Impact of on-body channel models on positioning success rate with UWB Wireless Body Area Networks

International audienceIn this paper, we aim to evaluate the positioning success rate of nodes placed on the body using different scheduling strategies at the Media Access Control (MAC) layer with Ultra Wide Band (UWB) Wireless Body Area Networks (WBAN) and under three different channel models. For this purpose, each node calculates its relative position with the estimation of its distances with the on-body anchors. Accordingly, the distance between two nodes can be estimated with the transmission of three packets, as defined by the '3-Way ranging' protocol (3-WR). However, these transactions can be affected by the WBAN channel leading into a packet loss and therefore positioning errors. In this work, we consider a PHY layer based on Impulse-Radio UWB (IR-UWB) with three different channels: (a) a theoretical path loss channel model based on the on-body CM3 channel (Anechoic chamber), (b) a simulated channel calculated with the PyLayers ray-tracing simulator and (c) experimental traces obtained by measurement. Moreover, we analyze the positioning success rate using three scheduling strategies (Single node localization (P2P), Broadcast Single node localiza-tion (P2P-B) and Aggregated & Broadcast (A&B)) with a MAC layer based on time division multiple access (TDMA) and under a realistic pedestrian walking scenario. Our results show that the scheduling strategy with A&B let the nodes to estimate more positions even through channels with slow and fast fading

Random Unslotted Time-Frequency ALOHA: Theory and Application to IoT UNB Networks

International audienceThe ALOHA protocol is regaining interest in the context of the Internet of Things (IoT), especially for Ultra Narrow Band (UNB) signals. In this case, the classical assumption of channelization is not verified anymore, modifying the ALOHA performances. Indeed, UNB signals suffer from a lack of precision on the actual transmission carrier frequency, leading to a behavior similar to a frequency unslotted random access. In this paper, the success probability and throughput of ALOHA is generalized to further describe frequency-unslotted systems such as UNB. The main contribution of this paper is the derivation of a generalized expression of the throughput for the random time-frequency ALOHA systems. Besides, this study permits to highlight the duality of ALOHA in time and frequency domain

Exploitation des propri{\'e}t{\'e}s de saturation synaptique pour obtenir un neurone {\`a} fr{\'e}quence sp{\'e}cifique

Energy consumption remains the main limiting factors in many promising IoT applications. In particular, micro-controllers consume far too much power. In order to overcome this problem, new circuit designs have been proposed and the use of spiking neurons and analog computing has emerged as it allows a very significant consumption reduction. However, working in the analog domain brings difficulty to handle the sequential processing of incoming signals as is needed in many use cases.In this paper, we propose to use a bio-inspired phenomenon called Interacting Synapses to produce a time filter. We propose a model of synapses that makes the neuron fire for a specific range of delays between two incoming spikes, but not react when this Inter-Spike Timing is not in that range. We study the parameters of the model to understand how to adapt the Inter-Spike Timing. The originality of the paper is to propose a new way, in the analog domain, to deal with temporal sequences.Comment: in French languag

Deriving Pareto-optimal performance bounds for 1 and 2-relay wireless networks

National audienceThis work addresses the problem of deriving fundamental trade-off bounds for a 1-relay and a 2-relay wireless network when multiple performance criteria are of interest. It proposes a simple MultiObjective (MO) performance evaluation framework composed of a broadcast and interference-limited network model; capacity, delay and energy performance metrics and an associated MO optimization problem. Pareto optimal performance bounds between end-to-end delay and energy for a capacity-achieving network are given for 1-relay and 2-relay topologies and assessed through simulations. Moreover, we also show in this paper that these bounds are tight since they can be reached by simple practical coding strategies performed by the source and the relays. Two different types of network coding strategies are investigated. Practical performance bounds for both strategies are compared to the theoretical upper bound. Results confirm that the proposed upper bound on delay and energy performance is tight and can be reached with the proposed combined source and network coding strategies

Impact of intra-flow network coding on the relay channel performance: an analytical study

International audienceOne of the most powerful ways to achieve trans- mission reliability over wireless links is to employ efficient coding techniques. This paper investigates the performance of a transmission over a relay channel where information is protected by two layers of coding. In the first layer, transmission reliability is ensured by fountain coding at the source. The second layer incorporates network coding at the relay node. Thus, fountain coded packets are re-encoded at the relay in order to increase packet diversity and reduce energy consumption. Performance of the transmission is measured by the total number of trans- missions needed until the message is successfully decoded at the destination. We show through both analytical derivations and simulations that adding network coding capabilities at the relay optimizes system resource consumption. When the source uses a random linear fountain code, the proposed two-layer encoding becomes more powerful as it reduces the transmission rate over the direct link between the source and the destination

Dedicated networks for IoT : PHY / MAC state of the art and challenges

International audienceThis paper focuses on the the emerging transmission technologies dedicated to IoT networks. We first analyze the classical cellular network technologies when taking into account the IoT requirements, and point out the need of dedicated technologies for IoT. Then, we present the PHY and MAC layers of the technologies that are already deployed, or likely to be deployed: UNB by SigFox, CSS by LoRa T M , Weighless, and RPMA by Ingenu. We then compare their performances to highlight their pros and cons. Finally, we discuss on the open research challenges that still need to be addressed

Massive Machine Type Communications Uplink Traffic: Impact of Beamforming at the Base Station

International audienceAs the number of machine type communications increases at an exponential rate, new solutions have to be found in order to deal with the uplink traffic. At the same time, new types of Base Stations (BS) that use a high number of antennas are being designed, and their beamforming capabilities can help to separate signals that have different angles of arrivals. In this paper, we consider a network where a BS serves a high number of nodes that lacks a receive chain, and we analyze the evolution of the outage probability as a function of the number of antennas at the BS. We then study the effect of an angle offset between the main beam and the desired node's direction in order to provide realistic results in a beam-switching scenario

Impact of Mobility on Ranging Estimation using UltraWideband

International audienceThis paper presents a study of the impact of mobility on the distance estimation between 2 nodes of a Wireless Body Area Network (WBAN) by comparing the Two-Way Ranging (2WR) and Three-Way Ranging (3WR) protocols. We consider a WBAN using a typical TDMA-based Medium Access Control (MAC) protocol and a IR-UWB physical layer defined by the standard IEEE802.15.6. We represent the impact by using the Root Mean Square Error (RMSE) in function of two types of parameters, the speed and the time of response. The results show that depending on the speed and the chosen reference point, it is better chose 2WR or 3WR if only mobility is considered. Finally, we propose to extend the study with a joint mobility and clock drift scenario with more sophisticated techniques such as cooperative scheduling algorithms or Aggregated and Broadcast mechanisms

Code Domain Non Orthogonal Multiple Access versus ALOHA: a simulation based study

International audienceNon Orthogonal Multiple Access (NOMA) is expected to play an important role for IoT networks, allowing to reduce signaling overheads and to maximize the capacity of dense networks with multiple packets simultaneous transmission. In the uplink, NOMA can improve significantly the performance of an ALOHA random access if the receiver implements a multiuser detection algorithm. In this paper we compare the performance of a code domain NOMA with a classical ALOHA protocol, through simulations. The code domain NOMA uses random Gaussian codes at the transmitters and exploits compressive sensing at the receiver to maximize users detection and to minimize symbol error rates