The Wideband System of Data Transfer through the Satellite
By Maxim Kimstach

The Review of the Decisions about the data transfer

As the Internet user the reader knows that the most unpleasant thing is delays (www - World Wide Waiting). Even with the 56K-modem the loading of large files and sites sometimes seems endless. The dedicated lines are faster but need more expenses and the provider with such services in the 5 km area. The reason of the delays is hidden in the connection with the server. Imagine the Internet as a huge sewerage system. A pipe of 1 cm diameter connects you with it. When you request a page this small packet of information is squeeze into your pipe very fast. At the same time your server is connected with the Internet by the more wide pipe, for example, 20...25 cm in diameter. Your request gets to the bus network, which has tens of pipings and gives the requested information to your server, which tries to flood big information volumes into the pipe of 1 cm in diameter. The result is obvious.

The decision of the data transfer through the satellite changes the situation. You continue making the requests through your provider, but he sends them to the server of the operator of data transfer through the satellite, which is connected to the bus network by a wide channel. This server redirects the request to the source of the information and after getting of the needed information sends it to the client through the satellite. That fastens the receiving, for example, 400 kbit/sec instead of 56 kbit/sec.

Such a decision is ideal for the most of clients as in the overwhelming majority of cases the high speed is required only for the incoming traffic. In particular, the sending of the request on the page reflection requires the transfer of about 100 bytes when the page itself with its graphics and other attributes can achieve the size of 500 KB. The cost of the subscription for such a service will be much less than the cost of the good dedicated line.

The traditionally wide covering of the territory by the satellites was their advantage at the delivery of the multi-channel video. With the appearance of the IP services such as the access to the Internet satellites become the platform for the creation of the additional services. For example, the financial information including the reports and forecasts of the analysts, study courses, weather forecasts, catalogues, etc. All these services can bring the additional revenues to the operators.

The approximate estimation shows that if the carrying capacity of transponder equals 40 Mbit/sec, speed of the active consumption of the traffic by the user is 128 Kbit/sec, the relation of active users to all the connected users is 1:10 then we will see that 320 of active users can get the data and 3200 users can be on-line. The general amount of the subscribers can be more than 32 thousands.

The Technical Description of SkyStream Networks Decision

The components of the decision offered by the SkyStream Networks, which is the leader in the field of IP transfer through the satellite, were chosen based upon the hackneyed in the real systems of technologies and the good price/functionality ratio:

• direct DVB channel the IP encapsulate SMR, which provides the insertion of IP packets into the transport DVB flow, coding (the system of conditional access) and the giving out of the formed transport flow to the modulators;
• the reverse VSAT channel is the most flexible VSAT system on the market, which includes the reverse DAMA SCPC and TDMA channels and an opportunity of dynamic redistribution of the frequency with the help of Vipersat software;
• NMS (Network Management System) Vipersat of the Vitacom Company is the system of control of network which proved its reliability by the 15 years of exploitation;
• QOS (Quality of Service) is the technology of controlling the service quality;
• VPN is the coding of traffic from the user to the satellite provider from the leader of the industry, Nortel Company, that prevents the 'sniffing', the intercept of someone's data. The creation of the coded tunnels between the router is possible as well;
• TCP Acceleration is the most often used system of Flash Networks, which includes the client software, group software for the corporation, server software on the site of transfer, software for reserving and distribution of work;
• StreamSecure is the system of the conditional access of the SkaStream Company, which is based on the specifications of the DVB Scrambling and provides the secured data transfer to the user;
• DVB Receiver Cards are chosen and supplied by the provider. At the moment for the decision of delivery of data of the SkyStream Company the B2C2 and Broadlogic cards are certified;
• Cache Server is the server provided by the provider for the local storage of the often-requested information.

The user connects with its provider and gets the dynamic IP address of the modem connection at the PPP protocol. The S-Link program assigns the MAC address to the PCI card of the satellite receiver established in the user's computer. This MAC address acts during the session of the connection instead of the address sewn into the receiver's card. In the Internet settings of the computer the VPN proxy server of the satellite Internet operator is indicated, and the operation is done through the VPN (Virtual Private Network). The requests from the client get to the needed site, the answers of the site are initially send to the IP address of the client but after the passing through the VPN server redirect to the SMR (Source Media Router). Another advantage of the VPN server is an opportunity of traffic coding by the Ipsec protocol specifically for each client, which prevent an opportunity of traffic intercept by the casual looking through if the MAC addresses.

The facility of QoS technology securing allows limiting the traffic by each IP address to the individually set magnitude to the provider.

For example, the client wants to look through the defined site in the Internet. The packet with the request would be send over the logic PPP interface. The initial packet would be griped, coded and inserted into the packet that is send from the IP address of the modem PPP connection on the IP address of VPN server. As usual this packet routings by the network and gets to the provider's router, which would deliver it to the VPN server.

The VPN server would accept the packet, decode and decompress the content, restore the initial IP packet and would give it out on its outlet interface. The provider's router would send it to the requested site. The site would give out an answer to the request to the PPP address of the client, situated in the provider's network. The provider's router would send the answer of the site to the SMR instead of the VPN server. The SMR would get the answer and insert it into the forming DVB flow giving the automatically formed MAC address to it.

The receiving client's card would get the packet with its MAC address and send it to the IP riding-crop. The IP riding-crop would receive the packet as its own as the IP address of the assignment corresponds to the one of the local IP interfaces, to the VPN/PPTP interface to be exact, and would resent it to the web browser. The process is over.

Spare Parts of the Decision and their Functionality

The Data Transfer Site (Uplink)

Scheme of data transfer via satellite

The data transfer site is the core of the system. The main components are the IP network, SMR subsystem and the transfer to the satellite site, The IP network provides the connection between the data sources such as FTP server, RADIUS server, VPN server, IP video conference server, and the zBand Content Management Server. In it presumed that these servers are operating by IP and their IP network can include the additional server applications corresponding to the offered services. Also IP network serves for the check-up and control of the network and for the inserting of the In-Band Signalling commands/messages for the transfer to the remote sites.

The Remote Sites

There are three types of the remote sites. Each type is capable to perform the next functions:

• receiving of the high-speed data and commands from the transfer site based on the DVB, MPEG and IP standards;
• recalling of IP packets from the DVB flow together with an opportunity of redirecting of the initial packeting UDP IP and redirecting of the IP packets along the network riding-crop;
• subsystem of the reverse channel by the earth or satellite channels.

The first type of the satellite receiver is the DVB router, which allows fulfilling of the asymmetrical double-sided data transfer through the satellite. The second type of the satellite receiver is the DVB router, which accepts the DVB flow and has the earth reverse channel. The third type of the satellite receiver is the computer resolution card with the reverse channel through the telephone line.

QoS (Quality of Service) is the technology, which controls the quality of service.

The problem is that the volume of traffic from the different users can be absolutely different even if they use the same service (for example, ADSL, telephone line). If the provider decides to form his own rates for the services based on the average traffic, generate by the users, he would do them more profitable for the active users of the traffic, but to the prejudice of the users with small consumption. Creating different traffic plans for the different types of users they should be divided more equally and by that to attract more customers.

NMS is the system for the network control for the decisions with the reverse channel based on the VSAT technology.

Scheme of data streams ways

The system of the network control chosen by the SkyStream Company for its decision of the data delivery is the ViperSat for the VSAT decisions of the high-end class and STM Wireless for the middle level decisions. Each one of the companies is the nicher leader. They vary in flexibility, cost and carrying capacity. Both systems allow the full-scale check and control the central site as well as the remote sites.

ViperSat is based of the 'client-server' technology and the standard hardware/software platforms. The system represents the whole network in the graphic view with an opportunity of specification of operating of each part of the network. The controlling servers can reflect one another for the uninterrupted operation of the network in the case of the falling out of one of them. In particular, the system allows controlling of the few SMR situated in the different places.

The SpaceWeb Network Management System (NMS) is the controlling system of the STM Wireless Company. It allows the full control of the SpaceWeb network from one controlling site. It allows configuring the transfer site and the remote sites looking through the statistics and protocols of the system operation, to react on the warning and mistakes, to control QoS and the user's settings. The system has a simple in use graphic interface.

The main opportunities are:

• the setting of the configuration at the network administrator routine;
• the reflection of the network condition (automatic and hand);
• the collection of statistics (automatic and hand);
• diagnostics and monitoring of the system compound facilities;
• the processing of mistakes, multilevel security, the giving out of reports;
• remote control;
• control of use PID.

The SpaceWeb separates by the wide band exit DVB flow from the reverse TDMA channel. The TDMZ control system controls the reverse channels and functions on the bases of the Sun Microsystems/Unix workstation with the graphic interface. The system can operate in the case of falling out of the NMS-TDMA as its whole configuration of the network is situated in the NCU.

The security

The VPN sever of the Nortel Connectivity series of the Nortel Company is set on the transfer site and the VPN clients set it on the workstations of users. The client software is distributed freely and serves for the fixing of the virtual tunnel between the remote sites and the VPN server. With the increase of the network the additional VPN servers can be set as well.

The Distribution of the Content

For the keeping of the clients it is necessary to provide them with the various services. The most attractive of such a services is the service of the distribution of content in the multicast routine. The SkyStream Company has such a decision for the control of the broadcasting IP data. Zband is an open, secured, routed program platform, which allows to the service providers and broadcasters supplying the video, audio, Internet content to the customers and has a wide opportunities of the personalization of services.

The packet allows providing the delivery of the paid services, based on the wide band access such as personal addition of data, electric commerce and direct or "requested" studying or entertaining programs. Zband has the complex of developing (SDK) for the integration with the existing applications or for the direct building-in of the zBand technology into the existing applications.

The various areas of the use of the multicast delivery are:

The Elogar Company.

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