JPH0750872A - Wireless communication device - Google Patents

Abstract

(57) [Abstract] [Purpose] A wireless device that performs communication using a wireless line and is capable of performing high-quality communication even in an environment in which line quality deterioration occurs due to fading or interference. The purpose is to realize the device. [Structure] When a bit error occurs, the identification level for determining the bit code of the detection output of the receiver is shifted from the normal identification level to set a temporary identification level (threshold) so that the error rate becomes large, and the input signal is A case where the threshold value is lower than the threshold is regarded as a temporary bit error (pseudo error), and a line quality monitoring means for measuring a pseudo error for each symbol for a certain period of time, and a reception from the fluctuation of the number of pseudo errors measured by the line quality monitoring means are received. When it is determined that the number of pseudo errors exceeds a predetermined value and the number of pseudo errors fluctuates, the level fluctuation prediction means for predicting level fluctuations is provided.
Configure to switch the channels used by the receiver and transmitter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless communication device capable of high quality communication even in an environment where line quality is deteriorated due to fading or interference.

[0002]

2. Description of the Related Art As a method for reducing the deterioration of the line quality due to fading, there is a channel switching system in which the line quality deterioration is detected by the eye monitor method and then the frequencies used for transmission and reception are switched.

The eye monitoring method described above is a temporary discrimination level (hereinafter referred to as a threshold level) in which the discrimination level for discriminating the bit code of the detection output of the receiver when a bit error occurs is shifted from the regular discrimination level to increase the error rate. (Also referred to as), set a temporary bit error (pseudo error) when it falls below the threshold, determine the pseudo error number by measuring the pseudo error for a certain period, and convert it to the pseudo error rate. This is a method of estimating the bit error rate using the relationship between the error rate and the bit error rate.

When the number of bit errors is small, the number of pseudo errors generated is small. On the contrary, when the number of bit errors tends to increase and the line quality tends to deteriorate, the number of pseudo errors generated increases. In the conventional channel switching method using the eye monitor method, it is determined that the line quality is deteriorated when the number of pseudo errors in a certain time exceeds a predetermined value, and frequency switching is performed.

FIG. 4 is a block diagram showing an example of the configuration of a conventional base station having the functions of diversity and frequency switching. In the figure, the received signals received by the two antennas 31 and 32 are the hybrid circuit 5 respectively.
It is input to the receivers 53 and 54 and the reception level comparison unit 55 via 1, 52.

Each of the receivers 53 and 54 converts the received signal from the radio frequency band to the intermediate frequency band, one of the intermediate frequency signals is selected by the switch circuit 56 and is input to the demodulator 57, and the baseband is selected. Is detected. The reception level comparison unit 55 compares the levels of the respective reception signals and controls the switch circuit 56 so as to select the receiver output with the higher reception level to perform reception diversity.

On the other hand, the modulator 58 modulates the transmission signal and sends it to the transmitter 59. The transmitter 59 converts the modulated signal into a radio frequency band and transmits it from the corresponding antenna via the switch circuit 60 selected similarly to the switch circuit 56, and performs transmission diversity.

The frequencies used for transmission and reception are set to the same frequency by using the frequency synthesizers 62 and 63 according to an instruction from the control unit 61. The line quality monitoring circuit 71 monitors the detection output signal of the demodulator 57 to measure a pseudo error. Here, it is determined that the line quality has deteriorated when the number of pseudo errors exceeds a predetermined value, and a channel switching instruction is sent to the control unit 61.

The control unit 61 searches for an empty slot on another frequency and determines a channel switching destination slot. Next, control data including information designating the channel switching destination slot is created, multiplexed with the transmission signal by the modulator 58 to form a transmission burst, and transmitted to the mobile station. On the other hand, the mobile station receiving the transmission burst from the base station reads the channel switching destination slot from the control data and switches the channel.

With the above operation, channel quality deterioration can be improved by switching channels between the base station and the mobile station. Since channel switching functions independently of diversity, a wireless communication device with one transmission and one transmission system can be similarly configured.

[0011]

As described above, in the channel switching method to which the conventional measurement method is applied, when the number of pseudo errors in one burst exceeds a predetermined value, transmission and reception are always performed. Since the condition was to switch the frequency to be used, even if the reception level tends to recover after detection, it is not considered,
If the number of pseudo errors is equal to or larger than a predetermined value, the channel is switched.

FIG. 5 shows the relationship between the reception level and the number of pseudo errors at any given time. As can be seen from the figure, in general, when the reception level 201 tends to decrease, the pseudo error number 202 tends to increase. In the figure,
The points A and B have the same number of pseudo errors and both exceed a predetermined value, but the reception level 201 tends to decrease near the point A, but increases near the point B. It is in.

In the conventional system, channel switching is performed as described above even when the reception level tends to increase like point B. However, if the reception level tends to recover, it is meaningless to switch channels, and channel resources are wasted. In view of such conventional problems, the present invention predicts the fluctuation of the reception level from the fluctuation of the number of pseudo errors, and performs transmission and reception only when the number of pseudo errors tends to increase and the reception level tends to decrease. The frequency to be used is switched, and it is an object of the present invention to realize high-quality communication in an environment that is greatly affected by fading and the like.

[0014]

According to the invention, the above mentioned objects are achieved by means of the patent claims.

That is, according to the present invention, the threshold value (identification level) of the signal level for determining the bit code of the detection output of the receiver is erroneous as compared with the normal identification level A when a bit error occurs. A temporary bit error (pseudo error) is set when the signal level is below the identification level B by setting the temporary identification level B such that the rate becomes large.

Line quality monitoring means for measuring a pseudo error for each symbol for a certain period of time; level fluctuation predicting means for predicting a fluctuation of a reception level based on a fluctuation of the number of pseudo errors measured by the line quality monitoring means; Used by the receiver and transmitter when the number of pseudo errors measured by the line quality monitoring means exceeds a predetermined value, and when the level fluctuation prediction means determines that the fluctuation of the number of pseudo errors tends to increase. The wireless communication device includes a channel switching unit that switches channels.

[0017]

As described above, the wireless communication device of the present invention is, for example, a base station and a mobile station, or a base station or a mobile station,
When a bit error occurs, the discrimination level for judging the bit code of the detection output of the receiver is shifted from the regular discrimination level to set a temporary discrimination level (threshold) at which the error rate becomes large, and the input signal falls below the threshold. Such a case is defined as a temporary bit error (pseudo error), and a line quality monitoring means for measuring the pseudo error for each symbol for a certain period is provided.

Further, there is provided level fluctuation predicting means for predicting fluctuations in the reception level from fluctuations in the number of pseudo errors measured by the line quality monitoring means, the number of pseudo errors exceeds a predetermined value, and the number of pseudo errors When it is determined that the fluctuation tends to increase, the channels used by the receiver and the transmitter are switched.

Since the line quality monitoring means monitors the amplitude fluctuation and phase fluctuation of the baseband input signal of the detection output of the demodulator for each symbol, it is possible to cope with instantaneous fluctuations such as fading. The level fluctuation predicting unit can predict the fluctuation of the reception level from the fluctuation of the number of pseudo errors measured by the line quality monitoring unit. Therefore, when it is determined that the reception level decreases and the line quality tends to deteriorate, channel switching is performed. Output instructions.

Therefore, when the reception level tends to recover, channel switching is not requested. Further, the channel switching means switches the frequency used for transmission and reception when the line quality tends to deteriorate, so that high quality communication can be realized in a fading environment.

[0021]

1 is a block diagram showing the configuration of an embodiment in which a radio communication apparatus of the present invention is applied to a base station.

In the figure, the antennas 31 and 32, the hybrid circuits 51 and 52, the receivers 53 and 54, the reception level comparing section 55, the switch circuit 56 and the demodulator 57 for receiving diversity, and the modulator 58,
The configuration for transmission diversity by the transmitter 59 and the switch circuit 60 is the same as the conventional configuration described above with reference to FIG.

In the present embodiment, the line quality monitoring circuit 11 for monitoring the detection output signal of the demodulator 57 and measuring the pseudo error.
And a level fluctuation prediction circuit 12 that predicts fluctuations in the reception level from fluctuations in pseudo error.
The control unit 13 switches the channel in response to the frequency switching instruction from.

In the level fluctuation prediction circuit 12, one burst is divided into several blocks, the number of pseudo errors in each block is measured, and when fluctuations in the measured pseudo errors show an increasing tendency, the reception level decreases. Then, it is determined that the line quality tends to deteriorate. When the number of pseudo errors measured by the line quality monitoring circuit 11 exceeds a predetermined value and the level variation prediction circuit 12 determines that the number of pseudo errors tends to increase, the frequency change instruction signal is used to predict the level variation. Circuit 12
To the control unit 13.

The control unit 13 searches for an empty slot on another frequency and determines a channel switching destination slot. Next, control data including information designating the channel switching destination slot is created, multiplexed with the transmission signal by the modulator 58 to form a transmission burst, and transmitted to the mobile station. On the other hand, the mobile station receiving the transmission burst from the base station reads the channel switching destination slot from the control data and switches the frequency.

With the above configuration, between the base station and the mobile station, a predetermined line quality is ensured by the reception diversity and the transmission diversity, and the line quality deterioration is improved by switching the frequency even when the diversity is difficult to improve. And high quality communication can be realized.

An example of the effect of improving the line quality by switching the frequency is shown in FIGS. 2 and 3. In FIG.
The horizontal axis is the fading frequency. The vertical axis is the bit error rate. And the fading frequency is 1 Hz,
The bit error rate characteristics when changing to 8 Hz and 15 Hz are shown.

In FIG. 3, the horizontal axis is the fading frequency. The vertical axis is the frequency switching cycle. The frequency switching frequency characteristics when the fading frequency is changed to 1 Hz, 8 Hz, and 15 Hz are shown. In the conventional example, a pseudo error is generated when the magnitude of the detection output signal of the demodulator falls below a provisional discrimination level (threshold) of 0.65, and the number of pseudo errors in one burst becomes a prescribed value of 6 or more. If it occurs, it is determined that the line quality has deteriorated and frequency switching is performed.

In the embodiment of the present invention, the magnitude of the detection output signal of the demodulator has a provisional discrimination level (threshold) of 0.6.
If the number of pseudo errors is less than 5, the number of pseudo errors in one burst is 6 or more, and if the fluctuation shows an increasing tendency, it is determined that the line quality is deteriorated and the frequency is switched. did. Furthermore, the processing time from switching the frequency after determining that the line quality is degraded to performing communication using the new frequency is considered as the frequency switching processing time. As a condition for this measurement, it is assumed that Eb / No is 30 dB, delay dispersion is 250 ns, and frequency switching processing time is 30 ms.

As shown in FIG. 2, in the embodiment of the present invention,
The fading frequency is about 40% at 15Hz and the fading frequency is 8Hz compared to the case where the frequency is not switched.
Shows an improvement effect of about 60% at a fading frequency of 1 Hz and about 75% at a fading frequency of 1 Hz. Further, as shown in FIG. 3, in the embodiment of the present invention, the average frequency switching period is about 2 as compared with the conventional example.
It is doubled, and the frequency switching frequency is reduced to about 1/2. In other words, it can be seen that the bit error rate can be improved with the number of times of frequency switching that is about half that of the conventional case.

[0031]

As described above, the radio communication apparatus of the present invention performs frequency switching only when the fluctuation of the reception level is predicted and the reception state tends to deteriorate.
Since efficient frequency switching can be performed, there is an effect that the bit error rate can be improved with a frequency switching number that is significantly smaller than that in the past.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a line quality improvement effect.

FIG. 3 is a diagram showing an example of a line quality improvement effect.

FIG. 4 is a diagram showing an example of a configuration of a conventional base station.

FIG. 5 is a diagram showing an example of a relationship between a reception level and the number of pseudo errors.

[Explanation of symbols]

 11 line quality monitoring circuit 12 level fluctuation prediction circuit 13 control unit 31, 32 antennas 51, 52 hybrid circuit 53, 54 receiver 55 reception level comparison unit 55, 60 switch circuit 57 demodulator 58 modulator 59 transmitter 61 control unit 62 , 63 Frequency synthesizer 71 Channel quality monitoring circuit 201 Reception level 202 Pseudo error number

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuzo Kato 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (1)

[Claims] 1. A signal level threshold value (identification level) for determining a bit code of a detection output of a receiver has a larger error rate than a normal identification level A when a bit error occurs. Set to a temporary identification level B such that
A case where the signal level is lower than the identification level B is defined as a temporary bit error (pseudo error), and a line quality monitoring unit that measures a pseudo error for each symbol for a certain period, and a pseudo line error monitoring unit that measures the pseudo error. Level fluctuation predicting means for predicting fluctuations in the reception level based on fluctuations in the number of errors, and the number of pseudo errors measured by the line quality monitoring means exceeds a predetermined value, and A wireless communication device comprising: a channel switching unit that switches a channel used by a receiver and a transmitter when it is determined that the fluctuation tends to increase.