JPH09107578A - Mobile communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent production of radio wave interruption by monitoring an electric field strength of an outgoing frequency channel from an adjacent radio base station at all times. SOLUTION: A radio base station 1 uses an electric field monitor receiver 15 to detect an electric field strength of a signal of an outgoing frequency channel communicated by an adjacent radio base station. A speech handset 16 allocates an incoming frequency channel and an outgoing frequency channel corresponding to a channel designation signal S4 fed from a channel control section 17 for a speech channel with a mobile radio terminal equipment. A variable band filter consisting of an HPF 13 and an LPF 14 limits a pass band of the outgoing frequency channel signal received from an antenna 11 and a multicoupler 12 to a band corresponding to band control signals S1, S2 and sends the result to an electric field monitor receiver 15. The electric field monitor receiver 15 sends an identification signal S3 of the detected frequency channel to a channel control section 17 and the speech handset 16. The speech handset 16 produces band control signals S1, S2 in response to the channel designation signal S4 and the identification signal S3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a plurality of radio zones, radio base stations installed in each of these radio zones, and an uplink frequency channel and a downlink frequency channel of radio waves to which dynamic channels are assigned. The present invention relates to a mobile communication system including a mobile wireless terminal that communicates with a station, and particularly to a mobile communication system including an electric field monitoring receiver that detects a signal electric field strength of a downlink frequency channel transmitted by an adjacent radio base station adjacent to the local station. .

[0002]

2. Description of the Related Art FIG. 1 is a block diagram of a conventional mobile communication system according to the present invention.
A description will be given with reference to the block diagram of the conventional radio base station 1A shown in FIG.

The mobile communication system shown in FIG. 1 is a cellular mobile telephone system, for example, a PDC system in Japan (Digital Mobile Telephone System Standard, RC
RSTD-27B, 1992-12, established by Radio System Development Center) and mobile phone systems. This mobile communication system comprises a plurality of radio zones 4, 3a and 3
b, the radio base station 1 (indicated by 1A in FIG. 4), 8a
And 8b are installed respectively. Hereinafter, description will be made focusing on the wireless base station 1 in the wireless zone 4, and the wireless zone 4 will be referred to as its own wireless zone and the wireless zone 3a adjacent to the wireless zone 4.
And 3b are also referred to as adjacent wireless base stations, and the wireless base stations 8a and 8b installed in the adjacent wireless zones 3a and 3b are also referred to as adjacent wireless base stations. A plurality of mobile radio terminals (only one of the mobile radio terminals 2 is shown as a representative in FIG. 1) can move freely in the radio zones 4, 3a and 3b. One of the PDC systems uses a radio wave of a plurality of frequency channels in an 800 MHz band with a frequency interval between an uplink frequency channel and a downlink frequency channel of 130 MHz to communicate between the radio base stations 1, 8 a and 8 b and the mobile radio terminal 2. Make a call. The carrier spacing of these frequency channels is 50 kHz
It is.

In this mobile communication system, a communication channel between the radio base stations 1, 8a and 8b and the mobile radio terminal 2 is dynamically allocated. In the dynamic channel allocation method, a specific frequency channel is not allocated in advance as a communication channel. For example, if the wireless base station 8a is an adjacent wireless base station to measure the electric field strength of a signal of a downlink frequency channel, when the wireless base station 1 talks with the mobile wireless terminal 2, the wireless base station 1 Downlink frequency channel signal F transmitted by the adjacent wireless base station 8a
2 is detected, and from this detection result, the frequency channel F1 (hereinafter, F1) that maintains the frequency interval of Δf or more that does not receive the radio wave interference of the frequency channel in which the adjacent wireless base station 8a is talking.
And F2 are denoted by f1 and f2 in FIG. 1) as the downlink frequency channel of the communication channel with the mobile radio terminal 2.

A radio base station 1A (see FIG. 4) used in this mobile communication system
While transmitting the signal of the downlink frequency channel F1 from the call transceiver 16A, the signal of the uplink frequency channel from the mobile radio terminal 2, and the downlink frequency channels F2 and F3 (FIG. 1) transmitted by the adjacent radio base stations 8a and 8b. f3) and the communication transceiver 16 of the own station.
A receives the signal of the downlink frequency channel F1 transmitted from A. Out of the signals received by the antenna 11, the signals of the downlink frequency channels F1, F2 and F3 are transmitted through the duplexer 12 for transmitting and receiving the signal of the uplink frequency channel and the signal of the downlink frequency channel, and are received by the electric field monitoring receiver 15A. Supplied to The electric field monitoring receiver 15A can detect a signal having an electric field strength equal to or higher than a predetermined level among signals of all downlink frequency channels. The electric field monitoring receiver 15 sends an identification signal S3 for identifying the detected downlink frequency channel to the channel control unit 17A.

The channel control unit 17A prepares a plurality of frequency channel candidates Fi for communication with the mobile radio terminal 2 in advance. The frequency interval of the communication channel candidate F is equal to or larger than Δf as described above. The channel control unit 17A determines a frequency channel for communication with the mobile radio terminal 2 by a predetermined algorithm in response to the identification signal S3, and specifies a channel (C
H) Supply the designation signal S4A to the call transceiver. The channel control unit 17A is a mobile communication switching center (not shown) that controls all the radio base stations of the mobile communication system.
May be provided.

[0007] The call receiver 16A receives a CH designation signal S4.
Mobile radio terminal 2 on the downlink frequency channel designated by A
And send a signal to talk to each other. This signal is transmitted to the mobile radio terminal 2 via the duplexer 12 and the antenna 11.
Sent to.

Since the signal of the downlink frequency channel F1 transmitted by the own radio base station 1A and the signals of the downlink frequency channels F2 and F3 from the adjacent radio base stations 8a and 8b are in the same frequency band, the radio base station In the operation of 1A, the signals of the downlink frequency channels F1 and F3 cause C / N deterioration of the signal of the downlink frequency channel F2, so the operation of the electric field monitoring receiver 16A is stopped. As described above, the electric field monitoring receiver 5 and the call receiver 4 operate at time-divisional reception timings, and both operate completely independently.

When detecting the signal of the downlink frequency channel F2 of the adjacent radio base station 8a whose electric field strength is to be monitored, the signal of the downlink frequency channels F1 and F3 of the radio base station 1A and the adjacent radio base station 8b is also detected. It is necessary to avoid radio interference between each other. Therefore, the CH designation signal S4A keeps the frequency interval of the downlink frequency channels F1, F2 and F3 (also the frequency interval of the uplink frequency channel) as described above, a specific frequency interval of ΔF or more that does not cause radio interference. Is set as follows.

[0010]

In the above-mentioned conventional mobile communication system, at the timing when the communication handset of the own radio base station transmits a signal of a predetermined frequency channel,
Since the signal of the downlink frequency channel transmitted by the radio base station is in the same frequency band in all radio zones, the electric field monitoring receiver for monitoring the electric field strength of the signal of the downlink frequency channel transmitted by the adjacent radio base station is provided by the radio base station. The signal of the downlink frequency channel transmitted by the station causes deterioration of C / N, and the signal of the downlink frequency channel transmitted by another adjacent radio base station different from the adjacent radio base station whose electric field strength is to be monitored causes radio interference. Had the disadvantage of receiving

In this mobile communication system, it is necessary to set the frequency intervals of the downlink frequency channels such that the signals of the downlink frequency channels do not interfere with each other, so that the frequency cannot be used effectively. was there.

Further, in this mobile communication system, the electric field monitoring receiver of the radio base station operates the reception timing in a time-division manner and completely independently of the communication transceiver. The station cannot monitor the state of the adjacent wireless base station during operation, and has a drawback that the line design of the wireless zone cannot be optimized.

[0013]

A mobile communication system according to the present invention comprises a plurality of radio zones, radio base stations installed in each of the radio zones, an uplink frequency channel of radio waves allocated to a dynamic channel, and A mobile radio terminal that communicates with the radio base station using a downlink frequency channel; and each of the radio base stations detects an electric field strength of a signal of the downlink frequency channel during a call. A mobile communication system comprising: a receiver; and a call transceiver for assigning an uplink frequency channel and a downlink frequency channel corresponding to the supplied channel designation signal to a call channel with the mobile radio terminal. Variable bandpass filter for limiting a pass band of the signal of the downlink frequency channel received to a band corresponding to a band control signal Furthermore, the electric field monitoring receiver further generates an identification signal of the downlink frequency channel indicating an electric field strength of a predetermined level or more, and the communication transceiver is responsive to the channel designation signal and the identification signal. The apparatus further includes band control means for generating the band control signal.

[0014] One of the mobile communication systems may be configured such that each of the radio base stations further includes a channel control unit that generates the channel designation signal in response to the identification signal.

Another one of the mobile communication systems has a configuration in which the variable bandpass filter uses a band of the signal of the downlink frequency channel transmitted by an adjacent radio base station to monitor an electric field as a signal pass band. Can be.

In the mobile communication system, the variable band filter may correspond to a high-pass filter that changes a low-frequency cutoff frequency in response to a supplied low-frequency control signal, and may correspond to a supplied high-frequency control signal. And a low-pass filter that changes a high-frequency cutoff frequency, and the band control signal can be configured to include the low-frequency control signal and the high-frequency control signal.

[0017]

Next, the present invention will be described with reference to the drawings. FIG. 2 is a block diagram of the radio base station 1 used in the mobile communication system according to one embodiment of the present invention. FIG. 3 is a diagram showing pass characteristics of the tunable high-pass filter (HPF) 13 and the tunable low-pass filter (LPF) 14 used in the wireless base station 1 of FIG.

Referring to FIGS. 1 and 2, the radio base station 1 used in the mobile communication system according to the present embodiment has the antenna 11, the duplexer 12 and the electric field monitoring receiver 15 described above.
And a telephone handset 1 having functions similar to those of the above-described telephone transceiver 16A and channel control unit 17A, respectively.
6 and a channel controller 17, an HPF 13 connected to the duplexer 12, and an LPF 14 inserted between the HPF 13 and the electric field monitoring receiver 15. The electric field monitoring receiver 15 also sends the identification signal S3 to the call transceiver 16. The HPF 13 is a high pass filter that changes the low cutoff frequency fcH in response to the supplied control signal S1, and the LPF 14 is a low pass filter that changes the high cutoff frequency fcL in response to the supplied control signal S2. It is a band-pass filter, and the HPF 13 and the LPF 14 form a variable band filter. HPF13 and LPF14
Can be realized by a dielectric filter, and the frequency characteristics of signal passage due to temperature fluctuations are extremely small and stable.

The communication transceiver 16 transmits the uplink frequency channel and the downlink frequency channel f1 corresponding to the CH designation signal S4 supplied from the channel control unit to the mobile radio terminal 2.
Channel. Further, the call transceiver 16 generates a band control signal of the variable band filter including the control signals S1 and S2 corresponding to the identification signal S3 and the CH designation signal S4. As described later, the variable band-pass filter passes signals of the downlink frequency channel to be monitored for the electric field, but does not pass signals of other downlink frequency channels.

The channel control unit 17 is a channel control unit 1.
Similarly to 7A, a frequency channel for communication with the mobile radio terminal 2 is determined by a predetermined algorithm in response to the identification signal S3, and a CH designation signal S4 is supplied to the transceiver for communication. However, the frequency interval of the communication channel designated by the CH designation signal S4 can be narrower than Δf, as described later.

Referring to FIGS. 1 to 3, a procedure for setting the passband of the HPF 13 and the LPF 14 in the wireless base station 1 in the wireless zone 4 when making a call connection with the mobile wireless terminal 2 will be described. Here, the wireless base station 1 has two adjacent wireless base stations 8a and 8b, and the wireless base station 8a is an adjacent wireless base station to monitor the electric field of the downlink frequency channel.

First, the electric field monitoring receiver 15 receives a signal of the downlink frequency channel f2 from the adjacent radio base station 8a (see FIG. 3). The electric field monitoring receiver 15 detects the signal of the downlink frequency channel f2 and sends an identification signal S3 indicating that the downlink frequency channel f2 has been detected to the channel control unit 17. Then, the channel control unit 17 initially sets the lower frequency channel f1 lower than the downlink frequency channel f2 by the frequency A to be the communication channel, and sends the CH specifying signal S4 for specifying the frequency channel f1 as the communication channel. Send to the call receiver 16.

When receiving the above-described CH designation signal S4, the communication transceiver 16 selects the downlink frequency channel as f1 and the uplink frequency channel as the channel corresponding to the downlink frequency channel f1, and communicates with the mobile radio terminal 2. Determine the call channel. At the same time as this decision, the call transceiver 16
The control signal S1 is sent to the HPF 13 and the control signal S2 is sent to the LPF1.
4 respectively. Then, the HPF 13 cuts off the lower side wave of the downlink frequency channel f2 including the downlink frequency channel f1 (frequency of attenuation 6 dB).
The frequency is automatically adjusted to fcH, and the LPF 14 is automatically adjusted to the cutoff frequency fcL1 for removing the upper wave of the downlink frequency channel f2. Cutoff frequency FcH of HPF13
Attenuates the signal of the downlink frequency channel f2 with a minimum amount of attenuation (insertion loss), and furthermore, the signal of the channel f1 influences the signal of the channel f2 as a spurious signal and C
/ N is a frequency to be attenuated so as not to deteriorate. Also, the cutoff frequency fcL1 of the LPF 14
Is a frequency at which the downlink frequency channel f2 has a minimum attenuation (insertion loss).

As described above, the HPF 13 and the LPF 14 form a variable band-pass filter so as to pass only a signal of a necessary frequency channel, that is, an adjacent radio base station for monitoring electric field strength, here, a radio base station 8a. The narrow band is limited so that only the signal of the downlink frequency channel f2 is passed. When the setting of the cutoff frequencies fcH and fcL1 of the HPF 13 and the LPF 14 is completed, the communication channel is finally set, and the communication transceiver 16 starts the communication with the mobile radio terminal 2.

Next, when the signal of the downlink frequency channel f3 of another adjacent radio base station 8b is further received, the electric field monitoring receiver 15 also sends an identification signal S3 for identifying the detection of the channel f3 to the channel control section 17. . The downlink frequency channel f3 is in a higher frequency band than the downlink frequency channel f2 and is separated from the downlink frequency channel f1 by a sufficiently high frequency B, so that the channel control unit 17 does not need to change the downlink frequency channel f1 for communication. In this case, the call transceiver 16 changes the content of the control signal S2,
The cut-off frequency fcL1 of the PF 14 is attenuated with a minimum amount of attenuation of the signal of the frequency channel f2, and the signal of the frequency channel f3 does not affect the signal of the frequency channel f2 as spurious or degrade the C / N. Cutoff frequency fcL in the frequency range to be attenuated
Reduce to 2. Note that the cutoff frequency fcH of the HPF 13 is not changed.

As described above, in the mobile communication system according to the present embodiment, the communication handset 4 built in the radio base station 1 is used.
Is received by the HPF 6 and the LPF 9 removes the signal of the lower frequency channel of the lower side wave and the signal of the lower frequency channel of the upper side wave is removed by the LPF 9. The signal of the downlink frequency channel f2 of the station 8a is transmitted to the radio wave monitoring receiver 5 without interference, and the radio base station 1 can always communicate with the mobile radio terminal 2. In other words, even at the reception timing of the electric field monitoring receiver 5, the telephone handset 4 can be used simultaneously.

In this mobile communication system, the lower radio wave of the downlink frequency channel f2 whose electric field strength is to be monitored is transmitted by the HP
In F13, the upper radio wave is removed by the LPF 14, so that any frequency of the downlink frequency channel f2 can be handled, and the frequency interval of the frequency channel f can be narrower than that in the related art.

[0028]

As described above, the present invention includes the variable band filter for limiting the pass band of the signal of the downlink frequency channel received by the electric field monitoring receiver to the band corresponding to the band control signal. Band control means for generating a band control signal in response to a channel designation signal and the identification signal, and a communication receiver for generating a downlink frequency channel identification signal exhibiting an electric field strength of a predetermined level or higher. Therefore, even when the transceiver for call is in operation, the radio monitoring receiver is used at the same timing without causing radio wave interference of the downlink frequency channel transmitted by the adjacent radio base station whose electric field strength is to be monitored. There is an advantage that you can.

Further, according to the present invention, the variable frequency bandpass filter uses a high-pass filter for removing a lower-side radio wave of a downstream frequency channel to be monitored for electric field strength and a low-pass filter for removing an upper-side radio wave. Since any frequency can be handled, it is possible to make the frequency interval of the communication channel narrower than in the prior art. As a result, the installation intervals of the wireless base stations are reduced, which not only facilitates the line design of the wireless zone, but also contributes to effective use of frequency.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a mobile communication system according to the present invention.

FIG. 2 is a block diagram of the wireless base station 1 according to one embodiment of the present invention.

FIG. 3 is a diagram illustrating pass characteristics of a tunable high-pass filter 13 and a tunable low-pass filter 14 used in the wireless base station 1 of FIG. 2;

FIG. 4 is a block diagram of a conventional radio base station 1A.

[Explanation of symbols]

 Reference Signs List 1 wireless base station 2 mobile wireless terminal 3a, 3b adjacent wireless zone 4 own wireless zone 8a, 8b adjacent wireless base station 11 antenna 12 duplexer 13 tunable high-pass filter (HPF) 14 tunable low-pass filter Wave filter (LPF) 15 Electric field monitoring receiver 16 Communication transceiver 17 Channel controller

Claims (4)

[Claims] 1. A communication with a plurality of wireless zones, a wireless base station installed in each of the wireless zones, and a communication with the wireless base station using an uplink frequency channel and a downlink frequency channel of a radio wave allocated to a dynamic channel. A mobile radio terminal, and each of the radio base stations, an electric field monitoring receiver for detecting the electric field strength of the signal of the downlink frequency channel during a call, and corresponding to the supplied channel designation signal. A communication transceiver that allocates an uplink frequency channel and a downlink frequency channel to a communication channel with the mobile radio terminal, wherein the passband of the signal of the downlink frequency channel received by the electric field monitoring receiver is A variable bandpass filter that limits the band to a band corresponding to the band control signal; Further generating an identification signal of the downlink frequency channel indicating an electric field strength of at least a bell, wherein the communication transceiver further includes a band control unit that generates the band control signal in response to the channel designation signal and the identification signal. A mobile communication system, comprising: 2. The mobile communication system according to claim 1, wherein each of said radio base stations further comprises a channel control unit for generating said channel designation signal in response to said identification signal. 3. The mobile communication system according to claim 1, wherein the variable band-pass filter sets a band of the signal of the downlink frequency channel transmitted by an adjacent radio base station to be monitored for an electric field as a signal pass band. . 4. The high-pass filter, wherein the variable band filter changes a low-pass cutoff frequency in response to a supplied low-pass control signal, and the high-pass cut corresponding to a supplied high-pass control signal. 4. A low-pass filter that changes an off frequency, wherein the band control signal is composed of the low-band control signal and the high-band control signal.
The mobile communication system described.