JPH02312422A - Radio line quality supervisory system - Google Patents

Abstract

PURPOSE:To constitute this system so that the interference quantity and the fading speed even in the case deterioration caused by a random FM noise is generated by discriminating where a phase of a signal is located in a discriminating area of the phase divided by a large number than the number of multivalue of a digital modulation. CONSTITUTION:The receiving equipment is provided with a means 4 for discriminating where a phase of a signal outputted from a phase detecting circuit 1 is located in a discriminating area of the phase divided by a larger number than the number of multivalue of a digital modulation, a means 2 for measuring an envelope level of a receiving signal by a period of a reproducing clock signal, and a means for classifying the measured envelop level in to plural sections, and also, accumulating and counting for a prescribed time the number of times of appearance of a signal appearing in the discriminating area corresponding to a prescribed phase error or above in the discriminating area being different from a phase discriminating area of a signal at the time of no-noise at every section. In this state, by using this time accumulating and counting result and a result of measurement of the envelope level, the fading speed and the interference quantity are derived. In such a way, even the system which adopts a modulation system can detect the deterioration caused by an interference.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a radio channel quality monitoring system for detecting the quality of a radio channel in mobile communications in a small zone configuration where interference waves and high-speed aging exist.

[Conventional technology]

Conventionally, as an interference detection method for mobile communications, there is a method that detects the size of the beat at the reception envelope level (for example,
Kozono et al., “Measurement method of co-channel interference in mobile communications,” Tsuken Jitsuho, 35, No. 2. Pl, 99-2
07.1986. ).

The principle of this method is that a beat with a speed corresponding to the difference in carrier frequency between the desired wave and the interference wave occurs at the envelope level of the received signal (i), and the size of the beat component is proportional to the ratio of the desired wave to the interference wave. It takes advantage of the fact that

In this conventional method, when a constant envelope modulation method such as FSX is used, variations in the reception envelope level are caused by fading specific to the mobile communication channel and by interference.

The pitch variation due to the former is several hundred Hz at the fastest. For example, even if the carrier frequency is about IGHz and the moving speed of the mobile station is about 100 km/h, the frequency is 90 Hz. Since the content of the wireless modulation signals of the interference wave and the desired wave are different, the fluctuating pitch due to the latter is usually 1 to 2k depending on the frequency deviation etc.
Hz or more.

Since both frequencies are different in this way, by processing the envelope level output with a bandpass filter, 7
It is possible to remove the influence of the A song, extract only the beat component due to interference, and determine the amount of interference. Furthermore, by passing the envelope through a low-pass filter, the amount of variation due to 7 A songs can be determined.

[Problem to be solved by the invention]

In normal mobile communications, a 5cpc method is used, so a receive IF filter is used to demodulate only the signal of the corresponding receive channel, but the band of this receive IF filter is larger than the modulation spectrum width. If the width is not large enough, part of the signal components will be removed by the IF filter, so even if only the desired signal is received,
The envelope level after passing through the reception IF filter varies depending on the frequency of the modulated signal.

In other words, the received signal is distorted due to band limitation. In particular, when the frequency of the modulated signal is small, the rate of fluctuation approaches that of 7-acing, making it impossible to separate the two, resulting in a large error in measuring the amount of interference.

In particular, when the carrier frequency drifts and there is a difference between the center frequency of the received IF filter and the IF frequency of the desired wave, the portion cut out by the signal component filter increases, and the distortion increases, resulting in errors. This situation is better understood with reference to FIG. 9, a diagram illustrating the characteristics of the IF filter and signal distortion.

That is, FIG. 9(a) shows a channel arrangement, in which a plurality of channels (center frequency fsc,
fsc±W,...) are arranged.

Figure 9(b) shows the case of normal reception, that is, when the passband width B of the I-do filter (the part shown by the broken line in the figure) is larger than the signal bandwidth S (the part shown by the solid line in the figure). It is.

No. 91M(e) is IF filter passband 119KB
is smaller than the signal bandwidth S, and the signal component in the shaded area is removed by the filter, causing distortion.

FIG. 9 (d>) shows a case where the center frequency fsc of the received signal deviates from the center frequency fee of the IF filter, and the signal component in the shaded area is deleted by the filter, causing distortion.

Furthermore, when a modulation method such as QPSK that does not have a constant envelope is adopted, a signal whose envelope level changes depending on the content of the modulated signal is transmitted, so on the receiving side, the state of the propagation path described above, i.e. , 7. The fundamental fluctuations in the modulation method are superimposed on the fluctuations in the envelope level due to icing and interference, making it difficult to extract only the beat component due to interference, and also having the disadvantage of increasing errors. .

Furthermore, as another conventional method, a method of monitoring line quality using soft decision output has been developed for satellite communications, but in mobile communications, the above-mentioned 7 aging not only monitors fluctuations in the received envelope level. Since random FM noise is generated in which the phase of the received wave changes rapidly and randomly, this has a disadvantage in that it affects the soft decision output and causes errors in the line quality measurement results.

An object of the present invention is to provide a method for detecting interference with high accuracy, which can be applied to systems using linear modulation methods such as QPSK, and even when applied to mobile communications where relatively fast pitch 71-nons occur. It is in.

[Means to solve the problem]

According to the present invention, the above object is achieved by the means described in the claims.

That is, the present invention provides mobile communication in which a digital signal is transmitted by a multilevel phase modulated wireless signal, in which the phase of the signal output from the phase detection circuit is detected in the receiving device.
means for determining where the phase is located in a phase discrimination region divided by a number greater than the number of multi-values of digital modulation; means for measuring the envelope level of the received signal with the period of the reproduced clock signal; The envelope level obtained is classified into multiple categories, and for each category, the signal appearing in the discrimination area corresponding to a predetermined phase error or more in the discrimination area different from the phase discrimination area of the signal when there is no noise is classified. This is a radio channel quality monitoring system that includes means for cumulatively counting the number of appearances over a predetermined period of time, and uses the time cumulative counting result and the measurement result of the envelope level to determine the fading rate and the amount of interference.

[For production]

The present invention provides mobile communication in which a digital signal is transmitted using a multilevel phase modulated wireless signal, for example, QPSK.
The phase of the received signal is changed to a phase plane (I-Q plane) by a number greater than the digital modulation multilevel number “4”, for example “36”.
This method calculates the speed of the song and the amount of interference by dividing the signal into two parts, determining the region where the signal phase is located at a finer level, and combining the results with the measurement results of the envelope level of the received signal. be.

This method differs from the conventional technology in that the amount of interference is determined using both the results of determining the phase region to a finer level than the multilevel number of digital modulation and the envelope level of the received signal.

〔Example〕

FIG. 1 is a diagram showing the first embodiment of the present invention, in which 1 is a phase detection circuit, 2 is an envelope detection circuit, 3 is a clock regeneration circuit (CK regeneration, 4 is a logic circuit, 5 is a clock delay circuit, 6 is a sample hold circuit (S/H) or A/D
The conversion circuit and 7 are processing circuits. The operating principle when QPSK is adopted as the modulation method in this embodiment will be described below.

FIG. 2 shows the correspondence between the determination phase and the output of the phase detection circuit 1, and will be explained by taking as an example the case where the phase detection circuit 1 performs synchronous detection.

As is well known, the QPSK method modulates two series of binary data, and it modulates four data combinations (0, 0).
, (0, 1), (1, 0), and (1, 1) correspond to the phases of four carrier waves of 90 degrees each.

Therefore, when synchronously detecting with two orthogonal phases ■ and Q,
A signal point on the IQ plane has 2-bit information, and data can be demodulated by classifying it into four ranges. The four ◎ marks in the figure represent signal points when there is no noise, and each quadrant is one of the four types of determination areas.

In other words, conventional detection circuits perform demodulation by detecting the quadrant in which the carrier phase exists.

For example, the first quadrant is (0.0>, the third quadrant is (0.0>),
111).

As shown in the fIS2 diagram, the phase detection circuit 1 of the present invention has the following features:
It is configured to output the results of identification into more types than the number of multi-values of digital modulation. For example, in QPSK, conventionally there were four types, but here an example is shown in which 36 types are identified.

The logic circuit 4 determines the quadrant based on the detection output divided into 36 types and outputs demodulated data, and the area containing the signal point in the noise-free period is set to 0, and each further away from the area is set to 1, 2, 3. .4 to represent the magnitude of the detection phase shift due to the disturbance, and the result is input to the processing circuit 7.

Specifically, the determination result N (0
.about.4) to the processing circuit 7.

On the other hand, the envelope detection circuit 2 detects the envelope level of the received signal, and for each time slot of each data, the delay circuit 5 performs a certain delay adjustment on the clock recovered by the clock recovery circuit 3, so that one time slot of the received data is detected. It is sampled at the timing at the center of the lot and inputted to the processing circuit 7. This situation is shown in FIG. Here the envelope level, recovered clock and data are shown.

At the envelope level, the solid line shows the envelope of the QPSK modulated wave, the dotted line shows the envelope sampled by the sample-and-hold (S/H) circuit 6, and the dashed line shows the QPSK modulated wave passed through the low-pass filter. The waveform after this is shown.

Data 00'' and 011'' indicate two series of data.

In addition, there are combinations of 01' and 10', but in order to emphasize the case where the envelope of the QPSK modulated wave falls to 0, that is, the phase shifts by 180°, we especially use 01' and 11'. '' is shown only.

The peaks of the QPSK modulated waveforms should be at the same level, but the peaks are shown to change taking into account reception level fluctuations due to aging.

The processing circuit 7 converts the output N from the logic circuit 4 into a discrimination area O.
The count is accumulated for a certain period of time every ~4. For example, if the average time T is 10·t (t: clock time width), then N
=0 three times, N=1 four times, N=2 O, N=3 twice, N=4 once, and so on.

In addition, the envelope level of the sample and hold circuit 6 is also
The average value of this constant darkness is calculated.

This now represents the average received electric field value of α.

Figure @4 is a diagram illustrating the principle that the modulation phase shifts when there is an interference wave. In the example in Figure 4, for the desired wave,
Interference wave U1. U2. It shows the phase detection output when U3 is present. If the interference wave is also a QPSK wave, the combined phase of the desired wave and the interference wave depends on the mutual phase relationship between the two and the four types of modulation phases of the interference wave, but in general, the modulation phases are random and equal. Since it can be considered as a probability, the interference waves [1, U2 . In each case of U3, regions 1-4
Taking the case of FIG. 4 as an example, the probability of being determined as follows is shown in the table below.

Here, we ignore Langum FM noise due to fading and thermal noise in the transmission path, so if there is no interference wave, the probability is that everything will be classified in the discrimination region 0, and in the case of interference wave U1, the probability will be in the discrimination region 0. is 1/2, and the probability of being in discrimination region 1 is also 1/2.9 As the difference increases, the probability of being discriminated as a region with a large deviation from the region when there is no noise increases.

In this way, if the level of the received signal is sufficiently large and there is almost no effect of thermal noise, and there is no aging, the signal will be determined to be in an area that deviates from the discrimination area when there is no noise in proportion to the size of the interference wave. Therefore, the quality of the wireless channel is judged based on the accumulated count value of this discrimination result, and if the average value of the received envelope level is extraordinary, it can be determined that the cause is interference waves rather than thermal noise. , the amount of interference can be detected.

In other words, if there is no effect of aging, it is determined whether the cause of the modulation phase shift is thermal noise interference based on the relationship between the measurement result of the probability of being equal to or greater than the discrimination region N and the measurement result of the average reception envelope level. . In other words, if the envelope level is small, thermal noise is large, but if the phase shifts, it is determined that it is due to interference waves. Furthermore, by using the measurement result of the probability of being equal to or greater than the discrimination region N, the quality of the wireless channel can be determined.

Here, the discrimination area N or more means, for example, if N=3,
The case where N=3.4 will be found, and if N=1 or more, all cases other than N=0 will be found.

The explanation above has been made assuming the case of synchronous detection, but in the case of delayed detection, the difference is that the deviation from the discrimination area when there is no noise increases by about twice as the interference wave directly affects the detection phase. However, it can also be applied to delayed detection.

The first embodiment described above operates normally without the 7A song, but if there is fading, it is impossible to distinguish between random FM noise and interference, so it cannot operate accurately. Here is an example to solve this problem.

Figure 5 is a diagram showing a second embodiment of the present invention,
is a phase detection circuit, 2 is an envelope detection circuit, 3 is a clock regeneration circuit (CK regeneration, 4 is a logic circuit, 5 is a clock delay circuit, 6 is a sample and hold circuit (S/H) or A/
D conversion circuit, 70 is a processing circuit, 8 is a selection circuit, 9-
12 is a counter, 13 is an averaging processing circuit, and 14 is a judgment processing circuit.

In this embodiment, the parts indicated by 1 to 6 operate in the same manner as in the embodiment described in FIG.

The counter 9 counts the number of phase shift scales N=0 to 4, and the averaging processing circuit 13 calculates the average value of the envelope level.

Therefore, in the previous embodiment, only the counter 9, the averaging processing circuit 13, and the determination processing circuit 14 were provided, but here, the counters 10 to 12 and the selection circuit 8 are provided.
This embodiment differs from the embodiment shown in FIG. 1 in that the following operations are performed.

That is, the envelope level for each time slot is input from the sample hold circuit 6 to the processing circuit 70, and the discrimination area N (N=1.2
．． 3.4>Control the input of a counter that cumulatively counts the number of items determined above. That is, the instantaneous envelope level for each time slot is classified into several ranges, and a cumulative count of the discrimination region N or more is performed for each classified range.

For example, when the envelope level is in the range of 0 to 5 dB, the counter 10 counts the number of pieces judged to be above the discrimination range N, and when the envelope level is in the range of 5 to 10 dB, the number of pieces judged to be above the discrimination range N is counted. The counter 11 counts. After a predetermined measurement time has elapsed, the probability of being determined to be above the discrimination region N for each envelope level is determined from the count value of each counter. The operation of this part is the same as in the first embodiment.

From these results, it is possible to measure not only the amount of interference but also the speed of aging.

FIG. 6 is a diagram explaining this. Figure 6 shows the relationship between each instantaneous envelope level and the probability of being equal to or higher than the discriminant region N in four cases of high fading speed and low fading speed, and the reception envelope Shows the number of line level samples. First, to explain the case where there is no interference wave, ◯ indicates the case of 7 A song low speed, and . indicates the case of 7 A song high speed. In either case, the distributions for each envelope level match as shown in the histogram shown in FIG. 6(b), and therefore the average values of the envelope levels also match.

So, as far as the envelope level is concerned, there is no difference depending on the speed of the 7-enong. However, when 7Acing is high speed, random FM noise causes a shift in the signal phase,
Generally, the probability of being determined to be greater than or equal to the discrimination area N increases.

It was difficult to distinguish between interference and random FM noise by simply using the average value of the probability of being above the discrimination range N. However, in this example, the reception envelope level and the probability of being above the discrimination range N are difficult to distinguish. Since the relationship between the probabilities of being judged is measured, the judgment can be made as follows. When the fading is slow, as shown by the data curve marked with ○ in Figure 6(a), a certain reception envelope level (15 dB in this example)
, the phase shift decreases rapidly.

On the other hand, when aging is at a high speed, as the envelope level increases, the phase shift decreases at a more or less constant rate, as illustrated by the * mark, and in general, the characteristics shown by the ○ mark is different.

Therefore, from the shape of this measurement curve it is possible to measure the speed of 7 aesong. A similar tendency exists even when there is an interference wave, so it is possible to measure the fading speed regardless of the presence or absence of interference waves.

In addition, when detecting the presence or absence of interference waves, there is a difference in the reception envelope level value corresponding to the same amount of phase shift, that is, the probability of being equal to or greater than the discriminant region N. It is possible.

For example, in Figure 6(a), the probability of N or more is 1
The envelope level at 0-2 is approximately 20 when there is no interference wave.
dB, and when there is an interference wave, it is about 60 dB, so it can be easily detected.

As described above, in a state where interference waves, thermal noise, and 7 A songs are mixed, the relationship between this envelope level and the probability of being equal to or higher than the discrimination area N is determined in advance, and by comparing it with the measurement results, these can be determined. Deterioration in radio channel quality can be detected by separating the cause, and the amount of interference and fading rate can be quantitatively determined.

In the embodiment shown in FIG. 5, only one type of N is counted as the probability that the discrimination area is N or more. For example,
When N=2, only the case of measuring the probability that N is 2 or more has been shown, but it is possible to find all or any combination of N=1.2.3.4 and use those results together. By doing so, even more accurate measurement becomes possible. Furthermore, although we have shown an example in which the selection circuit 8 selects the reception envelope level using an instantaneous value for each time slot, there is also a method of classifying the reception envelope level based on the average reception level (short period median value) over a preset time length. 6 There is also a method that can be used in combination with this method.

As it operates as described above, this embodiment can detect the amount of interference and also determine the fading speed even when there is a high-speed 7-A song, or when low-speed and high-speed 7 A songs are mixed. There is interest. Fading rate is also a measure of the quality of the S-line channel.

For example, in a car telephone system, the fading rate is
This is an important measurement value that can be used for transmission power control algorithms, frequency allocation algorithms for dynamic channel allocation in small zone mobile communications, and inter-wireless zone channel switching judgment algorithms.
This has the advantage that these control algorithms can be made more sophisticated.

Here, transmission (g power control) is a technology that controls the magnitude of transmission power according to the magnitude of the reception level, and
Dynamic channel allocation is a technique for dynamically allocating focal channels for communication in the 5cpc system.

21. The fading speed measurement in this example is not a method of directly detecting the speed of variation in the envelope level, but a method of indirectly obtaining it from the measurement of the amount of phase shift. This method also has the advantage of being easy to apply when the time to be measured cannot be measured continuously. In other words, TDM
In A, the signals of each channel are multi-developed on the time axis, so when focusing on a particular channel, the signal appears only intermittently.

Figure 7 shows a third embodiment of the present invention, in which 1 is a phase detection circuit, 2 is an envelope detection circuit, 3 is a clock regeneration circuit (CK regeneration, 4 is a logic circuit, 5 is a clock delay circuit, 6 is a sample hold circuit (S/H) or A/D
A conversion circuit, 7 a processing circuit, 20 a fading speed detection circuit, 21 a delay circuit, 22 an averaging processing circuit, 23 a level crossing detection circuit, and 24 a counter. In this embodiment, a function for directly measuring the fading rate is added to the first embodiment shown in FIG. 1. Portions 1 to 6 in the figure operate in the same manner as the embodiment described in FIG. Next, the operation of the fading speed detection circuit 20 will be described based on FIG.

The phasing speed detection circuit 20 includes real #12 in FIG.
A reception envelope level as shown in 5 is input. This waveform is a value sampled by a reproduced clock and is a discrete value, but in this figure, the time axis is greatly compressed and shown in analog form. The short-term average value of this envelope level is determined by the averaging processing circuit 22. The short-term average value is indicated by point @21 in FIG. Since this averaging operation requires a certain amount of time, the instantaneous envelope level for each time slot after inserting a delay corresponding to the averaging period in the delay m circuit 21 is determined relative to the average value output from the averaging processing circuit 22. The level crossing detection circuit 23 detects that the level curve 26 intersects with the level curve 26 to which a certain amount of offset has been added, and the counter 24
The number of level crossings per certain period of time is determined and output. The number of times this level is crossed is the 7-kong speed.

The above explanation assumes digital processing, but when performing analog processing, the instantaneous envelope level of the input can be passed through a low-cut filter instead of the parts indicated by numbers 21, 22, and 23. This can be realized by removing the DC component by using a comparator to detect the level crossing between this component and a certain offset.

This is conventionally often used in received electric field median value detection circuits.

With a system that uses TDMA, the time to be measured is
If it is only a part of the DMA7 frame, it is appropriate to perform digital processing as shown in this example and stop the processing at a time that does not correspond to the own channel.

In the processing circuit 7, as explained in the embodiment of FIG.
．． 2. Find the average probability determined in 3.4). Furthermore, by correcting the result with information regarding the 7-Nong speed from the 7-21 song speed detection circuit 20, it becomes possible to monitor the radio channel quality with high precision even in the presence of random FM noise.

That is, in the processing circuit 7, the signal phase shift due to both the amount of interference and aging is determined, but the amount of interference is also determined by separately measuring the Ferning speed.

This embodiment has the advantage that more accurate quality detection is possible because the correction is performed by direct measurement of the seven-stroke speed.

In addition, as in the above-mentioned embodiment, even when there is a high-speed 72-song, or when low-speed and high-speed 7-songs are mixed, the amount of interference is detected and the 7-nong speed is also determined. There is an advantage that various control algorithms can be improved by detecting the fading speed.

In addition, although the case of QPSK was explained in the first to third embodiments above, even when other digital modulation methods are used,
Any method using phase detection can be applied. Furthermore, the same can be applied even when frequency detection is used.

〔Effect of the invention〕

As described above, the present invention has the advantage that degradation due to interference can be detected even in a system that employs QPSK#, a modulation method that is not a constant envelope.

In addition, even when fast 7-aging occurs and deterioration occurs due to random FM noise, or when low-speed and high-speed 7-aging occur together, the radio channel quality can be improved by separating deterioration factors such as thermal noise, interference, and random FM noise. It has the advantage of being able to detect the amount of interference and measure the speed of the 721 song.

In a small zone mobile communication system, these detected values, especially the measurement results of phasing speed, can be used to develop transmission power control algorithms, frequency allocation algorithms in dynamic channel allocation for small zone mobile communications, and inter-zone channel switching decisions. By using it in algorithms, etc., there is an advantage that it is possible to improve the sophistication of control algorithms in order to improve the frequency utilization rate and reduce the control load.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a first embodiment of the present invention, and FIG. 2 is a diagram showing a QP
A diagram showing the correspondence between determination phase and output when SK is adopted,
FIG. 3 is a diagram explaining the detection of the envelope level, FIG. 4 is a diagram explaining the detection output when there is interference, FIG. 5 is a diagram showing the second embodiment of the present invention, and FIG. A diagram showing the relationship between each instantaneous envelope level and the probability of being equal to or higher than the discrimination region N, FIG. 7 is a diagram showing the third embodiment of the present invention, and FIG. 8 explains the operation of the 7-Nong speed detection circuit. FIG. 9 is a diagram explaining the characteristics of the IF filter and signal distortion. 1... Phase detection circuit, 2...
...Envelope detection circuit, 3 ...Clock recovery circuit, 4 ...Logic circuit, 5
・・・・・・ Clock delay circuit, 6 ・Old・
・Sample hold circuit or A/D conversion circuit,
7.7o... Processing circuit, 8...
...Select circuit, 9-12 ...Counter, 13 ...Averaging processing circuit,
14... Judgment processing circuit, 20...
... Fading speed detection circuit, 21 ...
Delay circuit, 22... Averaging processing circuit, 23... Level crossing detection circuit, 24... Counter, 2
5... Reception envelope level curve, 26.
・・・・・・Level curve with offset amount added to short-term average value, 27 ・・・・・・Short-term average value, 28
・・・・・・ Output waveform agent of level crossing detection circuit Patent attorney Honma Takashi Yakusho Pharmaceutical Vinegar IzdA

Claims (1)

[Claims] In mobile communication in which a digital signal is transmitted using a multi-level phase modulated radio signal, a receiving device has a system in which the phase of the signal output from a phase detection circuit is higher than the multi-level number of digital modulation. means for determining where the received signal is located in a phase discrimination area divided into a large number; means for measuring the envelope level of the received signal in accordance with the period of the reproduced clock signal; In addition to classifying into categories, for each category, cumulatively count the number of times a signal appears in a discrimination region corresponding to a predetermined phase error or more in a discrimination region different from the phase discrimination region of the signal in the absence of noise over a predetermined time period. 1. A radio channel quality monitoring system, comprising: means for determining a fading rate and an amount of interference using the time cumulative counting result and the measurement result of the envelope level.