JP2010232930A - Radio communication terminal, radio communication system, and radio communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To adaptively control changeover of a communication method in response to a content. <P>SOLUTION: The radio communication terminal 2 includes: a radio communication part 11 for transmitting/receiving communication data by signal waves; a DU ratio calculation part 46 for calculating a DU ratio representing a ratio of interference waves to the signal waves; a threshold table 31 having a plurality of thresholds varying on a communication data content basis as a plurality of thresholds to be compared with the DU ratio; and a comparison part 47 for selecting a threshold in response to the content of the communication data based on the threshold table 31 to compare the selected threshold with the DU ratio. The radio communication terminal transmits the level of the signal waves and that of the interference waves to a base station 3 based on the result of the comparison. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wireless communication terminal, a wireless communication system, and a wireless communication method for transmitting / receiving communication data to / from a base station using signal waves.

Patent Document 1 discloses a power line communication system.
In this power line communication system, the undesired wave received by the receiver is compared with a reference value. If the undesired wave is larger than the reference value, the communication method is set to coexist, and the undesired wave is less than the reference value. Is set so that communication methods do not coexist.
The power line communication system communicates data under a communication environment restricted by the setting.

JP 2007-221356 A

Even in a wireless communication system using a wireless communication terminal such as a PHS (Personal Handy Phone) terminal, communication interference becomes a problem because a plurality of wireless communication terminals and a plurality of base stations transmit and receive communication data to each other.
Therefore, in the wireless communication system, as in Patent Document 1, it is conceivable to switch the communication method according to the comparison result between the DU (Desire to Undesire) ratio and the reference value.
However, when the communication method is simply switched according to the comparison result between the DU ratio and the reference value, the throughput of communication data between the wireless communication terminal and the base station is uniformly limited.
Therefore, when communication data such as a moving image having a large amount of data is transmitted / received, there is a possibility that sufficient communication performance (throughput) cannot be secured.

  The present invention provides a wireless communication terminal, a wireless communication system, and a wireless communication method that can adaptively control switching of communication methods according to content.

  A wireless communication terminal according to a first aspect of the present invention includes a wireless communication unit that transmits and receives communication data by a signal wave, a DU ratio calculation unit that calculates a DU ratio indicating a ratio of an interference wave to the signal wave, and the DU ratio. A threshold holding unit having a plurality of different thresholds for each content of the communication data, and a threshold corresponding to the content of the communication data from the threshold holding unit, the selected threshold and A comparison unit that compares the DU ratio, and transmits the signal wave level and the interference wave level to the base station based on the comparison result.

  Preferably, a mobility detection unit that detects the mobility of the wireless communication terminal, and a first correction unit that corrects the threshold of the threshold holding unit according to the mobility detected by the mobility detection unit. You may have.

  Preferably, the wireless communication unit transmits / receives communication data to / from one base station selected from a plurality of base stations, and the wireless communication terminal switches the base station to which the wireless communication unit transmits / receives communication data, You may have the 2nd correction part which corrects the threshold value of the said threshold value holding part.

  Preferably, the wireless communication unit transmits / receives communication data to / from a base station in a channel allocated from a plurality of channels, and the DU ratio is smaller than a threshold selected according to the content in the comparison of the comparison unit, A new channel allocation request may be transmitted.

  Preferably, the DU ratio calculation unit calculates a DU ratio indicating the level of the undesired wave with respect to the level of the desired wave from the signal intensity of the desired wave to be received and the signal intensity of the undesired wave. The communication unit, when the DU ratio is larger than a threshold selected according to the content in the comparison of the comparison unit, the signal intensity of the desired wave and the signal intensity of the undesired wave used for calculating the DU ratio You may send it.

  Preferably, the wireless communication terminal selects an adaptive modulation / demodulation unit that adaptively switches a modulation process or a coding rate of the communication data transmitted / received by the wireless communication unit and a comparison unit selected according to the content When the DU ratio is larger than a minimum threshold of the set, the wireless communication unit includes a changing unit that changes a ratio between the signal strength of the desired wave and the signal strength of the undesired wave. When the DU ratio is larger than the minimum threshold of the set selected according to the content in the comparison, instead of the signal intensity of the desired wave and the signal intensity of the undesired wave used for calculating the DU ratio, The signal strength of the desired wave and the signal strength of the undesired wave whose ratios are changed by the changing unit may be transmitted.

  Preferably, the threshold value holding unit holds a plurality of threshold values for each content of the communication data by a table associated with a plurality of modulation schemes or a plurality of coding rates that can be switched in the adaptive modulation / demodulation unit, The changing unit is a threshold for other contents associated with the same modulation scheme or coding rate as the threshold larger than the DU ratio calculated by the DU ratio calculating unit from the table, and is stored in the base station. A threshold having the same value as that obtained may be acquired, and the ratio between the signal intensity of the desired wave and the signal intensity of the undesired wave may be changed so that the DU ratio is equal to or greater than the acquired threshold.

  Preferably, the threshold value table may include a threshold value for a moving image composed of a plurality of pictures and a threshold value for data as a plurality of different threshold values for each content of the communication data.

  A wireless communication system according to a second aspect of the present invention is a wireless communication system that transmits and receives communication data by a signal wave between a wireless communication terminal and a base station, and a DU ratio indicating a ratio of an interference wave to the signal wave DU ratio calculation unit that calculates the threshold value, a threshold value holding unit having a different threshold value for each content of the communication data as a plurality of threshold values to be compared with the DU ratio, and from the threshold value holding unit according to the content of the communication data A comparison unit is provided that selects a threshold value and compares the selected threshold value with the DU ratio, and transmits the signal wave level and the interference wave level to the base station based on the comparison result.

  A radio communication method according to a third aspect of the present invention is a radio communication method for transmitting / receiving communication data between a radio communication terminal and a base station using a signal wave, and a DU ratio indicating a ratio of an interference wave to the signal wave Selecting a threshold value corresponding to the content of the communication data from a threshold holding unit having different threshold values for each content of the communication data as a plurality of threshold values to be compared with the DU ratio; Comparing the threshold with the DU ratio, and transmitting the signal wave level and the interference wave level to the base station based on the comparison result.

  According to the present invention, switching of communication methods can be adaptively controlled according to content.

FIG. 1 is a configuration diagram of a radio communication system according to an embodiment of the present invention. FIG. 2 is a block diagram showing a hardware configuration of the PHS terminal shown in FIG. FIG. 3 is a functional block diagram of the wireless communication system of FIG. FIG. 4 is a diagram illustrating an example of the data structure of the threshold table in FIG. FIG. 5 is an explanatory diagram showing the throughput of a plurality of modulation schemes and coding rates in FIG. FIG. 6 is a flowchart of the processing of the DU ratio calculation unit and the comparison unit in FIG. FIG. 7 is a sequence chart of a communication procedure of the wireless communication system of FIG. FIG. 8 is a flowchart of threshold value table correction processing by the correction unit of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a system configuration diagram of a wireless communication system 1 according to an embodiment of the present invention.
In FIG. 1, a PHS terminal 2 is shown as a wireless communication terminal.
The position estimation system 1 includes a PHS terminal 2, a plurality of base stations 3, a communication network 4, and a server device 5 for moving image distribution.

The base station 3 and the PHS terminal 2 of the position estimation system 1 transmit and receive communication data using an OFDMA / TDD (Orthogonal Frequency Division Multiple Access / Time Division Multiplex) scheme.
The base station 3 and the PHS terminal 2 that transmit and receive communication data by the TDD scheme perform bidirectional communication in units of frames that are composed of, for example, four downlink slots and four uplink slots.
The downlink slot is a slot for transmitting communication data from the base station 3 to the PHS terminal 2.
The uplink slot is a slot for transmitting communication data from the PHS terminal 2 to the base station 3.
In the case of orthogonal frequency division multiple access, a plurality of base stations 3 can assign a plurality of PHS terminals 2 to one slot.

FIG. 1 shows a first base station CS1 and a second base station CS2 as a plurality of base stations 3 that can communicate with the PHS terminal 2.
The zone (microcell) A in which the first base station CS1 communicates with the PHS terminal 2 and the zone (microcell) B in which the second base station CS2 communicates with the PHS terminal 2 are those Adjacent with some overlapping.
Therefore, for example, when the PHS terminal 2 moves from the zone A to the zone B, the position estimation system 1 executes a handover process, and the base station 3 with which the PHS terminal 2 communicates wirelessly changes from the first base station CS1 to the second base station CS2. Switch to

The base station 3 controls communication data transmitted to and received from the PHS terminal 2 by autonomous distributed control.
As shown in FIG. 1, when the zones (microcells) of a plurality of base stations 3 overlap, the plurality of base stations 3 are vacant by autonomous distributed control for each super frame composed of a predetermined number of frames. A frame is detected, and communication is performed with the PHS terminal 2 in the zone by one downlink slot of the empty frame. In this way, the plurality of base stations 3 use the downlink slots for time division.
In addition, by this autonomous distributed control, even when the plurality of zones overlap each other, the plurality of base stations 3 do not collide with each other's communication data, and each of the plurality of base stations 3 exists within the respective radio wave arrival ranges. Communication with the PHS terminal 2 is possible.

The base station 3 assigns the PHS terminal 2 to an unused slot.
Thereby, the some PHS terminal 2 can transmit communication data to each base station 3 using a common frequency band.

FIG. 2 is a block diagram showing a hardware configuration of the PHS terminal 2 of FIG.
The PHS terminal 2 includes a radio communication unit (RF) 11, a reception strength determination unit (RSSI) 12, an operation unit (KEY) 13, a display unit (DISP) 14, an acceleration sensor (G_SEN) 15, and a voice modem unit (MODEM) 16. , A CPU (Central Processing Unit) 17, a memory (MEM) 18, and a system bus 19 for connecting them.

The wireless communication unit 11 establishes a communication channel with the base station 3 and transmits / receives communication data to / from the base station 3 using the slots assigned in the communication method of FIG. 2 described above.
The wireless communication unit 11 wirelessly transmits the communication data included in the input signal from the CPU 17 to the base station 3 and outputs a signal including the communication data received from the base station 3 to the CPU 17.

The reception intensity determination unit 12 receives a signal having a waveform corresponding to the received radio wave from the wireless communication unit 11.
The reception intensity determination unit 12 generates an RSSI value of the received radio wave.
The reception strength determination unit 12 generates a radio signal transmitted by itself by generating an RSSI (Receive Signal Strength Indicator) value of the radio wave received by the radio communication unit 11 when the radio communication unit 11 is transmitting communication data. RSSI values of received radio waves including can also be generated.
Then, the reception intensity determination unit 12 outputs a signal including the RSSI value of the radio wave received from each base station 3 by the wireless communication unit 11 to the CPU 17.

The operation unit 13 has a plurality of operation keys not shown.
The operation keys include, for example, a function key, a power key, a call key, a numeric key, a character key, and a call key. The operation keys are arranged on the surface of the PHS terminal 2.
Then, the operation unit 13 outputs a signal corresponding to the operation key operated by the user to the CPU 17.

The display unit 14 includes an LCD (Liquid Crystal Display Device), an organic EL (Electro-Luminescence) device, and the like that are not shown.
The LCD or the organic EL device has a structure in which a plurality of pixels (Pixels) are arranged in a matrix for each RGB color component, and is arranged on the surface of the PHS terminal 2.
The display unit 14 displays display data included in the signal input from the CPU 17. Thereby, the display part 14 displays the map which shows the present position of the PHS terminal 2, for example.

The acceleration sensor 15 is a semiconductor strain gauge type, servo type, or piezoelectric type sensor. The acceleration sensor 15 detects acceleration acting on the PHS terminal 2.
Further, the acceleration sensor 15 outputs a signal including the detected acceleration value to the CPU 17.

The voice modem unit 16 is connected to the speaker 20 and the microphone 21.
The voice modem unit 16 samples the voice input to the microphone 21 and outputs a signal including voice data to the CPU 17.
The voice modem unit 16 drives the speaker 20 with voice data included in an input signal from the CPU 17. As a result, sound corresponding to the sound data is output from the speaker 20.

The memory 18 includes a program that can be read and executed by the CPU 17, data that is read and written by the CPU 17, and the like.
Note that the program stored in the memory 18 may be a program installed on a computer-readable recording medium such as a CD-ROM (Compact Disc Read Only Memory). It is also possible to install what has been downloaded via the Internet.
The data stored in the memory 18 includes a threshold value table 31 as shown in FIG.

FIG. 4 is a diagram illustrating an example of the data structure of the threshold value table 31.
The threshold value table 31 has a record for each content of communication data.
The content of communication data includes audio data, moving image data, data other than moving images, and the like.
Each record of the threshold value table 31 stores a plurality of threshold values.
The plurality of threshold values stored in each record correspond to each of a plurality of modulation schemes and a plurality of coding rates that can be used by the adaptive modulation and coding unit 41 described later.

FIG. 5 is an explanatory diagram showing the throughput of a plurality of modulation schemes and a plurality of coding rates shown in FIG.
As shown in FIG. 5, the throughput of communication data increases in the order of BPSK, QPSK, 8PSK, 16QAM, 32QAM, and 64QAM in FIG.

In each record of the threshold value table 31 in FIG. 4, a plurality of threshold values are stored in order from the threshold value corresponding to the modulation scheme (coding rate) having a low data rate in FIG.
For example, a record for data other than moving images includes a threshold value 13.7 corresponding to BPSK, a threshold value 16 corresponding to QPSK, a threshold value 21.6 corresponding to 8PSK, a threshold value 23.2 corresponding to 16QAM, and a threshold value 26 corresponding to 32QAM. .4, with a threshold of 30.7 corresponding to 64QAM.
The record for audio data has a threshold value 13.7 corresponding to BPSK and a threshold value 16 corresponding to QPSK.
On the other hand, the moving image record includes a threshold value 10.7 corresponding to BPSK, a threshold value 13 corresponding to QPSK, a threshold value 18.6 corresponding to 8PSK, a threshold value 20.2 corresponding to 16QAM, and a threshold value corresponding to 32QAM. It has a threshold value 27.7 corresponding to 23.4 and 64QAM.
In this way, in the moving image record, a threshold value having a smaller value than the record for data other than the moving image is associated with each of the plurality of modulation schemes and the plurality of coding rates.

  The CPU 17 is a computer that reads and executes a program stored in the memory 18, and functions as a processing unit of the PHS terminal 2.

FIG. 3 shows functional blocks implemented in the PHS terminal 2 when the CPU 17 executes the program. FIG. 3 is a functional block diagram of the wireless communication system 1 of FIG.
As shown in FIG. 3, the PHS terminal 2 includes an adaptive modulation and coding unit (AMC) 41, a UI (User Interface) unit (UI) 42, a telephone unit (TEL) 43, a browser unit (BZR). ) 44, a moving image section (MOVIE) 45, a DU ratio calculation section (DU) 46, a comparison section (JD) 47, a correction section (MD) 48, and a handover processing section (HO) 49 are realized.

The adaptive modulation and coding unit 41 performs processing for encoding or decoding communication data transmitted and received by the wireless communication unit 11 and processing for modulation or demodulation.
Moreover, the adaptive modulation encoding unit 41 performs communication data encoding processing and modulation processing using one code rate and modulation scheme selected from a plurality of code rates and a plurality of modulation schemes shown in FIG. 5.

  The UI unit 42 manages the display unit 14 and the operation unit 13.

The call unit 43 outputs the voice data supplied from the voice modem unit 16 to the adaptive modulation and coding unit 41. The calling unit 43 may encode the audio data and output the encoded audio data to the adaptive modulation and coding unit 41.
Further, the communication unit 43 receives the communication data demodulated and combined from the adaptive modulation encoding unit 41.
When the input communication data is voice data, the call unit 43 outputs the voice data to the voice modem unit 16. The voice modem unit 16 drives the speaker 20 with voice data. As a result, sound corresponding to the sound data is output from the speaker 20.
When the input communication data is display data, the call unit 43 outputs the display data to the UI unit 42. The UI unit 42 causes the display unit 14 to display an image of display data.

When a URL (Uniform Resource Locator) or the like is input from the UI unit 42, the browser unit 44 outputs communication data requesting a web page of the URL to the adaptive modulation and encoding unit 41.
When demodulated and combined communication data is input from the adaptive modulation and coding unit 41, the browser unit 44 generates display data from the web page data included in the communication data, and outputs the display data to the UI unit 42. . The UI unit 42 displays an image based on the display data on the display unit 14.
As a result, the web page of the URL specified by the operation unit 13 is displayed on the display unit 14.

The moving image unit 45 receives moving image data including a plurality of picture data, and displays the moving image on the display unit 14.
When the moving image URL or the like is input from the UI unit 42, the moving image unit 45 outputs communication data requesting the moving image of the URL to the adaptive modulation and coding unit 41.
When the demodulated and combined communication data is input from the adaptive modulation and coding unit 41, the moving image unit 45 generates picture data from the moving image data included in the communication data, and outputs the picture data to the UI unit 42. The UI unit 42 displays a moving image based on the picture data on the display unit 14.
As a result, the moving image of the URL specified by the operation unit 13 is displayed on the display unit 14.

In the case of web page data etc., if some data is missing, proper display cannot be performed. In contrast, moving image data composed of a plurality of picture data can be displayed as a moving image even if some of the picture data is missing.
Due to such a characteristic as content, moving image data composed of a plurality of picture data can generally be transmitted by UDP (User Datagram Protocol) having a high transfer rate. On the other hand, web page data and the like need to be transmitted by TCP (Transmission Control Protocol) with high reliability.

The calling unit 43, the browser unit 44, and the moving image unit 45 correspond to the application function of the PHS terminal 2.
Then, application units such as the calling unit 43, the browser unit 44, and the moving image unit 45 output a notification signal to the comparison unit 47 during operation.
The application units 43 to 45 may output a notification signal to the comparison unit 47 using, for example, an inter-program communication function.

The DU ratio calculation unit 46 calculates the DU ratio from the RSSI value detected by the reception strength determination unit 12.
The DU ratio is a value obtained by dividing the received intensity value of a desired wave (D wave: Desire wave) to be received by the received intensity value of an undesired wave (U wave: Undesire wave).
The DU ratio is a value indicating the ratio of the interference wave to the signal wave, like the CN (Carrier to Noise) ratio, the SN (Signal to Noise) ratio, and the like.

The comparison unit 47 selects one threshold value from the threshold value table 31 based on the notification signals input from the application units 43 to 45.
The comparison unit 47 compares the selected threshold value with the DU ratio.
The comparison unit 47 outputs communication data corresponding to the comparison result between the threshold and the DU ratio to the adaptive modulation and coding unit 41 in order to transmit to the base station 3.
Communication data output from the comparison unit 47 to the wireless communication unit 11 includes, for example, communication data requesting establishment of a link channel, D-wave intensity value, and U-wave intensity value, as shown in FIGS. There is communication data to send.

The handover processing unit 49 executes a handover process when the PHS terminal 2 moves and moves from a zone of one base station 3 to a zone of another base station 3.
In the handover process, the handover processing unit 49 outputs, for example, a link channel establishment request to the adaptive modulation and coding unit 41 for transmission to the base station 3.
Further, the handover processing unit 49 outputs a signal notifying that to the correction unit 48 during the handover process.

A notification signal from the handover processing unit 49 and acceleration data from the acceleration sensor 15 are input to the correction unit 48.
The correction unit 48 includes a first correction unit 48A and a second correction unit 48B.
48 A of 1st correction parts correct the threshold value of the threshold value table 31 according to the acceleration data from the acceleration sensor 15. FIG.
The second correction unit 48B corrects the threshold value of the threshold value table 31 in accordance with the notification signal from the handover processing unit 49.

  FIG. 6 is a flowchart of processing of the DU ratio calculation unit 46 and the comparison unit 47 of FIG.

The DU ratio calculation unit 46 first measures the U wave level (step S1).
The DU ratio calculation unit 46 acquires the RSSI value at the time of detecting the U wave from the RSSI unit.

Next, the DU ratio calculation unit 46 measures the D wave level (step S2).
The DU ratio calculation unit 46 acquires the RSSI value at the time of detecting the D wave from the RSSI unit.

When the U-wave RSSI value and the D-wave RSSI value are acquired, the DU ratio calculator 46 calculates the DU ratio (step S3).
For example, the DU ratio calculation unit 46 divides the RSSI value of the D wave by the RSSI value of the U wave to obtain the DU ratio.

When the DU ratio is calculated by the DU ratio calculation unit 46, the comparison unit 47 performs a comparison process between the DU ratio and the threshold value.
In the comparison process between the DU ratio and the threshold value, the comparison unit 47 first determines the content of the communication data received by the PHS terminal 2 (step S4).
The comparison unit 47 determines the content type of the communication data from the notification signals input from the application units 43 to 45.
When the notification signal is input from the call unit 43, the comparison unit 47 determines that the content is audio.
When a notification signal is input from the browser unit 44, the comparison unit 47 determines that the content is data other than a moving image.
When the notification signal is input from the moving image unit 45, the comparison unit 47 determines that the content is moving image data.

When the content is audio data, the comparison unit 47 reads a record corresponding to the audio from the threshold table 31.
In addition, the comparison unit 47 compares a plurality of voice thresholds T (TEL) included in the read record with the DU ratio (step S5).
Specifically, the comparison unit 47 reads the voice threshold value 13.7 and the threshold value 16 in FIG. 4 and compares these threshold values T (TEL) with the DU ratio.

  When the DU ratio is smaller than the read minimum threshold value (here, 13.7), the comparison unit 47 transmits the establishment request to the base station 3 in order to transmit the establishment request to the adaptive modulation encoding unit. It outputs to 41 (step S6).

  When the DU ratio is larger than the read minimum threshold value (here, 13.7), the comparison unit 47 transmits the D-wave RSSI value and the D-wave RSSI value used to generate the DU ratio to the base station 3. Then, the RSSI value is output to the adaptive modulation and coding unit 41 (step S7).

When the content is data other than a moving image, the comparison unit 47 reads a record corresponding to the data from the threshold table 31.
Further, the comparison unit 47 compares a plurality of threshold values T (DATA) for data included in the read record with the DU ratio (step S8).
Specifically, the comparison unit 47 includes a plurality of threshold values 13.7, 16 and 21 for data in FIG. Threshold 6 and threshold 23. Threshold 2 and threshold 26. The threshold value 4 and the threshold value 30.7 are read, and the threshold value T (DATA) is compared with the DU ratio.

  When the DU ratio is smaller than the read minimum threshold value (here, 13.7), the comparison unit 47 transmits the establishment request to the base station 3 in order to transmit the establishment request to the adaptive modulation encoding unit. It outputs to 41 (step S6).

  When the DU ratio is larger than the read minimum threshold (here, 13.7), the comparison unit 47 transmits the D-wave RSSI value and the D-wave RSSI value used for generating the DU ratio to the base station 3. Then, the RSSI value is output to the adaptive modulation and coding unit 41 (step S7).

When the content is moving image data, the comparison unit 47 reads a record corresponding to the moving image from the threshold table 31.
Further, the comparison unit 47 compares a plurality of threshold values T (MOVIE) for moving images included in the read record with the DU ratio (step S9).
Specifically, the comparison unit 47 reads a plurality of threshold values 10.7, threshold 13, threshold 18.6, threshold 20.2, threshold 23.4, and threshold 27.7 for moving images in FIG. These threshold values T (MOVIE) are compared with the DU ratio.

  When the DU ratio is smaller than the read minimum threshold value (10.7 in this case), the comparison unit 47 transmits the establishment request to the base station 3 in order to send the establishment request to the adaptive modulation encoding unit. It outputs to 41 (step S6).

When the DU ratio is larger than the read minimum threshold value (10.7 here), the comparison unit 47 generates the RSSI value of the D wave for transmission and the RSSI value of the U wave for transmission (step S10).
The comparison unit 47 corrects one or both of the RSSI value of the D wave and the RSSI value of the U wave used for the calculation of the DU ratio, and generates an RSSI value for transmission.

What is necessary is just to perform the production | generation process of the RSSI value for transmission, for example in the following procedures.
The comparison unit 47 first arranges the read threshold values T (MOVIE) for a plurality of moving images and the DU ratios in ascending order, and selects the threshold value T (MOVIE) positioned next to the DU ratio in the arrangement order.
The selected threshold T (MOVIE) is a threshold larger than the DU ratio.
Next, the comparison unit 47 reads the threshold value T (DATA) for data corresponding to the selected threshold value T (MOVIE) from the threshold value table 31.
Next, the comparison unit 47 sets these two values so that the DU ratio between the RSSI value of the D wave for transmission and the RSSI value of the U wave for transmission is equal to or greater than the read data threshold value T (DATA). Modify one or both of the RSSI values.

For example, when the detected DU ratio is 26.5, as illustrated in FIG. 4, the comparison unit 47 selects the threshold 27.7 as the threshold T (MOVIE) located next to the DU ratio.
Next, the comparison unit 47 selects a threshold value T (DATA) for data corresponding to the threshold value 27.7. In FIG. 4, the comparison unit 47 selects the threshold value 30.7.
Next, the comparison unit 47 calculates the DU ratio so that the DU ratio between the RSSI value of the D wave for transmission and the RSSI value of the U wave for transmission is equal to or greater than the threshold value 30.7 for the read data. The RSSI value of one or both of the RSSI value of the D wave and the RSSI value of the U wave used in the above is corrected.

  After generating the RSSI value for transmission, the comparison unit 47 outputs the RSSI value to the adaptive modulation encoding unit 41 in order to transmit the generated RSSI value to the base station 3 (step S7).

  FIG. 7 is a sequence chart showing a communication procedure in the wireless communication system 1 of FIGS. 1 and 3.

The PHS terminal 2 transmits a link channel establishment request (step S11).
For example, the PHS terminal 2 transmits a link channel establishment request from the radio transmission unit to the base station 3 based on the link channel establishment request output from the handover processing unit 49 to the adaptive modulation and coding unit 41.
In addition, when the channel is allocated from the base station 3, the PHS terminal 2 monitors the U wave of the allocated channel.
When the U-wave level exceeds the second level of RCR STD-28 (PHS standard in Japan), the PHS terminal 2 sends a link channel probability re-request (when the link channel is established) to the base station 3. Send. Alternatively, the PHS terminal 2 transmits a transport channel switching re-request (at the time of transport channel switching).
When the DU ratio at the time of downlink synchronization burst reception falls below a predetermined threshold value, the PHS terminal 2 transmits a link channel probability re-request (when a link channel is established) to the base station 3. Alternatively, the PHS terminal 2 transmits a transport channel switching re-request (at the time of transport channel switching).

When receiving the link channel establishment request from the PHS terminal 2, the base station 3 measures the U wave and detects a free channel (step S12).
The base station 3 allocates the detected vacant channel to the PHS terminal 2 and transmits a link channel allocation notification to the PHS terminal 2 (step S13).

When the link channel assignment notification is received from the base station 3, the DU ratio calculation unit 46 of the PHS terminal 2 measures the U wave of the assigned channel by the process of step S1 of FIG. 6 (step S14).
For example, the DU ratio calculation unit 46 sets the maximum value in four consecutive synchronization burst periods as the detection level of the U wave.
Thereafter, the PHS terminal 2 transmits a radio wave for synchronization burst on the assigned channel (step S15).

The base station 3 monitors the channel assigned to the PHS terminal 2 and measures the D wave at the timing when the PHS terminal 2 transmits the radio wave for synchronization burst (step S16).
Thereafter, the base station 3 transmits a radio wave for synchronization burst using the channel assigned to the PHS terminal 2 (step S17).

The DU ratio calculation unit 46 of the PHS terminal 2 monitors the channel allocated from the base station 3.
Then, the DU ratio calculation unit 46 measures the D wave by the process of step S2 of FIG. 6 at the timing when the base station 3 transmits the radio wave for synchronization burst (step S18).
For example, the DU ratio calculation unit 46 sets the average value of the reception levels in one synchronization burst as the D wave detection level.

  The DU ratio calculation unit 46 of the PHS terminal 2 calculates the DU ratio from the detected D wave and U wave by the process of step S3 in FIG. 6 (step S18).

When the DU ratio is calculated in the PHS terminal 2, the comparison unit 47 performs a plurality of operations according to the operation status of the PHS terminal 2 from the threshold table 31 in FIG. 4 through the processes in steps S4, S5, S8, and S9 in FIG. Select a threshold.
The comparison unit 47 also compares the selected threshold with the DU ratio.

  When the detected DU ratio is smaller than the minimum threshold selected according to the operation status of the PHS terminal 2, the comparison unit 47 issues a link channel establishment re-request by the process of step S6 in FIG. (Step S19).

On the other hand, when the detected DU ratio is larger than the minimum threshold selected according to the operation status of the PHS terminal 2, the comparison unit 47 performs the process of step S7 in FIG. The RSSI value indicating the wave level is transmitted to the base station 3.
The wireless communication unit 11 of the PHS terminal 2 transmits the RSSI value indicating the D wave level and the U wave level to the base station 3 by the idle burst for notification (step S20).

The base station 3 receives the idle burst for notification and calculates the DU ratio from the D wave level and the U wave level included in the received signal (step S21).
The base station 3 has only a plurality of threshold values for data in the threshold value table 31 of FIG.
Then, the base station 3 compares these thresholds with the DU ratio calculated from the level notified from the PHS terminal 2.
The base station 3 selects a modulation scheme and a coding rate corresponding to a threshold smaller than the calculated DU ratio. For example, when the calculated DU ratio is 26.5, 32QAM is selected.

By the way, when the moving image unit 45 outputs the notification signal to the comparison unit 47 in the PHS terminal 2, the comparison unit 47 performs the transmission D wave level and U wave by the process of step S18 (step S10 in FIG. 6). An RSSI value indicating the level is generated.
The comparison unit 47 transmits the generated RSSI value for transmission to the base station 3.
Therefore, for example, when the moving picture unit 45 of the PHS terminal 2 outputs a notification signal, when the DU ratio calculation unit 46 of the PHS terminal 2 calculates the DU ratio 26.5, the comparison unit 47 of the PHS terminal 2 The RSSI value of the transmission D wave and U wave with a ratio of 30.7 is generated.
In step S21, the base station 3 calculates a DU ratio 30.7 from the RSSI values of the D wave and U wave received from the PHS terminal 2, and selects 64QAM.

For this reason, when the moving image unit 45 processes a moving image in the PHS terminal 2, the data throughput between the PHS terminal 2 and the base station 3 is improved.
Thereby, the moving image unit 45 can receive high-quality moving image data with a large amount of data and display it on the display unit 14.
Also, moving image data composed of a plurality of picture data can be displayed as a moving image even if some of the picture data is missing.
Therefore, the moving image unit 45 can continue to display moving images on the display unit 14 even if the moving image data is lost due to the improvement of the throughput of the moving image data.

As described above, the base station 3 determines the vertical modulation method in consideration of the D wave level and the U wave level notified from the PHS terminal 2.
Further, the base station 3 transmits an instruction idle burst for instructing the modulation method to the PHS terminal 2 (step S22).

When receiving the instruction idle burst from the base station 3, the PHS terminal 2 transmits the idle burst (step S23).
Further, the base station 3 switches the modulation scheme and coding rate of the adaptive modulation and coding unit 41 to the instructed modulation scheme (step S24).

When the idle burst is received from the PHS terminal 2, the base station 3 detects that the modulation method has been switched by the PHS terminal 2.
Then, the base station 3 switches the modulation scheme used for communication with the PHS terminal 2 to the modulation scheme notified to the PHS terminal 2 (step S25).
In addition, the base station 3 transmits an idle burst to the PHS terminal 2 (step S26).

  FIG. 8 is a flowchart of the correction process of the threshold value table 31 of FIG. 4 by the correction unit 48 of FIG.

  The first correction unit 48A of the correction unit 48 compares the detection speed of the acceleration sensor 15 with a predetermined threshold A (step S31).

If the detection speed of the acceleration sensor 15 is greater than the predetermined threshold A, the first correction unit 48A changes the threshold included in the threshold table 31 of FIG. 4 to a threshold that provides a low data rate (step S32).
Specifically, for example, first correction unit 48A increases each value, for example, by one for a plurality of threshold values for moving images.

  When the detection speed of the acceleration sensor 15 is smaller than the predetermined threshold A, the second correction unit 48B of the correction unit 48 further determines whether or not a handover process is being performed (step S33).

If the handover process is being performed, the second modification unit 48B changes the threshold value included in the threshold value table 31 of FIG. 4 to a threshold value that provides a low data rate (step S32).
Specifically, for example, the second correction unit 48B increases each value, for example, by one for a plurality of threshold values for moving images.

When the detection speed of the acceleration sensor 15 is smaller than the predetermined threshold A and the handover process is not being performed, the correction unit 48 changes the threshold included in the threshold table 31 of FIG. 4 to a threshold that provides a high data rate ( Step S34).
Specifically, for example, the correction unit 48 decreases each value, for example, by one for a plurality of threshold values for moving images.

As described above, in this embodiment, the switching of the modulation scheme and the coding rate is adaptively controlled according to the content.
Therefore, in the wireless communication system 1 of the present embodiment, communication performance (throughput) is improved, and practical communication can be realized in moving image distribution.

  The above embodiment is a preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications or changes are possible.

For example, in the above embodiment, the comparison unit 47 of the PHS terminal 2 always transmits the D wave level and the U wave level to the base station 3 in the process of FIG.
In addition to this, the comparison unit 47 of the PHS terminal 2 may transmit the D wave level and the U wave level to the base station 3 when the change of the modulation parameter in the transport channel is effective (possible). .

In the above embodiment, the adaptive modulation and coding unit 41, the UI unit 42, the call unit 43, the browser unit 44, the moving image unit 45, the DU ratio calculation unit 46, the comparison unit 47, the correction unit 48, and the handover of the PHS terminal 2 are The PHS terminal 2 is realized by software.
The PHS terminal 2 includes a reception strength determination unit 12.
All of these units may be realized by hardware, or all of them may be realized by software.

The wireless communication system 1 of the above embodiment has a PHS terminal 2.
In addition, for example, the wireless communication system 1 may include a mobile phone other than the PHS terminal 2, a PDA (Personal Data Assistant) having a communication function, a portable game device having a communication function, and a personal computer having a communication function. .

In the wireless communication system 1 according to the above embodiment, the PHS terminal 2 executes the process of FIG.
In addition to this, for example, the base station 3 may receive the D wave and U wave levels detected by the PHS terminal 2 from the PHS terminal 2 and execute the processing of FIG.

DESCRIPTION OF SYMBOLS 1 ... Wireless communication system, 2 ... PHS terminal (wireless communication terminal), 11 ... Wireless communication part, 15 ... Acceleration sensor (mobility detection part), 17 ... CPU (control part), 46 ... DU ratio calculating part, 31 ... Threshold table (threshold holding unit) 41... Adaptive modulation encoding unit (adaptive modulation / demodulation unit) 47... Comparison unit (change unit) 48... Correction unit 48 A. Wave: desired wave, U wave: undesired wave, DU ratio: DU ratio, T (TEL): threshold for audio, T (DATA): threshold for data other than moving images, T (MOVIE): threshold for moving images

Claims (10)

A wireless communication unit that transmits and receives communication data by signal waves;
A DU ratio calculation unit for calculating a DU ratio indicating a ratio of the interference wave to the signal wave;
As a plurality of thresholds to be compared with the DU ratio, a threshold holding unit having a plurality of thresholds different for each content of the communication data;
A comparison unit that selects a threshold corresponding to the content of the communication data from the threshold holding unit, and compares the selected threshold with the DU ratio;
And a radio communication terminal that transmits the signal wave level and the interference wave level to a base station based on the comparison result.
A mobility detector for detecting the mobility of the wireless communication terminal;
The wireless communication terminal according to claim 1, further comprising: a first correction unit that corrects a threshold value of the threshold value holding unit according to the mobility detected by the mobility detection unit.
The wireless communication unit
Send and receive communication data with one base station selected from multiple base stations,
The wireless communication terminal
The wireless communication terminal according to claim 1, further comprising a second correction unit that corrects a threshold value of the threshold holding unit when the wireless communication unit switches a base station that transmits and receives communication data.
The wireless communication unit
Send and receive communication data with the base station on channels assigned from multiple channels,
When the DU ratio is smaller than a threshold selected according to the content in the comparison of the comparison unit,
The radio communication terminal according to any one of claims 1 to 3, wherein a new channel allocation request is transmitted.
The DU ratio calculation unit
From the signal strength of the desired wave to be received and the signal strength of the undesired wave, a DU ratio indicating the signal strength of the undesired wave with respect to the signal strength of the desired wave is calculated
The wireless communication unit
When the DU ratio is larger than the threshold selected according to the content in the comparison of the comparison unit,
The wireless communication terminal according to claim 4, wherein the signal strength of the desired wave and the signal strength of the undesired wave used for calculating the DU ratio are transmitted.
The wireless communication terminal
An adaptive modulation / demodulation unit that adaptively switches modulation processing or coding rate of the communication data transmitted and received by the wireless communication unit;
A changing unit for changing a ratio between the signal strength of the desired wave and the signal strength of the non-desired wave when the DU ratio is larger than a minimum threshold of a set selected according to the content in the comparison of the comparison unit; Have
The wireless communication unit
When the DU ratio is larger than the minimum threshold of the set selected according to the content in the comparison of the comparison unit,
Instead of the signal strength of the desired wave and the signal strength of the undesired wave used for the calculation of the DU ratio,
The radio communication terminal according to claim 5, wherein the signal strength of a desired wave and the signal strength of an undesired wave whose ratio has been changed by the changing unit are transmitted.
The threshold holding unit
A plurality of sets of threshold values for each content of the communication data are held by a table associated with a plurality of modulation schemes or a plurality of coding rates that can be switched in the adaptive modulation / demodulation unit,
The changing unit is
From the table, the threshold value for other content associated with the same modulation scheme or coding rate as the threshold value larger than the DU ratio calculated by the DU ratio calculation unit, which is the same as that stored in the base station Get a threshold with a value,
The wireless communication terminal according to claim 6, wherein a ratio between the signal strength of the desired wave and the signal strength of the non-desired wave is changed so that a DU ratio is equal to or greater than the acquired threshold value.
The threshold table is
The wireless communication terminal according to any one of claims 1 to 6, wherein a plurality of threshold values different for each content of the communication data include a threshold value for a moving image composed of a plurality of pictures and a threshold value for data.
A wireless communication system that transmits and receives communication data by signal waves between a wireless communication terminal and a base station,
A DU ratio calculation unit for calculating a DU ratio indicating a ratio of the interference wave to the signal wave;
As a plurality of threshold values to be compared with the DU ratio, a threshold value holding unit having a different threshold value for each content of the communication data;
A threshold value selection unit configured to select a threshold value according to the content of the communication data from the threshold value holding unit, and to compare the selected threshold value with the DU ratio, and based on the comparison result, A wireless communication system that transmits the level of an interference wave to a base station.
A wireless communication method for transmitting and receiving communication data by signal waves between a wireless communication terminal and a base station,
Calculating a DU ratio indicating a ratio of an interference wave to the signal wave;
Selecting a threshold according to the content of the communication data from a threshold holding unit having different thresholds for each content of the communication data as a plurality of thresholds to be compared with the DU ratio;
And a step of comparing the selected threshold with the DU ratio, and transmitting the signal wave level and the interference wave level to a base station based on the comparison result.

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