JP3622725B2 - Mobile communication system and mobile radio terminal - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mobile communication system and a mobile radio terminal, and more particularly to a mobile communication system for controlling power control of a base station that performs radio communication with a mobile radio terminal such as a mobile phone and a mobile radio terminal used therefor About.
[0002]
[Prior art]
In recent years, simple mobile phones (PHS) and mobile phones have been owned by about half of the Japanese population. Such mobile radio terminals such as PHS and mobile phones communicate with the base station in the area of the base station and communicate with the counterpart terminal via a public network connected to the base station. In the mobile communication system including the mobile radio terminal and the base station, it is desired to expand the area of the base station. In order to expand the area of the base station, it is conceivable to increase the transmission power or improve the antenna accuracy of the mobile radio terminal.
[0003]
However, in a CDMA (code division multiple access) type mobile communication system, a single frequency is used from the viewpoint of effective use of frequency resources. It also becomes an interference wave for the area of the station. Therefore, it is indispensable for the CDMA system to control the transmission power of the mobile radio terminal based on a command from the base station.
[0004]
In the wideband CDMA (W-CDMA) system, the transmission power is reduced when the distance between the base station and the mobile radio terminal is short, and when the distance between the base station and the mobile radio terminal is long. For example, in order to increase the transmission power, it is required to perform power control in 70 to 80 stages. In such a case, in order to shorten the adjustment time of the control power as much as possible, the power for controlling the transmission power of the transmitter A method has been proposed in which a control circuit is divided into two and transmission power is controlled by a combination of individual control voltages to the two power control circuits (Japanese Patent Laid-Open No. 2000-332620).
[0005]
On the other hand, for improving the antenna accuracy of a mobile radio terminal, for example, a method according to Japanese Patent Laid-Open No. 8-186432 (name of invention “antenna and portable terminal for communication”) has been conventionally known. In this conventional method, a dielectric layer is formed by laminating a plurality of dielectrics, a main antenna element for transmission and / or reception is sandwiched between one of the dielectric layers, and diversity is sandwiched between the other one layer. By using an antenna in which a receiving antenna element is sandwiched, space is reduced and antenna accuracy is improved.
[0006]
[Problems to be solved by the invention]
However, in the conventional transmission power control method of the base station and the conventional transmission power control method described in Japanese Patent Laid-Open No. 2000-332620, the call quality for the mobile radio terminal in the area of the base station is guaranteed, Call quality is not guaranteed for mobile radio terminals outside the area.
[0007]
Further, Japanese Patent Laid-Open No. 8-186432 discloses an attempt to guarantee the call quality by increasing the reception sensitivity of the antenna. However, in this method, the mobile radio terminal equipped with the antenna is located outside the area of the base station. In some cases, the desired effect cannot be achieved because communication is not possible.
[0008]
The present invention has been made in view of the above points, and provides a mobile communication system and a mobile radio terminal that can guarantee call quality even outside the area of a base station and improve the utilization efficiency of the mobile radio terminal. Objective.
[0009]
Another object of the present invention is to provide a mobile communication system and a mobile radio terminal that can enable mobile communication in a wide area by simply adding a simple circuit to the mobile radio terminal. .
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a first mobile radio communication system of the present invention is a mobile communication system in which a base station performs radio communication with a mobile radio terminal located in the area of the base station. A first detecting means for detecting that the user is outside the area of the base station, and when the first detecting means detects that the user is located outside the area of the base station, the first detecting means is located outside the area of the base station. A first mobile radio terminal having a first transmission means for transmitting a downlink signal indicating that to another mobile radio terminal, and each of the area of the base station and the area of the first mobile radio terminal The second detection means for receiving and detecting the downlink signal transmitted from the first mobile radio terminal, and when the second detection means receives and detects the downlink signal, Added to the pilot channel A second mobile radio terminal having a second transmission means for transmitting an uplink signal whose power control signal is changed to a predetermined value to the base station, and an uplink signal from the second mobile radio terminal The base station transmits the signal to the first and second mobile radio terminals with the transmission power corresponding to the power control signal in the received signal.
[0011]
In the present invention, when the first mobile radio terminal wants to communicate wirelessly with the base station but is located outside the area of the base station, the first mobile radio terminal is located within the area of the base station and the first mobile radio terminal The second mobile radio terminal transmits a downlink signal indicating that it is located outside the area of the base station to the second mobile radio terminal that is also located in the area, so that the second mobile radio terminal Is transmitted to the base station and the transmission power of the base station is controlled to the transmission power corresponding to the power control signal, so that the area of the base station is the first mobile radio. Can be expanded to include terminals.
[0012]
In order to achieve the above object, in the second mobile communication system of the present invention, the second transmission means has a predetermined value that is greater than a value obtained by actually measuring a value indicating the reception quality of the signal from the base station. As a means for transmitting an uplink signal generated by adding a power control signal to a pilot channel when the power value is changed to a bad value to the base station, the base station transmits an uplink signal from the second mobile radio terminal. A signal is received, and the signal is transmitted to the first and second mobile radio terminals with transmission power according to the power control signal in the received signal.
[0013]
In the present invention, the value indicating the reception quality by the second mobile radio terminal is set to a value that is worse than the value actually measured by a predetermined value, so that the base station transmits and receives in an area larger than the previous area. Be controlled.
[0014]
Here, the first detecting means of the first mobile radio terminal is means for detecting that the mobile station is outside the area of the base station when the signal from the base station cannot be received. The value indicating the reception quality of the signal from the base station in the second transmission means of the body radio terminal may be the SIR value.
[0015]
In order to achieve the above object, the mobile radio terminal of the present invention receives a signal from the base station and measures the reception quality when it is in the area of the base station, In the mobile radio terminal that adds a power control signal to the pilot channel and transmits to the base station, controls the transmission power of the base station based on the power control signal, and performs radio communication with the base station. A first detecting means for detecting that the user is outside the area of the station, and being outside the area of the base station when the first detecting means detects that the user is located outside the area of the base station. A first transmission means for transmitting a downlink signal indicating to another mobile radio terminal, a second detection means for receiving and detecting a downlink signal transmitted from the other mobile radio terminal, Outside the area by means of And a second transmission means for transmitting to the base station an uplink signal in which a power control signal added to the pilot channel is changed to a predetermined value when a downlink signal indicating reception is detected. It is what.
[0016]
In the present invention, when it is desired to perform radio communication with a base station but is located outside the area of the base station, another mobile radio terminal located within the area of the base station and also within the area of the own terminal On the other hand, by transmitting a downlink signal indicating that the mobile station is located outside the area of the base station, another mobile radio terminal transmits an uplink signal in which the power control signal is changed to a predetermined value to the base station. Since the transmission power of the base station is controlled to the transmission power corresponding to the power control signal, the area of the base station can be expanded.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a system configuration diagram of an embodiment of a mobile communication system according to the present invention. In the figure, a base station 1 normally transmits and receives data to and from a mobile radio terminal (hereinafter simply referred to as a terminal) 2 located in area A. That is, area A is an area in which base station 1 guarantees call quality. Since the terminal 3 is located outside the area A, wireless communication cannot be performed directly with the base station 1.
[0018]
However, the terminal 3 is located in the area B where the terminal 2 guarantees the transmission / reception quality. In this case, in the present embodiment, the terminal 3 transmits / receives to / from the base station 1 by expanding the call quality assurance area of the base station 1 from A to the area C where the terminal 3 is located by a method described later. Can be performed.
[0019]
FIG. 2 shows a block diagram of an embodiment of a mobile radio terminal according to the present invention. The terminals 2 and 3 shown in FIG. 1 have the same configuration and the configuration shown in FIG. In FIG. 2, the transmitting / receiving antenna 11 is connected to a filter (Fil) 12. The filter 12 includes a reception filter and a transmission filter. An output end of the reception filter is connected to the reception unit 15, and an input end of the transmission filter is connected to the transmission unit 21.
[0020]
The voltage controlled oscillator (VCO) 13 is an oscillator that generates a local oscillation frequency for uplink, and the voltage controlled oscillator (VCO) 14 is an oscillator that generates a local oscillation frequency for downlink. In the DS-CDMA system, there is a difference of 190 MHz in frequency between the uplink and the downlink, and the mobile radio terminals 2 and 3 of the present embodiment are wireless between both the terminal side and the base station side. Two VCOs 13 and 14 are provided for transmission and reception.
[0021]
The demodulator 16 demodulates the received signal. The decoding unit 17 decodes the demodulated signal from the demodulation unit 16. Based on the decoded signal from the decoding unit 17, the power control signal generation unit 18 determines whether another terminal is in the communication quality assurance area of the own terminal, and responds to the determination result. A power control signal is generated. The encoding unit 19 performs encoding by incorporating the power control signal as a control signal having a signal power / noise power (interference power) ratio (SIR) used for transmission power control. The modulation unit 20 modulates the encoded signal from the encoding unit 19 using a predetermined modulation method. The transmission unit 21 converts the modulated signal into a transmission signal having an uplink or downlink transmission frequency based on the local oscillation frequency from the VCO 13 or 14.
[0022]
Next, the operation of this embodiment will be described with reference to FIGS. 1 and 2 and the flowchart of FIG. First, in FIG. 1, it is determined whether or not the terminal 3 requesting mobile communication via the base station 1 is located in the area A of the base station 1 (step S1 in FIG. 3). That is, the terminal 3 having the configuration shown in FIG. 2 supplies a signal received by the transmission / reception antenna 11 to the reception unit 15 through the reception filter in the filter 12, and based on the downlink local oscillation frequency signal from the VCO 14. A downlink received signal is obtained, and the received signal is demodulated by the demodulator 16 and then decoded by the decoder 17. When the decoded signal is obtained, since the signal from the base station can be received, the process of the present invention is not performed, and it is determined that a call is possible (step S2 in FIG. 3), and the process is terminated.
[0023]
Here, as shown in FIG. 1, since the terminal 3 is located outside the area A of the base station 1, the signal transmitted from the base station 1 is not received. I can't get it. In this case, the terminal 3 supplies the signal received by the transmission / reception antenna 11 to the reception unit 15 through the reception filter in the filter 12 and receives the downlink based on the local oscillation frequency signal for downlink from the VCO 14. A signal is obtained, and the received signal is demodulated by the demodulator 16 and then decoded by the decoder 17 to determine whether or not a decoded signal can be obtained (step S3 in FIG. 3).
[0024]
Here, since the signal from another terminal cannot be received when the decoded signal cannot be obtained, the terminal 3 is not located in the area A of the base station 1 or the area of another terminal, so Is determined to be impossible (step S4 in FIG. 3), and the process is terminated. Here, since the terminal 3 is located in the area B of the terminal 2 as shown in FIG. 1, a downlink signal from the terminal 2 is received. Note that whether the downlink signal is from the base station 1 or another terminal 2 can be identified by predetermined identification information.
[0025]
Then, the terminal 3 uses the internal power control signal generator 18 to generate a power control signal (information string) indicating that the terminal 3 is outside the area A of the base station 1. This power control signal is encoded by the encoding unit 19, further modulated by the modulation unit 20, and then supplied to the transmission unit 21, where the downlink transmission signal is based on the downlink local oscillation frequency signal from the VCO 14. (CDMA wave) is obtained. The downlink transmission signal is transmitted from the transmission / reception antenna 11 to the terminal 2 through the transmission filter in the filter 12 (step S5 in FIG. 3).
[0026]
As a result, the terminal 2 having the configuration shown in FIG. 2 receives the downlink transmission signal (CDMA wave) from the terminal 3 by the transmission / reception antenna 11 and supplies it to the reception unit 15, and the downlink local oscillation frequency from the VCO 14. A downlink received signal is obtained based on the signal, and the received signal is demodulated by the demodulator 16 and then decoded by the decoder 17. Since this decoded signal includes a power control signal indicating that the terminal 3 is outside the area A of the base station 1, the terminal 2 determines that the terminal 3 of the transmission source is the area based on the power control signal. Recognizing that it is located outside A and within area B, information based on the recognition is added to the SIR pilot channel usually used for transmission power control and encoded by the encoding unit 19 Thereafter, the signal is modulated by the modulator 20 and supplied to the transmitter 21.
[0027]
At this time, the information based on the above recognition added by the terminal 2 is a value that is worse by a predetermined value than the actual SIR value measured when the terminal 2 normally performs transmission power control with the base station 1. Is a power control signal when it is assumed to be and is added to the pilot channel of the SIR. The transmission unit 21 of the terminal 2 obtains an uplink transmission signal (CDMA wave) based on the uplink local oscillation frequency signal from the VCO 13. The uplink transmission signal is transmitted from the transmission / reception antenna 11 to the base station 1 through the transmission filter in the filter 12 (step S6 in FIG. 3).
[0028]
The base station 1 receives the transmission signal of the uplink frequency transmitted from the terminal 2, extracts the power control signal of the pilot channel in the received signal, varies the transmission power according to the power control signal, A signal having a downlink frequency is transmitted to the terminal 2 in the area A with the transmission power. Here, since the power control signal received by the base station 1 is a signal when the value of the SIR at the terminal 2 is worse than the actual measured value as described above, the base station 1 transmits the transmission power. Is larger than before (step S7 in FIG. 3). As a result, the area where the base station 1 can communicate with the terminal is changed to an area larger than the area A in FIG.
[0029]
After the area of the base station 1 is greatly expanded, the terminal 3 now determines whether or not the terminal 3 is located in the expanded area and whether or not the downlink frequency signal from the base station 1 can be received. (Step S1 in FIG. 3). If the terminal 3 cannot receive the downlink frequency, the control in steps S3, S5, S6, and S7 in FIG. 3 described above is performed again, and the base station 1 further downlinks with a large transmission power with an expanded area. Is transmitted.
[0030]
Thereafter, the same operation as described above is repeated until it is determined in step S1 of FIG. 3 that the terminal 3 is in the area of the base station 1. As a result, the terminal 3 enters the area C of the base station 1 as shown in FIG. That is, the transmission power of the base station 1 is increased until wireless communication with the terminal 3 becomes possible, and the area of the base station 1 is expanded to the area indicated by C in FIG. When the area of the base station 1 is expanded to the area C, wireless communication between the terminal 3 and the base station 1 becomes possible (step S2 in FIG. 3), and the process ends.
[0031]
Thus, according to the present embodiment, even if the terminal 3 is not located in the area A of the base station 1, the terminal 3 is located in the area A of the base station 1 and communicates with the terminal 3. Since the terminal 2 located in the possible area B is interposed, the transmission power of the base station 1 is largely controlled until the area of the base station 1 includes the terminal 3, so that the base station 1 guarantees the call quality. Can communicate with the terminal 3 located outside the area A. Therefore, according to the present embodiment, communication between the base station 1 and the terminal 3 can be performed without increasing the reception sensitivity of the antenna.
[0032]
Furthermore, according to the present embodiment, the base station 1 may have the same configuration as the conventional one, and can be realized by slightly changing the configuration of the mobile radio terminals 2 and 3, so that the cost increase of the mobile communication system is minimized. Can be stopped. In addition, in mobile communication systems such as the PDC system and the CDMA system, the present invention can be applied regardless of the manufacturer or the operator as long as the frame format is the same.
[0033]
Note that the present invention is not limited to the above-described embodiment, and the present invention is also applicable to a mobile communication system in which the uplink frequency and the downlink frequency are the same frequency, such as the W-CDMA TDD scheme. Can do. Further, since the present invention can be realized by changing the configuration of only the mobile radio terminal, it can also be applied to an existing mobile communication system. In the above embodiment, the power control signal included in the signal transmitted from the terminal 2 to the base station 1 is based on the SIR value. However, the signal indicating the reception quality is limited to the SIR value. For example, other signals such as an error rate of the received signal may be used.
[0034]
【The invention's effect】
As described above, according to the present invention, a mobile radio terminal that wants to communicate wirelessly with a base station but is located outside the area of the base station is located within the area of the base station, and the mobile radio terminal By transmitting a downlink signal indicating that the mobile station is located outside the area of the base station to another mobile radio terminal that is also located in the area of the terminal, another mobile radio terminal transmits a power control signal. By transmitting an uplink signal changed to a predetermined value to the base station, and controlling the transmission power of the base station to the transmission power according to the power control signal, the mobile radio terminal of the communication request source Communication with a mobile radio terminal located outside the original area where the base station guarantees the call quality does not increase the reception sensitivity of the antenna of the mobile radio terminal. You can.
[0035]
In addition, according to the present invention, the base station may have the same configuration as the conventional one, and can be realized only by slightly changing the configuration of the mobile radio terminal. Call quality can be guaranteed in the area.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of an embodiment of a system of the present invention.
FIG. 2 is a block diagram of an embodiment of a mobile radio terminal of the present invention.
FIG. 3 is a flowchart for explaining the operation of the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Base station 2, 3 Mobile radio | wireless terminal 11 Transmission / reception antenna 12 Filter 13 Voltage control oscillator (VCO) for uplinks
14 Downlink Voltage Controlled Oscillator (VCO)
15 receiving unit 16 demodulating unit 17 decoding unit 18 power control signal generating unit 19 encoding unit 20 modulating unit 21 transmitting unit A, C area of base station B area of terminal

Claims (6)

In a mobile communication system in which a base station performs radio communication with a mobile radio terminal located in the area of the base station,
A first detecting means for detecting that the area is outside the area of the base station; and when the first detecting means detects that the area is located outside the area of the base station. A first mobile radio terminal having first transmission means for transmitting a downlink signal indicating that the mobile station is located to another mobile radio terminal;
Second detection for detecting and detecting a downlink signal transmitted from the first mobile radio terminal in each of the base station area and the first mobile radio terminal area And a second signal for transmitting an uplink signal in which a power control signal added to a pilot channel is changed to a predetermined value to the base station when the downlink signal is received and detected by the second detection unit. A second mobile radio terminal having a transmission means of
The uplink signal from the second mobile radio terminal is received, and the signal is transmitted to the first and second mobile radio terminals with transmission power corresponding to the power control signal in the received signal. A mobile communication system comprising a base station. The second transmission means adds the power control signal when the value indicating the reception quality of the signal from the base station is changed to a value worse than the actually measured value by a predetermined value to the pilot channel. Means for transmitting the generated uplink signal to the base station, wherein the base station receives the uplink signal from the second mobile radio terminal and controls the power control in the received signal. The mobile communication system according to claim 1 or 2, wherein a signal is transmitted to the first and second mobile radio terminals with transmission power according to the signal. The first detection means is means for detecting that the signal is not received from the base station and is located outside the area of the base station, and from the base station in the second transmission means. 3. The mobile communication system according to claim 1, wherein the value indicating the reception quality of the signal is an SIR value. When in the area of the base station, the signal from the base station is received and the reception quality is measured, and a power control signal is added to the pilot channel based on the measurement result and transmitted to the base station. In the mobile radio terminal that controls the transmission power of the base station based on the power control signal and performs radio communication with the base station,
First detecting means for detecting being outside the area of the base station;
When the first detecting means detects that the mobile station is located outside the area of the base station, a downlink signal indicating that the mobile station is located outside the area is transmitted to another mobile radio terminal. Means for sending
Second detection means for receiving and detecting a downlink signal transmitted from another mobile radio terminal;
An uplink signal obtained by changing the power control signal added to the pilot channel to a predetermined value when the second detection means receives and detects a downlink signal indicating that it is located outside the area. A mobile radio terminal comprising: second transmission means for transmitting to the base station. The second transmission means adds the power control signal when the value indicating the reception quality of the signal from the base station is changed to a value worse than the actually measured value by a predetermined value to the pilot channel. 5. The mobile radio terminal according to claim 4, wherein the mobile radio terminal is means for transmitting the generated uplink signal to a base station. The first detection means is means for detecting that the signal is not received from the base station and is located outside the area of the base station, and from the base station in the second transmission means. 6. The mobile radio terminal according to claim 4, wherein the value indicating the reception quality of the signal is an SIR value.

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