CREaTION

Task description and Expected results
In this task we will develop a RF front-end based on a hybrid Filter Bank (FB) to acquire signals with a large bandwidth and high
dynamic range. A front-end with these characteristics will be a key component to build a Software Defined Radio, where the
whole spectrum of interest must be accessible in the digital format.
Moreover, a C ognitive Radio must be able to deal with a large bandwidth even if it uses only a small part of the converted
spectrum. After sensing the spectrum for free holes, the RF signal can be a sparse set of narrow bands scattered over a large
bandwidth.
This kind of signals will be quite difficult to acquire due to the following reasons:
1- The ADC must work at a high sampling rate. The radio front-end must convert to digital the whole bandwidth starting on the
hole with the lowest frequency and ending in the hole with the largest one.
2-The dynamic range of the ADC must be very high. When the bandwidth of the signal is increased its dynamic range will also
increase. Besides, the interference signals between the holes will also be included in the conversion. These interfere signals can
have higher power causing the well-known near-far problem demanding for higher dynamic range of the ADC .
Building an ADC with the required sampling rate and dynamic range is a challenge far beyond the present technology.
One possible solution to this problem can be a front-end with a large number of ADC s using a lower sampling rate and number
of bits in conjunction with an analog FB. We call this solution the cochlear radio due to the similarity with the solution found in the
Human hearing, where an impressive bandwidth and dynamic range is achievable using analog to discrete time sensors with
poor characteristics.
In such a system, the input signal will be split in many frequency bands using an analog FB of band-pass filters. Each filter output
will be converted to the digital domain using sub-sampling. We can use low performance ADC s and reduce the power
consumption over the one ADC design by a factor equal to the number of channels. Then, the digital signals are aggregated into
one single signal using a multirate digital synthesis FB. This FB will be responsible to cancel the aliasing terms due to the subsampling
and equalize the phase and amplitude distortion introduced by the analog filters.
There are several problems to study in order to build this kind of front-end based on a hybrid FB:
1- The design of the synthesis digital FB is based on the correct measurement of the analog FB. Some kind of measurement
technique or blind equalization must be developed in order to measure the filters in place.
2- On previous research we have identified that the hybrid FB can be very sensitive to measurement errors on the analog filters.
Further research should be performed.
3- With a C ognitive Radio, the received signal can be scattered over several spectrum holes. The Hybrid FB can take advantage
of this fact to reduce the number of samples of the digital synthesis filters by optimizing the frequency response of the FB only
over the bands of the holes. In this case, some of the ADC s could be redundant and turned off, reducing even more the power
consuption.
4- The structure of the hybrid filter bank make it a good candidate to integrate in its design spectrum aggregation. We believe
that some of the problems, such as the high PAPR can be solved by performing the spectrum aggregation using a hybrid filter
bank.
5- It can be advantageous to integrate the synthesis FB with the demodulation block. We intend to study this aspect.
6- The size of the analog FB is a key aspect in order to have a useful hybrid filter bank. This is a challenging problem and new
filter design techniques should be found. C eramic filters are good candidates to achieve the required miniaturization.

Mem bers of the research team in this task: (BI) Bolseiro de Investigação (Mestre) 4; Ana Maria Perfeito Tome; José Manuel Neto Vieira; Teófilo José Marques Monteiro;

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Task description and Expected results
This task will be entirely devoted to the study and design of reconfigurable digital hardware components for the cognitive radio
all-digital RF transmitter. In this sense the task will be divided into several sub-tasks focusing on:
- agile high performance all-digital transmitter architectures with advanced signal shaping techniques for superior multichannel
operation as well as for improved bandwidth and noise reduction.
- complete FPGA integration of the flexible transmitter supported by fast reconfiguration approaches.
Sub-task 5.1 – Power Efficient All-Digital Transmitters for C ognitive Radio
In the digital transmitter side, the main focus will be on designing high performance and agile FPGA-based All-Digital Transmitter
architectures suitable for C R-based applications (e.g. exploration of TV white spaces). This requires analyzing the tradeoffs
between important figures of merit, such as SNR, usable bandwidth, linearity and stability in order to propose new techniques
that enable to simultaneously achieve high adaptability, multichannel transmission and power efficiency. Some of the strategies
proposed by the team include the combined use of PWM with multi-level Delta-Sigma Modulation, novel noise cancellation
techniques and efficient exploration of the FPGA reconfigurable hardware resources, but also to study and explore new
approaches for implementing a new transmitter architecture where the tight coupling design of both digital and analog
components will favor the overall performance of the transmitter.
Sub-task 5.2 – FPGA Integration of the All-Digital Reconfigurable Transmitter for NC -OFDM-based C R Systems
This sub-task aims the integration of the results obtained in the previous sub-task with task 4 (Reconfigurable NC -OFDM
Processor for Multimode Spectrum Aggregation) and task 8 (Signal Processing for Hardware Optimization), in order to build a
fully FPGA integrated all-digital NC -OFDM reconfigurable transmitter with embedded digital compensation for improving the
linearity of the radio transmitter.
This sub-task will also address the efficient exploration of the high logic capacity and the heterogeneous resources of modern
FPGAs, as well as the integration of multiple transmitter blocks in the same C R node in order to improve important figures of
merit as flexibility, computational requirements, reconfiguration time, usable bandwidths, linearity, PAPR levels and power
efficiency. In fact, since the NC -OFDM system will use multiple noncontiguous narrower sub-bands, this approach will allow
exploring the partitioning of the transmitter into multiple cells as a way to improve the above mentioned figures of merit.
The work to be performed in this sub-task will benefit from the knowledge of the research team in the topics of FPGA-based upconversion
of GHz range signals, advanced signal shaping algorithms and partial dynamic reconfiguration methodologies.
At the end of this task it is expected that the state of the art will be advanced in the following points:
- Advanced digital signal shaping techniques and corresponding implementation circuits that allow a fully FPGA-based flexible
processing of high bandwidth signals.
- New noise cancellation models and its efficient implementation in reconfigurable hardware for enabling the RF signal
transmission with improved power efficiency and lower filtering requirements but without sacrificing the adaptability.
- Novel baseband to RF up-conversion techniques and corresponding fully integrated FPGA-based realization circuits that allow
using flexible hardware modules for configurable and simultaneous multichannel and multi-standard operation.
- Tight integration of signal shaping and up-conversion techniques with FPGA-based baseband processing engines for high
throughput, low latency and fast reconfiguration times.

Mem bers of the research team in this task: (BI) Bolseiro de Investigação (Mestre) 2; (BI) Bolseiro de Investigação (Mestre) 5; Arnaldo Silva Rodrigues de Oliveira; João
Paulo C astro C anas Ferreira; José Alberto Peixoto Machado da Silva; Manuel José Alves Ventura da Silva; Nelson José Valente
da Silva; Nuno Miguel Gonçalves Borges de C arvalho; WONHOON JANG;

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Task description and Expected results
This task will be entirely devoted to the study and design of reconfigurable digital hardware components for the cognitive radio
transceiver baseband. The novelty of the approach consists in the exploration of innovative NC -OFDM hardware processing
architectures, partial run-time reconfiguration of the system and the on-line capability of designing optimized waveforms
employing custom modulations for each NC -OFDM sub-band. This task will be divided in two sub-tasks focusing on:
- flexible modulation schemes supporting fine grained run-time waveform design for advanced spectrum aggregation systems.
- high efficiency on-line reconfigurable NC -OFDM processing engines based on reconfigurable hardware architectures.
Sub-task 4.1 – Multimode NC -OFDM Processing Engine
The objective of this sub-task is to investigate and validate different approaches that can be used to implement a NC -OFDM
flexible transceiver supporting run-time selection of the active sub-carriers and modulation schemes for each sub-band. This will
allow the fine grained waveform design in spectrum aggregation scenarios based on NC -OFDM approaches while fulfilling
robustness, range, throughput and adaptability requirements.
The adoption of FPGAs as the implementation platform for symbol level processing of NC -OFDM systems allows the exploration
of hybrid hw/sw architectures, flexible integration, run-time adaptation and field upgrades of the transceiver parameters. In the
scope of this sub-task different architectures and implementation approaches will be explored in order to build a very flexible
and high performance NC -OFDM engine, such as, hybrid hardware/software approach based on a heterogeneous architecture
combining FPGA embedded processors enhanced by custom parallel hardware accelerators. Different architectural and
implementation aspects, figures of merit and trade-offs will be analyzed and compared, such as logic complexity, flexibility,
number of OFDM sub-carriers, bandwidth, performance, operating frequency, resource usage, power efficiency and cost.
number of OFDM sub-carriers, bandwidth, performance, operating frequency, resource usage, power efficiency and cost.
Two important aspects of any OFDM receiver implementation are the synchronization and channel equalization, both requiring
further research in the case of NC -OFDM systems due to the increased complexity.
Sub-task 4.2 – FPGA-based Fast Partial Dynamic Reconfiguration Approaches
Higher levels of system adaptability, upgradeability and efficiency can be achieved by means of dynamic partial reconfiguration
of FPGAs, i.e. selectively changing portions of the logic circuit implemented in the FPGA. The objective of this sub-task is to
introduce reconfiguration capacities into the platform for the symbol level processing of the C R transceiver. The reconfiguration
can be partial or complete. Besides its potential advantages in terms of hardware savings and configuration overhead, enabling
dynamic partial reconfiguration of the FPGA remains a challenge, because parts of the circuit logic need to be modified while the
rest of the device is working and processing data. An additional challenge consists in developing approaches to effectively
mitigate or eliminate the latency introduced by the reconfiguration process, both by exploiting configuration communalities and
by using intelligent pre-fetching.
FPGAs with embedded processors can execute Linux-like operating systems providing most of the required features to develop
the dynamic partial reconfiguration framework to manage the adaptability of the NC -OFDM transceiver following a modular
approach, allowing easier upgrades, code reuse and real-time online adaptability.
At the end of this sub-task it is expected that the state of the art will be advanced in the following points:
- Efficient NC -OFDM processing architectures enabling data throughputs compatible with next generation wireless communication
systems.
- Reduction of the reconfiguration times and reactivity improvement of C R transceivers.

Mem bers of the research team in this task: (BI) Bolseiro de Investigação (Mestre) 2; (BI) Bolseiro de Investigação (Mestre) 5; Arnaldo Silva Rodrigues de Oliveira; João
Nuno Pimentel da Silva Matos; João Paulo C astro C anas Ferreira; Manuel José Alves Ventura da Silva; Nelson José Valente da
Silva

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Task description and Expected results
Finally the analog front-end design will devote some effort to the study of antennas specially designed for cognitive radio
approaches. This imposes at least a high bandwidth performance, but also some reconfigurable beam steering approaches for
maximizing antenna gain in certain directions. The steering is fundamental not only for data communication purposes, but also
for power transmission as it will maximize the energy absorption for powering up the RF transceivers.
In what respect to the compact multiband antenna design, one possibility is the use of fractal antennas namely due to the
compact size, multi-frequency operation and wide operation bandwidth. Basically, fractal geometries are self-filling structures
that can be scaled without increasing the overall size. This characteristic provides a chance for antenna designers to explore
more new geometries suitable for small antenna design. Another approach that has been employed in the design of compact
antenna is to introduce lumped elements such as chip inductors directly on the radiation element, which can effectively reduce
the size of the antenna. This is a research topic that appeared recently and currently there is limited research work in this
related field, and will be followed in this project.
Moreover, significant improvements on the transmission rate can be achieved by the integration of MIMO antenna arrays on the
wireless devices, something that has been included in the recent released standards such as IEEE 802.11n and Long Term
Evolution (LTE). This implies that at least two antennas are required to be equipped on one wireless device. In this TSK one
promising technique to be followed is to apply both the neutralizing and reconfigurable techniques on the antenna array. The
principle of the neutralizing technique is to introduce a shorting line to neutralize the current of the two antennas, which in turn
increases their isolation. This technique can also be explained as adding a suspending line to reduce the coupling between two
antennas. Reconfigurable antennas are predicted to be one of the best candidates for future high data rate wireless
communication systems.
Finally the advances in Materials that exhibit novel electromagnetic property that cannot be found in nature are attracting much
attention of the research community. Such structures, known as meta-materials, are designed to have properties and operate in
ways that bulk materials cannot. One example of such microwave metamaterials are electromagnetic band-gap (EBG)
structures. Many researchers are using Metallic Electromagnetic Band Gap (MEBG) on antenna design that exhibits two unique
characteristics: surface wave suppressing when used as EBG surface and in-phase reflection (90 degree to -90 degree) which
can be used as an Artificial Magnetic C onductor (AMC ). Since EBG is a recent technology, improvements on present techniques
for the design of microwave circuits and antennas are continuously being made. Some effort will also be put in this study and its
application to C R transceivers.
In this task it is expected that a strong collaboration exists between the other TSK, and some strategies will change depending
on the findings on other TSK’s.
At the end of this TSK it is expected that the state of the art will be improved in the following topics:
• Wide bandwidth antennas
• Beam steering for wireless power scavenging
• MIMO strategies for increasing data rate transmission
• Meta-material antennas for C R approaches
The task will be based mainly on the expertise of IT-Aveiro team, since the background in the area will allow a faster evolution
time. In this task 3 PhD researchers, 2 PhD students and one of the Bolseiros will devote its time to developed this work.

Mem bers of the research team in this task:(BI) Bolseiro de Investigação (Mestre) 1; João Nuno Pimentel da Silva Matos; Luis Pedro Marques Brás; Nuno Miguel Gonçalves
Borges de C arvalho; Pedro Renato Tavares Pinho; Tiago Miguel Valente Varum;

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Task description and Expected results:
By definition, cognitive radios are supposed to be capable of understanding a wide variety of signals. The problem is that the
communication standards, in use today, were not designed so that a single radio would be able to easily decode them all, and,
hence, the high bandwidth, linearity and large dynamic range are requirements usually associated with cognitive radios.
Improving any one of these key aspects, however, usually adds a significant cost in terms of energy consumption. This may be
acceptable if a steady energy source is always available, but, for battery-powered devices, that is definitely not the case. One
possibility to minimize this problem is to use electromagnetic radiation for actively charge and contribute to the radio front-end
power up. This task will be devoted exactly to study and to propose techniques for electromagnetic energy harvesting and
scavenging, by focusing its study in RF-DC converters, and, also, on power storage that could efficiently link with the RF
transceiver design. In this task the study of the nonlinear process inherent to this RF-DC conversion will be studied, and
combined with the RF front-end design of the previous tasks. So some of the objectives to follow in this task would be:
- Integrating aggressive partial shutdown capabilities into the devices from previous tasks (right at the design stage), so that at
any hardware module is only active when it absolutely needs to;
- The development of software routines for low-level energy management;
- Increasing RF efficiency by identifying and reducing the most significant power losses;
- Taking advantage of multiple non-conventional energy sources, like RF (because it can be fully controlled) and solar (generally
beyond control, yet abundant in many environments and thus worth looking at);
- Optimizing the efficiency of RF-DC c converters to maximize energy collection;
- Addressing issues related with energy storage (in addition to energy harvesting), because the capability to store excess of
energy for later use can be extremely useful;
While the aforementioned energy sources may not be able to produce enough energy to avoid the need for a battery (that would
be the best case scenario), they should be able to, at least, help to reduce its discharge rate substantially. It should be noted
that building high efficiency RF energy harvesters requires equally efficient antennas, and, hence, the design of energy efficient
antennas suitable for RF energy harvesting (coordinated with TSK 3) should also be considered;
In this task it is expected that a strong collaboration exists between among the other TSK,tasks and some strategies will change
depending on the findings on of other TSK’s tasks.
At the end of this TSK task it is expected that the state of the art will be improved in the following topics:
• Energy Efficiency;
• Use of better strategies for reducing energy spending in the radio transceiver;
• Study of collaborative ways between the physical and the higher layers in a transceiver to minimize consumption;
• System design architectures having in mind energy patterns;
• Electromagnetic Energy Harvesting and Scavenging;
• Optimized receivers for Wireless Power Transmission, with special focus on RF-DC converters;
• Extract energy from electromagnetic signals to power up mobile units;
• Integration of Energy Harvesting and All digital radios;
• C ollaborate with the antenna TSK to maximize energy collection;
• Energy Storage;
• Study alternative energy storage mechanism to cope with the energy scavenging circuits;
The task will be based mainly on the expertise of IT-Aveiro and IT-C ovilha team, since the background in the area will allow a
faster evolution time.
In this task 3 PhD researchers, 2 PhD students and one of the Bolseiros will devote its time to participate in the developing of
this work.

Mem bers of the research team in this task: (BI) Bolseiro de Investigação (Mestre) 1; Alírio de Jesus Soares Boaventura; João Nuno Pimentel da Silva Matos; Nuno Miguel
Gonçalves Borges de C arvalho; Pedro Renato Tavares Pinho; Ricardo Dias Fernandes;

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