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• A real-time application for secure data transmission using a different approach. • The receiver system requires a confirmation signal to perform necessary action. • Utilizing chaos dynamics for generating secret codes used in the algorithm. • The transmitted data can be a simple bit or any multimedia data of major systems. In today's technology, remote control or access is widely used in many platforms. However, the fact that remotely controlled platforms are open to external attacks or not secure enough which can have serious negative consequences. In this paper, a real-time LoRa modulation based data transmission application is achieved. The security of remotely transmitted data is not only provided with a basic encryption structure, but also a confirmation signal based transceiver system is designed in which the required process is performed only with a certain time interval. Firstly, the data to be transmitted is mixed with a secret key using XOR operation then transmitter creates a random period of time that specifies how long after the confirmation signal will be sent relative to the data signal. Hence, the entire system security is enhanced by the timing algorithm running with millisecond precision between the transceiver circuits. Encryption of the confirmation signal in a similar structure as the data signal improves security of the entire system. In this application, a PWM signal containing voltage information has been successfully transmitted in ciphered form using LoRa modulation. The designed algorithm for the receiver and transmitter circuits has been tested and verified in real time application. Experimental results show that the proposed scheme can be applied to any application-based communication system. [ABSTRACT FROM AUTHOR]

SUMMARY This paper investigates bidding strategy problems of generation companies in electricity markets. A new bidding model is set up, and a solution approach is presented. Compared with existing models, the model proposed in this paper has some different characteristics. First, the model adopts a bilevel optimization framework where the upper-level optimization is to maximize the profit of generation companies, and the aim of the lower-level optimization is the maximal social welfare and the security of the operation system considered by the Independent System Operator. This model combines practical situations faced by market agents in real-life operations and the requirement of both the system security and the social welfare. Second, the popular risk measure, called conditional value at risk, is used in the bidding model, which can quantify the market risk and describe the competitive mechanism effectively. For solving the complicated bilevel optimization model, a hybrid particle swarm optimization algorithm is presented. Numerical examples are used to validate the model and the algorithm. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Approaches to access control (AC) policy languages, such as eXtensible access control markup language, do not provide a formal representation for specifying rule- and policy-combining algorithms or for verifying properties of AC policies. Some authors propose formal representations for these combining algorithms. However, the proposed models are not expressive enough to represent formally history-based classes of these algorithms, such as ordered-permit-overrides. In addition, some other authors propose a formal representation but do not present automated support for formal verification of properties of AC policies that use these algorithms. This paper demonstrates a new representation that can express all existing AC rule and policy combinations of which the authors are aware. This representation can also be used to automate the formal verification of properties of AC policies related to these algorithms. A new modeling representation for rule- and policy-combining algorithms based on state machines is used to specify rule- and policy-combining algorithms. Examples of these algorithms are programmed in the language of the SPIN model checker, and the programs are then used to support the automated formal verification of properties of AC policies. We present our approach and then use the AC policies and properties of CONTINUE, a conference management system, to compare it with prior work. Our first contribution is a new modeling representation for combining algorithms based on state machines. The second contribution is the formal verification of AC properties under certain combining algorithms that are beyond the capability of other approaches. [ABSTRACT FROM AUTHOR]

During the past decade, there has been much standardization effort for indoor or shot-range networks, as communication devices and applications for such networks populate. As a prominent example of these activities, the IEEE 802.15.3 Task Group (TG) published a standard for high-rate wireless personal area network (HR-WPAN). To support strictly timed multimedia services, the TG adopts a time-slotted channel access protocol controlled by a central device (DEV). Although the channel time allocation algorithm plays a key role in deciding the network performance, it remains unspecified in the standard. Therefore, in this paper, we propose a novel feedback-assisted channel time allocation method for HR-WPAN. After initial channel times are allocated based on packet inter-arrival time statistics, the allocation is dynamically adjusted by utilizing feedback information from each DEV. The feedback information includes the buffer status, the packet transmission delay, and the physical transmission rate. By utilizing this feedback information, the central DEV can allocate sufficient channel time for transmissions of pending packets from a DEV. Moreover, the allocated channel times can be synchronized to the packet arrival times so that the overall transmission delay is reduced. To cope with time-varying wireless channels, a dynamic rate selection algorithm assisted by physical layer information is proposed in this paper. Performance evaluation is carried out through extensive simulations, from which significant performance enhancements are observed. [ABSTRACT FROM AUTHOR]

In this paper, three random access control mechanisms based on the well-known Slotted ALOHA, NP-CSMA, and 1P-CSMA protocols are presented. The basic idea is to limit the number of transmissions and retransmissions at high traffic loads in order to minimize collisions while keeping system stability. A new medium-access control protocol called Adaptive "fraflic Load (ATL) is proposed. With ATL, all users are assigned authorization of transmission probabilities that vary according to the prevailing average traffic conditions in the system. ATL ensures that the system throughput is kept constant at its maximum value regardless of the traffic load. A mathematical analysis to calculate the probability density function of the access delay in the ATL protocol under the assumption of infinite user population is also presented. Mean access delay follows increases exponentially with respect to the traffic load when conventional random access protocols are used. However, it follows a linear function with respect to the traffic load when ATL is used. The average traffic load of the system is an input of the ATL protocol in order to assign access authorization probabilities to all users attempting to access the network. A simple algorithm for traffic load estimation based on the probability of finding empty slots in the system within an estimation period is proposed in this paper to asses the average traffic load. In the numerical evaluations of ATL, the Enhanced Data for GSM Evolution (EDGE) system is considered as a case study. For high arrival rates, channel utilization can be low in EDGE even if the system has sufficient capacity to serve incoming data users. A mathematical analysis of ATL-Slotted ALOHA as well as ATL-CSMA is presented. In the case of ATL-CSMA, system throughput varies according to the cell size. Hence, the ATL protocol is evaluated in picocell, microcell and macrocell environments as recommended by ITU-R. Also, the performance of EDGE is evaluated in terms of average data rate and packet delay for both S-ALOHA and ATL S-ALOHA considering long range dependent traffic type. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a Block Time Bounded Time Division Multiple Access (BTB-TDMA) medium access control (MAC) protocol is proposed for mobile underwater nodes (UNs) in underwater acoustic networks (UANets). The BTB-TDMA determines transmission schedule of UNs based on UNs'' estimated propagation delays (EPDs), reflecting on UNs'' mobility. Furthermore, the scheduling algorithm gives UNs time bound for data transfer with a unit of time block in order to reduce overall delay and avoid packet collisions among UNs. To analyze the protocol''s performance, we divide BTB-TDMA into two cases, BTB-TDMA considering EPDs (BTB-TDMA1) and BTB-TDMA without considering EPDs (BTB-TDMA2), to show how the use of EPDs can improve overall network performance. In addition, we analytically derive the channel access delay and channel utilization of STUMP () and TDMA, and compare them with those of BTB-TDMA. The numerical analysis shows that BTB-TDMA1 can reduce channel access delay by 20% and increase channel utilization by 35% at the maximum compared to those of BTB-TDMA2. BTB-TDMA2 provides at least 14% lower channel access delay and 37% higher channel utilization than STUMP. Furthermore, BTB-TDMA significantly outperforms TDMA, regardless of the network environment. [Copyright &y& Elsevier]

In this paper, an enhanced cooperative, statistics-driven spectrum sensing algorithm, called Dynamically Optimized Spatiotemporal Prioritization (DOSP), is developed for improving spectrum sensing efficiency in the media access control (MAC) layer of cognitive radio (CR) systems. The target of the DOSP algorithm is to improve spectrum sensing efficiency and achieve better spectrum access opportunities by prioritizing channels for fine sensing. The sensing priority is determined dynamically and intelligently based on an optimal statistical fusion that jointly considers both the local statistics obtained by the individual cognitive radios as well as the long-term spatiotemporal statistics obtained by other cognitive radios in the network. As such, the individual cognitive radio peers work together to get the most out of available spectrum opportunities. Numerical results demonstrate that the proposed DOSP algorithm is capable of achieving better performance compared with recently reported cooperative spectrum sensing methods in terms of overhead and percentage of missed spectrum opportunities. Furthermore, results show that the DOSP algorithm is more robust to the environment of low cognitive radio densities than that by using other state-of-the-art cooperative spectrum sensing methods. [ABSTRACT FROM AUTHOR]

The 802.16e power management helps to increase the lifetime of Mobile Subscriber Stations (MSSs) by reducing their energy consumption, but this reduction results in Medium Access Control (MAC) Service Data Unit (SDU) response delay. Hence, both energy consumption and MAC SDU response delay are important performance metrics; however, they have a trade-off relationship. To guarantee the delay constraints of delay-sensitive applications, operating parameters in sleep-mode operation such as minimum sleep interval, Tmin, and maximum sleep interval, Tmax, should be considered seriously. Especially, large Tmax, results in high MAC SDU response delay. However, in the IEEE 802.16e standard, this point is not given enough attention. In this paper, we first propose a numerical model to determine Tmax based on MAC SDU response delay. Then, we propose a Delay -Guaranteed Energy Saving (DGES) algorithm to minimize energy consumption with a given MAC SDU response delay by finding the optimal Tmax under a fixed Tmin. Our proposed numerical model and DGES algorithm are verified by simulation results. [ABSTRACT FROM AUTHOR]

Hidden terminals can significantly lower the throughput of such competitive MAC protocols as CSMA. Therefore, a large number of MAC protocols that implement different hidden terminal strategies have been developed. In this paper we propose an algorithm for generating evaluation networks with different ratios of hidden terminals in order to evaluate the effect of hidden terminals on competitive MAC protocols. In addition, we use the same algorithm to report results that elucidate the characteristics of throughput as the ratio of hidden terminals that exist in a network is varied for both CSMA, a representative competitive MAC protocol, and MACA, a MAC protocol that makes use of RTS/CTS control, a representative hidden terminal strategy. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(4): 46–55, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20343 [ABSTRACT FROM AUTHOR]