Communication system, base station, communication method, and method for creating a communication system

Abstract

This communication system comprises: one integration station that transmits / receives signals; and N (where N is an integer greater than 1) dispatch stations. The N dispatch stations include: a first dispatch station that receives a signal from the integration station and transmits the signal to a second dispatch station; an ith (where i is an integer such that 2 ≦ i ≦ N-1) dispatch station that receives a signal from the (i-1)th dispatch station and transmits the signal to the (i+1)th dispatch station; and an Nth dispatch station that receives a signal from the (N-1)th dispatch station. The ratio of the magnitude of the signal received by the ith (1 ≦ i ≦ N-1) dispatch station to the magnitude of the signal transmitted by the ith dispatch station is (N-i+1) : (N-i).

Description

[Technical Field]

[0001] The present invention relates to a communication system, a base station, a communication method, and a method for creating a communication system. [Background technology]

[0002] Millimeter-wave radio waves have attracted attention due to their potential for high-speed transmission. However, because millimeter-wave radio waves have large propagation losses, they require the deployment of wireless base stations at high density.

[0003] As a method for deploying wireless base stations, Non-Patent Document 1 discloses a method of applying analog RoF (Radio-over-Fiber). Analog RoF is a technology in which an optical signal is intensity-modulated with a wireless signal and the intensity-modulated optical signal is transmitted over an optical fiber, and the original wireless signal can be extracted by O / E converting the transmitted optical signal.

[0004] By applying analog RoF, wireless base stations can be separated into a central station that processes signals and a base station that has antenna functions, and the signal processing function can be consolidated into the central station. This simplifies the base station and makes it easier to install.

[0005] Non-Patent Document 2 discloses that, to simplify the deployment of base stations, aggregation stations and base stations are connected in a cascade configuration. Each base station splits an optical signal input from an upstream device using an optical splitter, outputs a portion of the optical signal to a downstream device, and processes the remaining optical signal within the station. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Kodai Ito, Mizuki Suga, Hirofumi Shirato, Naoki Kita, Takeshi Onisawa, "Efficient Accommodation of Diverse High-Frequency Band Wireless Systems Using Analog Radio Fiber," NTT Technical Journal, 32(3), 15-17, 2020. [Non-patent document 2] E. -S. Kim, M. Sung, JH Lee, JK Lee, S. -H. Cho and J. Kim, "Coverage Extension of Indoor 5G Network Using RoF-Based Distributed Antenna System," IEEE Access, vol. 8, pp. 194992-194999, 2020. Summary of the Invention [Problem to be solved by the invention]

[0007] The optical splitters provided in the base stations in Non-Patent Document 2 all basically have the same splitting ratio. However, the more base stations there are between the base station and the central station, the smaller the amplitude of the optical signal received by the base station that is farther from the central station. Also, the amplitude of the optical signal received by each base station may differ. The present invention provides a communication system, a base station, a communication method, and a method for creating a communication system that reduce variations in the magnitude of optical signals supplied to a plurality of base stations. [Means for solving the problem]

[0008] One aspect of the present invention is a communication system comprising one central station that transmits and receives signals, and N base stations (N is an integer greater than or equal to 2), wherein the N base stations include a first base station that receives a signal from the central station and transmits the signal to a second base station, an i-th base station (i is an integer such that 2≦i≦N-1) that receives a signal from the i-1th base station and transmits the signal to the i+1th base station, and an N-th base station that receives a signal from the N-1th base station, wherein the ratio of the magnitude of the signal received by the i-th base station (1≦i≦N-1) to the magnitude of the signal transmitted is (N-i+1):(Ni).

[0009] One aspect of the present invention is a base station in an optical communication system in which a plurality of base stations are connected in series with a central station at the head, the base station having a splitter that splits a signal input from an upstream device into a signal to be processed at the own station and a signal to be transmitted to a base station connected downstream, and where, when the total number of base stations connected downstream is j, the ratio of the magnitude of the signal received by the splitter to the magnitude of the signal transmitted to the downstream device is (j+1):j.

[0010] One aspect of the present invention is a communication method by a base station in an optical communication system in which a plurality of base stations are connected in series with a central station at the head, the communication method including a branching step of branching a signal input from an upstream device and transmitting it to a base station connected downstream, wherein, when the total number of base stations connected downstream is j, the ratio of the magnitude of the signal received in the branching step to the magnitude of the signal transmitted to the base station connected downstream is (j+1):j.

[0011] One aspect of the present invention is a communication system comprising one central station for transmitting and receiving signals, and N (N is an integer greater than or equal to 2) base stations, wherein the N base stations include a first base station that receives a signal from the central station and transmits the signal to a second base station, an i-th base station (i is an integer satisfying 2≦i≦N-1) that receives a signal from the i-1th base station and transmits the signal to the i+1th base station, and an N-th base station that receives a signal from the N-1th base station, wherein the ratio of the magnitude of the signal processed by the i-th base station (1≦i≦N-1) to the magnitude of the signal it transmits is 1:(Ni).

[0012] One aspect of the present invention is a base station in an optical communication system in which a plurality of base stations are connected in series with a central station at the head, and the base station is equipped with a branching section that branches a signal input from an upstream device into a signal to be processed at the base station and a signal to be transmitted to a downstream device, and where, when the total number of base stations connected downstream is j, the strength of the signal branched by the branching section and transmitted to the downstream device is j times the strength of the signal to be processed at the base station.

[0013] One aspect of the present invention is a communication method by a base station in an optical communication system in which a plurality of base stations are connected in series with a central station at the head, the communication method including a branching step for branching a signal input from an upstream device into a signal to be processed by the base station itself and a signal to be transmitted to a base station connected downstream, and where, when the total number of base stations connected downstream is j, the size of the signal branched by the branching step and transmitted to the downstream device is j times the size of the signal to be processed by the base station itself.

[0014] One aspect of the present invention is a method for creating a communication system that sets the ratio between the magnitude of a signal transmitted to a base station and the magnitude of a signal to be transmitted, the method comprising the steps of: installing a central station; connecting N base stations (N is an integer greater than or equal to 2) in series to the central station, the N base stations each having a branching section that branches a received signal into a signal to be processed at the base station and a signal to be transmitted to other base stations; and setting a branching ratio of the branching section of each of the N base stations, wherein in the step of setting the branching ratio, the branching ratio of an i-th base station (1≦i≦N-1) is set so that the ratio between the strength of the signal to be transmitted and the strength of the signal to be processed at the base station is j:1, where j is the total number of other base stations connected downstream from the i-th base station. [Effects of the Invention]

[0015] According to the present invention, it is possible to reduce variations in the amplitude of optical signals supplied to a plurality of base stations. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram illustrating a configuration of an optical communication system in which a central station and a base station are connected in a cascade configuration. [Figure 2] FIG. 2 is a diagram illustrating the configuration of a central station. [Figure 3] FIG. 1 is a diagram illustrating the configuration of an ith base station (i is an integer satisfying the condition 1≦i≦N). [Figure 4] 10 is a flowchart showing a transmission method of the aggregation station. [Figure 5]10 is a flowchart showing a receiving method of the aggregation station. [Figure 6] 10 is a flowchart showing a method of communication between a base station and an upstream device. [Figure 7] 10 is a flowchart showing a method of communication between a base station and a downstream device. [Figure 8] 1 is a flowchart illustrating a method for creating an optical communication system. DETAILED DESCRIPTION OF THE INVENTION

[0017] Optical communication systems FIG. 1 is a diagram showing the configuration of an optical communication system 1 in which an aggregation station 10 and a base station 11 are connected in a cascade configuration. The optical communication system 1 has one aggregation station 10 and N base stations 11 (N is an integer equal to or greater than 2). In the optical communication system 1, the aggregation station 10 is at the head, and the N base stations 11 are connected in series. Hereinafter, when distinguishing between the N base stations 11, each base station 11 will be referred to as the i-th base station 11-i (i is an integer satisfying 1≦i≦N). However, when describing features common to all the i-th base stations 11-i, the base station 11 will simply be referred to as the base station 11. Note that the ordinal number i is equal to the number of hops from the aggregation station 10. In the optical communication system 1, the direction from the aggregation station 10 to the base station 11 is referred to as downstream, and the direction from the base station 11 to the aggregation station 10 is referred to as upstream.

[0018] The central station 10 performs E / O conversion on the generated wireless signal and transmits the generated downstream optical signal to the first base station 11-1. The first base station 11-1 branches the received downstream optical signal, transmits part of the optical signal to the second base station 11-2, processes the remaining optical signal within itself, and transmits a wireless signal according to the optical signal. The first base station 11-1, for example, O / E converts the optical signal and radiates the resulting wireless signal into space via an antenna. The second base station 11-2 to the N-1th base station 11-(N-1) also perform the same operation as the first base station 11-1. In other words, the ith base station 11-i (i is an integer satisfying 2≦i≦N−1) branches the optical signal received from the i-1th base station 11-(i-1), which is an upstream device, and transmits part of the optical signal to the i+1th base station 11-(i+1), which is a downstream device.

[0019] The ith base station 11-i (i is an integer satisfying 2≦i≦N−1) generates an upstream optical signal by E / O converting a radio signal received via an antenna, for example. The ith base station 11-i combines the optical signal received from a downstream device with the upstream optical signal and transmits the combined signal to an upstream device. In other words, the ith base station 11-i combines the optical signal received from the (i+1) base station 11-(i+1) with an optical signal obtained by multiplexing the radio signal received by the ith base station, and transmits the combined optical signal to the (i−1) base station 11-(i−1).

[0020] That is, the optical signal transmitted from the central station 10 travels downstream through the first base station 11-1 and the second base station 11-2, and finally reaches the Nth base station 11-N. The optical signal transmitted from the Nth base station 11-N travels upstream to the N-1th base station 11-(N-1), and finally reaches the central station 10. The central station 10 performs O / E conversion on the received optical signal to obtain a radio signal. The radio signal is subjected to, for example, signal processing.

[0021] As described above, in the optical communication system 1, N base stations 11 are connected in series with the central station 10 at the head. Radio signals received at the base stations 11 are converted into optical signals without undergoing signal processing at the base stations 11 and are then aggregated at the central station 10. The optical signals aggregated by the central station 10 are converted into radio signals, and the radio signals received at the base stations 11 are extracted. Because the base stations 11 do not need to include a configuration for processing radio signals, the base stations 11 can be easily implemented.

[0022] Aggregation Station 2 is a diagram showing the configuration of the central station 10. The central station 10 includes a transmitter 100, an E / O converter 101, a multiplexer 102, an O / E converter 103, and a receiver 104. The central station 10 includes N transmitters 100, E / O converters 101, O / E converters 103, and receivers 104, the number of which is the same as the number of base stations 11.

[0023] The transmitting units 100 are referred to as a first transmitting unit 100-1, a second transmitting unit 100-2, etc., and an N-th transmitting unit 100-N. The E / O converting units 101 are referred to as a first E / O converting unit 101-1, a second E / O converting unit 101-2, etc., and an N-th E / O converting unit 101-N. The O / E converting units 103 are referred to as a first O / E converting unit 103-1, a second O / E converting unit 103-2, etc., and an N-th O / E converting unit 103-N. The receiving units 104 are referred to as a first receiving unit 104-1, a second receiving unit 104-2, etc., and an N-th receiving unit 104-N.

[0024] The i-th transmitter 100-i (i is an integer satisfying 1≦i≦N) transmits an electrical signal to the i-th E / O converter 101-i. The i-th E / O converter 101-i (i is an integer satisfying 1≦i≦N) converts the received electrical signal into an optical signal and transmits the optical signal to the multiplexer 102. The wavelengths of the optical signals transmitted from the i-th E / O converter 101-i to the multiplexer 102 are different from each other. The wavelength of the optical signal transmitted from the i-th E / O converter 101-i is λ DLi and differs for each E / O converter 101. The optical signal transmitted by the i-th E / O converter 101-i is intended to ultimately reach the i-th base station 11-i. The central station 10 can switch the base station 11 to which the transmitted optical signal will ultimately reach by switching which transmitter 100 to use to transmit the electrical signal. This allows the central station 10 to perform handover and switch whether the base station 11 transmits or receives signals.

[0025] The multiplexing unit 102 multiplexes the optical signals received from the E / O conversion unit 101 and transmits the multiplexed optical signals to the first base station 11-1. The multiplexing unit 102 also demultiplexes the optical signals received from the first base station 11-1 and transmits the demultiplexed optical signals to the O / E conversion unit 103. The wavelength of the optical signal transmitted by the multiplexing unit 102 to the i-th O / E conversion unit 103-i is λ ULi and differs for each O / E conversion unit 103. ULi The optical signal is an optical signal transmitted from the i-th base station 11-i.

[0026] The i-th O / E converter 103-i (i is an integer satisfying 1≦i≦N) converts the received optical signal into an electrical signal and transmits the electrical signal to the i-th receiver 104-i. The i-th receiver 104-i (i is an integer satisfying 1≦i≦N) receives the electrical signal from the i-th O / E converter 103-i.

[0027] 〈Exhibition Bureau〉 3 is a diagram showing the configuration of the ith base station 11-i (i is an integer satisfying 1≦i≦N). The ith base station 11-i includes an ith optical splitter 110-i, an ith multiplexing unit 111-i, an ith O / E conversion unit 112-i, an ith transmitting amplifier 113-i, an ith circulator 114-i, an ith antenna 115-i, an ith receiving amplifier 116-i, and an ith E / O conversion unit 117-i. Like the i-th base station 11-i, the i-th optical splitter 110-i, the i-th multiplexing unit 111-i, the i-th O / E conversion unit 112-i, the i-th transmitting amplifier 113-i, the i-th circulator 114-i, the i-th antenna 115-i, the i-th receiving amplifier 116-i, and the i-th E / O conversion unit 117-i will also be referred to as the optical splitter 110, the multiplexing unit 111, the O / E conversion unit 112, the transmitting amplifier 113, the circulator 114, the antenna 115, the i-th receiving amplifier 116, and the E / O conversion unit 117, respectively, when explaining their characteristics that are independent of the position of the base station 11.

[0028] The ith optical splitter 110-i branches an optical signal received from an upstream device and transmits the branched optical signal to the ith multiplexer 111-i and the (i+1)th base station 11-(i+1). The first optical splitter 110-1 branches an optical signal received from the aggregation station 10, and the ith optical splitter 110-i (i is an integer satisfying 2≦i≦N−1) branches an optical signal received from the (i−1)th base station 11-(i−1). The i-th optical splitter 110-i combines the optical signals transmitted from the i-th multiplexer 111-i and the i+1-th base station 11-(i+1), which is a downstream device, and transmits the combined optical signal to an upstream device. The first optical splitter 110-1 transmits the combined optical signal to the aggregation station 10, and the i-th optical splitter 110-i (i is an integer satisfying 2≦i≦N−1) transmits the combined optical signal to the i-1-th base station 11-(i−1).

[0029] The i-th multiplexing unit 111-i is configured by, for example, an optical multiplexer / demultiplexer. The i-th multiplexing unit 111-i demultiplexes the optical signal received from the i-th optical splitter 110-i, and separates the optical signal having a wavelength λ DLi The i-th multiplexer 111-i extracts the signal of wavelength λ from the optical signal transmitted from the i-th E / O converter 101-i and outputs it to the i-th O / E converter 112-i. This allows the i-th multiplexer 111-i to extract the signal corresponding to its own station from the optical signal transmitted from the i-th E / O converter 101-i. The i-th multiplexer 111-i extracts the signal of wavelength λ from the optical signal received from the i-th E / O converter 117-i. ULi The optical signal received from the i-th E / O conversion unit 117-i has a wavelength λ ULi That is, the optical signal transmitted from the i-th E / O conversion unit 117-i is finally received by the i-th receiving unit 104-i.

[0030] The i-th O / E converter 112-i converts the optical signal received from the i-th multiplexer 111-i into an electrical signal and transmits it to the i-th transmitting amplifier 113-i. The i-th transmitting amplifier 113-i amplifies the electrical signal received from the i-th O / E converter 112-i and transmits the amplified electrical signal to the i-th circulator 114-i.

[0031] The i-th circulator 114-i transmits the electrical signal received from the i-th transmitting amplifier 113-i to the i-th antenna 115-i, and also transmits the electrical signal received from the i-th antenna 115-i to the i-th receiving amplifier 116-i.

[0032] The i-th antenna 115-i radiates the electrical signal received from the i-th circulator 114-i into space, and also transmits the received electrical signal to the i-th circulator 114-i.

[0033] The i-th receiving amplifier 116-i amplifies the electrical signal received from the i-th circulator 114-i and transmits the amplified electrical signal to the i-th E / O converter 117-i. The i-th E / O converter 117-i converts the electrical signal received from the i-th receiving amplifier 116-i into λ ULiThe optical signal is converted into an optical signal of the wavelength of the signal and transmitted to the ith multiplexing unit 111-i.

[0034] The N-th base station 11-N has almost the same configuration as the i-th base station 11-i (i is an integer satisfying 1≦i≦N−1), but does not need to include an optical splitter.

[0035] 4 is a flowchart showing a transmission method of the central station 10. The transmitter 100 transmits an electrical signal to the E / O converter 101 (step S1). The E / O converter 101 converts the electrical signal into an optical signal (step S2). The multiplexer 102 multiplexes the optical signal (step S3). The multiplexed optical signal is transmitted to the first base station 11-1.

[0036] 5 is a flowchart showing a receiving method of the central station 10. The multiplexing unit 102 demultiplexes the optical signal received from the first base station 11-1 (step S11). The O / E conversion unit 103 converts the optical signal into an electrical signal (step S12). The receiving unit 104 receives the electrical signal (step S13).

[0037] 6 is a flowchart showing a method of communication between the base station 11 and an upstream device. The optical splitter 110 branches an optical signal received from the upstream device (step S20). The branched optical signal is transmitted to the multiplexer 111 and the downstream device. The multiplexer 111 demultiplexes the optical signal received from the optical splitter 110 (step S21). The O / E converter 112 converts the optical signal into an electrical signal (step S22). The transmission amplifier 113 amplifies the electrical signal (step S23). The electrical signal is radiated from the antenna 115 via the circulator 114 (step S24).

[0038] 7 is a flowchart showing a method of communication between the base station 11 and downstream devices. The antenna 115 receives an electrical signal (step S31). The electrical signal is passed through the circulator 114 and amplified by the receiving amplifier 116 (step S32). The E / O converter 117 converts the electrical signal into an optical signal (step S33). The multiplexer 111 multiplexes the optical signal (step S34). The optical splitter 110 multiplexes the optical signal received from the multiplexer 111 with the optical signal received from the downstream device, and transmits the combined signal to the upstream device (step S35).

[0039] <Optical splitter branching ratio> The ith optical splitter 110-i branches the received optical signal so that the magnitude ratio is 1:(Ni). The ith optical splitter 110-i transmits the branched optical signal to the ith multiplexer 111-i and the (i+1)-th base station 11-(i+1), respectively, so that the magnitude ratio between the optical signal to be transmitted to the ith multiplexer 111-i and the optical signal to be transmitted to the (i+1)-th base station 11-(i+1) is 1:(Ni). The first optical splitter 110-1 branches the optical signal received from the central station 10, and the ith optical splitter 110-i (i is an integer satisfying 2≦i≦N−1) branches the optical signal received from the (i−1)-th base station 11-(i−1).

[0040] The branching ratio of the ith optical splitter 110-i may be set, for example, when the ith remote station 11-i is installed, but is not limited to this. For example, the ith optical splitter 110-i may include two optical fibers optically coupled together, an actuator that changes the distance between the cores of the optical fibers, and a control device that controls the actuator based on a control signal, and the branching ratio of the ith optical splitter 110-i may be set based on a control signal transmitted from another device such as the central station 10.

[0041] The i-th optical splitter 110-i combines the optical signals transmitted from the i-th multiplexing unit 111-i and the i+1-th base station 11-(i+1) and transmits the combined optical signal. The first optical splitter 110-1 transmits the combined optical signal to the aggregation station 10, and the i-th optical splitter 110-i (i is an integer satisfying 2≦i≦N−1) transmits the combined optical signal to the i−1-th base station 11-(i−1).

[0042] The optical signal transmitted from the ith optical splitter 110-i to the ith multiplexer 111-i is the optical signal remaining in the ith base station 11-i that includes the ith optical splitter 110-i. The ratio of the magnitude of the optical signal input to the ith base station 11-i to the magnitude of the optical signal output is (N-i+1):(Ni). The magnitude P of the optical signal received by the ith base station 11-i is i is expressed by equation (1) using the magnitude P0 of the optical signal transmitted from aggregation station 10.

[0043]

number

[0044] In addition, the magnitude of the optical signal transmitted by the N-1th base station 11-(N-1), that is, the magnitude P N is expressed by equation (2).

[0045]

number

[0046] As a result, the difference between the optical signal received by the base station 11 and the optical signal transmitted therefrom, that is, the magnitude of the optical signal input to the O / E converter 112 of each base station 11, is all equal.

[0047] In the optical communication system 1, the i-th base station 11-i branches the received optical signal so that the magnitude ratio is 1:(Ni), and transmits the optical signal to the i+1-th base station 11-(i+1) so that the magnitude of the received optical signal and the magnitude of the optical signal to be transmitted to the i+1-th base station 11-(i+1) are (N-i+1):(Ni). This makes it possible to equalize the magnitudes of the optical signals received but not transmitted by each base station 11.

[0048] 8 is a flowchart showing a method for creating the optical communication system 1. First, a central station 10 is installed (step S41). Then, N base stations 11, each equipped with an optical splitter 110 that splits a received signal into a signal to be processed at the central station and a signal to be transmitted to another base station, are connected in series to the central station 10 (step S42). The splitting ratio of the optical splitter 110 of each of the N base stations 11 is set (step S43).

[0049] In setting the branching ratio, the branching ratio of the i-th base station 11-i (1≦i≦N-1) is set so that the ratio between the size of the signal to be transmitted and the size of the signal to be processed by the base station is j:1, where j is the total number of other base stations connected downstream from the i-th base station 11-i.

[0050] Other Embodiments One embodiment of the present invention has been described above in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and includes designs within the scope of the present invention that do not deviate from the gist of the present invention.

[0051] In the optical communication system 1 according to the above-described embodiment, the string of multiple cascaded base stations 11 does not branch midway. However, in other embodiments, the string of base stations 11 may branch midway. That is, two or more base stations 11 may be connected to the downstream side of a certain base station 11. In this case, the branching ratio of the base station 11 is the ratio of the number of base stations 11 constituting the string of base stations connected to the downstream side. Furthermore, regarding the optical splitter of the base station in the downstream direction after branching, the ratio of the magnitude of the optical signal input to the jth base station (j is an integer satisfying 1≦j≦M) to the magnitude of the optical signal output is (M−j+1):(Mj), where M is the number of base stations in the downstream direction after branching and the first base station, second base station, ... are in order from the side closest to the branching point. There are no particular limitations on the method of multiplexing the optical signals by the multiplexing units 102 and 111. For example, the multiplexing units 102 and 111 may multiplex the optical signals by frequency division multiplexing or time division multiplexing.

[0052] The base station 11 may include a control unit 118. When the multiplexing unit 111 multiplexes optical signals by time division multiplexing, the circulator 114 may be a TDD switch, and the control unit 118 may control the TDD switch to switch between the connection between the transmitting amplifier 113 and the circulator 114 and the connection between the circulator 114 and the receiving amplifier 116. When the multiplexing unit 111 multiplexes optical signals by time division multiplexing, the wavelength λ of the optical signal transmitted by the i-th E / O conversion unit 101-i may be DLi and the wavelength λ of the optical signal received by the i-th O / E conversion unit 103-i. ULi may be the same wavelength, e.g., λ DL1 and λ UL1 may be at the same wavelength.

[0053] The antenna 115 is an array antenna with a controllable beam direction, and the control unit 118 may control the antenna 115 to change the beam direction in which the antenna 115 transmits and receives.

[0054] The control unit 118 may be controlled based on a control signal received from the central station 10. The control signal may be subcarrier-multiplexed, polarization-multiplexed, or wavelength-multiplexed onto a downstream optical signal transmitted by the central station 10, and then transmitted to the base station 11. The wavelength of the control signal is λ DLi and λ DLi In this case, a circulator or the like may be provided between the multiplexing unit 111 and the E / O conversion unit 117 to prevent a control signal from being input from the multiplexing unit 111 to the E / O conversion unit 117.

[0055] The optical communication system 1 employs, but is not limited to, an analog RoF. The optical communication system 1 may employ a digital RoF (for example, CPRI or eCPRI) or digital coherent transmission, in which the central station 10 includes an A / D converter, each base station 11 includes a D / A converter, and the central station 10 transmits a digital signal.

[0056] The present invention can be applied even when the central station 10 and the base station are connected by a mobile fronthaul in the optical communication system 1. [Explanation of symbols]

[0057] 10 aggregation station, 11 base station, 100 transmitting unit, 101 E / O conversion unit, 102 multiplexing unit, 103 O / E conversion unit, 104 receiving unit, 110 optical splitter, 111 multiplexing unit, 112 O / E conversion unit, 113 transmitting amplifier, 114 circulator, 115 antenna, 116 receiving amplifier, 117 E / O conversion unit

Claims

1. The system comprises one central station for transmitting and receiving signals and N base stations (N is an integer of 2 or more), The said base station receiving a signal from the central station or an upstream base station, and transmitting a signal to a downstream base station if there is a downstream base station; the ratio of the magnitude of the signal received by the base station to the magnitude of the signal transmitted by the base station is (j+1):j (j is the number of base stations downstream); When the base station branches a signal and transmits it to a plurality of base stations, the signal branching ratio is the ratio of the number of base stations constituting each row of base stations to which the branched signal is transmitted. Communication system.

2. A base station in an optical communication system in which a plurality of base stations are connected in series with a central station at the head, a splitter for splitting a signal input from an upstream device into a signal to be processed in the own station and a signal to be transmitted to a base station connected downstream, When the total number of base stations connected downstream is j, the ratio of the magnitude of the signal received by the splitter to the magnitude of the signal transmitted to the downstream device is (j+1):j; When a signal is branched and transmitted to a plurality of downstream devices, the signal branching ratio is the ratio of the number of base stations constituting each row of base stations to which the branched signal is transmitted. Zhang station.

3. A communication method by a base station in an optical communication system in which a plurality of base stations are connected in series with a central station at the head, a branching step of branching a signal input from an upstream device and transmitting the signal to a base station connected downstream, where j is the total number of base stations connected downstream, the ratio of the magnitude of the signal received in the branching step to the magnitude of the signal transmitted to the base station connected downstream is (j+1):j; In the case where a signal is branched and transmitted to a plurality of base stations connected downstream, the branching ratio of the signal is the ratio of the number of base stations constituting the row of each base station to which the branched signal is transmitted. Communication method.

4. The system comprises one central station for transmitting and receiving signals and N base stations (N is an integer of 2 or more), The said base station receiving a signal from the central station or an upstream base station, and transmitting a signal to a downstream base station if there is a downstream base station; The ratio of the magnitude of the signal processed by the base station to the magnitude of the signal transmitted by the base station is 1:j (j is the number of base stations downstream), When the base station branches a signal and transmits it to a plurality of base stations, the signal branching ratio is the ratio of the number of base stations constituting each row of base stations to which the branched signal is transmitted. Communication system.

5. A base station in an optical communication system in which a plurality of base stations are connected in series with a central station at the head, A splitter is provided for splitting a signal input from an upstream device into a signal to be processed in the station and a signal to be transmitted to a downstream device, where j is the total number of base stations connected downstream, the strength of the signal split by the splitter and transmitted to the downstream device is j times the strength of the signal processed by the local station; When a signal is branched and transmitted to a plurality of downstream devices, the signal branching ratio is the ratio of the number of base stations constituting each row of base stations to which the branched signal is transmitted. Zhang station.

6. A communication method by a base station in an optical communication system in which a plurality of base stations are connected in series with a central station at the head, a branching step of branching a signal input from an upstream device into a signal to be processed in the own station and a signal to be transmitted to a base station connected downstream, where j is the total number of base stations connected downstream, the magnitude of the signal branched by the branching step and transmitted to the downstream device is j times the magnitude of the signal processed by the local station; In the case where a signal is branched and transmitted to a plurality of base stations connected downstream, the branching ratio of the signal is the ratio of the number of base stations constituting the row of each base station to which the branched signal is transmitted. Communication method.

7. 1. A method for creating a communication system that sets the ratio between the magnitude of a signal transmitted to a base station and the magnitude of a signal to be transmitted, comprising the steps of: establishing an aggregation station; a step of connecting a base station, which has a splitter that splits a received signal into a signal to be processed in the base station and a signal to be transmitted to another base station, to the central station; setting a branching ratio of the splitter of each of the base stations, in the step of setting the branching ratio, the branching ratio is set so that, when a total number of other base stations connected downstream is j, the ratio of the magnitude of the signal to be transmitted to the magnitude of the signal processed by the base station is j:1; When the base station branches a signal and transmits it to a plurality of base stations, the signal branching ratio is the ratio of the number of base stations constituting each row of base stations to which the branched signal is transmitted. How to create a communication system.

8. The base station includes a splitter and a multiplexing unit, The splitter comprises: branching a signal received from the central station or the upstream base station, and outputting the signal to the multiplexing unit and the downstream base station; a signal input from the multiplexing unit and a signal input from the downstream base station are merged together, and the merged signal is output to the central station or the upstream base station; The multiplexing unit extracting a downstream signal of a wavelength corresponding to the own station from the signal received from the splitter; An upstream signal of a wavelength corresponding to the station is extracted from the signal generated by E / O conversion of the electrical signal received by the antenna and output to the splitter.

5. A communication system according to claim 1 or 4.

9. The base station further comprises a multiplexing unit, The splitter comprises: branching a signal received from the central station or the upstream base station, and outputting the signal to the multiplexing unit and the downstream base station; a signal input from the multiplexing unit and a signal input from the downstream base station are merged together, and the merged signal is output to the central station or the upstream base station; The multiplexing unit extracting a downstream signal of a wavelength corresponding to the own station from the signal received from the splitter; An upstream signal of a wavelength corresponding to the station is extracted from the signal generated by E / O conversion of the electrical signal received by the antenna and output to the splitter. The base station according to claim 2 or 5.

10. The base station includes a splitter and a multiplexing unit, The splitter comprises: branching a signal received from the central station or the upstream base station, and outputting the signal to the multiplexing unit and the downstream base station; a signal input from the multiplexing unit and a signal input from the downstream base station are merged together, and the merged signal is output to the central station or the upstream base station; The multiplexing unit extracting a downstream signal of a wavelength corresponding to the own station from the signal received from the splitter; An upstream signal of a wavelength corresponding to the station is extracted from the signal generated by E / O conversion of the electrical signal received by the antenna and output to the splitter. The communication method according to claim 3 or 6.

11. The base station further comprises a multiplexing unit, The splitter comprises: branching a signal received from the central station or an upstream base station, and outputting the signal to the multiplexing unit and a downstream base station; a signal input from the multiplexing unit and a signal input from the downstream base station are merged together, and the merged signal is output to the central station or the upstream base station; The multiplexing unit extracting a downstream signal of a wavelength corresponding to the own station from the signal received from the splitter; An upstream signal of a wavelength corresponding to the station is extracted from the signal generated by E / O conversion of the electrical signal received by the antenna and output to the splitter. A method for creating a communication system according to claim 7.

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