JP5128517B2 - Diversity communication device - Google Patents

Description

  In the present invention, a central base station and a plurality of remote base stations arranged at different positions are connected by an optical transmission line, and each remote base station transmits a signal (for example, TDMA) transmitted from a terminal station at the same time and the same frequency. The present invention relates to a diversity communication apparatus that transfers signals to a centralized base station and receives signals from each remote base station by diversity combining at the centralized base station.

  In recent wireless communication, it is necessary to efficiently perform communication with fewer frequency resources as the available frequency becomes tighter. In general, in order to expand the communicable area in a plane, the areas are divided as shown in FIG. 7, base stations are arranged in each area, and different frequencies are assigned to the respective areas, so that no interference occurs. There are ways to enable communication. In this example, each region has a hexagonal shape, the frequency F1 is used in the central region, and the frequencies F2 to F7 are used in the surrounding region to avoid interference, so a total of seven types of frequencies are required. . However, since actual frequency resources are finite, such planar development is not always possible. Furthermore, in order to maintain communication even if the terminal station moves between the respective regions in FIG. 7, a handover process for changing the base station with which the terminal station communicates occurs, and the system configuration becomes complicated.

  In view of this, SFN (Single Frequency Network) has been proposed in which the area in which communication can be performed at a single frequency is expanded. As shown in FIG. 8, the SNF has a configuration in which remote base stations using a single frequency F1 are arranged in each region, and each remote base station is connected to a centralized base station via an optical transmission line. In this configuration, in the downlink in which a signal is transmitted from the base station to the terminal station, a signal from the concentrated base station is transmitted to each remote base station, and is simultaneously transmitted from each remote base station to reach the terminal station. In the uplink in which a signal is transmitted from the terminal station to the base station, the signal transmitted from the terminal station is received by each remote base station, further reaches the concentrated base station, and is diversity-combined at the concentrated base station. As a result, a communicable area using a single frequency can be expanded in a plane. Further, since the remote base station has a simple configuration that only relays uplink and downlink signals, the SFN can reduce the overall device cost. Further, even if the terminal station moves in the area at the centralized base station, communication can be maintained without recognizing the movement, so that the handover process becomes unnecessary.

FIG. 9 shows a configuration example of a conventional diversity communication apparatus that realizes SFN.
In the figure, the centralized base station 10 and the remote base stations 40a, 40b, 40c are connected via downlink optical transmission paths 30a, 30b, 30c and uplink optical transmission paths 31a, 31b, 31c. The terminal stations 60a and 60b are connected to the remote base stations 40a, 40b and 40c, and further connected to the centralized base station 10.

First, downlink signals will be described.
The centralized base station 10 receives data from the external network 100 by the network interface 11 and converts it into a radio signal by the modulator 12. This radio signal and the control signal for remote base station control generated by the control unit 13 are frequency-multiplexed by the synthesizer 14. The radio signal and the control signal have different frequencies, and are hereinafter referred to as a radio signal frequency and a control signal frequency. The signal frequency-multiplexed by the synthesizer 14 is converted into an optical signal by the E / O converter 15 and distributed by the transmission optical coupler 16, and the remote base stations 40a, 40a, 40c are respectively transmitted through the optical transmission lines 30a, 30b, 30c. 40b and 40c are reached.

  The remote base station 40a (the same applies to the remote base stations 40b and 40c) converts the optical signal that has arrived from the optical transmission line 30a into an electrical signal by the O / E converter 41. Among these electrical signals, a signal having a radio signal frequency is amplified by the transmission amplifier 42, then transmitted as a radio signal via the switch 43 and the antenna 44, and received by the terminal stations 60a and 60b. In addition, the control signal frequency signal controls transmission / reception of the switch 43 (not shown).

Next, uplink signals will be described.
The transmission signals of the terminal stations 60a and 60b reach the remote base stations 40a, 40b and 40c. The remote base station 40a (the same applies to the remote base stations 40b and 40c) inputs the signal received by the antenna 44 to the reception amplifier 45a via the switch 43, and converts the signal amplified by the reception amplifier 45 to E / O conversion. It is converted into an optical signal by the device 46 and sent to the centralized base station 10 through the optical transmission path 31a.

  The central base station 10 also receives optical signals from the remote base stations 40b and 40c as well as optical signals from the remote base station 40a. These optical signals are converted into electrical signals by O / E converters 18a, 18b, and 18c, respectively, and demodulated by demodulators 19a, 19b, and 19c, respectively. Each demodulated signal is subjected to diversity combining after detection by a post-detection synthesizer 24 and then converted to binary data by a code determination unit 20. This binary data is sent to the external network 100 via the network interface 11.

  Note that the post-detection synthesizer 24 selects, as a post-detection diversity combining method, selective combining for selecting a signal with a high level described in Non-Patent Document 1, equal gain combining for combining the phases, and signal-to-noise ratio. Maximal ratio synthesis or the like that maximizes is used.

  Such a conventional diversity communication apparatus needs to prepare the same number of reception systems as the number of remote base stations in the centralized base station 10, so that even if SFN is used, the cost reduction effect is not sufficient. Also, as in Patent Document 1, a method of combining signals from a plurality of remote base stations converted into electrical signals has been proposed, but even in this case, the same number of O / E converters as the remote base stations are required. become.

Japanese Patent Laid-Open No. 11-252516

Yoichi Saito, Modulation and Demodulation of Digital Wireless Communication, IEICE, pp.189-193

  The diversity communication apparatus of FIG. 9 requires the same number of reception systems as the remote base station in the concentrated base station, resulting in a problem that the apparatus configuration becomes large and the apparatus cost increases.

  It is an object of the present invention to provide a diversity communication device that can reduce the number of reception systems in a centralized base station, achieve a simplified device configuration and lower costs, and obtain higher communication quality.

The present invention comprises a plurality of remote base stations connected to a terminal station via a wireless line, and a single central base station connected to each of the plurality of remote base stations via an optical transmission line, The downlink optical signal transmitted from the mobile station is received by a plurality of remote base stations, the plurality of remote base stations convert the optical signal into a radio signal and transmitted to the terminal station, and the uplink radio signal transmitted from the terminal station A terminal station that receives signals at a plurality of remote base stations, converts the radio signals into optical signals, transmits the signals to the centralized base station, and transmits them to the centralized base station via the multiple remote base stations In the diversity communication device that is configured to receive and transmit diversity transmission signals, the centralized base station transmits optical signals transmitted from a plurality of remote base stations via an optical transmission line from remote base stations that are not adjacent to each other. each one line of the optical signal to an optical signal Comprises two or more receiving optical coupler for pre-detection combining, have rows demodulates the optical signal of each path is converted into an electric signal, and configured to post-detection diversity combining the demodulated signals, a plurality of remote base stations The uplink optical transmission line connected to the central base station corresponds to the transmission signal of the same terminal station transmitted via each optical transmission line for the optical transmission line connected to each receiving optical coupler. The delay time is adjusted to such an extent that optical signals can be combined before detection.

  The remote base station detects the reception level of the uplink radio signal, performs optical signal transmission to the centralized base station when the reception level exceeds a predetermined value, and transmits the optical signal to the centralized base station when the reception level is lower than the predetermined value. Control means for stopping optical signal transmission to the station may be provided.

  The remote base station and the terminal station are configured so that a plurality of terminal stations perform wireless communication using different subcarriers at the same time using OFDMA, and the remote base station is superimposed on the downlink optical signal from the concentrated base station. Control means for performing optical signal transmission to the central base station or stopping optical signal transmission according to the control signal transmitted in the same manner, and the central base station transmits optical signals to a plurality of remote base stations during the communication preparation stage. A control signal for instructing transmission is transmitted, the optical signal transmitted for each remote base station is demodulated, and the reception level for each subcarrier corresponding to the terminal station is detected. A configuration may be adopted in which an optical signal transmission is instructed to a remote base station exceeding the value, and a control signal instructing an optical signal transmission stop is transmitted to a remote base station whose reception level level is a predetermined value or less.

  The control means may be configured to turn on / off the power of an E / O converter that converts an uplink radio signal transmitted from a terminal station into an optical signal.

  The diversity communication apparatus according to the present invention has a configuration in which a centralized base station combines optical signals from a plurality or all remote base stations before detection, converts the combined optical signals before detection into electrical signals, and demodulates them. The reception system of the stations can be aggregated to a number smaller than the number of remote base stations. Thereby, simplification and cost reduction of an apparatus structure are realizable.

  The diversity communication apparatus of the present invention controls the optical signal transmission from the remote base station or the optical signal transmission stop based on the reception level of each terminal station received by each of the plurality of remote base stations. As a result, noise components generated at a remote base station with a low signal reception level do not reach the centralized base station, and only optical signals from remote base stations having sufficient signal power can be synthesized before detection. High communication quality can be ensured by combining. Furthermore, higher communication quality can be ensured by combining diversity combining after detection.

It is a figure which shows the structural example of Example 1 of the diversity communication apparatus of this invention. It is a figure which shows the structural example of Example 2 of the diversity communication apparatus of this invention. It is a figure which shows the structural example of Example 3 of the diversity communication apparatus of this invention. It is a figure which shows the structural example of Example 4 of the diversity communication apparatus of this invention. It is a figure which shows the structural example of Example 5 of the diversity communication apparatus of this invention. FIG. 10 is a diagram illustrating an example of a signal power level for each uplink subcarrier in the fifth embodiment. It is a figure which shows the example of the surface expansion | deployment using a some frequency. It is a figure which shows the example of the planar expansion | deployment using SFN. It is a figure which shows the structural example of the conventional diversity communication apparatus which implement | achieves SFN.

FIG. 1 shows a configuration example of Embodiment 1 of a diversity communication apparatus of the present invention.
In the figure, the centralized base station 10 and the remote base stations 40a, 40b, 40c are connected via downlink optical transmission paths 30a, 30b, 30c and uplink optical transmission paths 31a, 31b, 31c. The terminal stations 60a and 60b are connected to the centralized base station 10 via the remote base stations 40a, 40b, and 40c.

  Network interface 11, modulator 12, controller 13, synthesizer 14, E / O converter 15, transmission optical coupler 16, O / E converter 18, demodulator 19 and code determiner constituting the centralized base station 10 20 has the same function as the conventional centralized base station 10 shown in FIG. The O / E converter 41, the transmission amplifier 42, the switch 43, the reception amplifier 45, and the E / O converter 46 constituting the remote base station 40a (the same applies to the remote base stations 40b and 40c) are shown in FIG. Has the same function as the remote base station 40a.

  A feature of the present embodiment is that the central base station 10 includes a receiving optical coupler 17 and combines optical signals transmitted from the remote base stations 40a, 40b, and 40c via the optical transmission paths 31a, 31b, and 31c before detection. In addition, the O / E converter 18 is configured to input one system of optical signals. Note that the delay times of the optical transmission lines 31a, 31b, and 31c are adjusted so as to be substantially equal to each other in a range in which inter-symbol interference does not occur in each optical signal combined before detection by the receiving optical coupler 17.

  The downlink signals are the same as in the conventional configuration, and the optical signals transmitted from the centralized base station 10 via the optical transmission paths 30a, 30b, 30c are converted into radio signals by the remote base stations 40a, 40b, 40c. And are received by the terminal stations 60a and 60b.

Next, uplink signals will be described.
The transmission signals of the terminal stations 60a and 60b are converted into optical signals by the remote base stations 40a, 40b, and 40c and transmitted to the centralized base station 10 through the optical transmission paths 31a, 31b, and 31c, as in the conventional configuration. . The centralized base station 10 synthesizes the optical signals from the remote base stations 40a, 40b, and 40c before detection by the receiving optical coupler 17 and inputs them to the O / E converter 18 as one system of optical signals. The signal is converted into a signal and input to the demodulator 19. The signal demodulated by the demodulator 19 is converted into binary data by the code determination unit 20 and further sent to the external network 100 via the network interface 11.

  In the configuration of the first embodiment, the three systems of light transmitted via the remote base stations 40a, 40b, and 40c are adjusted by adjusting the delay times of the uplink optical transmission lines 31a, 31b, and 31c to be approximately equal. The signals are combined by the receiving optical coupler 17 before detection, converted into an electrical signal as a single system optical signal, and demodulated. As a result, the O / E converter 18 and the demodulator 19 of the reception system in the centralized base station 10 can be integrated into one system regardless of the number of remote base stations, and the simplification of the device configuration and the reduction in cost can be realized. it can.

FIG. 2 shows a configuration example of Embodiment 2 of the diversity communication apparatus of the present invention.
In the figure, the centralized base station 10 and the remote base stations 40a, 40b, 40c are connected via downlink optical transmission paths 30a, 30b, 30c and uplink optical transmission paths 31a, 31b, 31c. The terminal stations 60a and 60b are connected to the centralized base station 10 via the remote base stations 40a, 40b, and 40c.

  Network interface 11, modulator 12, controller 13, synthesizer 14, E / O converter 15, transmission optical coupler 16, O / E converter 18, demodulators 19a and 19b, detectors constituting the centralized base station 10 The post-synthesizer 24 and the code determination unit 20 have the same functions as the conventional centralized base station 10 shown in FIG. The O / E converter 41, the transmission amplifier 42, the switch 43a, the antenna 44a, the reception amplifier 45a, and the E / O converter 46 constituting the remote base station 40a (the same applies to the remote base stations 40b and 40c) are shown in FIG. The same function as the conventional remote base station 40a shown in FIG.

  As in the first embodiment, the feature of this embodiment is that optical signals from the remote base stations 40a, 40b, and 40c are combined before detection by the receiving optical coupler 17 of the centralized base station 10 and are combined as one system of optical signals. In addition to the configuration that inputs to the O / E converter 18, a plurality of reception systems are arranged in each of the remote base stations 40a, 40b, and 40c, and the central base station 10 performs diversity combining after detection of signals of the plurality of reception systems. is there. For this purpose, the centralized base station 10 includes an oscillator 21, filters 22a and 22b, and a mixer 23. The remote base station 40a (the same applies to the remote base stations 40b and 40c) includes an antenna 44b, a switch 43b, a receiving amplifier 45b, a filter 47a, 47b, a mixer 48, and a synthesizer 49.

First, downlink signals will be described.
In the centralized base station 10, the synthesizer 14 frequency multiplexes the radio signal output from the modulator 12, the control signal output from the control unit 13, and the oscillator signal output from the oscillator 21. The signal frequency-multiplexed by the synthesizer 14 is converted into an optical signal by the E / O converter 15 and distributed by the transmission optical coupler 16, and the remote base stations 40a, 40a, 40c are respectively transmitted through the optical transmission lines 30a, 30b, 30c. 40b and 40c are reached.

  The remote base station 40a (the same applies to the remote base stations 40b and 40c) converts the optical signal that has arrived from the optical transmission line 30a into an electrical signal by the O / E converter 41, and inputs this electrical signal to the filters 47a and 47b. . The filters 47a and 47b frequency-separate and output the radio signal and the oscillator signal. Note that means for frequency-separating the control signal is omitted. The radio signal that has passed through the filter 47a is amplified by the transmission amplifier 42, transmitted through the switch 43a and the antenna 44a, and received by the terminal stations 60a and 60b.

Next, uplink signals will be described.
The transmission signals of the terminal stations 60a and 60b reach the remote base stations 40a, 40b and 40c. The remote base station 40a (the same applies to the remote base stations 40b and 40c) inputs the signals received by the antennas 44a and 44b to the receiving amplifiers 45a and 45b via the switches 43a and 43b, respectively. The signal amplified by the receiving amplifier 45a is input to the synthesizer 49. The signal amplified by the receiving amplifier 45b is multiplied by the oscillator signal that has passed through the filter 47b by the mixer 48 and input to the synthesizer 49. The synthesizer 49 frequency-multiplexes the transmission signals of the terminal stations 60a and 60b and the frequency-converted transmission signal, and further converts the signals to an optical signal by the E / O converter 15, and the centralized base station 10 via the optical transmission line 31a. To send.

  The centralized base station 10 synthesizes the optical signals from the remote base stations 40a, 40b and 40c by the receiving optical coupler 17 before detection, and inputs one system of optical signals to the O / E converter 18 for one system of electricity. This is converted into a signal, and this electric signal is branched into two and input to the filters 22a and 22b. The filters 22a and 22b receive the antennas 44a and 44b of each remote base station and separate and output the frequency-multiplexed transmission signals. The transmission signal that has passed through the filter 22a is input to the demodulator 19a, demodulated, and input to the synthesizer 24 after detection. The frequency-converted transmission signal that has passed through the filter 22b is multiplied by the oscillator signal output from the oscillator 21 by the mixer 23 to return to the original frequency, input to the demodulator 19b, demodulated, and after detection, the combiner 24. To enter. The transmission signals demodulated by the demodulators 19a and 19b are subjected to diversity combining after detection by the post-detection combiner 24. An output signal of the post-detection synthesizer 24 is converted into binary data by the sign determination unit 20 and further sent to the external network 100 via the network interface 11.

  In the configuration of the second embodiment, the three systems of light transmitted through the remote base stations 40a, 40b, and 40c are adjusted by adjusting the delay times of the uplink optical transmission lines 31a, 31b, and 31c to be substantially equal. The signals are combined by the receiving optical coupler 17 before detection and converted into an electrical signal as a single optical signal. Further, the uplink transmission signal is received by the remote base stations 40a, 40b, and 40c by a plurality of reception systems, and the signals of each reception system are frequency-multiplexed and transmitted to the centralized base station 10. Thus, the signals of the respective receiving systems are frequency-separated, and the signal of one receiving system is converted to the original frequency and demodulated. As a result, the O / E converter 18 and the demodulator 19 of the receiving system in the centralized base station 10 can be integrated into one system and two systems regardless of the number of remote base stations, thereby realizing simplification of the device configuration and cost reduction. can do. Furthermore, uplink communication quality can be improved by combining each demodulated signal with diversity after detection.

  Note that the mixer 23 of the centralized base station 10 and the mixer 48 of the remote base station 40 a are configured to multiply the oscillator signal output from the oscillator 21, so fluctuations due to the accuracy of the oscillator 21 are canceled out.

FIG. 3 shows a configuration example of Embodiment 3 of the diversity communication apparatus of the present invention.
In the figure, the centralized base station 10 and the remote base stations 40a, 40b, 40c, 40d are connected via downlink optical transmission paths 30a, 30b, 30c, 30d and uplink optical transmission paths 31a, 31b, 31c31d. The The terminal stations 60a and 60b are connected to the centralized base station 10 via remote base stations 40a, 40b, 40c and 40d.

  Network interface 11, modulator 12, controller 13, combiner 14, E / O converter 15, transmission optical coupler 16, O / E converters 18a and 18b, and demodulators 19a and 19b constituting the centralized base station 10 The post-detection combiner 24 and the sign determination unit 20 have the same functions as those of the conventional centralized base station 10 shown in FIG. The O / E converter 41, the transmission amplifier 42, the switch 43, the antenna 44, the reception amplifier 45, and the E / O converter 46 constituting the remote base station 40a (the same applies to the remote base stations 40b, 40c, and 40d) It has the same function as the conventional remote base station 40a shown in FIG.

  The feature of the present embodiment is that the centralized base station 10 includes optical couplers 17a and 17b for receiving less than the number of remote base stations, and among the optical signals from the remote base stations 40a, 40b, 40c and 40d, the optical coupler for receiving In 17a and 17b, optical signals from remote base stations that are not adjacent to each other are combined before detection, optical signals of different systems are converted into electrical signals, and diversity combining after detection is performed after demodulation. Here, the delay times of the optical transmission path 31a and the optical transmission path 31c accommodated in the receiving optical coupler 17a, and the delay times of the optical transmission path 31b and the optical transmission path 31d accommodated in the receiving optical coupler 17b are respectively It is assumed that the optical signals combined before detection are adjusted so as to be substantially equal within a range where no intersymbol interference occurs.

  The downlink signals are the same as those in the first embodiment, and the optical signals transmitted from the centralized base station 10 via the optical transmission lines 30a, 30b, 30c, and 30d are transmitted from the remote base stations 40a, 40b, 40c, and 40d. It is converted into a radio signal and transmitted, and received by the terminal stations 60a and 60b.

Next, uplink signals will be described.
Similarly to the first embodiment, the transmission signals of the terminal stations 60a and 60b are converted into optical signals by the remote base stations 40a, 40b, 40c, and 40d, and are concentrated base stations through the optical transmission lines 31a, 31b, 31c, and 31d. 10 is transmitted. The centralized base station 10 combines the optical signals from the remote base stations 40a and 40c with the receiving optical coupler 17a before detection, and combines the optical signals from the remote base stations 40b and 40d with the receiving optical coupler 17b before detection. Each is input to the O / E converters 18a and 18b as one optical signal, converted into one electric signal, and input to the demodulators 19a and 19b. The transmission signals demodulated by the demodulators 19a and 19b are subjected to diversity combining after detection by the post-detection combiner 24. An output signal of the post-detection synthesizer 24 is converted into binary data by the sign determination unit 20 and further sent to the external network 100 via the network interface 11.

  In the configuration of the third embodiment, the delay times of the uplink optical transmission lines 31a and 31c and the delay times of the optical transmission lines 31b and 31d are adjusted so as to be approximately equal to each other via the remote base stations 40a and 40c. The transmitted two optical signals are combined before detection by the receiving optical coupler 17a, and the two optical signals transmitted via the remote base stations 40b and 40d are combined before detection by the receiving optical coupler 17b. It is demodulated by converting it into an electrical signal as a single optical signal. Thereby, the O / E converter 18 and the demodulator 19 of the reception system in the centralized base station 10 can be aggregated to less than the number of remote base stations, and simplification of the apparatus configuration and cost reduction can be realized. Furthermore, communication quality can be improved by combining the demodulated signals with diversity after detection.

  In the configuration of the first embodiment, for example, when the terminal station 60 a exists between the remote base stations 40 a and 40 b, the optical signal transmitted from the remote base stations 40 a and 40 b to the centralized base station 10 is received by the receiving optical coupler 17. Therefore, there is a possibility that the transmission signal of the terminal station 60a cannot be restored due to cancellation when combining before detection. In the configuration of the third embodiment, optical signals from adjacent remote base stations are input to different receiving optical couplers. That is, each receiving optical coupler synthesizes optical signals from a plurality of non-adjacent remote base stations before detection, so that the signal is not canceled even if the terminal station is at an intermediate position between adjacent remote base stations. The transmission of the uplink transmission signal becomes possible. Even in a situation where optical signals from a plurality of remote base stations (40a, 40c) that are not adjacent to each other are canceled when they are combined before detection, the optical signal from the remote base station (40b) between them is used for receiving the other. Since it is input to the optical coupler, the communication quality of the uplink transmission signal can be ensured by diversity combining after detection.

  By the way, in the pre-detection combining of the receiving optical coupler 17 of the centralized base station 10 according to the first to third embodiments, optical signals from a remote base station having no terminal station nearby, that is, a remote base station not involved in communication are included. As a result of the synthesis, there is a risk that noise will increase and communication quality will deteriorate.

  Here, the noise of the optical signal will be described. In general, in optical transmission, laser noise caused by fluctuations in the optical output of an E / O converter (such as a laser diode), shot noise caused by fluctuations in detection current generated in the O / E converter (such as a photodiode), O Thermal noise due to the resistor and amplifier at the subsequent stage of the / E converter is added. In general, noise power added from an E / O converter to an O / E converter via an optical transmission line is much higher than noise power generated by a low noise amplifier used as a radio signal receiving amplifier. large. For this reason, when the signal power is already small compared with the noise power at the input of the E / O converter of the remote base station far from the terminal station, the noise is mainly transmitted as an optical signal from the remote base station. The In the receiving optical coupler 17 of the centralized base station 10, the optical signal mainly composed of such noise and the optical signal from the remote base station having sufficient signal power are combined before detection, and the original communication quality is improved. to degrade. A configuration for solving this problem will be described below.

FIG. 4 shows a configuration example of Embodiment 4 of the diversity communication apparatus of the present invention.
The feature of the present embodiment is that, in the configuration of the first embodiment shown in FIG. 1, the E / E is determined according to the signal power level output from the receiving amplifier 45 of the remote base station 40a (the same applies to the remote base stations 40b and 40c). A control unit 50 for controlling the power-on operation of the O converter 46 is provided. Other configurations are the same as those of the first embodiment.

  Since the downlink signal is the same as that in the first embodiment, the uplink signal will be described. The transmission signals of the terminal stations 60a and 60b reach the remote base stations 40a, 40b and 40c. The remote base station 40a (the same applies to the remote base stations 40b and 40c) inputs the signal received by the antenna 44 to the reception amplifier 45 through the switch 43, and converts the signal amplified by the reception amplifier 45 into E / O conversion. It is converted into an optical signal by the device 46 and sent to the centralized base station 10 through the optical transmission path 31a. Here, the control unit 50 detects the output signal of the receiving amplifier 45 and detects the signal power level. Further, the control unit 50 compares the noise power level (predetermined value) of the E / O converter 46 with the signal power level of the receiving amplifier 45, and when the signal power level necessary for signal transmission is obtained, E The power of the / O converter 46 is turned on.

  That is, if there is a terminal station 60a in the vicinity of the remote base station 40a and the signal power level is sufficient, it is converted into an optical signal by the E / O converter 46 and transmitted to the centralized base station 10 via the optical transmission line 31a. To do. On the other hand, when the terminal station 60a is located far from the remote base station 40a and the signal power level is small and the noise power level is relatively large, the E / O converter 46 does not operate and no optical signal is transmitted. As a result, noise components generated in remote base stations not involved in communication do not reach the centralized base station 10, and only optical signals from remote base stations having sufficient signal power are synthesized before detection. Quality can be ensured.

  The configuration of the fourth embodiment can be similarly applied to the configurations of the second and third embodiments.

FIG. 5 shows a configuration example of Embodiment 5 of the diversity communication apparatus of the present invention.
The feature of this embodiment is that, in the configuration of Embodiment 4 shown in FIG. 4, the control unit 13 of the centralized base station 10 grasps the reception level for each terminal station in each remote base station 40a, 40b, 40c, and A control signal for controlling the power-on operation of the E / O converter 46 of the stations 40a, 40b, and 40c is generated, and the control unit 50 of each remote base station 40a, 40b, and 40c extracts the control signal, and each E The power-on operation of the / O converter 46 is controlled.

  In this embodiment, it is assumed that OFDMA (Orthogonal Frequency Division Multiple Access) in which a plurality of terminal stations perform communication using different subcarriers at the same time is used.

  Since the downlink signal is the same as that in the first embodiment, the uplink signal will be described. The terminal station 60a transmits a signal using two subcarriers as shown in FIG. 6 (a). As shown in FIG. 6B, the terminal station 60b transmits a signal using two subcarriers different from the terminal station 60a.

  First, in the communication preparation stage, the control unit 13 of the centralized base station 10 transmits a control signal for sequentially turning on the power of the E / O converter 46 of each remote base station 40a, 40b, 40c, for example. The reception level from each terminal station 60a, 60b is grasped every time. FIG. 6C shows the reception level when only the power of the E / O converter 46 of the remote base station 40a is turned on, and shows a state where the signal power level from the terminal station 60a is sufficiently obtained. FIG. 6 (d) shows the reception level when only the E / O converter 46 of the remote base station 40b is turned on, and shows a state where the signal power level from the terminal station 60b is sufficiently obtained. FIG. 6 (e) shows the reception level when only the power of the E / O converter 46 of the remote base station 40c is turned on. The signal power levels of the terminal stations 60a and 60b are not sufficient, and the noise power level. Shows a state in which becomes higher. From the above state, it can be estimated that the control unit 13 of the centralized base station 10 has the terminal station 60a in the vicinity of the remote base station 40a and the terminal station 60b in the vicinity of the remote base station 40b.

  Next, in the communication stage, the control unit 13 of the centralized base station 10 transmits a control signal for turning on the E / O converter 46 of the remote base stations 40a and 40b, and the E / O conversion of the remote base station 40c. A control signal for turning off the power of the device 46 is transmitted. As a result, the transmission signals of the terminal stations 60a and 60b reach the centralized base station 10 via the remote base stations 40a and 40b, and are combined by the receiving optical coupler 17 before detection and converted into electrical signals. As shown in f), the transmission signals of the terminal stations 60a and 60b can be obtained at a high reception level, and noise superposition can be suppressed.

  As a result, the O / E converter 18 and the demodulator 19 of the reception system in the centralized base station 10 can be integrated into one system regardless of the number of remote base stations, and the simplification of the device configuration and the reduction in cost can be realized. it can. Furthermore, by stopping transmission from a remote base station mainly composed of noise, it is possible to avoid deterioration in communication quality even if the concentrated base station 10 combines before detection.

The configuration of the fifth embodiment can be similarly applied to the configurations of the second and third embodiments.
In the diversity communication apparatus of the present invention, multiplexing of the terminal stations 60a and 60b, that is, user multiplexing may be performed using OFDMA.

  The diversity communication apparatus of the present invention can consolidate the reception systems of the concentrated base stations to a number smaller than the number of remote base stations, and can realize simplification of the apparatus configuration and cost reduction.

  Since the diversity communication apparatus of the present invention can combine only optical signals from remote base stations having sufficient signal power before detection, high communication quality can be ensured even by combining before detection. Furthermore, higher communication quality can be ensured by combining diversity combining after detection.

DESCRIPTION OF SYMBOLS 10 Central base station 11 Network interface 12 Modulator 13 Control part 14 Synthesizer 15 E / O converter 16 Optical coupler for transmission 17 Optical coupler for reception 18 O / E converter 19 Demodulator 20 Code determination device 21 Oscillator 22 Filter 23 Mixer 24 Post-detection combiner 30 Downlink optical transmission path 31 Uplink optical transmission path 40 Remote base station 41 O / E converter 42 Transmitting amplifier 43 Switch 44 Antenna 45 Receiving amplifier 46 E / O converter 47 Filter 48 mixer 49 synthesizer 50 control unit 60 terminal station 100 network

Claims (4)

A plurality of remote base stations connected to the terminal station via a wireless line;
One centralized base station connected to each of the plurality of remote base stations via an optical transmission path,
The downlink optical signals transmitted from the centralized base station are received by the plurality of remote base stations, the plurality of remote base stations convert the optical signals into radio signals and transmit to the terminal station, and the terminal station Uplink radio signals transmitted from the plurality of remote base stations are received by the plurality of remote base stations, the plurality of remote base stations convert radio signals into optical signals and transmitted to the centralized base station, and In the diversity communication device that is configured to receive and combine diversity transmission signals of the terminal station transmitted through a plurality of remote base stations,
The centralized base station, among the plurality of transmitted optical signals via the optical transmission path from the remote base station, synthesized before detection in the optical signal of each one system the optical signal from the not adjacent said remote base station It comprises two or more receiving optical coupler, have rows demodulates the optical signal of each path is converted into an electric signal, and configured to post-detection diversity combining the demodulated signals,
The uplink optical transmission lines connected to the centralized base station from the plurality of remote base stations are the same as the optical transmission lines connected to the receiving optical couplers, transmitted through the respective optical transmission lines. A diversity communication apparatus, characterized in that the delay time is adjusted to such an extent that pre-detection synthesis of optical signals corresponding to transmission signals of a terminal station is possible. The diversity communication device according to claim 1,
The remote base station detects a reception level of the uplink radio signal, and when the reception level exceeds a predetermined value, transmits the optical signal to the centralized base station, and when the reception level is equal to or lower than a predetermined value. A diversity communication apparatus characterized by comprising control means for stopping optical signal transmission to the central base station. The diversity communication device according to claim 1,
The remote base station and the terminal station are configured to perform wireless communication using different subcarriers in the plurality of terminal stations at the same time using OFDMA (Orthogonal Frequency Division Multiple Access),
The remote base station comprises control means for performing optical signal transmission to the central base station or optical signal transmission stop according to a control signal transmitted from the central base station superimposed on the downlink optical signal,
The centralized base station transmits a control signal instructing transmission of an optical signal to the plurality of remote base stations during a communication preparation stage, and demodulates the optical signal transmitted for each of the remote base stations to thereby transmit the terminal station The reception level for each sub-carrier corresponding to is detected, and at the communication stage, an optical signal transmission is instructed to a remote base station whose reception level exceeds a predetermined value, and the remote level whose reception level is lower than the predetermined value is instructed. A diversity communication apparatus characterized by transmitting a control signal that instructs a base station to stop optical signal transmission. In the diversity communication device according to claim 2 or 3 ,
The diversity communication apparatus, wherein the control means is configured to turn on / off a power of an E / O converter that converts an uplink radio signal transmitted from the terminal station into an optical signal.

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