Population adaptation for genetic algorithm-based cognitive radios

Abstract — Genetic algorithms are best suited for optimization problems involving large search spaces. The problem space encountered when optimizing the transmission parameters of an agile or cognitive radio for a given wireless environment and set of performance objectives can become prohibitively large due to the high number of parameters and their many possible values. Recent research has demonstrated that genetic algorithms are a viable implementation technique for cognitive radio engines. However, the time required for the genetic algorithms to come to a solution substantionally increases as the system complexity grows. In this paper, we present a population adaptation technique for genetic algorithms that takes advantage of the information from previous cognition cycles in order to reduce the time required to reach an optimal decision. Our simulation results demonstrate that the amount of information from the previous cognition cycle can be determined from the environmental variation factor (EVF), which represents the amount of change in the environment parameters since the previous cognition cycle. I

The quest for a molecular capsule assembled via halogen bonds

A halogen-bonded capsule is obtained via directed assembly of a rigid tetra(3-pyridyl) cavitand and a flexible tetra(4-iodotetrafluorophenyl) calix[4]arene. The pyridyl nitrogen atoms from one cavitand molecule interact with the iodine atoms of a single calixarene molecule through short and directional I…N halogen bonds. The flexibility of the ethylenedioxy moieties on the calixarene platform results in positional flexibility of the iodotetrafluorobenzene sites which, coupled with a supramolecular chelating effect, allow for an effective partner-induced geometric fitting between four nitrogen atoms on the cavitand and four iodine atoms on the calixarene

Measurements and Analysis of Secondary User Device Effects on Digital Television Receivers

This is the published version. Copyright © 2009 Newman et al.This article presents results from a study of the potential effects of secondary users operating in unoccupied television spectrum. Television spectrum is known within the wireless communications community as being underutilized, making it a prime candidate for dynamic spectrum access. The proposed use of this open spectrum has prompted questions concerning the quantity of available channel space that could be used without negative impact on consumers who view digital television broadcasts and the viability of secondary use of open channels immediately adjacent to a digital television broadcast channel. In this work, we investigate secondary device operation in the channels directly adjacent to a desired television channel, and the effects upon a selection of consumer digital television (DTV) receivers. Our observations strongly suggest that secondary users could operate "White Space Devices" (WSDs) in unoccupied channel bandwidth directly adjacent to a desired digital television (DTV) channel, with no observable adverse impact upon the reception of the desired channel content

Shape evolution in the rapidly rotating 140^{140}Gd nucleus

Ground state band of $^{140}$Gd has been investigated following their population in the $^{112}$Sn($^{35}$Cl,~$\alpha$p2n)$^{140}$Gd reaction at 195 MeV of beam energy using a large array of Compton suppressed HPGe clovers as the detection setup. Apart from other spectroscopic measurements, level lifetimes of the states have been extracted using the Doppler Shift Attenuation Method. Extracted quadrupole moment along with the pairing independent cranked Nilsson-Strutinsky model calculations for the quadrupole band reveal that the nucleus preferably attains triaxiality with $\gamma$ = -30$^\circ$. The calculation though shows a slight possibility of rotation around the longest possible principal axis at high spin $\sim$ 30$\hbar$ which is beyond the scope of the present experiment

Implementing opportunistic spectrum access in LTE-Advanced

Long term evolution advanced (LTE-A) has emerged as a promising mobile broadband access technology aiming to cope with the increasing traffic demand in wireless networks. However, the enhanced spectral efficiency offered by LTE-A may become futile without a better management of scarce and overcrowded electromagnetic spectrum. In this sense, cognitive radio (CR) has been proposed as a potential solution to the problem of spectrum scarcity. Among all the mechanisms provided by CR, opportunistic spectrum access (OSA) aims at a dynamic and seamless use of certain licensed bands provided the licensee is not harmfully affected. This operation requires spectral awareness in order to avoid interferences with licensed systems. In spite of implementing some spectrum sensing mechanisms, LTE-A technology lacks other tools that are needed in order to improve the knowledge of the radio environment. This work studies the adoption of a Geo-located data base (Geo-DB) that cooperatively retrieves and maintains information regarding the location of unutilized portions of spectrum potentially available for OSA. Moreover, the potential benefit of this LTE-compliant OSA solution is evaluated using a calibrated simulation tool, by which numerical results allow us to optimally configure the system and show that the proposed opportunistic system is able to significantly improve its performance.The authors would like to thank the funding received from the Ministerio de Ciencia e Innovacion within the Project number TEC2011-27723-C02-02 and from the Ministerio de Industria, Turismo y Comercio TSI-020100-2011-266 funds. This article had been written in the framework of the CELTIC project CP08-001 COMMUNE. Study by X. Gelabert is funded by the BP-DGR 2010 scholarship (ref. 00192). The authors would like to acknowledge the contributions of their colleagues.Osa Ginés, V.; Herranz Claveras, C.; Monserrat Del Río, JF.; Gelabert, X. (2012). Implementing opportunistic spectrum access in LTE-Advanced. EURASIP Journal on Wireless Communications and Networking. 2012(99):1-17. https://doi.org/10.1186/1687-1499-2012-99S117201299Martín-Sacristán D, Monserrat JF, Cabrejas-Peñuelas J, Calabuig D, Garrigas S, Cardona N: On the way towards fourth-generation mobile: 3GPP LTE and LTE-Advanced. EURASIP J Wirel Commun Netw 2009, 2009: 1-10.Ratasuk R, Tolli D, Ghosh A: Carrier aggregation in LTE-Advanced. In IEEE 71st Vehicular Technology Conference (VTC 2010-Spring). Taipei; 2010:1-5.Wang H, Rosa C, Pedersen K: Performance of uplink carrier aggregation in LTE-advanced systems. In IEEE 72nd Vehicular Technology Conference Fall (VTC 2010-Fall). Ottawa; 2010:1-5.Tandra R, Sahai A, Mishra S: What is a spectrum hole and what does it take to recognize one? 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In International Congress on Ultra Modern Telecommunications and Control Systems and Workshops (ICUMT). Moscow; 2010:965-969.Hussain S, Fernando X: Spectrum sensing in cognitive radio networks: Up-to-date techniques and future challenges. In IEEE Toronto International Conference on Science and Technology for Humanity (TIC-STH). Toronto; 2009:736-741.Xu Y, Sun Y, Li Y, Zhao Y, Zou H: Joint sensing period and transmission time optimization for energy-constrained cognitive radios. EURASIP J Wirel Commun Netw 2010, 2010: 1-16.Yucek T, Arslan H: A survey of spectrum sensing algorithms for cognitive radio applications. IEEE Commun Surv Tutor 2009, 11: 116-130.Cabric D, Mishra S, Brodersen R: Implementation issues in spectrum sensing for cognitive radios. In Conference Record of the Thirty-Eighth Asilomar Conference on Signals, Systems and Computers. Volume 1. Pacific Grove; 2004:772-776.Zeng Y, Liang YC, Hoang A, Peh E: Reliability of spectrum sensing under noise and interference uncertainty. In IEEE International Conference on Communications Workshops, 2009. ICC Workshops. Dresden; 2009:1-5.Bixio L, Ottonello M, Raffetto M, Regazzoni CS: Comparison among cognitive radio architectures for spectrum sensing. EURASIP J Wirel Commun Netw 2011, 2011: 1-18.Mustonen M, Matinmikko M, Mammela A: Cooperative spectrum sensing using quantized soft decision combining. In 4th International Conference on Cognitive Radio Oriented Wireless Networks and Communications, 2009 (CROWNCOM'09). Hannover; 2009:1-5.Xiao L, Liu K, Ma L: A weighted cooperative spectrum sensing in cognitive radio networks. In International Conference on Information Networking and Automation (ICINA). Volume 2. Kunming; 2010:45-48.Pan Q, Chang Y, Zheng R, Zhang X, Wang Y, Yang D: Solution of information exchange for cooperative sensing in cognitive radios. In IEEE Wireless Communications and Networking Conference, 2009 (WCNC'2009). Budapest; 2009:1-4.Masri A, Chiasserini CF, Perotti A: Control information exchange through UWB in cognitive radio networks. In 5th IEEE International Symposium on Wireless Pervasive Computing (ISWPC). Modena; 2010:110-115.Celebi H, Arslan H: Utilization of location information in cognitive wireless networks. IEEE Wirel Commun 2007, 14(4):6-13.FCC: Notice of Proposed Rulemaking, in the Matter of Unlicensed Operation in the TV Broadcast Bands (ET Docket no. 04-186) and Additional Spectrum for Unlicensed.Marcus MJ, Kolodzy P, Lippman A: Reclaiming the vast wasteland: why unlicensed use of the white space in the TV bands will not cause interference to DTV viewers. New America Foundation: wireless future program, tech rep 2005.Nam H, Ghorbel M, Alouini M: Proc. of the Fifth International Conference on Cognitive Radio Oriented. In Proc of the Fifth International Conference on Cognitive Radio Oriented Wireless Networks Communications (CROWNCOM). Cannes; 2010:1-5.IEEE Std 80221-2008: IEEE Standard for Local and Metropolitan Area Networks-Part 21: Media Independent Handover. 2009.3GPP TS 36133: Evolved Universal Terrestrial Radio Access (E-UTRA); Requirements for support of radio resource management.Sesia S, Baker M, Toufik I: LTE, the UMTS long term evolution: from theory to practice. Wiley, New Haven; 2009.Digham FF, Alouini MS, Simon MK: On the energy detection of unknown signals over fading channels. In IEEE International Conference on Communications, 2003 (ICC'03). Volume 5. Anchorage; 2003:3575-3579.Ghasemi A, Sousa ES: Collaborative spectrum sensing for opportunistic access in fading environments. In First IEEE International Symposium on New Frontiers in Dynamic Spectrum Access Networks (DySPAN). Baltimore; 2005:131-136.Gelabert X, Akyildiz IF, Sallent O, Agustí R: Operating point selection for primary and secondary users in cognitive radio networks. Comput Netw 2009, 53(8):1158-1170. 10.1016/j.comnet.2009.02.009Taniuchi K, Ohba Y, Fajardo V, Das S, Tauil M, Cheng YH, Dutta A, Baker D, Yajnik M, Famolari D: IEEE 802.21: media independent handover: features, applicability, and realization. IEEE Commun Mag 2009, 47: 112-120.3GPP TS 36305: Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Stage 2 functional specification of User Equipment (UE) positioning in E-UTRAN.3GPP TS 36355: Evolved Universal Terrestrial Radio Access; LTE Positioning Protocol (LPP).3GPP TS 36455: Evolved Universal Terrestrial Radio Access; LTE Positioning Protocol A (LPPa).Ren W, Zhao Q, Swami A: Power control in cognitive radio networks: how to cross a multi-lane highway. IEEE J Sel Areas Commun 2008, 27(7):1283-1296.3GPP R1-084424: Control Channel Design Issues for Carrier Aggregation in LTE-A.Dajie J, Haiming W, Malkamaki E, Tuomaala E: Principle and performance of semi-persistent scheduling for VoIP in LTE system. In International Conference on Wireless Communications, Networking and Mobile Computing, 2007 (WiCom 2007). Shanghai; 2007:2861-2864.Rajbanshi R, Wyglinski AM, Minden GJ: An efficient implementation of NC-OFDM transceivers for cognitive radios. In Proc of 1st Conf on Cognitive Radio Oriented Wireless Networks and Commun. Mykonos; 2006:1-5.Wellens M, Riihijarvi J, Mahonen P: Modeling primary system activity in dynamic spectrum access networks by aggregated ON/OFF-processes. In 6th Annual IEEE Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks Workshops, 2009. SECON Workshops'09. Rome; 2009:1-6.3GPP TS 36214: Physical layer; Measurements.Ofuji Y, Morimoto A, Abeta S, Sawahashi M: Comparison of packet scheduling algorithms focusing on user throughput in high speed downlink packet access. In 13th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications. Volume 3. Lis-boa; 2002:1462-1466.ITU-R ITU M2135: Guidelines for evaluation of radio interface technologies for IMT-Advanced 2008

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

Quantitative comparison of agile modulation techniques for cognitive radio transceivers

In this paper, we present a quantitative comparison of two agile modulation techniques employed by cognitive radio transceivers operating in a dynamic spectrum access (DSA) network. One of the modulation technique is non-contiguous orthogonal frequency division multiplexing (NC-OFDM), which is designed to avoid interference with the transmissions of incumbent users by deactivating subcarriers within their vicinity. The other modulation technique under study is a variant of multicarrier code division multiple access (MC-CDMA). Although several studies comparing conventional OFDM and MC-CDMA has been conducted in literature to justify robust error performance of MC-CDMA, a quantitative performance evaluation of these schemes has not been performed when employed in a DSA network. Due to deactivated subcarriers in DSA networks, in this paper we showed their performance can be significantly different from the conventional setup. Analytical expressions for the error probability of an NC-OFDM transceiver have been derived and compared with computer simulation results. The results show that the error robustness of NC-OFDM is relatively constant regardless of the number of deactivated subcarriers, unlike MC-CDMA transmissions, whose error performance degrades with an increase in deactivated subcarriers.

Cataract Surgery in the Eye Camp and its Follow up

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