JP2012222723A - Radio communication system, mobile station device, and base station device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the overhead of control information transmitted from a base station device to a mobile station device while extending the length of a spread code of a demodulation reference signal applied to each SC-FDMA symbol.SOLUTION: The sign of a demodulation reference signal is reversed depending on an index specifying the cyclic shift and orthogonal cover code of the demodulation reference signal reported from a base station device to a mobile station device, and whether the index of a sub-frame transmitting the demodulation reference signal is odd or even.

Description

  The present invention relates to a communication technique, and more particularly to a technique for multiplexing an uplink demodulation reference signal, a transmission technique, and a reception technique in a base station apparatus for transmitting and receiving and a mobile communication system having a mobile station apparatus.

  Currently, the 3GPP (3rd Generation Partnership Project) is studying LTE Advanced (hereinafter referred to as “LTE-A”) to further increase the communication speed. In the uplink of LTE, a single carrier frequency division multiple access (SC-FDMA) system having excellent PAPR (Peak to Average Power Ratio) characteristics is adopted. Spatial multiplexing by MIMO (Multiple Input Multiple Output) can be used in LTE uplink, especially MU-MIMO (Multi-User MIMO) in which multiple mobile station devices perform spatial multiplexing using the same frequency and time resources Can be used.

  Channel of each antenna port (defined by each physical antenna or combination of two or more physical antennas) in transmission and reception to reduce degradation of MIMO communication characteristics due to noise and interference (also called propagation path) Can be calculated with high accuracy. In LTE, frequency division is performed by code multiplexing by assigning a sequence generated by applying a different cyclic shift to an uplink demodulation reference signal (UL DMRS) created based on a Zadoff-Chu sequence to each antenna port. Realizes orthogonality in the area. Furthermore, since UL DMRS has two sequences (ie, 2SC-FDMA symbols) in one subframe, LTE-A applies Walsh sequences to this sequence in the time domain, and achieves orthogonality in the time domain. (Non-Patent Document 1). The spreading sequence applied to the time domain is called an orthogonal cover code or OCC (Orthogonal Cover Code).

  In UL DMRS, the condition for achieving orthogonality by cyclic shift is limited to the case where assigned frequency regions are completely the same. For this reason, when implementing MU-MIMO in a mobile station apparatus to which different frequency regions are allocated, it is necessary to realize orthogonality using only OCC. Furthermore, as in Non-Patent Document 2, it has been proposed to use IFDM (Interleaved Frequency Domain Multiplexing) for DMRS.

R1-091772, Nokia Siemens Networks, Nokia, “Reference Signal structure for LTE-Advanced UL SU-MIMO” 3GPP TSG RAN WG1 Meeting # 57, May, 2009 R1-092801, NTT DOCOMO, “UL RS Enhancement for LTE-Advanced”, 3GPP TSG RAN WG1 # 57bis, June, 2009

  However, since the CSS sequence length can be secured only to the number of UL DMRS, there is a restriction on the number of multiplexing that can be realized by OCC in one subframe. On the other hand, IFDM / IFDMA has a problem in that orthogonality cannot be established if the RPF (Repetition Factor) is different, so that complete orthogonality in UL DMRS cannot be realized with an LTE mobile station apparatus that does not support IFDMA.

  The present invention has been made in view of such circumstances, and in a mobile communication system having a base station apparatus and a mobile station apparatus for transmission and reception, the upper limit of the number of code multiplexes while maintaining UL DMRS backward compatibility. An object of the present invention is to provide a radio communication system, a mobile station apparatus, a base station apparatus, and a communication method for extending a value.

  (1) In order to achieve the above object, the present invention takes the following measures. That is, a mobile station apparatus that transmits a data signal and a demodulation reference signal and a base station apparatus that receives the data signal, and a resource allocation for transmitting the data signal and the demodulation reference signal is a specific time unit. The wireless communication system is performed for each subframe, and the demodulation reference signal is generated by applying a cyclic shift to the root sequence to generate a transmission sequence of one SC-FDMA symbol, and at the same time, A control including a transmission code generated by spreading the transmission sequence into a plurality of SC-FDMA symbols by a cover code, and information including information on the resource allocation, the cyclic shift, and instruction information indicating the sequence of the orthogonal cover code The wireless communication system in which information is instructed from the base station apparatus to the mobile station apparatus, The reference signal for use is generated by multiplying the sequence to which the cyclic shift and the orthogonal cover code are applied by a common weight to the SC-FDMA symbol, and the common weight to the SC-FDMA symbol is And determining according to the type of subframe to be transmitted and the instruction information.

  In this way, even when UL DMRS orthogonality transmitted from each mobile station apparatus does not hold between one subframe, or when the cross-correlation is high and the influence of the interference causes a large quality degradation, The impact can be reduced by using the received UL DMRS.

  (2) Further, in the radio communication system of the present invention, a weight common to the SC-FDMA symbol is +1 or 1.

  Thus, by using +1 and −1 for the weight, complete orthogonality can be realized and the weight multiplication process can be simplified.

  (3) In the wireless communication system of the present invention, the type of the subframe is determined depending on whether an index number assigned to the subframe is an even number or an odd number.

  In this way, the processing can be simplified by reversing the sign between successive subframes.

  (4) Further, the mobile station apparatus of the present invention is a mobile station apparatus that transmits a data signal and a demodulation reference signal to a base station apparatus, and includes a resource for transmitting the data signal and the demodulation reference signal. Allocation is performed for each subframe which is a specific time unit, and the demodulation reference signal generates a transmission sequence of one SC-FDMA symbol by applying a cyclic shift to the root sequence. The transmission sequence is generated by spreading to a plurality of SC-FDMA symbols by a null cover code, and information on the resource allocation transmitted from the base station apparatus, the cyclic shift, and the orthogonal cover code A mobile station apparatus for receiving control information including instruction information for instructing a sequence, wherein the demodulation reference signal is the cyclic shift and A sequence to which the above-mentioned ortholog cover code is applied is generated by multiplying the SC-FDMA symbol by a common weight, and the common weight for the SC-FDMA symbol is the type of subframe to be transmitted and the indication It is determined according to information.

  In this way, even when UL DMRS orthogonality transmitted from each mobile station apparatus does not hold between one subframe, or when the cross-correlation is high and the influence of the interference causes a large quality degradation, The impact can be reduced by using the received UL DMRS.

  (5) Further, in the mobile station apparatus of the present invention, a weight common to the SC-FDMA symbol is +1 or 1.

  Thus, by using +1 and −1 for the weight, complete orthogonality can be realized and the weight multiplication process can be simplified.

  (6) In the mobile station apparatus of the present invention, the type of the subframe is determined depending on whether an index number assigned to the subframe is an even number or an odd number.

  In this way, the processing can be simplified by reversing the sign between successive subframes.

  (7) Further, the base station apparatus of the present invention receives a mobile station apparatus that transmits a data signal transmitted from the mobile station apparatus and a demodulation reference signal, and performs propagation path estimation using the demodulation reference signal. A base station apparatus that performs allocation of resources for transmitting the data signal and the demodulation reference signal for each subframe that is a specific time unit, and the demodulation reference signal is a route A transmission sequence of one SC-FDMA symbol is generated by applying a cyclic shift to the sequence, and at the same time, the transmission sequence is generated by spreading the transmission sequence into a plurality of SC-FDMA symbols using an orthogonal cover code. Control information including information related to the resource allocation, instruction information indicating the cyclic shift, and the sequence of the orthogonal cover code. The demodulation reference signal is obtained by multiplying a sequence to which the cyclic shift and the orthogonal cover code are applied by a common weight to an SC-FDMA symbol. The generated common weight for the SC-FDMA symbol is selected as +1 or 1 according to the type of subframe to be transmitted and the indication information, and the type of subframe is determined by the index number assigned to the subframe. Characterized by whether it is even or odd

  In this way, even when UL DMRS orthogonality transmitted from each mobile station apparatus does not hold between one subframe, or when the cross-correlation is high and the influence of the interference causes a large quality degradation, The impact can be reduced by using the received UL DMRS. Further, by using +1 and −1 for the weight in this way, complete orthogonality can be realized and the weight multiplication process can be simplified.

  (8) In the base station apparatus of the present invention, the number of subframes used for channel estimation is switched according to the number of mobile station apparatuses multiplexed by MU-MIMO and the weight.

  In this way, by changing the number of subframes used for channel estimation, the mobile station device speed is high, and it is not possible to follow fluctuations between subframes, or different frequency resources are allocated in two consecutive subframes. If the mobile station apparatus speed is sufficiently low or the same frequency resource is allocated in two consecutive subframes, channel estimation is performed in two subframes. Such optimal reception can be realized.

  According to the present invention, UL DMRS backward compatibility is maintained in a mobile communication system having a base station apparatus and a mobile station apparatus for transmission and reception in a mobile communication system having a base station apparatus and a mobile station apparatus for transmission and reception. Thus, it is possible to provide a radio communication system, a mobile station apparatus, a base station apparatus, and a communication method that extend the upper limit value of the number of code multiplexes.

It is a functional block diagram which shows the example of 1 structure of the transmitter which the mobile station apparatus of this invention comprises. It is a functional block diagram which shows the example of 1 structure of the receiver which the base station apparatus of this invention comprises. It is a figure showing arrangement | positioning of UL DMRS and allocation of OCC in this invention. It is a figure showing allocation of OCC between subframes in the present invention. 4 is a sequence chart showing allocation of PUSCH resources and OCCs in the present invention. It is a figure showing arrangement | positioning of UL DMRS in LTE and LTE-A, and allocation of OCC.

  Currently, the 3GPP (3rd Generation Partnership Project) is studying LTE Advanced (hereinafter referred to as “LTE-A”) to further increase the communication speed. In the uplink of LTE, a single carrier frequency division multiple access (SC-FDMA) system having excellent PAPR (Peak to Average Power Ratio) characteristics is adopted. Spatial multiplexing by MIMO (Multiple Input Multiple Output) can be used in LTE uplink, especially MU-MIMO (Multi-User MIMO) in which multiple mobile station devices perform spatial multiplexing using the same frequency and time resources Can be used.

  In order to reduce degradation of MIMO communication quality due to noise and interference, the propagation path (also called channel) of each antenna port (defined by each physical antenna or the combination of two or more physical antennas) in transmission and reception It is desirable to be able to calculate with high accuracy. In LTE, a sequence generated by applying a different cyclic shift to a sequence created based on the Zadoff-Chu sequence (hereinafter referred to as a root sequence) (this is a reference signal for uplink demodulation (UL DMRS: Uplink Demodulation). The orthogonality in the frequency domain is realized by code multiplexing by assigning a reference signal) to each antenna port. Furthermore, since UL DMRS has two sequences (that is, 2SC-FDMA symbols) in one subframe, LTE-A applies a Walsh sequence to this sequence (transmission sequence) in the time domain, and also in the time domain. Orthogonality can be realized. This spreading sequence applied to the time domain is called OCC (Orthogonal Cover Code).

  In UL DMRS, the condition for achieving orthogonality by cyclic shift is limited to the case where assigned frequency regions are completely the same. For this reason, when implementing MU-MIMO in a mobile station apparatus to which different frequency regions are allocated, it is necessary to realize orthogonality using only OCC.

  FIG. 6 is a diagram showing a time / frequency resource configuration, that is, a subframe configuration in LTE and LTE-A. However, FIG. 6 shows only the uplink shared channel (Physical Uplink Shared Channel) band mainly used for data transmission, and the frequency band of the channel (PUCCH: Physical Uplink Control Channel) that transmits only control information. Is omitted. The vertical axis in FIG. 6 is the frequency axis, and one block represents a subcarrier. In LTE, 12 consecutive subcarriers are collectively used as a resource allocation unit, which is called a resource block (RB). On the other hand, the horizontal axis is a time axis, in which the frequency domain is converted to the time domain, and the time is divided by a unit that gives a cyclic prefix. This is referred to as a 1SC-FDMA symbol. In LTE, one slot is composed of consecutive 7SC-FDMA symbols, and two sub-frames are composed of two slots. One subcarrier in one SC-FDMA symbol is called a resource element (RE). A subframe is a minimum division unit of resource allocation in the time domain in LTE and LTE-A, and is mainly allocated using PDCCH (Physical Downlink Control Channel), from the base station apparatus to the mobile station apparatus for each subframe. Information is notified.

  The location where UL DMRS is arranged in LTE and LTE-A differs depending on the setting of the base station apparatus, but as an example, it is arranged in the 3rd and 10th SC-FDMA symbols of each subframe as shown in FIG. Is done. Here, UL DMRSs arranged in SC-FDMA symbols as described above are referred to as first UL DMRS and second UL DMRS, respectively. In LTE and LTE-A, the base station apparatus can be configured to use the same or different route sequences in the first and second UL DMRSs, but in the following, it is assumed that the same route sequences are applied. In this case, the OCC sequence applied to UL DMRS, that is, information on whether to generate UL DMRS using W1 = + 1, W2 = + 1 or W1 = + 1, W2 = -1 is the base station. Notification from the apparatus to the mobile station apparatus. The mobile station apparatus generates a UL DMRS sequence based on the notified OCC sequence, that is, multiplies W1 and W2 for the entire sequence obtained by applying a cyclic shift to the root sequence.

  In the case of applying MU-MIMO, it is desirable to accurately calculate a channel for each mobile station apparatus, and therefore it is desirable that a fully orthogonal UL DMRS is assigned to each. If OCC is not applied, it is necessary to rely only on cyclic shifts and the frequency domain assignments must be the same in order to achieve UL DMRS orthogonality transmitted from each mobile station device. . On the other hand, when OCC is available, orthogonality can be realized by assigning different OCCs regardless of cyclic shift, root sequence, and frequency domain assignment. As a result, MU-MIMO can be performed between mobile station apparatuses having different frequency regions to be allocated, and further improvement of throughput characteristics can be realized. In LTE-A, the OCC sequence length is 2, that is, time-domain code spreading can be applied only within one subframe. In the present invention, the frequency position of the RB to which PUSCH is allocated is the same between consecutive subframes. By extending the application range of this OCC to these consecutive subframes, the sequence length can be further expanded, and as a result, it is possible to realize MU-MIMO with different frequency regions over three mobile station devices. it can. Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
The mobile communication system according to the first embodiment of the present invention includes mobile station apparatuses A1 and A2 and a base station apparatus B. Here, this embodiment describes means effective when three or four mobile station apparatuses having different frequency regions to which PUSCH is assigned perform MU-MIMO. In this sequence chart, the procedure for two mobile station apparatuses is shown for simplicity, but the generality is not lost even when this is extended to MU-MIMO with three or four mobile station apparatuses.

  FIG. 1 is a functional block diagram showing a configuration example of a transmitter in mobile station apparatuses A1 and A2 of the present invention. The mobile station apparatuses A1 and A2 of the present invention include a code generation unit 101, a scrambling unit 102, a modulation unit 103, a layer mapping unit 104, a DFT / frequency mapping unit 105, a UL DMRS sequence generation unit 106, and a data / UL DMRS multiplexing unit. 107, and a precoding unit 108 is provided. FIG. 2 is a functional block diagram showing a configuration example of the receiver in the base station apparatus B of the present invention. The base station apparatus B of the present invention includes a block for demodulating received signals in two consecutive subframes k and k + 1 in parallel (a demodulation processing block 210 and a demodulation processing block 211, respectively) and a despreading / channel estimation unit 202. It comprises. The demodulation processing block 210 and the demodulation processing block 211 are configured by a data / DMRS separation unit 201, an equalization unit 203, a space separation unit 204, an IDFT unit 205, and a data decoding unit 206, respectively.

  The mobile station apparatuses A1 and A2 generate a plurality of transport blocks according to the control information transmitted from the base station apparatus B. A transport block is a bit string passed from an upper layer, and is data corresponding to a channel called UL-SCH (Uplink Shared Channel) in the MAC layer. Further, the transport block corresponds to a processing unit of HARQ (Hybrid Automatic Repeat Request), and is determined by the number of spatial multiplexing layers by SU-MIMO. Each transport block is input to the code generation unit 101, divided into coding units called code blocks, CRC (Cyclic Redundancy Check) assignment, channel coding with turbo codes, bit thinning or repetition according to resources Processing (rate matching) and processing such as concatenating generated bits for all code blocks are performed.

  The output of the code generation unit 101 is input to the scrambling unit 102, and scrambling according to the transmission destination base station apparatus and the transmission base station apparatus is applied to each transport block.

  The output bit string of scrambling section 102 is input to modulation section 103 and converted into modulation symbols such as QPSK, 16QAM, and 64QAM.

  The output modulation symbol of modulation section 103 is input to layer mapping section 104, and the data of each transport block is mapped to each layer. Here, the layer corresponds to the spatial multiplexing number when SU-MIMO is applied. Specifically, when the number of transport blocks is smaller than the number of layers, serial / parallel conversion is applied to each transport block and mapped to a plurality of layers.

  The signal of each layer output from the layer mapping unit 104 is input to the DFT / frequency mapping unit 105. The DFT / frequency mapping unit 105 converts the input signal into a frequency domain signal by DFT, maps the signal to the frequency resource allocated to the mobile station apparatus, and outputs it.

  On the other hand, UL DMRS for demodulating information of each transport block is generated by UL DMRS sequence generation section 106. The UL DMRS sequence generation unit 106 is provided with route sequence, cyclic shift, and OCC sequence information from an upper layer. These pieces of information are supplied from the base station apparatus B, and when uplink data transmission is instructed, these pieces of information are known in the mobile station apparatuses A1 and A2. In OC, OCC is not defined, that is, only [W1, W2] = [+ 1, +1] is applied, and in LTE-A, [W1, W2] = indicated by the layer 1 control signal of the base station apparatus Either [+ 1, + 1] or [W1, W2] = [+ 1, -1] applies. In the present embodiment, as shown in FIG. 3, the OCC sequence W ′ determined depending on the subframe is multiplied by the first and second UL DMRSs, that is, the OCC sequence as a whole is expressed as W′x [W1, W2 ] = [W'xW1, W'xW2]. Here, like LTE-A, [W1, W2] is [+1, -1] or [-1, -1]. Hereinafter, W ′ is referred to as inter-subframe OCC.

  A specific method for designating W ′ will be described. First, whether or not to use the OCC between subframes is determined by the base station apparatus, and is set for each mobile station apparatus. The mobile station apparatus that is set not to use the inter-subframe OCC is always W ′ = + 1, and the operation at this time generates the same UL DMRS sequence as LTE-A. A mobile station apparatus set to use OCC between subframes determines W ′ according to a control signal notified from the base station apparatus for each subframe. Values that can be used as W 'are, for example, +1 and -1.

  The control signal notified from the base station apparatus for each subframe is specifically defined as the table shown in FIG. In LTE-A, the cyclic shift of UL DMRS and the OCC applied to the first and second UL DMRS in one subframe (hereinafter referred to as the intra-subframe OCC) are 3-bit information ( (Instruction information indicating a sequence of a cyclic shift and an orthogonal cover code). For example, if the index M indicated by the layer 1 control signal is 001 and PUSCH transmission in 2-layer MIMO is instructed, a cyclic shift 0 and an intra-frame OCC [W1, UL DMRS is generated using W2] = [+ 1, + 1], and cyclic shift 1 and intra-frame OCC [W1, W2] = [+ 1, + 1] are applied to the layer of λ = 1 Shown to use. W 'is defined as an extension of this table and is uniquely determined by M and subframe index n. Here, n is defined to be, for example, 0 when the subframe index is odd, and 1 when the subframe index is even, and vice versa. Specifically, when M is 001 and n is 1, W ′ = − 1 is selected.

  The UL DMRS signal of each layer generated by the UL DMRS sequence generation unit 106 is input to the layer mapping unit 104, arranged in the MIMO transmission layer, and input to the data / UL DMRS multiplexing unit 107. The data / UL DMRS multiplexer 107 also receives an output signal of the DFT / frequency mapping unit 105 corresponding to the data, and the data and UL DMRS are mapped to each SC-FDMA symbol by TDM as shown in FIG. This output is input to the precoding unit 108 and is mapped to each antenna port by multiplying the information of each layer by the precoder. The output of precoding section 108 is transmitted to the base station apparatus after being subjected to processing such as A / D conversion and up-conversion.

  Next, the operation of the receiver of the base station apparatus B shown in the figure will be described. When an uplink signal transmitted from the mobile station apparatus A1 or A2 is received, the received signal is converted into a frequency domain signal by FFT after processing such as down-conversion. The received signal received in the subframe k is input to the demodulation processing block 210 and is divided into the received antenna data signal and the UL DMRS by the data / DMRS demultiplexing unit 201. Similarly, the received signal received in the subframe k + 1 is also input to the demodulation processing block 211, and is divided into a data signal and UL DMRS by the data / DMRS separation unit 201. Each UL DMRS signal is input to despreading / channel estimation section 202.

  The signal input to the despreading / channel estimation unit 202 is multiplexed using the cyclic shift, intra-subframe OCC, or inter-subframe OCC, or all of the signals for the mobile station apparatus and the transmission antenna port. The received signal and the route sequence, cyclic shift, and OCC sequence information held in the base station apparatus. Using these, the received signal is despread and separated into signals for each mobile station apparatus and transmitting antenna port, and noise filtering is performed to estimate and output the channel between transmission and reception.

  The channel information that is the output of the despreading / channel estimation unit 202 is input to the equalization unit 203 in the demodulation processing blocks 210 and 211. Since the subsequent processing in the demodulation processing block is common to the demodulation processing blocks 210 and 211, only the demodulation processing block 210 will be described for simplicity. A data signal that is an output of the data / DMRS separation unit 201 is also input to the equalization unit 203 and is equalized using the channel information. The output of the equalization unit 203 is input to the space separation unit 204, and separates signals transmitted from a plurality of mobile station devices spatially multiplexed by MU-MIMO and signals spatially multiplexed by SU-MIMO. The output of the space separation unit 204 is input to the IDFT unit 205 and converted into a time domain signal. This signal is input to the data decoding unit 206, and signal detection, LLR (Log-Likelihood Ratio) calculation, descrambling, decoding processing, and the like are performed for each transport block unit of each mobile station apparatus.

  Next, the base station apparatus B sets the use of the OCC setting for the mobile station apparatuses A1 and A2, applies the OCC to the UL DMRS and transmits, and further shows the procedure for the receiver demodulation process. The sequence chart is shown in FIG. Note that mobile station apparatuses A1 and A2 do not apply SU-MIMO and rank 1 communication is performed.

  First, base station apparatus B sets for each mobile station apparatus whether or not to use inter-subframe OCC for mobile station apparatuses A1 and A2 (511 and 512, respectively). Here, it is assumed that “use” is set for both mobile station apparatuses A1 and A2, but only one mobile station apparatus may be set. After this setting is completed, base station apparatus B transmits an instruction signal (uplink grant) for transmitting PUSCH in subframe k to mobile station apparatuses A1 and A2. The uplink grant transmitted to the mobile station apparatus A1 is instructed by the allocated frequency domain, that is, RB information (here, the third to fifth RBs are allocated) and the layer 1 control signal shown in FIG. Index M (here, 000) is included (502). Further, the uplink grant transmitted to the mobile station device A2 includes information on allocated RBs (here, the second to fourth RBs are allocated) and an index M (here, 111) (512). ).

  Further, base station apparatus B transmits an instruction signal (uplink grant) for transmitting PUSCH in subframe k + 1 to mobile station apparatuses A1 and A2. The uplink grant transmitted to the mobile station apparatus A1 is instructed by the allocated frequency domain, that is, RB information (here, the third to fifth RBs are allocated) and the layer 1 control signal shown in FIG. Index M (here, 000) is included (503). Further, the uplink grant transmitted to the mobile station apparatus A2 includes information on allocated RBs (here, the second to fourth RBs are allocated) and an index M (here, 111) (513). ).

  In subframe k, mobile station apparatus A1 transmits PUSCH and UL DMRS in the third to fifth RBs according to the uplink grant received in subframe k-4 (504). If subframe k matches n = 0 in FIG. 4, since index M = 000 is specified in this uplink grant, [W1, W2] = [+ 1, +1] and W ′ = + 1 is used to generate the first and second UL DMRS. In subframe k, mobile station apparatus A2 transmits PUSCH and UL DMRS in the second to fourth RBs according to the uplink grant received in subframe k-4 (514). Since the index M = 111 is specified in this uplink grant, the first and second UL DMRSs are generated using [W1, W2] = [+ 1, +1] and W '= + 1. The

  In subframe k + 1, mobile station apparatus A1 transmits PUSCH and UL DMRS in the third to fifth RBs according to the uplink grant received in subframe k-3 (505). If subframe k + 1 matches n = 1 in FIG. 4, since index M = 000 is specified in this uplink grant, [W1, W2] = [+ 1, +1] and W ′ The first and second UL DMRS are generated using = + 1. In the subframe k + 1, the mobile station device A2 transmits PUSCH and UL DMRS in the second to fourth RBs according to the uplink grant received in the subframe k-3 (515). Since the index M = 111 is specified in this uplink grant, the first and second UL DMRSs are generated using [W1, W2] = [+ 1, +1] and W '=-1. The

  Since the base station apparatus that has received the PUSCH and UL DMRS transmitted by 504, 505, 514, and 514, the PUSCH transmitted in the subframe k from the mobile station apparatuses A1 and A2 has overlapping RBs as described above. MU-MIMO is configured, but since the assignments do not match, orthogonality by cyclic shift does not hold. Further, as shown in FIG. 4, since the mobile station apparatuses A1 and A2 use the same subframe OCC [W1, W2] = [+ 1, + 1], despreading between the first and second UL DMRSs is performed. I can't do it either. However, since the mobile station devices A1 and A2 use different inter-subframe OCCs and the allocated frequency positions, that is, the positions of the RBs match in the subframes k and k + 1, the subframes k and k + By despreading the four UL DMRS received in 1, the channels of mobile station devices A1 and A2 can be calculated (506)

  By using the respective channels of the mobile station devices A1 and A2 calculated by the processing of 506, the base station device B demodulates the PUSCH of each mobile station device received in subframes k and k + 1 (507). .

  In addition, when the moving speed of the mobile station apparatus is fast and the time variation of the channel is fast, the orthogonality due to the OCC between subframes may be reduced, and characteristic deterioration may occur. However, in such a case, if the index M is selected so that different intra-subframe OCCs are assigned to the base station apparatus B mobile station apparatuses A1 and A2, the time domain despreading is completed within one subframe. Therefore, this deterioration can be reduced.

  In the embodiment of the present invention, the SC-FDMA scheme has been described as an example, but the same effect can be obtained even when the Clustered DFT Spread OFDM scheme is used.

  In the embodiment of the present invention, the orthogonality of UL DMRS assuming MU-MIMO has been described. However, in the case of performing channel estimation using a plurality of subframes even in the case of SU-MIMO or single antenna transmission. Can improve the estimation accuracy by suppressing inter-cell interference.

  The program that operates in the mobile station apparatus A and the base station apparatus B related to the present invention is a program that controls a CPU (Central Processing Unit) and the like so as to realize the functions of the above-described embodiments related to the present invention. Program). Information handled by these devices is temporarily stored in RAM (Random Access Memory) during the processing, and then stored in various ROMs such as Flash ROM (Read Only Memory) and HDD (Hard Disk Drive). Reading, correction, and writing are performed by the CPU as necessary.

  In addition, you may make it implement | achieve a part or all of the mobile station apparatus A and base station apparatus B in embodiment mentioned above with a computer. In that case, the program for realizing the control function may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read by a computer system and executed. Here, the “computer system” is a computer system built in the mobile station apparatus A or the base station apparatus B, and includes an OS and hardware such as peripheral devices.

  The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” is a medium that dynamically holds a program for a short time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, In such a case, a volatile memory inside a computer system serving as a server or a client may be included and a program that holds a program for a certain period of time. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.

  Moreover, you may implement | achieve part or all of the mobile station apparatus A in the embodiment mentioned above and the base station apparatus B as LSI which is typically an integrated circuit. Each functional block of the mobile station device A and the base station device B may be individually chipped, or a part or all of them may be integrated into a chip. Further, the method of circuit integration is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. In addition, when an integrated circuit technology that replaces LSI appears due to progress in semiconductor technology, an integrated circuit based on the technology can also be used.

  As described above, the embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to the above, and various design changes and the like can be made without departing from the scope of the present invention. It is possible to

DESCRIPTION OF SYMBOLS 101 Code generation part 102 Scrambling part 103 Modulation part 104 Layer mapping part 105 DFT / frequency mapping part 106 UL DMRS sequence generation part 107 Data / UL DMRS multiplexing part 108 Precoding part 201 Data / DMRS separation part 202 Despreading / Channel estimation Unit 203 equalization unit 204 space separation unit 205 IDFT unit 206 data decoding unit 210, 211 demodulation processing block

Claims (8)

A subframe comprising a mobile station device that transmits a data signal and a demodulation reference signal and a base station device that receives the data signal, and a resource for transmitting the data signal and the demodulation reference signal is allocated in a specific time unit And the demodulation reference signal is generated by applying a cyclic shift to the root sequence to generate a transmission sequence of one SC-FDMA symbol, and at the same time, an orthogonal cover code. The transmission sequence is generated by spreading the transmission sequence into a plurality of SC-FDMA symbols, and control information including information regarding the resource allocation, and instruction information indicating the sequence of the cyclic shift and the orthogonal cover code is provided. A radio communication system instructed from the base station apparatus to the mobile station apparatus,
The demodulation reference signal is generated by multiplying a SC-FDMA symbol by a common weight for a sequence to which the cyclic shift and the orthogonal cover code are applied,
A wireless communication system, wherein a weight common to the SC-FDMA symbol is determined according to a type of a subframe to be transmitted and the indication information.   The wireless communication system according to claim 1, wherein a weight common to the SC-FDMA symbol is +1 or 1.   The wireless communication system according to claim 1, wherein the type of the subframe is determined by whether an index number assigned to the subframe is an even number or an odd number. A mobile station apparatus that transmits a data signal and a demodulation reference signal to a base station apparatus, wherein resource allocation for transmitting the data signal and the demodulation reference signal is performed for each subframe that is a specific time unit. In addition, the demodulation reference signal generates a transmission sequence of one SC-FDMA symbol by applying a cyclic shift to the root sequence, and at the same time, the transmission sequence is divided into a plurality of SC-FDMA by an orthogonal cover code. Control information generated by spreading into symbols and including information related to the allocation of the resources transmitted from the base station apparatus, instruction information indicating the sequence of the cyclic shift and the orthogonal cover code is received. A mobile station device,
The demodulation reference signal is generated by multiplying a SC-FDMA symbol by a common weight for a sequence to which the cyclic shift and the orthogonal cover code are applied,
A weight common to the SC-FDMA symbols is determined according to the type of subframe to be transmitted and the indication information.   The mobile station apparatus according to claim 4, wherein a common weight for the SC-FDMA symbol is +1 or 1.   The mobile station apparatus according to claim 4, wherein the type of the subframe is determined by whether an index number assigned to the subframe is an even number or an odd number. A base station apparatus that receives a data station transmitted from a mobile station apparatus and a mobile station apparatus that transmits a demodulation reference signal, and performs propagation path estimation using the demodulation reference signal, wherein the data signal and the The base station apparatus performs allocation of resources for transmitting a demodulation reference signal for each subframe which is a specific time unit, and the demodulation reference signal applies 1SC by applying a cyclic shift to a root sequence. -A transmission sequence of FDMA symbols is generated and simultaneously generated by spreading the transmission sequence into a plurality of SC-FDMA symbols by an orthogonal cover code, and information on resource allocation and the cyclic shift A base station apparatus that instructs control information including instruction information for instructing a sequence of the orthogonal cover code to the mobile station apparatus.
The demodulation reference signal is generated by multiplying a SC-FDMA symbol by a common weight for a sequence to which the cyclic shift and the orthogonal cover code are applied,
As the weight common to the SC-FDMA symbol, +1 or 1 is selected according to the type of subframe to be transmitted and the indication information,
The type of the subframe is determined by whether the index number assigned to the subframe is an even number or an odd number.   The base station apparatus according to claim 7, wherein the base station apparatus switches the number of subframes used for channel estimation according to the number of the mobile station apparatuses multiplexed by MU-MIMO and the weight. .