JP2012513689A - Multi-segment loss protection - Google Patents

Abstract

[Solution]
A method of providing error correction for media packets. A service node associated with the core network segment uses a first error correction process, and a service node associated with an access network segment uses a second error correction process. A service node associated with the local network segment may use a third error correction process. The present invention utilizes different error correction processes for different network segments as needed. The service node receives information from the monitoring agent that the error correction is insufficient, and in response, the service node may increase the amount of error correction associated with the network segment. Media packets are interleaved with forward error correction (FEC) blocks to increase the amount of packet recovery.
[Selection] Figure 1

Description

  This application claims the benefit of US Provisional Patent Application No. 61 / 083,710 (filed July 25, 2008), which is hereby incorporated by reference in its entirety.

  The present invention relates to providing packetized video signals over a segmented network, and in particular to using an error correction process based on the attributes of each network segment.

  Increasingly, video signals, such as television broadcasts and on-demand programs, are distributed to subscribers over a video distribution network in a packetized format. Generally, a digitized video signal is first packetized by encapsulating a sequential unit of the digitized video signal into a stream of Internet protocol packets, and then from the headend (Headend) to a residence, company, etc. Sent to the premises. Packetized video signals are not packetized, such as the ability to allocate network bandwidth more efficiently than before using new technologies such as Switched Digital Video It has many advantages over video signals. However, service providers have found it difficult to reliably deliver a consistent stream of packetized video signals to end users over a network that may span hundreds of miles. . Each packet traverses multiple network segments. The network segments are connected by different types of equipment that operate in different energy regions, for example optically or electrically. Each packet may encounter failures such as cable breaks, equipment failures, transient noise, and network node congestion along the way. Once the packet reaches the intended premises, it is carried over the local area network. Each local area network varies greatly depending on the premises, and the service provider has little knowledge or is uncontrollable, and can be arbitrarily changed by the end user. The packet is finally distributed to a device such as a set-top box or a computer, and displayed on a television or a liquid crystal display (LCD) computer screen.

  A video distribution network typically has three network segments: That is, a core network segment extending from the super head end to the video supply office in the district, an access network segment extending from the video supply office in each district to the premises, and a local network segment carrying video packets in the premises. Each network segment has different attributes, and there are inherent problems with the delivery of packetized video signals. The core network segment is generally a fiber network and the bandwidth may be sufficiently wide. The access network segment may be an xDSL network and may have a very limited bandwidth. The local network segment in one campus uses wired Ethernet technology and may have high robustness, while the local area segment in an adjacent campus uses wireless technology and has low robustness. And may be susceptible to interference.

  Service providers have found that the initial investment in a home network for packetized video services can be enormous. Similarly, service providers have found that the operating costs of service calls to correct or solve problems in the home network can be very large. Many of the problems associated with the delivery of packetized video signals on the premises are related to the video quality at the end user due to lost packets resulting from cable breaks and transient noise. Packet error correction techniques such as forward error correction (FEC) or automatic repeat request (ARQ) may be used to prevent the occurrence of packet loss from adversely affecting the quality of the video display. When FEC is used, it is generally provided from the service provider headend to the premises setbox, and the amount of FEC used is limited by the most bandwidth constrained segment of the network. As a result, FEC may be sufficient to correct most of the packet loss that may occur, for example, in the access segment of the network, while FEC may be in the core or local segment of the network. It may be insufficient to correct the packet loss that occurs. Furthermore, the amount of FEC required to correct a video signal quality problem that occurs in a local network segment on one premises is insufficient to correct a video signal quality problem that occurs on a local network segment on another premises. There is a possibility.

  ARQ is useful when used in the access network segment or the local network segment, but is generally used in the core network segment due to the amount of storage and processing required to perform ARQ in the core network segment. Not. As a result, service providers that perform ARQ do not perform error correction for the core network segment. Therefore, it is beneficial for the service provider to perform different error correction processes for different network segments based on the loss profile and bandwidth of a particular network segment. It is also beneficial for network providers to dynamically change the error correction process used in a network segment in response to feedback regarding real-time error conditions associated with the network segment.

  The present invention performs different error correction processes (sometimes referred to as loss mitigation processes) in different segments of the network connected by the service nodes. The error correction process includes forward error correction (FEC), automatic repeat request (ARQ), call admission control (CAC), other suitable mechanisms to prevent or correct packet loss, and combinations thereof. The present invention performs an appropriate error correction process based on the bandwidth associated with each network segment and the type of error generally or actually made by each network segment. The service node receives the packet via the first network segment, recovers the lost or corrupted packet using the first error correction process, and passes the packet to the second error correction process via the second network segment. Is used to send a lost or corrupted packet to a service node that recovers.

  According to one embodiment of the invention, a monitoring agent at one or more service nodes monitors the error status of an associated network segment, communicates with an upstream error correction controller (ECC), and communicates to the associated network segment. Dynamically modify the amount or type of error correction used. The error correction process associated with two different network segments may be a different error correction process, such as FEC or ARQ, using the same type of error correction process, such as FEC, but using different amounts of error correction. There may be different types of error correction processes. For example, a service node associated with a core network segment may use a suitable amount of FEC to protect the first number of lost packets that may be lost in the core network segment, and The associated service node may use a suitable amount of FEC to protect the second and small number of lost packets. This is because the access network segment has significantly less bandwidth than the core network segment.

  According to one embodiment of the invention, a service node associated with a core network segment uses a sufficient amount of FEC packets that are suitable to protect a relatively large amount of video packets. This video packet can be lost if a 50 ms to 100 ms protection switch event occurs on the core network, such as rerouting the disconnected fiber cable traffic. A service node associated with the access network segment uses a small amount of FEC packets suitable for protecting a relatively small amount of video packets. This video packet can be lost during a short-term impulse loss on the access network, such as due to transient noise. The FEC packets used in the access network segment are a subset of the FEC packets received via the core network segment. The present invention allows FEC packets to be reused to adjust the FEC for a particular network segment without using the overhead required to reencapsulate the FEC.

  Those skilled in the art will understand the scope of the present invention, and other aspects of the present invention may be understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings. I understand.

  The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several aspects of the present invention and, together with the detailed description, explain the principles of the invention.

1 is a block diagram of a switched digital media network according to one embodiment of the present invention. FIG. It is a block diagram of the campus of one embodiment of the present invention. It is a block diagram of the service node which performs error correction of one embodiment of the present invention. 2 is a flowchart illustrating a process for performing error correction at a headend service node in a switched digital media network of one embodiment of the present invention. It is a flowchart which shows the error correction process in the service node of one Embodiment of this invention. It is a flowchart which shows the error correction process in the service node of other embodiment of this invention. It is a block diagram of the service node which performs the monitoring agent of one Embodiment of this invention. FIG. 6 is a flowchart illustrating changing an error correction process in response to feedback regarding a modified loss profile associated with a network segment. FIG. 3 is a block diagram of a forward error correction (FEC) block of one embodiment of the present invention. FIG. 10 is a block diagram illustrating the loss of consecutive packets from an FEC block transmitted in interleaved order as shown in FIG. It is a block diagram of the FEC block of one embodiment of the present invention. It is a block diagram of the service node of one embodiment of the present invention. It is a block diagram of customer premise equipment (CPE) of one embodiment of the present invention.

  The embodiments described below represent information necessary for those skilled in the art to implement the present invention, and show the best mode for carrying out the present invention. Upon reading the following description with reference to the accompanying drawings, those skilled in the art will understand the concepts of the invention and will also understand the uses of those concepts not specifically mentioned herein. Like. These concepts and applications are included within the scope of the present disclosure and the attached drawings.

  Switched digital media networks allow for the delivery of streaming media in the form of media streams for various channels or on-demand programs that customers can select for viewing. A switched digital media network represents a satellite, cable, Internet protocol broadcast (IPTV) or similar network set up to deliver voice or video for public or personal use. In general, service providers rely on extensive and hierarchical networks. This network extends from a location where media content is aggregated to customer premises via various intermediate networks. An example of a simple switched digital media network is shown in FIG. The location where the media content is aggregated is a media head end (MHE) 10 configured to deliver various media streams for channels corresponding to premises 12 via core network segment 14 and access network segment 16. It is provided in the service node. The access network segment 16 provides wired or wireless access to the campus 12 and the core network segment 14 represents the primary transmission network that connects the various access network segments 16 to the MHE 10.

  The MHE 10, such as a video super headend, generally has access to various satellite television receiving antenna locations, media servers, encoders, and the like. The installation location of the receiving antenna, the media server, the encoder, and the like provide the MHE 10 with various media contents for the corresponding channel. For illustration purposes, the MHE 10 is represented as a singular, but the MHE 10 has multiple facilities to accomplish the necessary functions of the MHE 10, such as content management, content encoding, and providing video for on-demand services. It is good as well. The MHE 10 collects media content from various sources and allocates the media content for distribution to the premises 12 at an appropriate time and an appropriate channel. In particular, since media content is provided for video-on-demand services, it may be delivered to premises 12 according to a predetermined schedule or customer request. In particular, the media content may include advertising content that is contained in appropriate slots within the media content. In video or television-based switched digital media networks, the advertising content provided by MHE 10 is typically a national advertisement intended for delivery to customers over a wide geographical area. A switched digital media network may have multiple MHEs 10 for redundancy, as shown by the two MHEs 10 shown in FIG.

  Media content delivered to one or more premises 12 may pass through a media hub office (MHO) 18 provided in the core network segment 14. Although not a requirement, one MHO 18 may be assigned to one city or metropolitan area. The MHO 18 may have access to local media content including local advertisements. Local media content may be provided in association with media content provided by the MHE 10. In addition to providing local advertisements, local emergency alert messages or content may be introduced into the media content at MHO 18. MHE 10 and MHO 18 may perform transcoding as well as various types of encoding and decoding, and can efficiently change the encoding, compression and format associated with media content being delivered to customer premises 12.

  The next service node in the path to customer premises 12 may include a media serving office (MSO) 20. The media serving office 20 is typically located in a city or metropolitan area supplied to the MSO 20. Further, the MSO 20 may be located throughout the corresponding geographic location, such as associated with one or more neighborhoods. In each of these neighborhoods or corresponding regions, each MSO 20 may be associated with one or more access nodes (AN) 22. The access node (AN) 22 may also be referred to as an access multiplexer. The access node 22 efficiently collects all wired or wireless connections between the various premises 12. MSO 20 and access node 22 are generally associated with a corresponding access network segment 16. As shown, one access node 22 corresponds to any number of premises 12. Examples of the access network segment 16 include a broadband wireless network such as a digital subscriber line (DSL), a passive optical network (PON), an Ethernet network, a cellular network, and a WiMAX network. Examples of the access node 22 include a digital subscriber line access multiplexer (DSLAM), an optical line terminal (OLT), an Ethernet modem, a mobile phone base station, and a wireless access point. In particular, if the distance between the MSO 20 and the campus 12 is sufficiently small, the access node 22 is not necessary or desirable to accommodate the campus 12, and the MSO 20 may directly correspond to one or more campuses 12. Good.

  Once inside the premises 12, the media content is distributed to any number of devices, as shown in FIG. In particular, the customer premises 12 may have a premises gateway (PG) 24 such as a residential gateway, although this is not necessary. The campus gateway 24 provides gateway functions such as a set-top box (STB), personal video recorder (PVR), personal computer (PC) and telephone between the access network segment 16 and any customer premises equipment (CPE) 26. To do. The PG 24 may be connected to the CPE 26 via the local network segment 28. The local network segment 28 includes one or more switching devices 30 such as a router 30A and an Ethernet switch 30B. The PG 24 may be implemented as a stand-alone device or may be integrated into other network elements such as cables and DSL modems. The communication link 34 used in the local network segment 28 is conventional, such as wireless over WiFi, data over coaxial cable, Ethernet over various physical media such as category 5 cable or telephone line, etc. Any or proprietary network technology may be provided. Each communication link 34 has a different bandwidth and robustness from the other communication links 34. In particular, using FIG. 2, the local network segment 28 can take a variety of forms and has various types of communication links 34, CPEs 26, and switch-on devices 30.

  Loss, corruption or delay of media packets in any network segment 14, 16 and 28 leads to significant audio and video anomalies at CPE 26. Each network segment also typically has a separate and different loss profile that characterizes the type of packet loss. Packet loss can occur in each network segment or can occur in general. For example, packet loss in the core network segment 14 due to interference is relatively rare. However, this type of event can cause packet loss on the core network segment 14, such as cable disconnection or network element failure, which can lead to a relatively large amount of lost packets, The supplied campus 12 may be affected. In contrast, the general loss profile of the access network segment 16 has more frequent problems such as transient impulse noise and crosstalk, resulting in fewer lost packets than those due to cable breaks, The influence on the premises 12 is less than the influence of the cable disconnection in the core network segment 14. Of particular concern to the service provider is the local network segment 28 that is different on one premises 12 and the other premises 12. The local network segment 28 includes a myriad of different switching devices 30, CPEs 26 and communication links 34, and this configuration may be arbitrarily changed by the customer without prior notice to the service provider. Because the local network segment 28 is indeterminate and can change significantly, service providers set up a media service for the premises 12 and require significant expense to maintain the quality of the premises 12 media. It will be.

  Some service providers have attempted to reduce the effects of lost packets by mechanisms such as error correction. Error correction generally involves a trade-off between bandwidth and delay. Error correction techniques such as forward error correction (FEC) take advantage of additional bandwidth by including additional information between several media packets. Media packets are used to recreate lost or corrupted media packets without waiting for retransmission of lost media packets. Other error correction techniques such as automatic repeat request (ARQ) rely on retransmission of lost or corrupted media packets. Re-transmission of lost or corrupted media packets reduces bandwidth overhead but increases delay and increases the storage requirement for storage of media packets when retransmission is required.

  FIG. 3 is a block diagram of each path from the MHE 10 to the campus 12 through the switched digital media network of one embodiment of the present invention. The particular service nodes that can be used can be used in one or more network segments, such as the MHO 18 of the core network segment 14 or the access node 22 of the access network segment 16, but for convenience of explanation these are omitted in FIG. . In order to reduce or eliminate video or audio anomalies associated with lost or corrupted media packets, one or more error correction controllers (ECCs) 36A-36D are connected to respective service nodes such as MHE 10, MSO 20, PG 24 and CPE 26. In step 2, an error correction process is performed. According to one embodiment of the invention, the error correction process may be different at each service node. In order to ensure that sufficient media packets are recovered by MSO 20 in case of cable breaks or similar events, for example, MHE 10 may use either a FEC block of a particular size FEC block and a row and column FEC packet in the media packet. The FEC process that is used may also be executed. While such FEC processes require significant bandwidth, the core network segment 14 has a fiber network with excess bandwidth and capacity to allow such FEC processes.

  In contrast to MHE 10, MSO 20 may be connected to access network segment 16. The access network segment 16 has very limited bandwidth, such as an xDSL communication path, and is insufficient to provide similar FEC block sizes and row and column FEC packets. Have bandwidth. The MSO 20 can therefore change the size of the FEC block and generate only the column FEC packets to sufficiently reduce the amount of bandwidth required to perform FEC for the access network segment 16. Different FEC block sizes and smaller FEC packets reduce the amount of recoverable lost media packets, but such a trade-off is for the access network segment 16 that is different from the loss profile of the core network segment 14. Considering the actual loss profile, provide sufficient reliability.

  The PG 24 may be connected to the local network segment 28. The local network segment 28 has a high bandwidth communication link 34 that has significant media data packet loss problems due to radio or other electronic equipment interference at the premises 12. Therefore, PG24 lost on the way from PG24 to CPE26 by changing the size of the FEC block or generating both row and column FEC packets to better suit the loss profile associated with local network segment 28 Change the FEC encoding, such as by allowing the CPE 26 to recover a significant amount of possible media packets.

  FIG. 4 is a flowchart showing error correction processing that may occur in the MHE 10 according to an embodiment of the present invention. The MHE 10 receives a stream of media such as a broadcast television channel from a broadcast source (step 200). The media stream may be in analog or digital format. If analog, the MHE 10 digitizes the media stream, which is then sent to the media via a digital switched media network such as Moving Picture Experts Group 2 (MPEG-2) or MPEG-4. Encode to any format suitable for delivery. If the media stream has already been digitized, the MHE 10 may transcode the media stream to the desired bit rate or format (step 202). The encoded media stream is then segmented into media segments (step 204). The segmentation may comprise any suitable group of digitized media units, as will be appreciated by those skilled in the art, and may differ based on the digital encoding used. For example, if the encoding format is MPEG-2, the media segment has one or more transport stream packets. If the encoding is MPEG-4, the media segment has one or more network overview layers.

  The media segment is then packetized into an appropriate transport packet, such as a real-time transport protocol (RTP) packet (step 206). For purposes of explanation, assume that the FEC error correction process is utilized for the core network segment 14. The desired first FEC error correction process is then applied to the media packet to generate a plurality of error correction packets (step 208). As known to those skilled in the art, FEC error correction generally forms a two-dimensional block or matrix of media packets of the desired size to be protected, and then such media packets are routed over the network. The FEC packet that is used to regenerate one or more media packets is generated if it is lost or corrupted. Assume that the MHE 10 is connected to a core network segment 14 that is a fiber network segment and has excess bandwidth capacity. Further, assume that the core network segment 14 may be subject to network element failures or cable breaks that occur at any time, for example, while creating a new office building several miles away from the MHE 10. In addition, a redundant MHE 10 or network routing path that requires 50 milliseconds (ms) is connected to the core network segment 14 in order to switch over to route the function of the first MHE 10 or to route a failed network element. , Suppose that during a 50 millisecond time frame, as many as 16 media packets per channel may be lost for a 2 megabit per second (Mbps) video data stream. Therefore, the MHE 10 can recover up to 16 media packets by selecting the size of the FEC block and generating enough FEC packets, resulting in media packets lost during switchover, It can be restored by the downstream MHE 10 without interfering with the presentation of the media to the CPE 26. The media packet and FEC packet are then transmitted over the core network segment 14 (step 210). FEC packets are transmitted in line, mixed with media packets, or transmitted over separate channels or ports.

  FIG. 5 is a flowchart showing error correction processing in the MSO 20 according to the embodiment of the present invention. The MSO 20 receives the media packet and the FEC packet transmitted from the MHE 10 (step 300). MSO 20 may apply the first FEC process to the media packets to recover any media packets that may have been lost due to cable disconnection or other failure (step 302). Assume that the MSO 20 is connected to the access network segment 16. The access network segment 16 has an xDSL communication link and is bandwidth limited. Further, the loss profile of the access network segment 16 mainly has transient impulse noise events in which the number of lost packets is generally 4 or less for each loss event. The MSO 20 may apply a second FEC process that uses a second FEC block size that is different from the size of the FEC block used by the MHE 10, and generates fewer FEC packets than those generated by the MHE 10, resulting in: The FEC process is adapted to recover only up to 5 lost packets per FEC block (step 304), but requires less additional bandwidth for error correction packets. The MSO 20 then transmits the media packet and the FEC packet via the access network segment 16 (step 306).

  FIG. 6 is a flowchart showing error correction processing in the MSO 20 according to another embodiment of the present invention. As described with reference to FIG. 5, the MSO 20 receives a plurality of media packets and FEC packets (step 400) and uses the FEC process and FEC packets to recover any lost packets (step 402). ). However, it is assumed in this embodiment that MSO 20 utilizes the ARQ error correction process with access network segment 16. The ARQ process first stores the media packet in local storage before sending the media packet to PG 24 (step 404). The ARQ process then sends the media packet to PG 24 (step 406). When the PG 24 confirms reception of the media packet, the ARQ process deletes the media packet or overwrites the local storage device. Alternatively, the ARQ process retransmits the media packet until confirmation from the PG 24 is received. The ARQ process may also use a circular buffer long enough to cover typical loss profiles and respond to requests for retransmission of specific lost packets from PG 24. In still other embodiments, the ARQ process may be performed between MSO 20 and CPE 26 instead of between MSO 20 and PG 24.

  If no packet loss has occurred, ARQ requires less bandwidth than the FEC error correction process, but ARQ can introduce significant delays associated with retransmissions. Furthermore, ARQ may not be appropriate in the network segment in the following cases. In other words, if the retransmission request after a very large amount of packet loss exceeds the ability of the transmission service node to process the retransmission request, or the processing amount and storage amount for storing the media packet However, when excessive resources are required. For example, the ARQ error correction process may cause a significant amount of media packets transmitted over the core network segment 14 and a large number of retransmission requests that need to be handled in the event of packet loss such as cable breaks. The error correction process may not be appropriate for the network segment 14.

  Referring to FIG. 7, a block diagram of the service node shown in FIG. 3 is shown. One or more service nodes, such as MSO 20, PG 24, and CPE 26, have a monitoring agent (MA) 38 that can monitor each network segment to which the service node is connected, and a loss profile associated with a particular network segment. Determine. The MA 38 provides information or requests to the upstream ECC 36 and dynamically changes the error correction process used to recover the packet loss via the respective network segment. A monitoring agent suitable for use with the present invention is disclosed in US Pat. No. 11 / 961,879 (filed Dec. 20, 2007), which is incorporated by reference in its entirety.

  FIG. 8 is a flowchart illustrating a process for changing an error control process on a network segment according to one embodiment of the present invention. For convenience of explanation, FIG. 8 will be described together with FIG. Assume that PG 24 uses a first FEC process that provides sufficient error correction to CPE 26 to recover lost data packets sent by PG 24. The loss profile of the local network segment 28 is given to the PG 24 at a specific time. Further assume that an event occurs that changes the loss profile of the local network segment 28. For example, the customer reconfigures the switching device 30 in such a way as to increase the number of dropped packets at the local network segment 28 or move a large electronic device such as a microwave oven in the vicinity of the communication link 34 and generate it with the microwave oven. Assume that the transient packet loss is increased by the generated electromagnetic field. As a result, the first FEC process used by PG 24 and CPE 26 may not be sufficient to offset the large number of lost packets given the new loss profile for local network segment 28. The MA 38C determines that the loss profile of the local network segment 28 has changed (step 500). For example, MA38C may determine that, for a large amount of transmission, FEC packets are insufficient to recover all lost packets. The MA 38C provides an error control message to the upstream ECC 36C associated with the PG 24 to inform the ECC 36C that there are insufficient error correction processes (step 502). Error control messages are required for increased FEC packets, data identifying loss profiles, or a new error correction process that provides increased error protection for PG 24 to maintain proper media presentation quality. It can be any other message that can be notified.

  Assuming that the communication link 34 between the PG 24 and the CPE 26 has sufficient bandwidth, in response to receiving the error control message, the ECC 36C provides a different error correction than previously provided by the ECC 36C. An error control process is subsequently initiated for the received media packet (step 504). PG 24 assumes that a plurality of media packets destined for CPE 26 are received from MSO 20 via access network segment 16 (step 506). The ECC 36C performs error correction on the media packet according to the error correction process associated with the network segment 16 (step 178). Prior to receiving an error correction control message from the CPE 26, the ECC 36C provides the media packet with the size of a particular FEC block and provides enough FEC packets for the media packet, up to 5 consecutive lost packets. It may have recovered. The ECC 36C changes the size of the FEC block, generates a large number of FEC packets from the media packet, and allows the CPE 26 to recover up to 10 consecutive lost packets (step 510). The PG 24 sends a plurality of media packets to the CPE 26 using the new FEC block size and the increased FEC packets (step 512). This process may continue until the level of error control processing provided by the ECC 36C is sufficient to provide adequate media presentation quality at the CPE 26. In particular, the error control correction does not include any additional processing by upstream service nodes or any additional bandwidth of the upstream network segment 14 or 16. In particular, video delivery problems are automatically monitored and corrected without manual intervention by service provider personnel, thereby eliminating the costs associated with supporting associated call centers and truck rolls.

  According to one embodiment of the present invention, the service node does not need to regenerate the FEC packet received via the first network segment, on the first FEC error correction process on the first network segment and on the second network segment. The second error correction process can be performed. According to the present invention, the processing node can easily reduce the bandwidth used for error correction processing without spending resources to recalculate new FEC packets. The present invention uses the Professional MPEG Forum Rules of Practice (COP) # 3 FEC process described in SMPTE 2002-1 and SMPTE 2022-1 of the Association of Movie and Television Engineers (SMPTE) standards, which is incorporated herein in its entirety. . Pro MPEG FEC involves generating an FEC matrix with many columns, called the “L” dimension of the matrix, and having many rows, called the “D” dimension of the matrix. The dimensions of the FEC matrix are described herein with reference to the L dimension (number of columns) and then the D dimension (number of rows). For example, an FEC matrix having 5 columns and 10 rows is referred to herein as a 10 (L) × 5 (D) FEC matrix. Error correction is provided in the form of FEC packets. FEC packets are derived based on media packets in a particular row or column of the FEC matrix. FEC packets are generated to correct packet loss associated with a particular row and are herein referred to as row FEC packets. An FEC packet is generated to correct packet loss associated with a particular column, and is herein referred to as a column FEC packet. A relatively large amount of error correction is provided by generating row and column FEC packets. A small amount of error correction is provided by generating only sequence FEC packets. As will be appreciated by those skilled in the art, the size of the FEC matrix and the use of row and column FEC packets are a trade-off between the desired amount of error correction and the bandwidth utilized. If the ratio of the FEC packet to the media packet is high, the possibility of error correction increases, but similarly the bandwidth required to communicate the media packet and the FEC packet is increased. The term “FEC matrix” is used herein for each media packet matrix. The term “FEC block” is used to refer to both each FEC matrix and FEC packet generated based on the FEC matrix.

  As a result of the occurrence of lost packets, such as cable breaks on the core network segment 14 or impulse noise on the access network segment 16, a series of consecutive packets rather than a plurality of random packets are generally within the FEC block of the packet. Will be lost. Assuming that the lost consecutive packets are only the lost packets of the FEC block, when only the column FEC packets are generated for error correction, the same number of packets as the L lost continuous packets are recovered from the FEC block. Assume again that the lost consecutive packets are only those lost in the FEC block, and if row and column FEC packets are generated for error correction, the same number of packets as L + 1 lost continuous packets are recovered from the FEC block.

  The present invention interleaves the transmission of media packets and FEC blocks of FEC packets to increase the number of consecutive packets that can be recovered without having to generate additional FEC packets. The present invention also allows the appropriate subset of FEC packets for the next error correction on the second network segment to be reused without the need to regenerate the FEC packets when the size of the FEC block is changed.

  FIG. 9 is an example block diagram of an FEC block 50 showing a plurality of media packets 52 and FEC packets 54 in a 5 × 10 FEC matrix of one embodiment of the present invention. For the sake of explanation, both the media packet 52 and the FEC packet 54 are combined into packets 52 and 54. Note that only the media packet 52 is considered for the purpose of defining the L and D dimensions of the FEC matrix. This particular FEC block 50 has 50 media packets 52 and 16 FEC packets 54, shown in columns 56A-56F and rows 58A-58K. In particular, if the original rate required to send 50 media packets 52 without any FEC packets 54 is 2 megabits per second (Mb / s), then 50 media packets 52 and an additional 16 The increased bandwidth required to transmit a second FEC packet 54 is 2.64 (Mb / s), which represents an error correction bandwidth overhead of 32%.

  In the conventional FEC block 50, 16 FEC packets 54 are sufficient to correct the continuous packet loss of six media packets 52 (L (5) +1). In FIG. 9, each packet 52 and 54 has two numbers, and the leftmost number is separated from the rightmost number by “/”. For each media packet 52, the leftmost digit indicates the packet sequence number in the order in which the media packet 52 is successively decoded for display at the CPE 26. For each FEC packet 54, the leftmost number indicates a sequential order in which the FEC packets 54 are generally mixed into a media packet 52 arranged in a sequence. At the end of each row of FEC block 50 (column 56F), each FEC packet 54 can be used to correct or recover any media packet 52. This media packet 52 is in the same row as FEC packet 54 or can be recreated using column FEC packet 54 as long as other media packets 52 in the row of FEC packet 54 are not lost. At the end of each column of FEC block 50 (row 58K), each FEC packet 54 can be used to correct any one media packet 52. This media packet 52 is in the same column as the FEC packet 54 or can be recreated using the row FEC packet 54 as long as other media packets 52 in the column of FEC packets 54 are not lost.

  The numbers at the right end of each packet 52 and 54 indicate the interleave packet transmission order of one embodiment of the present invention. By interleaving the packets 52 and 54 before starting transmission over the network segment, the present invention increases the number of consecutive media packets 52. The continuous media packet 52 is restored from L + 1 = 6 continuous packets to L + D + 1 = 16 continuous packets. In particular, in the FEC block 50 shown in FIG. 9, the ability to recover 16 consecutive lost packets represents a 167% increase compared to the conventional FEC block 50. The interleaving order of packets 52 and 54 according to one embodiment of the present invention is described below. The first media packets 52 and 54 in the interleave order are the media packets 52 in row 58A and column 56A. The next media packets 52 and 54 in the interleave order are media packets 52 in row 58B and column 56B. Third media packets 52 and 54 in the interleave order are media packets 52 in row 58C and column 56C. This process continues along the diagonal path 60 until the FEC packets 54 in row 58F and column 56F are added to the interleave order. At this point, column 56F is the last column of FEC block 50, so the next column in the interleave order is column 56A, which is the first column. However, since row 58F is not the last row of FEC block 50, the next row in the interleaving order is row 58G. Thus, the next media packets 52 and 54 in the interleave order are media packets 52 in row 58G and column 56A. This process continues along diagonal path 62 until FEC packets 54 at row 58K and column 56E are added to the interleave order. At this point, row 58K is the last row of FEC block 50, so the next row in the interleaving order is row 58A, which is the first row. However, column 56E is not the last column of FEC block 50, so the next column in the interleave order is column 56F. Accordingly, the next media packets 52 and 54 in the interleaved order are FEC packets 54 in row 58A and column 56F, as shown in diagonal path 64. Note that the column 56F is the last column in the FEC block 50, and the next media packets 52 and 54 in the interleaving order are the media packets 52 in the row 58B and the column 56A. This process continues in the manner shown in diagonal paths 66-90 until all packets 52 and 54 have been added to the interleave order.

  After receiving interleaved packets 52 and 54 by downstream service nodes such as MSO 20, MSO 20 places interleaved packets 52 and 54 in the sequential order indicated by the leftmost digits associated with each packet 52 and 54 in FIG. . Assuming that a cable cut occurred during sending the FEC block 50 to the MSO 20 and during a switchover to the backup MHE 10, a number of consecutive packets 52 and 54 were lost.

  FIG. 10 is a block diagram of FEC block 50 shown in FIG. 9 after reception by MSO 20 and placement in sequential order. Packets 52 and 54 with X represent lost media packets. The 16 media packets 52 and 54 were lost due to cable disconnection. Furthermore, since the lost packets 52 and 54 are transmitted in an interleaved order, they are not in a continuous order in FIG. Since the present invention interleaves the transmission order of packets 52 and 54, each 16 lost packets 52 and 54 can be recovered. For the sake of clarity, recovery of lost packets will be described. Each lost packet is identified by the number of each lost packet in FIG. Lost packets 5, 42, 43, 50, 57 and 64 are first recovered by the respective FEC packet 54 associated with the row, or in the case of lost packet 42, the lost packet 42 is removed from the packet present in row 58G. It may be restored by re-creating it.

  Lost packets 35 and 12 are then recovered as the only packets that are not present in their respective columns 56E and 56F, since packets 5 and 42 have been previously recovered. Lost packet 34 is then recovered as the only packet that does not exist in row 58F because lost packet 35 has been previously recovered. Lost packet 26 is recovered next because it is the only packet that does not exist in column 56D after lost packet 34 is recovered. Lost packets 27, 21, 20, 14, 13, and 7 are recovered in a similar manner.

  FIG. 11 is a block diagram of an FEC block 92 according to another embodiment of the present invention. Assume that the MSO 20 has received the FEC block shown in FIG. 10 and recovered all lost packets. Further assume that the access network segment 16 does not have enough bandwidth to bear the 32% overhead required to include row and column FEC packets 54 with FEC blocks 50. Further assume that the loss profile associated with the access network segment 16 indicates that the average continuous packet loss is 5 consecutive packets or less. According to one embodiment of the invention, MSO 20 removes or drops row FEC packets 54 from FEC block 50 and reuses column FEC packets 54 to create FEC block 92 shown in FIG. Note that the five-column FEC packets 54 are sufficient to recover the general number of lost packets according to the loss profile associated with the access network segment 16. In particular, the column FEC packet 54 does not need to be regenerated from the FEC matrix but is reused, thereby reducing processing time and visual distortion in the CPE 26 caused by processing delay.

  FIG. 12 shows a block diagram of the service node 94. The service node 94 is a general-purpose control entity that can provide the functions of the MSO 20, MHE 10, MHO 18, or PG 24. Specifically, the service node 94 may have a control system 96 having sufficient memory 98 for the software 100 and data 102 necessary to improve operation as described above. In addition to providing device-wide functionality, software 100 may provide MA 38 and EEC 36 depending on its configuration. Further, the control system 96 may be associated with one or more communication interfaces 104 to improve communication as needed for operation. Service node 94 may be a stand-alone entity or part of another element, such as a switch or router.

  Referring to FIG. 13, a block diagram of CPE 26 is shown. The CPE 26 may have a control system 106 that has sufficient memory 108 for the software 100 and data 102 required to operate as described above. The software 110 generally provides the MA 38 and the EEC 36 in addition to the function of the CPE 26 depending on the configuration. The control system 106 may be associated with one or more communication interfaces 114 to improve communication as described above. In addition, the control system 106 may be associated with the user interface 116 to improve customer communication, provide streaming media in audible or visible format to the customer, and receive information from the customer. .

  Those skilled in the art will appreciate improvements and modifications made to the preferred embodiments of the present invention. Such improvements and modifications are considered to be within the scope of the concepts described herein and the following claims.

Claims (23)

A method of delivering multiple media packets of a switched digital video network from a headend to a customer premises equipment via a video serving office and a residential gateway, comprising:
Receiving a first plurality of video packets at the video serving office;
Performing a first error correction of the first plurality of video packets using a first error correction process;
Transmitting a second plurality of video packets comprising the first plurality of video packets to the residential gateway via the switched digital video network;
Performing a second error correction of the second plurality of video packets at the residential gateway using a second error correction process, wherein the first error correction process includes the second error correction process, A media packet delivery method characterized by being different from an error correction process.   2. The media packet distribution method according to claim 1, wherein the second plurality of video packets further includes a plurality of video packets restored by the first error correction process.   The method further comprises receiving a first plurality of forward error correction (FEC) packets associated with the first plurality of video packets, wherein the first error correction process uses the first plurality of FEC packets. The media packet distribution method according to claim 1, wherein the first error correction is performed.   Transmitting a second plurality of FEC packets associated with the second plurality of video packets to the residential gateway, wherein the second error correction process uses the second plurality of FEC packets. The media packet delivery method according to claim 3, wherein the second error correction is performed.   5. The media packet distribution method according to claim 4, wherein the second plurality of FEC packets are a subset of the first plurality of FEC packets. Receiving at the video serving office information that the second plurality of FEC packets is an insufficient amount of FEC packets;
Receiving a third plurality of video packets at the video serving office;
Performing a first error correction of the third plurality of video packets using the first error correction process;
Transmitting a fourth plurality of video packets comprising the third plurality of video packets to the residential gateway via the switched digital video network;
Responsive to the information, transmitting a third plurality of FEC packets associated with the fourth plurality of video packets to the residential gateway via the switched digital video network. 6. The media packet delivery method according to claim 5, wherein the fourth plurality of FEC packets have more FEC packets than the second plurality of FEC packets.   The first error correction process is a forward error correction (FEC) error correction process using a first plurality of row FEC packets and a first plurality of column FEC packets, and the second error correction process is a first error correction process. The media packet distribution method according to claim 1, wherein the media packet distribution method is an FEC error correction process using only a plurality of two column FEC packets.   The media packet distribution method according to claim 7, wherein the second plurality of column FEC packets include the first plurality of column FEC packets.   The first error correction process is a forward error correction (FEC) error correction process, and the second error correction process is an automatic repeat request (ARQ) error correction process. Media packet delivery method.   The method of claim 1, wherein the first error correction process is selected based on a loss profile associated with a network segment to which the video serving office is connected. A first plurality of videos via a network having a core network segment connected to an access network segment having a first service node and said access network segment connected to a local network segment having a second service node A method of transmitting packets,
Generating a first plurality of forward error correction (FEC) packets based on the first plurality of video packets;
Transmitting the first plurality of video packets and the first plurality of FEC packets to the first service node;
Removing a second plurality of FEC packets from the plurality of FEC packets to form a third plurality of FEC packets;
Transmitting the first plurality of video packets and the third plurality of FEC packets to the second service node, wherein the core network segment is a second of the access network segments. A video packet transmission method having a first bandwidth larger than a bandwidth. Receiving information from the second service node that the third plurality of FEC packets have an insufficient amount of FEC packets;
Receiving a second plurality of video packets;
Transmitting the third plurality of video packets to the second service node;
Responsive to the information, transmitting a fourth plurality of FEC packets associated with the third plurality of video packets to the second service node, wherein the fourth plurality of FECs The method of claim 11, wherein the packet has more FEC packets than the insufficient FEC amount of FEC packets. Receiving information that, in the first service node, the third plurality of FEC packets is an insufficient amount of FEC packets;
Transmitting a fourth plurality of FEC packets to the second service node in response to the information, wherein the fourth plurality of FEC packets are the third plurality of FEC packets. 12. The video packet transmission method according to claim 11, wherein the video packet transmission has a larger number of FEC packets than packets. A method for error correction through two network segments having different bandwidths, comprising:
Receiving a first plurality of data packets having a first plurality of video packets and a first plurality of forward error correction (FEC) packets at a first service node;
Transmitting a second plurality of data packets comprising the first plurality of video packets and a second plurality of FEC packets to a second service node, wherein each of the first plurality of data packets comprises: The data packets have an associated sequence number that identifies a sequential order associated with the first plurality of data packets, and the first plurality of data packets are received in an interleaved order at the first service node. , The second plurality of FEC packets comprises an appropriate subset of the first plurality of FEC packets, and the second plurality of data packets comprise the first plurality of video packets and the second plurality of FEC packets. A method of performing error correction, characterized by being transmitted in sequential order based on a sequence number associated with the FEC packet. An input first interface adapted to communicate with a first network segment;
An output interface adapted to communicate with the second network segment;
Connected to the input first interface and the output interface;
Receiving a first plurality of error correction packets and a first plurality of video packets associated with the first plurality of video packets via the first network segment;
Performing a first error correction of the first plurality of video packets using the first plurality of error correction packets;
Generating a second plurality of error correction packets based on the first plurality of video packets;
And a control system adapted to transmit a second plurality of video packets comprising the first plurality of video packets and the second plurality of error correction packets to a second service node. Service node to be executed.   The service node according to claim 15, wherein the second plurality of video packets further includes a plurality of restored video packets restored by the first error correction.   16. The service node of claim 15, wherein the second plurality of error correction packets is a suitable subset of the first plurality of error correction packets.   The first plurality of error correction packets includes a plurality of row error correction packets and a plurality of column error correction packets, and the second plurality of error correction packets are composed of the plurality of column error correction packets. The service node according to claim 17. The control system further comprises:
The second plurality of error correction packets receives information that is an insufficient amount of error correction packets;
Receiving a third plurality of video packets and a third plurality of error correction packets;
Transmitting a fourth plurality of video packets comprising a third plurality of video packets to the second service node;
In response to the information, a service node adapted to transmit a fourth plurality of error correction packets associated with the fourth plurality of video packets to the second service node, the fourth service node comprising: The service node of claim 15, wherein the plurality of error correction packets has more error correction packets than an insufficient amount of error correction packets.   The service node of claim 15, wherein the first error correction is selected based on a loss profile associated with the first network segment. A switched digital video network comprising a first service node connected to a second service node via a first network segment and the second service node connected to a third service node via a second network segment A method for delivering a plurality of media packets,
Receiving at the second service node a first plurality of video packets from the first service node via the first network segment;
Performing a first error correction of the plurality of video packets using a first error correction process in the second service node;
Transmitting a second plurality of video packets having the first plurality of video packets to the third service node via the second network segment;
Performing a second error correction of the second plurality of video packets using a second error correction process in the third service node, wherein the first error correction process includes: 2. A media packet delivery method, which is different from an error correction process.   A media packet delivery method further comprising receiving a first plurality of forward error correction (FEC) packets associated with the first plurality of video packets, the first error correction process comprising: The media packet distribution method according to claim 21, wherein the first error correction is performed using a plurality of FEC packets.   A media packet delivery method, further comprising: transmitting a second plurality of FEC packets associated with the second plurality of video packets to the third service node, wherein the second error correction process includes: 23. The media packet delivery method according to claim 22, wherein the second error correction is performed using a plurality of FEC packets.

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