JP2503855B2 - Paging system - Google Patents

Abstract

PURPOSE:To improve the synchronizing accuracy of modulation regardless of the fluctuation of the transmission delay amount of paging signals between transmission stations in a wide area radio paging system transmitting each radio frequency carrier wave of the same frequency modulated by the same paging signal from plural transmission stations. CONSTITUTION:A paging controller 10 generates a highly accurate time signal based on the reference signal from a GPS satellite 90 by a GPS receiver 150, and when the controller 10 receives the calling from a PSTN 40, it prepares a paging request signal, adds the time delayed more than the maximum delay time required for the signal transmission on preliminarily stored transmission lines 60 and 61 and the processings on sides of transmission stations 20 and 21 as transmission start designation time information and transmits it to each transmission station 20 and 21. Each transmission station 20 and 21 generates the highly accurate time signal and the clock pulse signal of the bit unit of a modulation signal by a GPS receiver 230 in the same way, performs the format conversion of a request signal to a digital paging signal at a designated time and modulates carrier waves by synchronizing them with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paging system, and more particularly to a plurality of transmissions of radio frequency carriers of the same frequency, which are synchronously modulated by the same digital selective call (paging) signal, and are spaced apart from each other. The present invention relates to a wide area wireless paging system for transmitting from each station.

[0002]

2. Description of the Related Art In a wireless paging system, an output 100 is provided in order to enable widening of a service area.
A plurality of transmitting stations each including a wireless transmitter of about W are installed at predetermined intervals, and these transmitting stations simultaneously transmit a plurality of radio frequency carriers of the same frequency modulated by the same digital paging signal. . In such a radio paging system, the phase difference between two reception carriers in an area where radio frequency carriers from two transmission stations adjacent to each other can be received, that is, in an interference area, is equal to or less than a certain value (usually the above digital paging signal). Within 1/4 of the bit interval). For example, POCSAG (Post Office)
Code Standardization Advi
512 BPS standardized by soryGroup)
In the paging system using the digital paging signal, that is, the POCSAG code, the phase difference is 48
Must be 8 μs or less. Therefore, the phase shift from the reference phase at each transmitting station must be about 250 μs or less.

On the other hand, a wireless paging system of this type includes a central station arranged between the plurality of transmitting stations and a telephone switching network which receives a paging request call. The central station comprises a paging controller for converting the data of the paging request from the calling subscriber into a predetermined signal format, for example a paging request signal format based on the POCSAG code.

The connection between the central station and the plurality of transmitting stations is formed by a wired or wireless time division multiplex line. The phase shift is compensated for by the delay caused by the signal transmission through the connection line between the central office and the transmitting station, and the phase shift is within the predetermined range (about 25
The variable delay means is arranged at each of the central station and the transmitting station so as to suppress it to 0 μs or less. On the other hand, the radio frequency carrier signal modulated by the phase correction code having a predetermined code pattern is transmitted from the central station to the transmitting station, and the transmitting station which receives this carrier signal and demodulates it into the phase correction code is based on this phase correction code. An example of a paging system for calculating and setting the delay amount of the variable delay means in the own station is described in US Pat. No. 4,709,401.

[0005]

Generally, the above connecting line between the central office and each of the plurality of transmitting stations has two working / spare lines.
In the phase synchronization method described in the above-mentioned U.S. patent specification, the delay amount is calculated and set again from the beginning when a failure occurs in the working line and switching to the protection line is performed because it consists of a route. There is a need.

Further, if the bit rate of the digital paging signal is further increased in order to satisfy the demand for effective use of radio frequencies, which has been recently strengthened, the phase correction according to the above-mentioned conventional technique is not sufficient in accuracy. That is, the accuracy of the phase correction in the wireless paging system corresponding to the POCSAG code with the bit rate of 9600 BPS is 2
It is required to be within 6 μs, but the phase correction accuracy at the transmitter modulation input point where the delay difference in the wireless transmission section and the delay error in the transmitter inevitably occur is 10 μs.
It is necessary to be within about s, which is difficult to realize.
Further, in the above-mentioned conventional technique, it is necessary to make the fluctuation of the delay amount in the transmission line connecting the central station and the transmitting station smaller than the allowable phase shift, but it is extremely difficult to achieve the accuracy in the time division multiplexing line. . The increase in the signal delay amount when the time-division multiplexed digital signal is line-separated in the transmission line constantly changes because the clock pulses of the paging controller and the time-division multiplexer are always independent from each other. If the degree of time division multiplexing is suppressed to suppress the amount, an increase in the number of wireless transmission lines cannot be avoided, and the cost for installing and maintaining the lines increases.

Furthermore, an increase in the number of transmitting stations for expanding the service area requires an increase in the number of connecting lines between the central station and transmitting stations, which increases costs for installing and maintaining the lines. .

To solve this problem, there are a multi-drop method in which a plurality of transmitting stations are connected to one line and a tree connection method (a signal distributor is arranged between the central station and the transmitting stations). In the multi-drop method, the configuration of the transmission line changes midway between the central station and the transmitting station, and as a result, if the delay amount changes, phase correction becomes extremely difficult. That is, the fluctuation of the delay amount generated on the side of the central office of the line is not a problem because the phases of all the transmitting stations connected to the line are changed in the same manner, but the fluctuation of the delay amount at the end of the line is the same as that of the transmitting station. There is a phase shift between them. Further, although the tree method enables the total extension distance of the line to be reduced, the variation of the delay amount is increased due to the need of the distribution device. Therefore, when the bit rate of the digital paging signal is increased, it is difficult to secure the phase synchronization between the transmission outputs of a plurality of transmitting stations. Further, when a plurality of distributors are provided, it becomes difficult for the transmitting station arranged downstream of the distributor to correct the phase.

Therefore, it is an object of the present invention to transmit the digital paging signal so that a plurality of radio frequency carriers of the same frequency synchronously modulated by the same digital aging signal can be transmitted from a plurality of transmitting stations. In a wireless paging system having a connection line for transmitting to each of the stations, a radio that can maintain high accuracy of synchronization of modulation of the plurality of radio frequency carriers by the digital paging signal regardless of variation in transmission delay amount in the connection line. To provide a paging system.

Another object of the present invention is to provide radio paging of this kind which can suppress the rate of increase in the number of connection lines as compared with the rate of increase in the number of transmitting stations and the rate of increasing the number of radio frequency carriers. To provide a system.

[0011]

The present invention is directed to a public switched telephone network (Public Switched Telephone).
and a paging controller for generating a paging request signal including a subscriber number unique to a called paging receiver corresponding to the call in response to a paging call received from a subscriber of the network (PSTN) through the telephone network. , Radio frequency carriers of the same frequency, each of which is connected to the paging controller by a plurality of transmission lines having different required transmission times and is synchronously modulated by a digital paging signal corresponding to the paging request signal. In a wide area wireless paging system including a plurality of transmitting stations that occur and providing a paging service to a large number of paging receivers distributed in the service area of the transmitting station, the paging controller is one of the plurality of required transmission times. A first time value equal to the maximum value and said A delay time storage circuit in which each of the line transmission stations stores in advance a second time value required from the reception of the paging request signal to the generation of the digital paging signal, and a plurality of NAVSTAR GPS (navi).
gatesatellite time and
ranging global positionin
g system: navigation satellite time and ranging global positioning system) A first GPS receiver that generates a time reference signal in response to a signal received from a satellite, and a world standard time in advance in response to the time reference signal. And a first time reference circuit for generating a high-precision time signal having a time relationship, and a sum of the first time value and the second time value added to the current time represented by the high-precision time signal. And a code adding means for adding a code indicating a time after the specified time to the paging request signal as a transmission start time designating code, wherein each of the wireless transmission stations receives the paging request signal and temporarily stores the reception buffer. Memory means and a second GPS receiver for generating a time reference signal in response to signals received from said plurality of GPS satellites. A second time reference circuit for generating a high-precision time signal having a predetermined time relationship with the world standard time in response to the time reference signal; and the paging request signal stored in the reception buffer memory means. A time collation circuit that detects a coincidence between the transmission start time designation code and the high-accuracy time signal from the second time reference circuit, and the paging request from the time when the output indicating the coincidence from the time collation circuit occurs A format conversion circuit for converting the signal into the digital paging signal in synchronization with the high precision time signal from the second time reference circuit, and generating a radio frequency carrier wave of a predetermined frequency modulated by the digital paging signal. And a wireless transmitter for controlling the paging system.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, in a paging system according to a first embodiment of the present invention shown as a block in this figure, a paging controller 10 provided in a central office is a public telephone network (PSTN) 40. Connected ordinary telephone terminal 4
1 receives the paging call signal. The paging controller 10 controls the connection with the PSTN 40 and receives the paging call acceptance signal generated by the PSTN 40 in response to the paging call signal, and the PSTN connection unit 110.
A central control unit 120 for generating a paging request signal with a transmission time designation code in response to the paging call acceptance signal, and transmission lines 60 and 61 connected to the transmitting stations 20 and 21 for transmitting the paging request signal. Output interface units 130 and 13 for transmitting respectively
1, a paging receiver 80 (only one is shown for convenience of illustration), a subscriber data file 140 containing registered / unregistered information for each subscriber number, and a NAVSTAR / GPS satellite 90 launched by the US Department of Defense. It receives a signal from the CPU, generates clock pulses and time information that are very accurately synchronized with the world standard time, and outputs them to the central control unit 1.
20 and a GPS receiver 150 to be supplied to 20. The transmitting station 20 includes an input interface unit 210 that receives a paging request signal through the transmission line 60, and a GPS receiver 1
Similar to 50, a GPS receiver 230 that receives a signal from a GPS satellite 90 and generates a clock pulse and time information that is extremely accurately synchronized with the world standard time, and a paging request with the transmission time designation code based on this time information. An encoding control unit 220 for converting a signal into a digital selective calling (paging) signal format at a time designated by the code, and a transmitter 240 for outputting a radio frequency carrier modulated by the digital paging signal are provided. Since the transmitting station 21 has the same configuration as the transmitting station 20, only the block shown in FIG.

The GPS receivers 150 and 230 may have the same structure and may be used. A means for generating a clock pulse and time information synchronized with the world standard time by a GPS receiver is known, and a method of calculating an accurate time based on the time information at each of two points far away from each other is known. It is described in US Pat. No. 5,070,537. On the other hand, details of the construction of the GPS receiver are described in US Pat. No. 5,134,407. GPS
The original purpose of the receiver is position detection, and the position of the receiver is determined based on orbit information from a plurality of GPS satellites and time reference information. Each of the GPS satellites is equipped with an atomic clock based on cesium and rubidium, and information about an error from the world standard time is also supplied from the ground, and substantially coincides with the world standard time. Therefore, the difference between the time information obtained by the GPS receivers 150 and 230 and the world standard time is within 5 μs, and the accuracy of this time information is high.

Next, referring to FIG. 2, the central control unit 120 whose detailed block diagram is shown in FIG. 2 temporarily stores the paging call acceptance signal from the PSTN connection unit 110 and performs queuing processing. Queuing processing circuit 121
A queuing timer 123 for generating a timing signal TQ at a predetermined time interval indicating an arrangement on the time axis of the call acceptance signal, the maximum delay time of the delay times on the transmission lines 60 and 61, and the transmitting station 20. And a delay time storage circuit 124 storing the respective values of the time processed in 21.
And a reference time pulse generation circuit 125 for generating a clock pulse and time information synchronized with the world standard time based on the output of the GPS receiver 150, and a queuing processing circuit for controlling these circuits each time the timing signal TQ is received. 1
The call acceptance signal in 21 is format-converted into a group of paging request signals, and the transmission start time is based on the current time represented by the output of the reference time pulse generation circuit 125 and the delay time represented by the output of the delay time storage circuit 124. The code corresponding to the time is added to the paging request signal,
The control circuit 122 is provided to the transmitting stations 20 and 21 via the output interface units 130 and 131, respectively.

Next, referring to FIG. 3, the encoding control unit 220, the details of which are shown in blocks in the figure, receives the paging request signal with the transmission time designation code from the input interface unit 210 and temporarily stores the reception buffer 221.
And a reference time pulse generation circuit 225 for generating a clock pulse and time information synchronized with the world standard time based on the output of the GPS receiver 230, the current time represented by the reference time pulse and the paging request in the reception buffer 221. Detection of coincidence with specified time of signal and transmission instruction signal SS
, A transmission data conversion circuit 224 for format-converting the paging signal into a digital paging signal and supplying it to the transmitter 240 as a modulation signal, and a paging request in the reception buffer 221 based on the transmission instruction signal SS. Signal transmission data converter 22
4 and the transmission control circuit 223 for controlling the selective supply to the P.4 and the format conversion.

Next, when the digital paging signal is 5
The operation of the above embodiment in the case of the 12 BPS POCSAG code will be described.

Referring to FIGS. 1 and 2 together with FIG.
The paging controller 10 constantly checks in the PSTN connection unit 110 whether or not there is a paging request call from the general telephone terminal 41 (S1), and when there is a call, the called subscriber number is received. The operation starts (S2).
This called subscriber number is generally MF (Multi Fr) in Japan when the connection with the PSTN 40 is a trunk connection.
signal). After receiving the called subscriber number, the queuing processing circuit 121 collates with the subscriber data file 140 (S3) and accepts the paging request only when the called subscriber number is registered as a subscriber. If the called subscriber is a paging service subject with a message service (S4), PB (P
The message data by the ushbutton) signal is received (S5). In this way, the queuing timer 12 receives a plurality of paging call acceptance signals that have been successively accepted.
The output of the timing signal TQ from 3 is accumulated in the queuing processing circuit 121. Next, the queuing processing circuit 121 generates a plurality of paging signal trains having a shape very close to the POCSAG code format (S6) (this processing is called queuing).

The control circuit 122 format-converts the paging acceptance signal stored in the queuing processing circuit 121 into the paging request signal each time it receives the timing signal TQ at a predetermined time interval, and outputs the format from the reference time pulse generation circuit 125. The data transmission time and the transmission processing time on the transmission station side indicated by the output from the delay time storage circuit 124 are added to the current time indicated by the output, and the time after the time indicated by the addition result is added to the paging request signal as the transmission start time. Then, the data is transmitted to the transmitting station 20/21 through the output interface unit 130/131 and the transmission line 60/61.

The transmission protocol of the paging request signal is
HDLC (High Level) as the second layer of OSI
Data Link Control), OS
I Use the format of FIG. 5 as the seventh layer. In FIG. 5, “TXNO” is the identification (I
D) number, "CHNO" is the channel number that specifies which radio frequency channel the transmission data is sent out,
“CODE” designates in what format the transmission data is to be transmitted (for example, POCSAG512BPS is “0”).
1 ") and" TIME "designates the transmission start time of the transmission data (for example," 100 "in the case of transmission at 12:10:00).
0 ")," TRNO "is the transaction number indicating the ID number of this packet," TPL "is the transaction packet length indicating the data length of this packet, and" POCSAG data "is information as one codeword (Codeword). Only bit 21 bits are transmitted in 3 bytes, and parity bit, preamble (Preamble), sync code word (Sync)
The transmission code is added to the transmission station side. By doing so, the transmission time of the line is shortened. As is apparent from the above description, the system of the present invention is characterized by inserting the transmission start time information before each paging request signal.

The ID number of each transmitting station is systematically designed so that individual stations can be designated, as well as group or all stations can be designated, and the central control unit 120 determines the state of the line and transmitting stations. Select the ID number with "TXNO". "CHNO" is used when the transmitting station has a plurality of radio frequency channels.

Referring to FIG. 6 in addition to FIG. 1 and FIG. 3, in the transmitting station 20, the input interface unit 210 receives a paging request signal designated as “TXNO” for itself or all stations, and the code The paging control unit 220 stores this paging request signal in the reception buffer 221 divided by the address. From the GPS receiver 230 to the reference time pulse generator 225, a pulse signal C3 having a repetition period of 1 second and a time signal C4 of serial data slightly delayed from the pulse signal C3 are supplied. Reference time pulse generation circuit 225
Includes a highly stable crystal oscillator 226, and a GPS receiver 2
The signal C3 / C4 from 30 determines the exact time. Since the time signal C4 is supplied to the reference time pulse generation circuit 225 later than the pulse signal C3, the time when the pulse signal C3 enters is added to the time indicated by the previously received signal C4 by 1 second. By setting, it is possible to synchronize with the world standard time. The reference time pulse generation circuit 225 supplies a clock pulse C1 for each bit and a clock pulse C2 for each code word to the transmission data conversion circuit 224, and the digital paging signal format, that is, the bit unit and code word of the transmission format data DS. Synchronize the units. The time information of the reference time pulse generation circuit 225 is the time collation circuit 222.
This time collating circuit 222 reads the designated transmission start time of the "TIME" area of the paging request signal from the receiving buffer 221 every time the pulse collating circuit 222 receives the pulse signal C3, and the reference time pulse generating circuit 225 reads it. Of the current time display pulse, and if they match, the transmission instruction signal SS is output to the transmission control circuit 223 together with the storage address of the data. The transmission control circuit 223 sequentially supplies the data in the "POGSAG data" area corresponding to the above address to the transmission data conversion circuit 224. The transmission data conversion circuit 224 operates in synchronization with the clock pulses C1 and C2, adds a parity bit to the input digital signal, and further adds a preamble and SC to the POCS.
It is converted into AG transmission format data DS and supplied to the transmitter 240 as a modulated signal. The transmitter 240 modulates a radio frequency carrier wave with a digital paging signal from the transmission data conversion circuit 224 and transmits it as an electromagnetic wave,
The paging receiver 80 specified by the digital paging signal is called. Since the transmitting station 21 operates in synchronization with the world standard time like the transmitting station 20, the phase difference between the digital paging signals forming the modulated signals of the electromagnetic waves from these transmitting stations is within 1/4 bit length. Can be suppressed to

As described above, in the system of the present invention, the reference of the phase comparison is generated by the GPS receiver for each of the transmitting stations, so that the paging controller (central station) and each of the transmitting stations are connected to each other. The synchronization of the modulated signal can be secured between the transmitting stations without being affected by the variation in the delay amount of the transmission line.

Referring to the timing chart of FIG. 7,
At time T0, the paging request signal with the transmission start time designated as TS is output from the output interface units 130 and 131 of the paging controller 10 of the central office, respectively. Paging request signal D1 output to line 60
Is received by the transmitting station 20 and temporarily stored at time T1 after the transmission delay time t1 has elapsed. The paging request signal D2 output to the line 61 is the time T after the elapse of the transmission delay time t2.
2 is received by the transmitting station 21 and temporarily stored. At time TS, the transmission stations 20 and 21 each form a digital paging signal by signal format conversion and start transmission of a radio frequency carrier modulated by the signal. The paging controller 10 has the maximum transmission delay time (t2 in FIG. 7).
And data reception and processing time in the transmitting station (tp in FIG. 7)
And the current time (T0 in FIG. 7) are added to the transmission start time T
Specify S. A system in which the calling subscriber specifies the transmission time when making a paging call (Patent application publication number: Sho 5)
In the case of applying the present invention to the specification of 9-85147), the object can be achieved by outputting the paging request signal from the paging controller before the total time of t2 and tp from the designated time TS.

Referring now to FIG. 8, which shows in block form a second embodiment in which the transmitting station transmits two radio frequency carriers having different frequencies, this embodiment is based on the transmitting station 20 and the transmitting station 20 in the system of FIG. 21 is replaced with transmitting stations 30 and 31 having the above two radio frequency carriers. In FIG. 8, the transmitting station 30 uses these two
Encoding control units 220 and 3 corresponding to radio channels CH1 and CH2 by one radio frequency carrier, respectively.
20 and transmitters 240 and 340, respectively. These components have the same configurations and functions as the encoding control unit 220 and the transmitter 240 in the embodiment of FIG. 1, respectively. Similarly, other components shown in FIG. 8 with the same reference numerals as those in FIG. 1 have the same configurations and functions as the corresponding components in the embodiment of FIG.

Next, the operation of this embodiment will be described. When the central control unit 120 receives a paging call from the telephone terminal 41 accommodated in the PSTN 40, it performs a queuing process according to the above flow of FIG. On the other hand, each of the plurality of paging receivers 80 and 81 (only two units are shown) is tuned in advance to one of the two radio channels CH1 / CH2, and the transmission channel number information corresponds to the subscriber number. Stored in the personal data file 140. When the central control unit 120 performs the queuing processing, it refers to the subscriber data file 140 to confirm that the called subscriber number is registered, and classifies each designated wireless channel number for queuing. Perform processing.
The central control unit 120 sequentially creates a paging request signal (FIG. 5) for each radio channel number according to the timing signal TQ and transmits it to the transmitting station 30/31 through the line 60/61. In each of the transmitting stations 30/31, the "CHN" of the paging request signal received by the input interface unit 210 is received.
The radio channel number in the O "area is identified, and the radio channel C
If it is H1, it is sent to the encoding control unit 220, and the wireless channel C
If it is H2, it is sent to the encoding control unit 320. Radio channel C
Encoding control unit 220 and transmitter 240 corresponding to H1
And an encoding control unit 320 corresponding to the radio channel CH2
And paging receivers 80/81 can be individually called at a designated time. The means for accurately calculating the current time by the signal from the GPS receiver 150/230 in the paging controller 10 and the transmitting station 30/31 is the same as that in the embodiment of FIG.

Referring to FIG. 9 showing the time position relationship between the input and output of each part of the paging request signal and the digital paging signal in the present embodiment, the transmission time T from the output interface section 130 to the radio channel CH1.
The paging request signal D11 designated by S1 is continuously transmitted from the time T01, the paging request signal D12 designated by the transmission time TS2 for the radio channel CH2 is continuously transmitted from the time T02 on the same transmission line 60, and the time T11 after the delay time t1 has elapsed , T12 is received by the transmitting station 30.
The encoding control unit 220 of the transmitting station 30 converts the format of the signal D11 at time TS1 to obtain the digital paging signal of the radio channel CH1. Radio channel CH1
Even if the signal of No. 2 is still being output, at time TS2, the encoding control unit 320 converts the format of the signal D12 into the digital paging signal of the radio channel CH2. The output interface unit 1 of the paging controller 10
The signals D11 / D12 are output from the transmission line 61 to the transmission line 61 from time T01 / T02, respectively, and are received by the transmitting station 31 after a delay time different from t1 has passed, but the paging signals of the radio channels CH1 and CH2 are transmitted. It goes without saying that the start is synchronized with those of the transmitting station 30, respectively.

As described above, even if the paging signals of a plurality of radio channels overlap each other in terms of time, they are transmitted via the transmission line between the paging controller 10 and each transmitting station 30/31. Since the transmission start time designation code is added to the paging request signal, it is possible to transmit a plurality of paging request signals on the same line at different times, and it is not necessary to add a line. of course,
The bit rate of the paging request signal on the transmission line needs to be N (= the number of wireless channels) times that of the transmission format, but conversely the degree of time division multiplexing can be increased. For example, in the case of 512 BPS POCSAG code, at least 10 if the bit rate of the paging request signal on the transmission line is 9600 BPS.
Multiplexing over channels is possible.

Next, referring to FIG. 10, in the third embodiment of the present invention shown in this figure, the transmission line between the paging controller 11 and the transmitting station 20/21 is modified. Has the same components as the above-mentioned embodiment. That is, one output interface unit 130 of the paging control device 11 and each input interface unit 210 of the plurality of transmitting stations 20/21 are multi-drop connected by the transmission line 70. As a paging request signal transmitted from the paging controller 11 to the line 70, "TX
“NO” may be designated for all stations, but in that case, the transmitting station 20
It is difficult for the paging control device 11 side to confirm whether or not each / 21 is normally received. That is,
This is because the confirmation signals (ACK) indicating the normal reception of the paging request signal from each of the transmitting stations 20/21 collide with each other. In order to solve this problem, an individual paging request signal is transmitted to each transmitting station 20/21 as shown in FIG. At time T03, the paging controller 11 sends out a paging request signal D3 in which the ID number (TX1) addressed to the transmitting station 20 is designated in the "TXNO" area, and then at time T04, the ID number (TX2) addressed to the transmitting station 21 is designated. The paging request signal D4 is sent. The signal D3 is received by the transmitting station 20/21 at time T3 after the transmission delay time t3 elapses, and the signal D4 is received by the transmitting station 20/21 at time T4 after the elapse of the transmission delay time t4. Can be returned. Needless to say, the transmission start time TS3 needs to be set to the time T5 or later when the paging request signal reaches all the transmitting stations. In the case of this method, the bit rate of the paging request signal transmitted through the line 70 needs to be M times that in the case of one station when the number of connected transmitting stations is M (M = 2 in FIG. 10). However, conversely, the degree of time division multiplexing can be increased. For example, in the case of 512 BPS POCSAG code, if the bit rate of the paging request signal on the transmission line is 9600 BPS, at least 10 stations can be connected to one line.

Referring to FIG. 12, in the fourth embodiment of the present invention shown in this figure, a paging signal is provided in the middle of the transmission line in response to the increase in the distance between the paging controller and each of the transmitting stations. And a tree connection configuration provided with a signal distribution device for relaying / distributing. In FIG. 12, the signal distribution device 50 is connected to the transmission line 71 from the paging control device 11, receives an input paging request signal, and distributes the paging request signal, and each paging request signal distributed by the input distribution part 510. Distribution output unit 520 for outputting data to transmission stations 20 and 21 via transmission lines 72 and 73, respectively.
And 521. Also in this embodiment, the number of transmission lines from the paging controller can be made smaller than the number of transmitting stations as in the embodiment of FIG.

The reference time pulse generation circuit 225 of each transmitting station is self-propelled by the highly stable crystal oscillator 226 when the clock pulse and time information from the GPS receiver 230 cannot be obtained. If a crystal oscillator having a stability of 0.01 PPM or less is used, the practicability can be sufficiently secured even at the bit rate of 9600 BPS. If the bit rate of the paging signal is smaller than this, the crystal oscillator may have lower stability. As a method other than using a self-propelled crystal oscillator, a backup means for creating a clock pulse in phase with the clock of the GPS receiver by using a synchronizing clock pulse of a transmission line, a synchronizing signal of television broadcasting waves, or a standard radio wave such as JJY Is provided
There is also a method of holding the synchronization by the backup means after once synchronizing with the GPS receiver. Further, the same applies to the reference time pulse generation circuit 125 of the paging control device, but the practicability can be secured even if the stability is lower than that of the transmitting station side. Therefore, it is possible to employ the reference time pulse generation circuit using only the backup means without depending on the GPS receiver 150.

[0031]

As described above, the wireless paging system according to the present invention adds the transmission start time information to the digital paging signal forming the modulated signal of the radio frequency carrier, while the GPS is used in each of the plurality of transmitting stations.
Since a plurality of radio frequency carriers having the same frequency are synchronously modulated by the paging signal at a designated time based on extremely high precision time information from the satellite,
It is possible to prevent interference between output signals from adjacent transmitting stations when the modulated radio frequency carrier is received by the paging receiver. In addition, a paging request signal transmission line between the paging control device and each of the transmitting stations is multi-drop connected,
Both tree connection and star connection, or a combination of these connections, can be used for phase synchronization for simultaneous transmission from multiple transmission stations, saving the number of transmission lines. The cost required can be reduced accordingly.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a detailed block diagram of a central control unit in the embodiment of FIG.

FIG. 3 is a detailed block diagram of an encoding control unit in the embodiment of FIG.

FIG. 4 is a flowchart of the operation of the paging controller in the embodiment of FIG.

5 is a timing chart showing the format of a paging request signal in the embodiment of FIG.

6 is a timing chart showing a time positional relationship of signals inside the encoding control unit of FIG.

FIG. 7 is a timing chart showing a time positional relationship of modulated signals in the embodiment of FIG.

FIG. 8 is a block diagram of a second embodiment of the present invention in which each transmitting station transmits two modulated radio frequency carriers different from each other.

9 is a timing chart showing a time positional relationship of modulated signals in the embodiment of FIG.

FIG. 10 is a block diagram of a third embodiment of the present invention.

FIG. 11 is a timing chart showing a time positional relationship of modulated signals in the embodiment of FIG.

FIG. 12 is a system configuration diagram of a fourth embodiment of the present invention.

[Explanation of symbols]

 10, 11 Paging controller 20, 21, 30, 31 Transmitting station 40 General public telephone network (PSTN) 41 Telephone terminal 50 Signal distribution device 60, 61, 70, 71, 72, 73 Transmission line 80, 81 Paging receiver 90 NAVSTAR / GPS satellite 110 110 PSTN connection unit 120 Central control unit 121 Queuing processing circuit 122 Control circuit 123 Queuing timer 124 Delay time storage circuit 125, 225 Reference time pulse generation circuit 130, 131 Output interface unit 140 Subscriber data file 150, 230 GPS receiver 210 Input interface unit 220,320 Encoding control unit 221 Reception buffer 222 Time matching circuit 223 Transmission control circuit 224 Transmission data conversion circuit 226 Crystal oscillator 240,340 Transmitter 510 Input Distribution unit 520 and 521 the distribution output unit

Claims (3)

(57) [Claims] 1. In response to a paging call received from a subscriber of a general public telephone network through the telephone network, a paging request signal including a subscriber number unique to a called paging receiver corresponding to the call is generated. Radios of the same frequency, each of which is connected to the paging control device by a paging control device and a plurality of transmission lines having mutually different required transmission times, and each of which is synchronously modulated by a digital paging signal corresponding to the paging request signal. Including a plurality of transmitting stations each generating a frequency carrier,
In a wide area wireless paging system that provides a paging service to a large number of paging receivers distributed in a service area of the transmitting station, the paging control device has a first time value equal to a maximum value of the plurality of required transmission times. And a delay time storage circuit in which each of the wireless transmission stations stores in advance a second time value required from the reception of the paging request signal to the generation of the digital paging signal, and a signal received from a plurality of NAVSTAR / GPS satellites. A first GPS receiver for generating a time reference signal in response to the time reference signal, and a first time reference circuit for generating a high precision time signal having a predetermined time relationship with the world standard time in response to the time reference signal. A time obtained by adding the sum of the first time value and the second time value to the current time represented by the high precision time signal. Code adding means for adding a code indicating a subsequent time to the paging request signal as a transmission start time designation code, and each of the wireless transmission stations receives the paging request signal and temporarily stores the reception buffer. Memory means, a second GPS receiver for generating a time reference signal in response to signals received from the plurality of GPS satellites, and a high-speed GPS receiver having a predetermined time relationship with world standard time in response to the time reference signal. A second time reference circuit for generating a precision time signal; a transmission start time designation code for the paging request signal stored in the reception buffer memory means; and the high precision time signal from the second time reference circuit. A time matching circuit for detecting a match, and the paging request signal is preceded from the time when the output indicating the match from the time matching circuit occurs. A format conversion circuit for converting the format into the digital paging signal in synchronization with the high precision time signal from the second time reference circuit, and a radio transmission for generating a radio frequency carrier of a predetermined frequency modulated by the digital paging signal. Paging system. 2. The second time reference circuit comprises a high stability crystal oscillator, and is responsive to the time reference signal from the second GPS receiver in a bitwise temporal manner of the digital paging signal. The paging system according to claim 1, wherein a clock pulse that defines a position is output, and the output of the clock pulse is maintained even when the supply of the time reference signal is interrupted. 3. The radio frequency carrier is composed of a plurality of carriers having different frequencies, each of the plurality of paging receivers is capable of receiving any one of the carriers, and the paging controller controls the carrier. The code adding means is provided correspondingly, the bit rate of the paging request signal is equal to the product of the bit rate of the digital paging signal and the number of the carrier waves, and each of the transmitting stations receives the reception signal. The buffer memory means, the format conversion circuit, and the transmitter are provided in a number equal to the number of the radio frequency carriers, and the transmission designated by the time designation code of the paging request signal corresponding to each of the radio frequency carriers. At the start time, the plurality of radio frequency carriers are transmitted from the transmitting stations, respectively. Claim 1 characterized by the above.
Or the paging system described in 2.