JP2018037958A - Communication method and communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the beam phase of an antenna with higher accuracy in the case of dividing functions of a base station between a device assuming signal processing and a device assuming wireless communication.SOLUTION: A communication method is executed by a wireless communication system including a signal processing device, i.e. a device for executing signal processing among functions of a base station and a plurality of wireless communication devices, i.e. devices for executing wireless communication of the functions of the base station. The communication method includes the steps of: measuring a propagation delay time between the signal processing device and the wireless communication devices for each of the wireless communication devices; and correcting differences of the propagation delay time among the wireless communication devices according to measurement results.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a communication technique in a communication system including a signal processing device and a plurality of moneyless communication devices.

  Dividing the function of a base station of a wireless communication system into a device that handles signal processing (Central node: CN) and a device that handles wireless communication (Remote node: RN) has been studied. Thus, it is expected to increase the flexibility of base station construction by configuring the base station function with a plurality of physically separated devices. In order to expand the band of the wireless system, it is also considered to mount a super multi-element antenna on the RN.

  In recent mobile communication systems, application of Centralized / Cloud-Radio Access Network (C-RAN) architecture has been promoted. The C-RAN architecture is expected to improve the flexibility of base station installation by reducing the size of the RN. Further, high performance of the coordinated multi-point transmission and reception (CoMP) function is expected due to the aggregation of signal processing. The optical link part between CN and RN in C-RAN is called Mobile Front-haul (MFH). In the current MFH, a transmission interface called Common Public Radio Interface (CPRI) is often used. This is because CPRI has a merit that the configuration of the RN can be simplified because it transmits up to IQ sampling data of a radio signal.

  As an example, an MFH network in which 32 RNs are connected to one CN is assumed. The CN is connected to 32 RNs by two optical fibers. Of the two optical fibers, one is used for uplink communication and the other one is used for downlink communication. Note that uplink indicates the direction from RN to CN, and downlink indicates the direction from CN to RN. Also, a configuration is assumed in which all optical fibers are transmitted using the same wavelength. A radio terminal (User equipment: UE) includes two antennas. The wireless terminal can improve the wireless transmission performance by, for example, CoMP of RN1 and RN32.

  In response to the rapid increase in wireless traffic, it has been studied to use a plurality of carrier frequency bands and increase the multilevel of signals for the purpose of speeding up. In the future, it is required to use a higher carrier frequency band, to achieve high-accuracy beam control with a multi-element antenna, and to increase spatial multiplexing. In particular, it is expected that high radio communication performance can be obtained by ensuring the gain of radio waves by highly accurate cooperative beamforming between super-element antennas of different RNs.

  As described above, under the situation where the transmission speed in the wireless section is much higher than the conventional one, the conventional optical projection method based on the interface such as the CPRI requires an enormous bandwidth for the MFH. There is a fear. For this reason, it is necessary to reduce the required capacity by functional separation between CN and RN and to ensure economic efficiency.

  Here, there is a method called MAC-PHY as one of the function division methods of CN and RN. Further, in order to perform CoMP more effectively, highly accurate time synchronization / frequency synchronization is required between a plurality of RNs. Therefore, techniques such as Precision Time Protocol (PTP) and Synchronous Ethernet (SyncE) have been used. Hereinafter, a conventional technique of MAC-PHY will be described. However, among the communications performed between the CN and the RN, the minimum configuration and operation necessary in the description of the present invention will be described.

  FIG. 10 is a diagram illustrating an example of the configuration of the CN 800 in MAC-PHY using PTP. The CN 800 has functions higher than the Media Access Control (MAC) layer. The CN 800 includes a media converter (MC) 801, a radio signal processing unit 802, a demultiplexer 810-3, a demultiplexer 810-4, a demultiplexer 810-5, a global positioning system (Global positioning system). GPS) receiver 803, clock supplying module (CSM) 804, PTP processing unit 805, RN-PTP processing unit 806, internal clock 807, and SyncE processing unit 808. The radio signal processing unit 802 includes a PDCP layer processing unit 811, an RLC layer processing unit 812, a MAC layer processing unit 813, a scheduling control unit 814, and a demultiplexer 810-2.

  In the following description (including the description of the embodiment), for each functional block indicated by a square, the left indicates input and the right indicates output (function or operation execution result). An arrow indicates a signal transmission direction. The CN 800 is connected to a host device and a plurality of (for example, 32) RNs by an optical fiber via a network such as Ethernet (registered trademark).

  A signal for a wireless section is transmitted from the host device on the optical fiber and received via the MC 801. The MC 801 converts a signal between an optical signal and an electric signal. The electric signal is converted as an electric signal using, for example, a UTP cable as a transmission medium. The radio signal processing unit 802 performs predetermined processing on the main signal and scheduling information. The radio signal processing unit 802 multiplexes the processed main signal and scheduling information to generate a radio signal.

  The demultiplexer 810-3 multiplexes the radio signal and the PTP signal. For PTP, mechanisms such as PTP over UDP over IPv4, PTP over UDP over IPv6, and PTP over Ethernet are defined. Also, an ID for identifying which PTP is used among these mechanisms is defined. Therefore, it is possible to realize demultiplexing of the radio signal and the PTP signal that are packetized at the time of the function division without impairing the communication quality.

  A GPS receiver 803 included in the CN receives time information serving as a reference from a GPS satellite. The GPS receiver 803 functions as a grand master (GM) in PTP. The demultiplexer 810-4 multiplexes the PTP upstream signal and separates the downstream signal. The PTP processing unit 805 performs a series of processes related to the PTP protocol in the CN. For example, the PTP processing unit 805 updates the time of the internal clock 807 based on a signal output from the GPS receiver 803. Further, the PTP processing unit 805 establishes time synchronization with the RN 900 by negotiation with the RN 900 (a slave of the CN 800). The RN-PTP processing unit 806 receives a PTP signal from the RN 900 via the demultiplexers 810-3, 810-4, and 810-5. The RN-PTP processing unit 806 outputs a signal to the PTP processing unit 805.

  The SyncE processing unit 808 ensures high frequency synchronization performance using a synchronous Ethernet mechanism. The SyncE processing unit 808 generates a reference frequency signal based on the clock signal supplied from the CSM 804. The SyncE processing unit 808 converts the frequency of the reference frequency signal to an Ethernet signal speed. The demultiplexer 810-5 multiplexes the signal and transmits the optical signal to the RN 900.

  FIG. 11 is a diagram illustrating an example of the configuration of the RN 900 in MAC-PHY using PTP. The RN 900 has a physical layer function (Physical layer media dependent: PHY). As shown in FIG. 11, the RN includes a demultiplexer 910-6, a demultiplexer 910-7, a demultiplexer 910-9, a radio signal processing unit 901, an intermediate frequency band processing unit (Intermediate frequency: IF) 902, A local oscillator (LO) 903, a PTP processing unit 904, an internal clock 905, a SyncE processing unit 906, and a mixer 907 are included. The radio signal processing unit 901 includes a demultiplexer 910-8, an encoding / decoding processing unit 911, a modulation / demodulation processing unit 912, a MIMO processing unit 913, an FFT / iFFT processing unit 914, and a PHY control unit 915. 11 shows an example of the RN 900 connected to the CN 800, but all of the RN 900 connected to the CN 800 may have the configuration shown in FIG. Each RN is connected to the CN via an optical fiber. The antenna included in the RN 900 may include a large number (for example, 256) of antenna elements. The IFs 902, LOs 903, and mixers 907 are provided in the same number as the number of antenna elements included in the antenna included in the RN 900. That is, the IF 902, the LO 903, and the mixer 907 are provided for each antenna element.

  The demultiplexer 910-6 separates the signal received from the CN 800 into a SyncE signal and a main signal (that is, a radio signal and a PTP signal). The demultiplexer 910-7 is demultiplexed into a radio signal and a PTP signal. The PTP processing unit 904 performs PTP negotiation with the RN-PTP processing unit 806 of the CN by performing communication via the demultiplexers 910-6, 910-7, and 910-9.

  The radio signal processing unit 901 performs predetermined processing on the main signal and scheduling information. A signal generated by executing the process is transmitted to the UE as a radio signal via the IF 902, the LO 903, and the mixer 907.

Kenji Miyamoto et al. “Proposal of base station function division method for future wireless access” IEICE Technical Report, vol.105, no.123, CS2015-15, pp. 33-38, July 2015. IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems (IEEE Std 1588-2008) ITU-T Recommendation G.826x series Seiji Yoshida et al., “Development of a collective media converter using synchronous Ethernet technology” IEICE B, Vol. J96-B, No.3, pp. 310-320, 2013.

  In the future, high-speed transmission characteristics are expected to be secured by cooperative beamforming from multiple base stations. In that case, in addition to high time synchronization and frequency synchronization, it is necessary to control the phase of the beam emitted from each antenna element with high accuracy. However, in the MFH of the C-RAN configuration, there is no such high-precision beam phase control means. For this reason, there is a problem that the communication characteristics in the wireless section are limited.

  In view of the above circumstances, the present invention is a technique that enables the beam phase of an antenna to be controlled with higher accuracy when the function of a base station is divided into a device that handles signal processing and a device that handles wireless communication. The purpose is to provide.

  One aspect of the present invention includes a signal processing device that is a device that performs signal processing among the functions of a base station, and a wireless communication device that is a device that performs wireless communication among the functions of a base station, and the wireless communication device A communication method performed by a wireless communication system including a plurality of wireless communication devices, measuring a propagation delay time between the signal processing device and the plurality of wireless communication devices for each wireless communication device, and depending on a measurement result Correcting a difference in the propagation delay time between the wireless communication devices.

  One aspect of the present invention includes a signal processing device that is a device that performs signal processing among the functions of a base station, and a wireless communication device that is a device that performs wireless communication among the functions of a base station, and the wireless communication device A communication method performed by a wireless communication system including a plurality of wireless communication systems, wherein the signal processing device transmits information having a value for controlling a beam phase of antenna elements of the plurality of wireless communication devices. A communication method comprising: transmitting to a device; and controlling the beam phase of an antenna element included in the device according to a value for controlling the beam phase.

  One aspect of the present invention includes a signal processing device that is a device that performs signal processing among the functions of a base station, and a wireless communication device that is a device that performs wireless communication among the functions of a base station, and the wireless communication device A wireless communication system comprising: a measuring unit that measures a propagation delay time between the signal processing device and the plurality of wireless communication devices for each wireless communication device; and depending on a measurement result, the wireless communication system A correction unit that corrects a difference in the propagation delay time between communication devices.

  One aspect of the present invention includes a signal processing device that is a device that performs signal processing among the functions of a base station, and a wireless communication device that is a device that performs wireless communication among the functions of a base station, and the wireless communication device A plurality of wireless communication systems, wherein the signal processing device transmits information having a value for controlling a beam phase of antenna elements of the plurality of wireless communication devices to the plurality of wireless communication devices. The communication system includes a phase control unit for transmitting, and the wireless communication device includes a phase control unit for controlling a beam phase of an antenna element included in the device according to a value for controlling the beam phase. .

  The present invention makes it possible to control the beam phase of the antenna with higher accuracy when the function of the base station is divided into a device responsible for signal processing and a device responsible for wireless communication.

It is a figure which shows the system configuration | structure of the communication system in this embodiment. It is a figure which shows the specific example of the antenna with which RN200 is provided. It is a figure which shows the example of a structure of CN100. It is a figure which shows the example of a structure of RN200. It is a sequence chart which shows the flow of a process in the communication system of this embodiment. It is a figure which shows the format of the extended PTP frame. It is a figure which shows the format of the extended PTP frame. The dependence of the relative gain of the beam at different numbers of antenna elements on the phase shift of the beam is shown. It is a figure which shows the structure of the radio | wireless communications system of a modification. It is a figure which shows the example of a structure of CN800 in MAC-PHY using PTP. It is a figure which shows the example of a structure of RN900 in MAC-PHY using PTP.

  FIG. 1 is a diagram showing a system configuration of a communication system in the present embodiment. The communication system includes CN 100 and a plurality of RNs 200. CN 100 is a device (signal processing device) that performs signal processing among the functions of the base station. The RN 200 is a device (wireless communication device) responsible for wireless communication among the functions of the base station. In the example of FIG. 1, the communication system includes 32 RNs 200 (200-1, 200-2,..., 200-32). Note that the number of RNs need not be limited to 32. UE (user terminal) 300 communicates with a plurality of RNs 200. The CN 100 is connected to the host device and a plurality of (for example, 32) RNs 200 by Ethernet using an optical fiber.

FIG. 2 is a diagram illustrating a specific example of an antenna included in the RN 200. The antenna included in the RN 200 may include a large number (for example, 256) of antenna elements 29.
FIG. 3 is a diagram illustrating an example of the configuration of the CN 100. The CN 100 includes an MC 101, a radio signal processing unit 102, a GPS 103, an internal clock 104, a PTP processing unit 105, a phase control unit 106, a phase information acquisition unit 107, a CSM 108, a StncE processing unit 109, and a plurality of demultiplexers 110 (110-3). 110-4, 110-5, 110-10, and 110-11) and an RN-PTP acquisition unit 115.

  The MC 101 receives an optical signal transmitted from a host device. The MC 101 converts a signal between an optical signal and an electric signal. The electric signal is converted as an electric signal using, for example, a UTP cable as a transmission medium.

The radio signal processing unit 102 performs predetermined processing on the main signal and scheduling information. The radio signal processing unit 102 includes, for example, a PDCP layer processing unit 111, an RLC layer processing unit 112, a MAC layer processing unit 113, a scheduling control unit 114, and a demultiplexer 110-2. The PDCP layer processing unit 111 performs processing related to Packet Data Convergence Protocol (PDCP) on the main signal. The RLC layer processing unit 112 performs processing related to Radio Link Control (RLC) on the main signal. The MAC layer processing unit 113 performs processing related to Media Access Control (MAC) on the main signal.
The demultiplexer 110-2 multiplexes the main signal and the scheduling information processed by the PDCP layer processing unit 111, the RLC layer processing unit 112, the MAC layer processing unit 113, and the scheduling control unit 114, and generates a radio signal.

The GPS receiver 103 receives reference time information from a GPS satellite. The GPS receiver 103 functions as a grand master (GM) in PTP.
The internal clock 104 outputs a signal indicating the time to each functional unit of the CN 100.

  The PTP processing unit 105 performs a series of processes related to the PTP protocol in the CN 100. In this processing, the PTP processing unit 105 measures the propagation delay time between the CN 100 and each RN 200 for each RN 200, and corrects the difference in propagation delay time with each RN 200 according to the measurement result. By this correction, time synchronization with each RN 200 is established. For example, the PTP processing unit 105 updates the time of the internal clock 104 based on a signal output from the GPS receiver 103. In addition, the PTP processing unit 105 establishes time synchronization with the RN 200 by negotiation with the RN 200 (slave of the CN 100).

  The phase control unit 106 controls the beam phase of the antenna element in each RN 200 by transmitting / receiving a message to / from each RN 200. This message may be defined, for example, by extending a PTP frame. Further, the phase control unit 106 acquires scheduling information of a radio section (a communication section between the RN 200 and the UE 300) from the scheduling control unit 114 of the radio signal processing unit 102. Further, the phase control unit 106 is connected to the internal clock 104 and acquires time information. The phase control unit 106 is connected to the PTP processing unit 105 and acquires a control signal related to PTP.

The phase information acquisition unit 107 acquires phase information of each antenna element of each RN 200 based on the received message.
The CSM 108 generates a clock signal based on a signal acquired from the Ethernet communication path. The CSM 108 outputs the generated clock signal to the SyncE processing unit 109.

The SyncE processing unit 109 generates a reference frequency signal based on the clock signal supplied from the CSM 108. The SyncE processing unit 109 executes processing related to SyncE based on the reference frequency signal.
The RN-PTP acquisition unit 115 receives a PTP signal from the RN 200. The RN-PTP acquisition unit 115 outputs the input PTP signal to the PTP processing unit 105.

FIG. 4 is a diagram illustrating an example of the configuration of the RN 200. The RN 200 includes a radio signal processing unit 201, IF 202, LO 203, a mixer 204, a PTP processing unit 206, an internal clock 207, a SyncE processing unit 208, a phase detection unit 221, a phase control unit 222, and a plurality of demultiplexers 210 (210-6). 210-7, 210-9, 210-11 and 210-13).
The radio signal processing unit 201 performs predetermined processing on the main signal and scheduling information.

  IF 202 is an intermediate frequency band processing unit. LO203 is a localized transmitter. The mixer 204 performs processing on signals output from the IF 202 and the LO 203. The same number of IF 202, LO 203, and mixer 204 as the number of antenna elements provided in the antenna of RN 200 is provided. That is, the IF 202, the LO 203, and the mixer 204 are provided for each antenna element. The IF 202, the LO 203, and the mixer 204 send out the signal output by the wireless signal processing unit 201 as a wireless signal via the antenna element.

The PTP processing unit 206 performs a series of processes related to the PTP protocol in the RN 200. For example, the PTP processing unit 206 synchronizes the time of the internal clock 207 with the master by negotiating with the CN 100 (the master of the RN 200).
The internal clock 207 outputs a signal indicating time to each function unit of the RN 200.
The SyncE processing unit 208 executes processing related to SyncE based on the reference frequency signal.
The phase detector 221 detects the phase information of the beam phase of the IF 202 and the LO 203 that the RN 200 has.
The phase control unit 222 acquires the phase information detected by the phase detection unit 221. The phase control unit 222 stores the acquired phase information of each antenna element in a predetermined message and sends it to the CN 100.

  FIG. 5 is a sequence chart showing the flow of processing in the communication system of the present embodiment. In the example illustrated in FIG. 5, two RNs 200 (200-1 and 200-2) are connected to the CN 100. However, the number of RNs 200 connected to the CN 100 is not limited to two.

  First, the phase control unit 106 of the CN 100 sends messages “Phaseget_Req_1” and “Phaseget_Req_2” to the RN 200-1 and the RN 200-2, respectively. The message Phaseget_Req is a message for the CN 100 to instruct the RN 200 to notify the CN of the beam phase information of each antenna element included in the RN 200. The phase control unit 222 of the RN 200 acquires the beam phase information of each antenna element of the own device according to the received Phaseget_Req. Then, the phase control unit 222 of the RN 200 stores the beam phase information of its own device in the Phaseget_Resp message and sends it to the CN 100. That is, RN 200-1 and RN 200-2 send Phaseget_Resp_1 and Phaseget_Resp_2 to CN 100, respectively.

  The phase control unit 106 of the CN 100 acquires information on the beam phase of each antenna element of each RN 200 by receiving Phaseget_resp. The phase control unit 106 of the CN 100 generates information on the phase to be set for each antenna element in order to align the beam phases of the antenna elements included in the RN 200-1 and the RN 200-2. The phase control unit 106 of the CN 100 stores the generated information in the Phaseset_req1 and Phaseset_req2 messages. The phase control unit 106 of the CN 100 sends Phaseset_req1 and Phaseset_req2 messages to the RN 200-1 and the RN 200-2, respectively. The phase control unit 222 of the RN 200-1 and the RN 200-2 sets the phase of each antenna element according to the instruction of the CN 100. Then, the phase control units 222 of the RN 200-1 and the RN 200-2 store the set phase information in Phaseset_Resp1 and Phaseset_Resp2 messages, respectively, and send them to the CN 100. The phase control unit 106 of the CN 100 receives the Phaseset_Resp1 and Phaseset_Resp2 messages. The phase control unit 106 of the CN 100 acquires information on the phase of each antenna element of each RN 200 after the phase setting based on the received message. By such processing, the phase (beam phase) of each antenna element of each RN 200 can be controlled with higher accuracy.

  Next, a method for storing phase information in transmitted / received messages will be described. In this embodiment, the phase information is stored in the message by extending the PTP frame defined by IEEE 1588. 6 and 7 are diagrams showing the format of the extended PTP frame. The PTP message has three blocks: Header, Body, and Suffix. Of these, Suffix does not necessarily need to be used, so the explanation is omitted. The demultiplexer 110-13 of the CN 100 and the demultiplexer 210-11 of the RN 200 have a function like a switch that demultiplexes a normal PTP frame and an extended PTP frame.

As shown in FIG. 6, many fields are prepared in the Header block. Among these, the messageType field stores information indicating what kind of message (for example, Sync message, Delay_Req, etc.) this PTP frame is. This field is a 4-bit area. Of the values represented by 4 bits, 4, 5, 6 and 7 are reserved and have room for expandability. These four values are defined as follows.
4: Phaseget_Req message 5: Phaseget_Resp message 6: Phaseset_Req message 7: Phaseset_Resp message

  Each functional unit of the CN 100 and the RN 200 can determine what kind of message is the PTP frame being transmitted / received to / from each other by storing or referring to the above value for the message transmitted / received.

  Next, information entering the Body block will be described with reference to FIG. Information for controlling the phase of the antenna element is stored in the Body block. Specifically, the following five fields are defined.

  ID_RN: Stores an ID for identifying the RN 200. The value is a positive integer and has a width of 4 bytes, for example.

  ID_Antenna: An ID for identifying an antenna element included in each RN 200 is stored. The value is a positive integer and has a width of 4 bytes, for example.

  Phase_Abs: Information indicating the beam phase of each antenna element included in each RN 200 is stored. The phase is expressed as an absolute value. The phase is expressed as a phase value between 0 and 2π. For example, it has a width of 2 bytes. In this case, it is possible to specify the phase information with a resolution of π / 32768.

  Phase_Off: Indicates the change amount (relative value) relative to the current phase information in each antenna element of the RN 200. Expressed as a phase value between 0 and 2π. For example, it has a width of 2 bytes. In this case, it is possible to specify the phase information with a resolution of π / 32768.

  ToD: Stores time information. The time information conforms to the expression format in PTP. It is used for the purpose of aligning the phases of the antenna elements of each RN 200 at the same timing. For example, it has a width of 10 bytes. RN 200 performs antenna element phase control in accordance with the time indicated by the value of ToD.

  Note that Phase_Abs and Phase_Off are used exclusively. For example, when Phase_Abs is used, 0 is set in Phase_Off. For example, when Phase_Off is used, 0 is set in Phase_Abs.

  As described above, in the present embodiment, a PTP frame extended to a message for realizing beam phase control is used. Since an optical transmission network for a wireless communication system originally requires a highly accurate time synchronization function, a case of adopting a protocol such as PTP is assumed. Therefore, it can be said that it is preferable to extend and use the PTP frame for precise beam phase control in terms of feasibility and economy.

  Next, transmission processing of each message will be described in detail. When the Phaseget_Req message is transmitted from the phase control unit 106 to the RN 200, the message is transmitted through the demultiplexer 110-10, the demultiplexer 110-11, the demultiplexer 110-3, and the demultiplexer 110-5. Sent to RN 200. The Phaseget_Req message is transmitted through an optical fiber, and is input to the phase controller 222 via the demultiplexer 210-6, demultiplexer 210-7, demultiplexer 210-11, and demultiplexer 210-13 of the RN 200. Is done.

  The phase detector 221 of the RN 200 detects phase information of the IF 202 and the LO 203 that the RN 200 has. The phase control unit 222 acquires the phase information detected by the phase detection unit 221. The phase control unit 222 stores the acquired phase information of each antenna element in a Phaseget_Resp message and sends it to the CN 100. The Phaseget_Resp message is transmitted to the CN 100 via the optical fiber via the demultiplexer 210-13, the demultiplexer 210-11, the demultiplexer 210-7, and the demultiplexer 210-6.

  The Phaseget_Resp message transmitted from the RN 200 is input to the phase information acquisition unit 107 via the demultiplexer 110-5, the demultiplexer 110-3, the demultiplexer 110-11, and the demultiplexer 110-10 of the CN 100. . The phase information acquisition unit 107 acquires information indicating the phase of each antenna element of each RN 200 based on the received message. The phase information acquisition unit 107 outputs the acquired information to the phase control unit 106.

  The phase control unit 106 is based on the phase of each antenna element, time information provided by the internal clock 104, radio section scheduling information provided from the scheduling control unit 114, and PTP information provided from the PTP processing unit 105. The phase value to be set for each antenna element is determined. The phase control unit 106 generates a Phaseset_req message including the determined phase value. Then, the phase control unit 106 transmits the generated message to the RN 200. At this time, the phase control unit 106 does not affect the transmission of the radio signal by the RN 200 based on the scheduling information of the radio section provided by the scheduling control unit 114 and the time information provided by the internal clock 104. Such a timing is selected and a Phaseset_Req message is transmitted to the RN 200.

  The Phaseset_Req message is input to the phase control unit 222 through the same route as the Phaseget_Req message. Based on the information stored in the Phaseset_Req message, the phase control unit 222 controls the beam phase of the IF 202 and the LO 203. At this time, the phase control unit 222 may directly control the beam phase of the IF 202 and the LO 203, or may control the phase of the reference clock low-frequency oscillator of the IF 202 and the LO 203.

  FIG. 8 shows the beam phase shift dependence of the relative gain of the beam with different numbers of antenna elements. FIG. 8 shows the calculation result of how much the gain is changed by the multi-element antenna when the phase shift is given. It can be seen that the beam gain decreases as the phase shift increases, and the gain decrease can be suppressed to about half by setting the phase shift between beams to about π / 4 or less.

(Modification)
In the present embodiment, the configuration in which the base station function is divided by MAC-PHY has been described. However, where the base station function is divided is not limited. For example, the present embodiment may be appropriately applied to a method in which the base station function is divided in the physical layer.

  ToD is not necessarily used. As another method, the output of the PTP processing unit 105 is input to the phase control unit 106, and propagation delay information between the CN 100 and each RN 200 is held. Therefore, the time at which the phase control information is transmitted from the CN 100 may be shifted by calculating backward from the propagation delay without using the ToD field. In this case, the RN 200 executes the phase control immediately after receiving a message regarding the beam phase control. The synchronization of the timing of phase control may be controlled in this way.

  FIG. 9 is a diagram illustrating a configuration of a wireless communication system according to a modification. 9 is different from the configuration shown in FIG. 1 in that the topology of the MFH is a wavelength division multiplexing passive optical network (WDM-PON) configuration. In the WDM-PON, a plurality of RNs 200 (for example, 32 RNs 200) are assigned different unique wavelengths and are connected to the CN 100 in a one-to-many configuration via a wavelength filter. In the case of WDM-PON, in addition to the distance between the CN 100 and each RN 200, the wavelength also differs for each RN 200. Therefore, the propagation delay differs between upstream and downstream. In this case, the PTP processing unit 105 can control the beam phase control time by calculating an accurate propagation delay from the wavelength dependence of the propagation speed in the optical fiber.

  You may make it implement | achieve the function of CN100 and RN200 in embodiment mentioned above with a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory inside a computer system serving as a server or a client in that case may be included and a program held for a certain period of time. Further, the program may be a program for realizing a part of the above-described functions, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system. You may implement | achieve using programmable logic devices, such as FPGA (Field Programmable Gate Array).

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

DESCRIPTION OF SYMBOLS 100 ... CN, 200 ... RN, 300 ... UE, 106 ... Phase control part, 107 ... Phase information acquisition part, 221 ... Phase detection part, 222 ... Phase control part

Claims (4)

A wireless communication system comprising: a signal processing device that is a device that performs signal processing among the functions of a base station; and a wireless communication device that is a device that performs wireless communication among the functions of the base station. Is a communication method performed by
Measuring a propagation delay time between the signal processing device and the plurality of wireless communication devices for each wireless communication device;
Correcting a difference in the propagation delay time between the wireless communication devices according to a measurement result;
A communication method comprising: A wireless communication system comprising: a signal processing device that is a device that performs signal processing among the functions of a base station; and a wireless communication device that is a device that performs wireless communication among the functions of the base station. Is a communication method performed by
The signal processing device transmitting information having a value for controlling a beam phase of antenna elements of the plurality of wireless communication devices to the plurality of wireless communication devices;
The wireless communication device controls a beam phase of an antenna element included in the device according to a value for controlling the beam phase;
A communication method comprising: A wireless communication system comprising: a signal processing device that is a device that performs signal processing among the functions of a base station; and a wireless communication device that is a device that performs wireless communication among the functions of the base station. Because
A measurement unit that measures a propagation delay time between the signal processing device and the plurality of wireless communication devices for each wireless communication device;
A correction unit that corrects a difference in the propagation delay time between the wireless communication devices according to a measurement result;
A communication system comprising: A wireless communication system comprising: a signal processing device that is a device that performs signal processing among the functions of a base station; and a wireless communication device that is a device that performs wireless communication among the functions of the base station. Because
The signal processing device includes a phase control unit that transmits information having a value for controlling a beam phase of antenna elements of the plurality of wireless communication devices to the plurality of wireless communication devices,
The wireless communication device includes a phase control unit that controls a beam phase of an antenna element included in the device according to a value for controlling the beam phase.
The communication system.

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