JP3177481B2 - Base station of mobile 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 personal handy phone system (hereinafter referred to as PHS) for performing wireless communication with mobile stations in a service area by a diversity system.
And a base station of a mobile communication system.

[0002]

2. Description of the Related Art In recent years, communication services for wirelessly communicating between a plurality of mobile stations and a base station have become widespread, and today, PHSs capable of providing such communication services at lower call rates are available. Has been put to practical use. In such a PHS, the transmission output of the base station side device is reduced to reduce the size and cost of the base station side device. By reducing the transmission output of the base station-side device, the service area of each base station is reduced, and accordingly, a large number of base stations are installed such that the mutual installation interval is reduced.

FIG. 21 shows a conventional TDMA / TDD for communication between a base station CS of a PHS and a mobile station PS.
(Time Division Multiple Access / Time Division Dup
lex) frame (hereinafter abbreviated as TDD frame). In the figure, “#” represents an individual time slot, “T” represents transmission, and “R” represents reception. Also, PHS standard (RCR STD-28)
Thus, each TDD frame is set to 5 msec, and each time slot is set to 625 μsec.

In the conventional PHS, each T shown in FIG.
# 1 (time slot 1) of the DD frame is used as a control physical slot, and # 2 (time slot 2), # 3 (time slot 3) and # 4 (time slot 4) are used as communication physical slots. It is used. Each base station CS transmits the control channel # 1 (ie, # 1T and # 1R) once every 100 msec.
, The mobile station P located in its own service area
Communication for location registration of S and setting of a communication channel for the mobile station PS is performed. Each base station CS and each mobile station PS perform communication on the control channel # 1, for example, the carrier number 71 (1) defined in the PHS standard.
916.150 MHz).

[0005] In the traffic channel setting process, the base station CS allocates one free slot of the traffic channels (# 2 to # 4) to the corresponding mobile station PS. Further, the mobile station PS is assigned one carrier frequency for making a call in the assigned slot from the available carriers for outdoor public communication carriers defined in the PHS standard. The mobile station PS moves to the assigned communication channel and performs a call using the assigned slot and frequency.

[0006] When communication between the base station CS and the mobile station PS is performed by wireless communication as in the above PHS, the base station CS and the mobile station PS are subject to fading or the like.
It is an unavoidable problem that the call state between the user and the server deteriorates. The fading is, for example, that a reflected wave or a diffracted wave when a radio wave transmitted from a base station is once reflected on a building or the like and reaches a mobile station and a radio wave directly reached from the base station to the mobile station interfere with each other. It refers to the deterioration of communication quality caused by mutual interaction. For this reason, conventionally, for example, a communication method such as reception diversity or transmission diversity has been used so as to keep communication between the base station and the mobile station in a stable communication state.

[0007] Diversity means that the correlation between them is small, that is, the probability that the communication quality is simultaneously deteriorated is small.
One or more systems are prepared and their outputs are selected or combined to reduce the effect of fading.
Among the reception diversity, for example, radio waves are received by a plurality of antennas installed at predetermined intervals or more, and the largest reception signal level (RSSI: Received SSignal Strength Indicator) of both antennas is received.
) Is selectively demodulated and used for the content received by the antenna that caused the above. In addition, transmission diversity includes, for example, a method in which communication is received by a plurality of antennas installed at predetermined intervals or more, and transmission is performed by the antenna that has generated the largest received signal level among the antennas. There is.

[0008] As described above, in the conventional PHS,
In order to provide the above-mentioned communication service to subscribers at a low telephone charge, the transmission output of the base station side device is reduced, thereby reducing the size and cost of the base station side device. In particular, in locations where the cost of securing individual base station installation locations is relatively high, such as in urban areas or in the central area of the Tokyo metropolitan area, if the number of installed base stations is large, the cost of the base station side device may be low. However, there is a problem that the installation cost of the base station becomes very high. For this reason, even if it is unavoidable to increase the price of each base station side device by increasing the functionality and output of the base station to some extent,
There is a strong demand to reduce the installation density of base stations.

[0009] In an urban area or a central area of the metropolitan area, not only the cost for securing the installation location of the base station is high, but also the communication traffic per unit area is often high. If the installation density of base stations is simply reduced in such a place, the quality of the communication service to be provided will be reduced, and it will not be an essential solution. In order to solve the above two problems, that is, to reduce the installation density and not to lower the communication service, the individual base station apparatuses not only increase the transmission power and increase the reception sensitivity but also increase the mobile reception. The number of simultaneous connections to the station per unit time must be increased.

On the other hand, the following method can be specifically considered. That is, by assigning different carrier frequencies to the same time slot and using a plurality of TDD frames at the same time, one base station can relay communication contents to more mobile stations. is there. FIG. 22 shows two TDs assigned different carrier frequencies to the same time slot.
FIG. 9 is an explanatory diagram showing channel assignment on the base station side of each TDD frame when using a D frame. In the figure, “#” represents an individual time slot, and “T”
Indicates transmission and “R” indicates reception.

The first TDD frame shown in FIG. 22 is composed of # 1 (time slot 1) to # 4 (time slot 4) for both uplink and downlink, and is the same as the TDD frame shown in FIG. That is, # 1 is used as a control channel, and communication on the control channel is performed using carrier number 7
1 (1916.150 MHz). # 2 to # 4 are used as communication channels.

[0012] The second TDD frame shown in FIG.
It is synchronized with the TDD frame, and consists of # 5 (time slot 5) to # 8 (time slot 8) for both uplink and downlink. Since # 1 of the first TDD frame has already been allocated as a control channel, # 5 to # 8 of the second TDD frame can all be used as communication channels.

Regarding the carrier frequency assigned to each communication channel, a carrier frequency different from that of the control channel # 1 is naturally assigned to the communication channel # 5. Further, among the communication channels used at the same time, different carrier wave frequencies are allocated to the first TDD frame and the second TDD frame from among the open frequencies for outdoor public communication other than the carrier number 71. For example, different carrier frequencies are assigned to # 2 of the first TDD frame and # 6 of the second TDD frame.

By using the two TDD frames set as described above, each base station can use two TDD frames.
It is possible to relay the communication to one more mobile station, that is, seven mobile stations than to relay the communication at 00. FIG. 23 is a PHS base station 50 that communicates with a mobile station using the two TDD frames shown in FIG.
It is a block diagram which shows the principal part of 0.

The base station 500 shown in FIG.
Antenna 504, transmission / reception changeover switch 511 to transmission / reception changeover switch 514, reception unit 521 to reception unit 524, determination unit 531, selection unit 532, HPA (High Power Amp.)
541, an HPA 542, a transmission / reception switch 551, a transmission / reception switch 552, and combiners 561 to 564.

The transmission / reception switches 511 to 514 switch transmission / reception of the corresponding antennas 501 to 504 in accordance with the downlink / uplink of the time slot of the TDD frame. The receiving units 521 to 524 have the same configuration, and the corresponding antennas 501
From the received signals received at .about.504, two modulated signals having a carrier frequency assigned to the time slot are extracted. Further, receiving sections 521 to 524 measure the received signal levels of the extracted modulated signals, and output the measured values to determination section 531.

The determining unit 531 receives the receiving unit 521 to the receiving unit 524 in each uplink time slot of the TDD frame.
Among the measured values of the received signal level of the system 1 according to the above, the measured value indicating the largest received signal level is determined, and the antenna that has given the maximum received signal level is determined, and the selecting unit 5
32. At the same time, the receiving units 521 to 524
Among the measured values of the received signal level of the system 2 by the above, the measured value indicating the largest received signal level is determined, the antenna that has given the maximum received signal level is determined, and the result is output to the selection unit 532.

In each of the downstream time slots of the TDD frame, the selecting section 532 further determines, by the determining section 531, of the two antennas determined by the determining section 531 in the corresponding immediately preceding uplink (receiving) time slot. A select signal is output to the transmission / reception switch 551 and the transmission / reception switch 552 so that one of the combiners 561 to 564 corresponding to the antenna having the higher maximum received signal level is selected.

The HPA 541 amplifies a modulation signal to be transmitted to a mobile station assigned to each time slot of the first TDD frame, that is, a modulation signal of the system 1, and outputs the amplified signal to the transmission / reception switch 551. HPA542
Amplifies the modulated signal to be transmitted to the mobile station allocated to each time slot of the second TDD frame, that is, the modulated signal of system 2, and
Output to 2.

The transmission / reception switch 551 is connected to a selection unit 532.
Synthesizers 561 to 5 according to the select signal from
One of the four output terminals connected to each of the 64 is selected, and an amplified modulated signal of the system 1 as an input thereof is output from the selected output terminal. The transmission / reception switch 552 selects one of the four output terminals connected to each of the combiners 561 to 564 according to the select signal from the selection unit 532, and selects one of the four output terminals from the selected output terminal. Amplified system 2 as input
Output the modulated signal. As a result, in the transmission / reception changeover switch 551 and the transmission / reception changeover switch 552, the selection unit 5
The output terminal connected to the same combiner is selected according to the select signal from 32.

Each of the combiners 561 to 564 has the same configuration, and when the modulation signal of the system 1 and the modulation signal of the system 2 are input according to the select signal of the selection unit 532, , And mixes the two inputs to output to the corresponding transmission / reception changeover switch. The mobile station corresponding to the base station 500 has a carrier frequency of the carrier number 71 (1916.150 MHz) while in the standby state.
The base station 500 communicates with the base station 500 using the control channel assigned to # 1 of the TDD frame, and performs its own location registration and the like. Further, after the communication channel and the carrier frequency are allocated by the base station 500, the base station 500 sets its own reception frequency and transmission frequency to the allocated frequencies,
Communication is performed using the assigned communication channel.

With the above configuration, the number of base stations 500 is one,
It is possible to relay communication to up to seven mobile stations in the service area, and to perform high-quality relay of mobile station communication by performing reception diversity and transmission diversity using four antennas. can do. In addition, since the base station 500 can relay communication without adding a new component to the configuration of the mobile station, a conventional mobile station can be used in the PHS.

Since the combiners 561 to 564 have the same configuration, a specific configuration of the combiner 561 will be described below. FIG. 24 is a diagram showing a specific configuration of the synthesizer 561. In the figure, the input side of the synthesizer 561 is shown on the left side with respect to the paper. This combiner 561 is formed, for example, in a branch line type pattern shown in FIG. 24, and one end on the output side of the pattern is provided with a 50Ω termination resistor that is impedance-matched in the transmission path of the modulation signal of each system. Grounded. The other end on the output side of the pattern is connected to a transmission / reception switch 511.

When the combiner 561 is selected by the transmission / reception switch 551 and the transmission / reception switch 552, the transmission / reception switch 55 is provided to the combiner 561.
1 and each input terminal corresponding to the transmission / reception switch 552,
The modulated signal amplified by the HPA 541 (the carrier frequency f
1) and the modulated signal (carrier frequency f2) amplified by the HPA 542 are input.

[0025]

The HPA 54
1 and the output of HPA 542 reach the antenna for the first time via the antenna switch, the combiner, and the transmission / reception switch, respectively. Each of the antenna changeover switch and the transmission / reception changeover switch is the HPA
In the transmission path from the antenna to the antenna, and the transmission power loss due to these is 1 dB in total for each system.
1.5 dB. Further, the loss of the transmission output in each combiner is even greater. Specifically, as is clear from the pattern shown in FIG. 24, in the combiner 561, any input is connected to the output terminal and the ground terminal. At the output end, about 50% of the input power is lost. FIG. 25 is an explanatory diagram illustrating power loss in the combiner 561. In FIG. 25, the horizontal axis represents the carrier frequency of the modulated signal input to the combiner 561, and the vertical axis represents the power ratio of the combiner 561. As shown in FIG. 25, the power loss of only the combiner 561 is 3 dB.

As described above, according to the base station 500 of the prior art, the HPA 541 or HPA 542 is
In the range from 1 to 504, if the loss due to the switch and the wiring is included in addition to the combiner, there is a problem that a transmission output loss of as much as 4 to 4.5 dB occurs at a power ratio. Also,
To increase the transmission power of the base station 500 to 500 mW against such a large power loss, the HPA 54
1 and the output of the HPA 542 need to be set at least twice as large. Since the HPA element itself is a very expensive component with good high frequency characteristics such as GaAs FET, the base station 500
There is a problem that a large cost is required for the manufacture of the product.

Further, since the output power is large, the power consumption is also large, and there is a problem that the cost for maintaining the base station such as the electricity bill is increased. Also, the synthesizers 561 to 5
HPA is provided at the subsequent stage of each of the 64
A method of compensating for the loss of 564 is also conceivable. In this case, the outputs of the combiners 561 to 564 must be collectively amplified by using one linear amplifier. However, similarly to the above-described method, the modulation signal is output while maintaining the linearity with good quality over a wide dynamic range. Since an expensive linear amplifier that can amplify must be used, the base station 5
However, there is a problem that a large cost is required for manufacturing the C.00.

Further, since each of the two systems of high-frequency outputs is distributed to an arbitrary one of the four antennas, the circuit configuration of the radio system (high-frequency circuit portion) is complicated, and wiring design is very difficult. There was also a problem. Because
This is because in a high-frequency circuit, coupling between lines is likely to occur, and consequently spurious is likely to occur. Therefore, it has been difficult to reduce the size of the high-frequency circuit.

In view of the above problems, an object of the present invention is to provide a base station of a mobile communication system capable of suppressing an increase in cost and performing more simultaneous connection processing while maintaining communication quality. It is another object of the present invention to provide a base station of a mobile communication system in which wiring design of a high-frequency circuit is easy and the size can be reduced.

[0030]

According to the present invention, there is provided a base station of a mobile communication system for performing diversity according to the present invention, comprising: first and second generating means for generating a high-frequency transmission signal; Antennas, switch means for switching the connection between the output terminal of each generating means and the plurality of antennas, first and second data output means provided in the same number as the generating means and outputting transmission data, first and second data output means, The transmission data from the data output means is replaced with straight or cross, and the first,
Replacement means for inputting to the second generation means.

[0031]

FIG. 1 is a circuit block diagram showing a configuration of a main part of a base station 600 according to an embodiment of the present invention. The base station 600 is roughly divided into an antenna switching unit, an RF (high frequency) unit, an IF (intermediate frequency) unit, and a baseband unit in order from the high frequency output side, and performs two reception / transmission diversity operations using four antennas. Using the carrier of the system, wireless communication is performed with a plurality of slaves using the TDMA / TDD frame shown in FIG.

The antenna switching unit includes four antennas 401 to 4 selectively used for reception / transmission diversity.
04, band-limiting filters 405 to 408 for passing only signals in the communication band from the received signal, and transmission / termination resistance changeover switches 481, 482, 487, 488.
And transmission / reception changeover switches 483, 484, 485, 4
86, circulators 491-494 which are multi-port passive non-reciprocal elements having a function of outputting a port input to an adjacent port in a specific direction, and antenna switching for connecting a transmission signal of each system to an arbitrary antenna in a transmission time slot Switches 495 and 496 and C / N ratio (carrier
low noise amplifiers 415 to 418 that amplify the received signal input through the band-limiting filters 405 to 408 in the reception time slot with little deterioration in the ratio of the received signal power to the receiver noise temperature) Isolators 419 and 420 that pass signals in only one direction, distributors 421 to 424 that distribute received signals of each antenna after amplification to two systems, respectively, and a high frequency that is an unnecessary wave generated during processing other than a carrier used for communication. Low-pass filters 425 and 426 for suppressing spurious signals, and a power amplifier (also referred to as HPA) 4 for amplifying to a power level for transmitting a signal.
27, 428.

In the antenna switching section, the circulators 491 to 494 function as a transmission / reception switch. Of these, circulators 492 and 493
Has a function of further selecting two types of transmission signals. Therefore, the circulators 492 and 493 are circuits to which diodes as shown in FIG. 2 are added. As shown in the figure, the circulator 492 (or 493)
Transmission / termination resistor changeover switch 482 (or 48
A diode that is turned on / off by a control signal from the control unit 446 is connected to the port on the 7) side. When this diode is on, the diode-connected port totally internally reflects the signal originally output to the outside. The totally reflected signal is output from the adjacent port. Thus, by turning on the diode, the transmission signal from the transmission / reception switch 485 can be totally reflected inside the diode-connected port and output to the port to which the antenna 402 is connected.

The antenna changeover switch 495 can switch the transmission signal of one system to the two antennas 401 and 402 and the antenna 403 via the circulator 493. The antenna changeover switch 496 is
The transmission signal of the other system is transmitted to the two antennas 403 and 404 and the antenna 402 via the circulator 492.
You can switch to In this configuration, it seems that only three of the four antennas can be used in each system, but it is configured to be able to use all four antennas in combination with switching of a cross switch 460 described later. However, the use of the same antenna at the same time is excluded.

The RF section includes a PLL synthesizer section 435,
Using the local frequency signal from 436, two stages of processing from the RF signal to the IF signal (from the IF signal to the RF signal) are performed for each of the two carrier waves. One system is configured around the receiving unit 431 and the transmitting unit 433, and the other system is configured around the receiving unit 432 and the transmitting unit 434. The local frequencies of the PLL synthesizers 435 and 436 are set by the PLL controllers 437 and 438, and are switched at the same time as the cross connection of the cross switch 460 described later.

In the RF unit, the receiving unit 431 receives RF signals from all four antennas via the RF unit at the time of reception, measures the received signal level of each antenna, and converts the RF signal into an IF signal. The detected measured value of the received signal level is output to the determination unit 445 via the A / D processing unit 443, and is used for antenna selection by reception / transmission diversity. Also, the transmitting unit 433 converts the IF signal from the IF unit into an RF signal at the time of transmission, and
PA 427, low-pass filter 425, isolator 4
Output to the antenna switching unit via 19. The same applies to the receiving unit 432 and the transmitting unit 434.

The IF section includes two systems, from an IF signal to a baseband signal (from a baseband signal to an IF signal).
The process up to the signal) is processed mainly by the modulation / demodulation units 451 and 452. The determination unit 445 and the control unit 446 in the IF unit
Performs diversity antenna selection control.

For each uplink (reception) time slot, the determination unit 445 determines the maximum reception signal level and the second highest reception signal level among the measurement values of the reception signal level input from the reception unit 431 via the A / D processing unit 443. And the second antenna with the maximum received signal level, and the second antenna
The second antenna to which the received signal level of the second is given is determined. Further, a combination of the maximum received signal level and the first antenna and the determined second antenna are output to the control unit 446 as a determination result. Similarly, the determination unit 445
Calculates the maximum reception signal level and the second highest reception signal level among the measurement values of the reception signal level input from the reception section 432 via the A / D processing section 444, and gives the maximum reception signal level. The first antenna and the second antenna given the second received signal level are determined. FIG. 3 shows an example of the determination result of the determination unit 445. In this figure, the order of the received signal level in each received time slot is shown for two carrier waves synchronized with the TDMA / TDD frame shown in FIG. In the figure, 1
Although all rankings from the eighth to the eighth are described, the judgment unit 4
In the case of two systems, only the first and second positions need to be determined for each system as described above. In the case of two systems, it is necessary to obtain up to the second place. If the two systems have the same received signal level and the first place antenna is the same, one is placed in the second place.
This is because the antenna is changed to the next antenna.

The control unit 446 determines the receiving unit 43 according to the determination result of the determining unit 445 in each reception time slot.
1 and 432 are instructed to convert the received signal corresponding to the first antenna determined from RF to IF. In addition, the control unit 446, based on the determination result, the cross switch 460, the antenna changeover switches 495 and 496,
By controlling the switch setting in combination with the circulators 492 and 493, two different carriers can be used.
Each of the four systems (based on the baseband signals of the TDMA processing units 471 and 472) is optimally distributed to the antennas among the four antennas.

More specifically, in each downlink (transmission) time slot, the determination unit 445 first determines that the two first antennas determined in the immediately preceding uplink time slot corresponding to the time slot correspond to the same antenna. Check if it is. As a result of the examination, if they are not the same, the switch setting of the above combination is controlled so that transmission is performed using the first antenna different for each system.

As a result of the examination, if they are the same, the maximum received signal level of the modulated signal of the system 1 and the maximum received signal level of the modulated signal of the system 2 are compared. A second antenna is selected for a modulation signal, and a first antenna is selected for a modulation signal of the other system, and transmission is performed using each antenna.
The switch setting of the above combination is controlled.

The baseband unit includes TDMA processing units 471 and 472 for inputting / outputting a baseband signal to / from the IF unit for each time slot so that data transmitted / received to / from a plurality of slave units is synchronized with a TDMA / TDD frame. 460. The cross switch 460 located between the baseband unit and the IF unit switches between straight connection and cross connection under the control of the control unit 446. In the cross connection, the TDMA processing unit 4
The two baseband signals from 71 and 472 are exchanged for the modulation / demodulation units 451 and 452 of the IF unit. In the case of cross connection, the PLL control unit 43 is controlled by the control unit 446 to simultaneously switch the carrier frequency.
7 and the local frequency setting for the PLL control section 438 are also exchanged. This makes it possible to switch the route from the baseband signal to the generation of the IF signal and the RF signal.

FIG. 4 shows a switch 409 by the control unit 446 in each transmission time slot and reception time slot.
414, and 414 are explanatory diagrams showing selection control logic for the cross switch 460. In the figure, the column of “selected antenna” shows the result of selection of the first and second transmission antennas by the control unit 446 during transmission. The selected antennas are excluded from the same antenna combination. At the time of reception, all four antennas are connected. The “antenna switching switch setting” column indicates the control logic of the switches 495, 496, 481 to 488, and 460 by the control unit 446, that is, the contents of the instruction to select the select signal output from the control unit 446 to each switch. "A,
B "indicates the distinction between the output terminals of the switches 495 and 496." a, b "indicates the switches 481 to 4 shown in FIG.
88 shows the input terminals. Cross switch 4
“S, C” of 60 means straight connection and cross connection, respectively. A to L in the “transmission” column indicate antenna selection patterns. FIGS. 6 to 17 are explanatory diagrams showing routes of transmission signals corresponding to this selection pattern. FIG. 18 is an explanatory diagram showing a route of a signal at the time of reception.

FIG. 5 is a flowchart showing the antenna selection processing for the downlink time slots of the first and second systems by the control unit 446, that is, the processing for determining the "selected antenna" shown in FIG. The control unit 446 receives the determination result of the determination unit 445 in the reception time slot, determines the transmission antenna for each system for the immediately following transmission time slot, and determines the transmission antenna determined for each system in the transmission time slot. Control to select.

First, when both the first system and the second system are in use in the time slot (step 231), the determination unit 445 determines the maximum received signal level in the first system and the second system. Is compared with the maximum received signal level (step 232). If the comparison result shows that the received signal level of the first system is smaller,
The antenna with the highest received signal level in the first system is provisionally determined as the next transmitting antenna for the first system (step 233), and the antenna with the highest received signal level in the second system is similarly determined. It is provisionally determined as the next transmission antenna for the second system (step 234). Further, when the result of the tentative determination of the first and second systems is the same antenna (step 235), the selection unit 132 further gives priority to the first system having the weakest maximum received signal level,
The transmitting antenna for the second system is changed, that is, an antenna other than the antenna tentatively determined for the first system (the second-ranked antenna) is determined as the transmitting antenna for the second system (step 236).

As a result of the comparison (step 232),
The same applies when the received signal level of the first system is not lower (steps 237 to 240). After that, the control unit 446 determines the antennas provisionally determined for the first system and the second system as transmission antennas in the next transmission time slot (step 241).

In this way, the first,
Different antennas are determined for the second system. In a transmission time slot immediately after the reception time slot, the control unit 446 controls each switch to select and transmit the first and second system antennas according to the determination result. As a result, the first and second transmission radio waves are output from different antennas.

The operation of the base station 100 according to the present embodiment configured as described above will be described. Now, in the determination result example of the determination unit 445 shown in FIG. 3, both the first system and the second system have the second time slot (RX2: RX2).
It is assumed that communication is performed using 6). In response to the determination result of the reception time slot, the control unit 446 follows the flow of FIG. 5 and determines that ANT1 (antenna 401) having the highest reception signal level in the first system and ANT4 (ANT4) having the highest reception signal level in the second system. Antenna 404) is determined as each transmitting antenna. Further, in the transmission time slot immediately after that, control section 446 performs the selection control. In this case, this corresponds to the selection pattern C in FIG. 4, and each switch is controlled as shown in the selection pattern C.
The route of the transmission signal of each system at this time is as shown in FIG.

Next, in the determination result of the determination unit 445 shown in FIG. 3, it is assumed that both the first system and the second system are communicating using the third time slot. In response to the determination result of the reception time slot, the control unit 446 follows the flow of FIG. 5, since the ANT1 has the highest reception signal level in both the first system and the second system. The system is determined as ANT1, and the second system is determined as ANT2 of the next rank. Further, in the transmission time slot immediately after that, control section 446 performs the selection control. In this case, it corresponds to the selection pattern A in FIG. The route of the transmission signal of each system at this time is as shown in FIG. In this case, the transmission signal of the second system is connected to the ANT 2 via the circulator 492 as shown in FIG.

In the determination result of the determination unit 445 shown in FIG. 3, it is assumed that both the first system and the second system are communicating using the fourth time slot. Also in this case the first
The system is determined to be ANT1, and the second system is determined to be ANT2. As a result, it is transmitted by the route of FIG. Note that the antenna changeover switches 495 and 496 may have three outputs instead of four outputs, and do not use a transmission path toward the transmission / reception switch 483 and the transmission / reception switch 486.

The positional relationship between the cross switch 460 and the modems 451 and 452 may be exchanged. In other words, even if the two systems are replaced with baseband signals,
The signal may be replaced by an IF signal. As described above, according to the present embodiment, the antennas are selected so that the transmission signals of each system are not transmitted by the same antenna.
A combiner becomes unnecessary, and power loss can be greatly reduced. As a result, the cost can be reduced with a low rank of the HPA.

In addition, since a part of the antenna switching is shared by the level of the baseband signal or the IF signal by the combination of the cross switch 460 and the circulators 492 and 493, the circuit configuration required for the switching for the RF component is accordingly provided. Is getting easier. The design and manufacture of the RF unit are facilitated. In the above embodiment, the base station includes four antennas. However, the number of antennas provided in the base station is not limited to four and may be any number. However, at least three or more are preferable. Also in this case, a receiving unit and a transmission / reception switch are provided for each antenna.

In the above embodiment, the base station
2 consisting of a first TDD frame and a second TDD frame
Although the communication with the mobile station is performed using two TDD frames at the same time, the number of TDD frames used by the base station is as follows.
Any number of frames may be used instead of two frames. As described above, when the base station uses three or more TDD frames at the same time, only one of the channels needs to be allocated as the control channel.
It is possible to relay communication to more mobile stations. However, if the base station simultaneously receives three or more frames of TDD
When frames are used, the base station includes the same number of HPAs, antenna changeover switches, reception selection switches, and demodulation circuits as the number of TDD frames used.
Further, each receiving unit is provided with the same number of tuning circuits and RSSI circuits as the number of TDD frames used. further,
The determination unit determines, for each TDD frame to be used, a combination of the received signal level in descending order and an antenna that gives the received signal level up to the rank corresponding to the number, and determines the determination result by a selection unit (or a control unit). Output.

Note that the selection unit (or the control unit) performs transmission diversity when the same antenna is determined as the first antenna for modulation signals of different systems corresponding to each TDD frame to be used. Allocates, to the first antenna, a modulated signal having the smallest maximum received signal level among the modulated signals having that antenna as the first antenna. Further, the modulated signal having the second lowest maximum received signal level is assigned to the second antenna of the modulated signal. If this second antenna is the same as the first antenna determined for modulated signals of other systems,
The modulated signal having the smaller received signal level provided by this antenna is assigned to this antenna. In this way, when the same antenna is determined for the modulation signals of different systems, the selection unit (or the control unit) gives priority to the modulation signal having the smaller received signal level given by the antenna. The modulated signal having a higher received signal level is assigned to a lower antenna.

For example, if the base station simultaneously receives three frames of TD
When using the D frame, the determination unit 131
TDD frame, second TDD frame and third TDD
For each modulated signal of system 1, system 2 and system 3 assigned to each of the same time slots in the frame, (maximum received signal level, first antenna giving the signal level), (second largest received signal Signal level,
The second antenna that gives the signal level) and the third antenna that gives the third highest received signal level and the signal level are determined.

FIG. 19 shows the received signal (RSSI) level of each system and the judgment result of the judgment unit for a certain up time slot when there are four antennas and three systems. The upper value of each system is the received signal level,
The lower numerical value is the ranking of the determination result. The values of the received signal level in the figure are those normalized for convenience. The selection unit (or the control unit) assigns an antenna using the above determination result. As can be seen in FIG.
Since the antenna 2 is determined to be the first order, the selection unit (or the control unit) compares the received signal levels of the systems 1 and 2 and assigns the antenna 2 to the smaller one. FIG.
In system 1, the reception signal level is 91, and system 2 is 90
Therefore, the antenna 2 is assigned to the system 2.

For system 1 to which the first-ranked antenna has not been allocated, the second-ranked antenna 1 is a candidate for allocation. Must be determined. In this case, the lower one of the received signal levels is assigned, so that the system 1 is assigned. As for the remaining system 3, since the antenna 2 is in the second order, unless there is another competing system,
Antenna 3 is assigned. FIG. 20 shows the correspondence between antennas and systems assigned as described above.

The above antenna allocating method at the time of transmission by the selection unit (or the control unit) is an example of selecting an antenna having the highest reception sensitivity as a transmission antenna for each system of modulated signals. However, each time the same antenna is selected as the transmitting antenna, the received signal level given by the corresponding modulated signal is compared even for the antenna determined as the first antenna without overlapping. For this reason, when the number of TDD frames used simultaneously increases, the time required for the transmission antenna selection processing becomes a problem. For this reason, if the same antenna is determined as the first antenna redundantly, the modulation signal having the smallest maximum received signal level among the corresponding modulation signals is assigned to the antenna as described above. For the modulation signals other than the modulation signal having the lowest maximum received signal level among the corresponding modulation signals, the second antenna is selected from the remaining antennas except for the antenna determined as the first antenna without overlapping. An antenna may be assigned.

To explain using a specific example, if the same antenna is determined as the first antenna in the modulation signal of the system 1 and the modulation signal of the system 2, as in the above-described embodiment, the system 1 The maximum received signal level of the modulation signal of the system 2 is compared with the maximum reception signal level of the modulation signal of the system 2, and when the maximum reception signal level of the modulation signal of the system 2 is smaller, the selecting unit 132 converts the modulation signal of the system 2 into the second modulation signal. Assign to the first antenna. As for the modulated signal of the system 1, the second antenna of the modulated signal of the system 1 is assigned as a transmitting antenna. When the second antenna of the modulated signal of the system 1 is the same as the first antenna of the modulated signal of the system 3, the selector 132
Assigns the modulated signal of system 3 to the first antenna as it is and the modulated signal of system 1 to the third antenna.

Further, the selection unit (or the control unit)
When the determined first antennas overlap, the transmitting antenna of each modulated signal may be assigned to the upper antenna in ascending order of the maximum received signal level of each modulated signal. That is, when it is determined that the first antenna is overlapped with the same antenna for the modulation signal of the system 1 and the modulation signal of the system 2, the selecting unit (or the control unit) determines the modulation signal of the system 3 From among the antennas that have not been determined as the first antennas, the antennas may be preferentially assigned to the upper antennas in ascending order of the maximum received signal level of each modulated signal.

Furthermore, # 1 (time slot 1) of the first TDD frame is allocated to the control channel, and all the remaining channels are allocated to the traffic channel. However, it is not always necessary to allocate in this way. Both # 1 of the second TDD frame and # 1 may be allocated to the control channel. Further, as for the method of allocating the carrier frequency to each communication channel, a different carrier frequency may be allocated to each of the communication channels (# 2 to # 8), or the communication channel (# 2) of the first TDD frame may be allocated. To # 4) are assigned a common carrier frequency, and the communication channels (# 5 to # 8) of the second TDD frame are
A common carrier frequency different from the carrier frequencies assigned to the communication channels (# 2 to # 4) of the first TDD frame may be assigned.

Further, in the present embodiment, the reception diversity is described using the antenna selection diversity. However, the method of the reception diversity is not limited to the antenna selection diversity, and may be, for example, a combination diversity. Is also good. When performing combining diversity, it is desirable to further include a phase control circuit. This is because the received signals received by the respective antennas have respective phase differences, and are to be combined after the phases of the received signals of the respective antennas are matched by the phase control circuit. However, even in the case of combining diversity, it is not always necessary to provide a transfer control circuit.

According to the base station of the present invention, one system selects and uses a plurality of antennas by using a combiner as in the related art, and only a plurality of antennas determined for each system are used. , And any system can select all antennas. Therefore, the quality of the wireless channel is stabilized (improved) without increasing the cost. In addition, since the antenna selection is assigned not only to the radio circuit but also to the digital circuit, the radio circuit is simplified, and the design and manufacture are facilitated.

Further, when an attempt is made to obtain the same diversity effect without using a synthesizer as in the prior art (the number of systems × the number of systems)
(Diversity number of one antenna = large number of antennas)
Since a plurality of systems can transmit and receive with a common antenna as compared with, the cost can be reduced. That is, miniaturization is facilitated, and, for example, when used for a PHS base station, installation and transportation of the base station are facilitated. In addition, HP
Since the output of A is low, power consumption is reduced.

[0065]

The base station of the mobile communication system according to the present invention comprises first and second generating means for generating high-frequency transmission signals, a plurality of antennas equal to or more than the number of generating means, and output terminals of each generating means. Switch means for switching the connection between the antenna and a plurality of antennas; first and second data output means for outputting transmission data, and transmission data from the first and second data output means, A switching means for switching to a cloth and inputting the first and second generating means to the first and second generating means; and controlling the switching of the switching means to each of a straight state and a cross state .
In each state, the output terminal of the first generation means is connected to one antenna.
And the output terminal of the second generator is connected to the remaining antenna.
And control means for controlling the switch means so as to be connected to (1), so that the switch means for switching the transmission signal, which is a high-frequency signal, and the switching means for replacing the transmission data at the stage of the low-frequency signal are combined. It has the effect of switching antennas and eliminates the need for a combiner, which was required in the past, so that the loss of high-frequency power can be reduced, and inexpensive elements can be used for generating means (amplifiers) that output transmission signals. Therefore, there is an effect that the cost can be reduced. In addition, since the number of wirings for switching the antenna in the high frequency part can be reduced by the operation of replacing the low frequency signal, there is an effect that the wiring design of the high frequency circuit is easy and the size is easily reduced.

Further, the first and second generating means each have a PLL section for generating a local frequency signal for determining the frequency of the transmission signal, and the control means sets the switching means to a cross connection. Since the local frequency of the PLL unit is controlled so that the carrier frequencies of the first and second generation units are interchanged, the carrier frequency can be easily exchanged simultaneously with the exchange of the transmission data.

Further, the plurality of antennas are first and second antennas.
And the switch means connects the output terminal of the first generation means to the antennas in the first antenna group.
A first switch unit for selectively connecting Te, an output terminal of the second generating means, a second switch unit for selectively connecting the second antenna in the antenna group, A in the first antenna group
A connection line between the antenna and the first switch unit and the second antenna.
In the connection line between the antenna in the antenna group and the second switch unit
And one antenna in the first antenna group.
The output terminal of the second generation means is connected to the
The output terminal of the first generating means to the first antenna, than comprising a third switch unit to bypass connection, it is possible to further reduce the number of wires in the high frequency part. As a result, the circuit coupling in the high-frequency portion can be reduced, so that there is an effect that the design and manufacturing are further facilitated and the size can be reduced. Moreover, the number of antennas from which each transmission signal can be selected does not decrease due to the bypass connection.

Further, the third switch section is provided with a circuit
A regulator, said control means, since a configuration for controlling the bypass connection by causing total reflection of power by opening or shorting one port of service over Curator, using less passive element loss of the circulator Ki de be realized switched at high frequency part, and a bypass function facilitates wiring and manufacturing design.

Further, the base station of the present invention is a base station of a mobile communication system that transmits and receives a time-division frame on two carriers in synchronization with a time-division bidirectional multiplexing system and performs diversity. Antennas, PLL units for generating local frequency signals for determining the carrier frequency of the transmission signal, and first and second generation means for generating a high-frequency transmission signal; and output terminals of the first generation means. A first switch unit that is switchably connected to one of the first and second antennas, and an output terminal of the second generation unit.
A second switch unit that is switchably connected to one of the third and fourth antennas, and an output terminal of the second generation unit is a first switch .
And a third switch unit bypass-connected to one of the second antennas, first and second data output means for outputting transmission data, and transmission data from the first and second data output means being straight or crossed. Switching means for switching and inputting to the first and second generating means, and controlling the first, second and third switch sections and the switching means so as to connect output terminals of the respective generating means to mutually different antennas; When the cross-connection is performed, control means is provided for controlling the PLL unit so that the carrier frequencies of the first and second generation means are switched. Therefore, a switch means for switching a transmission signal, which is a high-frequency signal, It has the function of switching antennas in combination with the switching means that switches transmission data at the stage of the frequency signal, eliminating the need for a combiner that was required in the past. To reduce the loss of high frequency power because,
An inexpensive element can be used for the generation means (amplifier) for outputting the transmission signal, and thus there is an effect that the cost can be reduced. In addition, since the number of wirings for switching the antenna in the high frequency part can be reduced by the operation of replacing the low frequency signal, there is an effect that the wiring design of the high frequency circuit is easy and the size can be easily reduced.

The third switch section includes the first switch section and the third switch section .
1, in the connection line with one of the second antennas, and in the second switch.
Inserted into the connection line between the switch and one of the third and fourth antennas.
And the control means is configured to control the bypass connection by causing total reflection of power by opening or shorting one port of each circulator. Switching at a high frequency part and a bypass function can be realized by using the element. Wiring and manufacturing design becomes easier.

The base station further comprises measuring means for measuring the level of the received signal corresponding to each transmission signal for each antenna, and level determining means for determining the antenna having the maximum received signal level corresponding to each carrier. The control means, for each carrier, allocating means for allocating an antenna determined to be the maximum level, overlap determination means for determining whether the same antenna is allocated to different carrier , overlapping in the overlap determination means When it is determined that the carrier signal has the highest received signal level among the carrier waves, a re-assignment unit that assigns to another antenna, and a switch that controls the switch unit according to the assignment result and the re-assignment result And control means, so that simultaneous transmission of two carrier waves from one antenna is excluded. It can be assigned with priority lower of the maximum received transmission level to the antenna in the case of conflicts. Therefore, the reduction of the transmission diversity effect is minimized.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram illustrating a configuration of a base station according to an embodiment of the present invention.

FIG. 2 is a diagram showing a circuit configuration around a circulator.

FIG. 3 shows an example of a determination result of a determination unit.

FIG. 4 is an explanatory diagram showing selection control logic of each switch by a control unit in a transmission / reception time slot.

FIG. 5 is a flowchart showing an antenna selection process for a downlink time slot of each of a first system and a second system by a control unit.

FIG. 6 is an explanatory diagram showing a route of a transmission signal.

FIG. 7 is an explanatory diagram showing a route of a transmission signal.

FIG. 8 is an explanatory diagram showing a route of a transmission signal.

FIG. 9 is an explanatory diagram showing a route of a transmission signal.

FIG. 10 is an explanatory diagram showing a route of a transmission signal.

FIG. 11 is an explanatory diagram showing a route of a transmission signal.

FIG. 12 is an explanatory diagram showing a route of a transmission signal.

FIG. 13 is an explanatory diagram showing a route of a transmission signal.

FIG. 14 is an explanatory diagram showing a route of a transmission signal.

FIG. 15 is an explanatory diagram showing a route of a transmission signal.

FIG. 16 is an explanatory diagram showing a route of a transmission signal.

FIG. 17 is an explanatory diagram showing a route of a transmission signal.

FIG. 18 is an explanatory diagram showing a route of a reception signal.

FIG. 19 illustrates an example of a reception signal level of each system and a determination result of the determination unit when there are four antennas and three systems.

FIG. 20 is a diagram showing a correspondence between an antenna and each system.

FIG. 21 is an explanatory diagram showing an example of a conventional TDMA / TDD frame for performing communication between a PHS base station and a mobile station.

FIG. 22 is an explanatory diagram showing channel assignment on the base station side of each TDD frame when two TDD frames to which different carrier frequencies are assigned to time slots at the same time are used simultaneously.

FIG. 23 is a block diagram illustrating a configuration of a main part of a PHS base station that performs communication with a mobile station using two TDD frames illustrated in FIG. 22;

FIG. 24 is an explanatory diagram showing a specific configuration of a synthesizer.

FIG. 25 is an explanatory diagram showing a power loss characteristic in the combiner.

[Explanation of symbols]

 Reference Signs List 100 base station 131 determination unit 132 selection unit 132 comparison unit 405 to 408 band limiting filter 409 to 414 switch 415 to 418 low noise amplifier 419 isolator 421 to 424 distributor 425 low pass filter 427 HPA 431 to 434 reception unit 435, 436 PLL synthesizer units 437, 438 PLL control units 443, 444 A / D processing units 445 Judgment units 446 Control units 451, 452 Modulation / demodulation units 460 Cross switches 471, 472 TDMA processing units 481 to 488 Switches 491 to 494 Circulators 495, 496 Antenna switching switch

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-10-51365 (JP, A) JP-A-9-215051 (JP, A) JP-A-10-163936 (JP, A) JP-A-9-205 69808 (JP, A) JP-A-9-289500 (JP, A) JP-A-9-8716 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 1 / 38-1 / 58 H04B 7/00 H04B 7/02-7/12 H04B 7/24-7/26 H04J 1/00-15/00 H04L 1/02-1/06 H04L 5/00-5/12 H04L 5/22 -5/26 H04Q 7/00-7/38

Claims (7)

(57) [Claims] 1. A base station of a mobile communication system for performing diversity, comprising: first and second generating means for generating a high-frequency transmission signal; a plurality of antennas equal to or more than the number of generating means; Switch means for switching the connection between the output terminals of the plurality of antennas and a plurality of antennas;
A second data output unit, a replacement unit that replaces the transmission data from the first and second data output units with a straight or a cross and inputs the data to the first and second generation units, and sets the replacement unit in each of a straight state and a cross state. Switching control is performed, and the replacement means is straight or cross.
State, the output terminal of the first generating means is connected to one antenna.
Connect the output terminal of the second generator to one of the remaining antennas
Control means for controlling the switch means so as to be connected to the base station. 2. The apparatus according to claim 1, wherein each of the first and second generation units has a PLL unit that generates a local frequency signal that determines the frequency of the transmission signal. 2. The base station according to claim 1, wherein the base station controls the local frequency of the PLL unit such that the carrier frequencies of the first and second generation units are switched. 3. The antenna according to claim 1, wherein said plurality of antennas include first and second antennas.
And a switch means for selecting an output terminal of the first generation means with respect to the antennas in the first antenna group.
The first switch unit to be selectively connected and the output terminal of the second generation unit are connected to the antenna of the second antenna group.
A second switch unit selectively connected to the antenna, an antenna in the first antenna group, and a first switch unit;
Connection line and the antenna in the second antenna group and the
2 is inserted into the connection line with the switch unit,
The output of the second generation means is output to one antenna in one antenna group.
First generation of terminal to one antenna in the second antenna group
3. The base station according to claim 1, further comprising a third switch unit that bypass-connects an output terminal of the unit. 4. Before Symbol third switch section is a circulator
There, the control means, the base station according to claim 3, wherein the controlling the bypass connection by causing total reflection of power by opening or shorting one port of service over Curator. 5. A base station of a mobile communication system for transmitting and receiving time-division frames on two carriers in synchronization by a time-division bidirectional multiplexing method and performing diversity, comprising: four antennas; First and second generating means for generating high-frequency transmission signals, each having a PLL section for generating a local frequency signal for determining a carrier frequency of the first and second antennas. A first switch unit that is switchably connected to one of the antennas, a second switch unit that is switchably connected to an output terminal of the second generation unit, and a second switch. The output terminal of the means to one of the first and second antennas
To the output terminal of the first generating unit of the third and fourth antenna
A third switch unit connected to one of the bypass switches and first and second data output means for outputting transmission data; and transmission data from the first and second data output means being replaced with straight or cross data to provide first and second data. A switching means for inputting to the generating means, and controlling the first, second, and third switch sections and the switching means so as to connect the output terminals of the respective generating means to mutually different antennas. A base station comprising: a control unit that controls the PLL unit so that the carrier frequencies of the first and second generation units are switched. 6. The third switch section includes a first switch section and a third switch section.
1, in the connection line with one of the second antennas, and in the second switch.
Inserted into the connection line between the switch and one of the third and fourth antennas.
6. The circulator according to claim 5 , wherein said control means controls said bypass connection by causing total reflection of power by opening or shorting one port of each circulator.
Base station as described. 7. The base station further comprises: measuring means for measuring a level of a received signal corresponding to each transmission signal for each antenna; and level determining means for determining an antenna having a maximum received signal level corresponding to each carrier. wherein the control means, for each carrier, and allocation means for allocating the maximum level and the determined antenna, and determining overlap determination means for determining whether or not the same antenna to different carriers are assigned, in the overlap determination unit When it is determined that they are overlapping, the re-assignment means for allocating to the other antenna the carrier having the highest received signal level among the carriers, and the switch means is controlled in accordance with the assignment result and the re-assignment result. The base station according to claim 1, further comprising: a switch control unit that performs switching.