On the shock thickness for a binary gas mixture

We discuss the structure of the shock wave solution for a system of Navier–Stokes equations, obtained as hydrodynamic limit of a BGK description of the dynamics of monoatomic gases at kinetic level. We investigate first the thickness of the transition region of the shock profile for a monoatomic gas, for varying Mach number and different physical options for the viscosity coefficient. The analysis is then extended to a binary gas mixture. Some numerical results for noble gases are presented and discussed

Wireless sensor networks: performance analysis in indoor scenarios

We evaluate the performance of realistic wireless sensor networks in indoor scenarios. Most of the considered networks are formed by nodes using the Zigbee communication protocol. For comparison, we also analyze networks based on the proprietary standard Z-Wave. Two main groups of network scenarios are proposed: (i) scenarios with direct transmissions between the remote nodes and the network coordinator, and (ii) scenarios with routers, which relay the packets between the remote nodes and the coordinator. The sensor networks of interest are evaluated considering different performance metrics. In particular, we show how the received signal strength indication (RSSI) behaves in the considered scenarios. Then, the network behavior is characterized in terms of end-to-end delay and throughput. In order to confirm the experiments, analytical and simulation results are also derived

Performance analysis of multi-hop framed ALOHA systems with virtual antenna arrays

We consider a multi-hop virtual multiple-input-multiple-output system, which uses the framed ALOHA technique to select the radio resource at each hop. In this scenario, the source, destination and relaying nodes cooperate with neighboring devices to exploit spatial diversity by means of the concept of virtual antenna array. We investigate both the optimum number of slots per frame in the slotted structure and once the source-destination distance is fixed, the impact of the number of hops on the system performance. A comparison with deterministic, centralized re-use strategies is also presented. Outage probability, average throughput, and energy efficiency are the metrics used to evaluate the performance. Two approximated mathematical expressions are given for the outage probability, which represent lower bounds for the exact metric derived in the paper

Markov chain-based analysis of multihop IEEE 802.15.4 wireless networks with finite node buffers

In this paper, we propose a Markov chain-based analytical framework for modeling the behavior of the medium access control (MAC) protocol in IEEE 802.15.4 wireless networks. Two scenarios are of interest. First, we consider networks where the (sensor) nodes communicate directly to the network coordinator. Then, we consider scenarios where (sensor) nodes communicate to the coordinator through an intermediate relay node, which forwards the packets received from the sources (i.e., the sensors). In both scenarios, no acknowledgment messages are used to confirm successful data packet deliveries, and communications are beaconed (i.e., they rely on synchronization packets denoted as “beacons”). In all cases, our focus is on networks where the relay and the source nodes have finite queues (denoted as buffers) to store data packets. Network performance is characterized in terms of aggregate network throughput and packet delivery delay. Our results show a very good agreement between the proposed analytical model and realistic ns-2 simulation results. In particular, the impact of the buffer size is accurately taken into account in our model

Joint channel decoding in non-cooperative block-faded orthogonal access schemes

none3noIn this paper, we study the performance of non-cooperative wireless multiple access systems with noisy separated channels, where correlated sources communicate to an access point (AP) in presence of block-faded links. Our goal is to explore the potential benefits which can be obtained when source correlation is exploited at the AP, comparing the performance with that obtained by using distributed source coding (DSC) at the nodes. We consider both the average bit error probability and the outage probability as performance indicators, and we derive a theoretical approach to evaluate their limits. Our results show that the improvement brought by the exploitation of the correlation at the AP is more evident when the correlation becomes sufficiently high. Moreover, some simulation results are presented for two classes of channels codes: serially concatenated convolutional codes (SCCCs) and low-density parity-check (LDPC) codes. Our results show that SCCCs can exploit better the correlation in scenarios with high values of the correlation coefficient (e.g., 0.999).M. Martalò; A. Abrardo; G. FerrariMartalo', Marco; A., Abrardo; G., Ferrar

Wireless Sensor Networks and Audio Signal Processing for Homeland Security

A plethora of solutions to homeland security problems have been proposed, during the last years, by academia, national governments, and industries. In this chapter, we focus on homeland security solutions based on efficient Wireless Sensor Network (WSN)-based audio signal pattern recognition. This is of interest for efficient surveillance of the perimeters of large areas, in order to detect the intrusion of humans or vehicles. We first propose a simple time domain approach to signal pattern detection and its commercial application through Unattended Ground Sensors (UGSs). Then, we extend this approach in the direction of a hybrid time-frequency approach, obtaining a very good performance yet with limited complexity

On Non-Cooperative Block-Faded Orthogonal Multiple Access Schemes with Correlated Sources

In this paper, we study the performance of noncooperative multiple access systems with noisy separated channels, where correlated sources communicate to an access point (AP) through block-faded links. In the considered scenario, perfect channel state information (CSI) is assumed at the receiver while no CSI is available at the transmitters. We first consider uncoded transmissions from the sources to the AP, which exploits the source correlation to carry out joint channel detection (JCD). In this scenario, we propose an analytical approach to evaluate the achievable performance in terms of average bit error rate (BER). We then investigate the impact of coding, considering the same fixed coding scheme at each source. Then, we consider an extrinsic information transfer (EXIT) chart-based framework to optimize the design of concatenated and low-density parity-check (LDPC) codes for JCD schemes

Multi-temperature Euler hydrodynamics for a reacting gas from a kinetic approach to rarefied mixtures with resonant collisions

Starting from a Boltzmann kinetic model for a gas mixture with bimolecular chemical reaction, hydrodynamic equations at Euler level are deduced by a consistent hydrodynamic limit in the presence of resonance, namely when the fast process driving evolution is constituted by elastic scattering between particles of the same species. The structure of the resulting multi-temperature and multi-velocity fluid-dynamic description is briefly commented on, and some results in closed analytical form are given for the special case of Maxwellian collision kernel