The project’s first objective was the development of a Data Collection Platform Transmitter for METEOSAT HRDCP as well as for SRDCP and GOES. The transmitter is an essential component within autonomous DCPs working in environments with little or even no infrastructure for communication and electrical power supply. The second objective was the definition and prototype implementation of a New Air DCP radio interface, the Enhanced DCP (EDCP) providing a service to a wider range of applications.
The Data Collection Platforms (DCP) are used to collect environmental data from sensors and to transmit those data within DCP messages to a DCP Control Centre. The field of DCP application covers beside others:
- Meteorological Data Collection
- Water Management
- Tsunami Warning Systems
- Hydro-meteorological Management
The first objective of the study was the development of a DCP Transmitter covering the GOES 300/1200 Baud, the international 100 Baud SRDCP as well as EUMETSAT’s 1200 Baud HRDCP specification. The certification of the DCP-Tx for HRDCP used via METEOSAT has been achieved at the end of the project.
The second objective was the definition and prototype implementation of a New Air DCP radio interface, Enhanced DCP (EDCP). One of the cornerstones for the definition of the interface was a survey within the group of DCP stakeholders. This technical questionnaire helps to get external inputs to:
- define future DCP system scenarios,
- define New Generation Air Interface specifications and
- define suitable transmitter requirements
The results of the questionnaire allow to precise the study work on the new generation interface. Two example specifications of the New Air Interface have been prototyped for the DCP transmitter and the receiver side.
The DCP transmitter shall autonomously work under harsh environmental conditions while meeting the demands of the radio certification standards. Due to this, a number of design drivers have been identified such as
- very high frequency stability and low phase noise
- requirements for very low standby power consumption
- wide operating temperature and self-heating during transmit operation
- likelihood of periods without GPS reception in certain environments (forest, etc.)
Furthermore, SCISYS aimed for a common DCP-Tx HW platform supporting the legacy DCP and the new generation air interface. This approach could not be confirmed unless the baseline specification of the new generation air interface was decided. Accordingly, the HW and FW design have to support Software Defined Radio to be flexible.
The DCP market is dominated by US companies and there were no European manufacturers of DCP transmitters. The DCP-Tx design can serve as a basis for European companies interested in the DCP market.
Beside this, the new generation radio interface specification could support new users that require movement-tolerant operation as well as the definition of a new international DCP standard closing the bridge between the different DCP specifications used by the different satellite operators.
The DCP-Tx system features are intended to be competitive with other DCP transmitters from the US. Beside the TRL Level 5, the current design has reached the EUMETSAT certification (No 2018-004-DCP-HDR). In addition, the same HW supports the proposed new generation air interface standard up to prototype level. The DCP-Tx is ready to allow EDCP tests via the METEOSAT satellite.
The system architecture as depicted in the following figure is mainly centred on a low power microcontroller, a digital signal processor (DSP) and a dedicated quadrature digital up-converter (QDUC) chip.
The software based transmitter tasks are split to two different processors. The microcontroller is in charge of providing the required serial interfaces for data exchange, monitoring & control, GPS receiver and real-time clock (RTC). It performs the time and frequency corrections based on the relevant GPS information on a regular basis. The actual signal processing tasks like formatting and encoding of the data, symbol mapping and pulse shaping are running on a DSP. This concept provides the highest degree of flexibility due to the fully “software defined radio” approach up to the I/Q symbols at a moderately low sample rate used up to this point. The remaining signal processing is performed within a dedicated quadrature digital up-converter. Further building blocks are a surface acoustic wave (SAW) band-pass filter before further amplification to the final RF output level by the following high-power amplifier (HPA).
The milestones of the project were as follows:
- MS1 Kick-off
- MS2 System Requirements Review (SRR-1)
- MS3 Baseline Design Review (BDR-1)
- MS4 System Requirements Review (SRR-2)
- MS5 Baseline Design Review (BDR-2)
- MS6 Preliminary Design Review (PDR-1)
- MS7 Detailed Design Review (DDR-1)
- MS8 Preliminary Design Review (PDR-2)
- MS9 Detailed Design Review (DDR-2)
- MS10 Final Test Review (FTR)
- MS11 Final Review (FR)
The “-1” milestones are dedicated to the legacy DCP development whereas the “-2” milestones are focusing the new generation air interface work packages.
The project was finished achieving all goals as stipulated by the statement of work. The DCP transmitter (DCP-Tx) hardware/firmware supports the legacy DCP missions of the GOES 300/1200 Baud, the international 100 Baud SRDCP as well as EUMETSAT’s 1200 Baud HRDCP specification. The certification of the DCP-Tx for the EUMETSAT HRDCP mission has been achieved (Certificate No 2018- 004-DCP-HDR).
The main study goals for the New Air DCP radio interface specification (Enhanced DCP) have been selected based upon questionnaire results from DCP stakeholders and a workshop between ESA, EUMETSAT and SCISYS. As a result, this study focusses on an EDCP implementation as follows:
- 400 Baud BPSK
- 400 Baud Pi/2 BPSK
- Priority on platform movement tolerance for RF modulation
- Shorter and/or variable code block FEC for efficient use with short messages
Both EDCP modulation schemes have been implemented at DCP-Tx and receiver side. Laboratory tests as well as simulations of the complete communication link, including Gaussian noise, phase noise and interference have been performed. The simulations cover a number of test cases and overall show that EDCP is working as designed and meeting goals of:
- Good power efficiency in terms of low Eb/No for an acceptable FER (Frame Error Rate).
- Good robustness when faced with phase noise and interference, both CW and pulsed.
We conclude that EDCP shows significant advantages for difficult reception environments and merits further consideration for a new DCP standard replacing the current international DCP 100 Baud BPSK standard.