KR101316622B1 - Wireless communication network system and method of transmitting multicast packet over the wireless communication network - Google Patents

Abstract

The present invention relates to the transmission and reception of multicast packets through a wireless communication network, and more particularly, to a structure of a MAC (Media Access Control) structure in which a retransmission request for a multicast packet is simultaneously transmitted through a multipath fading channel. According to the present invention, a method for transmitting and receiving a multicast packet includes transmitting a multicast packet from a transmitter to a plurality of receivers through a wireless channel, receiving the multicast packet at each receiver, and checking whether there is a transmission error with respect to the multicast packet. And checking and simultaneously transmitting response signals from at least one of the plurality of receiving terminals to the transmitting terminal in synchronization with each other according to the inspection result. According to the present invention, the transmission speed of a multicast packet can be improved by actively utilizing collisions between retransmission requests transmitted from a plurality of receivers based on characteristics of a radio channel.

Wireless network, multicast, multipath fading, NAK, collision, ARQ.

Description

TECHNICAL FIELD OF THE INVENTION Multicast packet transmission and reception over a wireless communication network and the wireless network system.

1 is a diagram illustrating a wireless multicast environment to which the present invention is applied.

2 is a timing diagram illustrating a process of transmitting a multicast packet from a transmitting node to a plurality of receiving nodes by the method according to the present invention.

3 is a flowchart illustrating a step-by-step method of transmitting a multicast packet according to the present invention.

4 is a flowchart illustrating a step-by-step method of receiving a multicast packet according to the present invention.

5 is a diagram illustrating the structure of a multicast packet transmission node according to the present invention.

6 is a diagram illustrating the structure of a multicast packet receiving node according to the present invention.

<Explanation of symbols for the main parts of the drawings>

110, 211: sending node

120, 212, 213: receiving node

221, 231, 232, 241: multicast packets

251, 252, 253, 261, 262: negative acknowledgment packet

The present invention relates to the transmission and reception of multicast packets through a wireless communication network. More specifically, the present invention relates to a media access control (MAC) structure in which a retransmission request for a multicast packet is simultaneously transmitted through a multipath fading channel. It is about.

Recently, as satellite broadcasting and digital multimedia broadcasting (DMB) services have been provided, and interest in broadcasting services in the shadow area has increased, so-called "bang convergence" of convergence of broadcasting services and communication services or broadcasting systems and communication systems There is an active discussion on the issue. As part of the discussion related to the convergence of communication, researches on the provision of broadcasting service using the existing communication network, especially wireless communication network, have been actively conducted.

Broadcast services that transmit the same data to an unspecified number are closely related to the multicast environment. However, in a multicast environment, since the same data is transmitted to multiple nodes, it is difficult to properly receive feedback from each receiving node whether the data has been transmitted without any problem. Accordingly, in a multicast environment, it is known that it is difficult to use an Automatic Repeat Request (ARQ) technique that is widely used to secure reliability of transmission data in a data communication system that transmits data in a frame or packet unit.

For this reason, the conventional MAC has been using a method of increasing the transmission reliability without feedback from the receiver by transmitting multicast data at a low transmission rate using a high transmission power. However, this conventional method wastes a lot of unnecessary transmission resources in order to transmit data without error. Furthermore, according to the conventional method, since a longer time is used to transmit the same amount of data, transmission power is not only large, but there is a problem that it is not suitable for large-capacity high-speed data transmission.

Recently, in order to solve the problem of the existing MAC, techniques for minimizing the waste of communication efficiency have been proposed in the absence of feedback from the receiver. One of them is receiver-driven layered multicast (RLM). According to the RLM technique, when data of different layers of different importance, such as in a multimedia application, are transmitted at the same time, important data such as control information is transmitted through a transmission channel of high reliability and relatively important such as multimedia data. Low data is transmitted at high speed over a low reliability transport channel.

RLM is a technique that induces as many nodes as possible to receive data with high reliability, while allowing nodes with good transmission paths to receive data transmitted with low reliability. However, the RLM technique has a problem in that communication quality is degraded because nodes with poor reception conditions cannot receive data transmitted with low reliability with a high probability.

Another approach proposed to solve the problems of the existing MAC is the pseudo-ARQ (Pseudo-ARQ) technique and the layered ARQ (Layered ARQ) technique. These two techniques allow the sender to first transmit data with low reliability on the primary channel, then send the primary recovery data on another channel after a certain time delay, and then recover secondary data on another channel after a certain time delay. This is a method of transmitting recovered data together through a plurality of channels without requiring retransmission. In this case, when the transmission error is detected in the data received through the basic channel, the receiving end can recover the first received data using the primary or secondary recovery data received with a time difference.

This method can reduce the power consumption of the receiver as compared to the conventional MAC structure of always transmitting data with high reliability. However, since the transmitting end must additionally transmit the primary and secondary recovery data, there is a problem in that a gain in power and transmission capacity is not obtained in comparison with the conventional MAC structure.

On the other hand, as mentioned above, not only methods for maximizing transmission efficiency without feedback from the receiver, but also techniques for properly receiving the feedback of the receiver in a multicast environment have been proposed. Particularly problematic when receiving feedback from a receiver in a multicast environment is that collisions may occur between retransmission requests when a plurality of receivers simultaneously detect a transmission error included in a multicast packet. As the number of receivers increases, network handling overhead for collision avoidance increases.

In a wired environment, when a plurality of receivers simultaneously transmit a retransmission request, each receiver transmits a retransmission request after a random backoff, and when it is confirmed that other receivers transmit the retransmission request in the same time frame, Techniques have been proposed to resolve the problem of retransmission request by suspending the retransmission request. However, such a technique has a problem in that it is difficult to be applied to a wireless communication network that cannot confirm the transmission contents of other nodes and cannot recognize packet collisions.

Accordingly, the present invention solves the problems of the prior art described above and proposes a new MAC structure for efficiently and efficiently transmitting multicast packets by simultaneously receiving retransmission requests from a plurality of nodes in a wireless communication network.

SUMMARY OF THE INVENTION The present invention has been made to improve the prior art as described above, and an object thereof is to provide a MAC structure capable of efficiently transmitting and receiving multicast packets at high speed in a wireless communication network.

Specifically, the present invention proposes a method for transmitting a retransmission request signal even in a wireless multicast environment, and aims to reliably transmit data while transmitting a multicast packet at high speed.

More specifically, the present invention transmits a retransmission request signal simultaneously in synchronization with a plurality of receivers, and transmits a retransmission request by receiving a plurality of retransmission request signals simultaneously received through a wireless channel using a multipath fading technique. The purpose is to eliminate the overhead for handling collisions between them.

In addition, the present invention transmits the FEC information with the multicast packet at the transmitting end, the receiving end corrects the transmission error of the multicast packet with reference to the FEC information prior to the retransmission request, the channel that may occur as the sender waits for the retransmission request The aim is to minimize waste of resources.

The present invention also provides a multicast adaptive channel coding scheme for channel coding the multicast packet at a lower coding rate than a previously transmitted multicast packet when the multicast packet is retransmitted when the transmitter receives the retransmission request. It is an object of the present invention to provide a packet transmission method.

In order to achieve the above object and to solve the above-mentioned problems of the prior art, a method of transmitting and receiving a multicast packet according to an aspect of the present invention is a plurality of receivers ( transmitting a multicast packet to each receiver, receiving a multicast packet at each receiving end, checking for transmission errors for the multicast packet, and responding to the transmitting end from at least one of the plurality of receiving ends according to the checking result. And transmitting the signal simultaneously in synchronization with the wireless channel.

According to another aspect of the present invention, a method of transmitting a multicast packet includes transmitting a multicast packet to a plurality of nodes on a wireless communication network through a wireless channel, and corresponding to the multicast packet from at least one of the plurality of nodes via a wireless channel. Receiving a retransmission request as a multipath signal, and retransmitting the multicast packet to a plurality of nodes in response to the received retransmission request.

In accordance with another aspect of the present invention, a method for receiving a multicast packet includes receiving a multicast packet through a wireless channel, checking whether there is a transmission error of the received multicast packet, and based on the result of the check; And transmitting a retransmission request to the transmitting node from the at least one of the plurality of nodes that have received the multicast packet.

In addition, a wireless communication network system according to another aspect of the present invention is a transmitting node for transmitting a multicast packet over a wireless channel, and receiving a multicast packet from the transmitting node, and retransmission request when a transmission error is detected in the multicast packet. It characterized in that it comprises a plurality of receiving nodes to transmit simultaneously in synchronization with the transmitting node via a wireless channel.

In addition, a multicast packet transmission node according to another aspect of the present invention is a multicast packet transmission unit for transmitting a multicast packet to a plurality of nodes on a wireless communication network through a wireless channel and the multicast from at least one of the plurality of nodes through the wireless channel And a receiving unit for receiving a retransmission request corresponding to the packet as a multipath signal, wherein the transmitting unit retransmits the multicast packet to the plurality of nodes in response to the received retransmission request.

Also, a multicast packet receiving node according to another aspect of the present invention receives a multicast packet through a wireless channel, and checks whether there is a transmission error of the received multicast packet and the multicast based on the check result. A transmitting unit for transmitting a retransmission request to a transmitting node of a packet, the transmitting unit synchronizing the retransmission request from the at least one of the plurality of nodes that have received the multicast packet to the transmitting node at the same time through the wireless channel Characterized in that the transmission.

Hereinafter, a method of transmitting and receiving a multicast packet in a wireless communication network and a wireless communication network system to which the method is applied will be described in detail with reference to the accompanying drawings.

1 illustrates a wireless multicast environment to which the present invention is applied. The wireless multicast environment of FIG. 1 includes one transmitting node 110 and a plurality of receiving nodes 120. Although only four receiving nodes 120 are shown in FIG. 1 for convenience of description, when multimedia data is transmitted to an unspecified number of users, such as in a broadcasting system, the number of receiving nodes 120 may range from tens to thousands of units. Can be.

As the number of receiving nodes 120 increases, the number of nodes that cannot receive a multicast packet normally due to a poor wireless channel situation increases, and as the present invention proposes, an automatic repeat request (Automatic Repeat Request) in a wireless environment is proposed. In order to support ARQ, retransmission requests for these multicast packets from these nodes must be forwarded to the transmitting node 110 in an appropriate manner.

FIG. 2 is a diagram illustrating packet transmission / reception timing when a retransmission request is transmitted to a transmitting node 211 when the receiving nodes 212 and 213 do not normally receive a multicast packet.

For reference, hereinafter, a negative acknowledgment (NAK) packet for notifying the transmitting node 211 that the multicast packet was not normally received by the receiving nodes 212 and 213 will be described as an example of a retransmission request. .

Referring to FIG. 2, the transmitting node 211 transmits the first multicast packet 221 indicated as “Data1” and waits for a predetermined time 220 for the response of the receiving nodes 212 and 213. Receiving nodes 212 and 213 that normally receive the first multicast packet 221 prepare to receive the second multicast packet 231 to be transmitted next without transmitting any response signal to the transmitting node 211. do.

The transmitting node 211, which has not received any response from the receiving nodes 212 and 213 so that the time 220 has elapsed, causes all of the receiving nodes 212 and 213 to which the first multicast packet 221 belongs to the multicast group. The second multicast packet 231, which is the next packet, is transmitted through the wireless channel.

However, FIG. 2 illustrates a case where the receiving nodes 212 and 213 fail to receive the second multicast packet 231 indicated as "Data2". Each receiving node 212, 213 that fails to receive the second multicast packet 231 waits for a predetermined time 230 and then simultaneously synchronizes the NAK packets 251, 252 with the transmitting node 211. To send. For reference, the receiving nodes 212 and 213 may detect a transmission error included in the received multicast packet 231 using a cyclic redundancy check (CRC) bit included in the multicast packet 231. Alternatively, if the multicast packet 231 is channel coded and transmitted, it is determined that reception of the multicast packet 231 has failed when the multicast packet 231 fails to decode the data from the received signal, thereby transmitting the NAK packets 251 and 252. Can be.

According to existing techniques for transmitting feedback on a packet reception result from a receiver to a transmitter in a multicast environment, a plurality of receivers that fail to receive a packet transmits its NAK to the transmitter at different timings. This is to prevent collisions between a plurality of NAKs. For this purpose, a random backoff timer for NAK transmission is provided at each receiving end or the transmission timings of the NAKs are arranged one by one.

However, in the present invention, a method of synchronizing the transmission timings of the NAKs 251 and 252 of all receiving nodes 212 and 213 by using the characteristics of the radio channel is selected. Almost all wireless communication systems are designed to be adaptable to wireless channels that are modeled as multi-path fading channels. Thus, when two nodes 212 and 213 transmit the same data at the same time, even if their headers are the same, the physical waveforms actually transmitted are the same, thereby creating a virtual multipath environment.

Accordingly, the transmitting node 211 recognizes the NAK packets 251 and 252 transmitted by the two receiving nodes 212 and 213 as multipath signals instead of collisions, and thus receives the NAK 253 without collisions. As such, when the NAK packet is transmitted from at least one of the plurality of receiving nodes 212 and 213 belonging to the multicast group, the transmitting node 211 belongs to the multicast group regardless of which node is transmitted. The multicast packet is retransmitted toward all of the receiving nodes 212 and 213.

More specifically, the transmitting node 211 properly adjusts different time delays and frequency offsets of the NAK packets 251 and 252 received from different receiving nodes 212 and 213. It compensates and recognizes it as one NAK packet 253. As such, one of techniques used to receive one NAK packet 253 from a virtual multipath signal is to use diversity. The diversity scheme is a method widely used in a wireless communication system to receive a multipath signal, so a detailed description thereof will be omitted herein.

As described above, in order to recognize the NAK 253 by receiving the NAK packets 251 and 252 simultaneously transmitted from the at least one receiving node 212 and 213 as a multipath signal, each NAK packet 251 and 252 is generated. Not only must it be received over the same channel, it must also contain exactly the same data up to its header. That is, each NAK packet 251, 252 must have the same Source Address (SA) and the same Destination Address (DA) regardless of which receiving node (212, 213) was sent. On the other hand, in the multicast environment, all of the NAK packets 251 and 252 have the network address of the transmitting node 211 as a common destination address and a multicast group address as a common source address. Can be.

As such, the present invention does not avoid collisions between NAK packets 251 and 252 but actively utilizes them, thereby eliminating the wasted waiting time to avoid collisions of NAK packets 251 and 252, and multicast communication network as a whole. It can contribute to increasing the data transfer throughput of the system.

Referring back to FIG. 2, while the receiving nodes 212, 213 transmit NAK packets 251, 252 simultaneously in synchronization, the transmitting node 211 performs the NAK packet (for a predetermined time 220 described above). Wait until 253) is received. In this case, since the NAK packet 253 has been received within the waiting time 220 from the receiving nodes 212 and 213, the transmitting node 211 has at least one of the receiving nodes 212 and 213 to receive the second multicast. It is determined that reception of the packet 231 has failed, and retransmits the second multicast packet 232 to all nodes 212 and 213 belonging to the multicast group.

However, as shown in FIG. 2, when the third multicast packet 241 which is the next packet is already loaded in the transmission buffer of the transmitting node 211, the third multicast packet 241 is transmitted first. The second multicast packet 232 may then be retransmitted. The multicast packet retransmitted as described above is not necessarily transmitted immediately after the previously transmitted multicast packet but may be transmitted in a different order depending on the transmission scheduling situation of the transmitting node 211.

According to an embodiment, the second multicast packet 232 retransmitted may be a packet of the same type as the second multicast packet 231 previously transmitted. When the channel characteristic changes with time or with the spatial movement of the mobile communication terminals, which are the receiving nodes 212 and 213, it may be meaningful to attempt to retransmit the same packet at regular intervals.

However, according to another exemplary embodiment, the retransmitted second multicast packet 232 may be a channel coded packet having a lower code rate than the previously transmitted second multicast packet 231. That is, when the multicast packet 231 is channel coded and transmitted, when the channel state is not good and the receiving nodes 212 and 213 fail to decode data from the received signal, the NAK packet (2) is transmitted to the transmitting node 211. 251 and 252 may be transmitted to request retransmission of the multicast packet 231.

In the present exemplary embodiment, a transmission signal pattern that is more robust to transmission errors may be formed by reducing the coding rate of the second multicast packet 232 to be retransmitted and channel coding the channel. As such, when the channel coding rate of the second multicast packet 232 which is retransmitted each time the NAK packets 251 and 252 are received is gradually reduced, an improvement in the transmission success rate may be more effectively achieved.

Furthermore, if the channel coding rate gradually decreasing as described above is continuously applied to a plurality of multicast packets continuously transmitted, the channel coding rate is determined when the multicast packet is successfully transmitted without retransmission a predetermined number of times. By increasing stepwise, it is possible to adaptively obtain the optimal channel coding rate suitable for the channel characteristics.

Meanwhile, according to another exemplary embodiment of the present invention, the multicast packet 231 includes forward error correction (FEC) information, and the receiving nodes 212 and 213 receive NAK packets 251 and 252. Prior to transmission, the transmission error included in the multicast packet 231 is corrected based on the FEC information. If the error correction is successful, the NAK packets 251 and 252 are not transmitted, and when the error correction is not successful, the transmission resources can be saved by transmitting the NAK packets 251 and 252.

For reference, FIG. 2 illustrates a case in which the second multicast packet 232 is successfully received at each receiving node 212 and 213 when retransmitted. However, if there is a node that fails to receive again despite retransmission, the corresponding multicast packet 232 may be transmitted again. In this case, if a predetermined threshold is set to prevent infinite repetition and the transmission fails repeatedly even after repeatedly transmitting the number of times corresponding to the threshold, the transmission of the corresponding multicast packet 232 is abandoned and the next multicast packet is discarded. You can decide to send.

As described above, when the NAK packet is transmitted from at least one node among the plurality of receiving nodes 212 and 213, the transmitting node 211 retransmits the corresponding multicast packet. The third multicast packet 241 indicated as "Data3" in FIG. 2 was not normally received at the receiving node 212 but was normally received at the receiving node 213. Therefore, the NAK packet 261 is transmitted only at the receiving node 212. The transmitting node 211 receives the NAK packet 262 as a multipath signal, recognizes that at least one of the plurality of receiving nodes 212 and 213 has failed to receive the third multicast packet 241, and retransmits it. do. At this time, since the second multicast packet 232 is already loaded in the transmission buffer for retransmission, the third multicast packet 241 will be retransmitted following the retransmission of the second multicast packet 232 (not shown). ).

3 is a flowchart illustrating a multicast packet transmission method according to the present invention from the perspective of a transmitting node. Referring to FIG. 3, a process of transmitting a multicast packet in a transmitting node is performed by the following steps.

When the packet transmission process is started by a transmission command for a specific multicast packet, first, in step S310, the value of the counter N that records the number of retransmissions of the multicast packet is initialized to '1'.

In step S320, the value of the counter N is compared with a predetermined threshold value. If N becomes larger than the threshold value due to subsequent retransmission, the transmission of the corresponding multicast packet is abandoned and the new multicast packet is prepared for transmission. However, if the comparison shows that N is not greater than the threshold, steps for packet transmission are performed.

In step S330, the multicast packet is transmitted to a plurality of receiving nodes through a wireless channel. In order to increase the packet reception success rate, the transmitting node may encode the multicast packet with a predetermined error correction code. In addition, by performing a puncturing operation to remove some of the parity bits after the encoding process, redundancy of the encoded code may be reduced. A representative example of the encoding is channel coding using turbo code, block code, convolutional code, and the like. The receiving node recovers the transmission data by decoding the multicast packet, which is encoded and received in various forms, in a promised manner.

The transmitting node transmitting the multicast packet waits until the NAK packet arrives from the receiving nodes for a predetermined time in step S340. The transmitting node receives NAK packets from the at least one receiving node synchronized simultaneously over a single channel and transmitted simultaneously as a multipath signal. That is, the NAK packet signals transmitted from the plurality of receiving nodes to the transmitting node, respectively, are recognized as one NAK packet signal being received through the multipath.

Thus, if a NAK packet is received within the waiting time in step S350, the transmitting node retransmits the multicast packet to all of the plurality of receiving nodes belonging to the multicast group regardless of which node the NAK packet was sent from. The packet transmission process starting from S320 is repeated. At this time, in order to record the number of retransmissions, the value of the counter N is increased by 1 in step S360.

According to an embodiment, the retransmitted multicast packet may be channel coded and transmitted at a lower coding rate than the previously transmitted multicast packet. This includes encoding more FEC information than before when retransmitting the same data over a channel that failed to transmit, so that the receiving node can recover the original data from less information in the event of poor channel conditions. To do this. As an example, the WiMedia standard provides four levels of code rates, in which case the transmitting node retransmits the multicast packet while lowering the code rate by one step each time it fails to transmit and receives a NAK packet. Can be.

On the other hand, if the NAK packet has not arrived from any node until the waiting time has elapsed, the transmitting node determines that all nodes have received the multicast packet normally without any problem, and prepares to transmit a new multicast packet. The transmission process of the multicast packet is terminated.

4 is a flowchart illustrating a method for receiving a multicast packet according to the present invention from the perspective of each receiving node. Referring to FIG. 4, a process of receiving a multicast packet transmitted from a transmitting node to a plurality of nodes at each receiving node is performed by the following steps.

In step S410, each receiving node receives a multicast packet from a transmitting node through a wireless channel.

Next, the receiving node checks the transmission error of the received multicast packet. As an example, the check of the transmission error may be performed based on the CRC bit or the like included in the multicast packet. In FIG. 4, as another example of the transmission error detection method, decoding the received multicast packet signal to extract the data transmitted from the transmitting node (S420) and determining whether there is a transmission error based on whether or not the decoding succeeded at the step is performed. Step S430 is shown.

If the decoding succeeds, the receiving node determines that the multicast packet has been successfully received, and terminates the reception process of the packet in order to prepare for reception of a new multicast packet. However, if decoding fails, steps are performed for sending a NAK packet to the transmitting node to request retransmission of the multicast packet. As described above, attempting to restore the original data from the FEC information included in the multicast packet before transmitting the NAK packet is a method for reducing the number of transmission of the NAK packet, and thus, it is possible to save transmission resources.

In step S440, each receiving node waits for a predetermined time to transmit NAK packets simultaneously. As described above, the reason why the NAK packet is transmitted at the same time in synchronization with the scheduled time without transmitting the NAK packet immediately after confirming the transmission error is as described above in order to generate a virtual multipath signal using the characteristics of the radio channel. to be.

That is, as shown in step S450, at least one receiving node transmitting the NAK packet all simultaneously transmits the NAK packet to a single transmitting node at the same timing, so that one NAK packet is transmitted through the wireless channel. The multipath fading effect is to create a NAK reception environment, such as those received with different time delays and different frequency offsets. Therefore, NAK packets transmitted from all receiving nodes have the same shape up to the header, which has been described in detail above.

Finally, in step S460, the receiving node maintains a counter N value that the transmitting node maintains to store the number of retransmissions, and whether the counter node gave up the multicast packet because the transmitting node exceeded the threshold. Check it. That is, if the value of N maintained by the receiving node becomes larger than the threshold value, it is determined that the value of N exceeds the threshold value in the transmitting node to give up the corresponding multicast packet, and preparing for (N + 1) th retransmission. In addition, in order to prepare for transmission of a new multicast packet, the reception process of the multicast packet is terminated.

However, if the N value has not yet exceeded the threshold, the packet reception process beginning from step S410 is performed again to receive the multicast packet retransmitted from the transmitting node.

For reference, the present invention can be applied to all types of wireless communication networks for transmitting and receiving multicast packets through a wireless channel modeled as a multipath fading channel. As an example, the present invention can be applied to a digital multimedia broadcasting (DMB) system, a portable Internet system, a wireless LAN system, and the like. It may be included in an Internet base station or an access point device of a wireless LAN. Similarly, the receiving end may be implemented in the form of a network device mounted on various types of mobile terminals and capable of receiving multicast packets wirelessly.

According to another embodiment, a wireless communication network to which the present invention is applied is a digital communication network configured with an ultra-wideband (UWB) wireless communication method, and a transmitting and receiving node is a UWB communication standard (Wireless Multimedia, WiMedia). Multicast packets can be transmitted and received according to the protocol.

Wireless communication systems such as DMB, portable Internet, wireless LAN, and UWB mentioned above exchange data by Orthogonal Frequency Division Multiplexing (OFDM), which is multipath fading and burst noise. Due to its robustness, it is known to be the most suitable method for wireless communication systems supporting high-speed data transmission. The present invention may be applied to the wireless communication network as described above and used to transmit real-time multimedia streaming data to a plurality of receiving nodes.

Although the present invention has been described with reference to one transmitting node, there may be more than one transmitting node that overlaps the area that is actually covered. In this case, different data transmitted from each transmitting node may have different multicast group identifiers. The packet headers may be transmitted to a plurality of receiving nodes included in each multicast group without a problem by being divided through a packet header including the packet header.

In addition, the multipath signal reception scheme used to receive all NAK packets simultaneously transmitted from a plurality of receivers in the transmitter of the present invention includes various types of diversity schemes. Applicable to those skilled in the art to which the present invention pertains is obvious.

So far, the method of transmitting and receiving a multicast packet according to the present invention has been described with reference to FIGS. 3 and 4 from the perspective of a transmitting node and a receiving node, respectively. Since the details of the embodiments described above with reference to FIG. 2 may be applied to the methods, the description of the details related to the method will be omitted. Similarly, it will be appreciated that the details of the embodiments described with reference to FIGS. 3 and 4 may be applied to the embodiments described with reference to FIG. 2.

5 is a diagram illustrating the structure of a multicast packet transmission node according to the present invention. The multicast packet transmitting node 500 transmits the multicast packet to a plurality of receiving nodes on a communication network through a wireless channel and the multicast packet from at least one of the plurality of receiving nodes through the wireless channel. Receiving unit 520 for receiving a retransmission request corresponding to the multi-path signal. The transmitter 510 retransmits the multicast packet to the plurality of receiving nodes in response to the received retransmission request.

When the transmitter 510 transmits a specific multicast packet to the plurality of receiving nodes on the communication network through the wireless channel, the multicast packet transmitting node 500 waits for a predetermined time and transmits the multicast packet. Review whether or not a retransmission request corresponding to is received.

If the retransmission request corresponding to the transmitted first multicast packet is not received through the receiving unit 520 within the predetermined time, the transmitting unit 510 transmits the previously transmitted first multicast packet. The second multicast packet to be transmitted next can be transmitted.

If a retransmission request corresponding to the transmitted multicast packet is received through the receiver 520 within the predetermined time, the transmitter 510 transmits the retransmission request to the first multicast packet. One receiving node may retransmit the first multicast packet toward all of the receiving nodes belonging to the multicast group.

According to an embodiment, when the second multicast packet is already loaded in the transmission buffer of the transmitter 510, the transmitter 510 transmits the second multicast packet, followed by the first multicast. You can resend the packet.

According to an embodiment, the multicast packet retransmitted by the transmitter 510 may be a packet having the same format as a previously transmitted multicast packet. However, according to another embodiment, the transmitter 510 may channel-code the retransmitted multicast packet at a lower coding rate than the previously transmitted multicast packet.

6 is a diagram illustrating the structure of a multicast packet receiving node according to the present invention. The multicast packet receiving node 600 receives a multicast packet through a wireless channel and checks whether there is a transmission error of the received multicast packet, and the received multicast packet based on the check result. And a transmitting unit 620 for transmitting a retransmission request corresponding to the received multicast packet to a transmitting node of. The transmitter 620 simultaneously transmits the retransmission request to the transmitting node in synchronization with at least one of the plurality of nodes that have received the multicast packet.

According to an embodiment, the received multicast packet includes forward error correction information, and the receiving unit 610 of the multicast packet receiving node 600 checks whether there is a transmission error of the received multicast packet, When a transmission error is detected as a result of the check, the transmission error may be corrected using the forward error correction information. When the reception unit 610 fails to correct the transmission error using the error correction information, the transmitter 620 may transmit a retransmission request corresponding to the received multicast packet.

The method for transmitting and receiving a multicast packet according to the present invention may be implemented in the form of program instructions that can be executed by various computer means and recorded in a computer readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the medium may be those specially designed and constructed for the present invention or may be available to those skilled in the art of computer software. Examples of the computer-readable recording medium include magnetic media such as a hard disk, a floppy disk and a magnetic tape, optical recording media such as CD-ROM and DVD, magnetic recording media such as a floppy disk Optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like.

The medium may be a transmission medium such as an optical or metal line, a wave guide, or the like, including a carrier wave for transmitting a signal designating a program command, a data structure, or the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

The scope of the present invention also provides a wireless channel in the form of a NAK packet for receiving a multicast packet from the above-described transmitting node and the transmitting node and retransmitting a request for the multicast packet when a transmission error is detected in the multicast packet. By including a plurality of receiving nodes to be synchronized to the transmission node at the same time through the synchronization to encompass a wireless communication network system for realizing ARQ in a wireless multicast environment.

Each receiving node constituting the system transmits a NAK packet when a transmission error is detected in the received multicast packet, and the transmitting node receives a NAK packet from at least one of the plurality of receiving nodes. Resend the multicast packet to the plurality of receiving nodes. For reference, a transmitting node receives NAK packets received from at least one receiving node as a multipath signal, recognizes them as one NAK packet, and multicasts packets to all nodes regardless of the location of the receiving node transmitting the NAK. Resend

Since the details of the embodiments described above with reference to FIGS. 1 to 4 may be applied to the wireless communication system as described above, detailed descriptions of the details are omitted.

In the present invention as described above has been described by the specific embodiments, such as specific components and limited embodiments and drawings, but this is provided to help a more general understanding of the present invention, the present invention is not limited to the above embodiments. For those skilled in the art, various modifications and variations are possible from such description.

Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

The multicast packet transmission / reception method and a wireless communication network system to which the method is applied provide a MAC structure capable of efficiently transmitting and receiving multicast packets at high speed in a wireless communication network. By transmitting a retransmission request signal even in a cast environment, it is possible to reliably transmit data included in the multicast packet while increasing the transmission speed of the multicast packet.

In addition, the present invention is a synchronization between the retransmission request by receiving a plurality of retransmission request signals simultaneously in synchronization with a plurality of receivers, and receiving a plurality of retransmission request signals simultaneously received over a wireless channel using a multipath fading technique. This can eliminate the overhead for handling

In addition, it is possible to efficiently use wireless communication resources without waste as a whole, and to transmit large-capacity multimedia data to a large number of users at high speed through a wireless multicast environment.

In addition, according to the present invention, the transmitting end transmits the FEC information together with the multicast packet, and the receiving end corrects the transmission error of the multicast packet with reference to the FEC information prior to the retransmission request. The waste of channel resources can be minimized.

In addition, according to the present invention, when retransmitting a multicast packet in response to a retransmission request, the channel coding rate of the multicast packet may be lowered stepwise to optimize the channel coding rate for each channel characteristic.

Claims (31)

In the method for transmitting and receiving multicast packets in a wireless communication network, Transmitting a multicast packet from a transmitter to a plurality of receivers through a wireless channel; A second step of receiving the multicast packet at each receiving end and checking a transmission error for the multicast packet; And A third step of simultaneously and simultaneously transmitting a retransmission request from the at least one of the plurality of receivers to the transmitter according to the inspection result, wherein the retransmission request has the same destination address and the same source address; Packet transmission and reception method comprising a. The method of claim 1, A fourth step of receiving the retransmission request from the at least one receiving end and retransmitting the multicast packet from the transmitting end to the plurality of receiving ends according to the received retransmission request Packet transmission and reception method characterized in that it further comprises. The method of claim 2, wherein the fourth step Reducing the channel coding rate of the multicast packet by a predetermined level; Channel coding the multicast packet again according to the reduced coding rate; And Retransmitting the channel coded multicast packet to the plurality of receivers Packet transmission and reception method comprising a. The method of claim 1, The multicast packet includes forward error correction information, The third step is Correcting the transmission error by referring to the forward error correction information when a transmission error is detected in the multicast packet; Packet transmission and reception method characterized in that it further comprises. 5. The method of claim 4, And the third step transmits the retransmission request when the transmission error cannot be corrected. The method of claim 1, And the retransmission request is transmitted in the form of a negative acknowledgment packet. The method of claim 1, The multicast packet is a packet transmission and reception method, characterized in that it comprises real-time multimedia streaming data. In the method for transmitting a multicast packet in a wireless communication network, Transmitting, by a transmitting end, the multicast packet to a plurality of receiving ends on the communication network through a wireless channel; Receiving, by the transmitting end, as a multipath signal a retransmission request corresponding to the multicast packet from at least one of the plurality of receiving ends via the wireless channel, the retransmission request having the same destination address and the same source address; And The transmitting end retransmitting the multicast packet to the plurality of receiving ends in response to the received retransmission request; Multicast packet transmission method comprising a. 9. The method of claim 8, Waiting for a predetermined time by the transmitting end until receiving the retransmission request from the at least one receiving end; The multicast packet transmission method further comprises. 10. The method of claim 9, Transmitting, by the transmitting end, the next multicast packet when the retransmission request is not received until the predetermined time elapses. The multicast packet transmission method further comprises. 9. The method of claim 8, And receiving the retransmission request from the at least one receiving end by the transmitting end via the diversity mode. 9. The method of claim 8, And retransmitting the multicast packet is channel coded at a lower coding rate than the previously transmitted multicast packet. In the method for receiving a multicast packet in a wireless communication network, Each receiving end receiving the multicast packet through a wireless channel, and checking whether there is a transmission error of the received multicast packet; And Transmitting a retransmission request from at least one of the respective receiving end to the transmitting end of the multicast packet based on the check result, wherein the retransmission request has the same destination address and the same source address; Including, The retransmission request is simultaneously transmitted in synchronization over the wireless channel from at least one of the respective receiving end receiving the multicast packet to the transmitting end Multicast packet receiving method characterized in that. 14. The method of claim 13, The multicast packet includes forward error correction information, The step of transmitting the retransmission request Correcting the transmission error by each receiving end by using the forward error correction information when the transmission error is detected in the multicast packet as a result of the checking; And Transmitting the retransmission request by each receiving end when the transmission error correction fails. Multicast packet receiving method comprising a. A computer-readable recording medium having recorded thereon a program for executing the method according to any one of claims 1 to 14. In the wireless communication network system for transmitting and receiving multicast packets, A transmitting node for transmitting the multicast packet over a wireless channel; And A plurality of receiving nodes receiving the multicast packet from the transmitting node Including, Each of the plurality of receiving nodes synchronously and simultaneously transmits a retransmission request for the multicast packet to the transmitting node through the wireless channel when a transmission error is detected in the received multicast packet. Has the same destination address and same starting address- Wireless network system, characterized in that. 17. The method of claim 16, Each of the plurality of receiving nodes transmits the retransmission request when a transmission error is detected in the received multicast packet, The transmitting node retransmitting the multicast packet to the plurality of receiving nodes when receiving the retransmission request from at least one of the plurality of receiving nodes. Wireless network system, characterized in that. 18. The method of claim 17, And the multicast packet being retransmitted is channel coded at a lower coding rate than the previously transmitted multicast packet. 17. The method of claim 16, The multicast packet includes forward error correction information, The receiving node corrects the transmission error by referring to the forward error correction information when a transmission error is detected in the multicast packet, and transmits the retransmission request when the transmission error correction fails. Wireless network system, characterized in that. 17. The method of claim 16, The retransmission request is sent in the form of a negative acknowledgment packet, A destination address of the negative acknowledgment packet is a network address of the transmitting node, and a source address of the negative acknowledgment packet is a multicast group address of the multicast packet. Wireless network system, characterized in that. 17. The method of claim 16, The plurality of retransmission requests transmitted from the plurality of receiving nodes are composed of packets of the same type as each other, The transmitting node receives a plurality of the retransmission requests as a multipath signal Wireless network system, characterized in that. 17. The method of claim 16, And the transmitting node and the plurality of receiving nodes transmit and receive the multicast packet and the retransmission request in an orthogonal frequency division multiplexing scheme. 17. The method of claim 16, And said transmitting node and said plurality of receiving nodes are connected in an ultra-wideband wireless communication system. 17. The method of claim 16, The transmitting node is installed in a mobile communication base station or wireless LAN access point device. A multicast packet transmission node for transmitting a multicast packet in a wireless communication network, A transmitter for transmitting the multicast packet to a plurality of nodes on the communication network through a wireless channel; And A receiving unit for receiving a retransmission request corresponding to the multicast packet from at least one of the plurality of nodes through the radio channel as a multipath signal, wherein the retransmission request has the same destination address and the same source address; Including, And a transmitter for retransmitting the multicast packet to the plurality of nodes in response to the received retransmission request. 26. The method of claim 25, And the transmitting unit waits for a predetermined time until the receiving unit receives the retransmission request from the at least one node. 26. The method of claim 25, And if the retransmission request is not received until the predetermined time elapses, the transmitter transmits a next multicast packet. 26. The method of claim 25, And a receiving unit receives the retransmission request from the at least one node through a diversity mode. 26. The method of claim 25, And a transmitter performs channel coding on the retransmitted multicast packet at a lower coding rate than the previously transmitted multicast packet. In the multicast receiving node for receiving a multicast packet in a wireless communication network, A receiving unit which receives the multicast packet through a wireless channel and checks whether there is a transmission error of the received multicast packet; And A transmitter for transmitting a retransmission request to the transmitting node of the multicast packet based on the check result, wherein the retransmission request has the same destination address and the same source address; Including, And the transmitting unit transmits the retransmission request simultaneously from the at least one of the plurality of nodes that have received the multicast packet to the transmitting node in synchronization over the wireless channel. 31. The method of claim 30, The multicast packet includes forward error correction information, The receiving unit corrects the transmission error using the forward error correction information when the transmission error is detected in the multicast packet as a result of the check; And the transmitting unit transmits the retransmission request when the transmission error correction fails.

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