Technological platform
Broadband platforms
STM DVB-RCS
Hungaro DigiTel Kft. – uniquely among Hungarian satellite data transmission service providers – has launched its fourth system (HUB and central antenna) providing independent broadband satellite data transmission services.
The HUB (center) meets all requirements of the DVB RCS (Digital Video Broadcast Return Channel via Satellite) standard, which defines the latest generation of satellite transmission and meets the latest standards.
System elements
HUB (center)
The central element of the system is the HUB providing services according to the DVB-RCS standard, which establishes separate and independently manageable virtual transmission channels to each remote terminal. These channels provide transmission of data traffic originating from the user ports of the equipment located at the remote terminal points, and they provide the remote management connections.
| Forward Link | |
|---|---|
| Modulation: | QPSK |
| Error correction coding: | 5/6 |
| Bit error rate: | 10(-7) |
| Channel access: | DVB-S |
| ASystem availability (annual): | 99.5 % |
| Ku band operation: | |
| uplink | 14 GHz |
| downlink | 12,5 GHz |
| Satellite: | AMOS |
| Antenna: | 3.7 m |
| Protection: | 1:1 hot backup, with automatic swap |
Network management (NMS)
The network management computer is continuously monitoring all network elements, provides continuous reports on events and statistical traffic data, comprehensively manages the remote terminals, provides on-line configuration changes and tracks the user ports and their protocols.
- User interface at the central side: 10/100 BASE-T Ethernet
- User protocol: IP (Internet Protocol)
Bandwidth management
There is a possibility to centrally control / monitor the bandwidth of each terminal point based on
- terminal points,
- terminal point groups,
- source IP address,
- target IP address,
- protocol,
- source port,
- target port.
Content filtering
Based on the central configuration, the system is capable of managing the servers accessible by the terminal points. Access of defined servers can be restricted.
AMOS satellite segment
The AMOS satellite used by Hungaro DigiTel Ltd. provides an exceptionally high coverage in Middle East Europe, which results in a reliable and high quality connection.
VSAT remote terminal
| Overview of the equipment | |
|---|---|
| Antenna: | 1.2 m (offset) |
| Operation: | Ku band |
| Cabling: | RG-11 |
| Distance between antenna and equipment: | 50 - 100 m |
| Management: | Continuous, automatized NMS |
| System availability (annual): | 99.5 % |
| Error correction coding: | 10(-7) (3/4 FEC) |
| Inroute port speed: | max. 1.125 Mbps |
Other data
- Exceptionally high reliability (10 years).
- MF-TDMA (multi-frequency hopping time division multiple access).
- Return link band access.
- Favorable response time (VSAT->Hub->Host->Hub->VSAT) < 1mp
- Available channel utilization 100 %.
User interfaces
- 10/100 Base-T Ethernet - IP protocol, static routing.
- TCP optimization for compensation of satellite delay.
Standard configuration
- One 10/100 Base-T Ethernet.
- Flash memory for storing the boot file – quick boot-up after power outage.
Other supported protocols
- DHCP (Dynamic Host Configuration Protocol).
- IP GRE tunnel (Generic Routing Encapsulation).
- NAT (Network Address Translation).
Dynamic priority management
The satellite unit can manage priorities of the IP packages. It supports DiffServ based priority management, and IP address/port/protocol based priority management is also possible.
TCP optimization
Satellite connections have larger delays then terrestrial ones. With regard to the satellite-Earth distance (~35,768 km), the theoretical minimum of the two-way delay (Round Trip Delay Time): 477.2 msec (2*238.6 msec). After adding the delay due to signal processing and terminal position differences, the minimum signal propagation time is approximately: 550 msec. Due to the above, we can improve the quality of TCP data transmission by using the following technologies:
- Path-MTU Discovery: IP attribute. Its task is to determine the maximum packet size that can be transmitted through the particular network without fragmentation. Fragmentation increases delay. With satellite networks, it is important to adjust packet sizes to the attached MPEG frames.
- FEC- Forward Error Correction: pre-emptive error correction. It is already used.
- TCP congestion control: slow start and congestion control are restricting the satellite transmission. However, they are required by the standards, so they can not be avoided. The Fast Retransmit and Recovery process can decrease the effects of slow start and congestion control in a certain extent. These are part of the present TCP/IP implementations.
- TCP Large Windows: transmission paths with high delay, like satellite links, require long transmission windows in order to utilize the available Forward Link bandwidth. Therefore it is practical to set large window sizes.
- Window scaling: provides setting window sizes above 64 kB (RFC 1323).
- Selective Acknowledgement: if multiple packets are lost, all packets following the first one must be re-sent. By using selective acknowledgement, ACK refers to a single individual segment.
So we recommend to adapt the client machines’ settings to the satellite transmission. For fine tuning of most Windows operating systems, HDT provides the user with the necessary utility programs and registry modification files.
Note
- The example figure shows a multiple terminal point structure that can be applied with reason for users with a single terminal point.
- A number of user terminals (PC) according to the local requirements can be connected at the terminal points.
iDirect
For meeting the increasing demand for broadband satellite services, Hungaro DigiTel Ltd. has launched its new iDirect central satellite system at the end of 2007.
The system is unique in Hungary, and due to its increased upload and download bandwidth, as well as to the new supported VSAT technologies, Hungaro DigiTel is able to support also the resource-demanding and critical business applications anywhere.
Network structure
Resulting from the VSAT technology, the user network has a star topology, so it can be fully adapted to the topology of the network to be implemented by our partner in all cases. Star topology assures that disturbances at different points of the network do not affect the regular operation of the other network parts and assures this way the high availability. The entire network traffic is IP based. Optionally, the system is also capable of operating according to the SCPC (point to point) and MESH topology, which provides direct communication between two remote stations by using a satellite "loop".
Hub
The central element of the system is the HUB, that establishes separate virtual transmission channels (backbone) with each remote terminal. The data traffic generated by the user ports of the terminals (VSAT) and the remote management data connections are multiplexed also into these channels. The HUB is modular, well scalable, so it can follow the changes in size of the client’s network.
| Forward Link | |
|---|---|
| Modulation: | QPSK vagy 8PSK |
| System availability (annual): | 99.9 % |
| Error correction coding: | TurboProductCode (+1,5dB!) |
| Channel access: | TDMA |
| Frequency range | Ku or C band operation |
| Satellite: | AMOS and AM-22 |
| Protection: | 1:1 hot backup, automatic switchover |
Network management (NMS)
The network management computer is continuously monitoring all network elements, provides continuous reports on events and statistical traffic data, comprehensively manages the remote terminals, provides on-line configuration changes and tracks the user ports and their protocols. Bandwidth / priorities of the individual connections can also be set (QoS).
CNO (Customer Network Observer) – it allows a restricted access for the user with monitoring mode. The user can monitor the terminal points and can get insight into the network operation.
VSAT (equipment installed at the user)
| The equipment in general | |
|---|---|
| Antenna: | 1,8 m (offset) vagy 2.4m (offset) |
| Operation: | Ku or C band |
| Cabling: | RG-11 |
| Distance of antenna and equipment: | 50 - 100 m |
| Management: | Continuous, automatized NMS |
| System availability (annual): | 99.9 % |
Other technical information
- Extraordinarily high reliability (10 years).
- MF-TDMA (Multi-frequency hopping time division multiple access).
- Return link band access.
- Integrated data compression enhancing bandwidth by up to four times.
- Integrated TCP and http acceleration.
- Automatic voltage regulation for better transmission power.
- Favorable response time (VSAT->Hub->Host->Hub->VSAT) < 1 mp
- Available channel utilization ~100 %.
Devices to be installed at terminal points
- VSAT antenna and bracket.
- Indoor unit (100-240 VAC 50/60 Hz, max. 2 A), with integrated 8-port Ethernet switch.
The iDirect indoor unit has been developed especially for critical business applications of business users.
