The home wireless networking is booming thanks to the rapid progress of wireless technologies and adoption of broadband. Next generation smart homes consist of a wide range of devices that will have radio receivers to enable control, monitoring, and easy configuration. Since most of these devices operate in ISM bands that are becoming congested, leading to capacity and interference limitations, new solutions to increase capacity need to be found. The digital switchover of TV broadcasting services has induced a review of the Ultra High Frequency (UHF) spectrum, releasing free channels in each territorial area, the so called “TV White Spaces” (TVWS). Huge debates are taking place within the wireless world among broadcasters, mobile operators, Internet service providers, and normative organizations about the possible utilization of the TVWS to deliver new services. From the technical viewpoint, new spectrum allocation techniques have been studied to exploit the TVWS, such as the dynamic spectrum access and Cognitive Radios (CRs). MCLab researchers performed signal power measurements in several European Countries on rural, suburban, and urban sites, providing a set of practical parameters upon which harmless unlicensed communication in the UHF TVWS is feasible. The MCLab investigates these issues in the following areas: CR applications for new broadcast services, D2D applications for vehicular communications, opportunistic communications.
- Cognitive Radios
To exploit the TVWS, dynamic spectrum access solutions based on Cognitive Radio (CR) technology has been proposed. MClab researchers have conducted several studies on detection techniques (i.e., spectrum sensing), compatibility problems, man made noise, and hidden node problem to investigate communications in the TVWS. Within the CR paradigm, the first full CR standard, the IEEE 802.22 Wireless Regional Area Network (WRAN), has been developed to bring wireless broadband access to remote and rural areas where other wireless networks, such as 3G/4G cellular networks or WAN, are not present due to low revenue impact or critical network deployment. We modelled the IEEE 802.22 WRAN PHY layer on the transmitter and receiver side to transmit real standard compliant signals and to receive evaluating the bit error rate (BER) in the presence of DVB-T2 transmissions; also the link budget for the coexistence in the first adjacent channel was evaluated.
An intense research activity around the potential applications of CR technology in the IoT field is being produced in the last years. Actually, the use of TVWS radio resources through the exploitation of CRs cooperating with other smart objects is being studied to allow new TV services in smart home environment.
- Veihicular communications
Vehicular Ad-hoc NETworks (VANETs) are wireless networks with constantly changing network topology, due to the mobility of the nodes. Vehicular communications can benefit from the opportunistic spectrum usage with CR technology, using additional spectrum opportunities in TV bands according to the QoS requests of the applications. Actually, VANETs use the IEEE 802.11p standard operating in the 5.9-GHz ISM band reserved for intervehicular and vehicleto-roadside BS wireless communication, for safety and traffic information and monitoring systems in urban environments. There is insufficient spectrum for reliable exchange of safety information over congested urban scenarios through the use of cooperative spectrum sensing provided by cars, used to locate white channels in the ISM bands. To solve this drawback, we proposed the use of TVWS to implement opportunistic ad-hoc short-range and low-power communication systems, such as systems based on the IEEE 802.11p standard. A coexistence study between VANETs communications based on IEEE 802.11p standard adapted to operate in the TVWS and DTT services based on DVB-T2 has been performed. Actually, MClab researchers are considering Device to Device (D2D) applications for vehicular communications especially to address mobility issues in smart cities. The use of radio resources opportunistically through the exploitation of CR is expected to increase the efficiency and reliability in D2D and Device to Internet communications.