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Mobile Phone Patent Abstract
A mobile phone includes an error detecting section and a channel
switching control section. The error detecting section detects a
frame error rate on a present communication of one of a plurality
of base stations. The channel switching control section determines
whether a communication quality is degraded, based on the detected
frame error rate and a past channel switching result. Also, the
channel switching control section determines that a channel switching
from the present communication channel to a new communication channel
should be performed, when it is determined that the communication
quality is degraded.
Mobile Phone Patent Claims
What is claimed is:
1. A mobile phone comprising:
an error detecting section detecting a frame error rate on a present
communication of one of a plurality of base stations; and
a channel switching control section determining whether a communication
quality is degraded, based on said detected frame error rate and
a past channel switching result, and determining that a channel
switching from said present communication channel to a new communication
channel should be performed, when it is determined that the communication
quality is degraded.
2. A mobile phone according to claim 1, wherein said channel switching
control section determines a frame error rate threshold value based
on said past channel switching result, compares said detected frame
error rate and said determined frame error rate threshold value,
and determines that the communication quality is degraded when said
detected frame error rate is equal to or larger than said determined
frame error rate threshold value.
3. A mobile phone according to claim 2, wherein said channel switching
control section sets a first threshold value as said determined
frame error rate threshold value when said past channel switching
result indicates that a success rate of past channel switching operations
is equal to or higher than a success rate threshold value, and a
second threshold value as said determined frame error rate threshold
value when said past channel switching result indicates that said
past channel switching result indicates that said success rate of
said past channel switching operations is lower than said success
rate threshold value, said second threshold value being larger than
said first threshold value.
4. A mobile phone according to claim 3, wherein said past channel
switching operations are hand-over operations.
5. A mobile phone according to claim 3, wherein said past channel
switching operations are intra-station channel switching operations.
6. A mobile phone according to claim 3, wherein said channel switching
control section calculates said success rate of said past channel
switching operations when said past channel switching operation
is executed a predetermined number of times.
7. A mobile phone according to claim 2, wherein said channel switching
control section sets one of first and second threshold values as
said determined frame error rate threshold value based on said past
channel switching result, said second threshold value being larger
than said first threshold value.
8. A mobile phone according to claim 7, wherein said past channel
switching result includes a first success rate of hand-over operations
and a second success rate of intra-station channel switching operations,
and
wherein said second threshold value is set when said first success
rate is lower than a first success rate threshold value, or when
said first success rate is equal to or higher than said first success
rate threshold value but said second success rate is lower than
a second success rate threshold value, and said first threshold
value is set when said second success rate is equal to or higher
than said second success rate threshold value.
9. A mobile phone according to claim 8, wherein said channel switching
control section calculates said first success rate when a hand-over
operation is executed a first predetermined number of times, and
said second success rate when an intra-station channel switching
operation is executed a second predetermined number of times.
10. A mobile phone according to claim 1, further comprising an
intensity detecting section detecting reception electric field intensities
from signals received from said plurality of base stations, and
wherein said channel switching control section determines whether
a hand-over process or an intra-station channel switching operation
should be performed, based on the detected reception electric field
intensities, when it is determined that said channel switching should
be performed.
11. A mobile phone according to claim 1, further comprising an
intensity detecting section detecting reception electric field intensities
from signals received from said plurality of base stations, and
wherein said channel switching control section includes:
a channel switching determining section determining whether the
communication quality is degraded, based on said detected frame
error rate and a frame error rate threshold value, and determining
that said channel switching from said present communication channel
to said new communication channel should be performed based on a
channel switching method, when it is determined that the communication
quality is degraded;
a setting section selecting one of a first threshold value and
a second threshold value as said frame error rate threshold value
in response to said past channel switching result to set to said
channel switching determining section, said first threshold value
being smaller than said second threshold value; and
a state monitoring section monitoring results of past channel switching
operations to output said past channel switching result to said
setting section.
12. A mobile phone according to claim 11, wherein said channel
switching determining section determines that the communication
quality is degraded, when said detected frame error rate is equal
to or larger than said frame error rate threshold value, and determines
which of a hand-over process or an intra-station channel switching
process should be performed, based on said detected reception electric
field intensities, when it is determined that the communication
quality is degraded.
13. A mobile phone according to claim 11, wherein said state monitoring
section monitors a success rate of said hand-over processes, determines
whether a hand-over failure does not occur frequently, based on
said hand-over success rate and a success rate threshold value,
and outputs said past channel switching result to said setting section
based on the determining result of whether a hand-over failure does
not occur frequently.
14. A mobile phone according to claim 13, wherein said setting
section selects said second threshold value as said frame error
rate threshold value, when it is determined by said state monitoring
section that said hand-over failure occurs frequently, and said
first threshold value as said frame error rate threshold value,
when it is determined by said state monitoring section that said
hand-over failure does not occurs frequently.
15. A mobile phone according to claim 14, wherein said second threshold
value is set to a value in a range with an upper limit value such
that a communication can be performed on said present communication
channel at least.
16. A mobile phone according to claim 13, wherein said state monitoring
section sets said success rate of said hand-over processes is increased,
when synchronization with a destination one of said plurality of
base stations is established at once hand-over process.
17. A mobile phone according to claim 12, wherein said state monitoring
section includes:
a hand-over monitoring section monitoring an execution result of
said hand-over process; and
an intra-station channel switching monitoring section monitoring
an execution result of said intra-station channel switching process,
and
wherein said state monitoring section outputs at least one of said
execution result of said hand-over process and execution result
of said intra-station channel switching as said past channel switching
result.
18. A mobile phone according to claim 17, wherein said hand-over
monitoring section monitors a number of times of execution of said
hand-over process and the execution result of said hand-over process,
calculates said success rate of said hand-over processes after a
predetermined number of times of the execution of said hand-over
process, and determines whether or not the hand-over process occurs
frequently.
19. A mobile phone according to claim 17, wherein said intra-station
channel switching monitoring section monitors a number of times
of execution of said intra-station channel switching process and
a communication channel establishment result in said intra-station
channel switching process, calculates a communication channel establishment
success rate after a predetermined number of times of the execution
of said intra-station channel switching process, and determines
whether or not said communication channel
Mobile Phone Patent Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mobile phone with a communication
channel switching determining unit suitable for the technique in
which unnecessary channel switching can be restrained.
2. Description of the Related Art
A system for a working area such as an office and a factory will
be described as an example of a digital cordless phone system. The
digital cordless phone system in the working area is generally operated
in the system configuration shown in FIG. 1.
The digital cordless phone system shown in FIG. 1 is composed of
a switching station 10, base stations 21 to 23 and a mobile station
40. The switching station 10 controls the base stations and the
lines. Each of the base stations 21 to 23 performs a radio communication
with the mobile station 40. Radio zones 31 to 33 are formed for
the respective base stations 21 to 23.
In the digital cordless phone system which has such a structure,
the mobile station 40 operates as follows.
Now, it is supposed that the mobile station 40 exists in the radio
zone 31 of the base station 21 and it is during communication with
the base station 21. As shown by an arrow in FIG. 1, when the mobile
station 40 moves away from the base station 21, a reception electric
field intensity in the mobile station 40 becomes low. At the same
time, the frame error rate becomes high so that the communication
quality degrades.
The mobile station 40 performs a channel switching determining
process, when the mobile station 40 detects the degradation of the
communication quality. At this time, the mobile station 40 selects
as a new communication channel, either of another communication
channel in the base station 21 and another communication channel
in the base station 22 or 23. The communication is continued by
use of the selected new communication channel.
Generally, the switching to the other communication channel of
the base station for which the communication channel has been established
is called a channel switching in the base station (intra-station
channel switching). Also, the switching to a communication channel
of the other base station is called hand-over (inter-station channel
switching).
When the mobile station 40 selects the channel switching to a new
communication channel in the base station as the result of the channel
switching determining process, the mobile station 40 measures an
interference wave to the new communication channel in the base station
21, i.e., performs carrier sense. The new communication channel
with the base station 21 is established, when it is determined that
the channel is usable. The communication with the base station 21
by use of a new communication channel is performed through the establishment
of the new communication channel and the communication is continued.
On the other hand, when the hand-over is selected for the channel
switching, the mobile station 40 first searches one of the base
stations 21 to 23 having the highest one of the reception signal
levels higher than a threshold value. In FIG. 1, it is supposed
that the reception signal level from the base station 22 is the
highest, because the mobile station 40 is positioned on a position
the closest to the base station 22. The mobile station 40 performs
the establishment of synchronization with the base station 22, when
the base station 22 with the highest reception electric field intensity
level is searched. When the synchronization establishment succeeds,
the carrier sense of the communication channel specified by the
base station 22 is performed and the communication channel is established.
The channel switching from the base station 21 to the base station
22 is performed as the result of the establishment of the communication
channel and the communication is continued.
In a case where the mobile station moves during communication,
the communication quality is degraded with the moving away of the
mobile station from the base station in the communication state
as described above. Also, even if the mobile station stops at a
position and continues the communication, the communication quality
is degraded when any interference wave against the communication
channel is generated. Therefore, in such cases, the communication
channel switching would become necessary.
The mobile station always monitors the frame error rate of the
communication channel during the communication, and detects the
degradation of the communication quality based on this frame error
rate. Also, in the channel switching determining process when the
degradation of the communication quality is detected, the frame
error rate and the reception electric field intensity levels of
the communication channel become the determination condition for
the selection of a channel switching destination. That is, the communication
channel switching in the mobile station is performed through the
selection of the channel switching destination on the basis of the
frame error rate, the communication quality degradation detection
derived from the frame error rate, and the reception electric field
intensity level.
However, in the above conventional technology, stable communication
continuation becomes difficult, in a case where the system is installed
in the factory in which an equipment is located around the system
to generate the electromagnetic waves to function as any cause of
the communication channel interference. In this case, the communication
quality degradation is detected and the mobile station repeats the
channel switching frequently under the environment in which the
interference wave is generated from the equipment in an impulse
manner to interfere with the radio communication channel.
As described above, in the channel switching, a communication channel
is established after the carrier sense of the switched channel is
performed. However, in case that an interference wave is not a continuous
manner but an impulse manner, the channel establishment sometimes
fails due to the interference wave generated when the communication
channel is established, even if it is determined at the time of
the carrier sense that the interference wave is not present. Especially,
when a hand-over process occurs frequently for the channel switching,
the establishment of the synchronization sometimes fails due to
the interference wave generated in an impulse manner. As a result,
it becomes more difficult to provide the stable communication due
to the frequent occurrence of interference such as the communication
breaking-off. Therefore, the channel switching operation should
be restrained to the degree that the minimum communication quality
can be secured, under the environment in which the synchronization
establishment and the communication channel establishment are difficult.
In this case, the communication breaking-off can be prevented so
that the communication is possible to be stabilized.
In conjunction with the above description, a radio channel switching
system in a mobile station is described in Japanese Laid Open Patent
Application (JP-A-Heisei 1-120135). In this reference, when the
degradation of communication quality is detected while a mobile
station communicates with a radio base station using a first radio
channel, the mobile station selects another base station to establish
a second radio channel. Then, the mobile station transmits a data
signal through said first and second radio channels while said first
and second radio channels are alternately switched for a switching
transmission and reception time interval. The mobile station switches
a use radio channel from the first radio channel to the second radio
channel, after the communication quality is confirmed in the second
radio channel. In this case, the same channel is used in a time
divisional manner to prevent the interference to another mobile
station which using the same channel.
Also, a mobile communication station is described in Japanese Laid
Open Patent Application (JP-A-Heisei 1-183221). In this reference,
a check of a new communication channel is performed as follows.
While a communication is performed using a time divisional multiple
communication channel, a frequency is switched to a new frequency
for the new communication channel after a time slot of the communication
channel is ended. The channel is again switched to the communication
channel when the check of the new communication channel is ended
or when a predetermined time interval elapses.
Also, a mobile communication channel switching control system is
described in Japanese Laid Open Patent Application (JP-A-Heisei
4-144429). In this reference, a plurality of base stations form
radio zones. When a mobile station moves between the plurality of
radio zones, the mobile station can continue the communication by
referring to a peripheral base station zone table which indicates
destination base stations and by switching a channel to a new channel
for a selected one of the destination base stations. The selected
destination base station satisfies a predetermined channel switching
condition. At this time, a priority level is allocated to each of
the destination base stations, and one of the destination base stations
is selected to satisfy the predetermined channel switching condition
in accordance with the priority levels.
Also, a communication switching system in a mobile communication
system is described in Japanese Laid Open Patent Application (JP-A-Heisei
8-256369). In this reference, a mobile station (21) performs connection
of a communication channel to a destination base station (12) using
a time slot which is not used for the communication with a source
base station (11). Then, the mobile station switches the communication
channel from the channel to the source base station (12) to the
channel to the destination base station (12), and then release the
channel to the source base station (12). At the same time, a communication
path to a counter station (31) is connected to the source and destination
base stations (11 and 12), and then the communication path connected
to the source base station (11) is released.
Also, a control channel switching system is described in Japanese
Laid Open Patent Application (JP-A-Heisei 8-289353). In this reference,
a TDMA-MCA system radio communication system has a (m.times.n) channel
structure which has m carriers different in frequency and one carrier
is divided into n time slots. When a failure occurs in a current
communication channel as the control channel (S1), the control channel
is shifted to a communication channel which is not used for communication
(S3). If it is impossible, after the disconnection of the communication
channel and the automatic re-connection are informed previously
(S5), the communication channel is disconnected and the control
channel is shifted to the communication channel (S6). A call for
the disconnected communication channel is allocated to the head
of a connection queue for the re-connection (S7). Thereafter, the
call of the disconnected communication channel is connected to the
channel in which the communication is ended (S8 and S9).
SUMMARY OF THE INVENTION
An object of the present invention is to provide a mobile phone
in which communication can be stabilized.
Another object of the present invention is to provide a mobile
phone in which channel switching can be restrained such that communication
is stabilized.
Still another object of the present invention is to provide a mobile
phone in which communication is stabilized, even in the environment
in which an interference wave to a communication channel is frequently
generated.
In order to achieve an aspect of the present invention, a mobile
phone includes an error detecting section and a channel switching
control section. The error detecting section detects a frame error
rate on a present communication of one of a plurality of base stations.
The channel switching control section determines whether a communication
quality is degraded, based on the detected frame error rate and
a past channel switching result. Also, the channel switching control
section determines that a channel switching from the present communication
channel to a new communication channel should be performed, when
it is determined that the communication quality is degraded.
The channel switching control section may determine a frame error
rate threshold value based on the past channel switching result,
and compare the detected frame error rate and the determined frame
error rate threshold value. Then, the channel switching control
section may determine that the communication quality is degraded
when the detected frame error rate is equal to or larger than the
determined frame error rate threshold value. In this case, the channel
switching control section may set a first threshold value as the
determined frame error rate threshold value, when the past channel
switching result indicates that a success rate of past channel switching
operations is equal to or higher than a success rate threshold value.
Also, the channel switching control section may set a second threshold
value as the determined frame error rate threshold value when the
past channel switching result indicates that the success rate of
the past channel switching operations is lower than the success
rate threshold value. Here, the second threshold value is larger
than the first threshold value. The past channel switching operations
may be hand-over operations, or intra-station channel switching
operations.
The channel switching control section may calculate the success
rate of the past channel switching operations, when the past channel
switching operation is executed a predetermined number of times.
The channel switching control section may set one of first and
second threshold values as the determined frame error rate threshold
value based on the past channel switching result. Here, the second
threshold value is larger than the first threshold value. In this
case, the past channel switching result may include a first success
rate of hand-over operations and a second success rate of intra-station
channel switching operations. The second threshold value is preferably
set when the first success rate is lower than a first success rate
threshold value, or when the first success rate is equal to or higher
than the first success rate threshold value but the second success
rate is lower than a second success rate threshold value. Also,
the first threshold value is preferably set when the second success
rate is equal to or higher than the second success rate threshold
value. The channel switching control section may calculate the first
success rate when a hand-over operation is executed a first predetermined
number of times, and the second success rate when an intra-station
channel switching operation is executed a second predetermined number
of times.
The mobile phone may further include an intensity detecting section
detecting reception electric field intensities from signals received
from the plurality of base stations. At this time, the channel switching
control section may determine whether a hand-over process or an
intra-station channel switching operation should be performed, based
on the detected reception electric field intensities, when it is
determined that the channel switching should be performed.
Also, the mobile phone may further includes an intensity detecting
section detecting reception electric field intensities from signals
received from the plurality of base stations. In this case, the
channel switching control section includes a channel switching determining
section, a setting section and a state monitoring section. The channel
switching determining section determines whether the communication
quality is degraded, based on the detected frame error rate and
a frame error rate threshold value. Also, the channel switching
determining section determines that the channel switching from the
present communication channel to the new communication channel should
be performed based on a channel switching method, when it is determined
that the communication quality is degraded. The setting section
selecting one of a first threshold value and a second threshold
value as the frame error rate threshold value in response to the
past channel switching result to set to the channel switching determining
section. Here, the first threshold value is smaller than the second
threshold value. The state monitoring section monitors results of
past channel switching operations to output the past channel switching
result to the setting section. In this case, the channel switching
determining section determines that the communication quality is
degraded, when the detected frame error rate is equal to or larger
than the frame error rate threshold value. Also, the channel switching
determining section determines which of a hand-over process or an
intra-station channel switching process should be performed, based
on the detected reception electric field intensities, when it is
determined that the communication quality is degraded.
The state monitoring section monitors a success rate of the hand-over
processes, and determines whether a hand-over failure does not occur
frequently, based on the hand-over success rate and a success rate
threshold value. Also, the state monitoring section outputs the
past channel switching result to the setting section based on the
determining result of whether a hand-over failure does not occur
frequently. In this case, the setting section selects the second
threshold value as the frame error rate threshold value, when it
is determined by the state monitoring section that the hand-over
failure occurs frequently. Also, the setting section sets the first
threshold value as the frame error rate threshold value, when it
is determined by the state monitoring section that the hand-over
failure does not occurs frequently. The second threshold value is
set to a value in a range with an upper limit value such that a
communication can be performed on the present communication channel
at least.
Also, the state monitoring section sets the success rate of the
hand-over processes is increased, when synchronization with a destination
one of the plurality of base stations is established at once hand-over
process.
The state monitoring section includes a hand-over monitoring section
monitoring an execution result of the hand-over process, and an
intra-station channel switching monitoring section monitoring an
execution result of the intra-station channel switching process.
The state monitoring section outputs at least one of the execution
result of the hand-over process and execution result of the intra-station
channel switching as the past channel switching result.
In this case, the hand-over monitoring section may monitor a number
of times of execution of the hand-over process and the execution
result of the hand-over process. Also, the hand-over monitoring
section may calculate the success rate of the hand-over processes
after a predetermined number of times of the execution of the hand-over
process, and determine whether or not the hand-over process occurs
frequently. Also, the intra-station channel switching monitoring
section may monitor a number of times of execution of the intra-station
channel switching process and a communication channel establishment
result in the intra-station channel switching process. Then, the
intra-station channel switching monitoring section may calculate
a communication channel establishment success rate after a predetermined
number of times of the execution of the intra-station channel switching
process, and determine whether or not the communication channel
is successfully established.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a structure diagram showing a conventional mobile phone
system;
FIG. 2 is a block diagram showing the structure of a mobile phone
according to a first embodiment of the present invention;
FIG. 3 is a flow chart showing the operation of the mobile phone
according to the first embodiment of the present invention;
FIG. 4 is a diagram showing the operation of the mobile phone according
to the first embodiment of the present invention;
FIG. 5 is a flow chart showing a specific example of the operation
of the mobile phone according to the first embodiment of the present
invention;
FIG. 6 is a block diagram showing the structure of the mobile phone
according to a second embodiment of the present invention;
FIG. 7 is a flow chart showing the operation of the mobile phone
according to the second embodiment of the present invention; and
FIG. 8 is a flow chart showing a specific example of the operation
of the mobile phone according to the second embodiment of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, a mobile phone with a channel switching determining
unit of the present invention will be described with reference to
the attached drawings.
FIG. 2 is a block diagram showing the structure of the mobile phone
with the channel switching determining unit according to the first
embodiment of the present invention. Referring to FIG. 2, the mobile
station according to the first embodiment is composed of a radio
section 1, a reception electric field intensity detecting section
2, a frame error rate detecting section 3, a channel switching determining
section 4, a frame error rate threshold value setting section 5,
a state monitoring section 6 and a channel switching executing section
(not shown). The radio section 1 performs a radio communication
with a base station. The reception electric field intensity detecting
section 2 detects reception electric field intensities of a received
signals by the radio section 1 from the base stations. The frame
error rate detecting section 3 detects a frame error rate based
on the receive signal. The channel switching determining section
4 determines a channel switching method when the degradation of
communication quality is detected. The frame error rate threshold
value setting section 5 sets to said channel switching determining
section 4, a frame error rate threshold value as the condition used
to detect the degradation of the communication quality. The state
monitoring section 6 monitors the result of the channel switching
operation.
These sections operate as follows, respectively.
The channel switching determining section 4 compares a frame error
rate detected by the frame error rate detecting section 3 for a
predetermined time interval and the threshold value set by the setting
section 5. When the detected frame error rate is equal to or higher
than the threshold value, the channel switching determining section
4 determines to be the degradation of the communication quality.
Then, the channel switching determining section 4 compares a reception
electric field intensity threshold value and the reception electric
field intensity detected by the reception electric field intensity
detecting section 2. As a result, the channel switching determining
section 4 determines as the channel switching method, a communication
channel switching process in the same base station with which the
current communication channel is established, when the reception
electric field intensity is equal to or higher than the reception
electric field intensity threshold value. Also, the channel switching
determining section 4 determines as the channel switching method,
a hand-over process to another base station when the reception electric
field intensity is lower than the reception electric field intensity
threshold value. The channel switching executing section executes
the channel switching based on the determined channel switching
method.
The frame error rate threshold value setting section 5 has two
kinds of threshold values. One of them is a threshold value for
a usual use and the other is a threshold value for the restraint
of the channel switching operation which is set to restrain unnecessary
channel switching operations due to the influence of the interference
wave. The frame error rate threshold value setting section 5 sets
the usual threshold value as the frame error rate threshold value
when it is informed from the state monitoring section 6 that the
hand-over failure does not occur frequently. Also, the frame error
rate threshold value setting section 5 sets the threshold value
for the channel switching operation restraint as the frame error
rate threshold value when it is reported when the hand-over failure
occurs frequently.
The state monitoring section 6 detects the number of times of execution
of the hand-over process and an execution result for every execution
of the hand-over process. The state monitoring section 6 calculates
a hand-over success rate from the detected result when the number
of times of the execution reaches a predetermined value, and determines
whether or not the hand-over failure does not occur frequently.
As such, the respective channel switching operations will be described
below. Here, the radio section 1, the reception electric field intensity
detecting section 2 and the frame error rate detecting section 3
in FIG. 2 are well known to a skilled person in the art.
In this way, the existence or non-existence of the influence of
an interference wave in case of the operation is determined based
on the results of the channel switching operation performed in the
past by the mobile station. As the result, the channel switching
operation having the possibility of failure due to the influence
of the interference wave can be restrained, because the frame error
rate threshold value as the communication quality degradation determining
condition is set to the appropriate value. Therefore, it is possible
to avoid the instability of communication in the generation of the
interference wave.
Next, the operation of the whole apparatus according to the first
embodiment will be described in detail with reference to the flow
charts of FIG. 2 and FIG. 3.
First, the channel switching determining process is started in
a communication state. In the frame error rate threshold value setting
section 5, the determination result of the channel switching operations
in the past informed from the state monitoring section 6 is confirmed
(a step A101 of FIG. 2).
The channel switching restraint threshold value Eb is set as the
frame error rate threshold value Et if the hand-over failure occurs
frequently (Step A102). Also, the usual use threshold value Ea is
set as the frame error rate threshold value Et, if not the hand-over
failure does not occur frequently (Step A103).
Next, in the channel switching determining section 4, the frame
error rate E detected by the frame error rate detecting section
3 and the frame error rate threshold value Et set in the step A102
or step A103 are compared with each other (Step A104). If E.gtoreq.Et,
it is determined that the communication quality is degraded and
a communication quality degradation count Q is incremented (Step
A105). Also, if E<Et, it is determined that there is not degradation
of the communication quality. In this case, the communication quality
degradation count Q is not incremented.
This summing process is repeated a predetermined number of times
N (Step A106), and then the communication quality degradation count
Q after the summing process is compared with a communication quality
degradation count threshold value Qt (Step A107). If Q.gtoreq.Qt,
it is determined that the communication channel switching operation
is necessary because of the degradation of the communication quality.
Subsequently, the reception electric field intensity detected for
the current communication channel by the reception electric field
intensity detecting section 2 is compared with the reception electric
field intensity threshold value Rt to determine a channel switching
method (Step A108). If Q<Qt, the degradation of the communication
quality is determined not to be present, the communication quality
degradation count Q is cleared (Step A111). Thereafter, the channel
switching determining process is ended.
If the comparing result in the step A108 indicates to be R<Rt,
the hand-over (inter-station channel switching) process is selected
as the channel switching method (Step A109). On the other hand,
if R.gtoreq.Rt, the channel switching process in the base station
(intra-station channel switching process) is selected as the channel
switching method (Step A110). After the channel switching method
is determined, the communication quality degradation count Q is
cleared (Step Alll). This is shown in FIG. 4. Then, the channel
switching determining process is ended. Thereafter, the channel
switching is executed by the channel switching executing section
(not shown).
Next, a specific example will be described with reference to FIG.
5.
As shown in FIG. 5, the two kinds of frame error rate threshold
values Ea and Eb as the communication quality degradation detection
conditions have been set to satisfy Eb>Ea. As a result, the channel
switching operation can be restrained in the case that the channel
switching restraint threshold value Eb is used, compared with the
case that the usual use threshold value Ea is used. Thus, the number
of channel switching operations can be reduced even when the frame
error rate is increased due to the interference wave which is generated
frequently.
In this way, it becomes difficult to detect the communication quality
degradation in the case that the frame error rate threshold value
Et is set as the threshold value Eb than in the case that it is
set as the threshold value Ea. However, the threshold value Eb is
set to a value such that the minimum communication can be provided
in the same communication channel. The reception electric field
intensity threshold value Rt is set to the reception electric field
intensity such that the stable communication state can be provided
in the minimum in the same base station.
The operation of the state monitoring section 6 is performed as
shown in FIG. 5.
First, when the hand-over operation is executed, a hand-over initiation
count H is incremented (a step S101 of FIG. 4). The hand-over initiation
count H is incremented every time the hand-over operation is executed.
Next, the establishment of the synchronization at the time of the
hand-over operation is confirmed to check the executing result of
the hand-over operation (Step S102). When the establishment of the
synchronization with a destination base station succeeds in a once
hand-over operation, it is determined to be the success of the hand-over
operation and the hand-over success count Hs is incremented (Step
S103). On the other hand, the establishment of the synchronization
sometimes fails in the hand-over operation in the environment in
which the interference wave generates in an impulse manner.
Therefore, when the establishment of the synchronization in the
hand-over destination does not succeed at once, it is determined
that the hand-over failure occurs due to the interference wave,
and the hand-over execution result measuring process is ended without
incrementing the hand-over success count Hs. This measuring process
is performed every time hand-over operation is executed. When the
hand-over initiation count H reaches a predetermined value (Step
S104), the hand-over success rate Hr (=Hs/H) is calculated (Step
S105). Then, the hand-over success rate Hr is compared with the
hand-over success rate threshold value Ht (Step S106).
If Hr<Ht, it is determined that the hand-over failure occurs
frequently due to the influence of the interference wave (Step S107).
Also, if Hr.gtoreq.Ht, it is determined that the hand-over failure
does not occur frequently due to the influence of the interference
wave (Step S108). Lastly, the hand-over initiation count H is cleared
(Step S109). Thereafter, the step A101 of FIG. 3 is executed.
When the report from the state monitoring section 6 indicates the
frequent occurrence of the hand-over failure, the frame error rate
threshold value Et is set as the threshold value Eb by the frame
error rate threshold value setting section 5 (step A101 and step
A102 of FIG. 3). In the channel switching determining section 4,
the frame error rate E and the frame error rate threshold value
Et are first compared with each other (Step A104). If the comparing
result of step A104 indicates E.gtoreq.Et, the communication quality
degradation count Q is incremented to becomes Q=1 (Step A106).
Here, it is supposed that the communication quality degradation
count threshold value Qt=N-3. By setting the channel switching restraint
threshold value Eb as the frame error rate threshold value Et, the
number of times determined as the communication quality degradation
decreases, compared with the case of the usual use threshold value
Ea. It is supposed that E.gtoreq.Et1 is satisfied (N-4)times in
the comparing result of the step A104 when the summing process is
repeated N time. In this case, the communication quality degradation
count Q=N-4. Because it becomes Q<Qt in the step A107, it is
determined that there is not the degradation of the communication
quality so that the channel switching operation becomes unnecessary.
Then, the communication quality degradation count Q is cleared.
Thus, the channel switching determining process is ended (Step A111).
Thereafter, the channel switching method is executed by the channel
switching executing section (not shown).
Next, the mobile phone according to the second embodiment of the
present invention will be described in detail with reference to
the drawings.
Referring to FIG. 6, the mobile station according to the second
embodiment is different from the first embodiment shown in FIG.
2 in the following point. That is, the state monitoring section
6 monitors the result of the channel switching operation (inter-station
channel switching operation) and is composed of a hand-over monitoring
section 61 for monitoring the hand-over execution result and a channel-switching-in-base-station
monitoring section 62 for monitoring the execution result of the
channel switching operation in the base station (intra-station channel
switching operation).
These methods are executed as follows, respectively.
Like the operation of the state monitoring section 6 of the first
embodiment shown in FIG. 2, the hand-over monitoring section 61
measures the number of times of execution of the hand-over process
as the communication channel switching method and the executing
result every time the hand-over process is executed. Then, the hand-over
monitoring section 61 calculates the hand-over success rate after
a predetermined number of times of measurement and determines whether
or not the hand-over occur frequently.
The channel-switching-in-base-station monitoring section 62 measures
the number of times of execution of the channel switching in the
base station and a communication channel establishment result every
time the channel switching in the base station is executed. Then,
the channel-switching-in-base-station monitoring section 62 calculates
a communication channel establishment success rate after the predetermined
number of times, and determines whether the channel switching state
is good or bad, namely, whether or not the channel switching operation
is successful.
Next, the operation of the whole of the mobile phone according
to the second embodiment will be described in detail with reference
to the flow charts of FIG. 7 and FIG. 8. The operations of the channel
switching determining section 4 shown in the steps A104 to A111
of FIG. 7 are the same as those of the channel switching determining
section 4 according to the first embodiment shown in FIG. 2. Therefore,
the description is omitted.
In the first embodiment shown in FIG. 2, the frame error rate threshold
value is set based on only the determination result of whether the
hand-over failure occurs frequently, reported from state monitoring
section 6 (step A101). However, in the second embodiment, the determination
result of the hand-over operation results in the past which is reported
from the hand-over monitoring section 61 is first confirmed, like
the first embodiment shown in FIG. 2 (Step A101).
The method (step A102) of setting the frame error rate threshold
value when the hand-over failure occurs frequently is the same as
that in the first embodiment shown in FIG. 2. However, when the
hand-over failure does not occur frequently, the determination result
of the operation results in the past of the channel switching in
the base station which is reported from the channel-switching-in-base-station
monitoring section 62 is confirmed (step B101 of FIG. 6).
In this case, if the channel switching state is good, the usual
use threshold value Ea is set as the frame error rate threshold
value Et, as in the first embodiment shown in FIG. 3 (Step A103).
However, if the channel switching state is not good, the channel
switching restraint threshold value Eb is set as the frame error
rate threshold value Et, as in the case where the hand-over failure
occurs frequently (Step A102).
In the second embodiment, in the case where the hand-over failure
does not occur frequently in the step A101, whether the channel
switching state is good or bad is further confirmed, and finally
the frame error rate threshold value Et is set.
In the above-mentioned specific example shown in FIG. 4, the frame
error rate threshold value Et is a threshold value set in such a
manner that the channel switching in the base station or the hand-over
is initiated as the channel switching operation when the frame error
rate E is E.gtoreq.Et. Therefore, in order to restrain all the channel
switching operation, it is desirable to set the frame error rate
threshold value Et, after the operation result of the channel switching
in the base station is confirmed in addition to the hand-over operation
result.
Next, a specific example will be described.
The operation of the hand-over monitoring section 61 is the same
as the operation of the state monitoring section 6 in the first
embodiment shown in FIG. 5. Therefore, the description is omitted.
The operation of the channel-switching-in-base-station monitoring
section 62 is performed as shown in FIG. 8. That is, when the channel
switching in the base station is executed as the channel switching
method, the channel-switching-in-base-station initiation count C
is first incremented (step R101 of FIG. 8).
Next, in order to measure the communication channel establishment
result at the time of the channel switching in the base station,
the result of the establishment of the destination communication
channel at the time of the channel switching in the base station
is confirmed (Step R102). When the establishment of the destination
communication channel at the channel switching succeeds at once,
the success of the communication channel establishment is determined
so that the communication channel establishment success counter
Cs is incremented (Step R103).
In the environment in which the interference wave is generated
in an impulse manner, the establishment of the destination communication
channel sometimes fails at the time of the channel switching in
the base station. This is similar to the establishment of the synchronization
at the time of the hand-over in the first embodiment shown in FIG.
5. Therefore, when the establishment of the destination communication
channel can not be succeeded at once, it is determined that the
establishment of the communication channel is failed due to the
interference wave. Then, the communication channel establishment
result measuring process is ended without incrementation of the
communication channel establishment success count Cs.
The measuring process is executed every time the channel switching
in the base station is executed. When the channel-switching-in-base-station
initiation count C reaches a predetermined value (Step R104), the
communication channel establishment success rate Cr(=Cs/C) is calculated
(Step R105). Then, the communication channel establishment success
rate Cr and the communication channel establishment success rate
threshold value Ct are compared with each other (Step R106).
If Cr<Ct, it is determined that the channel switching state
is not good (Step S107), because the communication channel establishment
failure due to the influence of the interference wave occurs frequently
at the time of the channel switching in the base station. Also,
if Cr.gtoreq.Ct, it is determined that the channel switching state
is good (Step R108), because the communication channel establishment
failure due to the influence of the interference wave does not occur
frequently. Subsequently, the channel-switching-in-base-station
initiation count C is cleared (Step R109).
When the report from the hand-over monitoring section 61 indicates
that the hand-over operation does not occur frequently, or when
the report from the channel-switching-in-base-station monitoring
section 62 indicates that the channel switching state is not good,
the usual use threshold value Eb is set as the frame error rate
threshold value Et by the frame error rate threshold value setting
section 5 (Step A101, step B101 and step A102 of FIG. 7).
After the summing process in the channel switching determining
section 4 shown in the steps A104 to A106 is repeated N times, the
channel switching restraint threshold value is set as the frame
error rate threshold value Et. Thus, all the comparing results of
step A104 become E<Et. At this time, the communication quality
degradation count Q becomes 0 so that it becomes Q<Qt (Step A108).
Because there is no degradation of the communication quality, the
selection of the channel switching method is not performed and the
channel switching determining process is ended.
The effect of the present invention is in that unnecessary channel
switching operation due to the influence of the interference wave
is restrained so that stable communication can be continued, in
the environment in which the interference wave which causes the
communication channel quality degradation, especially an impulse
interference wave is frequently generated.
The influence of the interference wave at the time of the channel
switching operation is determined from the results of the channel
switching in the past. Also, the communication quality degradation
detection condition is set based on the determining result to restrain
the unnecessary channel switching operation in which the possibility
of failure due to the influence of the interference wave is high.
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