JP3694487B2 - Cable loss equalization method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a communication apparatus in which apparatuses are connected by a cable and burst waves are transmitted by the cable.
[0002]
[Prior art]
As shown in FIG. 3, a system configuration in which the base station 10 and the subscriber stations 20A, 20B, and 20C are wirelessly connected to each other by P-MP (Point to MultiPoint) is adopted in FWA (Fixed Wireless Access) or the like. In this figure, only three subscriber stations (20A, 20B, 20C) are shown for simplicity of illustration, but the number of subscriber stations that can be accommodated by one base station 10 is generally larger. In addition, the wireless communication between the base station 10 and the subscriber stations 20A, 20B, and 20C has a common radio frequency in the upstream (subscriber station → base station) direction and the downstream (base station → subscriber station) direction. This is performed by a TDD (Time Division Duplex) method to be used or by a burst wave that is scheduled as shown in FIG. In FIG. 4, A, B, and C represent ON periods of burst signals related to the subscriber stations 20A, 20B, and 20C, respectively. The schedule management is control that prevents the on-burst periods from overlapping between different subscriber stations, and is executed by the IFU 12 of the base station 10, for example.
[0003]
The base station 10 has a configuration in which a radio frequency unit (RFU) 11 and an interface unit (IFU) 12 are connected by a coaxial cable 13 or the like. Similarly, the subscriber stations 20A, 20B, and 20C also have an RFU 21 and an IFU 22. Are connected to each other by a coaxial cable 23 or the like. The RFUs 11 and 21 are units that execute up-conversion of transmission burst waves, down-conversion of reception burst waves, amplification of those signals, and the like. The IFUs 12 and 22 are units that execute burst modulation / demodulation of transmission / reception burst waves, data modulation / demodulation, amplification / data processing, and the like. The IFU 12 of the base station 10 also executes the above-described schedule management and the like.
[0004]
Further, the RFU 11 of the base station 10 is installed at a high place using, for example, a pole-like structure such as a utility pole or a rooftop of a high-rise building together with an antenna (not shown). It is installed in a low place that is advantageous in terms of connection of In addition, the RFU 21 of the subscriber stations 20A, 20B, and 20C is installed in a location where it can communicate with the RFU 11 using, for example, a balcony or a roof of the subscriber's house, together with an antenna (not shown), and the IFU 22 is a personal that the subscriber uses. It is installed in the room of the subscriber's house so that it can be connected to a computer and its network-related equipment. Although the coaxial cables 13 and 23 depend on the installation environment of the stations (10, 20A, 20B, and 20C), they may be several meters at the shortest and several hundred meters at the longest.
[0005]
[Problems to be solved by the invention]
Thus, in a communication device that needs to be divided and installed in a plurality of units for the convenience of maintenance, network connection, etc., even though it is a single communication device, the signal power loss due to the cable connecting these units, That is, cable loss occurs. The amount of cable loss varies depending on the type, length, manufacturer, etc. of the cable, and thus varies from communication device to communication device. In the example shown in FIG. 3, since the structure of the subscriber's house, which is the installation location, and the arrangement of equipment / equipment in the subscriber's house (such as the location of the room where the personal computer is placed) are generally different, the subscriber station 20A In most cases, the cable loss in the coaxial cable 23 and the cable loss in the coaxial cable 23 of the subscriber station 20B have different values.
[0006]
In order to optimize the operation of the unit that receives the signal via the cable, it is generally necessary to equalize the cable loss that is different for each communication device (for each station). For example, a variable gain amplifier or a variable attenuator is provided in a circuit portion that inputs a transmission signal via the coaxial cable 23 in the RFU 22. If the cable loss in the coaxial cable 23 is known, the gain or attenuation rate of the variable gain amplifier or variable attenuator is set or controlled so that the deviation of the cable loss, that is, the difference between stations is compensated based on the cable loss value. Is possible. The transmission system circuit in the RFU 22 up-converts and amplifies the transmission burst wave in which the cable loss deviation is compensated. The control circuit in the RFU 22 performs operations such as detecting the arrival of a transmission burst wave and controlling a switch (transmitter / receiver duplexer) for antenna sharing in response thereto. In this way, by eliminating the influence of the cable loss deviation for each communication device (station) at the input circuit portion of the unit that receives the signal among the units constituting the communication device, the cable loss deviation is not affected. Unit operation is the same (cable loss equalization).
[0007]
To realize cable loss equalization, it is necessary to give the unit that receives the signal a cable loss value that is a value that determines the target of gain or attenuation rate, or a deviation from the standard cable loss value. is there. As a method therefor, firstly, there is a method of manual setting by a cable builder. For example, the cable builder gives information indicating the type and length of the coaxial cable 23 to the RFU 21 that is a unit that receives a transmission burst wave from the IFU 22 and the IFU 22 that is a unit that receives a reception burst wave from the RFU 21 by a switch operation or the like. Alternatively, a cable loss or a value corresponding to the deviation is input and set according to the type and length of the coaxial cable 23. In this method, there are some problems such as the problem that the cable builder bears the work burden, the factors such as differences in cable manufacturers and differences in characteristics (attenuation) for each cable product, etc. There was a problem.
[0008]
As a method for giving cable loss or its deviation, secondly, some measurement is performed at the unit that receives the burst wave from another unit via the cable, and the cable loss or its deviation estimated from the measurement result is obtained. There is a method of automatically determining a control target of gain or attenuation rate based on the above. For example, the IFU 22 applies a DC voltage of a predetermined value to the coaxial cable 23, and the RFU 21 measures the DC voltage appearing at the connection portion with the coaxial cable 23, and the drop from the predetermined value. Since the DC voltage drop is a value that varies depending on the length and type of the cable and has a temporary correlation with the cable loss, the cable loss or its deviation can be estimated from the DC voltage drop. Alternatively, the IFU 22 sends a signal to the coaxial cable 23 at a predetermined timing, and the RFU 21 detects the arrival timing of the signal and measures the elapsed time from the predetermined timing. The measured time, that is, the required signal propagation time is a value that varies depending on the cable length, etc. and has a temporary correlation with the cable loss, so the cable loss or its deviation is estimated from the required signal propagation time. can do. When the signal is received from the IFU 22 via the coaxial cable 23, the RFU 21 may return the signal to the IFU 22, and the IFU 22 may measure the required signal round-trip time. Since these methods are actually measured methods, they are more accurate than the first method described above, that is, the manual setting method at the time of construction, and also due to differences in cable manufacturers and differences in characteristics of individual cable products. It has the advantage that it can be used for the time being and the work burden on the cable installer is reduced. However, even though it is actually measured, it is a measurement of the DC voltage drop or signal propagation time, and the cable loss or its deviation itself is derived indirectly, so it is still inaccurate. Remains.
[0009]
The present invention has been made in order to solve such problems, and obtains a cable loss or its deviation more accurately and without a work burden, and equalizes the cable loss more lightly and accurately. Its purpose is to make it possible.
[0010]
[Means for Solving the Problems]
In order to achieve such an object, the present invention provides: (1) a transmission burst wave is transmitted from a first unit to a second unit via a cable; By connecting the antenna to the transmission system in response to the arrival of the burst wave, A cable loss equalization method that is executed by a communication device that transmits to the outside, wherein (2) the first unit has a predetermined power Continuous wave without burst modulation Send loss detection signal to cable And the process A request from the first unit to the second unit for the cable loss measurement operation in which the second unit inputs the loss detection signal from the cable and measures the cable loss or its deviation. To disconnect the transmission system of the second unit from the antenna Executed with the second unit controlled to stop transmission by And the process (3) At least in the burst-on period of the transmission burst wave, the second unit is provided with a transmission burst provided therein so that the cable loss appearing in the transmission burst wave is compensated and according to the information obtained by the above measurement. Automatic adjustment of gain or attenuation in the circuit through which the wave passes And including a process It is characterized by that.
[0011]
In the present invention, (1) the transmission burst wave is transmitted from the first unit to the second unit via the cable, and further transmitted from the second unit to the outside, while the burst wave is transmitted to the second unit. Is a cable loss equalization method executed in a communication device that receives the received burst wave from the outside and transmits the received burst wave from the second unit to the first unit via the cable. (2) First The cable loss measurement operation in which the second unit sends a loss detection signal of a predetermined power to the cable and the second unit inputs the loss detection signal from the cable and measures the cable loss or its deviation. Executed in a state in which the second unit is controlled to be in a transmission stop state by a request from the first unit to the second unit. (3) At the end of the cable loss measurement operation, the second unit Notifies the measurement is obtained information on the first unit And the process (4) At least in the ON period of the transmission burst wave, the second unit is provided with a transmission burst wave provided therein so that the cable loss appearing in the transmission burst wave is compensated and according to the information obtained by the above measurement. Automatically adjusts the gain or the attenuation factor in the circuit through which the signal passes, while the first unit is provided in the interior so that the cable loss appearing in the received burst wave is compensated and according to the information notified from the second unit. Automatic adjustment of gain or attenuation factor in the circuit through which the received burst wave passes And including a process It is characterized by that.
[0012]
As described above, in the present invention, the loss detection signal transmitted from the first unit is input via the cable in the second unit that receives the transmission burst wave from the first unit via the cable. Or the deviation is actually measured. Therefore, since the cable loss compensation operation in the present invention is a direct measurement of the cable loss or its deviation, it is lighter and more accurate than the conventional method involving manual setting by the cable installer, and the DC voltage drop or It is more accurate than the conventional method involving indirect measurement by measuring the signal propagation time. In particular, normal transmission waves and reception waves are burst waves, but the loss detection signal can be a continuous wave that is not burst-modulated, so that sufficient detection time can be secured. ) Measurement can be realized. Furthermore, it is only necessary to set the gain or attenuation rate based on the information obtained by the cable loss measurement operation, and it is not necessary to change the gain or the like by burst on / off. In addition, the cable loss measurement operation in the present invention can be performed by, for example, turning on the power to the first unit, operating a switch attached to the first unit, or a command from a control terminal attached to the first unit. Accordingly, if the execution is started, it is possible to prevent a malfunction from occurring in a normal signal transmission / reception operation.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Note that the present invention can be applied to the subscriber stations 20A, 20B, and 20C shown in FIG. 3, and therefore, in the following description, an example of application to a subscriber station is taken, but the present invention can also be applied to the base station 10. Further, more generally, the present invention can be applied to a communication device using a burst wave, particularly a communication device having a plurality of units connected via a cable.
[0014]
FIG. 1 shows a configuration of a subscriber station 20 according to an embodiment of the present invention. The subscriber station 20 according to the present embodiment has a configuration in which an outdoor unit 21 that is an RFU and an indoor unit 22 that is an IFU are connected by a cable 23. Moreover, both the outdoor device 21 and the indoor device 22 have a transmission system and a reception system, and the antenna 24 connected to the outdoor device 21 is switched for wireless communication with the base station 10 by the TDD method. However, it is shared by these transmission and reception circuits.
[0015]
The circuit system of the transmission system includes a digital processing unit 221 of the indoor device 22 to a modulation unit 222, a distribution unit 223, a coaxial cable 23, a distribution unit 211 of the outdoor device 21, a variable gain amplifier 212, a frequency conversion unit 213, an RF circuit 214, and It reaches the antenna 24 via the duplexer 215. During normal burst transmission operation, this system generates a transmission burst wave in which the modulation unit 222 is turned on and off at a predetermined timing based on the information signal supplied from the digital processing unit 221 and under the control of the digital processing unit 221. The distribution unit 223 supplies the transmission burst wave to the connection terminal side with the coaxial cable 23. This transmission burst wave is transmitted to the outdoor device 21 through the coaxial cable 23. The distribution unit 211 of the indoor device 21 supplies the transmission burst wave input via the coaxial cable 23 to the up-conversion circuit in the frequency conversion unit 213 via the variable gain amplifier 212, and the frequency conversion unit 213 receives the transmission burst wave. The RF circuit 214 up-converts the transmission burst wave up-converted to the radio frequency by power amplification or the like, and the duplexer 215 supplies the power-amplified transmission burst wave to the antenna 24. By such an operation, the information signal input from the indoor device of the subscriber's house, for example, the personal computer to the indoor device 22 and then the digital processing unit 221 is wirelessly transmitted from the antenna 24 by a burst wave.
[0016]
The circuit system of the receiving system includes the antenna 24 to the duplexer 215 of the outdoor device 21, the RF circuit 214, the frequency converter 213, the distributor 211, the coaxial cable 23, the distributor 223 of the indoor device 22, the variable gain amplifier 224, and the demodulation. The digital processing unit 221 is reached via the unit 225. During normal burst reception operation, in this system, the duplexer 215 of the outdoor device 21 supplies the received burst wave from the antenna 24 to the RF circuit 214, and the RF circuit 214 performs low noise amplification or the like on the received burst wave. A down-conversion circuit in the frequency conversion unit 213 down-converts the received burst wave from a radio frequency to an intermediate frequency, and the distribution unit 211 supplies the received burst wave to the connection terminal side with the shaft cable 23 carrying the received burst wave of the intermediate frequency. This received burst wave is transmitted to the indoor device 22 through the coaxial cable 23. The distribution unit 223 of the indoor device 22 distributes the received burst wave input via the coaxial cable 23 to the demodulation unit 225 via the variable gain amplifier 224, and the demodulation unit 225 demodulates the received burst wave, and the digital processing unit 221. Reproduces information from the demodulation result. By such an operation, the burst wave received wirelessly using the antenna 24 is output from the indoor device 22 and thus the digital processing unit 221 to the indoor device in the subscriber's house as a demodulated information signal.
[0017]
The feature of the present embodiment is that, in the subscriber station 20, which is a device that performs wireless communication by burst waves in accordance with the TDD system, cable loss equalization in the coaxial cable 23 is made possible to the construction operator of the coaxial cable 23. It is possible to perform the measurement accurately without incurring a special burden, and in particular, for this purpose, a cable loss correction procedure including direct measurement of the cable loss or its deviation is introduced.
[0018]
FIG. 2 shows a cable loss correction procedure. In the present embodiment, when the user turns on the power of the indoor device 22 by operating a switch or the like attached to the indoor device 22 or resets the operating state of the indoor device 22, the digital processing of the indoor device 22 is performed. The unit 221 determines that “request has occurred” and starts the cable loss correction procedure (301). When a cable loss correction command is received from a control terminal (such as a personal computer in the subscriber's residence room) connected to the indoor device 22, it is determined that “request has occurred”.
[0019]
As will be described later, in the cable loss correction procedure according to the present embodiment, a signal for detecting a cable loss or its deviation is supplied from the indoor device 22 to the outdoor device 21 via the coaxial cable 23. In addition, the signal is modulated instead of the burst wave used for normal communication for measuring the cable loss or its deviation in order to ensure sufficient time to stably perform the input power measurement in the outdoor device 21. Or a continuous wave with no modulation. In order to prevent the signal different from the normal transmission wave from being radiated from the antenna 24 in this way, the digital processing unit 221 first requests the outdoor device 21 to stop transmission when starting the same procedure (302). . The control unit 218 provided in the outdoor device 21 controls the duplexer 215 in response to this request, thereby disconnecting the transmission system from the antenna 24 (303). For example, the antenna 24 is connected to the circuit system of the reception system (when the duplexer 215 has two states of transmission / reception) or is disconnected from both transmission / reception systems (the duplexer 215 is the third If you have a state of). Note that the signal for requesting transmission stoppage is controlled with the signal line connected to the distribution unit 223, the coaxial cable 23, and further the distribution unit 211 by bypassing the modulation unit 222 from the digital processing unit 221 in the figure. Transmission is performed using a signal line connecting the unit 218. These signal lines are, for example, communication lines based on ASK modulation.
[0020]
Thereafter, the digital processing unit 221 requests the modulation unit 222 to transmit a detection signal, for example, a continuous modulated wave (304), and the modulation unit 222 transmits a signal corresponding to the request (305). The outdoor device 21 receives this signal via the coaxial cable 23 and measures the signal power (306). Therefore, a means for detecting signal power is provided in the transmission system circuit system of the outdoor device 21 before the device for variable gain amplification or variable attenuation of the transmission burst wave. In the illustrated example, a detection unit 216 that outputs a detection voltage corresponding to the signal power is provided in a portion positioned before the variable gain amplifier 212 and between the connection terminal with the coaxial cable 23 and the distribution unit 211. Yes. This detected voltage is input to the control unit 218 via the A / D converter 217 (307). The control unit 218 stores a table associating the detection voltage with the cable loss, and refers to the table according to the detection voltage input via the A / D converter 217, thereby determining the value of the cable loss value or its deviation. Is detected (308). The deviation here is a difference with respect to a predetermined reference input power. In addition, here, it is referred to as detecting the cable loss value or the deviation, but this does not mean that the absolute values thereof must be obtained. For example, it is possible to adopt a method of detecting a difference with respect to the previous detection value.
[0021]
The control unit 218 stores the detection result in its internal memory (309), while the fact that the actual measurement has been completed and the result are indicated in the direction opposite to the route from which the transmission stop request has been received in the indoor direction. The digital processing unit 221 of the apparatus 22 is notified (310). The digital processing unit 221 starts signal power control based on the notified cable loss value or its deviation (311). For example, the control of the gain and the attenuation rate in the device such as the variable gain amplifier 224 on the reception system circuit system of the indoor device 22 is started. This is control for equalizing the cable loss deviation appearing in the received burst signal. On the other hand, the control unit 218 starts signal power control based on the detection value stored in the memory (312). That is, the control of the gain or attenuation factor in the device such as the variable gain amplifier 212 on the transmission system circuit system of the outdoor device 21 is started. This is control for equalizing the cable loss deviation appearing in the transmission burst wave. In the present embodiment, the TDD method is assumed, and it is assumed that the intermediate frequencies of the transmission burst wave and the reception burst wave are the same. Therefore, the cable loss (deviation) common to the outdoor device 21 and the indoor device 22 is detected. The value can be used. Note that there is no need to switch the gain or attenuation rate by burst on / off. That is, since the gain or attenuation factor can be kept constant after shifting to the normal operation, the circuit operation is stable also in that respect.
[0022]
Then, the digital processing unit 221 of the indoor device 22 requests the outdoor device 21 to cancel the transmission stop (313), and the control unit 218 of the outdoor device 21 switches the duplexer 215 accordingly. The operation is shifted to a normal operation, that is, a switching operation synchronized with burst on / off (314). Thereafter, transmission / reception by burst waves is executed as usual. At least in the ON period of the transmission burst wave (more preferably, always during normal operation regardless of burst ON / OFF), the cable loss deviation appearing in the transmission burst wave is equalized by the variable gain amplifier 212, and at least the reception burst wave Because the cable loss deviation appearing in the received burst wave is equalized by the variable gain amplifier 224 during the ON period (more preferably, always during normal operation regardless of the burst on / off), The circuit is not affected by the cable loss deviation and operates favorably.
[0023]
As described above, according to the present embodiment, the (non-) modulated continuous wave is transmitted from the indoor device 22 onto the coaxial cable 23 at the time immediately after the power is turned on, the signal power is measured by the outdoor device 21, and the Cable loss equalization is performed based on the results. Therefore, compared with the conventional technique in which the cable installer sets the cable loss approximate value and the conventional technique in which the cable loss or its deviation is indirectly measured through the measurement of the DC voltage drop or the signal propagation time, the cable installer Effects such as reduction of work load, realization of accurate cable loss equalization, and extension of the allowable range regarding the length, manufacturer, and type of the coaxial cable 23 can be obtained.
[0024]
Further, for example, the subscriber station 20 and the base station 10 that perform radio communication based on the TDD scheme and using burst waves with a short signal transmission time of 1 μsec per burst detect the signal power during normal burst communication to reduce cable loss. It is difficult to equalize from time to time. That is, the time required for stabilization of the gain or attenuation factor of the variable gain amplifier or variable attenuator to be controlled tends to be so long that it cannot be ignored with respect to the burst on period. There is a problem that a part is lost and a substantial transmission rate is lowered. In other words, if a communication device communicates with continuous waves, even if power measurement and cable loss due to the result are performed during communication, information loss will not occur except immediately after power-on. If it is simply applied to a communication device for communication, it results in missing information every burst-on period. On the other hand, the method according to the present embodiment is a method that is executed using a continuous wave at a timing at which transmission by a burst signal is not executed, such as immediately after power-on, and does not change the gain during the burst on period. Therefore, cable loss equalization can be realized without loss of burst signals. As the variable gain amplifiers 212 and 224, it is possible to use a variable gain amplifier 212 and 224 that does not respond so quickly to the gain control signal.
[0025]
Furthermore, since the procedure shown in FIG. 2 can be started at any time by operating a switch or the like, when there is a change in cable loss, such as when the subscriber station 20 or its constituent unit is moved, the coaxial cable 23 is replaced, or the connector is attached or detached. The gains of the variable gain amplifiers 212 and 224 can be optimized at any time. Further, since this procedure is automatically activated upon power-on, there is no need for the user to activate this procedure with a particular awareness except when a reset operation is necessary for some reason.
[0026]
The detector 216 detects the arrival of a transmission burst wave from the indoor device 22, controls the duplexer 215, and connects the antenna 24 to the transmission system, and uses it for the detection of arrival.・ Can also be used.
[0027]
And this invention can be implemented not only in a TDD system but in the communication apparatus by a FDD (Frequency Division Duplex) system.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing a control procedure in the present embodiment.
FIG. 3 is a diagram showing an example of a system that can use an apparatus according to the present invention.
FIG. 4 is a diagram conceptually showing transmission by a burst wave.
[Explanation of symbols]
10 base station, 11 base station radio frequency unit (RFU), 12 base station interface unit (IFU), 13, 23 coaxial cable, 20, 20A, 20B, 20C subscriber station, 21 subscriber station outdoor unit ( RFU), 212 variable gain amplifier, 216 detection unit, 217 A / D converter, 218 control unit, 22 indoor unit (IFU) of subscriber station, 221 indoor unit digital processing unit, 222 modulation unit.

Claims (3)

The transmission burst wave is transmitted from the first unit to the second unit via the cable, and further, the second unit transmits the antenna to the outside by connecting the antenna to the transmission system in response to the arrival of the burst wave. A cable loss equalization method executed by a communication device,
The first unit sending a loss detection signal to the cable, which is a continuous wave that is not burst-modulated with a predetermined power;
A cable loss measurement operation in which the second unit inputs the loss detection signal from the cable and measures the cable loss or the deviation thereof is performed according to a request from the first unit to the second unit. A step of executing the second unit in a transmission stopped state by disconnecting the transmission system of
At least during the burst-on period of the transmission burst wave, the second unit is configured so that the deviation of the cable loss appearing in the transmission burst wave is compensated and according to the information obtained in the above measurement, Automatically adjusting the gain or attenuation factor in the passing circuit ;
Cable loss equalization method characterized by comprising a. The cable loss equalization method according to claim 1, wherein the second unit receives a burst wave from the outside, and further transmits the received burst wave from the second unit to the first unit via the cable. In the cable loss equalization method executed in the machine,
A step in which the second unit notifies the first unit of information obtained by the measurement at the end of the cable loss measurement operation;
At least during the burst-on period of the received burst wave, the first unit is configured to compensate for the cable loss appearing in the received burst wave and according to the information notified from the second unit. Automatically adjusting the gain or attenuation factor in the passing circuit ;
Cable loss equalization method characterized by comprising a. In the cable loss equalization method according to claim 1 or 2,
Including a step of starting execution of a cable loss measurement operation in response to a power-on to the first unit, an operation of a switch attached to the first unit, or a command from a control terminal attached to the first unit. A cable loss equalization method characterized by that.

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