WO2011001758A1

WO2011001758A1 - Wireless system and method for switching resolution level of moving image

Info

Publication number: WO2011001758A1
Application number: PCT/JP2010/058595
Authority: WO
Inventors: 政彰森島
Original assignee: 日本電気株式会社
Priority date: 2009-06-30
Filing date: 2010-05-21
Publication date: 2011-01-06
Also published as: TW201114283A

Abstract

A base station employs adaptive modulation that changes the modulation method according to the state of the radio waves. A terminal device selects a modulation method for data transmitted to the base station according to the reception state of radio waves transmitted from the base station, selects a resolution level for moving images that corresponds to said determined modulation method, and transmits moving image data captured by a camera to the base station at said selected resolution level.

Description

Wireless system and moving image resolution switching method

The present invention relates to a wireless system adopting adaptive modulation and a moving image resolution switching method suitable for the wireless system.

For example, WiMAX (Worldwide Interoperability for Microwave Access) efficiently transmits data using multi-level modulation schemes such as 64QAM (Quadrature Amplitude Modulation) and 16QAM when the radio wave condition is good, and QPSK when the radio wave condition is poor. Using the (Quadrature Phase Shift Keying) modulation method, adaptive modulation and coding (AMC: Adaptive Modulation and Coding) that reliably transmits data to the receiver even when the transmission rate decreases is adopted. This adaptive modulation is defined in IEEE 802.16 established by the WiMAX Forum.

When playing video data received over the network, buffer the received video data, pause the video when the communication speed decreases, and resume the video when the video data is sufficient Techniques are often used.

When transmitting and receiving moving image data using a wireless system to which WiMAX is applied, if the transmission speed decreases due to the above-described adaptive modulation, there is a possibility that the reproduced moving image may be dropped or paused.

It is very difficult to see dropped or paused videos, and security problems occur when using a wireless system that uses the WiMAX in a surveillance camera system (CCTV: Closed Circuit Television).

For example, Patent Literature 1 proposes a technology for sampling the communication speed and throughput for a certain period to obtain an average value, and switching the resolution and bit rate of a moving image to be distributed based on the average value. Has been.

However, in such background wireless systems, complicated processing such as sampling the communication speed and throughput, calculating the average value, and determining the resolution and bit rate of the video to be distributed based on the average value is performed. Must be executed constantly during data transmission / reception. Therefore, the processing load of the CPU provided in the terminal device increases, and the power consumption of the terminal device increases. Moreover, there is a problem that the cost of the terminal device increases by adopting a high-performance CPU that can cope with an increase in processing load.

JP 2007-329814 A

Therefore, an object of the present invention is to provide a wireless system and a moving image resolution switching method that can suppress dropping or pause of a moving image being played back without increasing the processing load.

To achieve the above object, a wireless system of the present invention includes a base station adopting adaptive modulation,
According to the reception state of the radio wave transmitted from the base station, a modulation method of data to be transmitted to the base station determined in advance is determined, and a predetermined moving image resolution corresponding to the determined modulation method is determined. A terminal device that selects and transmits the moving image data captured by the camera to the base station at the selected resolution;
Have

On the other hand, the moving image resolution switching method of the present invention determines a modulation method of data to be transmitted to the base station determined in advance according to the reception state of the radio wave transmitted from the base station,
Select a predetermined video resolution corresponding to the determined modulation method,
In this method, moving image data captured by a camera is transmitted to the base station at the selected resolution.

FIG. 1 is a schematic diagram illustrating an example of adaptive modulation used in a wireless system. FIG. 2 is a schematic diagram showing an example of the resolution of each area shown in FIG. 1 and the moving image transmitted by the terminal device in the area. FIG. 3 is a schematic diagram illustrating a configuration example of a frame used for data transmission / reception. FIG. 4 is a block diagram illustrating a configuration example of a terminal device used in the wireless system of the present invention. FIG. 5 is a flowchart showing a processing procedure of the terminal device provided in the wireless system of the present invention. FIG. 6 is a flowchart showing the processing procedure of the terminal device provided in the wireless system of the present invention.

Next, the present invention will be described with reference to the drawings.

In the present invention, in a wireless system adopting adaptive modulation, the resolution (moving image size) of moving image data transmitted from a terminal device equipped with a camera or a terminal device connected to the camera to a base station (hereinafter referred to as BS) is set. And switching according to the modulation scheme changed by adaptive modulation. For example, in a wireless system to which WiMAX is applied, the relationship between the modulation scheme and the throughput is associated in advance, and the data is held in the BS and the terminal device. In the present invention, the resolution of moving image data transmitted from the terminal device to the BS is optimized using these data.

FIG. 1 is a schematic diagram showing an example of adaptive modulation used in a wireless system.

As shown in FIG. 1, the radio wave radiated from the antenna device 100 connected to the BS is divided into a plurality of areas (first area 101 to fourth area 104 in FIG. 1) according to the radio field intensity. The The BS transmits / receives data using a modulation scheme that is different for each terminal device and each area in which the terminal device exists.

In FIG. 1, an ideal omnidirectional antenna is used for the antenna device 100 connected to the BS, and since there is no obstacle such as a building, the intensity of the radio wave radiated from the antenna device 100 is the distance from the antenna device 100. It shows how it declines in proportion. In this case, the first area 101 to the fourth area 104 are substantially concentric.

In the case of the wireless system shown in FIG. 1, for example, the BS transmits / receives data to / from a terminal apparatus in the first area 101 closest to the antenna apparatus 100 using 16QAM3 / 4 as a modulation scheme. Data is transmitted / received to / from a terminal apparatus in the second area 102 near the second area 102 using 16QAM1 / 2 as the modulation scheme, and QPSK3 / 4 is transmitted and received, and data is transmitted and received using a QPSK 1/2 modulation method with a terminal device in the fourth area 104 farthest from the antenna device 100.

FIG. 2 is a schematic diagram showing an example of the resolution of a moving image transmitted by each area shown in FIG. 1 and a terminal device in the area.

FIG. 2 shows the modulation scheme used by the terminal device and the BS to BS according to the area (first area 101 to fourth area 104) where the terminal device exists in the wireless system shown in FIG. An example of the resolution of a moving image to be transmitted is shown.

In this embodiment, as described above, when the terminal device transmits moving image data to the BS, the resolution of the moving image is changed in accordance with the modulation method for each area described above. For example, the terminal device transmits video data of SXGA (Super eXtended Graphics Array) from the first area 101 that uses 16QAM3 / 4 as a modulation method, and from the second area 102 that uses 16QAM1 / 2 as a modulation method. Quad-VGA (Quad Video Graphics Array) moving image data having a resolution lower than that of SXGA is transmitted, XGA moving image data is transmitted from the third area 103 using QPSK3 / 4 as a modulation method, and QPSK1 / SVGA (Super Video Graphics Array) moving image data is transmitted from the fourth area 104 using 2.

FIG. 3 is a schematic diagram showing a configuration example of a frame used for data transmission / reception. Note that the frame shown in FIG. 3 is an example of a frame used in a wireless system to which WiMAX is applied. Since the frame shown in FIG. 3 is well known to those skilled in the art, a detailed description thereof is omitted here.

A wireless system to which WiMAX is applied employs a TDD (Time Division Duplex) method, and as shown in FIG. 3, frames for transmitting and receiving data are downlink subframes (downlink: hereinafter referred to as DL) and uplink. A line subframe (uplink: hereinafter referred to as UL). For transmission of moving image data from the terminal device to the BS, UL Burst mapped to UL shown in FIG. 3 is used.

In WiMAX, each terminal apparatus measures the CINR (Carrier to Interference and Noise Ratio) of the radio wave received from the BS, and realizes the adaptive modulation based on the measured value. Since the CINR measurement method is well known to those skilled in the art, a detailed description thereof is omitted here.

The BS uses the DL Burst mapped to the DL of FIG. 3 for the CINR information request for reporting each CINR measurement value to each terminal device in each area 101 to 104 managed by the BS. To send. When the terminal device receives the CINR information request from the BS, the terminal device transmits the CINR value (CINR information) measured by the terminal device to the BS using the UL Burst mapped to the UL of FIG. The BS determines a modulation scheme to be used in DL for each terminal device based on CINR information reported from each terminal device.

Table 1 is a table (first table) showing the relationship between CINR information and modulation schemes used in DL and UL.

As shown in Table 1, a plurality of threshold values (CINR threshold levels) are set in advance for the CINR value, and the modulation used in DL and UL for each CINR value in a predetermined range with these CINR threshold levels as a boundary. A method is assigned. In the present embodiment, it is assumed that the data of the table shown in Table 1 is stored in advance in a memory included in the BS and the terminal device.

When the BS receives the CINR information from the terminal apparatus, the BS compares the CINR value indicated by the information with each CINR threshold level shown in Table 1 and determines the modulation method used in the DL. For example, when the CINR value is equal to or greater than the CINR threshold level a and smaller than the CINR threshold level b (= a + Δ1), QPSK1 / 2 is used for the DL modulation scheme. When the CINR value is equal to or greater than the CINR threshold level b and smaller than the CINR threshold level c (= b + Δ2), QPSK3 / 4 is used as the DL modulation scheme.

The terminal device basically uses the same modulation method as that used in DL in UL, but, for example, when the area is divided into four as shown in FIG. 1, the modulation degree is higher than that of 16QAM3 / 4. A deep modulation method is not used.

Table 2 is a table (second table) showing an example of the relationship between the modulation method and the throughput of transmission / reception data.

As shown in Table 2, the throughput of transmission / reception data is determined by the modulation method and QoS (Quality of Service). The transmission / reception data for each terminal device includes, for example, BE (Best Effort), UGS (Unsolicited Grant Service), RTPS (real-time Polling Service), NRTPS (non-real-time Polling Service), ERTPS defined by QoS. Bands corresponding to (Extended real-time Polling Service) are allocated. In the present embodiment, it is assumed that the data of the table shown in Table 2 is stored in advance in a memory included in the BS and the terminal device.

For example, in a terminal device to which UGS is applied, when the modulation scheme is QPSK1 / 2, the UL throughput value h1 is 1.613 Mbps, and when the modulation scheme is QPSK3 / 4, the UL throughput value h2 is 2. .408Mbps. When the modulation method is 16QAM1 / 2, the UL throughput value h3 is 3.270 Mbps, and when the modulation method is 16QAM3 / 4, the throughput value h4 is 4.917 Mbps.

For terminal devices to which BE, RTPS, NRTPS or ERTPS is applied, throughput values g1 to g4, k1 to k4, m1 to m4, and n1 to n4 are determined according to the modulation method.

Table 3 is a table (third table) showing an example of the relationship between the resolution of a moving image and the bandwidth (throughput) required for transmission.

As shown in Table 3, the transmission band necessary for reproducing a moving image without interruption or pause varies depending on the resolution and the frame rate. In the present embodiment, it is assumed that the data of the table shown in Table 3 is stored in advance in a memory included in the BS and the terminal device.

For example, when the frame rate of the moving image to be reproduced is 24 fps, the bandwidth s1 necessary for transmitting the moving image data having the resolution of SVGA is 1.44 Mbps. In addition, the bandwidth s2 required for transmission of moving image data with a resolution of XGA is 2.36 Mbps, and the bandwidth s3 required for transmission of moving image data with a resolution of Quad-VGA is 2.95 Mbps. Further, the bandwidth s4 necessary for transmitting the moving image data with the resolution SXGA is 3.93 Mbps, and the bandwidth s5 necessary for transmitting the moving image data with the resolution SXGA + is 4.41 Mbps.

Similarly, when the frame rate of the moving image to be reproduced is 15 fps and 10 fps, the bandwidths u1 to u5 and w1 to w5 necessary for transmitting the moving image data of each resolution are determined according to the frame rate.

In the present embodiment, the resolution of the moving image is determined based on the tables shown in Tables 2 and 3 so that the band required for transmission is smaller than the band (throughput) corresponding to the modulation method. As a result, as shown in FIG. 2, the resolution of the moving image for each modulation scheme used in the UL can be determined.

FIG. 4 is a block diagram showing a configuration example of a terminal device used in the wireless system of the present invention.

As shown in FIG. 4, the terminal device 1 has a configuration including a terminal antenna 2, a transmission / reception unit 3, a processing device 4, and a camera 5.

The transmission / reception unit 3 converts the baseband signal including the moving image data output from the processing device 4 into a radio signal and transmits it from the terminal antenna 2, and converts the radio signal received by the terminal antenna 2 into a baseband signal. To the processing device 4. The transmission / reception unit 3 includes a known mixer circuit, power amplification circuit, low noise amplifier, and the like.

The camera 5 captures a moving image and outputs the data (moving image data) to the processing device 4. FIG. 4 shows a configuration example in which the terminal device 1 includes the camera 5, but the camera 5 may be connected to the terminal device 1 via a cable or the like.

The processing device 4 includes a modulation method determination unit 6, a modulation method data storage unit 7, a resolution data storage unit 8, a resolution determination unit 9, and a UL video transmission unit 10.

In the modulation method data storage unit 7, for example, a table indicating the relationship between the CINR information shown in Table 1 and the modulation method used in DL and UL is stored in advance.

The modulation method determination unit 6 determines a modulation method used for transmission of moving image data based on the table stored in the modulation method data storage unit 7.

In the resolution data storage unit 8, for example, a table indicating the relationship between the modulation method and the throughput shown in Table 2 and a table indicating the relationship between the resolution of the moving image and the bandwidth necessary for transmission shown in Table 3 are stored in advance. Stored.

Based on the table stored in the resolution data storage unit 8, the resolution determination unit 9 selects the resolution of the moving image in which the bandwidth necessary for transmission is maximized within a range not exceeding the throughput corresponding to the modulation method.

The UL video transmission unit 10 converts the video data output from the camera 5 to the resolution selected by the resolution determination unit 9 and outputs the converted data to the transmission / reception unit 3. The moving image data output from the UL moving image transmission unit 10 is transmitted to the BS via the transmission / reception unit 3 and the terminal antenna 2.

4 includes, for example, an A / D (Analog to Digital) converter, a D / A (Digital to Analog) converter, a memory, various logic circuits, and a CPU that executes predetermined processing according to a program. It can be realized by a computer or the like.

5 and 6 are flowcharts showing the processing procedure of the terminal device provided in the wireless system of the present invention.

FIG. 5 shows a processing procedure for determining the UL modulation method by the terminal device, and FIG. 6 shows a processing procedure for determining the resolution of the moving image according to the modulation method by the terminal device.

As shown in FIG. 5, when an instruction to transmit a moving image is issued by an operator or the like (step S301), the terminal device 1 determines whether or not the own device is in the first area 101 shown in FIG. (Step S302). Whether or not the own apparatus is in the first area 101 can be determined from the measured value of CINR as described above.

When the device itself is in the first area 101, the terminal device 1 selects the resolution of the moving image corresponding to the modulation method of the first area 101, and the moving image having the selected first resolution (for example, SXGA) Data is transmitted (step S501). When the transmission of moving image data is started, the terminal device 1 operates a timer, and when a time set in advance in the timer has elapsed (step SS502), the terminal device 1 returns to the process of step S302 and repeats the same process. When there is no timer, even if the terminal device 1 moves to the area where the modulation method should be changed, the moving image data is continuously transmitted without optimizing the moving image resolution. Therefore, the timer is used to determine in which area the terminal device 1 is located at every predetermined time.

When the terminal device 1 is not in the first area 101, the terminal device 1 determines whether or not the terminal device 1 is in the second area 102 shown in FIG. 1 (step S303). Whether it is in the second area 102 can be determined from the measured value of CINR as described above.

When the device itself is in the second area 102, the terminal device 1 transmits moving image data of the second resolution (for example, Quad-VGA) (step S503), and the time set in advance in the timer has elapsed. (Step S504), returning to the process of step S302, the same process is repeated.

If the terminal device 1 is not in the second area 102, the terminal device 1 determines whether or not the terminal device 1 is in the third area 103 shown in FIG. 1 (step S304). Whether it is in the third area 103 can be determined from the measured value of CINR as described above.

When the device itself is in the third area 103, the terminal device 1 transmits moving image data having a third resolution (for example, XGA) (step S309), and when a time set in advance in the timer has elapsed (step S309). S506), returning to the process of step S302, the same process is repeated.

When the device itself is not in the third area 103, the terminal device 1 transmits moving image data of the fourth resolution (for example, SVGA) (step S507), and when a time set in advance in the timer has elapsed (step S507). S508), returning to the process of step S302, the same process is repeated.

FIG. 6 shows a procedure for selecting the resolution of the moving image to be transmitted in the processing of steps S501, S503, S505, and S507 shown in FIG. In the following, a case where USG is applied as QoS (see Table 2) and the frame rate is 24 fps (see Table 3) will be described as an example. However, services other than USG shown in Table 2 are used for QoS. The frame rate may be selected, and a value other than 24 fps shown in Table 3 may be selected.

As shown in FIG. 6, the terminal device 1 first sets an initial value 1 to a variable p (step S401), and a modulation scheme adopted by the band sp required for the resolution of the moving image to be transmitted is used according to the area of the device itself. It is determined whether it is larger than the throughput value ha corresponding to (step S402). The variable a shown in FIG. 6 is a value that changes according to the processing of steps S501, S503, S505, and S507 shown in FIG. When the variable a is 1, the terminal device 1 is in a state in which the process illustrated in FIG. 6 is executed in step S501 illustrated in FIG. When the variable a is 2, the terminal device 1 is in a state where the process shown in FIG. 6 is being executed in step S503 shown in FIG. Similarly, when the variable a is 3, the terminal device 1 is performing the process shown in FIG. 6 in step S505 shown in FIG. 5. When the variable a is 4, the terminal device 1 In this state, the process shown in FIG. 6 is executed in step S507 shown in FIG.

When the bandwidth sp required for transmission is smaller than the throughput value ha corresponding to the modulation method, the terminal device 1 adds 1 to the value of the variable p (step S403), and returns to the process of step S402 to perform the same process. repeat.

When the band sp required for transmission is larger than the throughput value ha corresponding to the modulation scheme, the terminal device 1 determines the resolution corresponding to the band sp-1 as the resolution of the moving image to be transmitted (step S404).

For example, when the terminal apparatus 1 is in the third area 103, the terminal apparatus 1 determines QPSK3 / 4 as the modulation scheme used for UL in step S505, and determines the throughput value h2 (= 2 based on Table 2). .408 Mbps).

Next, in the processes in steps S402 and s403, a necessary band s3 (= 2.95 Mbps) is selected at the resolution of the moving image satisfying ha <sp, and in the process in step S404, a band necessary for transmission is further selected. The resolution XGA of the moving image corresponding to the band s2 (= 2.36 Mbps) that is the largest in the range where the band sp-1 with the least amount of transmission, that is, the band necessary for transmission does not exceed the throughput ha corresponding to the modulation method is selected.

According to the present invention, in order to change the resolution of a moving image transmitted from the terminal device 1 including the camera 5 or the terminal device 1 to which the camera 5 is connected to the BS according to the modulation method used in the UL, the terminal device 1 The resolution of the moving image corresponding to the modulation method may be selected by referring to the table held by the own apparatus. Therefore, in the present invention, it is not necessary for the terminal device 1 to always execute complicated processing as in the background art during transmission / reception of moving image data. Therefore, the processing load of the CPU provided in the terminal device 1 does not increase. In addition, since the moving image data is transmitted at the maximum moving image resolution within the range in which the bandwidth required for transmission does not exceed the throughput corresponding to the determined modulation method, the receiving side apparatus that has received the moving image data reproduces it. Dropping or pausing the moving image is suppressed.

As mentioned above, although this invention was demonstrated with reference to embodiment, this invention is not limited to the said embodiment. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

This application claims priority based on Japanese Patent Application No. 2009-155004 filed on June 30, 2009, the entire disclosure of which is incorporated herein.

Claims

A base station employing adaptive modulation;
In accordance with the reception state of the radio wave transmitted from the base station, a predetermined modulation method of data to be transmitted to the base station is determined, and a predetermined moving image resolution corresponding to the determined modulation method is determined. A terminal device that selects and transmits the moving image data captured by the camera to the base station at the selected resolution;
A wireless system.
The terminal device
Necessary for transmitting the first table indicating the relationship between the measured value of the carrier level to interference noise ratio and the modulation method, the second table indicating the relationship between the modulation method and the throughput, and the resolution and moving image data of the resolution A third table showing a relationship with the bandwidth is stored in advance,
A modulation method of data to be transmitted to the base station from the measurement result of the carrier level to interference noise ratio by measuring the carrier level to interference noise ratio of the radio wave transmitted from the base station and referring to the first table And by referring to the second table and the third table, the resolution of the moving image in which the bandwidth necessary for transmission is maximized within a range not exceeding the throughput corresponding to the determined modulation method is selected. The wireless system according to claim 1, further comprising a processing device.
In the second table, the relationship between the modulation scheme and the throughput is shown for each service guaranteed by QoS,
The processor is
The radio system according to claim 2, wherein a resolution corresponding to the determined modulation scheme is selected according to a service guaranteed by the QoS.
According to the reception state of the radio wave transmitted from the base station, determine a modulation method of data to be transmitted to the base station determined in advance,
Select a predetermined video resolution corresponding to the determined modulation method,
A moving image resolution switching method for transmitting moving image data captured by a camera to the base station at the selected resolution.
Necessary for transmitting the first table indicating the relationship between the measured value of the carrier level to interference noise ratio and the modulation method, the second table indicating the relationship between the modulation method and the throughput, and the resolution and moving image data of the resolution A third table showing a relationship with a specific band is previously stored in a memory, and a carrier level to interference noise ratio of a radio wave transmitted from the base station is measured,
Referring to the first table, a modulation method of data to be transmitted to the base station is determined from the measurement result of the carrier level to interference noise ratio,
5. The resolution of a moving image in which the bandwidth required for transmission is maximized within a range not exceeding the throughput corresponding to the determined modulation method is selected with reference to the second table and the third table. How to switch video resolution.
In the second table, the relationship between the modulation scheme and the throughput is shown for each service guaranteed by QoS,
6. The moving image resolution switching method according to claim 5, wherein a resolution corresponding to the determined modulation method is selected according to a service guaranteed by the QoS.
A terminal device that transmits video data shot by a camera to a base station,
In accordance with the reception state of the radio wave transmitted from the base station, a predetermined modulation method of data to be transmitted to the base station is determined, and a predetermined moving image resolution corresponding to the determined modulation method is determined. A processing device to select; and
A transmission / reception unit for transmitting the moving image data to the base station at a resolution selected by the processing device;
A terminal device.
The processor is
A modulation method data storage unit in which a first table indicating a relationship between a measurement value of a carrier level to interference noise ratio and a modulation method is stored in advance;
A second table indicating the relationship between the modulation method and the throughput, and a resolution data storage unit in which a third table indicating the relationship between the resolution of the moving image and the bandwidth required for transmitting the moving image data of the resolution is stored in advance;
With reference to the first table, a modulation scheme determining unit that determines a modulation scheme of data to be transmitted to the base station from a measurement result of the carrier level to interference noise ratio of the base station;
With reference to the second table and the third table, a resolution determining unit that selects a resolution of a moving image that has a maximum bandwidth within a range in which a bandwidth required for transmission does not exceed the throughput corresponding to the determined modulation method; ,
The terminal device according to claim 7.
In the second table, the relationship between the modulation scheme and the throughput is shown for each service guaranteed by QoS,
The resolution determination unit
The terminal device according to claim 8, wherein a resolution corresponding to the determined modulation scheme is selected according to a service guaranteed by the QoS.