JP2013038631A - Scattered antenna system and delay correction method in scattered antenna system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scattered antenna system which prevents intersymbol interferences caused by a difference in delay between signals received by plural antennas.SOLUTION: A scattered antenna system according to the present invention has a plurality of scattered antenna units 200 arranged within a cell, each unit comprising: a distributor 202 which distributes optical signals among an optical signal for the scattered antenna unit 200 and optical signals for other scattered antenna units; a photoelectric converter 204 which converts an optical signal into an electric signal; a delay circuit 208 which delays the electric signal; a scattered antenna 212 which transmits the delayed electric signal; and a delay measurement terminal 210 which measures a delay in a plurality of radio signals. Characteristic of the scattered antenna system is that a control device 10 is provided which, after receiving a delay in the plurality of radio signals from each scattered antenna unit 200, determines the amount of delay in the electric signal in the delay circuit 208.

Description

  The present invention relates to a distributed antenna system and a delay correction method in the distributed antenna system.

  In recent years, a distributed antenna system (DAS: Distributed Antenna System) in which a plurality of antennas are distributed and arranged in one cell is being used for the purpose of service area expansion and coverage hole countermeasures (Patent Document 1, etc.). reference). Here, the coverage hole is an area where radio waves do not reach from the base station in the cell, and a communication terminal in the coverage hole cannot communicate with the base station.

  FIG. 4 shows a conceptual diagram of antenna installation in a cell. FIG. 4A shows a normal antenna installation method, in which one antenna is installed in the cell. The transmission power of the antenna is set to have a transmission power corresponding to the cell radius. FIG. 4B is an example of antenna installation by a distributed antenna system. In the distributed antenna system, a plurality of antennas are installed in a cell, and FIG. 4B shows an example in which four antennas are installed. When the cell ranges are substantially the same, the transmission power required for one antenna can be reduced by installing a plurality of antennas.

  FIG. 5 shows an example of the configuration of the distributed antenna system. The distributed antenna system includes a base station unit 400 and a plurality of distributed antenna units 500. Since the distance between each unit is usually a long distance, the units are often connected by an optical fiber 30 having a small transmission loss.

  In the distributed antenna system, the same downlink signal as the downlink signal transmitted from the main antenna 412 by the base station unit 400 is also distributed to the distributed antenna unit 500. The downlink signal is divided into two by the electric distributor 404, and the downlink signal distributed to the distributed antenna unit 500 is converted into an optical signal by the electro-optical converter 406 to reduce transmission loss, and then the optical fiber 30. To the distributed antenna unit 500.

  The distributed antenna unit 500 distributes the received optical signal to one of the photoelectric converters 504 by the distributor 502 and the other to the other distributed antenna units. The optical signal distributed to the photoelectric converter 504 is converted into an electrical signal, further amplified by the amplifier 506, and then transmitted from the distributed antenna 512.

  In the above description, the case of a downlink signal transmitting a signal from the base station 402 to the communication terminal has been described. However, in the case of an uplink signal receiving a signal from the communication terminal to the base station 402, the reverse procedure is executed. By doing so, the base station 402 can receive the uplink signal.

JP-A-11-261474

  The above distributed antenna system can distribute a signal to a remote distributed antenna unit 500 by using the optical fiber 30 having a small transmission loss. The distributed antenna unit 500 includes a distributor 502, an optical Since the converter 504 and the amplifier 506 can be used, the service area can be expanded at low cost.

  FIG. 6 shows a state where the base station unit 400 covers a wide area and the distributed antenna units 500-1 to 500-4 are taking a countermeasure against a coverage hole as an example of the distributed antenna system. In the example shown in FIG. 6, in addition to the base station unit 400, four distributed antenna units 500-1 to 500-4 are installed. The distributed antenna units 500-1 to 500-4 are connected in a daisy chain.

  In this configuration, the transmission delay of the optical fiber 30 connecting the base station unit 400 and the distributed antenna unit 500-1 or the distributed antenna units 500-1 to 500-4 becomes a problem. In the daisy chain connection, the transmission delay from the base station unit 400 of the downlink signal distributed to the distributed antenna units increases as the later stage. For example, in the distributed antenna unit 500-4, the transmission delay from the base station unit 400 is the sum of the transmission delays of the optical fibers 30 between the units. In the example shown in FIG. 6, td1 + td2 + td3 + It becomes td4.

  Here, assuming that the delay of the radio signal directly transmitted from the base station unit 400 to the vicinity of the distributed antenna unit 500-4 is tdr, the communication terminal near the distributed antenna unit 500-4 is almost tdr from the base station unit 400. A signal delayed by approximately td1 + td2 + td3 + td4 is received from the distributed antenna unit 500-4.

  When OFDM (Orthogonal Frequency Division Multiplexing) is adopted as a communication method, OFDM inserts a redundant signal called CP (Cyclic Prefix) between symbols as a guard interval. If the delay difference is within the CP length, intersymbol interference in the communication terminal can be prevented.

  However, when a long distance is transmitted through the optical fiber 30 in the configuration shown in FIG. 6, the difference in delay amount between td1 + td2 + td3 + td4 and tdr may be larger than the CP length. It is also assumed. In this case, the delay difference due to the CP cannot be absorbed, and intersymbol interference occurs.

  Therefore, an object of the present invention made in view of such a point is to prevent the occurrence of intersymbol interference caused by the difference in delay of signals received from a plurality of antennas even when the length of the optical fiber connecting the distributed antenna units is long. It is to provide a distributed antenna system.

The invention of the distributed antenna system according to the first aspect of achieving the above object,
A distributed antenna system in which a plurality of distributed antenna units are arranged in a cell,
Each of the distributed antenna units is
A distributor that distributes the received optical signal into an optical signal for the distributed antenna unit and an optical signal for another distributed antenna unit;
A photoelectric converter that converts the optical signal received from the distributor into an electrical signal;
A delay circuit for delaying the electrical signal;
A distributed antenna that receives and transmits the electrical signal delayed by the delay circuit;
A delay measurement terminal that measures delays of a plurality of radio signals received from the plurality of distributed antenna units, and the distributed antenna system further includes:
The apparatus includes a control device that receives delays of the plurality of radio signals from the respective distributed antenna units in a cell and determines a delay amount of the electric signal in the delay circuit.

  As described above, the solution of the present invention has been described as a system. However, the present invention can also be realized as a method, a program, and a storage medium storing the program, which are substantially equivalent to these. It should be understood that these are also included.

For example, the invention of the delay correction method in the distributed antenna system according to the second aspect of realizing the present invention as a method,
A delay correction method in a distributed antenna system in which a plurality of distributed antenna units are arranged in a cell,
In each of the distributed antenna units,
Distributing the received optical signal into an optical signal for the distributed antenna unit and an optical signal for another distributed antenna unit;
Converting the optical signal into an electrical signal;
Delaying the electrical signal;
Receiving and transmitting the electrical signal;
Measuring delays of a plurality of radio signals received from the plurality of distributed antenna units, and
Receiving delays of the plurality of radio signals from the respective distributed antenna units in a cell, and determining a delay amount of the electric signal in the delay circuit.

  ADVANTAGE OF THE INVENTION According to this invention, even when the length of the optical fiber which connects a distributed antenna unit is long, the distributed antenna system which does not generate | occur | produce the intersymbol interference resulting from the delay difference of the signal received from several antennas can be provided. .

It is a figure showing the outline of the distributed antenna system concerning one embodiment of the present invention. It is a block diagram which shows the outline of the delay measurement terminal which concerns on one Embodiment of this invention. It is a flowchart which shows the procedure which determines the delay amount installed in the distributed antenna system which concerns on one Embodiment of this invention. It is a conceptual diagram of antenna installation in a cell. . It is a figure which shows the outline of the conventional distributed antenna system. It is a figure which shows the transmission delay in a distributed antenna system.

  Hereinafter, a distributed antenna system according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a distributed antenna system according to an embodiment of the present invention. The distributed antenna system includes a base station unit 100 and a plurality of distributed antenna units 200. The plurality of distributed antenna units 200 are connected in a daisy chain. In FIG. 1, only one distributed antenna unit 200 is shown. The base station unit 100 is connected to the control device 10 via the network 20.

  The base station unit 100 includes a base station 102, an electric distributor 104, an electro-optical converter 106, a delay circuit 108, a delay measurement terminal 110, a main antenna 112, and a delay measurement antenna 114.

  The base station 102 transmits the downlink signal to a communication terminal (not shown) via the electric distributor 104, the delay circuit 108, and the main antenna 112. Further, the base station 102 receives an uplink signal from a communication terminal via the main antenna 112, the delay circuit 108, and the electric distributor 104. The base station 102 transmits and receives downlink signals and uplink signals as electrical signals.

  The electrical distributor 104 receives a downlink signal as an electrical signal from the base station 102 and distributes the downlink signal to the electro-optical converter 106 and the delay circuit 108.

  The electro-optical converter 106 converts the downlink signal received as an electric signal from the electric distributor 104 into an optical signal, and transmits the optical signal to the distributed antenna unit 200 through the optical fiber 30.

  The delay circuit 108 receives the downlink signal from the electrical distributor 104, delays the downlink signal according to the control signal received from the delay measurement terminal 110, and outputs the delayed signal to the main antenna 112.

  The delay measurement terminal 110 receives downlink signals from the main antenna 112 and the plurality of distributed antennas 212 via the delay measurement antenna 114, and uses the delay information of each downlink signal as the ID of the base station unit 100 and the distributed antenna unit. It is stored in association with the ID of 200.

  In addition, the delay measurement terminal 110 notifies the control device 10 of the stored delay information together with the ID assigned to the delay measurement terminal 110 itself. For the notification from the delay measurement terminal 110 to the control device 10, a route similar to the uplink route by a normal communication terminal can be used. The configuration of the delay measurement terminal 110 will be described later.

  The distributed antenna unit 200 includes a distributor 202, a photoelectric converter 204, an amplifier 206, a delay circuit 208, a delay measurement terminal 210, a distributed antenna 212, and a delay measurement antenna 214.

  The distributor 202 receives the downlink signal as an optical signal via the optical fiber 30, and distributes the received optical signal to the photoelectric converter 204 and other distributed antenna units.

  The photoelectric converter 204 converts the downlink signal received as an optical signal from the distributor 202 into an electrical signal and outputs it to the amplifier 206.

  The amplifier 206 amplifies the downlink signal received as an electrical signal from the photoelectric converter 204 to a transmission level required when the distributed antenna 212 transmits. If a sufficient transmission level is obtained without amplifying the downlink signal by the amplifier 206, the amplifier 206 may be omitted.

  The delay circuit 208 and the delay measurement terminal 210 have the same functions and configurations as the delay circuit 108 and the delay measurement terminal 110 in the base station unit 100, respectively, and thus description thereof is omitted.

  FIG. 2 is a block diagram showing the configuration of the delay measurement terminal 210. Although the following description will be described with reference to the delay measurement terminal 210, the delay measurement terminal 110 has the same configuration and function as the delay measurement terminal 210.

  The delay measurement terminal 210 includes a communication unit 302, a delay control unit 304, and a storage unit 306.

  The communication unit 302 receives downlink signals from the main antenna 112 and the plurality of distributed antennas 212 via the delay measurement antenna 214, converts them into baseband frequencies, and data in baseband signals such as FFT and demapping. The process is executed and the received data is output to the delay control unit 304.

  In addition, the communication unit 302 receives data obtained by adding the ID of the delay measurement terminal 210 itself to the delay information of the main antenna 112 and the plurality of distributed antennas 212 from the delay control unit 304, and data in a baseband signal such as mapping or IFFT The processing is executed, the baseband signal is converted into an RF (Radio Frequency) frequency, and transmitted through the delay measurement antenna 214.

  The delay control unit 304 receives the delay information of the main antenna 112 and the plurality of distributed antennas 212 from the communication unit 302 and stores the delay information in the storage unit 306. In addition, the delay control unit 304 adds the ID of each antenna to the delay information and outputs it to the communication unit 302 in order to transmit the delay information of the main antenna 112 and the plurality of distributed antennas 212 to the control device 10.

  Further, the delay control unit 304 outputs a control signal corresponding to the delay control information received from the control device 10 via the delay measurement antenna 214 and the communication unit 302 to the delay circuit 208, and the delay circuit 208 responds to the delay control information. Control to delay the downlink signal.

  The storage unit 306 receives and stores delay information of the main antenna 112 and the plurality of distributed antennas 212 from the delay control unit 304.

  The control device 10 is connected to the base station unit 100 via the network 20. The control apparatus 10 stores in advance the IDs of the delay measurement terminal 110 of the base station unit 100 and the delay measurement terminal 210 of each distributed antenna unit 200 (hereinafter referred to as “each unit”). The control device 10 determines an appropriate delay to be set in the delay circuits 108 and 208 of each unit from the delay information with ID information received from the delay measurement terminals 110 and 210 and the ID stored in the control device 10 itself. The amount can be determined.

  A procedure for setting the delay amounts of the delay circuit 108 of the base station unit 100 and the delay circuits 208 of the plurality of distributed antenna units 200 will be described with reference to the flowchart shown in FIG.

  The delay measurement terminals 110 and 210 receive the downlink signal from the antenna of each unit, analyze the reception timing, and store the delay information in the storage unit 306 (step S101).

  The delay measurement terminals 110 and 210 add the ID of the delay measurement terminal 110 or 210 itself to the delay information of the downlink signal received from the antenna of each unit, and notify the control apparatus 10 (step S102). For the notification from the delay measurement terminals 110 and 210 to the control device 10, a wireless uplink can be used.

  The control device 10 determines an appropriate delay amount to be set in each of the delay circuits 108 and 208 based on the delay information received from each of the delay measurement terminals 110 and 210 (step S103). For example, when there are antenna units A, B, C, and D, and the actual delays are 3, 2, 1, and 0, the delay amounts are 0, 1, and so that each transmission timing is leveled. 2 and 3 are determined.

  The control device 10 notifies the delay measurement terminals 110 and 210 of the delay amounts to be set in the determined delay circuits 108 and 208 (step S104). A wireless downlink can be used for notification from the control device 10 to the delay measurement terminals 110 and 210.

  The delay measurement terminals 110 and 210 set the delay amounts of the delay circuits 108 and 208 to appropriate values based on the delay amount received from the control device 10 (step S105).

  As described above, according to the present embodiment, each of the base station unit 100 and the plurality of distributed antenna units 200 appropriately sets the delay amount when transmitting the downlink signal so that the delay difference is within the CP length. As a result, the intersymbol interference can be reduced.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, functions included in each member, each means, each step, etc. can be rearranged so as not to be logically contradictory, and a plurality of means, steps, etc. can be combined or divided into one. Is possible.

  In the above-described embodiment, the case where the distributed antenna units are daisy chain connected has been described as an example. However, the present invention is not limited to this, and each distributed antenna unit is directly connected to the base station unit. Even so, the present invention can be similarly applied.

DESCRIPTION OF SYMBOLS 10 Control apparatus 20 Network 30 Optical fiber 100 Base station unit 102 Base station 104 Electric divider 106 Electric optical converter 108 Delay circuit 110 Delay measurement terminal 112 Main antenna 114 Delay measurement antenna 200 Distributed antenna unit 202 Divider 204 Photoelectric converter 206 Amplifier 208 Delay Circuit 210 Delay Measurement Terminal 212 Distributed Antenna 214 Delay Measurement Antenna 302 Communication Unit 304 Delay Control Unit 306 Storage Unit

Claims (2)

A distributed antenna system in which a plurality of distributed antenna units are arranged in a cell,
Each of the distributed antenna units is
A distributor that distributes the received optical signal into an optical signal for the distributed antenna unit and an optical signal for another distributed antenna unit;
A photoelectric converter that converts the optical signal received from the distributor into an electrical signal;
A delay circuit for delaying the electrical signal;
A distributed antenna that receives and transmits the electrical signal delayed by the delay circuit;
A delay measurement terminal that measures delays of a plurality of radio signals received from the plurality of distributed antenna units, and the distributed antenna system further includes:
A distributed antenna system comprising: a control device that receives delays of the plurality of radio signals from each of the distributed antenna units in a cell and determines a delay amount of the electrical signal in the delay circuit. A delay correction method in a distributed antenna system in which a plurality of distributed antenna units are arranged in a cell,
In each of the distributed antenna units,
Distributing the received optical signal into an optical signal for the distributed antenna unit and an optical signal for another distributed antenna unit;
Converting the optical signal into an electrical signal;
Delaying the electrical signal;
Receiving and transmitting the electrical signal;
Measuring delays of a plurality of radio signals received from the plurality of distributed antenna units, and
Receiving a delay of each of the plurality of radio signals from each of the distributed antenna units in a cell, and determining a delay amount of the electrical signal in the delay circuit.

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