JP4637798B2 - Communication apparatus and communication method - Google Patents

Description

  The present invention relates to a communication apparatus and a communication method which have a transmission / reception function corresponding to a plurality of communication methods and perform communication by any one of communication methods according to information related to the amount of data received within a predetermined period.

In recent years, the cdma2000 1x-EV DO system is known as a next-generation high-speed wireless communication system.
The above cdma2000 1x-EV DO method is a standardized version of the HDR (High Data Rate) method, which is an extension of the cdma2000 1x method. In the ARIB industry, Std.T-64 1S-2000 CS0024 “cdma2000 High Rate Packet Data Cdma2000 1x system that is standardized by the Air Interface Specification, and has expanded ARIB T-53 in Japan, EIA / TIA / IS-95, etc. in North America, Korea, etc., and is compatible with the third generation system (3G) Is a method aimed at further improving the communication speed by specializing in data communication.
In cdma2000 lx-EV DO, EV means Evolution and DO means Data only.

  In the cdma2000 1x-EV DO method, when the radio wave condition of the terminal is good by switching the modulation method of the data transmitted from the base station to the terminal based on the information notifying the radio wave condition received from the mobile terminal It is possible to use a high-speed data transmission rate with low error tolerance but a low-speed data transmission rate with high error tolerance when the radio wave condition is poor.

  In the cdma2000 1x-EV DO system downlink direction (direction from the base station to the mobile terminal), the time is divided in units of 1/600 seconds, and communication is performed with only one mobile terminal within that time. Time division multiplex access (TDMA), which communicates with a plurality of mobile terminals by switching partner mobile terminals according to time, is employed. As a result, it is possible to perform data transmission with optimum power to each mobile terminal, and the data communication speed for the mobile terminal can be maximized.

By the way, the cdma2000 1x-EV DO system described above has a characteristic that the reception state varies greatly depending on the environmental conditions. That is, high-speed communication of up to 2.4 Mbps can be realized in a place where the radio wave condition (for example, reception electric field strength, carrier-to-interference ratio = CIR) is good, but the communication speed is reduced to about several tens of kbps in a place where reception is bad. There are drawbacks.
Therefore, in places with good reception conditions, downloading of a relatively large amount of data can be completed comfortably in a short time, but the radio wave condition is poor and only a low downlink data communication speed can be obtained. If the download of a relatively large amount of data is started in some circumstances, it will take a long time to complete the data download, and there is a problem that it is not possible to provide an environment that can provide sufficient services to users. . In this case, the communication time becomes longer and the communication cost becomes higher.

  In addition, when downloading services such as downloading video data and music data while playing back these data in parallel (streaming playback of video and music), the downlink data communication speed of a predetermined value or higher is usually used. However, if the required downlink data communication speed cannot be obtained at this time, there may be effects such as image quality, sound quality degradation, video stoppage, sound interruption, etc., and sufficient service quality can be obtained. There was a problem that it was not possible.

On the other hand, if there are multiple other communication devices with better radio wave conditions than the local station even though the radio wave condition described above is good, Thus, since the channel capacity for data transmission is preferentially allocated, a relatively low data rate will continue.
In such a case, although it is indicated that the radio wave condition is good on the display screen of the mobile terminal, it is impossible to receive data as expected, which gives the user distrust. There was also a problem that could be.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a communication device and a communication method capable of always performing stable data communication.
Specifically, it is equipped with a transmission / reception circuit corresponding to the cdma20001x-EV DO method capable of high-speed data communication specialized for the above-mentioned data communication and the above-mentioned cdma2000 1x method, and in data communication by the cdma2000 1x-EV DO method Communication that can always perform stable data communication by switching the communication method to the cdma2000 1x method when the information related to the amount of data received within the predetermined period is less than the predetermined threshold for a predetermined period. An apparatus and a communication method are provided.

In order to achieve the above object, the following means were adopted.
The communication device according to the present invention includes a receiving unit that receives a radio signal from a base station, and a first predetermined predetermined value when a value indicating a radio wave intensity of the radio signal received by the receiving unit exceeds a predetermined value. A determination unit that determines whether or not a state in which a data amount received from the base station via the reception unit within a period is equal to or less than a preset threshold value continues for a second predetermined period; and the data amount Switching means for switching from one communication method adopted by the base station to another communication method adopted by another base station when a state equal to or less than the threshold value continues for the second predetermined period. It is characterized by comprising.

According to such an invention, any one communication method is selected from a plurality of communication methods installed based on information relating to the amount of data received within a predetermined period, and communication is performed using the selected communication method.
Thus, by selecting a communication method based on information (for example, reception data rate) related to the amount of data actually received within a predetermined period, rather than selecting a communication method to be adopted based on the radio wave condition. For example, when there are multiple communication devices with better signal conditions than the own station even though the signal condition is better, channels are allocated to these other communication devices, and the data as you wish Even in a state where it is not possible to receive the signal, it is possible to escape from this state, so that it is always possible to accurately grasp whether or not optimum communication can be performed by the currently employed communication method.
As a result, it is possible to always provide stable data communication of a certain quality or higher.

In addition, when performing data communication, priority is given to the cdma2000 1x-EV DO method, which can achieve the fastest data rate as one communication method, so that comfortable data communication can be achieved with this cdma2000 1x-EV DO method. Even when the amount of data received by the cdma2000 1x-EV DO method has been reduced and continues for a specified period, it is at least required to perform comfortable data communication by switching to another communication method. Ensure data communication speed.
As a result, it is possible to provide a communication device that can always perform data communication of a certain quality or higher.
In addition, by adopting a method such as the cdma2000 1x method in which a predetermined radio channel is assigned to each terminal as another communication method, a channel is assigned to another terminal even though the radio wave condition described above is good. Therefore, it is possible to continue comfortable communication while maintaining an optimum transmission rate.

The communication method according to the present invention includes a step of receiving a radio signal from a base station, and a value indicating a radio field intensity of the received radio signal exceeding a predetermined value, the first predetermined period includes for the amount of data received from the base station, the steps of the state is less than the threshold value which is set in advance to determine whether or not to continue the second predetermined time period, the said amount of data, the less than the threshold value state is the first And a step of switching from one communication method adopted by the base station to another communication method adopted by another base station when the second predetermined period is continued .

  The communication apparatus of the present invention is called PDA (Personal Digital Assistants: personal information equipment) in addition to a mobile phone such as a so-called CDMA (Code Division Multiple Access) system or PDC (Personal Digital Cellular System) system. Including portable terminals. Here, in the case of a PDA, a caller (incoming call, communication) process described below, which is a feature of the present invention, can be performed even if the communication means is connected from the outside in addition to the communication means built-in. What is performed in the above is included in the present invention.

  According to the communication apparatus of the present invention, one of the plurality of installed communication methods is selected based on information related to the amount of data received within a predetermined period, and communication is performed using the selected communication method. . In this way, the communication method is selected based on the information related to the amount of data actually received within the predetermined period, rather than selecting the communication method to be adopted based on the radio wave state. Nevertheless, even when data cannot be received as expected, switching the communication method makes it possible to get out of the bad reception data rate, and always provide stable data communication of a certain quality or higher. It becomes possible.

In addition, when performing data communication, priority is given to the cdma2000 1x-EV DO method, which can achieve the fastest data rate as one communication method, so that comfortable data communication can be achieved with this cdma2000 1x-EV DO method. Even if the information related to the amount of data received within a predetermined period is reduced for a predetermined period by the cdma2000 1x-EV DO system, switching to another communication system enables comfortable data communication. Ensure the minimum required data communication speed to do.
As a result, it is possible to provide a communication device that can always perform data communication of a certain quality or higher.

  In addition, by adopting a method such as the cdma2000 1x method that assigns a radio channel to each terminal as another communication method, a channel is assigned to another terminal even though the radio wave condition described above is good. Since the state can be avoided, comfortable communication can be continuously performed while maintaining the optimum transmission rate.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an internal configuration when a mobile phone is taken as an example of a communication apparatus according to an embodiment of the present invention.
As shown in FIG. 1, the mobile phone according to this embodiment includes an antenna 1, a multi-reception circuit 3 including a plurality of reception circuits respectively corresponding to a plurality of different wireless communication schemes, and signals output from the multi-reception circuit 3. A signal processing circuit 5 that performs digital processing, a CPU 7 that controls each part of the terminal, a multi-transmission circuit 8 that includes a plurality of transmission circuits respectively corresponding to a plurality of different wireless communication systems, and stores various programs. ROM 10, RAM 11, keypad, operation unit 12 such as a keyboard, display unit 13 including a liquid crystal display panel, etc., and a second predetermined period are preset, and a timer that counts the second predetermined period according to an instruction from the CPU 7 14 is provided.

The multi-reception circuit 3 includes two reception circuits including a reception circuit corresponding to the cdma2000 1x-EV DO system and a reception circuit corresponding to the cdma2000 1x system, and is based on a switching signal input from the CPU 7. The circuit for receiving data from the base station side is switched.
Similarly, the multi-transmission circuit 8 also includes two transmission circuits including a transmission circuit corresponding to the cdma2000 1x-EV DO system and a transmission circuit corresponding to the cdma2000 1x system. Based on this, the circuit for transmitting data is switched.
As described above, the mobile phone according to the present embodiment includes a plurality of reception circuits and transmission circuits respectively corresponding to a plurality of different wireless communication schemes, and these mobile phones receive these according to the amount of data received within a predetermined period. Stable data communication is ensured by switching the communication method.

The ROM 10 stores various programs to be executed by the CPU 7. The CPU 7 loads and executes the programs stored in the ROM 10 to perform various processes. The RAM 11 stores data generated during the process executed by the CPU 7.
It should be noted that an external interface (for example, serial port, parallel port, USB, blue-tooth, infrared communication, 10base-T LAN, etc.) with a personal computer (PC) is further provided so that the mobile phone can be used as a wireless modem. It may be.

Next, the operation of the mobile phone configured as described above will be described.
First, when the user desires to download data, the user operates the operation unit 12 to set information such as a connection destination address necessary for data communication and data to be downloaded. When a download instruction is given by such an operation, the download request information is output from the operation unit 12 to the CPU 7. When the CPU 7 receives the download start request, the CPU 7 outputs to the multi-receiving circuit 3 and the multi-transmitting circuit 8 a switching signal for selecting the cdma2000 1x-EV DO system compatible receiving circuit 31 and transmitting circuit 81, respectively. .
Thereby, the multi-receiving circuit 3 and the multi-transmitting circuit 7 select the cdma2000 1x-EV DO system compatible receiving circuit 31 and the cdma2000 1x-EV DO system transmitting circuit 81, respectively.

  Subsequently, the CPU 7 outputs information related to downloading such as download connection destination access, data to be downloaded, and the like input from the operation unit 12 to the signal processing unit 5. Information related to the download input to the signal processing unit 5 is subjected to digital processing in the signal processing unit 5, and then based on a predetermined modulation scheme by the cdma2000 1x-EV DO scheme compatible transmission circuit 81 of the multi-transmission circuit 8. And is transmitted via the antenna 1 to the cdma2000 1x-EV DO system compatible base station 30 (see FIG. 3) where the line is currently established.

Here, FIG. 3 shows a network configuration diagram including the mobile phone, each base station corresponding to a plurality of different communication systems mounted on the mobile phone, and a central office switch that supervises the plurality of base stations.
In the figure, reference numeral 30 denotes a cdma20001x-EV DO system compatible base station that is currently established with a mobile phone, and reference numeral 50 denotes a cdma2000 1x system compatible base station that exists in an area communicable with the mobile phone. is there. Reference numeral 70 denotes a central office switch that supervises a plurality of base stations corresponding to different wireless communication systems.

When the cdma2000 1x-EV DO system compatible base station 30 (hereinafter abbreviated as “base station 30”) receives information related to the download received from the mobile phone, the cdma2000 1x-EV DO system compatible base station 30 (base station 30) manages this information. To the existing central office switch 70.
The central office switch 70 issues a line connection request to the access destination based on the download information received from the base station 30. Thus, when the access destination responds to the line connection request, a line between the mobile phone and the download access destination is established, and data download is started. That is, download data from the access destination is transmitted to the mobile phone via the central office switch 70 and the base station 30.

At this time, a pilot signal of the base station 30 (a signal indicating a radio wave state between the base station and the mobile phone) is transmitted to the mobile phone together with the download data from the download access destination in a form multiplexed with the data. It will be.
This pilot signal is an important signal for determining the data communication speed performed between the mobile phone and the base station, and is transmitted from the base station 30 every 1/600 seconds in a form multiplexed with download data. . A signal obtained by multiplexing the pilot signal and the download data is input to the cdma2000 1x-EV DO system compatible receiving circuit 31 of the multi-receiving circuit 3 via the antenna 1.

  The cdma2000 1x-EV DO system compatible reception circuit 31 demodulates the multiplexed signal from the received signal in the baseband band by a demodulation system corresponding to the modulation system of the received signal received from the base station 30. In the present embodiment, demodulation is performed by any one of the three demodulation methods of QPSK (quadriphase phase shift keying), 8PSK (8 phase shift keying), and 16QAM (16 quadriphase amplitude modulation).

Then, the reception data demodulated by the cdma2000 1x-EV DO system compatible reception circuit 31 is transmitted to the subsequent signal processing circuit 5.
First, the signal processing circuit 5 despreads the pilot signal and the download data by despreading the spectrum-spread received multiplexed signal received from the multi-receiver circuit 3, and decodes the separated download data. It outputs to CPU7.

On the other hand, the signal processing circuit 5 further calculates Ec / Io (pilot signal strength vs. total received signal strength) based on the pilot signal, and calculates CIR (carrier-to-interference ratio) based on the following equation (1). calculate.
CIR = (Ec / lo) / (1-Ec / lo) (1) Subsequently, the signal processing circuit 5 determines the next reception slot timing (here, 1.66 ms = one slot) based on the calculated CIR. CIR value at 1/600 seconds) is predicted. The prediction method here is not particularly limited, but a method such as linear prediction can be cited as an example. Information indicating the number of slots after which the CIR should be predicted is included in various control signals transmitted from the base station when the mobile phone is powered on.

In this way, when the signal processing unit 5 predicts the CIR at the next reception slot timing, the signal processing unit 5 performs a process of converting the predicted CIR into a DRC value indicating the data communication speed. This is obtained simply by reading a corresponding value by referring to a predetermined conversion table stored in advance in the RAM 11 or the like. Since the DRC (predicted data communication speed) obtained here is a value obtained based on the predicted CIR, it can be said to be the data communication speed at the next reception slot timing. In addition, let the value of DRC obtained here be an estimated data communication speed.
When the signal processing unit 5 obtains the predicted data communication speed by performing the series of processes described above, the signal processing unit 5 transmits this value to the base station.

  On the other hand, data received by the signal processing circuit 5, that is, data received together with the pilot signal from the base station and separated by the signal processing circuit 5 (downloaded data) is input to the CPU 7. In this way, when the CPU 7 acquires the reception data, it is determined whether or not to switch the communication method based on the reception data rate D1 (calculated based on the reception data amount received during a predetermined period set in advance). Communication system switching determination processing is performed. Hereinafter, the communication system switching determination process performed by the CPU 7 will be described with reference to FIG. 2 is repeatedly performed by the CPU 7 at a predetermined timing.

First, the CPU 7 determines whether or not the reception data rate D1 exceeds a threshold value D_LMT stored in advance in the RAM 11 (step SP11 in FIG. 2).
Here, the reception data rate D1 is calculated based on the amount of data received by the mobile phone within the first predetermined period Td [ms].
Note that the amount of data received within the first predetermined period Td [ms] may be purely the amount of data received from the base station or an accurate amount of data calculated on the application, and both indicate received data. If it is a value, there may be some errors. For example, the following four methods can be cited as a method for calculating the reception data rate D1.

1. The reception data rate is obtained by measuring the reception data amount output from the signal processing unit 5 in the first predetermined period Td [ms] and dividing the measured total reception data amount by the first predetermined period Td [ms]. D1 is calculated.
2. The amount of received data in one frame, which is the minimum cycle of wireless communication, is measured, and the received data amount is multiplied by the number N of frames received per second to calculate the instantaneous received data rate. If this process is continued for 1 second, N instantaneous reception data rates are calculated. The average of the N instantaneous reception data rates (average instantaneous reception data rate) is defined as a reception data rate D1. In this case, the first predetermined period Td [ms] = 1 second.
3. When the first predetermined period Td [ms]> 1 second is set, the average instantaneous reception data rate is calculated repeatedly by the second method described above for the first predetermined period Td [ms]. Then, the average of the average instantaneous reception data rate in the first predetermined period Td [ms] is defined as the reception data rate D1.
4). The instantaneous reception data rate itself obtained by the second method described above is regarded as the reception data rate D1. In this case, the first predetermined period Td [ms] = 1 is a period for receiving one frame.

As a result, if the data rate D1 is equal to or lower than the threshold value D_LMT (“NO” in step SP11), the process proceeds to step SP12 to determine whether or not the timer 14 is activated. As a result, if the timer 14 is not activated (“NO” in step SP12), the process proceeds to step SP13, where the timer 14 is activated. As a result, the timer 14 starts measuring the second predetermined period T (ms) set in advance.
On the other hand, if the timer 14 is activated in step SP12 (“YES” in step SP12), the process is terminated as it is.

On the other hand, when the reception data rate D1 exceeds the threshold value D_LMT in step SP11 (“YES” in step SP11), the process proceeds to step SP14 and determines whether or not the timer 14 is activated. As a result, if the timer 14 is activated (“YES” in step SP14), the process proceeds to step SP15, and after resetting the timer 14, the timer 14 is stopped and the process is terminated.
On the other hand, if the timer 14 is not activated in step SP14 ("NO" in step SP14), the process is terminated as it is.

Here, FIG.4 and FIG.5 shows an example of the time transition of the reception data rate D1. 4 and 5, the vertical axis represents the reception data rate or the radio wave state (pilot strength), and the horizontal axis represents time. In both figures, the radio wave condition Ph always exceeds T_Cir, which is a threshold value that can ensure comfortable data communication.
As shown in both figures, when the reception data rate D1 falls below the threshold value D_LMT at time t1, the CPU 7 starts the timer 14 and starts measuring a predetermined period T (ms) from here.
Then, as shown in FIG. 4, before the predetermined period T (ms) has elapsed from time t1 when the reception data rate D1 becomes equal to or lower than the threshold value, that is, when it becomes equal to or higher than the threshold value D_LMT again at time t2, that time (time t2) The timer 14 is reset and stopped.
On the other hand, as shown in FIG. 5, when the state in which the reception data rate D1 is equal to or less than the threshold value D_LMT continues for a predetermined period T (ms), the timer 14 is timed up when the predetermined period T (ms) elapses. Is notified to the CPU 7. Specifically, a signal indicating that the timer has expired is output to the CPU 7.

  When the CPU 7 receives the signal, it determines that comfortable data communication cannot be performed, determines switching from the cdma2000 1x-EV DO system to the cdma2000 system, and performs the wireless communication system switching process described below.

  First, the CPU 7 outputs communication method switching instruction information to the signal processing unit 5. The output communication method switching instruction information is encoded by the signal processing unit 5, further modulated based on a predetermined modulation method by the cdma2000 1x-EV DO method compatible transmission circuit 81 of the multi-transmission circuit 3, and passes through the antenna 1. Then, it is transmitted to the base station 30 with which communication is currently established.

The base station 30 transmits information from the mobile phone to the central office switch 70. When receiving the communication system switching instruction information from the base station 30, the central office switch 70 acquires information on the cdma2000 1x system compatible base station associated with the base station 30, that is, information on the base station 50. Is transmitted to the base station 30.
Here, the exchange 70 stores the information of the base stations that can be switched to each other when the base station is switched between the respective communication methods within the range of the base station managed by the own station. Base station table. When the communication system switching instruction information is received from the base station under its management, the communication system switching instruction information is referred to this table, so that other communication stations corresponding to the base station that has transmitted the communication system switching instruction information to the authorities are referred to. Base station information corresponding to the communication system is acquired, and this base station information is transmitted to the transmission destination of the communication system switching instruction information.
Further, when the central office exchanges base station information corresponding to another communication method to the base station, data transmission to the base station is stopped.

When receiving information on the base station 50 from the central office switch 70, the base station 30 transmits this information to the mobile phone.
With this processing, the information of the base station 50 is demodulated by the cdma2000 1x-EV DO system compatible receiving circuit 31 via the antenna 1 of the mobile phone, subjected to predetermined digital processing by the signal processing circuit 5, and sent to the CPU 7. Entered. When the CPU 7 acquires the information of the base station that newly starts communication, the cdma2000 1x system-compatible receiving circuit, cdma2000 1x, is sent to the multi-receiving circuit 3 and the multi-transmitting circuit 8 in order to start communication with the new base station 50. A switching signal for switching to the system transmission circuit is output.
Thereby, the multi-reception circuit 3 switches from the cdma2000 1x-EV DO system compatible reception circuit 31 to the cdma2000 1x system compatible reception circuit 32, and similarly, the multi-transmission circuit 8 switches from the cdma2000 1x-EV DO system compatible transmission circuit 81 to cdma2000 1x. Switch to the system compatible transmission circuit.

Then, the CPU 7 performs various processes for establishing a line with the cdma2000 1x system compatible base station 50 which is a base station that newly starts communication. Thus, when a line with the cdma2000 1x system compatible base station 50 is established, the base station 50 transmits information indicating that the line has been established with the mobile phone to the central office switch 70. When the central office 70 recognizes that the line with the base station 50 has been established, it resumes the data download to the mobile phone that has been suspended via the base station 50.
Thereby, the switching of the communication method is completed, and the data download by the cdma2000 1x method via the base station 50 is started.

  Note that the series of processes related to the switching of the data communication method described above is a process that is necessary only during a period during which data communication is performed, and thus the CPU 7 finishes the comparison process between the received data rate D1 and the threshold value D_LMT. After that, it is determined whether or not data communication is continued, and when the data communication is completed, a series of processes related to the switching of the data communication system described above, that is, the communication system switching determination process shown in FIG. finish.

As described above, in the present embodiment, it is assumed that data communication is performed using the cdma2000 1x-EV DO method. However, the cdma2000 1x-EV DO method depends on factors such as the location and other communication devices existing in the vicinity. If the received data rate does not show the value you expect, even though the radio wave reception strength by the method shows a value that allows comfortable data communication, the comfortable data communication environment is Judging that it cannot be provided, switch the communication method to cdma2000 1x method, which is another communication method, and ensure the minimum data communication speed.
In this way, cdma2000 1x-EV DO, which aims to allocate channels to terminals with better radio conditions and perform data transmission at high speed, always assigns channels to all terminals in cdma2000 1x. Therefore, if the radio wave condition is good, comfortable data communication can be ensured even by the cdma2000 1x method.

  In the above description, both the cdma2000 1x-EV DO system compatible base station 30 and the cdma2000 1x system compatible base station 50 are arbitrarily switched within the same wireless communication system range as the user moves. And That is, normal handover is performed by movement of the communication device.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design and the like within a scope not departing from the gist of the present invention.

For example, in the above-described embodiment, the multi-reception circuit 3 and the multi-transmission circuit 8 are each provided with a reception circuit and a transmission circuit corresponding to the cdma2000 1x-EV DO system and the cdma2000 1x system. However, the present invention is not limited thereto, and a receiving circuit and a transmitting circuit using other wireless communication methods may be adopted.
That is, a receiving circuit and a transmitting circuit corresponding to a wireless communication system other than the wireless communication system may be provided in place of the receiving circuit and the transmitting circuit, and other wireless communication systems may be provided in the receiving circuit and the transmitting circuit. It is also possible to add a receiving circuit and a transmitting circuit corresponding to.

  Also, the pilot signal transmitted from the base station is information that is always transmitted from the base station every predetermined period regardless of whether or not the communication apparatus performs data communication. Since the switching of the wireless communication system during communication is the gist of the invention, the description of the control state when data communication is not performed is omitted.

It is a block diagram which shows an internal structure at the time of mentioning a mobile telephone as an example as a communication apparatus concerning one Embodiment of this invention. It is a flowchart which shows the communication system switch determination process which concerns on one Embodiment of this invention. It is a figure which shows the network structure which concerns on one Embodiment of this invention. It is a figure which shows an example of the time transition of a reception data rate. It is a figure which shows an example of the time transition of a reception data rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Antenna, 3 ... Multi-reception circuit, 5 ... Signal processing circuit, 7 ... CPU, 8 ... Multi-transmission circuit, 10 ... ROM, 11 ... RAM, 12 ... Operation part, 13 ... Display part, 14 ... Timer, 30 ... cdma2000 1x-EV DO system compatible base station, 31 ... cdma2000 1x-EV DO system compatible receiver circuit, 32 ... cdma2000 1x system compatible receiver circuit, 50 ... cdma2000 1x system compatible base station, 70 ... station switch, 81 ... cdma2000 1x- EV DO system compatible transmitter circuit, 82 ... cdma2000 1x system compatible transmitter circuit

Claims (2)

Receiving means for receiving a radio signal from the base station;
The amount of data received from the base station via the receiving unit within a first predetermined period when the value indicating the radio field intensity of the radio signal received by the receiving unit exceeds a predetermined value is set in advance. Determining means for determining whether or not the state that is equal to or less than the threshold value that is continued for a second predetermined period;
Switching means for switching from one communication method adopted by the base station to another communication method adopted by another base station when the data amount is not more than the threshold for the second predetermined period. When,
A communication apparatus comprising: Receiving a radio signal from a base station;
When the value indicating the radio field intensity of the received radio signal exceeds a predetermined value, the amount of data received from the base station within a first predetermined period is not more than a preset threshold. Determining whether to continue for a second predetermined period;
A step of switching from one communication method adopted by the base station to another communication method adopted by another base station when the state of being equal to or less than the threshold value continues for the second predetermined period with respect to the data amount; ,
A communication method comprising:

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