JPH0522243A - Idle channel detection system - Google Patents

Abstract

PURPOSE:To detect an idle channel efficiently with respect to the idle channel detection system in the time division multiplex communication system for an inter-radio station frame phase asynchronization using plural same carrier frequencies. CONSTITUTION:A reception level measurement system is provided with a mixer 3 converting each carrier into an intermediate frequency, a local oscillator 4 giving a local signal to the mixer 3 and deciding a frequency at which the mixer 3 makes a frequency, a detector 6 detecting the level of an intermediate frequency output of the mixer 3, a detector 6 detecting the level of the intermediate frequency output of the mixer 3, a storage circuit 7 storing the oscillating frequency of the oscillator 4 and the level output of the detector 6 and a control circuit 5 deciding newly the sequence of frequencies to be detected except the prescribed level of the frequency or over in the output of the detector 6 based on the information of the storage circuit 7 and sending sequentially the relevant oscillating frequency designation signal to the local oscillator 4.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacant channel detecting method for line allocation in communication using time division multiplexing (TDMA) with frame phase asynchronous between radio stations.

2. Description of the Related Art As an example of a mobile communication system for performing communication using time division multiplexing (TDMA), there are, for example, a car phone system and a mobile phone system. In such a mobile communication system, a service area is formed for each base station, and the mobile station communicates through the base station in the service area in which it is located. Then, when the mobile station moves and shifts to the service area of another base station, channel switching is performed to set a communication path with the corresponding base station. In such a system, if the need to detect a free channel arises, it can be done relatively easily. That is, in the case of the conventional system as described above, a carrier of a different frequency is used between adjacent or neighboring base stations, and each carrier is time-divided to provide a plurality of time slots to establish a communication path. It is multiplexed. Then, by allocating the time slot (channel) to each mobile station, communication with a plurality of mobile stations is performed. Therefore, when trying to detect an empty channel, it is possible to easily detect which channel (time slot) is empty by continuously monitoring the level of the frequency of the corresponding carrier.

In recent years, there has been an increasing need for more efficient use of carrier frequencies in order to deal with various services, and one of the methods is as follows. A method of using a plurality of same carrier frequencies in neighboring wireless stations (base stations) and asynchronously time-division multiplexing them has been studied. In such a system, it is impossible to detect a vacant channel by the simple method of monitoring the level of a specific frequency as in the above-mentioned conventional system. That is, in such a method, since the TDMA frame phase is asynchronous in each radio station, even if the burst signal from another station slightly overlaps with the time slot of its own station, co-channel interference occurs, so that there is no space. Channel detection cannot be reliably determined without measuring the levels at both ends of its own time slot.
Then, if this is done for a large number of frequencies, there is a problem that it takes a lot of time. In order to solve such a problem, an object of the present invention is to realize a means capable of efficiently detecting an empty channel in a time division multiplexing method of inter-radio station frame phase asynchronous using a plurality of carriers of the same frequency. I am trying.

According to the present invention, each of a plurality of carriers is time-divisionally divided into a plurality of time slots based on a predetermined frame format, and a plurality of wireless stations transmit the time slots of the plurality of carriers. In a time-division wireless communication system in which the frame phase is used in an asynchronous state, a mixer that converts each carrier into an intermediate frequency in a reception level measurement system, and a local oscillator that gives a local signal to the mixer and determines a frequency to be converted by the mixer A detector for detecting the level of the intermediate frequency output of the mixer, a storage circuit for storing the level output of the detector and the oscillation frequency of the oscillator, and an output of the detector based on the information of the storage circuit. Except for frequencies above a predetermined level, the order of frequencies to be detected is newly defined, and the oscillation frequency corresponding to the local oscillator is specified. It is a free channel detection method which includes a control circuit for sequentially sending the items.

In the present invention, in order to detect a vacant channel, the reception frequency of the receiver is sequentially switched (hereinafter also referred to as "sweep") to perform level detection. At this time, the frequency at which the detection level exceeds the specified level is detected even once. At the next sweep, the order of frequencies to be detected is determined for each sweep by omitting it from the level detection target frequency, thereby shortening the detection time of empty channels. As a result, it is possible to efficiently measure the levels at both ends of the time slot of the own station.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an example of the configuration of a receiving system embodying the present invention. In the figure, 1 is an antenna, 2
Is an RF amplifier, 3 is a mixer, 4 is a local oscillator, 5 is a control circuit, 6 is a level detector, and 7 is a memory circuit. The procedure for operating this is that a plurality of carriers received by the antenna 1 are amplified by the RF amplifier 2 and then input to the mixer 3 for frequency conversion into an intermediate frequency. The oscillation frequency of the local oscillator 4 which gives the local signal to the mixer 3 is controlled by the oscillation frequency designating signal from the control circuit 5, and each carrier is sequentially switched when being frequency-converted to an intermediate frequency and input to the level detector 6. The level is detected. The detected value and frequency are stored in the memory circuit 7 and used as control information of the control circuit 5. The control content of the control circuit 5 is such that the frequencies whose detection level exceeds a predetermined level in the first frequency sweep are excluded from the second and subsequent sweeps, and the order of the frequencies to be swept is also the first. And change it. An example of frequency switching control by this method is shown in FIG. In the figure, the horizontal axis is time, and the vertical axis is each carrier (f
₁ , f ₂ , f ₃ ... F _n ), the shaded areas indicate the presence of interference radio waves from other wireless stations. When the first frequency sweep is performed from the frequencies f _{1 to} f _n in one time slot of the TDMA frame as shown by the arrow in FIG. 2, it is assumed that the detection level of f ₂ exceeds the specified level. At this time,
When performing the second frequency sweep for the same time slot as the first time in the next TDMA frame, the control circuit 5 which has received the information about f ₂ from the memory circuit 7 in FIG.
Controls the local oscillator 4 so as to oscillate at frequencies corresponding to f _{1 to} f _n excluding f _2, and the frequency after f ₁ that was the frequency at which the sweep was started in the first frequency sweep The frequency of is controlled to be the sweep start frequency. In the case of this control example, the frequency sweep is performed as shown by the arrow at the time of the second sweep in FIG. Since f ₂ was previously occupied by another wireless station (there was an interference wave), the frequency at which the frequency sweep was started is f ₃ . Further, since f ₂ is excluded from the sweep target, the level of f ₃ can be measured again at the rear end of the time slot, and as a result, f _{3 which} cannot be detected in the first time is detected.
This means that it was possible to detect the presence of interfering radio waves from other wireless stations that were present in. An example of another control is shown in FIG. In this example,
In addition to the frequency and the detection level, the storage circuit 7 of FIG. 1 stores the level measurement position for the time slot. That is, in order to efficiently detect an interference radio wave from another wireless station that slightly overlaps, the level measurement positions need only be limited to both ends of the time slot, and therefore the measurement positions are stored and controlled. When the position of the interfering radio wave from another radio station is the same as in FIG. 2, the burst of f ₂ is detected by the first frequency sweep, as in the above example. When performing the second frequency sweep, the control circuit 5 detects the level of either the front or rear end of the time slot as a result of the first sweep of the local oscillator 4 and does not exceed the specified level. The order of frequency sweep is controlled so that the opposite end can be detected in level. The second arrow in FIG. 3 shows that case. According to such control, an empty channel can be detected even earlier.

As described above, according to the present invention,
Even if the burst signal from another wireless station slightly overlaps with the time slot of its own wireless station, it can be detected quickly by controlling the target frequency in the frequency sweep sequence. There is an advantage that an empty channel can be efficiently detected from among the carriers.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of the configuration of a receiving system that implements the present invention.

FIG. 2 is a diagram showing an example of frequency switching control.

FIG. 3 is a diagram showing another example of frequency switching control.

[Explanation of symbols]

 1 Antenna 2 RF Amplifier 3 Mixer 4 Local Oscillator 5 Control Circuit 6 Level Detector 7 Storage Circuit

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[Procedure amendment]

[Submission date] July 12, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Detailed explanation of the invention

[Correction method] Change

[Correction content]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacant channel detecting method for line allocation in communication using time division multiplexing (TDMA) with frame phase asynchronous between radio stations.

[0002]

2. Description of the Related Art As an example of a mobile communication system for performing communication using time division multiplexing (TDMA), there are, for example, a car phone system and a mobile phone system. In such a mobile communication system, a service area is formed for each base station, and the mobile station communicates through the base station in the service area in which it is located. Then, when the mobile station moves and shifts to the service area of another base station, channel switching is performed to set a communication path with the corresponding base station. In such a system, if the need to detect a free channel arises, it can be done relatively easily.

That is, in the case of the conventional system as described above, a carrier having a different frequency is used between adjacent or adjacent base stations, and this is time-divided to provide a plurality of time slots. The call path is multiplexed. Then, by allocating the time slot (channel) to each mobile station, communication with a plurality of mobile stations is performed. Therefore, when trying to detect an empty channel, it is possible to easily detect which channel (time slot) is empty by continuously monitoring the level of the frequency of the corresponding carrier.

[0004]

In recent years, there has been an increasing need for more efficient use of carrier frequencies in order to deal with various services, and one of the methods is as follows. A method of using a plurality of same carrier frequencies in neighboring wireless stations (base stations) and asynchronously time-division multiplexing them has been studied.

In such a system, it is impossible to detect a vacant channel by the simple method of monitoring the level of a specific frequency as in the conventional system described above. That is, in such a scheme, T
Since the DMA frame phase is asynchronous, a burst signal from another station may cause co-channel interference even if it slightly overlaps the own station's time slot. The level cannot be determined reliably without measuring the level. Then, if this is done for a large number of frequencies, there is a problem that it takes a lot of time.

In order to solve such a problem, the present invention provides a means capable of efficiently detecting an empty channel in a time division multiplexing method of inter-radio station frame phase asynchronous using a plurality of carriers of the same frequency. It is aimed at realization.

[0007]

According to the present invention, each of a plurality of carriers is time-divisionally divided into a plurality of time slots based on a predetermined frame format, and a plurality of wireless stations transmit the time slots of the plurality of carriers. In a time-division wireless communication system in which the frame phase is used in an asynchronous state, a mixer that converts each carrier into an intermediate frequency in a reception level measurement system, and a local oscillator that gives a local signal to the mixer and determines a frequency to be converted by the mixer A detector for detecting the level of the intermediate frequency output of the mixer, a storage circuit for storing the level output of the detector and the oscillation frequency of the oscillator, and an output of the detector based on the information of the storage circuit. Except for frequencies above a predetermined level, the order of frequencies to be detected is newly defined, and the oscillation frequency corresponding to the local oscillator is specified. It is a free channel detection method which includes a control circuit for sequentially sending the items.

[0008]

In the present invention, in order to detect a vacant channel, the reception frequency of the receiver is sequentially switched (hereinafter also referred to as "sweep") to perform level detection. At this time, the frequency at which the detection level exceeds the specified level is detected even once. At the next sweep, the order of frequencies to be detected is determined for each sweep by omitting it from the level detection target frequency, thereby shortening the detection time of empty channels. As a result, it is possible to efficiently measure the levels at both ends of the time slot of the own station.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an example of the configuration of a receiving system embodying the present invention. In the figure, 1 is an antenna, 2
Is an RF amplifier, 3 is a mixer, 4 is a local oscillator, 5 is a control circuit, 6 is a level detector, and 7 is a memory circuit. The procedure for operating this is that a plurality of carriers received by the antenna 1 are amplified by the RF amplifier 2 and then input to the mixer 3 for frequency conversion into an intermediate frequency.

The oscillation frequency of the local oscillator 4 which gives a local signal to the mixer 3 is controlled by an oscillation frequency designating signal from the control circuit 5, and each carrier is sequentially switched when the frequency is converted to an intermediate frequency, and the level detector 6 is selected. Is input to and the level is detected. The detected value and frequency are stored in the memory circuit 7
And used as control information for the control circuit 5. The control content of the control circuit 5 is such that the frequencies whose detection level exceeds a predetermined level in the first frequency sweep are excluded from the second and subsequent sweeps, and the order of the frequencies to be swept is also the first. And change it.

An example of frequency switching control by this method is shown in FIG. In the figure, the horizontal axis indicates time, the vertical axis indicates each carrier (f ₁ , f ₂ , f ₃ ... f _n ), and the shaded area indicates the presence of interference radio waves from other wireless stations. In the first time slot of the TDMA frame, the first frequencies f _{1 to} f _n
If the second frequency sweep is performed as shown by the arrow in Fig. 2, f
_It is assumed that the detection level for ₂ exceeds the specified level.

At this time, when performing the second frequency sweep for the same time slot as the first time in the next TDMA frame, the control circuit 5 which has received the information about f ₂ from the memory circuit 7 of FIG. The local oscillator 4 is controlled to oscillate a frequency corresponding to f _{1 to} f _n excluding f _2, and the frequency next to f ₁ which was the sweep start frequency in the first frequency sweep. Is controlled to be the sweep start frequency.

In the case of this control example, the frequency is swept as shown by the arrow at the time of the second sweep in FIG.
Since f ₂ was previously occupied by another wireless station (there was an interference wave), the frequency at which the frequency sweep was started is f ₃ . Further, since f ₂ is excluded from the sweep target, the level of f ₃ can be measured again at the rear end of the time slot, and as a result, the presence of interference radio waves from other wireless stations existing in f ₃ that could not be detected the first time is detected. It has been detected.

An example of another control is shown in FIG. In this example,
In addition to the frequency and the detection level, the storage circuit 7 of FIG. 1 stores the level measurement position for the time slot. That is, in order to efficiently detect an interference radio wave from another wireless station that slightly overlaps, the level measurement positions need only be limited to both ends of the time slot, and therefore the measurement positions are stored and controlled.

When the position of the interfering radio wave from another radio station is set to the same as in FIG. 2, the burst of f ₂ is detected by the first frequency sweep as in the above example. When performing the second frequency sweep, the control circuit 5 detects the level of either the front or rear end of the time slot as a result of the first sweep of the local oscillator 4 and does not exceed the specified level. The order of frequency sweep is controlled so that the opposite end can be detected in level. The second arrow in FIG. 3 shows that case. According to such control, an empty channel can be detected even earlier.

[0016]

As described above, according to the present invention,
Even if the burst signal from another wireless station slightly overlaps with the time slot of its own wireless station, it can be detected quickly by controlling the target frequency in the frequency sweep sequence. There is an advantage that an empty channel can be efficiently detected from among the carriers.

Claims (1)

Claim: What is claimed is: 1. Each of a plurality of carriers is time-divided into a plurality of time slots based on a predetermined frame format, and a plurality of wireless stations frame the time slots of the plurality of carriers. In a time division wireless communication method in which the phases are used in an asynchronous state, a mixer that converts each carrier into an intermediate frequency in a reception level measurement system, a local oscillator that gives a local signal to the mixer and determines a frequency that the mixer performs frequency conversion, A detector that detects the level of the intermediate frequency output of the mixer, a storage circuit that stores the level output of the detector and the oscillation frequency of the oscillator, and the output of the detector is predetermined based on the information of the storage circuit. Except for frequencies above the specified level, the order of frequencies to be detected is newly determined, and the oscillation frequency designation signal corresponding to the local oscillator is specified. An idle channel detection method characterized by comprising a control circuit for sequentially sending out.