The L*IP Satellite System developed by Joanneum Research and Graz University of Technology is a communication product hand-tailored for the Internet Protocol and its real time and non-real time applications. Video, voice and data applications can be supported via this network. |
Meshed systems like the L*IP avoid the drawbacks of star topology networks, i.e., it satisfies the requirements of real-time services with only a single hop. The available satellite bandwidth is used in an optimum fashion via QoS-aware DAMA control which balances the bandwidth for all the users in the uplink as well as in the downlink. The L*IP system encapsulates IP packets based on a time granularity and not the common cell (ATM,MPEG) granularity which results in less overhead on average compared to an ATM style encapsulation.
We see our hardware architecture as another big advantage over the approach of some competitors. By using a dual Pentium platform, we have a very powerful and future-proof platform, which is not the case for a lot of embedded processors. Thus, we have a flexible hardware architecture concerning access schemes and protocol requirements. Our software radio approach is based on PC and FPGA hardware, which is flexible, relatively cheap and also available in the coming years. We have developed with our platform every module from the Ethernet Interface to the 70MHz Modem interface, which includes: IP handling, IP header compression, QoS support, DAMA, MF-TDMA access and adaptive transmission.
In order to be prepared for future extensions and modifications, flexibility and reconfigurability have been essential aspects for the architectural design. Therefore, an open platform based on FPGA devices is realized, which allows the implementation and test of a great variety of modulation schemes, base-band shapes and synchronization algorithms. All subsequent processing, even error control coding, is carried out in pure software.
The hard real time tasks are executed on an FPGA -PCI card hosted in a dual Pentium IV (3.0 GHz) where also the tracker and codec is located. The higher layers are processed in a second PC with the same performance. With this architecture we are able to perform the processing of up to 4 Msymb/s with variable code rate (R = 1/3, 1/2, 2/3, 3/4, 4/5, 8/9), MF-TDMA access system, IP header compression, IP-optimized encapsulation, QoS-aware DAMA and a Java-based GUI for control and monitoring.
|Figure 1 shows the integrated gateway with Burst Modem PC, which hosts also the FPGA card. Further the gateway PC, the AD and DA converter box, an off the shelf L-band converter and keyboard / Monitor for both modem and gateway PC, which can be accessed with a keyboard/monitor/ mouse switch. || |
Figure 1: Integrated L*IP Satellite Gateway
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The architectural design of the complete system and their sub-modules was designed as the first stage of the project. Modulation, Channel codec, IP routing, IP header compression, QoS Support, DAMA, adaptive transmission and GUI for control and monitoring where then described in the detail design phase. Finally all modules where integrated and tested. All Tests passed the acceptance test.
We designed a satellite terminal for the meshed network market with single hop characteristic. The focus was the efficient transportation of IP traffic via satellite. This could be achieved by a low overhead encapsulation schema, an efficient codec, a low operational point of the modem and by an intelligent IP routing and IP header compression. On top of this is the operation of the Terminal at the Salve stations as well the Master station very user friendly with a JAVA based GUI. Master station and Slave station have identical hardware and can take over each others role in the network.
The L*IP System is a highly flexible platform which allows to implement various access, synchronisation, coding and modulation schemes. Because IP traffic is the major player in user traffic, we have concentrated our effort here in implementing the most efficient transportation of this sort of traffic over satellite. L*IP is a very secure platform for the future, because we propose an open platform for the base band processing in the modem and Intel Pentiums for codec, protocol and access modules. Both are reusable with different vendors and have the potential to increase their performance when more powerful processors become available. The innovative aspects can be summarised as follows:
- L*IP is an open platform offering a fully programmable gateway and a fully software-defined modem and codec (different modulation/synchronisation and FEC coding schemes can be implemented in VHDL/C++).
- L*IP is a meshed system addressing the corporate user which has more symmetric traffic requirements, whereas DVB-RCS is a star network targeted at fast Internet access with asymmetric traffic. L*IP therefore can support highly interactive applications between user terminals in single hop (this comparison implies transparent transponders).
- L*IP uses enhanced IP encapsulation to reduce overhead. The variable burst concept is well suited to IP traffic.
- L*IP guarantees QoS on IP level. It handles different IP-based applications and services, each with different QoS requirements, in different queues through its dynamic DAMA system.
- A patent was gained with a unique Turbo codec approach.
- The L*IP supports fade countermeasures by adaptive power, symbol rate and coding.
- A low operational point of < 5,5dB.
Last Update: 13 Aug 2012