Andrea Tani

A Low-Complexity Cyclostationary-Based Spectrum Sensing for UWB and WiMAX Coexistence With Noise Uncertainty

This paper focuses on a cognitive radio approach based on a noncooperative spectrum-sensing technique that is suitable for applications in detection and avoidance (DAA) schemes to allow coexistence between ultrawideband multiband (secondary user) and Worldwide Interoperability for Microwave Access (WiMAX; primary user) systems and, hence, improve spectral efficiency. In particular, the cyclostationary property of WiMAX signals due to the cyclic prefix is exploited here. The spectrum-sensing method devised in this paper is a statistical test that relies on cyclostationarity, and it belongs to the class of the single-cycle detector. The performance of the proposed detector, in terms of primary-user detection probability, is derived by computer simulations. The results obtained highlight that the proposed approach enables efficient downlink detection under conditions of low signal-to-noise ratio (SNR) and noise uncertainty. The implementation complexity of the proposed method is also discussed here to highlight advantages with respect to previously proposed alternatives. Finally, an analytical approach is presented to derive the false-alarm probability to allow the implementation of a constant false-alarm rate detector. In addition, the use of an efficient interference-mitigation scheme is also considered to improve the bit-error-rate performance.

Performance Evaluation of a Spectrum-Sensing Technique for Cognitive Radio Applications in B-VHF Communication Systems

This paper deals with a cognitive radio approach based on a noncooperative spectrum sensing technique for applications in a very-high-frequency (VHF) aeronautical communications system to detect idle VHF channels and allocate them to an additional overlay system or secondary users. In particular, the focus here is on a spectrum sensing technique belonging to the class of energy detectors based on the Welch windowed periodogram. The performance of the proposed detector is presented in terms of the missed detection probability of the primary user under different application conditions. The obtained results and resulting implementation complexity highlight better behavior of the proposed detector with respect to alternative schemes previously proposed in the literature on this subject.

Impulse noise mitigation techniques for xDSL systems in a real environment

The demand for broadband communications for high data-rate applications has pushed towards the development of novel access technologies. Even if wireless access networks have gained more importance in the last years, wired access networks still remain the most common alternative for in-home access. In particular, xDSL technology allows a broadband access in domestic environment by exploiting the already deployed Public Switched Telephone Network (PSTN). Within this scenario, one of the most significant drawbacks is the presence of the impulse noise in wired connections. In particular, this is fundamental whenever xDSL is used for carrying high data rate real-time services (e.g., video streaming). Aims of this paper are to present results derived by a measurement campaign over an actual SOHO telephone line and, in addition to this, to propose a suitable detection and mitigation technique for applications in xDSL in-home receivers. Performance comparisons with alternative techniques will be also provided by focusing on real impulses as result of an actual measurement campaign to validate the effectiveness of the proposed solutions.

Performance Evaluation of a Precorrelation Interference Detection Algorithm for the GNSS Based on Nonparametrical Spectral Estimation

This paper deals with a signal processing precorrelation method to detect the presence of interference at a global navigation satellite system (GNSS) receiver site. In particular, a nonparametric spectral estimation approach based on the Welch windowed periodogram will be considered here. The performance of the proposed detector, in terms of detection probability, for a given false-alarm probability value, will be derived by means of an analytical approach and resorting to computer simulations. A performance comparison with previously proposed precorrelation methods will also be presented in order to highlight the better behavior of the proposed approach that makes it suitable for safety of life (SoL) applications.

Container effects on growth and biomass allocation in Quercus robur and Juglans regia seedlings

Container size and shape impacts biomass allocation of nursery seedlings. Effects of different pot types on shoot and root growth and biomass allocation were evaluated in nursery cultivation of Quercus robur L. and Juglans regia L. We compared two containers currently used in Italian forest nurseries (ISSA-pot®; Plastecnic®) and two alternative types (Superoots Air-pot®; Tubex®); different pot sizes were also included: two for ISSA-pot and Plastecnic; four for Air-pot. Seedlings were evaluated during 1-year nursery growth and biomass allocation was determined on a sub-sample at the end of the growing season. For both species, seedlings grown in larger containers generally grew more and containers >4.5 l produced the largest seedlings. Root biomass was >50% of total biomass in all containers with the tap-root comprising the major root system component. Air pruning in the Air-pots inhibited seedling growth of both species in narrow deep pots, while in bigger sizes (wide and deep) it produced positive responses, especially for walnut. Container configuration differentially affected the studied species: shoot and root system development of walnut seedlings was more limited by pot diameter than depth. Q. robur had improved shoot and root system development when grown in Tubex.

Relation of Fraxinus excelsior seedling morphology to growth and root proliferation during field establishment

Abstract The demand for hardwood seedlings has increased in recent years in Italy, particularly for tree farming programmes oriented towards quality wood production; the availability of high-quality seedlings is a crucial step towards being successful in establishing such productive plantations. The aim of this work was to identify the most important morphological seedling quality attributes. Nursery stock consisting of 1-year-old bareroot Fraxinus excelsior seedlings was evaluated for field performance at the end of the first growing season on a plantation site in the Po Valley, northern Italy, in relation to the objective of producing high-quality timber plantations. The approach consisted of (1) morphological characterization (i.e. stem height, root collar diameter, shoot and root architecture) of the seedlings before outplanting; (2) morphological assessment (including root excavations) of the plants after the first year of field growth; (3) relating attributes observed during phases (1) and (2); and (4) identifying those morphological characteristics that effectively predict outplanting success. The results indicate that the highest quality seedlings are best selected on the basis of initial shoot height and root system morphological type (i.e. stem heights 40–50 cm with a fasciculate root system of at least 40 cm length and rich in fine roots). Planting these seedling morphological types may dramatically improve field performance (i.e. more than 100% increase of height increment in this case), which will help to promote the development of afforestation plantations oriented towards high-quality wood production.

Performance evaluation of an interference cancellation receiver for noncoherent optical CDMA systems

A multiuser detection scheme is presented, which is based on the interference cancellation principle for noncoherent optical direct-sequence code division multiple access (CDMA) systems. The performance of the proposed receiver, in terms of bit error probability, is derived by means of an analytical approach. Simulation results are also reported in order to validate the analytical predictions. Performance comparisons with the classical matched filter receiver and other non-coherent optical CDMA (OCDMA) receivers already proposed in the literature are discussed in order to highlight the good behavior of the receiver scheme under consideration.

A Low-Complexity Cyclostationary Spectrum Sensing for Interference Avoidance in Femtocell LTE-A-Based Networks

This paper focuses on a new spectrum sensing algorithm based on the exploitation of the primary signal cyclostationarity property, which is used to avoid the intercell interference in a heterogeneous Long-Term Evolution Advanced (LTE-A) network. The performance of the proposed spectrum sensing method will be evaluated by means of a suitable analytical approach whose accuracy will be validated by comparing analytical predictions with simulation results under different communication channel propagation conditions. Furthermore, it will be shown that the proposed approach requires the lowest computational complexity among the cyclostationarity-based methods and allows better performance, even in the case of noise uncertainty, in terms of false alarm, detection probability, and deflection coefficient.

Performance Evaluation of an Efficient and Reliable Multicast Power Line Communication System

Power line communication technology receives today a renewed attention for a wide class of advanced applications and services, thanks to the advantage of using the existing electrical infrastructure, which requires only limited deployment costs. However, wires have been originally designed for power and not for data, and signal propagation is affected by several impairments such as impulsive noise and frequency selectivity. On the other end, new emerging application perspectives-mainly related to the smart grid or Internet of Things paradigms-need reliable unicast and/or multicast information delivery methodologies. This paper deals with an efficient multicast power line communication system based on the use of a decision direct impulsive noise mitigation scheme and of multiple transmissions of symbols in the frequency domain, allowing an efficient exploitation of the communication channel frequency diversity. The performance of the reliable multicast power line communication system is derived by resorting to the application of the absorbing Markov chain theory in terms of mean overall delivery delay and throughput, in relation to different application scenarios. Moreover, a suitable optimization procedure is also proposed here in order to achieve the best performance. The advantages of the proposed optimized reliable multicast power line communication system are finally validated by comparisons with a classical system.

An efficient network coding scheme for reliable multicast power line communications

Abstract Nowadays, Power Line Communication (PLC) technology is receiving a renewed attention for a wide class of innovative applications and services, mainly thanks to the advantage of using the existing electrical infrastructures, thus reducing the deployment costs. However, such electrical infrastructures have been originally conceived for power distribution and not for data. Hence, signal propagation is affected by more severe impairments than traditional media, such as impulsive noise and frequency selectivity. Furthermore, new emerging PLC applications need more efficient information delivery schemes that encompass both unicast and multicast mode. Towards this end, this paper deals with an efficient Network Coding (NC) based multicast reliable PLC scheme that makes use of (i) a decision direct impulsive noise mitigation approach and of (ii) a scheme based on multiple transmissions of a same symbols in the frequency domain. A suitable optimization procedure is also proposed here with the aim of improving the performance of the proposed scheme, under the constraint of a specified maximum data flow delivery failure probability. Finally, comparisons with alternative solutions are provided in order to highlight the significant advantages of the proposed scheme in terms of data flow delivery delay and overall transmission energy cost, under specific service constraints.