JP2003289563A - Mobile terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely select a base station to which a portable terminal is connected to make a good communication. <P>SOLUTION: A mobile terminal MS1 receives through its antenna 10 radio signals transmitted from a base station BSn. A radio unit 11 converts the radio signals into base band signals and sends them to a receiving power detector 12 and a distance measuring unit 13. A controller 14 compares a power intensity detected by the receiving power detector 12 and a distance from the base station detected by the distance measuring unit 13 with reference values held in a memory 15, and decides whether the base station is capable of radio communication without deteriorating the communication quality. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to C as a communication system.
The present invention relates to a mobile terminal capable of performing wireless communication with at least one of a plurality of installed base stations in a wireless communication system adopting a DMA system.

[0002]

2. Description of the Related Art In a wireless communication system, a mobile terminal is wirelessly connected to an arbitrary base station to enable communication between the mobile terminals, which enables transmission and reception of data such as voice and images between the mobile terminals. It is being appreciated. When the mobile terminal performs wireless communication in this way, it is necessary for the mobile terminal itself to select a base station to be wirelessly connected and execute registration processing for this base station. The base station to be connected is determined by selecting the base station that has output the radio signal indicating the highest power intensity.

[0003]

However, the method as described above, that is, the method of selecting the base station to be connected only by the power strength of the radio signal transmitted by the base station still has a problem to be solved. There is. That is, in a wireless communication system, an area in which a mobile terminal can communicate is subdivided into a large number of areas called cells, and a base station is installed for each cell. Since the power to be transmitted is set accordingly, the mobile terminal may sometimes be able to receive a radio signal transmitted from a distant base station while maintaining sufficient power strength.

In such a case, the mobile terminal may select the base station as the connection destination because it shows the value of the power intensity from the distant base station. Then, the radio signal transmitted from the selected base station can be received with sufficient power strength, but the radio signal transmitted from the mobile terminal to the base station is normally in the base station because the communication distance exceeds the allowable range. Since it cannot be received, a situation arises in which communication cannot be performed at all, or even if communication is possible, the communication quality is extremely poor.

Therefore, according to the present invention, when the mobile terminal selects a base station, the occurrence of deterioration in communication quality due to the selection of a base station that is difficult to receive a radio signal transmitted by the mobile terminal is avoided, and good radio communication is performed. It is an object of the present invention to provide a mobile terminal capable of performing.

[0006]

In order to solve the above problems, the mobile terminal according to the first invention is such that a mobile terminal that performs wireless communication with at least one base station transmits and receives wireless signals. An antenna for performing the operation, a memory for holding the reference values of the power intensity and the distance, a received power detecting means for detecting the power intensity of the radio signal received by the antenna, and a transmission of the base station from the radio signal received by the antenna. Distance measuring means for extracting time and measuring the distance to the base station from the difference from the reception time, the power intensity detected by the received power detecting means and the distance obtained by the distance measuring means are stored in the memory. And a determination unit that determines whether or not the reference values of the power intensity and the distance retained in the are satisfied.

Therefore, in the mobile terminal having the above structure,
Since the power strength of the radio signal transmitted by the base station and the distance to the base station are calculated and it is determined whether the power strength and the distance satisfy a predetermined reference value, the communication quality does not deteriorate. It becomes possible to find a base station. A mobile terminal according to a second aspect of the present invention includes a satellite that transmits a signal relating to position information, a position information server and a base station that are connected to each other through a communication network, and the base station has its own position information. A mobile terminal used in a mobile communication system capable of wirelessly transmitting a first antenna for performing wireless communication with the base station, and a second antenna for receiving a signal from the satellite. An antenna, a memory holding a reference value of power strength and distance, a received power detection means for detecting power strength of a radio signal received by the first antenna, and a received power from the satellite received by the second antenna. From a signal, a phase difference between codes included in the signal is obtained, and position information managing means for making a position information calculation request to the position information server; and position information obtained by the position information server and the base station. A distance measuring means for obtaining a distance to the base station from the received position information of the base station, a power intensity detected by the received power detecting means, and a distance obtained by the distance measuring means are held in the memory. And a determination unit that determines whether the power intensity and the reference value of the distance are satisfied.

Therefore, also with this configuration, the mobile terminal calculates the power strength of the radio signal transmitted by the base station and the distance to the base station, and the power strength and the distance satisfy the predetermined reference value. Since the determination is made, it is possible to find the base station in the position where the communication quality does not deteriorate.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows the configuration of a wireless communication system, which includes three base stations BS1 and BS.
2, BS3 and one mobile terminal MS1 are included. Further, in the figure, areas (cells) C1 to C3 in which the base stations BS1 to BS3 provide radio signal transmission / reception services are shown. For example, when the mobile terminal MS1 exists in the cell C1. The mobile terminal MS1 performs location registration via the base station BS1 and also transmits / receives data including voice and images to / from other mobile terminals, fixed telephones, etc. via the base station BS1.

When the mobile terminal MS1 moves near the boundary between adjacent cells, the received power of the radio signal transmitted from the base station connected at that time becomes weak and falls below a predetermined threshold value. Handover processing is executed to perform wireless communication via the base station. On the other hand, FIG. 2 is a diagram showing a configuration of the mobile terminal MS1, which includes an antenna 10, a radio unit (RF) 11, a received power detection unit 12, a distance measurement unit 13, a control unit 14, and a memory 15. It consists of

Although the mobile terminal MS1 is further provided with a microphone, a speaker, a display, an operating section, etc., they are omitted because they are not necessary for explaining the present invention. In the mobile terminal MS1 of FIG. 2, the antenna 10 is for receiving a radio signal transmitted from the base station BSn (n is 1 to 3) and outputting the radio signal to the base station Cn, and is a housing of the mobile terminal MS1. It can be pulled out from. The wireless unit 11 performs conversion processing between a wireless signal and a baseband signal,
The radio signal received via the antenna 10 is converted into a baseband signal, and conversely, the signal transmitted via the antenna 10 is converted from the baseband signal into a radio signal.

The reception power detection unit 12 receives the baseband signal converted by the radio unit 11 and detects the power intensity from the baseband signal. The distance measuring unit 13 measures the distance to the base station BSn that has transmitted the radio signal received from the baseband signal. In addition, this distance measuring unit 1
The distance measurement in 3 uses a CDMA (Code Division Multiple Access) method in which the entire system is time-synchronized, and the difference between the transmission time at the base stations BS1 to the time received at the mobile terminal MS1 That is, the distance is measured based on the phase difference of the PN code transmitted from the base station BSn.

The control unit 14 controls the entire mobile terminal MS1, and based on the power intensity detected by the received power detection unit 12 and the distance measured by the distance measurement unit 13, the base station BSn.
It also determines whether or not wireless communication can be normally performed between and.
The memory 15 is a non-volatile memory that stores a reference value indicating whether the power intensity of the received wireless signal is a sufficient value and information about a threshold value of the distance that does not deteriorate the communication quality. Next, the operation of this embodiment will be described. Note that here, the transmission power of the base stations BS1 and BS3 has a strength enough to cover the cells C1 and C3, but the transmission power of the base station BS2 is equal to the cell C2 that provides the service.
Has a complicated shape or has a larger area than other cells, and thus has a higher strength. From this, the radio signal transmitted from the base station BS2 is transmitted to the cell C1 served by the base station BS1.
It will be reached while maintaining sufficient power intensity.

First, the user turns on a power switch (not shown).
When the mobile terminal MS1 is controlled to be in the standby state by controlling the radio wave, the radio signal transmitted by each base station BSn is received via the antenna 10. Then, the radio signal received via the antenna 10 is converted into a baseband signal by the radio unit 11, and then sent to the reception power detection unit 12, the distance measurement unit 13, and the control unit 14. The received power detection unit 12 detects the power intensity from the baseband signal sent from the wireless unit 11, and outputs the result to the control unit 14.

On the other hand, the distance measuring unit 13 extracts the transmission time of the base station BSn from the baseband signal sent from the radio unit 11 and obtains the transmission delay time from the reception time of the radio signal at the mobile terminal MS1. The distance from the base station BSn that has transmitted this radio signal is calculated and calculated from the delay time. Then, the obtained distance information is sent to the control unit 14.
This power intensity detection and distance calculation are performed by a plurality of base stations BS.
It is performed on the radio signal transmitted from n.

In addition, which base station BSn the power intensity and the distance from are derived is determined by each base station BSn.
It is determined by the PN code embedded in the wireless signal transmitted by. When the power intensity of the radio signal transmitted by each base station BSn and the distance to the base station BSn are obtained as described above,
The control unit 14 executes the following processing in order to determine to which base station BSn the connection processing is performed. First,
It is determined whether or not the power intensity of the radio signal of each of the base stations BS1 to BS3 is equal to or higher than the reference value stored in the memory 15.

Here, since the mobile terminal MS1 is present in the cell C1 and the transmission power of the base station BS2 is higher than the others as described above, the base station is judged in the strength judgment executed by the control unit 14. The power strength of the radio signal transmitted by BS1 and base station BS2 will satisfy the condition. Subsequently, the control unit 14 determines whether or not the distance notified by the distance measuring unit 13 is within a distance that the wireless signal transmitted by the mobile terminal MS1 can reach with sufficient accuracy.
Similarly, it is performed by comparing with a reference value stored in the memory 15.

Then, the base station BS1 in the vicinity exists within the allowable range, but the base station BS2 exists outside the allowable range. Therefore, the base station BS1 whose calculated distance is within the predetermined allowable range is The connection process is performed under the control of the selected control unit 14. Since the base station to be connected is selected based on the power strength of the received wireless signal and the obtained distance in this way, the wireless signal transmitted by the mobile terminal MS1 is not within the range in which it can be normally received. It is possible to avoid deterioration of communication quality due to selection of a base station.

In the above description, as the process of selecting the base station to be connected, the determination based on the distance obtained after the determination based on the power intensity is performed first. However, on the contrary, after the determination based on the distance is performed. The determination may be performed based on the power intensity. When there are a plurality of base stations that satisfy the two conditions, a base station that transmits a radio signal with high power intensity is selected. Next, another embodiment of the present invention will be described. FIG. 3 is a diagram showing a schematic configuration of a wireless communication system according to another embodiment.
Three base stations BS40, base station BS41, base station BS4
2, communication network 43, and GPS (Global Positioning)
System) processing server 44.

Also, each base station BS40-4 in FIG.
2 is a GPS receiver 4 for acquiring its own position information
01 and the position information calculation unit 402, the mobile terminal 3
0 is an antenna 301 for receiving radio signals transmitted from the base stations BS40 to 42, a GPS antenna 302 for receiving GPS signals transmitted from a satellite (not shown), and radio signals received by the antenna 301. Radio section 303 and GPS antenna 30 for converting the signal into a baseband signal
2, a GPS radio unit 304 that converts the GPS signal received in 2 into a baseband signal, a received power detection unit 305 that detects the power intensity of the radio signal received by the antenna 301, a control unit 306 that controls the operation of the mobile terminal 30, and It has a memory 307 that holds thresholds related to power intensity and distance.

In each of the base stations BS40 to 41, the GPS signal transmitted by the satellite is received via the GPS receiving section 401, and the position information calculating section 402 calculates the position information, and the calculated position is calculated. Information is converted into a wireless signal and wirelessly transmitted. Next, the operation of the wireless communication system having the above configuration will be described. First, as the user moves while using the mobile terminal MS30, the distance from the currently connected base station BS40 is increased, and the power intensity of the radio signal transmitted from this base station BS40 is weakened. Base station (base station BS41 or base station BS4
It is determined that a handover to 2) is necessary.

Then, the base station BS41 and the base station BS
A base station to be handed over is selected based on a radio signal transmitted by 42 and a GPS signal transmitted by a satellite (not shown). First, the radio signals transmitted from the base stations 41 and 42 are received via the antenna 301, and the GPS signals transmitted from the satellites are received via the GPS antenna 302. The wireless signal received via the antenna 301 is sent to the wireless unit 303, converted from the wireless signal to a baseband signal, and sent to the received power detection unit 305 and the control unit 306.

The received power detection unit 305 detects the power intensity of the radio signal from the baseband signal received from the radio unit 303 and notifies the control unit 306 of the result. When the power intensity is received from the received power detection unit 305, the control unit 306 determines whether the power intensity is equal to or higher than a preset intensity, and if it is equal to or higher than the preset intensity, the candidate base station of the connection destination is determined. On the contrary, when the strength is less than or equal to the set strength, it is determined that the connection destination is not a candidate. Then, each PN code transmitted by the base station BS41 and the base station BS42 is extracted from the baseband signal received from the wireless unit 303,
Correlate the power intensity with the base station.

On the other hand, G received by the GPS antenna 302
The PS signal is converted into a baseband signal by the GPS radio unit 304 and sent to the control unit 306. Control unit 306
When the baseband signal converted by the GPS radio unit 304 is received, extracts the code (satellite code) indicating the satellite that transmitted the GPS signal from the baseband signal and obtains the phase difference of the satellite code. The calculation of the phase difference of the satellite code needs to be performed for at least three satellites. When the phase difference of the satellite code is obtained in this way, the control unit 306 acquires the position information of itself,
A position information calculation request is made to the GPS processing server 44.

That is, the phase difference of the satellite code obtained by the control unit 306 is converted into a radio signal by the radio unit 303 and then the base station BS currently connected via the antenna 301.
Sent to 40. The base station 40 uses the mobile terminal MS30.
When it receives the wireless signal transmitted by, the wireless signal is converted into an analog signal or a digital signal in order to match the signal format of the communication network 43, and the converted analog signal or digital signal is sent to the GPS processing server 44. Is transmitted to the communication network 43.

When this signal is received by the GPS processing server 44, position information of the mobile terminal MS30, that is, latitude and longitude is calculated from the phase difference of the satellite code included in the signal.
The position information of the mobile terminal MS30 obtained by the GPS processing server 44 is sent to the base station BS40 via the communication network 43, converted into a radio signal by the base station BS40, and received by the antenna 301 of the mobile terminal MS30. It Antenna 3
The wireless signal received at 01 is similarly converted into a baseband signal by the wireless unit 303 and sent to the control unit 306.

When the control section 306 acquires the position information from this baseband signal, the reception power detection section 3 as described above.
The base station BS41 and the base station BS42 detected in step 05 compare the power intensity of the radio signal with the threshold value stored in the memory 307 to determine whether the condition is satisfied. The distance is calculated from the respective position information transmitted by the base station BS42 and the position information of the mobile terminal MS30 obtained by the GPS processing server 44, and whether the calculated distance satisfies the condition stored in the memory 307. Make a decision.

As a result, the base station BS41 in the vicinity satisfies the conditions of the power strength and the distance, and is selected as the handover destination base station. That is, also in this embodiment, not only the power strength at the time of receiving the radio signal transmitted by the base station but also the distance between the mobile terminal and the base station using the GPS system is referred to select the base station to be connected. Therefore, it is possible to avoid selection of a base station that causes deterioration of communication quality.

[0029]

As described above, according to the present invention, each base station transmits by selecting the base station when the power switch of the mobile terminal is turned on or selecting the base station during the handover process. Combined with the power strength at the time of receiving the wireless signal,
Since the base station is selected on the basis of the calculated distance between the base station and the mobile terminal, it is possible to select the base station that is difficult to receive the radio signal transmitted by the mobile terminal with sufficient power strength. Since it disappears, it is possible to avoid deterioration of communication quality due to selection of a base station.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a wireless communication system including a base station and a mobile terminal.

FIG. 2 is a diagram showing a configuration of a mobile terminal according to the exemplary embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a wireless communication system according to another embodiment of the present invention.

[Explanation of symbols]

MS1 ... Mobile terminal BS1 to 3, BS40 to 42 ... Base station C1-3 ... cell 10,301 ... Antenna 11,303 ... Radio section 12,305 ... Received power detector 13 ... Distance measuring unit 14,306 ... Control unit 302 ... GPS antenna 43 ... Communication network 44 ... GPS processing server

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Claims (3)

[Claims] 1. A mobile terminal for performing wireless communication with at least one base station, an antenna for transmitting and receiving a wireless signal, a memory for holding reference values of power intensity and distance, Received power detection means for detecting the power intensity of the radio signal received by the antenna, and the transmission time of the base station is extracted from the radio signal received by the antenna, and the distance to the base station is measured from the difference from the reception time. Distance measurement means, and determines whether the power intensity detected by the received power detection means and the distance obtained by the distance measurement means satisfy the power intensity and the reference value of the distance held in the memory. A mobile terminal comprising a determination means. 2. A mobile communication system comprising a satellite transmitting a signal relating to position information, a position information server and a base station connected to each other through a communication network so that the base station can wirelessly transmit its own position information. A mobile terminal used in the system, comprising: a first antenna for performing wireless communication with the base station; a second antenna for receiving a signal from the satellite; From the satellite received by the second antenna, the received power detection means for detecting the power intensity of the radio signal received by the first antenna, Position information managing means for obtaining the phase difference between the codes, and requesting the position information server to calculate the position information, and the position information obtained by the position information server and the base station transmitted from the base station. Distance measuring means for obtaining the distance to the base station from the position information, power intensity detected by the received power detecting means and distance obtained by the distance measuring means are the power intensity and the distance held in the memory. And a determination unit that determines whether or not the reference value is satisfied. 3. A base station determination that determines, when the determining unit determines that the power intensity and the distance satisfy the reference value, a base station that has transmitted a radio signal that satisfies the reference value, as a candidate for a connection destination. The mobile terminal according to claim 1, further comprising means.