DIGITAL COMMUNICATIONS (Part 2) by AD5XJ Ken
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XAPP616 "Huffman Coding" V1.0
Product Obsolete/Under Obsolescence Application Note: Virtex Series R Huffman Coding Author: Latha Pillai XAPP616 (v1.0) April 22, 2003 Summary Huffman coding is used to code values statistically according to their probability of occurence. Short code words are assigned to highly probable values and long code words to less probable values. Huffman coding is used in MPEG-2 to further compress the bitstream. This application note describes how Huffman coding is done in MPEG-2 and its implementation. Introduction The output symbols from RLE are assigned binary code words depending on the statistics of the symbol. Frequently occurring symbols are assigned short code words whereas rarely occurring symbols are assigned long code words. The resulting code string can be uniquely decoded to get the original output of the run length encoder. The code assignment procedure developed by Huffman is used to get the optimum code word assignment for a set of input symbols. The procedure for Huffman coding involves the pairing of symbols. The input symbols are written out in the order of decreasing probability. The symbol with the highest probability is written at the top, the least probability is written down last. The least two probabilities are then paired and added. A new probability list is then formed with one entry as the previously added pair. The least symbols in the new list are then paired. This process is continued till the list consists of only one probability value. The values "0" and "1" are arbitrarily assigned to each element in each of the lists. Figure 1 shows the following symbols listed with a probability of occurrence where: A is 30%, B is 25%, C is 20%, D is 15%, and E = 10%. -
Image Compression Through DCT and Huffman Coding Technique
International Journal of Current Engineering and Technology E-ISSN 2277 – 4106, P-ISSN 2347 – 5161 ©2015 INPRESSCO®, All Rights Reserved Available at http://inpressco.com/category/ijcet Research Article Image Compression through DCT and Huffman Coding Technique Rahul Shukla†* and Narender Kumar Gupta† †Department of Computer Science and Engineering, SHIATS, Allahabad, India Accepted 31 May 2015, Available online 06 June 2015, Vol.5, No.3 (June 2015) Abstract Image compression is an art used to reduce the size of a particular image. The goal of image compression is to eliminate the redundancy in a file’s code in order to reduce its size. It is useful in reducing the image storage space and in reducing the time needed to transmit the image. Image compression is more significant for reducing data redundancy for save more memory and transmission bandwidth. An efficient compression technique has been proposed which combines DCT and Huffman coding technique. This technique proposed due to its Lossless property, means using this the probability of loss the information is lowest. Result shows that high compression rates are achieved and visually negligible difference between compressed images and original images. Keywords: Huffman coding, Huffman decoding, JPEG, TIFF, DCT, PSNR, MSE 1. Introduction that can compress almost any kind of data. These are the lossless methods they retain all the information of 1 Image compression is a technique in which large the compressed data. amount of disk space is required for the raw images However, they do not take advantage of the 2- which seems to be a very big disadvantage during dimensional nature of the image data. -
Digital Communications
CCARC - BPRA Ham Basics 2010 ---------- Welcome! Digital Communications “AMATEUR RADIO IS THE HOBBY… EMERGENCY COMMUNICATIONS IS A COMMITMENT…” 1 Ham Basics 2010 K7GJT‐ Digital Communications 2 Subjects to cover • Amateur Radio Digital Mode History • Two Basic Digital Technologies • TNC Technology, Modes & Software • Soundcard Technology, Modes & Software • Accuracy • Making the connection without wires • Making the connection with wires • Dig ita l MiMessaging Systems • Making the “over‐the‐air” connection with radio Ham Basics 2010 K7GJT‐ Digital Communications 3 Amateur Radio Digital Mode History • The ‘Original Digital’ mode – Presence or absence of carrier (1, 0, 1, 0, 1, etc.) – CW! Ham Basics 2010 K7GJT‐ Digital Communications 4 Amateur Radio Digital Mode History • Started as Mechanical Hardware Specific – 1849 Landline based teleprinter operations began – 1920 Rudolf Hell invented Hellschreiber – 1930’s RTTY (Radio TeleTYpp)e) [y[Military RATT/]/SCRT] • 1980’s started computerizing the RTTY signals • Prior to 1995 the only ‘legal’ HF digital mode that was authorized by the FCC were those that used the standard Baudot codes; ege.g. RTTY Ham Basics 2010 K7GJT‐ Digital Communications 5 Amateur Radio Digital Mode History • In 1995, the FCC opened to door to other modes (ASCII based) and declared that any new mode coding were legal as long as they were published in the public domain. • And the “Barn Door” opened! Ham Basics 2010 K7GJT‐ Digital Communications 6 Amateur Radio Digital Modes Ham Basics 2010 K7GJT‐ Digital Communications -
Winwarbler 7.9.2
WinWarbler 7.9.2 Overview .....................................................................................................................................................................2 Prerequisites ...............................................................................................................................................................3 Download and Installation ..........................................................................................................................................4 Configuration ..............................................................................................................................................................5 General Settings .........................................................................................................................................................7 Display Settings ....................................................................................................................................................... 10 Push-to-talk (PTT) Settings ..................................................................................................................................... 13 Soundcard Settings ................................................................................................................................................. 15 Configuring Multiple Soundcards ............................................................................................................................. 16 Phone Settings -
The Strengths and Weaknesses of Different Image Compression Methods Samuel Teare and Brady Jacobson Lossy Vs Lossless
The Strengths and Weaknesses of Different Image Compression Methods Samuel Teare and Brady Jacobson Lossy vs Lossless Lossy compression reduces a file size by permanently removing parts of the data that may be redundant or not as noticeable. Lossless compression guarantees the original data can be recovered or decompressed from the compressed file. PNG Compression PNG Compression consists of three parts: 1. Filtering 2. LZ77 Compression Deflate Compression 3. Huffman Coding Filtering Five types of Filters: 1. None - No filter 2. Sub - difference between this byte and the byte to its left a. Sub(x) = Original(x) - Original(x - bpp) 3. Up - difference between this byte and the byte above it a. Up(x) = Original(x) - Above(x) 4. Average - difference between this byte and the average of the byte to the left and the byte above. a. Avg(x) = Original(x) − (Original(x-bpp) + Above(x))/2 5. Paeth - Uses the byte to the left, above, and above left. a. The nearest of the left, above, or above left to the estimate is the Paeth Predictor b. Paeth(x) = Original(x) - Paeth Predictor(x) Paeth Algorithm Estimate = left + above - above left Distance to left = Absolute(estimate - left) Distance to above = Absolute(estimate - above) Distance to above left = Absolute(estimate - above left) The byte with the smallest distance is the Paeth Predictor LZ77 Compression LZ77 Compression looks for sequences in the data that are repeated. LZ77 uses a sliding window to keep track of previous bytes. This is then used to compress a group of bytes that exhibit the same sequence as previous bytes. -
The FCC Filing
Dr. Theodore S. Rappaport, PE PO BOX 888 Riner, Virginia 24149 [email protected] November 10, 2018 Commissioners Federal Communications Commission 445 12th Street, SW Washington, DC 20554 Dear FCC Commissioners: This is a notice of ex parte, based on email communication I had with the CTO of the FCC, Dr. Eric Burger, on November 8, 2018, his reply on November 10, 2018, and my reply on November 11, 2018. The email communication is centered around a posting that appeared on the FCC ECFS system on November 7, 2018, and is part of an ongoing proceeding at the FCC, NPRM 16-239, that I and thousands of others view as a direct threat to the national security interests of the United States, as well as being detrimental to the hobby of amateur (“ham”) radio. Public comments made in FCC’s NPRM 16-239, and in FCC proceedings RM-11708, RM-11759, and RM-11306 proposed by the American Radio Relay League, show the vast number of rule violations and national security threats that continue to go unaddressed by the FCC. Commenters such as me view the lack of FCC acknowledgement of these problems as jeopardizing the safety of US citizens. NPRM 16-239 attempts to remove a limit on the baud rate of High Frequency (HF) shortwave transmissions, without first addressing ongoing rule violations pertaining to proper usage of the amateur radio service, the use of obscured, private messaging which is forbidden in Part 97 rules and creates national security concerns, as well as other violations. If allowed, NPRM 16-239 would perpetuate the current violations, and would authorize obscured transmissions of unlimited bandwidth over the global airwaves, further increasing the danger to our national security, since these transmissions cannot be intercepted or eavesdropped by other amateur radio operators or the FCC. -
Efficient Multi-Carrier Communication on the Digital Subscriber Loop
Efficient Multi-Carrier Communication on the Digital Subscriber Loop Donnacha Daly Department of Electrical and Electronic Engineering Faculty of Engineering and Architecture University College Dublin National University of Ireland A thesis presented to the National University of Ireland Faculty of Engineering and Architecture in fulfillment of the requirements for the degree of Doctor of Philosophy May 2003 Research Supervisors: Dr. C. Heneghan Prof. A. D. Fagan Head of Department: Prof. T. Brazil Abstract This thesis explores three distinct philosophies for improving the efficiency of multi-carrier com- munication on the digital subscriber loop. The first topic discussed is impulse response shortening for discrete multitone transceivers. The minimum mean-squared error impulse response shortener is reformulated to allow near-optimal rate performance. It is demonstrated that the best existing eigen-filter designed channel shortener is a particular case of the proposed reformulation. An adap- tive time-domain LMS algorithm is provided as an alternative to eigen-decomposition. The next part of the thesis examines bit- and power- loading algorithms for multitone systems. The problem of rate-optimal loading has already been solved. It is shown, however, that the rate-optimal solu- tion does not give best value for complexity, and that near optimal schemes can perform very well at a fraction of the computational cost. The final section of the thesis is a brief exposition of the use of wavelet packets to achieve multi-carrier communication. It is proposed that the non-uniform spectral decomposition afforded by wavelet packet modulation allows reduced inter-symbol inter- ference effects in a dispersive channel. -
FLDIGI Users Manual 3.23
FLDIGI Users Manual 3.23 Generated by Doxygen 1.8.10 Sat Sep 26 2015 10:39:34 Contents 1 FLDIGI Users Manual - Version 3.231 1.1 Fldigi Configuration and Operational Instructions........................... 1 2 Configuration 3 2.1 User Interface configuration...................................... 3 2.2 Windows Specific Install / Config................................... 3 2.3 Other Configuration options...................................... 3 2.4 Command Line Switches ....................................... 4 2.5 Modem Configuration Options..................................... 4 2.6 Configure Operator .......................................... 5 2.7 Sound Card Configuration....................................... 6 2.7.1 Right Channel Audio Output ................................. 9 2.7.2 WAV File Sample Rate.................................... 10 2.7.3 Multiple sound cards ..................................... 10 2.8 Rig Control .............................................. 12 2.8.1 Rig Configuration....................................... 13 2.8.2 RigCAT control........................................ 15 2.8.3 Hamlib CAT control...................................... 16 2.8.4 Xml-Rpc CAT......................................... 16 2.9 New Installation............................................ 17 2.10 Configure ARQ/KISS I/O ....................................... 20 2.10.1 I/O Configuration....................................... 22 2.10.1.1 ARQ I/O ...................................... 22 2.10.1.2 KISS I/O...................................... 23 -
Replacing 1200 Baud AFSK FM with PSK and Deploying DTN Iain Young [email protected]
Replacing 1200 Baud AFSK FM with PSK and Deploying DTN Iain Young [email protected] Agenda ● Introductions ● AX.25 Link Established! ● Exactly What Are We ● Adding TCP/UDP/IP Planning To Replace ? ● Adding DTN ● Why Replace It ? ● Results ● Computer Network Theory ● Conclusions ● How We Replaced It ● Future Experiments – Tools and Utilities Needed ● Acknowledgements – RF Setup and Maps Introductions ● Two major areas of focus – Replacing AX.25 1200 baud AFSK FM with PSK – Deploying DTN ● Who ? – Iain Young, G7III, MAXPAK Chairman – Dave Madew, M0DCM, MAXPAK Committee Member ● MAXPAK – Formed as a dedicated AX.25 Packet group for the Midlands – Constitution changed a couple of years ago, to include all digital modes So What Are We Replacing, And What Are We Not Replacing ? ● The AX.25 Physical Layer – In “Network” Parlance, Layer 1 – We mean the 1200 baud AFSK FM transmissions ● We are not replacing what the network world would call “Layer 2” or “The Data Link Layer” where you send and receive AX.25 frames to and from AX.25 addresses ● The mode we are all familiar with could be more formally described as AX.25 over 1200 baud AFSK FM ● The mode we will be creating could be more formally described as AX.25 over PSK Why Do This ? (1) ● 1200 baud AFSK FM is not exactly well known for it's effeciency, especially with regards to: – Spectrum usage, – Power requirements – Link budget ● Even it's 300 baud cousin is not particularly well thought of on HF, can be improved on and that's only a quarter the throughput! Why Do This ? (2) ● Plenty have claimed -
HF Digital Mode Primer
HF Digital Mode Primer By Val Campbell K7HCP INTRODUCTION Getting started using the Amateur Radio Digital Modes of communications can be confusing and frustrating at times but it doesn’t have to be that way. The purpose of this primer is to introduce you to the basics of using this fun to use mode of communication and to provide you with the understanding of the processes to setting up your hardware and software to easily and quickly start copying and later to start sending digital communications on the amateur radio HF shortwave bands. The minimum hardware requirements to receive or copy HF digital communications are a personal computer (PC) with a standard sound card and a short wave or ham radio receiver with SSB mode. A receiver with digital tuning display is preferred but a receiver with analog tuning can work also. You may have heard about various digital modes such as RTTY, SSTV, PACTOR, PSK31, and of course, CW. CW or Morse Code, as it is more commonly known, was the original digital mode used in communications; however few thought of it as digital until recently. Just like our old wristwatches were analog watches, we didn’t think of them as such until digital watches came into existence. PSK31 has become by far the most popular digital mode used by amateur radio operators lately. PSK31 stands for Phase Shift Keying with a bandwidth of only 31 hertz. That’s really all you need to know to use this mode of communications. The program does the rest for you. The ARRL has the following to say about PSK31 : Since the spring of 1999, PSK31 has taken off like wildfire. -
Overview of Ham Radio Software
OVERVIEW OF SOFTWARE FOR DIGITAL HAM RADIO Where to download free software: (often there are helpful help files also, so you might want to peruse around a bit more than just download) FLDIGI https://sourceforge.net/projects/fldigi/files/fldigi/fldigi- 3.23.15_setup.exe/download https://sourceforge.net/projects/fldigi/files/fldigi/ Downloading FLDIGI can be a bit tricky. Try going to the above page and then selecting (for Windows) the file ending with “setup.exe”. WINLINK EXPRESS http://www.winlink.org/sites/default/files/downloads/winlink_express_insta ll_1-4-2-0.zip UZ7HO http://uz7.ho.ua/modem_beta/soundmodem95.zip is the actual download. SOUNDMODEM.EXE WINDOWS BPQ http://www.cantab.net/users/john.wiseman/Downloads/LastestInstaller/ is the directory http://www.cantab.net/users/john.wiseman/Downloads/LastestInstaller/BPQ 32_6.0.13.1_20160927.exe is the actual download link Malware Detection Software: Many commercial virus checkers and malware detectors will consider very rare software to be automatically suspect, and delete or refuse to run or load it. You will have to find out how to tell your malware detection software to accept these quite- respectable programs. Every malware detection program works differently, so read your instructions! Digital Ham Radio has many facets. Characters from a computer become some version of “tones” going to a transmitter microphone input; audio from a receiver speaker output gets transformed into characters in a computer and possibly visible on the screen to a user. Software & hardware combine to make this magic happen. This paper will attempt to categorize the major software required to accomplish several communications. -
I William G Radicic, Amateur Radio Call Sign NS0A, Extra Class, License
I William G Radicic, amateur radio call sign NS0A, Extra class, license - endorse the position of the Members of this Board of Directors who unanimously are in support of the Commission’s proposal and encourage the elimination of the outdated and symbol rate limits. Opponents to WD Docket No. 16-239 have responded to internet and social media campaigns led by Theodore Rappaport, resulting in a multitude of comments that echo false or misleading technical points, driven by highly emotional arguments about “national security, crime and terrorism”. We address these arguments with the documented realities of science and logic in hopes that the Commission will find them balanced, informed, and trustworthy counterpoints for good decision making. The HF Symbol Rate Limitation in § 97.307(3) Should be Removed The current 300 baud symbol rate limitation was instituted around 1980 by the Commission as a mechanism to manage HF digital modes (both FEC and ARQ) that would be compatible with typical HF signal widths in use. The most common amateur HF digital modes in use then were AMTOR (similar to SITOR), later refined as Pactor 1 and HF packet (300 baud FSK). Since then, technical advancements in modulation, coding technology and Digital Signal Processing (DSP) now make it possible to implement significantly faster, more robust digital protocols with better spectrum efficiency (e.g. PSK31/63, MT63, Pactor 2, Pactor 3, WINMOR, ARDOP, VARA, Pactor 4, and other popular amateur modes). These modes are possible and affordable due primarily to the significant advancements in digital signal processing, cost reductions in computers, sound cards, and DSP processing chips since the original 300 baud symbol rate restriction was instituted.