Self-adapting algorithm to fair time sharing in wireless access networks

To adapt the data rate in accordance with the quality of the link, the IEEE 802.11 standard proposes the variable rate shifting functionality. This intrinsic functionality of the 802.11 products progressively degrades the bit rate when a host detects unsuccessful frame transmissions. Furthermore, the basic CSMA/CA channel access method guarantees that the long-term channel access probability is equal for all hosts. When one host captures the channel for a long time because its bit rate is low, it penalizes other hosts that use the higher rate, inciting a performance overall degradation. We propose a self-adapting algorithm to improve resources shared among the active hosts in the hot spot, thus avoiding the performance degradation caused by one or more low-rate hosts. This algorithm aims at avoiding this performance degradation and the consequent waste of bandwidth. An extensive evaluation is performed depicting the improvement achieved.     

Resilient data gathering and communication algorithms for?emergency scenarios

A typical application field of Wireless Sensor Networks (WSNs) is the collection of environmental data, which is sent to a base station. Routing protocols are needed to efficiently direct the information flows to the base station. Since sensor nodes have strict energy constraints, data gathering and communication schemes for WSNs need to be designed for an efficient utilization of the available resources. An emergency management scenario is investigated, where a sensor network is deployed as virtual lifeline for fire fighters entering a building. Besides of supporting their navigation, the virtual lifeline is also used for two further purposes. First it enables the exchange of short voice messages between fire fighter and command post. For this, a fast and reliable routing protocol (EMRO) has been developed based on a broadcasting scheme. Second, measuring data, like temperature and gas, in the environment and informing fire fighters and command post about it, is of high importance. For this purpose a network coding based data gathering algorithm has been designed. The feasibility of simultaneously using the virtual lifeline for data gathering and communication and thus the coexistence of a classical routing protocol with a network coding scheme is studied in this paper by means of simulation and real experiments. The resilience to packet loss and node failure, as well as the transmission delay are investigated by means of short voice messages for the communication part and temperature readings for data gathering.     

A Resource Allocation Framework for Scalable Video Broadcast in Cellular Networks

Video streaming is one of the most important applications that will make use of the high data rates offered by 4G networks. The current video transport techniques are already very advanced, and the more immediate problems lie in the joint optimization of video coding, AL-FEC, and PHY rate selection with the goal of enhancing the user perceived quality. In this work we provide an analysis of video broadcast streaming services for different combinations of layered coding and AL-FEC, using a realistic LTE PHY layer. Our simulation results show that the scalable content adaptation given by Scalable Video Coding (SVC) and the scheduling flexibility offered by the 3G-LTE MAC-layer provide a good match for enhanced video broadcast services for next generation cellular networks. Our proposed solution is compared to baseline algorithms and broadcast systems based on H.264/AVC streaming solutions. We emphasize the system quality improvement brought by our solution and discuss implications for a wide-scale practical deployment.     

Improving threat detection in networks using deep learning

Annals of Telecommunications - Detecting threats on the Internet is a key factor in maintaining data and information security. An intrusion detection system tries to prevent such attacks from...     

Empirical validation of different internal superficial heat transfer models on a full-scale passive house

Being highly insulated, low-energy buildings are very sensitive to variable solar and internal gains. In this context, some modelling assumptions frequently used in simplified building energy simulation tools might be called into question. While higher insulation levels reduce the influence of heat transmission through opaque walls, absorption of solar and internal gains at inner wall surfaces, and indoor superficial heat transfers, become concerning. The convective and long-wave radiative heat transfer models are investigated in COMFIE, a dynamic energy simulation platform. More detailed internal heat transfer models are developed by decoupling convective and long-wave radiative heat transfers and using time-dependent coefficients. Furthermore, an empirical validation process on both simplified and detailed models is carried out using measurements from a full-scale experimental concrete passive house, addressing the model uncertainty vs. complexity issue.     

Morphology and supermolecular structure of polypropylene–poly(1-butene)–hydrogenated oligo(cyclopentadiene) ternary blends

Ternary blends containing polypropylene, poly(1-butene), and hydrogenated oligo(cyclopentadiene) have been studied using microscopic, calorimetric, and X-ray diffraction techniques. While no phase separation was found to occur in the melt for all the considered compositions, demixing phenomena were observed by scanning electron microscopy in the ternary blends after crystallization of both polyolefins. On the other hand, a homogeneous surface without the presence of separate domains was observed for blends quenched avoiding the crystallization of polypropylene. The composition has been found to affect the crystallization and the melting properties of the ternary blends and the crystal modification of polypropylene. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1878–1882, 1998     

Adaptive QoS Management for IEEE 802.11 Future Wireless ISPs

Wireless Internet Service Providers (WISPs) are expected to be the new generation of access providers using the emerging IEEE 802.11 technology. Face to the high competition of providing network services, the WISP have to offer the best service to the users. For this purpose, the WISP networks' managers need to provide Quality of Service (QoS) with a minimum cost in their wireless networks. The current link layer IEEE 802.11b provides fair sharing of the radio resource with no service differentiation mechanism; similarly to the Internet best effort service. However, the ongoing standard IEEE 802.11e should implement a priority mechanism at the link layer to differentiate the users' traffic. In order to overcome the lack of differentiated mechanism in the current link layer IEEE 802.11b, hence controlling the utilization of the scarce radio resource, we propose in this article to deploy Diffserv architecture coupled with an adaptive provisioning of QoS to provide better services to the users with minimum WISP cost and improve the utilization of the radio resource. Compliant with the current and future IEEE 802.11 link layer, the proposed adaptive QoS provisioning mechanism reacts to the radio resource fluctuation and improves the number of accepted clients in the IEEE 802.11 wireless cells based on the WISP business policies. The network layer differentiation provided by the Diffserv architecture intends to control the concurrent access of the traffic to the scarce radio resources at the IP layer of the mobile hosts for the uplink traffic on one hand, and at the IP layer of the base stations for the downlink traffic on the other hand.     

Energy efficiency of some non-cooperative, cooperative and hybrid communication schemes in multi-relay WSNs

In this paper we analyze the energy efficiency of single-hop, multi-hop, cooperative selective decode-and-forward, cooperative incremental decode-and-forward, and even the combination of cooperative and non-cooperative schemes, in wireless sensor networks composed of several nodes. We assume that, as the sensor nodes can experience either non line-of-sight or some line-of-sight conditions, the Nakagami-m fading distribution is used to model the wireless environment. The energy efficiency analysis is constrained by a target outage probability and an end-to-end throughput. Our results show that in most scenarios cooperative incremental schemes are more energy efficient than the other methods.     

Virtual lifeline: Multimodal sensor data fusion for robust navigation in unknown environments

We present a novel, multimodal indoor navigation technique that combines pedestrian dead reckoning (PDR) with relative position information from wireless sensor nodes. It is motivated by emergency response scenarios where no fixed or pre-deployed global positioning infrastructure is available and where typical motion patterns defeat standard PDR systems. We use RF and ultrasound beacons to periodically re-align the PDR system and reduce the impact of incremental error accumulation. Unlike previous work on multimodal positioning, we allow the beacons to be dynamically deployed (dropped by the user) at previously unknown locations. A key contribution of this paper is to show that despite the fact that the beacon locations are not known (in terms of absolute coordinates), they significantly improve the performance of the system. This effect is especially relevant when a user re-traces (parts of) the path he or she had previously travelled or lingers and moves around in an irregular pattern at single locations for extended periods of time. Both situations are common and relevant for emergency response scenarios. We describe the system architecture, the fusion algorithms and provide an in depth evaluation in a large scale, realistic experiment.     

A blind mechanism to improve content distribution in delay/disruption tolerant networks

In delay/disruption tolerant networks (DTNs), content distribution is performed leveraging on the transient and dynamic contacts between moving users. Such a best effort mechanism is prone to unbounded downloading delays and bad user experience. To cope with these occurences, this paper introduces a novel mechanism to improve content distribution in DTNs. The proposed mechanism is based on the delay tolerant transport protocol and aims at controlling the diversity in the coded information transmission without increasing the use of network resources or including any feedback messages. In order to validate the proposed mechanism, different scenarios have been evaluated using known DTNs routing protocols. The results show significant gains achieved in terms of delivery ratio in all evaluated scenarios, confirming the efficiency and effectiveness of our protocol independently of the lower layer protocols in use.