JP5066236B2 - Base station apparatus and reception method - Google Patents

Description

  The present invention relates to a radio communication system, and more particularly to a base station apparatus, a mobile station, a radio communication system, and a communication control method.

  Long Term Evolution (LTE) has been studied by the W-CDMA standardization organization 3GPP as a successor to W-CDMA and HSDPA, and as a radio access method, the downlink is OFDM and the uplink SC-FDMA (Single-Carrier Frequency Multiple Access) has been studied (see, for example, Non-Patent Document 1).

  OFDM is a method in which a frequency band is divided into a plurality of narrow frequency bands (subcarriers) and data is transmitted on each frequency band, and the subcarriers interfere with each other even though they partially overlap on the frequency. By arranging them closely, it is possible to achieve high-speed transmission and increase frequency utilization efficiency.

  SC-FDMA is a transmission method that can reduce interference between terminals by dividing a frequency band and performing transmission using different frequency bands among a plurality of terminals. Since SC-FDMA has a feature that fluctuations in transmission power are reduced, it is possible to realize low power consumption and wide coverage of a terminal.

  An uplink reference signal (Reference signal) in E-UTRA refers to a pilot channel, and is used for synchronization, channel estimation for coherent detection, reception SINR measurement at power control, and the like. The reference signal is a known transmission signal on the receiving side, is periodically embedded in each subframe, and is received on the base station side.

  In W-CDMA, a signal sequence used for a reference signal (pilot channel) is a user-specific PN sequence, more precisely, a sequence obtained by multiplying a long-period Gold sequence and an orthogonal sequence. In addition, the length was long and many types of series could be made. However, since the PN sequence has poor correlation characteristics, there is a problem that channel estimation accuracy and the like deteriorate. That is, when the pilot channel is transmitted, interference with the pilot channel of other users is large. In the case of multipath, autocorrelation with the pilot channel sequence appears greatly in the delayed wave. In W-CDMA, simple reception processing such as RAKE is performed, but E-UTRA is designed on the assumption that multipath interference is suppressed using high-accuracy channel estimation such as an equalizer. Therefore, in E-UTRA, a CAZAC (Constant Amplitude and Zero Auto-Correlation) sequence is used instead of a user-specific PN sequence.

  Since the CAZAC sequence has excellent autocorrelation characteristics and cross-correlation characteristics of codes, it is possible to realize highly accurate channel estimation and to significantly improve demodulation accuracy compared to the case where a PN sequence is used. The CAZAC sequence has a relatively small signal amplitude fluctuation in both the frequency domain and the time domain, and is relatively flat. In the case of the PN series, the fluctuation of the amplitude is large in the frequency domain. Therefore, by using a CAZAC sequence, channel estimation for each frequency can be performed with high accuracy by an equalizer. In addition, since the CAZAC sequence has zero autocorrelation of the transmitted sequence, the influence of multipath can be reduced.

However, the CAZAC series has the following problems.
-Number of series is small: Since it cannot be a user-specific series, it is necessary to repeat the series of cells. The number of sequences becomes small especially when the transmission band is small in SC-FDMA. In particular, when the transmission band is small in SC-FDMA, the symbol rate becomes small, and the CAZAC sequence length decreases. That is, in E-UTRA, since a reference signal is input in time multiplexing, the symbol rate is reduced when the transmission band is narrow, and the sequence length is reduced. The number of series is the same as the series length. For example, when 12 symbols are obtained at 180 kHz, it cannot be a user-specific sequence, and it is necessary to repeatedly assign 12 sequences so that they do not overlap in the same cell.
The cross-correlation between CAZAC sequences having different sequence lengths has a relatively large variation depending on the combination. If the cross-correlation is large, the channel estimation accuracy deteriorates.

  Next, SC-FDMA used for uplink radio access in E-UTRA will be described with reference to FIG. The frequency band usable in the system is divided into a plurality of resource blocks, and each resource block includes one or more subcarriers. One or more resource blocks are allocated to a user equipment (UE: User Equipment). In frequency scheduling, resource blocks are preferentially allocated to terminals having good channel states according to the received signal quality or channel state information (CQI: Channel Quality Indicator) for each resource block of the downlink pilot channel reported from the user apparatus. As a result, the transmission efficiency or throughput of the entire system is improved. Further, frequency hopping in which usable frequency blocks are changed according to a predetermined frequency hopping pattern may be applied.

  In FIG. 1, different hatching indicates time / frequency resources allocated to different users. UE 2 has been assigned a wider band, but a narrow band is assigned in the next subframe. Each user is assigned a different frequency band so as not to overlap.

  In SC-FDMA, each user in a cell transmits using different time / frequency resources. In this way, orthogonality between users in the cell is realized. This minimum unit of time / frequency resources is called a resource unit (RU). In SC-FDMA, low PAPR (peak-to-average power ratio) single carrier transmission is realized by assigning continuous frequencies. In SC-FDMA, the time / frequency resource to be allocated is determined by the scheduler of the base station based on the propagation status of each user and the QoS (Quality of Service) of data to be transmitted. Here, the QoS includes a data rate, a required error rate, and a delay. Thus, throughput can be increased by allocating time / frequency resources with good propagation conditions to each user.

  Since each base station individually performs time / frequency resources to be allocated, a band allocated in one cell may overlap with a part of a band allocated in a neighboring cell. Thus, when a part of the band allocated by the adjacent cell overlaps, interference arises and it mutually deteriorates.

  Next, reference signals in uplink SC-FDMA will be described with reference to FIG. FIG. 2 shows an example of the frame configuration.

  The packet length of TTI called a subframe is 1 ms. The subframe includes 14 blocks to be subjected to FFT, two of which are used for reference signal transmission and the remaining 12 are used for data transmission.

  The reference signal is time-division multiplexed (TDM) with the data channel. The transmission bandwidth varies dynamically according to an instruction from the base station by frequency scheduling. For this reason, since the symbol rate decreases as the transmission bandwidth decreases, the sequence length of the reference signal transmitted with a fixed time length decreases, and as the transmission bandwidth increases, the symbol rate increases. The sequence length of the reference signal transmitted in is increased. In the case of a narrow band, for example, when a reference signal is transmitted with 1 resource unit, for example, 12 subcarriers, that is, when configured with 180 kHz, the number of symbols is 12, so the sequence length is about 12, and the number of sequences is also about 12 On the other hand, in the case of a wide band, for example, when a reference signal is transmitted with 25 resource units, for example, 300 subcarriers, that is, configured with 4.5 MHz, the number of symbols is 300, so the sequence length is also about 300. The number is also about 300.

  As an orthogonalization technique, it has been proposed to orthogonalize a plurality of reference signals by applying a cyclic shift of a CAZAC sequence. As shown in FIG. 3, by applying a cyclic shift of the CAZAC sequence, when all the multipaths are within the cyclic shift area, the reference signals between different users and between the antennas are orthogonal. In cyclic shift, even when different users are transmitting at the same timing and the bandwidth and the sequence are the same, it is possible to make the sequences orthogonal to each other by shifting the sequence.

  Also, it has been proposed that two reference signals can be orthogonalized by applying orthogonal sequence covering (Orthogonal covering). As shown in FIG. 4, users 1 and 2 may use different CAZAC sequences and cyclic shift amounts. However, the CAZAC sequence and the cyclic shift amount must be the same between two reference signals in a subframe. In this way, the user is orthogonal after despreading between the two reference signals.

3GPP TR 25.814 (V7.0.0), "Physical Layer Aspects for Evolved UTRA," June 2006

  However, the background art described above has the following problems.

  Since the reference signal using the CAZAC sequence can be suppressed to a very small cross-correlation (interference) when the own cell and the interference cell use the same frequency band in the same frequency band, good communication quality can be obtained.

  However, in SC-FDMA, the frequency band and frequency bandwidth used by each user change from time to time depending on the scheduling result, and it is rather rare to assign the same frequency bandwidth to a certain user in the same frequency band as the interfering station. . That is, even if the frequency band is the same as that of the interference station, the frequency band is often different. In this case, since interference becomes a correlation between CAZAC sequences having different frequency bandwidths, there are combinations of sequences that cause large interference, which may deteriorate communication quality. Here, since there are few types of CAZAC sequences used for the reference signal, a unique sequence is assigned to each cell. However, if one CAZAC sequence is always used according to the frequency bandwidth in each cell, When the combination of the frequency bandwidths is not good, large interference continuously occurs in all frames, which causes a large deterioration in communication quality. In W-CDMA, since the period of the reference signal is very long, even if a large interference happens to occur in a certain frame, it can be expected that the magnitude of the interference will decrease in the subsequent frame.

  Therefore, when considering avoiding that interference always increases in temporally continuous frames, a sequence hopping using different CAZAC sequences in consecutive frames and a shift that cyclically shifts in the time direction although using the same CAZAC sequence There are two methods of hopping (changing) the amount from frame to frame.

  Of these, cyclic shift hopping limits the effect of randomizing interference because the number of shifts that can be taken is limited to about six considering CP length and delay spread. On the other hand, sequence hopping can be expected to have a higher effect of interference randomization because a large number of sequences can be obtained especially when the band is large. However, when the bandwidth is small, for example, one resource unit (RU) has about 12 sequences, and if random hopping is used, the same CAZAC sequence may be used in neighboring cells about once every 12 frames. There is a problem that a packet error occurs.

  Therefore, in view of the above-described problems, the present invention can flexibly realize inter-cell reuse of reference signal sequences based on CAZAC sequences in a system to which E-UTRA is applied. An object of the present invention is to provide a base station apparatus, a mobile station, a radio communication system, and a communication control method that can reduce the influence of characteristic deterioration.

This base station device
A base station apparatus that communicates with a mobile station that transmits an uplink signal by a single carrier method,
Multiple types of signal sequences are defined for each of multiple types of bandwidths, and multiple sequence groups are defined so that at least one signal sequence defined for each bandwidth is combined across multiple types of bandwidths. The signal sequences included in each of the plurality of sequence groups are different from each other, and one of the plurality of sequence groups is selected, and a plurality of types of bandwidths are selected in the selected sequence group. A receiving unit for receiving a reference signal generated based on a signal sequence corresponding to any of the above,
A processing unit for processing a reference signal received by the receiving unit;
Is provided.

This receiving method is
A reception method for communicating with a mobile station that transmits an uplink signal by a single carrier method,
Multiple types of signal sequences are defined for each of multiple types of bandwidths, and multiple sequence groups are defined so that at least one signal sequence defined for each bandwidth is combined across multiple types of bandwidths. The signal sequences included in each of the plurality of sequence groups are different from each other, and one of the plurality of sequence groups is selected, and a plurality of types of bandwidths are selected in the selected sequence group. Receiving a reference signal generated based on a signal sequence corresponding to any of the above,
Processing the received reference signal;
Is provided.

  According to the embodiments of the present invention, in a system to which E-UTRA is applied, it is possible to flexibly realize inter-cell reuse of a reference signal sequence based on a CAZAC sequence, and reduce the influence of characteristic deterioration due to cross-correlation. A base station apparatus, a mobile station, a radio communication system, and a communication control method can be realized.

It is explanatory drawing which shows single carrier-FDMA. It is explanatory drawing which shows the structure of the reference signal in single carrier-FDMA. It is explanatory drawing which shows the structure of the reference signal in single carrier-FDMA. It is explanatory drawing which shows the structure of the reference signal in single carrier-FDMA. 1 is a block diagram illustrating a wireless communication system according to an embodiment of the present invention. It is explanatory drawing which shows the example of allocation of the reference signal series which concerns on one Example of this invention. It is a partial block diagram which shows the base station apparatus which concerns on one Example of this invention. It is a partial block diagram which shows the mobile station which concerns on one Example of this invention. It is explanatory drawing which shows the allocation method of the reference signal series which concerns on one Example of this invention. It is explanatory drawing which shows the proper use of orthogonalization and interference randomization in the base station apparatus which concerns on one Example of this invention. It is a flowchart which shows the process of the radio | wireless communications system which concerns on one Example of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In all the drawings for explaining the embodiments, the same reference numerals are used for those having the same function, and repeated explanation is omitted.

  A radio communication system having a mobile station and a base station apparatus according to an embodiment of the present invention will be described with reference to FIG.

The wireless communication system 1000 is a system to which, for example, Evolved UTRA and UTRAN (also known as Long Term Evolution, or Super 3G) is applied. The wireless communication system 1000 includes a base station apparatus (eNB: eNode B) 200 and a plurality of mobile stations 100 _n (100 ₁ , 100 ₂ , 100 ₃ ,... 100 _n , n, n communicating with the base station apparatus 200. > An integer of> 0). Base station apparatus 200 is connected to an upper station, for example, access gateway apparatus 300, and access gateway apparatus 300 is connected to core network 400. The mobile station 100 _n communicates with the base station device 200 in the cell 50 using Evolved UTRA and UTRAN.

Since each mobile station (100 ₁ , 100 ₂ , 100 ₃ ,... 100 _n ) has the same configuration, function, and state, the following description will be given as the mobile station 100 _n unless otherwise specified. For convenience of explanation, the mobile station communicates with the base station apparatus wirelessly, but more generally, a user apparatus (UE: User Equipment) including both a mobile terminal and a fixed terminal may be used.

  In the radio communication system 1000, OFDM (Orthogonal Frequency Division Multiple Access) is applied for the downlink and SC-FDMA (Single Carrier Frequency Division Multiple Access) is applied for the uplink as the radio access scheme. As described above, OFDM is a multi-carrier transmission scheme that performs communication by dividing a frequency band into a plurality of narrow frequency bands (subcarriers) and mapping data to each subcarrier. SC-FDMA is a single carrier transmission scheme that reduces interference between terminals by dividing a frequency band for each terminal and using a plurality of different frequency bands by a plurality of terminals.

  Here, communication channels in Evolved UTRA and UTRAN will be described.

For the downlink, a physical downlink shared channel (PDSCH) shared by each mobile station 100 _n and a physical downlink control channel (PDCCH) are used. The physical downlink control channel is also called a downlink L1 / L2 control channel. User data, that is, a normal data signal is transmitted through the physical downlink shared channel.

For the uplink, a physical uplink shared channel (PUSCH) shared by each mobile station 100 _n and a physical uplink control channel are used. User data, that is, a normal data signal is transmitted through the physical uplink shared channel. In addition, the downlink quality information (CQI: Channel Quality Indicator) for use in the shared physical channel scheduling processing and adaptive modulation and coding (AMC: Adaptive Modulation and Coding) in the downlink by the physical uplink control channel, and The acknowledgment information (Acknowledgement Information) of the physical downlink shared channel is transmitted. The content of the delivery confirmation information is expressed by either an acknowledgment (ACK: Acknowledgment) indicating that the transmission signal has been properly received or a negative acknowledgment (NACK: Negative Acknowledgment) indicating that the transmission signal has not been properly received. Is done.

  In the physical uplink control channel, in addition to CQI and delivery confirmation information, a scheduling request for requesting resource allocation of an uplink shared channel (Scheduling Request), a release request (Release Request) in persistent scheduling, etc. May be sent. Here, the uplink shared channel resource allocation means that communication may be performed using an uplink shared channel in a subsequent subframe using a physical downlink control channel of a certain subframe. Means to notify the mobile station.

  In the wireless communication system according to the present embodiment, cell repetition is applied to a sequence used for a reference signal (RS) having a small frequency bandwidth without performing sequence hopping. On the other hand, the sequence used for the reference signal with a large frequency bandwidth is divided into the same number of groups as the total number of sequences used for the reference with a small frequency bandwidth, and different subframes among the sequences in the group In sequence hopping using different CAZAC sequences. Here, the total number of sequences used for the reference signal having a small frequency bandwidth is equal to the number of cell repetitions. Hereinafter, a set of reference signal sequences in various bands grouped by the same number as the total number of sequences used for reference signals having a small frequency bandwidth is referred to as a sequence group. In this case, one of the sequence groups can be assigned to each cell, and different sequence groups can be used in adjacent cells.

  In this way, the reference signal having a small band is not subjected to sequence hopping, and the reference signal having a large band is subjected to sequence hopping, whereby the combination of the sequences being used changes for each subframe. For this reason, it is possible to avoid continuous occurrence of large interference, and it is possible to reduce the probability that consecutive packet errors occur.

For example, the number of RS sequences in the smallest band (W ₁ ) is N _1, and the number of RS sequences for a bandwidth (W _X ) X times W ₁ is XN ₁ . In the case of a CAZAC sequence, the number of sequences depends on the sequence length. In E-UTRA, where the RS transmission interval is constant regardless of the bandwidth, the bandwidth and the sequence length are proportional to each other. Proportional.

In the present embodiment, N _{1 is} created as an RS sequence group, and the k-th RS sequence group (k is an integer between 1 and N ₁ ) is an RS having a bandwidth of W _X , with sequence numbers k, k + N ₁ ,. .., K + (W _X / W ₁ ) N ₁ total (W _X / W ₁ ) sequences. Therefore, the same RS sequence does not belong to a plurality of RS sequence groups at the same time. In each cell, they used to select one of the _one RS sequence group N. Sequence hopping is performed only between RS sequences of the same bandwidth included in the selected RS sequence group.

  Specifically, as illustrated in FIG. 6, an RS sequence is assigned to RS sequence group numbers 1 to 12 with the smallest band as one resource unit (RU). In FIG. 6, the RS sequence [A, B] means the Bth sequence among the RS sequences whose transmission bandwidth corresponds to A.

  For example, base station # 1 has an RS sequence group number 1, base station # 2 has an RS sequence group number 2,..., Base station # 12 has an RS sequence group number 12, and so on. The cell repetition to which the group is assigned is applied. In addition, when the band is narrow, for example, in the case of 1 RU, sequence hopping is not applied, RS sequence 1 for base station # 1, RS sequence 2 for base station # 2, ..., base station # 12 The cell repetition in which a different sequence is assigned to each cell, such as RS sequence 12, is applied. Further, in the case of 2RU, since the reference signal band is doubled, the number of sequences is also doubled. This doubled series is repeated for each smallest series number (12), that is, a series pair is created and grouped. Each group includes two sequences that are not included in other groups. Hopping is performed between these two sequences. For example, in a base station to which RS sequence group number 1 is assigned, sequence 1 is used for 1 RU, and sequence 1 and sequence 13 are used for 2 RU. Similarly, in the adjacent cell, sequence 2 is used for 1 RU, and sequence 2 and sequence 14 are used for 2 RU.

  By doing so, it is possible to realize interference randomization by sequence hopping without causing a collision using the same RS sequence between adjacent cells.

  Next, the base station apparatus 200 according to the present embodiment is described with reference to FIG.

  A base station apparatus 200 according to the present embodiment includes a broadcast channel generation unit 202, an OFDM signal generation unit 204, a radio frame number / subframe number management unit 206, an uplink assignment permission signal transmission control signal generation unit 208, RS sequence number memory 210 for each bandwidth in the RS sequence group, cyclic shift number determination unit 212, demodulation RS generation unit 214, synchronization detection / channel estimation unit 216, channel decoding unit 218, and coherent detection unit 220, an uplink channel state estimation unit 222 for each user, and a scheduler 224.

  An uplink RS sequence group (number) is assigned to each cell at the time of cell design (station placement). In each sequence group, a sequence hopping pattern corresponding to a subframe number when a frequency band of 2 RU or more is allocated is determined in advance by specifications. In this case, different RS sequence groups (numbers) are allocated between adjacent base stations. In this way, randomization of interference can be realized.

  The assigned RS sequence group number is input to broadcast channel generating section 202 and memory 210 of RS sequence number for each bandwidth in the RS sequence group.

  The broadcast channel generation unit 202 generates a broadcast channel including the input RS sequence group number, a radio frame number (to be described later), and a system frame number input by the subframe number management unit 206, and inputs the broadcast channel to the OFDM signal generation unit 204. . The OFDM signal generation unit 204 generates an OFDM signal including a broadcast channel and inputs the OFDM signal to the transmission radio. As a result, the uplink RS sequence group is notified to all users in the cell through the broadcast channel.

On the other hand, the uplink channel transmitted from the mobile station 100 _n is input to the synchronization detection / channel estimation unit 216, the coherent detection unit 220, and the uplink channel state estimation unit 222 of each user.

  The synchronization detection / channel estimation unit 216 detects the synchronization of the input received signal, estimates the reception timing, and based on the demodulation RS (Demodulation Reference signal) input by the demodulation RS generation unit 214 described later. Channel estimation is performed, and the result is input to the coherent detection unit 220.

  The coherent detection unit 220 performs coherent detection on the received signal based on the channel estimation result and the assigned frequency and bandwidth input by the scheduler 224 described later, and inputs the demodulated received signal to the channel decoding unit 218. . The channel decoding unit 218 decodes the received demodulated received signal and generates a reproduction data signal corresponding to the assigned user number input by the scheduler 224. The generated reproduction data signal is transmitted to the network.

  Moreover, the uplink channel state estimation part 222 of each user estimates a channel state based on the input received signal, and inputs the uplink channel state estimation result of each user to the scheduler 224.

  The scheduler 224 performs, for example, frequency scheduling based on the input uplink channel state estimation result of each user and the QoS of each user, for example, the requested data rate, buffer state, required error rate, delay, etc. The bandwidth is input to the uplink allocation permission signal transmission control signal generation unit 208, the RS sequence number memory 210 for each bandwidth in the RS sequence group, and the coherent detection unit 220, and the assigned user number is controlled for uplink allocation permission signal transmission. The data is input to the signal generator 208 and the channel decoder 218.

Cyclic shift number determination section 212 determines a cyclic shift number based on, for example, a cooperation control signal exchanged between synchronous cells, and sends it to uplink allocation permission signal transmission control signal generation section 208 and demodulation RS generation section 214. input. Here, the cyclic shift number and the cyclic shift amount are associated with each other. This assignment is notified to the mobile station 100 _n via a broadcast channel, for example.

  The radio frame number / subframe number management unit 206 manages the radio frame number and subframe number, inputs the system frame number to the broadcast channel generation unit 202, and sets the radio frame number and subframe number to the bandwidth in the RS sequence group. Each RS sequence number is input to the memory 210.

  The RS sequence number memory 210 for each bandwidth in the RS sequence group stores the relationship between the RS sequence group number shown in FIG. 6, the bandwidth in each RS sequence group, and the RS sequence number. Further, the RS sequence number memory 210 for each bandwidth in the RS sequence group selects an RS sequence number corresponding to the allocated bandwidth input by the scheduler 224, and uses the selected RS sequence number as a demodulation RS generation unit. Input to 214.

  The demodulation RS generation unit 214 determines the demodulation RS based on the RS sequence number input by the memory 210 of the RS sequence number for each bandwidth in the RS sequence group and the cyclic shift number input by the cyclic shift number determination unit 212. Is input to the synchronization detection / channel estimation unit 216.

  The uplink assignment permission signal transmission control signal generation unit 208 generates a control signal (uplink assignment permission signal transmission control signal) including the input assigned frequency and bandwidth, the assigned user number, and the assigned cyclic shift number, The signal is input to the OFDM signal generation unit 204. The OFDM signal generation unit 204 generates an OFDM signal including a control signal and inputs it to the transmission radio. As a result, it is notified to the user to be scheduled by the downlink control channel.

  The OFDM signal generation unit 204 generates an OFDM signal including other downlink channels, for example, a downlink reference signal, a data channel, a paging channel, and the like in addition to the broadcast channel and the control channel described above, and inputs them to the transmission radio. As a result, the downlink channel is transmitted to the user.

Next, the mobile station 100 _{n according} to the present embodiment will be described with reference to FIG.

The mobile station 100 _{n according} to this embodiment includes an OFDM signal demodulator 102, an uplink assignment permission signal demodulator / decoder 104, a broadcast channel demodulator / decoder 106, and other control signals and data signal demodulator / decoders. 108, a radio frame number / subframe number counter 110, a cyclic shift amount determination unit 112, an RS sequence number memory 114 for each bandwidth in the RS sequence group, a demodulation RS generation unit 116, and a channel coding unit 118, a data modulator 120, and an SC-FDMA modulator 122. The mobile station 100 _n generates and transmits a transmission signal only when the allocated user number indicates its own mobile station in the decoding result of the uplink allocation permission signal.

  The received signal from the base station apparatus 200 is input to the OFDM signal demodulating section 102, subjected to demodulation processing, the uplink assignment permission signal transmission control signal is input to the uplink assignment permission signal demodulation / decoding section 104, and the broadcast channel is The control signal for uplink assignment permission signal transmission, the control signal other than the broadcast channel, and the data signal input to the broadcast channel demodulation / decoding unit 106 are input to the other control signal and data signal demodulation / decoding unit 108.

  Broadcast channel demodulation / decoding section 106 demodulates and decodes the input broadcast channel, inputs the RS sequence group number into memory 114 of RS sequence numbers for each bandwidth in the RS sequence group, and wirelessly transmits the system frame number. The frame number and subframe number counter 110 are input.

  The radio frame number / subframe number counter 110 counts the radio frame number and the subframe number, and inputs the radio frame number and the subframe number to the RS sequence number memory 114 for each bandwidth in the RS sequence group.

  Uplink assignment permission signal demodulation / decoding section 104 demodulates and decodes the input uplink assignment permission signal, inputs the assigned cyclic shift number to cyclic shift amount determination section 112, and assigns the assigned frequency to SC- The received bandwidth is input to the FDMA modulation unit 122 and the allocated bandwidth is input to the memory 114 of the RS sequence number for each bandwidth in the RS sequence group.

  The RS sequence number memory 114 for each bandwidth in the RS sequence group stores the relationship between the bandwidth in the RS sequence group shown in FIG. 6 and the RS sequence number. In addition, the RS sequence number memory 114 for each bandwidth in the RS sequence group is notified by the base station apparatus 200 and stores the relationship between the allocated band and the sequence in the RS sequence group allocated to the own cell. The RS sequence number memory 114 for each bandwidth in the RS sequence group includes the RS sequence group number input by the broadcast channel demodulation / decoding unit 106 and the allocated bandwidth input by the uplink allocation permission signal demodulation / decoding unit 104. The RS sequence number corresponding to is selected, and the selected RS sequence number is input to the demodulation RS generation unit 116.

  Cyclic shift amount determination unit 112 is input by uplink allocation permission signal demodulation / decoding unit 104, determines a cyclic shift amount corresponding to the allocated cyclic shift number, and uses the determined cyclic shift amount as demodulation RS generation unit 116. To enter.

  The demodulation RS generation unit 116 generates a demodulation RS based on the selected RS sequence number and the cyclic shift amount, and inputs the demodulation RS to the SC-FDMA modulation unit 122.

  On the other hand, the user data is subjected to channel coding in channel coding section 118, data modulated in data modulation section 120, and input to SC-FDMA modulation section 122.

  The SC-FDMA modulation unit (DFT-spread OFDM) 122 modulates the input demodulation RS and the modulated user data based on the assigned frequency, and outputs a transmission signal.

  Next, a reference signal sequence allocation method performed in base station apparatus 200 will be described with reference to FIG.

Here, the base station apparatus 200 ₁ to the RS sequence group, e.g., sequence group 2 has already been assigned, will be described when assigning RS sequence group to the base station apparatus 200 _2.

The base station apparatus 200 _2, selects a different RS sequence groups and RS sequence group assigned to the base station apparatus 200 _1. In this way, randomization of interference can be realized (step S902). For example, the base station apparatus 200 _2, selects a sequence group 1.

  At the time of cell design (station placement), an uplink RS sequence group is allocated to each cell (step S904). In each sequence group, a sequence hopping pattern corresponding to the subframe number is determined in advance by specifications.

The base station apparatus 200 ₂ notifies the sequence group of the uplink RS to all users in the cell broadcast channel (step S906).

The base station apparatus 200 _2, the scheduled users, together with bandwidth allocation information in a downlink control channel, and notifies the cyclic shift amount (step S908).

When scheduled, the mobile station (terminal) 100 _n detects the RS sequence to be used in the allocated band from the broadcasted RS sequence group table (FIG. 6) and the allocated subframe number, and controls the control channel. The uplink channel is transmitted by applying the cyclic shift amount notified in (Step S910).

  Here, as a method for notifying the terminal of the uplink reference sequence number to be used, a case has been described in which the sequence group number used by each cell is notified to the terminal through a broadcast channel. May be associated in advance, or the reference signal sequence number is assigned to the terminal in accordance with control information (control signal for uplink assignment permission signal transmission) indicating scheduling permission for users assigned by the scheduler by each cell. You may make it indicate. By associating the ID of each cell with the number of the sequence group to be used in advance, signaling can be made unnecessary for notification.

  Further, where, for each sequence group are determined either using the previously what hopping pattern, that is, in each sequence group, if the sequence hopping pattern according to the sub-frame number which is determined in advance by specifications As described above, the hopping pattern may be notified from the base station to the terminal. For example, the hopping pattern used in the broadcast channel may be notified, or dynamic hopping control may be performed to notify the determined hopping pattern.

  Also, here, the case has been described where the cyclic shift amount is notified as the format information of the uplink reference signal. That is, the cyclic shift amount corresponding to the cyclic shift number is determined in advance by the base station in consideration of the cell radius and the delay spread, and is notified through the broadcast channel, and the cyclic shift amount to be used is dynamically reported together with the scheduling permission. . For example, the cyclic shift number and the cyclic shift amount are associated in advance, and the correspondence is notified by broadcast information. Thereafter, the cyclic shift number is notified.

  Further, orthogonal sequence covering may be notified as the format information of the uplink reference signal. Orthogonal sequence covering is limited to the use of orthogonalization between antennas during MIMO in which one user uses multiple antennas. In this case, a user who is instructed to use MIMO performs orthogonalization of reference signals between antennas by orthogonal sequence covering without additional signaling. That is, the same CAZAC sequence and cyclic shift amount are used between two reference signals in a subframe. Moreover, you may make it use orthogonal sequence covering also for the orthogonalization between users. In this case, notification is dynamically made together with scheduling permission.

  Next, the proper use of orthogonalization and interference randomization will be described with reference to FIG.

  In FIG. 10, the uplink transmission timings of base station # 1, base station # 2, and base station # 3 are asynchronous. Each base station has two sectors and can be synchronized between sectors belonging to the same base station.

  Even if the RS sequence group is the same between the sectors, orthogonalization can be achieved by making the cyclic shift amount different. For example, in the base station # 1, the same RS sequence group, that is, the RS sequence group 1, is allocated, but orthogonalization is possible because the cyclic shift amount is different. Further, in the base station # 2, the same RS sequence group, that is, the RS sequence group 2, is allocated, but orthogonalization can be performed because the cyclic shift amount is different.

  Further, randomization of interference can be realized by assigning different RS sequence groups between the base station # 1 and the base station # 2. For example, since RS sequence group 1 is assigned to base station # 1 and RS sequence group 2 is assigned to base station # 2, randomization of interference can be realized.

  Also, in a MIMO terminal, antennas can be orthogonalized by applying orthogonal sequence covering. Alternatively, orthogonalization may be performed by applying a cyclic shift.

  Further, even in a synchronized cell like the sectors 1 and 2 of the base station # 3, priority may be given to interference randomization, and a different RS sequence group may be assigned.

  Here, the description has been made on the assumption that the inter-base station is asynchronous. However, when the base stations are synchronized, the same frequency band is allocated to the same frequency band by allocating the same RS sequence group and a different cyclic shift amount between the base stations. It is possible to realize orthogonalization between users using the width simultaneously.

  Next, a processing flow of the wireless communication system according to the present embodiment will be described with reference to FIG.

  In the base station 200, an RS sequence group used in advance is set. Each user terminal has information on all RS sequence groups prepared in advance in the system (what RS sequence is assigned to each sequence group and which sequence is used depending on the subframe / radio frame number ( Hopping pattern)) is stored. Also, MIMO using a multi-antenna is applied to the user 2.

  The base station apparatus 200 notifies system information through a broadcast channel (step S1102). For example, the base station apparatus 200 notifies an RS sequence group number and a system frame number.

  Base station apparatus 200 transmits a paging channel (step S1104). For example, a paging channel is transmitted when a mobile station is called from the network, specifically when a call is received.

  The user terminal receives the paging channel and transmits a random access channel as an initial access from the user terminal in a corresponding manner (steps S1106 and S1108).

  A control channel is exchanged between the base station apparatus 200 and the user terminals 1 and 2 (steps S1110 and S1112). A radio link is established between the base station apparatus 200 and the user terminals 1 and 2. The base station apparatus 200 recognizes that the user terminal 2 is MIMO at this point.

  From here, it becomes a packet communication state by downlink scheduling. The user terminal periodically transmits a broadband sounding reference signal for uplink CQI measurement.

  The base station apparatus 200 performs scheduling for the user terminal 1 (step S1114).

  The base station apparatus 200 transmits an uplink transmission permission signal to the user terminal 1 (step S1116). The uplink permission signal includes an assigned user number, an uplink assigned band, a cyclic shift number to be used, and the like.

  The user terminal 1 recognizes the RS sequence from the allocated bandwidth and the subframe number and radio frame number used for transmission. This RS sequence is transmitted with the cyclic shift notified by the uplink transmission permission signal (step S1118).

  The base station apparatus 200 performs scheduling for the user terminal 2 (step S1120).

  The base station apparatus 200 transmits an uplink transmission permission signal to the user terminal 2 (step S1122). The uplink permission signal includes an assigned user number, an uplink assigned band, a cyclic shift number to be used, and the like.

  The user terminal 2 recognizes the RS sequence from the allocated bandwidth and the subframe number and radio frame number used for transmission. A cyclic shift notified by the uplink transmission permission signal is given to the RS sequence, and since it is MIMO, antenna 1 and antenna 2 are multiplied by orthogonal sequence covering determined in advance by the system and transmitted (step S1124).

  The following items are further disclosed regarding the embodiment including the above examples.

(1) A base station apparatus that communicates with a mobile station that transmits an uplink signal using a single carrier method:
A sequence group different from the sequence group allocated to the adjacent cell is allocated, and in the sequence group, a sequence used for the reference signal is specified for the bandwidth of the radio resource,
The mobile station transmits an uplink signal using a sequence specified by the sequence group,
A scheduler for allocating radio resources so that a mobile station communicates using one or more resource units;
Notification means for notifying the allocated radio resource and the cyclic shift amount to the mobile station to be allocated;
Demodulating means for demodulating the received signal from the mobile station based on the sequence corresponding to the bandwidth of the radio resource and the cyclic shift amount;
With
Cell repetition is applied to a sequence used for a reference signal transmitted by one resource unit, and for a sequence used for a reference signal transmitted in a wider frequency bandwidth than the one resource unit, Sequence hopping using different sequences in successive subframes is applied.

(2) In the base station described in (1):
Informing means for informing the mobile station of the sequence group;
Is provided.

(3) In the base station described in (1) or (2):
A sequence used for a reference signal transmitted by the one resource unit is fixedly assigned one of a plurality of sequences to be used, and is used as a reference signal transmitted with a wider frequency bandwidth than the one resource unit. A sequence to be used is obtained by dividing a plurality of sequences to be used into groups of a plurality of sequences used for reference signals transmitted by the one resource unit, and different sequences in different subframes among sequences included in the group. Is assigned.

(4) In the base station described in (3):
The 1 resource unit has a minimum bandwidth W _1, said minimum bandwidth W for ₁ number of sequences of referencing Gunaru and N _1, the number of sequences of reference signals for bandwidth W _X of X times the minimum bandwidth W ₁ Is XN ₁ ,
N ₁ reference signal sequence groups are created, and the k-th (k is an integer 1 ≦ k ≦ N ₁ ) reference signal sequence group is a sequence number k, k + N as a reference signal having a bandwidth W _{X. 1} ,..., K + (W _X / W ₁ ) N ₁ in total (W _X / W ₁ ) sequences.

(5) In the base station described in (4):
N _One of the reference signal sequence groups is assigned.

(6) In the base station described in (4) or (5):
When the bandwidth of the radio resource allocated to the mobile station is W _X , the total of sequence numbers k, k + N ₁ ,..., K + (W _X / W ₁ ) N ₁ (W _X / Sequence hopping is performed between W ₁ ) sequences.

(7) In the base station described in (6):
A hopping pattern is predetermined for each series group.

(8) In the base station according to any one of (1) to (7):
The sequence is a Kazak sequence.

(9) A mobile station that transmits an uplink signal by a single carrier method:
Storage means for storing a sequence group in which a sequence used for a reference signal is designated with respect to a bandwidth of a radio resource;
Transmitting means for specifying a sequence corresponding to the radio resource bandwidth based on the radio resource and the cyclic shift amount allocated by the base station, and transmitting an uplink signal with the cyclic shift amount;
With
Cell repetition is applied to a sequence used for a reference signal transmitted by one resource unit, and for a sequence used for a reference signal transmitted in a wider frequency bandwidth than the one resource unit, Sequence hopping using different sequences in successive subframes is applied.

(10) In the mobile station described in (9):
A sequence used for a reference signal transmitted by the one resource unit is fixedly assigned one of a plurality of sequences to be used, and is used as a reference signal transmitted with a wider frequency bandwidth than the one resource unit. A sequence to be used is obtained by dividing a plurality of sequences to be used into groups of a plurality of sequences used for reference signals transmitted by the one resource unit, and different sequences in different subframes among sequences included in the group. Is assigned.

(11) In the base station described in (10):
A hopping pattern is predetermined for each series group.

(12) In the mobile station according to (9) to (11):
Multiple antennas;
With
The transmission means uses the same sequence between two reference signals in a subframe.

(13) In the mobile station according to any one of (9) to (12):
The sequence is a Kazak sequence.

(14) A wireless communication system including a mobile station that transmits an uplink signal by a single carrier scheme and a base station apparatus that communicates with the mobile station:
In the base station apparatus, a sequence group different from the sequence group allocated to the adjacent cell is allocated, and in the sequence group, a sequence used for a reference signal is designated with respect to a bandwidth of a radio resource,
The mobile station transmits an uplink signal using a sequence specified by the sequence group,
The base station device
A scheduler for allocating radio resources so that a mobile station communicates using one or more resource units;
Notification means for notifying the allocated radio resource and the cyclic shift amount to the mobile station to be allocated;
Demodulating means for demodulating the received signal from the mobile station based on the sequence corresponding to the bandwidth of the radio resource and the cyclic shift amount;
With
The mobile station
Storage means for storing the sequence group;
Transmitting means for specifying a sequence corresponding to the radio resource bandwidth based on the radio resource and the cyclic shift amount allocated by the base station, and transmitting an uplink signal with the cyclic shift amount;
With
Cell repetition is applied to a sequence used for a reference signal transmitted by one resource unit, and for a sequence used for a reference signal transmitted in a wider frequency bandwidth than the one resource unit, Sequence hopping using different sequences in successive subframes is applied.

(15) A communication control method in a radio communication system including a mobile station that transmits an uplink signal by a single carrier method and a base station apparatus that communicates with the mobile station:
A sequence group different from the sequence group allocated to the adjacent cell is allocated to the base station apparatus, and in the sequence group, a sequence used for a reference signal is designated for the bandwidth of the radio resource,
A radio resource allocation step in which the base station apparatus allocates radio resources so that a mobile station communicates using one or more resource units;
A notification step in which the base station device notifies the mobile station to be allocated of the allocated radio resource and the cyclic shift amount;
A transmitting step in which the mobile station transmits an uplink signal based on the notified radio resource and the cyclic shift amount;
A demodulation step in which the base station apparatus demodulates a received signal from the mobile station based on a sequence corresponding to a bandwidth of the radio resource and the cyclic shift amount;
Have
Cell repetition is applied to a sequence used for a reference signal transmitted by one resource unit, and for a sequence used for a reference signal transmitted in a wider frequency bandwidth than the one resource unit, Sequence hopping using different sequences in successive subframes is applied.

50 cells 100 ₁ , 100 ₂ , 100 ₃ , 100 _n mobile station 102 OFDM signal demodulator 104 uplink allocation permission signal demodulator / decoder 106 broadcast channel demodulator / decoder 108 Other control signal / data signal demodulator / decoder 110 Radio frame number / subframe number counter 112 Cyclic shift amount determination unit 114 Memory of RS sequence number for each bandwidth in RS sequence group 116 Demodulation RS generation unit 118 Channel encoding unit 120 Data modulation unit 122 SC-FDMA modulation unit 200 Base station apparatus 202 Broadcast channel generation section 204 OFDM signal generation section 206 Radio frame number / subframe number management section 208 Control signal generation section 210 for uplink assignment permission signal transmission Memory 212 for RS sequence number for each bandwidth in RS sequence group Shift number determination unit 214 Tuning RS generation unit 216 synchronization detection channel estimation unit 218 uplink channel decoding section 220 coherent detection unit 222 each user channel condition estimation unit 224 Scheduler 300 Access gateway 400 Core network

Claims (5)

A base station apparatus that communicates with a mobile station that transmits an uplink signal by a single carrier method,
Multiple types of signal sequences are defined for each of multiple types of bandwidths, and multiple sequence groups are defined so that at least one signal sequence defined for each bandwidth is combined across multiple types of bandwidths. The signal sequences included in each of the plurality of sequence groups are different from each other, and one of the plurality of sequence groups is selected, and a plurality of types of bandwidths are selected in the selected sequence group. A receiving unit for receiving a reference signal generated based on a signal sequence corresponding to any of the above,
A processing unit for processing a reference signal received by the receiving unit;
A base station apparatus comprising:   The base station apparatus according to claim 1, further comprising a transmission unit that transmits a notification for causing the mobile station to select a sequence group.   The base station apparatus according to claim 1, wherein a sequence group is selected based on a cell ID in the reference signal received by the receiving unit.   The base station apparatus according to claim 1, wherein the reference signal received by the receiving unit changes at a predetermined timing. A reception method for communicating with a mobile station that transmits an uplink signal by a single carrier method,
Multiple types of signal sequences are defined for each of multiple types of bandwidths, and multiple sequence groups are defined so that at least one signal sequence defined for each bandwidth is combined across multiple types of bandwidths. The signal sequences included in each of the plurality of sequence groups are different from each other, and one of the plurality of sequence groups is selected, and a plurality of types of bandwidths are selected in the selected sequence group. Receiving a reference signal generated based on a signal sequence corresponding to any of the above,
Processing the received reference signal;
A receiving method comprising:

Images