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Project: TACCS - Cognitive Radios Adaptable Wireless Transceivers

Acronym: TACCS
Main Objective: Software Defined Radio has already start its way to conquer traditional radio configurations, by moving base band (de)modulators
completely to the digital world and thus implementing it by software.
Nevertheless, it is expected that Cognitive Radio, CR, will be the next frontier in terms of radio architecture design, in fact the new
paradigm that CR can bring to traditional ways to think on radio architectures, is so huge, as it was the transition from Analog to
Digital systems.
CR will allow the optimization of radio spectra occupancy, but also the implementation of the supreme universal radio, that is radios
that talk to each other’s no matter the original implementation.
But in order to achieve such a new deployment, the radio should be constructed with some form of processing capabilities, which it is
not possible with traditional schemes, that processing capabilities arises from some kind of processor that treats the
transmitted/received signal in real time, and makes decisions over it. That processing capabilities should be done at the digital
counterpart, but also, and most of the time neglected, at the analog part. In fact the main conclusion of the last SDR forum meeting
was that the analog part, usually called agile radios, should have a huge research effort in order to implement most of the CR
concepts.
This project aims exactly to study most of the physical layers of CR, starting from agile RF front ends, but also considering digital
implementations, either FPGA based, but also DSP based.
The project will try to give an answer to software engineers, by carefully studying the last piece of the system that is avoiding the
complete implementation of CR.
The main difficulty of implementing these CR architectures is the non-ideal behavior of the analog components, due mainly to
bandwidth limitations, and to signal amplitude limitations, dynamic range, by creating nonlinear distortion that severely degrades
SNR.
Thus the correct identification of the system components behavior, that is nonlinear dynamic models, the correct understanding of
the new waveform behaviors, which will be created in the CR approaches, will allow the correct design of the transmitted signal. This
signal should be pre-distorted in order to be transmitted with perfect spectrum masks, but the received signal should also be
compensated either by overcoming the non-idealities of the receiver components but also by reducing interference distortion due to
the existence of jammers outside the band.
Thus the now proposed work will make new contributions on (1) behavior models for non-ideal analog RF components; (2) new
signal identification methods, either for evaluation of the analog needs at transmission or at receivers, but also for spectrum sensing;
(3) new waveform generation for CR applications, in order to maximize the SNR, but also for maximize the transmitted bit rate; (4)
new design of reconfigurable architectures based on FPGA, for efficient CR implementation; (5) improved receivers for spectrum
sensing sub-systems by maximizing the gathering of large bandwidths; (6) new improved receivers for maximization of dynamic
range; and finally (7) new transmitters for linear and high efficient signal communications.
The proponent team is composed of a number of different knowledgeable elements, coordinated by a senior researcher of IT with
previous international and recognized work on nonlinear distortion modelling, RF circuit/system design and SDR system
implementation. For signal processing capabilities the team has two researchers with very important achievements in the area of
Sampling Theory and Signal Reconstruction, plus a researcher with knowledge on FPGA-based reconfigurable architectures and
hardware accelerators, digital systems modeling, simulation and synthesis. The team is complemented by the work of three PhD
students that are working in these fields, and we hope to have the help of two “bolseiros” that will assist in the simulation,
laboratorial measurements, and design of most of the new proposed CR architectures.
Moreover there is no other Portuguese research team working in this new emergent and future area of communication circuits and
systems applied to SDR and CR RF front ends.
These team combined with the new ideas will allow the proposed project to give a step further in the state of art in the area of agile
RF front ends for CR implementations.
Reference: PTDC/EEA-TEL/099646/2008
Funding: FCT/PTDC
Start Date: 01-01-2010
End Date: 01-12-2012
Team: Nuno Miguel Gonçalves Borges de Carvalho, Pedro Miguel Duarte Cruz
Groups: Radio Systems – Av
Partners: IEETA
Local Coordinator: Nuno Miguel Gonçalves Borges de Carvalho
Links: Internal Page
Associated Publications