JP2019512925A - Scheduling vector generation method, successive interference cancellation method, base station, and mobile station - Google Patents

Abstract

Embodiments of the present invention provide a scheduling vector generation method, a successive interference cancellation method, a base station, and a mobile station. A scheduling vector generation method according to an embodiment of the present invention is performed by a base station, and the method is a code of a machine type communication (MTC) mobile station performing data transmission in each subband in the current transmission time interval (TTI). Acquiring a coding rate, generating a common MTC scheduling vector in accordance with the obtained coding rate, and notifying all the LTE mobile stations connected to the base station of the common MTC scheduling vector And a process.

Description

  The present invention relates to the field of wireless communication, and more particularly, to a scheduling vector generation method usable in a wireless communication system, a successive interference cancellation method, and a base station and a mobile station thereof.

  Non-Orthogonal Multiple Access (NOMA) is a radio access technology proposed in LTE (Long Term Evolution) Release 13 discussed in 3 GPP (3rd Generation Partnership Project). In the NOMA system, on the transmit side, the base station multiplexes data for a plurality of mobile stations at different power levels for each resource block to improve the system throughput, and on the receive side, the mobile station compares the received data to the received data. By performing interference cancellation (SIC) sequentially, the own data is acquired.

  On the other hand, machine type communication (MTC) has become an important technology used for 4G and 5G communication systems. In order to obtain a 15-20 dB coverage extension, the MTC technique retransmits the same packet 200-300 times. Compared to LTE mobile stations, MTC mobile stations transmit in a relatively narrow bandwidth. If the base station wants to multiplex data for LTE mobile stations and data for MTC mobile stations using NOMA technology, the frequency band used for one LTE mobile station is used for multiple MTC mobile stations It corresponds to the frequency band.

  Currently, in the NOMA system, a method is provided for simultaneously scheduling two LTE mobile stations. In the scheduling method, the base station generates a dedicated scheduling vector of the mobile station for one of the LTE mobile stations simultaneously scheduled, and another mobile station performs interference cancellation sequentially. Thus, the dedicated scheduling vector is notified to another mobile station. However, when the base station multiplexes data for LTE mobile stations with data for MTC mobile stations, current scheduling methods use a combination of NOMA and MTC since a large amount of control signaling is required Not applicable to wireless communication systems.

  According to one aspect of the present invention, there is provided a method of scheduling vector generation performed by a base station. The method comprises the steps of obtaining a coding rate of a machine type communication (MTC) mobile station performing data transmission in each subband in the current transmission time interval (TTI), and common MTC scheduling according to the obtained coding rate Generating a vector; and notifying the common MTC scheduling vector to all LTE mobile stations connected to the base station.

  According to another aspect of the present invention, there is provided a method for successive interference cancellation performed by an LTE mobile station. The method comprises blind detecting a modulation scheme of a machine type communication (MTC) mobile station paired with the LTE mobile station and identifying a modulation scheme of the MTC mobile station paired with the LTE mobile station Identifying a coding rate of an MTC mobile station paired with the LTE mobile station according to a common MTC scheduling vector notified from a base station, wherein the common MTC scheduling vector corresponds to each sub in the current TTI. A process including coding rate information indicating a coding rate of an MTC mobile station performing data transmission in a band, and an MTC mobile station paired with the LTE mobile station according to the identified modulation scheme and coding rate And performing a successive interference cancellation on the data.

  According to another aspect of the invention, a base station is provided. Said base station obtaining a coding rate acquisition unit configured to acquire a coding rate of a machine type communication (MTC) mobile station performing data transmission in each subband in the current transmission time interval (TTI); A scheduling vector generation unit configured to generate a common MTC scheduling vector according to the coded rate, and notifying the common MTC scheduling vector to all LTE mobile stations connected to the base station And a transmission unit configured in

  According to a further aspect of the invention, an LTE mobile station is provided. The LTE mobile station blind detects a modulation scheme of a machine type communication (MTC) mobile station paired with the LTE mobile station, and identifies a modulation scheme of the MTC mobile station paired with the LTE mobile station And a coding rate specifying unit for specifying a coding rate of an MTC mobile station paired with the LTE mobile station according to a modulation scheme specifying unit configured as described above and a common MTC scheduling vector notified from a base station. A coding rate identification unit configured to include the coding rate information indicating the coding rate of the MTC mobile station performing data transmission in each sub-band in the current TTI, and the common MTC scheduling vector being specified MTC mobile station paired with the LTE mobile station according to the specified modulation scheme and coding rate To perform the successive interference cancellation with respect to the data and a successive interference cancellation unit configured.

  According to the scheduling vector generation method, successive interference cancellation method, base station, and LTE mobile station according to the above aspect of the present invention, a common MTC scheduling vector is generated for an MTC mobile station performing data transmission in each subband in the current TTI By sequentially performing interference cancellation on data transmitted by the MTC mobile station, the base station does not have to generate a dedicated scheduling vector for each MTC mobile station, and thus, the wireless communication system can It is possible to support the combined use of NOMA and MTC while minimizing the increase in overhead.

The embodiments of the present invention will be described in detail with reference to the drawings, and the above and other objects, features and advantages of the present invention will become more apparent.
Fig. 6 shows a flowchart of a scheduling vector generation method performed by a base station according to an embodiment of the present invention. FIG. 7 shows a schematic diagram of a candidate modulation scheme and a candidate coding rate according to one illustration of the present invention. FIG. 5 shows a schematic diagram of a common MTC scheduling vector according to one example of the present invention. FIG. 5 shows a schematic diagram of assigning a user identifier to an MTC mobile station according to one example of the present invention. Fig. 5 shows a schematic view of a mobile station identifier vector generated according to the user identifier assigned in Fig. 4; Fig. 5 shows a flowchart of a successive interference cancellation method performed by a mobile station according to an embodiment of the present invention. Fig. 6 shows a flow chart of a method for buffering user identifiers and data of MTC mobile stations to perform successive interference cancellation quickly according to one example of the present invention. FIG. 6 shows a schematic diagram of a buffer for buffering user identifiers and data in an LTE mobile station according to one example of the present invention. Fig. 3 shows a block diagram of a base station according to an embodiment of the present invention. FIG. 6 shows a block diagram of an LTE mobile station according to one embodiment of the present invention. FIG. 6 shows a block diagram of an LTE mobile station according to another embodiment of the present invention.

  Hereinafter, a scheduling vector generation method, a successive interference cancellation method, a base station, and a mobile station according to an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same reference signs always denote the same elements. It should be understood that the embodiments described herein are exemplary only, and are not intended to limit the scope of the present invention. Also, the UE described herein may include, for example, user terminals of various types such as mobile terminals (also referred to as mobile stations) or fixed terminals, but for convenience, UE and mobile stations are used interchangeably in the text. In some cases.

  In the example according to the present invention, the base station can NOMA multiplex data for LTE mobile stations and data for MTC mobile stations in one TTI. Specifically, in one TTI, a frequency band for data transmission includes a plurality of sub bands (Sub Band, SB), and each MTC mobile station transmits data using one of the sub bands. However, each LTE mobile station performs data transmission using two or more subbands of them. In other words, the base station can NOMA multiplex data for one LTE mobile station and data for multiple MTC mobile stations.

  First, a scheduling vector generation method performed by a base station according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 shows a flowchart of the scheduling vector generation method 100. At the time of successive interference cancellation, one mobile station is required to obtain and use information such as the modulation scheme and coding rate of another mobile station paired with it. In order to further reduce the required control signaling, according to an embodiment of the present invention, the base station may not notify the LTE mobile station of the modulation scheme of the MTC mobile station. Also, the LTE mobile station can specify the modulation scheme of the MTC mobile station by blind detection, and the base station can notify the LTE mobile station of the coding rate of the MTC mobile station only by the scheduling vector. it can.

  As shown in FIG. 1, in step S101, the coding rate of the MTC mobile station that performs data transmission in each subband in the current TTI is acquired. Then, in step S102, a common MTC scheduling vector is generated according to the obtained coding rate. According to one example of the present invention, the corresponding coding rate may be indicated by performing coding for each type of usable coding rate of the MTC mobile station beforehand. In step S102, a codeword corresponding to the coding rate of the MTC mobile station that performs data transmission in each subband may be specified, and a common MTC scheduling vector may be generated according to each codeword.

  Current MTC mobile stations can use multiple modulation schemes such as QPSK, 16 QAM, 64 QAM, etc., and each modulation scheme may have multiple coding rates corresponding to the scheme. Preferably, a part of modulation schemes may be selected in advance as a candidate modulation scheme from a plurality of modulation schemes. The MTC mobile station uses one of the candidate modulation schemes for data transmission. Therefore, since the LTE mobile station needs to perform blind detection only for the modulation scheme selected as the candidate modulation scheme, the complexity of the blind detection operation by the LTE mobile station can be simplified. Alternatively, a part of coding rates may be selected as a candidate coding rate from a plurality of coding rates associated with each candidate modulation scheme in advance. The MTC mobile station uses one of the candidate coding rates for data transmission. Thus, control signaling required for notification of common MTC scheduling vectors can be further reduced.

  FIG. 2 shows a schematic diagram of a candidate modulation scheme and a candidate coding rate according to one example of the present invention. As shown in FIG. 2, QPSK and 16 QAM may be selected as candidate modulation schemes in advance from among a plurality of modulation schemes usable by the MTC mobile station. Therefore, when performing the blind detection, the LTE mobile station specifies the modulation scheme by the MTC mobile station only between the two modulation schemes of QPSK and 16 QAM.

  Further, from all the coding rates associated with QPSK in advance, three coding rates may be selected as candidate coding rates associated with QPSK. Similarly, from all the coding rates previously associated with 16 QAM, three coding rates may be selected as candidate coding rates associated with 16 QAM (as indicated by gray entries in FIG. 2) . According to one example of the present invention, candidate coding rates 0.11, 0.28 and 0.48 associated with QPSK may be indicated by codewords 1, 2 and 3 respectively . Similarly, candidate coding rates 0.31, 0.44 and 0.54 associated with 16 QAM may be indicated by codewords 1, 2 and 3, respectively.

  Although it has been described here that QPSK and 16 QAM both use codewords 1, 2 and 3 to indicate candidate coding rates, the present invention is not limited to this. In alternative embodiments of the present invention, different codewords may be used to indicate candidate coding rates. For example, candidate coding rates 0.11, 0.28, 0.48, 0.31, 0.44 and 0.54 are indicated by codewords 1, 2, 3, 4, 5, 6, respectively. May be

  FIG. 3 shows a schematic diagram of a common MTC scheduling vector according to one example of the present invention. In the example shown in FIG. 3, in the current TTI, it is assumed that the frequency band available for data transmission includes six subbands SB1 to SB6. The MTC mobile station at SB1 modulates using QPSK and encodes at a coding rate of 0.11. In SB2, there is no MTC mobile station that performs data transmission. The MTC mobile station at SB3 modulates using QPSK and encodes at a coding rate of 0.48. The MTC mobile station at SB4 modulates using 16 QAM and encodes at a coding rate of 0.31. In SB5, there is no MTC mobile station that performs data transmission. The MTC mobile station at SB6 modulates using 16 QAM and encodes at a coding rate of 0.54. According to step S102, the common MTC scheduling vector 300 is generated according to the coding method described with reference to FIG. 2 described above. As shown in FIG. 3, in the common MTC scheduling vector 300, the SB1 field includes codeword 1, the SB2 field includes codeword 0, the SB3 field includes codeword 3, and the SB4 field includes codeword 1. , SB5 field includes codeword 0, and SB6 field includes codeword 3, where '0' indicates that there is no MTC mobile station that performs data transmission with the base station in that SB.

  Referring back to FIG. 1, in step S103, the common MTC scheduling vector is notified to all LTE mobile stations connected to the base station. For example, the base station may scramble the common MTC scheduling vector using the radio network temporary identifier and notify the LTE mobile station of the scrambled common MTC scheduling vector.

  Unlike the conventional scheduling vector generation method of generating a dedicated scheduling vector related to a specific mobile station and notifying the dedicated scheduling vector to another mobile station paired with the specific mobile station. In S103, in order to notify all mobile stations of the common MTC scheduling vector, there is no need to scramble using a mobile station-specific wireless network temporary identifier, and scramble using a common wireless network temporary identifier. And all LTE mobile stations connected to the base station can descramble using the common radio network temporary identifier.

Specifically, a common MTC radio network temporary identifier is generated for all LTE mobile stations connected to the base station in advance, and the common MTC radio network temporary for all LTE mobile stations connected to the base station. Report an identifier. After generating the common MTC scheduling vector in step S102, the common MTC radio network temporary identifier scrambles the common MTC scheduling vector, and in step S103, for all LTE mobile stations connected to the base station, Broadcast the scrambled common MTC scheduling vector.
In the scheduling vector generation method of this embodiment, there is no need to generate a separate scheduling vector for each mobile station, and a common MTC scheduling vector according to the coding rate of the MTC mobile station that performs data transmission in each subband in the current TTI. To perform successive interference cancellation. This allows the wireless communication system to support the combined use of NOMA and MTC while minimizing the increase in signaling overhead.

  Further, in the scheduling vector generation method of the present embodiment, information on the modulation scheme of each mobile station may not be included. In addition, considering that the MTC mobile station performs data transmission in a narrow band and the occupied frequency band is a continuous resource block, the common MTC scheduling vector of this embodiment is occupied by the MTC mobile station. The information on the frequency resource to be stored may be omitted. Thus, the signaling overhead is further reduced.

  Also, the scheduling vector generation method 100 shown in FIG. 1 assigns a user identifier to the MTC mobile station and notifies the LTE mobile station so that the LTE mobile station identifies the received transmission data information of the MTC mobile station. May further include the following. Specifically, the scheduling vector generation method 100 comprises the steps of assigning a user identifier (ID) to the MTC mobile station connected to the base station, and of the MTC mobile station performing data transmission in each sub-band in the current TTI. The method may further include the steps of generating a mobile station identifier vector according to the user identifier, and notifying the mobile station identifier vector of all LTE mobile stations connected to the base station. In the MTC technology, since the same data packet is retransmitted 200 to 300 times, the LTE mobile station receives the MTC mobile station user identifier by assigning the user identifier to the MTC mobile station and notifying the LTE mobile station. A data packet can be stored in association, which eliminates the need to perform an operation such as decoding on the data packet each time the data packet is transmitted, and sequentially interferes using the stored data packet. Cancel promptly.

  FIG. 4 shows a schematic diagram of assigning a user identifier to an MTC mobile station according to one example of the present invention. FIG. 5 shows a schematic diagram of a mobile station identifier vector generated according to the user identifiers assigned in FIG. As shown in FIG. 4, in the current TTI, available frequency bands for data transmission include six subbands SB1 to SB6. In each of SB1, SB3, SB4 and SB6, the MTC mobile station performs data transmission with the base station. The base station assigns an ID value of 1 to the MTC mobile station performing data transmission in SB1, assigns an ID value of 2 to the MTC mobile station performing data transmission in SB3, and transmits the data to the MTC mobile station in SB4. Alternatively, the ID value 3 may be assigned, and the ID value 4 may be assigned to the MTC mobile station that performs data transmission in SB6. Then, the base station generates the mobile station identifier vector 500 shown in FIG. 5 in accordance with the ID assignment result shown in FIG. In the example shown in FIG. 5, the size of the mobile station identifier vector 500 is associated with the maximum number of MTC mobile stations that can connect to the base station in one TTI. Specifically, in the mobile station identifier vector 500, the ID value of the SB1 field is 1, the ID value of the SB2 field is 0, the ID value of SB3 is 2, the ID value of SB4 is 3, SB5 The ID value of is 0, and the ID value of SB6 is 4, where “0” indicates that there is no MTC mobile station that performs data transmission with the SB.

  As MTC employs frequency hopping techniques to obtain frequency gain, there may be different MTC mobile stations performing data transmission in each sub-band in each TTI. Therefore, the base station preferably generates and notifies a mobile station identifier vector of the current TTI in each TTI.

  According to one example of the present invention, the number of IDs assignable to MTC mobile stations may be the maximum number of MTC mobile stations connectable to a base station in one TTI. For example, in the example shown in FIG. 4 and FIG. 5, since the maximum number of MTC mobile stations connectable to the base station in one TTI is 6, ID 1-6 can be preset and assigned to the MTC mobile stations.

  There may be MTC mobile stations newly connected to the base station in the current TTI. In this case, in order to avoid overlapping with the ID assigned to the MTC mobile station already connected to the base station, for the MTC mobile station newly connected to the base station in the current TTI, It is preferable to assign an unassigned ID. For example, assuming that there is an MTC mobile station newly connected to the base station in the next TTI of TTI shown in FIGS. 4 and 5, an ID value of 5 for the MTC mobile station newly connected to the base station is assumed. May be assigned. Also, if all predetermined IDs have been assigned to the MTC mobile station, and there is an MTC mobile station newly connected to the base station in the current TTI, the current connection to the base station previously The ID value of the MTC mobile station not connected to the base station in TTI may be assigned to the MTC mobile station newly connected to the base station.

  Hereinafter, the successive interference cancellation method performed by the mobile station according to the embodiment of the present invention will be described with reference to FIG. FIG. 6 shows a flowchart of a successive interference cancellation method 600 performed by a mobile station. As shown in FIG. 6, in step S601, the modulation scheme of the MTC mobile station paired with the LTE mobile station is blindly detected, and the modulation scheme of the MTC mobile station paired with the LTE mobile station is specified. Specifically, in the NOMA system, the MTC mobile station paired with the LTE mobile station is an MTC mobile station whose frequency band for data transmission overlaps with the frequency band for data transmission of the LTE mobile station. In other words, in the current TTI, the MTC mobile station whose downlink frequency band overlaps with the downlink frequency band of one LTE mobile station is the MTC mobile station to be paired with the LTE mobile station. In step S601, the LTE mobile station may blindly detect the modulation scheme of the MTC mobile station that performs data transmission in the sub-bands included in the downlink frequency band.

  Also, as described above, QPSK and 16 QAM are selected as candidate modulation schemes in advance from among a plurality of modulation schemes usable by the MTC mobile station. That is, the modulation scheme of the MTC mobile station is one of QPSK and 16 QAM. Thus, when performing blind detection, the LTE mobile station identifies the modulation scheme used by the MTC mobile station only between the two modulation schemes of QPSK and 16 QAM, and the blind detection complexity of the LTE mobile station Was simplified.

  For example, in the example described with reference to FIG. 3 described above, the frequency band available for data transmission in the current TTI includes six subbands of SB1 to SB6, and the data transmission frequency band of one LTE mobile station is It is assumed that they are SB1 to SB3. According to step S601, the LTE mobile station performs blind detection on the modulation scheme of the MTC mobile station performing data transmission in SB1, SB2, and SB6, and the MTC mobile station in SB1 modulates using QPSK. It is specified that there is no MTC mobile station that performs data transmission in SB2, and that the MTC mobile station in SB6 modulates using 16 QAM.

  In step S602, the coding rate of the MTC mobile station paired with the LTE mobile station can be identified according to the common MTC scheduling vector notified from the base station, where the common MTC scheduling vector is the current TTI. Includes coding rate information that indicates the coding rate of the MTC mobile station performing data transmission in each subband. The common MTC scheduling vector may be generated by the method described with reference to FIGS. 1 to 4 above, and the description of the same will be omitted here. Also, as mentioned above, the common MTC scheduling vector transmitted by the base station may be a scrambled common MTC scheduling vector. According to one example of the present invention, when connected to a base station, the LTE mobile station receives a common MTC radio network temporary identifier from the base station and thereby descrambles the received vector. .

  For example, in the example described with reference to FIG. 3 described above, the step S601 specifies that the MTC mobile station at SB1 modulates using QPSK and the MTC mobile station at SB6 modulates using 16 QAM. After that, according to the common MTC scheduling vector 300 shown in FIG. 3, the SB1 field including codeword 1, the SB2 field including codeword 0, and the SB6 field including codeword 3 are further obtained, and according to a predetermined coding scheme , It can be specified that the MTC mobile station at SB1 codes at a coding rate of 0.11 and the MTC mobile station at SB6 codes at a coding rate of 0.54.

  Here, although the execution of step S602 after the execution of step S601 has been described as an example, the present invention is not limited to this. For example, when it is not necessary to specify the coding rate of the MTC mobile station according to the modulation scheme, steps S601 and S602 may be performed simultaneously.

  Finally, in step S603, interference cancellation is sequentially performed on data for the MTC mobile station paired with the LTE mobile station according to the identified modulation scheme and coding rate.

  In the successive interference cancellation method of this embodiment, the modulation scheme of the MTC mobile station is acquired by blind detection, and the coding rate of the MTC mobile station is acquired by the common MTC scheduling vector. Thus, the wireless communication system can support the combined use of NOMA and MTC while minimizing the increase in signaling overhead.

  Also, as described above, in the MTC technology, since the same data packet is retransmitted 200 to 300 times, the LTE mobile station may store the user identifier assigned to the MTC mobile station and the data packet in association with each other. Thus, it is not necessary to perform an operation such as decoding on the data packet each time the data packet is transmitted, and interference cancellation can be performed promptly using the stored data packet.

  Specifically, the method in FIG. 6 further includes buffering the user identifier and data of the MTC mobile station to quickly perform successive interference cancellation. FIG. 7 shows a flowchart of a method of buffering user identifiers and data of an MTC mobile station to quickly perform successive interference cancellation according to one illustration of the present invention. As shown in FIG. 7, in step S701, a user identifier of the MTC mobile station connected to the base station and data for the MTC mobile station associated with the user identifier are buffered. Here, the buffered user identifier and the data associated with the user identifier may be acquired in the preceding TTI.

  As described above, the number of IDs that can be assigned to an MTC mobile station may be the maximum number of MTC mobile stations that can connect to a base station in one TTI. Therefore, the maximum number of MTC mobile stations connectable to the base station in one TTI may specify the buffer size for buffering the user identifier and data in the LTE mobile station.

  FIG. 8 shows a schematic diagram of a buffer for buffering user identifiers and data in an LTE mobile station according to one example of the present invention. In the example shown in FIG. 8, it is assumed that the maximum number of MTC mobile stations connectable to a base station in one TTI is six. In the buffer 800, a storage table including entries corresponding to the IDs 1-6 of the MTC mobile station may be set in advance. Receive data aa for the MTC mobile station with ID = 1 in the preceding TTI, receive data bb for the MTC mobile station with ID = 2, and receive data dd for the MTC mobile station with ID = 4 When the data ff for the MTC mobile station with ID = 6 is received, data aa is stored in association with ID1, and data bb is stored in association with ID2, as shown in FIG. To store the data dd, and store the data ff in association with the ID6.

  Referring back to FIG. 7, in step S702, according to the mobile station identifier vector of the current TTI notified from the base station, the user identifier of the MTC mobile station performing data transmission in each subband in the current TTI is acquired. Then, in step S703, it is specified whether buffered data corresponding to the acquired user identifier exists. When buffered data corresponding to the obtained user identifier exists, in step 603, for buffered data corresponding to the obtained user identifier according to the specified modulation scheme and coding rate Interference cancellation may be performed sequentially. When there is no buffered data corresponding to the obtained user identifier, step 603 detects data for the MTC mobile station corresponding to the obtained user identifier, and the identified modulation scheme and Interference cancellation may be performed sequentially on the detected data according to the coding rate.

  For example, according to the mobile station identifier vector of the current TTI notified from the base station, IDs 1, 2 and 3 which are IDs of MTC mobile stations that perform data transmission in each subband in the current TTI are acquired. In the example shown in FIG. 8, data of MTC mobile stations whose IDs are 1 and 2 are buffered in advance, and the LTE mobile station utilizes buffered data according to the specified modulation scheme and coding rate. Interference cancellation may be performed sequentially for data for MTC mobile stations whose IDs are 1 and 2. Specifically, the LTE mobile station may first identify an SB occupied by data of MTC mobile stations whose IDs are 1 and 2 according to the mobile station identifier vector of the current TTI. And, the buffer data specifies whether or not it corresponds to the modulation scheme and coding rate of the MTC mobile station at the SB specified (for example, by steps S601 and S602). And, when the buffer data corresponds to the specified modulation scheme and coding rate, successive interference cancellation is performed. On the other hand, if the buffer data does not correspond to the specified modulation scheme and coding rate, the LTE mobile station needs to detect data for MTC mobile stations whose IDs are 1 and 2 again in the current TTI. And performs successive interference cancellation on the detected data. In addition, since the data of the MTC mobile station whose ID is 3 is not buffered in advance, the LTE mobile station needs to detect transmission data of the MTC mobile station corresponding to ID 3 and is detected. Perform interference cancellation on data one by one.

  Preferably, after detecting data for the MTC mobile station corresponding to the obtained user identifier, the buffered data may be updated according to the detected data.

  According to the method shown in FIGS. 7 and 8, the LTE mobile station stores the user identifier of the MTC mobile station and the data packet in association with each other, thereby decoding the data packet each time the transmission data packet is transmitted. It is not necessary to perform such operations, and interference cancellation can be performed promptly using stored data packets.

Hereinafter, a base station according to an embodiment of the present invention will be described with reference to FIG. FIG. 9 shows a block diagram of a base station 900 according to an embodiment of the present invention. As shown in FIG. 9, the base station 900 includes a coding rate acquisition unit 910, a scheduling vector generation unit 920, and a transmission unit 930. Although the base station 900 may include other components other than these three units, these components are not relevant to the contents of the embodiment of the present invention, and so the illustration and description thereof will be omitted here. Also, since the specific details of the following operations performed by the base station 900 according to an embodiment of the present invention are similar to the details described above with reference to FIGS. A duplicate description of similar details is omitted to avoid this.
In the case of successive interference cancellation, one mobile station needs to acquire and use information such as modulation scheme and coding rate of another mobile station paired with it. To further reduce the required control signaling, according to an embodiment of the present invention, the base station 900 may not notify the LTE mobile station of the modulation scheme of the MTC mobile station. And, the LTE mobile station can specify the modulation scheme of the MTC mobile station by blind detection, and the base station 900 notifies the LTE mobile station of the coding rate of the MTC mobile station only by the scheduling vector. Can.

The coding rate acquisition unit 910 acquires the coding rates of MTC mobile stations performing data transmission in each subband in the current TTI. The scheduling vector generation unit 920 then generates a common MTC scheduling vector according to the obtained coding rate. According to one illustration of the invention, the corresponding coding rate may be indicated in advance by coding for each type of coding rate available to the MTC mobile station. The scheduling vector generation unit 920 may specify a codeword corresponding to the coding rate of the MTC mobile station performing data transmission in each subband, and may generate a common MTC scheduling vector according to each codeword.
Current MTC mobile stations can use multiple modulation schemes such as QPSK, 16 QAM, 64 QAM, etc., and each modulation scheme may have multiple coding rates corresponding to the scheme. Preferably, base station 900 may further include a modulation scheme selection unit which selects a part of modulation schemes as a candidate modulation scheme from a plurality of modulation schemes in advance. The MTC mobile station uses one of the candidate modulation schemes for data transmission. Therefore, since the LTE mobile station needs to perform blind detection only for the modulation scheme selected as the candidate modulation scheme, the complexity of the blind detection operation by the LTE mobile station can be simplified.

  Also, the base station 900 may further include a coding rate selection unit that selects a part of the coding rates as a candidate coding rate from a plurality of coding rates associated with each candidate modulation scheme in advance. The MTC mobile station uses one of the candidate coding rates for data transmission. Thus, control signaling required for notification of common MTC scheduling vectors can be further reduced.

  The transmitting unit 930 notifies the common MTC scheduling vector to all LTE mobile stations connected to the base station. For example, the base station scrambles to the common MTC scheduling vector using the radio network temporary identifier, and notifies the LTE mobile station of the scrambled common MTC scheduling vector. In this case, the base station 900 may further include an identifier generation unit and a vector processing unit.

  Unlike the conventional scheduling vector generation method of generating a dedicated scheduling vector for a specific mobile station and notifying the dedicated scheduling vector to another mobile station paired with the specific mobile station. A unit 930 informs all mobile stations of the common MTC scheduling vector, so that it does not have to scramble using the mobile station specific radio network temporary identifier, but uses the common radio network temporary identifier. All LTE mobile stations connected to the base station can be descrambled using this common radio network temporary identifier.

  Specifically, the identifier generation unit generates a common MTC radio network temporary identifier for all LTE mobile stations previously connected to the base station, and the transmission unit is for all LTE mobile stations connected to the base station. In response, the common MTC wireless network temporary identifier is notified. After generating the common MTC scheduling vector, the scheduling vector generation unit 920 scrambles the common MTC scheduling vector with the common MTC radio network temporary identifier, and the transmission unit 930 connects to the base station The scrambled common MTC scheduling vector is broadcast to all the LTE mobile stations that have been selected.

  The base station of this embodiment does not need to generate a separate scheduling vector for each mobile station, and generates a common MTC scheduling vector according to the coding rate of the MTC mobile station that performs data transmission in each subband in the current TTI. And perform interference cancellation one by one. This allows the wireless communication system to support the combined use of NOMA and MTC while minimizing the increase in signaling overhead.

  Also, the base station 900 of the present embodiment may not include information on the modulation scheme of each mobile station. If the MTC mobile station transmits data in a narrow band and the occupied frequency band is a continuous resource block, the common MTC scheduling vector of this embodiment is occupied by the MTC mobile station. The information on the frequency resource to be stored may be omitted. Thus, the signaling overhead can be further reduced.

  Further, the base station 900 may further assign a user identifier to the MTC mobile station and notify the LTE mobile station of the transmission data information of the received MTC mobile station so that the LTE mobile station identifies it. Specifically, the base station 900 may further include an identifier assignment unit and an identifier vector generation unit. The identifier assignment unit may assign a user identifier (ID) to the MTC mobile station connected to the base station. The identifier vector generation unit may generate a mobile station identifier vector according to the user identifier of the MTC mobile station performing data transmission in each subband in the current TTI. Also, the transmitting unit 930 may further notify the mobile station identifier vector to all LTE mobile stations connected to the base station.

  In MTC technology, since the same data packet is retransmitted 200 to 300 times, the user identifier is assigned to the MTC mobile station and notified to the LTE mobile station, and the LTE mobile station transmits the user identifier of the MTC mobile station and the data packet Can be stored in association with each other, so that it is not necessary to perform an operation such as decoding for the data packet each time the data packet is transmitted, and interference cancellation is sequentially performed using the stored data packet. Do it promptly.

  The size of the mobile station identifier vector may correspond to the maximum number of MTC mobile stations that can connect to the base station in one TTI. In addition, since MTC adopts frequency hopping technology to obtain frequency gain, there is a possibility that MTC mobile stations performing data transmission in each sub-band may change in each TTI. Thus, preferably, the base station 900 may generate and notify a mobile station identifier vector of the current TTI in each TTI.

  According to one example of the present invention, the number of IDs assignable to the MTC mobile station by the identifier assignment unit may be the maximum number of MTC mobile stations connectable to the base station in one TTI. There may be MTC mobile stations newly connected to the base station in the current TTI. In this case, in order to avoid duplicating the ID assigned to the MTC mobile station already connected to the base station, the identifier assignment unit is a MTC mobile station newly connected to the base station in the current TTI. It is preferable to assign an ID that has not been assigned before. Also, if all the predetermined IDs have been assigned to the MTC mobile station, and there is an MTC mobile station newly connected to the base station in the current TTI, the identifier assignment unit will The ID value of the MTC mobile station that has been connected to the station and has not been connected to the base station in the current TTI may be assigned to the MTC mobile station newly connected to the base station.

  Hereinafter, an LTE mobile station according to an embodiment of the present invention will be described with reference to FIG. FIG. 10 shows a block diagram of an LTE mobile station 1000 in accordance with one embodiment of the present invention. As shown in FIG. 10, the LTE mobile station 1000 includes a modulation scheme identification unit 1010, a coding rate identification unit 1020, and a successive interference cancellation unit 1030. Although the LTE mobile station 1000 may include other components other than these three units, these components are not relevant to the contents of the embodiment of the present invention, and so their illustration and description will be omitted here. In addition, since the specific details of the following operations performed by the LTE mobile station 1000 according to the embodiment of the present invention are the same as the details described with reference to FIGS. So as to avoid duplicating descriptions of similar details.

  The modulation scheme identification unit 1010 blindly detects the modulation scheme of the MTC mobile station paired with the LTE mobile station, and identifies the modulation scheme of the MTC mobile station paired with the LTE mobile station. Specifically, in the NOMA system, the MTC mobile station paired with the LTE mobile station is an MTC mobile station whose frequency band for data transmission overlaps with the frequency band for data transmission of the LTE mobile station. In other words, the MTC mobile station whose downlink frequency band overlaps with the downlink frequency band of one LTE mobile station in the current TTI is the MTC mobile station paired with the LTE mobile station. The modulation scheme identification unit 1010 may blindly detect the modulation scheme of the MTC mobile station that performs data transmission in the subbands included in the downlink frequency band.

  Also, as described above, QPSK and 16 QAM may be selected as candidate modulation schemes in advance from among a plurality of modulation schemes usable by the MTC mobile station. That is, the modulation scheme of the MTC mobile station is one of QPSK and 16 QAM. Therefore, the modulation scheme identification unit 1010 identifies the modulation scheme used by the MTC mobile station only between the two modulation schemes of QPSK and 16 QAM when performing blind detection, and simplifies the complexity of blind detection. Turned

  The coding rate identification unit 1020 may identify the coding rate of the MTC mobile station paired with the LTE mobile station according to the common MTC scheduling vector notified from the base station, where the common MTC scheduling vector is And includes coding rate information indicating a coding rate of an MTC mobile station performing data transmission in each subband in the current TTI. According to one example of the present invention, first, blind detection is performed by the modulation scheme identification unit 1010, and according to the modulation scheme and common MTC scheduling vector identified by the coding rate identification unit 1020, with the LTE mobile station. The coding rate of the MTC mobile station to be paired may be specified. Alternatively, if it is not necessary to specify the coding rate of the MTC mobile station according to the modulation scheme, then the coding rate identification unit 1020 may specify the coding rate at the same time as performing blind detection by the modulation scheme specifying unit 1010 .

  Finally, the successive interference cancellation unit 1030 performs successive interference cancellation on the data for the MTC mobile station paired with the LTE mobile station according to the identified modulation scheme and coding rate.

  The LTE mobile station according to this embodiment acquires the modulation scheme of the MTC mobile station by blind detection, and acquires the coding rate of the MTC mobile station by the common MTC scheduling vector. Thus, the wireless communication system can support the combined use of NOMA and MTC while minimizing the increase in signaling overhead.

  Also, as described above, in the MTC technology, since the same data packet is retransmitted 200 to 300 times, the LTE mobile station may store the user identifier assigned to the MTC mobile station and the data packet in association with each other. Thus, it is not necessary to perform an operation such as decoding on the data packet each time the data packet is transmitted, and interference cancellation can be quickly performed using stored data packets.

  Specifically, the LTE mobile station may buffer the user identifier and data of the MTC mobile station to perform interference cancellation promptly. FIG. 11 shows a block diagram of an LTE mobile station 1100 in accordance with another embodiment of the present invention. As shown in FIG. 11, the LTE mobile station 1100 includes a modulation scheme identification unit 1110 and a coding rate identification unit 1120 similar to the modulation scheme identification unit 1010, the coding rate identification unit 1020, and the successive interference cancellation unit 1030, respectively. And successive interference cancellation unit 1130. Also, the LTE mobile station 1100 further includes a buffer unit 1140, an identifier acquisition unit 1150, and a data identification unit 1160.

  Specifically, the buffer unit 1140 buffers a user identifier of the MTC mobile station connected to the base station and data for the MTC mobile station corresponding to the user identifier. Here, the buffered user identifier and the data associated with the user identifier may be acquired in the preceding TTI.

  As described above, the number of IDs that can be assigned to an MTC mobile station may be the maximum number of MTC mobile stations that can connect to a base station in one TTI. Therefore, the maximum number of MTC mobile stations connectable to the base station in one TTI may specify the buffer size for buffering the user identifier and data in the LTE mobile station.

  The identifier acquisition unit 1150 acquires user identifiers of MTC mobile stations performing data transmission in each subband in the current TTI according to the mobile station identifier vector of the current TTI notified from the base station. Then, the data identification unit 1160 identifies whether there is buffered data corresponding to the acquired user identifier. When there is buffered data corresponding to the obtained user identifier, the successive interference cancellation unit 1130 may be configured to receive buffered data corresponding to the obtained user identifier according to the identified modulation scheme and coding rate. Alternatively, interference cancellation may be performed sequentially. On the other hand, when there is no buffered data corresponding to the obtained user identifier, the successive interference cancellation unit 1130 detects and identifies data for the MTC mobile station corresponding to the obtained user identifier. Interference cancellation may be performed sequentially on the detected data according to the modulation scheme and coding rate.

  Preferably, the buffer unit 1140 may update buffered data according to the detected data after detecting data for the MTC mobile station corresponding to the obtained user identifier.

  According to the method shown in FIG. 11, the LTE mobile station stores the user identifier of the MTC mobile station and the data packet in association with each other, thereby decoding the data packet each time the data packet is transmitted. There is no need to perform an operation, and the stored data packets are used to quickly perform successive interference cancellation.

The operations of the base station 900 and the LTE mobile stations 1000 and 1100 described above may be realized by hardware, may be realized by a software module executed by a processor, and are further realized by a combination of both. It is also good.
The software modules include RAM (random access memory), flash memory, ROM (read only memory), EPROM (Erasable Programmable ROM), EEPROM (electrically erasable programmable ROM), registers, hard disk, removable disk, CD-ROM, etc. It may be arranged in a storage medium of any format.

  Such a storage medium is connected to the processor such that the processor writes information to the storage medium or reads information from the storage medium. Such storage media may be stored on a processor. Such storage media and processors may be located in an ASIC. Such an ASIC may be deployed in the base station 900, the LTE mobile station 1000, 1100. Such storage media and processors may be located as discrete components in base station 900 and LTE mobile stations 1000, 1100.

  Accordingly, although the present invention has been described in detail using the above-described embodiments, it is apparent to those skilled in the art that the present invention is not limited to the embodiments described herein. The present invention can be realized as a modified or altered form without departing from the scope of the present invention which is limited by the claims. Accordingly, the description of the specification is illustrative only and is not intended to limit the present invention.

Claims (20)

A method of scheduling vector generation performed by a base station, comprising:
Obtaining a coding rate of a machine type communication (MTC) mobile station performing data transmission in each subband in the current transmission time interval (TTI);
Generating a common MTC scheduling vector according to the obtained coding rate;
Notifying the common MTC scheduling vector to all LTE mobile stations connected to the base station. Further including the step of selecting, in advance, a part of modulation schemes as candidate modulation schemes from a plurality of modulation schemes
The method according to claim 1, wherein the MTC mobile station uses one of the candidate modulation schemes for data transmission. The method further includes the step of selecting, as a candidate coding rate, a part of coding rates from a plurality of coding rates previously associated with the candidate modulation scheme,
The method according to claim 2, wherein the MTC mobile station uses a coding rate of one of the candidate coding rates in data transmission. Generating a common MTC radio network temporary identifier for all LTE mobile stations connected to the base station;
Notifying the common MTC radio network temporary identifier to all LTE mobile stations connected to the base station;
And Scramble the common MTC scheduling vector with the common MTC radio network temporary identifier.
Informing the common MTC scheduling vector to all LTE mobile stations connected to the base station,
The method according to claim 1, comprising: broadcasting a scrambled common MTC scheduling vector to all LTE mobile stations connected to the base station. Assigning a user identifier to the MTC mobile station connected to the base station;
Generating a mobile station identifier vector according to the user identifier of the MTC mobile station performing data transmission in each subband in the current TTI;
Notifying the mobile station identifier vector of all LTE mobile stations connected to the base station. A successive interference cancellation method performed by an LTE mobile station, comprising
Blind detecting a modulation scheme of a machine type communication (MTC) mobile station paired with the LTE mobile station, and identifying a modulation scheme of the MTC mobile station paired with the LTE mobile station;
Identifying a coding rate of an MTC mobile station paired with the LTE mobile station according to a common MTC scheduling vector notified from a base station, wherein the common MTC scheduling vector corresponds to each subband in a current TTI And d) including coding rate information indicating a coding rate of the MTC mobile station performing data transmission in
Performing successive interference cancellation on data for the MTC mobile station paired with the LTE mobile station according to the identified modulation scheme and coding rate. Buffering a user identifier of the MTC mobile station connected to the base station and data of the MTC mobile station corresponding to the user identifier;
Obtaining a user identifier of an MTC mobile station performing data transmission in each sub-band in a current TTI according to a mobile station identifier vector notified from a base station;
Identifying whether there is buffered data corresponding to the obtained user identifier;
If buffered data corresponding to the obtained user identifier is present, it sequentially interferes with the data for the MTC mobile station paired with the LTE mobile station according to the identified modulation scheme and coding rate The process to cancel is
The method according to claim 6, comprising the step of performing successive interference cancellation on buffered data corresponding to the obtained user identifier according to the identified modulation scheme and coding rate. If there is no buffered data corresponding to the obtained user identifier, it sequentially interferes with the data for the MTC mobile station paired with the LTE mobile station according to the specified modulation scheme and coding rate The process to cancel is
Detecting data for the MTC mobile station corresponding to the obtained user identifier;
And performing successive interference cancellation on the detected data in accordance with the identified modulation scheme and coding rate.   The method according to claim 8, further comprising: updating the buffered data according to the detected data after detecting data for the MTC mobile station corresponding to the obtained user identifier. In accordance with the maximum number of MTC mobile stations connectable to the base station in one TTI, specify the buffer size for buffering the user identifier and data in the LTE mobile station,
The method according to claim 7, wherein the size of the mobile station identifier vector corresponds to the maximum number of MTC mobile stations connectable to the base station in one TTI. A coding rate acquisition unit configured to acquire a coding rate of a machine type communication (MTC) mobile station performing data transmission in each subband in the current transmission time interval (TTI);
A scheduling vector generation unit configured to generate a common MTC scheduling vector according to the obtained coding rate;
A transmitting unit configured to notify the common MTC scheduling vector to all LTE mobile stations connected to the base station. Further including a modulation scheme selection unit configured to select a part of the modulation schemes as a candidate modulation scheme from a plurality of modulation schemes in advance;
The base station according to claim 11, wherein the MTC mobile station uses one of candidate modulation schemes in data transmission. And a coding rate selection unit configured to select a part of the coding rates as a candidate coding rate from a plurality of coding rates previously associated with the candidate modulation scheme,
The base station according to claim 12, wherein the MTC mobile station uses a coding rate of one of candidate coding rates in data transmission. An identifier generation unit configured to generate a common MTC radio network temporary identifier for all LTE mobile stations connected to the base station;
Further comprising: a vector processing unit configured to scramble the common MTC scheduling vector with the common MTC radio network temporary identifier;
The transmitting unit broadcasts a scrambled common MTC scheduling vector to all LTE mobile stations connected to the base station, and for all LTE mobile stations connected to the base station, The base station according to claim 11, wherein the common MTC radio network temporary identifier is notified. An identifier assignment unit configured to assign a user identifier to an MTC mobile station connected to the base station;
An identifier vector generation unit configured to generate a mobile station identifier vector according to the user identifier of the MTC mobile station performing data transmission in each subband in the current TTI.
The base station according to claim 11, wherein the transmitting unit is further configured to notify the mobile station identifier vector to all LTE mobile stations connected to the base station. Modulation configured to blind detect a modulation scheme of a machine type communication (MTC) mobile station paired with the LTE mobile station and identify a modulation scheme of the MTC mobile station paired with the LTE mobile station Method specific unit,
A coding rate identification unit for identifying a coding rate of an MTC mobile station paired with the LTE mobile station according to a common MTC scheduling vector notified from a base station, wherein the common MTC scheduling vector is a current TTI. A coding rate identification unit configured to include coding rate information indicating a coding rate of an MTC mobile station performing data transmission in each subband in
An LTE mobile, comprising: successive interference cancellation units configured to perform successive interference cancellation on data for MTC mobile stations paired with the LTE mobile station according to the identified modulation scheme and coding rate Station. A buffer unit configured to buffer a user identifier of an MTC mobile station connected to the base station and data of the MTC mobile station corresponding to the user identifier;
An identifier acquisition unit configured to acquire a user identifier of an MTC mobile station performing data transmission in each sub-band in the current TTI according to a mobile station identifier vector notified from the base station;
Further comprising a data identification unit configured to identify whether buffered data exists corresponding to the obtained user identifier.
If there is buffered data corresponding to the obtained user identifier, the successive interference cancellation unit may transmit buffered data corresponding to the obtained user identifier according to the specified modulation scheme and coding rate. The mobile station according to claim 16, wherein interference cancellation is performed sequentially. Further comprising a detection unit configured to detect data for the MTC mobile station corresponding to the obtained user identifier, if there is no buffered data corresponding to the obtained user identifier,
The mobile station according to claim 17, wherein the successive interference cancellation unit performs successive interference cancellation on detected data according to a specified modulation scheme and coding rate.   The mobile station according to claim 18, wherein the buffer unit updates buffered data according to the detected data after detecting data for an MTC mobile station corresponding to the obtained user identifier. Identify the size of storage space in the buffer unit according to the maximum number of MTC mobile stations connectable to the base station in one TTI,
The mobile station according to claim 17, wherein the size of the mobile station identifier vector corresponds to the maximum number of MTC mobile stations connectable to the base station in one TTI.