JP4765664B2 - Wireless communication system - Google Patents

Description

The present invention relates to a radio communication system configured with a wireless communication equipment to be performed real as a PHS base station, the synchronization signal generator for particular synchronizing frame timings of the adjacent wireless communication apparatus (base station) The present invention relates to an apparatus for receiving a predetermined signal such as an ISDN clock or a signal from a GPS satellite.

  A wireless communication device implemented as a base station of the PHS (Personal Handyphone System) enables communication without data collision with each wireless communication terminal by performing communication at the timing specified by the control signal. It has become. In order to realize smooth communication of the wireless communication terminal such as a handover, the ISDN (Integerated Services Digital Network) is used to synchronize the frame timing with adjacent wireless communication devices in which a part of each area overlaps each other. ) Is used to generate a timing signal that defines the frame timing of the wireless communication unit by using a highly accurate timing signal (ISDN clock) obtained by connecting to (). However, this synchronization signal generator must always be connected to ISDN, and if it is not connected to ISDN, the timing signal cannot be obtained.

On the other hand, as a general synchronizing signal generator (or reference frequency generator), as shown in Patent Document 1, a pulse signal (hereinafter referred to as 1PPS signal) output at a 1 second interval from a GPS receiver is highly accurate. An oscillator (for example, OCXO) is used to output a signal synchronized with UTC (Universal Standard Time). According to the prior art, the signal from the oscillator is used as the timing signal when the validity of the 1PPS signal is doubtful due to a GPS receiver failure, satellite position, communication environment, or the like. . Many PHS base stations are installed in an urban area, but in such an environment, multipath and noise are likely to occur, and the above-described problems are likely to occur.
JP-A-8-105984

In the above-described prior art, an oscillator used for backup is required to have a stable and high accuracy. For example, when the frame timing can be allowed to shift up to 10 μsec, 10 ⁻⁹ to 10 ⁻¹⁰ like a rubidium oscillator or the like. For about 48 hours, the oscillator can run for free and the pulse signal can be used to define the frame timing. However, such a high-accuracy oscillator is very expensive, for example, about 400,000 to 500,000 yen. For a base station of PHS that requires a small service area and a large number of units to be installed per unit area, a significant cost is required. There is a problem of inviting up.

An object of the present invention is to provide such a signal failure to define frame timing is to provide a non-line communication system is Ru can be realized backup at low cost.

The wireless communication system of the present invention includes a synchronization signal generating device and a wireless communication unit, and a wireless communication system in which a plurality of wireless communication devices serving as PHS base stations are connected to a management center via a communication line. The synchronization signal generating device receives an oscillator that generates a first timing signal that defines the frame timing and a predetermined signal from the wireless communication unit, and receives a predetermined signal based on the received signal. a reference signal generator for generating a second timing signal, and calibration means for calibrating the first timing signal by said second timing signal, receiving a control signal from an adjacent wireless communications apparatus, for detecting the frame timing When the detection means, the detection result of the detection means and the frame timing of the own station are compared, and the frame timing of the own station is shifted The saw including a communication control means for halting the communication operation of the radio communication terminal by the wireless communication unit, said communication control means detects an abnormality in the frame timing of another station via the communication line from the communication unit A notification is made to the management center, and the communication operation of the target wireless communication device is suspended by a command from the management center .

According to the above configuration, the wireless communication system includes the synchronization signal generating device and the wireless communication unit, and a plurality of wireless communication devices used as PHS base stations are connected to the management center via the communication line. in the synchronizing signal generator, in order to achieve a smooth communication of said wireless communication terminals, such as handover, to synchronize the frame timing of the neighboring wireless communication devices overlaps at least a part of each other area. Therefore , the synchronization signal generator includes an oscillator that generates a first timing signal that defines the frame timing of the wireless communication unit, and receives a predetermined signal, for example, from an ISDN clock or a GPS satellite signal. A reference signal generator for generating a second timing signal, for example, by generating a pulse signal (1PPS signal) having an interval of 1 second synchronized with UTC (Universal Standard Time), and the first timing signal by the second timing signal It comprises calibration means for calibrating .

Further, the synchronization signal generator receives a control signal from an adjacent wireless communication device, detects a frame timing, compares the detection result of the detection unit with the frame timing of the own station, and performs self-diagnosis. when the frame timing of its own station is shifted to the Keru set and a communication control means for halting the communication operation of the radio communication terminal by the wireless communication unit. Whether or not the frame timing of the local station is shifted is determined by receiving a control signal from a plurality of adjacent wireless communication devices, and all wireless communication devices that detect a frame timing shift greater than a predetermined threshold are detected. In this case, it can be realized by determining that the local station is abnormal, and otherwise determining that the counterpart wireless communication apparatus is abnormal. In addition, the suspension of the communication operation can be realized by stopping the oscillator or stopping the power supply of the transmission amplifier.

  Accordingly, when the free-running time of the oscillator becomes longer from the last calibration by the second timing signal and an error of a predetermined value or more is accumulated in the first timing signal, the communication operation by the wireless communication unit is suspended. Therefore, the influence on the wireless communication network can be reduced. As a result, it is not necessary to use a highly accurate oscillator, and even if an inexpensive voltage-controlled oscillator (VCXO) is used, it is possible to prevent the predetermined signal from being damaged for a short time. 1 timing signal backup can be realized, and even if the number of detection means increases, the cost of the synchronization signal generator can be greatly reduced as a whole.

Further, when the communication control unit detects an abnormality in the frame timing of another station, the communication unit notifies the management center via the communication line, and the communication operation of the target wireless communication device is performed according to a command from the management center. Therefore, even if the abnormality is not determined by the self-diagnosis of the wireless communication device in which an abnormality has occurred, it can be monitored by another wireless communication device. If it is determined, the communication operation is suspended via the management center, so that the reliability can be improved.

Furthermore, since a large number of PHS base stations need to be installed per unit area due to the narrow service area of each station, the significant cost reduction as described above is very effective.

In the radio communication system according to the present invention, the oscillator includes a voltage controlled oscillator and frequency conversion means for converting a frequency of an output signal of the voltage controlled oscillator to 1 Hz to create a pulse signal at intervals of 1 second. The reference signal generator is a GPS receiver that receives a signal from a GPS satellite as a second timing signal and creates a pulse signal with an interval of 1 second synchronized with the world standard time. A time interval measuring means for measuring the time difference between the pulse signal from the GPS receiver and the pulse signal from the frequency converting means, and a control for calculating a control amount so as to reduce the time difference obtained by the time interval measuring means. And a digital / analog conversion unit that converts the control amount calculated by the control unit into a voltage and supplies the voltage to the voltage controlled oscillator. That.

  According to said structure, a calibration means is realizable with the cheap structure of a normal PLL.

Furthermore, in the wireless communication system of the present invention, the detection means includes reception level determination means for excluding a control signal from a wireless communication apparatus whose reception level is a predetermined value or less from detection of the frame timing. To do.

  According to the above configuration, the detection means is provided with a reception level determination means, and a control signal from a wireless communication apparatus that is considered to be relatively far from the own station when the reception level is equal to or less than a predetermined value is received at the frame timing. By excluding from detection, frame timing is compared only with control signals from relatively nearby wireless communication devices that are less affected by propagation delay, and the accuracy of determination of frame timing deviation in the communication control means is improved. can do.

Further, in the radio communication system of the present invention, prior Symbol communication control unit accesses the management center from the communication means via said communication line, the propagation delay time of the control signal from the adjacent wireless communication apparatus to the own station It further comprises frame timing correction means for acquiring information regarding the frame timing and correcting the frame timing detected by the detection means based on the information.

According to the above configuration, when determining the frame timing deviation as described above, the frame timing correction unit corrects the propagation delay of the control signal due to the influence of the distance between adjacent wireless communication devices, etc. The determination accuracy can be improved .

As described above, the wireless communication system of the present invention includes the synchronization signal generating device and the wireless communication unit, and a plurality of wireless communication devices serving as PHS base stations are connected to the management center via communication lines. In order to realize smooth communication of the wireless communication terminal such as a handover , the synchronization signal generating device is configured to perform frame timing with an adjacent wireless communication device in which at least a part of each area overlaps. In order to synchronize the signal, an oscillator that generates a first timing signal that defines the frame timing of the wireless communication unit is provided, and a predetermined signal such as a signal from an ISDN clock or a GPS satellite is received, whereby the received signal is And a reference signal generator for generating a second timing signal based on the second timing signal And calibration means for calibrating the timing signal, receiving the control signals from the adjacent wireless communication apparatus compares the detection means for detecting frame timing and a frame timing detection result and the own station of the detection means, self when the frame timing of the diagnosis to the own station is shifted, the saw including a communication control means for halting the communication operation of the radio communication terminal by the wireless communication unit, the communication control unit, the frame timing of another station abnormalities Is detected from the communication means to the management center via the communication line, and the communication operation of the target wireless communication device is suspended according to a command from the management center .

  Therefore, when the free-running time of the oscillator becomes longer from the last calibration by the second timing signal and an error of a predetermined value or more is accumulated in the first timing signal, the communication operation by the wireless communication unit is suspended. Therefore, the influence on the wireless communication network can be reduced. As a result, it is not necessary to use a highly accurate oscillator, and even if an inexpensive voltage-controlled oscillator (VCXO) is used, it is possible to prevent the predetermined signal from being damaged for a short time. 1 timing signal can be backed up, and the cost of the synchronization signal generator can be greatly reduced even if the number of detection means increases.

Moreover, even if it is not determined abnormality by the self-test of the wireless communication device abnormality has occurred, if it is determined by the other wireless communication device, via the management center, halting the communication operation of the target wireless communication device Therefore , it is possible to improve the reliability by mutually monitoring the deviation of the first timing signal by the inexpensive oscillator.

[Embodiment 1]
FIG. 1 is a block diagram showing an electrical configuration of a PHS base station 1 which is a wireless communication apparatus according to the first embodiment of the present invention. The PHS base station 1 is installed adjacent to each other so that at least a part of the service areas SA, SB, and SC overlap each other as shown by reference characters A, B, and C in FIG. Communicate with.

  The PHS base station 1 generally includes a PHS communication unit 2 and a PHS antenna 3 that are radio communication units, and a synchronization signal generator 4 that generates a first timing signal that defines frame timing in the PHS communication unit 2. And is configured. The synchronization signal generator 4 receives the signal from the GPS satellite, which is a predetermined signal, and the oscillator 10 that generates the first timing signal, and generates a second timing signal based on the received signal. A reference signal generator 20, a calibration unit 30 that calibrates the first timing signal by the second timing signal, and PHS that is a detection means for receiving a control signal from an adjacent PHS base station and detecting a frame timing Communication that causes the PHS communication unit 2 to pause the communication operation with the radio communication terminal when the antenna timing of the antenna 40 and the detection result of the PHS antenna 40 are compared with the frame timing of the own station and the frame timing of the own station is shifted. And a control unit 41.

  The oscillator 10 is a voltage-controlled oscillator (VCXO) 11 and a signal generated thereby, which is a pulse signal at intervals of 1 second and a period of a control signal as the first timing signal requested by the PHS communication unit 2 is 100 msec. And a frequency converter 12 for frequency division. The voltage controlled oscillator 11 is inexpensive and has an accuracy of, for example, 1 ppm. Therefore, if it runs for 10 seconds without being calibrated, it will exceed the allowable range of the frame timing error of the 10 μsec PHS signal.

  The reference signal generator 20 includes a GPS antenna 21 that receives a GPS signal, and a 1PPS signal (pulse signal with an interval of 1 second) synchronized with UTC (World Standard Time) from the received signal as the second timing signal. And a GPS receiver 22 for outputting. The reference signal generator 20 is not limited to a GPS signal, and the second timing signal may be generated from an ISDN clock or the like.

  The calibration unit 30 is obtained by a time interval measurement unit 31 that measures a time difference between a 1 Hz pulse signal from the frequency converter 12 and a 1 PPS signal from the GPS receiver 22, and the time interval measurement unit 31. A control unit 32 that calculates a control amount that reduces the time difference, and a digital / analog converter 33 that converts the control amount calculated by the control unit 32 into a voltage (tuning voltage) and applies the voltage to the voltage controlled oscillator 11. It is realized by an inexpensive configuration of a normal PLL configured with the above. The calibration unit 30 repeats the PLL operation as described above at the frequency of the 1 Hz pulse signal from the frequency converter 12 that has been changed by controlling the tuning voltage.

  The communication control unit 41 has a function equivalent to that of a normal PHS receiver, and each signal is a unique word included in a control signal from a signal received by the PHS antenna 40 using a signal from the voltage controlled oscillator 11 as an operation clock. The frame timing calculation unit 42 for calculating the frame timing of the PHS base station, and the difference between the frame timing of each PHS base station calculated by the frame timing calculation unit 42, that is, the frame timing of the own station, determines the abnormality of the own station. The control signal of the frequency requested by the PHS communication unit 2 from the frequency converter 12 and the frame timing abnormality determination unit 43 to be determined are normally sent to the PHS communication unit 2 to enable communication by the PHS communication unit 2 When the frame timing abnormality determining unit 43 determines that the own station is abnormal, The prohibited constructed and an output control switch 44 for disabling the communication by the PHS communication unit 2.

  The frame timing abnormality determination unit 43 compares the difference between the frame timing of each PHS base station and the frame timing of its own station with a preset value (threshold value). It can be determined that the station's frame timing (VCXO frequency) is abnormal, and in other cases, the frame timing of the base station (base station larger than the threshold) is determined to be abnormal, thereby determining the abnormality of the own station. it can. Such an operation is performed every 100 msec which is the cycle of the control signal. If there is an abnormality, the output of the control signal is stopped, and if there are no more stations than the threshold, the output of the control signal is restarted. The reason why the base station larger than the threshold is determined to be abnormal in all cases is that the main cause of the stop of 1PPS signal and the fluctuation of the interval is due to multipath, noise, etc., and such an abnormality has occurred. This is because it is local, and it is unlikely that it will occur simultaneously in all of a plurality of adjacent PHS base stations.

  Further, in order to disable communication by the PHS communication unit 2, not only the control signal but also power supply to the transmission amplifier may be stopped.

  In synchronizing the frame timing with the adjacent PHS base station where at least a part of each area overlaps by the synchronization signal generating device 4 configured as described above, from the last calibration of the control signal by the GPS 1PPS signal, If the self-running time of the oscillator 10 becomes long and an error of a predetermined value or more is accumulated in the control signal, the communication operation with the wireless communication terminal by the PHS communication unit 2 is suspended by self-diagnosis. The influence given can be reduced. As a result, it is not necessary to use a highly accurate oscillator 10, and even if an inexpensive voltage controlled oscillator (VCXO) 11 or the like is used, for short-time reception failure of the GPS signal, etc. Control signal backup can be realized. As a result, the configuration of the PHS antenna 40 and the communication control unit 41 is increased as compared with the case where the high-precision rubidium oscillator is used, but the cost increase due to them can be reduced to about 10,000 yen. As a total, the cost of the synchronization signal generator 4 and, consequently, the PHS base station 1 that is a wireless communication device can be greatly reduced.

  Further, in the case of the PHS base stations A, B, and C, since the service areas SA, SB, and SC of each station need to be installed in large numbers per unit area, the significant cost reduction as described above is extremely high. It is valid.

[Embodiment 2]
FIG. 3 is a block diagram showing an electrical configuration of the PHS base station 51 which is a wireless communication apparatus according to the second embodiment of the present invention. The PHS base station 51 is similar to the PHS base station 1 described above, and corresponding portions are denoted by the same reference numerals, and description thereof is omitted. It should be noted that in this PHS base station 51, a reception level determination unit 52 is provided in the communication control unit 41a of the synchronization signal generator 4a, and this reception level determination unit 52 is calculated by the frame timing calculation unit 42a. The timing value of the adjacent base station whose reception level of the signal obtained simultaneously with the frame timing value of each adjacent base station is not more than a predetermined value is not input to the frame timing abnormality determination unit 43. That is, the base station with a low reception level is considered to be relatively far from the own station, and the control signal from the base station is expected to have a large propagation delay time and a large frame timing value even if it is not abnormal. Exclude from detection.

  As a result, the frame timing is compared only with the control signal from a relatively neighboring base station that is less affected by the propagation delay, and the determination accuracy of the frame timing deviation in the frame timing abnormality determination unit 43 is improved. Can do.

[Embodiment 3]
FIG. 4 is a block diagram showing an electrical configuration of a PHS system which is a wireless communication system according to the third embodiment of the present invention. The PHS system includes a plurality of PHS base stations 61 and a PHS base station information management center 62 that is a management center. The PHS base station information management center 62 manages information related to each PHS base station 61 such as the installation position of each PHS base station 61 and the radio wave condition between the PHS base stations 61 (the propagation delay, the electric field strength level, etc.). Yes.

  On the other hand, in the synchronization signal generator 4b of the PHS base station 62, the communication control unit 41b is provided with a frame timing correction unit 64 in the communication unit 63 for communicating with the PHS base station information management center 62. . The communication control unit 41 b acquires the data of the propagation delay time of the control signal from each adjacent base station from the PHS base station information management center 62 and gives it to the frame timing correction unit 64. The frame timing correction unit 64 corrects the frame timing obtained by the frame timing calculation unit 42 with the propagation delay time acquired by the communication unit 63 and gives the frame timing abnormality determination unit 43. Note that the information acquired from the PHS base station information management center 62 does not have to be the propagation delay time data of the control signal between adjacent base stations. The distance may be calculated and divided by the velocity of the radio wave), or any data that clarifies the propagation delay time such as the distance between the adjacent base station and the own station.

  By configuring in this way, in determining the frame timing deviation of the control signal, the frame timing correction unit 64 corrects the propagation delay of the control signal due to the influence of the distance between adjacent base stations, etc. The determination accuracy can be improved.

[Embodiment 4]
FIG. 5 is a block diagram showing an electrical configuration of a PHS system which is a radio communication system according to the fourth embodiment of the present invention. The PHS system includes a plurality of PHS base stations 71 and a synchronization signal generator monitoring center 72 that is a management center. The synchronization signal generator monitoring center 72 monitors the synchronization signal generator 4c of each base station based on information from adjacent base stations.

  On the other hand, in the synchronization signal generating device 4c of the PHS base station 72, the communication control unit 41c is provided with a communication unit 63c for communicating with the PHS base station information management center 62. A frame timing abnormality determination unit 43c is connected to the communication unit 63c. It should be noted that when the frame timing abnormality determination unit 43c detects a frame timing abnormality of another PHS base station, the PHS base station information management center 62 is notified via the communication unit 63c, and PHS base station information The management center 62 outputs a command indicating that the output of the control signal is stopped to the communication unit 63c of the target base station, whereby the frame timing abnormality determination unit 43c determines abnormality, and the output control switch 44 Is to switch.

  By configuring in this way, it is possible to mutually monitor the error of the signal from the inexpensive oscillator 10, and even if the abnormality is not determined by the self-diagnosis of the base station where the abnormality has occurred, it is determined by another base station. Then, the communication operation is suspended via the PHS base station information management center 62, and the reliability can be improved.

It is a block diagram which shows the electrical structure of the PHS base station which is a radio | wireless communication apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows a PHS system. It is a block diagram which shows the electric constitution of the PHS base station which is a radio | wireless communication apparatus which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the electric constitution of the PHS system which is a radio | wireless communications system which concerns on the 3rd Embodiment of this invention. It is a block diagram which shows the electric constitution of the PHS system which is a radio | wireless communications system which concerns on the 4th Embodiment of this invention.

1, 51, 61, 71; A, B, C PHS base station 2 PHS communication unit 3, 40 PHS antenna 4, 4a, 4b, 4c Synchronous signal generator 10 Oscillator 11 Voltage controlled oscillator (VCXO)
12 Frequency converter 20 Reference signal generator 21 GPS antenna 22 GPS receiver 30 Calibration unit 31 Time interval measurement unit 32 Control unit 33 Digital / analog converters 41, 41a, 41b, 41c Communication control unit 42, 42a Frame timing calculation unit 43, 43c Frame timing abnormality determination unit 44 Output control switch 52 Reception level determination unit 62 PHS base station information management center 63, 63c Communication unit 64 Frame timing correction unit 72 Synchronization signal generator monitoring center SA, SB, SC Service area

Claims (4)

In a wireless communication system comprising a synchronization signal generating device and a wireless communication unit, wherein a plurality of wireless communication devices serving as PHS base stations are connected to a management center via a communication line.
The synchronization signal generator is
To the radio communication unit, an oscillator for generating a first timing signal defining the frame timing,
A reference signal generator for generating a second timing signal based on the received signal by receiving a predetermined signal;
Calibration means for calibrating a first timing signal with the second timing signal ;
Detection means for receiving a control signal from an adjacent wireless communication device and detecting frame timing;
Comparing the frame timing of the detection result and the own station of the detecting means, when the frame timing of its own station is misaligned, saw including a communication control means for halting the communication operation of the radio communication terminal by the wireless communication unit ,
When the communication control means detects an abnormality in the frame timing of another station, it notifies the management center via the communication line from the communication means, and pauses the communication operation of the target wireless communication device according to a command from the management center. wireless communication system characterized in that it makes. The oscillator comprises a voltage-controlled oscillator and frequency conversion means for converting the frequency of the output signal of the voltage-controlled oscillator to 1 Hz to create a pulse signal with an interval of 1 second,
The reference signal generator is a GPS receiver that receives a signal from a GPS satellite as a second timing signal and creates a pulse signal at 1 second intervals synchronized with the world standard time,
The calibration means includes a time interval measurement means for measuring a time difference between the pulse signal from the GPS receiver and a pulse signal from the frequency conversion means, and a control amount for reducing the time difference obtained by the time interval measurement means. 2. The control unit according to claim 1, further comprising: a control unit that calculates a voltage; and a digital / analog conversion unit that converts a control amount calculated by the control unit into a voltage and supplies the voltage to the voltage controlled oscillator. Wireless communication system . 3. The wireless communication system according to claim 1, wherein the detection means includes reception level determination means for excluding a control signal from a wireless communication apparatus whose reception level is a predetermined value or less from detection of the frame timing. . Before SL communication control unit accesses the management center from the communication means via said communication line, and obtain information about the propagation delay time of the control signal from the adjacent wireless communication apparatus to the own station, based on the information The radio communication system according to claim 1 , further comprising a frame timing correction unit that corrects the frame timing detected by the detection unit.

Images