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Leistungen
The Bandwidth Allocation Manager (BAM) is the core and the decision point of the bandwidth allocation management system inside the MAMBO platform. Based on the various estimation modules and the policies assigned to services (priority, maximum and minimum bandwidth), the BAM aims at computing periodically the more optimal distribution of the bandwidth for the DVB and IP bouquets. It enforces that new distribution by requiring the transcoder and the IP traffic Regulator to modify the bit rate of the concerned services.
The BAM collects its inputs from:
- Bandwidth estimator, which delivers the current available bandwidth, the overall bandwidth and the bandwidth assigned to each service of the DVB bouquet.
- IP traffic regulator, which delivers the current available bandwidth, the overall bandwidth and the bandwidth assigned to each service of the IP bouquet.
- Policy server which stores policies assigned to each service of the DVB and IP bouquet.
- PQMS, which delivers quality of service measurements and provides, for MPEG-2 transport streams, marks related to various bit rates, enabling the BAM to assign a lower or higher bit rate to these streams.
After computing the new bandwidth allocation, the BAM will request:
- Transcoder via the Transcoding Manager either to adapt bit rate of MPEG-2 services or to adapt bit rate of MPEG-2 streams transcoded into MPEG-4 streams.
- IP traffic regulator to manage and control the bandwidth of the IP traffic to be conveyed over the DVB or IP network.
The BAM proposes an innovative approach based on traffic differentiation and priority mechanism to guarantee that enough bandwidth is available for the MPEG streams while maintaining an acceptable quality. Through the transcoder, the less priority streams will be adapted to match the traffic requirement either:
- By modifying on-the-fly bit rate of MPEG-2 services.
- Or by modifying on-the-fly bit rate of MPEG-2 services transcoded into MPEG-4 services.
Data services such as FTP, HTTP are managed by another module, the IP Traffic Regulator. The BAM communicates with this module to free or retrieve bandwidth assigned to services being conveyed towards the IP network.
The kernel of the BAM consists in periodically calculating a new bandwidth allocation for the DVB network and IP network. It enforces the new bandwidth allocation generating commands through the transcoder and the IP traffic regulator. The kernel relies on specific tasks in charge of retrieving the necessary information. These tasks communicate with external modules by means of proprietary protocols based on the TCP/IP stack communication to get their dedicated data.
Stream Transcoder (MGW 5100) is a carrier grade rack mounted solution that can accommodate tens of encoding, transcoding, recasting and transmission channels, and stream them over IP, Native ATM, IPoATM as well as other broadband access networks (such as DVB-T) using external multiplexer or network access device.
The platform was designed and built to meet the Telco market standards and therefore supports hot-swap and redundancy of service boards, power supplies and fans.
The main benefits are:
- Full Service Range: MGW 5100 is a complete solution for streaming media, with a single box offering live video and DVB encoding, decoding, transcoding and streaming over IP networks;
- Flexibility: By combining I/O boards, service boards and network interface cards (NICs and GBICs) in a single chassis, operators can optimise their range of service in a cost effective way;
- Carrier Grade Architecture: Provides high availability, reliability and robustness with no single point of failure;
- Central SNMP Management: An advanced and flexible SNMP based management application enables smooth integration into a centrally managed networking facility;
- Lower Operational Expenditure (OPEX): With its integrated solution you'll need fewer boxes resulting in a smaller Footprint, minimal inventory, less training and one management system;
- Smooth Migration Options: A standard reliable cPCI platform facilitates smooth expansion using standard off-the-shelf hardware;
MGW 5100's Mambo version has been released for evaluation and testing purposes and ships with a reduced feature set. The currently supported features are as follows:
- Streams 24 concurrent encoded channels plus multiple DVB to IP converted program transport streams;
- Encodes MPEG-1, MPEG-2 and MPEG-4 WMT streams;
- Transcodes DVB compliant MPEG-2 streams to IP compliant MPEG-1, MPEG-2 or MPEG-4 WMT streams;
- Transrates (reduces the bit-rate of) DVB compliant MPEG-2 streams to IP compliant streams;
- Converts MPEG-2 over DVB-ASI to MPEG-2 over IP;
- Lets you change bit-rates while encoding, transcoding, translating and transmitting MPEG-1, MPEG-2 and MPEG-4 WMT streams;
- Supports Unicast and Multicast outputs;
- Supports IP over Gigabit (1000SX) and Ethernet (10/100BT).
The goal of the QoS Estimator is to emulate the behaviour of the end user concerning quality perception of one or several programs. MAMBO's perceived quality system has two types of components: the Quality Meter modules (QM) and the Perceived Quality Management System (PQMS) module:
- The quality meters (QM): Each QM monitors one program and provides quality
information to the PQMS module.
- The actual PQMS module receives information from the QMs at several monitoring points in the broadcasting chain. A Perceived quality model emulates the visual system and the memory of the viewers in order to achieve their expected reaction.
The PQMS system is mainly used to monitor the quality of programs going through the MAMBO platform.
The Quality Meter operates the measurement at each required point. These monitoring points are located before and after the platform, in order to evaluate the impact of the transcoding a multiplexing processes, which are included in the platform, on perceived quality. An additional quality meter is located near the client or end user and is used only for information on service delivery qualification.
The quality measurements are sent directly through the feedback channel to the PQMS. The latter gathers the perceived quality information from quality Meters and delivers it to the MAMBO platform to improve its internal functions.
The MAMBO platform includes various processes including a transcoder, which impact on the quality of the pictures has to be evaluated. The Quality Meters implement a quality assessment methodology based on a "Double-ended with reduced reference information" approach, according to the classification proposed by ITU-T SG9. This approach is well adapted for automatic and continuous monitoring of the quality of signals in Digital Television systems. In MAMBO the PQMS is primarily intended to check the Transcoder impact and not the level of impairments added by the service delivery network.
The video server aims at recording and broadcasting in real-time programs supporting MPEG-2 DVB transport streams via any DVB compliant network: satellite, cable or terrestrial. The video server allows to build and supervise TV services by delaying, scheduling and multiplexing in real-time heterogeneous programmes coming from multiple sources.
The video server can handle up to 4 inputs and 4 outputs with a maximum bit rate of 40 Mbit/s per input or output (for ASI input/output).
The main features of the video server are:
- Simultaneous recording and playback of transport streams.
- Recording of segments extracted of the incoming stream, managed by a record list.
- Segments storage on hard disks with RAID security.
- GOP (Group Of Pictures) accurate editing for stored segments, before broadcast.
- Segments play list management. The segment to be broadcasted can be a pre-recorded segment within the record list, live streams or streams stored permanently on server.
- Manual interruption of each segment of the record list or of the play list.
- Splicing between each segment of the play list. It performs splicing between a live segment and a stored segment or between two stored segments.
- Analysis by sampling of the recorded and generated stream (loss of synchronisation rate from PCR, presence of PID, decoding and display small picture).
Two modes are covered: the multicast and the unicast ones:
- The first one (multicast) will allow to the end-users to access the same stream, whereas the server sends only one file. For each file, a multicast address will be affected to each service.
- The second one (unicast) will be used to video on demand and application such as interactive video browsing.
The video server takes control of TV services as follows:
- Some programs within the incoming streams can be filtered before recording or playback.
- The incoming programs can be directly transferred through the network or stored locally on the video server.
- The recording can be scheduled through a record list or manually triggered.
- The recorded programs can be edited by setting starting and ending "tabulators".
- The video server outputs can play back live incoming programs, pre-recorded programs or delayed programs.
- The outgoing programs can be multiplexed together, using OpenMux real time multiplexing software on each output of the video server.
All those operations can be performed simultaneously on the same server in real-time. The video server software is running on the Windows NT operating system. A client application can be triggered on other Windows NT operating system on the same LAN or WAN.
The overall integration of the MAMBO platform can be hierarchically divided into two main stages: i) the interconnection of all innovative modules to form the Multiplexing Kernel, and ii) the integration of the wireless access network and the end user equipment to form the final configuration of the MAMBO system.
All modules have been finalised, interconnected and their proper functionality has been verified. The exchange of signalling information among them has also been tested in various ways, which needs some final modifications.
The IP interconnection among the modules has been physically divided into two Ethernet sub-networks: the Signalling / Data Subnet (SDS), concentrated on a 24-port 10/100 hub, which conveys signalling and management information along with IP traffic for the end users, and the Streaming Video Subnet (SVS), on a 8-port 100 Mbps switch, dedicated to video transport. The SVS is required as the output MPEG-2 TS of the Transcoder and is provided in a multicast UDP/IP stream.
The second step of the MAMBO platform implementation was the integration of the wireless access network and the user equipment into the system. For the GSM-based return path configuration, one PC was used as the user-to-service interfaces, creating the necessary environment for applications such as streaming video and surfing the Internet. A DVB-T PCI card and the appropriate software were installed to serve as the interface for the downlink of the DVB-T signals.
The interactivity with the MAMBO platform is implemented via the return path using a GSM mobile phone and the GSM Network. The mobile phone is controlled by the appropriate user interface, which is installed in the PCs. The return channel is an IP-based GSM channel and terminal is connected to a specific address at the Ethernet part in the Host System by dialing the appropriate ISDN number. At the Host System site two ISDN lines (4 Basic Rate channels) are available for connecting the MAMBO platform with the mobile user. These lines are handled by the dial-up server, which forwards all the incoming requests from the PC to the Host MAMBO System.
The Statistical Remultiplexer is basically an equipment, PC based, able to generate a fixed bit rate output transport stream, from existing digital and already compressed video services, whatever their incoming bit rate (CBR or VBR). It is designed to multiplex in real time, various services such as DVB, IP, DVD and generate DVB or IP bouquets. The output of the multiplexing process will be DVB MPEG-2 TS or IP datagrams. The technical challenge is to process in real time the services, in order:
- To generate an output multiplex carrying the highest number of services, as a function of a picture quality criteria.
- To allow programming flexibility (modification of the service list) along with dynamic and seamless switching capability.
- To ensure that the services within this multiplex will always be decodable
- Possibly to inject other data such as IP or EPG.
In the remultiplexing process, both Internet and multimedia traffic are multiplexed with MPEG TV programs. In this context, the Remultiplexer produces the digital bouquet that contains digital television programs, Internet and multimedia services at the maximum bit rate available. Within the MAMBO platform, the Remultiplexer is composed of two components:
- DVB Multiplexer receiving DVB and IP based services and generating a DVB bouquet.
- Streaming Gateway managing and controlling audio-video services that are MPEG-1/2/4 based services conveyed over IP and data services such as http, ftp, telnet etc.
During the MAMBO framework, Thales developed and implemented the Streaming Gateway and a new multiplexing technique based on Opportunistic Data Insertion. The Opportunistic Data Insertion (ODI) deals with the spare bandwidth within a MPEG-2 Transport Stream (TS). This technology allows using the available bandwidth by inserting data within the Transport Stream instead of sending null packets. However, Opportunistic Data Insertion is generally a binary method: insertion or not of the transport packets. In this case, a data PID can have temporarily a very high instantaneous rate or a data PID can never be transmitted (famine).
OptiMux is a powerful Thales' patented technology, which is dedicated to optimise a transport stream in term of amount of transmitted data. OptiMux is an advanced Opportunistic Data Insertion that allows avoiding the disadvantages of the "standard" ODI. The Streaming Gateway enables to control the IP traffic and to prevent IP traffic from consuming too much bandwidth regarding the DVB services.
It provides:
- An IP traffic regulator to regulate the IP traffic that goes through the DVB Multiplexer and the MAMBO IP output.
- An IP traffic estimation so that the Bandwidth Allocation Manager relies on its estimation to compute the new bandwidth allocation;
The Streaming Gateway allows to manage IP data in multicast and unicast mode. Multicasting allows end-users to access the same stream. A multicast address is assigned to each stream service. Unicasting might be used for video on demand and applications such as interactive video browsing or file transfer.
The "Bouquetizer" (the name shall indicate that it is used to configure MAMBO service bouquets ) is a software tool that provides a user-friendly interface to configure and adjust high-level parameters of the MAMBO policy server, the MAMBO service multiplexer and streaming server and the transcoder.
By means of the Bouquetizer the system operator is be able to choose one of several service classes for each program to be multiplexed within the DVB data stream. Each service class corresponds to a certain degree of quality provided by the network and controlled by the policy server. It has been decided that the interface between bouquetizer and policy server will be based on the XML (extensible mark-up language) format and TCP/IP network connections.
As the Bouquetizer allows the system operator to access several major modules of the MAMBO platform it is the most frequently used tool for him. The following list shows the main functionality of the Bouquetizer software. It includes the provision of an overview of services that are running or on schedule:
1) The management of services by modification of technical parameters.
Overview of services, using "global" view of parameters:
- Monitoring of significant Data (e.g. services running, on schedule)
- Several combinable filters to modify view of services (e.g. "show IP over DVB only").
- Save and restore of complete settings under a template name for fast access of various alternatives.
2) The monitoring of system operation.
Management of services, using detailed view of parameters:
- Manipulation of bouquet composition (add and discard services).
- Configuration of DVB-based bouquets for broadcast and Internet services.
- Configuration of IP-based bouquets with multicast streams and unicast traffic.
- Validity checks of edited values to identify possible conflicts.
- Comfortable assistance for configuration of services by suggesting default settings.
- Save and restore of (partial) settings.
(3) Monitoring of connected Modules:
- Creation and logging of error-messages.
- Monitoring of selected parameters of connected modules.
The Bouquetizer software is running on a PC connected to a local area network (LAN) of the MAMBO platform. The Bouquetizer is accessible from any PC connected to the LAN by means of a standard web browser. It is implemented in C++ source code with usage of Microsoft's ActiveX-technology. Therefore the most suitable Browser for using the Bouquetizer is the MS Internet Explorer.
The PC hosting the Bouquetizer software is based on the MS Windows2000-Server operating system including a Microsoft IIS web server to allow network access via the web browser.
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