JP4800447B2 - Base station apparatus, transmission method, and mobile communication system - Google Patents

Description

  The present invention generally relates to the technical field of mobile communication, and more particularly to a base station apparatus, a user apparatus and a method for performing communication using a plurality of antennas.

In this type of technical field, research and development related to next-generation mobile communication systems are proceeding at a rapid pace. The standardization organization 3GPP of W-CDMA is considering Long Term Evolution (LTE) as a communication system that succeeds W-CDMA, HSDPA, and HSUPA. In LTE, as a radio access scheme, the OFDM scheme is planned for the downlink and SC-FDMA (Single-Carrier Frequency Division Multiple Access) is planned for the uplink (for example, see Non-Patent Document 1).
The Orthogonal Frequency Division Multiple Access (OFDM) system is a multi-carrier system that divides a frequency band into multiple narrow frequency bands (subcarriers) and transmits data on each frequency band. Moreover, by arranging them closely without interfering with each other even though they partially overlap, it is possible to realize high-speed transmission and increase the frequency utilization efficiency.

  Single-carrier FDMA (SC-FDMA) is a single-carrier transmission method that can reduce interference between terminals by dividing the frequency band and transmitting using different frequency bands among multiple terminals. . SC-FDMA has the feature that fluctuations in transmission power are reduced, so that low power consumption and wide coverage of the terminal can be realized.

  LTE is a system in which one or two or more physical channels are shared by a plurality of user apparatuses for both uplink and downlink. The channel shared by the plurality of user apparatuses is generally called a shared channel, and in LTE, uplink communication is performed using an uplink shared physical channel (PUSCH: Physical Uplink Shared Channel), and a downlink shared physical channel (PDSCH: Physical Downlink Shared). Channel) is used for downlink communication.

  In a communication system using these shared channels, it is necessary to signal to which user apparatus the shared channel is allocated for each sub-frame (1 ms in LTE). The control channel used for this signaling is called a physical downlink control channel (PDCCH: Physical Downlink Control Channel) or a downlink L1 / L2 control channel (DL-L1 / L2 Control Channel) in LTE. The physical downlink control channel information includes, for example, downlink scheduling information or downlink scheduling information (Downlink Scheduling Information), acknowledgment information (ACK / NACK), uplink scheduling grant (Uplink Scheduling Grant), A load indicator (Overload Indicator), a transmission power control command bit (Transmission Power Control Command Bit), etc. are included (for example, refer nonpatent literature 2).

  The downlink scheduling information and the uplink scheduling grant are information for signaling which user apparatus is assigned the shared channel. The downlink scheduling information includes, for example, downlink resource block (RB) allocation information, UE ID, the number of streams when MIMO is performed, and a precoding vector (Precoding Vector) regarding a downlink shared channel. ), Data size, modulation method, information on HARQ (Hybrid Automatic Repeat reQuest), and the like. The uplink scheduling grant includes, for example, uplink resource allocation information, UE ID, data size, modulation scheme, uplink transmission power information, uplink MIMO (Uplink MIMO) related to the uplink shared channel. ) Includes information of a demodulation reference signal (Demodulation Reference Signal).

  The multi-input multi-output (MIMO) system is a multi-antenna system communication that uses a plurality of antennas for communication to increase the speed and / or quality of transmission signals. Furthermore, by duplicating the stream of the transmission signal and combining and transmitting each of the duplicated streams with appropriate weights, it is possible to send a signal to the communication partner with a beam having a controlled directivity. This is called a precoding scheme, and the weighting factor (weight) used is called a precoding vector.

  FIG. 1 schematically shows how precoding is performed. The two streams (transmission signals 1 and 2) are duplicated in two systems by the copy unit, multiplied by the precoding vector in each system, combined and transmitted. From the viewpoint of using a more appropriate precoding vector, closed loop precoding as shown in the figure is preferable. In this case, the precoding vector is adaptively controlled to be a more appropriate value based on feedback from the reception side (user apparatus). In the precoding method, since each stream is transmitted spatially differently, a large quality improvement effect can be expected for each stream.

3GPP TR 25.814 (V7.0.0), "Physical Layer Aspects for Evolved UTRA," June 2006 R1-070103, Downlink L1 / L2 Control Signaling Channel Structure: Coding

  By the way, in order to appropriately demodulate the precoded shared data channel, it is necessary to accurately perform channel compensation for the shared data channel. One way to do this is to have a separate dedicated reference signal that is precoded as with the shared data channel. Certainly, if there is such a reference signal, channel estimation may be performed with high accuracy. However, since there are not a few resources for reference signals that must be prepared exclusively, the overhead becomes considerably large. Therefore, this method is not desirable from the viewpoint of improving the throughput of the entire system.

  From such a relation, it is conceivable to perform channel estimation based on a common reference signal common to all users. In this case, information indicating how precoding applied to the shared data channel needs to be notified to the user apparatus. For convenience of explanation, this information will be called a pre-coding matrix indicator (PMI).

  As shown in FIG. 2, one method for notifying the user equipment of the precoding content is that a PMI indicating a precoding vector applied to the channel is always transmitted together with the precoded downlink physical shared channel. Is to do so. In FIG. 2, PMI indicating some precoding vector is fed back from the user apparatus UE to the base station apparatus eNB. The base station apparatus eNB transmits the downlink physical shared channel together with the PMI indicating the precoding vector designated by the user apparatus UE or another precoding vector. According to this method, the PMI most suitable for the communication situation can be determined by the base station apparatus eNB, and effective use of resources in the downlink can be achieved. For example, when the user apparatus UE transmits precoding vectors for four streams to the base station apparatus eNB, two streams may be sufficient for downlink traffic. In this case, the base station apparatus eNB prepares precoding vectors for two streams and communicates with them, so that resources can be effectively utilized without excess or deficiency. However, since it is necessary to always notify PMI on the downlink, the overhead becomes at least as much. In addition, the amount of information occupied by PMI increases and decreases with the number of multiplexed users on the downlink, and blind detection on the receiving side tends to be difficult.

  As shown in FIG. 3, another method for making the precoding vector known by the user apparatus is to force the base station apparatus eNB to always follow the PMI fed back from the user apparatus UE. This method is preferable from the viewpoint of saving overhead because PMI does not have to accompany the downlink physical shared channel. However, if this is done, the base station apparatus eNB cannot change the precoding vector to a more appropriate one, which is not preferable from the viewpoint of effective use of resources. Also, in the unlikely event that the PMI detected by the base station apparatus eNB is incorrect, the base station apparatus performs precoding with a vector different from that expected by the user apparatus. In this case, since the user apparatus does not know that the PMI has been misidentified, the user apparatus wastefully processes a received signal with poor quality.

  An object of the present invention is to reduce downlink overhead and effectively use radio resources in a MIMO mobile communication system that performs precoding.

A base station apparatus according to an embodiment
A base station apparatus used in a MIMO mobile communication system that performs precoding,
A receiver for receiving a precoding matrix indicator (PMI) indicating a specific precoding vector from the user equipment;
A determination unit that determines a value of a flag indicator indicating whether or not to use the precoding vector specified by the PMI for downlink communication;
A control signal generation unit for generating a downlink control signal including at least the flag indicator;
A transmission unit for transmitting a signal including the downlink control signal in the downlink,
When the precoding vector specified by the PMI is not used for downlink communication, a default vector known by both the base station apparatus and the user apparatus is used as a precoding vector for downlink communication,
The flag indicator is represented by multiple bits, and the flag indicator specifies any of a plurality of default vectors,
The control signal generation unit channel-encodes an information part including control information, a flag indicator, and error detection information as an encoding unit,
The base station apparatus is characterized in that the error detection information is derived by performing a predetermined calculation on a calculation target including at least the control information and the flag indicator.

  According to one embodiment, it is possible to reduce downlink overhead and effectively use radio resources in a MIMO mobile communication system that performs precoding.

It is a figure which shows a mode that precoding is performed typically. The figure for demonstrating the problem of a prior art is shown. The figure for demonstrating the problem of a prior art is shown. The conceptual diagram of the base station apparatus eNB and user apparatus UE which are used with one form of this invention is shown. It is a flowchart which shows the operation example in the user apparatus by one Example of this invention. It is a flowchart which shows the operation example in the base station apparatus by one Example of this invention. It is a figure which shows a mode that the error detection bit in the case of X = 1 is derived | led-out. It is a figure which shows an error detection bit and channel coding unit in the case of X = 0. It is a figure which shows a mode that feedback PMI is convolved with a control bit. It is a functional block diagram of the base station apparatus by one Example of this invention. It is a functional block diagram of the user apparatus by one Example of this invention.

  FIG. 4 shows a conceptual diagram of the base station apparatus eNB and the user apparatus UE used in one embodiment of the present invention. First, a precoding matrix indicator (PMI) indicating a specific precoding vector is fed back from the user apparatus UE to the base station apparatus eNB. The base station apparatus eNB determines whether or not the precoding vector specified by the PMI is actually used for downlink communication, and prepares a flag indicator indicating the determination result. The base station apparatus eNB transmits the downlink physical shared channel together with the flag indicator. By checking the value of the flag indicator, the user apparatus UE can determine whether or not the precoding vector that has been fed back to the base station apparatus eNB in the past by PMI is actually used in the downlink. As an example, the flag indicator is expressed by 1 bit, and when taking a value of “0”, a precoding vector specified by PMI is used for downlink communication. In the case of a value of “1”, a known default vector is used as a precoding vector before the start of communication in the base station apparatus eNB and the user apparatus UE. Since the number of bits of the flag indicator is smaller than that of the PMI, the overhead can be considerably reduced as compared with the conventional method in which the PMI is notified every downlink. Moreover, since there is room for the base station apparatus eNB to select a precoding vector different from that specified by the PMI fed back from the user apparatus UE, it is possible to effectively use resources.

  By the way, the precoding vector used by the base station apparatus eNB for downlink communication and the precoding vector prepared by the user apparatus UE according to the flag indicator do not always match. For example, when the base station apparatus eNB erroneously receives the PMI from the user apparatus UE and the vector indicated by the erroneously recognized PMI is used as a downlink precoding vector, or when the flag indicator is erroneously detected in the user apparatus UE It may be received. In such a case, if weighting of a received signal and subsequent demodulation processing are performed using a precoding vector prepared by the user apparatus UE, there is a possibility that a significantly deteriorated signal may be derived uselessly. From such a viewpoint, the user apparatus UE may confirm whether the notification from the base station apparatus eNB is correct.

  In one form of the present invention, the base station apparatus performs channel coding using an information portion including control information, a flag indicator, and error detection information as a coding unit. This error detection information is derived by performing a predetermined calculation on a calculation target including at least control information and a flag indicator. When the flag indicator is a predetermined value, the PMI is included in the calculation target, and when the flag indicator is another predetermined value, the PMI is not included in the calculation target. The user apparatus performs a predetermined calculation on the calculation target including the control information, the flag indicator, and, if necessary, the PMI, and derives error detection information. Then, the error detection information prepared by the base station apparatus is compared with the error detection information prepared by the user apparatus. Thereby, it is possible to determine whether or not the precoding vector prepared by the user apparatus UE is used for downlink communication according to the flag indicator.

  Since the number of bits of the flag indicator is smaller than that of PMI, it is not easy to obtain a sufficiently large error correction capability with the flag indicator alone. As described above, in one embodiment of the present invention, not only the flag indicator but also the control indicator and error detection information are encoded. Therefore, a larger coding gain can be obtained than when only the flag indicator is used, and it may be possible to expect an error correction capability as high as that of the control bits.

  The flag indicator may be expressed by any number of bits, but may be expressed by a minimum of 1 bit. When the precoding vector specified by PMI is not used for downlink communication, a default vector known by both the base station apparatus and the user apparatus may be used as a precoding vector by downlink communication. As a result, if the vector specified by PMI is not actually used, the default vector is always used. Therefore, the vector actually used can be specified by determining the value of the flag indicator having a smaller number of bits than PMI.

  When the flag indicator indicates that the default vector is not used (X = 0), an information part including information in which PMI is convolved with control information, a flag indicator, and error detection information is channel-coded, and the user equipment May be sent to. This is preferable from the viewpoint of transmitting the PMI to the user apparatus without increasing the number of bits of the control information. However, it is necessary to separately notify the user apparatus how many bits the PMI occupies.

  According to an aspect of the present invention, the base station apparatus may perform error detection on the PMI fed back from the user apparatus. This is preferable from the viewpoint of reliably determining whether a default vector should be used for downlink communication. PMI and error detection information for PMI are received by the base station apparatus, and error detection is performed by comparing the error detection information calculated by the user apparatus with the error detection information calculated by the base station apparatus. May be. Error detection may be performed according to whether the reception quality of the uplink reference signal received from the user apparatus is good or bad. Error detection may be performed based on likelihood information of the shared data channel received from the user apparatus.

  Examples of the present invention will be described below. Although specific numerical examples may be used to facilitate understanding of the invention, these numerical values are merely examples and any appropriate value may be used unless otherwise specified.

<Description of operation (before starting downlink communication)>
Hereinafter, operations of the base station apparatus eNB and the user apparatus UE in the mobile communication system according to an embodiment of the present invention will be described. In a mobile communication system, multi-input multi-output (MIMO) communication is performed while performing precoding. Accordingly, each of the base station apparatus eNB and the user apparatus UE has a plurality of transmission / reception antennas, and signals transmitted through the antennas are weighted with precoding vectors so as to be directed in appropriate directions.

FIG. 5 shows an operation example in a user apparatus according to an embodiment of the present invention, and FIG. 6 shows an operation example in a base station apparatus according to an embodiment of the present invention. The precoding vector is adaptively controlled based on feedback (PMI) from the user apparatus UE to the base station apparatus eNB. In step 502 of FIG. 5, the PMI to be fed back to the base station apparatus eNB is determined. Typically, the precoding vector is any one of a predetermined number of vectors (U ₁ , U ₂ ,..., U _P ) stored in advance in the code book. Therefore, PMI designates any one (Ui) of a predetermined number of vectors (U ₁ , U ₂ ,..., U _P ). More generally, the precoding vector is not an alternative option and may be adaptively adjusted to any suitable vector. However, it is preferable to limit the vectors that can be precoding vectors to alternative options from the viewpoint of enabling adaptive control while reducing the burden of vector control calculation.

  In step 504, the determined PMI is transmitted to the base station apparatus eNB.

  As shown in step 602 of FIG. 6, the base station apparatus eNB receives PMI from the user apparatus UE.

  In step 604, what is the precoding vector specified by PMI is specified. Then, it is determined whether or not the identified precoding vector is suitable for downlink communication. This determination may be made based on the number of streams, the number of transmission antennas, the amount of downlink traffic, and the like. In this embodiment, when the precoding vector specified by PMI is not suitable for downlink communication, a known default vector is used as the precoding vector before the start of communication in the base station apparatus eNB and the user apparatus UE. Is done. Any number of default vectors may be prepared, but for the sake of simplicity of explanation, it is assumed that only one default vector is prepared. That is, in this embodiment, two options are prepared as downlink precoding vectors, one is a vector specified by PMI, and the other is a default vector. Furthermore, in the present embodiment, a flag indicator indicating what is used as a downlink precoding vector is defined and expressed by 1 bit. Therefore, a default vector or a precoding vector specified by PMI is used according to the value of the flag indicator (for example, 1 or 0). When more than one default vector is prepared, the value of the flag indicator may be expressed by a number of bits greater than one. In this case, for example, three types of default vectors are prepared, and a 2-bit flag indicator may be used to notify the user apparatus which one of them is used for downlink communication.

  In step 606, error detection bits are calculated when the default vector is used as the precoding vector.

  As shown in FIG. 7, the error detection bit is derived by applying a predetermined calculation to information including a control bit (control information) and a flag indicator value (“1” in the illustrated example). . The error detection bits are typically check bits used in a cyclic redundancy check (CRC) as shown, but any other suitable error check bit may be used. Furthermore, in the present embodiment, a user identifier (UE-ID) convoluted with a CRC check bit is used as an error detection bit. The control bit includes various information notified to the user equipment in the downlink, and typically includes information included in the L1 / L2 control channel, but even if only a part thereof is included. Alternatively, information other than L1 / L2 may be included. In any case, the “control bit” that is the object of operation of the error detection bit in this step includes information that is neither a flag indicator nor PMI.

  In step 608 of FIG. 6, channel coding for error correction is performed. The encoding may be performed by any appropriate method known in the art, such as convolutional encoding and turbo encoding. In this embodiment, an information part including a control bit, a flag indicator (“1”), and an error detection bit is encoded as one encoding unit.

  In step 610, error detection bits are calculated when a vector specified by PMI is used as a precoding vector.

  As shown in FIG. 8, the error detection bit applies a predetermined calculation to information including a control bit, a flag indicator value (“0” in the illustrated example), and the PMI that has been fed back. It is derived by this. The error detection bits are typically check bits used in CRC as shown, but any other suitable error check bit may be used. Furthermore, in the present embodiment, a UE-ID convoluted with a CRC check bit is used as an error detection bit. It should be noted that, unlike the case of FIG. 7, in the present case, the PMI that has been fed back is included in the calculation target when the error detection bits are derived. The error detection bits are typically check bits used in CRC as shown, but any other suitable error check bit may be used. The control bit includes various information notified to the user equipment in the downlink, and typically includes information included in the L1 / L2 control channel, but even if only a part thereof is included. Alternatively, information other than L1 / L2 may be included.

  In step 612 of FIG. 6, channel coding for error correction is performed. The encoding may be performed by any appropriate method known in the art, such as convolutional encoding and turbo encoding. In this embodiment, an information portion including a control bit, a flag indicator (“0”), and an error detection bit is encoded as one encoding unit.

  As shown in FIG. 8, it should be particularly noted that this encoding unit does not include the fed back PMI. That is, the PMI that has been fed back is included in the calculation target for deriving the error detection bits, but is not the target of channel coding. Also note that in both step 608 and step 610, channel coding uses a unit of information including control bits, flag indicators, and error detection bits, so they are of similar size. Cost.

  In step 614 of FIG. 6, a signal including a channel-coded information part is appropriately transmitted on the downlink. In order to simplify the illustration, general signal processing for generating a downlink transmission signal is omitted in FIG. The transmission signal may include not only the control channel but also a signal such as a downlink physical shared channel (PDSCH) and a reference signal. Specific examples of signal processing may include, for example, data modulation (QPSK, 16QAM, etc.), precoding weighting, inverse Fourier transform, guard interval assignment, digital analog conversion, band limitation, power amplification, and the like.

  In step 602, whether or not there is an error in the received feedback PMI may be additionally confirmed by the base station apparatus. For example, when not only the PMI but also an error check bit for the PMI is received from the user apparatus, the correctness / incorrectness of the PMI may be confirmed using the error check bit. Also, the base station apparatus may confirm whether the received PMI is correct or not based on the quality of the uplink reference signal received from the user apparatus (eg, received SINR). Further, when the uplink shared data channel is received by the base station apparatus, the correctness / incorrectness of the received PMI may be confirmed based on the likelihood obtained when the uplink shared data channel is decoded. The likelihood obtained when decoding the received PMI itself may be used. These methods may be used alone, or a combination of two or more may be used.

  Prior to channel coding in step 612, information indicating PMI may be convoluted with control bits as shown in FIG. In this way, when information indicating PMI is transmitted on the downlink, it is not necessary to increase the number of bits of the signal. However, information indicating how many control bits are used for convolution needs to be notified to the user apparatus by some means.

<Description of operation (after starting downlink communication)>
In Step 506 of FIG. 5, the downlink physical shared channel is received by the user apparatus UE. In order to simplify the illustration, general signal processing for preparing a downlink reception signal is omitted in FIG. The received signal may include not only the control channel but also a signal such as a downlink physical shared channel (PDSCH) and a reference signal. Specific examples of signal processing may include, for example, power amplification, band limitation, analog-digital conversion, guard interval removal, Fourier transform, and the like.

  In step 508, channel decoding is performed on the control information portion of the received signal. As described in steps 608 and 610 of FIG. 6, channel coding is performed by using an information portion including a control bit, a flag indicator, and an error detection bit as one unit. After decoding, the value X of the flag indicator is confirmed. If X = 1, the flow proceeds to step 510, and if X = 0, the flow proceeds to step 512.

  In step 510, error check bits for X = 1 are calculated. When this step is reached, the precoding vector used for downlink communication is the default vector. Accordingly, in the base station apparatus, the error detection bit in step 606 in FIG. 6 is added, as shown in FIG. Therefore, also in step 510 of FIG. 5, a predetermined calculation is performed on the information portion including the control bit and the flag indicator (“1”), and an error detection bit is derived.

  In step 512, error check bits for X = 0 are calculated. When this step is reached, the precoding vector used for downlink communication is a vector specified by PMI. Therefore, in the base station apparatus, the error detection bit in step 610 in FIG. 6 is added, as shown in FIG. Therefore, in step 512 of FIG. 5, a predetermined calculation is performed on the information portion including the control bit, the flag indicator (“0”), and the PMI, and an error detection bit is derived. Since this PMI is what the user apparatus UE transmitted to the base station apparatus eNB in Step 504, it is known to the user apparatus if stored in a buffer, for example.

  In step 514, an error check is performed by comparing the error detection bit added by the base station apparatus eNB and the error detection bit derived by the user apparatus UE. Thereby, it can be correctly confirmed whether the precoding vector used for downlink communication is a default vector or a vector specified by PMI.

  In step 516, based on the correct precoding vector confirmed in step 514, channel compensation and demodulation of the downlink physical shared channel are performed with high accuracy.

  According to the present embodiment, when the base station apparatus eNB erroneously receives PMI from the user apparatus UE or when the user station UE erroneously receives notification content from the base station apparatus eNB, negative error detection is performed. The result is obtained on the user device. Thus, the user equipment may immediately discard information about the wrong precoding vector, or it may maintain a low likelihood and be ready for later packet synthesis. According to a present Example, the difference in recognition regarding the precoding vector between user apparatus UE and the base station apparatus eNB can be detected reliably.

<Configuration of base station device>
FIG. 10 is a functional block diagram of a base station apparatus according to an embodiment of the present invention. FIG. 10 shows an RF receiver unit 102, an uplink received signal demodulation unit 104, a data signal decoding unit 106, a control information decoding unit 108, a PMI correctness determination unit 110, a precoding vector selection unit 112, a CRC addition unit 114, a PMI Removal unit 116, channel coding unit 118, control information modulation unit 120, serial-parallel conversion unit 122, channel coding unit 124, data modulation unit 126, precoding vector multiplication unit 128, signal multiplexing unit 130, inverse Fourier transform unit 132 And the RF transmitter section 134 is depicted.

  The RF receiver unit 102 performs signal processing for converting each of the signals received by the plurality of antennas # 1 to #M into a baseband digital signal. The signal processing may include, for example, power amplification, band limitation, analog / digital conversion, and the like.

  The uplink received signal demodulation section 104 appropriately separates the uplink PUSCH, control channel (L1 / L2 control channel, etc.), reference signal, etc., transmitted and received on the uplink. Based on the reception state of the reference signal, channel estimation and reception signal quality measurement are also performed. The received signal quality may be measured by SINR, for example.

  The data signal decoding unit 106 separates a signal transmitted and received from each transmission antenna into one or more streams, and performs decoding for each stream. Decoding is performed corresponding to the encoding performed on the transmission side. In decoding, error correction is performed together with likelihood information.

  The control information decoding unit 108 decodes the control channel and extracts information included in the L1 / L2 control channel. In the present embodiment, the control information decoding unit 108 extracts the PMI and specifies the precoding vector notified from the user apparatus. When not only PMI but also a CRC error detection bit associated with PMI is received, error detection processing for PMI is performed and a CRC detection result is also output.

  The PMI correctness determination unit 110 confirms whether or not the PMI fed back from the user apparatus UE is incorrect. For example, when not only the PMI but also an error check bit for the PMI is received from the user apparatus, the correctness / incorrectness of the PMI may be confirmed using the error check bit. Also, the correctness / incorrectness of PMI may be confirmed based on the quality of reception quality (for example, reception SINR) of the uplink reference signal received from the user apparatus. The correctness / incorrectness of the PMI may be confirmed based on the likelihood obtained when decoding the uplink shared data channel. Furthermore, the likelihood obtained when decoding the received PMI itself may be used. In FIG. 10, the CRC detection result, the received SIR, and the likelihood information are all prepared, but one of them may be used alone, or two or more combinations are used. May be.

  The precoding vector selection unit 112 determines a precoding vector to be used for downlink communication based on the determination result from the PMI correctness determination unit 110 and a predetermined determination criterion. The predetermined criterion may be the number of streams, the number of antennas, the traffic amount, etc. necessary for downlink communication. For example, when the PMI is correctly received, the vector indicated by the PMI may be used as the precoding vector. If the PMI is wrong, it is not practical to use the precoding vector indicated by the PMI. In this case, a default vector determined in advance between the base station apparatus and the user apparatus may be used as the precoding vector. Furthermore, even if the PMI is correctly received, a vector different from that indicated by the PMI may be used as the precoding vector depending on the amount of traffic actually required for downlink communication. The precoding vector selection unit 112 displays a flag indicator indicating whether the precoding vector actually used for downlink communication is as desired by the user apparatus (X = 0) or default (X = 1). Prepare it and notify it to the CRC grant unit 114. When X = 0, the PMI is also notified to the CRC assigning unit 14.

  The CRC adding unit 114 performs a predetermined operation on the information portion including the control bit (control signal), the flag indicator, and the PMI as necessary, and derives a CRC error detection bit.

  The PMI removal unit 116 removes PMI if it is included in the calculation target in the CRC error detection bit derivation process, and controls the control bit, flag indicator, and CRC error detection regardless of the value of the flag indicator. An information part including a bit is prepared.

  Channel encoding section 118 performs channel encoding using the information part as an encoding unit.

  Control information modulation section 120 performs data modulation on the signal after channel coding.

  The serial / parallel converter 122 converts a serial transmission signal transmitted through the downlink physical shared channel into a plurality of parallel streams.

  The channel encoding unit 124 performs channel encoding for each stream.

  The data modulation unit 126 performs data modulation on the signal after channel coding.

  The precoding vector multiplication unit 128 weights each stream with a precoding vector. The precoding vector is determined by the precoding vector selection unit 112.

  The signal multiplexing unit 130 multiplexes the control channel, the physical shared channel, and other channels.

  The inverse Fourier transform unit 132 performs inverse fast Fourier transform on each multiplexed stream and performs OFDM modulation.

  The RF transmitter unit 134 performs processing for converting each stream into signals that are wirelessly transmitted from a plurality of transmission antennas. Such processing may include provision of guard intervals, digital-analog conversion, band limitation, power amplification, and the like.

<Configuration of user device>
FIG. 11 shows a functional block diagram of a user apparatus according to an embodiment of the present invention. FIG. 11 shows a data signal coding and modulation unit 202, a control signal coding and modulation unit 204, an uplink transmission signal generation unit 206, an RF transmitter unit 208, an RF receiver unit 210, a Fourier transform unit 212, precoding Vector selection unit 214, PMI accumulation unit 216, control information demodulation unit 218, channel decoding unit 220, PMI addition unit 222, CRC detection unit 224, precoding vector multiplication unit 230, signal separation unit 232, channel decoding unit 234, and parallel serial A conversion unit 236 is depicted.

  The data signal encoding / modulation unit 202 performs channel encoding and data modulation of the uplink physical shared channel.

  The control signal encoding / modulation unit 204 performs channel encoding and data modulation of the uplink L1 / L2 control channel.

  The uplink transmission signal generation unit 206 appropriately maps the control channel and the data channel, and prepares a transmission stream. For example, processes such as discrete Fourier transform, mapping in the frequency domain, and inverse Fourier transform are performed for each stream.

  The RF transmitter unit 208 performs processing to convert a baseband stream into a signal for wireless transmission from a plurality of transmission antennas. Such processing may include, for example, digital-to-analog conversion, bandwidth limitation, power amplification, and the like.

  In contrast to the RF transmitter unit 208, the RF receiver unit 210 performs a process of converting radio signals obtained from a plurality of reception antennas into a baseband stream. Such processing may include performing power amplification, band limitation, analog-digital conversion, and the like for each stream.

  The Fourier transform unit 212 performs fast Fourier transform on each stream, and performs demodulation using the OFDM method.

The precoding vector selection unit 214 determines a precoding vector suitable for the downlink based on the reception status of the reference signal in the received signal, and outputs a PMI indicating it. Typically, the precoding vector is any one of a predetermined number of vectors (U ₁ , U ₂ ,..., U _P ) stored in advance in the code book. Therefore, PMI designates any one (Ui) of a predetermined number of vectors (U ₁ , U ₂ ,..., U _P ). More generally, the precoding vector is not an alternative option and may be adaptively adjusted to any suitable vector.

  The PMI accumulation unit 216 holds the PMI determined by the precoding vector selection unit 214 for a certain period.

  The control information demodulator 218 demodulates the control signal in the received signal.

  The channel decoding unit 220 performs channel decoding using an information part including control information, a flag indicator, and a CRC error detection bit as one decoding unit. The unit of channel decoding is performed in accordance with the unit of encoding performed on the transmission side. As a result of decoding, the value X of the flag indicator is determined.

  When the value of the flag indicator is a predetermined value (in the above example, X = 0), the PMI adding unit 222 extracts the PMI transmitted to the base station device from the PMI storage unit 216 in the past, Prepare for derivation of detection bits. In this case, a CRC error detection bit is derived by performing a predetermined operation on the information portion including the control bit, the flag indicator value X = 0, and the prepared PMI. If the value of the flag indicator is another predetermined value (in the above example, X = 1), no PMI is prepared and preparation for derivation of error detection bits is performed. In this case, a CRC error detection bit is derived by performing a predetermined operation on the information portion including the control bit and the flag indicator value X = 1.

  The CRC detection unit 224 compares the error detection bit prepared in the base station device with the error detection bit prepared in the user device (PMI adding unit 222), thereby confirming whether the notification from the base station device is correct. To do. If no error is detected, the subsequent processing proceeds according to the notification from the base station apparatus. When an error is detected, the notification content from the base station apparatus may be discarded or may be retained in preparation for later packet combining.

  The precoding vector multiplication unit 230 weights the received downlink physical shared channel with a precoding vector. The precoding vector may be one that the user apparatus has previously reported to the base station apparatus by feedback, or may be a vector determined by default. What it is depends on the detection result in the CRC detection unit 224.

  The signal separation unit 232 separates the received signal into each stream using any signal separation algorithm known in the art.

  The channel decoding unit 234 performs channel decoding of the downlink physical shared channel.

  The parallel-serial conversion unit 236 converts the parallel stream into a serial signal sequence, and the converted signal is output as a signal restored to the signal before being transmitted from the base station apparatus.

  Although the present invention has been described above with reference to specific embodiments, each embodiment is merely illustrative, and those skilled in the art will appreciate various variations, modifications, alternatives, substitutions, and the like. Let's go. Although specific numerical examples have been described in order to facilitate understanding of the invention, these numerical values are merely examples and any appropriate values may be used unless otherwise specified. For convenience of explanation, an apparatus according to an embodiment of the present invention has been described using a functional block diagram, but such an apparatus may be realized by hardware, software, or a combination thereof. The present invention is not limited to the above embodiments, and various modifications, modifications, alternatives, substitutions, and the like are included in the present invention without departing from the spirit of the present invention.

  The means taught by the examples are listed below as an example.

(Section 1)
A base station apparatus used in a MIMO mobile communication system that performs precoding,
Receiving means for receiving a precoding matrix indicator (PMI) indicative of a specific precoding vector from the user equipment;
Means for determining a value of a flag indicator indicating whether or not to use the precoding vector specified by the PMI for downlink communication;
Control signal generating means for generating a downlink control signal including at least the flag indicator;
Means for transmitting a signal including the downlink control signal on the downlink;
A base station apparatus.

(Section 2)
The control signal generation means channel encodes an information part including control information, a flag indicator and error detection information as a coding unit,
The error detection information is derived by performing a predetermined calculation on a calculation target including at least the control information and the flag indicator,
The base station apparatus according to claim 1, wherein whether or not the PMI is included in the calculation target is determined according to a value of the flag indicator.

(Section 3)
When the precoding vector specified by the PMI is not used for downlink communication, a default vector known by both the base station apparatus and the user apparatus is used as a precoding vector in downlink communication. 3. A base station apparatus according to item 2.

(Section 4)
The base station apparatus according to any one of first to third, wherein the flag indicator is expressed by 1 bit.

(Section 5)
The base station apparatus according to any one of the first to third aspects, wherein the flag indicator is expressed by multiple bits so as to designate any of a plurality of default vectors.

(Section 6)
When the flag indicator is a predetermined value, the control signal generation means uses the information part including the information in which the PMI is convolved with the control information, the flag indicator, and the error detection information as a channel as a coding unit. 6. The base station apparatus according to any one of first to fifth encoding.

(Section 7)
The base station apparatus according to claim 1, further comprising means for performing error detection on the PMI.

(Section 8)
The receiving means receives the PMI and error detection information for the PMI, and compares the error detection information calculated by the user apparatus with the error detection information calculated by the base station apparatus, The base station apparatus according to claim 7, wherein the error detection is performed.

(Section 9)
The base station apparatus according to claim 7, wherein the means for performing error detection performs the error detection in accordance with reception quality of an uplink reference signal received from the user apparatus.

(Section 10)
The base station apparatus according to claim 7, wherein the means for performing error detection performs the error detection based on likelihood information of the shared data channel received from the user apparatus.

(Section 11)
A method used in a MIMO base station apparatus that performs precoding,
Receiving from a user equipment a precoding matrix indicator (PMI) indicating a particular precoding vector;
Determining a value of a flag indicator indicating whether or not to use the precoding vector specified by the PMI for downlink communication;
A control signal generation step of creating a downlink control signal including at least the flag indicator;
Transmitting a signal including the downlink control signal on the downlink;
Having a method.

(Section 12)
A user apparatus used in a MIMO mobile communication system that performs precoding,
Means for identifying a precoding vector to be used in the downlink;
Means for transmitting a precoding matrix indicator (PMI) indicating the identified precoding vector to the base station device;
Means for receiving and decoding a signal including a flag indicator indicating whether the precoding vector specified by the PMI is used for downlink communication, control information, and error detection information from the base station apparatus; ,
Means for performing a predetermined calculation and deriving error detection information for a calculation target including at least the control information and the flag indicator;
The error detection information prepared by the base station apparatus is compared with the error detection information prepared by the user apparatus, and it is determined whether or not the precoding vector specified by the PMI is used for downlink communication. Means,
And whether or not the PMI is included in the calculation target is determined according to the value of the flag indicator.

(Section 13)
When the precoding vector specified by the PMI is not used for downlink communication, a default vector known by both the base station apparatus and the user apparatus is used as a precoding vector in downlink communication. A user device according to item.

(Section 14)
The user apparatus according to the twelfth or thirteenth aspect, wherein the flag indicator is expressed by 1 bit.

(Section 15)
The user apparatus according to the twelfth or thirteenth aspect, wherein the flag indicator is expressed by multiple bits so as to designate any one of a plurality of default vectors.

(Section 16)
16. The user apparatus according to any one of twelfth to fifteenth aspects, wherein a PMI convoluted with the control information is extracted when the flag indicator is a predetermined value.

(Section 17)
The user apparatus according to any one of twelfth to sixteenth aspects, wherein the PMI and error detection information derived by performing a predetermined calculation on the PMI are transmitted to the base station apparatus.

(Section 18)
A method used in MIMO user equipment for precoding,
Identifying a precoding vector to be used in the downlink;
Transmitting a precoding matrix indicator (PMI) indicating the identified precoding vector to the base station device;
Receiving a signal including a flag indicator indicating whether the precoding vector specified by the PMI is used for downlink communication, control information, and error detection information from the base station apparatus, and decoding the signal; ,
For a calculation target including at least the control information and the flag indicator, performing a predetermined calculation and deriving error detection information;
The error detection information prepared by the base station apparatus is compared with the error detection information prepared by the user apparatus, and it is determined whether or not the precoding vector specified by the PMI is used for downlink communication. Steps,
And determining whether or not the precoding vector specified by the PMI is included in the operation target according to the value of the flag indicator.

102 RF receiver unit 104 uplink received signal demodulation unit 106 data signal decoding unit 108 control information decoding unit 110 PMI correctness determination unit 112 precoding vector selection unit 114 CRC addition unit 116 PMI removal unit 118 channel encoding unit 120 control information modulation Unit 122 serial-parallel conversion unit 124 channel coding unit 126 data modulation unit 128 precoding vector multiplication unit 130 signal multiplexing unit 132 inverse Fourier transform unit 134 RF transmitter unit 202 data signal coding and modulation unit 204 control signal coding and modulation Unit 206 uplink transmission signal generation unit 208 RF transmitter unit 210 RF receiver unit 212 Fourier transform unit 214 precoding vector selection unit 216 PMI accumulation unit 218 control information demodulation unit 220 channel decoding unit 222 PMI addition unit 224 CRC detection unit 230 The Recoding vector multiplication unit 232 Signal separation unit 234 Channel decoding unit 236 Parallel-serial conversion unit

Claims (5)

A base station apparatus used in a MIMO mobile communication system that performs precoding,
A receiver for receiving a precoding matrix indicator (PMI) indicating a specific precoding vector from the user equipment;
A determination unit that determines a value of a flag indicator indicating whether or not to use the precoding vector specified by the PMI for downlink communication;
A control signal generation unit for generating a downlink control signal including at least the flag indicator;
A transmission unit for transmitting a signal including the downlink control signal in the downlink,
When the precoding vector specified by the PMI is not used for downlink communication, a default vector known by both the base station apparatus and the user apparatus is used as a precoding vector for downlink communication,
The flag indicator is represented by multiple bits, and the flag indicator specifies any of a plurality of default vectors,
The control signal generation unit channel-encodes an information part including control information, a flag indicator, and error detection information as an encoding unit,
The base station apparatus, wherein the error detection information is derived by performing a predetermined calculation on a calculation target including at least the control information and the flag indicator. A base station apparatus used in a MIMO mobile communication system that performs precoding,
A precoding matrix indicator (PMI) indicating a specific precoding vector, and a flag indicator indicating whether or not to use the precoding vector specified by the PMI received from the user equipment for downlink communication A control signal generator for creating a downlink control signal including at least,
A transmission unit for transmitting a signal including the downlink control signal in the downlink,
When the precoding vector specified by the PMI is not used for downlink communication, a default vector known by both the base station apparatus and the user apparatus is used as a precoding vector for downlink communication,
The flag indicator is represented by multiple bits, and the flag indicator specifies any of a plurality of default vectors,
The control signal generation unit channel-encodes an information part including control information, a flag indicator, and error detection information as an encoding unit,
The base station apparatus, wherein the error detection information is derived by performing a predetermined calculation on a calculation target including at least the control information and the flag indicator. A transmission method used in a base station apparatus of a MIMO mobile communication system that performs precoding,
Receiving from a user equipment a precoding matrix indicator (PMI) indicative of a specific precoding vector;
Determining a value of a flag indicator indicating whether or not to use the precoding vector specified by the PMI for downlink communication;
Creating a downlink control signal including at least the flag indicator;
Transmitting a signal including the downlink control signal in the downlink,
When the precoding vector specified by the PMI is not used for downlink communication, a default vector known by both the base station apparatus and the user apparatus is used as a precoding vector for downlink communication,
The flag indicator is represented by multiple bits, and the flag indicator specifies any of a plurality of default vectors,
The step of creating the downlink control signal, channel coding the information portion including control information, flag indicator and error detection information as a coding unit,
The transmission method, wherein the error detection information is derived by performing a predetermined calculation on a calculation target including at least the control information and the flag indicator. A transmission method used in a base station apparatus of a MIMO mobile communication system that performs precoding,
A precoding matrix indicator (PMI) indicating a specific precoding vector, and a flag indicator indicating whether or not to use the precoding vector specified by the PMI received from the user equipment for downlink communication Creating a downlink control signal including at least;
Transmitting a signal including the downlink control signal in the downlink,
When the precoding vector specified by the PMI is not used for downlink communication, a default vector known by both the base station apparatus and the user apparatus is used as a precoding vector for downlink communication,
The flag indicator is represented by multiple bits, and the flag indicator specifies any of a plurality of default vectors,
The step of creating the downlink control signal, channel coding the information portion including control information, flag indicator and error detection information as a coding unit,
The transmission method, wherein the error detection information is derived by performing a predetermined calculation on a calculation target including at least the control information and the flag indicator. A MIMO mobile communication system that performs precoding,
A base station device that transmits signals in the downlink;
A user apparatus that receives a signal from the base station apparatus,
The base station device
A precoding matrix indicator (PMI) indicating a specific precoding vector, and a flag indicator indicating whether or not to use the precoding vector specified by the PMI received from the user equipment for downlink communication A control signal generator for creating a downlink control signal including at least,
A transmission unit for transmitting a signal including the downlink control signal in the downlink,
When the precoding vector specified by the PMI is not used for downlink communication, a default vector known by both the base station apparatus and the user apparatus is used as a precoding vector for downlink communication,
The flag indicator is represented by multiple bits, and the flag indicator specifies any of a plurality of default vectors,
The control signal generation unit channel-encodes an information part including control information, a flag indicator, and error detection information as an encoding unit,
The mobile communication system, wherein the error detection information is derived by performing a predetermined calculation on a calculation target including at least the control information and the flag indicator.

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