JP3389076B2 - Wireless communication system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile phone and a wireless L.
The present invention relates to a wireless communication system such as AN.

[0002]

2. Description of the Related Art In a conventional wireless communication system such as a cellular phone, a range called a location registration area is set. The position registration of the wireless terminal is performed every time the terminal moves between the position registration areas, so that the rough position of the wireless terminal can be grasped. One location registration area usually includes a plurality of cells. A cell refers to a communication area covered by one base station.

A transmission signal from a wireless terminal within the location registration area is received by any base station within the area, and the base station can detect a call from the wireless terminal. Also, if a call is made to the location registration area in which the location of the wireless terminal has been registered, it is possible to notify the wireless terminal of an incoming call.

By the way, in a wireless communication system for realizing high-speed wideband wireless transmission, free space propagation loss per unit distance (hereinafter
This is called propagation loss. It is effective to use a large frequency band. In order to ensure transmission quality using a frequency band with large propagation loss, it is necessary to increase transmission power or antenna gain. Further, in a wireless communication system in which the portability of a wireless terminal is required, it is required to suppress the transmission power of the terminal and reduce the power consumption.

In order to secure the transmission quality without increasing the transmission power, it is possible to use an antenna with a high gain in the base station or the wireless terminal. However, if a cell is constructed with an antenna with a high gain, the radius of the cell becomes smaller, so an area equivalent to the communication area of a wireless communication system configured with an antenna with a low gain is covered with an antenna with a high gain. In order to do so, it is necessary to arrange a larger number of cells or a larger number of base stations.

[0006] Further, since a radio communication system using a high frequency band such as a millimeter wave band which can easily secure a frequency bandwidth has a high rectilinearity of radio waves, a radio wave from a transmitting point to a receiving point is transmitted by a person. The shadowing of objects and other objects has a large effect on communication quality.

Site diversity, which increases the number of base stations that a terminal can receive, is effective as a countermeasure against shadowing. However, in this case, it is necessary to arrange a larger number of base stations as compared with a wireless communication system using a low frequency band.

Therefore, in a wireless communication system for realizing high-speed wideband wireless transmission, there are technical problems such as an efficient cell placement method, a calling terminal detection method, a terminal incoming call notification method, and a terminal acquisition method. It is the current situation. further,
A technical problem is how to efficiently arrange a large number of base stations and how to efficiently connect them.

[0009]

SUMMARY OF THE INVENTION The present invention is intended to solve such a problem and is intended to reduce the total cost when arranging a large number of base stations in one service area and the cost of a single base station. It is an object of the present invention to provide a wireless communication system capable of achieving the above.

Further, according to the present invention, the antenna directivity of the base station used for communication and the antenna directivity of the terminal are used while improving the transmission efficiency by suppressing the ratio of the transmission amount of the control signal in the entire signal band. An object of the present invention is to provide a wireless communication system capable of efficiently determining a combination.

Further, according to the present invention, the control load on the base station can be reduced by allowing the terminal side to determine the combination of the antenna directivity of the base station used for communication and the antenna directivity of the terminal. It is an object of the present invention to provide a wireless communication system capable of achieving high speed and speeding up the system.

[0012]

In order to achieve the above-mentioned object, the wireless communication system of the present invention has a plurality of cells each covering a communication area with a wireless terminal as described in claim 1. a plurality of base stations having a corresponding plurality of base station antennas sector, the same direction of each base station
From the base station antenna sector ,
The first control signal including the identification information of the
And a second control signal containing identification information of the base station
Means for controlling the base station antenna sector to transmit while periodically switching at different times, and receiving the first control signal from each base station while periodically switching the terminal antenna sector. The terminal antenna
Before measuring the received power for each sector and using it for communication based on the measured received power for each terminal antenna sector
Serial to determine the terminal antenna sectors with the base station antenna sector, the first received through the antennas sector
Wireless terminal having means for transmitting a third control signal to the base station based on the identification information of the base station included in the second control signal .

Further, according to a second aspect of the present invention, there is provided a plurality of base stations having a plurality of base station antenna sectors respectively corresponding to a plurality of cells covering a communication area with a wireless terminal. Station and each of the base stations
From the base station antenna sector in the same direction, the base station
A first control signal containing identification information of the antenna sector
At the same time, a second control signal including identification information of the base station is also provided.
Signal at different times, a centralized station that controls the base station antenna sector to transmit while periodically switching, a line that serially connects the base stations to the centralized station, and a terminal antenna sector periodically. The first control signal from each of the base stations while switching to
Measured and measured the received power for each terminal antenna sector
Determine the said terminal antenna sectors with the base station antenna sector to be used for communication based on the received power of each of the terminal antenna sector, receiving through these antenna sectors
Characterized in that a radio terminal having a third hand <br/> stage that sends a control signal to the base station based on the identification information of the base station included in the second control signal signal And

Further, according to the present invention, as described in claim 3, in the wireless communication system according to claim 1 or 2 , the means of the wireless terminal is provided with a transmission time assigned to each of the base stations. using a time slot corresponding to the desired base station among the slot group and transmits the third control signal to the base station.

[0015]

Further, according to the present invention, as described in claim 4 , in the wireless communication system according to claim 2, a plurality of switching means for respectively opening and closing the lines of the central station and the individual base stations are provided. There, a plurality of switching means opened and closed based on the switching control signal output from the central station,
It further comprises means for controlling the power of the RF signal or the IF signal transmitted to the line at least at a change point of the value of the switching control signal.

[0017] Thus, according to the radio communications system of the present invention, since the control signal for each time the terminal position detection of a common base station antenna sector of each base station is transmitted, a control signal to the total signal bandwidth It is possible to suppress the ratio of the transmission amount of the above, and it is possible to improve the transmission efficiency. Further, according to the present invention, the combination of the terminal antenna sector (directivity of the base station antenna) and the base station antenna sector (directivity of the terminal antenna) used for communication is determined by the wireless terminal, so that the base station It is possible to reduce the control load of, and it is possible to contribute to the speedup of the system.

Further, according to the present invention, it is possible to realize a system configuration in which a plurality of base stations are serially connected to a central station for controlling each base station, so that a large number of base stations are installed in one service area. In this case, the total cost can be kept low, and the cost for each base station can be kept low by collectively providing the modulator / demodulator and the like in the central station.

Further, by controlling the power of the RF signal or the IF signal transmitted to the line to 0 at the change point of the value of the switching control signal, the response speed of the line switching means in the base station becomes relatively high. It is possible to set a gradual value, and it is possible to suppress the cost of the base station itself while preventing the expansion of the signal band.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an outline of the configuration of the entire wireless communication system which is an embodiment of the present invention.

In the figure, 10 is the entire service area (60 m × 60) covered by this wireless communication system.
m). In this area 10, a plurality of, for example, four base stations 11, 12, 13, 14 are arranged. Each of the base stations 11, 12, 13, 14 has an antenna capable of operating the antenna directivity, and means for varying the antenna directivity,
It has a wireless communication means. Reference numeral 15 denotes a cell which is a region covered by the antenna directivity of the base station. Here, the cell means a region where the received electric field intensity is equal to or higher than a predetermined value. The cells 15 are arranged in an overlapping manner to prevent shadowing due to site diversity. All base stations 1 located in the service area 10
1, 12, 13, and 14 are serially connected to one central station 16 through signal lines. Within the service area 10, there are a plurality of moving wireless terminals 17 (including wireless terminals that do not move). Each of the wireless terminals 17 shares the resources of the wireless communication system with the base stations 11, 1
Two-way communication is performed with 2, 13, and 14 in a time division manner.

FIG. 2 is a diagram showing the cell arrangement in the service area 10 shown in FIG. 1 in plane coordinates. The positions of the four base stations 11, 12, 13, 14 are A,
B, C, D are shown. Each base station is, for example, 1
1 direction in all directions (360 °) by adopting 6-sector antenna
It is covered with 6 cells. For example, the omni-direction of the base station at position A has 16 cells a'1, a'2, a'3, ...
Covered by a'n. In the vicinity of each base station, cells a'0, b'0, c'by the lower antennas are provided.
It is covered by 0, d'0.

The service area 10 is composed of a plurality of base stations 11, 12, 13, 14 having such a cell arrangement.
Cells are covered with cells almost without gaps, and an overlap area is secured to prevent shadowing. The wireless terminal 17 in the service area 10 performs wireless communication with the base station while moving between cells.

In this embodiment, the service area of 60 m × 60 m is covered by four base stations, but the present invention is not limited to the shape, size, number of base stations, and number of cells of the service area. Absent. Further, the angles covered by the individual cells may be equal among the cells, or an arbitrary angle may be set for each cell. This method
This is an effective method when it is not necessary to transmit in a specific direction when viewed from the base station, or when the shape of the service area is deformed. The effect of reducing unnecessary transmission and the effect of reducing interference with other service areas Can be expected.

FIG. 3 is a diagram showing a frame structure of a signal transmitted and received between the base station and the wireless terminal. As shown in the figure, the frame 101 is reserved (all-cell scan) 10
2, control 1 (base station ID notification) 103, terminal capture (specific terminal scan) 104, control 2 (communication timing allocation) 105, and information (specific terminal communication) 106.

Reserved (all cell scan) subframes (hereinafter referred to as all cell scan subframes) 102.
Is a communication resource mainly used for location registration of a terminal, detection of a terminal call, notification of an incoming call to a terminal, and determination of a base station antenna sector and a terminal antenna sector.

Control 1 (base station ID notification subframe) 103 (hereinafter referred to as base station ID notification subframe) 103
Is a communication resource mainly used to notify the IDs (identifiers) of a plurality of base stations installed in the service area.

Subframe for terminal acquisition (specific terminal scan) (hereinafter referred to as specific terminal scan subframe)
Reference numeral 104 is a communication resource mainly used for inter-cell movement acquisition of a communication continuing terminal and a base station antenna sector change request.

The control 2 (communication timing allocation) subframe (hereinafter referred to as communication timing allocation subframe) 105 mainly notifies the terminal of the response to the reservation signal received from the terminal and the timing of specific terminal communication, and intermittently. It is a communication resource used to handle reception.

Information (specific terminal communication) subframes (hereinafter referred to as specific terminal communication subframes) 106 are communication resources mainly used for information communication between terminals and base stations.

The all-cell scan subframe 102 includes a plurality of subsubframes BA-A1, BA-A2, ..., BA.
-Nn. "BA-A1" is base station A
It indicates that the sub-subframe is assigned to the cell 1 belonging to the sub-frame. Similarly, “BA-B4” indicates that the sub-subframe is assigned to the cell 4 belonging to the base station B. These sub-subframes are 1
There are the maximum number of cells belonging to the base stations existing in one service area. For example, if there are four base stations in one service area and the number of cells belonging to each base station is 7, 8, 9, and 4, respectively, the number of sub-subframes is 9 which is the maximum value. .

Each sub-subframe has a base station transmission slot Tx and a base station reception slot R which are alternately repeated.
Contains x. The base station transmission slot Tx and the base station reception slot Rx are provided for each base station existing in the service area. The base station transmission slot Tx is used for location registration of a wireless terminal, detection of a terminal call, notification of a terminal call, and determination of a base station antenna and a terminal antenna sector. The base station transmission slot Tx is used for transmission of a control signal from the base station including an identifier indicating all-cell scan, base-station antenna sector number, all-cell scan sub-subframe number, slot number, and called-terminal identifier. Used for.

Among the wireless terminals existing in the service area, the wireless terminal trying to register the location or make a call receives the all-cell scan signal periodically transmitted from the base station and receives the all-cell scan subframe. When recognizing 102, the reservation signal is transmitted to the base station using the base station reception slot Rx corresponding to a desired base station described later in the contention slot of the all-cell scan subframe 102.

Further, the called terminal that has detected its own terminal ID from the signal transmitted from the base station (that is, the terminal receives the all-cell scan signal, and the control signal transmitted from the base station includes the own terminal ID). In the same manner, the incoming call request is determined and the terminal becomes a called terminal.) Similarly, when receiving the all-cell scan signal and recognizing the all-cell scan subframe 102, the contention slot of the all-cell scan subframe 102 is detected. The reservation signal is transmitted to the base station using the base station reception slot Rx corresponding to the desired base station therein.

The base station grasps the position of the terminal by the timing of the reservation signal transmitted from the wireless terminal. That is, the base station captures the wireless terminal by the sub-subframe number of the contention slot that received the reservation signal from the wireless terminal. The called terminal ID is included in all control signals transmitted from the base station in the all-cell scan signal. This completes the paging.

The number of base stations or an integral multiple of the number of base stations is provided as the contention slot of the all-cell scan frame. Since the base station reception slot Rx used for transmitting the reservation signal from the wireless terminal to the base station is a random access, collision is likely to occur. Therefore, it is effective to provide a plurality of competing slots in order to keep the probability of collision low.

Also, the base station transmission slot Tx is used to transmit the control signal transmitted from the base station with the number of competing slots added, and the terminal randomly sets the timing of transmitting the reservation signal based on the information. It is also possible to do so.

The control signal transmitted from the base station to the terminal using the base station transmission slot Tx of the all-cell scan subframe is a signal of the same content transmitted in the same direction from all the base stations in the service area. is there. This control signal includes an identifier indicating the all-cell scan, the number of the base station antenna sector, the number of all-cell scan sub-subframes, the slot number, and the identifier information of the called terminal. In the all-cell scan sub-subframe, the same control signal different in slot number is transmitted multiple times in duplicate. The slot number is reset every sub-cell scan subframe and incremented by 1 every time a control signal is transmitted.

The reason why control signals having different slot numbers only are transmitted a plurality of times is to determine the base station antenna sector and the terminal antenna sector. Wireless terminals
This control signal determines the set of base station antenna sector and terminal antenna sector used for communication with the base station.

Next, a method for determining the combination of the base station antenna sector and the terminal antenna sector used for communication will be described below with reference to FIG.

The wireless terminal receives the all-cell scan signal and periodically creates a received power table using the base station antenna sector number and the terminal antenna sector number as parameters. This created period will be called a table update interval. All base stations transmit the same signal a plurality of times using the slots # 1 to # 4 of the all-cell scan subframe. The wireless terminal receives the same signal while switching the terminal antenna sector and measures the received power. As a result, the terminal creates a reception power table when a certain base station antenna sector is used. afterwards,
The base station switches the base station antenna sector and repeats the same signal transmission in the same manner. As described above, at the end of all-cell scanning, the reception power table with the base station antenna sector number and the terminal antenna sector number as parameters is completed. The wireless terminal determines a combination of the base station antenna sector and the terminal antenna sector having the maximum received power from this received power table.

Next, the base station ID notification subframe 103 will be described with reference to FIG. Here, the number of base stations existing in the service area is 4, and each of them is A, B,
Let C and D. In the figure, “ID-A” is the base station A
Base station ID notification sub-subframes assigned to cells belonging to, likewise "ID-B""ID-C""ID-
Let “D” be a base station ID notification sub-subframe assigned to each of the cells belonging to base stations B, C and D. Base station I
The D broadcast sub-subframe is composed of a base station transmission slot Tx and a null slot (empty slot) Rx. That is, taking the base station ID sub-subframe “ID-D” for the base station D as an example, the base station ID sub-subframe has twice as many slots as the number of base station antenna sectors. With this base station transmission slot Tx, a control signal including a base station ID and a base station antenna sector number is transmitted. The base station reception slot Rx is an empty slot.

The base station D sets the base station antenna sector number "# 1", and the base station antenna sector number "# 1" is set.
1 "and the control signal including the base station ID are inserted into the base station ID sub-subframe" ID-D "and transmitted. Next, the base station D switches the base station antenna sector to # 2, and thereafter similarly repeats the transmission of the control signal including the base station antenna sector number and the base station ID for the number of base station antenna sectors.

The wireless terminal receives the control signal thus transmitted from the base station by using the terminal antenna sector determined by using the reception power table, and grasps the base station antenna sector number therein. Base station ID when this base station antenna sector number is the same as the base station antenna sector number previously determined using the received power table
Is the ID indicating the desired base station, that is, the base station to which the reservation signal is transmitted. By this means, the wireless terminal can know the desired base station ID from the base station antenna sector number, even if it receives control signals from a plurality of base stations. For example, the wireless terminal receives a control signal including the base station antenna sector number “# 2” of the sub-frame of ID-A and a control signal including the base station antenna sector number “# 3” of the sub-subframe of ID-C. In this case, since the base station antenna sector already determined using the received power table is “# 3”, it can be determined that the desired base station is C.

Here, when the base station sector numbers are the same, that is, when the control signal in # 2 of the sub-subframe of ID-A and the control signal in # 2 of the sub-subframe of ID-C are received, the base station The station IDs are indistinguishable, but this case cannot occur. This is because when the base station antenna sector numbers are the same, the notification is made at the same timing in all cell scans, so there must be no area where both can be received at the same time.
If there is an area where both can be received at the same time, interference occurs because signals transmitted from different base stations arrive at the terminal at the same timing in that area.

Specific terminal scan subframe 104 and communication timing allocation subframe 10 shown in FIG.
5. The detailed description of the specific terminal communication subframe 106 is as described in the specification of Japanese Patent Application No. 9-146933 filed earlier, and will not be repeated here.

Next, the configuration of the base station and the connection form between the base station and the central station in the wireless communication system of this embodiment will be described.

As shown in FIG. 6, in this radio communication system, one central station 16 is provided with a plurality of base stations and one signal line 8 is provided.
It is configured to be serially connected through 01. Signal transmission between the central station 16 and each base station is performed by, for example, a time division multiplexing system. A coaxial cable or an optical fiber cable can be used for the signal line 801 that connects the central station 16 and each base station. The multiplexer / demultiplexer 8 is connected to the signal line 801.
02 is connected, and the signal line demultiplexed and combined by the multiplexer / demultiplexer 802 is connected to the base station.

The base station module 803 uses the SW1 (80
4), directional multiplexer / demultiplexer 805, high power amplifier 806, directional multiplexer / demultiplexer 807, SW2 (808), antenna 80
9-11-809-n, control device 810, low noise amplifier 8
11 and the like.

The base station transmission signal sent from the central station 16 to each base station is received by only a specific base station by SW1 (804) of each base station module 803 connected to the signal line 801. SW1 (804) and SW2 (8
The switching control of 08) is performed by the control device 810.
The base station transmission signal that has passed through SW1 (804) is demultiplexed by the directional multiplexer / demultiplexer 805 and amplified by the large power amplifier 806 to a desired power. The output of the amplifier 806 is combined by the directional multiplexer / demultiplexer 807 and input to SW2 (808). Control device 810 controls SW2 (808) to select a desired antenna. The base station transmission signal output from SW2 (808) is radiated from the selected antenna.

Further, the base station module 803 switches the signals received by the base station antennas 809-1 to 809-n to SW.
2 (808). The received signal selected by SW2 (808) is demultiplexed by the directional multiplexer / demultiplexer 807 and amplified by the low noise amplifier 811. Low noise amplifier 811
The output of the signal is multiplexed by the directional multiplexer / demultiplexer 805, and SW1
It is input to (804). SW1 (804) is turned on at a timing set so as to transmit a signal from each base station to the central station. As a result, it is possible to avoid collision of base station reception signals sent from each base station to the central station. As described above, the base station reception signals received by the base station antennas 80911 to 809-n are sent to the central station 16.

An amplifier 812 for securing a signal level necessary for transmission is connected in the middle of the signal line 801.

The above is an example of the configuration when an RF (radio frequency) signal is transmitted to the signal line 801. Therefore, a configuration example of the base station module when an IF (intermediate frequency) signal is transmitted to the signal line 801 will be described next.

As shown in FIG. 7, this base station module is the same as the base station module of the RF signal transmission type shown in FIG. 6 except that frequency converters 813-1 and 813-2, a local frequency oscillator 814 and a filter. 815-1, 815-
2 is added. The base station transmission signal input to this base station module is demultiplexed by the directional multiplexer / demultiplexer 805, mixed with the output of the local oscillator 814 by the frequency converter 813-1, and frequency-converted to a desired RF frequency. It The output of the frequency converter 813-1 is the filter 815-.
1 into which the image signal is removed. The output of the filter 815-1 is input to the high power amplifier 806. The following is as described above.

The received signal from the base station is a low noise amplifier 81.
After being amplified by 1, the frequency is converted into a desired IF frequency by being mixed with the output of the local oscillator 814 by the frequency converter 813-2. The output of the frequency converter 813-2 is input to the filter 815-2, and after the image is removed, it is multiplexed by the directional multiplexer / demultiplexer 805 and the centralized station 1
Sent to 6.

The oscillation frequency of the frequency converter may be fixed or variably controlled. For example, it is possible to configure the control device 810 to control the output frequency of the local oscillator 814 to an optimum value under the control of the central station. In the configuration of the base station module shown in FIGS. 6 and 7, SW1 (80
4) is connected between the input / output unit of the base station and the directional multiplexer / demultiplexer 805, but as shown in FIGS. 8 and 9, two switches 901 are provided at the subsequent stage of the directional multiplexer / demultiplexer. -1,901-
Two may be arranged.

Next, a configuration example of another base station and a configuration example of the connection between this base station and the central station in the radio communication system of this embodiment will be described.

As shown in FIG. 10, in this example, an optical fiber cable 1005 is used as a signal line for serially connecting the central station and each base station. Central station module 10
01 and each base station module 1002, 1003, 100
An optical signal interface unit 4 is provided.
The base station module includes an optical demultiplexer 1006 and an optical multiplexer 1
It is connected to the optical fiber cable 1005 via 007. In this example, signal transmission from the central station to the base station,
Although separate optical fiber cables are used for signal transmission from the base station to the central station, bidirectional signals can be multiplexed and transmitted on one fiber cable.

The optical signal output from the central station module 1001 is input to the optical demultiplexer 1006 through the optical fiber cable 1005, and the optical signal demultiplexed by the optical demultiplexer 1006 is input to the base station 1002. The base station is
The O / E converter 1008 converts an optical signal into an electric signal,
This is taken in as a central station transmission signal. The output signal of the base station module 1002 is converted from an electric signal to an optical signal by the E / O converter 1009, and then the optical multiplexer 1007.
And are transmitted to the central station module 1001 through the optical fiber cable 1005.

The base station module 1002 has a configuration in which an O / E converter 1008 and an E / E converter are provided in the interface section with the central station.
The configuration is the same as that of the base station shown in FIG. 6 except that an O converter 1009 is provided.

Further, the optical fiber cable 1005 is connected with an optical amplification amplifier 1010 for securing an optical signal level necessary for transmission.

With the above configuration, it is possible to provide a wireless communication system that achieves distribution from a central station to a plurality of base stations and multiplexing of signals transmitted from each base station to the central station, and that keeps installation costs low. Is possible. Further, since the modulator / demodulator and the like can be collectively managed by the central station, the cost of the base station can be kept low.

By the way, when connecting a central station and a base station with an optical fiber, it is conceivable to introduce a method of wavelength division multiplexing a signal distributed to each base station. As a method for realizing such a method, there is a "Technical Research Report RCS
97-41, Working on Broadband Wireless Access Technology for Millimeter-wave Band ". This transmission method is shown in FIG. In this transmission system, the central station and the base station are wavelength-multiplexed for each antenna sector of the base station. However, it is known that the equipment (optical wavelength division multiplexer WDM) required to realize wavelength multiplexing is generally expensive.

On the other hand, in the radio communication system according to the present invention, since time division multiplexing is performed in the state of electric signals, expensive WDM is not required, and the cost can be suppressed.

Although SW1 is an electrical switch in FIG. 10, it may be replaced with an optical switch. In this case, SW1 is the optical demultiplexer 1006.
And O / E converter 1008 and E / O converter 1009
And the optical multiplexer 1007. Further, although the example in which the RF signal is transmitted to the optical fiber cable 1005 is described in FIG. 10, the IF signal may be transmitted.

When transmitting an IF signal through an optical fiber cable, a frequency converter is required at the base station. Figure 1
2 shows a configuration example of the base station in this case. As shown in the figure, this IF signal transmission type base station has two frequency converters 1101-1 and 111-1 in addition to the base station configuration shown in FIG.
01-2, a local frequency oscillator 1102, and two filters 1103-1 and 1103-2 are added.

Next, the transmission of control signals between the base station and the central station will be described.

FIG. 13 shows an arrangement of the frequencies of the RF or IF signal transmitted to the signal line or the optical fiber cable and the control signal transmitted from the central station to the base station in the present wireless communication system. The RF signal is a signal radiated from the antenna of the base station or received by the antenna, and the IF signal is a signal radiated from the antenna of the base station or frequency-converted through the frequency conversion. The frequency of the control signal from the centralized station to the base station exists in a lower range than the RF signal or the IF signal.

The control signal transmitted from the central station to the base station is a signal for controlling SW1 and SW2 and for controlling the local oscillation frequency, and is a separate signal for each base station. The control signal of each base station is transmitted by frequency division or code division multiplexing, and separated and extracted by the control device of each base station. Each base station is assigned a unique number (base station module address) in a base station group connected to a certain central station, and the control signal separation / extraction method is changed for each address. The base station module address is set by the address setting device provided in the base station.

FIG. 14 shows a simplified time response waveform of the RF or IF signal transmitted to the signal line or the optical fiber cable and the control signal transmitted from the central station to each base station. Actually, the RF signal or I
Since the F signal and the control signal are multiplexed, such a waveform does not occur. Further, the control signal for each base station is modulated and multiplexed for each base station. As shown in the figure,
The RF or IF signal transmitted to the signal line or the optical fiber cable has a portion 1201 where the power is not 0 and a portion 1202 where the power is 0. The base station module control signals # 1 to #n (1203-1 to 1203-n) are
In the portion 1202 where the power of the RF signal or the IF signal is 0, it changes to H or L. Where H and L
Indicates the level of the control signal, which corresponds to the state in which the SW is ON or OFF, respectively.

Generally, the switch for switching the signal is
It has a constant operation delay with respect to a change of → L and a change of L → H. Therefore, even if the control signal changes at high speed, the switch has a limit in tracking speed due to this operation delay. As a matter of course, there is an operation delay also in SW1 and SW2 provided in the base station.

If the operation delay of this switch causes RF
When the signal or the IF signal is cut off, the signal band of the RF signal or the IF signal is expanded (the spectrum is expanded). This is the same phenomenon that the spectrum spreads when a certain continuous signal is cut out with a certain window width.
Since the RF signal or the IF signal is a burst signal in the first place, a ramp-up signal and a ramp-down signal are added to the beginning and the end of the burst in order to prevent the signal band from expanding due to this phenomenon. When this ramp up ramp down signal is being transmitted, SW1 and SW2
When the state transition (H → L or L → H) in (3) is matched, the signal band is expanded.

Therefore, in this embodiment, at the change point of the value of the control signal for switching the switch, the RF from the central station to the RF of each base station is set so that the power of the RF or IF signal transmitted to the signal line becomes zero. It controls the transmission of signals or IF signals. This makes it possible to set the switch response speed in the base station to a relatively moderate value. That is, it is possible to suppress the cost of the base station itself while preventing the expansion of the signal band.

Next, details of the centralized station in the wireless communication system of this embodiment will be described with reference to FIG.

As shown in the figure, the central station is an interface device 150 with the barkbone network.
1, an IF or RF signal transmission / reception device 1502, a base station module control signal transmission / reception device 1503, a hybrid circuit 1504, and a control device 1505.
The IF or RF signal transmission / reception device 1502 is a modem 15 that performs modulation / demodulation of IF or RF signals and signal processing
11, a DAC (digital-analog converter) 1512 that converts a digital signal output from the modem 1511 into an analog signal, a filter 1513 that blocks harmonic components included in the DAC output, LNAs (low noise amplifiers) 1514a and 1514b, direction matching Duplexer 151
5, a signal power control device 1516, a filter 1517 for blocking unnecessary waves other than the signal band, a filter 1518 for blocking harmonic components of a signal input to the ADC, and an ADC (analog-digital converter) 1519.

Base station module control signal transmission / reception device 1
Reference numeral 503 denotes a modem 1521 that performs modulation / demodulation of the base station module control signal and signal processing, a DAC (digital-analog converter) 1522 that converts a digital signal output from the modem 1521 into an analog signal, and a harmonic component included in the DAC output. 1523, LN for blocking
A (low noise amplifier) 1524a and 1524b, direction matching demultiplexer 1525, filter 1526 that blocks unnecessary waves other than the control signal band, filter 1527 that blocks harmonic components of the signal input to the ADC, ADC (analog-digital) Converter) 1528. The control signal of the base station module and the RF or IF signal are
The signals are multiplexed in the frequency arrangement shown in FIG. Signal power control device 151 in IF or RF signal transmission / reception device
Reference numeral 6 controls the power of the RF or IF signal transmitted to the signal line, that is, controls to set the power of the RF or IF signal to 0 at the change point of the value of the control signal for switching the switch of the base station.

The control device 1503 controls the modem 1511 and the signal power control device 1516 of the IF or RF signal system transmitting / receiving device 1502, and further controls the base station module control signal system transmitting / receiving device 1503.

The information signal demodulated by the modems 1511 and 1521 and subjected to signal processing is input to the control device 1505. The information signal input to the control device 1505 is a terminal identifier, a cell number in which the terminal is located, an ID indicating the type of control signal, and other information transmitted from the terminal to the base station. The control device 1505 manages the resources based on these pieces of information and controls the modems 1511 and 1521 to generate the frame shown in FIG. At the same time, the control device 1505 controls the modem 1521 of the base station module control signal transmission / reception device 1503 to generate control signals such as enable (enable / disable control) of the base station module and enable of the sector antenna of the base station module. To do.

In the configuration of the centralized station shown in FIG. 15, the base station module control signal transmission / reception device 1502 is shown as capable of transmitting / receiving, but it may be capable of transmitting only. Further, each transmission / reception device can also be configured by incorporating a frequency conversion device.

Next, the operation procedure of the wireless communication system of this embodiment will be described.

FIG. 16 shows the operation procedure of the wireless terminal. The figure is a flowchart showing the operation when the wireless terminal shifts to the communication mode at the same time when the power is turned on.

When the power is turned on, the wireless terminal receives the transmission signal from the base station while switching the terminal antenna sector, and monitors the control signal including the identifier indicating the all-cell scan (step 1301). Wireless terminals
This monitoring operation is performed only for several frame times, and if the control signal including the identifier indicating all-cell scanning cannot be received, it is determined that the service signal is outside the service area. The wireless terminal uses Step 13 of the all-cell scan search.
At 01, symbol synchronization, slot synchronization, and frame synchronization are performed, and the timing at which all-cell scan subframes are transmitted is specified. Each burst slot signal contains a synchronization preamble.

Next, the wireless terminal creates a reception power table using the signal transmitted in the all-cell scan subframe (step 1302). As described above, this received power table is created using the base station antenna sector number and the terminal antenna sector number as parameters. The reception power table is created as described above with reference to FIG. The wireless terminal uses this received power table to determine the terminal antenna sector and the base station antenna sector used for the subsequent communication. At this stage, the wireless terminal knows only the base station antenna sector number.

Next, the wireless terminal receives the base station ID notification subframe and grasps the base station number from the base station antenna sector number (step 1303). The details of the method for ascertaining the base station ID are as described above with reference to FIG.

Next, the wireless terminal transmits a reservation signal to the base station using the contention slot corresponding to the desired base station in the all-cell scan subframe (step 1).
304). Since the competition slot is provided for each base station ID, it is necessary to grasp the base station ID in step 1303. Examples of the reservation signal transmitted from the wireless terminal to the base station include location registration, call request notification, and call notification response. The reservation signal transmitted to the base station includes an ID indicating the type of the control signal (an ID indicating a call request, an ID indicating an incoming call notification, an ID indicating a location registration) and the I of the own terminal.
D, other information is included. Examples of other information include QoS. By transmitting QoS information, high-speed demand assignment control and bandwidth allocation control,
It is possible to support non-immediate data communication.

Next, the wireless terminal receives the signal transmitted from the base station in the communication timing allocation subframe, checks whether or not the signal includes an ID (identifier) indicating its own terminal, and the reservation signal is transmitted to the base station. It is judged whether or not it is transmitted to the station (step 1305). The terminal, which has not received the response signal addressed to itself in the communication timing allocation subframe, attempts transmission of the reservation signal again according to an arbitrary probability in the next all-cell scan. The terminal which has received the response signal addressed to itself in the communication timing allocation subframe grasps the communication timing in the specific terminal communication subframe from the response signal. By transmitting the communication timing information, the terminal can receive intermittently. As a result, the power consumption of the terminal can be reduced.

Next, the terminal performs burst communication with the base station at a predetermined timing in the specific terminal communication subframe (step 1306).

The transmission of the reservation signal of the terminal which communicates over a plurality of frames shifts to the specific terminal scan subframe. This contributes to the reduction of the collision occurrence rate in the contention slot of the all-cell scan subframe. This is because the contention slot is random access. In the specific terminal scan subframe, the base station transmits a signal carrying a terminal identifier. The wireless terminal receiving this signal transmits a reservation signal similar to the reservation signal transmitted in step 1304 (step 1307). The wireless terminal updates the received power table periodically (table update interval). Step 1 if updating the table
Before 307, the received power table is updated using the signal transmitted in the all-cell scan subframe (step 1308), and the base station ID is grasped in the subsequently transmitted base station ID notification subframe (step 1308). 130
9). A wireless terminal that needs to change the base station antenna sector requests the base station to change the base station antenna sector by a reservation signal in the specific terminal scan. The wireless terminal that has completed the communication shifts from the communication mode to the standby mode after the specific terminal communication. The terminal that has entered the standby mode monitors the all-cell scan signal and performs intermittent reception until an incoming call notification is made.

The frame structure adopted in the control signal transmission system according to the present invention is specified by time timing management with reference to the transmission timing of all-cell scan subframes. The following shows that frames are specified by time timing management. It is assumed that the wireless terminal receives a base station transmission signal in an all-cell scan subframe. The received signal includes an identifier indicating all-cell scan, the number of all-cell scan subframes n _BS , base station antenna sector number u (u = 1, 2, ..., N _BS ), slot number v (v = 1 , 2, ..., N _MS , n _MS includes the maximum number of terminal antenna sectors, that is, the number of repetitions of base station transmission signals transmitted in all cell scan sub-subframes.

The time difference Δt ₁ between the reception slot and the start timing of the all-cell scan subframe is given by the following equation.

Δt ₁ = T _SS · (u−1) + 2T _slot · (v−1) (1) Here, all cell scan sub-subframe length T _ss = 2T
is a _{slot · (n MS + K B} · α). K _B indicates the number of base station modules collectively managed by the central station.

The wireless terminal creates a reception power table determined from the set of base station antenna sector and terminal antenna sector, and determines the optimum set of base station antenna sector and terminal antenna sector. After that, the reservation signal is transmitted to the base station in the contention slot corresponding to the desired base station antenna sector.

The w-th base station (w = 1, 2, ..., K _B ),
Time Δt from the start timing of the all-cell scan subframe of the contention slot of the u-th base station antenna sector
₂ is given by Δt ₂ = T _ss · (u−1) + 2 · T _slot · (n _MS + w−1) + T _slot (2) A desired contention slot is specified by Δt ₁ and Δt ₂ . From the above, the frame is specified by the time timing management based on the all-cell scan subframe signal.

The central station manages frames, resources, and terminals. As described above, the frames are sequentially controlled according to the timing.

Next, the procedure of controlling the central station will be described with reference to FIG.

First, the centralized station creates an all-cell scan signal by controlling the modem 1511 of the IF or RF signal transmission / reception device 1502 shown in FIG. next,
The reservation signal transmitted from the wireless terminal in the contention slot is received and demodulated (step 1401). After that, the modem 1 of the base station module control signal transmission / reception device 1503
A base station ID notification signal is generated and transmitted by controlling 521 (step 1402).

After this, the specific terminal scan is started. In the specific terminal scan, a terminal whose communication has not ended in one frame is captured. In order to transmit the control signal from the cell in which the terminal is located, the central station controls the modem 1521 of the base station module control signal transmission / reception device 1503 to generate a control signal for controlling the desired base station module. At the same time, it controls the modem 1511 of the IF or RF signal transmission / reception device 1502 to generate a specific terminal scan signal. Further, the reservation signal from the terminal is demodulated (step 1403).

After that, resources are distributed to the terminals that have transmitted the reservation signal in the all-cell scan and the specific terminal scan, using the information included in the reservation signal (step 1404). At this point, the start timing of the specific terminal communication is determined.

[0100] Next, the communication timing is assigned.
In the communication timing allocation, the central station transmits the control signal from the cell in which the wireless terminal is located, so that the central station controls the modem 1521 of the base station module control signal transmission / reception device 1503 to control the desired base station module. Generate a control signal. At the same time, it controls the modem 1511 of the IF or RF signal transmission / reception device 1502 to generate a communication timing allocation signal (step 1405).

Next, the specific terminal communication is started. In specific terminal communication, a control signal is generated in the same manner, and communication is performed using the serving cell of the wireless terminal (step 1406). After the communication with the specific terminal, the whole cell scan is performed again.

The order of the subframes described above is an example and may be set arbitrarily.

Further, the present invention can be implemented by variously modifying the above-described embodiment within the scope of the technical idea thereof.

[0104]

As described above, according to the present invention,
Since a control signal for terminal position detection is simultaneously transmitted from the common base station antenna sector of each base station,
It is possible to suppress the ratio of the transmission amount of the control signal to the entire signal band, and improve the transmission efficiency.

According to the present invention, the wireless terminal determines the combination of the terminal antenna sector (directivity of the base station antenna) and the base station antenna sector (directivity of the terminal antenna) used for communication. The control load on the base station can be reduced, and the system can be speeded up.

Further, according to the present invention, it is possible to realize a system configuration in which a plurality of base stations are serially connected to a central station for controlling each base station, so that a large number of base stations are installed in one service area. In this case, the total cost can be kept low, and the cost for each base station can be kept low by collectively providing the modulator / demodulator and the like in the central station.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of a wireless communication system according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of cell arrangement in the wireless communication system of the present embodiment.

FIG. 3 is a diagram showing a configuration of a frame of a signal transmitted / received between a base station and a wireless terminal in the wireless communication system of the present embodiment.

FIG. 4 is a diagram for explaining a method of determining a combination of a base station antenna sector and a terminal antenna sector used for communication in the wireless communication system of the present embodiment.

FIG. 5 is a diagram showing a configuration of a base station ID notification subframe of the wireless communication system of the present embodiment.

FIG. 6 is a diagram showing a configuration of a base station and a connection form between the base station and the central station in the wireless communication system of the present embodiment.

FIG. 7 is a diagram showing another embodiment of a base station in the wireless communication system of the present invention.

FIG. 8 is a diagram showing mounting positions of switches of a base station module in the wireless communication system of the present invention.

FIG. 9 is a diagram showing another mounting position of the switch of the base station module in the wireless communication system of the present invention.

FIG. 10 is a diagram showing a configuration of a base station and a connection form between the base station and the central station in a wireless communication system according to another embodiment of the present invention.

FIG. 11 is a diagram showing a conventional example of a wireless communication system in which a base station and a central station are connected by an optical fiber cable.

FIG. 12 is a diagram showing a configuration example of a base station in the case of transmitting an IF signal using an optical fiber cable in the wireless communication system according to the embodiment of the present invention.

FIG. 13 is an RF or IF transmitted through a signal line connecting a base station and a central station of the wireless communication system of this embodiment.
It is a figure which shows the frequency distribution of a signal and a control signal.

FIG. 14 is a diagram showing a simplified time response waveform of an RF or IF signal and a control signal transmitted to a signal line in the wireless communication system of the present embodiment.

FIG. 15 is a diagram showing a configuration of a central station in the wireless communication system of the present embodiment.

FIG. 16 is a flowchart showing an operation procedure of a wireless terminal of the wireless communication system of the present embodiment.

FIG. 17 is a flowchart showing an operation procedure of a base station of the wireless communication system of the present embodiment.

[Explanation of symbols]

10 ... Service area 11, 12, 13, 14 ... Base station 15 …… Cell 16: Central station 17: Wireless terminal 102 ... All-cell scan subframe 103 ... Base station ID notification subframe 801 ... Signal line 803 ... Base station module 804, 808 ... Switches (SW1, SW2) 805, 807 ... Directional multiplexer / demultiplexer 809-1 to 809-n ... Base station antenna 1502 ... IF or RF signal transmission / reception device 1503 ... Base station module control signal transmission / reception device 1516 ... Signal power control device

Claims (4)

(57) [Claims] And 1. A plurality of base stations having a plurality of base station antenna sector corresponding to a plurality of cells that cover the communication area of the wireless terminal, said from the base station antenna sector in the same direction of each base station, The first including the identification information of the base station antenna sector
Each of the control signals simultaneously includes the identification information of the base station.
Means for controlling the second control signal to be transmitted at different times while switching the base station antenna sector periodically, and the first control signal from each base station while periodically switching the terminal antenna sector. the terminal Ann receives the control signal
Before the received power measured for each Tenasekuta, the determined terminal antenna sector and with said base station antenna sector to be used for communication based on the received power of each of the terminal antenna sector was measured and received through the antennas sector
A wireless communication system comprising: a wireless terminal having means for transmitting a third control signal to the base station based on identification information of the base station included in the second control signal . 2. A plurality of base stations having a plurality of base station antenna sector corresponding to a plurality of cells that cover the communication area of the wireless terminal, said from the base station antenna sector in the same direction of each base station, The first including the identification information of the base station antenna sector
Each of the control signals simultaneously includes the identification information of the base station.
A central station for controlling the second control signal to transmit while periodically switching the base station antenna sector at different times; a line for serially connecting the base stations to the central station; While periodically switching the antenna sector, the first control signal from each of the base stations is received to receive the terminal control signal.
Before the received power measured for each Tenasekuta, the determined terminal antenna sector and with said base station antenna sector to be used for communication based on the received power of each of the terminal antenna sector was measured and received through the antennas sector
Serial wireless communication system, characterized by a radio terminal having a third hand stage that sends a control signal to the base station based on the second the identification information of the base station included in the control signal. 3. An apparatus according to claim 1 or 2, wherein the wireless communication system, time slots said means of said wireless terminal, corresponding to the desired base station among the base stations each assigned transmission timeslot group To the third control signal
Wireless communication system, characterized by transmitting to the base station. 4. The wireless communication system according to claim 2, comprising a plurality of switching means for respectively opening and closing lines between the central station and the individual base stations, the switching control signal being output from the central station. It further comprises a plurality of switching means opened and closed based on the above, and means for controlling the power of the RF signal or the IF signal transmitted to the line at least at the change point of the value of the switching control signal. Wireless communication system.