| Abstract
The new requirements have led the French MOD to develop a medium data rates (64 kbps to 2 Mbps) modem using an orthogonal frequency hopping in order to provide robust and protected user communications for his Satcom system SYRACUSE 3.
The performances of the system are analyzed at first by simulation and then by tests with a breadboard on a satellite transponder simulator and on a real satellite channel.
1 - System description
The system provides data rates from 64 kbps to 2.048 Mbps by step of 64 kbps, the traffic links are established in a PAMA mode.
In order to establish and maintain the synchronization, you need to build a synchronization network which is composed of 3 links :
- The FOW_B (Forward OrderWire Broadcast) link broadcasted by the Network Controller to all the communication units (CU) to find the right time synchronization. It is the first step to enter the network.
- The long loop composed of 2 links FOW_L (Forward Order Wire) and ROW_L (Return Order Wire) to maintain the orthogonal hopping.
2 - Waveform design and simulation results
The waveform is composed of a QPSK modulation with a square root raised cosine filter and a concatenated coding scheme based on a outer RS encoder and an inner convolutional encoder. Interleavers are inserted in order to break error bursts.
The performances are analyzed by simulation with white noise and PBNJ (Partial Band Noise Jamming).
3 - Tests with the breadboard
A breadboard was developed by the contractor THALES in order to validate some critical points :
- Procedure to enter the network and maintain the synchronization of the orthogonal hopping with a real channel
- Performances in a hard limited mode and with different types of jammers
2 data rates, 64 and 256 kbps, were developed in order to validate the signal processing and were evaluated on a satellite transponder simulator in different conditions and with different types of jammers (CW, multitone, PBNJ, pulse jammer).
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| Gaston LEVANNIER was born in Normandy (FRANCE) in August 1956. He received his degree in Electrical Engineering in 1981 from INSA Institute in Rennes.
Since 1982, he has been working in the technical center CELAR for the Minister of Defence. Since 1990, he has been involved in military Satcom Systems, his areas of interest include modulation/demodulation, channel coding, spread spectrum techniques and their applications to Satcom and Radio systems. |