Information Theory

RET 2013:Information in Radio WavesKen JacobsTim ScadutoFundamentals of EM spectra with emphasis on radio frequenciesHistory of radio astronomyInformation theory and Remote SensingInformation transmitted through radioNatural sources of radio Technology of radio transmissionCore UnitsOverview of the whole unit.Information Theory The foundation of telecommunicationsLearning ObjectivesAt the end of this unit students will be able to:Communicate technical information about how some technological devices use the principles of wave behavior and wave interactions with matter to transmit and capture information and energy.

Summative assessment:Students will look at a case study of radio astronomy and provide a technical report on the strategies for investigating the radio emissions of Jupiter.Which of these images contains informationThis slide and the following images are to be used as a starter activity to get students thinking about what information is and how we can use it to do science remotely. Some guiding questions: What do you see here? Does this image convey any form of information to the viewer? Are there any patterns?

1st image, close up of a wave - same guiding questions2nd image, wave field 3rd image, rain on water1st image 'without words'2nd with wordsInformation is relative why did you have more information about the object when the white border

1st image - orion2nd - sagittarious your ideas?information - transfer of ideas, forces, patterns, properties, energy, What do we mean by the term 'information'Claude Shannon(1906-2001)inventor of information theory and modern telecommunicationSenders and receiversClaude Shannon was an MIT Mathematician who first put forth a method for quantifying the information content in a message. This idea coupled with developments in the fields of electrical engineering, computer science, and computer programing brought about the foundational principles of modern telecommunications systems. The amount of information in every symbol of a message can be quantified as the entropy of the message.The transmission channel has rules dependent on the physical properties of the signal, source, and medium.

Information concepts (learning objectives)With your teammate:Have one person think of number between 0-100record the number of yes/no questions required to guess the numberrepeat for a number between 0-10000-1,000,000any whole numberguess a sequence of numbers in a patternCoding warm up This is a warm up game to get students working in groups, recording results, and reflecting on the outcome. The Number of Guesses per teamTeam1-1001-10001-1,000,000sequencesentence123Guess a sentencerules:Your group will be given a sentence of four to six words with each of the letters (including spaces) as unknowns. Your job is to guess the sentence exactly by asking yes/no questions only.examples 'is this letter a b?''does it come before m in the alphabet?'

Game 1: Measuring information contentYou were each given a different sentencedid they each contain the same amount of information ?

Why did one have more information than another?

Scoring/ReflectionConcept: information is relative. Prior knowldege of a statement or phrase can decrease the information value and increase the time it takes to guess the sentence. Students may Game 2: Vincent-Phil-Shep

Rules:The game is played with a two player teamone player is the robot and the other the navigatorEach team must devise a way for the navigator to manipulate the robot accomplishing a simple (or not so simple) task using just three words,Vincent, Phil, ShepYou have approx. 30 minutes to devise your strategyhere are some practice tasks:easy: pick up an object, rotate, ....medium: clap your hands, touch your nosehard: find a bottle, do a forward roleGame 2: Vincent-Phil-ShepMaterials needed:1 chair per teamBlindfolds for the robots of each teamOne object to be picked up by the robot (preferably light weight)

Game set up: Align the chairs in the front of the classroom and designate a minimum distance where the navigators will stand and call out to the robots. Robots should all be blindfolded outside the classroom and escorted into the room so that they are standing behind the chair at the beginning of the first round. Prepare activity cards for each navigator team. There will be two activities:The robot must be instructed to simply sit down in the chair and wait for the next activity The robot must reach beneath the chair and raise the object that is there above their heads.The first team to complete the tasks is the winner.

A non-competitive approach may be to make the goal of the class to get all the robots to accomplish their task.

Make an analogy to information transmissionWhat is the transfer channel?What is the information?What are the rules of the transfer channel and how did it affect the time and accuracy of your task?

Describe your coding strategy, strengths? Weaknesses? Game 2: ReflectionRulesOne student is given a copy of text That student must re-write the text using only uppercase letters or numbers and spacesThe goal is to use as few symbols as possible Once completed the other partner must reconstruct the message losing 20 pts for each incorrect word.the score is 1 pt for every character that was saved. Game 3: Text Messaging GameGames 3 and 4 are optional and only add to students observations about factors that influence the transmission channel, the amount of information in a message, and the rate at which information can be sent (or communicated).You are given a sentence by your instructor and the only way to transmit the information to your partner is by knocking on the door. You have approximately 20 minutes to devise a scheme for your transmissionGame 4: The Knocking GameInformation is dependent on what you already knowMoving information requires a transmission channel that has rulesRules of the transmission channel requires encoding the message somehow.

Take home messageYou can only modify 4 things to send a messageAmplitude FrequencyPhasePolarization

These rules correspond to the limited words available in the games transmission channelElectromagnetic Radiation (EMR) as a transmission channel has rules

Contributions of information THeoryAstronomers were some of the first scientists who recorded data over time and made models that predicted the motion of the objects they sawIn order to prove their theories they had to use observations that were made remotely.There was no way to directly observe the materials of the moon or mars YET!Astronomy as a first science

As the nature of the physical world was researched and developed, new findings would allow us to conduct different experiments with the light gathered from night sky objects.Examples:Knowledge about optics and the reflection/refraction of light allowed for the first telescopes Knowledge about the nature of light as a continuous spectrum allowed us to view objects and derive their temperature.Knowledge of the quantum mechanical structure allowed astronomers to develop and understanding of the composition of materials I both luminous and non-luminous Direct observations applied to remote observationsEngineered Transmissions

Your eyes are the original remote sensing detector!We collect visible band EMR

Just like our eye, manufactured sensors must all be build to detect changes in the incoming radiation.Most often we want to create maps or images of the variations in order to look at light and dark patterns which could tell us something about the source.

Remote sensing primer

http://en.wikipedia.org/wiki/Image:Mimas_moon.jpgPassive sensing detects radiation from natural sources.Either directly from source or reflected/refracted by objects or other medium

Active sensing requires a source with known properties be generated and the effects of interactions with a target are observed at the detector. Active vs. Passive remote sensing

Case Study: Finding Cold Hydrogen in SpaceInformation can be quantified and the amount depends on what you already know about the messageInformation carried in radio waves as a transmission channel can be modified in 4 ways: Amplitude, Frequency, Phase, and, Polarization.In formation in radio waves from natural sources can help us understand the properties of the source, the objects they interact with, and the medium through which they are travelling. The technique of collecting information form distant objects is called remote sensingMay be active, we send a signal and measure the results of interactions with targetPassive, look and the signals contained in natural sources and infer properties of the source, interacting objects, or the medium.ConclusionRefer to the RET 2013 Unit: Natural Sources of Radio to discover how radio science has increased our understanding of how the universe works.For Further Study