JP2011147048A - Mobile communication system and repeater used therefor, base station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problem in a conventional mobile communication system: when transmitting a signal from a mobile object to a base station, a dynamic range of an E/O converter or an O/E converter is limited by an ROF (Radio On Fiber) system, and it is difficult to ensure a CNR (Carrier to Noise Ratio) for increasing a transmission rate. <P>SOLUTION: A mobile communication system includes a plurality of repeaters 2 installed along a moving route of a mobile object 90 and capable of wirelessly communicating with the mobile object 90 and a base station 1 capable of optically communicating with the plurality of repeaters 2, wherein communication areas formed by the repeaters 2 are collected to form one communication area along the moving route. Each of the repeaters 2 includes a demodulating section 65 for demodulating a radio signal received from the mobile object 90 and outputting a demodulated signal, and an E/O converter 74 as a converting section for converting the demodulated signal in the demodulating section 65 and outputting an optical signal. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a mobile communication system and a relay station and a base station used therefor, and more particularly to a mobile communication system that enables high-speed communication between a mobile object such as a vehicle and ground equipment and a relay used therefor. Related to aircraft and base stations.

  Conventionally, there has been a problem that communication cannot be performed when a moving body is moving at high speed in a system that performs data communication between a vehicle such as a bullet train moving on a track or an automobile moving on a road and a ground facility. It was. Because the communication area of one radio base station is as small as several hundred meters or less, if the moving body moves at a high speed, the area staying time will be shortened, and sufficient time will not be available for communication establishment (handover). This is because it becomes impossible.

  As a countermeasure, in a conventional mobile communication system as disclosed in Patent Document 1, a plurality of relays installed along a moving path of a mobile body and a base station that transmits signals to the plurality of relays And an optical fiber as a transmission line connecting each of the plurality of repeaters and the base station, and the base station transmits the same signal to the plurality of repeaters via the optical fiber, and the same radio is transmitted to all the repeaters. By emitting a signal, the plurality of communication areas formed by each of the plurality of repeaters operate so as to become one communication area formed along the movement path. As a result, the communication area that can be covered by one base station has been expanded.

  In this system, when a signal is transmitted from a mobile unit and the signal is received at a base station, first, the radio signal transmitted from the mobile unit is converted into electrical / optical conversion by a repeater using a ROF (Radio on Fiber) method. (E / O conversion), and reaches the optical / electrical converter (O / E converter) of the base station via the optical fiber. Further, the base station receives a signal from the repeater subjected to O / E conversion. At this time, the dynamic range of the ROF type E / O and O / E converter is smaller than the electric field fluctuation width of the signal in the wireless section. Therefore, conventionally, the transmission power control circuit is provided in the mobile unit. Communication is performed by controlling the transmission power so as to be within the dynamic range of the / O and O / E converters.

  Also, in a conventional mobile communication system, when a mobile unit transmits a signal in a place where communication areas provided by each repeater overlap, if there is a difference in the optical fiber length connecting the repeater and the base station, The transmission delay times of these signals are different, and the signals interfere with each other. As a result, communication quality is degraded. As a countermeasure, conventionally, a delay compensator for adjusting the optical fiber length and reducing the transmission delay time difference is provided in order to make the transmission delay time from each repeater to the base station uniform.

JP 2005-191905 A

  In a conventional mobile communication system, when a signal is transmitted from a mobile unit and the signal is received by a base station, a radio signal from the mobile unit is passed through an optical fiber via a repeater by the ROF method, and the base station Is used to synthesize and receive signals from each repeater. Since the dynamic range of this ROF type E / O converter and O / E converter is smaller than the electric field fluctuation width of the signal in the wireless section, a transmission power control circuit is installed on the mobile unit so that it falls within that dynamic range. It was necessary to take measures such as installing and communicating with the base station. Furthermore, due to this dynamic range, there is a limit to the method of improving the CNR (Carrier to Noise Ratio) as the transmission power of the mobile body is increased. It was difficult to secure the required CNR for the above.

  Also, in a conventional mobile communication system, when a mobile unit transmits communication data in a place where communication areas provided by each repeater overlap, there is a difference in the length of the optical fiber connecting the repeater and the base station. Since the transmission delay time of the signals from each other is different and the signals interfere with each other, the optical fiber length is adjusted to make the transmission delay time of the signal from each repeater to the base station uniform, and the transmission delay time difference is reduced. A delay compensator was provided. As an example, when the communication data transmitted by the mobile body is 10 Mbps, the transmission delay time of the optical fiber is about 5 μs / km. Therefore, considering that the 1-bit data width is 0.1 μs, the position is ± 20 m. It is necessary to adjust the optical fiber length with matching accuracy. This accuracy also varies depending on the error rate allowed in the system. When the data transmitted from the mobile unit to the base station has a high data rate of 10 Mbps or more, adjustment with higher accuracy is required. Therefore, there is a problem that it is technically difficult to avoid the influence of the interference wave when adjusting the optical fiber length for a high bit rate.

  The present invention has been made to solve the above problems, avoids the influence of the dynamic range of the E / O converter and O / E converter by the ROF method, and from the difference in optical fiber length, An object of the present invention is to provide a mobile communication system capable of avoiding the influence that the same communication data arriving from a plurality of repeaters becomes interference waves with each other in the base station, and to provide a repeater and a base station used therefor And

  A first aspect of the present invention includes a plurality of repeaters that are installed along a moving path of a mobile unit and capable of wireless communication with the mobile unit, and a base station that is capable of optical communication with the plurality of relay units, Each communication area formed by each of the repeaters is a mobile communication system in which one communication area is formed along the movement path, and each of the repeaters receives from the mobile A demodulator that demodulates a radio signal and outputs the demodulated signal; and a converter that converts the demodulated signal in the demodulator and outputs an optical signal.

  Moreover, the relay machine concerning the 2nd aspect of this invention is a relay machine used for said mobile communication system.

  According to a third aspect of the present invention, there is provided a plurality of repeaters that are installed along a moving path of a mobile unit and capable of wireless communication with the mobile unit, and a base station that is capable of optical communication with the plurality of relay units. Each communication area formed by each repeater is gathered to form one communication area along the movement path, wherein the base station outputs from the mobile body When each of the plurality of repeaters receives the received wireless signal, a selection unit is provided that selects any one of the repeaters and receives the wireless signal.

  Moreover, the base station concerning the 4th aspect of this invention is a base station used for said mobile communication system.

  According to the first aspect of the present invention, a plurality of repeaters that are installed along a moving path of a mobile unit and are capable of wireless communication with the mobile unit, and a base station that is capable of optical communication with the plurality of relay units. Each communication area formed by each of the repeaters is gathered to form one communication area along the movement path, and each of the repeaters is separated from the mobile object. A radio signal and an optical signal are converted by including a demodulator that demodulates a received radio signal and outputs a demodulated signal, and a converter that converts the demodulated signal in the demodulator and outputs an optical signal It is possible to avoid the limitation of the dynamic range.

  Further, according to the second aspect of the present invention, it is possible to avoid restriction of the dynamic range when converting a radio signal and an optical signal by being a relay device used in the above mobile communication system. It becomes.

  Further, according to the third aspect of the present invention, a plurality of repeaters that are installed along a moving path of a mobile unit and are capable of wireless communication with the mobile unit, and a base station that is capable of optical communication with the plurality of relay units A communication system in which communication areas formed by the repeaters are gathered to form one communication area along the movement path, wherein the base station When a plurality of each relay device receives a radio signal output from a plurality of relay devices, a selection unit that selects any one of the relay devices and receives the wireless signal is provided. It is possible to avoid that the received signals become interference waves with each other.

  Further, according to the fourth aspect of the present invention, since the base station is used in the mobile communication system, it is possible to avoid that signals received from a plurality of repeaters become interference waves with each other. It becomes.

1 is a configuration diagram showing an entire system of a mobile communication system according to a first exemplary embodiment. It is a block diagram which shows the block of the relay machine concerning Embodiment 1. FIG. It is a block diagram which shows the block of the receiver mounted in the relay machine concerning Embodiment 1. FIG. FIG. 2 is a block diagram showing a block of a base station according to the first exemplary embodiment. FIG. 2 is a configuration diagram showing a block of a receiver mounted on a base station according to the first exemplary embodiment; It is a block diagram which shows the block of the receiver mounted in the relay machine concerning Embodiment 1. FIG. FIG. 2 is a configuration diagram showing a block of a receiver mounted on a base station according to the first exemplary embodiment; 3 is a flowchart showing a flow of processing of a receiver mounted on the base station according to the first exemplary embodiment. In the mobile communication system according to the first exemplary embodiment, it is a configuration diagram illustrating a case where a mobile transmits communication data at a place where communication areas provided by two relays overlap. It is a block diagram which shows the block of the receiver mounted in the base station concerning Embodiment 2. FIG. It is a block diagram which shows the block of the receiver mounted in the relay machine concerning Embodiment 2. FIG. 6 is a flowchart showing a processing flow of a receiver mounted on a base station according to the second exemplary embodiment;

<A. Embodiment 1>
<A-1. Configuration>
FIG. 1 shows the entire system of a mobile communication system according to Embodiment 1 of the present invention. As shown in FIG. 1, the mobile communication system according to the present invention includes a plurality of repeaters 2a to 2n having a predetermined communication area, repeaters 2a to 2n, and optical fibers 3a to 3n as transmission paths. And a base station 1 capable of optical communication. The repeaters 2a to 2n are configured such that adjacent communication areas overlap to form one communication area along a moving path of a moving body (not shown).

  FIG. 2 is a block diagram showing one configuration of the repeaters 2a to 2n in FIG. As shown in FIG. 2, the repeaters 2 a to 2 n each communicate with an antenna 81 that performs wireless communication of communication data with a mobile body, and an RF (Radio Frequency) band signal from the mobile body via the antenna 81. It includes a receiver 51 that receives data, down-converts it into a baseband signal, and performs demodulation, and an E / O converter 74 as a conversion unit that converts the output of the receiver 51 into an optical signal.

  FIG. 3 is a block diagram showing a configuration of the receiver 51 shown in FIG. As shown in FIG. 2, the receiver 51 includes an RF unit 61 that converts communication data, which is an RF band signal from a mobile body, into an IF (Intermediate Frequency) band signal, and a predetermined filter on the output from the RF unit 61. A filter 62 for applying IF, an AD converter 63 for converting communication data of an IF band signal, which is an analog signal output through the filter 62, into a digital signal, and communication data of an IF band signal from the AD converter 63 as baseband An IF sampling unit 64 that converts to a band signal and a demodulation unit 65 that demodulates communication data of the baseband signal from the IF sampling unit 64 are provided.

  On the other hand, FIG. 4 is a block diagram showing a configuration of the base station 1. As shown in FIG. 4, the base station 1 receives outputs from the O / E converters 75a to 75n that convert the optical signals output from the repeaters 2a to 2n into electrical signals, and the O / E converters 75a to 75n. And a data processing unit 52 for reception.

  FIG. 5 is a block diagram showing the configuration of the data processing unit 52 of FIG. As shown in FIG. 5, the data processing unit 52 selectively receives the power calculation units 31 a to 31 n that calculate the output power of the O / E converters 75 a to 75 n and the result output of the power values of the power calculation units 31 a to 31 n. And a data selection unit 32 as a selection unit.

  FIG. 6 is a block diagram showing a configuration different from that of FIG. 3 of the receiver 51 shown in FIG. The configurations denoted by the same reference numerals as in FIG. 3 indicate the same or corresponding configurations, and thus detailed description thereof is omitted.

  The power calculation units 31a to 31n in FIG. 5 are installed in the data processing unit 52 of the base station 1, but as shown in FIG. 6, the RF unit 61 of the receiver 501 installed in each repeater 2a to 2n. The power calculator 33 may be configured between the filter 62 and the filter 62. When configured in this manner, the power calculation unit 33 receives the output of the RF unit 61 and calculates the power.

  At this time, the configuration of the data processing unit 502 of the base station 1 is as shown in FIG. Unlike FIG. 5, outputs from the O / E converters 75 a to 75 n are directly received by the data selection unit 32.

<A-2. Operation>
FIG. 8 is a flowchart for describing control in which the data selection unit 32 in the data processing unit 52 selects and receives only communication data from the mobile body among the outputs from the power calculation units 31a to 31n. The following flowchart will be described based on the configuration shown in FIGS. 1 to 5, but the configuration shown in FIGS. 6 and 7 can operate similarly.

  First, it is necessary to be in a state where signal power is calculated in the power calculators 31a to 31n (step S1). Next, the power calculation units 31a to 31n in the data processing unit 52 receive the outputs from the O / E converters 75a to 75n in the base station 1 (step S2).

  Next, the power calculators 31a to 31n in the data processor 52 detect the presence / absence of communication data from the moving body (step S3). As this detection method, a power value threshold value is first set in the power calculation units 31a to 31n, and the threshold value is used as a criterion for determining the presence or absence of communication data. In the case of the configuration shown in FIGS. 6 and 7, the power determination unit 33 in the receiver 501 performs the same determination and outputs the result to the data processing unit 502. That is, the power calculation unit 33 receives the output of the RF unit 61 and calculates the power. At this time, first, a threshold value of the power value is set, and the power calculation unit 33 sets the threshold value as a criterion for determining the presence or absence of communication data. When the power calculation unit 33 satisfies the threshold value indicating that the communication data from the mobile body is included, the E / O converter 74, the optical fibers 3a to 3n, and the O / O The data selection unit 32 is notified via the E converters 75a to 75n. And the data selection part 32 selects and receives one output from the receiver 501 in which the electric power calculation part 33 which notified that it has communication data is installed. Thereby, it can avoid that the signal from each relay machine 2a-2n becomes an interference wave mutually. Therefore, you may install the electric power calculation part 33 in any of the base station 1 and the relay machines 2a-2n.

  When it is determined in step S3 that the communication data is not included, no output is transmitted from the power calculation units 31a to 31n to the data selection unit 32 (step S4).

  If it is determined in step S3 that the communication data is included, the power calculation units 31a to 31n indicate that the communication data is included, the E / O converter 74, the optical fibers 3a to 3n, and the O / E. The data selection unit 32 is notified via the converters 75a to 75n (step S5).

  At this time, the plurality of power calculation units 31a to 31n may have communication data. As shown in FIG. 9, when the mobile unit 90 transmits communication data in a place where the communication areas provided by the relay devices 2a to 2n overlap, the communication data is transmitted from the relay device 2a and the relay device 2b to the base station 1. Will be. In such a case, the plurality of power calculation units 31a and 31b corresponding thereto have communication data.

  In such a case, the data selection unit 32 selects one of the power calculation units 31a to 31n that has received the notification that it has communication data, and receives the output (step S6).

  As described above, the data processing unit 52 includes the data selection unit 32 that selects and receives one of a plurality of communication data coming from the repeaters 2a to 2n. It is possible to avoid the problem that the signals from the repeaters 2a to 2n become interference waves due to different transmission delay times due to differences in the lengths of optical fibers connecting the 2a to 2n. As a result, for example, in the OFDM modulation method used for a wireless LAN or the like, the guard interval time can be reduced, and the effective communication speed can be increased.

<A-3. Effect>
According to the first embodiment of the present invention, a plurality of repeaters 2 that are installed along the movement path of the moving body 90 and can wirelessly communicate with the moving body 90, and a base that can optically communicate with the plurality of repeaters 2. 1 is a mobile communication system in which each communication area formed by each repeater 2 is gathered to form one communication area along a movement path. A demodulator 65 that demodulates a radio signal received from the body 90 and outputs the demodulated signal; and an E / O converter 74 that is a converter that converts the demodulated signal in the demodulator 65 and outputs an optical signal. Thus, it is possible to avoid the limitation of the dynamic range when converting the radio signal and the optical signal.

  Further, it is not necessary to provide a transmission power control circuit in the moving body 90, and the configuration is simplified. Furthermore, the required CNR for improving the transmission rate such as multi-level modulation can be secured, and the transmission rate between the mobile unit 90 and the base station 1 can be improved.

  In addition, according to the first embodiment of the present invention, it is a repeater used in the mobile communication system described above, thereby avoiding restriction on the dynamic range when converting a radio signal and an optical signal. It becomes possible.

  Further, according to the first embodiment of the present invention, a plurality of relays 2 that are installed along the moving path of the moving body 90 and can wirelessly communicate with the moving body 90, and can optically communicate with the plurality of relays 2. A mobile communication system in which each communication area formed by each repeater 2 is gathered to form one communication area along a movement path. When each of the plurality of relays 2 receives a radio signal output from the mobile body 90, the data selection unit 32 is provided as a selection unit that selects any one of the relays 2 and receives the radio signal. Thus, it is possible to avoid that signals received from the plurality of repeaters 2a to 2n become interference waves.

  In addition, it is possible to avoid degradation of communication quality due to interference waves, and further, it is not necessary to consider the influence of interference waves, so a transmission method for improving the transmission speed is applied to communication data transmitted by the mobile unit 90. It becomes possible to do.

  Moreover, according to Embodiment 1 concerning this invention, it is a base station used for said mobile communication system, and it avoids that the signal received from several repeater 2a-2n becomes an interference wave mutually It becomes possible to do.

  Further, according to the first embodiment of the present invention, in the mobile communication system, the data selection unit 32 as the selection unit receives the radio signal output from the mobile unit 90 based on the signal power of the radio signal. By determining the repeaters 2a to 2n based on the signal power of the output signal for selecting the repeater 2, the communication data from the repeater determined based on the power threshold can be selected and received. It becomes possible to avoid that signals become interference waves with each other.

  Further, according to the first embodiment of the present invention, in the mobile communication system, each repeater 2 demodulates the radio signal received from the mobile unit 90 and outputs the demodulated signal, and the demodulator By further including an E / O converter 74, which is a conversion unit that converts the demodulated signal in 65 and outputs an optical signal, it is possible to avoid restriction of the dynamic range when converting a radio signal and an optical signal. It becomes possible.

<B. Second Embodiment>
<B-1. Configuration>
FIG. 10 is a block diagram illustrating a configuration of the data processing unit 512 of the base station 1. As shown in FIG. 10, the data processing unit 512 includes unique word detection units 34 a to 34 n that search for and detect unique words as identifiers from outputs of the O / E converters 75 a to 75 n, and unique word detection units 34 a to 34 n. A data selection unit 35 that detects the presence / absence of communication data transmitted by the mobile unit 90 from the unique word detection result and receives outputs from the unique word detection units 34a to 34n having the communication data. Here, the unique word is information for identifying that the signal is communication data from the moving body 90. Here, as an example, the unique word detection units 34a to 34n are installed in the base station 1, but, similarly to the power calculation units 31a to 31n and 33 in the first embodiment, the base station 1 and the repeaters 2a to 2n. It doesn't matter which one you install.

  At this time, the receivers 511 of the repeaters 2a to 2n are as shown in FIG. When it is determined that the signal is communication data from the mobile unit 90 using the result of demodulating the signal received by the demodulator 65, the unique word unit 66 as an adder is applied to the demodulated signal. A unique word is given by and output. 3 is the same as or equivalent to that shown in FIG. 3, and detailed description thereof will be omitted.

<B-2. Operation>
FIG. 12 is a flowchart for describing control in which the data selection unit 35 in the data processing unit 512 selects and receives only the communication data from the mobile object 90 out of the outputs from the unique word detection units 34a to 34n.

  First, the unique word detectors 34a to 34n must be in a state of searching for a unique word (step S11). Next, the unique word detection units 34a to 34n in the data processing unit 512 receive the outputs from the O / E converters 75a to 75n in the base station 1 (step S12).

  Next, the presence / absence of communication data from the moving body 90 is detected by the unique word detection units 34a to 34n in the data processing unit 512 (step S13). As this detection method, since the unique word inserted in the unique word unit 66 in the receiver 511 is also known in the unique word detection units 34a to 34n, the signal is transmitted to the mobile object 90 by detecting the unique word. It is assumed that it is communication data from.

  If it is determined in step S13 that communication data is not included, no output is transmitted from the unique word detectors 34a to 34n to the data selector 35 (step S14).

  If it is determined in step S13 that the communication data is included, the unique word detection units 34a to 34n notify the data selection unit 35 that the communication data is included (step S15).

  At this time, the plurality of unique word detection units 34a to 34n may have communication data. In such a case, the data selection unit 35 selects one of the unique word detection units 34a to 34n that has received the notification that it has communication data, and receives its output (step S16).

<B-3. Effect>
According to the second embodiment of the present invention, the repeater 2 further includes a unique word unit 66 that is a grant unit that assigns a unique word as an identifier to a radio signal, and the data selection unit 35 that is a selection unit includes: Based on the unique word given to the wireless signal in the unique word unit 66, the relay 2 that has received the wireless signal output from the mobile unit 90 is identified, thereby avoiding multiple signals from interfering with each other. It becomes possible to do.

  1 base station, 2a-2n repeater, 3a-3n optical fiber, 31a-31n, 33 power calculator, 32, 35 data selector, 34a-34n unique word detector, 51, 501, 511 receiver, 52, 502, 512 Data processing unit, 62 filter, 63 converter, 64 sampling unit, 65 demodulating unit, 66 unique word unit, 74 E / O converter, 75a to 75n O / E converter, 81 antenna, 90 moving body.

Claims (7)

A plurality of repeaters installed along a moving path of the moving body and capable of wireless communication with the moving body;
A base station capable of optical communication with the plurality of repeaters,
Each communication area formed by each relay unit is a mobile communication system in which one communication area is formed along the movement path,
Each said repeater is
A demodulator that demodulates a radio signal received from the mobile body and outputs a demodulated signal;
A converter that converts the demodulated signal in the demodulator and outputs an optical signal;
Mobile communication system. A plurality of repeaters installed along a moving path of the moving body and capable of wireless communication with the moving body;
A base station capable of optical communication with the plurality of repeaters,
Each communication area formed by each relay unit is a mobile communication system in which one communication area is formed along the movement path,
The base station
When each of the plurality of relay devices receives a wireless signal output from the mobile body, the wireless device includes a selection unit that selects the relay device and receives the wireless signal.
Mobile communication system. The selection unit determines the relay device that has received the radio signal output from the mobile body based on the signal power of the radio signal.
The mobile communication system according to claim 2. The repeater further includes a grant unit that gives an identifier to the wireless signal,
The selection unit determines the relay device that has received the radio signal output from the mobile body based on the identifier given to the radio signal in the grant unit.
The mobile communication system according to claim 2 or 3. Each repeater is
A demodulator that demodulates the radio signal received from the mobile body and outputs a demodulated signal;
A conversion unit that converts the demodulated signal in the demodulation unit and outputs an optical signal;
The mobile communication system according to any one of claims 2 to 4.   A repeater used in the mobile communication system according to claim 1.   A base station used in the mobile communication system according to claim 2.

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