Luca De Nardis

(UWB) 2 : uncoordinated, wireless, baseborn medium access for UWB communication networks

A MAC protocol for Ultra Wide Band (UWB) radio networks named (UWB)2 is proposed. The algorithm exploits typical features of impulse radio such as large processing gain, and is conceived in conjunction with a synchronization strategy which foresees the presence of a synchronization sequence in each transmitted packet. (UWB)2 adopts a pure Aloha approach; Performance analysis of the synchronization tracking mechanism showed in fact that under the preliminary simplistic hypothesis of an AWGN channel, and for a sufficient number of pulses in the synchronization sequence, a fairly high probability of successful synchronization can be achieved, even in the presence of several users and Multi User Interference (MUI). The multiple access scheme is based on the combination of a common control channel provided by a common Time Hopping (TH) code with dedicated data channels associated to transmitter specific TH codes.Results obtained by simulation indicate that (UWB)2 can be successfully applied when the number of users spans from a few tens to about one hundred, for data rates ranging from a few thousands to a few hundreds of bits per second. Network throughput was above 99.8% in all considered simulation settings. Such achievement confirms that (UWB)2 is a suitable and straightforward solution for large networks of terminals using impulse radio for transmission at low bit rates.

Cognitive Satellite Terrestrial Radios

In this paper we present the concept of cognitive satellite terrestrial radios (CSTR) for hybrid satellite-terrestrial systems (HSTS). The cognitive radio (CR) technology is being motivated by the radio regulatory bodies for efficient utilization of the radio spectrum. The future satellite ground terminals therefore need to integrate and co-exist with the spectrally crowded terrestrial wireless systems and hence we propose the idea of CSTR. The key issues are addressed and the concepts of developing CR based satellite ground terminals in HSTS for dynamic spectrum access on the ground are presented. Furthermore, the concept of 3D-Spatial reuse of the spectrum is also presented using the CSTR considering low elevated satellite ground stations. Two particular HSTS applications to illustrate the CSTR concept, a) the hybrid satellite-UWB (ultra wideband) communication system for personal area networks (PAN) with short range on ground communications, and b) the hybrid satellite-WRAN (wireless regional area networks) for long range on ground communications are presented. In both the applications the satellite uplink and the terrestrial radios adopt the CR functionalities. The key enabling technologies and their integrated architecture for the CSTR are also presented.

Cognitive radio for medical body area networks using ultra wideband

Wearable wireless medical sensors beneficially impact the healthcare sector, and this market is experiencing rapid growth. In the United States alone, the telecommunications services market for the healthcare sector is forecast to increase from

UWB body area network coexistence by interference mitigation

7.5 billion in 2008 to

Tuning UWB signals by pulse shaping: towards context-aware wireless networks

11.3 billion in 2013. Medical body area networks improve the mobility of patients and medical personnel during surgery, accelerate the patients¿ recovery, and facilitate the remote monitoring of patients suffering from chronic diseases. Currently, MBANs are being introduced in unlicensed frequency bands, where the risk of mutual interference with other electronic devices can be high. Techniques developed during the evolution of cognitive radio can potentially alleviate these problems in medical communication environments. In addition, these techniques can help increase the efficiency of spectrum usage to accommodate the rapidly growing demand for wireless MBAN solutions and enhance coexistence with other collocated wireless systems. This article proposes a viable architecture of an MBAN with practical CR features based on ultra wideband radio technology. UWB signals offer many advantages to MBANs, and some features of this technology can be exploited for effective implementation of CR. We discuss the physical and MAC layer aspects of the proposal in addition to the implementation challenges.

Combining UWB with Time Reversal for improved communication and positioning

This work analyzes the performance of a BAN composed of IEEE 802.15.4a Ultra Wide Band (UWB) sensors in terms of Bit Error Rate (BER), BAN throughput and network lifetime. The BAN performance is evaluated in presence of an external Low Data Rate (LDR) interfering network, that we suppose represented by a second BAN operating in the same hospital room. Coexistence between the two wireless networks is discussed and the reference BAN performance is improved by the adoption of an optimized time hopping code assignment strategy. A possible strategy to extend the lifetime of the network is also introduced.

Cognitive Radio and Networking for Cooperative Coexistence of Heterogeneous Wireless Networks

Tuning spectra by pulse shaping is feasible in both impulse radio (IR) and continuous radio transmissions, since, as well known, the impulse response of the pulse shaper affects the spectral properties of radiated signals. What is peculiar to IR-UWB, and makes pulse shaping particularly appealing, is the impulsive nature of the carrier. Given their very short duration, transmitted pulses in different intervals overlap neither on clock beats nor in between two clock beats. Spectrum matching in IR can thus be restricted with reasonable approximation to a single inter-pulse interval, and as such be redirected in a rather straightforward way into a waveform representation problem.This paper analyzes the above problem of tuning radiated IR-UWB signals to reference spectral patterns by pulse shaping, and shows the correspondence between spectrum and waveform matching problems. Examples of application include three case studies: matching the FCC emission masks, mitigating interference in the ISM bands, and reducing inter-system interference for two coexisting UWB networks. The proposed approach goes beyond the signal processing analysis to tentatively propose a procedure and related protocol for integrating spectral adaptation mechanisms into network operating principles.

Mobility-aware design of cognitive radio networks: Challenges and opportunities

This work investigates the use of Time Reversal (TR) applied to UWB systems for communication and positioning applications. Potential performance boosts, that are achievable over a single UWB communication link by the sole adoption of TR, are investigated. In the case of multiuser UWB communications, it is shown that TR modifies the distribution of Multi User Interference (MUI) and that further performance improvement can be obtained by adapting the receiver to the specific MUI distribution characteristics. As regards UWB positioning, an enhancement in position estimation accuracy can be achieved when TR reinforces DOA estimation thanks to increased robustness to decreased homogeneity in the propagation medium.

Clustered hybrid energy-aware cooperative spectrum sensing (CHESS)

COST Action IC0902, “Cognitive Radio and Networking for Cooperative Coexistence of Heterogeneous Wireless Networks”, was launched in December 2009 and coordinates and integrates the research activities on cognitive radio and networks of more than 60 institutions and research projects throughout Europe and worldwide, involving more than 200 researchers. IC0902 aims at becoming the reference point in Europe for research on cognitive radio, leading to the creation of a European platform for cognitive radio and networks by addressing all major technical challenges related to cognitive radio networks design and deployment. One of the major research topics addressed in IC0902 is the operation of cognitive devices in the TV White Spaces. In this work recent results obtained in the framework of IC0902 on the design and deployment of positioning systems in the TV White Spaces are presented. A comparison between traditional Wi-Fi-based positioning systems working in the ISM band and TVWS positioning systems is carried out by means of computer simulations, and results show that the favourable propagation conditions characterizing the TVWS frequencies may lead to better positioning accuracy with the additional benefit of lower transmit power levels.

Energy efficiency in future wireless networks: Cognitive radio standardization requirements

This work deals with mobility-related issues in cognitive radio network design. With few notable exceptions, research activity on cognitive radio networks focused until now on the case of static networks, neglecting to take into account the impact of mobility on network design. In this work the key issues posed by mobility at the different layers of the protocol stack are discussed, and a case study focusing on routing in cognitive Ultra Wide Band networks is presented, in order to quantitatively assess the impact of mobility on network performance. Next, existing solutions for mobility management in cognitive networks are reviewed, and open issues and future research lines for mobiler cognitive network design are identified. The analysis leads to the conclusion that mobility-related issues should be addressed from a network-wide point of view, taking advantage of terminal cooperation at the local and global level in order to effectively manage mobility in cognitive networks.