses on two types of solutions:

[0020] • Coordinated Beamforming (CBF) 1 : based on gNB-gNB steering vector. Steering vector: A set of complex weights applied to the signal at each antenna element in an array. These weights determine the direction and shape of the radio beam.

[0021] • Coordinated Beamforming 2: based on gNB-gNB channel measurement. Leverages measurements of channels between gNBs to make informed decisions about beamforming. For effective CBF, measurements need to be shared.

[0022] The two methods proposed represent a two-end approach for addressing the identified problems. The first method is more spectral and computationally effective, and it's quicker to implement but may be less accurate, especially in highly dynamic environments. Conversely, the second method involves dynamic adaptation but necessitates significant signaling. References:

[0023]

[0001] 3GPP (2023). Study on Evolution of NR Duplex Operation (Release 18). T ech. Rep. 38.858.

[0024] V 1.1.0.

[0025] [2] 3GPP TSG-RAN WG1 Meeting #1 14 - R1 -2308336. Discussion on evaluation and methodologies on evolution of NR duplex operation

[0026] Furthermore, suitable precoding in the multi user multiple input multiple output (MU-MIMO) systems typically also requires more detailed knowledge of the channel experienced by each device, compared to precoding in the case of transmission to single device. For this reason, New Radio (NR) defines two types of channel state information (CSI) that differ in the structure and size of the pre-coder codebooks. Introduced CSIs are Type I CSI and Type II CSI.

[0027] Type I CSI primarily targets scenarios where a single user is scheduled within a given time / frequency resource (no MU-MIMO), potentially with transmission of a relatively large number of layers in parallel (high-order spatial multiplexing).

[0028] Type II CSI primarily targets MU-MIMO scenarios with multiple devices being scheduled simultaneously within the same time / frequency resource but with a more limited number of spatial layers per scheduled device.

[0029] The codebooks for Type I CSI are relatively simple and primarily aim at focusing the transmitted energy at the target receiver. Interference between the potentially large number of parallel layers is assumed to be handled primarily by means of receiver processing utilizing multiple receive antennas.

[0030] The codebooks for Type II CSI are significantly more extensive allowing for the Precoding Matrix Indicator (PMI) to provide channel information with much higher spatial granularity. The more extensive channel information allows the network to select a downlink precoder that not only focuses the transmitted energy at the target device but also limits the interference to other devices scheduled in parallel on the same time / frequency resource. The higher spatial granularity of the PMI feedback comes at the cost of significantly higher signaling overhead. While a PMI report for Type I CSI will consist of at most a few tens of bits, a PMI report for Type II CSI may consist of several hundred bits.

[0031] In general, each PMI information W expressed as the product of two matrices w = W±W2with information about the selected w and w2reported separately as different parts of the overall PML The matrix w±is assumed to capture long-term frequency-independent characteristics of the channel. A single w is therefore selected and reported for the entire reporting bandwidth (wideband reporting). In contrast, the matrix j2is assumed to capture more short-term and potentially frequency-dependent characteristics of the channel. w2is therefore selected and reported on a sub-band basis, where a sub-band covers a fraction of the overall reporting bandwidth.

[0032] All the problems mentioned above have made it necessary to make an innovation in the relevant technical field as a result.

[0033] BRIEF DESCRIPTION OF THE INVENTION

[0034] The present invention relates to methods to eliminate the above-mentioned disadvantages and bring new advantages to the relevant technical field.

[0035] An object of the invention is to provide a method that reduces interference between two neighboring base stations while realizing sub-band full duplex.

[0036] Another object of the invention is to provide a method that reduces interference between two user equipment served by the same base station while realizing sub-band full duplex.

[0037] Another object of the invention is to provide methods that reduces the overhead significantly.

[0038] To achieve all the objects mentioned above and that will emerge from the following detailed description, the present invention relates to a base station beamforming method for reducing cross link interference (CLI) on an uplink (UL) band of a first base station caused by a second base station realized by a system comprising the first base station, and the second base station having line of sight with the first base station capable of communicate in sub-band full duplex (SBFD) mode; and at least a first user equipment and at least a second user equipment capable of communicate in SBFD mode. Accordingly, it comprises the steps of

[0039] - by the first base station, during a SBFD slot, when the first base station is to transmit downlink data to the first user equipment, wherein the SBFD slot has a plurality of uplink sub-bands and downlink sub-bands where uplink sub-bands which are located approximate to downlink subbands are defined as edge uplink sub-bands and rest of the uplink sub-bands are defined as far uplink sub-bands; and where downlink sub-bands which are located approximate to uplink sub-bands are defined as edge downlink sub-bands and rest of the downlink sub-bands are defined as far downlink sub-bands, transmit beamforming on the downlink edge sub-bands using multi-user multiple input multiple output (MU-MIMO) based on a Type-ll channel state information (CSI);

[0040] - by the first base station transmit beamforming on the far downlink sub-bands using single- user multiple input multiple output (SU-MIMO) based on a Type-1 CSI;

[0041] - by the second base station, during the SBFD slot, when the second base station is to receive uplink data from a user equipment, receive beamforming on the uplink edge sub-bands multiuser multiple input multiple output (MU-MIMO) based on the Type-ll CSI;

[0042] - by the second base station receive beamforming on the far uplink sub-bands using single- user multiple input multiple output (SU-MIMO) based on the Type-1 CSI. Thus, interference is reduced while reducing overhead significantly.

[0043] Invention is also a user equipment beamforming method for reducing cross link interference (CLI) on an uplink (UL) band of a first user equipment caused by a second user equipment realized by a system comprising a first base station, and a second base station capable of communicate in sub-band full duplex (SBFD) mode; and at least one first user equipment and at least one second user equipment capable of communicating in SBFD mode where the first user equipment and the second user equipment are connected to the first base station characterized in that

[0044] - by the first base station, transmitting channel state information reference signal (CSI-RS) to the second user equipment wherein CSI-RS comprising nullified symbols allocated for the first user equipment’s sounding reference signals (SRS);

[0045] - by the second user equipment realizing SRS transmission to first user equipment using nullified symbols;

[0046] - by the second user equipment receiving SRS symbols from the first user equipment;

[0047] - by the second user equipment estimating a Type-ll channel state information (CSI) and Type- I CSI based on received SRS and CSI-RS;

[0048] - by the second user equipment transmitting Type-ll CSI and Type-1 CSI to the first base station,

[0049] - by the first base station, transmitting Type-ll CSI and Type-1 CSI to the first user equipment;

[0050] - by the first user equipment, during a SBFD slot, when the user equipment is to transmit uplink data to the first base station, wherein the SBFD slot has a plurality of uplink sub-bands and downlink sub-bands where uplink sub-bands which are located approximate to downlink subbands are defined as edge uplink sub-bands and rest of the uplink sub-bands are defined as far uplink sub-bands; and where downlink sub-bands which are located approximate to uplink sub-bands are defined as edge downlink sub-bands and rest of the downlink sub-bands are defined as far downlink sub-bands, transmit beamforming on the uplink edge sub-bands using multi-user multiple input multiple output (MU-MIMO) based on a Type-ll channel state information (CSI);

[0051] - by the first user equipment transmit beamforming on the far uplink sub-bands using single- user multiple input multiple output (SU-MIMO) based on a Type-1 CSI;

[0052] - by the second user equipment, during the SBFD slot, when the second user equipment is to receive downlink data from the first base station, receive beamforming on the downlink edge sub-bands using multi-user multiple input multiple output (MU-MIMO) based on the Type-ll CSI;

[0053] - by the second user equipment receive beamforming on the far downlink sub-bands using single-user multiple input multiple output (SU-MIMO) based on the Type-1 CSI. Thus, interference is reduced while reducing overhead significantly.

[0054] BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 is a drawing illustrating schematic view of the system.

[0056] Figure 2 is a drawing illustrating sub-band full duplex (SBFD) slot.

[0057] Figure 3 is drawing illustrating channel state information reference signal (CSI-RS).

[0058] REFERENCE NUMBERS GIVEN IN THE FIGURE

[0059] 110 First base station

[0060] 120 Second base station

[0061] 200 User equipment

[0062] 210 First user equipment

[0063] 220 Second user equipment

[0064] 300 SBFD slot

[0065] 310 Uplink sub-band

[0066] 311 Edge uplink sub-band

[0067] 312 Far uplink sub-band

[0068] 320 Downlink sub-band

[0069] 321 Edge downlink sub-band

[0070] 322 Far downlink sub-band

[0071] DETAILED DESCRIPTION OF THE INVENTION In this detailed description, the subject matter is explained with references to examples without forming any restrictive effect only in order to make the subject more understandable.

[0072] Invention relates to a base station beamforming method and a user equipment (200) beamforming method realized by a system.

[0073] Referring to figure 1 , the system comprises a first base station (1 10) and a second base station (120). System comprises a plurality of user equipment (200). At least one first user equipment (210) and at least a second user equipment (220) is provided. Base stations and user equipment (200) are capable of communicating in sub-band full duplex (SBFD) mode and capable of multiple input multiple output (MIMO) communication. Base stations and user equipment (200) comprise antenna elements, processing elements and other well-known components for realizing above mentioned functions (not shown in the figures).

[0074] In said system interference occurs between two base stations and between user equipment (200). As disclosed in the prior art section interference (interference type 2) occurs at the first base station (110) caused by the second base station (120) transmitting on non-overlapping frequency resources. In other words, cross-link interference (CLI) occurs on an uplink (UL) band of the first base station (110) caused by the downlink transmission of the second base station (120). Another interference occurs (interference type 4 as disclosed in prior art section) at the first user equipment (210) receiver caused by the second user equipment (220) connected to the same cell (same base station) and transmitting on non-overlapping frequency resources. Subject matter methods reduces mentioned two type of interferences.

[0075] A base station beamforming method is realized by the first base station (1 10) and the second base station (120). The method reduces cross link interference (CLI) on an uplink (UL) band of the first base station (110) caused by the second base station (120) realized.

[0076] Communication is realized during SBFD slots (300). Referring to figure 2, each SBFD slot (300) comprises a plurality of uplink sub-bands (310) and downlink sub-bands (320). Uplink sub-bands (310) which are located approximate to downlink sub-bands (320) are defined as edge uplink sub-bands (31 1 ) and rest of the uplink sub-bands (310) are defined as far uplink sub-bands (312). Downlink sub-bands (320) which are located approximate to uplink subbands (310) are defined as edge downlink sub-bands (321 ) and rest of the downlink sub-bands (320) are defined as far downlink sub-bands (322). It is determined by the studies that interference level is significantly higher at the edge subbands comparing to far sub-bands in SBFD.

[0077] The first base station (1 10) and the second base station (120) are in line of sight with each other. Thus, channel state information (CSI) between the first base station (1 10) and the second base station (120) is known on both sides and stored on the first base station (110) and on the second base station (120). Type-I CSI and Type-ll CSI is stored on the first base station (110) and on the second base station (120).

[0078] When the first base station (110) is to transmit downlink data to the first user equipment (210) during a SBFD slot (300), it realizes transmit beamforming on the downlink edge sub-bands using multi-user multiple input multiple output (MU-MI MO) based on a stored Type-ll channel state information (CSI) of the channel between the first base station (110) and the second base station (120). The first base station (110) realizes transmit beamforming on the far downlink sub-bands (322) using single-user multiple input multiple output (SU-MIMO) based on a stored Type-I CSI. When the second base station (120) is to receive uplink data from a user equipment (200) during the SBFD slot (300), it realizes receive beamforming on the uplink edge sub-bands multi-user multiple input multiple output (MU-MIMO) based on the Type-ll CSI. The second base station (120) realizes receive beamforming on the far uplink sub-bands (312) using single-user multiple input multiple output (SU-MIMO) based on the Type-I CSI. Thus, MU-MIMO is realized on the edge sub-bands where interference level is significantly higher than the far sub-bands; reducing interference significantly.

[0079] In the base station beamforming method, MU-MIMO is employed differently. First base station (110) treats the second base station (120) as an additional user equipment (200) alongside its intended user equipment (200) for MU-MIMO transmit beamforming at the edge subband. Similarly, second base station (120) treats the first base station (1 10) as an additional user equipment (200) alongside its intended user equipment (200) for MU-MIMO receive beamforming at the edge sub-band. While MU-MIMO typically utilizes Type II CSI, which can consist of several hundred bits, the disclosed method requires only the w2information of edge subbands from the CSI, rather than whole Type II CSI, for effective operation. Therefore, the disclosed method reduces the overhead significantly. In the CLI2scenario, UE treats UE2as an additional UE alongside its intended BS±for MU-MIMO transmit beamforming at the edge subband. A user equipment (200) beamforming method is realized by the first user equipment (210) and the second user equipment (220) and a first base station (110) of the system.

[0080] The first base station (110), transmits channel state information reference signal (CSI-RS) to the second user equipment (220) wherein CSI-RS comprising nullified symbols (figure 3) allocated for the first user equipment’s (210) sounding reference signals (SRS). The second user equipment (220) realizes SRS transmission to the first user equipment (210) using nullified symbols. The second user equipment (220) receives SRS symbols from the first user equipment (210). The second user equipment (220) estimates a Type-ll channel state information (CSI) and Type-I CSI based on received SRS and CSI-RS of the channel between the first user equipment (210) and the second user equipment (220). The second user equipment (220) transmitting Type-ll CSI and Type-I CSI to the first base station (1 10). The first base station (1 10), transmits Type-ll CSI and Type-I CSI to the first user equipment (210). When the first user equipment (210) is to transmit uplink data to the first base station (1 10) during a SBFD slot (300), it realizes transmit beamforming on the uplink edge sub-bands using multi-user multiple input multiple output (MU-MIMO) based on a Type-ll channel state information (CSI). The first user equipment (210) realizes transmit beamforming on the far uplink sub-bands (312) using single-user multiple input multiple output (SU-MIMO) based on a Type-I CSI. When the second user equipment (220) is to receive uplink data from a base station during SBFD slot (300), it realizes receive beamforming on the downlink edge subbands using multi-user multiple input multiple output (MU-MIMO) based on the Type-ll CSI. The second user equipment (220) realizes receive beamforming on the far downlink sub-bands (322) using single-user multiple input multiple output (SU-MIMO) based on the Type-I CSI.

[0081] First user equipment (210) treats the second user equipment (220) as an additional user equipment (200) alongside its intended base station for MIMO receive beamforming at the edge sub-band.

[0082] Referring to figure 3, the conventional "2xCDM + 2xTDM + 2xFDM" arrangement for the eightport CSI-RS and SRS "2 combs on 1 symbol" configuration is illustrated. Nullification shown with dashed rectangles and SRS signals shown with hatch rectangles. Subsequently, second user equipment (220) can estimate above mentioned channels state information with CSI-RS and SRS.

[0083] The scope of protection of the invention is specified in the attached claims and cannot be limited to those explained for sampling purposes in this detailed description. It is evident that a person skilled in the art may exhibit similar embodiments in light of the above-mentioned facts without drifting apart from the main theme of the invention.

Claims

CLAIMS1. A base station beamforming method for reducing cross link interference (CLI) on an uplink (UL) band of a first base station (1 10) caused by a second base station (120) realized by a system comprising the first base station (110), and the second base station (120) having line of sight with the first base station (1 10) capable of communicate in sub-band full duplex (SBFD) mode and capable of multiple input multiple output (MIMO) communication; and at least a first user equipment (210) and at least a second user equipment (220) capable of communicate in SBFD mode and capable of MIMO communication characterized in that- by the first base station (1 10), during a SBFD slot (300), when the first base station (110) is to transmit downlink data to the first user equipment (210), wherein the SBFD slot (300) has a plurality of uplink sub-bands (310) and downlink sub-bands (320) where uplink sub-bands (310) which are located approximate to downlink sub-bands (320) are defined as edge uplink sub-bands (311 ) and rest of the uplink sub-bands (310) are defined as far uplink sub-bands (312); and where downlink sub-bands (320) which are located approximate to uplink sub-bands (310) are defined as edge downlink sub-bands (321 ) and rest of the downlink sub-bands (320) are defined as far downlink sub-bands (322), transmit beamforming on the downlink edge sub-bands using multi-user multiple input multiple output (MU- MIMO) based on a stored Type-ll channel state information (CSI) of the channel between the first base station (1 10) and the second base station (120);- by the first base station (110) transmit beamforming on the far downlink sub-bands (322) using single-user multiple input multiple output (SU-MIMO) based on a stored Type- 1 CSI;- by the second base station (120), during the SBFD slot (300), when the second base station (120) is to receive uplink data from a user equipment (200), receive beamforming on the uplink edge sub-bands multi-user multiple input multiple output (MU-MIMO) based on the Type-ll CSI;- by the second base station (120) receive beamforming on the far uplink sub-bands (312) using single-user multiple input multiple output (SU-MIMO) based on the Type- 1 CSI.

2. A user equipment (200) beamforming method for reducing cross link interference (CLI) on an uplink (UL) band of a first user equipment (210) caused by a second user equipment (220) realized by a system comprising a first base station (1 10), and asecond base station (120) capable of communicate in sub-band full duplex (SBFD) mode and capable of multiple input multiple output (MIMO) communication; and at least one first user equipment (210) and at least one second user equipment (220) capable of communicating in SBFD mode and capable of MIMO communication and where the first user equipment (210) and the second user equipment (220) are connected to the first base station (1 10) characterized in that- by the first base station (110), transmitting channel state information reference signal (CSI-RS) to the second user equipment (220) wherein CSI-RS comprising nullified symbols allocated for the first user equipment’s (210) sounding reference signals (SRS);- by the second user equipment (220) realizing SRS transmission to first user equipment (210) using nullified symbols;- by the second user equipment (220) receiving SRS symbols from the first user equipment (210);- by the second user equipment (220) estimating a Type-ll channel state information (CSI) and Type-I CSI based on received SRS and CSI-RS of the channel between the first user equipment (210) and the second user equipment (220);- by the second user equipment (220) transmitting Type-ll CSI and Type-I CSI to the first base station (1 10),- by the first base station (110), transmitting Type-ll CSI and Type-I CSI to the first user equipment (210);- by the first user equipment (210), during a SBFD slot (300), when the user equipment (200) is to transmit uplink data to the first base station (1 10), wherein the SBFD slot (300) has a plurality of uplink sub-bands (310) and downlink sub-bands (320) where uplink sub-bands (310) which are located approximate to downlink sub-bands (320) are defined as edge uplink sub-bands (311 ) and rest of the uplink sub-bands (310) are defined as far uplink sub-bands (312); and where downlink sub-bands (320) which are located approximate to uplink sub-bands (310) are defined as edge downlink subbands (321 ) and rest of the downlink sub-bands (320) are defined as far downlink subbands (322), transmit beamforming on the uplink edge sub-bands using multi-user multiple input multiple output (MU-MIMO) based on a Type-ll channel state information (CSI);- by the first user equipment (210) transmit beamforming on the far uplink sub-bands (312) using single-user multiple input multiple output (SU-MIMO) based on a Type-I CSI;- by the second user equipment (220), during the SBFD slot (300), when the second user equipment (220) is to receive downlink data from the first base station (110), receive beamforming on the downlink edge sub-bands using multi-user multiple input multiple output (MU-MIMO) based on the Type-ll CSI;- by the second user equipment (220) receive beamforming on the far downlink subbands (322) using single-user multiple input multiple output (SU-MIMO) based on the Type- 1 CSI.

3. A system comprising a first base station (110) and a second base station (120) having line of sight with the first base station (110) capable of communicate in sub-band full duplex (SBFD) mode and capable of MIMO communication; and at least a first user equipment (210) and at least a second user equipment (220) capable of communicate in SBFD mode and capable of MIMO communication characterized in that the system is configured to realize the method of claim 1 .

4. A system comprising a first base station (110), and a second base station (120) having line of sight with the first base station (110) capable of communicate in sub-band full duplex (SBFD) mode and capable of capable of MIMO communication; and at least a first user equipment (210) and at least a second user equipment (220) capable of communicate in SBFD mode and capable of MIMO communication characterized in that the system is configured to realize the method of claim 2.

Images