International audience

ASVspoof challenges are designed to advance the understanding of spoofing speech attacks and encourage the development of robust countermeasure systems. These challenges provide a standardized database for assessing and comparing spoofing-robust automatic speaker verification solutions. The ASVspoof5 challenge introduces a shift in database conditions compared to ASVspoof2019. While ASVspoof2019 has mismatched conditions only in spoofing attacks in the evaluation set, ASVspoof5 incorporates mismatches in both bona fide and spoofed speech statistics. This paper examines the impact of these mismatches, presenting qualitative and quantitative comparisons within and between the two databases. We show the increased difficulty for genuine and spoofed speech and demonstrate that in ASVspoof5, not only are the attacks more challenging, but the genuine speech also shifts toward spoofed speech compared to ASVspoof2019.

Hardware multithreading is a common approach for tolerating memory latency by utilizing idle cycles and avoiding CPU stalling. Nowadays, multithreading architectures are commonly used across many processors and various embedded edge devices to improve performance. This work suggests a new multithreading in-order pipeline microarchitecture design for RISC-V and proposes an efficient event-based issue scheduling algorithm. The proposed scheduling algorithm is based on the unique RISC-V ISA that enables decoding of the instruction type in an early stage of the pipeline. The RISC-V-based multithreading architecture is evaluated using a dedicated software simulator. Simulation results show that the proposed algorithm outperforms the classical Round Robin and the coarse grain algorithms. The proposed architecture is evaluated using the standard MiBench benchmark and other common applications, demonstrating pipeline utilization improvement of up to about 26% in terms of IPC using four threads.

This paper presents an efficient method for data acquisition and automatic meter reading (AMR) system from smart electric meters (SM) using power-line communications (PLC) networks. A PLC network uses existing electrical wiring to simultaneously carry both data and electric power. However, since the transmission medium in a PLC network is not designed for high quality data transfer, its efficiency in carrying out AMR applications is limited. The PLC network's traffic load is significantly affected both by the routing algorithm and the polling ordering of the SM. This paper suggests two novel smart polling algorithms based on application layer approach. The proposed algorithms demonstrate efficient utilization of both proactive and reactive routing protocols for AMR applications in narrowband PLCs networks. The benefit of the proposed approach is demonstrated for the two most common protocols, the routing protocol for low-power and lossy networks and the lightweight on-demand ad hoc distance-vector routing protocol.

Abstract We examine a new problem called the Zone Selection Problem (ZSP) in wireless Orthogonal Frequency‐Division Multiple Access (OFDMA)‐based systems. We consider the case where the mobile station (MS) informs the base station of its preferences regarding possible working modes supported by the system. In Worldwide Interoperability for Microwave Access (WiMAX) systems, which are used as a practical reference system for constraints and specific modes of operations, each working mode must be assigned at a different time interval called aZone. Such zone may, in the downlink subframe, define a specific transmission scheme, which can be either single‐input single‐output or one of the multiple‐in multiple‐out (MIMO) modes supported by the system. We define ZSP as a problem where the base station assigns MSs to zones in a way that optimizes the system utilization (in terms of resource usage) while trying to satisfy the preferences of the users as much as possible. This makes ZSP a bi‐objective optimization problem. We derive assignment costs from physical channel models that integrate specific MIMO schemes and channel conditions. We provide an exact solution to ZSP by using a combinatorial optimization abstraction. We propose a simplified and practical mode ranking approach that enables the MS to define its preferences regarding operation in the optional MIMO modes in the system. We prove that ZSP is NP‐hard and describe two heuristic solutions: a greedy approach and a local search approach. Simulation results show the performance of the exact algorithms on a realistic WiMAX system assumptions and present the trade‐off between the user preferences and system preferences. Copyright © 2016 John Wiley & Sons, Ltd.

Abstract This paper addresses the problem of efficient mapping and allocation of voice over IP (VoIP) traffic with multiple VoIP vocoders in WiMAX systems. We show that by taking advantage of the periodicity of VoIP frames, generated by multiple vocoder types, and by applying semi‐fixed allocations in the existing resource allocation process, the mapping overhead can be reduced substantially. We present a system model that allows the evaluation of the proposed solutions for the problem at hand. Using this model, we show that the problem is NP hard and present a set of observations on the resource allocation process leading to good mapping decisions from the perspective of mapping overhead. We present a new mapping algorithm that implement the decisions and show by extensive simulations that the proposed mapping algorithm can reduce the overhead down to 25% of the overhead experienced in orthogonal frequency division multiple access (OFDMA)‐based systems such as WiMAX and IEEE802.16, while retaining a low computational complexity. Copyright © 2009 John Wiley & Sons, Ltd.

We study interference-aware, many-to-many cooperative routing algorithms in wireless networks. Network performance is measured in terms of effective rate achieved when multiple frames are transmitted sequentially over a single cooperative path. Motivated by the overall network performance when multi

This paper addresses the problem of efficient broadcasting of resource allocations descriptors for CBR applications (e.g., VoIP) in OFDMA-based wireless systems. In such systems mapping is the process of allocating resources and representing them is the mapping overhead. Existing mapping algorithms require an allocation descriptor to be broadcast in each frame for each allocated resource for every served subscriber. Information concerning the allocations is crucial for proper system operation, therefore it is broadcast on the wireless down link with low modulation and high repetition rate. The mapping overhead which is a function of the number of served subscribers is usually large and consumes a substantial part of down link resources. We present the notion of semi fixed allocations that allows a substantial reduction of the mapping overhead. We show that by taking advantage of the periodicity of VoIP frames and by applying semi fixed allocations in the existing resource allocation process, the mapping overhead can be reduced substantially. We present an innovative system model for the problem on hand and for evaluating the solutions. Using this model we show that the problem is in NP hard and present a set of observations on the resource allocation process leading to good mapping decisions from the perspective of mapping overhead. We present new mapping algorithms implementing those mapping decisions and show that by extensive simulations with these mapping algorithms the overhead can be reduced to 10% of the overhead experienced in OFDMA-based systems such as WiMAX and IEEE802.16, while retaining a low computational complexity.

This work presents a MAC protocol for wireless ad hoc networks that is adaptive to stations load. LOCO MAC novelty lies in its backoff scheme that achieves short time collision resolution among many competing stations, even when they are hidden from each other. In LOCO-MAC the channel access time is calculated as a function of the station load, thus enabling to estimate the load of stations at the receiver side, regardless of the successful reception of transmission request. This load estimation is used to grant channel access to one of the stations whose load is the highest. Station's load is measured and normalized adaptively in terms of queue length and maximum end-to-end packet delay time. An analytical analysis to the throughput reveals that the expected throughput of LOCO MAC is ~80%. A network simulator was used to verify the effectiveness of the protocol under more realistic communication scenarios. Simulations results show that the high throughput is achieved almost regardless of the traffic load and is maintained at bursty traffic load distributions and even at loads that momentarily exceed the channel capacity. In addition, the fact that LOCO- MAC serves the most loaded station promotes fairness among stations, while maintaining high goodput, short queue lengths as well as short packet delays.

This article addresses a real-life problem - obtaining communication links between multiple base stations sites, by positioning a minimal set of fixed-access relay antenna sites on a given terrain. Reducing the number of relay antenna sites is considered critical due to substantial installation and maintenance costs. Despite the potential significant cost saving by eliminating even a single antenna site, a hardly optimal manual approach is employed due to the computation complexity of the problem. We suggest several alternative automated heuristics, relying on terrain preprocessing to find educated potential points for positioning relay stations. A large-scale experiment was conducted showing that the saving potential increases when more BSs are required to be interconnected and in any case is better than the one obtained by ah uman expert.

Abstract In this work, we continue the analysis of a probabilistic approach and the corresponding stochastic multi‐parametric model of wave propagation, in built‐up areas with randomly distributed buildings. We have concentrated on the spectral properties of signal strength spatial variations and on Doppler spread spectrum distribution of signal power. The analysis is based on a unified stochastic approach of radio wave propagation above the built‐up terrain with applications to mobile communications. We analyze the signal power spectrum of spatial frequencies and the signal power distribution in the Doppler domain for moving vehicles, taking into account a Doppler shift proportional to the vehicle antenna speed relative to the base station. The comparison between the theoretical prediction and experimental data was motivated by the proposed stochastic model and other existing statistical models to verify the signal power distribution in the Doppler domain for various urban environments and terminal heights with respect to building rooftops. New effects of terrain features on signal spectrum are obtained, examined and compared with existing models. Copyright © 2006 John Wiley & Sons, Ltd.

Trees of special properties are required to provide efficient network management of group communications in mobile ad hoc networks. Usually, such trees try to balance between the requirements to minimize the total tree cost and the requirement to minimize the maximal shortest path. This work presents a novel solution for efficient multicast trees that fulfill both requirements called SPLAST. The following discussion covers the development process, starting from centralized static solution, through distributed implementation to a complete distributed algorithm that cope with various scenarios that are relevant to wireless ad hoc networks by efficient management and maintenance of the underlying components of the algorithm. Simulation inquiry shows that the average performance of SPLAST is attractive as well.