FIELD OF THE DISCLOSURE

[0001] Embodiments of the present disclosure generally relate to feedback enhancement, and more particularly, to methods and apparatuses of feedback enhancement for multiuser superposition transmission with closed-loop precoding.

BACKGROUND OF THE DISCLOSURE

[0002] In downlink multiuser superposition transmission (hereinafter referred to as MUST for short), multiple user equipment (UEs) is paired to enable their simultaneous transmission of more than one layer of data without time, frequency and spatial layer separation (i.e. using the same spatial precoding vector or the same transmit diversity scheme over the same resource elements).

[0003] For example, Fig. 1 depicts such an environment. In Fig. 1, user equipment 1 (UEl) will suffer seriously from user equipment 2 (UE2) because UE2 is at cell edge and allocated a large transmission power. UEl with an advanced receiver firstly decodes UE2's signal and then removes it from the received signal, and then decodes its own physical downlink shared channel (PDSCH) data. Therefore, whether the interference caused by UE2 can be cancelled and how much interference can be cancelled is critical for UEl to decode its own data. To decode UE2's signal at UEl, the information of the allocated transmit power between the paired two UEs (i.e. UEl and UE2) is crucial to the receiver at UEl. Without the power allocation information, it will be quite difficult to correctly decode the interference signal at the near/victim UE (i.e. UEl) , and the decoding correctness of UEl's own PDSCH data after removing the interference caused by the far/interfering UE (i.e. UE2) will also be impacted.

[0004] There are currently ten different transmission modes (TMs) defined for LTE. They differ in terms of the specific structure of the antenna mapping and also in terms of what reference signals are assumed to be used for demodulation (cell- specific reference signals (CRS) or demodulation reference signals (DM-RS) respectively) and how channel state information (CSI) is acquired by the terminal and fed back to the network. In case of transmission modes 1 to 6, CRS are to be used for channel estimation, and thus also referred to CRS-based TMs. Closed-loop codebook-based coding is associated with transmission mode 4 (TM4). In case of closed-loop precoding, it is assumed that the network selects the precoder matrix based on the feedback from the UE. It is defined in current 3GPP standards that the UE selects a transmission rank and a precoder matrix based on measurements on CRS, of which the information is then reported back to the eNB in the form of precoder-matrix indication (PMI) and rank indication (RI).

[0005] However, in downlink MUST, superposed signals of paired UEs are transmitted with each allocated transmit power, which could impact the accuracy of obtaining the CSI through the measurement of CRS, as well as the selection of suitable PMI and RI, since single-user multi-input multi-output (SU-MIMO) instead of MUST is implicitly assumed by the UE. More importantly, in addition to those selected for the successful decoding the near UE's (e.g. UE1) signal, the PMI and RI selected should be suitable for the decoding of the far UE's (e.g. UE2) signal at the near UE (e.g. UE1), for example, to remove interference caused by the far UE. Furthermore, the eNB has to indicate the selected PMI and RI to the near UE and the far UE.

SUMMARY OF THE DISCLOSURE

[0006] The embodiments of the present disclosure are intended to provide a method and apparatus of feedback enhancement for multiuser superposition transmission with closed-loop precoding.

[0007] According to a first aspect of the present disclosure, there is provided a method of feedback enhancement for multiuser superposition transmission with closed-loop precoding. The method comprises: receiving a first channel state information from a first user equipment; receiving a second channel state information from a second user equipment paired with the first user equipment; and selecting, based on the first channel state information and the second channel state information, a first precoder information for the first user equipment and a second precoder information for the second user equipment.

[0008] In some embodiments, each of the first channel state information and the second channel state information comprises at least one of: precoder matrix indication, rank indication and channel quality indication. [0009] In some embodiments, each of the first precoder information and the second precoder information comprises at least one of: precoder matrix indication and rank indication.

[0010] In some embodiments, the first user equipment and the second user equipment are located in the same cell, and wherein the first user equipment is much closer to the center of the cell than the second user equipment.

[0011] In some embodiments, the method further comprises: sending the first precoder information and the second precoder information to the first user equipment; and sending the second precoder information to the second user equipment.

[0012] In some embodiments, the method further comprises: sending power allocation information to the first user equipment so that the first user equipment provides feedback of the first channel state information based on the power allocation information, the power allocation information being used for indicating power allocation between the first user equipment and the second user equipment.

[0013] In some embodiments, sending power allocation information to the first user equipment comprises: sending a plurality of power allocation information to the first user equipment so that the first user equipment provides feedback of a plurality of first channel state information corresponding to the plurality of power allocation information.

[0014] In some embodiments, selecting, based on the first channel state information and the second channel state information, a first precoder information for the first user equipment and a second precoder information for the second user equipment comprises: selecting the first precoder information for decoding signals of the first user equipment at the first user equipment; and selecting the second precoder information for decoding signals of the second user equipment at the first user equipment and the second user equipment.

[0015] In some embodiments, selecting, based on the first channel state information and the second channel state information, a first precoder information for the first user equipment and a second precoder information for the second user equipment further comprises: determining whether the first channel state information and the second channel state information match or not; and based on determining that the first channel state information and the second channel state information do not match, performing at least one of: causing the first user equipment to be used for single-user transmission; and causing the first user equipment to be paired with third user equipment so as to be used for multiuser superposition transmission.

[0016] According to a second aspect of the present disclosure, there is provided a method of feedback enhancement for multiuser superposition transmission with closed-loop precoding. The method comprises: sending a first channel state information to a base station; receiving from the base station a first precoder information for the first user equipment and a second precoder information for a second user equipment paired with the first user equipment; and decoding, based on the first precoder information and the second precoder information, signals received from the base station, wherein the first user equipment and the second user equipment are located in the same cell, and wherein the first user equipment is much closer to the center of the cell than the second user equipment.

[0017] In some embodiments, the method further comprises: receiving power allocation information from the base station, the power allocation information being used for indicating power allocation between the first user equipment and the second user equipment.

[0018] In some embodiments, the method further comprises: acquiring the first channel state information through the measurement of cell-specific reference signals based on the power allocation information.

[0019] In some embodiments, receiving power allocation information from the base station comprises: receiving a plurality of power allocation information from the base station.

[0020] In some embodiments, sending a first channel state information to a base station comprises: sending to the base station a plurality of first channel state information corresponding to the plurality of power allocation information, wherein each first channel state information is obtained through the measurement of cell-specific reference signals based on each power allocation information.

[0021] In some embodiments, decoding, based on the first precoder information and the second precoder information, signals received from the base station comprises: decoding signals of the second user equipment based on the second precoder information; removing interference caused by the second user equipment based on decoded signals of the second user equipment; and decoding, based on the first precoder information, signals from which interference has been removed.

[0022] According to a third aspect of the embodiments of the present disclosure, there is provided a method of feedback enhancement for multiuser superposition transmission with closed-loop precoding. The method comprises: sending second channel state information to a base station; receiving from the base station second precoder information for second user equipment; and decoding, based on the second precoder information, signals received from the base station.

[0023] In some embodiments, the second channel state information comprises at least one of: precoder matrix indication, rank indication and channel quality indication.

[0024] In some embodiments, the second precoder information comprises at least one of: precoder matrix indication, and rank indication.

[0025] According to a fourth aspect of the present disclosure, there is provided an apparatus of feedback enhancement for multiuser superposition transmission with closed-loop precoding. The apparatus comprises: a first receiving unit configured to receive first channel state information from first user equipment; a second receiving unit configured to receive second channel state information from a second user equipment paired with the first user equipment; and a selecting unit configured to select, based on the first channel state information and the second channel state information, a first precoder information for the first user equipment and a second precoder information for the second user equipment.

[0026] In some embodiments, each of the first channel state information and the second channel state information comprises at least one of: precoder matrix indication, rank indication and channel quality indication.

[0027] In some embodiments, each of the first precoder information and the second precoder information comprises at least one of: precoder matrix indication and rank indication.

[0028] In some embodiments, the first user equipment and the second user equipment are located in the same cell, and wherein the first user equipment is much closer to the center of the cell than the second user equipment.

[0029] In some embodiments, the apparatus further comprises: a first sending unit configured to send the first precoder information and the second precoder information to the first user equipment; and second sending unit configured to send the second precoder information to the second user equipment.

[0030] In some embodiments, the apparatus further comprises: a third sending unit configured to send power allocation information to the first user equipment so that the first user equipment to provides feedback of the first channel state information based on the power allocation information, the power allocation information being used for indicating power allocation between the first user equipment and the second user equipment.

[0031] In some embodiments, the third sending unit is configured to: send a plurality of power allocation information to the first user equipment so that the first user equipment provides feedback of a plurality of first channel state information corresponding to the plurality of power allocation information.

[0032] In some embodiments, the selecting unit is configured to: select the first precoder information for decoding at the first user equipment signals of the first user equipment; and select the second precoder information for decoding signals of the second user equipment at the first user equipment and the second user equipment.

[0033] In some embodiments, the selecting unit is further configured to: determine whether the first channel state information and the second channel state information match or not; and based on determining that the first channel state information and the second channel state information do not match, perform at least one of: causing the first user equipment to be used for single-user transmission; and causing the first user equipment to be paired with third user equipment so as to be used for multiuser superposition transmission.

[0034] According to a fifth aspect of the present disclosure, there is provided a apparatus of feedback enhancement for multiuser superposition transmission with closed-loop precoding. The apparatus comprises: a fourth sending unit configured to send first channel state information to a base station; a third receiving unit configured to receive from the base station first precoder information for the first user equipment and second precoder information for a second user equipment paired with the first user equipment; and a first decoding unit configured to decode, based on the first precoder information and the second precoder information, signals received from the base station, wherein the first user equipment and the second user equipment are located in the same cell, and wherein the first user equipment is much closer to the center of the cell than the second user equipment.

[0035] In some embodiments, the apparatus further comprises: a fourth receiving unit configured to receive power allocation information from the base station, the power allocation information being used for indicating power allocation between the first user equipment and the second user equipment.

[0036] In some embodiments, the apparatus further comprises: an acquiring unit configured to acquire the first channel state information through the measurement of cell-specific reference signals based on the power allocation information.

[0037] In some embodiments, the fourth receiving unit is configured to: receive a plurality of power allocation information from the base station.

[0038] In some embodiments, the fourth sending unit is configured to: send to the base station a plurality of first channel state information corresponding to the plurality of power allocation information, wherein each first channel state information is obtained through the measurement of cell-specific reference signals based on each power allocation information.

[0039] In some embodiments, the first decoding unit is configured to: decode signals of the second user equipment based on the second precoder information; remove interference caused by the second user equipment based on decoded signals of the second user equipment; and decode, based on the first precoder information, signals from which interference has been removed.

[0040] According to a sixth aspect of the embodiments of the present disclosure, there is provided an apparatus of feedback enhancement for multiuser superposition transmission with closed-loop precoding. The apparatus comprises: a fifth sending unit configured to send second channel state information to a base station; a fifth receiving unit configured to receive from the base station second precoder information for second user equipment; and a second decoding unit configured to decode, based on the second precoder information, signals received from the base station.

[0041] Methods and apparatuses of feedback enhancement for multiuser superposition transmission with closed-loop precoding according to the embodiments of the present disclosure enable the base station to select suitable precoder information from channel state information reported by paired user equipments and send the suitable precoder information to the paired user equipments, wherein the near/victim UE can decode interference signals caused by the far/interfering UE based on the precoder information and increase the accuracy of decoding its own PDSCH data by removing interference signals caused by the far/interfering UE.

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The accompanying drawings depicted here are for providing further understanding of the present disclosure, constituting a part of the present disclosure. Illustrative embodiments of the present disclosure and their explanations are for explaining the present disclosure, rather than constituting inappropriate limitation of the present disclosure. In the accompanying drawings:

[0043] Fig. 1 depicts a schematic view of an environment 100 in which the embodiments of the present disclosure can be implemented;

[0044] Fig. 2 depicts a flowchart of a method 200 of feedback enhancement for multiuser superposition transmission with closed-loop precoding according to an embodiment of the present disclosure;

[0045] Fig. 3 depicts a flowchart of a method 300 of feedback enhancement for multiuser superposition transmission with closed-loop precoding according to an embodiment of the present disclosure;

[0046] Fig. 4 depicts a flowchart of a method 400 of feedback enhancement for multiuser superposition transmission with closed-loop precoding according to an embodiment of the present disclosure;

[0047] Fig. 5 depicts a block diagram of an apparatus 500 of feedback enhancement for multiuser superposition transmission with closed-loop precoding according to an embodiment of the present disclosure;

[0048] Fig. 6 depicts a block diagram of an apparatus 600 of feedback enhancement for multiuser superposition transmission with closed-loop precoding according to an embodiment of the present disclosure; and

[0049] Fig. 7 depicts a block diagram of an apparatus 700 of feedback enhancement for multiuser superposition transmission with closed-loop precoding according to an embodiment of the present disclosure. [0050] The same or corresponding numerals denote the same or corresponding parts throughout the figures.

DETAILED DESCRIPTION OF EMBODIMENTS

[0051] Various exemplary embodiments of the present disclosure are described below in detail with reference to the accompanying drawings. It should be understood according to the description below, alternative embodiments of structures and methods disclosed here are to be devised easily, and they may be used without departing from principles as claimed by the present disclosure.

[0052] It should be understood that these exemplary embodiments are presented only for enabling those skilled in the art to better understand and further implement the present disclosure, rather for limiting the scope of the present disclosure in any manner.

[0053] The term "comprise", "include" and similar terms used here are open-ended terms, i.e., "comprise/include without limitation". The term "based on" is "at least partially based on". The term "one embodiment" represents "at least one embodiment"; the term "another embodiment" represents "at least one another embodiment". Relevant definition of other terms will be presented in the following description.

[0054] With reference to the figures below, detailed description is presented to the technical solution of feedback enhancement for multiuser superposition transmission using closed-loop precoding, according to the embodiments of the present disclosure.

[0055] Fig. 2 depicts a flowchart of a method 200 of feedback enhancement for multiuser superposition transmission using closed-loop precoding according to an embodiment of the present disclosure. As shown in Fig. 2, the method 200 comprises steps S201 to S203. Now detailed description is presented to various steps of method 200 with reference to Figs. 1 and 2. According to the embodiment of the present disclosure, the method 200 may be executed by, for example, the eNB in Fig. 1. As shown in Fig. 1, UEl and UE2 are paired UEs for multiuser superposition transmission. They are located in the same cell, among which UEl is located at a position closer to a center while UE2 is located at cell edge.

[0056] In step S201, a first channel state information is received from UEl. The first channel state information (CSI) may include channel quality indication (CQI), precoder-matrix indication (PMI) and/or rank indication (RI). The first CSI may be obtained by UEl through measurement of CRS, which is sent by the eNB.

[0057] According to the embodiment of the present disclosure, prior to step S201, the eNB may send to UEl power allocation information so that UEl obtains CSI through the measurement of CRS by using the power allocation information. The CSI is used for recommending to the eNB the most suitable CQI, RMI and RI to a receiver of UEl. The power allocation information may, for example, indication power allocation between paired UEl and UE2. The eNB may also send to UEl a plurality of power allocation information so that UEl provides feedback of a plurality of first CSI corresponding to the plurality of power allocation information. For example, the plurality of power allocation information sent to UEl may indicate a power allocation ratio between the UE2 and UEl during MUST is 90% and 10%, 80% and 20%, or 70% and 30%. UEl may provide feedback of multiple groups of CQI, RMI and RI to the eNB accordingly.

[0058] Likewise, in step S202, a second CSI is received from paired UE2. The second CSI may also include CQI, PMI and/or RI. Furthermore, the second CSI may be obtained by UE2 from measurement of CRS, which is sent by the eNB.

[0059] Next, the method 200 proceeds to step S203 in which a first precoder information for UEl and a second precoder information for UE2 are selected based on the first CSI and the second CSI. Through steps S201 and S202, the eNB has received multiple groups of CQI, PMI and/or RI from UEl and UE2, from which the eNB may select the first precoder information for decoding signals of UEl and the second precoder information for decoding signals of UE2.

[0060] According to the embodiment of the present disclosure, the selected first precoder information may be used for decoding at UEl signals of UEl itself, and the selected second precoder information may be used for decoding at UEl signals of UE2, in addition to decoding at UE2 signals of UE2 itself. That is because, as described above, UEl and UE2 are user equipments that are paired for multiuser superposition transmission, UE2 is at cell edge and might cause serious interference to UEl as being allocated obviously higher transmit power than UEl. Consequently, UEl first has to decode the signal of UE2, and then removes the signal of UE2 from the received signals so as to increase accuracy of decoding its own signals.

[0061] According to the embodiments of the present disclosure, when the first CSI and the second CSI fed back to the eNB are the same, the first precoder information and the second precoder information may be determined according to PMI and RI included in the same CSI. When the first CSI and the second CSI fed back to the eNB are different, for example, if PMI and RI included in the CSI fed back by UE2 (i.e. the second CSI) can cause UEl to decode signals of UE2 and have a high enough signal-to-noise ratio, they may be used as the second precoder information for decoding signals of UE2 at UEl and UE2. In addition, for example, the selected first precoder information and the second precoder information may have the same PMI, and the same or different RI, etc.

[0062] According to the embodiments of the present disclosure, step S203 may further comprise determining whether the first CSI and the second CSI match or not, i.e., determining whether the precoder information can be selected which is suitable for both decoding signals of UE2 at UEl and decoding signals of UE2 at UE2 itself. When it is determined that the first CSI and the second CSI do not match, i.e., it is determined that the precoder information cannot be selected which is suitable for both decoding signals of UE2 at UEl and decoding signals of UE2 at UE2 itself, the eNB may have UEl selected for single-user transmission; or the eNB may also pair UEl with another far UE (i.e. UE3) for multiuser superposition transmission. Thereby, the eNB can perform dynamic switching among single-user transmission (SU-MEVIO), multiuser transmission, and different pairing with near UE and different far UEs. That is, there are many combinations for the utilization of each PRB, for example, for MUST, SU-MIMO, UE1/UE2 pairing, UE1/UE3 pairing, MUST at layer 1, or MUST at layer 1/2, etc.

[0063] According to the embodiments of the present disclosure, the method 200 further comprises: sending to UEl the first precoder information and the second precoder information so as to enable UEl to decode signals of UE2 by means of the second precoder information and then to decode signals of itself by means of the first precoder information by removing signals of UE2 from the received signals. In addition, the method 200 further comprises sending to UE2 the second precoder information so as to enable UE2 to decode signals of itself by means of the second precoder information.

[0064] So far, the method 200 ends.

[0065] Fig. 3 depicts a flowchart of a method 300 of feedback enhancement for multiuser superposition transmission with closed-loop precoding according to an embodiment of the present disclosure. As shown in Fig. 3, the method 300 comprises steps S301 to S303. Now with reference to Figs. 1 and 3, detailed description is presented to the steps of the method 300. According to the embodiments of the present disclosure, the method 300 may be executed by UE1 in Fig. 1, for example.

[0066] In step S301, a first CSI is sent to the eNB. The first CSI may comprise CQI, PMI and/or RI. The first CSI may be obtained by UE1 through the measurement of CRS, which is sent by the eNB.

[0067] According to the embodiments of the present disclosure, prior to step S301, UE1 may receive from the eNB power allocation information specific to UE1. By means of the power allocation information, UE1 may perform CRS measurement to obtain CSI and feed back the CSI to the eNB. The CSI fed back (i.e. first CSI) is used for recommending to the eNB the most suitable CQI, PMI and RI to a receiver of UE1. The power allocation information may, for example, indicate power allocation between the paired UE1 and UE2. A plurality of power allocation information may be received from the eNB, so that a plurality of first CSI corresponding to the plurality of power allocation information is fed back. For example, the plurality of power allocation information received from the eNB may indicate the UE2 to UE1 power allocation ratio during MUST is 90% and 10%, 80% and 20%, or 70% and 30%. UE1 may feed back multiple groups of CQI, RMI and RI to the eNB accordingly.

[0068] According to the embodiments of the present disclosure, in order to allow the eNB to determine channel state information for downlink multiuser superposition transmission, the paired UEs should report to the eNB multiple groups of CQI, PMI and/or RI, corresponding to different hypotheses (for example with respect to different power allocation scenarios and potential codebook restrictions), for the selection of a precoder matrix at the eNB for MUST. For example, UE1 may provides feedback to the eNB multiple groups of CQI, PMI and/or RI based on the measurement of CRS with different power allocation hypotheses. UE1 may be further configured with an extra group of power allocation indications by which UE1 is required to derive and report all CSI for all possible power allocation hypotheses. Note here, "all possible power allocation hypotheses" means all the scenarios with available power allocation indications with respect to UEl, i.e., under these scenarios, UEl still can achieve acceptable performance with a high enough signal-to-noise ratio (SNR).

[0069] In addition, according to the embodiments of the present disclosure,

UEl may be configured to report CSI to the eNB at specific time intervals or in time triggering, for example, UEl may be configured with a parameter codebooksubsetrestriction (indicating the subset of the precoding codebooks which is restricted to be used).

[0070] Then method 300 proceeds to step S302 in which the first precoder information for UEl and the second precoder information for UE2 paired with UEl are received from the eNB. As described above, after the eNB receives multiple groups of CQI, PMI and/or RI from the paired UEs, the eNB may select therefrom first precoder information for decoding signals of UEl and second precoder information for decoding signals of UE2, wherein the selected first precoder information may be used for decoding at UEl signals of UEl itself, and the selected second precoder information may be used for decoding at UEl signals of UE2 in addition to decoding at UE2 signals of UE2 itself. The eNB may send to UEl the selected first precoder information and second precoder information. Therefore, in step S302, UEl may receive from the eNB the first precoder information and the second precoder information.

[0071] Afterwards, the method 300 proceeds to step S303 in which signals received from the eNB is decoded based on the first precoder information and the second precoder information. As described above, through steps S301 and S302, UEl has received the first precoder information and the second precoder information, as selected by the eNB to be used for decoding signals of UEl and signals of UE2 respectively, wherein the first precoder information may be used for decoding at UEl signals of UEl itself, and the second precoder information may be used for decoding at UEl signals of UE2 in addition to decoding at UE2 signals of UE2 itself. Therefore, UEl may decode signals of UE2 based on the second precoder information; then remove interference caused by the second user equipment based on the decoded signals of UE2; and decode signals of itself from which interference has been removed, based on the first precoder information. [0072] So far, the method 300 ends.

[0073] Fig. 4 depicts a flowchart of a method 400 of feedback enhancement for multiuser superposition transmission with closed-loop precoding according to an embodiment of the present disclosure. As shown in Fig. 4, the method 400 comprises steps S401 and S402. Now with reference to Figs. 1 and 4, detailed description is presented to the steps of the method 400. According to the embodiment of the present disclosure, the method 400 may be executed by UE2 in Fig. 1, for example.

[0074] In step S401, UE2 sends a second CSI to the eNB. The second CSI may also include CQI, PMI and/or RI. The second CSI may be obtained by UE2 through the measurement of CRS, which is sent by the eNB. As described above, after receiving multiple groups of CQI, PMI and/or RI from paired UEs, the eNB may selected therefrom first precoder information for decoding signals of UE1 and second precoder information for decoding signals of UE2, and send the second precoder information to UE2. Accordingly, in step S402 UE2 may receive the second precoder information from the eNB, and in step S403 decodes a received PDSCH signal based on the received second precoder information. So far, the method 400 ends.

[0075] Fig. 5 depicts a block diagram of an apparatus 500 of feedback enhancement for multiuser superposition transmission with closed-loop precoding according to an embodiment of the present disclosure. As shown in Fig. 5, the apparatus 500 comprises: a first receiving unit 501 configured to receive first channel state information from a first user equipment; a second receiving unit 502 configured to receive a second channel state information from a second user equipment paired with the first user equipment; and a selecting unit 503 configured to select a first precoder information for the first user equipment and a second precoder information for the second user equipment, based on the first channel state information and the second channel state information.

[0076] According to the embodiment of the present disclosure, each of the first channel state information and the second channel state information comprises at least one of: precoder matrix indication, rank indication and channel quality indication.

[0077] According to the embodiment of the present disclosure, each of the first precoder information and the second precoder information comprises at least one of: precoder matrix indication and rank indication. [0078] According to the embodiment of the present disclosure, the first user equipment and the second user equipment are located in the same cell, and wherein the first user equipment is much closer to the center of the cell than the second user equipment.

[0079] According to the embodiment of the present disclosure, the apparatus

500 further comprises: a first sending unit configured to send the first precoder information and the second precoder information to the first user equipment; and the second sending unit configured to send the second precoder information to the second user equipment.

[0080] According to the embodiment of the present disclosure, the apparatus

500 further comprises: a third sending unit configured to send power allocation information to the first user equipment so that the first user equipment provides feedback of the first channel state information based on the power allocation information, the power allocation information being used for indicating power allocation between the first user equipment and the second user equipment.

[0081] According to the embodiment of the present disclosure, the third sending unit is configured to send a plurality of power allocation information to the first user equipment so that the first user equipment provides feedback of a plurality of first channel state information corresponding to the plurality of power allocation information.

[0082] According to the embodiment of the present disclosure, the selecting unit 503 is configured to: select the first precoder information for decoding at the first user equipment signals of the first user equipment; and select the second precoder information for decoding signals of the second user equipment at the first user equipment and the second user equipment.

[0083] According to the embodiment of the present disclosure, the selecting unit 503 is further configured to: determine whether the first channel state information and the second channel state information match or not; and based on determining that the first channel state information and the second channel state information do not match, perform at least one of: causing the first user equipment to be used for single-user transmission; and causing the first user equipment to be paired with a third user equipment so as to be used for multiuser superposition transmission. [0084] Fig. 6 depicts a block diagram of an apparatus 600 of feedback enhancement for multiuser superposition transmission with closed-loop precoding according to an embodiment of the present disclosure. As shown in Fig. 6, the apparatus 600 comprises: a fourth sending unit configured to send a first channel state information to a base station; a third receiving unit configured to receive from the base station a first precoder information for the first user equipment and second precoder information for a second user equipment paired with the first user equipment; and a first decoding unit configured to decode signals received from the base station, based on the first precoder information and the second precoder information, wherein the first user equipment and the second user equipment are located in the same cell, and wherein the first user equipment is much closer to the center of the cell than the second user equipment.

[0085] According to the embodiment of the present disclosure, the apparatus 600 further comprises: a fourth receiving unit configured to receive power allocation information from the base station, the power allocation information being used for indicating power allocation between the first user equipment and the second user equipment.

[0086] According to the embodiment of the present disclosure, the apparatus 600 further comprises: an acquiring unit configured to acquire the first channel state information through the measurement of cell- specific reference signals based on the power allocation information.

[0087] According to the embodiment of the present disclosure, the fourth receiving unit is configured to receive a plurality of power allocation information from the base station.

[0088] According to the embodiment of the present disclosure, the fourth sending unit is configured to send to the base station a plurality of first channel state information corresponding to the plurality of power allocation information, wherein each first channel state information is obtained through the measurement of cell-specific reference signals based on each power allocation information.

[0089] According to the embodiment of the present disclosure, the first decoding unit is configured to: decode signals of the second user equipment based on the second precoder information; remove interference caused by the second user equipment based on decoded signals of the second user equipment; decode signals from which interference has been removed, based on the first precoder information.

[0090] Fig. 7 depicts a block diagram of an apparatus 700 of feedback enhancement for multiuser superposition transmission with closed-loop precoding according to an embodiment of the present disclosure. As shown in Fig. 7, the apparatus 700 comprises: a fifth sending unit configured to send second channel state information to a base station; a fifth receiving unit configured to receive from the base station second precoder information for second user equipment; and a second decoding unit configured to decode signals received from the base station, based on the second precoder information.

[0091] To sum up, according to the embodiments of the present disclosure there are provided methods and apparatuses of feedback enhancement for multiuser superposition transmission with closed-loop precoding, so that the base station can select suitable precoder information from channel state information reported by paired user equipments and send the suitable precoder information to the paired user equipments, wherein the near/victim UE can decode interference signals caused by the far/interfering UE based on the precoder information and increase the accuracy of decoding its own PDSCH data by removing interference signals caused by the far/interfering UE.

[0092] Generally, various example embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of the example embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representation, it will be appreciated that the blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0093] Additionally, various blocks shown in the flowcharts may be viewed as method steps, and/or as operations that result from operation of computer program code, and/or as a plurality of coupled logic circuit elements constructed to carry out the associated function(s). For example, embodiments of the present disclosure include a computer program product comprising a computer program tangibly embodied on a machine readable medium, the computer program containing program codes configured to carry out the methods as described above.

[0094] In the context of the disclosure, a machine readable medium may be any tangible medium that may contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The machine readable medium may be a machine readable signal medium or a machine readable storage medium. A machine readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the machine readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0095] Computer program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These computer program codes may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor of the computer or other programmable data processing apparatus, cause the functions/operations specified in the flowcharts and/or block diagrams to be implemented. The program code may execute entirely on a computer, partly on the computer, as a stand-alone software package, partly on the computer and partly on a remote computer or entirely on the remote computer or server.

[0096] Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of any disclosure or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular disclosures. Certain features that are described in this specification in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

[0097] Various modifications, adaptations to the foregoing example embodiments of this disclosure may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. Any and all modifications will still fall within the scope of the non-limiting and example embodiments of this disclosure. Furthermore, other embodiments of the disclosures set forth herein will come to mind to one skilled in the art to which these embodiments of the disclosure pertain having the benefit of the teachings presented in the foregoing descriptions and the drawings.

[0098] It will be appreciated that the embodiments of the present disclosure are not to be limited to the specific embodiments as discussed above and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are used herein, they are used in a generic and descriptive sense only and not for purposes of limitation.