JPS59158138A - In-use channel controlling method of mobile ratio communication system - Google Patents

Abstract

PURPOSE:To secure the communication quality of all channels and to utilize even a channel having a disturbing wave effectively by switching a call to a channel with a low disturbing wave level when the ratio of a desired wave level and a disturbing wave level decreases below a specific value. CONSTITUTION:A base station receive wave is inputted from a terminal 11 and mixed by a mixing circuit 12 with a local oscillation frequency signal from a local oscillation circuit 13 to obtain an intermediate frequency band signal. This signal is branched into three, and one is passed through a band-pass filter 14 where a sound modulated spectrum passes to demodulate a voice signal by a demodulator 15. This is outputted to a terminal 18. Other intermediate frequency band signals are supplied to receiving circuits 16 and 17 for pilot signals f1 and f2 to receive components of frequencies f1 and f2, thereby knowing the desired wave level and disturbing wave level by the levels of the received components. When a call in communication is switched to another channel, the service channel switching procedure of the current car telephone system is applied as it is.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a channel switching control method in a mobile communication system in which the same frequency is commonly used in a plurality of wireless communication zones. In particular, it relates to a method of reducing interference of the same frequency from other zones.

[Description of prior art]

In the mobile communication system, a method is known in which a zone is set around one base station in which it can effectively communicate with mobile stations, and this base station and mobile stations communicate by specifying a channel. . In order to make effective use of frequencies in such a system, a method is adopted in which the radius of the zone is made small and the same radio frequency is commonly allocated to different zones for use.

On the other hand, fluctuations in the radio wave propagation characteristics of land mobile communications include short-term fluctuations caused by short-range movement of the mobile station (for example, within several tens of meters in the case of an 800 MHz band car telephone system), and long-term median values of these short-range fluctuations. There is a long interval fluctuation for movement of an interval (for example, number n). Furthermore, the median value of this long-term variation is defined by distance characteristics that vary depending on the distance to the base station. In many cases, short-term fluctuations follow the Lehre distribution,
The short-term median variation follows a lognormal distribution. Further, the distance characteristic exhibits a characteristic as shown in FIG. In FIG. 1, the horizontal axis shows the distance between the base station and the mobile station, and the vertical axis shows the transmission tritf4 loss.

For example, in order to manage call quality, the median desired signal-to-disturbance ratio (rD/
It's called lJj. ) is required to be 20 dB or more, the distance between base stations using the same frequency is determined as follows. That is, referring to FIG. 2, when the mobile station reaches point A near the desired wave zone and closest to the interference wave zone, D/U is 2.
Decide to satisfy 0 dB. For example, if the radio zone radius r is 5km, the propagation loss at point 51un from Figure 1 is 137dB, but in order to make the propagation loss of the interference wave 157dB or more so that D/[J>20dB, From the figure below, base stations in zones that generate interference waves and A
What is the distance d to the point? , Okm or more.

In this way, when the same frequency is used in common in multiple zones, the distance between base stations can be determined so that there is no interference problem, but this is just a matter of setting it so that interference does not occur on average. In reality, if the short-term median value fluctuates low for desired waves and high for interfering waves, interference will occur. For this reason, in the past, when using a certain channel, the presence of interference waves was checked, and if the interference waves exceeded a certain value, the channel was not used. It was not possible to deal with cases where the interference wave level was low but then changed to become higher.

[Purpose of the invention]

The present invention solves these drawbacks, and aims to provide a control method that can ensure a predetermined communication quality for all channels and also make effective use of channels with interference waves.

[Features of the invention]

The present invention sweeps each channel, measures the desired wave level and the interference wave level, calculates the desired wave level and interference wave level ratio, and when the ratio is less than a predetermined value, the channel with the lower interference wave level It is characterized by controlling to switch between calls.

Furthermore, regarding the channel made vacant by this switching, if there is a call whose desired signal level is sufficiently high among calls communicating on the standard channel and whose ratio to the interference signal level exceeds a predetermined value even in this vacant channel, this The present invention is characterized in that the call is switched to the above-mentioned vacant channel and control is performed to increase channel utilization efficiency.

According to the present invention, a base station is equipped with a control device using a microcomputer, and is configured to automatically execute measurement control, calculation, and switching control according to a program.

[Explanation based on examples]

n channels for communication are allocated to one zone, and a large number of mobile stations (mobile phone subscribers) within that zone
communicates with the base station in that zone. Since the calling from the mobile station side or the calling from the base station side is a well-known technique, a detailed explanation will be omitted.

The base station is equipped with a microcomputer control device, and controls sweep measurement, calculation, and switching of each channel according to its program.

FIG. 3 is a flowchart of the main part of the control procedure. i
, L and k are channel numbers, respectively, and correspond to the first channel, second channel and third channel in the claims. j k+1-→ indicates that each of i and L k is set by incrementing them by 1, and when i, j, and k each reach n, n+1 = 1.

The channel control method of the present invention will be explained with reference to FIG. 3. First, i is set to 1 and it is checked whether the first channel is in use. If there is no call in progress, increment j by 1, and when it hits a channel in use, that i
For the th channel, the desired wave level Di and the interference wave level Ui are measured. The method of this measurement will be explained in detail later. Next, the ratio D between the desired signal level and the interference signal level is
i/U i is calculated, and it is determined whether or not this is less than a predetermined value of 20 dB. If it exceeds 20 dB, it is assumed that there is no problem with communication, and i is incremented and the same check is repeated for the next channel.

If there is a value lower than the predetermined value of 20 dB, a vacant j-th channel other than the i channel is searched for. Measure the interference wave level Uj for the j-th channel, calculate the ratio of the desired wave level D1 of the first channel and the interference wave level Uj of the j-th channel, and calculate the Find your channel. Once it is found, it switches the i-th chaffle's call to its j-th channel.

Here, the i-th channel is now vacant, but even though the level of interference waves in this i-th channel is high,
If the level of the desired wave is sufficiently high, it is possible that the ratio between the desired wave level and the interference wave level exceeds a predetermined value of 20 dB, and a search is made to see if there are any other signals with such a desired wave level. That is, the desired wave level (Dk) is measured for the th channel, and the ratio of this desired wave level Dk to the interference wave level Ui of the 1st channel, which is currently an empty channel, is calculated, and this is determined to be the predetermined value of 20 dB. If so, the call on the second channel is switched to the i-th channel.

In this way, calls on the kth channel will have worse call quality than before, but communication that satisfies the predetermined quality is possible, and the newly empty channel will have even better communication quality. It can now be used for signals with low desired wave levels.

By repeatedly performing the above control for i, j, and k from 1 to n, the quality of each channel is always ensured at a predetermined value or higher, and the channels can be used effectively.

Next, a method for measuring the desired wave level and interference wave level of each channel will be explained.

FIG. 4 shows an example of the configuration of a mobile station transmitting circuit for distinguishing between desired waves and interference waves. 1 is an audio input terminal, 2 is a modulator,
3 is a pilot signal generation circuit, 4 is an intermediate station waveband synthesizer,
5 is a mixing circuit, 6 is a local oscillation circuit, 7 is an amplifier, and 8 is an output terminal to an antenna or a duplexer. An audio signal input from terminal 1 is modulated by modulator 2 and becomes an intermediate frequency band signal. The pilot signal generated by the pilot signal generation circuit 3 is synthesized by the intermediate frequency band synthesizer 4, and mixed with the output frequency of the local oscillation circuit 6 by the mixing circuit 5 to become a radio frequency band signal. This signal is amplified by an amplifier 7 and guided from an output terminal 8 to an antenna.

FIG. 5 is a diagram showing an example of a transmission wave spectrum of a mobile station. S is the spectrum of the audio signal, and P is the pilot signal. Here, the frequency of the pilot signal is set to a different frequency for each base station in each zone that uses the same frequency, and based on the designation from the base station, the mobile station uses the pilot signal frequency P designated for that zone. configured to send.

FIG. 6 is a diagram showing an example of the configuration of a base station receiver for detecting the levels of desired waves and interfering waves. II is the input terminal from the antenna or duplexer, 12 is the mixing circuit, 13 is the local oscillation circuit, 14 is the bandpass filter that extracts the audio modulation spectrum, I5 is the demodulator, I8 is the demodulation output terminal, I6 is the pilot A receiving circuit for the signal f1, and 17 a receiving circuit for the pilot signal r2.

Figure 7 shows the spectrum of received waves at the base station when there is an interference wave, where S□ is the voice signal spectrum of the desired wave, SU is the voice modulation spectrum of the interference wave, and PD is the pilot signal spectrum of the desired wave. , P are the pilot signal spectra of the desired wave and the interference wave. As mentioned above, since the pilot signal frequencies to which the mobile station is designated for each zone are different frequencies, the pilot signal frequencies f1 and r2 of the desired wave and the interference wave are different from each other.

A base station received wave is inputted from a terminal 11 and mixed with a local frequency signal from a local oscillation circuit 13 in a mixing circuit 12 to become an intermediate frequency band signal. This intermediate frequency band signal is split into three branches, one passes through a bandpass filter 14 that passes the audio modulation spectrum, and the audio signal is modulated by a demodulator 15.

This is output to terminal 18.

As for other intermediate frequency band signals, components of frequencies f1 and f2 are received by receiving circuits 16 and 17, respectively.
The desired wave level and the interfering wave level can be determined based on the level.

Although the method of inserting a pilot signal in the intermediate frequency band has been described above, the present invention is not limited to this, and other methods such as inserting a pilot signal in the baseband are also applicable.

To switch a call in progress to another channel, it is possible to apply the call channel switching procedure for switching the channel in a call in the current car telephone system as is.

[Explanation of effects]

As described above, according to the present invention, a channel in which the communication quality has deteriorated due to an increase in the level of interference waves is automatically detected and switched to a channel that can ensure communication quality equal to or higher than a predetermined value.

Further, as a result of this switching, a call with a sufficiently high desired signal level can be switched and used for a channel that becomes an empty channel. Therefore, channels can be used effectively while always maintaining a predetermined communication quality for all channels.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of radio wave propagation loss characteristics in land mobile communication. FIG. 2 is a diagram explaining the relationship between the desired wave zone and the zone where interference waves are generated. FIG. 3 is a flowchart of the main part of the control procedure according to the embodiment of the present invention. FIG. 4 is a configuration diagram of main parts of the mobile station device of the present invention. FIG. 5 is a diagram showing one 1i+ of the transmission signal spectrum of the mobile station. FIG. 6 is a block diagram of the main parts of the base station receiving device. FIG. 7 is a diagram showing the frequency of the base station received waves. 1...Audio signal input terminal, 2...Modulator, 3...
, <Irosoto signal generation circuit, 4... combiner, 5...
Mixing circuit, 6... Local oscillation circuit, 7... Amplifier, 8
... Output terminal, 11 ... Input terminal, 12 ... Mixer, 13 ... Local oscillator 1-pin circuit, 14 ... Bandpass filter, 15 ... Demodulator, 16.17・)〈Ironoto signal receiving circuit, 18...output terminal. Patent Applicant Nippon Telegraph and Telephone Public Corporation Agent Patent Attorney Takashi Ide 1 Figure 20 3 Figures

Claims (1)

[Claims] (1) A plurality of zones are arranged around one base station, and mobile stations in the zone are configured to communicate with the base station, and the channels of the same frequency are used for the plurality of zones. In a mobile radio communication system in which a common channel is assigned to When the ratio of the level of U and the level of the interference wave is less than a predetermined value, measure the level of the interference wave on a channel other than the first channel that is not in communication (hereinafter referred to as the "U second channel"), and When the ratio of the level of the desired wave of the first channel to the level of the interfering wave of the second channel is equal to or higher than a predetermined value, the call of the first channel is controlled to be switched to the second communication channel. A method for controlling channels used in a mobile radio communication system, characterized in that: (2) In the method for controlling channels used in a mobile radio communication system according to claim 1, the channel during communication other than the first and second channels (hereinafter referred to as the "third channel") When the desired signal level and the interference signal level of the first channel are equal to or higher than the predetermined value, the call of the third channel is transferred to the first channel. 1. A method for controlling channels used in a mobile radio communication system, characterized by controlling the channels to be switched.