The objective of the activity is to develop and test signal reception techniques that enable uncoordinated satellite access schemesin the maritime bands for VHF Data Exchange (VDE) by a population of maritime transmitters in the presence of in-band interference from maritime and external sources such as in-land terrestrial services. The techniques will be implemented and evaluated in a prototype receiver to be developed as part of the activity. The activity will also carry out over-the-air test feeding the receiver with VHF signal samples previously collected in space. Targeted Improvements: Allow to operate at least 10 dB below the noise and interference level. Improve the signal detection by at least factor of 2 in the presence of overlapping signal (due to the random nature ofdata transmission of messages). Description: The World Radiocommunication Conference 2019, endorsed the allocation of maritime VHF frequencies for two-way VHF Data Exchange system via satellites, making space communication an integrated component of the VDES. Theallocation of frequency in WRC2019, rectified uncertainties and potential regulatory risks in the deployment of VDES for two-way communications, to and from vessels via satellite. This has opened up opportunities for communicating short messages from vessels to the satellite using VHF uplink capacity. The return data link from remote nodes (on-board of vessels) can have variety of applications including fleet management, autonomy of vessels, navigation and geo-localisation. The VDES can provide an uncoordinated access viasatellite to remote nodes. This however requires sophisticated detection techniques on board of the satellite to detect and decode colliding signals from different sources. Using random access techniques together with interference cancellation at the receiver allows a very efficient use of the limited spectrum allocated thus maximising the number of terminals supported. The impact and the useof interference cancellation for different scenarios will be investigated and trade-off analyses will be performed. Recent measurements have shown that there are also external interference sources (from land mobile as well as long-range RADAR) that could introduce interference on the uplink VDE-SAT channel. Starting from lessons learned from previous VDES via satellite experiments, as alreadyreported in the ITU Recommendations, this activity shall target the development signal reception techniques that are suitable for the effective implementation of the VDES space segment, targeting small satellite platforms, while maintaining the technical requirements of the RF and baseband processing and antenna radiation requirements. To achieve this objective, the activity will evaluate, simulate and implement in software interference cancellation or mitigation algorithms specifically designed for VDE-SAT uplink waveform. Based on the software and simulations, an interference cancelling receiver prototype for VDE-SAT spread spectrum format will be developed. The performance gain of the receiver will be first evaluated in the lab and then a test campaign will be carried out usingexisting space assets. Footnote: On Delegation Request activities will only be initiated on the explicit request of at least one National Delegation.

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