Using Video over IP Inter and Intra Mission Control Centers and Beyond

Transcription

1 SpaceOps 2008 Conference (Hosted and organized by ESA and EUMETSAT in association with AIAA) AIAA Using Video over IP Inter and Intra Mission Control Centers and Beyond Felix Lang 1 and Taryn Tomlinson 2 Talkdynamics Technologies Inc., 1440 Hocquart Street, Suite 221, St-Bruno-de-Montarville, Quebec, Canada, J3V 6E1 Whereas many international Mission Control Centers use still analogue video transmission technologies, the Columbus Control Center in Oberpfaffenhofen, Germany, has taken the approach to digitalize their video services completely. This paper is a follow up on paper "Digital Video Distribution for ISS/Columbus: Future Operations and Strategies" presented at SpaceOps It will present the newest developments in integrating the video services into an all-over-ip (Internet Protocol) scenario. It will provide the background of and the road to the new design. There will be evaluations on the technical and financial benefits of the new design, as well as its limitations. The all-over-ip approach is based on the most recent services already widely spread in the so-called "IP TV" industry. The limitations of the new video service will mainly depend on the required high Quality of Service (QoS) of the underlying IP network. Amongst the benefits will be low end-to-end latencies, easy maintainability and sustainability, enhanced network security features and easy integration with other services, e.g. data and voice services. Another advantage will be cost efficiency due to using off-the-shelf products and off-the-shelf transmission services. Finally a first step into the world of High Definition TV will be taken. It will also be very easy to integrate these services into the Intranet of the Mission Control Centers. As such, every console position can have their own predefined set of video channels on their workstation to choose from. This service could even be extended to TV broadcast stations and the Internet for Public Relations purposes. The paper will as well provide a look into the near future, where this service can in fact be provided not only end-to-end between Mission Control Centers, but also including the International Space Station (ISS) itself into the loop. The European Space Agency (ESA) has already installed the necessary equipment on board the ISS and performed several successful tests. This new video service will be effectively used to monitor the docking of the Automated Transfer Vehicle (ATV) at the ISS, scheduled for its first launch in spring Systems Engineer, Safety and Mission Assurance 2 Systems Engineer, Systems Engineering 1 Copyright 2008 by the, Inc. All rights reserved.

2 Nomenclature ASI = see DVB-ASI ATM = Asynchronous Transfer Mode ATV = Automated Transfer Vehicle ATV-CC = Automated Transfer Vehicle Control Center Col-CC = Columbus Control Center CADMOS= Centre d'aide au Développement des activités en Micro-pesanteur et des Opérations Spatiales) CADU = Channel Access Data Unit COVRS = Columbus On-Board Video Reconstruction System DaSS = Data Subsystem DVB-ASI = Digital Video Broadcast - Asynchronous Serial Interface EAC = European Astronaut Center ESA = European Space Agency EVA = Extra Vehicular Activity GSOC = German Space Operations Center HDTV = High Definition Television HOSC = Huntsville Operations Center IP = International Partner IP = Internet Protocol IPTV = Internet Protocol Television ISDN = Integrated Services Digital Network ISS = International Space Station JAXA = Japan Aerospace Exploration Agency LAN = Local Area Network LUC = Lazio User Center (Rome) MARS = Microgravity Advanced Research and Support Center MCC-H = Mission Control Center Houston MCC-M = Mission Control Center Moscow MBit/s = Megabit per second MPEG-2 = Moving Pictures Expert Group Video Encoding Standard no. 2 MPLS = Multiprotocol Label Switching MUSC = Microgravity User Support Center MVDS = MPEG-2 Video Distribution System NASA = National Aeronautics and Space Administration NTSC = National Television Systems Committee PAL = Phase Alternation Line PKI = Public Key Infrastructure PMP = Point-to-Multipoint PTP = Point-to-Point PVC = Permanent Virtual Circuit QoS = Quality of Service SAN = Storage Area Network SDI = Serial Digital Interface SVC = Switched Virtual Circuit UHB = User Home Base USOC = User Support Operations Center ZUP = Mission Control Center Moscow 2

3 I. Introduction ANY international Mission Control Centers use still analogue video transmission technologies. The MColumbus Control Center (Col-CC) in Oberpfaffenhofen, Germany, has instead taken the approach to digitalize their video services completely. This paper is a follow up on paper "Digital Video Distribution for ISS/Columbus: Future Operations and Strategies" presented at SpaceOps 2006 i. It presents the newest developments in integrating the video services into an all-over-ip (Internet Protocol) scenario. It provides the background of and the road to the new design. The technical and financial benefits of the new design, as well as its limitations are evaluated in this paper. A glance at the near future of video technology is given at the end. II. Current Design of the MPEG-2 Video Distribution System The MPEG-2 (Moving Pictures Expert Group Video Encoding Standard no. 2) Video Distribution System (MVDS) is based on an overall MPEG-2 architecture. MPEG-2 compression is very well suited in the current environment of Col-CC, since It uses small bandwidth, currently about 3.5 MBit/s per video channel; It facilitates easy storage of video on the Col-CC s IP based Storage Area Network (SAN), which is shared between all services: video / voice / data and others. The MVDS has an interface to the analog video distribution system of the German Space Operations Center (GSOC) as well. As such it supports the multi-mission environment of the GSOC including its satellite missions. The MVDS supports video contribution and distribution between International Partners (IP), IPs and Col-CC as well as Col-CC internal. A number of equipment has been integrated centrally at the Col-CC as well as at the IP s sites. These sites are: MCC-H (Mission Control Center Houston) HOSC (Huntsville Operations Support Center) MCC-M (Mission Control Center Moscow) ATV-CC (Automated Transfer Vehicle Control Centre in Toulouse) EAC (European Astronaut Center in Cologne) 13 User Support Operation Centres (USOC) spread over Europe The Col-CC is connected to its IPs via an Asynchronous Transfer Mode (ATM) network. Several of the USOCs are connected to the Col-CC via ATM as well. However, the majority of these are connected via Integrated Service Digital Network (ISDN). Following figure shows the MVDS locations and the interconnecting network. 3

4 Figure 1. Col-CC and its partners locations This design requires installation of equipment in all these locations. Most equipment of the MVDS is located at the Col-CC including a Backup Col-CC. The major IP sites have backup facilities as well. These are MCC-H, MCC- M and ATV-CC. A. Col-CC The MVDS at the Col-CC provides the services of Contribution of video content from IPs Distribution of video content to IPs Storage, Archiving and Retrieval of video content on the Col-CC SAN Providing internal video sources like Control Room cameras Providing interfaces to public broadcasters locally and via satellite Providing video services to the Flight Control Team and other users at the Col-CC Video processing services like Time, Logo and Text Insertion 4

5 These services are realized using the following equipment: Analog and Digital Video Switching Equipment MPEG-2 Encoders and Decoders ATM Equipment for concentrating and deconcentrating video content into ATM cells Transcoding Equipment for adjusting video bandwidth Quarter Split Time, Logo and Text Insertion Equipment Video Element Manager Storage Manager Standards Conversion Equipment All video services are provided at the Col-CC in digital, meaning MPEG-2 format only. The interface to the legacy analog GSOC video system is provided in analog form, hence the need for analog switching equipment as well as MPEG-2 encoders and decoders. The interface to public broadcasters is provided in SDI, (Serial Digital Interface) MPEG-2 over DVB-ASI (Digital Video Broadcast - Asynchronous Serial Interface) or analog PAL (Phase Alternation Line) format, either via satellite connections or locally at the Col-CC to the outside broadcast van. At the Backup Col-CC, the same functionality is provided as for the Prime Col-CC. However, the capacity is limited to providing emergency services only, e.g. providing a reduced number of video channels only. B. International Partners All IPs locations (except the majority of the USOCs) are connected to the Col-CC via an ATM network. At each IP s site a so-called Video Relay was installed providing the following equipment: Standards Conversion Equipment (US sites only) MPEG-2 Encoding and Decoding Equipment ATM Equipment concentrating and deconcentrating the digital video content into ATM cells Analog Video Switching Equipment Quarter Split Equipment H.323 Encoders for low-rate video in case the nominal video fails (so far never had to be used) All the USOCs are connected via ISDN except the following four: The USOCs co-located with major IPs: MUSC (Microgravity User Support Center) and CADMOS (Centre d'aide au Développement des activités en Micro-pesanteur et des Opérations Spatiales) share the ATM network with EAC respective ATV-CC. The MARS (Microgravity Advanced Research and Support) Center in Naples, Italy and the Col-ESC (Columbus Engineering Support Center) in Bremen, Germany have ATM connections to the Col-CC as well. They need to be able to receive Columbus telemetry via the Col-CC Data Subsystem (DaSS) High-Rate service. Therefore these two centers are able to receive video via ATM as well. MUSC and the Col-ESC benefit from having the ATM connection in another fashion: They receive Columbus video via a high-rate data service. See section III B. below. The ISDN connections are switched on only in need for a video service (or other services, like data), because in comparison with ATM it is very expensive: It is not billed as flat rate like the ATM channels, but on time and number of B-Channels. The interface to the IPs is analogue video with associated audio. All sites but the US sites provide analog PAL video signals. The US sites provide and receive their video content in NTSC (National Television Systems Committee) format, hence the need for Standards Conversion. For video contribution to the Col-CC the analog video content with associated audio will be converted from NTSC to PAL (US sites only) and digitally compressed using MPEG-2. These MPEG-2 packets will be encapsulated into ATM cells for transport to the Col-CC. At the Col-CC the MPEG-2 information will be extracted from the ATM cells and e.g. transported to the SAN for storage. Following figure shows an example for the transmission of a single video channel from MCC-H to the Col-CC internal video IP network. 5

6 Figure 2. Video transmission from MCC-H to Col-CC The opposite direction functions accordingly in the reverse order. The distribution on ISDN does not need any equipment at the remote site except IP switching equipment. The video is distributed as MPEG-2 over IP over ISDN directly, and the video is viewed directly on the USOC s workstation. No video contribution from the USOCs to the Col-CC is supported. III. Latest Enhancements A. Use of SVCs The MVDS was originally designed to use ATM Switched Virtual Circuits (SVC) in order to support Point-to- Multipoint (PMP) video distribution. There were however technical and financial problems to use this technology from the beginning. Therefore ATM Permanent Virtual Circuits (PVC) were used. ATM PVCs support Point-to- Point (PTP) connections only with the current equipment of the MVDS. This was not a problem, since the MVDS was only used for certain events, which did not require the fully specified capacity. Since nowadays nearly all available video channels have to be used as specified, using ATM PVCs are no longer the correct medium for video distribution. As both technical and financial problems have been solved in the meantime these SVCs are used intensely for distribution of video channels. The first time SVCs were used was during the first ATV mission, Jules Verne, in April This technology saves a lot of outgoing ATM ports at the Col-CC and therefore a lot of bandwidth, which in return leverages the cost of the slightly more expensive SVC functionality. B. Columbus On-Board Video Reconstruction Recently the European Columbus module made its way to the International Space Station (ISS) and has been successfully commissioned. Located on-board Columbus is an Encoder, which compresses Columbus video using MPEG-2. This MPEG-2 information is converted to CADU (Channel Access Data Unit) format and multiplexed with other telemetry. This multiplexed data sent via a high-rate data stream to Col-CC s DaSS. The video relevant information is stripped off by the DaSS and transferred to the MVDS. Since the video information is still contained in CADU packets, a Columbus On-Board Video Reconstruction System (COVRS) has been developed by 6

7 Talkdynamics Inc. to strip out the standard MPEG-2 video information to Col-CC s MVDS. There this video content can be used like any other video channel for archive, display or transport to external sites. The USOCs MUSC and Col-ESC video interfaces have been enhanced with a U-COVRS (USOC-COVRS) in order to be able to view the on-board video of Columbus as well. The U-COVRS basically has the same functionality as the COVRS with some minor modifications. C. ATV Docking Video Transport A digital video service is not only suitable to be used between control centres. It can actually be utilized end-toend between the ISS itself and control centres. The European Space Agency (ESA) has kicked off and implemented a project ATV Docking Video. The video of the docking of the Automated Transfer Vehicle (ATV) is very critical to a successful ATV docking. The video needs to be available in the shortest possible timeframe to the MCC-M. MCC-M is the prime in ATV s docking, since the ATV docks to the Russian Zvezda Service Module. For this reason the normally available video path was unusable due to its high latency. Many conversions, encoding and decoding processes are too time-intensive. E.g. in the MVDS network alone the video would undergo the following eleven steps: 1) Conversion from NTSC to PAL in MCC-H 2) Compression to MPEG-2 over ASI format in MCC-H 3) Encapsulation into ATM in MCC-H 4) Transport to Col-CC via ATM 5) Extraction from ATM to MPEG-2 over ASI 6) Switching MPEG-2 in ASI format to the MCC-M channel 7) Encapsulation of the MPEG-2 information into ATM again 8) Transport to MCC-M via ATM 9) Extraction from ATM to MPEG-2 over ASI 10) Decoding to analog PAL 11) Transport to the Mission Control Room at the ZUP (Mission Control) Steps 1, 2 and 10 are computing time intense operations each take at least 200 ms. Therefore it was decided to have the least amount of conversions possible. An MPEG-2 Encoder was developed by Televidenie in St. Petersburg under contract by ESA and integrated on-board the ISS in the Russian Service Module. This Encoder was optimized for the shortest possible encoding time (4 MPEG-2 frames = 160 ms). The bandwidth used is 4 MBit/s, which provides good enough quality for the black and white video of the docking. The MPEG-2 information is being transported to the MCC-H via NASA s White Sands complex in unmodified MPEG-2/IP format. The MVDS Relay in MCC-H has been enhanced with an IP-ASI Video Gateway, which strips off the IP from the MPEG-2 information and inserts this into ASI. This MPEG-2 ASI signal is then converted by the ATM Concentration Equipment and sent via Col-CC to MCC-M. At MCC-M, the MPEG-2 information is extracted out of the ATM using the ATM Concentration Equipment as well. Here also another IP-ASI Video Gateway was installed to support extraction of the MPEG-2 from ASI into IP directly. This IP signal is routed using the Local Area Network (LAN) at the ZUP directly into the Mission Control Room. The video is decoded and watched finally directly at the console in the Mission Control Room on a PC using a NASA provided MPEG-2 decoding software. See following figure for the MVDS end-to-end implementation: 7

8 Figure 3. ATV Docking Video Transmission The video signal now undergoes the following conversions: 1) Conversion from MPEG-2/IP to MPEG-2/ASI in MCC-H 2) Encapsulation into ATM in MCC-H 3) Transport to Col-CC via ATM 4) Extraction from ATM to MPEG-2 over ASI 5) Switching MPEG-2 in ASI format to the MCC-M channel 6) Encapsulation of the MPEG-2 information into ATM again 7) Transport to MCC-M via ATM 8) Extraction from ATM to MPEG-2/ASI 9) Conversion from MPEG-2/ASI to MPEG-2/IP 10) Transport to the Mission Control Room at the ZUP (Mission Control) Using the previous nominal video path as depicted in Fig. 2, the video transmission end-to-end (ISS to MCC-M) would have taken around 3 seconds. With this new approach the end-to-end video signal latency was reduced to 1.2 seconds, which was well below specification (1.5 seconds). This is mainly achieved by not touching the MPEG-2 information itself. It stays always the same despite the multiple conversions from IP to ASI to ATM and vice versa. No decoding or (re-) encoding takes place. This concept has been proven very successful during the docking of the first ATV, Jules Verne, in April

9 IV. Current Operations A. Pre-Columbus Operations Although Columbus was integrated with the ISS just recently in early 2008, the MVDS was used before in interim operations. The highlights of these operations are: ENEIDE: The first operational use of MVDS in April Video of the Soyuz 10S mission including ESA astronaut Roberto Vittori was down linked to the Lazio User Centre (LUC) in Rome. Progress Docking Video: Col-CC is the Prime in transporting video of the docking of Progress modules to MCC-M and has proven to be a reliable partner in providing this video service. PromISS4 (Protein Microscope for the International Space Station): This experiment using a Microgravity Science Glove box was filmed on-board the ISS and down linked via the Col-CC to the Belgian USOC in Brussels and a User Home Base (UHB) at the Brussels University in Astrolab: ESA astronaut Thomas Reiter supported ISS operations in a Long Duration Mission from July to December 2006 for half a year on-board the ISS. The MVDS was intensely used for on-board experiments, news conferences and interviews, Reiter s Extra-Vehicular Activity (EVA) and other important events. B. Post-Columbus Activation Operations Since Columbus has now been integrated successfully with the ISS, the MVDS is being used 24/7 for Final checkout of the Columbus module On-board experiments News conferences and other Public Relations events Support troubleshooting for Columbus payloads ATV Docking Video support V. Upgrade to All-IP environment The all-over-ip approach is based on the most recent services already widely spread in the so-called "IP TV" industry. The limitations of the new video service will mainly depend on the required high Quality of Service (QoS) of the underlying IP network. Therefore a MPLS (Multiprotocol Label Switching) network was chosen. MPLS allows in general for video: 100 % video packet delivery Guaranteed in-sequence Less than 10 ms jitter Fast failover for network recovery (under 1 second) Further benefits will be low end-to-end latencies, easy maintainability and sustainability, enhanced network security features and easy integration with other services, e.g. data and voice services. Another advantage will be cost efficiency due to using off-the-shelf products and off-the-shelf transmission services. Finally a first step into the world of High Definition Television (HDTV) will be taken. It will be even easier to integrate these services into the Intranet of the Mission Control Centers, since no conversion whatsoever is required. As such, every console position can have their own predefined set of video channels on their workstation to choose from. This service could even be extended to TV broadcast stations and the Internet for Public Relations purposes. 9

10 A. Background The project to switch the video service to an all-ip was kicked off not only for the MVDS. All other subsystems (Voice, etc.) of the Col-CC will be migrated into this network as well. This migration provides the benefits as described in the following. Easier maintainability of the underlying network All services use the same network now. Everything will be over IP now. More bandwidth available The underlying network is a flat rate network providing 100 MBit/s for each connection. All subsystems share these pipes. The bandwidth can be tailored between the services very flexibly. E.g. if high bandwidth is required for high-rate data service, the video can be downsized, if no high quality video is required momentarily. Flexible and quick allocation of the bandwidth to the services In the case of the ATM network the network provider has to be notified in due time in order to make the changes in the network configuration, e.g. enhancing video bandwidth, switching and cancelling channels etc. Now this lies all in the hands of the Col-CC engineers enabling quicker decisions and quicker turnaround. Lower latency The new approach saves time required for conversions from / to ATM cells. Improvement of the video interface to USOCs Since the new technology allows the channel to be always on, no switching of ISDN channels is needed anymore. Also, there will be return channels from the USOCs to Col-CC without further cost. Less cost for the transport services The new network provides a flat-rate kind of network. The ATM network has to be paid for on a per-use basis, i.e. each channel is billed separately. The new network provides one-time cost only, no matter what and how much content is transported. This makes in addition cost estimation and controlling much easier. Less equipment cost A number of equipment can be saved. There is no need for MPEG-2 / ATM units anymore. As well less units implies less maintenance cost. Better quality Since it now does not really matter, how much bandwidth is used, the bandwidth can be easily cranked up to between six and eight MBit/s, which provides the optimum video quality visible to the human eye with regard to MPEG-2. Enhanced security features 1 It will be much easier to control which video channel goes where using standard firewalls. Since all video channels will be based on IP now, all of these can be controlled just like legacy IP traffic. This includes Col-CC inhouse traffic as well as the distribution to external partners. Enhanced security features 2 Although not implemented in this first step, the video could be encrypted easily using standard security measures like PKI (Public Key Infrastructure). See the chapter below for future enhancements. 10

11 MPEG-4 vs. MPEG-2 It was intensely discussed, which technology was to be used. MPEG-4 is being used by the IPTV community to bring video content to their customers home. It was decided not to step up to MPEG-4 yet, because MPEG-4 has a higher latency than MPEG-2 due to the higher processing power required MPEG-2 needs more bandwidth in comparison to MPEG-4 in order to provide the same quality. However, bandwidth is not problematic, since 100 MBit/s are available, and only six to eight MBit/s are required. MPEG-4 equipment is currently much more expensive than MPEG-2 equipment MPEG-4 supports HDTV, which is however currently not a requirement for the MVDS. B. Road to Implementing the New Service As the Col-CC is now fully operational, there must be no interruption of the nominal services including the MVDS. Therefore the MVDS has to be upgraded in a very sensitive way. The following measures will be taken in order to minimize service outages. 1) The MVDS has to be upgraded step-by-step, meaning one site after another and not all at the same time. As not all sites need to be active at the same time, this eases finding time slots for the necessary upgrades. 2) The old ATM network has to co-exist with the new MPLS network during the time required for the transition. 3) The redundancy of the sites Col-CC, MCC-H, MCC-M and ATV-CC needs to be utilized, i.e. an upgrade would take place like the following: Activate the Prime string as required Upgrade the Backup String Test the Backup String Switch over to the Backup String Upgrade the Prime String Test the Prime String Finally switch back to the Prime String if required. The upgrade is planned to take place in late VI. Future Upgrades A. Video Encryption As shortly mentioned above, the new design of the MVDS allows end-to-end encryption. This would require an upgrade of the MPEG-2 encoding and decoding units of the MVDS with e.g. a PKI system. The video content would be encrypted at the source with a recipient s public key, of which only the recipient would have the private equivalent. This would be quite useful in case of medical video or video conferencing of crewmembers with their families. This encryption however would be only end-to-end in the MVDS. Meaning, it cannot control what happens at the external partners sites. In order to control this in a real end-to-end fashion, e.g. between an ISS crewmember and his / her family, this would mean upgrading the ISS on-board equipment in order to provide the encryption service already at the source and providing the decryption key only to his / her family and vice versa. Another solution would be to do the encryption directly in the underlying MPLS network. It is currently not yet decided where encryption will take place; it may be to cost-intensive to do it in the MVDS itself. 11

12 B. New HDTV Interfaces Currently there are discussions to establish a new video interface with JAXA (the Japan Aerospace Exploration Agency). Also the HOSC would like to change its video interface with Col-CC and upgrade it to HDTV. Basically the equipment of the MVDS already supports migration to HDTV. There will be minimum cost impact, since the upgrade to HDTV can be achieved with a simple software upgrade of the relevant equipment. This would actually be possible already today, without an all-ip network. So this can be pursued independently from the migration to all- IP. C. Transition to MPEG-4 and HDTV The above-mentioned interface with JAXA may mark the first step into the new trend to have all information available in High Definition. The upgrade would be quite smooth. Already most equipment used in the MVDS today would allow migration to MPEG-4 and as such to HDTV with a simple software upgrade. This would allow much higher video quality and resolution. VII. Conclusion The MVDS has proven itself operationally without any major problems. It has supported numerous ISS operations and is currently widely used in day-to-day operations of Columbus. It also has proven itself a flexible service, which can be adjusted to daily changing needs of its users. New services can be integrated easily and seamlessly like the recent enhancement for ATV docking video. The MVDS is open to and benefits from new technologies like an all-ip network. The MVDS can be easily adapted and upgraded to include new features like security enhancements, HDTV and changing external interfaces. Acknowledgments F. Lang thanks Dave McMahon, Patrick Brun and Ilinca Ioanid, all from SESS GbR in Wessling, Germany, for their technical and financial support in preparing this paper and presenting it at the SpaceOps Proceedings References i Lang, F., Tomlinson, T., Digital Video Distribution for ISS/Columbus: Future Operations and Strategies, AIAA , SpaceOps 2006 Conference, Rome, Italy, June 19-23,