SINGLE CHANNEL FULL DUPLEX TECHNIQUES FOR SATELLITE COMMUNICATIONS

While satellite communication systems are capable of providing the necessary coverage even to the remote and under-served areas. Peak demands in feeder and forward links can occur simultaneously and are difficult to satisfy. In this context, the full duplex operation (i.e., simultaneous transmit and receive functionality) applied to both links seems to be especially promising. Simultaneously transmitting and receiving information in a single frequency channel has already proven a viable approach in other wireless communication application domains and has the potential to double total system throughput. Such systems typically employ a combination of both analogue and digital Self-Interference Cancellation (SIC) techniques, together with a careful antenna design and a suitable placement, to achieve the necessary isolation between transmit and receive signals, and such techniques have therefore advanced rapidly over the last few years. Single channel full duplex operation has consequently been supported within consumer (cable) networks since the release of DOCSIS 4.0 in 2017, and integrated wireless access and backhaul for 5G using full duplex is also now becoming a reality. LTE products are already available using full duplex such as LTE User Equipment Relays which enable a small cell LTE eNodeB to backhaul to an LTE macro base station using the same access frequencies for both the small cell and the macro network.

In most satellite communication systems, full duplex operation is achieved by using two separate frequency channels with spectral filtering employed to achieve the required isolation between signals (Frequency Division Duplexing, FDD). Although less widely utilised in satellite communications, single channel bi-directional communications is also sometimes realised by Time Division Duplexing (TDD), e.g. by the Iridium inter-satellite links (ISLs). Despite the recent advances, there remain significant barriers to applying full duplex operation within a SatCom system, chiefly due to the very high-power imbalance between the transmit and receive signals (a direct result of the very long transmission distances) and the large fractional bandwidths of SatCom frequency allocations. The objective of the proposed activity is therefore to assess the feasibility of applying single channel full duplex techniques within satellite communication networks. The study shall begin with a survey of the current state of the art for SIC techniques and technology, as well as an evaluation of the suitability of commonly used full duplex air interfaces to SatCom scenarios, identifying any necessary adaptions. The activity shall consider all frequency bands currently used for satellite communication, i.e., from VHF to mm-wave frequencies, and seek to identify the most promising potential use cases and application domains, e.g., backhauling, feeder and user links, ISLs, etc. As the current Radio Regulations do not allow for single channel duplex operation in most of the existing satellite communication frequency allocations, the activity shall also consider what adaptions would be needed to the regulations if the techniques proved technically feasible. In addition, the implications for satellite payload design shall be identified, given that a full digitisation of the communication signals is likely to be necessary, as well as adaptations of the antenna architectures.

Funding: This project is funded by the European Space Agency (ESA)

Project Starting Date: March 2023

Project Duration: 9 Months

Research Team:

Prof. Symeon Chatzinotas

Dr. Steven Kisseleff

Dr. Victor Monzon Baeza

Dr. Juan Andres Vasquez-Peralvo

Dr. Juan Carlos Merlano Duncan

Dr. Jorge Luis Gonzalez Rios

Partners:

University of Vigo, Spain

Gradiant, Spain