Wireless communication system and wireless communication method

Abstract

This wireless communication system has a Point-to-MultiPoint (P2MP) configuration. The wireless communication system includes: an RoF slave unit for transmitting a pseudo random number sequence code predetermined for the own unit to an RoF master unit when receiving an uplink signal; and an RoF master unit control unit for executing autocorrelation acquisition processing for taking autocorrelation of the pseudo random number sequence code that has passed through a multiplexer / demultiplexer included in the RoF master unit.

Description

Wireless Communication System and Wireless Communication Method

[0001] The present invention relates to a wireless communication system and a wireless communication method.

[0002] A-RoF (Analog-RoF) that transmits an analog signal over an optical cable divides the wireless base station function into an aggregation station and a remote station, and is being studied to achieve flexible and economical wireless area expansion by deploying a simple remote station.

[0003] An SFN (Single Frequency Network) using P2MP (Point to Multi-Point) that extends multiple antennas (i.e., multiple RoF (Radio Over Fiber) slave units) from one RF (Radio Frequency) point is a network topology necessary for expanding areas where it is difficult to construct a wireless area due to high propagation loss and high directivity of high-frequency band wireless in particular.

[0004] As a D-RoF (Digital-RoF) system, a device that replicates data has been standardized by installing an FHM (Fronthaul Multiplexer) in the fronthaul section between the O-DU and O-RU in Open RAN (see Non-Patent Document 1).

[0005] In P2MP, it is necessary to exclude the influence of combining noise in which noise corresponding to the number of RoF slave units (= number of extended antennas) is added, especially in uplink (UL: Uplink) communication. (For example, when the number of RoF slave units is 2, the noise increases by 3 dB compared to the case where the number of RoF slave units is 1).

[0006] One method of removing combining noise in A-RoF is to turn on the paths that are arriving at the timing when the uplink signal arrives based on the resource mapping information, and turn off the other paths. This method requires knowing which RoF slave unit the UE (User Equipment) communicating is located in.

[0007] O-RAN.WG7.IPC-HRD-Opt7-2.0-v03.00 Technical Specification, “ O-RAN Hardware Reference Design Specification for Indoor Picocell (FR1) with Split Architecture Option 7-2,“. https: / / www.o-ran.org / specifications

[0008] However, the P2MP configuration involves multiple RoF slaves being connected via multiplexers / demultiplexers, and particularly for the uplink, incoming signal information from each RoF slave is lost in the multiplexer / demultiplexer. As a result, it is not possible to obtain the UE's location information (i.e., information indicating which RoF slave the UE is connected to), and the above method could not remove the ingress noise. Therefore, the challenge was how to obtain the UE's location information.

[0009] In view of the above circumstances, the present invention aims to provide a technology for acquiring information indicating which RoF slave unit a UE is located in.

[0010] One aspect of the present invention is a wireless communication system in a P2MP (Point-to-MultiPoint) configuration, comprising: an RoF slave unit that transmits a predetermined pseudorandom number sequence code to an RoF master unit at the timing of receiving an uplink signal; and an RoF master unit control unit that performs an autocorrelation acquisition process to obtain the autocorrelation of the pseudorandom number sequence code that has passed through a multiplexer / demultiplexer provided by the RoF master unit.

[0011] One aspect of the present invention is a wireless communication system in a P2MP (Point-to-MultiPoint) configuration, comprising: an RoF slave unit that transmits a predetermined pseudo-random number sequence code to an RoF master unit at the timing of receiving an uplink signal; and an RoF master unit control unit that performs an autocorrelation acquisition process to obtain the autocorrelation of the pseudo-random number sequence code that has passed through a multiplexer / demultiplexer provided by the RoF master unit, the wireless communication method being performed by the wireless communication system comprising: a transmission step in which the RoF slave unit transmits a predetermined pseudo-random number sequence code to the RoF master unit at the timing; and a PN autocorrelation acquisition step in which the RoF master unit control unit performs the autocorrelation acquisition process.

[0012] This invention makes it possible to obtain information indicating which RoF slave unit a UE is located in.

[0013] An explanatory diagram illustrating the wireless communication system of the embodiment. A flowchart showing an example of the processing flow performed by the wireless communication system in the embodiment. A diagram showing an example of the configuration of the RoF slave unit and RoF master unit in the embodiment. A diagram showing a more specific example of the hardware configuration of the RoF slave unit in the embodiment. A diagram showing a more specific example of the hardware configuration of the RoF master unit in the embodiment.

[0014] (Embodiment)

[0015] Figure 1 is an explanatory diagram illustrating an embodiment of the wireless communication system 100. The wireless communication system 100 is a P2MP (Point-to-MultiPoint) wireless communication system. Therefore, the wireless communication system 100 comprises at least an RoF (Radio Over Fiber) slave unit, an RoF master unit equipped with a multiplexer / demultiplexer, and a aggregation station. The connection between the RoF master unit and the RoF slave unit may be analog RoF, digital RoF, or coaxial cable. The wireless communication system 100 will be explained more specifically using the example in Figure 1.

[0016] The wireless communication system 100 includes a plurality of RoF slave units 1. In Figure 1, RoF slave unit 1-n to RoF slave unit 1-(n+k) are examples of RoF slave units 1, where n is an integer greater than or equal to 1 and k is an integer greater than or equal to 1. Each RoF slave unit 1 is equipped with an overhanging antenna 10.

[0017] In the example shown in Figure 1, RoF slave unit 1-n receives the uplink signal transmitted by UE (User Equipment) 9-m (hereinafter referred to as the "uplink signal") and the uplink signal transmitted by UE (User Equipment) 9-(m+1). In the example shown in Figure 1, RoF slave unit 1-(n+k) receives the uplink signal transmitted by UE (User Equipment) 9-(m+1) and the uplink signal transmitted by UE (User Equipment) 9-(m+l). Hereinafter, l is an integer greater than or equal to 1.

[0018] When RoF slave unit 1 receives an uplink signal, it transmits a predetermined pseudo-random number sequence code to RoF master unit 2.

[0019] The wireless communication system 100 includes an RoF master unit 2. The RoF master unit 2 includes a combiner / demultiplexer 20. In the example in Figure 1, the combiner / demultiplexer 20 is connected to at least RoF slave units 1-n and 1-(n+k). Therefore, the combiner / demultiplexer 20 receives at least the signal transmitted by RoF slave unit 1-n and the signal transmitted by RoF slave unit 1-(n+k). That is, the combiner / demultiplexer 20 receives at least the pseudo-random number sequence code transmitted by RoF slave unit 1-n and the pseudo-random number sequence code transmitted by RoF slave unit 1-(n+k).

[0020] The RoF master unit 2 performs autocorrelation acquisition processing. Autocorrelation acquisition processing is the process of obtaining the autocorrelation of the PN (Pseudo Random Noise) code that has passed through the multiplexer / demultiplexer 20. The autocorrelation of the pseudorandom number sequence code indicates information that identifies the RoF slave unit 1 that transmitted the pseudorandom number sequence code (hereinafter referred to as "source identification information") and information that indicates the timing at which the RoF slave unit 1 received the uplink signal (hereinafter referred to as "reception timing information"). In other words, source identification information and reception timing information can be obtained by obtaining the autocorrelation of the pseudorandom number sequence code. The pseudorandom number sequence code may be, for example, an m-sequence, a Zadoff-Chu sequence, or a Gold sequence.

[0021] The aggregation station 3 is an aggregation station such as a CU (Central Unit) or DU (Distributed Unit). The aggregation station 3 is connected to the RoF master unit 2.

[0022] <Effects of Autocorrelation Acquisition Processing> If the RoF master unit 2 can identify which RoF slave unit received the signal that has passed through the multiplexer / demultiplexer 20, it can obtain information indicating which RoF slave unit the UE is located in. Therefore, the wireless communication system 100 that performs autocorrelation acquisition processing can obtain information indicating which RoF slave unit the UE is located in.

[0023] Figure 2 is a flowchart showing an example of the processing flow performed by the wireless communication system 100 in the embodiment. The RoF master unit transmits a synchronization signal such as SSB to the UE (step S101). At this time, the synchronization signal passes through the RoF slave unit and reaches the UE.

[0024] Next, the UE transmits Msg1 to the RoF master unit (step S102). Msg1 passes through the RoF slave units and reaches the RoF master unit. Next, the RoF master unit transmits information to the aggregation station indicating the end of Msg1 (step S103). That is, the RoF master unit notifies the aggregation station that Msg1 has ended. Next, the aggregation station transmits Msg2 to the UE (step S104). Msg2 passes through the RoF master unit and RoF slave units and reaches the UE.

[0025] Next, the aggregation station transmits schedule information and TA (Timing Advance) information to the RoF master unit (step S105). As is well known, the schedule information is information indicating resource blocks. The process in step S105 may be executed simultaneously with the process in step S104, or it may be executed after the process in step S103 and before the process in step S104.

[0026] Next, the UE transmits Msg3 to the aggregation station (step S106). Msg3 passes through the RoF slave and RoF master units to reach the aggregation station.

[0027] Next, when Msg3 reaches the RoF slave, the RoF slave activates squelch (step S107). When Msg3 reaches the RoF slave, the RoF slave transmits a pseudo-random number sequence code to the RoF master (step S108). Next, the RoF master performs autocorrelation acquisition processing (step S109).

[0028] Next, the aggregation station transmits Msg4 to the UE (step S110). Msg4 passes through the RoF master unit and RoF slave unit to reach the UE.

[0029] Next, the UE performs a PUSCH (step S111). The execution of the PUSCH causes a message from the UE user to its communication partner to be sent from the UE to the aggregation station. This message passes through the RoF slave and RoF master units to reach the aggregation station. The message is, for example, "Hello".

[0030] When the message reaches the RoF slave unit, the RoF slave unit activates squelch (step S112). Next, the RoF slave unit sends a pseudo-random number sequence code to the RoF master unit (step S113). Then, the RoF master unit performs autocorrelation acquisition processing (step S114).

[0031] Figure 3 shows an example of the configuration of the RoF slave unit 1 and RoF master unit 2 in an embodiment. The RoF slave unit 1 includes an extended antenna 10, an RoF slave unit control unit 11, an E / O converter 12, and a squelch circuit 13.

[0032] The RoF slave unit control 11 is a control unit that includes a processor such as a CPU (Central Processing Unit), GPU (Graphics Processing Unit), or NPU (Neural Network Processing Unit), and memory. The RoF slave unit control 11 controls the operation of the RoF slave unit 1. The RoF slave unit 1, for example, generates a pseudo-random number sequence code. The generated pseudo-random number sequence code may be a digital signal or an analog signal.

[0033] The E / O converter 12 converts an electrical signal into an optical signal. The E / O converter 12 receives a pseudo-random number sequence code generated by the RoF slave unit control unit 11 as input. The optical signal obtained by the E / O converter 12 propagates through the transmission path 4 to the RoF master unit 2. The transmission path 4 can be any medium that can transmit optical signals, such as an optical fiber or air.

[0034] The squelch circuit 13 is OFF when a signal with power below a predetermined level is input, and ON when a signal with power above a predetermined level is input. When ON, the signal input to the squelch circuit 13 is output from the squelch circuit 13 and input to the RoF slave unit control unit 11. In this way, squelch is performed in the RoF slave unit 1 by the squelch circuit 13.

[0035] The overhang antenna 10 receives the uplink signal. The radio signal received by the overhang antenna 10 is converted into an electrical signal by the overhang antenna 10 itself and then input to the squelch circuit 13.

[0036] The RoF master unit 2 comprises a multiplexer / demultiplexer 20, an RoF master unit control unit 21, and an O / E converter 22. The RoF master unit control unit 21 is a control unit comprising a processor such as a CPU, GPU, or NPU connected by a bus, and memory. The RoF master unit control unit 21 controls the operation of the RoF master unit 2. For example, the RoF master unit control unit 21 performs autocorrelation acquisition processing. The output of the multiplexer / demultiplexer 20 is input to the RoF master unit control unit 21.

[0037] The O / E converter 22 converts the optical signal into an electrical signal. The optical signal that has propagated through the transmission line 4 is input to the O / E converter 22. The electrical signal obtained by the O / E converter 22 is input to the multiplexer / demultiplexer 20.

[0038] Figure 4 shows a more specific example of the hardware configuration of the RoF slave unit 1 in the embodiment. The RoF slave unit 1 includes an RoF slave unit control unit 11 that executes a program. Upon execution of the program, the RoF slave unit 1 functions as a device comprising an extended antenna 10, an RoF slave unit control unit 11, an E / O converter 12, a squelch circuit 13, an interface unit 15, and a storage unit 16.

[0039] More specifically, the processor 91 reads the program stored in the storage unit 16 and stores the read program in the memory 92. By executing the program stored in the memory 92, the processor 91 functions as a device comprising the extended antenna 10, the RoF slave unit control unit 11, the E / O converter 12, the squelch circuit 13, the interface unit 15, and the storage unit 16. As mentioned above, the configuration of the RoF slave unit 1 in Figure 4 is merely an example, and the RoF slave unit 1 does not necessarily need to include the interface unit 15.

[0040] The RoF slave unit control unit 11, the E / O converter 12, the squelch circuit 13, the interface unit 15, and the storage unit 16 are connected by a bus. The overhang antenna 10 is connected to the squelch circuit 13.

[0041] In addition to the processes described above, the RoF slave control unit 11 also performs a process to acquire information stored in the memory unit 16. Specifically, the process to acquire information stored in the memory unit 16 is reading.

[0042] The interface unit 15 includes a communication interface for connecting the RoF slave unit 1 to an external device. The interface unit 15 communicates with the external device via wired or wireless connection.

[0043] The interface unit 15 may be configured to include input devices such as a mouse, a keyboard, a touch panel, etc. The interface unit 15 may be configured as an interface for connecting these input devices to the RoF slave unit 1. Thus, the input devices of the interface unit 15 receive the input of various information or signals to the RoF slave unit 1 via wired or wireless means. Note that the information or signal does not necessarily have to be input to the communication interface of the interface unit 15 and may be input to the input devices of the interface unit 15.

[0044] The interface unit 15 outputs various information, for example. The interface unit 15 is configured to include display devices such as a CRT (Cathode Ray Tube) display, a liquid crystal display, an organic EL (Electro-Luminescence) display, etc., and a speaker. The interface unit 15 may be configured as an interface for connecting these display devices or speakers to the RoF slave unit 1. Therefore, the interface unit 15 may output, for example, the information indicated by the information or signal input to the input devices of the interface unit 15 as an image or sound.

[0045] The storage unit 16 is configured using a computer-readable storage medium device (non-transitory computer-readable recording medium) such as a magnetic hard disk device or a semiconductor storage device. The storage unit 16 stores various information related to the RoF slave unit 1. The storage unit 16 stores, for example, various information generated by the operation of the RoF slave unit control unit 11.

[0046] FIG. 5 is a diagram showing an example of a more specific hardware configuration of the RoF master unit 2 in the embodiment. The RoF master unit 2 includes a RoF master unit control unit 21 and executes a program. By executing the program, the RoF master unit 2 functions as a device including a multiplexer / demultiplexer 20, a RoF master unit control unit 21, an O / E converter 22, an interface unit 23, and a storage unit 24.

[0047] More specifically, the processor 93 reads out the program stored in the storage unit 24 and stores the read program in the memory 94. By executing the program stored in the memory 94, the RoF master unit 2 functions as a device including the multiplexer / demultiplexer 20, the RoF master unit control unit 21, the O / E converter 22, the interface unit 23, and the storage unit 24. As described above, the configuration of the RoF master unit 2 in FIG. 5 is merely an example, and the RoF master unit 2 does not necessarily need to include the interface unit 23.

[0048] The multiplexer / demultiplexer 20, the RoF master unit control unit 21, the interface unit 23, and the storage unit 24 are connected by a bus. The O / E converter 22 is connected to the multiplexer / demultiplexer 20.

[0049] In addition to the above-described processing, the RoF master unit control unit 21 executes, for example, a process of acquiring information stored in the storage unit 24. The process of acquiring information stored in the storage unit 24 is specifically a read operation.

[0050] The interface unit 23 is configured to include a communication interface for connecting the RoF master unit 2 to an external device. The interface unit 23 communicates with the external device via wired or wireless means.

[0051] The interface unit 23 may be configured to include an input device such as a mouse, a keyboard, a touch panel, etc. The interface unit 23 may be configured as an interface for connecting these input devices to the RoF master unit 2. Thus, the input device of the interface unit 23 receives input of various information or signals to the RoF master unit 2 via wired or wireless means. Note that the information or signal does not necessarily need to be input to the communication interface of the interface unit 23 and may be input to the input device of the interface unit 23.

[0052] The interface unit 23 outputs various types of information, for example. The interface unit 23 includes, for example, a display device such as a CRT display, liquid crystal display, or organic EL display, and a speaker. The interface unit 23 may be configured as an interface for connecting these display devices or speakers to the RoF master unit 2. Therefore, the interface unit 23 may output information indicated by information or signals input to the input device of the interface unit 23 as an image or sound.

[0053] The storage unit 24 is configured using a computer-readable recording medium such as a magnetic hard disk drive or a semiconductor memory device. The storage unit 24 stores various information related to the RoF master unit 2. For example, the storage unit 24 stores various information generated by the operation of the RoF master unit 2.

[0054] The wireless communication system 100 configured in this way performs autocorrelation acquisition processing. As a result, as described in <Effects of Autocorrelation Acquisition Processing>, it is possible to obtain information indicating which RoF slave unit a UE is located in. Furthermore, as a result, the wireless communication system 100 can remove ingress noise by turning ON the path where the uplink signal is arriving and OFF the other paths based on resource mapping information.

[0055] (Modification) The same pseudorandom number sequence code may be assigned to RoF slave devices 1 that are predetermined to belong to the same group according to a set of rules. The number of RoF slave devices 1 belonging to a group may be multiple or one. For example, if there is only one RoF slave device 1 in each group, it means that a different pseudorandom number sequence code is assigned to each RoF slave device 1.

[0056] The RoF master control unit 21 may also perform pseudo-random number sequence code value instruction processing. Pseudo-random number sequence code value instruction processing is the process of determining a pseudo-random number sequence code for each RoF slave unit according to a predetermined rule. Determining a pseudo-random number sequence code is the process of recording information indicating the pseudo-random number sequence code generated by the RoF slave unit control unit 11 in the storage unit 16 by controlling the operation of the RoF slave unit control unit 11 via the interface unit 23 and interface unit 15.

[0057] The RoF master control unit 21 may also perform pseudo-random number sequence code management processing. Pseudo-random number sequence code management processing is a process of updating information indicating which group each RoF slave unit 1 belongs to (hereinafter referred to as "group information") and information indicating the pseudo-random number sequence code assigned to each group (hereinafter referred to as "assigned PN information"). The group information and assigned PN information are stored in the storage unit 24 in advance. Therefore, the pseudo-random number sequence code management processing is a process of updating the group information and assigned PN information that are stored in the storage unit 24 in advance. The pseudo-random number sequence code assigned to a group is a pseudo-random number sequence code determined for all RoF slave units 1 belonging to that group.

[0058] Furthermore, the RoF slave unit 1 may be implemented using multiple devices connected to each other via a network. For example, the RoF slave unit 1 may be implemented using a device comprising an E / O converter 12, an RoF slave unit control unit 11, a squelch circuit 13, and a device comprising an overhanging antenna 10. Also, for example, each process performed by the RoF slave unit control unit 11 may be performed by multiple information processing devices in a distributed manner.

[0059] Here, we will describe a scenario in which a wireless communication system already exists that uses a device equipped with an overhang antenna 10 but without an E / O converter 12, an RoF slave control unit 11, and a squelch circuit 13 as an RoF slave. In this scenario, a device equipped with an E / O converter 12, an RoF slave control unit 11, and a squelch circuit 13 may be added to the RoF slave. In this case, a device combining the device equipped with an E / O converter 12, an RoF slave control unit 11, and a squelch circuit 13 with the already existing RoF slave may be used as a new RoF slave.

[0060] Furthermore, the RoF master unit 2 may be implemented using multiple devices connected to each other via a network. For example, each process executed by the RoF master unit control unit 21 may be performed by multiple information processing devices in a distributed manner.

[0061] The memory unit 24 may store information indicating the connection relationship between the RoF slave unit 1 and the RoF master unit 2 (hereinafter referred to as "connection relationship information"). In this case, the RoF master unit control unit 21 may change the connection relationship between the RoF slave unit 1 and the RoF master unit 2 when predetermined conditions are met. Changing the connection relationship means updating the connection relationship using a switch or by assigning a specific optical wavelength.

[0062] Specifically, the information indicating the connection relationship refers to information indicating the RoF slave unit 1 that transmits a pseudo-random number sequence code to each RoF master unit 2.

[0063] The specified condition is, for example, when a certain RoF master unit 2 exceeds a certain amount of communication traffic, from the perspective of resource distribution.

[0064] Furthermore, all or part of the functions of each of the RoF slave unit 1 and RoF master unit 2 may be implemented using hardware such as ASIC (Application Specific Integrated Circuit), PLD (Programmable Logic Device), or FPGA (Field Programmable Gate Array). The program may be recorded on a computer-readable recording medium. Computer-readable recording media include, for example, portable media such as flexible disks, magneto-optical disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into computer systems. The program may also be transmitted via a telecommunications line.

[0065] Furthermore, the device referred to as "RoF slave unit" may also be called "remote station," "relay station," "Remote Radio Unit (RRU)," "Radio Unit (RU)," "Distributed Antenna (DA)," "slave unit," or "antenna," depending on the technical field and context. Similarly, the device referred to as "RoF master unit" may also be called "aggregation station," "relay station," "CS (Central Station)," "Base Station," "CU (Central Unit)," "DU (Distributed Unit)," "Radio Unit (RU)," or "master unit," depending on the technical field and context. The device referred to as a "base station" may also be called a "wireless base station," "NodeB," "eNodeB," "gNodeB," "access point," "cell," "macrocell," "smallcell," "femtocell," or "picocell," depending on the technical field and context.

[0066] While embodiments of this invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and includes designs and the like that do not depart from the spirit of this invention.

[0067] 100... Wireless communication system, 1... RoF slave unit, 2... RoF master unit, 3... Aggregation station, 4... Transmission line, 10... Projection antenna, 11... RoF slave unit control unit, 12... E / O converter, 13... Squelch circuit, 20... Multiplexer / demultiplexer, 21... RoF master unit control unit, 22... O / E converter, 15... Interface unit, 16... Memory unit, 23... Interface unit, 24... Memory unit, 91... Processor, 92... Memory, 93... Processor, 94... Memory

Claims

1. A wireless communication system in a P2MP (Point-to-MultiPoint) configuration, comprising: an RoF slave unit that transmits a predetermined pseudo-random number sequence code to an RoF master unit at the timing of receiving an uplink signal; and an RoF master unit control unit that performs an autocorrelation acquisition process to obtain the autocorrelation of the pseudo-random number sequence code that has passed through a multiplexer / demultiplexer provided by the RoF master unit.

2. The same pseudorandom number sequence code is assigned to RoF slave units that are predetermined to belong to the same group according to a predetermined rule, the wireless communication system according to claim 1.

3. The wireless communication system according to claim 1, wherein the RoF master control unit changes the connection relationship between the RoF slave unit and the RoF master unit when predetermined conditions are met.

4. A wireless communication method performed by a wireless communication system having a P2MP (Point-to-MultiPoint) configuration, comprising: an RoF slave unit that transmits a predetermined pseudorandom number sequence code to an RoF master unit at the timing of receiving an uplink signal; and an RoF master unit control unit that performs an autocorrelation acquisition process to obtain the autocorrelation of the pseudorandom number sequence code that has passed through a multiplexer / demultiplexer provided by the RoF master unit, the wireless communication method comprising: a transmission step in which the RoF slave unit transmits a predetermined pseudorandom number sequence code to the RoF master unit at the timing; and an autocorrelation acquisition step in which the RoF master unit control unit performs the autocorrelation acquisition process.

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