SDR TT&C Modem

Competitiveness & Growth

Status

Ongoing
Status date

2024-05-07
Activity Code

6A.083

Objectives

The objective of the project is to develop a Software Defined Radio (SDR) Modem for addressing Telemetry, Tracking and Command (TT&C) functions in satellite testing Electrical Ground Support Equipment (EGSE) systems and simulation environments for telecom market and ground stations market.

The project is starting from the existing prototype work (from former GSTP activity), which is for the implemented features mainly on TRL5, with the Technology Phase to add missing modem functionality and enhance the existing prototype to bring all features to TRL5/6.

In the next step, the Product Phase shall productise the SDR Modem (all features shall be fully implemented, all admin functions shall be available, all features shall be verified and validated on module and system level up until TRL8).

The figure below shows the main components of Terma's SDR Modem. Terma's SDR Modem is a distributed system that consists of a generic hardware backend (rack mounted Dell workstation) connected to an RF frontend (Ettus USRP X310) via SFP+ optical cables, capable of dual 10Gbps connections. The RF frontend can be positioned close to the antenna to reduce signal loss, while the backend can be located in a server room.

Challenges

The main challenges were found in the SDR technology, implementation of the required capabilities, modulation types (BPSK/PM, OQPSK, GMSK), Turbo coding, Doppler correction and Impairments correction, Ranging as well as the related performances.

Another challenge was the selection of the baseline solution (HW and SW platform). The main criteria was the processing performance, cost and the portability of the implementation, as the SDR Modem is desired to be as much as possible HW independent.

Benefits

Terma's SDR approach is the use of a distributed SDR system, where the generic HW acts as the backend of the SDR connected to an RF frontend for maximum flexibility.

Wide Protocol Support: Comprehensive support for modulation and coding schemes compatible with the CCSDS standard.
Flexibility: The SDR Modem can be reconfigured to support multiple types of (de)modulation and (de)coding schemes.
Multiple Processing Channels in parallel: It is possible to configure 4 RX signals in parallel or a combination of 1 TX and 3
RX and 2 TX and 2 RX. One SDR Modem can support up to four satellites.
Maintainability: The SDR design does natively justify maintainability by having most of the TT&C Modem in software.
Distributed Architecture: The distributed approach with a flexible RF frontend and a separate backend allows for greater flexibility and proximity to the antenna.
Compact Design: Offering a 1U form factor design for ease of integration and space conservation.
Hardware independent: Terma's SDR Modem is built to run independent of hardware, which has the potential for virtualization.
Scalability: The Modem allows flexibility by adding and removing additional applications as needed.
Cyber secured by Design. All communications are protected through the Linux Security Module.

Features

The SDR Modem offers the following features:

Reading of doppler prediction files, interpolation, configuration of frequency offset
Ranging signal generation, ranging estimation
Modulation schemes:
- Remnant Carrier SPL (PCM/PM/Bi-Phase), PCM/PSK/PM
- Suppressed Carrier BPSK, QPSK, OQPSK, GMSK
Correction of SDR HW impairments
Transfer of received science data directly to the network card.
Coding Schemes:
- BCH Encoder & Decoder
- Reed Solomon Encoder & Decoder,
- Convolutional Coding
- Viterbi Decoding (Hard & Soft)
- Turbo Encoder & Decoder Coding
Differential Encoder and Decoder to resolve the phase ambiguities in signals.
Time Synchronization
RS422 HW Interface to send and receive TM/TC
CADU and CLTU generation
Frequency search (FFT based)
Frequency correction (RX and TX)
Frequency sweep (TX signal)
Ambiguity resolution
BER measurement
Noise signal generator
Cyber security features

System Architecture

Terma's SDR Modem is a distributed system that operates on generic hardware. The backend controller PC (rack mounted Dell workstation) is connected to an RF frontend (Ettus USRP X310) via SFP+ optical cables, capable of dual 10Gbps connections. The RF frontend can be positioned close to the antenna to reduce signal loss, while the backend can be located in a server room, allowing for multicore, multithreaded processing, real-time scheduling, a Linux operating system, C++ and Python programming, and GUI with flowgraphs.

The figure below shows the SDR Modem architecture and internal an external interfaces.

Plan

Technology Phase was used to de-risk the SDR Modem functionality and to enhance the existing prototype to bring all features to TRL5/6. Technology Phase will be completed in June 2024.

The Product Phase which then starts shall productise the SDR Modem. All features shall be fully implemented, all admin functions shall be available, all features shall be verified and validated on module and system level up until TRL8. After 10 months the Final Review is scheduled.

Current status

Currently the test and verification of the main SDR Modem functionality is still ongoing. Phase Closure of the Technology Phase is scheduled in the upcoming weeks.