WO2014181443A1 - Communication system, transmitting station, receiving station, and communication method - Google Patents

Abstract

This communication system (100) is provided with transmitting stations (110) and a receiving station (130). Each transmitting station (110) transmits a wireless signal in which a periodic time resource is allocated to a series of synchronization signals corresponding to identifying information for that transmitting station (110) and a time resource corresponding to said series of synchronization signals is allocated to a specific signal. The receiving station (130) detects the aforementioned synchronization signals from the wireless signal transmitted by a transmitting station (110), and on the basis of the detected series of synchronization signals, identifies the time resource allocated to the aforementioned specific signal. Then, on the basis of the identified time resource, the receiving station (130) detects said specific signal from aforementioned wireless signal.

Description

Communication system, transmitting station, receiving station, and communication method

The present invention relates to a communication system, a transmission station, a reception station, and a communication method.

Conventionally, a technique for associating a position of a blank subframe with a shift amount of transmission timing between a macro cell and a pico cell is known (see, for example, Patent Document 1 below). In addition, a technique is known in which a pico cell synchronization signal and a PBCH (Physical Broadcast Channel) transmission subframe are time-shifted to a macro cell MBSFN (MBMS Single Frequency Network) transmission area (for example, the following patent) Reference 2).

JP 2011-223113 A JP 2011-223114 A

However, the above-described conventional technique has a problem that the control information transmitted to the terminal increases in order to notify the terminal of the resource storing the specific signal such as PBCH.

In one aspect, an object of the present invention is to provide a communication system, a transmission station, a reception station, and a communication method that can reduce control information.

In order to solve the above-described problem and achieve the object, according to one aspect of the present invention, a transmission station assigns a synchronization signal of a sequence corresponding to identification information of the transmission station to a periodic resource, and the synchronization signal Transmitting a radio signal in which a specific signal is assigned to a resource corresponding to a sequence of the signal, detecting a synchronization signal from a radio signal transmitted by the transmitting station by a receiving station, and determining the specific signal based on the detected sequence of the synchronization signal A communication system, a transmitting station, a receiving station, and a communication method for specifying a resource to which a signal is assigned and detecting the specific signal from the radio signal based on the specified resource are proposed.

According to another aspect of the present invention, a transmitting station assigns a synchronization signal of a sequence corresponding to identification information of the transmitting station to a periodic resource, and assigns a specific signal to the resource corresponding to the identification information. Transmitting a radio signal, detecting the synchronization signal from the radio signal transmitted by the transmitting station by the receiving station, identifying identification information of the transmitting station based on the detected synchronization signal sequence, and identifying the identified identification information A communication system, a transmitting station, a receiving station, and a communication method for specifying a resource to which the specific signal is allocated based on the radio signal and detecting the specific signal from the radio signal based on the specified resource are proposed.

According to one aspect of the present invention, there is an effect that control information can be reduced.

FIG. 1A is a diagram of an example of a communication system according to the first embodiment. 1B is a diagram illustrating an example of a signal flow in the communication system illustrated in FIG. 1A. FIG. 2A is a diagram illustrating an example of a radio signal transmitted from each base station according to the second embodiment. FIG. 2B is a diagram illustrating an example of subframe number correction. FIG. 3 is a diagram of an example of the base station according to the second embodiment. FIG. 4 is a diagram illustrating an example of a hardware configuration of the base station. FIG. 5 is a diagram of an example of a terminal according to the second embodiment. FIG. 6 is a diagram illustrating an example of a hardware configuration of the terminal. FIG. 7A is a flowchart illustrating a first example of processing by the base station according to the second embodiment. FIG. 7B is a flowchart illustrating a second example of processing by the base station according to the second embodiment. FIG. 7C is a flowchart illustrating a third example of processing by the base station according to the second embodiment. FIG. 8A is a flowchart illustrating a first example of processing by the terminal according to the second embodiment. FIG. 8B is a flowchart illustrating a second example of processing by the terminal according to the second embodiment. FIG. 8C is a flowchart illustrating a third example of the process performed by the terminal according to the second embodiment. FIG. 9 is a diagram of an example of a radio signal transmitted from each base station according to the third embodiment. FIG. 10 is a diagram of an example of the base station according to the third embodiment. FIG. 11 is a diagram of an example of a terminal according to the third embodiment. FIG. 12A is a flowchart illustrating a first example of processing by the base station according to the third embodiment. FIG. 12B is a flowchart illustrating a second example of processing by the base station according to the third embodiment. FIG. 12C is a flowchart illustrating a third example of the process performed by the base station according to the third embodiment. FIG. 13A is a flowchart illustrating a first example of processing by the terminal according to the third embodiment. FIG. 13B is a flowchart illustrating a second example of the process performed by the terminal according to the third embodiment. FIG. 13C is a flowchart illustrating a third example of the process performed by the terminal according to the third embodiment. FIG. 14 is a diagram illustrating an example of a relationship between a series and a cell group.

Hereinafter, embodiments of a communication system, a transmission station, a reception station, and a communication method according to the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
(Communication system according to Embodiment 1)
FIG. 1A is a diagram of an example of a communication system according to the first embodiment. 1B is a diagram illustrating an example of a signal flow in the communication system illustrated in FIG. 1A. As illustrated in FIGS. 1A and 1B, the communication system 100 according to the first embodiment includes a transmission station 110, a transmission station 120, and a reception station 130. For example, the receiving station 130 is connected to the transmitting station 110 and performs wireless communication with the transmitting station 110.

Each of the transmission stations 110 and 120 includes an allocation unit 111 and a transmission unit 112. The allocating unit 111 allocates a series of synchronization signals corresponding to the identification information of the own station to a periodic time resource. The identification information is, for example, a cell ID. The sequence of the synchronization signal is, for example, a waveform pattern of the synchronization signal. The time resource is, for example, a subframe.

Also, the assigning unit 111 assigns the specific signal to the time resource corresponding to the synchronization signal sequence. Then, the assigning unit 111 notifies the sending unit 112 of the assignment result. The transmission unit 112 transmits a radio signal based on the allocation result notified from the allocation unit 111.

Thereby, each of the transmission stations 110 and 120 assigns a synchronization signal of a sequence corresponding to the identification information of the own station to a periodic time resource, and a radio signal in which a specific signal is assigned to the time resource corresponding to the sequence of the synchronization signal. Can be sent. For this reason, in each radio signal transmitted from the transmitting stations 110 and 120, the time resources in which the specific signal is stored can be shifted from each other, and the collision of the specific signal can be suppressed.

The receiving station 130 includes a receiving unit 131, a first detecting unit 132, a specifying unit 133, and a second detecting unit 134. The receiving unit 131 receives a radio signal from the transmitting station 110. Then, the reception unit 131 outputs the received signal (electric signal) to the first detection unit 132 and the second detection unit 134.

The first detection unit 132 performs cell search by detecting a synchronization signal from the signal output from the reception unit 131. For example, the first detection unit 132 determines whether or not the signal output from the reception unit 131 includes a synchronization signal of the target sequence for a plurality of sequences of synchronization signals stored in advance. Detect sync signal. Then, the first detection unit 132 outputs the detected synchronization signal to the specifying unit 133.

The identifying unit 133 identifies the time resource to which the specific signal is assigned by the transmitting station 110 based on the synchronization signal sequence output from the first detecting unit 132. As described above, since the time resource to which the specific signal is assigned is determined according to the sequence of the synchronization signal, the time resource to which the specific signal is assigned can be specified from the sequence of the synchronization signal. The specifying unit 133 notifies the second detection unit 134 of the specified time resource.

The second detection unit 134 detects the specific signal from the signal output from the reception unit 131 based on the time resource notified from the specification unit 133. Then, the second detection unit 134 outputs the detected specific signal.

Thus, in the communication system 100, the time resource in which the transmitting station 110 stores the specific signal can be associated with the sequence of the synchronization signal. As a result, even without notifying the receiving station 130 of the time resource for storing the specific signal, the receiving station 130 specifies the time resource in which the specific signal is stored from the detected sequence of synchronization signals, and detects the specific signal. be able to.

Therefore, it is possible to eliminate the need for control information for notifying the receiving station 130 of the time resource for storing the specific signal while suppressing the collision of the specific signal by shifting the time resource for the transmitting station 110 and 120 to store the specific signal. it can. For this reason, the control information transmitted to the receiving station 130 can be reduced. For example, the receiving station 130 can detect the specific signal without adding to the specification a control signal for notifying the receiving station 130 of the time resource for storing the specific signal.

<Modification>
Alternatively, the assignment unit 111 of the transmission stations 110 and 120 may assign a specific signal to a time resource corresponding to the identification information of the own station. Thereby, each of the transmission stations 110 and 120 assigns a synchronization signal of a sequence corresponding to the identification information of the own station to a periodic time resource, and a radio signal in which a specific signal is assigned to the time resource corresponding to the sequence of the synchronization signal. Can be sent. For this reason, in each radio signal transmitted from the transmitting stations 110 and 120, the time resources in which the specific signal is stored can be shifted from each other, and the collision of the specific signal can be suppressed.

In this case, the specifying unit 133 of the receiving station 130 specifies the identification information of the transmitting station 110 based on the synchronization signal sequence, and the time resource to which the specific signal is allocated by the transmitting station 110 based on the specified identification information. Is identified. As described above, since the time resource to which the specific signal is allocated is determined according to the identification information of the transmitting station 110, the time resource to which the specific signal is allocated can be specified from the identification information of the transmitting station 110.

As described above, in the communication system 100, the time resource in which the transmission station 110 stores the specific signal may be associated with the identification information of the transmission station 110. As a result, the receiving station 130 identifies the identification information of the transmitting station 110 from the detected sequence of synchronization signals without reporting the time resource for storing the specific signal to the receiving station 130, and the specific signal is obtained from the identified identification information. The stored time resource can be identified and a specific signal can be detected.

Therefore, it is possible to eliminate the need for control information for notifying the receiving station 130 of the time resource for storing the specific signal while suppressing the collision of the specific signal by shifting the time resource for the transmitting station 110 and 120 to store the specific signal. it can. For this reason, the control information transmitted to the receiving station 130 can be reduced. For example, the receiving station 130 can detect the specific signal without adding to the specification a control signal for notifying the receiving station 130 of the time resource for storing the specific signal.

(Embodiment 2)
(Radio signal transmitted from each base station according to the second embodiment)
FIG. 2A is a diagram illustrating an example of a radio signal transmitted from each base station according to the second embodiment. The base stations 211 to 213 shown in FIG. 2A are, for example, base stations that form overlapping cell areas. The base station 211 is a macro base station that forms a wide-area cell, for example. Base stations 212 and 213 correspond to the transmission stations 110 and 120 shown in FIGS. 1A and 1B and are small cells, pico cells, or femto cells provided in the cell of the base station 211. A terminal (UE: User Equipment) connected to the radio signals 221 to 223 corresponds to the receiving station 130 illustrated in FIGS. 1A and 1B.

Wireless signals 221 to 223 are wireless signals transmitted from the base stations 211 to 213, respectively. Each of the radio signals 221 to 223 includes DL_CCH 201 (DownLink_Control Channel: downlink control channel), PDSCH 202 (Physical Downlink Shared Channel: physical downlink shared channel), and MBSFN 203 (No Data).

In each of the radio signals 221 to 223, “S” indicates a synchronization signal, and “B” indicates PBCH. Examples of the synchronization signal include PSS (Primary Synchronization Signal) and SSS (Secondary Synchronization Signal). PSS and SSS are signals for the terminal to perform cell search. The terminal uses the PSS and SSS sequences to perform time synchronization and frequency synchronization with the cell and acquisition of the cell ID. In each of the radio signals 221 to 223, # 0 to # 7 indicate subframe numbers. The subframe is a time resource of 1 [ms].

Each of the base stations 211 to 213 transmits the PSS and the SSS in a cycle of 5 [ms] by storing the PSS and the SSS in a subframe whose subframe number is a multiple of 5, for example. Further, each of the base stations 211 to 213 stores the PBCH (broadcast signal) in a subframe whose subframe number is a multiple of 10, for example, thereby transmitting the PBCH at a cycle of 10 [ms].

N _ID (2) indicates a PSS sequence and is determined by the cell ID of the own station. N _ID (2) is one of “0”, “1”, and “2”. In the example shown in FIG. 2A, N _ID of the base station 211 (2) is "0", N _ID of the base station 212 (2) is "1", N _ID (2) of the base station 213 " 2 ”.

Each of the base stations 211 to 213 transmits a PSS corresponding to its own N _ID (2) by radio signals 221 to 223, respectively. In addition, each of the base stations 211 to 213 shifts the subframe according to its own N _ID (2). Thereby, each of the base stations 211 to 213 can shift time resources for transmitting each signal including the synchronization signal and the PBCH.

For example, since the N _ID (2) of the base station 211 is “0”, the base station 211 shifts the subframe by the shift amount “0” (no shift). Since the N _ID (2) of the base station 212 is “1”, the base station 212 shifts the subframe by the shift amount “1”. As a result, the radio signal 222 is shifted by one subframe with respect to the radio signal 221. Since the N _ID (2) of the base station is “2”, the base station 213 shifts the subframe by the shift amount “2”. As a result, the radio signal 223 is shifted by two subframes with respect to the radio signal 221.

(Correction of subframe number)
FIG. 2B is a diagram illustrating an example of subframe number correction. In FIG. 2B, the same parts as those shown in FIG. A terminal connected to the base station 211 detects the PSS from the radio signal 221 transmitted from the base station 211. The terminal connected to the base station 211 determines that the shift amount of the subframe of the base station 211 is “0” because the detected PSS sequence is “0”. For this reason, the terminal connected to the base station 211 does not correct each subframe number (# 0, # 1,...) In which the subframe in which the PSS is detected is # 0, and the subframe number is a multiple of 10. The broadcast signal (B) can be detected by demodulating a certain subframe.

The terminal connected to the base station 212 detects the PSS from the radio signal 222 transmitted from the base station 212. The terminal connected to the base station 212 determines that the subframe shift amount of the base station 212 is “1” because the detected PSS sequence is “1”. Therefore, the terminal connected to the base station 212 sets each subframe number (# 0, # 1,...) With # 0 as the subframe where the PSS is detected, and # 1 as the subframe where the PSS is detected. Correct to subframe numbers (# 1, # 2,...). The terminal connected to the base station 212 can detect the broadcast signal (B) by demodulating a subframe (for example, # 1) whose corrected subframe number is a multiple of 10 + 1.

The terminal connected to the base station 213 detects the PSS from the radio signal 223 transmitted from the base station 213. The terminal connected to the base station 213 determines that the subframe shift amount of the base station 213 is “2” because the detected PSS sequence is “2”. For this reason, the terminal connected to the base station 213 sets each subframe number (# 0, # 1,...) With # 0 as the subframe where the PSS is detected, and # 2 as the subframe where the PSS is detected. Correction to subframe numbers (# 2, # 3,...). A terminal connected to the base station 213 can detect the broadcast signal (B) by demodulating a subframe (for example, # 2) whose corrected subframe number is a multiple of 10 + 2.

As described above, when the base stations 211 to 213 time-shift subframes, the base stations 211 to 213 associate the PSS sequences with the time shift amounts. As a result, the terminal can identify the shift amount in the base stations 211 to 213 from the detected PSS sequence and correct the subframe number, for example, even if the shift amount in the base stations 211 to 213 is not notified. become.

Although the case where the shift amount of the subframe shift is associated with the PSS sequence has been described, the shift amount of the subframe shift may be associated with the SSS sequence. In this case, the terminal can specify the shift amount in the base stations 211 to 213 from the detected SSS sequence and correct the subframe number.

Alternatively, the shift amount of the subframe shift may be associated with the cell IDs of the base stations 211 to 213. In this case, the terminal can identify the cell ID from the detected SSS sequence and PSS sequence, identify the shift amount in the base stations 211 to 213 from the identified cell ID, and correct the subframe number. Become.

Also, the terminal may perform cooperative communication with other cells based on the specified shift amount. For example, it is assumed that the terminal is connected to the base station 211 and further performs cooperative communication with the cell of the base station 212. In this case, the terminal identifies the shift amount of the subframe number in the base station 211, and corrects the subframe number of the own cell with the identified shift amount in communication with the cell of the base station 212. Match the recognition of the subframe number with other cells.

(Base station according to the second embodiment)
FIG. 3 is a diagram of an example of the base station according to the second embodiment. Each of base stations 211 to 213 can be realized by base station 300 shown in FIG. 3, for example. The base station 300 includes an antenna 301, a Tx / Rx switching unit 302, a receiving unit 311, a CH estimation unit 312, a control signal demodulation / decoding unit 313, a data signal demodulation / decoding unit 314, and a reception quality calculation unit. 315. In addition, the base station 300 includes a scheduler 321, a data signal generation unit 322, a control signal generation unit 323, an RS generation unit 324, a synchronization signal generation unit 325, a shift addition unit 326, a notification signal generation unit 327, An allocation / arrangement unit 328 and a transmission unit 329.

The antenna 301 receives a signal wirelessly transmitted from another communication device and outputs the signal to the Tx / Rx switching unit 302. The antenna 301 wirelessly transmits the signal output from the Tx / Rx switching unit 302. The Tx / Rx switching unit 302 outputs the signal output from the antenna 301 to the receiving unit 311. Further, the Tx / Rx switching unit 302 outputs the signal output from the transmission unit 329 to the antenna 301.

The reception unit 311 performs reception processing of the signal output from the Tx / Rx switching unit 302. The reception processing by the reception unit 311 includes, for example, amplification and frequency conversion. The reception unit 311 outputs the signal obtained by the reception process to the CH estimation unit 312, the control signal demodulation / decoding unit 313, and the data signal demodulation / decoding unit 314.

The CH estimation unit 312 performs channel estimation based on an RS (Reference Signal) included in the signal output from the reception unit 311. Then, CH estimation section 312 outputs a CH estimation value indicating the result of channel estimation to control signal demodulation / decoding section 313, data signal demodulation / decoding section 314, and reception quality calculation section 315.

The control signal demodulation / decoding unit 313 performs demodulation and decoding of the control signal included in the signal output from the reception unit 311 based on the CH estimation value output from the CH estimation unit 312. Control signal demodulation / decoding section 313 outputs control information obtained by demodulation and decoding to data signal demodulation / decoding section 314 and scheduler 321.

The data signal demodulation / decoding unit 314 is a data signal included in the signal output from the reception unit 311 based on the CH estimation value from the CH estimation unit 312 and the control information from the control signal demodulation / decoding unit 313. Is demodulated and decoded. Then, the data signal demodulation / decoding unit 314 outputs the data obtained by the demodulation and decoding to the scheduler 321.

Reception quality calculation section 315 calculates reception quality at base station 300 based on the CH estimation value output from CH estimation section 312. Then, the reception quality calculation unit 315 notifies the scheduler 321 of the calculated reception quality.

The scheduler 321 performs scheduling based on the control information output from the control signal demodulation / decoding unit 313, the data output from the data signal demodulation / decoding unit 314, and the reception quality notified from the reception quality calculation unit 315. Do. Specifically, the scheduler 321 performs scheduling for assigning each signal to a radio resource. The radio resource is a combination of a frequency resource and a time resource, for example.

The scheduler 321 outputs allocation information indicating the scheduling result to the allocation / arrangement unit 328. In addition, the scheduler 321 outputs various signal generation requests based on the scheduling result to the data signal generation unit 322, the control signal generation unit 323, the RS generation unit 324, and the synchronization signal generation unit 325. Further, scheduler 321 outputs cell ID information indicating the cell ID of base station 300 to synchronization signal generation section 325.

The data signal generation unit 322 generates a data signal based on the signal generation request output from the scheduler 321. Then, the data signal generation unit 322 outputs the generated data signal to the allocation / arrangement unit 328. The control signal generation unit 323 generates a control signal based on the signal generation request output from the scheduler 321. Then, the control signal generation unit 323 outputs the generated control signal to the allocation / arrangement unit 328. The RS generation unit 324 generates an RS based on the signal generation request output from the scheduler 321. Then, the RS generation unit 324 outputs the generated RS to the allocation / arrangement unit 328.

The synchronization signal generation unit 325 generates a synchronization signal based on the signal generation request and cell ID information output from the scheduler 321. For example, the synchronization signal generation unit 325 generates a sequence of PSS and SSS based on the cell ID information as a synchronization signal. Then, the synchronization signal generation unit 325 outputs the generated synchronization signal to the allocation / arrangement unit 328. Synchronization signal generation section 325 outputs the generated synchronization signal sequence information indicating the PSS and SSS sequences and cell ID information to shift addition section 326.

The shift addition unit 326 selects the shift amount of the subframe in the base station 300 based on the sequence indicated by the synchronization signal sequence information output from the synchronization signal generation unit 325. Alternatively, the shift addition unit 326 may select the shift amount of the subframe in the base station 300 based on the cell ID indicated by the cell ID information output from the synchronization signal generation unit 325.

For example, the memory of the base station 300 stores correspondence information between the synchronization signal series or cell ID and the shift amount. Based on the correspondence information, shift adding section 326 selects a shift amount corresponding to the sequence indicated by the synchronization signal sequence information or the cell ID indicated by the cell ID information. Then, the shift addition unit 326 notifies the allocation / arrangement unit 328 of the selected shift amount.

The notification signal generation unit 327 generates a notification signal (PBCH). Then, the notification signal generation unit 327 outputs the generated notification signal to the allocation / arrangement unit 328.

The allocation / arrangement unit 328 is output from the data signal generation unit 322, the control signal generation unit 323, the RS generation unit 324, the synchronization signal generation unit 325, and the notification signal generation unit 327 based on the allocation information output from the scheduler 321. Assign and place each signal. Also, allocation / arrangement section 328 shifts the subframe with respect to the reference radio signal (for example, radio signal 221 of base station 211) based on the shift amount notified from shift addition section 326 and shifts the subframe. Each signal is allocated and arranged for a subframe. Allocation / arrangement section 328 outputs the signal on which the allocation and arrangement of each signal has been performed to transmission section 329.

The transmission unit 329 performs transmission processing of the signal output from the allocation / arrangement unit 328. The transmission processing by the transmission unit 329 includes, for example, frequency conversion and amplification. Transmitting section 329 outputs the signal subjected to the transmission process to Tx / Rx switching section 302.

1A and 1B can be realized by, for example, scheduler 321, synchronization signal generation unit 325, shift addition unit 326, notification signal generation unit 327, and allocation / arrangement unit 328. The transmission unit 112 illustrated in FIGS. 1A and 1B can be realized by, for example, the transmission unit 329, the Tx / Rx switching unit 302, and the antenna 301.

(Base station hardware configuration)
FIG. 4 is a diagram illustrating an example of a hardware configuration of the base station. The base station 300 shown in FIG. 3 can be realized by, for example, the communication apparatus 400 shown in FIG. The communication device 400 includes a processor 401, a memory 402, an analog circuit 403, a digital circuit 404, a wireless I / F 405, and a transmission network I / F 406. The processor 401, the memory 402, the analog circuit 403, the digital circuit 404, the wireless I / F 405, and the transmission network I / F 406 are connected by, for example, a bus.

The processor 401 controls the entire communication device 400. The memory 402 includes, for example, a main memory and an auxiliary memory. The main memory is, for example, a RAM (Random Access Memory). The main memory is used as a work area for the processor 401. The auxiliary memory is, for example, a nonvolatile memory such as a magnetic disk, an optical disk, or a flash memory. Various programs for operating the communication device 400 are stored in the auxiliary memory. The program stored in the auxiliary memory is loaded into the main memory and executed by the processor 401.

The analog circuit 403 is a circuit for processing an analog signal. The analog circuit 403 is controlled by the processor 401. The digital circuit 404 is a circuit that processes a digital signal. The digital circuit 404 is controlled by the processor 401.

The wireless I / F 405 is a communication interface that performs communication with the outside of the communication device 400 (for example, a mobile communication terminal) wirelessly. The wireless I / F 405 is controlled by the processor 401. The transmission network I / F 406 is a communication interface that performs communication with the outside (for example, a host device) of the communication device 400 by, for example, a wired connection. The transmission network I / F 406 is controlled by the processor 401.

The antenna 301 and the Tx / Rx switching unit 302 illustrated in FIG. 3 can be realized by a wireless I / F 405, for example. The reception unit 311 and the transmission unit 329 illustrated in FIG. 3 can be realized by the analog circuit 403 and the wireless I / F 405, for example. The CH estimation unit 312, the control signal demodulation / decoding unit 313, the data signal demodulation / decoding unit 314, and the reception quality calculation unit 315 illustrated in FIG. 3 can be realized by the processor 401, the digital circuit 404, and the memory 402, for example.

3 can be realized by the processor 401, the digital circuit 404, the memory 402, and the transmission network I / F 406, for example. The data signal generation unit 322, the control signal generation unit 323, the RS generation unit 324, the synchronization signal generation unit 325, and the shift addition unit 326 illustrated in FIG. 3 can be realized by the processor 401, the digital circuit 404, and the memory 402, for example. . The notification signal generation unit 327 and the allocation / arrangement unit 328 illustrated in FIG. 3 can be realized by the processor 401, the digital circuit 404, and the memory 402, for example.

(Terminal according to the second embodiment)
FIG. 5 is a diagram of an example of a terminal according to the second embodiment. A terminal (mobile communication terminal) connected to the base stations 211 to 213 can be realized by, for example, the terminal 500 shown in FIG. Terminal 500 includes an antenna 501, a Tx / Rx switching unit 502, a receiving unit 511, a synchronization signal detecting unit 512, a cell ID specifying unit 513, a CH estimating unit 514, a notification signal detecting unit 515, and a shift amount. A specifying unit 516. In addition, terminal 500 includes control signal demodulation / decoding section 517, data signal demodulation / decoding section 518, reception quality calculation section 519, data signal generation section 521, control signal generation section 522, and RS generation section 523. , An allocation / arrangement unit 524, and a transmission unit 525.

The antenna 501 receives a signal wirelessly transmitted from another communication device and outputs the signal to the Tx / Rx switching unit 502. Further, the antenna 501 wirelessly transmits the signal output from the Tx / Rx switching unit 502. The Tx / Rx switching unit 502 outputs the signal output from the antenna 501 to the receiving unit 511. Further, the Tx / Rx switching unit 502 outputs the signal output from the transmission unit 525 to the antenna 501.

The reception unit 511 performs reception processing of the signal output from the Tx / Rx switching unit 502. The reception processing by the reception unit 511 includes, for example, amplification and frequency conversion. Receiving section 511 outputs the signal obtained by the receiving process to synchronizing signal detecting section 512, CH estimating section 514, broadcast signal detecting section 515, control signal demodulation / decoding section 517, and data signal demodulation / decoding section 518.

The synchronization signal detection unit 512 detects synchronization signals (PSS and SSS) included in the signal output from the reception unit 511. Then, the synchronization signal detection unit 512 outputs the detected synchronization signal to the notification signal detection unit 515. In addition, synchronization signal detection section 512 outputs synchronization signal sequence information indicating the detected synchronization signal sequence to cell ID identification section 513 and shift amount identification section 516.

The cell ID identification unit 513 identifies the cell ID of the base station 300 based on the synchronization signal sequence indicated by the synchronization signal sequence information output from the synchronization signal detection unit 512. Then, the cell ID specifying unit 513 outputs cell ID information indicating the specified cell ID to the shift amount specifying unit 516.

The CH estimation unit 514 performs channel estimation of the uplink channel based on the RS included in the signal output from the reception unit 511. Then, CH estimation section 514 outputs an uplink CH estimation value indicating the result of channel estimation to control signal demodulation / decoding section 517, data signal demodulation / decoding section 518, and reception quality calculation section 519.

The notification signal detection unit 515 is included in the signal output from the reception unit 511 based on the timing of the synchronization signal output from the synchronization signal detection unit 512 and the shift amount information output from the shift amount specification unit 516. The broadcast signal (PBCH) to be detected is detected. Then, broadcast signal detection section 515 outputs the detected broadcast signal to control signal demodulation / decoding section 517, data signal demodulation / decoding section 518, and reception quality calculation section 519.

The shift amount identifying unit 516 identifies the shift amount of the subframe in the base station 300 based on the PSS or SSS sequence indicated by the synchronization signal sequence information output from the synchronization signal detecting unit 512. Alternatively, the shift amount specifying unit 516 may specify the shift amount of the subframe in the base station 300 based on the cell ID indicated by the cell ID information output from the cell ID specifying unit 513.

For example, in the memory of the terminal 500, the same correspondence information as the correspondence information stored in the base station 300, the correspondence information of the synchronization signal series or cell ID and the shift amount is stored. Shift amount identifying section 516 identifies the amount of subframe shift in base station 300 based on the sequence indicated by the synchronization signal sequence information or the cell ID indicated by the cell ID information and the correspondence information. Shift amount specifying section 516 outputs shift amount information indicating the specified shift amount to broadcast signal detecting section 515, control signal demodulating / decoding section 517, data signal demodulating / decoding section 518, and reception quality calculating section 519.

The control signal demodulation / decoding unit 517 demodulates and decodes the control signal included in the signal output from the reception unit 511. Specifically, the control signal demodulation / decoding section 517 receives the uplink CH estimation value output from the CH estimation section 514, the notification signal output from the notification signal detection section 515, and the shift output from the shift amount identification section 516. Based on the quantity information, the control signal is demodulated and decoded. Control signal demodulation / decoding section 517 outputs the decoding result (control information) to data signal demodulation / decoding section 518 and control signal generation section 522. Control signal demodulation / decoding section 517 outputs allocation information included in the control information to allocation / arrangement section 524.

The data signal demodulator / decoder 518 demodulates and decodes the data signal included in the signal output from the receiver 511. Specifically, the data signal demodulation / decoding unit 518 includes an uplink CH estimation value from the CH estimation unit 514, control information from the control signal demodulation / decoding unit 517, a notification signal from the notification signal detection unit 515, and a shift amount. Demodulation and decoding are performed based on the shift amount information from the specifying unit 516. Then, the data signal demodulation / decoding unit 518 outputs the decoding result (data) to the control signal generation unit 522.

Reception quality calculation section 519 calculates reception quality in terminal 500 based on the uplink CH estimation value from CH estimation section 514, the notification signal from notification signal detection section 515, and the shift amount information from shift amount identification section 516. To do. The reception quality calculated by the reception quality calculation unit 519 is, for example, PMI (Precoding Matrix Indicator), CQI (Channel Quality Indicator), RI (Rank Indication), or the like. Reception quality calculation section 519 notifies control signal generation section 522 of the calculated reception quality.

The data signal generator 521 generates an upstream data signal. Then, the data signal generation unit 521 outputs the generated data signal to the allocation / arrangement unit 524. The control signal generation unit 522 generates an uplink control signal. The uplink control signal includes, for example, a reception response (Ack / Nack) based on the decoding results from the data signal demodulation / decoding unit 518 and the control signal demodulation / decoding unit 517, and the reception quality notified from the reception quality calculation unit 519. Etc. are included. The control signal generation unit 522 outputs the generated control signal to the allocation / arrangement unit 524. The RS generation unit 523 generates an RS. Then, the RS generation unit 523 outputs the generated RS to the allocation / arrangement unit 524.

The allocation / arrangement unit 524 allocates and allocates the signals output from the data signal generation unit 521, the control signal generation unit 522, and the RS generation unit 523 based on the allocation information output from the control signal demodulation / decoding unit 517. I do. Then, allocation / arrangement section 524 outputs the signal that has been allocated and allocated to each signal to transmission section 525.

The transmission unit 525 performs transmission processing of the signal output from the allocation / arrangement unit 524. The transmission processing by the transmission unit 525 includes, for example, frequency conversion and amplification. Transmitting section 525 outputs the signal subjected to the transmission process to Tx / Rx switching section 502.

1A and 1B can be realized by the antenna 501, the Tx / Rx switching unit 502, and the receiving unit 511. The first detection unit 132 illustrated in FIGS. 1A and 1B can be realized by the synchronization signal detection unit 512. The specifying unit 133 illustrated in FIGS. 1A and 1B can be realized by the shift amount specifying unit 516. The second detection unit 134 illustrated in FIGS. 1A and 1B can be realized by the notification signal detection unit 515.

(Device hardware configuration)
FIG. 6 is a diagram illustrating an example of a hardware configuration of the terminal. The terminal 500 shown in FIG. 5 can be realized by, for example, the communication device 600 shown in FIG. The communication device 600 includes a processor 601, a memory 602, an analog circuit 603, a digital circuit 604, and a wireless I / F 605. The processor 601, the memory 602, the analog circuit 603, the digital circuit 604, and the wireless I / F 605 are connected by, for example, a bus.

The processor 601 governs overall control of the communication device 600. The memory 602 includes, for example, a main memory and an auxiliary memory. The main memory is, for example, a RAM. The main memory is used as a work area for the processor 601. The auxiliary memory is, for example, a nonvolatile memory such as a magnetic disk, an optical disk, or a flash memory. Various programs for operating the communication device 600 are stored in the auxiliary memory. The program stored in the auxiliary memory is loaded into the main memory and executed by the processor 601.

The analog circuit 603 is a circuit that processes an analog signal. The analog circuit 603 is controlled by the processor 601. The digital circuit 604 is a circuit that processes a digital signal. The digital circuit 604 is controlled by the processor 601. The wireless I / F 605 is a communication interface that performs communication with the outside of the communication device 600 (for example, a base station) by wireless. The wireless I / F 605 is controlled by the processor 601.

The antenna 501 and the Tx / Rx switching unit 502 illustrated in FIG. 5 can be realized by the wireless I / F 605, for example. The reception unit 511 and the transmission unit 525 illustrated in FIG. 5 can be realized by an analog circuit 603 and a wireless I / F 605, for example.

The synchronization signal detection unit 512, the cell ID identification unit 513, the CH estimation unit 514, the broadcast signal detection unit 515, and the shift amount identification unit 516 illustrated in FIG. 5 can be realized by, for example, the processor 601, the digital circuit 604, and the memory 602. it can. Further, the control signal demodulation / decoding unit 517, the data signal demodulation / decoding unit 518, and the reception quality calculation unit 519 illustrated in FIG. 5 can be realized by the processor 601, the digital circuit 604, and the memory 602, for example. Further, the data signal generation unit 521, the control signal generation unit 522, the RS generation unit 523, and the allocation / arrangement unit 524 illustrated in FIG. 5 can be realized by the processor 601, the digital circuit 604, and the memory 602, for example.

(Processing by the base station according to the second embodiment)
FIG. 7A is a flowchart illustrating a first example of processing by the base station according to the second embodiment. When associating the shift amount with the PSS sequence, base station 300 executes, for example, each step shown in FIG. 7A. Each step shown in FIG. 7A is executed, for example, when base station 300 is activated.

First, base station 300 determines the PSS and SSS sequences transmitted from base station 300 according to the cell ID of base station 300 (own station) (step S711). Next, the base station 300 starts subframe shift according to the PSS sequence determined in step S711 (step S712). That is, base station 300 shifts the subframe by a shift amount corresponding to the PSS sequence.

FIG. 7B is a flowchart illustrating a second example of processing by the base station according to the second embodiment. When associating the shift amount with the SSS, the base station 300 executes, for example, each step shown in FIG. 7B. Each step shown in FIG. 7B is executed, for example, when base station 300 is activated.

First, base station 300 determines the PSS and SSS sequences transmitted from base station 300 according to the cell ID of base station 300 (own station) (step S721). Next, the base station 300 starts subframe shift according to the SSS sequence determined in step S721 (step S722). That is, base station 300 shifts the subframe by a shift amount corresponding to the SSS sequence.

FIG. 7C is a flowchart illustrating a third example of processing by the base station according to the second embodiment. When associating the shift amount with the cell ID, base station 300 executes, for example, each step shown in FIG. 7C. Each step shown in FIG. 7C is executed, for example, when base station 300 is activated.

First, base station 300 determines the PSS and SSS sequences transmitted from base station 300 according to the cell ID of base station 300 (own station) (step S731). Next, the base station 300 starts subframe shift according to the cell ID of the base station 300 (step S732). That is, base station 300 shifts the subframe by a shift amount corresponding to the cell ID sequence.

(Processing by the terminal according to the second embodiment)
FIG. 8A is a flowchart illustrating a first example of processing by the terminal according to the second embodiment. When associating the shift amount with PSS, terminal 500 executes the steps shown in FIG. 8A, for example. Each step shown in FIG. 8A is executed, for example, when terminal 500 is connected to base station 300.

First, terminal 500 detects a PSS included in a radio signal transmitted from base station 300 (step S811). Next, terminal 500 identifies the amount of subframe shift in base station 300 based on the PSS detected in step S811 (step S812).

Next, terminal 500 corrects the subframe number based on the shift amount specified in step S812 (step S813), and performs processing based on the corrected subframe number. For example, terminal 500 detects PBCH based on the timing of the subframe in which PSS is detected and the correction result of the subframe number.

FIG. 8B is a flowchart illustrating a second example of processing by the terminal according to the second embodiment. When associating the shift amount with SSS, terminal 500 executes each step shown in FIG. 8B, for example. Each step shown in FIG. 8B is executed, for example, when terminal 500 is connected to base station 300.

First, terminal 500 detects a PSS included in a radio signal transmitted from base station 300 (step S821). In addition, terminal 500 detects an SSS included in a radio signal transmitted from base station 300 (step S822). Next, terminal 500 identifies the amount of subframe shift in base station 300 based on the SSS detected in step S822 (step S823).

Next, terminal 500 corrects the subframe number based on the shift amount specified in step S823 (step S824), and performs processing based on the corrected subframe number. For example, terminal 500 detects PBCH based on the timing of the subframe in which PSS is detected and the correction result of the subframe number.

FIG. 8C is a flowchart illustrating Example 3 of processing by the terminal according to the second embodiment. When associating the shift amount with the cell ID, terminal 500 executes, for example, each step shown in FIG. 8C. Each step shown in FIG. 8C is executed, for example, when terminal 500 is connected to base station 300.

First, terminal 500 detects a PSS included in a radio signal transmitted from base station 300 (step S831). Also, terminal 500 detects an SSS included in a radio signal transmitted from base station 300 (step S832). Next, terminal 500 specifies the cell ID of base station 300 based on the PSS sequence detected in step S831 and the SSS sequence detected in step S832 (step S833).

Next, terminal 500 specifies the amount of subframe shift in base station 300 based on the cell ID specified in step S833 (step S834). Next, terminal 500 corrects the subframe number based on the shift amount specified in step S834 (step S835), and performs processing based on the corrected subframe number. For example, terminal 500 detects PBCH based on the timing of the subframe in which PSS is detected and the correction result of the subframe number.

Thus, according to the second embodiment, in the configuration in which the subframes are time-shifted between the base stations 211 to 213, the time resources in which the base stations 211 to 213 store the PBCH (specific signal) are used as the synchronization signal series. Alternatively, it can be associated with a cell ID. As a result, even if the time resource for storing the PBCH and the shift amount are not notified to the terminal 500, the terminal 500 identifies the time resource in which the PBCH is stored from the detected synchronization signal sequence or cell ID, and detects the PBCH. can do.

Therefore, it is possible to eliminate the need for control information for notifying the terminal 500 of the time resource for storing the PBCH while suppressing the collision of the PBCH by shifting the time resource for the base stations 211 to 213 to store the PBCH. Therefore, it is possible to reduce the control information transmitted to terminal 500.

(Correction of subframe number)
Here, correction of the subframe number will be described. For example, when a subframe shift is performed between cells, the master cell notifies the target cell of the shift amount. When a small cell exists in the coverage area of the macro cell, for example, the macro cell becomes the master. Here, when the time shift of the subframe is performed, the time resource of the synchronization signal is shifted. And a terminal connects to a cell by performing a cell search based on the synchronizing signal which a cell transmits. At this time, the terminal recognizes the subframe in which the synchronization signal can be detected as the start of the subframe, but since the synchronization signal itself is located at a different location from the master cell, the terminal recognizes the subframe number depending on the connected cell. Deviation occurs.

For this reason, when cooperative communication is performed between cells, it is necessary to match the recognition of subframe numbers. For example, in each cell, the subframe number is corrected to match the master cell. Between cells, the shift amount can be shared by a backhaul interface such as an optical fiber. However, in order to notify the terminal of the shift amount, a new control signal needs to be added.

For example, it is conceivable to store the shift amount in the control signal and send it, but such specifications are not formulated in the current LTE (Long Term Evolution) and LTE-A specifications. Further, in order to store the shift amount in the control signal and send it, it is necessary to change the format of the control signal.

On the other hand, according to the base station 300, by associating the synchronization signal sequence or cell ID with the shift amount, the terminal recognizes the shift amount without affecting the control signal, and the subframe number or SFN (System). Frame Number) can be recognized and matched.

(Embodiment 3)
The third embodiment will be described with respect to differences from the second embodiment.

(Radio signal transmitted from each base station according to the third embodiment)
FIG. 9 is a diagram of an example of a radio signal transmitted from each base station according to the third embodiment. Base stations 911 to 915 shown in FIG. 9 are, for example, base stations that form overlapping cell areas. Base stations 911 to 915 correspond to the transmission stations 110 and 120 shown in FIGS. 1A and 1B and are small cells, pico cells, or femto cells that are close to each other.

Wireless signals 921 to 925 are wireless signals transmitted from the base stations 911 to 915, respectively. In each of the radio signals 921 to 925, “CRS” indicates a CRS (Cell-Specific Reference Signal) of NCT (New Carrier Type). In each of the wireless signals 921 to 925, # 0 to # 10 indicate subframe numbers.

Although not shown, each of the base stations 911 to 915 transmits PSS and SSS in a cycle of 5 [ms] by storing the PSS and SSS in a subframe whose subframe number is a multiple of 5, for example ( (Similar to the example of FIGS. 2A and 2B). Further, as shown in FIG. 9, each of the base stations 911 to 915 stores the CRS every 5 subframes, thereby transmitting the CRS at a cycle of 10 [ms].

Also, each of the base stations 911 to 915 uses a CRS transmission pattern (transmission subframe) corresponding to the cell ID of the own station. The cell ID is, for example, a PCID (Physical-layer Cell Identity). For example, there are five CRS transmission patterns (# 0, # 5), (# 1, # 6), (# 2, # 7), (# 3, # 8), and (# 4, # 9). is there.

PCID mod 5 indicates a remainder obtained by dividing the cell IDs of the radio signals 921 to 925 by 5. In the example shown in FIG. 9, the PCID mods 5 of the radio signals 921 to 925 are “0” to “4”, respectively. Each of the base stations 911 to 915 selects a transmission pattern according to its own PCID mod 5, and transmits a CRS according to the selected transmission pattern.

For example, since the PCID mod 5 of the own cell is “0”, the base station 911 selects the transmission pattern (# 0, # 5), and adds the CRS to each subframe of the subframe numbers “# 0” and “# 5”. Is stored. A terminal connected to the base station 911 detects PSS and SSS from the radio signal 921 transmitted from the base station 911. Then, the terminal connected to the base station 911 specifies the cell ID of the base station 911 from the detected PSS and SSS sequences, and calculates the PCID mod 5 of the base station 911 based on the specified cell ID.

In the example illustrated in FIG. 9, since the PCID mod 5 of the base station 911 is “0”, the terminal connected to the base station 911 determines that the CRS transmission pattern in the base station 911 is (# 0, # 5). . Then, the terminal connected to the base station 911 uses the subframe in which the PSS and SSS are detected as the subframe of # 0, and subframes with the subframe numbers “# 0” and “# 5” based on the identified transmission pattern. CRS is detected by demodulating.

The base station 912 selects the transmission pattern (# 1, # 6) because the PCID mod 5 of its own cell is “1”, and stores the CRS in each subframe of the subframe numbers “# 1”, “# 6”. To do. A terminal connected to the base station 912 detects PSS and SSS from the radio signal 922 transmitted from the base station 912. Then, the terminal connected to the base station 912 specifies the cell ID of the base station 912 from the detected PSS and SSS sequences, and calculates the PCID mod 5 of the base station 912 based on the specified cell ID.

In the example shown in FIG. 9, since the PCID mod 5 of the base station 912 is “1”, the terminal connected to the base station 912 specifies that the CRS transmission pattern in the base station 912 is (# 1, # 6). . Then, the terminal connected to the base station 912 sets the subframe in which the PSS and SSS are detected as the subframe of # 0, and subframes of the subframe numbers “# 1” and “# 6” based on the specified transmission pattern. CRS is detected by demodulating.

In this way, when the base stations 911 to 915 shift the CRS transmission patterns from each other, the base stations 911 to 915 associate the cell IDs of the base stations with the CRS transmission patterns. As a result, the terminal can identify the CRS transmission pattern in the base stations 911 to 915 from the identified cell ID and detect the CRS without being notified of the CRS transmission pattern in the base stations 911 to 915, for example. become.

Although the case where the CRS transmission pattern and the cell ID are associated with each other has been described, the CRS transmission pattern and the PSS sequence may be associated with each other. In this case, the terminal can identify the CRS transmission pattern in the base stations 911 to 915 from the detected PSS sequence and detect the CRS. Alternatively, the CRS transmission pattern and the SSS sequence may be associated with each other. In this case, the terminal can identify the CRS transmission pattern in the base stations 911 to 915 from the detected SSS sequence and detect the CRS.

(NCT and CRS)
Here, NCT and CRS will be described. NCT performs communication using a carrier (New Carrier) different from a conventional carrier (Legacy Carrier), and uses a wireless format different from the conventional one on the carrier (New Carrier).

On NCT, it has been proposed to transmit CRSs only in specific subframes instead of transmitting CRSs, which are cell-specific pilot signals (reference signals), in all subframes as in conventional carriers. This is sometimes called RCRS (Reduced CRS). The specification of the method for notifying the RCRS transmission pattern has not yet been established.

(Base station according to the third embodiment)
FIG. 10 is a diagram of an example of the base station according to the third embodiment. In FIG. 10, the same parts as those shown in FIG. As illustrated in FIG. 10, the base station 300 according to the third embodiment includes a CRS pattern determination unit 1001 instead of the shift addition unit 326 of the base station 300 illustrated in FIG. The CRS pattern determination unit 1001 can be realized by the processor 401, the digital circuit 404, and the memory 402 shown in FIG.

Synchronization signal generation section 325 outputs synchronization signal sequence information and cell ID information to CRS pattern determination section 1001. CRS pattern determination section 1001 determines a CRS transmission pattern in base station 300 based on the PSS or SSS sequence indicated by the synchronization signal sequence information output from synchronization signal generation section 325. Alternatively, the CRS pattern determination unit 1001 may determine the CRS transmission pattern in the base station 300 based on the cell ID indicated by the cell ID information output from the synchronization signal generation unit 325.

For example, the memory of the base station 300 stores correspondence information between a synchronization signal series or cell ID and a transmission pattern. Based on the correspondence information, the CRS pattern determining unit 1001 selects a transmission pattern corresponding to the sequence indicated by the synchronization signal sequence information or the cell ID indicated by the cell ID information. Then, the CRS pattern determination unit 1001 outputs CRS pattern information indicating the determined transmission pattern to the RS generation unit 324.

The RS generation unit 324 generates a CRS based on the transmission pattern indicated by the CRS pattern information output from the CRS pattern determination unit 1001, and outputs a reference signal including the generated CRS to the allocation / arrangement unit 328.

1A and 1B can be realized by, for example, scheduler 321, synchronization signal generation unit 325, CRS pattern determination unit 1001, notification signal generation unit 327, and allocation / arrangement unit 328.

(Terminal according to the third embodiment)
FIG. 11 is a diagram of an example of a terminal according to the third embodiment. In FIG. 11, the same parts as those shown in FIG. The terminal 500 according to the third embodiment includes, for example, a CRS pattern specifying unit 1101 instead of the shift amount specifying unit 516 of the terminal 500 illustrated in FIG. The CRS pattern specifying unit 1101 can be realized by the processor 601, the digital circuit 604, and the memory 602 shown in FIG.

Synchronization signal detection section 512 outputs synchronization signal sequence information to cell ID identification section 513 and CRS pattern identification section 1101. The cell ID specifying unit 513 outputs the cell ID information to the CRS pattern specifying unit 1101.

The CRS pattern identifying unit 1101 identifies the CRS transmission pattern in the base station 300 based on the PSS or SSS indicated by the synchronization signal sequence information output from the synchronization signal detecting unit 512. Alternatively, the CRS pattern specifying unit 1101 may specify the CRS transmission pattern in the base station 300 based on the cell ID indicated by the cell ID information output from the cell ID specifying unit 513.

For example, the same information as the correspondence information stored in the base station 300 is stored in the memory of the terminal 500, and the correspondence information between the synchronization signal series or cell ID and the transmission pattern is stored. The CRS pattern specifying unit 1101 specifies the CRS transmission pattern in the base station 300 based on the synchronization signal sequence or cell ID and the correspondence information. CRS pattern identifying section 1101 outputs CRS arrangement information indicating the identified transmission pattern to CH estimating section 514, control signal demodulating / decoding section 517, data signal demodulating / decoding section 518, and reception quality calculating section 519.

The CH estimation unit 514 detects CRS included in the signal output from the reception unit 511 based on the CRS arrangement information output from the CRS pattern specifying unit 1101, and performs channel estimation of the uplink channel based on the detected CRS. .

The control signal demodulation / decoding unit 517 demodulates and decodes the control signal based on the CRS arrangement information output from the CRS pattern specifying unit 1101. The data signal demodulation / decoding unit 518 performs demodulation and decoding of the data signal based on the CRS arrangement information output from the CRS pattern specifying unit 1101. Reception quality calculation section 519 calculates reception quality in terminal 500 based on the CRS arrangement information output from CRS pattern identification section 1101.

The specifying unit 133 illustrated in FIGS. 1A and 1B can be realized by the CRS pattern specifying unit 1101. The second detection unit 134 illustrated in FIGS. 1A and 1B can be realized by the CH estimation unit 514, the control signal demodulation / decoding unit 517, the data signal demodulation / decoding unit 518, and the reception quality calculation unit 519.

(Processing by the base station according to the third embodiment)
FIG. 12A is a flowchart illustrating a first example of processing by the base station according to the third embodiment. When associating the transmission pattern with the PSS sequence, base station 300 executes, for example, each step shown in FIG. 12A. Each step shown in FIG. 12A is executed, for example, when base station 300 is activated.

First, base station 300 determines the PSS and SSS sequences to be transmitted from base station 300 according to the cell ID of base station 300 (own station) (step S1211). Next, base station 300 determines a CRS transmission pattern in accordance with the PSS sequence determined in step S1211 (step S1212), and starts CRS transmission based on the determined transmission pattern.

FIG. 12B is a flowchart illustrating a second example of processing by the base station according to the third embodiment. When associating the transmission pattern with the SSS, the base station 300 executes, for example, each step shown in FIG. 12B. Each step shown in FIG. 12B is executed, for example, when base station 300 is activated.

First, base station 300 determines the PSS and SSS sequences transmitted from base station 300 according to the cell ID of base station 300 (own station) (step S1221). Next, base station 300 determines a CRS transmission pattern according to the SSS sequence determined in step S1221 (step S1222), and starts CRS transmission based on the determined transmission pattern.

FIG. 12C is a flowchart illustrating a third example of processing by the base station according to the third embodiment. When associating a transmission pattern with a cell ID, base station 300 executes, for example, each step shown in FIG. 12C. Each step shown in FIG. 12C is executed, for example, when base station 300 is activated.

First, base station 300 determines the PSS and SSS sequences transmitted from base station 300 according to the cell ID of base station 300 (own station) (step S1231). Next, base station 300 determines a CRS transmission pattern according to the cell ID of base station 300 (step S1232), and starts CRS transmission based on the determined transmission pattern.

(Processing by the terminal according to the third embodiment)
FIG. 13A is a flowchart illustrating a first example of processing by the terminal according to the third embodiment. When associating the transmission pattern with the PSS, the terminal 500 executes the steps shown in FIG. 13A, for example. Each step shown in FIG. 13A is executed, for example, when terminal 500 is connected to base station 300.

First, terminal 500 detects a PSS included in a radio signal transmitted from base station 300 (step S1311). Next, terminal 500 identifies the CRS transmission subframe in base station 300 based on the PSS detected in step S1311 (step S1312), and detects the CRS from the radio signal from terminal 500 based on the identification result. .

FIG. 13B is a flowchart illustrating a second example of processing by the terminal according to the third embodiment. When associating the transmission pattern with the SSS, the terminal 500 executes the steps shown in FIG. 13B, for example. Each step shown in FIG. 13B is executed when terminal 500 is connected to base station 300, for example.

First, terminal 500 detects a PSS included in a radio signal transmitted from base station 300 (step S1321). In addition, terminal 500 detects an SSS included in a radio signal transmitted from base station 300 (step S1322). Next, terminal 500 identifies the CRS transmission subframe in base station 300 based on the SSS detected in step S1322 (step S1323), and detects the CRS from the radio signal from terminal 500 based on the identification result. .

FIG. 13C is a flowchart illustrating Example 3 of processing by the terminal according to the third embodiment. When associating a transmission pattern with a cell ID, terminal 500 executes, for example, each step shown in FIG. 13C. Each step shown in FIG. 13C is executed, for example, when terminal 500 is connected to base station 300.

First, terminal 500 detects a PSS included in a radio signal transmitted from base station 300 (step S1331). In addition, terminal 500 detects SSS included in the radio signal transmitted from base station 300 (step S1332). Next, terminal 500 specifies the cell ID of base station 300 based on the PSS sequence detected in step S1331 and the SSS sequence detected in step S1332 (step S1333).

Next, terminal 500 identifies a CRS transmission subframe in base station 300 based on the cell ID identified in step S1333 (step S1334), and detects CRS from the radio signal from terminal 500 based on the identification result. .

As described above, according to the third embodiment, in the configuration in which subframes for storing CRS (specific signals) are shifted between base stations 211 to 213, base stations 211 to 213 transmit subframes for storing CRS as synchronization signals. Can be associated with a series or cell ID. Thus, even without notifying terminal 500 of the time resource for storing the CRS, terminal 500 can identify the time resource in which the CRS is stored from the detected synchronization signal sequence or cell ID, and detect the CRS. it can.

Therefore, it is possible to eliminate control information for notifying the terminal 500 of the time resource for storing the CRS while shifting the time resource for storing the CRS by the base stations 211 to 213 to suppress the collision of the CRS. Therefore, it is possible to reduce the control information transmitted to terminal 500.

(Relationship between PSS and SSS and cell ID)
Next, the relationship between the PSS and SSS and the cell ID will be described. In LTE and LTE-A, there are 504 cell IDs. The 504 types of cell IDs are classified into 168 types of groups, and each group has three types of identifiers. If this is expressed by an equation, for example, N _ID (cell) = 3N _ID (1) + N _ID (2).

Here, N _ID (cell) indicates a cell ID. N _ID (1) indicates 168 types of groups (cell groups). N _ID (2) indicates three types of identifiers. Thereby, 504 types of cell IDs can be expressed. In LTE and LTE-A, by associating a PSS sequence with an SSS sequence, the cell ID can be identified by identifying the PSS and SSS sequences.

(Synchronous signal series)
Next, a PSS sequence (root sequence) will be described. The PSS sequence is generated using a Zadoff-Chu sequence in the frequency domain, and can be expressed by the following equation (1), for example.

Here, the route index u is associated with the cell group identifier N _ID (2). The terminal can blind-estimate the PSS sequence and identify N _ID (2) from the detected sequence.

Next, the SSS series will be described. The SSS sequence can be expressed by the following equation (2), for example. The SSS sequence has a structure in which a binary sequence of length 31 is interleaved, and is scrambled using a scramble sequence (c ₀ (n), c ₁ (n)) given by the PSS sequence.

m ₀ and m ₁ are associated with N _ID (1) and can be expressed by the following equation (3).

FIG. 14 is a diagram illustrating an example of a relationship between a series and a cell group. A table 1400 shown in FIG. 14 shows the relationship between m ₀ and m ₁ and N _ID (1) according to the above equation (3). Further, s ₀ (m ₀ ) (n) is generated by cyclic shifting the m sequence ｓs (n). That is, s ₀ (m ₀ ) (n) can be expressed by the following equation (4).

Also, the m series ^ s (n) can be expressed by the following equation (5).

In the initial state, x (0) = 0, x (1) = 0, x (2) = 0, x (3) = 0, x (4) = 1.

Next, c ₀ (n) and c ₁ (n) will be described. c ₀ (n) and c ₁ (n) are scrambled sequences that depend on the PSS sequence, and are represented as cyclic shifts of the m sequence ^ s (n). That is, c ₀ (n) and c ₁ (n) can be expressed by the following equation (6), for example.

^ C (n) is expressed as ^ c (i) = 1−2x (i) as in the m-sequence ^ s (n), but x (i) is expressed by the following equation (7) Is different from m sequence ^ s (n).

Next, z ₁ (m ₀ ) (n) and z ₁ (m ₁ ) (n) will be described. z ₁ (m ₀ ) (n) and z ₁ (m ₁ ) (n) are also generated by cyclic shifting the m sequence ^ s (n), and can be expressed by, for example, the following equation (8).

^ Z (n) is also expressed as ^ z (i) = 1−2x (i) as in the m-sequence ^ s (n), but x (i) is as shown in the following equation (9) Is different from m sequence ^ s (n).

Since the terminal generates a SSS sequence generation mechanism (such as m-sequence and PSS scrambling), m ₀ and m ₁ are identified based on these information, and N _ID (1) is derived. Can do. Then, it is possible to derive the N _ID (cell) based on N _ID (1) and N _ID (2).

As described above, according to the communication system, transmission station, reception station, and communication method, it is possible to reduce control information.

100 Communication System 110, 120 Transmitting Station 111 Allocation Unit 112, 329, 525 Transmitting Unit 130 Receiving Station 131, 311, 511 Receiving Unit 132 First Detection Unit 133 Identification Unit 134 Second Detection Unit 201 DL_CCH
202 PDSCH
203 MBSFN
211 to 213, 300, 911 to 915 Base station 221 to 223, 921 to 925 Radio signal 301, 501 Antenna 302, 502 Tx / Rx switching unit 312, 514 CH estimation unit 313, 517 Control signal demodulation / decoding unit 314, 518 Data signal demodulation / decoding unit 315, 519 Reception quality calculation unit 321 Scheduler 322, 521 Data signal generation unit 323, 522 Control signal generation unit 324, 523 RS generation unit 325 Synchronization signal generation unit 326 Shift addition unit 327 Notification signal generation unit 328 , 524 Allocation / arrangement unit 400, 600 Communication device 401, 601 Processor 402, 602 Memory 403, 603 Analog circuit 404, 604 Digital circuit 405, 605 Wireless I / F
406 Transmission network I / F
500 terminal 512 synchronization signal detection unit 513 cell ID identification unit 515 broadcast signal detection unit 516 shift amount identification unit 1001 CRS pattern determination unit 1101 CRS pattern identification unit

Claims (18)

A transmission station that assigns a synchronization signal of a sequence according to identification information of the own station to a periodic resource, and transmits a radio signal in which a specific signal is assigned to a resource according to the sequence of the synchronization signal;
The synchronization signal is detected from a radio signal transmitted by the transmitting station, a resource to which the specific signal is allocated is identified based on the detected sequence of the synchronization signal, and the identification is performed from the radio signal based on the identified resource. A receiving station that detects the signal;
A communication system comprising: The transmitting station assigns a specific signal to a resource corresponding to the synchronization signal sequence by shifting a subframe of the radio signal by a shift amount corresponding to the synchronization signal sequence,
The receiving station identifies the shift amount based on the detected sequence of synchronization signals, and identifies a resource to which the specific signal is allocated based on the identified shift amount;
The communication system according to claim 1. The communication system according to claim 2, wherein the specific signal is a physical broadcast channel. The transmitting station and the receiving station share correspondence information between the synchronization signal sequence and the shift amount,
The transmitting station shifts the subframe of the radio signal by a shift amount based on the sequence of the synchronization signal and the correspondence information,
The receiving station specifies the shift amount based on the sequence of the synchronization signal and the correspondence information;
The communication system according to claim 2 or 3, wherein The communication system according to any one of claims 2 to 4, wherein the receiving station performs coordinated communication with another cell based on the specified shift amount. The transmitting station assigns the specific signal to a subframe corresponding to the synchronization signal sequence,
The receiving station specifies a subframe to which the specific signal is assigned based on the detected sequence of synchronization signals, and detects the specific signal from the specified subframe;
The communication system according to claim 1. The communication system according to claim 6, wherein the specific signal is a cell-specific reference signal. The transmitting station and the receiving station share correspondence information between the synchronization signal sequence and the subframe,
The transmitting station assigns the specific signal to a subframe based on the synchronization signal sequence and the correspondence information;
The receiving station specifies a subframe to which the specific signal is assigned based on the sequence of the synchronization signal and the correspondence information;
The communication system according to claim 6 or 7, characterized by the above. The synchronization signal includes a primary synchronization signal;
The transmitting station assigns the specific signal to a resource corresponding to the primary synchronization signal sequence;
The receiving station specifies a resource to which the specific signal is allocated based on the detected primary synchronization signal sequence;
The communication system according to any one of claims 1 to 8, characterized in that: The synchronization signal includes a secondary synchronization signal;
The transmitting station assigns the specific signal to a resource corresponding to the sequence of the secondary synchronization signal,
The receiving station specifies a resource to which the specific signal is allocated based on the detected sequence of secondary synchronization signals.
The communication system according to any one of claims 1 to 8, characterized in that: A transmission station that assigns a synchronization signal of a sequence according to identification information of the own station to a periodic resource, and transmits a radio signal in which a specific signal is assigned to the resource according to the identification information;
The synchronization signal is detected from a radio signal transmitted by the transmission station, identification information of the transmission station is identified based on the detected synchronization signal sequence, and the specific signal is assigned based on the identified identification information A receiving station that identifies a resource and detects the specific signal from the radio signal based on the identified resource;
A communication system comprising: The synchronization signal includes a primary synchronization signal and a secondary synchronization signal,
The receiving station specifies identification information of the transmitting station based on each sequence of the detected primary synchronization signal and secondary synchronization signal;
The communication system according to claim 11. An allocation unit that allocates a synchronization signal of a sequence according to identification information of the own station to a periodic resource, and allocates a specific signal to the resource according to the sequence of the synchronization signal;
A transmission unit for transmitting a radio signal based on an allocation result by the allocation unit;
A transmission station comprising: An allocation unit that allocates a synchronization signal of a sequence according to identification information of the own station to a periodic resource, and allocates a specific signal to the resource according to the identification information;
A transmission unit for transmitting a radio signal based on an allocation result by the allocation unit;
A transmission station comprising: A synchronization signal of a sequence corresponding to the identification information of the transmitting station is allocated to a periodic resource, and the radio signal is received from the transmitting station that transmits a radio signal in which a specific signal is allocated to the resource corresponding to the sequence of the synchronization signal. A receiving unit to
A first detection unit for detecting the synchronization signal from a radio signal received by the reception unit;
A specifying unit that specifies a resource to which the specific signal is allocated based on a sequence of synchronization signals detected by the first detection unit;
A second detector for detecting the specific signal from the radio signal based on the resource specified by the specific unit;
A receiving station comprising: A synchronization signal of a sequence corresponding to the identification information of the transmitting station is allocated to a periodic resource, and the radio signal from the transmitting station that transmits a radio signal in which a specific signal is allocated to the resource corresponding to the sequence of the identification information is received. A receiving unit to
A first detection unit for detecting the synchronization signal from a radio signal received by the reception unit;
A identifying unit that identifies identification information of the transmitting station based on a sequence of synchronization signals detected by the first detection unit, and that identifies a resource to which the specific signal is allocated based on the identified identification information;
A second detector for detecting the specific signal from the radio signal based on the resource specified by the specific unit;
A receiving station comprising: A transmitting station assigns a synchronization signal of a sequence corresponding to identification information of the transmitting station to a periodic resource, and transmits a radio signal in which a specific signal is assigned to a resource corresponding to the sequence of the synchronization signal,
The receiving station detects the synchronization signal from the radio signal transmitted by the transmitting station, specifies a resource to which the specific signal is allocated based on the detected sequence of the synchronization signal, and determines the radio based on the specified resource Detecting the specific signal from the signal;
A communication method characterized by the above. A transmitting station assigns a synchronization signal of a sequence corresponding to the identification information of the transmitting station to a periodic resource, and transmits a radio signal in which a specific signal is assigned to the resource corresponding to the identification information,
The receiving station detects the synchronization signal from the radio signal transmitted by the transmitting station, specifies identification information of the transmitting station based on the detected synchronization signal sequence, and specifies the specific signal based on the specified identification information Identifies the allocated resource and detects the specific signal from the radio signal based on the identified resource;
A communication method characterized by the above.

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