JP2011223505A - Delay time measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that a communication system including a relay station 8 relaying communication between a mobile station and a base station 1 through a leakage coaxial cable (LCX) and an optical fiber, the communication system having a problem of a difference in delay time between communication via the optical fiber 9 and communication via the LCX 300-1, and a momentary break of communication between the mobile station and base station.SOLUTION: A base station 1 transmits a delay adjustment signal through the LCX 300-1 and optical fiber 9, and a relay station 8 receives the delay adjustment signal arriving through the LCX 300-1 and optical fiber 9, and generates a beat signal from the delay adjustment signal. A beat frequency f1 is known from the beat signal, so that the delay time difference is further calculated using modulation repetition cycles T and a modulation width β.

Description

  The present invention relates to an optical repeater for mobile communication applied to a train radio system that relays communication between a mobile station and a base station via a leaky coaxial cable (LCX: Leakage CoaXial cable, hereinafter referred to as LCX) and an optical fiber. The present invention relates to a delay time measurement method implemented in a system.

  As a conventional wireless communication system that relays communication between a mobile station and a base station via an LCX and an optical fiber transmission line, there is one disclosed in Patent Document 1, for example. In this system, the transmission path length from the base station differs at the break (hereinafter referred to as the LCX transition section) between the LCX terminal connected to the preceding relay station and the LCX transmitting end connected to the succeeding relay station. This may cause a difference in delay time between communication via optical fiber and communication via LCX, and communication between the mobile station and the base station may be interrupted. Therefore, in the wireless relay system of Patent Document 1, the phase of the signal in each LCX crossing section is adjusted by adjusting the length of the optical fiber mounted in the delay correction device of the base station. The adjustment amount of the optical fiber length is determined by the signal propagated from the base station to the end of the LCX through the optical fiber transmission line and the relay station, and the LCX from the base station through the optical fiber transmission line and the relay station downstream of the relay station. The relative delay time difference of the signal propagated to the transmission end is measured, and the relative delay time difference is converted into the optical fiber length.

  An example of a method for measuring a relative delay time difference between signals will be described. First, a base station transmits a π / 4 shift QPSK (Quadrature Phase Shift Keying) modulation signal of a data sequence in which data in one symbol such as “00 00 11 00 00... The signal is received by a receiver connected to the signal input terminal of the relay station downstream of the relay station via LCX and the transmitter terminal of the relay station downstream of the relay station via an optical fiber transmission line. Next, an oscilloscope is connected to the receiver, and an RSSI (Received Signal Strength Indicator) waveform of the signal is observed. By using the fact that the RSSI waveform is depressed when the “11” data series of the signal is received, the cursor position is set at the point where the RSSI waveform of each of the signals received from both paths falls. , Measure the arrival time difference. Note that the propagation delay between the relay station and the LCX by the approach cable is separately measured and reflected in the arrival time difference to calculate the relative delay time difference to the LCX crossing section.

JP 2004-236165 A

  When measuring the relative delay time difference between signals as described above, observation is performed using an oscilloscope because the measurement target is RSSI. However, since the measurement point of the received waveform displayed on the measuring instrument is not clear in the above measurement method, the setting of the cursor position at the time of measurement depends on the sense of the measurer. Therefore, there are problems that the measurement results vary depending on the measurer and that the measurement accuracy required when the system has a high data rate of 10 Mbps or more may not be satisfied. In addition, because the measurement with RSSI is difficult to observe with radio waves leaking from LCX in the LCX transition section due to the influence of wireless wraparound, the propagation delay due to the approach cable from the relay station to LCX requires separate measurement, There has been a problem that the measurement error is increased. The present invention has been made to solve the above-described problems, and an object thereof is to improve the measurement accuracy of the relative delay time difference.

  A delay time measurement method according to the present invention includes a leaky coaxial cable and an optical fiber in a communication system including a leaky coaxial cable (LCX) and a relay station that relays communication between a mobile station and a base station via an optical fiber. In a delay time measuring method for measuring a delay time generated during data transmission by a fiber, a signal having a modulation repetition period T and a modulation width β, which is FM-modulated with a triangular wave, is created, and the signal is used as a delay adjustment signal. As a delay adjustment signal transmission process transmitted via a leaky coaxial cable and an optical fiber, a reception process of receiving a delay adjustment signal transmitted via the leaky coaxial cable and an optical fiber, and a delay received from the leaky coaxial cable A process for generating a beat signal from the adjustment signal, a delay adjustment signal received from the optical fiber, and a modulation repetition period T And delay time measurement processing for calculating a delay time using the modulation width β and the beat frequency of the beat signal.

  A delay time measurement method according to the present invention includes a leaky coaxial cable and an optical fiber in a communication system including a leaky coaxial cable (LCX) and a relay station that relays communication between a mobile station and a base station via an optical fiber. In a delay time measuring method for measuring a delay time generated during data transmission by a fiber, a signal having a modulation repetition period T and a modulation width β, which is FM-modulated with a triangular wave, is created, and a base station and a relay station are Delay adjustment signal transmission processing for transmitting a signal as a delay adjustment signal via the first leaky coaxial cable and optical fiber to be connected, and a delay adjustment signal transmitted via the first leaky coaxial cable and the optical fiber Receiving processing, transmitting processing for transmitting the delay adjustment signal received via the optical fiber to the second leaky coaxial cable, and first leakage Using the delay adjustment signal received from the coaxial cable, the process of generating a beat signal from the delay adjustment signal received from the second leaky coaxial cable, the modulation repetition period T, the modulation width β, and the beat frequency of the beat signal And a delay time measurement process for calculating the delay time.

  A delay time measurement method according to the present invention includes a leaky coaxial cable and an optical fiber in a communication system including a leaky coaxial cable (LCX) and a relay station that relays communication between a mobile station and a base station via an optical fiber. In a delay time measuring method for measuring a delay time generated during data transmission by a fiber, a signal having a modulation repetition period T and a modulation width β, which is FM-modulated with a triangular wave, is created, and the signal is used as a delay adjustment signal. As a delay adjustment signal transmission process transmitted via a leaky coaxial cable and an optical fiber, a reception process of receiving a delay adjustment signal transmitted via the leaky coaxial cable and an optical fiber, and a delay received from the leaky coaxial cable A process for generating a beat signal from the adjustment signal, a delay adjustment signal received from the optical fiber, and a modulation repetition period T , A delay time measurement process for calculating a delay time by using the modulation width β and the beat frequency of the beat signal, so that the optical fiber in the LCX cross section of the optical relay system for mobile communication applied to the train radio system There is an effect of improving the measurement accuracy of the relative delay time between the communication via the LCX and the communication via the LCX.

  A delay time measurement method according to the present invention includes a leaky coaxial cable and an optical fiber in a communication system including a leaky coaxial cable (LCX) and a relay station that relays communication between a mobile station and a base station via an optical fiber. In a delay time measuring method for measuring a delay time generated during data transmission by a fiber, a signal having a modulation repetition period T and a modulation width β, which is FM-modulated with a triangular wave, is created, and a base station and a relay station are Delay adjustment signal transmission processing for transmitting a signal as a delay adjustment signal via the first leaky coaxial cable and optical fiber to be connected, and a delay adjustment signal transmitted via the first leaky coaxial cable and the optical fiber Receiving processing, transmitting processing for transmitting the delay adjustment signal received via the optical fiber to the second leaky coaxial cable, and first leakage Using the delay adjustment signal received from the coaxial cable, the process of generating a beat signal from the delay adjustment signal received from the second leaky coaxial cable, the modulation repetition period T, the modulation width β, and the beat frequency of the beat signal Delay time measurement processing for calculating the delay time, so that between the communication via the optical fiber and the communication via the LCX in the LCX cross section of the optical relay system for mobile communication applied to the train radio system There is an effect of improving the measurement accuracy of the relative delay time.

It is explanatory drawing explaining an example of the test system which measures the transmission delay time which generate | occur | produces in the conventional radio | wireless communications system which relays communication of a mobile station and a base station via LCX and an optical fiber transmission line. The example shows the time change example of the frequency of each of the delay adjustment signal arrived from the LCX path and the time of the delay adjustment signal arrived from the optical fiber path and the time change example of the beat frequency f1 of the mixer output signal. It is explanatory drawing explaining an example of the test system which measures the transmission delay time concerning Embodiment 2 of this invention. It is a flowchart which shows the process which measures the transmission delay time of this invention.

Embodiment 1 FIG.
FIG. 1 is an explanatory diagram for explaining an example of a test system for measuring a transmission delay time generated in a conventional wireless communication system that relays communication between a mobile station and a base station via an LCX and an optical fiber transmission line. The test system shown in FIG. 1 is a delay correction operation for correcting a difference in transmission delay time generated between communication via LCX and communication via optical fiber in the LCX cross section of the optical relay system. Used to measure relative delay time. In FIG. 1, a relay station 2 is connected to a base station 1 via an approach cable 4 and an LCX 300-1 array approach cable 5 in the line vicinity area 3, and further connected to the base station 1 via an optical fiber transmission line 9. I am letting. FIG. 4 is a flowchart showing a process for measuring the transmission delay time according to the present invention.

  A specific method of the relative delay time measurement in the LCX transition section 301 will be described. First, the “delay adjustment signal” generated by the delay adjustment signal generator (SG) 102 installed in the base station 1 is transmitted. This delay adjustment signal is a signal having a known modulation repetition period T and modulation width β, which has been subjected to FM modulation with a triangular wave. The delay adjustment signal transmitted from the delay adjustment signal generator (SG) 102 reaches the LCX signal input unit 6 of the relay station 2 via the approach cable 4, the LCX 300-1, and the approach cable 5. Hereinafter, for convenience of explanation, a route that reaches the relay station 2 via the approach cable 4, the LCX 300-1, and the approach cable 5 is referred to as an “LCX route”.

  The delay adjustment signal output from the delay adjustment signal generator (SG) 102 is distributed inside the base station 1 and converted into an optical signal by the electro-optical signal converter (E / O) 100. The signal reaches the optical-electrical signal converter (O / E) 200 of the relay station 2 via the delay adjuster 101 and the optical fiber transmission line 9. Hereinafter, for convenience of explanation, a route that reaches the relay station 2 via the optical fiber transmission line 9 is referred to as an “optical fiber route”. The process of transmitting the delay adjustment signal through the LCX path and the optical fiber path corresponds to step 1 in FIG.

  The delay adjustment signal received by the relay station 2 through the LCX path is input from the LCX signal input unit 6 provided in the relay station 2 to the mixer 800 of the delay measurement system 8. The delay adjustment signal received by the relay station 2 through the optical fiber path is converted from an optical signal to an electric signal by an optical-electrical signal converter (O / E) 200 provided in the relay station 2. This electric signal is amplified by the signal amplifying unit 201, transmitted to the LCX 300-2 via the coupler 202 and the approach cable 7, distributed by the coupler 202, and input to the mixer 800. The above reception processing of the delay adjustment signal by the relay station 2 corresponds to Step 2 in FIG.

In Step 3 of FIG. 4, the mixer 800 of the relay station 2 mixes the delay adjustment signal that has arrived from the LCX path and the delay adjustment signal that has arrived from the optical fiber path, and outputs a beat signal having the beat frequency f1. FIG. 2 shows an example of the time change of the frequency of the delay adjustment signal arriving from the LCX path and the time of the delay adjustment signal arriving from the optical fiber path, and an example of the time change of the beat frequency f1 of the output signal of the mixer 800. It is. In FIG. 2, f0 is the center frequency of the delay adjustment signal, T is the modulation repetition period, β is the FM modulation width, and the signals from the LCX path and the optical fiber path have a difference in arrival time of the relative delay time τ. It represents that. In accordance with the relative delay time τ, the mixer 800 of FIG. 1 outputs a beat signal having a frequency f1. In step 4 of FIG. 4, the relative delay time τ is calculated. That is, since f1 is expressed by the following equation, the relative delay time difference τ can be obtained.
Δτ = f1 · T / 2β

  Since the output signal of the mixer 800 includes many high frequencies in addition to the beat signal, the high frequency is removed by a low-pass filter (LPF) 801 and the beat frequency f1 is measured by the frequency counter 802. Further, the propagation delay time by the approach cable 5 and the approach cable 7 is measured separately or calculated from the cable length by desktop calculation and reflected in the relative delay time, thereby obtaining the relative delay time in the LCX transition section 301. it can.

  There is an effect of improving the measurement accuracy of the relative delay time between the communication via the optical fiber and the communication via the LCX in the LCX cross section of the optical relay system for mobile communication applied to the train radio system.

Embodiment 2. FIG.
In the first embodiment, the frequency of the beat signal is measured by connecting the delay adjustment signal input from the LCX path and the optical fiber path to the delay measurement system 8 in the relay station 2. On the other hand, in the second embodiment, the frequency measurement of the beat signal is performed using the radio wave leaking from the LCX in the LCX crossing section in the line vicinity area 3. FIG. 3 is an explanatory diagram for explaining an example of a test system for measuring the transmission delay time according to Embodiment 2 of the present invention. In FIG. 3, the same reference numerals as those in FIG. 1 denote the same or corresponding parts, and a description thereof will be omitted. In the second embodiment, the installation location of the delay measurement system 8 is the line vicinity area 3, and the LCX signal receiving antenna 10 is used. The flow of the delay adjustment signal through the LCX path and the optical fiber path is the same as in the first embodiment.

  The LCX signal receiving antenna 10 receives the delay adjustment signal flowing in the LCX 300-1 and the delay adjustment signal flowing in the LCX 300-2 input from the optical fiber path in the LCX cross section in the line vicinity area 3. The received signal is input to the mixer 800 of the delay measurement system 8, and the mixer 800 outputs a beat signal. The subsequent flow is the same as in the first embodiment.

  According to the second embodiment, since the propagation delay caused by the approach cable 5 and the approach cable 7 is reflected in the measurement result, it is not necessary to separately measure and the measurement error can be reduced.

1 base station, 100 electrical-optical signal converter, 101 delay adjuster,
102 signal generator (SG) for delay adjustment, 2 relay station,
200 optical-electrical signal conversion unit, 201 signal amplification unit, 202 coupler,
3 Line vicinity area, 300-1 to 300-2 LCX, 301 LCX crossing section,
4-5, 7 approach cable, 8 delay measurement system, 800 mixer,
801 Low-pass filter (LPF), 802 frequency counter,
9 Optical fiber, 10 LCX signal receiving antenna

Claims (2)

In a communication system having a leaky coaxial cable (LCX: Leakage CoaXial cable) and a relay station that relays communication between a mobile station and a base station via an optical fiber, a delay caused during data transmission by the leaky coaxial cable and the optical fiber In the delay time measuring method for measuring time,
A signal having a modulation repetition period T and a modulation width β, which is FM-modulated with a triangular wave, is generated, and the signal is transmitted as a delay adjustment signal through the leaky coaxial cable and the optical fiber. Signal transmission processing,
A reception process for receiving the delay adjustment signal transmitted via the leaky coaxial cable and the optical fiber;
Processing for generating a beat signal from the delay adjustment signal received from the leaky coaxial cable and the delay adjustment signal received from the optical fiber;
A delay time measuring method comprising: a delay time measuring process for calculating a delay time using the modulation repetition period T, the modulation width β, and a beat frequency of the beat signal. In a communication system having a leaky coaxial cable (LCX: Leakage CoaXial cable) and a relay station that relays communication between a mobile station and a base station via an optical fiber, a delay caused during data transmission by the leaky coaxial cable and the optical fiber In the delay time measuring method for measuring time,
A signal having a modulation repetition period T and a modulation width β, which is FM-modulated with a triangular wave, is created, and the first leaky coaxial cable connecting the base station and the relay station and the optical fiber Delay adjustment signal transmission processing for transmitting a signal as a delay adjustment signal;
Receiving processing for receiving the delay adjustment signal transmitted via the first leaky coaxial cable and the optical fiber;
A transmission process for transmitting the delay adjustment signal received via the optical fiber to the second leaky coaxial cable;
A process for generating a beat signal from a delay adjustment signal received from the first leaky coaxial cable and a delay adjustment signal received from the second leaky coaxial cable;
A delay time measuring method comprising: a delay time measuring process for calculating a delay time using the modulation repetition period T, the modulation width β, and a beat frequency of the beat signal.

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