KR20070006024A - Method and apparatus for transmitting and receiving in the wireless network controlling encoding and transmitting mechanism using video data s importance and network circumstance - Google Patents

Abstract

A method and a system for transmitting and receiving data are provided to improve transmission efficiency by controlling a transmission mode and an encoding mode according to the transmission state of a wireless network and importance of video information. State information of a wireless network is received(S701). Data to be transmitted are classified based on the state information(S702). Transmission data to which information for recovering an error is added when the error is generated in the classified data are encoded. A decision factor for transmitting the transmission data to the wireless network is set according to the state information. The encoded transmission data is transmitted to the wireless network according to the set result(S730).

Description

Method and apparatus for transmitting and receiving in the wireless network controlling encoding and transmitting mechanism using video data s importance and network circumstance}

1 is a diagram illustrating a configuration of a transmitter and a receiver for transmitting video data over the air in the related art.

2 is an exemplary view showing the configuration of a video transmitter and a video receiver according to an embodiment of the present invention.

3 is an exemplary diagram illustrating interaction between an encoder and a QoS control unit according to an embodiment of the present invention.

4 is an exemplary diagram illustrating an interaction between a MAC manager and a QoS controller according to an embodiment of the present invention.

5 is an exemplary diagram illustrating a data flow in a video transmitter according to an embodiment of the present invention.

6 is an exemplary view illustrating a data flow in a video receiver according to an embodiment of the present invention.

7 is a flowchart illustrating a process of processing a job by a video transmitter according to an embodiment of the present invention.

8 is a flowchart illustrating a process of processing a job in a video receiving unit according to an embodiment of the present invention.

9 is a flowchart illustrating a process in which a QoS controller controls an encoder and a MAC manager according to network conditions in order to encode data according to an embodiment of the present invention.

10A, 10B, and 10C are graphs showing a transmission success rate when an embodiment of the present invention is applied.

11 is a graph showing an error occurrence rate according to an encoding rate according to an embodiment of the present invention.

12 is a graph showing an error occurrence rate according to a block size during interleaving according to an embodiment of the present invention.

<Explanation of symbols for main parts of the drawings>

100: video transmission unit 121: frame classification unit

122: encoder 141: MAC management unit

150: QoS control unit 200: video receiving unit

221: statistics collector 222: decoder

223: packet alignment unit

The present invention relates to the transmission and reception of video data in a wireless network, and more particularly, to a method and apparatus for controlling transmission and reception by encoding and transmission according to the transmission situation of the wireless network and the importance of video information.

With the development and popularization of wireless communication technologies such as IEEE 802.11a / b / g, cdma2000, UMTS, and WiBro, home networks and wireless Internet will be widely used, and video streaming is expected as a killer application of these services. In particular, as a broadcasting system such as DMB (Digital Multimedia Broadcasting) is being built, the importance of video streaming in wireless communication is emerging.

However, existing video compression technology such as MPEG is designed without considering wireless communication with high channel error rate. If an error occurs in data that has a lot of information during transmission, the error is propagated to other video data and the video quality is rapidly increased. Can be dropped.

1 is a diagram illustrating a configuration of a transmitter and a receiver for transmitting video data over the air in the related art. The video transmitter 10 receives a video input such as MPEG and performs the streaming through the streaming application 12. The streamed data may apply a Forward Error Correction (FEC) technique to the video signal during streaming. It is transmitted to the video receiver 20 through a transport protocol, a media access control layer and a physical layer of a lower layer. The video receiver 20 generates a video output by decoding the received video data. At this time, when the video transmitter 10 and the video receiver 20 are wirelessly connected, such as IEEE 802.11a / b / g Wireless LAN, packet loss occurs due to an unstable channel condition, and thus the video quality felt by the user on the receiver side is lost. Can cause problems.

According to the US patent (US 6,317,462 B1), when the video transmitter transmits the video data, the video data is divided into two categories, and the video data is applied to the high-priority video data by applying the Reed-Solomon FEC technique. Even if a packet is lost during transmission by transmitting it, a method for recovering the received packet is proposed.

To this end, the transmitter divides the video data into two categories, adds data for recovery to high priority video data, and encodes and processes video data having low priority.

In wireless networks, however, data rates are highly affected by changes in the surrounding environment, so it is difficult to increase the efficiency of video streaming by simply transmitting recovery data adaptively with high and low priorities. Therefore, when transmitting video data through a wireless network, there is a need for a method and apparatus for flexibly adapting to increase the transmission rate according to the situation of the wireless network.

The present invention has been made to solve the above problems, and an object of the present invention is to improve transmission efficiency by adjusting a transmission method and an encoding method according to a situation of a wireless network.

Another object of the present invention is to encode and transmit in consideration of the importance of each data.

The objects of the present invention are not limited to the above-mentioned objects, and other objects that are not mentioned will be clearly understood by those skilled in the art from the following description.

The present invention relates to a method and apparatus for controlling transmission and reception of encoding and transmission according to the transmission situation of a wireless network and the importance of video information.

According to an embodiment of the present invention, a method of encoding and transmitting data according to a transmission situation of a wireless network and importance of video information may include receiving state information of a combined wireless network, and classifying data to be transmitted according to the state information. Encoding the transmission data including information for recovering when the error occurs in the classified data, setting a decision factor for transmitting the transmission data to the wireless network according to the status information, and encoding the transmitted transmission. And transmitting data to the wireless network according to the set result.

According to an embodiment of the present invention, a method of receiving data according to a transmission situation of a wireless network and the importance of video information may include receiving data through a combined wireless network, classifying according to characteristics of the data, and classifying the data. Combining the data by classification, reproducing the combined data, collecting state information of the wireless network through the reception state of the data, and transmitting the state information.

An apparatus for transmitting data according to an embodiment of the present invention receives status information on a combined wireless network and sets a decision factor for transmitting data to the wireless network according to the status information, and transmits according to the status information. A frame classifying unit for classifying data, an encoder for encoding the transmission data to which the classified data is added for recovering when an error occurs, and a MAC for transmitting the encoded transmission data to the wireless network according to the set result. / PHY control unit, wherein the QoS control unit controls the encoding scheme of the encoder according to the state information.

In accordance with another aspect of the present invention, a data receiving apparatus includes a MAC / PHY controller for receiving data through a combined wireless network, a packet sorter for classifying data according to characteristics of the data, and combining the classified data by classification. And a statistics collector for collecting the state information of the wireless network through the decoder for reproducing data and the reception state of the data.

Specific details of other embodiments are included in the detailed description and the drawings.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms, only the embodiments are to make the disclosure of the present invention complete, the general knowledge in the art to which the present invention belongs It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

Hereinafter, the present invention will be described with reference to a block diagram or a flowchart illustrating a method and apparatus for controlling transmission and reception of encoding and transmission according to the transmission situation of a wireless network and the importance of video information according to embodiments of the present invention. Explain about. At this point, it will be understood that each block of the flowchart illustrations and combinations of flowchart illustrations may be performed by computer program instructions. Since these computer program instructions may be mounted on a processor of a general purpose computer, special purpose computer, or other programmable data processing equipment, those instructions executed through the processor of the computer or other programmable data processing equipment may be described in flow chart block (s). It creates a means to perform the functions. These computer program instructions may be stored in a computer usable or computer readable memory that can be directed to a computer or other programmable data processing equipment to implement functionality in a particular manner, and thus the computer usable or computer readable memory. It is also possible for the instructions stored in to produce an article of manufacture containing instruction means for performing the functions described in the flowchart block (s). Computer program instructions may also be mounted on a computer or other programmable data processing equipment, such that a series of operating steps are performed on the computer or other programmable data processing equipment to create a computer-implemented process to create a computer or other programmable data. Instructions for performing the processing equipment may also provide steps for performing the functions described in the flowchart block (s).

In addition, each block may represent a portion of a module, segment, or code that includes one or more executable instructions for executing a specified logical function (s). It should also be noted that in some alternative implementations, the functions noted in the blocks may occur out of order. For example, the two blocks shown in succession may in fact be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending on the corresponding function.

2 is an exemplary view showing the configuration of a video transmitter and a video receiver according to an embodiment of the present invention.

As used herein, the term 'unit', that is, 'module' or 'table' or the like, refers to a hardware component such as software, a field programmable gate array (FPGA), or an application specific integrated circuit (ASIC). The module performs some functions. However, modules are not meant to be limited to software or hardware. The module may be configured to be in an addressable storage medium and may be configured to play one or more processors. Thus, as an example, a module may include components such as software components, object-oriented software components, class components, and task components, and processes, functions, properties, procedures, subroutines. , Segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functionality provided within the components and modules may be combined into a smaller number of components and modules or further separated into additional components and modules. In addition, the components and modules may be implemented to reproduce one or more CPUs in a device.

The video transmitter 100 includes a video input unit 110 for receiving video data, a video streaming application 120 for streaming the received video data, a transmission protocol 130 for transmitting the streamed video in a wireless network environment, and And a MAC / PHY 140 control unit for transmitting data generated according to the transmission protocol.

The video input unit 110 receives video data such as MPEG. The received video data is streamed, and the video streaming application 120 performs this. The video streaming application 120 includes a frame classifier 121 and an encoder 122 for distinguishing I, P, and B frames constituting the MPEG frame. The frame classifier 121 distinguishes frames that affect the performance of other frames, such as I frames.

Since the I frame is a frame referenced by the B frame and the P frame, if an error occurs in the I frame, the error occurs in the B frame and the P frame which refer to it. Therefore, in the case of an I frame, even if an error occurs, a code capable of recovering the error may be added and transmitted. In addition, since the P frame is also a frame referred to by the B frame, a code for recovering an error may be added and transmitted to the P frame. However, since the importance of the I frame and the P frame is different from each other, a code capable of recovering an error may be added differentially. Therefore, the frame classifier 121 classifies each frame to perform encoding.

Encoder 122 performs coding to recover the error. In this case, interleaving may be performed to prevent the transmission rate from being lowered due to an error packet. Interleaving means dividing one packet back into several entities, integrating other packets with the interleaved entities into new packets. This means that if an error occurs when transmitting one packet as it is, all the frames or video data indicated by the packet may be lost. However, if the packet is distributed and transmitted in multiple packets, even if an error occurs in one packet, When decoding, the error is generated by being divided into several packets, thereby preventing the loss of all frames or video data. A case in which packets are interleaved is described with reference to FIG. 3.

The encoder 122 may use several coding schemes to recover from errors. For example, additional information, such as Forward Error Correction (FEC), can be used to recover lost or failed data. Reed-Solomon Coding algorithm, Viterbi algorithm, etc. may be applied in a manner applicable to FEC. The video streaming application 120 may include an interleaver that mixes data so that an error may be distributed among several packets even if an error occurs in a packet unit during transmission.

On the other hand, if the transmitted data does not match the transmission order and arrival order may include a transport packetizer for adding a sequence number and the like necessary for sorting the header portion.

In addition, the encoder 122 may adjust the encoding scheme according to the quality of service controller 150. For example, when it is determined by the QoS controller 150 that the error occurrence rate is small in the data rate of the wireless network, the amount of data added by the encoder 122 during encoding may be reduced. Alternatively, the encoder 122 may change the encoding scheme so that the recovery data is added only to the I frame and the recovery data is not added to the P frame.

The transmission protocol 130 provides a protocol for transmitting data. Protocols such as Transmission Control Protocol / Internet Protocol (TCP / IP) and Real Time Protocol (RTP) can be used.

The medium access control layer (MAC) / physical layer control unit 140 allows data generated by a higher layer to be transmitted through a wireless medium. The transmission scheme may be adjusted according to the characteristics or the situation of the wireless medium. The part controlling this is the MAC management unit 141. The QoS control unit 150 controls the MAC management unit 141 to select an appropriate method according to the characteristics or the situation of the wireless medium.

The MAC manager 141 manages MAC parameters, classifies and transmits data, and includes a priority queue for classifying and transmitting data according to the importance of the data. The MAC management unit 141 may include a retransmission setting unit for setting a retry limit parameter required for retransmission when a transmission error occurs, a data rate setting unit for setting a data rate to be transmitted, and an MTU (Maximum) which is the size of data to be transmitted at one time. MTU size setting unit for setting the transfer unit) may be included.

The QoS controller 150 may set the size of the FEC code to be added by the encoder 122 by grasping the state of the wireless network, and control the MAC manager 141 to set items such as the number of retransmissions, the transmission data rate, and the MTU. Can be. The interaction between the QoS control unit 150 and the encoder 122, or the QoS control unit 150 and the MAC management unit 141 will be described later.

The video receiver 200 includes a MAC / PHY controller 240 for receiving data through a wireless network, a transmission protocol 230 for providing a protocol, and a video reproducing application 220 for reproducing the received video data. It includes a video output unit 210 for outputting.

The MAC / PHY control unit 240 includes a plurality of priority queues. Received data by priority can be stored in a queue.

The video playback application 220 includes a statistics collector 221, a decoder 222, and a packet aligner 223.

The packet sorter 223 sorts packets that are not transmitted sequentially through a plurality of priority queues. The decoder 222 performs de-interleaving, which recombines the interleaved packet again, and performs FEC decoding. It also includes a statistics collector 221 to collect the information on the error distribution of the received packets to inform the video transmitter 100.

3 is an exemplary diagram illustrating interaction between an encoder and a QoS control unit according to an embodiment of the present invention. The QoS controller 150 may set how the encoder should encode data according to the state of the wireless network sent from the video receiver.

3 controls three parameters. The QoS controller 150 may set a size (encoding rate) that the encoder 122 encodes, a size of a block to interleave, and a size of a UDP packet according to a current network situation.

An example of using the Reed-Solomon algorithm is as follows. The encoding rate may be represented by RS (N, K) when the actual data size is K bytes and the encoded data is N bytes. The size R of the added data according to the coding is N-K. If the error occurred in the Reed-Solomon algorithm is smaller than R / 2, the data can be recovered. Therefore, the larger the size of R, the larger the range that can recover the error. However, in order to increase R, N must be increased, which means that the size of data to be transmitted increases. Therefore, the QoS controller may adjust the encoding rate according to the case where a large number of errors or a small number of errors occur according to a network condition received through the video receiving unit 200. In addition, important data, for example, I size can be set to increase the size of N, P frame is set to medium N, and B frame can be set to send video data without encoding. The QoS controller may control the encoding rate through the Reed Solomon coder 125.

When the encoded data is transmitted in one packet, when the corresponding packet is lost, the entire data or a substantial portion of the data may be lost. Therefore, in order to prevent this, an interleaving method of transmitting encoded data by dividing it into several packets may be used. As shown in FIG. 3, interleaving is a method of dividing data encoded into 301, 302, 303, and 304 packets, storing a portion in 311 packets, and storing portions in 312, 313, and 314 packets. In this case, before the interleaving, if an error occurs in the 301 packet, the entire 301 packet is lost, and as a result, all data of a specific frame of the 301 packet is lost. However, in the case of interleaving, even if an error occurs in the 311 packet, not all of the 301 packets are lost, but some of the 301, 302, 303, and 304 packets are lost, thereby preventing all or a large portion of the data of a specific frame from being lost. Therefore, when the size of an error in each frame is smaller than R / 2, data lost by the FEC can be recovered. Since interleaving may also vary according to network conditions, the QoS controller 150 may adjust the size of a block to be interleaved. You can also adjust the size of the packet to be sent. If the data rate is high, the size of the UDP packet can be increased. On the contrary, if the error is frequent, the size of the packet can be reduced. Therefore, the QoS controller 150 controls a transport packetizer 127 that adjusts the size of the packet according to the state of the wireless network.

4 is an exemplary diagram illustrating an interaction between a MAC manager and a QoS controller according to an embodiment of the present invention. The QoS controller 150 may set how to transmit data from the MAC manager 141 according to the state of the wireless network sent from the video receiver.

4 controls three parameters. The QoS controller 150 may adjust the number of retransmissions, the data rate by data transmission, and the size of the maximum transfer unit according to the current network situation.

The retransmission setting unit 145 may set the number of retransmissions. If an error occurs in the transmitted data, the data is retransmitted. The number of retransmissions can be set. In the case of important data, for example I-frames, the number of retransmissions can be increased because they can affect other data if they are lost. On the other hand, in case of B frames, even if lost, the number of retransmissions can be reduced because they do not significantly affect other frames. You can also decide whether to retransmit more or less depending on the network conditions. The QoS controller 150 may adaptively set the number of retransmissions according to the characteristics of the data such as the importance of the data or the state of the network.

The data rate setting unit 146 sets a transmission rate. Wireless networks offer different data rates, allowing devices to select and transmit specific data rates. For example, 802.11a offers multiple rates, including 54Mbps, 48Mbps, 36Mbps, 24Mbps, and 11Mbps. If the network is capable of high-speed data transfer, the device can transmit data at 54 Mbps, while the device can transmit at lower data rates, such as 11 Mbps, depending on the network conditions. The QoS controller 150 may control which data rate is selected according to the state of the network. In addition, the data rate may be adjusted by controlling the data rate setting unit 146 according to the importance of the data.

The MTU size setting unit 147 sets the size of the maximum transmission unit (MTU). The MTU may likewise be variable depending on the state of the network. If the network is in good condition, the size of the MTU can be increased. Therefore, the QoS controller 150 may control the size of the MTU by checking the state of the network.

5 is an exemplary diagram illustrating a data flow in a video transmitter according to an embodiment of the present invention. Frames input through the video input unit are classified into I frames, P frames, and B frames through the frame classification unit 121.

When each frame data is divided into MPEG TS (Transport Stream) packets, the frame separator 121 indicates an I / P / B frame type for each TS packet. An FEC encoder receives and stores each TS packet and performs coding, interleaving, and packetizing of previous frame data stored when a new type of TS packet comes. In each case, the encoding rate, interleaving block size, and UDP packet size set by the QoS control unit are applied to match the importance of the I / P / B frame type.

On the other hand, in addition to video frames, information about the system, headers, and audio TS packets are also transmitted. Among them, system information and headers may be processed and coded with the same importance as I frames. The audio TS packet may be included in each I / P / B frame and encoded together.

Packets that have been packetized, which is a process of making packets, are stored in the priority queue of the MAC stage through a transport protocol according to the frame type. Priority queues can be stored differently depending on the importance of the data. For example, the priority can be set differently for each frame and stored in the priority queue. If the number of retransmissions is set for a particular queue, if an error occurs in the data transmitted from the corresponding queue, the number of retransmissions can be retransmitted as many times as the set retransmission.

6 is an exemplary view illustrating a data flow in a video receiver according to an embodiment of the present invention.

The receiver stores various types of frame data received through the MAC / PHY control unit in the packet sorter 223 in a separate queue, and then stores the header data added by the transport packetizer of the transmitter. They are sorted using sequence numbers and stored in the sequence queue. In this case, the sorting method takes one packet from each frame queue, stores the packet with the smallest sequence number in the sequence queue, and takes the next packet from the frame queue where the selected packet comes from and compares the smallest sequence number again. This is repeated until the frame queue is empty.

In this case, a specific packet may be lost or an error may occur. For example, in FIG. 6, when an error occurs or is lost in the 331 packet, an error occurs in the packet, which is a set of interleaved blocks, and thus errors are distributed in the deinterleaved data 340. As a result, it is possible to prevent the entire frame or a substantial portion of the frame from disappearing.

The missing portion of the encoded data 340 is recovered to generate frame data, which is reproduced through an MPEG decoder in a video reproduction application.

7 is a flowchart illustrating a process of processing a job by a video transmitter according to an embodiment of the present invention.

The video transmitter receives the state information of the wireless network (S701). The state information of the wireless network is information including an error rate generated from previously sent data, or the strength of the wireless signal. Therefore, if there are a lot of errors in the previously sent data, it can be judged that there is a high possibility that a lot of errors will occur. The video data is classified (S702). As described above, the video data is composed of I frames, P frames, B frames, and the like, and the I frames affect data of other frames. Therefore, the data can be classified according to the importance of data for each frame. In operation S710, the data error rate included in the state information is higher than a predetermined size. The predetermined size may be half of the bit R added when the Reed-Solomon algorithm is used. Depending on whether the value of R / 2 is higher or lower than the number of bits in which an error occurs, it is possible to know whether the current encoding rate is appropriate. If the data error rate is high, the recovery code rate for the I frame is increased (S711). Increasing the recovery code rate means increasing the amount of data needed for recovery. As a result, more information to recover is added than actual video data. On the other hand, if the data error rate is low, the recovery code ratio for the I frame is lowered (S712). The above process may be performed by the encoder and the QoS control unit.

On the other hand, if data to be transmitted is encoded, it is determined how to send the encoded data. As described above, various decision factors required for transmission to the wireless medium can be set, and these decision factors can be set according to the situation of the current wireless network. In step S720, it is checked whether the error rate of the transport packet is higher than a predetermined size. If the error is high, since there are many errors in the wireless medium, operations such as increasing the number of retransmissions, decreasing the data rate to be transmitted, and reducing the size of the maximum transmission unit may be performed (S721). It is possible to set the determinants of the MAC and PHY layers before sending data over the wireless medium. On the contrary, if the error is low, since the wireless medium is stable, the number of retransmissions can be reduced, the data rate to be transmitted can be increased, and the size of the maximum transmission unit can be increased (S722). When encoding according to the state of the network and setting information related to the transmission method, video data is transmitted (S730).

8 is a flowchart illustrating a process of processing a job in a video receiving unit according to an embodiment of the present invention. The receiver receives data transmitted through the wireless medium (S801). The received data may be classified by priority through the priority queue (S802). Priority is classified according to the characteristics of the data. As described above, the video data may be I, P, or B frames. Then, the classified data is combined (S803). The combined data is reproduced through de-interleaving and decoding (S804). De-interleaving refers to a process of extracting original video data from data to which recovery information is added for error recovery at a transmitter. At this time, statistics about whether a large number of errors or errors have not occurred can be made. In accordance with these statistics, the state information of the wireless network is transmitted (S805).

9 is a flowchart illustrating a process in which a QoS controller controls an encoder and a MAC manager according to network conditions in order to encode data according to an embodiment of the present invention.

The QoS controller receives information on the wireless network from the receiver or the transmitter itself (S901). Status information for the wireless network includes a transport packet error rate, a data error rate after FEC recovery, a hamming distance, and the like. The transport packet error rate refers to a ratio of packets in which an error occurred when transmitting encoded data. The data error rate after FEC recovery refers to the rate at which an error has not been recovered even after receiving and recovering a packet to which recovery data has been added through FEC coding. Hamming distance refers to a case where different characters (bits) occur at each position of two strings having the same length. Hamming distances are often used to measure errors.

If the data error rate is higher than the target error rate in the received information (S902), the operation for reducing the error rate is performed. If the transmission packet error rate is lower than ((R / 2) / RS block size) (S910), since the error is lower than expected, the flow proceeds to step S920 to increase the efficiency by sending more data. If the result of calculating the hamming distance in step S920 is larger than the (R / 2) / RS block size and the probability is larger than the target error rate, it is necessary to increase the coding rate. Therefore, the network checks whether there is a margin (S924), and increases the coding rate (S926). If not, proceed to step S930. If the current throughput is sufficient in step S930, the interleaving block size is reduced (S936), and the UDP packet size and MAC MTU size are adjusted (S938).

On the other hand, if the transmission packet error rate is higher than ((R / 2) / RS block size) in step S910, the operation to reduce the error is performed. It is examined whether the number of retransmissions has already been increased before (S940). As a result, if the number of retransmissions is not increased, when there is a marginal bandwidth in the network (S932), the number of retransmissions is increased (S934). On the other hand, if the number of retransmissions has already been increased, the data transmission rate is lowered (S914). The error rate can be lowered by increasing the number of retransmissions or by lowering the data rate.

10A, 10B, and 10C are graphs showing a transmission success rate when an embodiment of the present invention is applied.

10A shows a transmission success rate when the data rate (data rate) is 54 Mbps, the number of retransmissions is 0, and the packet size is 178 bytes. As can be seen in Figure 10a, it can be seen that a lot of transmission errors occur. Therefore, if this error occurs a lot, it can be controlled to increase the number of retransmissions or to decrease the data rate.

10B illustrates a case in which the QoS control unit increases the number of retransmissions to 2 and sets the data rate to 54 Mbps. It can be seen that the error is drastically reduced in comparison with FIG. 10A. By increasing the number of retransmissions to two, all data that was not transmitted in the embodiment of FIG. 10A was successfully transmitted.

10C shows a case where the QoS control unit increases the number of retransmissions to 4 and sets the data rate to 54 Mbps. Compared with FIG. 10A, the error was drastically reduced. It can also be seen that the error is reduced compared to FIG. 10B. By increasing the number of retransmissions, all data that was not transmitted in the embodiment of FIG. 10A were successfully transmitted.

10A, 10B, and 10C, it can be seen that the number of retransmissions, the data rate, and the like have an important effect on transmitting and receiving video data according to the network situation. According to an embodiment of the present invention, the QoS control unit may select a transmission mode in an appropriate manner according to the situation of the network.

11 is a graph showing an error occurrence rate according to an encoding rate according to an embodiment of the present invention. In the case of using the Reed-Solomon algorithm, the range that can be recovered depends on the encoding rate.

rscode (255, 127) has a size of 127 bytes of data to be sent, and encoded data is 255 bytes. Therefore, the added data is 128 bytes. In this case, recovery is possible even if an error occurs. If the packet error rate is 0% to 15% or less, since the actual data is recovered, it can be seen that the data error rate of the transmitted data is close to 0%. In addition, since the recovery is performed at a packet error rate of 15% to 20%, it can be seen that the actual data error rate is maintained at about 5%.

rscode (255, 223) has 223 bytes of data to be sent, and encoded data is 255 bytes. Therefore, the added data is 32 bytes. In this case, recovery is possible even if an error occurs. However, it is less capable of recovering than rscode (255, 127). As can be seen in FIG. 11, when the packet error rate is 0% to 5% or less, the data error rate is close to 0% since recovery is performed. On the other hand, even when the packet error rate of 5% to 20%, it can be seen that the actual data error rate is lower than the packet error rate by some recovery.

In the case of other transmission errors, the data error rate is higher than that of rscode (255, 127).

As shown in FIG. 11, the more information for recovery is added, the higher the possibility of recovering even if an error occurs in a packet. Therefore, it is possible to reduce the overall data error rate by adding a lot of information for recovery to important data such as I frames.

12 is a graph showing an error occurrence rate according to a block size during interleaving according to an embodiment of the present invention.

If the block size, i.e., the size of the block divided for interleaving in one packet is 178 bytes, the actual data error rate is close to 0% even if an error occurs less than 5% in the packet. Even in the case of packet error of 5% to 10%, the data error rate is less than 10%. If the block size is 712 bytes, the error rate is higher than this. If the block size is 1424 byte, the highest error rate is shown. Therefore, if the error is high when measuring the status of the wireless network, it is possible to reduce the block size to prevent the error from propagating throughout.

Those skilled in the art will appreciate that the present invention can be embodied in other specific forms without changing the technical spirit or essential features of the present invention. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. The scope of the present invention is indicated by the scope of the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and the equivalent concept are included in the scope of the present invention. Should be interpreted.

By implementing the present invention, it is possible to adjust the transmission method and the encoding method according to the situation of the wireless network.

By implementing the present invention it is possible to encode and transmit differentially depending on the importance of each data.

Claims (25)

Receiving status information of the combined wireless network; Classifying data to be transmitted according to the state information; Encoding the transmission data to which the classified data is appended with information for recovery when an error occurs; Setting a determining factor for transmitting the transmission data to the wireless network according to the status information; And And transmitting the encoded transmission data to the wireless network according to the set result, according to the transmission situation of the wireless network and the importance of video information. The method of claim 1, The receiving step is a step of receiving the status information transmitted from the receiving unit for receiving the transmission data, the transmission method for controlling the encoding and transmission according to the transmission status of the wireless network and the importance of the video information. The method of claim 1, The data to be transmitted is video data, The classifying includes indicating whether the frame is an I frame, a P frame, or a B frame. The method of encoding and transmitting data according to a transmission situation of a wireless network and the importance of video information. The method of claim 1, After the encoding step, And interleaving the encoded transmission data according to the state of the received wireless network, and encoding and transmitting the data according to the transmission situation of the wireless network and the importance of video information. The method of claim 1, And the determining factor is any one of a factor for determining the number of retransmissions, a data rate to be transmitted, and a size of a maximum transmission unit, according to a transmission situation of a wireless network and importance of video information. The method of claim 1, And the status information includes information on a rate of loss or error in data transmitted through a wireless network, and encodes and transmits the data according to the transmission status of the wireless network and the importance of video information. The method of claim 1, The status information encodes the data according to the transmission status of the wireless network and the importance of video information, including one or more of an error rate of a transport packet, a data error rate after FEC recovery, a hamming distance, and an error distance. How to send. The method of claim 1, The encoding is a step of performing Forward Error Correction (FEC) encoding, the method of encoding and transmitting the data according to the transmission status of the wireless network and the importance of the video information. Receiving data via the combined wireless network; Classifying according to the characteristics of the data; Combining the classified data by classification; Reproducing the combined data; And collecting the state information of the wireless network through the reception state of the data, and transmitting the state information. The method of claim 9, The received data is video data, The classifying step includes classifying the data according to information indicating whether the data is an I frame, a P frame, or a B frame. The method of claim 9, The combining step And deinterleaving the received data according to the transmission status of a wireless network and the importance of video information. The method of claim 9, The playing step And decoding the combined data, according to the transmission situation of the wireless network and the importance of video information. The method of claim 9, The state information receives data according to the transmission status of a wireless network and the importance of video information, including one or more of an error rate of a transport packet, a data error rate after FEC recovery, a hamming distance, and an error distance. How to. A QoS control section for receiving status information on the combined wireless network and setting decision factors for transmitting data to the wireless network according to the status information; A frame classifier classifying data to be transmitted according to the state information; An encoder for encoding the transmission data to which the classified data is added for recovering when an error occurs; And A MAC / PHY controller for transmitting the encoded transmission data to the wireless network according to the setting result; And the QoS control unit controls an encoding scheme of the encoder according to state information. The method of claim 14, And the QoS control unit receives state information in which a reception unit which receives the transmission data transmits data. The method of claim 14, The data to be transmitted is video data, And the frame classification unit indicates whether the frame classification unit is an I frame, a P frame, or a B frame. The method of claim 14, And the encoder interleaves the encoded transmission data according to the state of the received wireless network. The method of claim 14, And the determining factor is any one of a factor for determining the number of retransmissions, the data rate to be transmitted, and the size of the maximum transmission unit. The method of claim 14, And the status information includes information about a rate of loss or error in data transmitted over a wireless network. The method of claim 14, And the status information includes one or more of an error rate of a transport packet, a data error rate after FEC recovery, a hamming distance, and an error distance. The method of claim 14, And the encoder performs forward error correction (FEC) encoding. A MAC / PHY controller for receiving data through the combined wireless network; A packet sorter for classifying the data according to the characteristics of the data; A decoder which combines the classified data by classification to reproduce the combined data; And And a statistics collector which collects state information of the wireless network through the state of receiving the data and transmits the state information. The method of claim 22, The received data is video data, And the packet aligning unit classifies the data according to information indicating whether the data is an I frame, a P frame, or a B frame. The method of claim 22, And the decoder deinterleaves the received data. The method of claim 22, And the status information includes one or more of an error rate of a transport packet, a data error rate after FEC recovery, a hamming distance, and an error distance.

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