KR100708190B1 - Method for effectively transmitting or receiving data via wireless network, and wireless device thereof - Google Patents

Abstract

The present invention relates to a method and apparatus for improving stability and transmission efficiency in data transmission through a wireless network.

According to an aspect of the present invention, there is provided a method of transmitting wireless data, the method comprising: transmitting a first data frame including a plurality of data units to a receiving device, and in response to the data frame, for each of the plurality of data units; Receiving an acknowledgment from the receiving device, and transmitting a second data frame including, among the plurality of data units, a data unit which is determined not to be normally transmitted based on the acknowledgment.

IEEE 802.11, MAC, PHY, ACK, Wireless Network, Bitmap, Separator

Description

Method for effectively transmitting or receiving data via wireless network, and wireless device according to the present invention.

1 is a diagram illustrating a communication method on a conventional wireless LAN.

2 is a diagram illustrating a conventional process for a case where an error occurs during communication between wireless devices.

3 is a view showing the time wasted in the conventional wireless communication process.

4 is a view for explaining the structure of the frame according to an embodiment of the present invention.

5 is a diagram illustrating a configuration of a MAC header according to an embodiment of the present invention.

6 is a diagram illustrating a configuration of a PHY header according to an embodiment of the present invention.

FIG. 7 illustrates the configuration of the data frame of FIG. 4 in more detail.

8 is a schematic diagram illustrating a process in which a transmitting device transmits a plurality of TSs to a receiving device.

FIG. 9 is a diagram illustrating a data frame according to another embodiment than the data frame of FIG. 7.

FIG. 10 is a diagram illustrating the configuration of the block ACK frame of FIG. 4 in more detail.

11 is a diagram illustrating a communication process according to an embodiment of the present invention.

12 is a diagram illustrating the configuration and operation of a wireless device according to an embodiment of the present invention.

FIG. 13 is a block diagram illustrating a detailed configuration of the payload processing unit of FIG. 12.

14 is a diagram illustrating a form in which a plurality of TSs generated in an application are processed for each layer.

FIG. 15 is a diagram illustrating the configuration of the bitmap processing unit of FIG. 12 in more detail.

FIG. 16 illustrates an example of a data frame including a plurality of data units that are initially transmitted. FIG.

17A to 17I are diagrams for describing various retransmission mechanisms.

18 is a flowchart illustrating a communication method between wireless devices according to an embodiment of the present invention.

19 is a graph comparing experimental results according to the present invention and experimental results according to the method presented in TGn Sync.

(Symbol description of main part of drawing)

41: PHY header 42: MAC header

43: separator 44, 45, 46, 470: data unit

47: bitmap 51, 61: control unit

52: Packet Counter 53: Time Stamper

54, 64: buffer 55: check sum check unit

56: check sum generation unit 62: bitmap generation unit

63: bitmap reader 70: transport stream

71: Packet No. Field 72: PN CRC Field

73: Time Stamp Field 74: CRC Field

75: header CRC field 100: data frame

200: block ACK frame 500: transmitting device

510, 610: Application 520, 620: Device Driver

521, 621: transmit queue 522, 622: receive queue

530, 630: MAC module 531, 631: Software MAC module

532, 632: interface 533, 633: hardware MAC module

540, 640: PHY module 541, 641: baseband processor

542, 642: RF module 550, 650: wireless antenna

560, 660: I / O port 580, 680: data processing unit

581 and 681: Payload processing unit 582 and 682: Bitmap processing unit

The present invention relates to a wireless communication technology, and more particularly, to a method and apparatus for improving stability and transmission efficiency when transmitting data through a wireless network.

Networks are becoming wireless and researches on effective transmission methods in wireless network environments have been required due to the increasing demand for large-capacity multimedia data transmission. Due to the nature of a wireless network in which multiple devices share and use a given radio resource, increasing competition is likely to waste valuable radio resources due to collisions during communication. In order to reduce the collision or loss and to transmit and receive data stably, in a wireless LAN (wireless local area network) environment, a competitive-based distributed coordination function (DCF) or a contention-free point coordination function (PCF) In the wireless personal area network (PAN) environment, a time division scheme called channel time allocation is used.

Although such a method can be applied to a wireless network to reduce collisions to some extent and provide stable communication, there is still a high possibility of collision between transmission data compared to a wired network. This is because there are many elements in the wireless network environment that inherently interfere with stable communication such as multi-path, fading, and interference. In addition, as the number of wireless networks participating in the wireless network increases, the possibility of problems such as collisions and losses increases.

Such collisions require retransmissions that have a fatal adverse effect on the throughput of the wireless network. In particular, when better quality of service (QoS) is required, such as audio / video data (AV data), it is very important to secure more available bandwidth by reducing the number of retransmissions.

1 is a diagram illustrating a communication method on a conventional wireless LAN. If a device on the wireless network, i.e. a transmitting device, wishes to send a data frame to another device on the wireless network, i.e. a receiving device, the transmitting device may send a header through the MAC layer and the PHY layer. Creates a header and appends it to the data for transmission.

The receiving device that receives the data may detect an error through a frame check sequence (FCS), and if there is no error, the receiving device uploads the received data to an upper layer.

The protocol of the IEEE 802.11 series guarantees a minimum interval between frames called Short InterFrame Space (SIFS). SIFS includes a delay at the PHY layer, a time to process a frame at the MAC layer, and a turnaround time of the receiver / transmitter (RX / TX). In other words, SIFS is a time for a wireless device to receive one frame, process it, and prepare to send a response frame. Therefore, if the transmitting device intends to transmit a plurality of frames to the receiving device, in addition to the time for transmitting the plurality of frames, a plurality of SIFS times and a time for transmitting the plurality of response frames are required.

2 is a diagram illustrating a conventional process for a case where an error occurs during communication between wireless devices. 2 illustrates a processing method between a transmitting device and a receiving device, particularly when a frame transmission fails or an error occurs in a transmitted frame on a wireless network for various reasons. At the transmitting device end, the counter "ACK Timeout" is decremented from the moment of transmitting the frame. If the ACK frame (hereinafter simply referred to as "ACK") does not arrive from the receiving device until the counter becomes zero, the transmitting device retransmits the frame as a transmission failure. In FIG. 2, a frame in which transmission fails or an error occurs is shown by a dotted line.

The number of times of retransmission follows the "Retry limit" value set in the transmitting device, and if the retransmission fails, the corresponding frame is skipped. 2, the skipped frame includes data 2. If there is no error, the receiving device performs MAC FCS error checking on the received frame, and transmits the data included in the received frame to a higher layer and sends a response frame, that is, an ACK, to the transmitting device. Will be sent. If an error occurs as a result of the error checking, the corresponding frame is dropped.

As shown in FIG. 3, from the point of view of the transmitting device, all the time other than the time during transmitting the frames can be regarded as wasted time. This wasted time includes the time between transmitted frames and the time (header overhead) consumed by the MAC header and PHY header added for each frame, and thus incurs inefficiencies in the overall wireless network. . When the length of a frame to be transmitted is small, for example, when transmitting an MPEG-2 transport stream having a unit size of 188 bytes, a relatively large overhead occurs as the number of transmissions increases. do. This is because the IEEE 802.11 standard requires an ACK for each frame transmitted.

According to the standard, the length of the MAC header included in the data frame reaches 30 bytes, and the time length of the PHY header reaches 20 μsec. Therefore, it is difficult to see that such overhead is negligibly small compared to the actual data to be transmitted.

The present invention provides a method and apparatus for increasing overall throughput and ensuring stable transmission by recovering the error and performing more efficient retransmission when an error occurs during data transmission in a wireless network environment. For the purpose of

Technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

According to another aspect of the present invention, there is provided a wireless data transmission method comprising: (a) pre-transmitting a first data frame including a plurality of data units to a receiving device; (b) receiving, from the receiving device, an acknowledgment for each of the plurality of data units in response to the data frame; And (c) pre-transmitting, among the plurality of data units, a data frame including a data unit which is determined not to be normally transmitted based on the acknowledgment.

According to an aspect of the present invention, there is provided a wireless data transmission method comprising: (a) receiving a first data frame including a plurality of data units from a transmitting device; (b) sending an acknowledgment for each of the plurality of data units to the transmitting device in response to the data frame; And (c) receiving, from the transmitting device, a second data frame including, among the plurality of data units, a data unit that is determined to have an error based on the acknowledgment.

According to an aspect of the present invention, there is provided a wireless device including an application for executing an application, a data processor for generating a MAC payload including a plurality of data units provided from the application, and the MAC. A MAC module for generating a MAC Protocol Data Unit (MPDU) by adding a MAC header to a payload, and a PHY module for generating a first data frame by adding a PHY header to the MPDU and transmitting the data frame to a receiving device. The data processing unit includes a data unit that is determined to be not normally transmitted among the transmitted data units based on an acknowledgment of each of the plurality of data units, which is received from the receiving device as a response to the data frame. Generate a MAC payload and the M The AC module adds a MAC header to the MAC payload, and the PHY module adds a PHY header to the MAC header to generate a second data frame and transmit the second data frame to the receiving device. .

According to an aspect of the present invention, there is provided a wireless device comprising: a PHY module for receiving a data frame from a transmitting device and removing a PHY header to restore a MAC Protocol Data Unit (MPDU); and a MAC in the MPDU. A MAC module for removing a header and restoring a MAC payload, a data processor for checking an error of a plurality of data units included in the MAC payload, and an error free data unit among the plurality of data units are provided. And an application for executing a program, wherein the data processor generates a bitmap indicating an acknowledgment for each of the data units according to the presence or absence of the error, and the MAC module adds a MAC header to the bitmap. The module adds a PHY header to the MAC header to generate a block ACK frame and receives the received device. Characterized in that the transmission bus.

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 will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention, and the general knowledge in the art to which the present invention pertains. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout. Hereinafter, with reference to the accompanying drawings illustrating a method according to an embodiment of the present invention.

4 is a view for explaining the structure of the frame (100, 200) according to an embodiment of the present invention. The present invention uses a block ACK frame having information in the form of a bitmap as a response frame.

The data frame 100 according to an embodiment of the present invention includes a PHY header 41, a MAC header 42, a plurality of data units 44, 45, and 46, and a plurality of delimiters 43. Is done. As used herein, the term "data unit" refers to an MSDU (MAC Service Data Unit) transmitted from an upper layer of the MAC layer to the MAC layer. The delimiter 43 is located between each frame, and may include number information of data units capable of distinguishing frames, checksum information for error detection, and information (eg, time stamp) for synchronization. Of course, since the payload size is limited to 2304 bytes in the IEEE 802.11 series standard, the sum of the data units 44, 45, 46 and the separators 43 may be limited within the size.

In the present invention, the response to the data frame 100 is assumed to be made by one block ACK frame 200. Since the data frame 100 included in the plurality of data units 44, 45, and 46 is only one frame, according to the conventional ACK policy, an immediate ACK for a single frame should be answered. However, according to the present invention, the ACK as a response to the frame 100 is in the form of a block ACK 200. This is because a plurality of acknowledgments are required for the plurality of data units 44, 45, and 46 included in one frame 100.

The block ACK frame 200 is loaded with a bitmap indicating whether or not there is an error for the frame. The transmitting device determines whether to retransmit which data unit according to this information. The block ACK frame 200 includes a PHY header 41, a MAC header 42, and a bitmap field 47.

5 and 6 illustrate the structure of the MAC header 42 and the PHY header 41 according to an embodiment of the present invention. As shown in FIG. 5, the MAC header 42 may have the same structure as the conventional IEEE 802.11 standard. The MAC header 42 may include a Frame Control field, a Duration / ID field, at least one address field (Address 1 to 4), and a Sequence Control field. The definition and detailed structure of each field is the same as defined in the above standard.

6 shows an example of the PHY header 41 when using an Orthogonal Frequency Division Multiplexing (OFDM) modulation scheme that supports MIMO (Multi Input Multi Output), and is defined in the IEEE 802.11 series standard. . Since this is only an example, an appropriate PHY header may be used according to various modulation schemes such as Direct Sequence Spread Spectrum (DSSS) and Frequency Hopped Spread Spectrum (FHSS).

FIG. 7 illustrates the configuration of the data frame 100 of FIG. 4 in more detail. In particular, FIG. 7 illustrates an example in which a transport stream having a fixed size of 188kbyes (hereinafter, abbreviated as TS) is mounted on the frame body part as a data unit. As in FIG. 4, the delimiters are shaded. In consideration of the size of an IEEE 802.11 series MAC frame body, 12 TSs may be included in the frame body.

One data unit, that is, TS is a Packet No. The field 71, the PN CRC field 72, the Time Stamp field 73, and the CRC field 74 form one repeating unit.

Packet No. In the field 71, the sequence number of the data unit carried in the frame body portion is recorded. In FIG. 7, serial numbers 1 to 12 (or 0 to 11) are sequentially assigned to 12 TSs from TS1 to TS12 in order of reaching the MAC layer from an upper layer. Will be recorded in field 71.

The PN CRC field 72 indicates the Packet No. A checksum for checking whether there is an error in the field 71 is recorded. Cyclic redundancy check (CRC) is generally used as the checksum.

In the Time Stamp field 73, the time (count value of the internal clock) when the data unit arrives from the upper layer to the MAC layer is recorded as a tag value. The time stamp field 73 is used for transmitting isochronous data such as TS, and may not be used for transmitting asynchronous data units.

Assuming a situation in which a plurality of TSs are transmitted between the transmitting device and the receiving device as shown in Fig. 8, t1 is written in the tag of TS1, t2 is written in the tag of TS2, and t3 is written in the tag of TS3.

When the TSs are transmitted through the network, the TSs are filled and transmitted without time intervals. The destination device receives the TSs transmitted in this way, restores the original time interval, and delivers the MPEG-2 TS to the AV decoder 10 through the stream I / F. If TS1 is output through stream I / F at t4, TS2 waits for a time interval between tag2 and tag1, i.e., outputs TS2 at t5. TS3 waits for the time interval between tag 3 and tag 2, that is, outputs TS3 when t6.

In this way, the AV decoder 10 helps to decode the AV stream at the correct time by outputting through the stream I / F at the original time interval in the transmitting device.

Returning to FIG. 7 again, a checksum for checking whether there is an error in the TS data 70 is recorded in the CRC field 74. As a method of obtaining the checksum, a cyclic redundancy check method is mainly used. As another example, a check sum for an error of the Time Stamp field 73 and the TS data 70 may be recorded in the CRC field 74. On the other hand, the HDR CRC field 75 recording the check sum indicating whether the MAC header 42 is in error may also be included in the frame body.

The structure of the data frame 100 of FIG. 7 may not be compatible with the conventional MAC frame structure. Considering the compatibility with the conventional MAC frame, the data frame 150 according to another embodiment of the present invention may be defined as shown in FIG. 9, the structure is compatible with the MAC frame structure of the conventional IEEE 802.11 standard. That is, the data frame 150 includes a MAC header 42, a frame body, and an FCS field 91. The FCS field 91 is a field in which the checksum of the entire MAC frame is recorded, and checks whether there is an error in the MAC header 43 and the entire frame body. The frame body consists of a set of repeating units configured as in FIG.

FIG. 10 is a diagram illustrating the configuration of the block ACK frame 200 of FIG. 4 in more detail. The block ACK frame 200 includes at least a PHY header 41, a MAC header 42, and a bitmap field 47, and may further include an FCS field 48. According to the IEEE 802.11 standard, in the case of an ACK frame, the MAC header 42 includes a Frame control field, a Duration / ID field, an RA field in which a receiver address is recorded, and a transmitter address. It consists of a TA field to be recorded.

The bitmap field 47 is composed of a plurality of bits, each bit being a Packet No. Corresponds to each data unit number recorded in the field 71 sequentially. As shown in FIG. 7, if the data frame 100 includes 12 data units, that is, 12 TSs, the nth bit of the bitmap 47 corresponds to the nth TS (TSn). The bit indicates whether the corresponding data unit was normally received. For example, if the bit is 1, it may be defined to mean that it is normally received, and if it is 0, it means that it is not normally received.

In FIG. 7, the bitmap 47 is represented by 2 bytes (that is, the bitmap 47 is composed of 16 bits) is only one embodiment and is not necessarily limited to this size.

11 is a diagram illustrating a communication process according to an embodiment of the present invention. 5 shows a method of processing the transmission device and the reception device, especially when an error occurs in the frame transmission process.

If an error occurs in the second or third data unit among the three data units included in the data frame transmitted from the transmitting device, the error is detected in the whole frame, and thus the receiving device transfers the received data frame to the upper layer. It is not sent up. However, only the data unit 1 in which no error occurs among the received data frames is stored in the buffer. In addition, the receiving device sets the bit to 1 only for the first, that is, data unit 1, and sets the rest to 0. Then, the bitmap (1, 0, 0) consisting of the set bits is transmitted in a block ACK frame to the transmitting device.

The transmitting device receiving the block ACK reads the bitmaps (1, 0, 0) included in the block ACK and finds that transmission of the data unit 2 and the data unit 3 has failed, and the data unit 2 and the data unit 3 are read. Retransmit (primary retransmission) the included data frame.

If an error occurs in the data unit 3 of the two data units transmitted again, the receiving device does not send the received data frame to the upper layer, and stores only the data unit 2 in which the error does not occur among the received data frames in the buffer. Put it. The receiving device also sets the first and second bits to 1 and the third bit to 0. The bitmap (1, 1, 0) consisting of the set bits is transmitted in a block ACK frame to the transmitting device.

The transmitting device receiving the block ACK reads the bitmaps (1, 1, 0) included in the block ACK and finds that transmission of the data unit 3 has failed, and transmits the data frame including the data unit 3 again. Second retransmission).

If no error occurs in the retransmitted data frame, the receiving device reads data unit 1 and data unit 2 stored in the buffer before sending the received data unit 3 to the upper layer. The receiving device then sends the data units 1, 2 and 3 to the upper layer. In addition, the receiving device sets all bits to 1, and transmits the bitmaps 1, 1, and 1 made up of the set bits in a block ACK frame to the transmitting device.

12 is a diagram illustrating the configuration and operation of a wireless device 500, 600 according to an embodiment of the present invention. In FIG. 12, the transmission device 500 and the reception device 600 are merely used to distinguish the two, and in reality, both are wireless devices having the same components.

The application 510 of the transmitting device 500 is a software module that executes an application program, and downloads a data unit (eg, TS) generated as a result of the program execution to the device driver 520. The device driver 520 is a kind of inter-layer interface, and includes a transmission queue 521 for temporarily storing data units provided from the application 510 and a reception queue 522 for temporarily storing data units delivered from a lower layer. do. The queues 521 and 522 store data units according to a first in, first out (FIFO) scheme. In other words, when a queue of a certain size is full, the first data unit entered in the queue is output.

The data unit 570 stored in the transmission queue 521 is transferred to the data processor 580. The data processor 580 may include a payload processor 581 and a bitmap processor 582. The payload processing unit 581 inserts the separator 43 as shown in FIG. 4 into a data unit (eg, TS) provided from the application 510 to configure the MAC payload according to the present invention. The delimiter 43 has Packet No. The field 71, the PN CRC field 72, the Time Stamp field 73, and the CRC field 74 may be included. In addition, when an error occurs in the transmission of the data frame, the payload processing unit 581 generates a MAC payload again with the specific data unit in which the error occurs and the corresponding separator to prepare for retransmission. The determination of whether the error occurs depends on the information recorded in the bitmap of the block ACK frame transmitted from the receiving device 600.

13 is a block diagram showing a detailed configuration of the payload processing unit 581. The buffer 54 temporarily stores the data unit 570 descending from the transmission queue 521. The packet counter 52 assigns a serial number to the data unit 570 whenever the data unit 570 descends from the transmission queue 521, and a time stamper 53 gives the data unit 570 down. Each time, an internal clock count value is assigned to the data unit 570. The checksum generation unit 56 generates a packet no. The value recorded in the field 71 and the checksum for the data unit 570 are calculated.

The control unit 51 stores the packet number for the data unit 570 based on the assigned serial number. Write in field 71, check sum for field 71 in PN CRC field 72, write the clock count value in Time Stamp field 73, write in data unit 570 The checksum is recorded in the CRC field 74 to generate a delimiter. The generated payload is combined with a predetermined number of data units 570 to form a MAC payload. If an error occurs in some data units after receiving the block ACK frame and retransmission is necessary, the controller 51 generates an error based on the number of the data unit in which an error is notified from the bitmap processor 582. Configure a MAC payload that includes data units.

The buffer 54 temporarily stores the configured MAC payload and sends it to the MAC module 630.

On the other hand, when a data frame is received from another wireless device, the checksum check unit 55 operates. The checksum check unit 55 is the Packet No. It is checked whether the checksum for the value recorded in the field 71 and the value recorded in the PN CRC field 72 are the same. Then, it is checked whether the check sum for the data unit and the value recorded in the CRC field 74 are the same. The control unit 51 stores the data unit having no error in the buffer 54 according to the check result, and discards the data unit having an error. In addition, the check result is provided to the bitmap processing unit 582.

When a plurality of TSs are generated from the application 510, a form of a packet generated for each layer may be illustrated as shown in FIG. 14. The data processor 580 generates a MAC payload by combining twelve TSs (TS1 to TS12) that can be accommodated in the MAC payload among the plurality of TSs generated by the application 510 and a separator (indicated by shades).

The generated MAC payload is delivered to the MAC module 530. From the perspective of the MAC module 530, the delivered MAC payload will be recognized as a MAC Service Data Unit (MSDU). The MAC module 530 generates a MAC Protocol Data Unit (MPDU) by adding a MAC header to the MAC payload. Finally, the PHY module 540 receives the MPDU frame and adds a PHY header to it to complete the data frame to be finally transmitted.

12, the bitmap processor 582 analyzes the bitmap included in the block ACK frame transmitted from the receiving device 600. That is, each bit constituting the bitmap is read to find out that an error has occurred among the data units included in the transmitted data frame, and the payload processing unit 581 is notified of the result.

15 is a diagram showing in more detail the configuration of the bitmap processing unit 582. The bitmap processing unit 582 is, for example, a control unit 61, a bitmap generation unit 62, and a bitmap reading unit 63. As shown in FIG. ), And a buffer 64. The bitmap reader 63 reads the bitmap (47 of FIG. 4) included in the block ACK frame to determine whether an error occurs in each of the data units included in the transmitted data frame, and determines the result of the controller 61. The payload processing unit 581 is provided. On the other hand, the bitmap generation unit 62 creates a bitmap indicating whether a reception error for each data unit is performed based on the checksum check performed by the payload processing unit 581. The created bitmap is temporarily stored in the buffer 64 and then transferred to the MAC module 530.

The MAC module 530 generates an MPDU by adding a MAC header to the MAC payload provided from the data processor 580. The configuration of the MAC header is as described with reference to FIG. The MAC module 530 is a software MAC module 531 implemented in a software form, a hardware MAC module 533 implemented in a hardware form, and an interface 532 for relaying communication between the modules 531 and 533. It may be configured to include. Software MAC module 531 is primarily responsible for non-time-critical MAC functions, and hardware MAC module 531 is primarily responsible for time-critical MAC functions.

The PHY module 540 receives the MPDU delivered from the MAC module 530 to generate a packet protocol data unit (PPDU), converts the radio signal, and transmits the converted wireless signal. Here, the PPDU means a data frame according to the present invention. The PHY module 540 again generates a baseband processor 91 that processes the baseband signal, and generates an actual radio signal from the processed baseband signal and transmits it to the air through the antenna 550. It may be subdivided into radio frequency (RF) modules 92.

As described above, the application 510 may generate a data unit through a complicated algorithm. However, when the data unit is a signal output directly from a broadcast receiver such as a TS, the application 510 may directly generate a data unit through the I / O port 560. It may be implemented to be input and delivered to the hardware MAC module 533. This implementation eliminates the need to use a main CPU (not shown) of the transmitting device 500 and can result in faster processing speeds. However, even in this case, since the processing in the data processing unit 580 is required, the data processing unit 580 should be implemented as a hardware module included in the hardware MAC module 533.

On the other hand, the receiving device 600 also has the same structure as the transmitting device 500. The receiving device 600 receives an RF signal from the transmitting device 500 through the antenna 650, processes the received RF signal through the PHY module 640, and restores the MPDU, which is then processed by the MAC module 630. To pass on.

The MAC module 630 transmits the MAC payload from which the MAC header is removed from the MPDU to the data processor 680. The payload processing unit 681 of the data processing unit 680 reads a delimiter (43 in FIG. 4) included in the MAC payload. Field 71, PN CRC field 72, Time Stamp field 73, and CRC field 74. Meanwhile, when a bitmap is provided from the data processor 680, the MAC module 630 adds a MAC header to the PHY module 640.

Payload processing unit 681 is a Packet No. After checking through the PN CRC field 72 whether the field 71 was transmitted without error, Packet No. The number of the data unit recorded in the field 71 is read out. Then, the CRC field 74 determines whether the data unit having the number has been transmitted without error. The payload processor 681 stores the data unit 670 transmitted without error in a predetermined buffer (not shown) and provides the received data unit 670 to the reception queue 622 of the device driver 620.

On the other hand, the bitmap processor 682 generates bits that indicate whether an error occurs in the data unit included in the received data frame, that is, a bitmap, and provides the bitmap to the MAC module 630. The structure of the bitmap has been described above with reference to FIG. 10.

The reception queue 622 temporarily stores a data unit (eg, TS) provided from the data processing unit 680 and delivers the data unit discharged according to the first in, first out (FIFO) to the application 610.

The application 610 executes the application program using the transferred data unit as an input and outputs the execution result (for example, the decoded audio / video signal) to the outside through the display unit 690.

Meanwhile, if the data processing unit 680 is implemented as a hardware module in the hardware MAC module 633, the MPDU provided from the PHY module 640 may be directly processed and restored to the data unit 570. The data unit 570 may be output through an I / O port. If the output data unit 570 is in the form of an A / V stream such as TS, an external video decoder may directly process the A / V stream output from the I / O port to restore audio or video. Can be.

The configuration of the MAC module 530 and the PHY module 540 of the form shown in FIG. 12 is merely an example, and the present invention is not limited thereto.

The various illustrative logic blocks, modules, and circuits described in connection with the embodiments disclosed herein are general purpose processors, digital signal processors (DSPs), application specific integrated (ASIC) designed to perform the functions described herein. circuit, field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic device, discrete hardware components, or any combination thereof. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented in a combination of computing devices, eg, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other configuration.

In the above description, the transmitting device retransmits only the data unit in which an error has occurred, but various retransmission mechanisms can be considered. Hereinafter, as a retransmission mechanism using bandwidth effectively, a retransmission method using various methods such as Tx rate, adaptation according to the size of transmission data, distribution, redundancy, etc. will be presented.

Initially, when a data frame including a plurality of data units as shown in Fig. 16 is transmitted from the transmitting device to the receiving device, it is assumed that TS 2, 6, and 8 of these are not normally transmitted. At this time, the retransmission mechanism proposed in the present invention is as shown in Figs. 17A to 17H.

17A illustrates a case of retransmitting a data frame including only a data unit in which an error occurs as described above. As such, when a data frame composed of only data units that have failed to be transmitted is transmitted, the size of the data frame is reduced during retransmission, thereby reducing the possibility of error repetition.

 However, the present invention is not necessarily limited to the example of FIG. 17A, and may retransmit a data frame in which the transmitting device attempts the first transmission as shown in FIG. 17B.

In addition, in the case of FIG. 17A, when a total of 12 data units can be contained in one data frame, it can be seen that there is a waste part of the MAC payload. Accordingly, there is also a method of retransmitting a data frame combining the data units TS2, TS6, and TS8 in which an error occurs, and the data units TS13 to TS21 to be transmitted thereafter. As such, when the data unit having an error and the data unit to be transmitted later are transmitted together, not only bandwidth use efficiency may be improved, but also the streaming speed may be improved when the data unit is streaming data.

In addition, in an environment with high error probability, an error may occur again even when the retransmission mechanism of FIG. 17A is used. Therefore, a method of repeatedly including a plurality of error-prone data units as shown in FIG. 17D may be considered. .

However, in general, since transmission errors are likely to occur in the form of burst errors, it may be difficult to ensure reliable transmission if a data frame is configured as shown in FIG. 17D. In this case, as illustrated in FIG. 17E, the robustness against the burst error may be improved by repeatedly including the units in which the error occurs in the data frame.

As described above, while the embodiment of FIG. 17A retransmits only some data units in which an error occurs, network traffic can be reduced, whereas the embodiment of FIG. 17D or 17E repeatedly arranges the same data unit in a data frame. This ensures reliable retransmission even if some data units are lost. Therefore, a combination of these two advantages generally allows retransmission as in the embodiment of FIG. 17A, but only in the case of the last retransmission, a method of retransmission as in the embodiment of FIG. 17D or 17E can be considered.

If the last retransmission fails, depending on the wireless communication method, abandon the retransmission or retry the retransmission after a considerable time has elapsed. In either case, even if the last retransmission corresponding to the retry limit fails, significant problems arise. Therefore, at the time of the last retransmission, try to retransmit as shown in Fig. 17d or 17e even at the cost of traffic inefficiency.

FIG. 17F combines the embodiment of FIG. 17A and the embodiment of FIG. 17D, and transmits only a data unit for which transmission failed, but at the last retransmission, the data unit to be retransmitted is repeatedly filled to fill all MAC payloads and then retransmitted. At this time, the data units to be resent are repeatedly arranged in succession.

Meanwhile, FIG. 17G is a combination of the embodiment of FIG. 17A and the embodiment of FIG. 17E, and transmits only data units for which transmission failed, but alternately repeats data units to be retransmitted to fill all MAC payloads at the last retransmission. Then resend.

In addition to this retransmission mechanism, link adaptation can be applied. That is, transmission parameters such as TX rate, TX power, and antenna type (MIMO or SISO (Single Input Single Output) are changed. The change of this parameter may be performed by the MAC module 530. As the retransmission is repeated, the MAC module 530 may ensure more stable transmission by lowering the TX rate, increasing the TX power, or changing the transmission from the MIMO type transmission to the SISO type transmission. Hereinafter, six examples of retransmission mechanisms (hereinafter, referred to as 'link adaptation mechanisms') in consideration of such link adaptation will be described.

First, there is a method of adaptively changing the Tx rate according to the number of retransmissions. This is to set a predetermined number of retransmission intervals and corresponding data rates, and then retransmit the data frames at a data rate corresponding to the number of times of actual retransmission. The number of retransmissions and the transmission rate are inversely related.

For example, suppose that the number of retransmission intervals is divided into 1 or less sections, 2 or more and 3 or less sections, 4 or more and 5 or less sections, and 6 or more and 7 or less sections, and 108 Mbps, 96 Mbps, 72 Mbs, and 54 Mbps, respectively. Therefore, according to this, the first retransmission is actually performed at 108 Mbps, but if additional retransmission is needed, retransmission is performed at the corresponding transmission rate (96, 72, or 54 Mbps).

Second, there is a method of adaptively changing the data rate according to the size of the data frame to be retransmitted. This is to set a predetermined number of 'retransmission size intervals' and corresponding data rates, and then retransmit the data frames at the corresponding data rates according to the size of the data frames to be retransmitted. The size of the data frame and the data rate are inversely related.

For example, the size of a data frame to be retransmitted is defined as the number of data units included therein, and the 'retransmission size section' is divided into a section having a data unit of 4 or less, a section of 5 or more and 8 or less, and a section of 9 or more and 12 or less, respectively. Assume that 108 Mbps, 72 Mbs, and 54 Mbps are set. Then, in actual retransmission, the data frame is retransmitted at 108 Mbps, 72 Mbs, or 54 Mbps depending on the number of data units of the data frame. As the retransmission is repeated, the data unit that has been successfully transmitted is not included in the next retransmission, so the retransmission size can be reduced, and thus the transmission rate will increase as the retransmission is repeated.

Third, there is a method of adaptively changing the retransmission size (Tx Size) according to the number of retransmissions. This is to set a predetermined number of retransmission intervals and a corresponding retransmission size, and then retransmit the data frame with a corresponding retransmission size according to the size of the actual retransmission data frame. The number of retransmissions and the retransmission size are in proportion. The transmission size of the retransmitted data frame may be defined as the number of data units included therein.

Referring to FIG. 17H, it is assumed that a 'number of retransmission intervals' is divided into three or less sections, four or more sections, five or less sections, and six or more sections and seven sections or sections, and set four data units, eight data units, and 12 data units, respectively.

In the first retransmission, there are three data units to be actually retransmitted (TS2, TS6, and TS8), but retransmit the data frame including four data units according to the above-described rules. The data unit added at this time (although it may be another one) is regarded as the data unit TS2 at the forefront. If only transmission of TS8 is successful in the first retransmission, the second retransmission retransmits the data frame having four data units in which TS2 and TS6 are repeatedly arranged.

If the TS2 and TS6 still need to be retransmitted in the fourth retransmission, then eight data units should be transmitted since the number of retransmissions corresponds to four or more sections. Therefore, TS2 and TS6 retransmit the data frame having eight data units repeatedly arranged.

Fourth, there is a method of adaptively changing the retransmission size (Tx Size) according to the number of data units to be retransmitted. This is to set a predetermined number of data unit number intervals and a corresponding retransmission size, and then retransmit the data frame at the corresponding retransmission size. The number of data units and the retransmission size are in proportion.

Referring to FIG. 17I, it is assumed that a 'number of data unit sections' is divided into four or less sections, five or more sections, eight or less sections, and nine or more sections and 12 sections, and set as four data units, eight data units, and twelve data units, respectively.

In the first retransmission, there are three data units to be actually retransmitted (TS2, TS6, and TS8), but retransmit the data frame including four data units according to the above-described rules. If only transmission of TS8 is successful in the first retransmission, the second retransmission retransmits the data frame having four data units in which TS2 and TS6 are repeatedly arranged.

If the transmission of TS6 succeeds in the second transmission, the remaining data unit to be retransmitted is one TS2 but retransmits the data frame in which TS2 is duplicated four times according to the above-described rule.

In order to be compatible with the communication scheme according to the existing IEEE 802.11 standard, the frame transmission and block ACK mechanism according to the present invention may be selectively used. For example, whether to use the reserved bit (61, 62) of the PHY header can be recorded.

18 is a flowchart illustrating a communication method between wireless devices according to an embodiment of the present invention. The method can be divided into three main processes. Specifically, the transmitting device 500 transmits a first data frame (first transmitted frame) including a plurality of data units to the receiving device 600 (S10), and the receiving device 600 transmits the data frame. In step S20, transmitting a receipt to each of the plurality of data units as a response to the transmitting device 500, and wherein the transmitting device 500 is based on the received acknowledgment among the plurality of data units. And transmitting to the receiving device 600 a second data frame (retransmission data frame) comprising a data unit which is determined to have not been normally transmitted.

First, referring to step S10, the payload processing unit 581 of the transmitting device 500 generates a MAC payload including a plurality of data units and a separator (43 in FIG. 4) provided from the application 510 ( S11). The MAC module 530 generates an MPDU by adding a MAC header to the MAC payload (S12). The PHY module 540 adds a PHY header to the MPDU to generate a first data frame and transmits it to the receiving device 600 (S13).

Next, referring to step S20, first, the first data frame is provided to the payload processor 681 through the PHY module 640 and the MAC module 630. The payload processing unit 681 checks whether the data unit included in the provided first data frame is in error (S21), and buffers the data unit determined to be free of errors (S22). The error check result is provided to the bitmap processor 682. The bitmap processing unit 682 generates a bitmap including an acknowledgment for each data unit included in the first data frame according to the error margin check result (S23), and the MAC module 630 generates the bitmap. The MAC header is added to the terminal (S24), and the PHY module 640 adds the PHY header thereto to generate a block ACK frame, and then transmits it to the transmitting device 500 (S25).

Finally, referring to step S30, the block ACK frame is first provided to the bitmap processor 582 via the PHY module 540 and the MAC module 530 of the transmitting device 500. The bitmap processing unit 582 determines a data unit in which an error occurs by reading the bitmap included in the block ACK frame (S32). The number of the determined data unit is provided to the payload processing unit 581. The payload processing unit 581 generates a MAC payload including a data unit and a separator that are determined to have occurred the error (S33). Then, the MAC module 530 adds a MAC header to the MAC payload to generate an MPDU (S34). The PHY module 540 generates a second data frame by adding a PHY header to the MPDU, and transmits it to the receiving device 600 (S35).

19 is a graph comparing experimental results according to the present invention and experimental results according to the method presented in "TGn Sync". The TGn Sync is a group participated by various industries for the purpose of 802.11n standardization. In this experiment, the maximum data rate is 108 Mbps, and one data frame includes eight TSs.

The graph shows how the throughput changes as the Packet Error Rate (PER) increases. At low PER, that is, a good communication environment, the results do not show much difference. However, as the PER increases, the result of TGn Sync decreases rapidly, whereas the result of the present invention shows that the rate decreases relatively slowly. Indeed, a wireless communication environment is a very poor environment that is prone to errors in transmission as many wireless devices competitively use wireless channels. Therefore, in this environment, the proposed methods of the present invention may be used more efficiently.

Although embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features thereof. I can understand that. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

As described above, according to the present invention, a plurality of data units can be efficiently transmitted through one data frame.

As described above, according to the present invention, when an error occurs in some data units during the transmission of the data frame, the overall transmission efficiency is increased by monitoring the possibility of error occurrence or the number of retransmissions during retransmission through an efficient retransmission method for recovering the data frame. It works.

Claims (13)

(a) transmitting a first data frame comprising a plurality of data units to a receiving device; (b) receiving an acknowledgment for each of the plurality of data units from the receiving device in response to the first data frame; And (c) transmitting, from the plurality of data units, a second data frame including a data unit that is determined to not be normally transmitted based on the acknowledgment; The acknowledgment for each of the plurality of data units is expressed in the form of a bitmap included in one acknowledgment frame. The method of claim 1, wherein the second data frame A wireless data transmission method comprising the data unit in which the error has occurred. The method of claim 1, wherein the second data frame The same wireless data transmission method as the first data unit. The method of claim 1, wherein the second data frame And a data unit determined to be not normally transmitted, and a data unit subsequent to the data unit included in the first data frame. The method of claim 1, wherein the second data frame And continuously repeating a predetermined number of data units determined to be not normally transmitted. The method of claim 1, wherein the second data frame And when there are two or more data units that are determined to have not been normally transmitted, repeatingly including the two or more data units alternately. The method of claim 1, If the step (c) does not correspond to the last retransmission corresponding to the retry limit, the second data frame consists of the data unit in which the error occurs, If the step (c) corresponds to the last retransmission, wireless data transmission method comprising continuously repeating a predetermined number of data units that are determined to be not normally transmitted. The method of claim 1, If the step (c) does not correspond to the last retransmission corresponding to a retry limit, the second data frame consists of the data unit in which the error occurred, And if step (c) corresponds to the last retransmission, the second data frame alternately repeats the data unit in which the error occurred. The method of claim 1, wherein step (c) Setting a plurality of retransmission number intervals; Determining where the number of retransmissions in the transmission of step (c) corresponds to one of the plurality of retransmission number intervals; And And transmitting the second data frame at a transmission rate corresponding to the determined number of retransmission intervals. The method of claim 1, wherein step (c) Setting a plurality of retransmission size intervals; Determining where the retransmission size in the transmission of step (c) corresponds to among the plurality of retransmission size intervals; And And transmitting the second data frame at a transmission rate corresponding to the determined retransmission size interval. The method of claim 1, wherein step (c) Setting a plurality of retransmission number intervals; Determining where the number of retransmissions in the transmission of step (c) corresponds to one of the plurality of retransmission number intervals; And And transmitting the second data frame in a retransmission size corresponding to the determined retransmission number interval. 12. The method of claim 10 or 11, wherein the retransmission size is The wireless data transmission method is determined by the number of data units included in the second data frame. The method of claim 1, wherein step (c) Setting a plurality of data unit number intervals; Determining where the number of data units in the transmission of step (c) corresponds to among the plurality of data unit number intervals; And And transmitting the second data frame having a retransmission size corresponding to the determined number of data unit intervals.

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