This study shows why bubble volume is a much better indicator of SonoVue's efficacy than is bubble count. A low threshold in diameter was found for SonoVue microbubbles at approximately 2 microm, under which size bubbles do not contribute appreciably to the echogenicity at medical ultrasound frequencies.

No abstract

Ultra narrow band transmission (UNB) systems have already been deployed and have proved to be ultra-efficient for point-to-point communications. This paper presents this technology and gives some insights on the scalability of UNB for a multi-point to point network. This configuration corresponds to an uplink scenario where multiple nodes compete to send their packets, with neither coordination nor feedback from the sink. In particular, we present and analyze two multiple access schemes based on random frequency selection: discrete random FDMA (DR-FDMA) and the new continuous random FDMA (CR-FDMA). An ideal system where the carrier frequencies are exactly obtained is first considered and extended to a more realistic case, with rough carrier frequencies. We analyze the system performance in terms of bit error rate and outage probability. The presented results clearly show that, even if in the ideal case, the DR-FDMA scheme outperforms the CR-FDMA scheme; in the realistic case, both schemes lead to similar performance. Thus, this paper highlights the fact that the use of CR-FDMA is very relevant in a realistic network as it bypasses the need of an accurate carrier frequency control, and thus permits the use of even the cheapest transmitters without loss of performance.

Recent advances in information theory have provided achievability bounds and converses for the coding rate for the finite blocklength regime. In this paper, recent results on the non-asymptotic coding rate for fading channels with no channel state information at the transmitter are exploited to analyze the goodput in additive white Gaussian noise (AWGN) and the energy-efficiency spectral-efficiency (EE-SE) tradeoff where the fundamental relationship between the codeword length and the EE is given. Finally, the true outage probability in Ricean and Nakagami-m block fading channels is investigated and it is proved that the asymptotic outage capacity is the Laplace approximation of the average error probability in finite blocklength regime.

No abstract

No abstract

No abstract

Abstract-Recent years have witnessed a tremendous growth of research in the field of wireless systems and networking protocols. Consequently, simulation has appeared as the most convenient approach for the performance evaluation of such systems and several wireless network simulators have been proposed in the last years. However, the complexity of the wireless physical layer (PHY) induces a clear tradeoff between the accuracy and the scalability of simulators. Thereby, the accuracy of the simulation results varies drastically from one simulator to another. In this paper, we focus on this tradeoff and we investigate the impact of the physical layer modeling accuracy on both the computational cost and the confidence in simulations. We first provide a detailed discussion on physical layer issues, including the radio range, link and interference modeling, and we investigate how they have been handled in existing popular simulators. We then introduce a flexible and modular new wireless network simulator, called WSNet. Using this simulator, we analyze the influence of the PHY modeling on the performance and the accuracy of simulations. The results show that the PHY modeling, and in particular interference modeling, can significatively impact the behavior of the evaluated protocols at the expense of an increased computational overhead. Moreover, we show that the use of realistic propagation models can improve the simulation accuracy without inducing a severe degradation of scalability.