Ronald Rietman

An efficient framed-slotted ALOHA algorithm with pilot frame and binary selection for anti-collision of RFID tags

Reducing the number of tag collisions is one of the most important issues in RFID systems, as collisions induce inefficiency. This paper presents a mechanism of grouping of tags via a bit mask, quick tag estimation by a pilot frame and near optimal binary tree-based collision resolution with a frame. Performance analysis and simulation results show that the proposed anti-collision algorithm consumes fewer time slots as compared to previous work, and approaches to the case with the optimal frame size using binary tree collision resolution.

Uniform Illumination Rendering Using an Array of LEDs: A Signal Processing Perspective

An array of a large number of LEDs will be widely used in future indoor illumination systems. In this paper, we investigate the problem of rendering uniform illumination by a regular LED array on the ceiling of a room. We first present two general results on the scaling property of the basic illumination pattern, i.e., the light pattern of a single LED, and the setting of LED illumination levels, respectively. Thereafter, we propose to use the relative mean squared error as the cost function to measure the uniformity of the realized illumination pattern, and provide an analysis for this cost function. Based on the analysis, the design of a basic illumination pattern is discussed. The performances of a few basic illumination patterns are compared, and an approach for optimizing the basic illumination pattern through a weighted combination of these basic patterns is also proposed. A weighted combination of Gaussian and raised-cosine functions is found to yield the best results. Finally, three basic regular grid shapes for an LED array are compared. The results show that 13% and 39% of LEDs can be saved for the same degree of uniformity, using the hexagonal instead of the rectangular and triangular grid, respectively.

An analytical model for the illuminance distribution of a power LED

Light-emitting diodes (LEDs) will play a major role in future indoor illumination systems. In general, the generalized Lambertian pattern is widely used as the radiation pattern of a single LED. In this letter, we show that the illuminance distribution due to this Lambertian pattern, when projected onto a horizontal surface such as a floor, can be well approximated by a Gaussian function.

A finite‐source queuing model for the IEEE 802.11 DCF

The most mature medium access control protocol for wireless local area networks is the IEEE 802.11 standard. The primary access mode of this protocol is based on the mechanism of carrier sense multiple access with binary exponential backoff. We develop a finite-source feedback queueing model for this access mode. In this model, we derive expressions for the throughput and the first moment of the delay and a set of equations to compute the Laplace Stieltjes Transform and higher moments of the delay. The accuracy of the model is verified by simulation.

The MMO problem

We consider a two polynomials analogue of the polynomial interpolation problem. Namely, we consider the Mixing Modular Operations (MMO) problem of recovering two polynomials <i>f</i> ∈ Z_<i>p</i>[<i>x</i>] and <i>g</i> ∈ Z_<i>q</i>[<i>x</i>] of known degree, where <i>p</i> and <i>q</i> are two (un)known positive integers, from the values of <i>f</i>(<i>t</i>) mod <i>p</i>+<i>g</i>(<i>t</i>) mod <i>q</i> at polynomially many points <i>t</i> ∈ Z. We show that if <i>p</i> and <i>q</i> are known, the MMO problem can be reduced to computing a close vector in a lattice with respect to the infinity norm. Using the Gaussian heuristic we also implemented in the SAGE system a polynomial-time algorithm. If <i>p</i> and <i>q</i> are kept secret, we do not know how to solve this problem. This problem is motivated by several potential cryptographic applications.

INTERPOLATION AND APPROXIMATION OF POLYNOMIALS IN FINITE FIELDS OVER A SHORT INTERVAL FROM NOISY VALUES

[summary] We consider a modification of the noisy polynomial interpolation problem of recovering an unknown polynomial from approximate values of the residues of f(t) modulo a prime p at polynomially many points t taken from a short interval.

An M / G /1 Queueing Model with Gated Random Order of Service

We analyse an M/G/1 queueing model with gated random order of service. In this service discipline there are a waiting room, in which arriving customers are collected, and a service queue. Each time the service queue becomes empty, all customers in the waiting room are put instantaneously and in random order into the service queue. The service times of customers are generally distributed with finite mean. We derive various bivariate steady-state probabilities and the bivariate Laplace–Stieltjes transform (LST) of the joint distribution of the sojourn times in the waiting room and the service queue. The derivation follows the line of reasoning of Avi-Itzhak and Halfin [4]. As a by-product, we obtain the joint sojourn times LST for several other gated service disciplines.

Compressive Sampling for Non-Intrusive Appliance Load Monitoring (NALM) using Current Waveforms

We propose a NALM technique by exploiting the compressive sampling and sparse reconstruction framework. We estimate the contribution of the individual appliances by measuring the current of the total load. We further assume to know the steady-state current waveform of each appliance. We exploit the sparsity of the current signal to compress the measurement via random sampling, which lowers significantly the processing complexity, the storage and the communication burden. Using the proposed sparse reconstruction approach, we can still identify the on/off status of each appliance from the compressed measurement as if the original non-compressed measurement is used.

Multi-appliance power disaggregation: An approach to energy monitoring

Consumers increasingly want to make informed and proactive decisions based on an understanding of their energy consumption. However, current energy monitoring solutions are either too limited in the information they provide or are too intrusive. We consider a solution for disaggregating the electrical power consumption of individual appliances connected in a residential electricity network, with a single point of measurement. We pose the power disaggregation problem in the framework of multi-user detection. Two linear detection algorithms are then provided to determine which appliances are active in the network and in turn to determine their individual power consumptions. An experimental setup is described that was used to evaluate the performance of the algorithms along with simulation results.

A Comprehensive and Lightweight Security Architecture to Secure the IoT Throughout the Lifecycle of a Device Based on HIMMO

Smart objects are devices with computational and communication capabilities connected to the Internet forming the so called Internet of Things IoT. The IoT enables many applications, for instance outdoor lighting control, smart energy and water management, or environmental sensing in a smart city environment. Security in such scenarios remains an open challenge due to the resource-constrained nature of devices and networks or the multiple ways in which opponents can attack the system during the lifecycle of a smart object. This paper firstly reviews security and operational goals in an IoT scenario inspired in a smart city environment. Then, we present a comprehensive and lightweight security architecture to secure the IoT throughout the lifecycle of a device. Our solution relies on the lightweight HIMMO scheme --- a novel key pre-distribution scheme that is both collusion resistance and efficient --- as the building stone enabling not only efficient resource-wise but also advanced and scalable IoT protocols and architectures. Our design and analysis show that our HIMMO-based security architecture can be easily integrated in existing communication protocols such as IEEE 802.15.4 or OMA LWM2M providing a number of advantages that existing solutions cannot provide both performance and operation-wise.