JP2006033703A - Communication system, base station apparatus, reference clock generation circuit, and synchronization method - Google Patents

Abstract

A technique for synchronizing devices without providing a wired line between the devices is provided.
A frequency component is extracted from a signal of an AC power supply (S404), the frequency component of the extracted signal is multiplied to a predetermined frequency (S405 / 406), and the frequency of the multiplied signal is set to a reference clock. Frequency division is performed (S407). The frequency phase of the divided reference clock is corrected (S408), the corrected reference clock is output (S409), and a predetermined frame synchronization process is performed (S410).
[Selection] Figure 5

Description

The present invention relates to a synchronization method between radio base stations of a TDMA (Time Division Multiple Access) communication system and a technique for reducing radio wave interference.

In a TDMA type mobile communication system, in order to perform call control between a radio base station and a radio slave unit, there is a control method for controlling a call by allocating a communication frequency using a predetermined control signal. , Established by ARIB (Association of Radio Industries and Businesses). Since the frequency of this control signal is common in the mobile communication system of the same system, in order to avoid radio wave interference, the transmission position of the time slot of the control signal transmitted from the radio base station in the own system and other systems It is necessary not to overlap. As a method for avoiding these interferences, in general, when a radio base station is turned on, the radio base station sends out a control signal. There is a method of searching for the sending position and determining the sending position of the time slot so as not to overlap. By this method, the control signal transmitted from each radio base station is divided. Further, as a method of matching the timing of the control signal transmitted by the radio base station among a plurality of radio base stations, a synchronization signal with a small deviation is transmitted from a control device (eg, private branch exchange, radio base station control device). There is a method realized by matching the synchronization timings of all the radio base stations. For example, a method for supplying a synchronization signal from an ISDN (Integrated Services Digital Network) network uses this method (Patent Document 1). Between wireless base stations, there are a method of synchronizing by connecting a wired line (Patent Document 2), and a method of sending a synchronization signal from a switch to a wireless base station via a wired line (Patent Documents 3 and 4). And 5). There is also a method that uses a satellite such as GPS (Global Positioning System) and the wireless base station synchronizes with the satellite.

JP 2003-319431 A JP 2000-184436 A JP 11-243580 A JP-A-7-322344 Japanese Patent Laid-Open No. 7-193859

In the conventional method, in order to synchronize the synchronization between the radio base stations, it is necessary to prepare a dedicated wired line for the network side private branch exchange or the ISDN network or to make a line contract. Furthermore, for wireless base stations compatible with IP networks that have been introduced in recent years, synchronization signals cannot be transmitted / received as in the ISDN network, so between wireless base stations for wireless base stations compatible with IP networks. There is a problem that synchronization cannot be synchronized. In addition, when using GPS, there are many technical problems due to an increase in equipment cost by mounting the receiving device on the radio base station and mounting a plurality of radios.

  In order to solve the above-described problems, an object of the present invention is to provide a technique for synchronizing devices without providing a wired line between the devices.

  In order to solve the above-described problem, the present invention provides a communication system that performs communication by synchronizing with a predetermined frame, and includes a generation unit that generates a reference clock from an AC power supply, and a reference clock generated by the generation unit. A processing unit that performs the frame synchronization process; and a communication unit that performs communication using the frame subjected to the synchronization process by the processing unit. The generating unit includes an extracting unit that extracts a frequency component from the AC power source, a multiplying unit that multiplies the frequency component extracted by the extracting unit to a predetermined frequency, and a frequency multiplied by the multiplying unit. , Frequency dividing means for dividing the frequency of the reference clock, and correcting means for correcting the phase of the frequency of the reference clock divided by the frequency dividing means and outputting the corrected reference clock.

  According to the present invention, by generating a reference clock from an AC power source of power of the same system (for example, power of the same substation, business, etc.), no dedicated wired line facility is required, and synchronization between devices is performed. Can be combined. For this reason, it is possible to reduce radio wave interference due to a predetermined frame shift.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration example in which two types of digital cordless telephone systems 120 and 130 for offices are arranged as mobile radio systems in a premises such as an office or a factory. One office digital cordless telephone system 120 includes a private branch exchange 102, radio base stations 103, 104, and 105 connected to the private branch exchange 102, and an office digital cordless telephone 106. The other office digital cordless telephone system 130 includes an IP controller 107, IP-compatible radio base stations 108, 109, and 110 connected to the IP controller 107, and a digital cordless telephone 111.

  The private branch exchange 102 extracts the synchronization signal from the control signal periodically transmitted from the ISDN network 101, and distributes the synchronization signal subordinate to the synchronization signal to the subordinate radio base stations 103, 104, and 105. The TDMA frames of the control signals transmitted by the wireless base stations 103, 104, and 105 in the wireless section are unified, and the TDMA slot positions in the wireless section are unified. In the digital cordless telephone system 120 for offices, the radio base stations 103, 104, and 105 can periodically receive synchronization signals from the private branch exchange 102 or the ISDN network 101, so that stable operation can be performed without losing synchronization during operation. ing.

  On the other hand, in the digital cordless telephone system 130 for offices, the IP compatible wireless base stations 108, 109 and 110 under the IP controller 107 cannot periodically transmit / receive a synchronization signal because of packet communication. It is necessary to synchronize the base stations 108, 109 and 110. Therefore, in this embodiment, a reference clock is generated from an AC power source in order to synchronize TDMA frame synchronization between radio base stations in an IP compatible radio base station that cannot receive a synchronization signal from the network side. The TDMA frame is synchronized with the reference clock. Thereby, it is possible to synchronize by unifying the positions of the TDMA frames of the control signals in the radio section transmitted from the respective radio base stations.

  Hereinafter, specific procedures will be described with reference to FIGS.

  FIG. 2 shows an explanatory diagram of a TDMA-TDD frame in a radio section used in a radio base station in the digital cordless telephone systems 120 and 130 for offices. The TDMA-TDD frame shown in FIG. 2 is standardized by ARIB and used in the radio section of the second generation cordless telephone system standard. One slot, which is the minimum unit, is 625 μs, and one frame (frame 201) is composed of eight slots, and one frame has a period of 5 ms (200 Hz).

  FIG. 3 is an explanatory diagram showing a phase difference between frames. The radio base stations A and B shown in FIG. 3 use a high-accuracy timing clock, and the stability is defined by the standard described above, but the accuracy of each radio base station is used. Due to the hardware, deviation occurs even within the standard. For example, when there is a TDMA-TDD frame 202 of the radio base station A and a TDMA-TDD frame 203 of the radio base station B, when the head slot position coincides on the time axis at a certain timing, the time passes. FIG. 3 shows how the timing is shifted. When the first slots of the TDMA-TDD frames of the radio base station A and the radio base station B match, the phase difference 204 is small in a short period, but a large phase difference such as the phase differences 205 and 206 over a long period of time. Will occur. For this reason, when the radio base stations A and B that have used different slots without any interference between the slots at the beginning are operated for a long period of time, interference occurs due to a shift for each frame. For this reason, there is an influence in a system that distributes a synchronization signal that matches the heads of TDMA frames of all radio base stations 103, 104, and 105 under the private branch exchange 102, such as the office digital cordless telephone system 120 shown in FIG. Although it is low, IP-compatible radio base stations 108, 109, and 110 such as the office digital cordless telephone system 130 that do not distribute a synchronization signal require means for synchronizing TDMA frames.

  FIG. 4 shows a block configuration diagram of IP-compatible radio base stations 108, 109, and 110 in the present embodiment. For a device that cannot receive a synchronization signal from the network side, in this embodiment, a reference clock is generated based on an AC power source of the same system power (for example, power from the same substation, the same office, etc.). . The radio base stations 108, 109 and 110 include an antenna 301 for transmitting / receiving radio waves, a switching unit 302 for two antennas, a transmission unit 303, a reception unit 305, a synthesizer unit 304 for generating a frequency, and a modem (MODEM for modulation / demodulation). : Modulator-DEModulator) unit 306, TDMA-TDD processing unit 307, IP line interface unit 308, memory unit 309, control unit CPU 310, and reference clock generation unit 311.

  The antenna 301 transmits and receives signals to and from the digital cordless telephone 111. The antenna switcher 302 switches signals from a plurality of antennas 301. The transmission unit 303 transmits a signal to the digital cordless telephone 111. The synthesizer unit 304 outputs a high frequency signal. The receiving unit 305 receives a signal from the digital cordless telephone 111. The modem unit 306 modulates and demodulates the signal. The TDMA-TDD processing unit 307 compresses / decompresses the signal, synchronizes the TDMA-TDD frame based on the reference clock, and transmits / receives the signal to / from the LAN via the IP line interface 308. The memory unit 309 stores data, programs, and the like used by the IP compatible radio base station. The CPU 310 is a control unit in the IP-compatible radio base station, and operates according to a program stored in the memory unit 309 to perform overall control.

  The reference clock generation unit 311 includes a frequency component extraction circuit 315, a multiplier 313, a frequency divider 314, and a reference clock correction circuit 316. The reference clock generation unit 311 extracts a frequency component of the AC power source and generates a reference clock. The operation clocks inside the IP-compatible radio base stations 108, 109, and 110 are matched with the reference clock extracted from the frequency component of the AC power supply.

  The frequency component extraction circuit 315 extracts the frequency component of the AC power supplied from each power supply unit 312. Each unit power supply unit 312 may be a commercial AC power source or a commercial AC power source. The power sources in the respective power supply units 312 of the radio base stations 108, 109, and 110 are supplied with power of a stable frequency that is not shifted in phase in the same system. Further, when a clock signal having the frequency of the AC power supply is distributed, such as a commercial AC power supply, the frequency component extraction circuit 315 may use the clock signal as it is.

  The multiplier 313 multiplies the frequency component of the signal extracted by the frequency component extraction circuit 315 to a predetermined frequency.

  The frequency divider 314 divides the frequency of the signal multiplied by the multiplier 313 to a predetermined reference clock frequency.

  The reference clock correction circuit 316 corrects the phase of the frequency of the reference clock divided by the frequency divider 314, and outputs the corrected reference clock. At the time of correction, a clock output from an oscillator 317 such as a crystal oscillator is compared with a reference clock output from a frequency divider 314 to correct the phase. For example, the oscillator 317 outputs a clock obtained by dividing a 19.2 MHz crystal oscillator by a frequency divider to the frequency of the reference clock (200 Hz).

  A method for generating the reference clock from the power supply of each unit power supply unit 312 will be specifically described.

  The frequency component extraction circuit 315 extracts a frequency component (50 Hz / 60 Hz) from an AC power source (50 Hz / 60 Hz) whose accuracy is constant in Japan, and the multiplier 313 multiplies the signal to 3000 Hz. Since the period of the TDMA frame in the wireless section of the office digital cordless telephone system 130 is 5 ms (200 Hz), the frequency of the signal extracted from the AC power source is multiplied, and further divided by the frequency divider 314, 200 Hz Generate a reference clock. The generated 200 Hz clock is compared with the high-accuracy clock of the oscillator 317 mounted on the IP-compatible radio base station, and the corrected reference clock is used as the drive clock in the apparatus.

  The reference clock generation unit 311 may be configured as a hardware circuit, or may be processed by the CPU 310 by software. FIG. 5 shows a flowchart when processing is performed by the CPU 310 by software. A program corresponding to the flowchart illustrated in FIG. 5 may be stored in the memory unit 309.

  In FIG. 5, the IP-compatible radio base stations 108, 109, and 110 receive AC power (S401), create circuit drive power using an A / D converter (S402), and supply power to each circuit in the apparatus. (S403). Further, it is determined whether or not the frequency of the AC power supply is 50 Hz (S404). If it is 50 Hz, the frequency is multiplied by 60 times to 3000 Hz (S405). If it is not 50 Hz, it is 60 Hz, so it is multiplied by 50 (S406). Next, the 3000 Hz signal is divided by 1/15 to 200 Hz (S407), and the divided signal is compared with the clock from the oscillator to perform correction processing (S408) to generate a reference clock in the apparatus. (S409). The generated reference clock is sent to the TDMA-TDD processing unit 307 (S410).

  The TDMA-TDD processing unit 307 synchronizes the TDMA-TDD frame according to the reference clock. In this case, the TDMA-TDD processing unit 307 processes the head position of the slot 1 of the TDMA-TDD frame so as to be synchronized with the reference clock 210 as a trigger, as shown in FIG.

  As described above, by mounting the reference clock generation unit 311 in this embodiment on all IP-compatible radio base stations, it is possible to generate a reference clock dependent on an AC power supply of the same system power, Since the radio section TDMA-TDD frame can be synchronized according to this reference clock, radio wave interference due to a TDMA-TDD frame shift in the radio section can be reduced. In addition, synchronization can be achieved for an IP-compatible radio base station that cannot supply a synchronization signal from the private branch exchange 102. If this method is applied to all radio base stations, it can be realized as long as there is an AC power supply of the same system, and there is no need to introduce an ISDN line or a private branch exchange for achieving synchronization. Can also be reduced.

  In the present embodiment, the case of a wireless communication system is taken as an example, but the present invention may be applied to a wired communication system using a predetermined frame configuration.

  According to the present embodiment, a communication device that performs communication by synchronizing with a predetermined frame without supplying a synchronization signal can always generate a constant clock component, and frame timing can be generated in all communication devices. Can be the same.

1 is a configuration diagram of an asynchronous mobile communication system. Explanatory drawing of the TDMA-TDD frame of a radio area. Explanatory drawing which shows the phase difference of a flame | frame. The hardware block diagram of a radio base station. The flowchart which produces | generates the reference clock from AC power supply.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... ISDN network (basic interface), 102 ... Private exchange for digital cordless telephone system for offices, 103, 104 and 105 ... Wireless base station for digital cordless telephone system for offices, 106 ... Slave unit for digital cordless telephone, 107 ... IP Corresponding control device, 108, 109 and 110 ... IP-compatible radio base station, 112 ... premises area, 201 ... TDMA-TDD frame, 202 ... TDMA-TDD frame of radio base station A, 203 ... TDMA-TDD of radio base station B Frame, 204, 205, and 206: Misalignment of radio base station A and radio base station B in units of frames, 301: Antenna of IP compatible radio base station, 302 ... Antenna switching unit of IP compatible radio base station, 303 ... IP compatible Wireless base station transmitter 304, IP-compatible wireless base station Synthesizer unit, 305... Receiver unit of IP-compatible radio base station, 306... Modem unit of IP-compatible radio base station, 307... TDMA-TDD processing unit of IP-compatible radio base station, 308. Department.

Claims (6)

In a communication system that performs communication by synchronizing with a predetermined frame,
A generator for generating a reference clock from an AC power supply;
A processing unit that performs synchronization processing of the frame using the reference clock generated by the generation unit;
A communication unit that performs communication using a frame that has been subjected to synchronization processing by the processing unit.   The communication system according to claim 1, wherein the communication unit performs wireless communication. The communication system according to claim 1,
The generating unit is configured to extract a frequency component from the AC power source;
Multiplication means for multiplying the frequency component extracted by the extraction means to a predetermined frequency;
Frequency dividing means for dividing the frequency multiplied by the frequency multiplying means to the frequency of the reference clock;
And a correction unit that corrects the phase of the frequency of the reference clock divided by the frequency dividing unit and outputs the corrected reference clock. In a base station apparatus of a wireless communication system that performs wireless communication by synchronizing with a predetermined frame,
A generator for generating a reference clock from an AC power supply;
A processing unit that performs synchronization processing of the frame using the reference clock generated by the generation unit;
A communication unit that performs communication using a frame that has been subjected to synchronization processing by the processing unit. In a reference clock generation circuit that generates a reference clock,
Extraction means for extracting a frequency component from the signal of the AC power source;
Multiplication means for multiplying the frequency component of the signal extracted by the extraction means to a predetermined frequency;
Frequency dividing means for dividing the frequency of the signal multiplied by the frequency multiplying means to the frequency of the reference clock;
And a correction means for correcting the phase of the frequency of the reference clock divided by the frequency dividing means and outputting the corrected reference clock. A synchronization method in which communication is performed by synchronizing with a predetermined frame,
Extract frequency components from AC power signal,
The frequency component of the extracted signal is multiplied to a predetermined frequency,
Dividing the frequency of the multiplied signal to the frequency of the reference clock;
Correct the phase of the frequency of the divided reference clock;
Outputting the corrected reference clock;
A synchronization method, wherein the frame is synchronized with the output reference clock.

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