JP3793029B2 - Mobile station - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to channel switching control of a mobile station used in a mobile communication system.
[0002]
A mobile phone used as an example of a mobile station is convenient because it can continue communication (for example, a call) even if it moves. This continuation of communication is realized by handover control triggered by a report on the electric field strength of the received signal from the base station by the mobile station.
[0003]
[Prior art]
Handover control in a conventional mobile communication system will be described with reference to FIG.
[0004]
In FIG. 4, 80 is a mobile station, 81 and 82 are base stations, 83 is a base station controller for managing these base stations 81 and 82, and 84 is a mobile switching center. The mobile switching center 84 is connected to a fixed telephone network or the like via a gateway switching center (not shown), and the mobile station 80 includes a base station (81 or 82), a base station controller 83, a mobile switching center 84, etc. It communicates with other mobile stations and landline telephones. The base station control device 83 and the mobile switching center 84 are collectively referred to as a base station host device.
[0005]
Next, a situation where handover control is performed will be briefly described. First, it is assumed that the mobile station 80 exists at the point X shown in FIG. 4 and performs communication (for example, a telephone call) via the base station 81. Here, it is assumed that the mobile station 80 moves (for example, the user of the mobile phone moves while holding the mobile phone) and moves to the point Z via the point Y.
[0006]
The mobile station 80 periodically determines the received electric field strength of the signal received from the base station 81 via the speech channel so that it can detect that communication via the base station 81 is difficult, far from the base station 81. taking measurement. Further, in order to switch from communication via the base station 81 to communication via another adjacent base station (in this case, the base station 82) that seems to allow better communication (so-called handover), control of the neighboring base stations The received field strength of the channel is measured.
[0007]
Therefore, the mobile station 80 periodically reports the received field strength information to the base station (in this case, the base station 81) (referred to as a radio status report 1).
[0008]
As the mobile station 80 moves from the point X to the point Y, the reception field strength (L1) of the reception signal of the speech channel from the base station 81 decreases, and the reception field of the reception signal of the control channel from the base station 82 decreases. The strength (L2) will increase. Although the base station 80 measures the received electric field strength as described above, when the level L1 is lower than the level L2 by a predetermined level or more, the mobile station 80 detects this and the base station 81 detects these receptions. Field strength information is reported (referred to as radio status report 2).
[0009]
Then, the base station 81 receives this report and transfers it to the base station host apparatus. Based on this report, the base station host apparatus performs control to switch from the base station 81 to communication with the base station 82 having a higher received electric field strength. That is, the free call channel of the base station 82 is assigned to the mobile station 80, and information specifying the call channel of the assignment destination is transmitted to the mobile station 80 via the base station 81.
[0010]
The mobile station 80 recognizes the switching destination call channel according to this designation, and switches the reception channel so as to make a call through the recognized call channel. As described above, handover control is performed.
[0011]
[Problems to be solved by the invention]
Among the base stations used in the mobile communication system as described above, about 800 Mhz band (so-called “band” conventionally used for analog mobile phones), which is a process of transition from analog mobile phones to digital mobile phones. There is a base station that uses both of the band of about 90 Mhz band (so-called digital band) that is a band newly used for a digital mobile phone and a band newly used for a digital mobile phone.
[0012]
This digital band is heavily used for both the control channel and the call channel, and the analog band is used for the call value.
[0013]
The problem here is that with the transition from analog to digital mobile phones, the base station uses different antennas in the analog and digital bands, and does not match the respective reference transmission powers completely, making them independent settings. There is a case, and the relationship that any transmission power is always high or low is not always established. That is, at the time of handover, the mobile station compares the received electric field strength of the communication channel from the communicating base station with the received electric field strength of the control channel from the adjacent base station. This is especially a problem.
[0014]
Now, assume that the reference transmission power of the control channel of the base station 81 is P, and the reference transmission power of the communication channel is Q (here, P <Q). On the other hand, the reference transmission power of the control channel of the base station 82 is R, and the reference transmission power of the speech channel is S (here, S <R). FIG. 5 shows an example of the relationship between the reference transmission powers of these base stations.
[0015]
It is assumed that the mobile station 80 moves and the received electric field strength of the communication channel at the base station 81 is lower than the received electric field strength of the control channel at the surrounding base stations by a predetermined level or more.
[0016]
Then, the mobile station 80 detects it and transmits the radio status report 2 to the base station 81 as described above. Accordingly, handoff control is performed based on the control of the base station host apparatus, and the mobile station 80 switches to communication via the base station 82.
[0017]
However, the reference transmission power S of the communication channel of the base station 82 is smaller than the reference transmission power of the control channel, and the reference transmission power P of the control channel of the base station 81 is larger than the reference transmission power Q of the communication channel. 80, the received electric field strength of the control channel of the base station 81 that is the switching source is equal to or higher than a predetermined level from the received electric field strength of the communication channel of the base station 82 even though the communication has just been switched to the communication via the base station 82. Since it is large, the radio status report 2 is transmitted again to the base station 82, and handover control may be performed.
[0018]
Even after this handover, the mobile station 80 transmits the radio status report 2 to the base station 81 again, and there is a high possibility that the handover will be performed, and there is a problem that unnecessary handovers are repeatedly performed, resulting in a decrease in call quality.
[0019]
An object of the present invention is to solve the above-described problems and to provide a mobile station that can suppress frequent channel switching due to a difference in transmission power depending on a band used by a base station.
[0020]
[Means for Solving the Problems]
(1) In the present invention, the received electric field strength of the first signal received from the communicating base station, and the received electric field of the second signal received from the base station different from the communicating base station via the control channel. A control for controlling to perform a handover request when the received field strength of the second signal is larger than the received field strength of the first signal by a predetermined level or more. In the mobile station provided with a unit, the control unit uses a mobile station characterized in that the first signal is a signal received via a control channel of the base station in communication.
[0021]
The mobile station according to the present invention compares the reception levels of the first signal transmitted from the base station in communication through the relocation channel with the second signal transmitted from the different base station through the control channel, A handover request is made when the received electric field strength of the signal is greater than a predetermined level by the received electric field strength of the first signal. Then, after a handover to a base station different from the base station in communication is executed in response to the handover request, a signal transmitted on the control channel from the base station that has newly become a communication partner is immediately transmitted. The received electric field strength of the signal transmitted from the base station via the control channel is compared.
[0022]
Therefore, the channel (in this case, the control channel) through which the signal to be compared with the received electric field strength is transmitted does not change. For example, even if there is an imbalance between the transmission power of the control channel and the communication channel in each base station Can be prevented.
[0023]
(2) In the present invention, the control unit further controls the control signal of the communicating base station only when the communication channel used with the communicating base station belongs to a predetermined band. The mobile station is characterized in that it is a signal received through the network.
[0024]
Therefore, for example, when the communication channel belongs to the analog band, the mobile station determines that there is a possibility that the transmission power of the control channel and the communication channel may be unbalanced in the communicating base station. However, if the speech channel does not belong to the analog band, it is not necessary to measure the received electric field strength of the signal received by the control channel of the base station in communication.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram showing a configuration of a mobile station according to the present invention. This mobile station is configured as a mobile phone used in, for example, a PDC (Personal Digital Cellular) system.
[0026]
In FIG. 1, 1 is a mobile station, 2 is a radio transmission / reception unit, 3 is a memory, 4 is a display unit, 5 is an operation unit, 6 is a control unit, and 7 is an antenna.
[0027]
In the mobile station, when the user of the mobile station 1 operates the key button of the operation unit 5 to make a call, the operation information is input to the control unit 6. The control unit 6 controls the wireless transmission / reception unit 2 to transmit a call setting message from the antenna 7 and exchange a predetermined signal with a base station (this base station not shown is X). I do. When the radio channel designation message is received from the base station (X), the control unit 6 controls the radio transmission / reception unit 2 to adjust the reception frequency to the designated frequency and perform a predetermined cycle. After that, a call with another communication apparatus is performed by transmitting and receiving a signal (including voice information and the like) via the call channel of the base station (X).
[0028]
The mobile station 1 not only performs transmission / reception of voice information related to a call, but also receives other bases different from the received electric field strength of the signal received from the base station (X) via the control channel and the base station (X). The received electric field strength of the signal received from the station (here, the base station Y) via the control channel is measured by the wireless transmission / reception unit 2, and the measurement result is given to the control unit 6.
[0029]
The control unit 6 performs transmission / reception processing of voice information and the like, and compares given received electric field strengths. That is, assuming that the reception level of the signal received from the base station (X) via the control channel is Lcx and the reception level of the signal received from the base station (Y) via the control channel is Lcy, Lcy is a predetermined level from Lcx. When the above (this predetermined level may be notified from the base station X, for example, or may be stored in the memory 3 in advance) is large, the control unit 6 causes the wireless transmission / reception unit 2 to Under control, a radio state report (handover request) including the measured received field strength (Lcx, Lcy) is transmitted to the base station (X) via the antenna 1.
[0030]
The base station (X) transfers a radio status report (handover request) to the base station host device composed of the base station controller, mobile switching center, etc. connected to the base station (X), and In accordance with the control of the device, a switching destination radio channel designation message is transmitted to the mobile station, and the mobile station control unit 6 performs radio transmission / reception so as to switch the reception frequency to the frequency designated by the received switching destination radio channel designation message. The receiving unit 2 is controlled.
[0031]
As a result, the mobile station has performed a so-called handover for switching the communication destination base station from communication with the base station (X) to communication with the base station (Y).
[0032]
Even after handover, the mobile station similarly receives the received field strength (Lcy) of the signal received from the base station (Y) via the control channel and the received field strength of the received signal from the base station (X) via the control channel. (Lcx), and when Lcx is greater than Lcy by a predetermined level or more, the wireless transmission / reception unit 2 is controlled and the wireless state report including the measured received field strength information (Lcx, Lcy) (handover request) Is transmitted to the base station (Y) via the antenna 1 to perform handover.
[0033]
As described above, in the present invention, the transmission condition of the radio status report (handover request) that triggers handover is controlled from the received field strength of the signal received from the communicating base station via the control channel and from the other base station. Each base station requests frequent handovers and switches channels even when there is an imbalance between the control channel and the speech channel at each base station because it is based on a comparison with the received field strength of the signal received via the channel. Can be prevented from occurring frequently.
[0034]
When the mobile station receives a radio channel designation message from the base station (X), the channel designated by this message is a predetermined band (for example, an analog band), and the control channel of the base station (X) is Only when it is out of a predetermined band (for example, digital band), Lcx is measured and compared with the Lcy, and the channel specified by this message is out of the predetermined band (for example, digital band) If the control channel of the station (X) is out of a predetermined band (for example, digital band), it is received via the call channel, which is the channel used for communication with the base station (X) as in the conventional case. It is also possible to measure the received electric field strength (Ltx) of the signal and compare it with the Lcy. Thereby, the measurement time of Lcx can be limited.
[0035]
Whether or not the designated channel is a predetermined band (for example, analog band) is determined by storing channel information belonging to the analog band in the memory 3 in advance and designated by a radio channel designation message from the base station. This is possible by determining whether or not the channel matches channel information belonging to the analog band stored in the memory 3.
[0036]
The reception electric field strength measurement timing performed by the mobile station will be described with reference to FIG. FIG. 2 is a diagram showing transmission / reception timing in the mobile station.
[0037]
In the figure, R indicates a reception slot in which a mobile station receives information such as a voice signal from a base station via a call channel, and T indicates that the mobile station transmits information such as a voice signal to the base station via a call channel. Indicates a transmission slot. I is an empty slot, during which the received field strength of the signal transmitted from the neighboring base station via the control channel is measured.
[0038]
Therefore, preferably, the control channel of the base station (X), the communication channel, the control channel of the base station (Y), the signal transmitted through the communication channel are received in the empty slots, and the received electric field strength is measured for each. It is desirable to do.
[0039]
FIG. 3 is a processing flow of channel switching (during handover) of the control unit (6 in FIG. 1).
[0040]
In this process, it is assumed that the start by the communication channel (Tch) designated by the base station (X) in the wireless zone where the mobile phone is present is completed (the channel switching is completed) and that the communication is in progress (see FIG. 3 (S1), a communication channel (Tch) band discrimination process is performed, and it is discriminated whether it is a digital band (S2). When the communication channel is a digital band, since it has the same frequency timing as the control channel, it shifts to a normal channel switching standby state (S5 in FIG. 3) and the normal channel switching condition matches (for example, the current communication channel). If the value obtained by adding a certain threshold to the reception level of (Tch) is compared with the reception level of the control channel of the neighboring base station, it matches the condition that the reception level of the control channel of the neighboring base station is higher (see FIG. 3 (S6), a radio status report (handover request) is transmitted to the base station (X), and the designation of the switching destination communication channel from the base station (X) is received (S7).
[0041]
If it is determined in step S2 that the communication channel (Tch) band is an analog band (when it is determined that the frequency timing is different from the control channel), the base station (X ) To measure the reception level (Ltx) of the signal transmitted via the communication channel (Tch), and receive the signal transmitted via the control channel of the neighboring base station at idle timing (I slot in FIG. 3). Measure the level (Lcy)
Ltx + a <Lcy
Is determined (S3 in FIG. 3). Note that Lcy is the reception level of the signal transmitted through the control channel of the base station (for example, Y) other than the base station (X) in the mobile phone, and is desirably the highest. In the above formula, a is a threshold value specified by the base station (X), and is given, for example, 10 dB.
[0042]
If the expression of the step S3 is not satisfied, the measurement of the again received level, to perform a comparison (step S3).
[0043]
On the other hand, if the above equation holds, the reception level (Lcx) of the signal transmitted via the control channel from the base station (X) is newly measured at the reception timing (R) (or already measured). Receive level),
Lcx + a <Lcy
Is determined (S4 in FIG. 3). This a may be the same as a in the expression of step S3. If this equation holds, the process of step S5 is performed to perform a process of switching the current communication channel to the communication channel of the neighboring base station, that is, a handover request. If the expression in step S4 is not satisfied, the reception level is measured and compared again (S3).
[0044]
(Supplementary Note 1) Receiving electric field strength of the first signal received from the communicating base station, and receiving electric field strength of the second signal received from the base station different from the communicating base station via the control channel And a control unit that controls to perform a handover request when the received field strength of the second signal is larger than the received field strength of the first signal by a predetermined level or more. In the mobile station, the control unit uses the first signal as a signal received via a control channel of the base station in communication.
[0045]
(Supplementary Note 2) In the mobile station according to Supplementary Note 1, the control unit transmits the first signal only when the communication channel used with the communicating base station belongs to a predetermined band. A mobile station characterized in that it is a signal received via a control channel of a base station in the middle.
[0046]
【The invention's effect】
According to the present invention, it is possible to suppress frequent channel switching due to a difference in transmission power depending on the band used by the base station. Therefore, in the mobile station in the mobile communication system typified by the mobile phone, the occurrence of call quality degradation, call disconnection, etc. is reduced.
[0047]
Further, according to the present invention, the measurement and reporting of the received electric field strength of the signal received via the control channel of the communicating base station may cause a problem of channel switching due to the difference in transmission power depending on the band used by the base station. This is only necessary when there is a possibility (when a channel of a predetermined band is assigned as a call channel).
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of the present invention.
FIG. 2 is a diagram illustrating transmission / reception timing in a mobile station.
FIG. 3 is a diagram showing a processing flow of channel switching of a control unit.
FIG. 4 is an explanatory diagram of handover control in a conventional mobile communication system.
FIG. 5 is a diagram illustrating an example of a relationship of reference transmission power of each base station.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Mobile station 2 Wireless transmission / reception part 3 Memory 4 Display part 5 Operation part 6 Control part 7 Antenna

Claims (1)

Reception field strength of the received electric field strength of the signal received via the speech channel from a base station in communication, a first control signal received via the control channel from the base station in the communication, the base in the communication A reception field strength measuring function for measuring the reception field strength of the second control signal received from the base station different from the station via the control channel,
When the communication channel used with the base station in communication belongs to a predetermined band, the reception electric field strength of the second control signal is set to the reception electric field strength of the signal received through the communication channel and the first If from the reception field strength of the first control signal over a predetermined level greater, the mobile station characterized by a kite comprising a control unit for controlling to perform a handover request.

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