JP2013211668A - Mobile communication system, base station, and signal transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To review communication conditions as needed.SOLUTION: A demodulator (52) of a mobile terminal (12-1) measures the signal quality of a received downlink signal, and supplies the measured signal quality to an environmental change detector (54). The environmental change detector (54) detects whether the prescribed change occurs that involves reviewing communication conditions, on the basis of the comparison result of different statistics for different time periods of the signal quality from the demodulator (52). The mobile terminal (12-1) transmits the results of environmental change detection by the environmental change detector (54) to a base station (10A) over the uplink. A controller (20) of the base station (10A) notifies a management server (14) of the results of environmental change detection from the mobile terminal (12-1). The management server (14) reviews communication conditions for base stations (10A, 10B), such as base station parameters, according to the results of environmental change detection from the base stations (10A, 10B).

Description

  The present invention relates to a mobile communication system, a base station, and a signal transmission system.

  In mobile communication systems, communication conditions vary greatly depending on the usage environment of the mobile terminal, so it is common to automatically adjust communication conditions such as transmission power and modulation conditions based on the signal quality of the received signal on the receiving side. It is. As a technique for optimizing base station parameters based on radio quality information (SINR: signal-to-interference and noise ratio) acquired by base stations and mobile terminals, the presence of neighboring cells and base stations, and these quality information, SON (Self-Organizing Network) is known. The base station parameters adjusted here include transmission power, spreading code, antenna tilt angle, transmission timing, allocation of resource blocks to terminals, threshold values for starting handover processing, and the like. The parameter that depends on the base station parameter is indirectly changed by changing the base station parameter.

  For example, Patent Document 1 describes a handover technique in which a base station is switched according to the signal quality of a received signal received by a mobile terminal when a mobile terminal in communication moves at high speed.

JP 2009-010989 A

  In a mobile communication system, the communication environment fluctuates in both the long term and the short term. Although it is necessary to adjust the communication conditions, for example, the above-described base station parameters according to the change in the communication environment, the immediate adjustment makes the communication unstable. In addition, when reviewing at a constant cycle, it may be lost later, and it is preferable to review the communication conditions based on some criteria.

  If the index value indicating the communication environment exceeds a certain fixed threshold value, a method of reviewing the communication conditions can be considered, but such a method is not only necessary to set the threshold value appropriately, but also assumed It is difficult to determine a constant value that corresponds to changes in the communication environment.

  In a situation where communication with a plurality of base stations is possible, it is necessary to adjust base station parameters in cooperation with a plurality of adjacent base stations. Frequent review of base station parameters reduces the load on the entire mobile communication system. It will increase.

  An object of the present invention is to provide a mobile communication system, a base station, and a signal transmission system that solve such disadvantages and realize efficient and stable mobile communication.

  A mobile communication system according to the present invention is a mobile communication system comprising a base station and one or more mobile terminals communicating with the base station via an uplink and a downlink. The communication condition is reconsidered in the downlink communication environment according to the comparison result of the signal quality measuring means for measuring the signal quality of the downlink received signal and the different statistical values of the signal quality in different periods. An environment change detecting means for detecting whether or not there is a predetermined change, and a control means for revising the communication condition when the predetermined change is detected by the environment change detecting means arranged in the base station. It is characterized by comprising.

  A mobile communication system according to the present invention is a mobile communication system comprising a base station and one or more mobile terminals communicating with the base station via an uplink and a downlink. The signal quality measuring means for measuring the signal quality of the received signal of the uplink, and a predetermined communication condition to be reconsidered in the uplink communication environment according to the comparison result of different statistical values of the signal quality in different periods. An environmental change detecting means for detecting whether there is a change, and a control means for reviewing the communication condition when the predetermined change is detected by the environmental change detecting means.

  A base station according to the present invention is a base station of a mobile communication system, receiving means for receiving the signal quality of a received signal measured by the mobile terminal in the downlink to the mobile terminal, According to a comparison result of different statistical values for different periods, an environmental change detection unit for detecting whether or not there is a predetermined change in the communication environment of the downlink that should be reviewed, and the predetermined change by the environmental change detection unit And a control means for reviewing the communication condition when the communication condition is detected.

  A base station according to the present invention is a base station of a mobile communication system, a receiving means for receiving an uplink signal from a mobile terminal, and a signal quality measuring means for measuring the signal quality of the received signal of the receiving means And an environment change detecting means for detecting whether there is a predetermined change in the communication environment of the uplink according to a comparison result of different statistical values of the signal quality for different periods, and the environment change And a control unit that reviews the communication condition when the predetermined change is detected by the detection unit.

  The signal transmission system according to the present invention includes a signal quality measuring unit that measures the signal quality of a received signal, and a predetermined communication condition that should be reviewed in the communication environment according to a comparison result of different statistical values of the signal quality in different periods. An environment change detection unit that detects whether there is a change, and a control unit that reviews the communication condition when the predetermined change is detected by the environment change detection unit.

  According to the present invention, it is possible to appropriately detect a change in the communication environment where the communication conditions should be reviewed, and accordingly, the review of the communication conditions can be started at an appropriate timing. This eliminates an excessive load on the system due to the review of communication conditions.

It is a schematic block diagram of the first embodiment of the present invention. 1 shows a schematic block diagram of an environment change detection device. An example of the cumulative probability density distribution of received signal quality is shown. It is a schematic block diagram of the second embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic block diagram of an embodiment of the present invention applied to a downlink of a mobile communication system, that is, a link from a base station to a mobile terminal.

  Each of the base stations 10A and 10B can accommodate a plurality of predetermined numbers of mobile terminals. In FIG. 1, for the sake of explanation, the mobile terminal 12-1 communicates the base station 10A with the downlink data Dd (1) and the uplink data Du (1), and the mobile terminal 12-2 communicates with the base station 10A with the downlink data Dd (2). ) And uplink data Du (2), and the mobile terminal 12-3 communicates downlink data Dd (3) and uplink data Du (3) with the base station 10B. Each mobile terminal 12-1 to 12-3 has the same configuration.

  Although not shown, the base stations 10A and 10B are connected to the upper network and mediate communication with the mobile terminals 12 (12-1 to 12-3). The management server 14 manages the base stations 10A and 10B. In order to manage and control the base stations 10A and 10B, the management server 14 includes a parameter setting device 16 that sets base station parameters of the base stations 10A and 10B.

  The basic communication operation between the base station 10A and the mobile terminal 12 will be described by taking the mobile terminal 12-1 as an example. The control device 20 controls each part of the base station 10 as a whole. Downlink data Dd (1) and Dd (2) for the mobile terminals 12-1 and 12-2 are input from the upper network to the modulation device 22. The modulation device 22 includes the downlink data Dd (1), Dd (2), control signals (including various request signals and response signals) for the mobile terminals 12-1 and 12-2 from the control device 20, and the like. Is modulated with a modulation condition (for example, the number of modulation levels) specified by the control device 20, and each modulated signal is supplied to the RF transmission device 24. The RF transmission device 24 multiplexes the downlink data Dd (1), Dd (2) and the modulated signal carrying the control signal from the modulation device 22 by frequency division multiplexing or time division multiplexing to perform frequency conversion (for example, up The downstream RF signal is generated and supplied to the circulator 26. Although details will be described later, the RF transmission device 24 adjusts the transmission power of the downlink RF signal for each mobile terminal in accordance with the power control signal from the control device 20.

  The circulator 26 supplies the downlink RF signal from the RF transmitter 24 to the antenna 28, and the antenna 28 radiates the downlink RF signal toward the mobile terminals 12-1 and 12-2 as a radio wave signal.

  Each of the mobile terminals 12-1 and 12-2 receives a downlink RF signal addressed to itself among the downlink RF signals from the base station 10A. The configuration and operation of the mobile terminal 12-1 will be described as an example.

  The control apparatus 40 controls each part of the mobile terminal 12-1. The antenna 48 receives the downlink RF signal from the base station 10 </ b> A and supplies it to the RF receiver 50 via the circulator 46. The RF receiver 50 frequency-converts (eg, down-converts) the downstream RF signal from the circulator 46, separates the component addressed to itself (addressed to the mobile terminal 12-1), and supplies the separated component to the demodulator 52. The demodulator 52 demodulates the downlink signal from the RF receiver 50 and outputs the downlink data Du (1) in the downlink signal for internal use or to an external apparatus. The downlink signal includes a control signal and a status signal related to communication between the mobile terminal 12-1 and the base station 10A, and the demodulator 52 supplies these signals to the controller 40. The demodulator 52 also measures SINR (signal-to-interference noise ratio) when demodulating the downlink data Dd (1), and supplies the measured SINR value to the environment change detector 54. Although the details will be described later, the environment change detection device 54 reexamines the base station parameter with respect to a signal indicating the environment change detection result, specifically, a predetermined change in the SINR value supplied from the demodulation device 52. The base station parameter change request signal to be requested is output to the modulation device 42.

  The modulation device 42 outputs the uplink data Du (1), the control signal for the base station 10A from the control device 40, and the environment change detection result output of the environment change detection device 54 to a modulation condition ( For example, the modulated signal is supplied to the RF transmitter 44. The RF transmitter 44 frequency-converts the modulated signal output from the modulator 42 to generate an uplink RF signal, and outputs the uplink RF signal to the circulator 46 with transmission power according to the power control signal from the controller 40. The circulator 46 supplies the uplink RF signal from the RF transmitter 44 to the antenna 48, and the antenna 48 radiates the uplink RF signal toward the base station 10A as a radio wave signal.

  The antenna 28 of the base station 10 </ b> A receives the uplink RF signal from the mobile terminals 12-1 and 12-2 and supplies it to the RF receiver 30 via the circulator 26. The RF receiver 30 frequency-converts the uplink RF signal from the circulator 26, separates it into uplink signals from the mobile terminals 12-1 and 12-2, and supplies the demodulator 32. The demodulator 32 demodulates the uplink signals from the mobile terminals 12-1 and 12-2 from the RF receiver 30, and supplies the uplink data Du (1) and Du (2) of the uplink signals to the upper network. To do. The uplink signal includes control signals and status signals related to communication between the mobile terminals 12-1 and 12-2 and the base station 10, and the environment change detection result of the environment change detection device 54. Supplies these signals to the control device 20.

  When receiving the environmental change detection result corresponding to the base station parameter change request from the mobile terminal 12-1, the control device 20 starts the base station parameter review process.

  The communication between the base station 10A and the mobile terminal 12-2 and the communication between the base station 10B and the mobile terminal 12-3 are the same as the communication between the base station 10A and the mobile terminal 12-1. The same.

  The operation for controlling the base station parameters of the base station 10A according to the received signal quality at the mobile terminal 12-1 will be described in detail by taking communication between the base station 10A and the mobile terminal 12-1 as an example.

  As described above, the environment change detection device 54 modulates the base station parameter change request signal that requests the base station to review the base station parameters in response to a predetermined change in the SINR value supplied from the demodulation device 52. Output to the device 42.

  FIG. 2 shows a schematic block diagram of the environment change detection device 54. The signal quality SINR of the reception data Dd (1) detected by the demodulator 52 is sequentially input to the delay line 60 of the environment change detector 54. The delay line 60 has a configuration in which n delay units 62-1 to 62-n of unit time Δt are serially connected, and the total delay time is T1. The signal quality value of the period T1 output from each delay device 62-1 to 62-n of the delay line 60 is input to the accumulation processing device 64, and k delay devices 62-1 to 62-1 on the input side of the delay line 60 are input. The signal quality value of the period T2 output from 62-k is also input to the average calculation device 66. In other words, the signal quality value in the range that goes back from the current time by the period T1 is input to the cumulative processing device 64, and the signal quality value in the range that goes back from the current time by the time period T2 (however, T2 <T1). Enter. When applied to a third generation (so-called 3G) mobile communication system, for example, T1 is about several tens of seconds to several minutes, and T2 is about several seconds.

  The cumulative processing device 64 calculates the cumulative probability density distribution of the signal quality value in the period T1 from the signal quality values from the n delay units 62-1 to 62-n, and the upper limit value of the signal quality from the cumulative probability density distribution. Tmax and lower limit value Tmin are determined. FIG. 3 shows an example of the cumulative probability density distribution. The horizontal axis indicates the signal quality value, and the vertical axis indicates the cumulative probability density of the signal quality. Curve 80 shows the cumulative probability density distribution obtained from the signal quality value for period T1. Upper limit quality probability value 82 is used to determine upper limit value Tmax, and lower limit quality probability value 84 is used to determine lower limit value Tmin. For example, the upper limit quality probability is 90%, and the lower limit quality probability is 10%, which are set in the cumulative processing device 64 in advance.

  The cumulative processing device 64 draws a cumulative probability density distribution as shown by the curve 80 from the n signal quality values from the delay line 60, and sets the upper limit quality probability value 82 and the preset cumulative probability density distribution to the obtained cumulative probability density distribution. The lower limit quality probability value 84 is applied to determine the upper limit value Tmax and the lower limit value Tmin, respectively.

  On the other hand, the average calculation device 66 calculates the average value of the signal quality values from the k delay units 62-1 to 62-k on the input side of the delay line 60. That is, the average calculation device 66 adds k signal quality values from the delay units 62-1 to 62-k, and divides by k.

  The comparators 68 and 70 and the adder 72 are devices that determine whether the average value calculated by the average calculation device 66 is between the upper limit value and the lower limit value determined by the accumulation processing device 64.

  Specifically, the comparator 68 compares the upper limit value Tmax from the accumulation processing device 64 with the average value AVR from the average calculation device 66, and when the average value AVR is smaller than the upper limit value Tmax, the binary value " When the average value AVR is equal to or greater than the upper limit value Tmax, the binary value “1” is output. Further, the comparator 70 compares the lower limit value Tmin from the accumulation processing device 64 with the average value AVR from the average calculation device 66, and when the average value AVR exceeds the lower limit value Tmin, the binary value “0” is obtained. When the average value AVR is equal to or lower than the lower limit value Tmin, the binary value “1” is output. The adder 72 adds the output values of the comparators 68 and 70.

  The output value “1” of the comparator 68 indicates that the signal quality is not temporarily improved, and the output value “1” of the comparator 70 is that the signal quality is not temporarily deteriorated. Indicates. Since these do not occur simultaneously, the output value of the adder 72 is “0” or “1”, and the output value “1” of the adder 72 indicates that the signal quality of the received signal has changed greatly. However, since the evaluation is based on the average value of the period T2 with respect to the change of the period T1, the temporary change is excluded, and the change in the signal quality that continues over time is evaluated to some extent.

  The addition result of the adder 72 is the environment change detection result output of the environment change detection device 54, and the output value 1 of the adder 72 is a base station parameter change request signal for requesting the base station 10A to review the base station parameters. The signal is supplied to the modulation device 42 and transmitted to the base station 10A via the RF transmission device 44, the circulator 46, and the antenna 48.

  The control device 20 of the base station 10A transfers the base station parameter change request signal from the mobile terminal 12-1 to the management server 14. The management server 14 can know from the base station parameter change request signal that a non-negligible change has occurred in the communication environment between the base station 10A and the mobile terminal 12-1. The parameter setting device 16 of the management server 14 relates to communication between the base station 10A and the mobile terminal 12-1 and between the base station 10A and the mobile terminal 12-2 in consideration of the other base station 10B. The base station parameter of the base station 10A and the base station parameter of the base station 10B related to the communication between the base station 10B and the mobile terminal 12-3 are determined, and the control device 20 of the base station 10A and the control device 20 of the base station 10B are determined. Notify The control device 20 sets the base station parameters corresponding to the contents notified from the parameter setting device 16 of the management server 14 to the related means.

  When the management server 14 is not involved in reviewing the base station parameters, the control device 20 may start the base station parameter review process of the base station 10A or the base station 10B alone, and the base that has been reviewed as necessary. The contents of the station parameter may be notified to the management server 14.

  FIG. 4 shows a schematic block diagram of a second embodiment of the present invention applied to the uplink. The number of environment change detection devices 154-1 to 154-n having the same function as the environment change detection device 54 is arranged on the base station side in accordance with the number of mobile terminals that can be accommodated, so that each mobile terminal goes to the base station. A change in uplink communication status can be detected, and a review of the base station parameters for the uplink can be initiated for a certain change. The means 122 to 132 and 142 to 152 of the embodiment shown in FIG. 4 correspond to the means 22 to 32 and 42 to 52 of the embodiment shown in FIG. 1, and the basic functions themselves are the same.

  Each of the base stations 110A and 110B can accommodate a plurality of predetermined numbers of mobile terminals. In FIG. 4, for the purpose of explanation, the mobile terminal 112-1 communicates the base station 110A with the downlink data Dd (1) and the uplink data Du (1), and the mobile terminal 112-2 communicates with the base station 10A with the downlink data Dd (2). ) And uplink data Du (2), and the mobile terminal 112-3 communicates downlink data Dd (3) and uplink data Du (3) with the base station 110B. Each mobile terminal 112 (112-1 to 12-3) has the same configuration.

  The base stations 110A and 110B are connected to the higher level network like the base stations 10A and 10B, and mediate communication with the mobile terminals 112 (112-1 to 112-3). The management server 114 manages the base stations 110A and 110B. In order to manage and control the base stations 110A and 110B, the management server 114 includes a parameter setting device 116 that sets base station parameters of the base stations 110A and 110B.

  Since the basic communication operation itself between the base station 110A and the mobile terminal 112 is the same as that of the first embodiment, the detailed description is omitted, and the differences between the base station 110A and the mobile terminal 112-1 are described. To do.

  The demodulation device 132 of the base station 110A measures the signal quality (for example, SINR value) of the uplink signal from the mobile terminal 112-1, and supplies the measurement result to the environment change detection device 154-1. The environment change detection device 154-1 has the same configuration as the environment change detection device 54-1, and according to the signal quality value input from the demodulation device 132, the upper limit value determined from the cumulative probability density distribution of the signal quality value in the period T1. The presence or absence of an environmental change is detected from the lower limit value and the average value of the signal quality value during the period T2. This operation is the same as that of the environment change detection device 54-1. The environment change detection device 154-1 supplies a base station parameter change request signal based on the detection result of the environment change to the parameter setting device 116 of the management server 114. The detection result of the environmental change by the environmental change detection device 154-1 may of course be transferred to the management server 114 via the control device 120.

  The management server 114 uses a base station parameter change request signal from the base station 110A (environment change detection device 154-1 or control device 120) to change the communication environment between the base station 110A and the mobile terminal 112-1 that cannot be ignored. And the base station parameter review process of the subordinate base station is started. In particular. The parameter setting device 116 of the management server 114 takes into account the other base station 110B, base station parameters of the base station 110A relating to communication between the base station 110A, the mobile terminal 112-1, and the mobile terminal 112-2, And the base station parameter of the base station 110B regarding the communication between the base station 110B and the mobile terminal 112-3 is determined and notified to the control device 120 of the base station 110A and the control device 120 of the base station 110B. The control device 120 sets the base station parameters corresponding to the contents notified from the parameter setting device 116 of the management server 114 to the related means.

  When the management server 114 is not involved in reviewing the base station parameters, the control device 120 may start the base station parameter review process of the base station 110A or the base station 10B alone, The management server 114 may be notified of the contents of the station parameters.

  The configuration shown in FIG. 4 can also be applied to change of base station parameters regarding the downlink. When applied to the downlink, the operation is as follows.

  The demodulator 152 of the mobile terminal 112-1 measures the signal quality of the received signal and supplies the measurement result to the controller 140. The control device 140 supplies information indicating the received signal quality from the demodulation device 152 to the modulation device 142 so as to be transmitted to the base station 110A. The received signal quality information is transmitted to the base station 110A via the modulator 142, the RF transmitter 144, the circulator 146, and the antenna 148. The base station 110A includes the antenna 128, the circulator 126, the RF receiver 130, and the demodulator 132. To the environment change detection device 154-1. Similarly to the environment change detection device 54-1, the environment change detection device 154-1 detects a downlink environment change according to the downlink received signal quality.

  In the second embodiment, the demodulator 132 measures the signal quality of the received signal, whereas in the third embodiment, the demodulator 152 measures the signal quality of the received signal.

  In the mobile communication system, the communication environment varies in the short term and in the short term, and it is necessary to adjust the communication conditions in accordance with the change in the communication environment. However, the immediate adjustment makes the communication unstable. However, in each of the above embodiments, the uplink and downlink communication environments are individually measured for the communication between the base station and the mobile terminal, and the signal quality of the received signal is evaluated by the cumulative probability density distribution, so that stable operation can be performed. Since the upper limit value and lower limit value indicating the range are determined, the range (upper limit value / lower limit value) in which the base station parameters should be retained is appropriately determined even in mobile communication in which the stable level of signal quality varies over the long term. Can be determined. When the average value measured in a shorter period deviates from the range of the upper limit value / lower limit value determined in this way, the review of the communication environment, specifically the base station parameters, is started. Therefore, it is possible to realize review control that is more appropriate and timely than the conventional example in which the review of the communication environment is determined. As a result, stable communication can be realized regardless of the long-term / short-term fluctuation of the communication environment.

  Although the invention has been described with reference to specific illustrative embodiments, various modifications and alterations may be made to the above-described embodiments without departing from the scope of the invention as defined in the claims. This is obvious to an engineer in the field to which the present invention belongs, and such changes and modifications are also included in the technical scope of the present invention.

10A, 10B: base station 12 (12-1 to 12-3): mobile terminal 14: management server 16: parameter setting device 20: control device 22: modulation device 24: RF transmission device 26: circulator 28: antenna 30: RF Receiver 32: Demodulator 40: Controller 42: Modulator 44: RF transmitter 46: Circulator 48: Antenna 50: RF receiver 52: Demodulator 54: Environment change detector 60: Delay lines 62-1 to 62- k to 62-n: delay unit 64: accumulating processing unit 66: average calculating unit 68, 70: comparator 72: adder 80: cumulative probability density distribution curve 82 of signal quality: upper and lower quality probability value 84: lower limit quality probability value 110A, 110B: Base station 112 (112-1 to 112-3): Mobile terminal 114: Management server 116: Parameter setting device 120: Control device 12 : Modulator 124: RF transmitter 126: Circulator 128: Antenna 130: RF receiver 132: Demodulator 140: Controller 142: Modulator 144: RF transmitter 146: Circulator 148: Antenna 150: RF receiver 152: Demodulated Apparatus 154-1 to 154-n: Environment change detection apparatus

Claims (14)

From the base station (10, 110) and one or more mobile terminals (12-1 to 12-3, 112-1 to 112-3) communicating with the base station via uplink and downlink A mobile communication system comprising:
Signal quality measuring means (52, 152) arranged in the mobile terminal and measuring the signal quality of the downlink received signal;
Environment change detection means (54, 154-1) for detecting whether or not there is a predetermined change in the communication environment of the downlink according to the comparison result of different statistical values of the signal quality in different periods. When,
Control means (14, 114, 20, 120) arranged in the base station to review the communication conditions when the predetermined change is detected by the environment change detection means
And a mobile communication system. The environment change detection means is arranged in the mobile terminal,
The mobile communication system according to claim 1, wherein the mobile terminal comprises means for transmitting the detection result of the environment change detection means to the base station via the uplink. The environment change detection means is arranged in the base station,
2. The mobile unit according to claim 1, wherein the mobile terminal comprises means for transmitting information indicating the signal quality measured by the signal quality measuring means to the base station via the uplink. Communications system. The base station comprises uplink signal quality measuring means (32, 132) for measuring the signal quality of the uplink received signal,
In accordance with the comparison result of different statistical values of the signal quality measured by the uplink signal quality measuring unit and different periods, the environment change detecting unit has a predetermined change in which the communication condition is to be reviewed in the uplink communication environment. Detect if there is,
And a control means (114, 120) for revising the uplink communication condition when the predetermined change to be reconsidered in the uplink communication environment is detected by the environment change detecting means. The mobile communication system according to claim 3. The environmental change detection means is
A cumulative processing means for calculating a cumulative probability density distribution of the signal quality in the first period T1 and determining an upper limit value and a lower limit value defining a range for detection of the predetermined change;
Average calculating means for calculating an average value of the signal quality in a second period shorter than the first period T1,
Means for detecting whether the average value is out of a range defined by the upper limit value and the lower limit value,
5. The signal according to claim 1, wherein a signal indicating detection of the predetermined change is output when the average value is out of a range defined by the upper limit value and the lower limit value. The mobile communication system described. A mobile communication system comprising a base station (110) and one or more mobile terminals (112-1, 112-2) communicating with the base station via uplink and downlink,
The base station
Signal quality measuring means (132) for measuring the signal quality of the uplink received signal;
An environmental change detection means (154-1) for detecting whether there is a predetermined change in the communication environment of the uplink according to a comparison result of different statistical values of the signal quality for different periods;
Control means (120) for reviewing the communication condition when the predetermined change is detected by the environment change detection means
And a mobile communication system. The environmental change detection means is
A cumulative processing means for calculating a cumulative probability density distribution of the signal quality in the first period T1 and determining an upper limit value and a lower limit value defining a range for detection of the predetermined change;
Average calculating means for calculating an average value of the signal quality in a second period shorter than the first period T1,
Means for detecting whether the average value is out of a range defined by the upper limit value and the lower limit value,
The mobile communication system according to claim 6, wherein when the average value is out of a range defined by the upper limit value and the lower limit value, a signal indicating detection of the predetermined change is output. A base station for a mobile communication system,
Receiving means (130) for receiving the signal quality of the received signal measured at the mobile terminal in the downlink to the mobile terminal;
An environmental change detection means (154-1) for detecting whether there is a predetermined change in the communication environment of the downlink according to a comparison result of different statistical values of the signal quality in different periods;
Control means (114, 120) for reviewing the communication condition when the predetermined change is detected by the environment change detection means
And a base station. The receiving means receives an uplink signal from the mobile terminal;
And further comprising signal quality measuring means for measuring the signal quality of the uplink received signal,
The environment change detection means has a predetermined change in which the communication conditions should be reviewed in the uplink communication environment according to a comparison result of different statistical values of the signal quality measured by the signal quality measurement means in different periods. Detect if
The control means reviews the uplink communication conditions when the environment change detection means detects whether there is a predetermined change in the uplink communication environment where the communication conditions should be reviewed. The base station according to claim 8. The environmental change detection means is
A cumulative processing means for calculating a cumulative probability density distribution of the signal quality in the first period T1 and determining an upper limit value and a lower limit value defining a range for detection of the predetermined change;
Average calculating means for calculating an average value of the signal quality in a second period shorter than the first period T1,
Means for detecting whether the average value is out of a range defined by the upper limit value and the lower limit value,
The base station according to claim 8 or 9, wherein a signal indicating detection of the predetermined change is output when the average value is out of a range defined by the upper limit value and the lower limit value. A base station for a mobile communication system,
Receiving means (130) for receiving an uplink signal from a mobile terminal;
Signal quality measuring means (132) for measuring the signal quality of the received signal of the receiving means;
An environmental change detection means (154-1) for detecting whether there is a predetermined change in the communication environment of the uplink according to a comparison result of different statistical values of the signal quality for different periods;
Control means (114, 120) for reviewing the communication condition when the predetermined change is detected by the environment change detection means
And a base station. The environmental change detection means is
A cumulative processing means for calculating a cumulative probability density distribution of the signal quality in the first period T1 and determining an upper limit value and a lower limit value defining a range for detection of the predetermined change;
Average calculating means for calculating an average value of the signal quality in a second period shorter than the first period T1,
Means for detecting whether the average value is out of a range defined by the upper limit value and the lower limit value,
The base station according to claim 11, wherein when the average value is out of a range defined by the upper limit value and the lower limit value, a signal indicating detection of the predetermined change is output. Signal quality measuring means for measuring the signal quality of the received signal;
An environment change detecting means for detecting whether or not there is a predetermined change in the communication environment in which the communication condition should be reviewed according to a comparison result of different statistical values of the signal quality for different periods;
A signal transmission system comprising: a control unit that reviews the communication condition when the predetermined change is detected by the environment change detection unit. The environmental change detection means is
A cumulative processing means for calculating a cumulative probability density distribution of the signal quality in the first period T1 and determining an upper limit value and a lower limit value defining a range for detection of the predetermined change;
Average calculating means for calculating an average value of the signal quality in a second period shorter than the first period T1,
Means for detecting whether the average value is out of a range defined by the upper limit value and the lower limit value,
The signal transmission system according to claim 13, wherein when the average value is out of a range defined by the upper limit value and the lower limit value, a signal indicating detection of the predetermined change is output.

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