Maurizio Murroni

Optimization of Non-Convex Multiband Cooperative Sensing With Genetic Algorithms

In cognitive radios (CRs), secondary users (SUs) transmit alongside primary users (PUs). In order to avoid interference SU perform spectrum sensing and adaptive transmission. Reliable detection in wide geographical regions needs to perform collaborative sensing. The state of the art for efficient cooperative sensing is linear statistics combination. Spatial-spectral joint detection also provides multiband cooperative sensing to access opportunistically several bands at a time. Convex maximization is able to solve only an approximation of the optimization within a restricted solution domain, due to its non-convex nature. In this paper, we demonstrate that convex constraints are counterproductive and we propose an alternative optimization technique based on genetic algorithms. The genetic programming performs direct search of the optimal solution one step before the reformulations needed previously. We demonstrate that, by operating directly on the objective and abstracting from the convexity, the collaborative multiband sensing is optimized consistently with the problem formulation.

On the feasibility of unlicensed communications in the TV white space: Field measurements in the UHF band

In practical unlicensed communications in TV band, radio devices have to identify, at first, the transmission opportunities, that is, the portion of the spectrum licensed for broadcasting services unoccupied in a certain region at certain time, that is, the so-called TV white space. In this paper the outcome of field measurements in the UHF TV band (470–860 MHz) conducted in EU is presented. To obtain empirical values for the parameters upon which unlicensed radio devices are able to distinguish in a real scenario between empty and occupied TV channels, signal power measurements have been performed in Italy, Spain, and Romania on rural, suburban, and urban sites, at different heights over the ground by using different analysis bandwidths. The aim of this work is to provide a set of practical parameters upon which harmless unlicensed communication in the UHF TV white space is feasible. The results have been analyzed with respect to the hidden node margin problem, spectrum sensing bandwidth, and occupancy threshold.

Performance analysis of fractal modulation transmission over fast-fading wireless channels

Fractal modulation schemes have been under investigation for signal transmission over time-varying channels because of their advantages in data transmission at different frequency bands. This also allows efficient reception when channel conditions are varying by selecting the optimal frequency/time resolution based on the current channel condition. We present a performance analysis of fractal modulation transmission over Rician fast-fading channels in the presence of AWGN. A quadrature transmission scheme is simulated and compared, in terms of error robustness, to a QAM transmission system. Other papers analysing fractal modulation system performance do not consider time-varying channels, which are important as they represent the main configuration for communication systems based on this modulation technique. The novelty of our paper lies in the comparison of a fractal modulation system to a QAM one (core of the OFDM modulation technology, extensively used in broadcasting) using a testbed simulation environment where additive noise and fast fading are considered as typical error sources for transmission over wireless channels. Several wavelet families for a fractal modulation scheme have been considered and performance for each one measured; results reported show the effectiveness of the fractal modulation paradigm and confirm its effective utilization in data broadcasting.

Integration of renewable energy sources, energy storage systems, and electrical vehicles with smart power distribution networks

In order to increase efficiency in the distribution of electrical energy, optimize energy consumption and increase the percentage of energy from renewable sources, thereby reducing emissions of greenhouse gases, the distribution networks and the equipment connected to them should be made more intelligent. The development of the future energy system will be based on planning and management of the distribution system in accordance with the philosophy of Smart grid (SG). This approach involves the extensive use of Information and Communication Technology (ICT) and innovative control systems in order to enable the realization of smart distribution systems, the active participation of demand, the availability of energy storage, as well as the integration of renewable energy sources (RES) and Distributed Generation (DG), as well as the growing number of electric vehicles. In the paper a review of the main current challenges and possible solutions to open problems in the development of smart distribution grids are presented.

PAPR reduction in multicarrier modulations using Genetic Algorithms

This work presents a novel approach to the reduction of Peak-to-Average Power Ratio (PAPR) in multicarrier modulation: Partial Transmit Sequence (PTS) is optimized by opportune tailored Genetic Algorithms (GA) which allow achieving solution with pre-selected accuracy and reduced computational burden. A comparative study on both Orthogonal Frequency Division Multiplexing (OFDM) and Wavelet Packets Multi-Carrier Modulation (WP-MCM) has been conducted. Results show that although WP-MCM outperforms conventional OFDM schemes in terms of PAPR, GA applied to PTS are more effective in reducing PAPR for OFDM rather than for WP-MCM.

TV white spaces exploitation for multimedia signal distribution

The new spectrum regulation policies for dynamic spectrum access, especially those concerning the use of the white spaces in the Digital Terrestrial Television (DTT) bands, arise the need for fast and reliable signal identification and classification methods. In this paper we present a two-stage identification method for signals in the white spaces, using combined energy detection and feature detection. The band of interest is divided by means of the Discrete Wavelet Packet Transformation (DWPT) in sub-bands where the signal power is calculated. Modulation classifiers taking into account the statistical parameters of the signal in the wavelet domain are used as features for identifying the modulation schemes, in this case specifically for the DVB-T broadcast standard. Finally, a signal transmission architecture based on Motion JPEG XR has been implemented in order to explore and evaluate a practical application of indoor signal distribution over white-spaces.

Co-Channel and Adjacent Channel Interference and Protection Issues for DVB-T2 and IEEE 802.22 WRAN Operation

This paper presents a study on the coexistence issue of digital terrestrial TV broadcasting and cognitive broadband access operation in the TV white spaces (TVWS). Extended measurements were performed to evaluate the protection of the existing Second generation of digital video broadcasting terrestrial standard (DVB-T2) services in the presence of IEEE 802.22 WRAN co-channel and adjacent channel interference. The absence of picture failure over 30 consecutive seconds on decoded DVB-T2 streams has been monitored to obtain the maximum tolerable level of IEEE 802.22 WRAN interference, which ensures the protection of the primary broadcast system. This paper considers practical DVB-T2 system configuration options by varying parameters of the standard, such as constellation and code rate, FFT size, pilot pattern and guard interval, and rotated constellations and compares them in terms of robustness with respect to the interference generated by IEEE 802.22 WRAN operation. The goal is to provide cognitive broadband operators in the TVWS with guidelines to optimize their network by choosing the parameters that best fit their needs in case of coexistence with DVB-T2 broadcasting services.

An Unlicensed Indoor HDTV Multi-Vision System in the DTT Bands

Multimedia contents distribution through wireless networks in the home environment is a challenging issue. At present, several systems are proposed mainly relying on 802.11g/n standards which offer adequate bandwidth for HD video contents. However, the rapid revolution in wireless communication in past years has increased the demand of radio spectrum to fulfill the requirements of wireless applications, leading to spectrum overcrowding. The licensed-free ISM band is now overexploited and experiences serious coexistence issues. However, the transition from analog to digital TV is in progress worldwide and digital switchover plans have driven a thorough review of TV spectrum exploitation. Huge debates are taking place within the wireless world about the possible exploitation of the unused portion of the TV spectrum. Within this framework, this paper proposes a multi-vision system working on the TV band for the short-range indoor transmission of HDTV contents. The proposed system relies on geo-location databases for the TV band, it is based on the OFDM core technology and it is compliant with the DVB-T/T2 standard for HDTV. The authors investigated the feasibility of the system whereas preserving the integrity of incumbent services: computer simulations have been supported by hardware implementations on USRP2 SDR board for test-bed measures and transmission in real conditions.

Opportunistic Wideband Spectrum Sensing for Cognitive Radios with Genetic Optimization

In cognitive radios (CR) secondary users (SU) transmit alongside primary users (PU). In order to avoid interference SU perform spectrum sensing and adaptive transmission. Ultra-wideband sensing is of primary importance to sense and access opportunistically several bands at a time. The state of the art for opportunistic wideband sensing is given by Multiband Joint Detection (MJD). Constraints on interference and utilization have to be imposed to solve the multiband optimization with convex maximization. In this paper we propose an alternative optimization technique based on the genetic algorithms. The genetic programming performs direct search of the optimal solution one step before the aforementioned mathematical limitations. By operating directly on the objective of the optimization we show that the wideband sensing problem can be solved consistently with the problem formulation and without limitations.

Slow motion replay of video sequences using fractal zooming

The purpose of This work is to present a technique combining fractals and wavelet transform to obtain a selectively pleasant zoom and slow motion of digital video sequences. Active scene detection and post processing are used to reduce computational cost and improve visual quality respectively.