• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6
  7. 7
  8. 8

Signal Theory - Communications Technology. Analogue signals are converted to digital using sampling, basically at least two samples are made per cycle, and the more samples the higher quality of the digital output.

Extracts from this document...


Task 2 - P5 Table of Contents Signal Theory 2 Frequency 2 Phase Difference 2 Amplitude 2 Wavelength 2 How Analogue Signals are converted to Digital Signals 3 Data Sizes 3 Synchronous & Asynchronous 4 Bandwidth 5 Error Detection & Error Correction 5 Checksum 6 CRC (Cyclic Redundancy Check) 6 Reed-Solomon 6 Comparison of Mediums 6 Data Compression 7 Huffman Encoding 7 Lossy 7 Loss-Less 8 RLL - Run Length Limited 8 JPEG - Joint Photographic Experts Group 8 Table of Figures Figure 1 - Sine Wave 2 Figure 2 - Analogue Signal With Sampling 3 Figure 3 - Digital Signal After Sampling 3 Figure 4 - Asynchronous Packet 4 Figure 5 - Synchronous Packet 4 Figure 6 - Shannon's Law Formulae () 5 Figure 7 - Reed-Solomon Error Detection 6 Figure 8 - Huffman Tree Diagram [] 7 Figure 9 - JPEG Image [] 8 Task 2a - P5 Signal Theory Figure 1 - Sine Wave Frequency Frequency is the number of cycles per second; this is measured in Hertz (Hz). This is calculated by the reciprocal of time (1/T ). Phase Difference Phase Difference is two Sine waves with the same frequency but the two waves are delayed in time; the delay in time is measured in degrees. ...read more.


Different types of noise can conflict with the signal; there are different types of noise such as: White Noise Pink Noise Johnson Noise Error Detection & Error Correction Parity Bit - RS232 There are a few types of error correction types; I will explain what these are and which ones are more efficient. With RS232 - Serial you had a parity bit; this was part of the packet when you sent data. This worked by calculating the odd or even numbers. For example if the parity bit looks for an even number of 0's and there is an odd number it will detect that there is an error and flip a bit to make it even. However this is bad because RS232 has a limitation of one bit detection, when more than one bit flips over and it won't detect any errors because it will show that it is even. Another downfall is that there is no retransmission on RS232 so the packet can't be requested if there is an error that cannot be fixed. Checksum Checksum is where you have a fixed size of data which can be compared to rule out any accidental errors in transmission, this is done by calculating how many 1 bits they are and it will compare it with the sender, if the amount of 1 bits match you will have a successful transmission. ...read more.


This is a very complex method. There are two different variations of data compression one is lossy and one is loss-less. Huffman Encoding uses Loss-Less compression. Lossy With file formats such as JPEG, MP3, MPEG, and PNG you can afford to drop and lose some bits here and there and quality won't decrease noticeably. Loss-Less This is used with data compression where if you lose one bit your data will be corrupted. RLL - Run Length Limited Run length limited is a loss-less compression method, this is a simple method of reducing a file size for use in media such as CDs, DVDs and Flash Drives. RLL simply counts how many ones and zero's they are in a binary code. For example if you had this code "000111001 11110000 1101011 00" RLL would change it to this: "3,0s;3,1s;2,0s;1,1s;4,1s;4,0s;2,1s;1,0s;1,1s;1,0s;2,1s;2,0s" JPEG - Joint Photographic Experts Group JPEG is a compressed image format that is a lossy form; JPEG can easily be a fifth of the original file format which would usually be a .BMP or .TIF file. You cannot use JPEG in: CAD-CAM Applications Images that have had mask and or shadow effects added Images containing 256 colours or less. [4] Figure 9 - JPEG Image [5] 1 http://en.wikipedia.org/wiki/Shannon-Hartley_theorem 2 http://en.wikipedia.org/wiki/Cyclic_redundancy_check 3 http://en.wikipedia.org/wiki/Huffman_coding 4 http://www.prepressure.com/library/compression_algorithms/jpeg 5 http://vesta.astro.amu.edu.pl/Library/WWW/Tutorial1/graphics/jpeg_graphics.html ?? ?? ?? ?? Antony Bond Unit 10 - Communications Technology P5 1 ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Information Systems and Communication section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Information Systems and Communication essays

  1. Communications Technology - Assignment 1

    and analogue signals (electrical frequencies). This is usually done using a modem (modulator demodulator). A computer or transmission device sends bits (binary digits) to a modem which converts these to electrical pulses. A modem on the receiving end then coverts these electrical pulses back to 0's and 1's for another

  2. The Digital Divide is used to describe the progressively growing gap between those who ...

    In most cases, countries that are in poverty are more concerned about the basic things of life such as clean water, teaching, hygiene and putting food on the table, than they are about getting a computer so that they can access the internet as these are not the essential things in life when basic necessities are not present.

  1. unit 8 communication technology

    you plug it in, once plugged in you are connected to the internet, USB is also used for other resources, such as connecting mobile phones to computer and also connecting digital cameras, etc. Task 3 - Communication Protocols Wi-Fi - * Allows users to connect with their pc or laptop

  2. BTEC Unit 8: The Theory of Data Communications

    and data circuit-terminating equipment (DCE). Another type of communication devices would be Wireless devices. These will be explained in detail. Data Terminal Equipment (DTE) DTE is a term for a device that is at the end of the line. Examples of this could be a modem (including cable modems), network card, mobile phone or Bluetooth.

  1. Communication Methods and Media

    The main disadvantage of optical fibre is that it is very expensive. The insurance company's network has an optical fibre backbone. The optical fibre backbone connects all devices and handles the major traffic. Optical fibre back bone is fast (up to 160Gbps)

  2. Unit 5 - Communications Technology

    FDDI uses dual-ring architecture with traffic on each ring flowing in opposite directions called counter-rotating. The dual rings consist of a primary and a secondary ring. During normal operation, the primary ring is used for data transmission, and the secondary ring remains inactive.

  1. Discuss the Causes and Effects of the Digital Divide

    house knowing that there train is going to come as soon as they reach the train station.The Divide does not just mean the difference between developed and undeveloped countries it can also mean the regional differences and problems that affect your local area, many people in places like the UK

  2. Communication & Employability Skills for IT. OCR Cambridge Technicals Unit 1 LO1-P1

    The manager will have to organise work for other employees to do and plan work for them, also the manager will plan other things such as trips for employees and regular inspections of employees. Problem Solving 7 I think that this is the least important task because the IT manager

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work