JP3253419B2 - Mobile communication device and mobile station device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is applied to a mobile communication system using a plurality of frequency bands in a small zone configuration. In particular, it relates to determination of a zone in which a mobile station is located.

[0002]

2. Description of the Related Art A mobile telephone system is known as a typical example of a mobile communication system having a small zone configuration. In such a communication system, a mobile station and a radio base station (hereinafter simply referred to as “base station”)
) For time-division multiple access (TDMA)
A method is used. As the frequency band, the 800 MHz band has been conventionally used, but more recently, the 1.5 GHz band can be used. Became possible.

When a plurality of frequency bands are used as described above, zone determination is performed using a time band not used for communication and using a frequency band different from the frequency band used for the communication. be able to. That is, when the mobile station is 1.5
During a call in the GHz band, the reception level of the 800 MHz band in the frequency zone is measured in a time slot not used for the call, and the zone is determined based on the measurement result. This makes it possible to speed up the zone determination and to distribute the load on the control device of the base station.

[0004] The zone shift detection by the mobile station is performed as follows. That is, the mobile station compares the received electric field level of the wireless channel with which the mobile station is communicating with the received electric field level of the peripheral zone. If the received electric field level of the peripheral zone is higher, it is determined that the zone transfer has been performed.

[0005]

However, when signals are transmitted in a plurality of frequency bands from the base station side, the propagation distance differs depending on the frequency band due to the nature of radio waves. For example, when the propagation distance of the frequency band for zone determination is longer than the propagation distance of the frequency band during communication, the frequency band for zone determination reaches farther, and the reception electric field level at the mobile station is lower than that during communication. It is higher than the frequency band. In such a case, if the reception level is compared directly, the reception level from the neighboring base station is obtained even though the zone where the mobile station is located is actually the radio zone of the base station with which communication is being performed. Is high, it is determined that the zone has been shifted. However, since the frequency band in which communication is actually performed has a short propagation distance, a sufficient reception level cannot be obtained even if communication is performed in a new zone using the frequency band. In order to avoid this, even for radio waves from the same base station, all control channels for a plurality of frequency bands from surrounding zones must be received. Therefore, the power consumption of the mobile station increases.

An object of the present invention is to solve such a problem and to provide a mobile communication device capable of accurately determining a zone where a mobile station is located.

[0007]

A first aspect of the present invention is a mobile communication device, which communicates with a plurality of wireless base stations arranged in a service area and each wireless base station by a time division multiple access method. A mobile station capable of receiving respective radio signals from the communicating radio base station and surrounding radio base stations and measuring its received electric field level; and A mobile communication device including means for comparing an electric field level to determine a zone in which the user is located, wherein a plurality of radio base stations transmit and receive a control channel and a communication channel in a plurality of frequency bands, respectively. The station controls the means for selecting any of a plurality of frequency bands as the transmission / reception frequency and the means for selecting the frequency band so that the received signal is supplied to the means for measuring the received signal in the time slot during communication. In a time slot not used for communication, control means for selecting a frequency band not used for the communication and supplying it to a means for measuring a radio signal from a nearby radio base station, and Means for notifying the measured value of the received electric field level of the radio base station to the radio base station, wherein the radio base station obtains a correction value for the measurement value notified from the mobile station based on the difference in the frequency band. And a correction value notifying unit for notifying the mobile station of the correction value, wherein the determining unit determines the reception electric field level corrected by the correction value from the correction value notification unit and the reception electric field level from the surrounding radio base station. Is included.

[0008] A second aspect of the present invention is an apparatus used as a mobile station in the mobile communication apparatus according to the first aspect, wherein a means for selecting one of a plurality of frequency bands as a transmission / reception frequency and a means for selecting the frequency band are provided. In the time slot during communication, the received signal is supplied to the means for measuring the received signal, and in the time slot not used for communication, a frequency band not used for the communication is selected, and the frequency band from the surrounding radio base station is selected. Control means for supplying a means for measuring a radio signal, and measurement value notifying means for notifying the measured value of the received electric field level from the radio base station of the communication partner to the radio base station, and a correction value from the base station Means for comparing the corrected received electric field level with the received electric field level from the surrounding radio base station.

[0009]

In the mobile station, the received electric field level of the frequency band during communication and the received electric field level of the frequency band for zone determination from the surrounding zone are measured, and the measurement result of the received electric field level of the frequency band during communication is measured. To the base station. The communicating base station obtains a correction value of the electric field level of the communicating wireless channel based on information from the mobile station, and transmits the correction value to the mobile station. As a method of obtaining the correction value, for example, the relationship between the received electric field levels of a plurality of frequency bands may be measured and stored in advance, and may be read out according to information from the mobile station. The mobile station receiving the correction value
The reception electric field level of the wireless channel being communicated is corrected as if a radio wave in the frequency band for zone determination was received, and the corrected electric field level is compared with the reception electric field level of the peripheral zone. At this time, if the received electric field level of the peripheral zone frequency band is higher, the processing of the zone shift is performed, and if the received electric field level is lower, the processing is not performed. Therefore, the mobile station can determine its own serving zone.

[0010]

1 to 3 are diagrams showing a configuration of a mobile radio apparatus embodying the present invention. FIG. 1 shows an arrangement of a mobile station and a base station during communication and their surrounding base stations, and FIG. FIG. 3 shows a relationship between the mobile station and the base station.

The mobile radio apparatus includes a plurality of radio base stations arranged in a service area, and a mobile station capable of communicating with each radio base station by a time division multiple access method.
FIG. 1 shows only base stations 11 to 17 as radio base stations and only mobile station 20 as mobile stations. It is assumed that the mobile station 20 is communicating with the base station 11. Base stations 11-1
7 uses two frequency bands A and B in each zone, and at least one control channel to be used is set for each frequency band of the zone. This control channel is always transmitted at the maximum power that can be set in each base station.

FIG. 3 shows two types of mobile stations 20 and 30 for the base station 11. The base station 11 has two frequency bands A,
Using B, the mobile station 20 can also transmit and receive in frequency bands A and B. On the other hand, the mobile station 30 is a conventional mobile station, and corresponds to the frequency band A only.
And can communicate. The mobile station 20 has frequency band A,
B is a dual mobile station because it is a form in which two mobile stations such as the mobile station 30 that support one frequency band are combined.

FIG. 4 is a diagram showing a control flow of the base station 11 and the mobile station 20 for the mobile station 20 to determine the zone in which the mobile station 20 is located.

The mobile station 20 receives radio signals from the communicating base station 11 and its surrounding base stations 12 to 17 and measures the received electric field level. That is, the mobile station 20 receives the received electric field level of the frequency band during communication (hereinafter referred to as “first received electric field level”) and the received electric field level of the zone determination frequency band from the peripheral zone (hereinafter referred to as “first received electric field level”). The second receiving electric field level).
The measurement result of the first reception electric field level is transmitted to the base station 11. Based on the received first received electric field level, the base station 11 transmits to the mobile station 20 information for converting the received electric field level of the frequency band to the received electric field level of the zone determination frequency band as correction information. . This correction information can be easily transmitted using, for example, a bit for notifying the transmitting mobile station of the transmission power control information of the base station realized by the current technology. Based on this correction information, the mobile station 20 corrects the first received electric field level as if it had received the zone determination frequency band. The mobile station 20 further determines its own zone by comparing the corrected value with the second received electric field level received from the surrounding zone.

FIG. 5 is a block diagram showing an example of the mobile station 20. As shown in FIG. The mobile station 20 includes a modulation circuit 21, a demodulation circuit 22, a frequency synthesizer 23, a reception level measurement circuit 24, a timing generation circuit 25, an encoding circuit 26, a control circuit 27, and a decoding circuit 28.

The modulation circuit 21 modulates the code input from the encoding circuit 26 and transmits the modulated code. The demodulation circuit 22 demodulates the received signal. The frequency synthesizer 23 supplies a local oscillation signal to the modulation circuit 21 and the demodulation circuit 22. The reception level measurement circuit 24 measures the reception power level in the demodulation circuit 22. At this time, the reception level measurement circuit 24 switches the oscillation frequency of the frequency synthesizer 23 under the control of the control circuit 27 so that the radio signals can be received from the base station in communication and the base stations in the vicinity thereof. Measure the received electric field level of. The timing generation circuit 25 reproduces the frame timing from the reception code, and receives the reception level measurement circuit 24 and the encoding circuit 2
6 is controlled. The encoding circuit 26 encodes the information signal input from the outside and multiplexes the information signal together with the control signal from the control circuit 27 into a TDMA frame.
The control circuit 27 controls the operation of the mobile station according to the control information from the base station decoded by the decoding circuit 28, and further compares the received electric field level measured by the received level measuring circuit 24 to It determines the zone in which it is located. The decoding circuit 28 decodes the received signal, separates the received signal into a control signal and an information signal, and outputs the control signal to the control circuit 27.

Here, the frequency synthesizer 23 can select any one of a plurality of frequency bands A and B as a transmission / reception frequency, and the reception level measurement circuit 24 supplies the reception signal to the demodulation circuit 22 in a communication time slot. In a time slot not used for communication, a frequency band not used for communication is selected, and a frequency synthesizer 23 is controlled to supply a radio signal from a peripheral base station to a demodulation circuit 22. The received electric field level at 22 is measured. The measured value is stored in a memory in the control circuit 27. For the measured value of the received electric field level from the base station of the communication partner, the control circuit 27 uses the control channel via the encoding circuit 26 and the modulating circuit 21 to control the base station. Notify stations. The control circuit 27 also receives a correction value of the received electric field level notified from the base station by the control channel via the demodulation circuit 22 and the decoding circuit 28, and corrects the received electric field level from the base station based on the correction value. , And compares the corrected received electric field level with the received electric field levels from the surrounding base stations.

FIGS. 6A and 6B are diagrams for explaining the operation of measuring the reception electric field level in the mobile station, wherein FIG. 6A shows the reception signal of the mobile station, and FIG. 6B shows the reception frequency of the mobile station. The mobile station receives an information signal from a communication partner base station in a frame of frequency F1 belonging to frequency band A, and further receives a common control channel in frequency band B from peripheral base stations in frames of frequencies F2 to F7. More specifically, when the mobile station starts communication, the base station selects one of the frequencies of the common control channel used by the neighboring base stations.
Each one is selected, and the frequencies F2 to F7 are notified to the mobile station. The mobile station receives the signal from the peripheral zone by sequentially switching the reception frequency during the time of the slot not used for communication to the frequencies F2 to F7, and measures the reception electric field level.

FIG. 7 is a diagram for explaining the relationship between the level measurement result at the mobile station and the correction operation. The mobile station measures the received electric field level of the communication channel from the communicating base station and the received electric field level of the common control channel in a frequency band different from that of the communication channel from the peripheral base station. In FIG. 7, the reception electric field level of the communication channel is indicated by a broken line.

FIG. 8 shows an operation sequence between the mobile station and the base station. Here, it is assumed that the mobile station performs communication with the base station on the communication channel of frequency band A, and receives a common control channel from a peripheral base station in frequency band B different from frequency band A.

The mobile station measures a communication channel with the base station in communication and records it in the memory in the control circuit. Further, the mobile station notifies the base station of the measured reception electric field level using the control channel. The base station obtains, from the received electric field level information received from the mobile station, a value for converting the reception level of the frequency band A to the reception level when receiving the radio wave of the frequency B, and notifies the mobile station of this as a correction value. . The mobile station measures a reception electric field level of a common control channel from a peripheral base station using a time slot not used for communication of the mobile station. Further, the reception electric field level of the channel under communication is corrected by the correction value from the base station, and the corrected level is regarded as the reception electric field level from the base station during communication.

Assuming that the level of the received electric field from the second neighboring base station is the highest as shown in FIG.
The level of the received electric field from the second peripheral base station is compared with the level of the received electric field from the base station during communication after the correction. At this time, if the reception electric field level of the base station during the call is higher than the reception electric field level of the peripheral base station, the mobile station determines that it is not a zone shift. If the received electric field level of the base station during a call is lower than the received electric field level of the peripheral base station, the mobile station determines that the mobile station has shifted to the zone.

In the example shown in FIG. 7, the received electric field level from the base station during communication before correction is lower than the received electric field level from the second peripheral base station, and the corrected electric field (solid line) is from the base station during communication. The reception electric field level is higher. In such a case, the correction value of the received electric field level is notified from the base station to the communicating mobile station, so that even if the base station is communicating in frequency band A, the control of the frequency band B of the peripheral base station can be performed. Only by measuring the channel, the mobile station can make an accurate zone transition determination.

That is, if the mobile station is not notified of the correction value at the time of frequency band conversion at the base station, the actual received electric field level from the base station during communication is compared with the received electric field level from the peripheral base station. Therefore, the mobile station determines the second peripheral base station whose received electric field level is higher than that during a call as the destination zone, and switches the zone. On the other hand, if the received electric field level is corrected, the received electric field level from the base station during communication is corrected and becomes higher than the received electric field level from the second peripheral base station, and the received electric field level from the other peripheral base stations is increased. All levels are lower, and the mobile station does not perform a zone transfer.

When converting the frequency band, a value smaller or larger than the actual correction value can be notified to the mobile station. If the mobile station notifies the mobile station of a small value, the mobile station determines that the mobile station has shifted to the zone before the level of the zone boundary, so when traffic is concentrated in a specific area,
Mobile station communications can be distributed to peripheral zones.
For example, when traffic is concentrated in the zone of the base station where the mobile station is located, and the received electric field level from a certain peripheral base station is higher than that of the other peripheral base station, the mobile station sets the zone of the peripheral base station. Move to zone.

Conversely, if a large value is notified to the mobile station, it is not determined that the mobile station has shifted to the zone even if the zone boundary is exceeded to a certain extent. Channel switching to the base station can be suppressed.

In the above embodiment, the case where the base station notifies the mobile station of the correction value and the mobile station corrects the value of the received electric field level has been described as an example. The value of the electric field level can be notified, and the mobile station can use the value as it is. Also, instead of measuring the reception electric field level for all of the communicating base station and the surrounding base stations and then notifying the receiving electric field level to the communicating base station, measuring the receiving electric field level from the communicating base station The present invention can be implemented in the same manner by immediately notifying the base station during communication and measuring the received electric field level from the peripheral base station.

The case where the number of frequency bands is 2 has been described, but the present invention can be similarly implemented in the case where the number of frequency bands is 3 or more.

[0029]

As described above, the mobile communication apparatus of the present invention, when a mobile station is communicating in a certain frequency band, changes the received electric field level from the peripheral base station to a frequency band different from that frequency band. And the electric field level received from the communicating base station is corrected by the difference in the frequency band. As a result, accurate zone determination can be performed.

Also, since it is sufficient to measure the electric field level received from the peripheral base station for one frequency band, it is necessary to consider that when measuring the level for each frequency band, twice as many frames must be received. Therefore, it is possible to reduce the power consumption of the mobile station.

Further, by manipulating the correction value to be notified to the mobile station, it is possible to prevent the traffic distribution of the area from being concentrated on a specific zone, and it is possible to reduce the call loss rate.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a mobile radio apparatus embodying the present invention, showing an arrangement of a mobile station and a base station during communication and base stations therearound.

FIG. 2 is a diagram in which a part of the configuration of FIG. 1 is rewritten.

FIG. 3 is a diagram showing a relationship between a mobile station and a base station.

FIG. 4 is a diagram showing a flow of control of a base station and a mobile station for the mobile station to determine a zone in which the mobile station is located.

FIG. 5 is a block diagram showing an example of a mobile station.

6A and 6B are diagrams illustrating a measurement operation of a reception electric field level in a mobile station, wherein FIG. 6A illustrates a reception signal of the mobile station, and FIG. 6B illustrates a reception frequency of the mobile station.

FIG. 7 is a view for explaining a relationship between a level measurement result in a mobile station and a correction operation.

FIG. 8 is a diagram showing an operation sequence between a mobile station and a base station.

[Explanation of symbols]

 11 to 17 Base station 20, 30 Mobile station 21 Modulation circuit 22 Demodulation circuit 23 Frequency synthesizer 24 Reception level measurement circuit 25 Timing generation circuit 26 Encoding circuit 27 Control circuit 28 Decoding circuit

────────────────────────────────────────────────── (5) References JP-A-4-207534 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 7/24-7/26 113 H04Q 7 / 00-7/38

Claims (3)

(57) [Claims] 1. A wireless base station, comprising: a plurality of wireless base stations arranged in a service area; and a mobile station capable of communicating with each of the wireless base stations by a time division multiple access method. Means for receiving each radio signal from the station and its surrounding radio base station and measuring the received electric field level, and means for comparing the measured received electric field level to determine a zone where the station is located. In the mobile communication device, the plurality of radio base stations are configured to transmit and receive a control channel and a communication channel in a plurality of frequency bands, respectively, and the mobile station selects any one of the plurality of frequency bands as a transmission / reception frequency. And the selecting means are controlled, and in a time slot during communication, the received signal is supplied to the measuring means, and a time slot not used for communication is supplied. Control means for selecting a frequency band not used for the communication and supplying a radio signal from a surrounding radio base station to the above-described measuring means, and measuring a reception electric field level from a radio base station of a communication partner. A measurement value notifying unit for notifying the radio base station of the value, the radio base station obtains a correction value for the measurement value notified from the mobile station based on the difference in the frequency band, and Correction value notification means for notifying the mobile station, wherein the determination means compares the reception electric field level corrected by the correction value from the correction value notification means with the reception electric field level from the surrounding radio base station. A mobile communication device comprising: 2. The mobile communication device according to claim 1, wherein the plurality of frequency bands are 800 MHz and 1.5 GHz. 3. A means for communicating with a radio base station by a time division multiple access method, and receiving a radio signal from a radio base station in communication and a radio base station in the vicinity thereof to receive a radio signal. A mobile station device comprising: means for measuring a level; and means for comparing a measured received electric field level to determine a zone in which the mobile terminal is located. A means for selecting any one of a plurality of frequency bands as a transmission / reception frequency And controlling the selecting means to supply the received signal to the measuring means in a time slot during communication, and to select a frequency band not used in the communication in a time slot not used for communication. Control means for causing the above-mentioned measuring means to supply a radio signal from a peripheral radio base station; and notifying the radio base station of a measured value of the reception electric field level from the radio base station of the communication partner. A mobile station, comprising: a measured value notifying unit, wherein the determining unit includes a unit for comparing a received electric field level corrected by a correction value from the base station with a received electric field level from a peripheral wireless base station. apparatus.