The IST-ET-101 has analysed the relevance of the emerging in-band full duplex transceiver technology for future military applications. In-band full duplex transceiver technology here means that a device can simultaneously transmit and receive radio signals on the same frequency. The primary focus was on applications in mobile tactical communications, but the consideration were not limited to this domain. For instance, also combinations of communications and electronic warfare have been discussed. Historically in-band full duplex transceivers have been considered to be technically impossible due to the strong self-interference from the transmit path to the reception path of the transceiver. To avoid this self-interference problem, in the past quasi full duplex approaches have been proposed which, e.g., either use the same frequency at different times for transmit and receive operations (time division multiplex operation) or use different frequencies at the same time (frequency division multiplex operation). Obviously, these quasi full duplex approaches reduce the spectral efficiency if compared to a true in-band full duplex transceiver which offers both types of operations at the same time on the same frequency. The IST-ET-101’s analysis of the relevance of the emerging in-band full duplex transceiver technology for future military applications started with a discussion of two conflicting trends with respect to frequency spectrum. On the one hand, the present and future tactical communication services in NATO-led operations like NATO Response Forces (NRF), Very High Readiness Joint task Force (VJTF), Enhanced Forward Presence (EFP), and also in NATO initiatives like Federated Mission Networking (FMN) are raising more and more attention. Consequently, more military frequency spectrum is required to satisfy the information exchange needs in the wireless tactical communications domain. In addition, the information exchange needs to be protected against electronic warfare threats (e.g. intentional jamming, interception, reconnaissance). On the other hand, frequency spectrum is a scarce and limited resource which cannot be augmented. This leads to the challenge of using the frequency spectrum as efficiently as possible. Several solutions to cope with the spectrum challenge have been briefly discussed by the IST-ET-101. One of them is the emerging in-band full duplex radio technology.When designing a full-duplex systems, the intrusion of a self-interference signal in the reception path causes the key challenge. This self-interference signal needs at first to be modelled properly and secondly, be eliminated from the reception path. Several state-of-the-art approaches which have been proposed from researchers at different universities have been reviewed by the IST-ET-101. One conclusion of the group was that all the proposals have in common that they use a two-staged approach, one stage in the analog domain and another stage in the digital domain. The assessment of a relevant subset of state-of-the-art prototypes lead to two general observations:?Firstly, the feasibility of full-duplex operation has been convincingly proven for lower-power commercial mobile communication systems in a laboratory environment. The independent state-of-the-art prototypes around the world achieve beyond 100 dB of total self-interference cancellation (SIC), even with rather large operation bandwidth (up to 80 MHz).
?Secondly, almost without exceptions, the existing experimental research is limited to the 2.4 GHz industrial, scientific, and medical (ISM) band. From these two observations it follows immediately that?the results need to be confirmed under realistic conditions in field environments for a selection of relevant operational scenarios.?further research is still needed to confirm the prospects of full duplex radios
The objectives for RTG on Full Duplex Technology are to:
• further identify candidate areas of military application for the emerging full duplex technology
• further assess state of the art solutions for tackling the self-interference cancellation problem (both, in the analog and digital domain)
• identify and describe concepts for transferring the findings from the civil/commercial domain to the military domain, e.g. :
o from the civil/commercial ISM-band to military relevant frequency spectrum (e.g. NATO V/UHF bands),
o from rather restricted transmit powers (typically less than 0,1 Watt) to military relevant transmit powers (e.g. 20 or 50 Watts), ...
• identify and describe concepts for making the results (to the largest possible extent) frequency agnostic
• pave the way for a common multinational demonstrator :
o identify and describe internal and external interfaces of a full duplex system,
o outline a implementation from commercial off-the-shelf SDR technology.
The RTG will also pay attention to the results from IST-080 (RTG) Software Defined Radio, IST-077 (RTG) Cognitive Radio in NATO, IST-104 (RTG) Cognitive Radio in NATO II, and IST-140 Cognitive Radio Networks.
The following topics will be addressed:
• Which tactical communication applications can benefit from using full duplex technology?
• Which efforts are needed for the integration of full duplex principles in existing communication systems?
• Which primarily non-communication systems can also benefit from this technology (e.g. Jamming Detection)?
• How to transfer the findings from the civil/commercial domain (e.g. ISM-band, 0,1 Watt) to military domain (e.g. NATO V/UHF bands, 20 or 50 Watts)?
• How to set up a common multinational demonstrator based on commercial off-the-shelf SDR components?
• What are the short, middle, and long term challenges and opportunities of the emerging full duplex technology?