JP3348818B2 - Free channel detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cellular mobile telephone system (CMTS).
Microcellular system System hereinafter) to share a frequency band (hereinafter MCS: relates Check-out channel detector that detect a free channel of the CMTS in) of Micro Cellular System.

[0002]

2. Description of the Related Art Conventionally, allocation of a control channel and a communication channel in an MCS that shares a frequency band with a CMTS is performed by the same method and configuration as that of the CMTS, and is generally referred to as Cell Split.
This is done by means of locally reducing the size of the CMTS.

[0003]

However, the above-mentioned conventional means has the following problems.

(1) When an MCS is to be installed in a certain area, it is necessary to rearrange the used frequencies including the CMTS around the MCS.

(2) When a plurality of MCSs are three-dimensionally arranged in a high-rise building or the like, it becomes extremely difficult to plan a frequency arrangement.

As described above, it has been extremely difficult to assign a frequency to the MCS sharing the frequency band with the CMTS.

The present invention solves the above-mentioned problems, and is intended to enable the MCS to allocate a free channel of a CMTS in that area as its own control channel and communication channel by its own judgment . and to provide an air-out channel detector.

[0008]

Check-out channel detection apparatus of the present invention According to an aspect of the storage means for storing the monitoring means to continuously monitor the downlink control channel CMTS, a traffic channel information included in the downlink control channel Detecting means for detecting, from the stored communication channel information, a channel that has not been allocated as a communication channel for a certain number of times or more, and detects the channel detected by the detection means as M
It is determined that the CMTS is a vacant channel in the CS installation area and allocates it to the MCS call or control channel.

According to the present invention, the constantly detects a free channel of the CMTS region, which MCS of the control channel and the air-out channel detecting apparatus is Ru can be assigned as a call channel is obtained.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of an entire communication system including an embodiment of an empty channel detecting apparatus in an MCS according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing this communication system. In the figure, the CMTS is a public switched telephone network (PSTN: Public Switched Telephone).
Network) 1 and a mobile telephone exchange (hereinafter referred to as MTSO: Mobile Telephone Switching Office) 2 and a base station (hereinafter B) connected to this MTSO 2
S: Base Station) 3, and MCS
Is a control unit (hereinafter referred to as CU: Control) connected to the PSTN 1
Unit 4) and a base station (hereinafter referred to as MCBS: Micro Cellular Base Station) 5 connected to the CU 4
And the receiving device of the downlink control channel of the CMTS (hereinafter, CC
M: Cellular Control Channel Monitor) 6.

The solid circle in the figure indicates the area covered by BS3, and the broken circle indicates the area covered by MCBS5 of the MCS. Generally, the coverage area by BS3 is set to a radius of several kilometers, the coverage area by MCBS5 is set to a radius of tens of meters, and the MCS is set in the building,
It shall be installed in densely populated areas such as urban areas and underground malls.

The mobile terminal station (hereinafter referred to as ML) 7 accesses the CMTS while moving at high speed by car or the like, and accesses the MCS by manual or automatic switching when entering the densely populated area while walking. And the CMTS and the MCS commonly use the same frequency band.

[0013] Regarding channel selection in the MCS in this communication system, a channel that is not used in the CMTS at a place where the MCS is installed is determined.
Alternatively, even if the channel is used, a channel having a sufficiently low reception electric field strength at that location and a very low possibility of mutual interference is selected and used.

In this case, it is natural that a channel that is not used in the CMTS is used. However, even if the channel is used in the CMTS, for example, as shown in FIG. Cell x
Operated in a three-sector system and its cellular zone
When the MCS is located in the cellular zone 11c in the zones 11a to 11e, the CMTS sets the cellular zones 11a, 11b, 11
The channels used in d and 11e are less likely to interfere with the MCS area than the channels in other zones.
If the transmission output of the MCS is sufficiently small, there is a possibility that it can be reused in the MCS area. Other than this, for example, MC
If S is originally located in a place where radio waves from the CMTS are unlikely to arrive, such as in a building or underground shopping mall, there should be more channels that can be used as MCS.

On the other hand, in the CMTS, a different control channel is used for each sector shown in FIG. 2, and the ML 7 stays at the control channel having the highest electric field strength and receives an instruction of the communication channel. Since this communication channel is configured to instruct the ML7 on the control channel from the BS3 to a channel not used in that sector from among the fixed channels allocated to each sector and to use that channel, It is considered that a communication channel not indicated here is not used in the sector.

Therefore, if the communication channel instruction information on the downlink control channels of all the CMTSs that can be received in the area where the MCS is installed is monitored, information on the use status of the CMTS communication channel in the area can be obtained. .

The present invention pays attention to this point, and provides an empty channel detection device in the MCS for enabling the MCS to use its own empty channel as its own control channel and communication channel by its own judgment. The basic configuration of the CMT is as described above.
The communication channel instruction information obtained by the receiving device 6 for monitoring the communication channel instruction information in the control channel of S is fed back to the CU 4 so that the CU 4 allocates the use channel.

Hereinafter, the embodiments will be specifically described with reference to the drawings. FIG. 3 shows a configuration of a CCM which constitutes a main part of a vacant channel detecting device in the microcellular system of the present invention and serves as a means for monitoring the above-mentioned traffic channel instruction information, and FIG. 3 (a) shows a basic configuration thereof. FIG. 3B is a block diagram showing a detailed configuration of the receiving unit shown in FIG. 3A. In FIG. 3A, 31
Is the received field strength after receiving the CMTS downlink control channel.
(Hereinafter RSSI: Received Signal Strength Indicator
A receiving unit that outputs received data content; a control unit that performs control of channel designation and the like to the receiving unit 31; analyzes received data; and detects an empty channel; and 33, a receiving electric field for each channel of the receiving unit 31 The memory for storing the strength and the communication channel instruction information, and 34 stores the searched free channel information in the CU of the MCS.
4 is an interface unit that provides an interface for transmission to the CCM 4. The CCM is composed of these components. As shown in FIG. 3 (b), the receiving unit 31 includes a downlink control channel receiving unit 311 of the CMTS,
A synthesizer unit 312 for generating a local signal of the downlink control channel receiving unit 311 of the TS, an RSSI detecting unit 313 for converting the RSSI of the downlink control channel receiving unit 311 of the CMTS into a DC voltage, and a demodulated output of the downlink control channel receiving unit 311 of the CMTS And a data decoding unit 314 that decodes the received data. The receiving unit 31 may be connected by the same number as the number of downlink control channels of the maximum CMTS, or may be connected by only one.

The operation in the MCS will be described below. The first case is that the CCM is started before the operation of the MCS, and the receiving units 31 are connected by the same number as the number of control channels of the CMTS. According to the second case in which only one device is connected, an empty channel at that location is searched as follows.

First Case (1) When the CCM is started, the control unit 32 designates a channel to be received by each control unit 32, and each control unit 32 receives all downlink control channels having different CMTSs.

(2) Each of the receiving units 31 receives the traffic channel instruction message in the downlink control channel, and
To report the communication channel.

(3) The control unit 32 stores the communication channel obtained from each receiving unit 31 in the memory 33.

(4) After a predetermined time has passed, the control unit 32
The number and the number of communication channels in the network are searched, and a channel that has never been used or a channel that has been used less than a certain number of times is searched. give feedback.

(5) While always storing the above item (3),
Continue the feedback to CU4 in (4).

In the first case, when the reception (monitoring) of the downlink control channel is performed for as long as possible, the reliability as an empty channel becomes higher.

Second Case (1) When the CCM is activated, it scans all downlink control channels of the CMTS and stores the RSSI in the memory 33.

(2) The downlink control channel having the RSSI equal to or higher than the prescribed level is received at regular intervals, and
Perform the same operations as in (2) to (5).

(3) The scan of the second case (1) is periodically performed to update the channel to be received.

The second case has the advantage that only one receiving unit 31 is required as compared with the first case, but a communication channel instruction message is frequently transmitted in a cellular dense area such as an urban area. In addition, since it is often possible to receive a plurality of control channels of the CMTS and the probability of missing the communication channel indication message is high, the reception (monitoring) of the control channel needs to be performed for a longer time than in the first case. .

As described above, according to the present embodiment, it is possible to easily detect a vacant channel of the CMTS in the area, and to allocate the vacant channel as a control channel and a communication channel of the MCS. Therefore, if the frequency utilization efficiency in the area is greatly improved, especially if the transmission power in the MCS is suppressed to be small and the zone is minimized, this effect becomes extremely large.

[0031]

As described above, according to the present invention, the CMTS
If an MCS that shares a frequency band with an MCS is to be installed in a certain area, it is not necessary to change the frequency allocation of the entire area including the CMTS, and the MCS installation flexibility is greatly improved. Has a unique effect of setting up a communication line using a vacant channel in the area, so that the advantageous effect of greatly improving the frequency use efficiency in the area can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of an entire communication system including an embodiment of an empty channel detection device in a microcellular system according to the present invention.

FIG. 2 is a diagram showing a cell configuration and a channel arrangement of a cellular automobile telephone system sharing a frequency band with a micro cellular system to which the present invention is applied.

FIG. 3 is a block diagram showing a configuration of a receiving device which is a main part of an embodiment of an empty channel detecting device in the microcellular system of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1: Public telephone communication network (PSTN), 2: Mobile telephone exchange (MTSO), 3: Base station (BS), 4: Control device
(CU), 5: Base station (MCBS), 6: Receiving device (C
CM) 7 Mobile terminal station (ML).

Claims (1)

(57) [Claims] In a micro cellular system sharing a frequency band with a cellular mobile telephone system, a monitoring means for continuously receiving a downlink control channel of the cellular mobile telephone system, and storing communication channel information included in the downlink control channel. Storage means for detecting a channel which has not been allocated as a communication channel more than a predetermined number of times from the stored communication channel information, wherein the channel detected by the detection means is used as a cellular mobile phone in a microcellular system installation area. finding that free channels of the system, air-out channel detector you characterized in that it was allocated to the call or the control channel of the microcellular system.