JP3653351B2 - Delay correction method for radio paging system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a delay correction method in a radio paging system. In particular, the present invention relates to a system for performing delay correction for transmission by a modem in a radio paging system that uses a modem that requires appropriate training for transmission between a radio paging central station and a radio paging base station. In the present invention, for example, when a multiplexing device that multiplexes a plurality of channels and performs transmission on one dedicated line is used for transmission between the radio paging central station and the radio paging base station, the delay correction of the radio paging base station is performed. This can be applied to a delay correction method that automatically sets a delay correction time for a part.
[0002]
[Prior art]
As is well known, the demand for portable receivers (hereinafter simply referred to as pagers) such as pagers and message decoders has increased rapidly in recent years. One of the typical radio link signal systems used in a radio paging system (radio paging system) is the POCSAG (British Post Office Code Standardization Advisory Group) system. The POCSAG method is a data communication method that employs 512 or 1200 bps as a transmission rate and FSK (Freqency Shift Keying) as a modulation method. The data transmission unit in the POCSAG system is called a batch, and one batch is composed of one synchronization code and eight frames following it.
[0003]
FIG. 5 is a block diagram of a conventional radio paging system. Here, the radio paging system is composed of a radio paging central station (hereinafter referred to as a central station) 1 and a radio paging base station (hereinafter referred to as a base station) 2, and the relationship between these and the caller side telephone and public telephone network is also shown. Yes. The base station 2 also exists outside the figure.
[0004]
As shown in the figure, the telephones 10 to 1m (T in the figure) on the caller side are connected to the public telephone network 20, and the central office 1 of the wireless calling system is connected to the public telephone network 20, respectively. The central office 1 controls the regional control device 30 (same LC), channel devices 40 to 4n (same CH), demultiplexing control device 50 (same MUX), and modem 60 (same MOD and DEM). It consists of the control part 22 to do. Of the modem 60, the output of the modulator (MOD) is connected to an analog transmission line 70, which is a dedicated line between stations, and the input of the demodulator (DEM) is connected to the analog transmission line 71. The channel device 4n, which is one of the channel devices 40 to 4n, is provided not for data transmission but exclusively for monitoring control. The control unit 22 performs general control for each configuration and necessary exchange between the configurations.
[0005]
On the other hand, the base station 2 includes a modem 80, a demultiplexing control device 90, channel devices 100 to 10n, delay correction units 110 to 11 (n-1) (DL in the drawing) also called phase synchronization devices, and transmissions. Machine 120-12 (n-1) and the control part 82 which controls these collectively.
[0006]
In the above configuration, first, the caller dials the subscription number of the pager (hereinafter referred to as “target pager”), which is the purpose of calling, by the telephone 10, for example. This outgoing call is sent to the regional control device 30 via the public telephone network 20, where it is converted into a POCSAG signal. In the channel devices 40 to 4 (n−1), POCSAG signals are encoded, multiplexed by the demultiplexing control device 50, modulated by the modulator of the modem 60, and transmitted to the base station 2. In the base station 2, the data is demodulated by the demodulator of the modem 80, separated by the demultiplexing control device 90, passed through the channel devices 100 to 10 (n−1), and the delay correction units 110 to 11 (n−1). Is input. Here, the necessary delay correction is performed, and then the data is sent to the transmitters 120 to 12 (n-1), and a wireless call is made to the target pager.
[0007]
In general, in a radio paging system, simultaneous radio paging is performed from a plurality of base stations in consideration that the owner of the target pager moves. For this reason, processing for correcting the transmission delay from the central station 1 to each base station 2 to the same value, that is, delay correction is required. If delay correction is not performed, a plurality of base stations will call out to the target pager at different timings, and these radio signals may cause mutual interference and cause problems such as data corruption. .
[0008]
Conventionally, the setting of the delay time for delay correction has been manually performed when the base station 2 is installed, as in the case where multiplexing is not performed. FIG. 6 is a diagram schematically showing a delay correction procedure in the conventional radio paging system. In the figure, the transmission terminal S and the reception terminal R of the channel device 4n in the central office 1 are connected back to back. With this configuration, a 200 Hz square wave (1200 bps data “111000”), for example, is transmitted to the central station 1 from the transmission terminal S of the channel device 10 n of the opposite base station 2. This data is turned back by the channel device 4n of the central station 1 and finally appears at the receiving terminal R of the channel device 10n of the base station 2. Therefore, the original transmission waveform and reception waveform are measured by, for example, the storage oscilloscope 130 capable of observing two events, and the round-trip time of the data is measured. FIG. 7 is a diagram showing the transmission waveform and the reception waveform observed in this way, in which the latter is compared with the former by T._DOnly late. Since this is a round trip time, this ½, ie T_D/ 2 is a transmission delay from the central station 1 to the base station 2.
[0009]
Subsequently, a delay correction time for the delay correction units 110 to 11 (n−1), that is, a delay time to be given for delay correction is set. Delay correction time T_MFor each base station,
T_M= T0-T_D/ 2 (Formula 1)
Calculated by T0 is T_MIs a constant value determined so as not to be negative. That is, according to Equation 1, the transmission delay from the central station 1 to the base station 2 is all the result of delay correction,
T0 = T_M+ T_D/ 2
To achieve the intended purpose.
[0010]
[Problems to be solved by the invention]
When the number of multiplexing in the demultiplexing control device 50 increases, the modems 60 and 80 require high-speed modems of, for example, 9600 bps or equivalent. Such high-speed modems usually have a transversal filter type automatic equalizer (Adaptive Equalizer), and operate in training mode first when the power is turned on for the first time or when the power is turned on again after a power failure or power interruption. Thus, the automatic equalizer is adjusted. The problem here is that the internal delay of the high-speed modem is not always constant during training. On the other hand, of course, the delay correction must include the internal delay of the high-speed modem.
[0011]
When delay correction as in the prior art is performed when such a high-speed modem is employed, the following problems arise.
[0012]
1. Since the training is performed for each high-speed modem, the delays in the high-speed modems on the central station 1 side and the base station 2 side do not have the same value._D/ 2 does not match the true transmission delay. For this reason, an error occurs in the set value of the delay correction time.
[0013]
2. Suppose that Even if there is no error, the internal delay of the high-speed modem changes when training is performed again due to an instantaneous interruption or the like. As a result, the set delay correction time includes an error.
[0014]
[Object of the present invention]
The present invention has been made in view of the above problems, and its purpose is to automatically obtain an optimal delay correction time and to reset it automatically when training a high-speed modem mainly on the base station side. Accordingly, it is an object of the present invention to provide a delay correction method that prevents the occurrence of a setting error.
[0015]
[Means for Solving the Problems]
(1) The delay correction method of the present invention realizes simultaneous call in a plurality of radio call base stations in a radio call system using a main modem that requires appropriate training for transmission between the radio call central station and the radio call base station. In order to compensate for this, both the radio paging central station and the radio paging base station are provided with a sub-modem that does not require training in addition to the main modem, and through data transmission by these sub-modems. After determining the basic timing relationship between both stations and training the main modem, through the data transmission by the main modem, the timing relationship resulting from the training is detected between the two stations, and the basic timing relationship is detected. From the timing relationship and the resulting timing relationship, a delay correction time to be set for each radio paging base station is calculated.
[0016]
Here, the “main modem” is usually a high-speed modem. On the other hand, the “secondary modem” does not require training and is usually a low speed modem. In the present invention, first, a sub-modem is provided in both the radio paging central station and the radio paging base station. Since this secondary modem does not need to be trained, the internal delay is constant. For this reason, first, data transmission is experimentally performed with this sub-modem, and the basic timing relationship between both stations is determined. The “basic timing relationship” refers to, for example, a transmission delay between both stations, a signal timing shift to be referred to when delay correction is performed between both stations, and the like. “Decision” is a process performed for the purpose of obtaining or storing the timing relationship between both stations, such as acquiring and storing the timing relationship between the two stations, or synchronizing or phase locking by a PLL circuit. Say.
[0017]
Subsequently, the main modem is trained, and then data transmission is performed by the main modem. Based on this data, after training, the resulting timing relationship between both stations is detected.
[0018]
Through the above process, a delay correction time to be set for each radio paging base station is calculated from the basic timing relationship and the resulting timing relationship. The delay correction time is a delay time that should be given to realize the delay correction.
[0019]
(2) Another aspect of the delay correction method of the present invention is that, as in (1), first, both stations are provided with auxiliary modems that do not require training. After this, when training for the main modem of the radio paging base station becomes necessary,
1. Measuring round trip delay of data using submodem of radio paging central station and radio paging base station
2. Prior to transmission of the training signal, a step of acquiring a timing relationship that initially exists between the two stations by performing data transmission by the secondary modem from the radio paging central station to the radio paging base station
3. A step of transmitting a training signal from the main modem of the radio paging central station to the main modem of the radio paging base station and training the main modem of the radio paging base station
4). After the training signal is transmitted, a process of acquiring a timing relationship resulting between the two stations through training by performing data transmission by the main modem from the radio paging central station to the radio paging base station.
The delay correction time to be set for each radio paging base station is calculated based on 1/2 of the round trip delay, the initially existing timing relationship, and the resulting timing relationship.
[0020]
(3) In an aspect of the present invention, in (2), the step of measuring the round-trip delay is performed in advance before training for the main modem of the radio paging base station is required to obtain the round-trip delay. When the training for the main modem of the radio paging base station becomes necessary, this process is not performed again.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described with reference to the drawings as appropriate.
[0022]
Embodiment 1. FIG.
[Constitution]
FIG. 1 is a configuration diagram of a radio paging system for realizing the delay correction method according to the first embodiment. In the figure, a central station 3 and a base station 4 are shown. Although the telephone and the public telephone network are not shown, they are connected to the central office 3 side as in FIG. In FIG. 1, members equivalent to those in FIG. 5 are given the same reference numerals, and description thereof will be omitted as appropriate.
[0023]
In FIG. 1, the main modem of the central office 3 is a high-speed modem 60 that requires training. As a modulation method by the high-speed modem 60, for example, QAM or TCM modulation can be adopted. In the new configuration on the central station 3 side, when performing delay correction, a reference signal generator 200 that generates a reference signal to be referred to on the base station 4 side in order to derive a delay correction time, and a modulator MOD includes, for example, an FSK. A low-speed modem 204 such as 1200 bps that performs modulation, and a switch 206 that connects one of the modulator of the high-speed modem 60 or the modulator of the low-speed modem 204 to the analog transmission line 70 based on a command from the control unit 202. In the present embodiment, it is assumed that the reference signal generator 200 generates a 200 Hz square wave. In this embodiment, the low speed modem 204 corresponds to the secondary modem. In the present embodiment, it is assumed that the control unit 202 is composed of a one-chip microcontroller and necessary peripheral circuits, and the control content is different from the conventional technology.
[0024]
On the other hand, the base station 4 also has a high-speed modem 80 which is the main modem. Other new configurations are a low-speed modem 222 and a switch 220 similar to those on the central office 3 side, and the configuration and operation of the control unit 224 are also different from those in FIG. The control unit 224 includes a software or hardware timer that is reset every 5 ms as will be described later. In the present embodiment, the delay correction time in the delay correction units 110 to 11 (n−1) is automatically set from the control unit 224. The delay correction units 110 to 11 (n−1) are configured by a variable shift register, that is, a shift register in which the number of shift stages can be set by software. The delay correction time is determined by the number of shift stages.
[0025]
[Operation]
FIG. 2 is a diagram showing training of the high speed modem in the radio paging system of FIG. 1 and a delay correction procedure performed at that time. In the figure, a broken line indicates transmission by a low-speed modem, and a solid line indicates transmission by a high-speed modem. Here, in order to train the high-speed modem 80 of the base station 4, a training request is issued from the base station 4 side and a training signal is issued from the central station 3. At this time, the base station 4 Information exchange for setting an optimal delay correction time is included in the four-side delay correction units 110 to 11 (n−1).
[0026]
As shown in the figure, when the equalization adjustment of the high-speed modem is out of order due to, for example, a power failure, a training request is first issued from the base station 4 when retraining is required. In response, the central office 3 stops transmission by the high-speed modem 60 and returns an ACK signal indicating that the training request has been recognized. Subsequently, a 200 Hz square wave (hereinafter referred to as a reference signal) generated by the reference signal generator 200 is transmitted to the base station 4 for a predetermined time. The reference signal is transmitted by the low speed modem 204. Here, since the low-speed modem is 1200 bps, the reference signal corresponds to repeated data of “111000”.
[0027]
In the base station 4 that has received the reference signal, the output of the low-speed modem 222 is connected back to the input, the reference signal is sent back to the central station 3 as it is, and a timing relationship that initially exists between the central station 3 and the base station 4 That is, the timing shift τ1 is measured. In the present embodiment, “timing deviation τ1” means that when the reference signal is received by the base station 4, the rising time of the reference signal (the time when the data changes from 0 to 1) and its own built-in timer are reset every 5 ms. This is a difference from the time. τ1 is different for each base station 4 because the built-in timers of the base stations 4 are not synchronized with each other.
[0028]
FIG. 3 is a diagram illustrating a method of measuring the timing shift τ1. As shown in the figure, the built-in timer of the control unit 224 of the base station 4 is reset to 0 every 5 ms, and thereafter, for example, the time is counted every several μs. If the count is performed every 1 μs, the count value of the built-in timer takes a value of 0-4999. In the figure, the count value of the built-in timer at the rising time of the reference signal is τ1. In consideration of errors due to modem jitter, the average of the count values over several times may be τ1.
[0029]
On the other hand, the reference signal returned by the base station 4 returns to the central station 3 and the control unit 202 makes a round trip delay T._DIs measured. T_DDiffers for each base station 4. T_DWhen the measurement of_DIs transmitted to the base station 4. The base station 4 receives the received T_DAre stored in the memory, the demodulator of the high-speed modem 80 is switched to the training mode, and the ACK signal is returned to the central station 3.
[0030]
Upon receiving the ACK signal, the central office 3 switches the switch 206 to disconnect the modulation unit of the low-speed modem 204 from the analog transmission path 70 and connects the modulation unit of the high-speed modem 60 instead. Subsequently, a known training signal is transmitted to the base station 4 using the high speed modem 60. The base station 4 adjusts the automatic equalizer using this training signal. At this time, for example, establishment of synchronization necessary for the demultiplexing control apparatus is also performed. Thereafter, the base station 4 transmits a training completion notification to the central station 3.
[0031]
Upon receiving this notification, the central office 3 stops the transmission of the training signal, and transmits the reference signal from one of the channel devices, for example, the transmission terminal S of the channel device 4n for monitoring control through the multiplexer 50 and the high-speed modem 60. Transmit to station 4. Since the transmission speed of each channel device is 1200 bps, which is the same as that of the low-speed modem, the reference signal also corresponds to repeated data of “111000”.
[0032]
When the base station 4 receives this reference signal, the reference signal is output from the channel device 10n opposite to the channel device 4n. The timing relationship, that is, the timing shift τ2 is measured. Similarly to FIG. 3, τ2 is determined by measuring the rising time of the reference signal by the built-in timer of the control unit 224 of the base station 4. τ2 is also different for each base station 4. If τ2 is obtained, the T_D, Τ1, τ2, and a constant T0 that is somewhat large as described in the prior art, and the delay correction time T_MIs calculated and set in each of the delay correction units 110 to 11 (n−1). At this time, since the interval between the transmission of the reference signal by the low-speed modem 204 and the transmission of the reference signal by the high-speed modem 60 is an integral multiple of a period of 5 ms of 200 Hz, the delay correction time can be derived by a single internal timer of 5 ms. It becomes possible.
[0033]
T_M= T0-T_D/ 2-Δτ (Formula 2)
Where Δτ is
Δτ = τ2−τ1 (τ2 ≧ τ1) (Formula 3)
Δτ = τ2−τ1 + 5 ms (τ2 <τ1) (Formula 4)
Here, Δτ is obtained in order to subtract τ1 depending on the reset timing of the built-in timer from τ2 indicating the delay time generated including the delay component due to training. By subtracting τ1, it is possible to eliminate the influence of variations among the built-in timers of the plurality of base stations 4. The case where Δτ is divided according to the magnitude relationship between τ1 and τ2 is based on the following consideration. That is, when the same reference signal is transmitted by the high-speed modem 60 and the low-speed modem 204, it is considered that the transmission delay by either one of the base stations 4 (usually a high-speed modem) is greater. Therefore, the magnitude relationship between τ1 and τ2 should be the same in any base station 4, and this is reversed because the rising time just before (or after) the rising edge of the reference signal to be timed is counted by the built-in timer. This is probably due to this. Therefore, in order to correct this situation, 5 ms which is one cycle of the reference signal is added.
[0034]
When the delay correction in the base station 4 is completed by the above procedure, the base station 4 sends a delay correction completion notification to the central station 3. Upon receiving this notification, the central station 3 returns an ACK signal to notify the base station 4 that the transmission of the reference signal is stopped and that the normal communication mode is restored.
[0035]
In FIG. 2, the transmission from the base station 4 to the central station 3 is depicted as being performed by the low-speed modem 222. This is because communication from the base station 4 to the central station 3 does not require high speed. Naturally, the equalization adjustment of the high speed modem 60 on the base station side must be out of order for transmission other than the return of the reference signal. For example, a high-speed modem 80 may be used. In this embodiment, both stations have two types of modems in parallel, and data transmitted from the other party is input in parallel to the two types of modems, so one station uses a high-speed modem for transmission, It is also possible for the other station to use a low speed modem for transmission.
[0036]
In the present embodiment, it is preferable that the elapsed time from the measurement of τ1 to the measurement of τ2 in the base station 4 is short. This is because the clock source used in the reference signal generator 200 of the central station 3 and the clock source used in the built-in timer of the base station 4 are independent, and measurement errors cannot be ignored according to the elapsed time. Now, these clock sources are crystal oscillators, and their frequency deviation is ± 5 × 10^-6Since the time required for training is normally considered to be about 1 second, if the elapsed time from the measurement of τ1 to the measurement of τ2 is assumed to be 2 seconds, the maximum error is
2s × (+5-(− 5)) × 10^-6= 20μs
It becomes. On the other hand, since the deviation of the radio call timing normally permitted in the 1200 bps radio call system is about 50 μs, this value can be sufficiently allowed. Of course, when higher accuracy is required, for example, ± 1 × 10^-6It is only necessary to use a high-precision crystal oscillator such as the above and to shorten the elapsed time from the measurement of τ1 to the measurement of τ2.
[0037]
The above is the outline of the delay correction according to the present embodiment. According to this embodiment, since the delay correction can be automatically executed at the time of training in which the delay may vary, it is efficient. Note that the following improvements and modifications can be considered for this embodiment.
[0038]
1. Here, a square wave of 200 Hz is used as the reference signal, but it does not need to be 200 Hz or a square wave. For example, if a clock of about 200 Hz can be generated from the frequency division of the clock used in the control unit 202, the demultiplexing control device 50, etc., this may be used as it is. In that case, the reference signal generator 200 can be deleted.
[0039]
2. Similarly, the low speed modems 204, 222 need not be FSK modems. Any modem that does not require training, that is, whose internal delay does not fluctuate, can be used as the low-speed modems 204 and 222.
[0040]
3. Here, the rising time of 200 Hz is used for the measurement of τ1 and the measurement of τ2, but it is possible to use another time such as the falling.
[0041]
Embodiment 2. FIG.
In the first embodiment, a round trip delay T for each training._DAnd the transmission delay T_D/ 2. However, this T_DIs normally an invariant value, and can be obtained in advance when the base station 4 is installed.
[0042]
FIG. 4 is a diagram showing the training of the high speed modem according to the second embodiment and the procedure of delay correction performed at that time. Also in this figure, the configuration of the radio paging system is assumed to be that of the first embodiment. 2 differs from FIG. 2 in that the reference signal transmitted from the central station 3 to the base station 4 by the low-speed modem 204 is not returned on the base station 4 side, and only τ1 is measured. T at central office 3_DMeasurement is not performed, so measurement completion and T_DIs not notified. T_DIs naturally stored in advance in the memory of the base station 4 and is used for calculating the delay correction time. The other points are the same as in FIG.
[0043]
As described above, according to the second embodiment, the procedure for delay correction can be simplified. The second embodiment can be improved and modified in the same manner as the first embodiment.
[0044]
Other embodiments
In the first and second embodiments, the base station 4 has a delay correction unit for itself. However, the central station 3 may have a separate delay correction unit for each base station 4, and this may be collectively managed by the control unit 202. In this case, the delay correction data (Δτ) is measured for each base station, and is transmitted individually by a low-speed modem or a high-speed modem provided for each base station. With this configuration, it is possible to concentrate monitoring control for delay correction in one place.
[0045]
In addition, when a multiplexer and a high-speed modem are introduced for transmission between a central station and a base station, which conventionally used a plurality of low-speed modems and a plurality of dedicated lines, a modification is made so that the dedicated line can be completed with one line. Fixed delay T_DWhen the existing equipment can be used for the delay correction of / 2, the delay correction units 110 to 11 (n−1) may be used only for the correction of the variation delay Δτ.
[0046]
That is, the set value T of the existing delay correction equipment_M1The
T_M1= T₀₁-T_D/ 2
On the other hand, the set value T of the delay correction units 110 to 11 (n−1)_M2The
T_M2= T₀₂−Δτ
Then T_DIf the low-speed modem used to measure τ1 and τ1 are the same, (T_D/ 2 + Δτ) is the correct delay time for high-speed modems, so the total delay correction time
T_M1+ T_M2= (T₀₁+ T₀₂)-(T_D/ 2 + Δτ)
Gives the correct delay correction.
[0047]
In the first and second embodiments, the timing shift between the central station 3 and the base station 4 is acquired in the form of τ1 and τ2, but another method is conceivable. For example,
1. Extracting a 200 Hz clock component from the reference signal transmitted by the low speed modem 202;
2. A step of inputting the extracted clock component into a PLL (Phase Locked Loop) circuit to reproduce a 200 Hz reference signal;
3. Sampling the reference signal transmitted by the high speed modem 60 using the reproduced reference signal as a sampling clock;
It is also possible to adopt a configuration in which a numerical value directly corresponding to Δτ is obtained. In the case of this configuration, the reference signal reproduction process by the PLL circuit has an effect of averaging the numerical values. Therefore, the same effect as that obtained by acquiring τ1 several times in the first and second embodiments can be obtained.
[0048]
【The invention's effect】
According to the delay correction method of the present invention, since the timing relationship between the central station and the base station is determined by the sub-modem whose delay time does not vary before the main modem training, an accurate delay correction time to be given after the main modem training is determined. Can be calculated. As a result, delay correction can be performed automatically and efficiently, which is useful, for example, in a multiplexing system using a high-speed modem as a main modem.
[0049]
When the round-trip delay of data from the radio paging central station to the radio paging base station is acquired in advance, the procedure for delay correction necessary for each training can be simplified.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a radio paging system for realizing a delay correction method according to a first embodiment.
FIG. 2 is a diagram showing a procedure of high-speed modem training and delay correction performed at that time in the radio paging system shown in FIG. 1;
FIG. 3 is a diagram illustrating a method of measuring a timing shift τ1 in the first embodiment.
FIG. 4 is a diagram illustrating training of a high-speed modem according to the second embodiment and a delay correction procedure performed at that time.
FIG. 5 is a configuration diagram of a conventional radio paging system.
FIG. 6 is a diagram schematically showing a procedure for delay correction in a conventional radio paging system.
FIG. 7 is a diagram showing a transmission waveform and a reception waveform observed when data is reciprocated.
[Explanation of symbols]
3 central office, 4 base station, 10 to 1 m telephone, 20 public telephone network, 30 regional control device, 40 to 4n, 100 to 10n channel device, 50 demultiplexing control device, 60,80 high-speed modem, 70,71 analog transmission Path, 90 demultiplexing control device, 110-11 (n-1) delay correction unit, 120-12 (n-1) transmitter, 200 reference signal generator, 202, 224 control unit, 204, 222 low speed modem, 206 , 220 switch.

Claims (3)

In a radio paging system that uses a modem that requires appropriate training for transmission between a radio paging central station and a radio paging base station, a method for performing delay correction to realize simultaneous paging at a plurality of radio paging base stations,
The modem is a main modem, and a sub-modem that does not require training is provided in addition to the main modem in each of the radio call central station and the radio call base station,
Determine the basic timing relationship between both stations through data transmission by these secondary modems,
After training the main modem, through the data transmission by the main modem, detect the resulting timing relationship between both stations by training,
A delay correction method for calculating a delay correction time to be set for each radio paging base station based on the basic timing relationship and the resulting timing relationship. In a radio paging system that uses a modem that requires appropriate training for transmission between a radio paging central station and a radio paging base station, a method for performing delay correction to realize simultaneous paging at a plurality of radio paging base stations,
The modem is the main modem, and both the radio paging central station and the radio paging base station are provided with a sub-modem that does not require training in addition to the main modem, and training for the main modem of the radio paging base station is required. When it becomes
Measuring the round trip delay of data using a radio paging central station and a radio paging base station secondary modem;
Before transmitting the training signal, by performing data transmission by the secondary modem from the radio paging central station to the radio paging base station, obtaining a timing relationship that initially exists between the two stations,
Transmitting a training signal from the main modem of the radio paging central station to the main modem of the radio paging base station, and training the main modem of the radio paging base station;
After transmission of the training signal, by performing data transmission by the main modem from the radio paging central station to the radio paging base station, obtaining a timing relationship resulting from the two stations through training,
The delay correction time to be set for each radio paging base station is calculated based on the half of the round-trip delay and the comparison of the resulting timing relationship and the initially existing timing relationship. A delay correction method characterized by: The step of measuring the round trip delay is performed in advance before training for the main modem of the radio paging base station is required, and the round trip delay is obtained in advance, and training for the main modem of the radio paging base station is required. 3. The delay correction method for a radio paging system according to claim 2, wherein the step is not performed again.

Images