Apparatus and method for transmitting data to one or more users

Abstract

A base station (BS) for a wireless communication network is provided. The wireless communication network comprises a plurality of base stations each for serving one or more users (UEs). The one or more users are served by the plurality of base stations to receive a first data signal from a base station and a second data signal from at least one further base station using a multi-user superposition transmission (MUST). The base station (BS) comprises a backhaul interface for communicating with one or more of the plurality of base stations of the wireless communication network. To transmit the first data signal to the one or more users served by the base station and by the further base station, the base station (BS) is configured to negotiate MUST settings with the further base station via the backhaul interface and to map data of the first data signal using a first transmission constellation set in accordance with the negotiated MUST settings.

Description

[0001] This application is a divisional application of the Fraunhofer Society for the Promotion of Applied Research, filed on August 10, 2018, with application number 201880065274.5, entitled "Apparatus and Method for Transmitting Data to One or More Users". Technical Field

[0002] This invention relates to the field of wireless or wired communication networks or systems, and more particularly, to a concept for transmitting data to one or more users. Embodiments of the invention relate to multi-user superimposed (MUST) transmission of data to one or more users by multiple transmitters, such as base stations. Other embodiments of the invention relate to transmitting data to multiple users by transmitters, such as base stations, using multiple-input multiple-output (MIMO) technology. Background Technology

[0003] Figure 1 This is a schematic representation of an example of a wireless network 100 including a core network 102 and a radio access network 104. The radio access network 104 may include multiple base stations eNB1 to eNB5, each serving a specific area surrounding a base station schematically represented by corresponding cells 1061 to 1065. The base stations provide services to users within the cells. Users can be fixed or mobile devices. Additionally, the wireless communication system can be accessed via mobile or fixed IoT devices connected to the base stations or users. Mobile devices or IoT devices may include physical devices, ground vehicles (such as robots or cars), aircraft (such as manned or unmanned aerial vehicles (UAVs, also known as drones), buildings, and other items embedded with electronics, software, sensors, actuators, etc., and network connections enabling these devices to collect and exchange data over existing network infrastructure. Figure 1 An exemplary view showing only five cells is provided, but wireless communication systems can include more such cells. Figure 1 Two users, UE1 and UE2, also referred to as user equipment (UE), are shown in cell 1062 and served by base station eNB2. Another user, UE3, is shown in cell 1064 and served by base station eNB4. Arrows 1081, 1082, and 1083 schematically represent uplink / downlink connections used for transmitting data from users UE1, UE2, and UE3 to base stations eNB2 and eNB4, or for transmitting data from base stations eNB2 and eNB4 to users UE1, UE2, and UE3. Additionally, Figure 1Two IoT devices, 1101 and 1102, in cell 1064 are shown; these can be fixed or mobile devices. IoT device 1101 accesses the wireless communication system via base station eNB4 to receive and transmit data, as schematically indicated by arrow 1121. IoT device 1102 accesses the wireless communication system via user UE3, as schematically indicated by arrow 1122. The corresponding base stations eNB1 through eNB5 can, for example, be located via... Figure 1 The corresponding backhaul links 1141 to 1145, schematically indicated by arrows pointing to the "core," are connected to the core network 102 via the S1 interface. The core network 102 can connect to one or more external networks. Additionally, for example, some or all of the corresponding base stations eNB1 to eNB5 can, for example, be connected via... Figure 1 The corresponding backhaul links 1161 to 1165, schematically indicated by arrows pointing to "enBs", are connected to each other via the X1 or X2 interface.

[0004] Figure 1 The wireless network or communication system described herein can be a heterogeneous network with two distinct coverage networks: a macro cell network, where each macro cell includes macro base stations (such as base stations eNB1 to eNB5), and small cell base stations (…). Figure 1 (Not shown in the image) (such as a femtocell or picocell) network.

[0005] For data transmission, a physical resource grid can be used. A physical resource grid may include a set of resource elements to which various physical channels and physical signals are mapped. For example, physical channels may include physical downlink and uplink shared channels (PDSCH, PUSCH) carrying user-specific data (also known as downlink and uplink payload data), physical broadcast channels (PBCH) carrying, for example, Master Information Blocks (MIBs) and System Information Blocks (SIBs), physical downlink and uplink control channels (PDCCH, PUCCH) carrying, for example, downlink control information (DCIs), and so on. For uplink, physical channels may also include physical random access channels (PRACH or RACH) used by the UE to access the network once the UE is synchronized and has acquired the MIB and SIB. Physical signals may include reference signals (RS), synchronization signals, etc. A resource grid may include frames with a certain duration (e.g., 10 milliseconds) in the time domain and a given bandwidth in the frequency domain. Frames may have a certain number of subframes of predefined length, such as two subframes of 1 millisecond each. Depending on the cyclic prefix (CP) length, each subframe may include two gaps of 6 or 7 OFDM symbols.

[0006] The wireless communication system can be any single-tone or multi-carrier system using frequency division multiplexing, such as orthogonal frequency division multiplexing (OFDM) systems, orthogonal frequency division multiple access (OFDMA) systems, or any other IFFT-based signal with or without CP (e.g., DFT-s-OFDM). Other waveforms can be used, such as non-orthogonal waveforms for multiplexing, such as filter bank multicarrier (FBMC), generalized frequency division multiplexing (GFDM), or universal filtered multicarrier (UFMC). The wireless communication system can operate, for example, according to the LTE-Advanced pro standard or the 5G or NR (New Radio) standard.

[0007] exist Figure 1 In the wireless communication network shown, the radio access network 104 can be a heterogeneous network including networks of primary cells. Each primary cell network includes a primary base station, also known as a macro base station. Additionally, multiple auxiliary base stations, also known as small cell base stations, can be provided for each macro cell. Figure 2 It is similar to Figure 1 The schematic representation of cell 1061 shows that this cell has two distinct coverage networks, including a macrocell network with macrocell 1061 and a small cell network. Although Figure 2 This only represents a single macrocell, but it should be noted that... Figure 1 One or more of the other cells in the network can also use the coverage network. The small cell network includes multiple small cell base stations SeNB1 to SeNB5, each operating within a corresponding area 1201 to 1205, also known as the small cell's coverage area. Small cell base stations SeNB1 to SeNB5 can be controlled by a macro cell base station MeNB1, and each small cell base station SeNB1 to SeNB5 is connected to the macro cell base station via corresponding backhaul links 1221 to 1225. It is not that the small cell base stations are connected to the macro cell base station via backhaul links, but rather that one or more of the small cell base stations can be coupled to the core network via corresponding backhaul links. Figure 2 User equipment (UE) is also shown, which is served by macro cell base station MeNB1 (as indicated by arrow 1241) and by small cell base station SeNB1 (as indicated schematically by arrow 1242).

[0008] Figure 3 This is another schematic representation of multiple smaller cells 1201 to 1203 of a macrocell (not shown). A macrocell can be similar to... Figure 2 Macro cells within a system. Each small cell can serve one or more UEs. Besides... Figure 2In addition to the main network, the corresponding small cell base stations SeNB1, SeNB2, SeNB3, ... are connected to the core network 102 via backhaul links or connections 1021 to 1023. The corresponding small cells 1021 to 1023 can be directly connected to each other via the X2 interface, such as... Figure 3 The diagram illustrates this. The transport network connecting the corresponding small cells to the core network 102 can be an optical fiber network including one or more points of presence (PoPs) where multiple small cells are connected to the transport network. Reference [1] describes the relevant information. Figure 3 More details of the return trip architecture shown.

[0009] Small cells (also known as secondary mobile communication cells, SC) form a coverage network extending to macro cells (also known as primary mobile communication cells, PC). Small cells can connect to macro cells via backhaul links (BL). Figure 2 ) and / or core network ( Figure 3 The backhaul link can be a wired or wireless link, and in cases where a small cell is connected to the core network via the backhaul link, the transport network ( Figure 3 The Point of Presence (PoP) can be used as an interface to the core network. Each small cell can serve multiple mobile user UEs within its coverage area via the Radio Access Link (AL) 1242. Additionally, a UE can connect to the main cell, for example, to receive control signals, and this connection can be referred to as the Control Link (CL).

[0010] The above reference Figures 1 to 3 In the wireless communication network described above, multi-user superimposed transmission (MUST) of data can be used. For example, according to LTE, a MUST for downlink (DL) is described in reference [2]. MUST is used as a downlink scheme, i.e., a multiple access scheme in which multiple users cooperate in scheduling on the same physical resource elements without spatial separation. This non-orthogonal transmission allows for increased capacity of multi-user (MU) systems and / or the number of connected devices in the network. The base station (BS) on the transmitting side creates a composite transmission (TX) constellation for independent data streams. On the receiver side, for example, continuous interference can be used to cancel the separation of data streams by the receiver structure. For the downlink (DL) direction, three MUST categories are specified in reference [2] as shown in Table 1 below.

[0011]

[0012]

[0013] Table 1: Classification and Key Characteristics of the MUST Program

[0014] Figure 4An example of transmitter - side processing for Category 1 is shown. Data to be transmitted using MUST is provided in the first transport block TB1 and the second transport block TB2. After independent channel coding, rate matching (RM), and scrambling at 2021, 2022 and independent mapping to modulation symbols at 2041, 2042, signals carrying data for the first UE (also called the near - MUST UE) close to or near the transmitter and data for the second UE (also called the far - MUST UE) far from the transmitter (the first UE is closer to the transmitter than the second UE) are weighted separately using amplitude weights and (where α is the transmission power ratio for the near - MUST user) and combined at 208. Figure 5 An example composite constellation for MUST Category 1 is shown. The above - mentioned DL - MUST is designed for point - to - multi - point transmission. However, it does not support multi - point transmission. Thus, for example, it is impossible to use MUST to achieve cooperative multi - point transmission of data.

[0015] In addition, the above - mentioned DL - MUST is implemented to transmit data to near - MUST and far - MUST UEs (also called near and far UEs), that is, only UEs with significant SNR gaps or large SNR differences are selected for MUST and jointly scheduled on the same resource elements. Assume a high SNR near UE (with channel gain |h1| 2 ) and a low SNR far UE (with channel gain |h2| 2 ), |h1| > |h2|. Thus, using a specific decoding order and assuming a SIC receiver, the individual rates can be calculated as follows:

[0016]

[0017]

[0018] The individual rates can be achieved by using appropriate channel coding for each non - orthogonal multiple access (NOMA) layer. However, in the case where users have similar SNRs, that is, when From (1) and (2), for fair power allocation the individual rates are different, that is r2 < r1, because the SIC receiver needs to first decode one stream and subtract that stream from the other stream. Compared with orthogonal transmission (i.e., OFDMA), this results in different ( = unfair) SUM rates over time and no gain. Thus, no MUST is applied to users with equal or substantially equal SNRs.

[0019] In as Figures 1 to 3In the wireless communication system schematically depicted, multi-antenna technology can be used, for example, according to LTE, to improve user data rates, link reliability, cell coverage, and network capacity. To support multi-stream or multi-layer transmission, linear precoding is used at the physical layer of the communication system. Linear precoding is performed by a precoder matrix that maps data layers to antenna ports. Precoding can be viewed as a generalization of beamforming, a technique that spatially directs / focuses data transmission to the intended receiver. Multiple users can be served by a single base station using MIMO technology, which allows spatial precoding to serve each user through a dedicated beam. Up to this point, it has been assumed that spatial precoding allows for “orthogonal” transmission between layers, i.e., interference-free transmission. However, in reality, cross-layer interference, also known as crosstalk, exists, leading to performance degradation, for example due to limited feedback, quantized beamformers, etc. The effects of the aforementioned cross-layer interference are now explained in more detail with reference to Figure 6.

[0020] Figure 6(a) illustrates a base station (BS) or gNB using beamforming technology, which can also be a small cell base station. The base station provides data to multiple users UE1 and UE2 using corresponding transmission beams B1 and B2, formed by linear precoding and directed toward their respective users UE1 and UE2. The corresponding data or data streams D1 and D2 for users UE1 and UE2 are transmitted on beams B1 and B2. Additionally, Figure 6(a) schematically illustrates interference caused by crosstalk between the corresponding beams B1 and B2. Interference at the first user UE1 caused by the second beam B2 is represented by the dashed line I. 21 Indicative representation. Similarly, represented by the dashed line I. 12 This indicates the interference experienced by UE2 due to beam B1. Figure 6(a) also shows the corresponding receive constellations at users UE1 and UE2, indicating how signals carrying only data D1 and D2 are received at the respective users UE1 and UE2, and how interference I is received. 12 I 21 And the signals that are generated.

[0021] Figure 6(b) illustrates the impact of crosstalk interference at the corresponding user locations when the base station gNB simultaneously transmits data signals using beams B1 and B2. Figure 6(b) shows the transmission constellation at the base station, where data D1 for the first user UE1 is represented by constellation points in the upper left quadrant of the constellation diagram, while data D2 for the second user UE2 is represented by constellation points in the upper right quadrant. The actual reception at users UE1 and UE2 is based on the reception constellation indicated for the respective user in Figure 6(b), and depends on the interference I experienced by the respective users UE1 and UE2. 21 I 12 It can be seen that for the first user UE1, the interference I from the second beam B2...21 The received signal R1 is moved to the y-axis of the constellation diagram, preventing it from being correctly decoded at UE1, because UE1 cannot determine whether the received signal R1 should belong to the upper left or upper right quadrant of the reception diagram. For UE2, interference I from the first beam... 12 This also causes a shift in the constellation point; however, it remains within the upper right quadrant of the receiving constellation, allowing user UE2 to correctly decode signal D2. Therefore, in the scenario depicted with reference to FIG6, due to interference between the corresponding beams causing the originally transmitted data at one or more locations among the users to be unable to be correctly decoded, it is impossible to simultaneously transmit data from a single base station to multiple users via the corresponding beams. Summary of the Invention

[0022] The purpose of this invention is to provide an improved method for transmitting data to one or more users.

[0023] Embodiments of the present invention enable CoMP (Cooperative Multi-Point) transmission with a limited number of feedbacks using MUST. Further embodiments of the present invention allow MUST to be applied to users with equal or substantially equal SNRs.

[0024] Further embodiments of the present invention address cross-layer interference between MIMO layers used for transmitting data to multiple users. Attached Figure Description

[0025] Embodiments of the invention will now be described in more detail with reference to the accompanying drawings, in which:

[0026] Figure 1 A schematic representation illustrating an example of a wireless communication system;

[0027] Figure 2 A schematic representation of the cell is shown, such as Figure 1 The cells in the network have two different coverage networks: a macro cell network (including macro cells) and a small cell network (including small cell base stations connected to macro cell base stations via backhaul links).

[0028] Figure 3 This shows a further schematic representation of multiple small cells within a macrocell, similar to... Figure 2 Small cell base stations are interconnected via backhaul links and connected to the core network;

[0029] Figure 4 A block diagram showing the transmission path of the base station for downlink MUST is shown;

[0030] Figure 5 A schematic diagram of the composite constellation of MUST category 1 is shown;

[0031] Figure 6 illustrates the simultaneous transmission of data to multiple users using corresponding beams formed at the base station, wherein Figure 6(a) shows the data signal and interference signal generated by the transmission and received at the user, and wherein Figure 6(b) shows the effect of the interference signal on the signal received at the user;

[0032] Figure 7 This is a schematic representation of a wireless communication network operating according to the principles described in this article;

[0033] Figure 8 is a schematic representation of a constellation for superimposed data signals, wherein Figure 8(a) shows a constellation resulting from power distribution at two base stations serving one or more users, and wherein Figure 8(b) shows a constellation for superimposed data signals when phase offset compensation is additionally applied at at least one of the base stations due to power distribution.

[0034] Figure 9 This is a block diagram of a user and a base station for transmitting data signals to the user in an overlay manner, according to an embodiment of this application.

[0035] Figure 10 An embodiment of the method of the present invention is shown, according to which a UE is served by two base stations BS1 and BS2;

[0036] Figure 11 illustrates an embodiment in which two base stations serve different users, wherein at least one user operates in MUST-UECoMP mode, wherein Figure 11(a) shows the setup for serving a first user by a first base station and serving a second user by a second base station, and wherein Figure 11(b) shows the constellation rotation of the data signal received at the UE due to the channel phase offset of the channel (through which the data signal arrives at the UE);

[0037] Figure 12 This is a schematic block diagram of a user according to an embodiment of the present invention;

[0038] Figure 13 illustrates the data rate over time when MUST is applied at users with equal or substantially equal SNR, wherein Figure 13(a) shows the data rate over time achievable by prior art methods, and wherein Figure 13(b) shows the data rate over time achievable according to an embodiment of the present invention.

[0039] Figure 14 Crosstalk compensation is illustrated in an embodiment of the method according to the present invention;

[0040] Figure 15 Showing the reference Figure 14 A block diagram of the network describing the method; and

[0041] Figure 16Examples of computer systems are shown on which the units or modules described in the method according to the invention and the steps of the method can be executed. Detailed Implementation

[0042] According to the present invention, a method for downlink communication using MUST to one or more users is provided. This allows for more efficient use of resources available for communication between the base station and the user, and also allows for improved data transmission.

[0043] This invention provides a base station for a wireless communication network. The wireless communication network includes multiple base stations. Each base station serves one or more users, wherein the one or more users are served by multiple base stations to receive a first data signal from the base station and a second data signal from at least one additional base station using Multi-User Overlay Transmission (MUST). The base station includes a backhaul interface for communicating with one or more of the multiple base stations in the wireless communication network, wherein in order to transmit the first data signal to the one or more users served by the base station and by the additional base stations, the base station is configured to negotiate a MUST setting with the additional base stations via the backhaul interface, and is configured to map data of the first data signal using a first transport constellation set according to the negotiated MUST setting.

[0044] This invention provides a user equipment for a wireless communication network. The wireless communication network includes multiple base stations, each base station serving one or more user equipments. The user equipment is served by the multiple base stations to receive a first data signal from a first base station and a second data signal from a second base station using Multi-User Overlay Transmission (MUST). The user equipment is configured to receive and apply MUST settings to perform demapping on the overlay of the first and second data signals to obtain information data for each data signal.

[0045] According to an embodiment, the aforementioned MUST settings negotiated between BSs may include or indicate physical resources allocated to one or more users for transmitting first and second data signals, and power allocation for one or more users. According to another embodiment, information regarding the constellation diagram used by the base station may also be indicated, the constellation diagram representing a complex representation of binary data, e.g., a bit-to-QAM mapping. When both the allocated power and the constellation diagram are indicated, this may be referred to as the MUST layer. Information regarding the constellation diagram may include information about phase offsets between constellation diagrams. For example, the constellation diagram may include power allocation, and the length of the complex vectors in the constellation diagram may represent the power.

[0046] Figure 7 This is a schematic representation of a wireless communication network operating according to the principles described herein. The wireless communication system can be used as a reference. Figures 1 to 3 The communication system described in one of the above, or it may include a combination of the networks described above. Figure 7 Showing multiple base stations BS1 to BS n Each base station includes an interface I / F for connecting to the network backhaul, which can be a backhaul connection via the network core, such as via the S1 interface, and / or a direct connection to the corresponding base station, such as via the X1 / X2 interface. Each of the base stations may include an antenna ANT for wireless communication within the network, and, according to the method of the present invention, to provide wireless communication to multiple users UE1 to UE2. n Provides downlink communication. According to the present invention, multiple coordinated base stations are used to provide downlink communication to user UE1 to UE2 using MUST. n Data transmission between one or more of the base stations. For example, data from base station BS1 to BS2. n Two or more of them can be used to UE1 or to a selection from UE1 to UE1. n Downlink communication among multiple users in a network is used for downlink data communication using MUST. For example, each MUST layer, also known as a near / far MUST layer, can be coordinated by a set of base stations BS1 to BS2. n Transmitted to a coordinated group of user UE1 to UE n This also includes the transmission of data from multiple base stations to a single user. To allow at least two base stations to use the MUST (Must-Have) service for one or more users, the method of this invention coordinates the base stations involved via their backhaul connections. For example, when considering base stations BS1 and BS2 transmitting individual MUST layers to user UE1 or to both users UE1 and UE2, base stations BS1 and BS2 negotiate the MUST settings with each other via the backhaul interface I / F, such that each of the base stations can use the corresponding transport constellation mapping configured according to the negotiated MUST settings to transmit the corresponding data signal via the downlink superuser.

[0047] According to embodiments, for example, the MUST setting indicates physical resources allocated to one or more users, such as resource blocks or resource elements for scheduling UEs. According to another embodiment, information regarding power allocation for one or more users may be included in the MUST setting, and / or information regarding the constellation diagram to be used by the base station. The constellation diagram represents a complex representation of binary data, such as a bit-to-QAM mapping and power allocation. One or more of the above parameters may be included in the MUST setting, which is negotiated between base stations involved in downlink MUST communications with one or more users. Additionally, according to other embodiments, phase offsets between corresponding constellation diagrams may be included in the MUST setting, for example, where differences in distance between the base station and the user result in substantial phase offsets between the channels from the respective base station to the respective user, or in scenarios where phase offsets may be caused by other means.

[0048] Figure 8 is a schematic representation of a constellation showing superimposed data signals.

[0049] Figure 8(a) illustrates the effect of power distribution control at the first and second base stations BS1 and BS2, where the second base station uses MUST to transmit its data. In the example shown in Figure 8(a), BS1 maps its data to be transmitted to constellation point CP1 in the upper left quadrant, as indicated by the dashed arrow, and BS2 maps its data to be transmitted to constellation point CP2 in the upper left quadrant, as indicated by the solid arrow. The user can demap the superposition of the received data signals, for example, by subjecting the mapped superposition (superposition indicated by the solid arrow) to a continuous interference cancellation process. Figure 8(a) also shows the rotation of the QAM constellation point of the second base station BS2 relative to the constellation point of the QAM constellation of the first base station BS1 in the complex domain. The rotation can be caused by the phase offset between the first channel from the first base station BS1 to the user and the second channel from the second base station BS2 to the user, for example, due to arbitrary differences in the channels. Both base stations are power-controlled, which means that data signals from BS2 reach users with less power compared to data signals from BS1 that are less diffused or reduced in the QAM constellation of BS2 relative to the QAM constellation of BS1.

[0050] According to embodiments, phase offset compensation can also be implemented, for example, to compensate for the rotation of the QAM constellation points of the second base station BS2 relative to the constellation points of the QAM constellation of the first base station BS1 in the complex domain due to arbitrary differences in the channel. Phase offset compensation may include signaling between base stations involved in MUST DL communication, such that at least some of the base stations prepare for pre-rotating their QAM constellations. According to other embodiments, a base station may have a fixed phase for its constellation diagram, and one or more other base stations may receive phase offset information for pre-rotating their QAM constellations relative to the fixed-phase constellation of that base station. For example, when the phase of the first base station is fixed, the second base station may receive the phase offset between the first and second base stations from users served by the second base station and apply the received phase offset to its constellation diagram, such that the second base station can pre-rotate its constellation relative to the fixed-phase constellation of the first base station.

[0051] Figure 8(b) shows an example of a fixed-phase constellation assumed for BS1, where phase shifts have been compensated (represented by the rotation in Figure 8(a)). Both base stations BS1 and BS2 are power-controlled as described above. Compensation can be performed by properly pre-rotating the BS2 QAM constellation to compensate for or reduce the phase shift experienced by data signals from BS1 and BS2 on their path to the user. As can be seen from Figure 8(b), the constellation points of BS2 are now registered to the axes of the complex domain just like the constellation points of BS1. In this example, where the constellations of BS1 and BS2 are of the same type, i.e., QAM, the constellation points of BS2 can be transformed to the constellation points of BS1 simply by translation and isotropic scaling in the complex domain, i.e., without rotation.

[0052] To compensate for the phase shift, for example, in the manner described above, it is necessary to determine the phase offset. According to an embodiment, this can be done as follows: Figure 9 The phase shift is determined in the manner described in the text. Figure 9 The diagram illustrates users UE1 and UE2, and base stations BS1 and BS2. For the following discussion, it is assumed that both base stations BS1 and BS2 use MUST to transmit data to UE1. However, according to other embodiments (as indicated by the dashed arrows), first data can be transmitted from base station BS1 to UE1, and second data can be transmitted from base station BS2 to UE2 using MUST. Details of BS1 are described below, and depending on the circumstances, BS2 may or may not have the same structure.

[0053] UE1 receives data signals transmitted by BS1 and BS2 using multi-user overlay coding or MUST on radio channels 250a and 250b. BS1 includes a Phase Shift Estimation Reference Signal (PSERS) transmitter 252, configured to transmit a PSERS signal to UE1. The PSERS signal enables UE1 to estimate the phase shift between channels 250a and 250b. Similarly, BS2 performs the same operation, transmitting PSERS to UE1 via its connecting channel 250b. UE1 includes a phase shift estimator 254 for estimating the phase shift between channels 250a and 250b. For this purpose, the phase shift estimator 254 can evaluate the PSERS signals received from BS1 and BS2, respectively. UE1 includes a phase shift compensation signal transmitter 256, which receives information about the phase shift between channels 250a and 250b from the phase shift estimator 254 and transmits a phase shift compensation signal to at least one of base stations BS1 and BS2. Figure 9In this example, assume that BS1 receives a phase shift compensation signal transmitted by transmitter 256. For this purpose, BS1 includes a phase shift compensation signal receiver 258. The phase shift compensation signal is selected such that it causes a reduction or compensation for any phase shift between channels 250a and 250b. This phase shift may be due to the different distances between BS1 and BS2 and UE1.

[0054] BS1 includes a mapper 260, which maps the data 262 to be transmitted to UE1 in a phase-shift compensated manner using a specific constellation based on a phase-shift compensated signal, thereby obtaining a final data signal 264 to be transmitted to UE1 via channel 250a in a manner superimposed on the corresponding data signal transmitted from BS2. For example, the data mapper 260 maps the data 262 to be transmitted to a specific constellation, such as QPSK, QAM, etc., selected based on specific channel conditions. The data mapper 260 rotates its constellation to account for the phase shift between its channel 250a and the channel 250b of its multi-user superposition partner BS2. Then, for example, the obtained data signal 264 is used to form a specific OFDM subcarrier for the OFDM or SC-FDM or OFDMA or SC-FDMA signal ultimately transmitted from BS1 to UE1, such that the mentioned subcarrier is consistent with the subcarrier to which the corresponding mapper of BS2 maps its own data. BS1 and BS2 include corresponding backhaul interfaces 266, 268, such as S1, X1, or X2 interfaces, for communicating with each other via backhaul link 270. The backhaul link can be a wired link, such as an electrical or optical link, or a wireless link, such as a microwave link. In the described embodiment, it is assumed that BS1 and BS2 negotiate a MUST setting to the extent that BS1 and BS2 are aware of shared resources (such as RBs or REs) and the power allocated for data transmission from BS1 to UE1 and from BS2 to UE1. This can be negotiated via signaling through backhaul link 270. Information regarding phase offset can also be notified by signaling.

[0055] UE1 includes a demapper 272 that receives superimposed data signals, i.e., superimposed data signals on corresponding OFDM subcarriers indicated at 274, pointing to a specific point in the complex plane, and obtains information data for each data signal (i.e., data signal 276 transmitted from BS1 and the corresponding data signal transmitted from BS2) by performing demapping. For this purpose, demapper 272 may perform successive interference cancellation (SIC), such that demapper 272 first obtains information data for the “stronger” data signal (i.e., the data signal from the “nearer” transmitter) and then derives information data for the “farther” transmitter. Demapping can be hard demapping, where the information data is one or more bits, or it can be soft demapping, where the information data is a value between 0 and 1, both included. The information data 276 thus obtained by demapper 272 for BS1 and BS2 respectively then undergoes further processing, such as channel decoding performed independently for each base station BS1 and BS2, including, for example, deinterleaving, forward error correction, descrambling, de-piercing, etc. In such a scenario, BS1 and BS2 may include corresponding channel encoders, interleavers, scramblers and / or punchers upstream of data mapper 260, and UE1 may include a decomposer upstream of demapper 272, which decomposes inbound OFDM, SC-FDM or OFDMA or SC-FDMA symbols into OFDM subcarriers, one of which carries superimposed data signals.

[0056] According to an embodiment, when mapping is used for data transmitted to UE1, BS2 may not consider any phase shift compensation; for example, BS2 may use a fixed phase for its constellation diagram. BS2 may send phase offset information received from UE1 to BS1 via backhaul 270 to allow BS1 to pre-rotate its QAM constellation relative to the fixed-phase constellation.

[0057] According to another embodiment, when mapping data for transmission to UE1, BS2 may not include a phase-shift compensated signal receiver and / or may disregard any phase-shift compensation. BS2 may even be unaware of the fact that transmitter BS1 piggybacks additional data signals, and then the data signals undergo multi-user superposition decoding at UE1 in the manner described above.

[0058] According to further embodiments of this application, UE1 may optionally include (as shown in the dashed box) a power ratio estimator 278, which is configured to estimate the power ratio among a plurality of base stations to obtain power ratio information. Transmitter 280 transmits a power ratio compensation signal based on the power ratio information to at least one of BS1 and BS2, which may optionally include a power ratio compensation signal receiver 282. BS1 may set the power of its transmitted data signal 264 based on the power ratio compensation signal. In practice, the power setting can affect the entire set of subcarriers of the data signal 264. That is, the entire OFDM / SC-FDM / OFDMA / SC-FDMA symbol carrying multiple OFDM subcarriers may undergo a power setting based on the received power ratio compensation signal, wherein the multiple OFDM subcarriers include one OFDM subcarrier to which data 262 has been mapped by data mapper 260. The power ratio compensation signal can be used to reduce the power deviation (data signals participating in multi-user overlay coding are superimposed on each other at UE1) so that constellation points can be most effectively distributed in the complex domain.

[0059] Figure 10 An embodiment of the method of the present invention is shown, according to which a UE is served by two base stations BS1 and BS2. The UE can be referred to as a MUST UE in CoMP mode (Cooperative Multipoint Mode). Multipoint-to-point transmission is implemented, according to which the two base stations BS1 and BS2 transmit each MUST layer to a user UE via corresponding channels 250a and 250b. In order to coordinate the operation of base stations BS1 and BS2, the two base stations... Figure 10 Data is transmitted in the manner shown in the constellation diagram (which corresponds to the manner explained above with reference to FIG8(b)). The base station negotiates one or more MUST settings, such as the resource elements to be used, power locations, and / or phase offsets mentioned above. Figure 10 In the scenario described above, the user UE and base stations BS1 and BS2 can be referenced as above. Figure 9 Describe the operation method in detail.

[0060] The above embodiments assume that base stations BS1 and BS2 both use MUST to transmit data to UE1. However, according to other embodiments, data can be transmitted from base station BS1 to UE1, and additional data can be transmitted from base station BS2 to UE2 using MUST.

[0061] Figure 11 illustrates an embodiment in which two base stations, BS1 and BS2, serve corresponding users UE1 and UE2, with user UE2 operating in the aforementioned MUST-UE CoMP mode. Figure 11(a) shows the setup provided by BS1 serving UE1 and BS2 serving UE2. Additionally, similar to one of the setups in Figure 8(a), the constellation diagram shows BS1 mapping its data to constellation points in the upper left quadrant as indicated by the dashed arrows, and BS2 mapping its data to be transmitted to constellation points also in the upper left quadrant as indicated by the solid arrows. Figure 11(b) shows the constellation rotation of the data signal received at the UE or receiver due to the channel phase shift of the channel through which the data signal reaches the receiver, while also showing the resulting phase shift, i.e., the phase shift from BS1 to BS2 as seen at UE2.

[0062] More specifically, Figure 11(b) illustrates how the constellation of the incoming component data signal at UE2 is affected by the channel phase. The data signal whose constellation is shown on the left side of Figure 11(b) arrives at an angle β1-α1, such that the upper right constellation point of the QAM is at angle β1, while the QAM constellation of the second data signal is tilted at an angle β2-α2, such that the upper right constellation QAM point appears at angle β2. There is a relative phase offset or phase shift between the two data signals of β1-β2.

[0063] The embodiments described above with reference to Figure 11 can be provided to allow interference coordination when transmitting data from BS1 to UE1 and when using the same resources and MUST method for transmitting data from BS2 to UE2. (This is in accordance with the above reference...) Figures 7 to 10Similarly, in the embodiment of FIG11, base stations BS1 and BS2 can be connected via a backhaul connection (such as the X1, X2, or S1 interface) for signaling that allows interference coordination and management. According to embodiments, resource and power allocations are exchanged as described above, allowing the respective base stations to adjust their MCS levels based on interference from the MUST layer. For example, a base station can exchange information with another base station about the transmission power on MUST resources to adjust its MCS level based on interference from the MUST layer used by another base station. According to embodiments, the information about the transmission power on MUST resources may include or contain resource and power allocations. The transmitted information may be an offset or interference estimate from the normal transmission power, rather than the actual power allocation. According to some other embodiments, additional signaling assistance networks from the UE may be required. For example, received power level (CSI) representing the attenuation of the path from the respective UE to the base station can be provided to calculate the interference seen by the UE. Additionally, according to other embodiments, UE2 can send phase offset information, such as the information explained above with reference to FIG11(b), to adjust the phase difference between BS1 and BS2. This can be done using an absolute phase difference or iteratively by tracking and adjusting the phase of one base station. Signaling from UE2 can be transmitted to base station BS2, which is connected to UE2, via UCI or RRC. According to other embodiments, this information can be transmitted from base station BS2 to base station BS1 via a backhaul link. Alternatively, the information can be provided directly from UE2 to BS1 via a radio link.

[0064] Therefore, the embodiment of Figure 11 can be implemented to improve inter-cell DL interference, wherein UE1 and UE2 are placed close to each other and UE2 is in MUST mode to receive DL signals piggybacked on the signals received by UE1 from BS1 on the same physical resources. In this case, UE1 can even be unknown. Possibly, neither UE1 nor UE2 is in carrier aggregation mode. BS2 can transmit PSERS by its transmitter 252, and as referenced... Figure 9 The operation described in detail is used to map the data to be sent. According to an embodiment, BS1 may only send out PSERS, but it may not implement a reference. Figure 9 The technology is described in detail. UE2 may have the aforementioned special demapping function, but it is not interested in obtaining the information data from the data signal transmitted from BS1, but only uses MUST to separate the information data conveyed by the data signal from BS2 from the information data conveyed by the data signal from BS1. Otherwise, UE2 may have the above-described... Figure 9The structure described herein. UE1 may or may not have a MUST demapping function. UE2 receives two PSERS, one from BS1 and the other from BS2. When UE2 is served by BS2, it can signal the phase shift compensation signal to BS2. BS2 can forward the phase shift compensation signal it receives from UE2 to BS1 for controlling phase shift compensation in the data mapping and / or controlling phase shift compensation in the data mapping itself. Similar distribution can be performed for power control. Any backhaul or network interconnect, such as an X2 interface, can be used for signal forwarding or information exchange between BS1 and BS2.

[0065] Figure 12 This is a schematic block diagram of a user according to an embodiment of the present invention. Figure 12 The UE described in the above reference can be as follows. Figures 1 to 3 The description includes users in a wireless communication network with multiple base stations, and each base station serves one or more users in the wireless communication network. Figure 12 The UE described herein can be served by multiple base stations to receive a first data signal from a first base station and a second data signal from a second base station via antenna 300 and receiver / transmitter circuit 302 using multi-user overlay transmission. Additionally, the UE receives the aforementioned MUST settings via antenna 300 and receiver / transmitter circuit 302 to perform mapping on the overlay of the first and second data signals to obtain information data for each data signal.

[0066] According to another embodiment, the user equipment may optionally include measurement circuitry 304 to measure one or more of (i) phase offset between channels through which the user equipment receives first and second data signals, (ii) attenuation on the channel, and (iii) interference on the channel. Measurement circuitry 304 may include, for example, those referenced above. Figure 9 The phase shift estimator and power ratio estimator are described. Using receiver / transmitter circuitry 302 and antenna 300, the UE can signal the measurement results to one or more base stations serving the UE. According to an embodiment, the phase shift compensation signal transmitter, power ratio compensation transmitter, and demapping unit may be part of receiver / transmitter circuitry 302.

[0067] For example, for TTI, RRC can be used statically, DCI messages in PDCCH can be used dynamically, or semi-persistent scheduling (SPS) can be used to signal the information required by the user, such as the MUST layer allocation or exchange mode (see below).

[0068] Based on the above references Figures 7 to 1 In the embodiments described in 1, especially with reference to Figure 10In the example illustrated in Figure 11, the distance between the corresponding UE and base stations BS1 and BS2 is shown to be the same. However, according to other embodiments, Figure 10 The UE can be located closer to BS1 or closer to BS2. Similarly, in Figure 11(a), UE1 can be closer to BS1 or closer to BS2, and likewise, UE2 can be closer to BS1 or closer to BS2. In either case, when using MUST to implement data transmission, the achievable data rate on the link between the base station and the UE can degrade, for example, when the distance from the UE to the respective base station is the same, resulting in equal or substantially equal SNRs for reception. This can be achieved in... Figure 10 In the embodiments described above, this occurs for transmissions from base station BS1 to UE and for transmissions from base station BS2 to UE, or in the embodiment of FIG11, for data transmissions from BS1 to UE1 and from BS2 to UE2.

[0069] To address this issue and avoid a reduction in the data rate transmitted on the corresponding links, layer mapping between the two MUST users is alternated, as shown in Figure 13, which illustrates the data rate over time for users with equal or substantially equal SNRs using MUST. Figure 13(a) indicates the data rate achievable over time (e.g., over several TTIs or time slots) using existing methods, and it can be seen that the data rate remains low for UE1 and high for UE2. To address this drawback, according to the method of the present invention, as shown in Figure 13(b), during a first transmission cycle, data of a first data signal is mapped by a base station using a first MUST layer with a first transport constellation and / or a first power allocation, and data of a second data signal is mapped by another base station using a second MUST layer with a second transport constellation and / or a second power allocation. This produces initial rates r1 and r2 corresponding to those rates implemented in the prior art. However, unlike existing technologies, in the next transmission cycle, i.e. the second transmission cycle, the MUST mode alternates, in which the base station uses the second MUST layer to map the data of the first data signal and the other base station uses the first MUST layer to map the data of the second data signal, so that the higher rate r2 is associated with UE1 and the lower rate r1 is associated with UE2.

[0070] In other words, as shown in Figure 13(b), the data mapping between the two MUST users, UE1 and UE2, alternates, providing a substantially constant sum-rate over time. For example, in a base station using an alternating transmission mode, one base station modulates a subset of resources, such as the RE of an RB, in a near-MUST manner and a complement of resources in a far-MUST manner. The other base stations use complementary modulation modes. According to an embodiment, the interleaver at the base station is designed using this mode. According to an embodiment, the decoding mode during the MUST transition is indicated to the respective user, for example, by signaling the near-far MUST switching mode indicating the decoding order for each user. For example, this can be done in... Figure 12 The signal is received at the UE via an antenna and receiver / transmitter circuitry.

[0071] The above embodiments have already been described in the context of base stations and users, although they are as follows: Figure 1 The method described herein has been found in wireless communication networks; however, the method of the present invention is equally applicable to heterogeneous networks including macro cells and small cells. For example, as referenced above... Figures 7 to 1 The method described in section 3 can be applied to serve one or more UEs by a macro cell base station and one or more small cell base stations (such as femtocell base stations or picocell base stations). In such a scenario, according to an embodiment, the macro cell base station may have the aforementioned fixed phase for its constellation diagram, and only the small cell base stations adapt their constellation as described above by pre-rotation based on phase offset information for phase offset compensation. The macro cell base station may notify the small cell base stations of the MUST settings for one or more users who typically use MUST via a backhaul link. According to yet another embodiment, one or more UEs may be served by one or more macro cell base stations and one or more small cell base stations.

[0072] In the above embodiments, it is assumed that multiple base stations perform joint MUST coding, and coding is performed at each of the involved base stations. However, the present invention is not limited to this method, but joint MUST coding can also be performed in a distributed manner. For example, a base station can perform the MUST coding step and transmit the MUST layer to one or more base stations involved in the data transmission via a backhaul connection or a fast interconnection between base stations. Therefore, according to such an embodiment, a base station can use a second transport constellation configured according to the negotiated MUST settings to map a second data signal to be provided to the UE. The mapped data of the second data signal is transmitted to a second base station serving the UE via a backhaul interface to wirelessly transmit the second data signal to one or more users served by the second base station using the second transport constellation.

[0073] Below, another embodiment of the present invention's method for resolving cross-layer interference between MIMO layers will be presented. As described above with reference to FIG. 6, when a single base station serves multiple users via multiple beams, the received signal at the respective user also includes interference components, which can render the entire signal received at the UE undecodeable. This situation may occur due to cross-layer interference or crosstalk between the respective transmit beams formed by the base station and transmitted to the respective UEs. This can apply to situations where the beams are directed toward a supposedly located position of the UE; however, in reality, the UE is not at the exact location but may be at a position offset, which can increase crosstalk problems and associated performance degradation.

[0074] According to embodiments of the invention, this problem is solved by utilizing knowledge of crosstalk between MIMO layers in a manner similar to that performed according to a vectorization process. The base station can estimate the crosstalk between MIMO layers, and since it also knows the two transmissions to the user, it can estimate the crosstalk impact on the transmissions to other users, allowing the base station to precode the MIMO layers so that the crosstalk is compensated.

[0075] Figure 14 Crosstalk compensation according to an embodiment of the method according to the present invention is shown. Similar to FIG6, Figure 14 The diagram shows a base station gNB emitting beams B1 and B2 for transmitting first and second data signals D1 and D2. The data signals D1 and D2 for users UE1 and UE2 are initially mapped to desired constellation points; for UE1, the desired constellation point is in the upper left quadrant, and for UE2, the desired constellation point is in the upper right quadrant, as shown below. Figure 14 The constellation diagram at the top is shown. According to the method of the present invention, based on the understanding of crosstalk or interference occurring between beams B1 and B2, the base station gNB performs pre-distortion of the signal to be transmitted to the UE. In fact, the signal transmitted via beams B1 to B2 takes into account crosstalk or interference I. 12 I 21 This causes the actually transmitted signals D1' and D2' to point to different constellation points, such as Figure 14 As shown in the central constellation diagram. At UE1 and UE2, as... Figure 14 The bottom receiver constellation diagram shows the interference I experienced at UE1. 21 Interference I experienced at UE2 12 The pre-distorted data signals D1' and D2' are adjusted back to the desired constellation points.

[0076] Figure 15 Showing the reference Figure 14 A block diagram of the network describing the method. Figure 15 As shown in the reference above Figures 1 to 3The wireless communication network described herein uses a base station (BS). The base station BS will serve two users, UE1 and UE2. According to other embodiments, it can serve more than two users, such as... Figure 15 The information is indicated by a dashed box labeled "Additional UE". A first user UE1 is served by a base station BS to receive a first data signal D1, and a second user UE2 is served by the base station BS to receive a second data signal D2. The base station BS includes an antenna 400, which may include multiple antenna elements or an antenna array including multiple antenna elements, for forming multiple beams B1, B2 to simultaneously transmit data D1, D2 to the respective users UE1 and UE2. The antenna 400 allows wireless communication with UE1 and UE2 served by the base station BS. The base station also includes a precoder 402 connected to the antenna 400, which causes the antenna 400 to form a first transmission beam B1 for transmitting the first data signal D1 to the first user UE1, and a second transmission beam B2 for transmitting the second data signal D2 to the second user. To transmit the first data signal to the first user, the base station maps the data of the first data signal using a first transmission constellation, and to transmit the second data signal for the second user, the base station maps the data of the second data signal using a second transmission constellation. The pre-encoder 402 applies predistortion in response to estimated crosstalk between the first transmit beam B1 and the second transmit beam B2, so that the actual transmitted signal is not the data signals D1 and D2, but as shown above. Figure 14 The explained predistorted data signals D1' and D2'.

[0077] According to an embodiment, the base station BS receives data to be transmitted to UE1 and UE2, as shown in 404. Data D1 and D2 are applied to a precoder 402, which receives from a codebook corresponding weights for forming corresponding beams by antenna 400 and additional predistortion coefficients for generating predistorted transmitted data signals D1' and D2'. According to an embodiment, the base station receives feedback information from UE1 and UE2 via one or more feedback channels. This feedback information is obtained at the respective users through channel measurements, and based on this feedback information, the base station can estimate crosstalk. According to an embodiment, the base station can estimate crosstalk using measurements received from one or more users. The base station can receive information from users regarding attenuation and phase shift on the channel between the base station and the users. Appropriate distortion coefficients can be selected using feedback, and these appropriate distortion coefficients can be applied together with codebook coefficients to the precoder to obtain predistorted signals D1' and D2'. According to other embodiments, crosstalk is estimated at one or more users, and the base station can receive estimates of crosstalk from one or more users.

[0078] Figure 15 It also shows how to implement it according to the reference. Figure 14 and Figure 15The UE operates according to the described embodiment. Only UE1 is described in detail; however, other UEs may have similar structures. UE1 includes an antenna 4101 via which signals on a corresponding channel connected to a base station are received, as shown in 4121. The received signal 4121 includes a signal component originating from a signal transmitted via beam B1 and a signal component originating from a signal transmitted via beam B2, i.e., interference component I. 21 UE1 also includes measurement circuitry 4401 for performing channel estimation, for example, based on a reference signal initially transmitted by the base station on both channels or at a specific time during transmission, to allow for channel estimation. The reference signal may include the reference signal described above. Figure 9 The phase estimation reference signal described, and the measurement circuit 4141, can have the reference signal as described above. Figure 9 The structure described. Based on the signal received from the base station, i.e., the reference signal, channel attenuation, channel quality, phase offset between channels, and interference between channels, i.e., crosstalk, can be determined. Feedback information can be transmitted to the base station via antenna 4101 to allow the aforementioned predistortion of the data signal. In other words, according to an embodiment, UE1 is positioned by means of measurement circuit 4141 to provide vectorized parameters for the first and second transmission beams, and based on the vectorized parameters, predistortion is performed at the base station to compensate for crosstalk I at users UE1 and UE2. 12 I 21 According to other embodiments, the measurement circuit 4141 may use the measurement and estimation of phase shift and attenuation at the UE to estimate crosstalk, and the UE transmits the crosstalk estimate to the base station instead of transmitting the complete measurement.

[0079] The transmission of a reference signal used to estimate crosstalk based on measurements performed by the UE and fed back to the base station can occur before data transmission to the two users begins, and / or can occur periodically during the time period in which data is transmitted to the UE.

[0080] Based on the above references Figure 14 and Figure 15 In the described embodiments, a reference base station, such as Figure 1 A base station in a wireless communication network; however, a base station can also be like... Figure 2 and Figure 3 The macro base station used in the heterogeneous network, or the base station can be a small cell base station in such a network. According to other embodiments, such as those described herein... Figures 7 to 1 As described in section 3, the base station can also be implemented by a user equipment (UE) with MIMO capability and served by a macrocell base station or a small cell base station, or both. Such a UE can be used, for example, as a repeater to further utilize two beams to simultaneously transmit data to another UE connected to the relay UE via a sidelink connection. The relay UE can be a mobile phone, while the connected UE can be a variable IoT device, such as a smartwatch.

[0081] Although some aspects of the concept have been described in the context of the apparatus, it is clear that these aspects also represent a description of the corresponding method, where a block or device corresponds to a method step or feature of the method step. Similarly, aspects described in the context of method steps also represent a description of a corresponding block or item or feature of the corresponding apparatus.

[0082] The various elements and features of the invention are implemented in hardware using analog and / or digital circuitry, in software by executing instructions by one or more general-purpose or special-purpose processors, or as a combination of hardware and software. For example, embodiments of the invention may be implemented in the environment of a computer system or another processing system. Figure 16 An example of a computer system 500 is illustrated. Units or modules, and the steps of methods performed by these units, can be executed on one or more computer systems 500. The computer system 500 includes one or more processors 502, such as dedicated or general-purpose digital signal processors. The processors 502 are connected to a communication infrastructure 504, such as a bus or network. The computer system 500 includes main memory 506 (e.g., random access memory (RAM)) and auxiliary memory 508 (e.g., hard disk drives and / or removable storage drives). The auxiliary memory 508 may allow computer programs or other instructions to be loaded into the computer system 500. The computer system 500 may also include a communication interface 510 to allow software and data to be transferred between the computer system 500 and external devices. Communication may take the form of electronic, electromagnetic, optical, or other signals that can be handled by the communication interface. Communication may use wires or cables, optical fibers, telephone lines, cellular telephone links, RF links, and other communication channels 512.

[0083] The terms "computer program medium" and "computer-readable medium" are generally used to refer to tangible storage media, such as removable storage units or hard disks installed in hard disk drives. These computer program products are means for providing software to computer system 500. The computer program, also known as computer control logic, is stored in main memory 506 and / or auxiliary memory 508. The computer program may also be received via communication interface 510. When executed, the computer program enables computer system 500 to implement the present invention. In particular, when executed, the computer program enables processor 502 to perform the processes of the present invention, such as any of the methods described herein. Thus, such a computer program can represent a controller of computer system 500. When implementing this disclosure using software, the software can be stored in the computer program product and loaded into computer system 500 using a removable storage drive or an interface (such as communication interface 510).

[0084] Hardware or software implementations can be executed using digital storage media (e.g., cloud storage, floppy disk, DVD, Blu-ray, CD, ROM, PROM, EPROM, EEPROM, or flash memory) that store electronically readable control signals that cooperate (or are capable of cooperating with) a programmable computer system to cause the corresponding methods to be executed. Therefore, the digital storage medium can be computer-readable.

[0085] Some embodiments of the invention include a data carrier having electronically readable control signals that are capable of cooperating with a programmable computer system to perform one of the methods described herein.

[0086] Generally, embodiments of the present invention can be implemented as a computer program product having program code that, when run on a computer, is operable to perform one of the methods. The program code may, for example, be stored on a machine-readable medium.

[0087] Other embodiments include a computer program stored on a machine-readable medium for performing one of the methods described herein. In other words, therefore, an embodiment of the inventive method is a computer program having program code for performing one of the methods described herein when the computer program is run on a computer.

[0088] Therefore, another embodiment of the inventive method is a data carrier (or digital storage medium, or computer-readable medium) comprising a computer program recorded thereon for performing one of the methods described herein. Thus, another embodiment of the inventive method is a data stream or signal sequence representing a computer program for performing one of the methods described herein. The data stream or signal sequence may be configured, for example, to be transmitted via a data communication connection (e.g., via the Internet). Another embodiment includes a processing means, such as a computer or programmable logic device, configured or adapted to perform one of the methods described herein. Another embodiment includes a computer on which a computer program for performing one of the methods described herein is installed.

[0089] In some embodiments, a programmable logic device (e.g., a field-programmable gate array) may be used to perform some or all of the functions of the methods described herein. In some embodiments, the field-programmable gate array may cooperate with a microprocessor to perform one of the methods described herein. Generally, the methods are preferably performed by any hardware device.

[0090] The embodiments described above are merely illustrative of the principles of the invention. It should be understood that modifications and variations of the arrangements and details described herein will be readily apparent to those skilled in the art. Therefore, the intent of the invention is limited only by the scope of the forthcoming patent claims, and not by the specific details given through the description and explanation of the embodiments herein.

[0091] References

[0092] [1] NGMN Consortium White Paper A, “Small Cell Backhaul Requirements”, Version 1.0, June 4, 2012

[0093] [2]3GPP TR 36.859v13.0.0(2015-12)

[0094] Abbreviations

[0095] eNB Evolved Node B LTE Long-term evolution IRC Interference suppression merging SIC Continuous interference cancellation UE User equipment (user terminal) RRM Radio resource management TDD Time Division Duplex FDD Frequency Division Duplex MIMO Multiple Input Multiple Output OFDM Orthogonal Frequency Division Multiplexing OFDMA Orthogonal Frequency Division Multiple Access CQI Channel quality information CRC Cyclic Redundancy Check DMRS Demodulation reference signal SPS Semi-persistent scheduling DCI Downlink control information UL uplink DL downlink (s)TTI (Short) transmission time interval PUSCH Physical uplink shared channel PUCCH Physical uplink control channel PDSCH Physical downlink shared channel PDCCH Physical downlink control channel SIC Continuous interference cancellation URLLC Ultra-reliable and low latency communication MBSFN Multimedia Broadcast Single Frequency Network C-RNTI Temporary identifier for community radio network

Claims

1. A base station (BS) for a wireless communication network, the base station serving two or more users (UEs), wherein, A first user is served by the base station to receive a first data signal from the base station, and a second user is served by the base station to receive a second data signal from the base station, wherein the base station (BS) comprises: An antenna array for wireless communication with the two or more users served by the base station. A precoder, connected to the antenna array, causes the antenna array to beamform a first transmit beam for transmitting the first data signal to the first user, and causes the antenna array to beamform a second transmit beam for transmitting the second data signal to the second user. Specifically, in order to transmit the first data signal to the first user, the base station (BS) is configured to map the data of the first data signal using a first transport constellation, and in order to transmit the second data signal to the second user, the base station (BS) is configured to map the data of the second data signal using a second transport constellation. In response to estimated crosstalk between the first and second transmit beams, the precoder is configured to apply predistortion to the first and second data signals, and The base station is configured to transmit a first transmit beam and a second transmit beam that include a predefined reference signal for measuring phase shift and attenuation.

2. The base station (BS) of claim 1, wherein the precoder is configured to predistort the symbols to be transmitted in response to attenuation and phase shift of the channel between the base station and the user.

3. The base station (BS) as described in claim 2, wherein the base station is configured to: Receive measurements from the user, and The received measurements are used to estimate the channel attenuation and phase shift between the base station and the user.

4. A wireless communication network, comprising: Multiple base stations (BSs) as described in claim 1; and Multiple users.

5. The wireless communication network as described in claim 4, wherein... The base station includes one or more of macro cell base stations and small cell base stations; and The users include one or more of the following: mobile terminals, IoT devices, physical devices, ground vehicles, aircraft, drones, buildings, and other items with network connectivity.

6. The wireless communication network of claim 4, using IFFT (Inverse Fast Fourier Transform) based signals, wherein the IFFT based signals include OFDM with CP, DFT-s-OFDM with CP, IFFT-based waveforms without CP, f-OFDM, FBMC, GFDM, or UFMC.

7. The wireless communication network according to claim 4, wherein The users (UE1, UE2) are configured to receive a first transmission beam and a second transmission beam from the base station (BS), and The users (UE1, UE2) are configured as follows: - Measure the phase offset between the first and second transmit beams and the attenuation on the first and second transmit beams, and transmit the signal to the base station (BS); or - Measure the phase offset between the first transmit beam and the second transmit beam and the attenuation on the first transmit beam and the second transmit beam, estimate the crosstalk, and transmit the estimate to the base station (BS).

8. The wireless communication network of claim 4, wherein the users (UE1, UE2) are configured to receive the first transmit beam and the second transmit beam, which include a predefined reference signal for measuring phase offset and attenuation.

9. A method for transmitting data to a plurality of users (UEs) in a wireless communication network, the wireless communication network including a base station serving the plurality of users, wherein a first user is served by the base station to receive a first data signal from the base station, and a second user is served by the base station to receive a second data signal from the base station, the method comprising: The antenna array is controlled to beamform to transmit the first data signal to the first user's first transmission beam, and the antenna array is controlled to beamform to transmit the second data signal to the second user's second transmission beam. The data of the first data signal is mapped using the first transmission constellation, and the first data signal is transmitted to the first user. The second data signal is mapped using the second transmission constellation, and the second data signal is transmitted to the second user. Specifically, in response to the estimated crosstalk between the first and second transmit beams, predistortion is applied when forming the first and second transmit beams, and The base station is configured to transmit a first transmit beam and a second transmit beam that include a predefined reference signal for measuring phase shift and attenuation.

10. A non-transitory computer program product comprising a computer-readable medium storing instructions that, when executed on a computer, perform the method of claim 9.

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