JP7817907B2 - Base unit and wireless communication system - Google Patents

Description

The present invention relates to a base unit and a wireless communication system for a distributed antenna system, and in particular to a base unit and a wireless communication system that can reduce the circuit scale without degrading the signal quality of the downstream signal output from the slave unit.

Description of the Prior Art
Distributed Antenna Systems (DAS) are becoming increasingly common in enclosed spaces such as inside buildings and tunnels. A multi-carrier DAS (infrastructure sharing compatible DAS) transmits and receives radio waves from multiple carriers.

[Example of infrastructure sharing compatible DAS configuration: Figure 5]
An example of the configuration of an infrastructure sharing compatible DAS will be described with reference to Fig. 5. Fig. 5 is an explanatory diagram showing an example of the configuration of an infrastructure sharing compatible DAS.
The infrastructure sharing compatible DAS comprises a parent device (parent device #1 in the figure) 110 that transmits and receives data with base stations 100 of multiple operators, a plurality of aggregation devices 120 (aggregation #1 to aggregation #M in the figure) connected to the parent device 110 by optical cables, and a plurality of child devices 130 (child devices #1 to #M*N in the figure) connected to each aggregation device 120 by optical cables.
In the example of FIG. 5, a base station 100a of an operator A and a base station 100d of an operator D are shown as the base stations 100 of the operators.

The parent device 110 receives radio signals (downstream signals/DL) from multiple base stations 100, converts them into optical signals, and outputs them to the aggregation device 120, and converts the optical signals (upstream signals/UL) from the aggregation device 120 into radio signals and outputs them to the corresponding base stations 100.
The master unit 110 and each base station 100 are connected by a coaxial cable, and perform analog communication for uplink and downlink signals. The number of coaxial cable interfaces is determined according to the frequency allocation (number of radio signal bands) and the number of MIMO (Multiple-Input and Multiple-Output) supported by each operator.

The aggregation device 120 connects the parent device 110 and multiple child devices 130 via an optical cable to perform data communication. It receives optical signals from the parent device 110 and distributes them to the multiple child devices 130, and also receives optical signals from the multiple child devices 130 and outputs them to the parent device 110.

The slave device 130 is connected to the aggregation device 120 via an optical cable, converts optical signals from the aggregation device 120 into wireless signals, and outputs the signals from an antenna. The slave device 130 also converts wireless signals received by the antenna into optical signals and outputs the signals to the aggregation device 120.
The slave devices 130 are wireless communication devices equipped with directional antennas, and are installed in various locations (ceilings, walls, floors, etc.) within a building, for example, and perform wireless communication with wireless terminal devices 140 of multiple operators. Fig. 5 shows a configuration in which N slave devices 130 are connected to M aggregation devices 120, respectively.

In Figure 5, wireless terminal devices 140 are shown as wireless terminal device 140a of operator A and wireless terminal device 140d of operator D. By using a shared operator DAS, wireless terminal devices 140 of multiple operators located within a building, etc., can send and receive data via a shared slave device 130.

[Example of infrastructure sharing compatible DAS operation]
For example, an infrastructure sharing-compatible DAS with four operators and 32 sub-devices may be configured with four operators' base stations 100, one base station 110, four aggregation devices 120, and 32 sub-devices 130, with eight sub-devices 130 connected to each aggregation device 120.

Furthermore, when an infrastructure sharing compatible DAS is constructed within a building, one to several slave units 130 are placed on each floor, and there are cases where one system is assigned to multiple floors of multiple buildings.
In infrastructure sharing, it is necessary to control the operation of each business operator on a building or floor basis, and each slave 130 controls the operation (ON)/stop (OFF) of each business operator.

[Example of operation ON/OFF for each operator: Figure 6]
An example of operation ON/OFF for each business operator in an infrastructure sharing compatible DAS will be described with reference to Fig. 6. Fig. 6 is an explanatory diagram showing an example of operation ON/OFF for each business operator.
Figure 6 shows the output of downstream signals in an infrastructure sharing compatible DAS equipped with the above-mentioned 32 sub-devices 130 (sub-device #1 to sub-device #32) when operation is set on a per-operator basis for each sub-device.

Of the 32 handset units 130, handset units #1 to #6 are set to operate ON for all operators A, B, C, and D, and the downlink signals from handset units #1 to #6 output the frequencies of all operators, as shown in Figure 6(a).

For handset #7 to handset #18, operation is set to ON for operators A, B, and D, and operation is set to OFF for operator C. As shown in Figure 6(b), these handset units output frequencies corresponding to operators A, B, and D, but output of the frequency corresponding to operator C is stopped.

For handsets #19 to #24, operation is set to ON for operators A and C, and operation is set to OFF for operators B and D. As shown in Figure 6(c), frequencies corresponding to operators A and C are output, but frequencies corresponding to operators B and D are not output.

Handsets #25 to #32 are set to operate ON for operators B and C, and to operate OFF for operators A and D, and as shown in Figure 6 (d), only frequencies corresponding to operators B and C are output.
In this way, the operations of the business operators are controlled on a building-by-building or floor-by-floor basis.

[Configuration of a conventional wireless communication system: Figure 7]
Next, the configuration of a conventional wireless communication system will be described with reference to Fig. 7. Fig. 7 is an explanatory diagram showing the configuration of a conventional wireless communication system.
7 shows the configuration of the downstream signal processing units of the parent device and the child device of the infrastructure sharing compatible DAS operated by four operators (operators A to D). Note that the aggregation device 130 is omitted.
As shown on the left side of FIG. 7, the frequency allocation of operators A to D is in ascending order of operator A, operator B, operator C, and operator D.

As shown in Figure 7, the downstream signal processing unit of the conventional base unit 4 includes analog circuit units 41a to 41d (sometimes referred to as analog circuit unit 41) corresponding to operators A to D, respectively, A/D conversion units 42a to 42d (sometimes referred to as A/D conversion unit 42), digital signal processing units 43a to 43d (sometimes referred to as digital signal processing unit 43), and a transceiver circuit unit 44.

The analog circuit unit 41 receives downstream signals from the base stations of the corresponding carriers and performs analog processing.
The A/D converter 42 converts the analog signal output from the analog circuit 41 into a digital signal.
The digital signal processing unit 43 includes a digital filter, limits the input digital signal to the band of the corresponding carrier, and performs digital signal processing required for transmission.
The transceiver circuit unit 44 integrates the electrical signals from the digital signal processing units 43, converts them into optical signals, and outputs them to the slave unit 3 via an optical cable.

The handset 3 also includes a transceiver circuit unit 31, ON/OFF processing units 32a-32d (sometimes referred to as ON/OFF processing units 32) provided for each operator, digital signal processing units 33a-33d (sometimes referred to as digital signal processing units 33), a digital multiplexing unit 34, a D/A conversion unit 35, and an analog circuit unit 36.

The transceiver circuit unit 31 converts the optical signal from the optical cable into an electric signal, separates it for each operator's band, and outputs it to the ON/OFF processing units 32a to 32d.
As described above, the ON/OFF processing units 32a to 32d switch the signal output for each operator between ON and OFF. Signals from operators that are set to ON are output to the digital signal processing unit 33, and signals from operators that are set to OFF are not output.

The digital signal processing unit 33 performs digital signal processing for each operator.
The digital multiplexing unit 34 multiplexes the signals for each operator that have been subjected to digital signal processing.
The D/A converter 35 converts the multiplexed digital signal into an analog signal.
The analog circuit section 36 performs analog processing such as modulation and amplification on the analog signal.

In conventional wireless communication systems, signals input to the base station 4 from each operator's base station are analog-processed by the corresponding analog circuit 41, A/D-converted by the corresponding A/D converter 42, digital-processed by the corresponding digital signal processor 43, converted to an optical signal by the transceiver circuit 44, and sent to the handset 3.

The optical signal received by the slave unit 3 is converted into an electrical signal by the transceiver circuit unit 31 and input to the ON/OFF processing unit 32 for each operator, and only when the ON/OFF processing unit 32 is set to ON is the signal output to the digital signal processing unit 33 for digital signal processing.
The signals are then multiplexed by a digital multiplexing section 34, converted into analog signals by a D/A conversion section 35, subjected to analog processing by an analog circuit section 36, and sent out from an antenna.

Here, in the conventional base unit 4, the analog circuit 41, A/D conversion unit 42, and digital signal processing unit 43 are each configured independently for each operator, so they are less susceptible to the influence of signals from other operators using adjacent frequency bands.
Therefore, the signals digitally multiplexed by the slave unit 3 are hardly affected by signals from other operators, and the quality of the signals from each operator output from the slave unit 3 is good.

[Related Technology]
Incidentally, a conventional technology for a wireless communication system is disclosed in Japanese Patent Laid-Open Publication No. 2014-187450, entitled "Optical Transmission Device" (Patent Document 1).
Patent Document 1 describes an optical transmission device that can reduce the optical transmission capacity while satisfying the signal standards when optically transmitting using multiple shared frequencies.

JP 2014-187450 A

However, conventional base stations require an A/D converter for each operator, which increases the circuit size and equipment costs.

Note that Patent Document 1 does not describe analog synthesis of downstream signals from multiple operators using a single analog synthesis unit, or combining downstream signals from operators whose frequency bands are not adjacent and analog synthesising them using multiple analog synthesis units.

The present invention was made in consideration of the above situation, and aims to provide a base station and wireless communication system that can reduce the circuit scale without degrading the signal quality of downstream signals in a system using an infrastructure sharing-compatible DAS.

The present invention, which solves the problems of the above-mentioned conventional examples, is a base station used in a distributed antenna system, and is characterized by having a plurality of analog circuits that perform analog processing of downstream signals from base stations of each operator, a plurality of analog combiners that combine, among the analog-processed downstream signals, downstream signals of operators that do not have adjacent frequency bands, a number of A/D converters equal to the number of analog combiners that convert the outputs from the plurality of analog combiners from analog signals to digital signals, a plurality of digital signal processing units that separate the digital signals into downstream signals for each operator, and a transmitting unit that transmits the separated downstream signals as optical signals.

The present invention is also characterized in that the parent unit includes a first analog combiner and a second analog combiner as the multiple analog combiners, and a first A/D converter connected to the subsequent stage of the first analog combiner and a second A/D converter connected to the subsequent stage of the second analog combiner as the A/D converters.

The present invention also provides a wireless communication system comprising any one of the above base units, and a handset that includes a processing unit that turns on or off signals received from the base unit for each operator, a processing unit that performs digital signal processing on the signals turned on by the processing unit for each operator, and a multiplexing unit that digitally multiplexes the signals that have been digitally processed for each operator.

According to the present invention, a base unit used in a distributed antenna system is a base unit having a plurality of analog circuits that perform analog processing of downlink signals from base stations for each operator, a plurality of analog combiners that combine downlink signals of operators that do not have adjacent frequency bands from among the analog-processed downlink signals, the same number of A/D converters as the analog combiners that convert the output from the plurality of analog combiners from analog signals to digital signals, a plurality of digital signal processing units that separate the digital signals into downlink signals for each operator, and a transmitting unit that transmits the separated downlink signals as optical signals.Therefore, by combining and combining the downlink signals of operators that do not have adjacent frequency bands in the analog combiners, it is possible to suppress the influence of frequency components of other operators on the signals for each operator separated by the digital signal processing unit, thereby preventing deterioration in the quality of the downlink signals, and further has the effect of reducing the number of A/D converters to the same number as the analog combiners, thereby reducing the circuit scale.

FIG. 1 is an explanatory diagram showing the configuration of a first wireless communication system. FIG. 2 is an explanatory diagram showing an output signal from a slave device in the first wireless communication system. FIG. 10 is an explanatory diagram showing the configuration of a second wireless communication system. FIG. 10 is an explanatory diagram showing an output signal from a slave device in the second wireless communication system. FIG. 1 is an explanatory diagram illustrating an example of the configuration of an infrastructure sharing compatible DAS. FIG. 10 is an explanatory diagram showing an example of operation ON/OFF for each business operator. FIG. 1 is an explanatory diagram showing the configuration of a conventional wireless communication system.

An embodiment of the present invention will be described with reference to the drawings.
[Outline of the embodiment]
The base station (first base station) according to the first embodiment of the present invention is a base station used in a distributed antenna system, and has a plurality of analog circuits that perform analog processing of downstream signals from base stations for each operator, an analog combiner that combines the downstream signals of the multiple operators, an A/D converter that converts the output from the analog combiner into a digital signal, a plurality of digital signal processing units that separate the digital signal into downstream signals for each operator, and a transmitting unit that transmits the separated downstream signals as an optical signal, thereby enabling a significant reduction in the number of A/D converters and reducing the circuit size and device costs.

In addition, a base station (second base station) according to a second embodiment of the present invention is a base station used in a distributed antenna system, and includes multiple analog circuits that perform analog processing of downstream signals from base stations for each operator, multiple analog combiners that combine downstream signals from operators with non-adjacent frequency bands, the same number of A/D converters as the analog combiners that convert the output from the multiple analog combiners into digital signals, multiple digital signal processing units that separate the digital signals into downstream signals for each operator, and a transmitter that transmits the separated downstream signals as optical signals.By combining downstream signals from multiple operators without being affected by signals from other operators and performing A/D conversion on the combined signal, the number of A/D converters can be reduced without degrading the quality of the downstream signals, and this can be achieved without implementing filters with steep filter characteristics in the digital signal processing units, thereby reducing device costs.

Furthermore, the wireless communication system according to an embodiment of the present invention is a wireless communication system equipped with a first base unit or a second base unit.

[Configuration of a wireless communication system according to a first embodiment: FIG. 1]
The configuration of a wireless communication system according to a first embodiment of the present invention (first wireless communication system) will be described with reference to Fig. 1. Fig. 1 is an explanatory diagram showing the configuration of the first wireless communication system.
As shown in Fig. 1, the first wireless communication system is an infrastructure sharing-compatible DAS operated by four operators (operators A to D), similar to the conventional wireless communication system shown in Fig. 7. Note that the aggregation device 130 is omitted.

As shown on the left side of FIG. 1, the frequency allocation of operators A to D is in ascending order of operator A, operator B, operator C, and operator D.
Here, the frequency bands of operators A and B, operators B and C, and operators C and D are adjacent to each other.

As shown in Figure 1, the first wireless communication system includes a first base station 1 and a handset 3. Here, the configuration of the downlink signal processing unit for the first base station 1 and handset 3 is shown, but the handset 3 has the same configuration and operation as the conventional handset 3 shown in Figure 7, so a description of it will be omitted.

The first base unit 1, which is a characteristic part of the first wireless communication system, will be specifically described.
The downstream signal processing unit of the first base unit 1 includes analog circuit units 11a, 11b, 11c, and 11d, an analog synthesis unit 12, digital signal processing units 14a, 14b, 14c, and 14d, digital signal processing units 14a, 14b, 14c, and 14d, and a transceiver circuit unit 15.

Analog circuit units 11a to 11d are provided corresponding to each of operators A to D, as in the past, and perform analog processing on signals input from the base station 100 of each operator. Analog circuit units 11a to 11d are sometimes referred to as analog circuit unit 11.

The analog synthesis unit 12 is a characteristic part of the first base unit 1, and inputs and synthesizes the analog signals output from the analog circuit units 11a to 11d. In other words, it synthesizes all analog-processed signals from operators A to D and outputs the result to the A/D conversion unit 13.

The A/D converter 13 receives the synthesized signal output from the analog synthesizer 12, converts it into a digital signal, and outputs it.
Therefore, in the first base unit 1, only one analog synthesis unit 12 and one A/D conversion unit 13 are required, which is a significant reduction in number compared to the conventional system, and allows for a reduction in circuit scale.

The digital signal processing units 14a to 14d receive the digital signals branched after A/D conversion by the A/D conversion unit 13, and separate and extract data in the bands of the corresponding operators using digital filters. The digital signal processing units 14a to 14d may also be referred to as the digital signal processing unit 14.
The transceiver circuit unit 44 receives a digital signal, converts it into an optical signal, and sends it to the slave unit 3 in the same manner as in the conventional case. The transceiver circuit unit 44 corresponds to a transmitting unit as defined in the claims.

The operation of the first base unit 1 will now be described.
The signals output from the base stations 100 of the operators A to D are input to the analog circuits 41a to 41d, respectively, where they are subjected to analog processing, and then combined in the analog combiner 12 to generate an analog combined signal.
That is, the analog composite signal at the first base unit 1 is a composite of downstream signals from four operators A to D.

The analog composite signal is converted from an analog signal to a digital signal by the A/D converter 13, branched, and input to the digital signal processing sections 14a to 14d.
Then, in the digital signal processing units 14a to 14d, the frequency bands of the corresponding operators are separated by digital filters, and the signals are converted into optical signals in the transceiver circuit unit 15 and transmitted to the slave unit 3 via an optical cable.

In the slave unit 3, processing is carried out in the same manner as before, with the optical signal received by the transceiver circuit 31 converted into an electrical signal, multiplexed by the ON/OFF processing unit 32 corresponding to each operator and the digital multiplexing unit 34, converted into an analog signal by the D/A conversion unit 35, subjected to analog processing by the analog circuit unit 36, and then transmitted from the antenna.

Here, the digital signal processing unit 14 of the first base unit 1 A/D converts the combined signal, which is an analog combination of signals from multiple operators with adjacent frequency bands, and performs digital processing. Therefore, it is difficult to completely remove the signal components from adjacent operators. As a result, the digital multiplexing unit 34 of the handset 3 combines the signals while leaving the frequency components from adjacent operators, resulting in a degradation of signal quality.

[Output signal from a slave unit in the first wireless communication system: FIG. 2]
The signal output from the slave unit 3 in the first wireless communication system will be described with reference to Fig. 2. Fig. 2 is an explanatory diagram showing the signal output from the slave unit in the first wireless communication system.
2, the frequency bands of operators A and B are adjacent to each other, operators B and C are adjacent to each other, and operators C and D are adjacent to each other. Here, since the operation of operator C is OFF, the signal of operator C is not output from slave 3.

However, since it is difficult to completely remove adjacent frequency components in the frequency separation performed by the digital processing of the first base unit 1, the adjacent frequency components are combined in the slave unit 3 while retaining their influence, as shown in Figure 2.
Therefore, in the first wireless communication system, the quality of the downstream signal of each operator from the slave unit 3 is degraded due to the influence of the frequency components of other adjacent operators.

In addition, to prevent degradation of signal quality in the configuration of the first base unit 1 and the first wireless communication system, it is necessary to implement a digital filter with steep filter characteristics in the digital signal processing unit 14 so as to completely remove frequency components from adjacent operators, but this is difficult in terms of circuit size and cost.

[Configuration of a wireless communication system according to the second embodiment: FIG. 3]
A wireless communication system according to a second embodiment (second wireless communication system) will be described with reference to Fig. 3. Fig. 3 is an explanatory diagram showing the configuration of the second wireless communication system.
3, the second wireless communication system is an infrastructure sharing compatible DAS in which a base station (second base station) 2 according to the second embodiment is provided instead of the first base station 1 in the first wireless communication system. Note that the slave station 3 is the same as in the conventional and first wireless communication systems.

The second wireless communication system reduces the circuit scale of the master unit compared to the conventional system, and prevents deterioration in the quality of downstream signals output from the slave units.
In the first base unit 1 described above, signals from operators with adjacent frequency bands are combined in an analog manner, which causes adjacent frequency components to influence each other and degrade signal quality. However, in the second base unit 2, signals from operators with non-adjacent frequency bands are combined in an analog manner, thereby preventing quality degradation.

In the example of Figure 3, as shown on the far left, the frequency bands of operators A and C, and operators B and D are not adjacent, so the second base unit 2 analog-combines the downstream signals of operators A and C, and operators B and D.

As shown in FIG. 3, the downstream signal processing section of the second base unit 2 includes analog circuit sections 21a, 21c, 21b, and 21d, analog synthesis sections 22a and 22b, A/D conversion sections 23a and 23b, digital signal processing sections 24a, 24c, 24b, and 24d, and a transceiver circuit 25.

Analog circuit units 21a, 21c, 21b, and 21d have the same configuration and operation as analog circuit units 11a, 11c, 11b, and 11d of first base unit 1, respectively, and input downstream signals from the base stations of operators A, C, B, and D, respectively, and perform analog processing.

The analog synthesis unit 32a synthesizes the output signals from the analog circuit unit 21a and the analog circuit unit 21c. As described above, the frequency band of the operator A and the frequency band of the operator C are not adjacent to each other.
The analog synthesis unit 32b synthesizes the output signals from the analog circuit unit 21b and the analog circuit unit 21d. The frequency band of the operator B and the frequency band of the operator D are not adjacent to each other.

The A/D converter 23a converts the combined analog signal output from the analog combiner 32a into a digital signal.
The A/D converter 23b converts the combined analog signal output from the analog combiner 32b into a digital signal.
As a result, in the second base unit 2, the number of analog synthesis units and A/D conversion units that were previously required to be equal to the number of operators (four in this case) can be significantly reduced to two each.

The digital signal processing unit 24a uses a digital filter to separate data in operator A's frequency band from the branched digital signal output from the A/D conversion unit 23a.

Here, since the frequency band of operator A and the frequency band of operator C are not adjacent, when separating and extracting data of the frequency band of operator A from the output signal from the A/D conversion unit 23a, there is little influence from the signal of operator C.
Therefore, the digital filter of the digital signal processing unit 24a does not need to have a particularly steep filter characteristic, but it can sufficiently remove signals from other operators (in this case, operator C), thereby reducing circuit size and costs.

Similarly, the digital signal processing unit 24c separates data in the frequency band of operator C from the digital signal from the A/D conversion unit 23a. The digital signal processing unit 24c can easily separate data from operator C without using a digital filter with particularly steep filter characteristics, because there are no signals from other operators (in this case, operator A) in adjacent frequency bands.

The same is true for digital signal processing unit 24b and digital signal processing unit 24d. Because the frequency bands of operators B and D are not adjacent, digital signal processing unit 24b can separate data from the frequency band of operator B, and digital signal processing unit 24d can separate data from the frequency band of operator D from the digital signal obtained by A/D converting the combined analog signal, without mixing in frequency components from other operators.

In this way, in the second base unit 2, the analog synthesis unit 22 synthesizes downstream signals from operators in frequency bands that are not adjacent to each other (leaving gaps), so that the digital signal processing unit 24 can accurately separate the data from each frequency band without the signals from each operator affecting each other.

As a result, in handset 3, the signals multiplexed by the digital multiplexing unit 24 are signals that are not affected by other operators, so the quality of the downstream signals sent from handset 3 can be improved compared to the first wireless communication system, and signal quality can be maintained compared to conventional systems.

[Output signal from the slave unit in the second wireless communication system: FIG. 4]
The signal output from the slave unit 3 in the second wireless communication system will be described with reference to Fig. 4. Fig. 4 is an explanatory diagram showing the signal output from the slave unit in the second wireless communication system.
FIG. 4 shows an example in which the operation of operator C is stopped, but the signals of operators A, B, and D are output with good quality without being affected by the neighboring operators.

In this way, the second wireless communication system using the second base unit 2 can reduce the A/D conversion unit and the circuit scale of the base unit compared to conventional systems, while maintaining good quality of the downstream signal from the handset.

[Effects of the embodiment]
The first base unit and the first wireless communication system have a plurality of analog circuits 11a to 11d that perform analog processing of downstream signals from the base stations of each operator, an analog combiner 12 that combines the downstream signals of the multiple operators, an A/D converter 13 that converts the output from the analog combiner 12 into a digital signal, a plurality of digital signal processing units 14a to 14d that separate the digital signal into downstream signals for each operator, and a transceiver circuit 15 that transmits the separated downstream signals as optical signals, and have the effect of significantly reducing the number of A/D converters 13 and reducing the circuit size and device costs.

The second base unit and second wireless communication system also include analog circuits 21a-21d that perform analog processing of downlink signals from base stations for each operator, analog combiners 22a, 22b that combine and synthesize downlink signals from operators with non-adjacent frequency bands, A/D converters 24a, 24b that convert the output from analog combiners 22a, 22b into a digital signal, multiple digital signal processing units 24a-24d that separate the digital signals into downlink signals for each operator, and a transceiver circuit 25 that transmits the separated downlink signals as an optical signal. By synthesizing downlink signals from multiple operators without being affected by signals from other operators and then performing A/D conversion on the combined signal, the number of A/D converters can be reduced without degrading the quality of the downlink signals, thereby reducing the circuit size. This can also be achieved without implementing filters with steep filter characteristics in the digital signal processing units, thereby reducing device costs.

The present invention is suitable for a base unit of a distributed antenna system and a wireless communication system, which can reduce the circuit scale without degrading the signal quality of the downstream signal output from the slave unit.

1...First base unit, 2...Second base unit, 3, 130...Slave unit, 4...Conventional base unit, 11, 21, 41, 36...Analog circuit unit, 12, 22, 42...Analog synthesis unit, 13, 23, 43...A/D conversion unit, 14, 24, 33, 44...Digital signal processing unit, 15, 25, 31...Transceiver circuit unit, 32...ON/OFF control unit, 34...Digital multiplexing unit, 35...D/A conversion unit, 100...Base station, 110...Base unit, 120...Aggregation device, 140...Wireless terminal device

Claims (3)

A master unit used in a distributed antenna system, comprising:
a plurality of analog circuits for analog processing of downstream signals from base stations of respective carriers;
a plurality of analog combiners for combining downstream signals of operators whose frequency bands are not adjacent to each other among the downstream signals that have been subjected to the analog processing;
A/D converters, the number of which is equal to the number of the analog combiners, for converting outputs from the plurality of analog combiners from analog signals to digital signals;
a plurality of digital signal processing units that separate the digital signal into downstream signals for each of the operators;
a transmitter that transmits the separated downstream signal as an optical signal. the plurality of analog combiners include a first analog combiner and a second analog combiner;
2. The base unit according to claim 1, further comprising: a first A/D converter connected to a stage subsequent to the first analog combiner; and a second A/D converter connected to a stage subsequent to the second analog combiner. a base unit according to claim 1 or 2;
a slave unit including a processing unit that turns on or off signals received from the master unit for each operator, a processing unit that performs digital signal processing of the signals that have been turned on by the processing unit for each operator, and a multiplexing unit that digitally multiplexes the signals that have been digitally processed for each operator;
A wireless communication system comprising: