U.S. patent application number 09/123526 was filed with the patent office on 2001-11-29 for mobile radio communication device provided with functions for detecting and informing interference.
Invention is credited to MIZOGUCHI, TAMIYUKI.
Application Number | 20010046867 09/123526 |
Document ID | / |
Family ID | 16523420 |
Filed Date | 2001-11-29 |
United States Patent
Application |
20010046867 |
Kind Code |
A1 |
MIZOGUCHI, TAMIYUKI |
November 29, 2001 |
MOBILE RADIO COMMUNICATION DEVICE PROVIDED WITH FUNCTIONS FOR
DETECTING AND INFORMING INTERFERENCE
Abstract
A mobile radio communication device for performing communication
with a base station comprises an interference detection measure for
detecting occurrence of interference to the downlink frequency
and/or the uplink frequency, and an interference informing measure
for transmitting information about the occurrence of the
interference to the base station. The base station which received
the information about the interference assigns the mobile radio
communication device new time slots or a new communication carrier
frequency. The mobile radio communication device has a transmission
system and two reception systems which are composing a
post-detection selective space diversity system, and each of the
two reception systems is composed of a double superheterodyne
system, in the same way as general conventional mobile radio
communication devices. Interference to the downlink frequency is
detected utilizing the data error rate in the demodulated reception
signal in one reception system, and interference to the uplink
frequency is detected utilizing the field intensity of a radio wave
having the uplink frequency received by an antenna of the other
reception system. The detection and informing of interference is
realized by addition of a simple circuit composed of a circulator,
a high frequency amplifier, a mixer and a switch to a general
conventional mobile radio communication device.
Inventors: |
MIZOGUCHI, TAMIYUKI; (TOKYO,
JP) |
Correspondence
Address: |
MCGINN AND GIBB
SUITE 100
1701 CLARENDON BOULEVARD
ARLINGTON
VA
22209
|
Family ID: |
16523420 |
Appl. No.: |
09/123526 |
Filed: |
July 28, 1998 |
Current U.S.
Class: |
455/452.2 ;
455/62 |
Current CPC
Class: |
H04W 48/08 20130101;
H04B 7/005 20130101; H04W 72/0446 20130101; Y02D 70/444 20180101;
Y02D 70/44 20180101; Y02D 30/70 20200801; H04B 17/318 20150115;
H04B 17/309 20150115; H04B 17/345 20150115; H04W 24/00 20130101;
H04B 17/23 20150115; H04W 72/0453 20130101; H04B 7/082
20130101 |
Class at
Publication: |
455/452 ; 455/62;
455/63 |
International
Class: |
H04B 015/00; H04B
017/00; H04B 001/10; H04Q 007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 31, 1997 |
JP |
206440/1997 |
Claims
What is claimed is:
1. A mobile radio communication device for performing communication
with a base station comprising: an interference detection means for
detecting occurrence of the mixing of interfering signals into the
downlink frequency and/or the uplink frequency which are used for
the communication between the base station and the mobile radio
communication device; and an interference informing means for
transmitting information about the occurrence of the mixing of
interfering signals into the downlink frequency and/or the uplink
frequency to the base station in order to let the base station
assign the mobile radio communication device new time slots or a
new communication carrier frequency.
2. A mobile radio communication device as claimed in claim 1,
wherein: the mobile radio communication device is provided with a
transmission system and two reception systems which are composing a
post-detection selective space diversity system in which one
demodulated signal is selected from two demodulated signals
outputted by the two reception systems based on the levels of RSSI
(Received Signal Strength Indicator) signals which correspond to
the field intensity of post-detection reception signals, and each
of the two reception systems is composed of a double
superheterodyne system in which demodulation of the reception
signal is executed after two steps of frequency conversions.
3. A mobile radio communication device as claimed in claim 1,
wherein the communication between the base station and the mobile
radio communication device is performed according to TDMA-FDD (Time
Division Multiplexing Access-Frequency Division Duplex) method, and
transmission by the base station is executed according to TDM (Time
Division Multiplexing) method.
4. A mobile radio communication device as claimed in claim 1,
wherein the detection of occurrence of the mixing of interfering
signals into the downlink frequency is performed by means of
judgment with respect to the data error rate in demodulated
reception signals.
5. A mobile radio communication device as claimed in claim 1,
wherein the detection of occurrence of the mixing of interfering
signals into the uplink frequency is performed by means of judgment
with respect to an RSSI (Received Signal Strength Indicator) signal
whose signal level varies corresponding to the field intensity of
an interfering reception signal having a carrier frequency equal to
the uplink frequency.
6. A mobile radio communication device as claimed in claim 1,
wherein the interference informing means informs the base station
of the occurrence of the mixing of interfering signals into the
downlink frequency and/or the uplink frequency, using the control
channel.
7. A mobile radio communication device as claimed in claim 1,
wherein the interference informing means informs the base station
of the occurrence of the mixing of interfering signals into the
downlink frequency and/or the uplink frequency, by repeating
transmission using the uplink frequency.
8. A mobile radio communication device as claimed in claim 2,
wherein each of the two reception systems includes: a reception
means provided with an antenna for receiving signals; a first
frequency conversion means for converting the reception signal
supplied from the reception means into a first intermediate
frequency signal; a second frequency conversion means for
converting the first intermediate frequency signal supplied from
the first frequency conversion means into a second intermediate
frequency signal; a demodulation means for demodulating the second
intermediate frequency signal supplied from the second frequency
conversion means and thereby outputting a demodulated signal; and
an RSSI section for outputting an RSSI (Received Signal Strength
Indicator) signal whose signal level varies corresponding to the
intensity of the second intermediate frequency signal supplied from
the second frequency conversion means and thereby indicating the
field intensity of the reception signal.
9. A mobile radio communication device as claimed in claim 8,
wherein one of the reception systems further includes: an antenna
function switching means for switching the function of the antenna
of the reception system between reception and transmission by
selectively connecting the transmission system to the antenna of
the reception system in order to utilize the antenna for
transmission; and an interference detection signal generation means
for converting an interfering reception signal having the uplink
frequency which has been received by the antenna of the reception
system into an interference detection signal whose frequency is
equal to the first intermediate frequency and supplying the
interference detection signal to the second frequency conversion
means of the reception system so that the mixing of interfering
signals into the uplink frequency can be detected.
10. A mobile radio communication device as claimed in claim 9,
wherein the interference detection signal generation means
includes: an antenna common use means for drawing out the
interfering reception signal having the uplink frequency which has
been received by the antenna of the reception system in the case
where the antenna is used for reception of the interfering
reception signal, and supplying a transmission signal outputted by
the transmission system to the antenna in the case where the
antenna is used for transmission; a mixing means for mixing the
interfering reception signal having the uplink frequency which has
been drawn out by the antenna common use means with a reception
signal having the downlink frequency which has been received by the
antenna of the other reception system and thereby converting the
interfering reception signal into the interference detection
signal; and a selection means for executing selection between the
first intermediate frequency signal supplied from the first
frequency conversion means and the interference detection signal
supplied from the mixing means, and supplying the selected signal
to the second frequency conversion means.
11. A mobile radio communication device as claimed in claim 10,
wherein the antenna common use means is a circulator which is
placed between the antenna function switching means and the
transmission system.
12. A mobile radio communication device as claimed in claim 10,
wherein the interference detection signal generation means further
includes a high frequency amplifier which is placed between the
antenna common use means and the mixing means.
13. A mobile radio communication device as claimed in claim 8,
further comprising band pass filters and amplifiers which are
placed in front of the first frequency conversion means, between
the first frequency conversion means and the second frequency
conversion means, and after the second frequency conversion
means.
14. A mobile radio communication device as claimed in claim 1,
further comprising an automatic information means for automatically
activating the interference informing means when occurrence of the
mixing of interfering signals into the downlink frequency or the
uplink frequency is detected by the interference detection means,
and automatically informing the base station of the occurrence of
the interference utilizing the interference informing means.
15. A mobile radio communication device as claimed in claim 1,
further comprising: an interference display means for displaying
occurrence of interference when occurrence of the mixing of
interfering signals into the downlink frequency or the uplink
frequency is detected by the interference detection means; and a
manual operation information means for receiving manual operation
of the user who has seen the display on the interference display
means and who is requesting transmission of information about the
occurrence of the interference to the base station, and informing
the base station of the occurrence of the interference utilizing
the interference informing means if the user executed the manual
operation.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a mobile radio
communication device such as a portable telephone which performs
communication with a base station using a downlink frequency and an
uplink frequency which are assigned to the mobile radio
communication device by the base station, and in particular, to a
mobile radio communication device which is provided with functions
for detecting occurrence of interference to the downlink frequency
and/or the uplink frequency and informing the base station of the
occurrence of the interference.
DESCRIPTION OF THE PRIOR ART
[0002] Post-detection selective space diversity systems provided
with two reception systems are generally employed for ensuring
stable radio wave reception and communication even when electric
field intensity is decreased due to fading which is characteristic
of mobile communication, in which a post-detection reception signal
having higher post-detection field intensity is selected from two
reception signals which have been received by the two reception
systems.
[0003] FIG. 1 is a block diagram showing composition of a
conventional mobile radio communication device (a mobile terminal
5) which employs the post-detection selective space diversity
system. The mobile terminal 5 is provided with two reception
systems RA and RB each of which is composed of a double
superheterodyne system in which demodulation of the reception
signal is executed after two steps of frequency conversions. Along
with the reception systems RA and RB, the mobile terminal 5 is
provided with a transmission system TA. A first oscillator 35 and a
second oscillator 36 are provided in order to generate a first
local oscillation signal and a second local oscillation signal to
be used for the first frequency conversion and the second frequency
conversion (double superheterodyne) which are performed in each of
the reception systems RA and RB. The first oscillator 35 is also
used by the transmission system TA for converting the frequency of
a modulated signal for being transmitted into a transmission
frequency.
[0004] The reception system RA of the mobile terminal 5 is provided
with an antenna ANT1 for receiving a radio wave having a downlink
frequency frx (a frequency transmitted by an unshown base station
to the mobile terminal 5). The reception system RB is provided with
an antenna ANT2 for receiving a radio wave having the downlink
frequency frx and transmitting a radio wave having an uplink
frequency ftx (a frequency transmitted by the mobile terminal 5 to
an unshown base station).
[0005] The reception system RB is provided with an antenna switch
30 for switching the function of the antenna ANT2 between reception
and transmission. Hereafter, with respect to components which are
common to both the reception systems RA and RB, explanation will be
given on the reception system RA only, and reference numbers in
round brackets ( ) represent components of the reception system RB
which are equivalent to components of the reception system RA. In
the example of FIG. 1, the reception system RA (RB) is provided
with a band pass filter (BPF) 10 (20) for limiting the bandwidth of
the reception signal (i.e. for rejecting unnecessary signals)
supplied from the antenna ANT1, and a high frequency amplifier 11
(21) for amplifying the reception signal.
[0006] Further, the reception system RA (RB) of the mobile terminal
5 is provided with a BPF 12 (22) for further limiting the bandwidth
of the reception signal supplied from the high frequency amplifier
11 (21), a first mixer 13 (23) for converting the reception signal
into a first intermediate frequency signal (first IF signal)
utilizing the first local oscillation signal supplied from the
first oscillator 35, a BPF 14 (24) for limiting the bandwidth of
the first IF signal supplied from the first mixer 13 (23), and a
first intermediate frequency amplifier 15 (25) for amplifying the
first IF signal supplied from the BPF 14 (24).
[0007] Further, the reception system RA (RB) is provided with a
second mixer 16 (26) for converting the first IF signal into a
second intermediate frequency signal (second IF signal) utilizing
the second local oscillation signal supplied from the second
oscillator 36, a BPF 17 (27) for limiting the bandwidth of the
second IF signal supplied from the second mixer 16 (26), and a
second intermediate frequency amplifier 18 (28) for amplifying the
second IF signal supplied from the BPF 17 (27). After the second
intermediate frequency amplifier 18 (28), the reception system RA
(RB) is provided with an RSSI section 19 (29) for outputting an
RSSI (Received Signal Strength Indicator) signal whose signal level
varies according to the field intensity of the reception signal
(the second IF signal), and a demodulator 19a (29a) for
demodulating the second IF signal and thereby outputting a
demodulated signal such as a baseband signal.
[0008] The transmission system TA of the mobile terminal 5 is
provided with a modulator 31 for modulating the baseband signal
utilizing the first local oscillation signal supplied from the
first oscillator 35, a driver amplifier 32 as a preliminary
amplifier for obtaining gain, and a power amplifier 31 for
amplifying the modulated signal and supplying the amplified
transmission signal to the antenna ANTI via the antenna switch
30.
[0009] In the following, the operation of the conventional mobile
radio communication device will be described. Incidentally,
explanation of the operation of the transmission system TA is
omitted for brevity.
[0010] In the reception system RA, a reception signal with the
downlink frequency frx which has been received by the antenna ANT1
and whose bandwidth has been limited by the BPF 10 is supplied to
the high frequency amplifier 11. Meanwhile, in the reception system
RB, a reception signal with the downlink frequency frx which has
been received by the antenna ANT2 at the same time is supplied to
the antenna switch 30. When signal reception is performed, the
antenna switch 30 is controlled by an unshown CPU etc. so as to
connect the movable terminal c to the fixed terminal b, and thus
the reception signal is supplied from the antenna switch 30 to the
high frequency amplifier 21 via the bandwidth limiting BPF 20.
[0011] Thereafter, the reception systems RA and RB operate in the
same way, therefore, only the operation of the reception system RA
will be described in the following. Incidentally, reference numbers
in round brackets ( ) represent components of the reception system
RB. The reception signal outputted by the high frequency amplifier
11 (21) is supplied to the first mixer 13 (23) via the bandwidth
limiting BPF 12 (22). The first mixer 13 (23) is also supplied with
the first local oscillation signal from the first oscillator 35,
and the reception signal is frequency converted by the first mixer
13 (23) into the first IF (intermediate frequency) signal having
the first intermediate frequency which is lower than the downlink
frequency frx.
[0012] The first IF signal is supplied to the second mixer 16 (26)
via the BPF 14 (24) and the first intermediate frequency amplifier
15 (25). The second mixer 16 (26) is also supplied with the second
local oscillation signal from the second oscillator 36, and the
first IF signal is frequency converted by the second mixer 16 (26)
into the second IF (intermediate frequency) signal whose frequency
is lower than the first IF signal. The second IF signal outputted
by the second mixer 16 (26) is supplied to the RSSI section 19 (29)
and the demodulator 19a (29a).
[0013] The demodulator 19a (29a) demodulates the second IF signal
and thereby outputs a demodulated signal such as a baseband signal
to the unshown CPU etc. Meanwhile, the RSSI section 19 (29) outputs
the RSSI (Received Signal Strength Indicator) signal having a
signal level corresponding to the field intensity of the reception
signal (the second IF signal) into the CPU via an unshown A/D
converter. Then, the CPU selects one demodulated signal having
larger intensity from the two demodulated signals supplied from the
reception systems RA and RB by comparing the RSSI signals, and
acquires the demodulated signal having larger intensity. Signal
reception according to the post-detection selective space diversity
system is performed by the conventional mobile radio communication
device as described above.
[0014] However, in the above conventional mobile radio
communication device of FIG. 1, when interference occurred between
the reception signal having the downlink frequency frx and other
radio waves (interfering signals), or between the transmission
signal having the uplink frequency ftx and other radio waves
(interfering signals), communication between the base station and
the mobile terminal 5 becomes impossible. In such cases, the
sources of the interfering radio waves have to be tracked down and
transmission of the interfering waves have to be stopped. However,
it is very difficult to determine the sources of interfering waves,
and it is substantially impossible to track down the sources or the
directions of the sources utilizing directional antennas especially
when the interference waves come from far-off sources, mobile
stations, etc.
[0015] There have been some techniques proposed for resolving the
interference problem. In a conventional mobile radio communication
device which is disclosed in Japanese Patent Application Laid-Open
No.HEI4-249949, "CORDLESS TELEPHONE", a fixed station is provided
with a fixed station reception circuit as well as a mobile terminal
reception circuit, and the fixed station performs judgment on idle
channels by further detecting radio wave signals transmitted by
other fixed stations. By the information concerning the idle
channels obtained by the detection of the signals from other fixed
stations, interference between transmission signals of the fixed
station and transmission signals of other fixed stations is
avoided.
[0016] However, the above second conventional mobile radio
communication device needs to be provided with the fixed station
reception circuit for detecting transmission signals from other
fixed stations and a judgment circuit for performing judgment on
idle channels, and thus construction of the mobile radio
communication device is necessitated to be complicated.
SUMMARY OF THE INVENTION
[0017] It is therefore the primary object of the present invention
to provide a mobile radio communication device in which the mixing
of interfering signals to the downlink frequency and/or the uplink
frequency can be avoided and interruption of communication can be
prevented, and thereby communication reliability and transmission
efficiency can be improved.
[0018] Another object of the present invention is to provide a
mobile radio communication device in which the avoidance of the
mixing of interfering signals can be attained by a simple
additional circuit, and thereby enlargement of circuit scale and
signal processing scale of the device can be avoided and increase
in power consumption can be prevented.
[0019] Another object of the present invention is to provide a
mobile radio communication device in which the communication
carrier frequency can be switched to another frequency when the
mixing of interfering signals occurred, and thereby effective use
of frequencies can be realized.
[0020] Another object of the present invention is to provide a
mobile radio communication device in which whether the occurrence
of mixing of interfering signals should be informed to the base
station or not can be judged and determined on the side of the
mobile terminal, and thereby flexibility in usage and device
construction of can be increased.
[0021] In accordance with a first aspect of the present invention,
there is provided a mobile radio communication device for
performing communication with a base station comprising an
interference detection means and an interference informing means.
The interference detection means detects occurrence of the mixing
of interfering signals into the downlink frequency and/or the
uplink frequency which are used for the communication between the
base station and the mobile radio communication device, and the
interference informing means transmits information about the
occurrence of the mixing of interfering signals into the downlink
frequency and/or the uplink frequency to the base station in order
to let the base station assign the mobile radio communication
device new time slots or a new communication carrier frequency.
[0022] In accordance with a second aspect of the present invention,
in the first aspect, the mobile radio communication device is
provided with a transmission system and two reception systems which
are composing a post-detection selective space diversity system in
which one demodulated signal is selected from two demodulated
signals outputted by the two reception systems based on the levels
of RSSI (Received Signal Strength Indicator) signals which
correspond to the field intensity of post-detection reception
signals, and each of the two reception systems is composed of a
double superheterodyne system in which demodulation of the
reception signal is executed after two steps of frequency
conversions.
[0023] In accordance with a third aspect of the present invention,
in the first aspect, the communication between the base station and
the mobile radio communication device is performed according to
TDMA-FDD (Time Division Multiplexing Access-Frequency Division
Duplex) method, and transmission by the base station is executed
according to TDM (Time Division Multiplexing) method.
[0024] In accordance with a fourth aspect of the present invention,
in the first aspect, the detection of occurrence of the mixing of
interfering signals into the downlink frequency is performed by
means of judgment with respect to the data error rate in
demodulated reception signals.
[0025] In accordance with a fifth aspect of the present invention,
in the first aspect, the detection of occurrence of the mixing of
interfering signals into the uplink frequency is performed by means
of judgment with respect to an RSSI (Received Signal Strength
Indicator) signal whose signal level varies corresponding to the
field intensity of an interfering reception signal having a carrier
frequency equal to the uplink frequency.
[0026] In accordance with a sixth aspect of the present invention,
in the first aspect, the interference informing means informs the
base station of the occurrence of the mixing of interfering signals
into the downlink frequency and/or the uplink frequency, using the
control channel.
[0027] In accordance with a seventh aspect of the present
invention, in the first aspect, the interference informing means
informs the base station of the occurrence of the mixing of
interfering signals into the downlink frequency and/or the uplink
frequency, by repeating transmission using the uplink
frequency.
[0028] In accordance with an eighth aspect of the present
invention, in the second aspect, each of the two reception systems
includes a reception means provided with an antenna for receiving
signals, a first frequency conversion means for converting the
reception signal supplied from the reception means into a first
intermediate frequency signal, a second frequency conversion means
for converting the first intermediate frequency signal supplied
from the first frequency conversion means into a second
intermediate frequency signal, a demodulation means for
demodulating the second intermediate frequency signal supplied from
the second frequency conversion means and thereby outputting a
demodulated signal, and an RSSI section for outputting an RSSI
(Received Signal Strength Indicator) signal whose signal level
varies corresponding to the intensity of the second intermediate
frequency signal supplied from the second frequency conversion
means and thereby indicating the field intensity of the reception
signal.
[0029] In accordance with a ninth aspect of the present invention,
in the eighth aspect, one of the reception systems further includes
an antenna function switching means and an interference detection
signal generation means. The antenna function switching means
switches the function of the antenna of the reception system
between reception and transmission by selectively connecting the
transmission system to the antenna of the reception system in order
to utilize the antenna for transmission. The interference detection
signal generation means converts an interfering reception signal
having the uplink frequency which has been received by the antenna
of the reception system into an interference detection signal whose
frequency is equal to the first intermediate frequency, and
supplies the interference detection signal to the second frequency
conversion means of the reception system so that the mixing of
interfering signals into the uplink frequency can be detected.
[0030] In accordance with a tenth aspect of the present invention,
in the ninth aspect, the interference detection signal generation
means includes an antenna common use means, a mixing means, and a
selection means. The antenna common use means draws out the
interfering reception signal having the uplink frequency which has
been received by the antenna of the reception system in the case
where the antenna is used for reception of the interfering
reception signal, and supplies a transmission signal outputted by
the transmission system to the antenna in the case where the
antenna is used for transmission. The mixing means mixes the
interfering reception signal having the uplink frequency which has
been drawn out by the antenna common use means with a reception
signal having the downlink frequency which has been received by the
antenna of the other reception system and thereby converts the
interfering reception signal into the interference detection
signal. And the selection means executes selection between the
first intermediate frequency signal supplied from the first
frequency conversion means and the interference detection signal
supplied from the mixing means, and supplies the selected signal to
the second frequency conversion means.
[0031] In accordance with an eleventh aspect of the present
invention, in the tenth aspect, the antenna common use means is a
circulator which is placed between the antenna function switching
means and the transmission system.
[0032] In accordance with a twelfth aspect of the present
invention, in the tenth aspect, the interference detection signal
generation means further includes a high frequency amplifier which
is placed between the antenna common use means and the mixing
means.
[0033] In accordance with a thirteenth aspect of the present
invention, in the eighth aspect, the mobile radio communication
device further comprises band pass filters and amplifiers which are
placed in front of the first frequency conversion means, between
the first frequency conversion means and the second frequency
conversion means, and after the second frequency conversion
means.
[0034] In accordance with a fourteenth aspect of the present
invention, in the first aspect, the mobile radio communication
device further comprises an automatic information means for
automatically activating the interference informing means when
occurrence of the mixing of interfering signals into the downlink
frequency or the uplink frequency is detected by the interference
detection means, and automatically informing the base station of
the occurrence of the interference utilizing the interference
informing means.
[0035] In accordance with a fifteenth aspect of the present
invention, in the first aspect, the mobile radio communication
device further comprises an interference display means and a manual
operation information means. The interference display means
displays occurrence of interference when occurrence of the mixing
of interfering signals into the downlink frequency or the uplink
frequency is detected by the interference detection means. The
manual operation information means receives manual operation of the
user who has seen the display on the interference display means and
who is requesting transmission of information about the occurrence
of the interference to the base station, and informs the base
station of the occurrence of the interference utilizing the
interference informing means if the user executed the manual
operation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] The objects and features of the present invention will
become more apparent from the consideration of the following
detailed description taken in conjunction with the accompanying
drawings, in which:
[0037] FIG. 1 is a block diagram showing composition of a
conventional mobile radio communication device which employs the
post-detection selective space diversity system;
[0038] FIG. 2 is a block diagram showing composition of a mobile
radio communication device according to an embodiment of the
present invention; and
[0039] FIG. 3 is a flow chart showing the operation of the mobile
radio communication device of FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0040] Referring now to the drawings, a description will be given
in detail of preferred embodiments in accordance with the present
invention, in which the same reference characters as those of FIG.
1 designate the same or corresponding parts to those of FIG. 1.
[0041] FIG. 2 is a block diagram showing composition of a mobile
radio communication device (a mobile terminal 5) according to an
embodiment of the present invention. The mobile terminal 5 is
provided with two reception systems RA and RB which are composing
the aforementioned post-detection selective space diversity system.
Each of the reception systems RA and RB is composed of a double
superheterodyne system in which demodulation of the reception
signal is executed after two steps of frequency conversions. In
this example, TDMA-FDD (Time Division Multiplexing Access-Frequency
Division Duplex) method is employed for communication between the
mobile terminal 5 and an unshown base station, for example.
[0042] Along with the reception systems RA and RB, the mobile
terminal 5 is provided with a transmission system TA. A first
oscillator 35 and a second oscillator 36 are provided in order to
generate a first local oscillation signal and a second local
oscillation signal to be used for the first frequency conversion
and the second frequency conversion (double superheterodyne) which
are performed in each of the reception systems RA and RB. The first
oscillator 35 is also used by the transmission system TA for
converting the frequency of a modulated signal for being
transmitted into a transmission frequency.
[0043] The reception system RA of the mobile terminal 5 is provided
with an antenna ANT1 for receiving a radio wave having a downlink
frequency frx (a frequency transmitted by an unshown base station.
The reception system RB is provided with an antenna ANT2 for
receiving a radio wave having the downlink frequency frx and
transmitting a radio wave having an uplink frequency ftx (a
frequency transmitted by the mobile terminal 5 to an unshown base
station), and an antenna switch 30 for switching the function of
the antenna ANT2 between reception and transmission.
[0044] Hereafter, with respect to components which are common to
both the reception systems RA and RB, explanation will be given on
the reception system RA only, and reference numbers in round
brackets ( ) represent components of the reception system RB which
are equivalent to components of the reception system RA. The
reception system RA (RB) is provided with a band pass filter (BPF)
10 (20) for limiting the bandwidth of the reception signal (i.e.
for rejecting unnecessary signals) supplied from the antenna ANT1,
a high frequency amplifier 11 (21) for amplifying the reception
signal, a BPF 12 (22) for further limiting the bandwidth of the
reception signal supplied from the high frequency amplifier 11
(21), a first mixer 13 (23) for converting the reception signal
into a first intermediate frequency signal (first IF signal)
utilizing the first local oscillation signal supplied from the
first oscillator 35, a BPF 14 (24) for limiting the bandwidth of
the first IF signal supplied from the first mixer 13 (23), and a
first intermediate frequency amplifier 15 (25) for amplifying the
first IF signal supplied from the BPF 14 (24).
[0045] Further, the reception system RA (RB) is provided with a
second mixer 16 (26) for converting the first IF signal into a
second intermediate frequency signal (second IF signal) utilizing
the second local oscillation signal supplied from the second
oscillator 36, a BPF 17 (27) for limiting the bandwidth of the
second IF signal supplied from the second mixer 16 (26), and a
second intermediate frequency amplifier 18 (28) for amplifying the
second IF signal supplied from the BPF 17 (27). After the second
intermediate frequency amplifier 18 (28), the reception system RA
(RB) is provided with an RSSI section 19 (29) for outputting an
RSSI (Received Signal Strength Indicator) signal whose signal level
varies corresponding to the field intensity of the reception signal
(the second IF signal), and a demodulator 19a (29a) for
demodulating the second IF signal and thereby outputting a
demodulated signal such as a baseband signal. The composition of
the reception systems RA and RB described above is basically the
same as that of the reception systems RA and RB of the conventional
mobile radio communication device which has been shown in FIG.
1.
[0046] The reception system RB of the mobile radio communication
device of FIG. 2 is further provided with a circulator 40 which is
placed between the antenna switch 30 and the transmission system TA
for drawing out a specific reception signal (interfering signal)
having the uplink frequency ftx which has been received by the
antenna ANT2 via the port P3 and the port P2, a high frequency
amplifier 41 for amplifying the reception signal (interfering
signal) supplied via the circulator 40, a mixer 42 for mixing the
interfering reception signal supplied from the high frequency
amplifier 41 with the reception signal having the downlink
frequency frx which has been received by the antenna ANT1 and
thereby generating an interference detection signal, and a switch
43 for executing selection between the first IF signal supplied
from the first mixer 23 and the interference detection signal
supplied from the mixer 42 and supplying the selected signal to the
BPF 24.
[0047] Incidentally, the above circuit composed of the circulator
40, the high frequency amplifier 41, the mixer 42, the switch 43
and the BPF 24 is provided in order to draw out the interfering
reception signal whose frequency is equal to the uplink frequency
ftx. In the mixer 42, the interference detection signal whose
frequency is equal to the difference between the frequency of the
interfering reception signal and the downlink frequency frx is
generated. Therefore, the BPF 24 is utilized by the circuit for
passing an interference detection signal whose frequency is equal
to the difference between the uplink frequency ftx and the downlink
frequency frx. On the other hand, the BPF 24 is also utilized by
the reception system RB for passing the first IF signal (for
limiting the bandwidth of the first IF signal) supplied from the
first mixer 23. Therefore, in the mobile terminal 5 shown in FIG.
2, the first IF (intermediate frequency) is predetermined so as to
be equal to the difference between the uplink frequency ftx and the
downlink frequency frx, in other words, the frequency of the first
local oscillation signal generated by the first oscillator 35 is
preset so as to be equal to the uplink frequency ftx.
[0048] The transmission system TA of the mobile terminal 5 shown in
FIG. 2 is provided with a modulator 31 for modulating the baseband
signal utilizing the first local oscillation signal supplied from
the first oscillator 35, a driver amplifier 32 as a preliminary
amplifier for obtaining gain, and a power amplifier 31 for
amplifying the modulated signal and supplying the amplified
transmission signal to the antenna ANT1 via the circulator 40 and
the antenna switch 30.
[0049] In the following, an outline of communication between the
base station and the mobile terminal 5 of FIG. 2 will be
described.
[0050] The mobile terminal 5 performs communication with the base
station according to the TDMA-FDD method etc. Therefore,
communication according to time division multiplexing in which
particular time slots are assigned to the mobile terminal 5 is
executed between the base station and the mobile terminal 5. In the
communication between the base station and the mobile terminal 5, a
downlink frequency frx and an uplink frequency ftx which is
different from the downlink frequency frx are assigned to the
mobile terminal 5 by the base station, and the downlink frequency
frx is used for transmission from the base station to the mobile
terminal 5, and the uplink frequency ftx is used for transmission
from the mobile terminal 5 to the base station.
[0051] For example, in the case where the transmission frequency of
the mobile terminal 5 is equal to ftx and the reception frequency
of the mobile terminal 5 is equal to frx, the following equation
(1) holds.
ftx=frx.+-.fIF (1)
[0052] Here, the x is an integer as a numerical subscript, and the
fIF is a fixed frequency. Even when a plurality of (N pieces of)
carrier wave frequencies are prepared for communication between the
base station and the mobile terminal 5, the difference between a
downlink frequency frx and a corresponding uplink frequency ftx is
maintained constant so as to be equal to fIF. The equation (1) can
also be expressed as the following equation (2).
.vertline.ft0-fr0.vertline.=.vertline.ft1-fr1.vertline.=ft2-fr2.vertline.=
. . . =.vertline.ftN-frN.vertline.=fIF (2)
[0053] By use of the downlink frequency carrier wave, the base
station keeps on transmitting some kind of data according to the
TDM (time division multiplexing) method, continuously.
Incidentally, the downlink frequency frx and the uplink frequency
ftx is used for control channel communication
[0054] In the following, the operation of the mobile radio
communication device (mobile terminal 5) of FIG. 2 after connection
between the mobile terminal 5 and the base station is established
will be described, first. Incidentally, explanation of the
operation of the transmission system TA is omitted for brevity.
After connection between the mobile terminal 5 is established,
communication between the base station and the mobile terminal 5 is
executed using a communication carrier frequency (a downlink
frequency frx and an uplink frequency ftx) which has been assigned
to the mobile terminal 5 by the base station.
[0055] In the reception system RA, a reception signal with the
downlink frequency frx which has been received by the antenna ANT1
and whose bandwidth has been limited by the BPF 10 is supplied to
the high frequency amplifier 11. Meanwhile, in the reception system
RB, a reception signal with the downlink frequency frx which has
been received by the antenna ANT2 at the same time is supplied to
the antenna switch 30. In the reception standby state, the antenna
switch 30 is controlled by an unshown CPU etc. so as to connect the
movable terminal c to the fixed terminal b, and thus the reception
signal in the reception system RB is supplied from the antenna
switch 30 to the BPF 20 to be limited its bandwidth and is supplied
to the high frequency amplifier 21.
[0056] Thereafter, the reception systems RA and RB operate almost
in the same way, therefore, the operation of the reception system
RA will be mainly described in the following, in which reference
numbers in round brackets ( ) represent components of the reception
system RB. The reception signal outputted by the high frequency
amplifier 11 (21) is executed bandwidth limiting by the BPF 12 (22)
and is supplied to the first mixer 13 (23). The first mixer 13 (23)
is also supplied with the first local oscillation signal from the
first oscillator 35, and the reception signal is frequency
converted by the first mixer 13 (23) into the first IF
(intermediate frequency) signal having the first intermediate
frequency which is lower than the downlink frequency frx.
[0057] The first IF signal in the reception system RA is supplied
to the BPF 14 to be limited its bandwidth, and is supplied to the
first intermediate frequency amplifier 15 to be amplified, and is
supplied to the second mixer 16. The first IF signal in the
reception system RB is supplied to the BPF 24 via the switch 43 to
be limited its bandwidth, and is supplied to the first intermediate
frequency amplifier 25 to be amplified, and is supplied to the
second mixer 26. The second mixer 16 (26) is also supplied with the
second local oscillation signal from the second oscillator 36, and
the first IF signal is frequency converted by the second mixer 16
(26) into the second IF (intermediate frequency) signal whose
frequency is lower than the first IF signal. The second IF signal
outputted by the second mixer 16 (26) is supplied to the RSSI
section 19 (29) and the demodulator 19a (29a).
[0058] The demodulator 19a (29a) demodulates the second IF signal
and thereby outputs a demodulated signal such as a baseband signal
to the unshown CPU etc. Meanwhile, the RSSI section 19 (29) outputs
the RSSI (Received Signal Strength Indicator) signal having a
signal level corresponding to the field intensity of the reception
signal (the second IF signal) into the CPU via an unshown A/D
converter. Then, the CPU selects one demodulated signal having
larger intensity from the two demodulated signals supplied from the
reception systems RA and RB by comparing the RSSI signals, and
acquires the demodulated signal having larger intensity. Signal
reception according to the post-detection selective space diversity
system is performed by the mobile radio communication device of
FIG. 2 as described above. Incidentally, post-detection selective
space diversity reception is also performed by the mobile terminal
5 during the reception standby state, at control channel carrier
frequency.
[0059] In the following, the operation of the mobile radio
communication device (mobile terminal 5) of FIG. 2 before
connection between the mobile terminal 5 and the base station is
established will be described.
[0060] FIG. 3 is a flow chart showing the operation of the mobile
radio communication device (mobile terminal 5) of FIG. 2 according
to the present invention. After the power switch of the mobile
terminal 5 is turned ON (step S1), the mobile terminal 5 goes into
the reception standby state. In the reception standby state, the
mobile terminal 5 waits for reception of a call using a control
channel (using a control channel carrier frequency (a downlink
frequency frx and an uplink frequency ftx)) which is common to a
plurality of mobile terminals 5 (step S2). If reception of a call
from the base station or a request for transmission by the user of
the mobile terminal 5 occurred (step S3), the carrier frequency
used by the mobile terminal 5 is switched from the control channel
carrier frequency to a communication carrier frequency (a downlink
frequency frx and an uplink frequency ftx) according to assignment
by the base station (step S4). In the reception standby state of
the step S2, the mobile terminal 5 executes post-detection
selective space diversity reception of the common control channel
utilizing both the reception systems RA and RB, with the movable
terminal c of the antenna switch 30 connected to the fixed terminal
b, and with the movable terminal c of the switch 43 connected to
the fixed terminal a. On the switching to the communication carrier
frequency according to instructions of the base station (step S4),
the movable terminal c of the antenna switch 30 is switched to the
side of the fixed terminal a, and the movable terminal c of the
switch 43 is switched to the side of the fixed terminal b, in order
to prepared for the next steps in which detection of interference
to the downlink frequency frx and the uplink frequency ftx is
performed. Here, the interference can be the mixing of interfering
signals transmitted by illegal radio communication devices into
signals on the downlink frequency frx or the uplink frequency ftx
which are used between the base station and the mobile terminal 5,
the mixing of interfering signals transmitted by other mobile
terminals which are out of order into time slots on the downlink
frequency frx or the uplink frequency ftx which are assigned by the
base station to the mobile terminal 5, etc.
[0061] In step S5, detection of interference into the downlink
frequency frx is performed using the reception system RA. The
detection of the interference into the downlink frequency frx is
performed by checking the data error rate of the demodulated signal
which is supplied from the demodulator 19a in the time slots which
are assigned to the mobile terminal 5. It is judged by the unshown
CPU whether or not the data error rate of the demodulated signal in
the assigned time slots is larger than a predetermined threshold
value TH1 (step S5). If the data error rate is larger than the
threshold value TH1, it is judged that the mixing of interfering
signals into the time slots on the downlink frequency frx occurred,
and the result of the judgment (that the mixing of interfering
signals into the time slots on the downlink frequency frx occurred)
is stored in a RAM etc. by setting a first interference flag in the
RAM ON for example, and process directly proceeds to step S8. If
else, it is judged that interference into the time slots on the
downlink frequency frx is not occurring, and process proceeds to
the next step S6 for performing detection of interference into the
uplink frequency ftx.
[0062] In the step S6, detection of interference into the uplink
frequency ftx is performed. The detection of the mixing of
interfering signals into the uplink frequency ftx is executed as
follows. First, if an interfering signal having a carrier frequency
which is equal to the uplink frequency ftx existed, the interfering
signal is received by the antenna ANT2. The interfering reception
signal received by the antenna ANT2 is supplied to the circulator
40 via the antenna switch 30, and is drawn out by the circulator 40
to be supplied to the high frequency amplifier 41 via the port P3
and the port P2. The interfering reception signal is amplified by
the high frequency amplifier 41 and supplied to the mixer 42.
[0063] The mixer 42 is also supplied with the reception signal
having the downlink frequency frx which has been received by the
antenna ANT1, via the BPF 10, the high frequency amplifier 11 and
the BPF 12. The unshown base station is continuously performing TDM
transmission at the downlink frequency frx, and the reception
signal having the downlink frequency frx is continuously supplied
to the mixer 42 so that frequency conversion by the mixer 42 can be
performed at any time. The mixer 42 mixes the interfering reception
signal having the uplink frequency ftx which has been received by
the antenna ANT2 with the reception signal having the downlink
frequency frx which has been received by the antenna ANT1, and
thereby generates the interference detection signal. The
interference detection signal, whose frequency is equal to the
difference between the uplink frequency ftx and the downlink
frequency frx (i.e. equal to the first IF (intermediate frequency)
for the reason which has been mentioned before), is supplied to the
BPF 24 via the switch 43 to be limited its bandwidth.
[0064] The interference detection signal is supplied to the RSSI
section 29 and the demodulator 29a, via the first intermediate
frequency amplifier 25, the second mixer 26, the BPF 27 and the
second intermediate frequency amplifier 28. The RSSI section 29
outputs an RSSI signal having a signal level corresponding to the
intensity of the interfering reception signal (the second IF
signal) into the CPU via an unshown A/D converter. By use of the
RSSI signal supplied from the RSSI section 19 via the A/D
converter, the CPU performs detection of the mixing of interfering
signals into the uplink frequency ftx (step S6). In the step S6, it
is judged by the unshown CPU whether or not the RSSI signal is
larger than a predetermined threshold value TH2. If the RSSI signal
is larger than the threshold value TH2 in the step S6, it is judged
that the mixing of interfering signals into the uplink frequency
ftx occurred, and the result of the judgment (that the mixing of
interfering signals into the uplink frequency ftx occurred) is
stored in the RAM etc. by setting a second interference flag in the
RAM ON for example, and process proceeds to step S8. If the RSSI
signal is not larger than the threshold value TH2 in the step S6,
it is judged that interference is not occurring to the downlink
frequency frx or the uplink frequency ftx, and process proceeds to
step S7.
[0065] In the step S7, the movable terminal c of the switch 43 is
switched to the side of the fixed terminal a, and communication
between the base station and the mobile terminal 5 is started using
the downlink frequency frx and the uplink frequency ftx (the
communication carrier frequency) which have been assigned by the
base station. In the communication between the base station and the
mobile terminal 5, the movable terminal c of the antenna switch 30
is connected to the fixed terminal a when transmission is executed
by the mobile terminal 5, and the movable terminal c of the antenna
switch 30 is connected to the fixed terminal b when the
post-detection selective space diversity reception which has been
described before is executed by the mobile terminal 5.
[0066] In the step S8, the results of the above judgments that
interference occurred to the downlink frequency frx and/or the
uplink frequency ftx are displayed on the display of the mobile
terminal 5 by the control of the CPU. Subsequently, it is checked
whether the mobile terminal 5 is preset to inform the base station
of the occurrence of the interference automatically or according to
operation of the user such as pushing a button. The selection
between the `automatic information` and the `manual operation
information` has been done previously by the user and the setting
concerning `automatic/manual information` has been prestored in the
RAM etc.
[0067] If the `automatic information` has been preset (step S9:
YES), process directly proceeds to step S11 and preparation for
transmission by the transmission system TA is executed in order to
inform the base station of the occurrence of interference. In the
step S11, the movable terminal c of the switch 43 is switched to
the side of the fixed terminal a (with the movable terminal c of
the antenna switch 30 connected to the fixed terminal a) according
to the control of the unshown CPU. If the `manual operation
information` has been preset (step S9: NO), it is checked by the
CPU whether or not the operation of the user such as pushing a
button has been done for instructing transmission (step S10). If
the operation of the user has been done, process proceeds to the
step S11 and preparation for transmission by the transmission
system TA is executed in the same way as the case of the automatic
information.
[0068] Subsequently, transmission for informing the base station of
the occurrence of interference is executed by the transmission
system TA (step S12). Information transmitted to the base station
may include the details of the interference, such as whether the
interference occurred to the downlink frequency frx or to the
uplink frequency ftx, etc. The transmission can be performed, for
example, using the control channel frequency carrier wave (i.e.
transmission after switching the carrier frequency from the
communication carrier frequency to the control channel carrier
frequency). However, it is also possible to execute the
transmission of the information by repeating transmission using the
interfered uplink frequency ftx (communication carrier frequency)
until the information is received by the base station.
[0069] Then, the base station which received the information
performs procedure for making the communication between the base
station and the mobile terminal 5 possible (step S13). In the step
S13, the base station assigns other time slots to the mobile
terminal 5 which has executed the transmission of information, or
assigns another communication carrier frequency (a downlink
frequency frx and an uplink frequency ftx) to the mobile terminal
5. After the step S13, process is returned to the step S4 and the
steps S4 through S13 is repeated until communication between the
base station and the mobile terminal 5 without interference is made
possible.
[0070] As set forth hereinabove, in the mobile radio communication
device according to the present invention, when interference
occurred to the downlink frequency frx or the uplink frequency ftx
which have been assigned by the base station, the occurrence of
interference is detected by the mobile radio communication device
and informed to the base station. The base station which received
the information can assign the mobile radio communication device
new time slots or a new communication carrier frequency. Therefore,
the mixing of interfering signals into the communication carrier
frequency (i.e. the downlink frequency frx and the uplink frequency
ftx) is avoided and interruption of communication is prevented, and
thereby communication reliability and transmission efficiency are
improved.
[0071] Further, the avoidance of the mixing of interfering signals
can be attained by a simple additional circuit composed of a
circulator, a high frequency amplifier, a mixer and a switch.
Therefore enlargement of circuit scale and signal processing scale
of the device is avoided and increase in power consumption is
prevented.
[0072] Furthermore, the communication carrier frequency is switched
to another frequency when the mixing of interfering signals
occurred. Therefore, effective use of frequencies is realized.
[0073] Moreover, whether the occurrence of mixing of interfering
signals should be informed to the base station or not can be judged
and determined on the side of the mobile terminal. Therefore,
flexibility in usage and device construction is increased.
[0074] While the present invention has been described with
reference to the particular illustrative embodiments, it is not to
be restricted by those embodiments but only by the appended claims.
It is to be appreciated that those skilled in the art can change or
modify the embodiments without departing from the scope and spirit
of the present invention.
* * * * *