JP4727401B2 - Wireless multicast transmission system, wireless transmission device, and wireless multicast transmission method - Google Patents

Wireless multicast transmission system, wireless transmission device, and wireless multicast transmission method Download PDF

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JP4727401B2
JP4727401B2 JP2005349241A JP2005349241A JP4727401B2 JP 4727401 B2 JP4727401 B2 JP 4727401B2 JP 2005349241 A JP2005349241 A JP 2005349241A JP 2005349241 A JP2005349241 A JP 2005349241A JP 4727401 B2 JP4727401 B2 JP 4727401B2
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transmission
data block
wireless
transmission method
multicast
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JP2007158592A (en
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豊 久埜
正文 吉岡
信也 大槻
大樹 柴山
健悟 永田
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日本電信電話株式会社
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  The present invention relates to a wireless multicast transmission system, a wireless transmission device, and a wireless multicast transmission method for transmitting moving image data by wireless multicast communication.

  Conventionally, as a method for transmitting moving image data using a device compliant with the standard as shown in Non-Patent Document 1, a method based on unicast (UC: UniCast) and a multicast ( There are two methods: MC: MultiCast). When moving image data is transmitted by the unicast method, since it is necessary to perform one transmission for each receiving device, a large amount of bandwidth is used when transmitting the same moving image data to a plurality of receiving devices. There is a problem of end up.

 On the other hand, when transmission is performed by the multicast method, since it is possible to transmit to a plurality of receiving apparatuses by one transmission, the above problem does not occur. Therefore, the multicast method is suitable for transmission to a plurality of receiving apparatuses. Next, when performing multicast transmission of moving image data in a wireless transmission device to which the multicast method is applied, moving image data is transmitted by selecting one transmission rate from a plurality of transmission rates. The transmission rate selected at this time can be normally received even by a receiving device having the worst propagation path condition among receiving devices that receive moving image data by the lowest transmission rate or multicast among normal transmission rates. The transmission rate will be selected.

  However, when transmitting by the multicast method, since it is necessary to transmit to all receiving devices using the same transmission rate, when transmitting at a low transmission rate, even receiving devices with poor propagation path conditions, A receiving apparatus having a good propagation path condition can also be correctly received. On the other hand, when the transmission is performed at a high transmission rate, only a receiving apparatus having a good transmission condition can receive correctly. In the case of wireless communication, the propagation path condition is generally poor when the distance between transmission and reception is long, and the propagation path condition is good when the distance is short.

  Hereinafter, the operation of the wireless transmission apparatus to which the conventional wireless multicast method is applied will be described in more detail with reference to FIGS. 11 to 16. FIG. 11 is a schematic block diagram showing a configuration of a conventional wireless transmission device 5. FIG. 12 is a schematic block diagram showing the configuration of a conventional radio receiving apparatus 6. In FIG. 11, the wireless transmission device 5 transmits data output from the encoder 10 at regular intervals at a designated transmission rate. At this time, even if there are a plurality of wireless reception devices 6 having different propagation path conditions, transmission can be performed only at one transmission rate due to the characteristics of multicast.

  In FIG. 12, the radio receiver 6 demodulates data from the received signal received by the receiver 40 by the demodulator 41, determines whether or not there is an error in the data demodulated by the error detector 42, and an error exists. If not, the decoder 46 reproduces the moving image. If there is an error, the data is discarded. Although the operation of the decoder 46 differs depending on the applied system, generally, when there is an error, a phenomenon occurs such that the reproduced moving image stops or is disturbed.

  In FIG. 13, an AP (Access Point) 5a as the wireless transmission device 5 and three STAs (STAtion) 6a, 6b, and 6c as the wireless reception device 6 exist, and the STA 6a is the closest to the AP 5a, and hereinafter the STA 6b. , 6c in order of distance from the AP 5a.

 FIG. 14 is a diagram illustrating a state in which transmission is performed using a low transmission rate that can be normally received by the STA 6c in the configuration of FIG. When a low transmission rate is used, all the STAs 6a, 6b, and 6c can receive normally, but the bandwidth used is very large. FIG. 15 is a diagram illustrating a state in which transmission is performed using a high transmission rate that can be normally received only by the STA 6a. Since a high transmission rate is used, the band used is small, and only the STA 6a can receive normally. However, the STA 6b and the STA 6c cannot receive normally, and naturally cannot reproduce the moving image.

FIG. 16 shows a case where a bit rate lower than those in FIGS. 14 and 15 is used as a bit rate applied when encoding moving image data to be transmitted, and a low transmission rate that can be normally received by the STA 6c is used. FIG. Compared to FIG. 14, it can be seen that the bandwidth used is reduced. Compared with FIG. 15, since a low transmission rate is used, all STAs 6a, 6b, 6c can receive normally. However, in general, a moving image encoded at a low bit rate has poor quality, and therefore, the quality of moving image data reproduced in all the STAs 6a, 6b, and 6c deteriorates. In particular, in the STA 6a that can be normally received even if it is transmitted at a high transmission rate, the degradation of the quality of the moving image data to be reproduced becomes remarkable.
Power Saving Data System / Broadband Mobile Access System (CSMA) Standard, ARIB STD-T71 1.0 Edition, Radio Industry Association, 2000, Chapter 6.2.4.6

  When multicasting moving image data using a wireless transmission device as described above, it is necessary to use the same transmission rate for all wireless reception devices.

  However, in general, the wireless propagation path varies greatly depending on the positional relationship between the wireless transmission device and the wireless reception device and the surrounding conditions. Accordingly, when there are a plurality of wireless reception devices, the propagation path status differs for each wireless reception device. When performing transmission by multicast under such a situation, it is necessary to transmit using a transmission method with good quality so that the wireless reception apparatus with the worst propagation path condition can receive normally. As a method of realizing a high-quality transmission method, a method of reducing a physical transmission rate for transmitting a packet, a method of using an error correction code with a low coding rate as a communication channel code, a temporal, a frequency, For example, a method of transmitting the same information while spatially shifting and giving a diversity effect on the wireless receiver side can be used.

  However, applying these methods generally means that more bandwidth is used, and a problem arises when there is a limit on the bandwidth used. In addition, it is possible to reduce the band to be used by applying a lower bit rate encoding in order to solve this problem. However, encoding at a low bit rate has another problem that the quality of a moving image is deteriorated even in a wireless reception device having a poor propagation path condition or a wireless reception apparatus having a good propagation path condition. .

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a wireless multicast transmission system and a wireless transmission capable of reproducing a quality according to a propagation path state while suppressing an increase in a use band. An apparatus and a wireless multicast transmission method are provided.

In order to solve the above problems, the present invention provides data to enhance the quality of playback by combining the video data input and minimum required data block and the previous SL minimum required data block for reproduction encoded to include a block, it divides the moving image data encoded for each of the data blocks, select the transmission mode for each prior Symbol divided data blocks, by multicasting the data block in the transmission method selected A wireless transmission device to transmit and a data block received by the transmission method selected by the wireless transmission device, and the data block received normally in the received data block is combined and decoded, or the normal The received data block is recorded in the storage means, or the normally received data block is transferred to another wireless receiver. To 1 and more of the wireless reception device, wherein the wireless transmission device, the reception status of the radio receiving apparatus each data estimates or measures how a poor or a good, on the basis of the said reception status As the transmission method, one of the first transmission method and the second transmission method that uses a larger band or higher reliability than the first transmission method is selected, and the reception status is determined for each of the wireless reception devices. If the data blocks are different from each other, the minimum necessary data block is transmitted by multicast using the second transmission method, and the first data block is combined with the minimum necessary data block to improve the quality during reproduction. If the transmission status is good for all the wireless reception devices, the minimum necessary data block is transmitted. And the data block which improves the quality at the time of reproduction by combining with the minimum required data block is transmitted by multicast in the first transmission method, and the reception status is poor in all the wireless reception devices In this case, only the minimum necessary data block, or both the minimum necessary data block and the data block that improves the quality at the time of reproduction by combining the minimum necessary data block with the minimum necessary data block. A wireless multicast transmission system, wherein transmission is performed by multicast using a second transmission method .

The present invention, in the invention described above, the second transmission method is a transmission method of a low transmission rate, wherein the first transmission scheme is a transmission scheme of a high transmission rate.

In the present invention described above, the second transmission method is a transmission method using an error correction code having a low coding rate, and the first transmission method is an error correction code having a high coding rate. It is the transmission system used.

In the present invention described above, the second transmission method is a transmission method for transmitting information of the same data block using a plurality of communication paths that are temporally, spatially, or different in frequency . , the first transmission scheme is characterized by a transmission system for transmitting information of the same data block by using a channel number smaller than said plurality of communication paths.

The present invention is lowest Upon that sends a radio signal by multicast, for reproducing moving image data that is input for 1 or more radio receiving apparatus for reproducing a moving picture in quality based on successfully received data encoded to include a data block to enhance the quality of playback by binding to limit the required data block and the previous SL minimum required data blocks, it divides the moving image data encoded for each of the data blocks, select the transmission mode for each prior Symbol divided data blocks, in a radio transmitting apparatus that transmits by multicast the data block in a transmission scheme selected, poor or the receiving status of the radio receiving apparatus each data is good The first transmission method and the first transmission method are estimated or measured as the transmission method based on the reception status. If the second transmission method having a larger bandwidth or higher reliability than the second transmission method is selected and the reception status is different in each of the wireless reception devices, the minimum necessary data block is set to the second transmission method. 2 is transmitted by multicast in the transmission method 2 and is combined with the minimum necessary data block to improve data quality during reproduction, and is transmitted by multicast in the first transmission method, and the reception status is the wireless reception. If all the devices are good, both the minimum required data block and the data block that is combined with the minimum required data block to improve the quality at the time of reproduction are multicast by the first transmission method. When the reception status is poor in all the wireless reception devices, the minimum required A data block only such, or transmits the multicasting on both the second transmission method of a data block to enhance the quality of playback by binding to the minimum required data block and the minimum required data block This is a wireless transmission device characterized by the above.

The present invention, in the invention described above, the second transmission method is a transmission method of a low transmission rate, wherein the first transmission scheme is a transmission scheme of a high transmission rate.

In the present invention described above, the second transmission method is a transmission method using an error correction code having a low coding rate, and the first transmission method is an error correction code having a high coding rate. It is the transmission system used.

In the present invention described above, the second transmission method is a transmission method for transmitting information of the same data block using a plurality of communication paths that are temporally, spatially, or different in frequency . , the first transmission scheme is characterized by a transmission system for transmitting information of the same data block by using a channel number smaller than said plurality of communication paths.

The present invention is a wireless multicast transmission method in a wireless multicast transmission system comprising a wireless transmission device that transmits moving image data and one or more wireless reception devices that receive the moving image data from the wireless transmission device, wherein such radio transmission apparatus, and a data block to enhance the quality of playback by binding to the minimum required data block and the previous SL minimum required data blocks for reproducing video data input a step of encoding, the wireless transmission device, the steps of dividing the moving picture data encoded for each of the data blocks, the wireless transmitting device selects the transmission mode for each prior Symbol divided data blocks, selected A step of transmitting the data block by multicast using the transmission method, and the wireless receiver A step of receiving a data block by a transmission method selected by the device; and the wireless receiving device combines and decodes the data block received normally among the received data blocks or receives the data block normally Recording the data block in the storage means, or transferring the normally received data block to another radio receiving device , wherein the transmitting step is performed by the radio transmitting device. Estimating or measuring whether the reception status of each data is good or bad, and based on the reception status, as the transmission method, there are a first transmission method and a band to be used as compared with the first transmission method. Selecting either a large or highly reliable second transmission scheme, wherein in the selecting step, the reception status If different in each of the wireless reception devices, the second transmission method is selected for the minimum necessary data block and combined with the minimum necessary data block to improve the quality during reproduction. When the first transmission method is selected for a block and the reception status is good in all the wireless reception devices, the minimum necessary data block and the minimum necessary data block are combined. If the first transmission method is selected for both the data block that improves the quality during reproduction and the reception status is poor in all the wireless reception devices, only the minimum necessary data block is selected. Or a data block that improves the quality during playback by combining the minimum required data block and the minimum required data block. The wireless multicast transmission method is characterized in that the second transmission method is selected for both the network and the network .

According to the present invention, a wireless multicast transmission system includes a data block that is the minimum necessary for reproduction of input moving image data and a data block that improves the quality at the time of reproduction by combining the minimum necessary data block with the data block. The encoded moving image data is divided for each data block, and a transmission system having a large bandwidth or a high reliability is applied to the minimum necessary data block. A transmission method is selected for each divided data block, and the data block is transmitted by multicast using the selected transmission method, and the data block is received by the transmission method selected by the wireless transmission device. The data blocks that are normally received among the received data blocks are combined and decoded. Was configured with a radio reception device for transferring or recording the normally received data block to the storage unit, or the normally received data block to another radio receiver.
As a result, on the wireless transmission device side, the minimum required data block for reproduction is multicast transmitted using a transmission method with a large bandwidth or high reliability, and the wireless reception device side can receive normally. By reproducing the moving image using only the data block, it is possible to reproduce the moving image with quality according to the data block received by all the wireless reception devices. In addition, with this configuration, while minimizing the increase in the bandwidth to be used, the minimum required moving image data distribution to a wireless reception device with a poor propagation path condition, and the wireless reception with a good propagation path condition It is possible to distribute high-quality moving image data to the apparatus.

In addition, according to the present invention, the wireless transmission apparatus according to the wireless multicast transmission system transmits the minimum necessary data block by multicast at a transmission method with a low transmission rate and combines it with the minimum necessary data block. The data block that enhances the quality at the time of reproduction is configured to be transmitted by multicast using a transmission method with a high transmission rate.
As a result, a transmission method with a low transmission rate was applied as a transmission method with a large bandwidth or high reliability, and a transmission method with a high transmission rate was applied as a transmission method with a small bandwidth or a low reliability. A wireless transmission device according to the wireless multicast transmission system can be obtained. In general, it is possible to increase a possibility that a radio signal transmitted by a transmission method having a low transmission rate is normally received even under a situation where a propagation path condition is poor. On the other hand, a radio signal transmitted by a transmission method having a high transmission rate is less likely to be normally received when the propagation path condition is poor.
Therefore, it is possible to reproduce a moving image for the minimum necessary viewing in many wireless reception devices, and it is possible to view a higher quality moving image in a wireless reception device having a good propagation path condition. In general, a transmission method with a high transmission rate occupies a small bandwidth, so even if high-quality moving image data is transmitted, the increase in bandwidth is compared to the case of transmission with a transmission method with a low transmission rate. Become smaller. In addition, with this configuration, while minimizing the increase in the bandwidth to be used, the minimum required moving image data distribution to a wireless reception device with a poor propagation path condition, and the wireless reception with a good propagation path condition It is possible to distribute high-quality moving image data to the apparatus.

Further, according to the present invention, the wireless transmission device according to the wireless multicast transmission system transmits the minimum necessary data block by multicast using a transmission method using an error correction code with a low coding rate, and the minimum necessary data block A data block that is combined with the data block to improve the quality at the time of reproduction is configured to be transmitted by multicast using a transmission method using an error correction code with a high coding rate.
As a result, a transmission method that uses an error correction code with a low coding rate is applied as a transmission method with a large bandwidth or high reliability, and is encoded as a transmission method with a small bandwidth or low reliability. A wireless transmission device according to a wireless multicast transmission system to which a high-rate error correction code is applied can be obtained. In general, an error correction code with a low coding rate has a high error correction capability, and can be normally received even when the channel condition is poor. On the other hand, an error correction code with a high coding rate has a low error correction capability and a poor channel condition, but the possibility of normal reception is low, but the occupied band is small.
Therefore, even if high-quality moving image data is transmitted, the increase in bandwidth is smaller than when transmission is performed using a transmission scheme that employs an error correction code with a low coding rate. In addition, with this configuration, while minimizing the increase in the bandwidth to be used, the minimum required moving image data distribution to a wireless reception device with a poor propagation path condition, and the wireless reception with a good propagation path condition It is possible to distribute high-quality moving image data to the apparatus.

Further, according to the present invention, the wireless transmission apparatus according to the wireless multicast transmission system uses a plurality of communication paths that are temporally, spatially, or frequency different from each other for the minimum necessary data block. The same data is transmitted by using a smaller number of communication paths than the plurality of communication paths for data blocks that improve the quality at the time of reproduction by transmitting the same data by multicast and combining with the minimum necessary data blocks. It was set as the structure transmitted by multicast.
As a result, as a transmission method with a large bandwidth or high reliability, the same data is transmitted by multicast using a plurality of different communication paths shifted in time, space or frequency, and used. For data blocks that improve the quality at the time of playback by combining with the minimum required data block as a transmission system with a small band or low reliability, the same data as the data is used by using a smaller number of communication paths than a plurality of communication paths. A wireless transmission apparatus according to a wireless multicast transmission system that transmits data by multicast can be obtained. A diversity effect can be obtained by transmitting the same data a plurality of times, and even when the propagation path condition is poor, it can be normally received. On the other hand, if the number of communication paths is reduced, the possibility of correct reception is reduced, but the occupied bandwidth is reduced.
Therefore, even if high-quality moving image data is transmitted, the increase in the bandwidth can reduce the bandwidth to be used. In addition, with this configuration, while minimizing the increase in the bandwidth to be used, the minimum required moving image data distribution to a wireless reception device with a poor propagation path condition, and the wireless reception with a good propagation path condition It is possible to distribute high-quality moving image data to the apparatus.

In addition, according to the present invention, the wireless transmission device according to the wireless multicast transmission system is configured to estimate or measure the data reception status of the wireless reception device and change the transmission method used based on the reception status.
As a result, the reception state of the wireless reception device can be measured or estimated on the wireless transmission device side, so that the transmission method to be used can be changed when the propagation path state of the wireless reception device changes. . When wireless is used, both the wireless transmission device and the wireless reception device can move within a short period of time, so select the optimal transmission method even when the propagation path status of each device changes. It becomes possible to do.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the following description, an embodiment of the wireless transmission device according to the wireless multicast transmission system of the present invention will be described as a wireless multicast transmission device, and an embodiment of the wireless reception device will be described as a wireless multicast reception device.

(Internal configuration of wireless multicast transmitter)
FIG. 1 is a schematic block diagram showing the internal configuration of the wireless multicast transmission device 1 according to the present embodiment.
A wireless multicast transmission apparatus 1 shown in FIG. 1 is an apparatus to which a wireless LAN (Local Area Network) system compliant with IEEE 802.11 is applied as a wireless transmission system, and transmits data using the multicast system.

  In the wireless multicast transmission device 1, an encoder 10 performs encoding on input moving image data by an encoding method having scalability. The encoding method having scalability is to encode moving image data into low-quality moving image data, medium-quality moving image data, and high-quality moving image data. The data dividing unit 11 divides the moving image data encoded so as to have scalability input from the encoder 10 into data blocks, and inputs the divided data blocks to the frame generating unit 12.

  Here, with reference to FIG. 2, the encoding method with scalability by the encoder 10 will be described. The quality in the present embodiment refers to the SN (Signal-to-Noise) ratio due to the resolution of the moving image, the frame rate, and the quantization error.

  Of the encoded moving image data, only the low-quality moving image data is reproduced, but only the moving image with a deteriorated quality is reproduced. It is possible to reproduce a moving image having a quality that allows the user to view and understand the content. When medium-quality moving image data is reproduced together with low-quality moving image data, medium-quality moving images can be reproduced. Furthermore, when medium-quality moving image data and high-quality moving image data are reproduced together with low-quality moving image data, a high-quality moving image can be reproduced. The data dividing unit 11 converts the moving image data encoded so as to have scalability into (1) a low-quality moving image data block (hereinafter referred to as a data block (1)), and (2) medium-quality moving image data. The moving image data is divided into three data blocks: a block (hereinafter referred to as data block (2)), and (3) a high quality moving image data block (hereinafter referred to as data block (3)). The divided data block is output together with the quality information indicating.

  The frame generation unit 12 generates a frame when a data block input from the data division unit 11 is added with a header or a tailor and is transmitted as a radio signal, and associates the generated frame with quality information. To the transmission control unit 13.

  FIG. 3 is a diagram illustrating a data configuration of a frame generated by the frame generation unit 12. In the header shown in FIG. 3, an ID (IDentification) indicating a transmitting station (MAC (Media Access Control) address in IEEE802.11 wireless LAN) is shown in the header, and an ID indicating a receiving station in the multicast scheme (MAC (Media in IEEE802.11 wireless LAN). Access Control) address) and control information such as the type of payload to be transmitted are stored. Further, the data block after division is stored in the payload. Further, the Taylor mainly stores an error detection FCS (Frame Check Sequence).

  The transmission control unit 13 stores the transmission rate input from the transmission rate setting unit 29 in advance in association with the quality information. Further, the transmission control unit 13 reads quality information from information including the frame and quality information input from the frame generation unit 12, selects a transmission rate corresponding to the read quality information, and selects the selected transmission rate and frame. Is input to the modulation unit 14. For example, when the moving image data is divided into three data blocks as shown in FIG. 2, the transmission control unit 13 selects the transmission rate to be used based on the quality information associated with each data block. It will be. The transmission control unit 13 transmits a frame when no carrier is detected based on information indicating whether or not the carrier input from the carrier detection unit 28 has been detected, and the carrier is detected. If so, the transmission timing is controlled such as postponing the transmission.

  The modulation unit 14 modulates the frame input from the transmission control unit 13 by a modulation scheme based on the transmission rate input from the transmission control unit 13. The transmission unit 15 transmits a radio signal including the modulated frame input from the modulation unit 14 through the antenna 16.

  Since the wireless multicast transmission device 1 is premised on the application of a wireless LAN system conforming to IEEE 802.11, the wireless multicast reception device 2 makes a connection request to the wireless multicast transmission device 1 in advance and performs multicast transmission. It is necessary to receive unicast communications before doing it. For this purpose, the receiving unit 20 and a function of processing a reception frame received by the receiving unit 20 are provided.

  The receiving unit 20 receives a radio signal through the antenna 16. The receiving unit 20 down-converts the received signal into an IF (Intermediate Frequency) band and a baseband band as necessary, and inputs the received signal to the demodulating unit 21. The receiving unit 20 measures RSSI (Received Signal Strength Indicator) and the like, and inputs the measurement results to the carrier detection unit 28 and the propagation path state measurement unit 27.

  The demodulator 21 demodulates the received signal input from the receiver 20 and inputs the received frame obtained by the demodulation to the error detector 22. Further, the demodulation unit 21 inputs the demodulation result to the carrier detection unit 28 and the propagation path condition measurement unit 27. The error detection unit 22 uses the FCS unit included in the reception frame input from the demodulation unit 21 to detect whether there is an error in the reception frame. Further, the error detection unit 22 discards the received frame when an error is detected, and outputs the received frame to the frame selection unit 23 when no error is detected. Further, the error detection unit 22 inputs the presence / absence of the detected error to the propagation path state measurement unit 27 and the transmission rate setting unit 29.

  The frame selection unit 23 determines whether or not the device itself should receive the received frame from the destination ID in the header included in the received frame. If the frame selection unit 23 determines that the frame is to be received, the frame selection unit 23 inputs the reception frame to the reception frame processing unit 23. If the frame selection unit 23 determines that the frame is not to be received, the frame selection unit 23 discards the reception frame.

  The reception frame processing unit 24 requests the transmission control unit 13 to transmit ACK when it is necessary to respond with an acknowledgment (ACK) to the reception frame. In addition, when the wireless multicast transmission device 1 is connected to another wired network or the like, the reception frame processing unit 24 reads the payload from the reception frame if it is necessary to transfer the reception frame to the network side. Perform processing necessary to transfer to the network and send it to the network side. In addition, when the reception frame includes information on the propagation path condition, the reception frame processing unit 24 inputs the information to the propagation path condition measurement unit 27. In addition, when the received frame includes information on a transmission rate used when the next frame is transmitted, the received frame processing unit 24 inputs the information to the transmission rate setting unit 29.

  The propagation path state measurement unit 27 measures or estimates the state of the propagation path based on information input from each function unit in the wireless multicast transmission device 1 and inputs the result to the transmission rate setting unit 29. Specifically, the state of the propagation path is estimated based on the received intensity value transmitted from the wireless multicast receiver 2.

  The transmission rate setting unit 29 selects a transmission rate to be used at the time of frame transmission based on information input from the propagation path condition measurement unit 27 and other functional units in the wireless multicast transmission device 1, and a transmission control unit 13 is input.

  The transmission rate setting unit 29 can also input instruction information that does not divide data to the data dividing unit 11 when the same transmission rate is applied to all data blocks. In addition, the transmission rate setting unit 29 reproduces a high-quality moving image when the propagation channel state measurement unit 27 determines that the propagation channel state with all the wireless multicast reception devices 2 described later is inferior. It is also possible to input an instruction not to transmit the necessary data block to the transmission control unit 13.

  The carrier detector 28 detects the carrier transmitted from the wireless multicast receiver 2 based on the information input from the receiver 20 and the demodulator 21 and controls transmission of information indicating whether the carrier has been detected. Input to the unit 13.

  In FIG. 1, the moving image data to be transmitted is only targeted for moving image data output from the encoder 10. For example, when moving image data encoded from the connected network side is input. The moving image data may be re-encoded by a scalable encoding method and input to the data dividing unit 11.

  In addition, when the moving image data is already encoded by a scalable encoding method, the moving image data may be input to the data dividing unit 11. In addition, when it is already encoded by a scalable encoding method and divided for each quality, it may be input directly to the transmission control unit 13.

(Internal configuration of wireless multicast receiver)
Next, the wireless multicast receiver according to this embodiment will be described. FIG. 4 is a schematic block diagram showing the internal configuration of the wireless multicast receiver 2. The wireless multicast receiving device 2 is a device to which a wireless LAN system compliant with IEEE802.11 is applied, like the wireless multicast transmitting device.

  The frame generation unit 52, the transmission control unit 53, the modulation unit 54, and the transmission unit 55 in the wireless multicast reception device 2 are the frame generation unit 12, the transmission control unit 13, the modulation unit 14, and the transmission unit of the wireless multicast transmission device 1 described above, respectively. 15 is a functional unit having the same configuration as FIG. In addition, the receiving unit 40, the demodulating unit 41, the error detecting unit 42, the frame selecting unit 43, the propagation path state measuring unit 47, the carrier detecting unit 48, and the transmission rate setting unit 49 in the wireless multicast receiving device 2 are each a wireless multicast transmitting device. 1 is a functional unit having the same configuration as the reception unit 20, demodulation unit 21, error detection unit 22, frame selection unit 23, propagation path state measurement unit 27, carrier detection unit 28, and transmission rate setting unit 29.

Hereinafter, in the wireless multicast receiving device 2, a functional unit having a configuration different from the functional unit in the wireless multicast transmitting device 1 will be described.
The reception frame processing unit 44 removes the header and tailer from the reception frame input from the frame selection unit 43, extracts the payload, and the data stored in the payload is a data block of moving image data or moving image data It is determined whether the data itself or other data. Further, the reception frame processing unit 44 inputs the data stored in the payload to the data combining unit 45 when the data is a data block of moving image data or the moving image data itself.

 When the data input from the received frame processing unit 44 is a data block of moving image data, the data combining unit 45 waits for input of another data block for a certain time slot, and the time of the time slot has elapsed. Then, the data blocks existing at the time are combined. In addition, when the data input from the reception frame processing unit 44 is the moving image data itself, the data combining unit 45 inputs it to the decoder 46 as it is. When the data is a data block, the data combining unit 45 inputs the combined moving image data to the decoder 46. To do.

  If only the data block (1) in FIG. 2 is input during the above time slot in the data combining unit 45, only the data block (1) is input to the decoder 46, and the data block (1) When only the data block (2) is input, the data block (1) and the data block (2) are combined, and the combined data is input to the decoder 46.

  The decoder 46 decodes the moving image data input from the data combining unit 45. At this time, even when all of the moving image data cannot be received, the data combining unit 45 performs decoding with the quality within the received range. Also, in the wireless multicast receiving apparatus 2, when it is necessary to transmit data for some reason, the data to be transmitted is input to the frame generation unit 52 and transmitted by the same procedure as that of the wireless multicast transmitting apparatus 1.

  Note that the decoder 46 may reproduce the moving image by using all the data blocks combined by the data combining unit 45, or sets the quality to be reproduced in advance, Even when a high-quality data block unnecessary for reproduction is normally received and combined and input by the data combining unit 45, it may not be used for reproduction.

 The output from the decoder 46 is moving image data. For example, the output from the data combination unit 45 is an interface for a computer such as a network, a PCI (Peripheral Component Interconnect) bus, a card bus, a PCI express bus, or an express card bus. You may make it transmit to another apparatus via this.

 Alternatively, the encoded moving image data that is output from the data combining unit 45 may be converted by another encoding method and transmitted to another device. Further, the data block in a divided state before being input to the data combining unit 45 may be transmitted as it is to another device.

  Next, operations in the three configurations of the above-described wireless multicast transmission system 3 including the wireless multicast transmission device 1 and the wireless multicast reception device 2 will be described with reference to FIGS. In the following description, the wireless multicast transmission device 1 is applied to an AP (Access Point) 1a in the wireless multicast transmission system 3, and a plurality of STAs (STAtion) 2a, 2b, and 2c in the wireless multicast transmission system 3 are used. The wireless multicast receiver 2 is applied. Further, the function units inside the AP 1a are indicated by the reference numerals with “a” added to the respective function units of the wireless multicast transmission device 1, and the STAs 2a, 2b, and 2c are assigned to the respective function units of the wireless multicast reception device 2, respectively. It shall be shown with the code | symbol which each added "a", "b", and "c".

(First configuration)
FIG. 5 is a diagram illustrating a positional relationship between the AP 1a and the STAs 2a, 2b, and 2c in the wireless multicast transmission system 3 having the first configuration. The STA 2a is located at a position closer to the AP 1a than the STAs 2b and 2c, and the STA 2b and 2c are located at positions far from the AP 1a in order. In general, in wireless communication, since the propagation path condition becomes worse as the distance is longer, the propagation path condition of the STA 2a is the best in the positional relationship of FIG. 5, and the propagation path condition of the STA 2b is compared to the STA 2a. Although it is inferior, it is better than STA2c, and the propagation path condition of STA2c is inferior.

  FIG. 6 is a diagram showing a state of data transmission / reception in the wireless multicast transmission system 3 having the positional relationship shown in FIG.

  First, when the moving image data 100 is input to the encoder 10a of the AP 1a, the encoder uses the scalable encoding method to convert the input moving image data into three quality moving image data as shown in FIG. That is, encoding is performed so as to have three moving image data blocks of low quality, medium quality, and high quality. The encoder 10a inputs the encoded data to the data dividing unit 11a. The data dividing unit 11a divides the input data into a data block (1), a data block (2), and a data block (3), and inputs the data together with quality information indicating the quality to the frame generating unit 12a.

  As shown in FIG. 3, the frame generation unit 12a adds headers including the IDs of the STAs 2a, 2b, and 2c to the data block (1), the data block (2), and the data block (3), respectively. A frame for transmission by a radio signal with a tailer added is generated, and the generated frame and quality information are associated with each other and input to the transmission control unit 13. FIG. 6 shows a frame in which the header and tail portions are omitted from the frame shown in FIG.

  The carrier detection unit 28a performs carrier sense prior to frame transmission. When the carrier detection unit 28a detects carriers from the STAs 2a, 2b, and 2c, the carrier detection unit 28a inputs information on detection of each carrier to the transmission control unit 13a. When the information from which the carrier is detected from the STAs 2a, 2b, and 2c is input from the carrier detection unit 28a, the transmission control unit 13a receives the transmission rate based on the quality information corresponding to the three frames input from the frame generation unit 12a. The transmission rate corresponding to each frame is selected from the transmission rates input from the setting unit 29a, and the selected transmission rate and the frame are associated with each other and input to the modulation unit 14a. The modulation unit 14a modulates the frame by a modulation method based on the transmission rate input from the transmission control unit 13a, and each data modulated by the modulation unit 14a is transmitted as a radio signal by the transmission unit 15 via the antenna 16. The

  In FIG. 6, the data block (1) is the minimum data block necessary for reproducing moving image data, and is therefore transmitted at a low transmission rate. Hereinafter, data blocks (2) and (3) are transmitted in the order of higher transmission rates. Therefore, the length of the occupation time of each frame is in the order of data block (1)> data block (2)> data block (3). At this time, since the data block (1) has a low transmission rate, it is normally received by all the STAs 2a, 2b, and 2c. However, the data block (2) cannot be normally received by the receiving unit 40c in the case of the STA 2c having the longest distance from the AP 1a. Further, only the receiving unit 40a of the STA 2a can normally receive the data block (3).

  Here, the operation when the STA 2a receives is described. The receiving unit 40a of the STA 2a performs processing such as down-conversion on the received radio signal, and inputs the received signal obtained by the processing to the demodulating unit 41a. The demodulator 41a inputs a received frame obtained by demodulating the received signal to the error detector 42a. The error detection unit 42a detects whether or not there is an error in the reception frame by using the FCS unit included in the reception frame, and inputs the reception frame having no error to the frame selection unit 43a. The frame selection unit 43a determines whether or not the frame is received based on the destination ID of the received frame, and inputs the received frame to the received frame processing unit 44a.

  When it is necessary to send an acknowledgment (ACK) to the received frame, the received frame processing unit 44a requests the transmission control unit 53a to transmit ACK, reads the payload from the received frame, and reads the read payload. The data is input to the data combining unit 45a. The data combining unit 45a has a certain time slot. When the data block (1), the data block (2), and the data block (3) are input in the time slot, the data block (1 ), The data block (2) and the data block (3) are combined, and the combined data is input to the decoder 46a. The decoder 46a decodes the moving image data input from the data combining unit 45 to reproduce the moving image.

As a result, since the STA 2a can receive all the data blocks (1), (2), and (3), the user of the STA 2a can view high-quality moving images. It is.
On the other hand, since the STA 2b receives the data block (1) and the data block (2), the user of the STA 2b can view a moving image with medium quality. The STA 2c can receive only the data block (1), but the user of the STA 2c can view a moving image that can understand the content although the quality is minimum.

(Second configuration)
Next, FIG. 7 is a diagram illustrating a positional relationship between the AP 1a and the STAs 2a, 2b, and 2c in the wireless multicast transmission system 3 having the second configuration. In the first configuration shown in FIG. 5, the propagation path conditions of the STAs 2a, 2b, and 2c are different from each other. However, in FIG. 7, the STAs 2b and 2c move and all the STAs 2a, 2b, and 2c and AP1a move. Are substantially the same distance, and the propagation path conditions of the STAs 2b and 2c are good.

  FIG. 8 is a diagram showing a state of data transmission / reception in the wireless multicast transmission system 3 having the positional relationship shown in FIG. As shown in FIG. 8, when all the STAs 2a, 2b, and 2c exist at a short distance from the AP 1a, the propagation path conditions of all the STAs 2a, 2b, and 2c are also good. When such a state is detected by the propagation path condition measurement unit 47 of the AP 1a, as shown in FIG. 8, all the divided data blocks (1), data blocks (2), and data blocks (3) are transmitted at a high rate. Even if transmitted at a rate, all STAs 2a, 2b, 2c can receive all data blocks (1), data blocks (2), and data blocks (3). Can be viewed.

  There are the following methods for measuring the quality indicating the condition of the propagation path. For example, in the wireless multicast transmission device 1 (base station), there is a method of measuring the quality of the propagation path by measuring the reception power and RSSI using the signal transmitted from the wireless multicast reception device 2 (terminal station). is there.

  In addition, when the wireless multicast transmission device 1 (base station) and the wireless multicast reception device 2 (terminal station) perform unicast communication other than multicast, the number of frames transmitted by the wireless multicast transmission device 1 and ACK There is a method of measuring the quality of the propagation path by counting the presence / absence of reception of (arrival confirmation) and measuring the error rate based on each counted value.

  In addition, the wireless multicast receiver 2 (terminal station) measures the received power and RSSI, transmits to the wireless multicast transmitter 1 (base station) using unicast, and receives the received power and RSSI. 1 is a method for measuring quality.

  Further, the position information is obtained by the position measurement technique using GPS (Global Positioning System) or wireless LAN, and the position information is obtained by the wireless multicast transmission apparatus 1 (base station) and the wireless multicast reception apparatus 2 (terminal station), and the wireless multicast reception apparatus 2 (terminal station) transmits the position information to the wireless multicast transmission apparatus 1 (base station), and the propagation path is determined based on the position information received by the wireless multicast transmission apparatus 1 (base station), particularly the distance information. There is a way to measure quality.

  In the case of the configuration of FIG. 7, as another means, the data dividing unit 11 may transmit the data as one data without dividing the moving image data.

(Third configuration)
Next, FIG. 9 is a diagram illustrating a positional relationship between the AP 1a and the STAs 2a, 2b, and 2c in the wireless multicast transmission system 3 having the third configuration. In FIG. 9, the STAs 2a, 2b, and 2c move, and the propagation path conditions are deteriorated in all the STAs 2a, 2b, and 2c.

  FIG. 10 is a diagram showing a state of data transmission / reception in the wireless multicast transmission system 3 having the positional relationship shown in FIG. As shown in FIG. 9, when all the STAs 2a, 2b and 2c are located far from the AP 1a, the channel conditions of all the STAs 2a, 2b and 2c are inferior. When such a state is detected by the propagation path condition measurement unit 27 of the AP 1a, all data blocks (1), data blocks (2), and data blocks (3) are transmitted at a low transmission rate as shown in FIG. To do.

  In the configuration of FIG. 9, as another means, a method of transmitting moving image data as a single data without dividing it, or transmitting only the data block (1), or the data block (1) and Only the data block (2) may be transmitted.

  With the configuration of the above embodiment, the following effects can be obtained. That is, the wireless multicast transmission apparatus 1 divides the moving image data encoded by the scalable encoding method into a plurality of data, and the minimum data necessary for viewing the moving image according to the importance is as follows. Use a transmission system with a large bandwidth or a high reliability, that is, a transmission system with a low transmission rate, and a block necessary for viewing a high-quality moving image has a small bandwidth or a transmission with a low reliability. By using a scheme, that is, a transmission scheme having a high transmission rate, the wireless multicast receiver 2 with good propagation path conditions can reproduce high-quality moving images, and the wireless multicast receiver 2 with poor propagation path conditions Although it is low quality, it is possible to reproduce a moving image necessary for viewing at a minimum. Accordingly, it is possible to reproduce the quality according to the propagation path state while suppressing the increase in the use band. With this configuration, the minimum data block necessary for viewing a moving image can be received even by a wireless reception device having a poor propagation path state, for example, a long distance between transmission and reception, and more wireless It is possible to reproduce a moving image in the receiving device. On the other hand, for wireless receivers with good propagation path conditions, for example, a short distance between transmission and reception, it is possible to receive data blocks necessary for reproducing high-quality moving images, resulting in higher quality. It is possible to reproduce a moving image.

  In the above description, a method of changing the transmission rate is cited as a method of changing the propagation path condition, but another means can be considered as a means for that purpose. For example, data block (1) is transmitted with a transmission scheme using an error correction code with a low coding rate, and data block (2) is transmitted with a transmission scheme using an error correction code with a medium coding rate. The data block (3) may be transmitted by a transmission method using an error correction code having a high coding rate.

  Further, the data block (1) is transmitted by a transmission method in which information of the same data block (1) is transmitted using a plurality of communication paths that are temporally, spatially, or frequency different, and the data block ( 2) The number of transmission paths may be gradually reduced and transmitted in the order of data block (3).

  Also, with the configuration of the above-described embodiment, the wireless multicast transmission device 1 selects the optimal transmission method according to the propagation path state by measuring or estimating the propagation path state of the wireless multicast reception device 2 Is possible. When wireless is used, both the wireless transmission device and the wireless reception device can move within a short period of time, so select the optimal transmission method even when the propagation path status of each device changes. It becomes possible to do.

  In the above embodiment, the moving image data is divided into three. However, the present invention is not limited to this, and has a plurality of qualities at the time of scalable encoding performed by the encoder 10. Such encoding may be performed. In that case, the data dividing unit 11 performs division according to the number.

It is the block diagram which showed the internal structure of the radio | wireless multicast transmission apparatus by this embodiment. It is a figure for demonstrating operation | movement of the encoder and data division part in the embodiment. It is a data block diagram of the frame produced | generated by the frame production | generation part in the embodiment. It is the block diagram which showed the internal structure of the wireless multicast receiver in the same embodiment. It is a block diagram (the 1) of the wireless multicast transmission system in the embodiment. It is the figure (the 1) which showed the process which concerns on the wireless multicast transmission system in the embodiment. It is a block diagram (the 2) of the wireless multicast transmission system in the embodiment. It is the figure (the 2) which showed the process which concerns on the wireless multicast transmission system in the embodiment. It is a block diagram (the 3) of the radio | wireless multicast transmission system in the embodiment. FIG. 6 is a diagram (No. 3) illustrating the process of the wireless multicast transmission system in the embodiment. It is the block diagram which showed the internal structure of the wireless multicast transmission apparatus based on a prior art. It is the block diagram which showed the internal structure of the wireless multicast receiver concerning a prior art. It is a block diagram of the wireless multicast transmission system which concerns on a prior art. It is the figure (the 1) which showed the process of the wireless multicast transmission system which concerns on a prior art. It is the figure (the 2) which showed the process of the wireless multicast transmission system which concerns on a prior art. It is FIG. (The 3) which showed the process of the radio | wireless multicast transmission system which concerns on a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wireless multicast transmission apparatus 10 Encoder 20 Data division part 12 Frame generation part 13 Transmission control part 14 Modulation part 15 Transmission part 16 Antenna 20 Reception part 21 Demodulation part 22 Error detection part 23 Frame selection part 24 Reception frame process part 27 Propagation path condition Measurement unit 28 Carrier detection unit 29 Transmission rate setting unit 100 Moving image data

Claims (9)

  1. Encoded to include a data block to enhance the quality of playback by combining the video data input and minimum required data block and the previous SL minimum required data blocks for reproduction, encoded dividing the moving image data for each of said data blocks, select the transmission mode for each prior Symbol divided data blocks, and a radio transmitting apparatus that transmits by multicast the data block in a transmission scheme selected,
    Data block is received by the transmission method selected by the wireless transmission device, and the received data block is combined and decoded in the received data block, or the normally received data block is stored One or more wireless receivers that record to the means or transfer the normally received data block to another wireless receiver;
    Equipped with a,
    The wireless transmission device
    Estimating or measuring whether the data reception status of each of the wireless reception devices is good or poor, and based on the reception status, the transmission method is more than the first transmission method and the first transmission method. Select one of the second transmission methods with a large bandwidth or high reliability,
    When the reception status is different in each wireless reception device,
    The minimum necessary data block is transmitted by multicast in the second transmission method, and a data block that improves quality at the time of reproduction by combining with the minimum necessary data block is multicast by the first transmission method. Send
    When the reception status is good in all the wireless reception devices,
    Sending both the minimum necessary data block and the data block that improves the quality at the time of reproduction by combining with the minimum necessary data block by multicast in the first transmission method,
    When the reception status is poor in all the wireless reception devices,
    Only the minimum necessary data block, or both the minimum necessary data block and the data block that improves the quality at the time of reproduction by combining the minimum necessary data block with the second transmission method. wireless multicast transmission system and transmits by multicast.
  2. The second transmission method is a transmission method of a low transmission rate,
    Wireless Multicast transmission system according to claim 1, wherein the first transmission scheme is a transmission scheme of a high transmission rate.
  3. The second transmission method is a transmission method using a low error correcting codes having the encoding rate,
    Wireless Multicast Transmission system according to claim 1 wherein the first transmission scheme, which is a transmission system using a high error correction code having the encoding rate.
  4. The second transmission scheme is a transmission scheme that transmits information of the same data block using a plurality of communication paths that are temporally, spatially, or different in frequency.
    Wireless Multicast transmission system according to claim 1 wherein the first transmission scheme, which is a transmission system for transmitting information of the same data block by using a channel number smaller than said plurality of communication paths .
  5. Upon that sends a radio signal by multicast to one or more radio receiving apparatus for reproducing a moving picture in quality based on successfully received data,
    Encoded to include a data block to enhance the quality of playback by combining the video data input and minimum required data block and the previous SL minimum required data blocks for reproduction, encoded dividing the moving image data for each of said data blocks, select the transmission mode for each prior Symbol divided data blocks, in a radio transmitting apparatus that transmits by multicast the data block in a transmission scheme selected,
    Estimating or measuring whether the data reception status of each of the wireless reception devices is good or poor, and based on the reception status, the transmission method is more than the first transmission method and the first transmission method. Select one of the second transmission methods with a large bandwidth or high reliability,
    When the reception status is different in each wireless reception device,
    The minimum necessary data block is transmitted by multicast in the second transmission method, and a data block that improves quality at the time of reproduction by combining with the minimum necessary data block is multicast by the first transmission method. Send
    When the reception status is good in all the wireless reception devices,
    Sending both the minimum necessary data block and the data block that improves the quality at the time of reproduction by combining with the minimum necessary data block by multicast in the first transmission method,
    When the reception status is poor in all the wireless reception devices,
    Only the minimum necessary data block, or both the minimum necessary data block and the data block that improves the quality at the time of reproduction by combining the minimum necessary data block with the second transmission method. A wireless transmission device that transmits by multicast .
  6. The second transmission method is a transmission method of a low transmission rate,
    The radio transmitting apparatus according to claim 5, wherein the first transmission scheme is a transmission scheme of a high transmission rate.
  7. The second transmission method is a transmission method using a low error correcting codes having the encoding rate,
    Wherein the first transmission scheme is the radio transmitting apparatus according to claim 5, characterized in that the transmission using high error correction code having the encoding rate.
  8. The second transmission scheme is a transmission scheme that transmits information of the same data block using a plurality of communication paths that are temporally, spatially, or different in frequency.
    Wherein the first transmission scheme is the radio transmitting apparatus according to claim 5, characterized in that the transmission system for transmitting information of the same data block by using a channel number smaller than said plurality of communication paths.
  9. A wireless multicast transmission method in a wireless multicast transmission system, comprising: a wireless transmission device that transmits moving image data; and one or more wireless reception devices that receive the moving image data from the wireless transmission device,
    Wherein such radio transmission apparatus, and a data block to enhance the quality of playback by binding to the minimum required data block and the previous SL minimum required data blocks for reproducing video data input Encoding, and
    The wireless transmission device divides the encoded moving image data for each data block;
    A step in which the radio transmitting device selects the transmission mode for each prior Symbol divided data blocks are transmitted by multicast the data block in a transmission scheme selected,
    The wireless reception device receiving a data block in a transmission method selected by the wireless transmission device;
    The wireless reception device combines and decodes data blocks received normally among the received data blocks, records the normally received data blocks in a storage means, or receives the data normally Transferring the processed data block to another wireless receiving device;
    With
    The transmitting step includes
    The wireless transmission device estimates or measures whether the data reception status of each of the wireless reception devices is good or bad, and based on the reception status, as the transmission method, the first transmission method and the first transmission method are used. The step of selecting one of the second transmission methods having a larger band or higher reliability than the first transmission method.
    Including
    In the selecting step,
    When the reception status is different in each wireless reception device,
    The second transmission method is selected for the minimum necessary data block, and the first transmission method is selected for a data block that is combined with the minimum necessary data block to improve quality during reproduction. Selected,
    When the reception status is good in all the wireless reception devices,
    Selecting the first transmission method for both the minimum necessary data block and the data block that improves the quality at the time of reproduction by combining with the minimum necessary data block;
    When the reception status is poor in all the wireless reception devices,
    Only for the minimum necessary data block, or for both the minimum necessary data block and the data block that is combined with the minimum necessary data block to improve the quality at the time of reproduction. A wireless multicast transmission method characterized by selecting a transmission method.
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