Zornitza Genova Prodanoff

Optimal frame size analysis for framed slotted ALOHA based RFID networks

We offer an analytical solution for the optimal frame size of the non-muting version of the Basic Frame Slotted ALOHA collision resolution protocol for RFID networks. Previous investigations of RFID frame size have been empirical and have not yielded a general result. Our theoretical analysis provides a generalized result. Our solution can be used to determine the optimal frame size for any given number of RFID tags. Suboptimal selection for the frame size can result in substantially longer than minimum census delays and can unnecessarily increase energy consumption. We were able to demonstrate about 20% performance improvement in reduced census delay for a given range of values. Our results can help speed-up reader-side processing times, lower the implementation complexity of RFID readers, and increase their energy efficiency.

RFID Model for Simulating Framed Slotted ALOHA Based Anti-Collision Protocol for Muti-Tag Identification

Radio Frequency Identification (RFID) networks use radio signal broadcast to automatically identify items with attached RFID tags. A tag consists of a microchip that stores a unique identifier and an antenna. The tag’s antenna is attached to the chip and can transmit a unique tag identifier to a reader (also called interrogator). The reader is capable of learning the set of tags within its interrogation range. The process of learning in-range tags is called a census. After an initial census is completed, the reader can answer queries about the presence of specific tag(s) within its range sent to it from other type of devices. RFID systems have abundant benefits as compared to the barcode and smart card systems. RFID networks use radio frequency as a method of data transmission. Thus, unlike barcode labels, a tag does not need to be placed in a line of sight position from the reader, or even get in contact with a reader as smart cards, in order to be identified successfully. Depending on whether they use low, high, or ultrahigh transmission frequencies, RFID tags are identifiable within 3 meters span in case of a typical far-field reader [Want06] or at even further distances. Therefore, RFID tags are used more flexibly and conveniently than existing barcode and smart card implementations. Moreover, some commercial implementations of RFID tags can store data in the amount of 16bytes 64Kbytes [Finkenzeller03]. RFID tags can hold the same amount of data compared to smart cards, and much larger volume than barcodes. In addition, RFID tags are getting less expensive. The cost of RFID chips at the time of this study is less than 10 cents, while back in 1999, for example, was around 2 US dollars. Since tag readers have limits on their operations range imposed by the frequency of the wireless signal used, when RFID networks need to cover large spaces, multiple readers need to be used. The cost of current reader implementations is hundreds of US dollars. As a result, RFID networks may not be yet suitable to track large inventories of inexpensive items, but they are certainly becoming more affordable and can be used to track different types of items, e.g. live stock, pets, and valuable goods. Due to these advantages RFID systems are emerging as one of the alternative technologies of our time.

Performance Model of a Campus Wireless LAN

In this study we measured simulated end user HTTP response times in a 802.11g WLAN. Our results show that, ceteris paribus, modeling heavy tailed file sizes at an HTTP server, results in two times worse response times as compared to modeling Web pages of lognormal file sizes. Accesses to content containing large images and embedded documents appear to result in tolerable end user response times, as long as HTTP server directories contain a small number of such large files, that is, if file sizes are modeled by a heavy tailed Pareto distribution, where minimum file sizes are 100 Kbytes or less. When file size at the server become larger, with a minimum size of 1Mbytes, response times increase substantially and may quickly become intolerable by users. Our results confirm related findings in (3) and demonstrate that studies which do not consider these findings may present too optimistic results, misrepresenting real end user delays of Web accesses.

CRC32 Based Signature Generation Methods for URL Routing

Signature algorithms have already been proposed for use in URL routers. Cyclic Redundancy Check (CRC) codes can be used as URL signatures. When a packet is received, CRCs are generated on the fly with the use of very simple hardware circuits. Existing network adapters are not programmed to generate CRCs on packet subfields. However, it is possible to use the CRC circuit of a network adapter to simultaneously generate the packet CRC and CRCs on any subfield (such as the URL string in the HTTP GET request header) of the packet. The intermediate CRC codes (available from the CRC circuit) can then be used to produce a URL signature for each incoming HTTP request and do URL routing table look-up. In this paper we evaluate alternatives for URL signature generation that rely on hardware or software computation of CRC32 codes. Our results indicate that the delay of producing the signature in software is smaller (100s of nanoseconds) as compared to the alternative of using the CRC circuit in existing adapters (10s of microseconds).

Queueing Behavior of Hashing Methods Used to Build URL Routing Tables

This study pioneers a new way to study the performance of hashing algorithms by evaluating their queueing behavior. We examine hashing as applied to URL routing used in Content Distribution Networks (CDNs). URL routing tables can be built as self-adjusting hash tables to reduce network bandwidth consumption in CDNs and at the same time take advantage of the high temporal locality of Web document requests. We show through a trace-driven simulation that the existing Aggressive hashing (based on move-to-front rule) improves upon H1 hashing (based on the transposition rule). Surprising results were found: even though the expected improvement in look-up time over H1 hashing is modest, the improvement from a queueing perspective appears to be very significant. The long range dependence in look-up time of H1 hashing contributes to its extreme queueing delay. This shows that using queueing delay as a means of evaluating hashing algorithms can be very insightful. Fig. 1 URL router forwarding or redirecting a request

Piece-wise constant models for RFID traffic

Available security standards for RFID networks (e.g. ISO/IEC 29167) are designed to secure individual tag-reader sessions and do not protect against active attacks that could also compromise the system as a whole (e.g. tag cloning or replay attacks). Proper traffic characterization models of the communication within an RFID network can lead to better understanding of operation under “normal” system state conditions and can consequently help identify security breaches not addressed by current standards. We consider the adaptation of two known piece-wise linear models for the purposes of modeling RFID command arrivals at a reader: Bayesian Blocks and Knuths rule. Our preliminary results indicate that both methods could potentially be used to detect changes in system state (e.g. changes in the rate of command arrivals at a reader).

A framework for integrating multicultural issues in mobile health apps design

Mobile health applications have been found to facilitate earlier and more effective intervention of both physical and mental illness. The applications offer unique opportunities for monitoring progress, providing education materials, receiving personalized prompts and support, collecting ecologically valid data, and using self-management interventions when and where they are needed. Mobile Health will help doctors to reach out effectively to minority populations and remote areas where healthcare is seriously or even totally lacking. From a cultural perspective, culturally sensitive ethical principles are needed to safeguard privacy between patient and family members. Many mobile health apps are available now and there is gap between multicultural and privacy issues. There are few research papers to discuss the multicultural issues in mobile health. This project is attempting to analyze the factors of mental health apps in a multicultural perspective and to give guideline of designing each app with considering cultural factors.

Determining predisposition to insider threat activities by using text analysis

Insider threats are difficult to deal with because employees in any organization have a certain level of access to the companys secure network which bypasses the external security measures such as firewalls that have been put in place to protect the organization. The goal of this paper is to design and implement a predictive model which uses linguistic analysis as well as K-means to determine an employees risk level computer-mediated communication specifically emails and related social networking. Computer-mediated communication (CMC) is a form of communication over virtual spaces where users cannot see each others face. CMC includes email and communication over social networks, amongst others. This will be accomplished by determining whether or not employees meet certain personality criteria which establish how much of a risk they pose to their employers. In this study, various datasets are used including a real-world case study as a test bed for designed algorithm and tested results.

Performance of BFSA Collision Resolution: RFID Including Non-unique Tag IDs

As RFID technology becomes ever more affordable, its large scale implementation has been a growing trend in recent years. While current protocols allow for non-unique tag IDs, most existing implementations largely optimize RFID system’s performance based on the assumption of unique tag IDs and treat the existence of non-unique tag IDs within reader’s range as a rare occurrence. Nevertheless, unless formally evaluated, it is not clear, what is the degree of performance degradation in the presence of non-unique tag IDs . We evaluate the behavior of Basic Frame Slotted ALOHA (BFSA) collision resolution for an RFID system using OPNET Modeler 14.5 as both simulation, as well as, analytical results visualization platform. The system is built assuming muting of tags by the reader and contains a mix of unique and non-unique tag IDs. Our findings are compared with results obtained from the evaluation of a similar model for a system consisting solely of unique tag IDs . The comparison of total census delay and throughput under variable frame sizes showed an increase in total census delay with an increase in number of tags and a decrease in network throughput with increase in the number of tags for the system allowing non-unique IDs.