H-MAC: A Hybrid MAC Protocol for Wireless Sensor Networks

In this paper, we propose a hybrid medium access control protocol (H-MAC) for wireless sensor networks. It is based on the IEEE 802.11's power saving mechanism (PSM) and slotted aloha, and utilizes multiple slots dynamically to improve performance. Existing MAC protocols for sensor networks reduce energy consumptions by introducing variation in an active/sleep mechanism. But they may not provide energy efficiency in varying traffic conditions as well as they did not address Quality of Service (QoS) issues. H-MAC, the propose MAC protocol maintains energy efficiency as well as QoS issues like latency, throughput, and channel utilization. Our numerical results show that H-MAC has significant improvements in QoS parameters than the existing MAC protocols for sensor networks while consuming comparable amount of energy.Comment: 10 pages, IJCNC Journal 201

A low-power opportunistic communication protocol for wearable applications

© 2015 IEEE.Recent trends in wearable applications demand flexible architectures being able to monitor people while they move in free-living environments. Current solutions use either store-download-offline processing or simple communication schemes with real-time streaming of sensor data. This limits the applicability of wearable applications to controlled environments (e.g, clinics, homes, or laboratories), because they need to maintain connectivity with the base station throughout the monitoring process. In this paper, we present the design and implementation of an opportunistic communication framework that simplifies the general use of wearable devices in free-living environments. It relies on a low-power data collection protocol that allows the end user to opportunistically, yet seamlessly manage the transmission of sensor data. We validate the feasibility of the framework by demonstrating its use for swimming, where the normal wireless communication is constantly interfered by the environment

An Energy-efficient Rate Adaptive Media Access Protocol (RA-MAC) for Long-lived Sensor Networks

We introduce an energy-efficient Rate Adaptive Media Access Control (RA-MAC) algorithm for long-lived Wireless Sensor Networks (WSNs). Previous research shows that the dynamic and lossy nature of wireless communications is one of the major challenges to reliable data delivery in WSNs. RA-MAC achieves high link reliability in such situations by dynamically trading off data rate for channel gain. The extra gain that can be achieved reduces the packet loss rate which contributes to reduced energy expenditure through a reduced numbers of retransmissions. We achieve this at the expense of raw bit rate which generally far exceeds the application’s link requirement. To minimize communication energy consumption, RA-MAC selects the optimal data rate based on the estimated link quality at each data rate and an analytical model of the energy consumption. Our model shows how the selected data rate depends on different channel conditions in order to minimize energy consumption. We have implemented RA-MAC in TinyOS for an off-the-shelf sensor platform (the TinyNode) on top of a state-of-the-art WSN Media Access Control Protocol, SCP-MAC, and evaluated its performance by comparing our implementation with the original SCP-MAC using both simulation and experiment

IEEE 802.15.4 MAC Protocol Study and Improvement

IEEE 802.15.4 is a standard used for low rate personal area networks (PANs). It offers device level connectivity in applications with limited ower and relaxed throughput requirements. Devices with IEEE 802.15.4 technology can be used in many potential applications, such as home networking, industry/environments monitoring, healthcare equipments, etc, due to its extremely low power features. Although the superframe beacons play the key role in synchronizing channel access in IEEE 802.15.4, they are sources for energy inefficiency. This research focuses on exploring how to optimize the beacons, and designing novel schemes to distribute the information that are supposed to be delivered to a subset of PAN devices. In this work, an acknowledgement based scheme is proposed to reduce the energy consumption in the distribution of guaranteed time slot (GTS) descriptors. Based on the observation that the superframe beacon frame has global impact on all PAN devices, an energy-efficient channel reservation scheme is presented to deliver the information (GTS descriptors and pending addresses). In addition, the problem of channel underutilization is studied in the contention free period. To address the problem, a new GTS allocation scheme is proposed to improve the bandwidth utilization

IMDfence: Architecting a Secure Protocol for Implantable Medical Devices

Over the past decade, focus on the security and privacy aspects of implantable medical devices (IMDs) has intensified, driven by the multitude of cybersecurity vulnerabilities found in various existing devices. However, due to their strict computational, energy and physical constraints, conventional security protocols are not directly applicable to IMDs. Custom-tailored schemes have been proposed instead which, however, fail to cover the full spectrum of security features that modern IMDs and their ecosystems so critically require. In this paper we propose IMDfence, a security protocol for IMD ecosystems that provides a comprehensive yet practical security portfolio, which includes availability, non-repudiation, access control, entity authentication, remote monitoring and system scalability. The protocol also allows emergency access that results in the graceful degradation of offered services without compromising security and patient safety. The performance of the security protocol as well as its feasibility and impact on modern IMDs are extensively analyzed and evaluated. We find that IMDfence achieves the above security requirements at a mere less than 7% increase in total IMD energy consumption, and less than 14 ms and 9 kB increase in system delay and memory footprint, respectively

A Framework for WirelessHART Simulations

Due to stringent timing requirements of the WirelessHART protocol, we need to extend previously known hybrid simulation approaches with WirelessHART specific functionality. Because of intermediary devices that connect simulation and real environments a communication delay significantly exceeds time boundaries of a WirelessHART slot. Our solution is to add a WirelessHART-enabled intermediary device operating at the Physical and the Data Link layers that can handle time critical tasks of the WirelessHART protocol. This approach allows to evaluate the performance of a WirelessHART network and WirelessHART-enabled devices in a hybrid simulation environment

Near Field Communication Applications

Near Field Communication (NFC) is a short-range, low power contactless communication between NFC-enabled devices that are held in the closed proximity to each other. NFC technology has been moving rapidly from its initial application areas of mobile payment services and contactless ticketing to the diversity of new areas. Three specific NFC tags highlighted in the thesis have different structures in terms of memory, security and usage in different applications. NFC information tags exploit the data exchange format NDEF standardized by NFC Forum. NFC applications are rapidly stepping into novel and diverse application areas. Often they are deployed in combination with different devices and systems through their integrability and adaptability features. The diverse application areas where NFC tags and cards are used cover smart posters, contactless ticketing, keys and access control, library services, entertainment services, social network services, education, location based services, work force and retail management and healthcare. In designing different NFC applications, it is necessary to take into consideration different design issues such as to choosing the NFC tools and devices according to the technical requirements of the application, considering especially the memory, security and price factors as well as their relation to the purpose and usage of the final product. The security aspect of the NFC tags is remarkably important in selecting the proper NFC device. The race between hackers attacking and breaking the security systems of programmable high level products and manufacturers to produce reliable secure systems and products seems to never end. This has proven to be case, for example, for trying MIFARE Ultralight and DESFire MF3ICD40 tags. An important consideration of studying the different applications of NFC tags and cards during the thesis work was to understand the ubiquitous character of NFC technology.Lähitunnistus yhteys tekniikka (NFC) on lyhyen tähtäimen, pienitehoinen, kontaktiton yhteydenpito NFC yhteensopivien laitteiden välillä, jossa laitteet pidetään toistensä välittömässä läheisyydessä tiedon siirtämiseksi niiden välillä. NFC-teknologia on siirtynyt nopeasti sen alkuperäisiltä toimialueilta eli mobiili maksupalvelujen ja kontaktittomien lippujen sovellusalueilta moninaisille uusille alueille. Kolmella NFC tagillä, joita on käsitelty tässä tutkielmassa, on muistin, turvallisuuden ja käytön kannalta erilaisiä rakenteita, joita käytetään eri sovelluksissa. NFC-tagit käyttävät tiedonvälityksessä NFC Forumin standardoimaa NDEF-tiedonvaihtoformaattia. NFC sovellukset esiintyvät yhä enenevässä määrin nopeasti kehyttyvillä, uudenlaisilla ja monipuolisilla sovellusalueilla, usein yhdessä eri laitteiden ja järjestelmien kanssa. NFC on käytettävissä erinäisten laitteiden kanssa erilaisissa järjestelmäympäristöissä. Monipuoliset sovellusalueet, joissa muun muassa NFC-tagejä ja -kortteja käytetään sisältävät seuraavanlaisia sovelluksia: älykkäät julisteet, kontaktittomat liput, avaimet ja pääsynvalvonta, kirjastopalvelut, viihdepalvelut, sosiaalisen verkoston palvelut, kasvatukseen ja koulutukseen liittyvät palvelut, sijaintiperustaiset palvelut, työvoiman ja vähittäiskaupan hallinto-palvelut ja terveyspalvelut. Erilaisten NFC-sovelluksien suunnittelussa on väistämätöntä ottaa erilaisia suunnitteluasioita huomioon kuten valita NFC-työkalut ja laitteet sovelluksen teknisten vaatimusten mukaan. Erilaiset tärkeät tekijät kuten muisti, tietoturvallisuusominaisuudet ja hinta ja niiden kaikkien toimivuus lopputuotteen kannalta on otettava huomioon. Tietoturvallisuusnäkökohta on erityisen tärkeä oikean NFC laitteen valitsemisessa, sillä käynnissä on loputon kilpajuoksu hakkerien, jotka yrittävät rikkoa ohjelmoitavien korkeatasoisten laitteiden ja tuotteiden tietoturvajärjestelmiä, ja valmistajien, jotka pyrkivät tuottamaan luotettavia varmoja järjestelmiä, välillä. Tietoturvariskiin liittyviä ongelmia on löydetty esimerkiksi MIFARE Ultralight ja DESFire MF3ICD40 tageista. Tärkeä havainto, joka saatiin erilaisten NFC sovelluksien tutkimisesta, oli oivaltaa NFCteknologian potentiaalinen kaikkialle ulottuva, yleiskäyttöinen luonne