JP2008005382A - Communications system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communications system, capable of allowing a plurality of transmitters to easily execute signal transmission at a suitable transmission rate, corresponding not only to the state of the transmitter side but also to the state of the receiver side. <P>SOLUTION: In the communications system, having a plurality of transmitters each of which transmits stream data and a receiver for receiving the stream data from the plurality of transmitters; the receiver is provided with a calculation means for calculating a range, allowing the transmission rate of the data of respective transmitters and a notification means for notifying the calculation result to the transmitters; and each transmitter is provided with a transmission rate adjusting means for receiving the notification and adjusting the data transmission rate within the range. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a communication system for transmitting stream data such as video and audio information.

  A system for compressing real-time signals such as video and audio using wireless communication by using compression encoding such as MPEG2-TS and transmitting the signals to a network has been recognized. In wireless communication, 802.11b using the 2.4 GHz band, 802.11a using the 802.11g, and 5.2 GHz band are known.

  In 2.4 GHz, there are three frequencies at which video can be transmitted (actually, there are 1 to 13 channels that can be used, but in order to prevent interference, it is common to perform spectrum spreading around 1CH, 7CH, and 13CH. 3 is the maximum frequency that can be used at the same time). At each frequency, one SDTV [Standard TV] is used for 802.11b, one HDTV [High Definition TV] is used for 802.11g, or one SDTV is used. There are three bands that can be transmitted. In 5.2 GHz, there are eight frequencies at which video can be transmitted, and in each frequency, there is a band that can transmit one HDTV or three SDTVs in 802.11a.

  However, in wireless communication, the longer the transmission distance, the more susceptible to multipath fading, which may increase the packet error rate. When the error rate becomes high and the receiving apparatus cannot receive all video images, the video is interrupted.

  In addition, since a video source located at a distant place can be displayed by using wireless communication, a system that receives a real-time signal transmitted from a plurality of transmitting devices and performs two-screen display in one receiving device. For example, it is disclosed in Patent Document 1.

  According to this prior art, by providing two wireless reception units, when the transmission data from one transmission device is HDTV video, the reception device receives a real-time signal at 802.11g, and the other The real-time signal from the transmitter is received by 802.11a.

JP 2003-324661 A

  For example, when receiving video signals from two distant transmission devices and displaying them on a TV screen in two screens as in the prior art described above, a single reception device may be used depending on the transmission rate of the video signal and the status of the communication channel. Then, it may be in a state where it cannot be properly processed.

  As an example, the rate (transmission speed) of video data by HDTV is 20 to 25 Mbps, the rate of video data by SDTV is 6 to 10 Mbps, and each transmission is performed on the same channel (frequency band where the maximum wireless communication speed is 25 Mbps). Assume that it is used. At this time, it is difficult to receive HDTV video data and HDTV video data, or HDTV video data and SDTV video data by a single receiving unit. This is because the data overflows in the channel (the amount of data to be transmitted becomes excessive with respect to the transmission capability in the transmission path).

  In addition, as in the prior art described above, providing a plurality of wireless reception units is one method for improving the reception capability. However, increasing the number of wireless receivers increases the circuit scale, which in turn hinders downsizing and cost reduction of the product.

  On the other hand, for example, when the two-screen display is performed as described above, the screen size used for each display is small, so that even if HDTV or SDTV video data is used, the difference in image quality is felt small. It becomes like this. Therefore, in this case, even if the quality of the video data transmitted from the two transmission devices has been reduced to some extent (the amount of information required per unit time has been reduced), it does not matter much.

  Rather, when these transmitters transmit on the same channel, it is more important to prevent the data from overflowing on the channel even if the data quality is slightly reduced within a range where a certain video quality can be secured. It can be said that there is. Also, by doing so, it is relatively easy to perform appropriate reception processing with a single receiver.

  Thus, it can be said that it is very useful to be able to adjust the transmission rate according to the usage status (how it is used) of the data received by the receiving apparatus. Accordingly, in the present invention, in view of the above-described problems, it is possible to easily perform signal transmission at a suitable transmission speed in accordance with the situation on the receiving apparatus side as well as on the transmitting apparatus side for a plurality of transmitting apparatuses. An object is to provide a simple communication system.

  In order to achieve the above object, a communication system according to the present invention is a communication system having a plurality of transmission devices each transmitting stream data and a reception device receiving the stream data from the plurality of transmission devices. The receiving device comprises: calculating means for calculating a permissible range as the data transmission speed of each transmitting device; and notifying means for notifying the transmitting device of the calculation result, wherein the transmitting device Accordingly, a configuration (first configuration) is provided that includes transmission rate adjustment means for adjusting the data transmission rate within the range.

  According to this configuration, since the allowable range of the data transmission speed of each transmission device is calculated on the reception device side, the data output status on the reception device side (for example, what size image display is performed) Etc.) can be easily calculated. In each transmission apparatus, the data transmission speed is adjusted within the allowable range. Therefore, it is possible to make the data transmission speed by the transmission apparatus according to the situation on the transmission apparatus side while setting the transmission speed allowed on the reception apparatus side.

  As a result, it is possible to realize a communication system capable of causing a plurality of transmission apparatuses to perform signal transmission at an appropriate transmission rate according to the situation.

  Further, in the first configuration, the calculation unit may be configured to calculate the range (second configuration) so that a sum of data transmission rates of the transmission devices does not exceed a predetermined rate.

  According to this configuration, for example, by setting the predetermined speed so as not to exceed the data processing capability on the receiving device side, it is possible to prevent the receiving device from being defective due to excessive data transmission. Further, by setting the maximum transmission speed of data in the transmission channel (frequency band) as the predetermined speed, even if each transmission apparatus performs transmission on the same channel, data overflows in the communication band. It becomes possible to prevent the situation.

  Further, in the second configuration, each of the transmission devices performs the transmission using the same transmission channel, and the predetermined rate does not exceed a maximum transmission rate in the transmission channel (third configuration). ).

  According to this configuration, since each transmitting apparatus performs transmission using the same transmission channel, the receiving apparatus need only correspond to the frequency band of this transmitting channel. Therefore, it is possible to make the receiving device more concise than that corresponding to a plurality of frequency bands. Furthermore, since the predetermined speed is set so as not to exceed the maximum transmission speed (maximum amount of information that can be transmitted per unit time) in the transmission channel, it is possible to prevent a situation where data overflows in the channel. It has become.

  Further, in any one of the first to third configurations, the transmission device includes an encoding rate adjusting unit that adjusts the encoding rate for stream data encoded at a variable encoding rate, and the code Packet generation means for generating a packet from data whose data rate has been adjusted, and a transmission buffer for temporarily storing the packet, and transmitting the packet stored in the transmission buffer, thereby transmitting the stream data May be configured (fourth configuration).

  According to this configuration, since the packet generation means and the transmission buffer are provided, packet transmission can be realized and stable data transmission can be performed as compared with a case where no buffer is used. Furthermore, since the encoding rate adjusting means is provided, it is possible to adjust the encoding rate appropriately according to, for example, the adjustment result of the data transmission rate.

  In the fourth configuration, the coding rate adjustment unit may adjust the coding rate according to a data transmission rate adjustment result by the transmission rate adjustment unit (fifth configuration).

  In general, the appropriate value of the encoding rate is limited depending on the data transmission rate. For example, even if the data transmission rate is low, if the encoding rate is increased too much, the encoded data cannot be properly streamed.

  Therefore, according to the present configuration, the encoding rate is adjusted according to the adjustment result of the data transmission rate. Therefore, even in such a case, it is possible to cope by adjusting the encoding rate to be smaller. Become.

  Further, in the fourth or fifth configuration, the transmitting device includes a communication status measuring unit that measures a communication status in communication with the receiving device, and the coding rate adjusting unit is based on the communication status measuring unit. A configuration (sixth configuration) may be employed in which the encoding rate is adjusted based on the measurement result.

  According to this configuration, since the encoding speed is adjusted according to the communication status between the transmission apparatus and the reception apparatus, it is possible to obtain a more appropriate encoding speed. More specifically, the communication status measurement unit measures at least one of the error rate, C / N ratio, and free state of the transmission buffer as the measurement of the communication status ( The seventh configuration may be used.

  In addition, each of the plurality of transmission devices is a communication system according to any one of the first to seventh configurations in which video data is transmitted, and the reception device is based on each of the video data. Thus, a configuration (eighth configuration) may be provided that includes display means capable of displaying each video on the same screen.

  According to this configuration, it is possible to display a video through the display unit using the received stream data. Also, since each video can be displayed on the same screen, it is not necessary to provide a screen for each video.

  In the eighth configuration, the display means can display each video on the same screen at an arbitrary area ratio, and the calculation means calculates the range based on the area ratio ( A ninth configuration may be adopted.

  According to this configuration, it is possible to increase the display area ratio for, for example, a video with higher importance or a video that requires high display quality among the videos. In addition, since the allowable transmission rate range is calculated based on this area ratio, data transmission more in line with the current situation is realized. For example, for video data transmission that does not increase the area ratio so much, it is possible to widen the range (relax the restriction) and not to obtain a high transmission rate.

  As described above, according to the present invention, the allowable range for the data transmission speed of each transmitting device is calculated on the receiving device side, so the data output status on the receiving device side (for example, the size of the image) It is possible to easily calculate the allowable range of the transmission rate according to whether display is performed. In each transmission apparatus, the data transmission speed is adjusted within the allowable range. Therefore, it is possible to make the data transmission speed by the transmission apparatus according to the situation on the transmission apparatus side while setting the transmission speed allowed on the reception apparatus side.

  As a result, it is possible to realize a communication system capable of causing a plurality of transmission apparatuses to perform signal transmission at an appropriate transmission rate according to the situation.

  As an embodiment of the present invention, a communication system that performs real-time transmission of audio and video data (stream data transmission) will be described below. An outline of the communication system is shown in FIG. As illustrated in FIG. 1, the communication system 110 includes a first transmission device 101, a second transmission device 102, a reception device 103, and the like.

  The first transmission device 101 is a home server for home use, and receives video and audio data as streaming data from a broadcasting station 106 or an AV source 107 such as STB [Set Top Box], DVD, video, Internet, etc. This is transmitted as streaming data to the receiving apparatus.

  The second transmission device 102 is connected to a video camera 108 installed at the entrance in the home. For example, when there is a visitor, the second transmission device 102 detects that fact and notifies the reception device 103. When there is a request for transmission of imaging data from the receiving apparatus 103, the imaging data of the video camera 108 is transmitted to the receiving apparatus 103 as stream data.

  Further, the data acquired by any transmission apparatus is data encoded with variable compression / encoding speed by, for example, MPEG2-TS. The encoding speed (encoding rate) represents the state of the encoded data (encoding degree). For example, if the encoded result is 10 Mbps data, the encoding speed is Is 10 Mbps.

  In general, the higher the coding speed, the less the data quality degradation, but the larger the amount of information per unit time, and the lower the coding speed, the lower the data quality, but the smaller the information amount per unit time. Therefore, the data transmission burden is reduced. In general, this encoding rate can be changed as appropriate even after encoding, at least in the direction of decreasing the encoding rate (in the direction of reducing the amount of information).

  The reception device 103 is connected to a display device 109 such as a television or a personal computer, receives streaming data transmitted from each transmission device (101, 102), and outputs video / audio through the display device 109. Further, when receiving a notification from the second transmission device 102 that there has been a visitor, it is determined whether or not to display the imaging content, and when performing the display, the imaging data is sent to the second transmission device 102. Execute the send request.

  When receiving apparatus 103 receives stream data relating to video data from both transmitting apparatuses (101, 102), receiving apparatus 103 displays two screens based on both stream data (two areas on one display). And display different data in each area). Each area ratio in the two-screen display is set based on, for example, an instruction from the user or a calculation process by a predetermined program, and can be arbitrarily changed after the setting.

  Next, a detailed configuration of the transmission apparatuses (101, 102) will be described with reference to FIG. As shown in the figure, the transmission apparatus (101, 102) includes an encoding rate management unit 201, an encoding rate change unit 202, a packet generation unit 203, a transmission buffer 204, a communication path state measurement unit 205, a communication unit 206, and an antenna. 207 and the like.

  The encoding speed management means 201 includes information on the stream such as HDTV or SDTV, the type of stream, the ability to change the encoding speed, and information on the supported communication speed (hereinafter referred to as “communication capacity information” as appropriate). For example, by receiving from the outside, and transmitting to the receiving device 103. As will be described later, when communication is permitted by the receiving apparatus 103, an instruction is given to the coding rate changing means 202 and the like to start communication within the permitted range.

  After the communication is started, the current channel state is estimated by looking at the current packet error rate, C / N [Carrier / Noise] ratio measured by the channel state measuring means 205, and the free state of the transmission buffer 204. To do. Then, the coding speed changing unit 202 is instructed to change the coding speed within an allowable range notified from the receiving apparatus and within a range where the video is not interrupted.

  The encoding rate changing unit 202 changes the encoding rate according to information from the encoding rate managing unit 201 for stream data compressed and encoded by MPEG2-TS or the like.

  For example, the packet generation unit 203 divides and synthesizes data which is encoded with 188 bytes as one block in MPEG2-TS as a packet for transmitting several blocks to one network.

  The transmission buffer 204 temporarily stores the packet data generated by the packet generation unit 203. The communication unit 206 adds a MAC header, a PLCP header, and the like to the packet data, further adds encryption and an error correction code if necessary, and transmits the packet data to the network via the antenna 207. Note that the transmission rate (data transmission amount per unit time) can be adjusted according to an instruction from the coding rate management means 201.

  Next, a detailed configuration of the receiving apparatus 103 will be described with reference to FIG. As shown in the figure, the receiving apparatus includes a control information management unit 301, an antenna 302, a communication unit 303, a first reception buffer 304, a second reception buffer 305, a first packet division unit 306, a second packet division unit 307, and the like. ing.

  The control information management unit 301 receives and stores the communication capability information sent from the transmission device (101, 102), and permits communication with the transmission device (101, 102) based on the communication capability information. Judge whether to do. When communication is permitted, the transmission device (101, 102) is notified of the allowable transmission speed range.

  Also, stream data is transmitted to the display device 109. When the first stream is displayed, the screen is displayed on one screen, and when the second is displayed, the screen is displayed on two screens. Further, it is assumed that the area ratio of the screen used for each display can be arbitrarily set by the user. When two-screen display is performed, if the screen ratio is updated from the outside, it is determined again based on the stored information about the transmission device, and the communication speed allowed for the transmission device is determined. Notify the range.

  The communication unit 303 receives a packet transmitted from the transmission device via the network by the antenna 302 after the communication with the transmission device (101, 102) is started. Further, overhead portions unnecessary for video reproduction such as a MAC header are deleted, and the video data is distributed to the first reception buffer 304 or the second reception buffer 305 for temporary storage.

  Then, the first packet dividing unit 306 and the second packet dividing unit 307 reconstruct the packets divided and combined by the transmission apparatuses (101, 102) into a form that can be decoded again, and output them as stream data to the display apparatus.

  With the configuration described above, in the communication system 110, stream data wirelessly transmitted from a plurality of transmission devices (101, 102) can be received by the reception device 103 and reproduced using the display device 109. is there. Next, the flow of communication processing in the transmission apparatuses (101, 102) and the reception apparatus 103 will be described in detail with reference to FIGS.

  When there is a communication start request from a user through a user interface (not shown), the receiving apparatus 103 first detects this instruction (step S21), and a signal (communication start signal) for informing the start of communication of stream data is set in the instruction. The data is transmitted to the corresponding transmission device (101 or 102) (step S22). Thereafter, the receiving device 103 stands by until the communication capability information described above is received from the transmitting device (step S23).

  On the other hand, the transmitting devices (101, 102) monitor the presence / absence of a communication start signal from the receiving device 103 (step S11). When receiving the communication start signal corresponding to itself, the coding rate management unit 201 transmits its own communication capability information to the receiving device 103 (step S12).

  Upon receiving the transmission in step S12, the receiving apparatus 103 determines whether or not to permit transmission of stream data in the transmitting apparatus (step S24). This determination is made as follows.

  First, when executing video display using the stream data, a range (allowable range) of data transmission speed necessary for appropriately performing video display by the display device 109 is examined. As the lower limit value of this range, the minimum transmission speed required to ensure the display quality of the video at a certain level or more is examined. In other words, if the transmission speed of the transmission device is too low, the necessary display quality cannot be obtained, and this is to avoid this.

  The lower limit value of the data transmission speed is determined in consideration of the area ratio of the screen used for the video display. For example, when the display is performed using only the area of 30% of the entire screen, the data transmission speed may be 30% as compared with the case of displaying the entire screen.

  The upper limit of this range is the case where there is already stream transmission (existing stream transmission) by another transmitting apparatus, and the stream data is transmitted on the same channel as this existing stream transmission. In addition, the data transmission speed is checked so that the data does not overflow into the frequency band of the channel. In other words, for example, when the maximum communication speed in the channel is substantially 36 Mbps, if the sum of the data transmission speeds of both the transmitting devices exceeds 36 Mbps, there is a possibility that communication may be hindered (data overflows). It is for preventing.

  Specifically, first, it is determined whether the existing stream transmission and the stream transmission to be performed are the same channel. If they are the same, the upper limit value is calculated in consideration of the area ratio of the screens used in the video display for each. If they are not the same, the upper limit value may be the maximum communication speed in the channel used for transmission.

  When the allowable range is determined as described above, it is determined based on the communication capability information whether or not the transmission apparatus that is going to perform transmission can perform transmission within the allowable range. As a result, if it is determined that the transmission cannot be performed, the transmission of the stream data by the transmission device is not permitted (N in step S24).

  In this case, the transmission device is notified of the disapproval, and the process returns to step S21. In addition, when the transmission device receives the notification of non-permission, the transmission device returns to the process of step S11. In this case, the display device 109 may display that the video playback instruction has been rejected. Thereby, the user can easily grasp the current state.

  On the other hand, when it is determined that transmission within the allowable range can be performed, transmission of stream data by the transmission device is permitted (Y in step S24). In this case, if there is an existing stream transmission (Y in step S25), the transmission apparatus that performs the existing stream transmission is notified again of information on the allowable range corresponding to the transmission apparatus. (Step S26). In addition to this, the information about the allowable range corresponding to the transmission apparatus is notified to the transmission apparatus that is about to perform a new stream transmission (step S27). If there is no existing stream transmission (N in step S25), the process in step S26 is omitted.

  On the other hand, after the process of step S12, the transmission apparatus waits until there is a notification of allowable range information related to the process of step S27 from the reception apparatus 103 (step S13). However, as described above, if there is a non-permission notification from the receiving apparatus 103, the process does not wait.

  When the permissible range information is notified, transmission of stream data is started at a transmission rate within the permissible range (step S14). For example, transmission is started at the maximum transmission rate (maximum transmission rate) within such a range in order to transmit as high-quality stream data as possible.

  Further, after the transmission of the stream data is started, the communication path condition measuring unit 205 measures the packet error rate, the vacant condition of the transmission buffer 204, and the C / N, and compares these measurement results with a predetermined threshold value, for example. Thus, it is monitored whether the communication state is good at present (step S15).

  If the communication state is not good in this monitoring (Y in step S15), data transmission is performed in a direction in which the communication state is improved within the already notified allowable range and a range where the video display is not interrupted for a certain amount or more. The coding speed or transmission speed is changed (step S16). For example, if the packet error rate is too high, the transmission amount may exceed the communication capacity or the encoding speed may be too high, so the communication speed is reduced within the allowable range or the encoding speed is reduced. Like that.

  In addition to the monitoring related to step S15, the coding rate management unit 201 monitors whether or not a re-notification of information on the allowable range has been received from the receiving apparatus 103 (step S17). This re-notification is made as a result of the process of step S26 in the receiving apparatus 103 when another communication apparatus starts data transmission. If there is a re-notification of information on the allowable range (Y in step S17), the process of step S14 based on the information on the allowable range is executed.

  Here, the content of the processing mainly relating to steps S24 to S27 described above will be described below with a specific example. Here, in the situation where the first transmission apparatus 101 is already performing stream transmission (using the full screen (area ratio 100%) for video display), a case where a new stream transmission is being performed by the second transmission apparatus 102 is newly performed. Is assumed.

  For the first transmission apparatus 101, it is assumed that the transmission channel is a 2.4 GHz band and the range of allowed communication speed is 20 to 25 Mbps. As for the second transmission apparatus 102, it is assumed that the transmission channel is a 2.4 GHz band and the supported communication speed is up to 50 Mbps. The substantial maximum communication speed (considering various communication obstruction factors) that can be realized with a 2.4 GHz band channel is 36 Mbps. In addition, it is assumed that the ratio of the area occupied by the screen in the video display by the data of the first transmission device and the video display by the data of the second transmission device is set to 70% and 30%, respectively.

  First, when there is a request to start transmission by the second transmission device 102, the reception device 103 transmits a communication start signal, and in response to this, the second transmission device 102 transmits communication capability information to the reception device 103 (step). S11, S12, S21, S22).

  In response to this, the control information management unit 301 calculates the allowable range of the data transmission rate for each transmission device. First, regarding the lower limit of the transmission speed, a transmission speed of at least 20 Mbps is necessary to display a video on a full screen with a certain quality or higher. Therefore, for the first transmission apparatus 101, the second transmission speed is 14 Mbps (20 Mbps × 0.7). The transmission apparatus 102 is defined as 6 Mbps (20 Mbps × 0.3).

  Next, regarding the upper limit of the transmission speed, since the first transmission apparatus 101 and the second transmission apparatus 102 use the same channel (2.4 GHz band), the total transmission speed of both transmission apparatuses is the maximum communication of the channel. It is determined not to exceed the speed (36 Mbps). Here, in consideration of the screen area ratio in video display, the first transmission apparatus 101 is 25.2 Mbps (36 Mbps × 0.7), and the second transmission apparatus 102 is 10.8 Mbps (36 Mbps × 0.3). Is defined as the upper limit.

  As described above, 14 to 25.2 Mbps for the first transmission device 101 and 6 to 10.8 Mbps for the second transmission device 102 are determined as allowable transmission speed ranges. Then, since the second transmission device that is going to perform transmission supports a communication speed of up to 50 Mbps, data transmission can be performed within the allowable range of the transmission speed. Therefore, the receiving apparatus 103 permits data transmission by the second transmitting apparatus (Y in step S24).

  Further, the receiving apparatus 103 notifies the first transmitting apparatus that the transmission speed of 14 to 25.2 Mbps is within the allowable range (step S26), and 6 to 10 for the second transmitting apparatus. It is notified that the transmission rate of .8 Mbps is within the allowable range (step S27). Thereafter, on the transmitting device (101, 102) side, stream data is transmitted to the receiving device 103 while keeping the notified allowable range.

  In addition, when the display screen area ratio is changed or there is an instruction to stop one of the video display while the two screen display is performed by the stream data from each transmission device, the receiving device 103 causes such a situation. The allowable range reflecting the above is calculated and notified again to the transmitting apparatus side. However, when it is determined that such an instruction cannot be executed based on the communication capability information (a data transmission speed within an allowable range cannot be secured), the instruction may not be executed.

  In each transmission apparatus, the encoding rate is adjusted by the encoding rate changing unit 202 in accordance with the adjustment result of the data transmission rate. In general, the appropriate value of the encoding rate is limited depending on the data transmission rate. If the encoding rate becomes too high even though the data transmission rate is small, the encoding rate is encoded. Data cannot be properly streamed. However, such a problem can be avoided by adjusting the encoding speed in this way.

  For example, when transmission is performed at an encoding rate of 20 Mbps and a communication rate of 54 Mbps, if the communication rate is changed from 54 Mbps to 36 Mbps, the throughput is about 70%. Therefore, the coding speed is also reduced to about 14 Mbps (20 Mbps × 0.7).

  Further, the allowable range information from the receiving apparatus 103 may include the allowable range of the encoding rate in addition to the information related to the transmission rate. As described above, it is possible to adjust the coding rate only on the transmission device side according to the adjustment result of the data transmission rate. However, the receiving apparatus 103 can give more accurate adjustment of the coding speed by giving information on the allowable range of the coding speed to the transmitting apparatus side.

  As described above, in the present embodiment, the allowable range for the data transmission speed of each transmission device (101, 102) is calculated by the reception device 103. It is possible to easily calculate the allowable range of the transmission speed according to whether the image is displayed with the size.

  In each of the transmission devices (101, 102), the data transmission speed is adjusted within the allowable range. Therefore, it is possible to make the data transmission rate by the transmission device according to the situation on the transmission device side while making the transmission rate permitted by the reception device side.

  In this embodiment, the transmission channels of the transmission apparatuses (101, 102) are not necessarily the same as each other. However, the transmission channels may be fixed so that they are always the same. Good. In this case, since each transmitting apparatus performs transmission on the same transmission channel, the receiving apparatus need only correspond to the frequency band of this transmission channel.

  Therefore, the receiving apparatus 103 can have a simpler configuration than that corresponding to a plurality of channels. Even in this manner, as described above, each transmitting apparatus (101, 102) transmits data within a predetermined allowable range, so that a situation where data overflows in the channel can be avoided. .

  Although one embodiment of the present invention has been described in detail as described above, the scope of the present invention is not limited to such an embodiment, and various modifications can be made without departing from the spirit of the invention. is there.

1 is a schematic configuration diagram of a communication system in an embodiment of the present invention. It is a block diagram of the transmission apparatus in embodiment of this invention. It is a block diagram of the receiver in embodiment of this invention. It is a flowchart (the first half) of the process which concerns on embodiment of this invention. It is a flowchart (second half) of the process which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 1st transmission apparatus 102 2nd transmission apparatus 103 Reception apparatus 106 Broadcast station 107 AV source 108 Video camera 109 Display apparatus 110 Communication system 201 Encoding rate management means 202 Encoding rate change means 203 Packet generation means 204 Transmission buffer 205 Communication path Status measurement means 206 Communication means 207 Antenna 301 Control information management means (calculation means)
302 Antenna 303 Communication Unit 304 First Reception Buffer 305 Second Reception Buffer 306 First Packet Division Unit 307 Second Packet Division Unit

Claims (9)

A communication system comprising a plurality of transmission devices each transmitting stream data and a reception device receiving the stream data from the plurality of transmission devices,
The receiving device is:
Calculating means for calculating a permissible range for the transmission speed of the data of each of the transmitting devices; and notifying means for notifying the transmitting device of the calculation results;
The transmitter is
A communication system comprising: a transmission rate adjusting means for receiving the notification and adjusting the data transmission rate within the range. The calculating means includes
The communication system according to claim 1, wherein the range is calculated so that a sum of data transmission rates of the transmission devices does not exceed a predetermined rate. Each of the transmission devices performs the transmission on the same transmission channel,
The communication system according to claim 2, wherein the predetermined rate does not exceed a maximum transmission rate in the transmission channel. The transmitter is
Encoding rate adjusting means for adjusting the encoding rate for stream data encoded at a variable encoding rate;
Packet generating means for generating a packet from the data whose encoding rate is adjusted;
A transmission buffer for temporarily storing the packet,
The communication system according to any one of claims 1 to 3, wherein the stream data is transmitted by transmitting the packets stored in the transmission buffer.   5. The communication system according to claim 4, wherein the encoding rate adjusting unit adjusts the encoding rate according to a result of adjusting a data transmission rate by the transmission rate adjusting unit. The transmitter is
Communication status measuring means for measuring a communication status in communication with the receiving device;
6. The communication system according to claim 4, wherein the coding rate adjusting unit adjusts the coding rate based on a measurement result by the communication state measuring unit. The communication status measuring means measures the communication status as follows:
An error rate of the packet, a C / N ratio, and an empty state of the transmission buffer;
The communication system according to claim 6, wherein at least one of them is measured. The communication system according to any one of claims 1 to 7, wherein each of the plurality of transmitting devices transmits video data.
The receiving device is:
A communication system comprising display means capable of displaying each video on the same screen based on each video data. The display means can display each video on the same screen at an arbitrary area ratio,
The communication system according to claim 8, wherein the calculation unit calculates the range based on the area ratio.

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