JPH0346422A - Channel selecting system - Google Patents

Abstract

PURPOSE:To attain accurate channel selection by comparing the reception state of each channel in a time length when a reception level of a radio wave from a base station exceeds a prescribed value and selecting a signal with good condition among reception signals fluctuated largely. CONSTITUTION:When a control circuit 5 gives a data selecting a channel 1 to a synthesizer 3, a receiver 2 receives the radio wave of the channel 1. The intermediate band signal of the reception signal of the channel 1 is detected and fed to the input terminal of a comparator 61. The comparator 61 compares the quantity of the detection signal with that of a reference voltage from a D/A converter 4 and outputs 1 in the case of detection signal >reference voltage to obtain a prescribed waveform. Since the gate 63 is opened only when the level of the waveform is 1, the clock from a clock generator 62 is counted by a counter 64 and stored in the control circuit 5. Similarly, the counted value is obtained from channels 2, 3. Thus, the maximum counted value is decided and a channel having the maximum channel is selected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a channel selection method 1, and in particular, to a mobile communication device of a mobile communication system using a plurality of base stations.
The present invention relates to a channel selection method that makes it possible to select a channel receiving high-quality T-waves.

[Conventional technology]

FIG. 5 shows a conceptual diagram of a conventional mobile communication system called a so-called cell system. Communication areas 80 to 82 are formed around base stations 90 to 92, respectively, and mobile communication device 100 selects the nearest base station to form a communication link. One way to select the nearest base station is to select the base station with the strongest reception.
For example, a channel selection method as shown in FIG. 6 is known.

In the figure, radio waves received by an antenna 1 are received and amplified by a receiver 2. The intermediate frequency band (I
F)! The signal is detected by the detector (a), and the detector ω
An amplitude variable [(AM) signal is output from. Its output is converted into a digital value by an analog-to-digital converter (ADC) 41.

The control circuit 5 can know the reception level by reading the output of the ADC 41.@When the reception level of the reception channel is detected, the control circuit 5 controls the synthesizer 3 to switch the channel, The receiver 2 receives radio waves of other channels. Then, in the same manner as above, the reception level of the channel is measured.

In this way, the control circuit 5 measures the reception level of each channel and selects the base station from which the maximum reception level can be obtained.

The conventional channel selection method is, for example, disclosed in Japanese Unexamined Patent Application Publication No. 1987-1991).
It is disclosed in Japanese Patent No. 3-39222 and is well known.

[Problem to be solved by the invention]

However, in mobile communications, the reception level may become extremely unstable due to a phenomenon called multipath fading.

For example, assume that the reception level of channel 1.2 fluctuates as shown in FIG.

At this time, the average level of both is assumed to be the same. like this'
In the alpha wave state, the signal of channel 2 is of better quality,
The final selection should be made.

Now, at time t0, both values are sampled by the ADC 41, and the sampled values are compared by the control circuit 5, and if the larger channel is selected, channel 1 will be selected. Deteriorate.

Therefore, it may be possible to average the reception levels and compare them. Averaging may be a digital average of sample values, or may be averaged and sampled using a circuit. However, in the example of FIG. 7, since the two average values are the same, there is a possibility that channel 1 will be selected, which is not preferable.

The present invention has been made in view of the problems of the conventional method described above, and its purpose is to select a signal with good conditions from among received signals that fluctuate widely, perform accurate channel selection, and select a single channel. The goal is to provide a method.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a comparison means for comparing the received signal level and a predetermined reference level for each receiving channel, and a time measuring means for measuring the time when the received (N signal level is equal to or higher than the reference level). The present invention is characterized in that it includes a measuring means and a channel selecting means for selecting the channel having the maximum value within the measuring time.

[Effect]

The detection output is input to the comparison means, and the comparison means outputs the '''1#1# level when the detection output becomes equal to or higher than the reference level. Count the clocks when the output of is Ill''. As a result, it is possible to determine the time corresponding to each channel when the detected output is equal to or higher than the reference level.

The channel selection means selects the channel having the maximum value within the time period.

As a result, a signal of a channel whose received level fluctuates greatly takes a longer time to be below the reference level than other signals, and the possibility of being selected becomes smaller. therefore,
Accurate channel selection can be made.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

#I1 shows a block diagram of the first embodiment of the present invention. In Fig. 1, the points that differ from the conventional example shown in Fig. 6 are A, DC4
1, a voltage comparator 611, a clock generator 62, a gate ω, a counter, and a digital-to-analog converter (DAC) 4 are provided. 6th
The same reference numerals as in the figures indicate the same or equivalents.

When performing channel selection, the control circuit 5 outputs predetermined data to the DAC 4. The allocation data is converted into an analog signal by the DAC 4 and applied to one input terminal of the comparator 61. The analog signal becomes a reference voltage for the comparator 61. The control circuit 5 also provides data to the synthesizer 3 so that the receiver 2 receives a specific channel.Furthermore, at approximately the same timing,
One gate can be opened by simply applying a pulse of @l'' with a constant time width to the gate.

If the reception level of the channel is sufficiently high, the output of the comparator 61 will be in the @1" state, so the clock 62 will be in the @1" state.
The signal is input to the counter and counted. After a certain period of time has elapsed, the control circuit 5 applies one pressure of lO'' to the gate lever to close it, and reads and stores the value on the counter.

Next, the control circuit 5 gives other data to the synthesizer 3 to switch the reception channel of the receiver 2. Also, reset the counter and repeat the above operation. and,
The value of the counter corresponding to the channel is read and stored.

The same operation as above is repeated for each channel, and when all the counter values corresponding to the receiving channels are obtained, the control circuit 5 selects the channel corresponding to the large value.

Next, the operation of the SAMIA example will be specifically explained with reference to the timing chart of FIG. 81!2. The horizontal axis in FIG. 2 indicates time.

When the control circuit 5 gives the synthesizer 3 data for selecting channel 1, the receiver 2 receives the radio waves of channel 1. The intermediate waveband signal of channel I (No. 12) is detected between detectors and applied to one input terminal of the comparator 61. On the other hand, a reference voltage is applied to the other input terminal of the comparator 61. The comparator 6
1 compares the magnitude of the detection signal and the cough at pressure, and when the former is greater than the latter, outputs a "'1" signal. As a result, it is assumed that the output signal of the nuclear comparator 61 has a waveform as shown at 1m in FIG.

When the waveform 1a is applied to the gate, the gate ω is opened only when the waveform 1m is 11", so that the clock b output from the clock generator 62 has the rectangular shape 1a @1".
During this period, it passes through the elbow gate ω and is counted on the counter. The count value 1 of the armpit counter is stored in the control circuit 5.

Similarly, the reception level is detected for channels 2.3, and the counter wanders to determine the respective count values e2.・3 is required.

Detection of the reception level of channel 3 is completed.

and the count value e1. e2. A determination is made as to which value is the largest among e3, and if it is assumed that the count value e2 is now the largest, selection of channel 2 is determined.

Note that the reference level (#no voltage) of the comparator 61 is
(f() If it is too low compared to the signal level and the comparator output is always "1" on all channels, you can change the data of DAC4 and add correction to raise the reference level. The level should be slightly lower than the average reception level.

Further, the precision of the DAC 4 may be low, and even 2 bits (4 step cutoff 41) poses no practical problem. Therefore, a very simple resistor circuit is sufficient.

Further, the control circuit ff15 can be constructed by a logic circuit, but can be easily manufactured by using a microprocessor.

FIG. 3 shows a 1g2 embodiment of the invention. In the figure,
20 indicates the gain side (84 + amplifier (AGC amplifier) 8,
Other symbols indicate the same or equivalent elements as in FIG.

This embodiment differs from the embodiment shown in FIG. 1 in that the reference voltage (Vr@f) of the comparator 61 is fixed, and one detector is used instead. A human GC amplifier 20 is provided in front of the I60, and the level of the intermediate wave band signal can be controlled by the control circuit 51ζ. The gain of the AGC amplifier 200) can be changed using the 1#llK'1 of the comparator 61.
This is equivalent to changing the IFL pressure, and the same effect as in Example #1*M can be obtained. If an AGC amplifier is used in the receiver 2, it is also possible to use it.

FIG. 4 shows a fourth embodiment of the invention. In the figure, 7 indicates a multiplexer, 611 to SIN indicate comparators, and other symbols indicate the same or similar components as in FIG.

In this embodiment, the output of the detection circuit ω is commonly input to one terminal of a plurality of comparators 611 to 61N.

On the other hand, reference voltage No. 48 Vreft to VrefN is applied to the other terminal of each comparator. The reference signal vehicle pressures Vret1 to Vr*fx have different magnitudes, and are given, for example, a constant voltage difference.

The outputs of comparators 611 to 61N are multiplexer 7
and are switched according to selection data from the control circuit 5.

Now, Vrefl > Vref2 >−−−−−−・−
・> Vrets, multiplexer 7 sets Vrefl
was applied to the comparator 611, but the signal level from the detection circuit ω was too low and the comparator
When the outputs of 11 become all @01'', the control circuit 6 outputs a selection signal to the multiplexer 7 to select the comparator 612 to which Vref2 is applied.

If the Vrvf2 is still too high with respect to the signal level, the control circuit 6 sets the next lower reference signal voltage Vr@H.
Outputs a signal that selects the comparator to which is applied.

Through the above operations, according to this embodiment, the optimum reference signal voltage can be easily selected.

The operation after the reference signal is determined is the same as that in the first embodiment, so the explanation will be omitted.

[Effects of the Invention] According to the present invention, the reception status of each channel is compared for the length of time during which the reception level of radio waves from the base station exceeds a certain value, so multipath fading etc. Even if the reception level fluctuates, it is possible to accurately select a channel with less fluctuation. As a result, it is possible to select a channel on which high-quality radio waves are always being received.

[Brief explanation of drawings]

Figure #41 is a circuit diagram of the 1% embodiment of the present invention. Figure 2 is an operation timing chart of the first embodiment, and
The figure is a circuit block diagram of the second 5A embodiment, Figure 4 is a circuit block diagram of the third embodiment, Figure 5 is a conceptual diagram of the communication system, Figure @6 is a circuit block diagram of the conventional system, and Figure 7 is a circuit block diagram of the second 5A embodiment. FIG. 2 is a diagram illustrating fluctuations in received signal level. 2... Receiver 3... Detection circuit 4...
Digital-analog converter (DAC) 5...Control circuit 7...Multiplexer 20...Gain control amplifier (AGC amplifier mark...Detection circuit 61, 611-61N river comparator 62...Clock generator ω・・・Gate U・・Counter）

Claims (3)

[Claims] (1) In a channel selection method of a mobile communication system in which a base station is selected from the mobile communication device side and communication is started, means for comparing the received signal level and a scheduled reference level for each channel, and A channel selection method comprising means for measuring a time when a signal level is equal to or higher than the predetermined reference level, and means for selecting a channel corresponding to a maximum value within the measurement time. (2) The channel selection method according to claim (1), further comprising gain control means for varying the received signal level. (3) The channel selection method according to claim 1, further comprising means for varying the reference level.