Combination of Spatial Modulation and Full-Duplex for future Wireless transceivers
CITI Lab. Centre of Innovation in Telecommunications and Integration of Service (www.citilab.fr)
Context and background
Usually in wireless communications, the wireless medium is a shared and limited resource. Current wireless standards always share the medium with Half-Duplex principle: the transmission and reception of signals are done in two separate time slots or two different frequency bands. Besides, the transceiver can only transmit and receive one signal at the same time at the same frequency.
More recent research works [1-3] are focusing on an alternate approach: instead of sharing the medium with Half-Duplex principle, the entire licensed frequency band is shared for simultaneous transmission and reception, what is called Full-Duplex. The major drawback of this kind of Full-Duplex system is therefore that a very high level of interference is created by the transceiver itself while trying to receive a distant signal (known as the self-interference). Besides, the concept of MIMO communications is widely used, but supposes a large increase in the complexity, cost and energy consumption of multi-antenna transceivers. Using Spatial Modulation is a very promising way of developing simpler MIMO transceivers , and could be particularly relevant in combination with Full-Duplex.
Our laboratory has already a strong and recognized background on Full-Duplex communications [4-9]. A first thesis was dedicated to this subject, paving the way for more realistic developments and applications. Besides, another thesis has started last year, to study the theoretical bounds of physical layer secrecy by using FD.
Therefore, we have already proposed an architecture enabling FD communications. To approach this goal, we use an active analog radio frequency self-interference cancellation (AARFSIC) method or a combination scheme of the AARFSIC and active digital self-interference cancellation in time domain (ADSICT) to cancel the strong self-interference (SI) induced by the Full-Duplex principle. Based on the Full-Duplex radio, we proposed a flexible Full-Duplex Dual-Band (FDDB) OFDM radio transceiver by combining the Dual-Band RF front-end with Full-Duplex.
These proposed architectures have been studied in theory and in simulations, thus one goal of this thesis will be to develop some practical experimentations of Full-Duplex communications, based on Vector Signal Generators and Vector Signal Analyzers, in connection with simulated parts for digital processing purpose. Furthermore, some experiments in the Cortexlab facility is also an objective of this work (www.cortexlab.fr).
Wireless communications, RF architecture, digital processing, full-duplex, MIMO, Spatial modulation.
In the past years, considerable efforts have been devoted to prove the potential of using in-band full-duplex for future wireless communications, both from the hardware side and the networking side. The major difficulty of IBFD being the large amount of self-interference (SI), this interference is mitigated at three levels in the transceiver: antenna cancellation, analog cancellation, and digital cancellation. However, most of the proposed structures are inherently limited to fixed narrowband operations and almost no system-level demonstrations exist that prove the value of IBFD beyond a straightforward bi-directional link. Moreover, most of existing studies are based on theoretical analyses, simulations, or simple experimental testbeds.
Therefore, the goal of this thesis is threefold:
– To propose and develop some wideband and/or flexible radio architectures dedicated to full-duplex communications, using Spatial Modulation, from the antenna to the digital compensation implementation;
– To develop a complete study and optimization of this kind of architecture, starting from theoretical performance, going to simulation frameworks, and developing a proof of concept;
– To establish some reference scenarios to be tested with this proof of concept, for specific applications in practice beyond the usual toy-example of a straightforward bi-directional. In particular, we plan to explore and demonstrate applications such as secure communications through self-jamming, or the use of primary-user detection in Cognitive Radios.
As stated above, the main problem of Full-Duplex is to mitigate the strong Self-Interference created in the structure. Using Spatial Modulation enable to switch between several antennas to emit the signal of interest. Then, the challenge will be to receive a distant signal on unused antennas during this emission time, cancelling the Self-Interference and reconstructing the distant signal while switching at a high rate between the antennas.
To the best of our knowledge, it exists no actual combination of Spatial modulation and Full-Duplex. Only some theoretical bounds of potential performance of such a combination was proposed in  but without taking into account any realistic RF architecture. Thus an actual and functional architecture combining Full-Duplex and Spatial Modulation would be a great breakthrough.
Scientific program and schedule
The overall schedule of the thesis is quite simple. The first six months will be dedicated to an exhaustive state-of-the-art not only on Full-Duplex systems and Spatial Modulation, but also on all progress on wideband and flexible radio systems and on interference cancellation algorithms. The remaining of the first year will focus on building the framework of theoretical studies and the associated simulation tools.
The second year will be devoted to extensive theoretical and simulation investigations, as long as choice of the required equipment for experimentations. By the end of this second year, everything should be fixed in order to be able to begin experimentations in the third year.
The third and final year of the thesis will see the production of scientific results via publications of the most significant works, extensive experimentations with feedback on theoretical and simulation studies and global drawing of the potentialities of exploitation of the proposed techniques. A large dissemination to the community is planned in order to encourage the use of these approaches in future communication networks. Finally the thesis manuscript will be written and the thesis will be defended.
Apart from the material part, the proposed tools are the Matlab and the Keysight’s ADS software. The thesis will take place within the Inria Socrate team of the CITI laboratory (http://www.citi-lab.fr/).
Guillaume Villemaud (HDR, 50%), Florin Hutu (50%)
Of course, a large dissemination of the proposed works will be ensured in international conferences, high quality journals and potentially via patents. Our goal is also to collaborate in COST actions, particularly we are strongly involved in the new IRACON action (merge of the NEWCOM# and COST IC1004) and therefore this will offer a good place of interaction with other European partners. We also expect that this project will be a first step to build a larger consortium for future H2020 calls and to participate in the definition of new standards, particularly to encourage the integration of Full-Duplex in the 5G networks.
Moreover, this work could be naturally applied to IoT scenarios, therefore the context of the SPIE IoT Chair hosted at the CITI laboratory could be a rich place of interaction and collaboration.
Expected profile of the candidate
Master of Sciences or Engineering degree in Telecommunications or Electrical Engineering with a strong background in radiocommunications, RF architectures and signal processing.
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