Packet Retransmission Method in a Wireless Transmitter with Possibility of Suspension

The present invention generally relates to wireless transmission, and in particular to a retransmission mechanism.

This section is intended to introduce the reader to various technical aspects. These technical aspects may relate to various aspects of the invention described below and / or described in the following claims. We believe that this description will help to provide the reader with background information for a better understanding of the various aspects of the invention. Therefore, it should be understood that these statements should be read in view of this point and do not admit prior art.

Residential gateways are configured to connect a residential network to the Internet. Residential gateways allow the reception and distribution of any video content transmitted over the Internet Protocol (IP) over a residential network. Inside a residential gateway, video may be transmitted over a wireless or wired network. If you know that a wired network is suitable for transmitting video services, you need to keep your home appliances connected to the wired network. This is not suitable for mobile equipment. Wireless technologies such as IEEE802.11 are convenient for reaching mobile devices on local networks, but they do not provide the sufficient quality of service required for video applications. In particular, radio interference degrades the quality of radio transmission and, as a result, video quality. The IEEE 802.11 standard for wireless LAN medium access control (MAC) and physical layer (PHY) specifications dated June 12, 2007, described below as 802.11, describes recovery processing and retransmission limits in Section 9.2.5.3. Defines the retransmission mechanism in. The retransmission mechanism is part of the distributed coordination function (DCF) mechanism specified in Section 9.2. In particular, in frame exchange, the transmitter implements an error recovery mechanism by retrying transmission during the frame exchange sequence. The transmitter repeats the retransmission until the retransmission is successful or the retry limit is reached. Normally, the retry limit is set to "7". This mechanism is not sufficient to allow the transfer of acceptable video frames over wireless media.

The present invention seeks to dispel at least some of the concerns associated with packet transmission in the prior art by providing a transmission mechanism suitable for video services.

The present invention relates to a retransmission mechanism that improves quality of service for wireless networks for video services.

To this end, the present invention relates to methods in wireless devices that transmit packets. The method includes setting a lifetime value for the packet to be transmitted and transmitting the packet. According to the present invention, if the transmission fails, the method retransmits the packet until the retry limit is reached, while the packet retransmission fails and the packet lifetime has not expired. Includes a step of waiting for a break before retransmitting a packet until the trial limit is reached.

Surprisingly, moreover, unlike what is normally done in wireless transmission systems, retransmissions are done in several steps, including multiple retransmissions. This retransmission is not based on the redelivery of multiple consecutive packets. Suspend and resume retransmissions to bypass the interference period. This retransmission mechanism has been found to provide good quality of service for video services. Instead of resending the packet several times at short intervals, this mechanism delays the retransmission. This allows at least some interference problems to be avoided continuously.

This retransmission mechanism has proven useful when used for video transmission. The retransmission mechanism significantly reduces the packet error rate. In addition, this retransmission mechanism has the advantage of reducing the use of radio media as compared to standard embodiments.

According to one embodiment of the present invention, the interruption time corresponds to the time required to transmit the packet for the retry limit number of times.

According to another embodiment of the invention, the interruption time corresponds to the time required to transmit the packet for the retry limit number of times at the lowest transmission rate.

According to one embodiment of the invention, the method is performed for audio and video packets only.

Another object of the present invention is to set a lifetime value for a wireless interface for performing communication in a wireless network and a packet to be transmitted, the packet lifetime has not expired, and the packet transmission has failed. In the meantime, it is a wireless device including a retransmission means for transmitting a packet until the retry limit is reached and interrupting the transmission of the interruption time packet before the transmission of the packet until the retry limit is reached.

According to one embodiment, the wireless device comprises interference detecting means for detecting interference in the wireless network.

Another object of the present invention is computer program products, which, when a program of this computer program products is executed on a computer, program code that performs the steps of the method according to the present invention. Computer program products, including instructions. "Computer Program Products" means computer program support, which exists not only in storage spaces containing programs such as computer memory, but also in signals such as electrical and optical signals. May also include things.

The particular aspect is consistent with the scope of the embodiment and is disclosed below. The presentation of these aspects is merely to provide the reader in a schematic manner with certain embodiments that the invention may employ, and these aspects are intended to limit the scope of the invention. It should be understood that it is not the case. In fact, the invention may include various aspects not described below.

The present invention will be better understood and exemplified by the following embodiments and examples with reference to the accompanying drawings. These embodiments and examples are by no means limiting.

<figref num="1">It is a block diagram of an access point according to an embodiment.</figref><figref num="2">It is a figure which shows the retransmission mechanism according to an embodiment.</figref><figref num="3">It is a figure which shows the flow chart of the retransmission mechanism according to an embodiment.</figref>

The blocks shown in FIG. 1 are purely functional and do not necessarily correspond to physically separate ones. That is, these blocks may be in the form of hardware, may be in the form of software, and may be implemented in one or several integrated circuits.

The drawings and description of the present invention have been simplified to illustrate relevant elements for a clear understanding of the present invention, and for clarity purposes, conventional digital multimedia content distribution methods and It should be understood that it removes many other elements that exist in the system. However, these elements are well known in the art and no detailed description of such elements is provided herein. The disclosure of the present invention relates to all such modifications and modifications known to those skilled in the art.

An exemplary embodiment is within the framework of IEEE 802.11, but the invention is not limited to this particular environment, and retransmissions are similar to those specified in the IEEE 802.11 standard. It may also be applied within other frameworks that are retransmitted in.

An access point (AP) device 1 according to this embodiment is shown in FIG. AP1 includes a wireless interface 11 that complies with the IEEE 802.11 standard. AP1 includes an interference detection module 13 configured to detect interference in the radio medium. The interference detection mechanism is outside the scope of the present invention. AP1 includes a retransmission module 14 configured to perform retransmissions as described below. Further, the interference detection module is configured to notify the retransmission module when interference is detected. Further, AP1 includes a memory 12 for storing packets transmitted on the wireless medium.

Even if the embodiments apply to APs, the mechanisms of the embodiments also apply to radio stations.

Next, the retransmission mechanism according to the embodiment will be described. The retransmission module controls two parameters. The first parameter is the packet lifetime. The packet lifetime corresponds to the time the packet is stored in memory. When the packet lifetime has expired, and if no packet has been sent, the packet is removed from memory. When a packet is sent, it is dropped from memory.

The packet lifetime can be selected according to the following constraints. The packet lifetime is longer than the normally expected interference period. Packet lifetime is less than the maximum AP buffer capacity, which depends on video bandwidth and available memory. In addition, the packet lifetime is less than the amount of video buffered at the receiving station. Specifically, some values can be a buffer capacity on the AP of about 5 seconds, a buffer capacity on the video player of about 10 seconds, and a packet lifetime of 2.5 seconds.

The second parameter is the retransmission_suspend value. This value specifies how long the AP suspends transmissions between two series of retransmissions.

This mechanism is summarized below and illustrated in Figure 3. In step S1, the AP has a packet to send to the station. In step S2, the AP sets the packet lifetime value on the packet. Packets are not being received correctly by the station. This is detected by the AP because the AP has not received the acknowledgement packet. In step S3, the AP retransmits the packet according to the mechanism specified in the IEEE 802.11 specification. If necessary, the AP resends the packet until the retry limit is reached. If the retransmission is successful, in step S4, the AP can send the next packet. If the retransmission is still unsuccessful, the interference detection module informs the retransmission module that an interference is occurring. A retransmission mechanism is set up according to the embodiment. If the packet lifetime has expired, in step S5, the AP discards the packet and sends the next packet. While the packet lifetime has not expired, in step S6 the AP suspends the retransmission and in step S3 initiates another set of retransmissions. The retry limit of this embodiment relates to the ShortRetryLimit parameter specified in Section 9.2.4 of the IEEE 802.11 standard. Of course, this mechanism can also be applied to the LongRetryLimit parameter.

The AP device sends a series of retransmission packets that are spaced apart by the interruption period. This is illustrated in Figure 2. In FIG. 2, each vertical line corresponds to a transmission attempt, and the height of the line indicates the transmission rate. This transmission rate can be changed within a series of retransmissions or between two series of retransmissions. As shown in Figure 2, the AP allows the retransmit packet to be sent after 24 failed retransmissions. Multiple retransmissions are grouped into a series of seven retransmissions. If the seventh retransmission fails, the AP suspends the retransmission until another set of retransmissions begins. The medium is free during a series of retransmissions. During this interruption, the same AP may send data to other related stations, and other devices on the same channel may send data. The AP allows other devices to use the medium without contaminating the radio medium with unnecessary retransmissions (occupying the bandwidth of the radio medium).

This corresponds to using the standard retransmission mechanism several times and the retry limit is set to 7. In the standard mechanism, packets are dropped after the retry limit is reached. Here, the AP uses several standard retransmission mechanisms, with interruptions in between, until the packet lifetime is reached.

This mechanism can be configured for each quality of service (QoS) class. The IEEE802.11 standard, in particular the IEEE802.11e standard for media access control for quality of service, defines four classes: background, best effort, voice, and video. According to embodiments, video and voice traffic classes use this mechanism, and background and best effort traffic classes do not use this mechanism. A suitable embodiment that supports transmitting video to multiple stations at the same time has four QoS queues per station, and transmission issues for one station affect the video quality of another station. You must not give it.

The interruption between two series of retransmissions may be the same as the length required for a series of retransmissions. For example, the retransmission_suspend value can be set to 25 milliseconds.

In particular, the interruption time corresponds to the time required to transmit one series of retransmitted packets at the minimum transmission rate of the BSSBasicRateSet specified in Section 7.3.2.2 of the IEEE 802.11 specification. In the worst case, this corresponds to the time required for a series of retransmissions.

In other words, the AP according to the embodiment is a standard AP with a retransmission module and an interference detection module added. A standard AP includes a recovery module that uses the retry limit parameter of the parameters for retransmission to perform the retransmission as specified in the IEEE 802.11 standard. A standard AP will retransmit until the retry limit is reached.

The retransmission module uses the functions of the recovery module to perform retransmission. In particular, first, the retransmission module requires the recovery module to retransmit until the retry limit is reached. If the retransmission is unsuccessful, the retransmission module again requests the recovery module to perform the retransmission. More generally, the retransmission module is configured to drive the recovery module according to parameters such as the retransmission_suspend value, the number of retry limits, and the packet lifetime. The retransmission_suspend value can be configured through the AP's user interface.

The retransmission module may further check that the receiver supports the retransmission mechanism before using the retransmission mechanism according to the embodiment. The retransmission mechanism checks the buffering capacity of the receiver to evaluate the maximum packet lifetime that can be set. If the packet lifetime is too short, the retransmission mechanism is not used and only standard recovery processing is used. This may be done in any proprietary way outside the scope of the present invention.

The references disclosed in the specification, claims, and drawings may be provided independently or in the appropriate combination. The function can be carried out as appropriate by hardware, software, or a combination of hardware and software.

When referred to in the present specification as "one embodiment" or "an embodiment", it means that a specific function, structure, or property according to an embodiment is included in at least one embodiment of the present invention. The statement "in one embodiment" present in various parts of the specification does not necessarily refer to all the same embodiments, but separate or alternative embodiments may be other embodiments. It is not mutually exclusive to.

The reference symbols present in each claim are for illustrative purposes only and do not have a limiting effect on the scope of the claims.<u style="single">Other embodiments of the present invention will be illustrated below.</u><u style="single">[Appendix 1] A method for wireless devices that transmit packets.</u><u style="single"> Step (S2) to set the lifetime value for the packet to be sent,</u><u style="single"> While the packet lifetime has not expired (S5) and the packet transmission is failing</u><u style="single"> Step (S3) to send the packet until the retry limit is reached,</u><u style="single"> A step (S6) of suspending the transmission of the packet for an interruption time before transmitting the packet until the retry limit is reached.</u><u style="single">The method described above.</u><u style="single">[Appendix 2] The method according to Appendix 1, wherein the interruption time corresponds to the time required to transmit a packet for the number of retry limits.</u><u style="single">[Appendix 3] The method according to Appendix 1, wherein the interruption time corresponds to the time required to transmit a packet for the number of retry limits at the minimum transmission rate.</u><u style="single">[Supplementary Note 4] The method according to any one of Supplementary note 1 to 3, comprising a step (S7) of discarding the packet when the packet lifetime has expired or the packet has been successfully transmitted.</u><u style="single">[Appendix 5] The method according to any one of Appendix 1 to 4, wherein the method is performed only for audio packets and video packets.</u><u style="single">[Appendix 6] Wireless device (1)</u><u style="single"> A wireless interface (11) for communication in a wireless network and</u><u style="single"> With a means of retransmission (14),</u><u style="single"> The retransmission means (14)</u><u style="single"> Set a lifetime value for the packet to be sent,</u><u style="single"> While the packet lifetime has not expired and the packet transmission is failing, the packet is sent until the retry limit is reached, and the interruption time before sending the packet until the retry limit is reached. The wireless device that interrupts the transmission of packets.</u><u style="single">[Appendix 7] The wireless device according to Appendix 6, further comprising an interference detecting means for detecting interference in the wireless network.</u>