On-body and Off-body Transmit Power Control in IEEE 802.15.6 Scheduled Access Networks

Wireless Body Area Networks (WBANs) have received much attention due to the possibility to be used in healthcare applications. For these applications, energy saving is a critical issue, as in many cases, batteries cannot be easily replaced. A transmit power control scheme, able to adapt tothe variations of the wireless body channel, will allow consistent energy saving and longer battery life. In this paper we propose a transmit power control scheme suitable for IEEE 802.15.6 narrowband scheduled access networks,in which the transmission power is modulated frame by frame according to a run-time estimation of the channel propagation conditions. A simple and effective line search algorithm is proposed to estimate the channel quality based on the signal power received from the hub; in addition, an adaptive fade margin estimator is presented to determine an optimum margin based on the channel conditions. The approach allows tracking the highly variable propagation conditions due to the body mobility and the deployment of the sensors close to the human body. An experimental study in different test cases proves the effectiveness of the scheme in comparison with alternative solutions in the literature

Channel estimation and transmit power control in wireless body area networks

Wireless body area networks have recently received much attention because of their application to assisted living and remote patient monitoring. For these applications, energy minimisation is a critical issue since, in many cases, batteries cannot be easily replaced or recharged. Reducing energy expenditure by avoiding unnecessary high transmission power and minimising frame retransmissions is therefore crucial. In this study, a transmit power control scheme suitable for IEEE 802.15.6 networks operating in beacon mode with superframe boundaries is proposed. The transmission power is modulated, frame-by-frame, according to a run-time estimation of the channel conditions. Power measurements using the beacon frames are made periodically, providing reverse channel gain and an opportunistic fade margin, set on the basis of prior power fluctuations, is added. This approach allows tracking of the highly variable on-body to on-body propagation channel without the need to transmit additional probe frames. An experimental study based on test cases demonstrates the effectiveness of the scheme and compares its performance with alternative solutions presented in the literature

1 Hop or 2 hops: Topology analysis in Body Area Network

Wireless Body Area Networks (WBANs) have recently received much attention due to the possibility to be used in healthcare applications. For these applications, link reliability and energy efficiency are critical issues, as in many cases, information carried can be vital for the patient and batteries cannot be easily replaced. The wireless on-body channel experiences significant temporal variation due to body movements and the use of relays is sometimes necessary in order to guarantee reliability or improve lifetime. In this paper, an experimental evaluation is used to give a better understanding about reliability, energy consumption and lifetime in a single hop or a two hops communication. This analysis keeps into consideration the correlations between propagation on different links which affect simultaneously the time-varying connectivity on different links of the body. Theresults shows that an off-body relays could be used to increase data reliability, minimize energy requirements and maximize network lifetime

Learning from Errors: Detecting ZigBee Interference in WiFi Networks

—In this work we show how to detect ZigBee inter- ference on commodity WiFi cards by monitoring the reception errors, such as synchronization errors, invalid header formats, too long frames, etc., caused by ZigBee transmissions. Indeed, in presence of non-WiFi modulated signals, the occurrence of these types of errors follows statistics that can be easily recognized. Moreover, the duration of the error bursts depends on the transmission interval of the interference source, while the error spacing depends on the receiver implementation. On the basis of these considerations, we propose the adoption of hidden Markov chains for characterizing the behavior of WiFi receivers in presence of controlled interference sources (training phase) and then run-time recognizing the most likely cause of error patterns. Experimental results prove the effectiveness of our approach for detecting ZigBee interference

Dynamic MAC Parameters Configuration for Performance Optimization in 802.11e Networks

Quality of service support in wireless LAN is a theme of current interest. Several solutions have been proposed in literature in order to protect time-sensitive traffic from best-effort traffic. According to the EDCA proposal, which is a completely distributed solution, the service differentiation is provided by giving probabilistically higher number of channel accesses to stations involved in real-time applications. To this purpose, the MAC parameter settings of each contending stations can be tuned dynamically. In this paper, we face the problem of tuning the EDCA MAC parameters in common scenarios in which a given number of low-rate delay-sensitive traffic flows share the channel with some stations involved in data transfer. Our contribution is threefold. First, we show that, whenever possible, the delay constraints of the high priority class can be satisfied in both the cases of contention windows differentiation and inter-frame space differentiation. However, these mechanisms have different side effects in terms of bandwidth availability for the best effort stations. Second, we propose to exploit the MAC parameter dynamic settings of EDCA in order to probabilistically guarantee the delay requirements and to jointly maximize the aggregated throughput of the network. Finally, we suggest a very simple solution to automate these parameter settings in a real scenario, where traffic flows can be activated/deactivated dynamically, by simply monitoring the channel activity. The proposed solution is very robust, since it does not require any a priori traffic model or any network load estimator

Privacy-preserving Overgrid: Secure Data Collection for the Smart Grid

In this paper we present a privacy-preserving scheme for Overgrid, a fully distributed peer-to-peer (P2P) architecture designed to automatically control and implement distributed Demand Response (DR) schemes in a community of smart buildings with energy generation and storage capabilities. To monitor the power consumption of the buildings, while respecting the privacy of the users, we extend our previous Overgrid algorithms to provide privacy preserving data aggregation ( extit{PP-Overgrid}). This new technique combines a distributed data aggregation scheme with the Secure Multi-Party Computation paradigm. First, we use the energy profiles of hundreds of buildings, classifying the amount of ``flexible'' energy consumption, i.e. the quota which could be potentially exploited for DR programs. Second, we consider renewable energy sources and apply the DR scheme to match the flexible consumption with the available energy. Finally, to show the feasibility of our approach, we validate the PP-Overgrid algorithm in simulation for a large network of smart buildin

SDR-LoRa, an open-source, full-fledged implementation of LoRa on Software-Defined-Radios: Design and potential exploitation

In this paper, we present SDR-LoRa, an open-source, full-fledged Software Defined Radio (SDR) implementation of a LoRa transceiver. First, we conduct a thorough analysis of the LoRa physical layer (PHY) functionalities, encompassing processes such as packet modulation, demodulation, and preamble detection. Then, we leverage on this analysis to create a pioneering SDR-based LoRa PHY implementation. Accordingly, we thoroughly describe all the implementation details. Moreover, we illustrate how SDR-LoRa can help boost research on the LoRa protocol by presenting three exemplary key applications that can be built on top of our implementation, namely fine-grained localization, interference cancellation, and enhanced link reliability. To validate SDR-LoRa and its applications, we test it on two different platforms: (i) a physical setup involving USRP radios and off-the-shelf commercial devices, and (ii) the Colosseum wireless channel emulator. Our experimental findings reveal that (i) SDR-LoRa performs comparably to conventional commercial LoRa systems, and (ii) all the aforementioned applications can be successfully implemented on top of SDR-LoRa with remarkable results. The complete details of the SDR-LoRa implementation code have been publicly shared online, together with a plug-and-play Colosseum container

Experimental evaluation of privacy-preserving aggregation schemes on planetlab

New pervasive technologies often reveal many sen- sitive information about users’ habits, seriously compromising the privacy and sometimes even the personal security of people. To cope with this problem, researchers have developed the idea of privacy-preserving data mining which refers to the possibility of releasing aggregate information about the data provided by multiple users, without any information leakage about individual data. These techniques have different privacy levels and communication costs, but all of them can suffer when some users’ data becomes inaccessible during the operation of the privacy preserving protocols. It is thus interesting to validate the applicability of such architectures in real-world scenarios. In this paper we experimentally evaluate two promising privacy- preserving techniques on PlanetLab, analyzing the execution time and the failure rate that each scheme exhibits

Cross-technology WiFi/ZigBee communications: Dealing with channel insertions and deletions

In this paper we show how cross-technology in- terference can be exploited to set-up a low-rate bi-directional communication channel between heterogeneous WiFi and ZigBee networks. Because of the environment noise and receivers' imple- mentation, the cross-technology channel can be severely affected by insertions and deletions of symbols, whose effects need to be taken into account by the coding scheme and communication protocol