Francesco Potortì

Bluetooth and Wi-Fi wireless protocols: a survey and a comparison

Bluetooth and IEEE 802.11 (Wi-Fi) are two communication protocol standards that define a physical layer and a MAC layer for wireless communications within a short range (from a few meters up to 100 m) with low power consumption (from less than 1 mW up to 100 mW). Bluetooth is oriented to connecting close devices, serving as a substitute for cables, while Wi-Fi is oriented toward computer-to-computer connections, as an extension of or substitution for cabled LANs. In this article we offer an overview of these popular wireless communication standards, comparing their main features and behaviors in terms of various metrics, including capacity, network topology, security, quality of service support, and power consumption.

Evaluating Ambient Assisted Living Solutions: The Localization Competition

Evaluation of ambient assisted living (AAL) systems is particularly challenging due to the complexity of such systems and the variety of solutions adopted and services offered. Yet analyzing and comparing AAL solutions is paramount for assessing research results in this area. Evaluating AAL Systems through Competitive Benchmarking (EvAAL) is a recently established international competition that aims to address this problem, letting benchmarking and comparison methodologies of AAL systems emerge from experience. Here, the authors describes the first EvAAL competition, which was devoted to localization and tracking. They also review the proposed evaluation criteria, benchmarks, and results. All evaluation data is freely available from the EvAAL website.

EvAAL: Evaluating AAL Systems through Competitive Benchmarking

Owing to the complexity of Ambient Assisted Living (AAL) systems and platforms, the evaluation of AAL solutions is a complex task that will challenge researchers for years to come. However, the analysis and comparison of proposed solutions is paramount to enable us to assess research results in this area. We have thus organized an international contest called EvAAL: Evaluating AAL Systems through Competitive Benchmarking. Its aims are to raise interest within the research and developer communities in the multidisciplinary research fields enabling AAL, and to create benchmarks for the evaluation and comparison of AAL systems.

Maximizing single connection TCP goodput by trading bandwidth for BER

SUMMARY All other conditions being equal, the end-to-end throughput of a TCP connection depends on the packet loss rate at the IP level. This is an issue when IP runs on a wireless link, where the bit error rate is variable and typically much higher than it i s on fixed links. Especially on ph ysical l inks where the bandwidth d elay product is high, TCP performance is s ignificantly impaired by apparently low values of the bit error rate. Generally speaking, on a wireless link b andwidth can be traded for information quality (error r ate), the simplest method being to change the type or parameters of forward error correction. On this basis, we show a general method of taking advantage of this trade-off in order to maximize the throughput of a TCP connection.

Frame error model in rural Wi-Fi networks

Commonly used frame loss models for simulations over Wi-Fi channels assume a simple double regression model with threshold. This model is widely accepted, but few measurements are available in the literature that try to validate it. As far as we know, none of them is based on field trials at the frame level. We present a series of measurements for relating transmission distance and packet loss on a Wi-Fi network in rural areas and propose a model that relates distance with packet loss probability. We show that a simple double regression propagation model like the one used in the ns-2 simulator can miss important transmission impairments that are apparent even at short transmitter-receiver distances. Measurements also show that packet loss at the frame level is a Bernoullian process for time spans of few seconds. We relate the packet loss probability to the received signal level using standard models for additive white Gaussian noise channels. The resulting model is much more similar to the measured channels than the simple models where all packets are received when the distance is below a given threshold and all are lost when the threshold is exceeded.

Simulating dynamic bandwidth allocation on satellite links

In the last years, DVB-RCS has emerged as a flexible technology offering broadband Internet access to a large community of users at a relatively low cost. At the same time, the spreading of networked multimedia applications has highlighted the need to investigate mechanisms that guarantee a certain level of Quality of Service (QoS) to the end users. In particular, the DVB-RCS standard specifies different capacity request categories to support QoS at the link layer.We describe Tdma-bod, an ns-2 improvement that implements generic bandwidth-on-demand allocation in TDMA satellite systems; the patch is available as free software. This simulator has been validated through experimental tests performed on the Skyplex satellite system. Specifically, we run CBR UDP flows to measure the characteristics of the satellite link in terms of throughput and delay and to verify that the simulative model output matches the experimental dynamic throughput and one-way delay behaviour. The simulations and experiments show that bandwidth-on-demand allocation mechanisms may cause large delays when sudden variations in the incoming traffic rate occur, a behaviour typical of multimedia flows.

Evaluating indoor localization solutions in large environments through competitive benchmarking: The EvAAL-ETRI competition

The increasing demand for services and higher comfort levels inside buildings, together with the rise in time spent indoor, ensure an upward trend in indoor localization demand for the future. Evaluation of indoor localization systems is particularly challenging due to the complexity of such systems and to the variety of solutions adopted and services offered. EvAAL is an international competition aimed at evaluating and assessing indoor localization systems. The fifth edition of EvAAL promotes competitions on indoor localization in large environments. This paper describes its technical aspects, the competing systems and the results.

Accuracy limits of in-room localisation using RSSI

An ML approach is able to exploit all available information, and has proven to be a powerful method to evaluate RSSI localisation methods. We plan to use it to attack problems like optimal anchor placement, exploiting multiple mobile receivers, and localisation coupled to tracking.

Platforms for AAL applications

AAL - Ambient Assisted Living. When the topic “AAL” comes up, everybody thinks first of fascinating technology that is unobtrusively integrated in “smart home environments” and supports people in their daily lives. This thinking is surely be driven by the ongoing development of impressive services that was and is still provided by the AAL research community as well as the growing number of companies that bring these technology to market.

Measurement-based frame error model for simulating outdoor Wi-Fi networks

We present a measurement-based model of the frame error process on a Wi-Fi channel in rural environments. Measures are obtained in controlled conditions, and careful statistical analysis is performed on the data, providing information which the network simulation literature is lacking. Results indicate that most network simulators use a frame loss model that can miss important transmission impairments even at a short distance, particularly when considering antenna radiation pattern anisotropy and multi-rate switching.