1,721,004 research outputs found
Spectrum sensing in the DVB-T Bands using Combined Energy Detection and Signal Classification in the Wavelet Domain
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TV white spaces exploitation for multimedia signal distribution
No full textThe 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
Robust multi-rate modulation for cognitive radio communications over land mobile satellite channel at Ku-band
Full text linkThe usable satellite spectrum is becoming scarce because of continuously increasing demand for broadcast, multimedia and interactive services. Because of the extensive use of predictive coding, multimedia data exhibit different sensitivities to transmission errors, which makes them suitable for unequal error protection (UEP) techniques. UEP mainly relies on differentiated error control coding which raises the robustness of data, but also increases the transmission bandwidth, which can be unwanted in case of limited resources often occurring in satellite communications. In this context, cognitive radio (CR) satellite communications has received important attention lately in the research community. In multi-rate modulations (MRM), the properties of dy-homogeneous signals are exploited to transmit over multiple band frequencies and time scales. MRM have been proved to be effective on unknown channels either in bandwidth or time. These conditions occur in CR networks where opportunistic communications are set up while preserving primaries licensed users. In CR, the uncertainty of transmission opportunity makes the use of error correcting codes not trivial. Therefore, to achieve robustness, this work proposes unequal power allocation (UPA) over the symbols of MRM according to both data sensitivity to channel errors and spectrum availability. As optimization criterion, the mean square error between the original and the decoded message, which has shown strong correlation with subjective perception, is used. To assess the effectiveness of the proposed scheme in realistic condition for CR satellite networks, the Land Mobile Satellite (LMS) model at Ku-band is used to reproduce the memory associated with real channels. The non-linearity of the satellite channel because of high power amplifier (HPA) prior to transmission has been accounted using the Saleh model. Copyright © 2016 John Wiley & Sons, Ltd
An Unlicensed Indoor HDTV Multi-Vision System in the DTT Bands
No full textMultimedia 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
Enabling a Scalable and Adaptive Cloud Infrastructure for Virtual Users in the Social Internet of Things
No full textThe Internet of Things (IoT) is a global network of intelligent interconnected objects, enabling remote recognition, detection, and control. Through virtualization, these devices exchange knowledge in the Cloud, bridging physical and virtual worlds. However, the rapid growth in connected objects and data production necessitates innovative system designs. While virtualization offers scalability and flexibility, it proves insufficient alone. Recent studies recommend integrating social network concepts into IoT, forming the Social Internet of Things (SIoT). SIoT, mirroring human social networks, enhances smart devices with relational capabilities, addressing challenges in managing the surge in connected devices. This paper introduces the "Virtual User" concept-an autonomous entity streamlining user-device interactions in the digital realm. The research proposes, elucidates, and evaluates a Cloud infrastructure integrating the Virtual User into the SIoT paradigm. This novel approach offers a modular, extendable, and secure communication platform, marking the first Cloud solution tailored for the Virtual User concept, leveraging SIoT virtualization through containerization and automated service setup processes
Coexistence issues for IEEE 802.22 WRAN and DVB-T2 networks
No full textCognitive Radio systems have been studied to be deployed especially in the so-called TV White Spaces (TVWS) which are defined as the TV free channels left unused in specific territorial area as direct consequence of the digital switchover plans. The IEEE 802.22 Wireless Regional Area Network (WRAN) standard has been developed to exploit the TVWS bands to assure broadband access for remote and rural areas. WRAN devices are designed to operate in the frequency range 54-862MHz alongside Digital Terrestrial Television (DTT) transmissions. This paper studies the influence of adjacent channel interference of DTT signals on IEEE 802.22 WRAN transmission. The performance of IEEE 802.22 WRAN devices in the presence of with DVB-T2 broadcasting systems is evaluated
Multi-rate modulation for cognitive radio over land mobile satellite channel
No full textMultiple transmission of heterogeneous multimedia services is a central aspect of satellite communication technology. In this framework, often the design of efficient communication systems is complicated by stringent bandwidth constraint. Due to the extensive use of predictive coding, compressed data exhibit different sensitivities to transmission errors which makes them suitable for unequal error protection (UEP) techniques. UEP mainly relies on differentiated error control coding which raises the robustness of data, but also increases the transmission bandwidth. Reed-Solomon (RS) or Turbo Codes (TC) are frequently used, but also more performing techniques, based on Rate-Compatible (RC) codes have been proposed by the research community. In multi-rate modulations (MRM) the properties of dy-homogeneous signals are exploited to transmit over multiple band frequencies and time scales. MRM have been proved on unknown channels in either bandwidth or time. These conditions occur in cognitive radio (CR) networks where opportunistic communications are set up while preserving primaries licensed users. In CR the uncertainty of transmission opportunity makes the use of error correcting codes not trivial. Therefore, to achieve robustness this work proposes unequal power allocation (UPA) over the symbols of MRM according to both data sensitivity to channel errors and spectrum availability. As optimization criterion the mean square error between the original and the decoded message, which has showed strong correlation with subjective perception, is used. To assess the effectiveness of the proposed scheme in realistic condition for CR satellite networks the Land Mobile Satellite (LMS) model is used to reproduce the memory associated with real channels
A cognitive radio indoor hdtv multi-vision system in the TV white spaces
No full textThis paper proposes a cognitive radio (CR) indoor distribution system of HDTV contents in the TV white spaces, with immediate implementations as home entertainment system. A proof-of-concept digital terrestrial television (DTT) compliant prototype has been implemented on a test-bed based on commercial DTT receivers in combination with software defined radio (SDR) hardware devices. Extended measurements performed in real indoor environments assessed the feasibility of the proposed system with respect to the protection of the existing broadcasting TV services. © 2012 IEEE
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