JPH05206942A - Idle channel detection system - Google Patents

Abstract

PURPOSE:To immediately decide an idle channel and to make channel selection efficienct by providing an idle channel detection part apart from a transmission/ reception part having relevance to communication and always storing the state of all the channels. CONSTITUTION:The reception levels of all channel reception inputs are detected in an envelope detection part 22 and are inputted to a level detection judgement part 24. The level average operation part 25 of the judgement part 24 operates an average reception level from the reception levels and it is stored in a reception level storage part 26. The level measurement is repeated as to all the channels and the content of a memory is updated at each measurement. It is judged whether the channels are idle or not from level values in an idle channel judgement part 27. When the channel is judged to be idle, a channel frequency and a number are written into an idle channel storage part 28, and channel information is supplied by a request from a channel control part. Thus, the communication channel can be selected in short time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a free channel detection method for selecting a communication channel from a plurality of channels in wireless communication using a plurality of wireless channels.
INDUSTRIAL APPLICABILITY The present invention is suitable for use in, for example, detecting a free channel in a mobile communication system.

[0002]

2. Description of the Related Art In mobile radio or the like, a method for allocating channels, that is, a channel allocation method, considers a fixed channel allocation method in which channels used in each zone are fixed in advance, or an allocation condition every time communication is started. There is a dynamic channel allocation method that determines freely the channels used. In the fixed channel placement method,
The channel to be used is known in advance, and when the channel is designated to the mobile station, it is sufficient to grasp the channel use condition in each zone, and the control is simple, but there is a problem in that it is disadvantageous in terms of frequency utilization efficiency. On the other hand, the dynamic channel allocation method that does not fix the channels can improve the frequency utilization efficiency by several tens of percent compared to the fixed channel allocation method, but consider the interference in the entire service area for each call. However, there is a problem that more complicated functions are required because it is necessary to perform channel control.

When frequency utilization efficiency is increased or one frequency band is shared by a plurality of independent wireless communication systems, it is necessary to dynamically arrange channels, and therefore, when selecting a channel, other channels need to be arranged dynamically. A technique for detecting a free channel that does not suffer from interference is essential. Further, in the case of the time division multiple access (TDMA) system, it is necessary to detect an empty channel for each time slot.

Conventionally, when detecting an empty channel for selecting a communication channel, the access channel is regularly or irregularly changed for each receiver used after the detection request is generated, and the reception level is observed, When the reception sensitivity was lower than a certain level, it was judged as an empty channel. Regarding this conventional empty channel detection method, the structure of the empty channel detection method of the base station will be described with reference to FIG.

In this conventional example, the base station apparatus includes a plurality of n receiving units and transmitting units, and a channel control unit 74 for performing channel control, and each receiving unit 71 determines an empty channel from its reception output. Free channel determination unit 7
3 are provided.

This operation will be described. When trying to connect a wireless line, the receiver 71 of the transceiver to be used accesses the channel designated by the channel control signal from the channel controller 74 and obtains a reception input to the receiver 71 in that channel. This reception input is branched to the free channel determination unit 73, and it is determined from the value of the reception level whether or not it is a free channel. If this channel is determined to be an empty channel, line connection is established, but if it is determined to be an in-use channel, the same measurement and determination are newly performed for other channels.

[0007]

As described above, in the conventional empty channel detection method, the empty channel is detected after the empty channel detection request for line connection is generated. Detection can be time consuming and can result in a non-negligible delay in establishing the communication link. For example, if an empty channel is detected at the end of searching the total number of channels, the detection time is 1
It takes time for all the channels required to measure the reception level of the channels, and other channels may become empty within this time, which is not efficient. Further, since the reception level fluctuates instantaneously, it is necessary to perform processing such as averaging of the reception level in order to improve the detection accuracy, and further detection time is required.

As described above, when the free channels are detected by the individual receivers as in the conventional free channel detection method,
There is a drawback that it takes a long time to detect an empty channel and the channel cannot be efficiently allocated.

It is an object of the present invention to provide a free channel detection method capable of always detecting the states of all channels, efficiently detecting free channels, and selecting a communication channel in a short time. To do.

[0010]

SUMMARY OF THE INVENTION The present invention provides a free channel detection method for wireless communication in which a free channel is detected from a plurality of channels and a communication channel is assigned to the free channel for use. A free channel detection unit is provided separately from the related receiving unit, and the free channel detection unit is characterized by being provided with means for repeatedly measuring the reception level of each channel of a plurality of channels and storing the state of each channel.

[0011]

An empty channel detecting section is provided independently of the receiving section related to communication. In this empty channel detecting section,
The reception level of each channel is sequentially measured to detect an empty channel, and the latest information of each channel is stored. The information of each channel of the idle channel detection section can be provided immediately by a command from the channel control section.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a basic configuration of an empty channel detection system of the present invention, which will be described by taking an example of the configuration in a radio base station.

Here, the feature of the present invention is that the vacant channel detecting section 13 is provided independently of the receiving section 11 relating to communication, and the receiving input levels of all the channels are constantly scanned sequentially. Is to grasp the usage status of the channel and store the latest usage status of each channel in the internal memory.

FIG. 2 shows the configuration of this empty channel detection unit 13.
Shown in.

The empty channel detection unit 13 includes a bandpass filter 21, an envelope detection unit 22, an A / D converter 23 to which all channel reception inputs are given, and a level detection determination for performing level determination of each channel. And a detection channel control unit 29 for giving a detection channel control signal to the bandpass filtering unit 21 and the level averaging calculation unit 25 by a channel synchronization signal. ing. The free channel determination unit 24
It includes a level average calculation unit 25, a reception level storage unit 26, and an empty channel determination unit 27.

The operation of the idle channel detector 13 will be described.

The band-pass filter 21 extracts only the frequency band corresponding to the detection channel from the reception inputs of all channels, and the envelope detector 22 obtains the reception level of that channel. The measured reception level is converted into a digital signal by the A / D converter 23 and taken into the level detection determination unit 24. For the reception level, for example, the time slot of the detection channel is divided in time, each instantaneous reception level is measured, and the maximum value is set as the reception level of that channel. The average reception level is obtained from and is written in the reception level storage unit 26. Here, the averaging of the reception level is for avoiding the error detection of the empty channel due to the instantaneous fluctuation of the reception level due to fading or the like. This level measurement is repeated by the system for all channels in synchronization with the unique channel synchronization signal, and the memory contents are updated each time the measurement is performed.
Each time the average reception level is obtained, the free channel determination unit 27 determines from the level value whether or not it is a free channel. When it is determined that the channel is an empty channel, the channel number corresponding to the frequency and time slot of the channel is written in the empty channel storage unit 28, and the empty channel information is provided immediately when the empty channel information is requested from the channel control unit. ..

FIG. 3 shows an embodiment of a bandpass filter using a frequency synthesizer. All channels receive input is mixer 3
At 2, the frequency is converted by being multiplied by the frequency corresponding to the detection channel output from the frequency synthesizer 31, and the band-pass filter (BPF) 33 obtains the reception input of only the frequency band corresponding to the detection channel.

FIG. 4 shows another structure of the band-pass filter using a hopping filter. Hopping filter 41
Is a filter whose pass band is variable by a control signal from the outside, and by using this filter, it is possible to obtain a reception input of only the frequency band corresponding to the detection channel.

FIG. 5 shows a configuration example of the memory table of the reception level storage unit 26. In FIG. 5, r (f _h,
f _k ) indicates the average level at the channel frequency f _h and the slot t _k . In this configuration example, an input address corresponding to the carrier frequency and the time slot is prepared, and the average reception level for that address is set for each measurement. Written.

Further, FIG. 6 shows a configuration example of the memory table of the empty channel storage unit 28. In FIG. 6, (f _hm , t _km ) indicates the frequency f _h and the channel number of the slot t _k determined to be the mth empty channel. In this configuration example, the channel numbers are written in the order determined to be empty channels every time all channels are scanned, and the stored empty channel numbers are read out when the channel control unit requests the empty channel information. ing.

[0023]

As described above, according to the present invention,
By providing an empty channel detection unit independently of the transmission / reception unit related to communication and always storing the states of all channels, it is possible to immediately determine the empty channels, which enables efficient channel selection. effective.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a free channel detection system according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration example of a free channel detection unit according to an embodiment of the present invention.

FIG. 3 is a diagram showing a configuration example of a bandpass filter according to the embodiment.

FIG. 4 is a diagram showing a configuration example of a bandpass filter according to an embodiment.

FIG. 5 is a diagram showing a configuration example of a reception level storage unit of the embodiment.

FIG. 6 is a diagram showing a configuration example of an empty channel storage unit of the embodiment.

FIG. 7 is a diagram showing a configuration example of a conventional empty channel detection method.

[Explanation of symbols]

 11, 71 Receiver 12, 72 Transmitter 13 Free channel detector 14, 74 Channel controller 21 Bandpass filter 22 Envelope detector 23 A / D converter 24 Level detection judgment unit 25 Level average calculator 26 Received level Storage unit 27 Free channel determination unit 28 Free channel storage unit 29 Detection channel control unit 31 Frequency synthesizer 32 Mixer 33 Band pass filter 41 Hopping filter 73 Free channel determination unit

Claims (1)

[Claims] 1. A free channel detection method for wireless communication, wherein a free channel is detected from a plurality of channels, and a communication channel is assigned to the free channel to be used. A vacant channel detection method, comprising: a detection unit, wherein the vacant channel detection unit includes means for repeatedly measuring a reception level of each channel of a plurality of channels and storing a state of each channel.