Patent Publication Number: US-2007107025-A1

Title: System and method for placement of servers in an internet protocol television network

Description:
TECHNICAL FIELD  
      The inventive subject matter hereof relates to the field of Internet protocol television networks and more specifically to efficiently configuring an IPTV network.  
     COPYRIGHT  
      A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever. The following notice applies to the software and data as described below and in the drawings that form a part of this document: Copyright 2005, SBC Knowledge Ventures L.P. All Rights Reserved.  
     BACKGROUND  
      In one proposed Internet protocol television (IPTV) network architecture, each subscriber receives live television programs in a multi-cast data stream from a video-acquisition server. Using multicast delivery, only one copy of the video programming may be sent to branch locations where the video programming may be duplicated and sent to multiple locations at the edge of the network. In addition, “instant” channel change capability is provided by video-distribution servers that distribute program content in a unicast data stream. Unicast data streams carry one copy of programming to a specific subscriber. These servers may also be used to recover video packet losses from the multicast stream to maintain acceptable quality of service. In this architecture, the video distribution servers are usually placed together with the video-acquisition servers at a video hub office. Whenever a subscriber switches to a new channel (or detects a video packet loss), the subscriber equipment contacts the video distribution servers to receive instant channel streams (or recovery packets) in a burst mode. The burst video streams from video distribution servers increase the backbone network traffic load. In addition, the video distribution servers&#39; service latencies may also impact the subscribers&#39; video quality.  
     SUMMARY OF THE INVENTION  
      The inventive subject matter hereof provides system, method, and data structure for efficiently configuring an IPTV network. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIGS. 1, 2  and  3  illustrate an IPTV network in accordance with one example embodiment of the inventive subject matter hereof; and  
       FIG. 4  illustrates a flow chart of a method for locating servers according to one example embodiment of the inventive subject matter hereof. 
    
    
     DETAILED DESCRIPTION  
      In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the inventive subject matter can be practiced. It is understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. The leading digit(s) of reference numbers appearing in the Figures generally corresponds to the Figure number in which that component is first introduced, such that the same reference number is used throughout to refer to an identical component which appears in multiple Figures. Signals and connections may be referred to by the same reference number or label, and the actual meaning will be clear from its use in the context of the description.  
      According to one example embodiment, described in more detail below, the placement of video distribution servers and acquisition servers in a live television IPTV network is considered to be a separate process. This process may be based, for example, on historical data, number of subscribers, subscribers&#39; service quality, some video distribution servers may be selectively placed closer to the subscribers, i.e., at some central offices or intermediate offices, instead of at the video hub office. These local video distribution servers (those video distribution servers not located at video hub office) may selectively receive popular TV channel streams just like regular video subscribers based on the multicasting protocol from the acquisition server. Whenever a subscriber wants to switch to a channel (or recover packet loss for an on-going channel), if the channel is on the popular channel list, the service may be accomplished by the local video distribution servers. Otherwise, the service will be provided by the remote video distribution servers (those placed together with acquisition servers). This approach may facilitate faster channel change and quick packet loss recovery, decreased traffic load on the service networks, and improvement in the subscribers video packets delivery performance.  
      Referring now to  FIGS. 1, 2  and  3  illustrate a first example embodiments of the inventive subject matter hereof will be described in more detail.  FIGS. 1, 2  and  3  are schematic diagrams depicting a configuration of an IPTV network  100  in accordance with one embodiment of the inventive subject matter hereof. As shown in  FIG. 1 , the network  100  includes a super hub office (SHO)  120  for acquisition and encoding of video content, one or more video hub offices (VHO)  120  in each demographic market area (DMA), one or more intermediate offices (IO)  130 , one or more central offices (CO)  140  located in each metropolitan area, and finally the subscribers (S)  150 , which may be located in single or multiple dwelling units. In one example embodiment, the network  100  may be connected through a plurality of high speed communication links  160  using physical transport layers such as fiber, cable, twisted pair, air or other media.  
      In one example embodiment, of the IPTV video delivery system, the SHO  110  distributes content to the VHOs  120  which may be spread across the a wide geographic territory, such as an entire country. In one example IPTV network configuration, the SHO  110  may be in a central location for acquisition and aggregation of national-level broadcast TV (or linear) programming. A redundant SHO  110  may be provided for backup in case of failure. The SHO  110  may also the central point of on-demand content acquisition and insertion into the IPTV network. Linear programming may be received at the SHO  110  via satellite and processed for delivery to the VHOs  120 . On demand content may be received from various sources and processed/encoded to codec and bit-rate requirements for the communication network for transmission to the VHOs  120  over the high speed communication links. VHOs  120  are the video distribution points within each demographic market area (DMA) or geographic region.  
      Referring now to  FIG. 2 , there is illustrated in more detail an example network architecture  200  between the CO  140  and the subscriber  150 . A serving area interface (SAI)  210  is connected to the CO  140 . SAI  210  may, for example, be located in a weather-proof enclosure proximate the subscriber premises, and may include FTTN equipment. FTTN equipment may also be located in the CO  140 . Customer premise equipment (CPE)  220  includes, for example, a network interface device (NID) and a residential gateway (RG)  230 , for example with a built-in VDSL modem or optical network termination (ONT). In both cases the RG  230  may be connected to the rest of the home set top boxes (STBs)  240  via an internal network such as an Ethernet. Each STB  240  has an associated remote control (RC)  250  which provides data entry to the STB  240  to control the IPTV selections from the IPTV data streams.  
      Referring now to  FIG. 3 , there is shown an example embodiment of placement of video distribution servers  330   a,    330   b  and  330   c  in an IPTV system according to the inventive subject matter hereof. As illustrated, a SHO acquisition server  310  may be used to acquire national content that may be distributed towards the VHOs  120 . In an alternative embodiment, live television content may be acquired using an acquisition server in the VHOs  120 .  
      In one example embodiment, the VHO  120  includes a live television acquisition server  320 , which forwards the live television and/or other content toward the subscriber through the intermediate offices (IOs)  130  and the central office (CO)  140  in a multicast data stream  370 . The routers, switches and other network elements that would normally be present in the IOs  130  and COs  140  are not shown in  FIG. 3  in order to simplify the drawing. The number of programs or channels sent in the multicast stream may, without limitation, range up to 800 channels or more using present technology with it being understood that advances in technology may allow many more channels to be sent. The multicast protocol allows for efficient distribution of these signals to a large number of end subscribers.  
      A video acquisition server  330   a  is also positioned at the VHO  120 , and distributes live television to subscribers  150  using unicast data streams  380 . In addition, for example, two additional video distribution servers  330   b  and  330   c  are positioned, respectively, in an IO  130  and a CO  140 . In this embodiment, the video distribution servers  330   a,    330   b  and  330   c  may all receive the multicast data stream  370  and distributes selected ones of the live television signals, extracted from the stream  370 , using unicast data streams  380   a,    380   b  and  380   c,  to specific subscribers  150 . In this embodiment, however, each video distribution server  330   a,    330   b  and  330   c  may be configured to serve unicast data streams to a subset of the total number of subscribers served by the VHO  120 . For instance, video distribution server  330   a  may serve subscribers  150   a  and  150   b,  video distribution server  330   b  may server subscribers  150   c  and  150   d,  video distribution server  330   c  may server subscribers  150   e  and  150   f.    
      In another example embodiment, a VHO  120  may also include application systems  340 , regional subscriber database systems  350 , and video-on-demand (VOD) servers  360 . The COs  140  are connected to the IOs  130  to further distribute traffic towards the subscribers  150 . Traffic may reach the subscribers  150  at least partially via either fiber to the node (FTTN) or fiber to the premises (FTTP), or by other types of transmission medium.  
      Thus, in one example embodiment, each subscriber  150  receives live television programs from the video-acquisition server  320  based on IP-based multicasting services, while the video-distribution servers  330  are used to provide subscribers “instant” channel change and recover video packet losses to maintain acceptable quality of service. Further, in such an architecture, the video distribution server&#39;s service quality greatly affects the performance of the system&#39;s ability to deliver live television programs to individual subscribers.  
      In addition, in one configuration, the video distribution servers  330  are usually placed together with the video-acquisition servers  320  at the VHO  120 . Whenever a subscriber switches to a new channel (or detects a video packet loss), it needs to contact the video distribution servers  330  to receive instant channel streams (or recovery packets). As opposed to the acquisition servers  320 , which send all the video packets based on multicast, video distribution servers  330  provide services based on unicast. The burst video streams from video distribution servers  330  will necessarily increase the backbone network traffic load. In addition, the video distribution servers&#39;  330  service latencies will also impact the subscribers&#39; video quality.  
      As described further below, there is provided in one example embodiment a multi-tier architecture to place and connect all the video distribution servers  330 . By considering the subscribers&#39; video service quality, channel popularity, and video distribution server service capacity, the servers  330  can be placed so as to attempt to enable fast channel change and quick packet loss recovery, decrease the traffic load on the service networks, and improve the subscribers&#39; video packets delivery performance.  
      Thus, according to one example embodiment, the placement of video distribution servers  330  and the acquisition servers  320  is considered to be a separate process. Based, for example, on historical data, number of subscribers, subscribers&#39; service quality, some video distribution servers  330  are selectively placed closer to the subscribers, i.e., at some COs  140  or IOs  130  instead of the VHO  120 . These local video distribution servers  330  (those video distribution servers not located at VHO) may selectively receive popular TV channel streams just like regular video subscribers based on the multicasting protocol from the acquisition server  320 . Whenever a subscriber wants to switch to a channel (or recover packet loss for an on-going channel), if the channel is on the popular channel list, the service may be accomplished by the local video distribution servers  330 . Otherwise, the service will be provided by the remote video distribution servers  330  (those placed together with acquisition servers  320 ).  
      Referring now to  FIG. 4 , there is illustrated a process or method  400  for determining the placement of video distribution servers  330 . In one example embodiment, the method for placement and adjustment of the local video distribution servers  330  may consider the number of subscribers at each region, the subscribers&#39; existing service quality, popularity of IPTV channels, video distribution server capacity, and other factors.  
      As represented by flow chart box  410 , the method  400 , in one example embodiment, determines a minimum number of required video distribution servers  330  and places them together with the acquisition servers  320  at a VHO  120 . The number of desirable video distribution servers  330  can be derived based on the existing M/M/m queuing theory. The constraints are: the predicted subscriber size, average number of channel changes per unit time per subscriber size, average number of channel changes per unit time per subscriber, packet loss probability, video distribution servers  330 ′ average concurrent service capacity, and the maximal permissible queuing delay (D Q ) for each request.  
      As represented by flow chart box  420 , the method  400 , in one example embodiment, after some time period from the initial placement represented by box  410  above, based on historical data, the average number of instant channel changes and packet loss recovery requests originated from each CO  140  and/or IO  130  is determined. As represented by flow chart box  420 , the method  400 , in one example embodiment, for each CO  140 , the method may: 
          a. Choose the top N popular channels for this CO  140  (N is the number channels each video distribution server can serve).     b. Check the past customers&#39; video quality complaints (Or historical video service quality measurement results) from this CO  140  (it is mainly because of path loss rate or delay).     c. If the number of complains from this CO  140  is over some arbitrary threshold, update the value of maximal permissible queuing delay (D Q ) for each packet loss recovery request in proportion to the number of complaints (m). That is, D Q =D Q −α*m.     d. Using M/M/m queuing theory, determine the number of required video distribution servers  330  for the N popular channels in this CO  140 .     e. If the number of required video distribution servers  330  is over one and the total cost till now is below a threshold, place the corresponding number of video distribution servers  330  at this CO  140 .     f. If the number of required video distribution servers  330  is less than one and it already has video distribution servers  330  placed, remove the video distribution server  330 .        

      As represented by flow chart box  430 , the method  400 , in one example embodiment, for each IO  130 , considers the downstream COs  140  video distribution servers  330  service capacity for the IO  130 , repeat the process represented in box  420  as described above, and place or remove the necessary video distribution servers  330  at each IO  130 .  
      As represented by flow chart box  440 , the method  400 , in one example embodiment, repeats the process represented by box  410 , and adjust (if needed) the number and locations of remote video distribution servers  330  from a VHO while considering the VHO&#39;s downstream video distribution servers  330  capacity (those located at IOs  140  and COs  140 s).  
      As represented by flow chart box  450 , the method  400 , in one example embodiment, after some period of time, returns to the process represented by box  420 .  
      In one example embodiment, the empirical data used for the purpose of the above described method may be obtained through the use of monitoring hardware of software disbursed throughout the network  100 . For example, a type of data collection and monitoring technology that may be adapted for the subject method and system is disclosed in U.S. patent application entitled “Algorithm for Optimal Video Server Placement and Video Content Aggregation/Distribution in a Switched IP Network”, filed X date, and assigned to SBC Knowledge Ventures L.P.  
      Thus, according to the various example embodiments described above, the systems and method of the inventive subject matter can gradually and dynamically place the video distribution servers  330  in advantageous locations based on existing video service quality, shorter distance, popularity of video channels, and the number of subscribers. Thus, one or more embodiments of the above described system and method address two potential reasons can cause IPTV service degradation: long channel change latency and video quality degradation. For the first case, shortening video distribution server  330  service time (putting the video distribution servers  330  close to subscribers and reducing the service time) will quickly fill the subscribers with video packets for the new channels and achieve instant channel changes. Also, video packet loss is one of the main reasons for video service degradation. Shortening video distribution server  330  service time not only can quickly recover video packet loss, but also can increase the number of packet recovery requests in short time. Improving these factors should provide for enhancement of subscribers&#39; video service quality. Also, the local video distribution servers  330  can receive the live TV video traffic in the same way as regular video subscribers, so it can eliminate the burst traffic caused by instant channel change and packet loss recovery between VHO  120 , IOs  130  and COs  140 . The traffic from acquisition server to an IO  130  and CO  140  area network may be more stable and predictable. This may also improve the traffic engineering performance, which will potentially improve the video service quality. In addition, a multi-tier distributed video distribution server architecture can avoid the center point video distribution server failure at VHO  120  and improve the reliability of IPTV video service.  
      In accordance with still another example embodiment, the above described system and method may be applied to determine the location of VOD (video-on-demand) servers  360 . For instance, but not by way of limitation, VOD servers  360  may be positioned at the VHOs  120 , the ICOs  130  or the COs  140  in accordance with the same principles and process as described for the video distribution servers  330 .  
      Further, in accordance with various embodiments of the inventive subject matter hereof, the methods described herein are intended for operation as software programs running on a computer processor. Dedicated hardware implementations including, but not limited to, application specific integrated circuits, programmable logic arrays and other hardware devices can likewise be constructed to implement the methods described herein. Furthermore, alternative software implementations including, but not limited to, distributed processing or component/object distributed processing, parallel processing, or virtual machine processing can also be constructed to implement the methods described herein.  
      It should also be noted that the software implementations of the inventive subject matter hereof as described herein are optionally stored on a tangible storage medium, such as: a magnetic medium such as a disk or tape; a magneto-optical or optical medium such as a disk; or a solid state medium such as a memory card or other package that houses one or more read-only (non-volatile) memories, random access memories, or other re-writable (volatile) memories. A digital file attachment to e-mail or other self-contained information archive or set of archives may be considered a distribution medium equivalent to a tangible storage medium. Accordingly, the invention may be considered to include a tangible storage medium or distribution medium, as listed herein and including art-recognized equivalents and successor media, in which the software implementations herein are stored.  
      Although the present specification describes components and functions implemented in the embodiments with reference to particular standards and protocols, the invention may be not limited to such standards and protocols. Each of the standards for Internet and other packet switched network transmission (e.g., TCP/IP, UDP/IP, HTML, HTTP) represent examples of the state of the art. Such standards are periodically superseded by faster or more efficient equivalents having essentially the same functions. Accordingly, replacement standards and protocols having the same functions are considered equivalents.  
      Although the inventive subject matter has been described with reference to several example embodiments, it may be understood that the words that have been used are words of description and illustration, rather than words of limitation. Changes may be made within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the inventive subject matter in all its aspects. Although the inventive subject matter has been described with reference to particular means, materials and embodiments, the inventive subject matter is not intended to be limited to the particulars disclosed; rather, the subject matter extends to all functionally equivalent structures, methods, and uses such as are within the scope of the appended claims.