DOCSLIB.ORG

Comparison of FFT and Goertzel Algorithms Used in DTMF Detection

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Comparison of FFT and Goertzel Algorithms Used in DTMF Detection IJRECE VOL. 6 ISSUE 4 ( OCTOBER- DECEMBER 2018) ISSN: 2393-9028 (PRINT) | ISSN: 2348-2281 (ONLINE) Comparison of FFT and Goertzel Algorithms Used in DTMF Detection System Using GUI Pediredla Hima Bindu1, Sateesh Virothu2, Dr.M.Satya Anuradha3 1M.Tech Student, 2 Research Scholar, 3 Associate Professor Department of Electronic and Communication Engineering, Andhra University, Visakhapatnam, India (E-mail: pediredlahimabindu@gmail.com) Abstract— Dual Tone Multi Frequency (DTMF) signalling function when used with a microcontroller for automation of system is now-a-days a prevalent part of Industrial automation systems. and many other communication systems. In DTMF system, a At the transmitter of the DTMF system, a composite signal dial tone composed of two sine waves is generated at is generated with two tones when a key is pressed on touch tone transmitter end. At the receiver, the detection of DTMF signal keypad and is transmitted. This signal is detected at the DTMF can be achieved using different methods viz. digital filters, Fast receiver using different analog and digital detection methods. In Fourier Transform algorithm, Goertzel algorithm, correlation analog methods, analog filters are used to detect signal. In digital algorithm etc. In this paper, FFT and Goertzel algorithms are methods, Digital filters, FFT algorithm, Goertzel algorithm, used for detection of DTMF signal and these algorithms are Correlation algorithm are used. Earlier analog methods were compared under different SNR conditions. The entire system is used. But due to the rapid development in digital implemented in MATLAB Graphical User Interface (GUI). communication, these methods are replaced by efficient Digital Additive White Gaussian Noise is added. The parameters of methods. analysis considered for this work are Twist and computational EARLIER WORKS complexity. A. A. Deosthali et.al. [1] proposed the DTMF system which Keywords— DTMF; FFT; Goertzel algorithm; MATLAB, is developed by using second order Finite Impulse response AWGN; snr; Twist adaptive notch filters to eliminate unwanted noise. They have used a sophisticated Decision Logic system to validate the detected signal. The system is studied under different SNR I. INTRODUCTION values. DTMF detection using Goertzel algorithm using MATLAB is implemented by Miloš Trajkovié [2]. It introduced In today’s digital world, various methods are being the parameter tests like Twist test, SNR test and N test to test the developed to control devices wirelessly. Mobile phone is being system performance. used everywhere from household applications to industrial and military applications to operate devices from remote areas. Dual Suvad Selman[3] presented a DTMF system using various Tone Multi Frequency (DTMF) system has become an detection algorithms viz. Filter design approach, FFT algorithm, economic solution for this purpose. Goertzel algorithm and Sub-Band NDFT algorithm are used to develop the DTMF Detectors in MATLAB and this system is DTMF signaling was developed by Bell labs in United States implemented using TMS320C6713, digital signal processor. in 1960s in order to achieve the purpose of long distance The performance is compared using the parameters Figure of telephone calling. It is also being used in communication Merit and computational complexity. systems, Automation systems. It was an ideal replacement for slower pulse dialing system where it was necessary to use rotary Yongbao Song [4] had achieved the DTMF detection using type dials which are quite slow. the algorithms-FFT, Goertzel algorithm and SB-NDFT algorithm. The three algorithms are analysed and their Tone dialing is used in DTMF systems instead of pulse advantages and disadvantages were given for comparison. Liu dialing. Tone dialing uses specific tones to indicate the number Yuying [5] gave a detailed analysis of the Goertzel algorithm that was entered while pulse dialing uses a number of signal filter banks and developed the DTMF system using Goertzel pulses. This tone dialing is very quick and easy to use method detection algorithm in the MATLAB environment. for long distance communication using telephone lines. In this paper, the implementation of DTMF system using two Dual tone multi frequency signaling system or touch tone detection algorithms i.e., FFT algorithm and Goertzel algorithm. system uses a signal composed of two specific frequencies when Further, a comparison analysis is given for these detection a tone is dialed in the touch tone keypad. The touch tone keypad algorithms. consists of digits from 0 -9, alphabets A, B, C, D and symbols * and #. Each of these keys can be used to achieve a specific The paper is structured as: section 2 gives DTMF transmission and reception, section 3 gives Detection algorithms INTERNATIONAL JOURNAL OF RESEARCH IN ELECTRONICS AND COMPUTER ENGINEERING A UNIT OF I2OR 69 | P a g e IJRECE VOL. 6 ISSUE 4 ( OCTOBER- DECEMBER 2018) ISSN: 2393-9028 (PRINT) | ISSN: 2348-2281 (ONLINE) section 4 gives flowcharts and description, section 5 gives B. DTMF Reception results discussion followed by conclusion and references. At the receiver, the signal received might be the original transmitted signal or the signal with noise added to it. In practical systems, the signal gets corrupted with noise in the II. DTMF TRANSMISSION AND RECEPTION channel before reaching the receiver. Thus in our system, an Additive White Gaussian Noise (AWGN) is added to the A. DTMF Transmission received signal to validate the key under noisy conditions to replicate the practical systems. DTMF Transmitter system produces the dual tone signal by Some of the detection methods that are used are FFT selecting frequencies from a set of eight audible frequencies. algorithm, Goertzel algorithm, Correlation algorithm, SB- These frequencies are selected by AT&T and BELL Labs. This NDFT algorithm etc. In this work, FFT and Goertzel algorithms set of frequencies is transmitted in pairs to represent 16 signals, are implemented and their performance is compared using the that represent digits 0-9, the letters A- D, and the symbols * and parameters - Twist, power and Computational complexity. # in Touch tone keypad as shown in figure (1). III. DETECTION ALGORITHMS These frequencies are selected in such a way that they have the following unique properties: The detection algorithms that are used in this work are given as follows. (i)When a key is pressed then it can be detected by human ear since all tones are in audio frequency range. (ii)No frequency A. Fast Fourier Transform Algorithm is harmonic to other frequency. (iii)Difference or sum of any two Fast Fourier Transform is basically a faster way of frequencies is not equal to any other frequency. computing Discrete Fourier Transform of a signal in digital The frequencies used are divided into row and column signal processing. It is also the efficient way to calculate an N- groups depending on low and high frequencies respectively as point DFT if the number of samples is chosen to be a power of shown in figure (1). 2. The DTMF signal generated for a tone can be represented as In FFT algorithm, a discrete signal is represented as an in equation (1). algebraic sum of its frequency components. The general representation of FFT of a discrete signal 푦̈[푛] is given in 푥푡푟(푡) = 퐴0 sin(2휋푓1푡) + 퐴1 sin(2휋푓2푡) (1) equation (2). Where 퐴0=amplitude of low frequency sine signal 퐹퐹푇 {푦̈[푛]} = 푌̈ (퐾) 2휋 퐴1= amplitude of high frequency sine signal 푁−1 −푗 푛푘 = ∑푛=0 푦̈(푛)푒 푁 , 0 ≤ 푘 ≤ 푁 − 1 (2) 푓 = signal from low frequency group 1 The continuous signal that is received at the DTMF detector 푓2= signal from high frequency group be represented as 푥푟(t) and this is signal is sampled and is represented as 푥 [n] and these are given in equations (3) and (4) 푟 respectively. 푥푟(푡) = 퐵0 sin(2휋푓1푡) + 퐵1 sin(2휋푓2푡) (3) 푛 푛 푥푟[푛] = 퐵0 sin (2휋푓1( )) + 퐵1 sin (2휋푓2( )) (4) 퐹푠 퐹푠 Where 퐵0, 퐵1 = amplitudes of the two sine signals 푓1, 푓2 = frequencies of the two sine waves Fs= sampling frequency Now, FFT for the signal 푥푟[n] is given in equation (5) as follows Figure 1: Touch tone Keypad 2휋 −푗 푛푘 푋 (푘) = ∑푁−1 푥 (푛)푒 푁 , 0 ≤ 푘 ≤ 푁 − 1 (5) 푟 푛=0 푟 푁−1 −푘푛 The generated signal is transmitted to the DTMF receiver = ∑푛=0 푥푟(푛) 푊푁 , 0 ≤ 푘 ≤ 푁 − 1 (6) which is at remote distance and the corresponding key is Where N=Number of samples detected using various detection algorithms. 2휋 −푗 and 푊푁 = 푒 푁 For DFT with N number of samples, number of complex additions required are N (N-1) and number of complex multiplications required are 푁2. But by using FFT algorithm, the INTERNATIONAL JOURNAL OF RESEARCH IN ELECTRONICS AND COMPUTER ENGINEERING A UNIT OF I2OR 70 | P a g e IJRECE VOL. 6 ISSUE 4 ( OCTOBER- DECEMBER 2018) ISSN: 2393-9028 (PRINT) | ISSN: 2348-2281 (ONLINE) computations are reduced to about N푙표푔2 푁 complex additions 푁 and 푙표푔 푁 complex multiplications. The reduction in 2 2 computations is achieved by using the properties of the complex 푘푛 number 푊푁 . The properties that are used are symmetricity and periodicity. For a DTMF signal only a specific set of frequencies are to be studied, but FFT algorithm analyses the entire spectral components which leads to power wastage and increase in computational complexity. Thus more efficient algorithm is introduced i.e., Goertzel algorithm. B. Goertzel Algorithm Goertzel algorithm analyses the spectrum only at the specific frequency/set of frequencies thus is more suitable for systems like DTMF. The computational efficiency depends upon the number of samples considered for the system analysis. For the time-domain sequence푥푟[푛] , N-point DFT is 푋푟(푘) , and we know that 푊푁 − 푘푁=1, so, Figure 2: Goertzel Filter bank 푁−1 푛푘 푋푟(푘) = 퐷퐹푇{푥푟[푛]} = ∑푛=0 푥푟[푛]푊푁 (7) The transfer function for the Goertzel filter is given in −푘푁 푁−1 푛푘 equation (14) = 푊푁 ∑푛=0 푥푟[푛]푊푁 (8) ̈ ̈ 1 −(푁−푛)푘 퐻푘(푍) = 푍푇{ℎ푘(푛)} = 푗2휋푛푘 (14) 푁−1 − = ∑푛=0 푥푟[푛]푊푁 (9) (1−푒 푁 푧−1) To reduce the complex calculations, the first order single pole filter is changed into a second order double pole filter as Now consider a new sequence 푦 (푛) as defined in equation (10) 푟 given in equation (15).
Load more
Loading...
Loading...
Loading...
Loading...
Loading...

2 pages remaining, click to load more.

Recommended publications
  • What Made Bell Labs Special? Ley in Recent Years, the High Pay and Excellent Working Conditions at Bell Labs Attracted Many Who Might Look Elsewhere Today
    physicsworld.com Christmas books Andrew Gelman What made Bell Labs special? ley in recent years, the high pay and excellent working conditions at Bell Labs attracted many who might look elsewhere today. Second, there was nothing to do at the labs all day but work. I have known lots of middle-aged profes- sors who don’t spend much time teaching but don’t do any research either. At Bell Labs it was harder to be deadwood. Located as it was in the middle of nowhere, the Murray Hill campus was not a place to relax, and if you were going into the lab every weekday anyhow, you might as well work – there was nothing better to do. Several researchers, including Shannon and Shockley, had sharp mid-career productivity declines – but after they left Murray Hill. In my own experience working at Bell Labs for three summers during Bell Laboratories/Alcatel-Lucent USA/AIP Emilio Segrè Visual Archives, Hecht Collection the 1980s, I vividly recall a general feeling of comfort and well-being, Innovation central Bell Labs was a legendary place, an Idea Factory. I say this not at all as a along with the low-level intensity Ali Javan (left) and industrial lab in the outer suburbs of criticism of its author, the journalist that comes from working eight-hour Donald R Herriott New York where thousands of scien- Jon Gertner; rather, there was just so days, week after week after week. work with a helium- tists, working nine to five, changed much going on at Bell that it cannot I did the research underlying my neon optical gas the world’s technological history.
    [Show full text]
  • G.W.A.T.T. (Global 'What If' Analyzer of Network Energy Consumption)
    G.W.A.T.T. New Bell Labs application able to measure the impact of technologies like SDN & NFV on network energy consumption WHITE PAPER Increased energy consumption is a key challenge for the Information and Communications Technologies (ICT) industry. Network energy bills represent more than 10 percent of operators’ operational expenses. With the advent of the Internet of Things era, and the inexorable consumption of video and cloud services promising to drive massively increased traffic across networks, it is even more important for operators to have a complete view of the energy impact of different technology and architectural evolution options. G.W.A.T.T. (Global “What if” Analyzer of NeTwork Energy ConsumpTion) has been built to allow operators and industry stakeholders to better understand these challenges. This application visualizes the current and future communication networks and forecasts key trends in energy consumption, energy efficiency, cost and carbon emissions based on a wide variety of traffic growth scenarios and technology evolution choices. It is intended as a mind-sharing tool to grasp the importance of the energy challenge and how innovation and new technologies can help address these issues in the future. EXECUTIVE SUMMARY The explosion of the Internet traffic volume resulting from both the worldwide broadband subscriber base extension and the increasing number and diversity of available applications and services require a relentless deployment of new technologies and infrastructures to deliver the expected user-experience. At the same time, it also raises the issue of the energy consumption and energy cost of the Internet and more generally of the Information and Communication Technologies (ICT).
    [Show full text]
  • DTMF Control System
    P a g e | 38 Vol. 10 Issue 11 (Ver. 1.0) October 2010 Global Journal of Computer Science and Technology A2Z Control System- DTMF Control System Er. Zatin Gupta1, Payal Jain2 , Monika3 GJCST Classification (FOR) H.4.3 Abstract-Dual Tone Multi Frequency (DTMF) technique for c) Microcontroller (At89s52) controlling the domestic and industrial appliances is being presented in this paper. A simple mobile phone which works on Microcontroller is the control unit of this system. We have DTMF tone, used to control the domestic as well as industrial used AT89S52. It is low power, high performance CMOS 8- electrical appliances which with the control system which we Bit controller with 4K bytes of ROM and 128 bytes of RAM. have designed here for experimental study. In recent state of affairs, domestic, military and industrial applications use this d) Dtmf Signal technique because it can be operated from remote location. Radio frequency (RF) is also used for wireless communication but DTMF is most widely known method of Multi Frequency DTMF is an alternate for RF. Mobile phone is used to send the Shift Keying (MSFK) data transmission technique. DTMF DTMF code from remote location to the control system. The was developed by Bell Labs to be used in the telephone blocks of system are mobile phone, Microcontroller (AT89S52), system. Most telephones today uses DTMF dialing (or “tone” DTMF Decoder (MT8870D), Relays and power supply. This dialing). paper shows the working areas where the system is applicable and how it has advantages over RF. 1209 1336 1477 1633 Hz Hz Hz Hz I.
    [Show full text]
  • Measurement of the Cosmic Microwave Background Radiation at 19 Ghz
    Measurement of the Cosmic Microwave Background Radiation at 19 GHz 1 Introduction Measurements of the Cosmic Microwave Background (CMB) radiation dominate modern experimental cosmology: there is no greater source of information about the early universe, and no other single discovery has had a greater impact on the theories of the formation of the cosmos. Observation of the CMB confirmed the Big Bang model of the origin of our universe and gave us a look into the distant past, long before the formation of the very first stars and galaxies. In this lab, we seek to recreate this founding pillar of modern physics. The experiment consists of a temperature measurement of the CMB, which is actually “light” left over from the Big Bang. A radiometer is used to measure the intensity of the sky signal at 19 GHz from the roof of the physics building. A specially designed horn antenna allows you to observe microwave noise from isolated patches of sky, without interference from the relatively hot (and high noise) ground. The radiometer amplifies the power from the horn by a factor of a billion. You will calibrate the radiometer to reduce systematic effects: a cryogenically cooled reference load is periodically measured to catch changes in the gain of the amplifier circuit over time. 2 Overview 2.1 History The first observation of the CMB occurred at the Crawford Hill NJ location of Bell Labs in 1965. Arno Penzias and Robert Wilson, intending to do research in radio astronomy at 21 cm wavelength using a special horn antenna designed for satellite communications, noticed a background noise signal in all of their radiometric measurements.
    [Show full text]
  • I : the Discovery of the Cosmic Microwave Background
    Class 19 : The cosmic microwave background and the “Hot Big Bang” theory Discovery of the cosmic microwave background Basic idea of the Hot Big Bang I : The discovery of the cosmic microwave background Penzias & Wilson (Bell-Labs) 1 Arno Penzias & Robert Wilson (1964) Were attempting to study radio emissions from our Galaxy using sensitive antenna built at Bell-Labs Needed to characterize and eliminate all sources of noise They never could get rid of a certain noise source… noise had a characteristic temperature of about 3 K. They figured out that the noise was coming from the sky, and was approximately the same in all directions… The COBE mission Built by NASA-Goddard Space Flight Center Launched Nov. 1989 Purpose was to survey infra-red and microwave emission across the whole sky. Primary purpose – to characterize the CMB. Had a number of instruments on it: FIRAS (Far infra-red absolute spectrophotometer) DMR (Differential Microwave Radiometer) DIRBE (Diffuse Infrared background Experiment) 2 Our Galaxy observed by the DIRBE instrument on COBE 3 Almost uniform intensity of microwaves in all directions (isotropic 2.7K black body radiation) 4 Subtracting off the mean level leaves with a “dipole” pattern… what is this?? Subtracting off the dipole finally reveals the emission from the Galaxy that Penzias and Wilson were looking for! 5 Subtracting contribution from Galaxy reveals fluctuations in the CMB WMAP (2004) 6 II : The hot big bang model Penzias & Wilson had discovered radiation left over from the early universe… The hot big bang model… Independently developed by James Peebles and George Gamov They suggested that the universe started off in an extremely hot state.
    [Show full text]
  • THE UNIVERSE IS HISSING at US by Locke Patton
    TJO Newsletter Summer 2017 THE UNIVERSE IS HISSING AT US By Locke Patton This story doesn’t start with a Big Bang. It starts was in fact an astrophysical phenomenon coming from with an unrelenting hiss from the universe. In 1960, Bell beyond our galaxy in need of an explanation. Labs built a horn antenna, a radio telescope in Holmdel, They called astrophysics theorist Robert Dicke, New Jersey. It was 20 feet long and hypersensitive to who worked nearby at Princeton University. His focus microwave radio signals, on the low-energy side of the was on the newest hot topic in astronomy at the time: the spectrum of light. Scientists kept the detector cooled to Big Bang theory. Recent observations showed that only 4 degrees Kelvin above absolute zero using liquid galaxy clusters – the visible parts of our universe – were nitrogen – the equivalent of cooling your freezer down to flying away from each other. In other words, the fabric of -269 ºC. Working with the incredibly sensitive data, the universe – space itself – was expanding at an Robert Wilson and Arno Penzias discovered a accelerating rate and carrying matter along for the ride! background noise, much like the static you might have This contradicted even Einstein: the universe heard in your car radio, except this signal was persistent was not in fact a static steady-state universe. Instead, as and uniformly coming from all visible portions of the sky. you roll back time, all objects in the universe fly together, Furthermore, the microwave strength was 100 times becoming more compact until all energy, mass, light and more intense than what current theories had anticipated.
    [Show full text]
  • Bell Laboratories Record Tomer Wishes
    THE PICTURE OF THE FUTURE The Bell System is about to add PICTURE- PHONE® service to the many services it now of- fers customers. A major trial of a Picturephone system is presently under way, and commercial service is scheduled for mid 1970. Because Pic- turephone service is a large undertaking that will have a profound effect on communications, the RECORD is pleased to be able to present this special issue describing the new system for our readers. Special issues have become an important part of the RECORD's continuing story of science and technology at Bell Labs. The first one, in June 1958, dealt with the transistor and marked the tenth anniversary of its invention at Bell Labs. Since then there have been special issues on the TELSTAR® project, No. 1 Ess, and integrated elec- tronics. In addition, there have been single-topic issues devoted to the N-3 and L-4 carrier trans- mission systems. We hope to continue to present such special issues from time to time as a way of highlighting subjects of special importance. Contents PAGE 134 PICTUREPHONE Service-A New Way of Communicating An introduction by Julius P. Molnar, Executive Vice President, Bell Telephone Laboratories. 136 PICTUREPHONE Irwin Dorros A broad view of the PICTUREPHONE system sets the stage for the more detailed discussions that f ollow. 142 Getting the Picture C. G. Davis The acceptance of PICTUREPHONE service depends largely on the equipment that people will see and use-the PICTUREPHONE set itself. 148 Video Service for Business J. R. Harris and R.
    [Show full text]
  • Re-Creating the Big Bang in a Laboratory (Actually Two Labs)
    Re-Creating the Big Bang In a Laboratory (actually two labs) The Big Bang was the Birth of the Universe Osher Lifelong Learning Institute at Vanderbilt Intellectual Sampler Prof. Charles F. Maguire Department of Physics and Astronomy Vanderbilt University Nashville, TN 37215 Born on December 20, 1944 in The Bronx, New York City Crucial Battle of the Bulge date in WW II, Anchor Baby First generation American, parents were Northern Ireland immigrants Father crossed the Canadian border into the US illegally in 1933 Attended schools in NYC area until 21 (St. Barnabas elementary and Mount St. Michael HS in The Bronx, Iona College in New Rochelle) Graduate school in Nuclear Physics at Yale University, Ph.D. 1973 Married to Roberta Maria DeCarlo in Yale Chapel on October 2, 1971 Roberta was a school teacher in New Haven area, and she likes Osher classes Cannot be here today as she has other business to do (will show her picture) First job as a post-doctoral research associate in Berkeley CA, 1973-1975 Assistant Professor at Vanderbilt in September 1975, Full Professor in 1988 Questioned as suspected IRA terrorist by French police at Strasbourg airport, 1990 but talked my way out it of in French, with the help of valid French documents Currently director of a large physics data analysis computer center at Vanderbilt Serves the needs of the 3000 person CMS collaboration at the LHC in Geneva Planning to retire in August, 2017, and return to France a few more times February 26, 2016 Osher Lifelong Learning Institute At Vanderbilt2 Are You in the
    [Show full text]
  • Efficient Detection Approach for DTMF Signal Detection
    applied sciences Article Efficient Detection Approach for DTMF Signal Detection Cheng-Yu Yeh 1,* and Shaw-Hwa Hwang 2 1 Department of Electrical Engineering, National Chin-Yi University of Technology, 57, Section 2, Chung Shan Road, Taiping, Taichung 41170, Taiwan 2 Department of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan; hsf@nctu.edu.tw * Correspondence: cy.yeh@ncut.edu.tw; Tel.: +886-4-2392-4505 (ext. 7236) Received: 22 December 2018; Accepted: 22 January 2019; Published: 27 January 2019 Abstract: A novel tone detection approach, designated as the multi-frequency detecting (MFD) algorithm, is presented in this work as an alternative to conventional single point detection approaches but it is an efficient way to achieve the aim of further computational load reduction for a dual-tone multi-frequency (DTMF) signal detection. The idea is that an optimal phase search is performed over the frequency band of interest in each tone detection, and then the optimal frequency response of a detector is built accordingly. In this manner, a DTMF detection task is done following one-time detection computation. This proposal demonstrates an overall computational load reduction of 80.49% and 74.06% in comparison with a discrete Fourier transform (DFT) approach and the Goertzel algorithm, respectively. This detection complexity reduction is an advantage and an important issue for applying DTMF detection technique to embedded devices. Keywords: dual-tone multi-frequency (DTMF); remote control; tone detection; Goertzel algorithm; discrete Fourier transform (DFT) 1. Introduction Dual-tone multi-frequency (DTMF) signals [1–4] were developed by Bell Labs for the purpose of automatic fulfilled long-distance calls.
    [Show full text]
  • The Bell Labs Security Framework: Making the Case for End-To-End Wi-Fi Security
    TECHNOLOGY WHITE PAPER The Bell Labs Security Framework: Making the Case for End-to-End Wi-Fi Security Wi-Fi technology has dramatically improved the flexibility and productivity of end users. At the same time, however, it has created serious security concerns for service providers and enterprise IT managers, risking exposure of critical data across a wide range of networks. What steps can you take to make sure that this critical data is protected? This white paper explores the security implications of wireless LAN from the perspective of enabling service providers to prepare their enterprise customers’ security in end-to- end network environments; and delivers the insights necessary to identify gaps and recommend potential solutions in the security of various Wi-Fi standards, such as 802.11i, WPA (Wi-Fi Protected Access) WPA 2, and WEP (Wired Equivalent Privacy). Additionally, this paper explores the Bell Labs Security Framework, the foundation for security archi­ tecture standards ITU-T X.805 and ISO/IEC 18028-2. This framework delivers a compre- hensive methodology for assessing and upgrading end-to-end network security across the enterprise analyzing end-to-end security at each stage of a WLAN’s lifecycle: design, planning, implementation, and maintenance. Table of Contents 1 Introduction 2 Bell Labs Security Framework Overview 2 Assembling a Comprehensive Security Model 3 Security Layers 3 Security Planes 3 Security Dimensions 3 Modular Methodology 4 Using the Bell Labs Security Framework to Secure Wi-Fi Networks 4 The Reference Architecture 5 Scope of the Analysis 5 Wi-Fi Threat Model 5 Wi-Fi Layers 6 Wi-Fi Planes 6 Applying Security Dimensions 6 Access Control 7 Authentication 7 Data Confidentiality 8 Data Integrity 8 Availability 9 Analysis Summary 10 Recommendations 11 For More Information 11 Sources 12 About the Authors 12 Ashok Gupta 12 Theresa Buthmann Wi-Fi networks can transform an enterprise, freeing end-users from ties to a desktop computing setup and allowing them to be far more productive.
    [Show full text]
  • Dual Tone Multi Frequency Signaling
    Contents 1 Introduction 2 2 History and Evolution 3 3 Technology 5 3.1 DTMF Keys 5 3.2 DTMF Frequencies 6 3.3 Special Tones 7 3.4 DTMF Transmission 8 3.5 DTMF Programming 9 4 Technical Standards 11 5 Applications 12 5.1 Applications in the Call Center Industry 13 6 VoIP and DTMF 14 7 Advantages of Using DTMF 15 8 Conclusion 16 9 References 17 1 © Specialty Answering Service. All rights reserved. 1 Introduction Dual Tone Multi Frequency, or DTMF as it is popularly known as, is the technical term for the sound frequencies produced when a telephonic key is pressed. DTMF, also known as touch tone, was primarily used for telephone signaling to and from the local exchange, though today it finds several applications in the field of telecommunications and call centers. A different frequency is assigned to each key in the telephone and there are two tones – one low frequency and another high frequency – that are played simultaneously when a key is pressed. This combination of two tones makes it nearly impossible to reproduce by the human voice. Each of the four rows of keys in a telephone is assigned a low frequency tone and each of the three columns is assigned a high frequency tone. A fourth column of keys labeled as A, B, C, and D is optional and is mostly used in military networks. 2 © Specialty Answering Service. All rights reserved. 2 History and Evolution Before DTMF was introduced, telephone networks were dependent on pulse dialing. In pulse dialing, pulses are generated by rapidly connecting and disconnecting the telephone connection.
    [Show full text]
  • National Register of Historic Places Registration Form
    NPS Form 10-900 OMB No. 1024-0018 United States Department of the Interior National Park Service National Register of Historic Places Registration Form This form is for use in nominating or requesting determinations for individual properties and districts. See instructions in National Register Bulletin, How to Complete the National Register of Historic Places Registration Form. If any item does not apply to the property being documented, enter "N/A" for "not applicable." For functions, architectural classification, materials, and areas of significance, enter only categories and subcategories from the instructions. Place additional certification comments, entries, and narrative items on continuation sheets if needed (NPS Form 10-900a). 1. Name of Property historic name Bell Laboratories-Holmdel other names/site number Bell Labs 2. Location street & number 101 Crawfords Corner Road not for publication city or town Holmdel Township vicinity state NJ code 034 county Monmouth code 025 zip code 07733 3. State/Federal Agency Certification As the designated authority under the National Historic Preservation Act, as amended, I hereby certify that this nomination _ request for determination of eligibility meets the documentation standards for registering properties in the National Register of Historic Places and meets the procedural and professional requirements set forth in 36 CFR Part 60. In my opinion, the property _ meets _ does not meet the National Register Criteria. I recommend that this property be considered significant at the following level(s) of significance: national statewide local Signature of certifying official/Title Date State or Federal agency/bureau or Tribal Government In my opinion, the property meets does not meet the National Register criteria.
    [Show full text]