human informationprocessing li liu human computer interaction how much information can she receive?...
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Human InformationProcessing
Li Liu
Human Computer Interaction
How much information canshe receive?
”Human InformationProcessing”
Case 1
Personal Area Network
Principle
Speech – Control Technology
Name Dialing
Hand Free
Speech Recognizer
SpeechRecognizer
”repeat”
Speech Signal Waveform
Effect of Background Noises
Performance
Speech-to-Noise Ratio (dB)
Word
s C
orr
ect
Rate
(%
)
-30 0
100
0
Lip Tracker
Performance of Speech Recognition
Speech-to-Noise Ratio (dB)
Word
s C
orr
ect
Rate
(%
)
-30 0
100
0
Auditorycues only
Auditory andvisual cues
How to Design A Headset?
Tip ?
Mobile Phones
Braille Code for English
Tactile Display
Problem: Usable?
Efficiency?
Reliability?
Braille Code for English
How Many Letters Can be Represented?
Combination
Tactile Pins
Braille Code for English
W=2.4093The average number of active tactile pins.
Wopt=1.2118Letters in written English
New Code
W=1.2316
Information
If all eight horses are equally good, then the chance for a horse to win the race is 1/8!
Information Theory
What is the probability?
The probability for a horse to win is
Pi=1/8
Information Theory
If a horse wins the game, how much information is it given?
How to measure information?
Measure of information
• A source A={a1,a2…aN} the probability of each event P={P1,P2…PN}
• More information if Pi is low, less information is Pi is high
• I(ai)=log(1/Pi) is called self information1/81/41/2 1/1
6
1/81/81/8 1/8
Entropy
Taking the mean value over all symbols with the alphabet
i 2 iH(x) P log P (bits / symbol) 1/81/41/2 1/1
6
1/81/81/8 1/8
Communication Theory I
If R < H error-free representation impossible!
H
source
R
Coding
1/81/81/8 1/8
000 001 010 111
1/81/41/2 1/16
0 10 110 1110111100111101111110111111
How much information does a picture contain?
255
254
0
How much information does a picture contain?
Suppose the size of a picture is 256 x256,And each pixel is represented by 8 bits, thenTotal bits to represent such a picture is
8x256x256= 524288 bits/picture
How many pictures can be represented by a half Mbits?0100110101000011101110101010..............
Total number of pictures
2524288 = 10158000
How many pictures have human beings been perceived
Up to now, the number of all pictures which have been perceived by human beings is only1019.
Assume that 30 frames of pictures per second are perceived by human eyes. If the averagelife-span is 70 years and 8 hours per day are spent on sleep, then about 108 frames arereceived by one person in all his/her life. Furthermore, if the total number of human beings who lived in the earth is 1011, then, thetotal number of all pictures which have been perceived by human beings is only1019. 1019 <<< 10158000
Entropy of an image
H=6.9
45 001123 00010208 00011
intensity
probability
Entropy of human face images
A face image = 50 bytes (400 bits) !
Communication
Brain Wave
C
channelsource
H
Communication Channel
Abstract Channel Model
Ex. Noiseless Binary Channel
0
1 1
0Channel Capacity
C= 1 bit
Communication Channel
Abstract Channel Model
Ex. Noisy Binary Channel
Channel Capacity
C= 1 + p log2 p + (1-p) log2 (1-p) bits
1 1
0 0
p
p1-p
1-p
Communication & Design
transmittertransmitter
receiverreceiver
Different Decoders
”When a group of people look at an object, none of them sees exactly the same thing as anyone else. Even if they receive approximately the same image on their retina and interpret the image in basicallythe same way, this image is always revised by theobserver’s personality and situation.” Rune Monö
Real-World Channel Model
Ex. Band-limited Gaussian Channel
Z(t) Gaussian noise
X(t) Y(t)
C = Wlog2(1+P/N) bits/s
W: channel bandwidthP/N: signal to noise ratio
Telephone signals are band-limited to 3300Hz and have a SNR of 20 dB (P/N=100),
C=3,300 log (1+100)= 22,000 bits/s
Practical modems achieve transmission rates up to 19,200 bits/s
Real-World Channel Model
Communication Theory II
If H <= C lossless transmission possible
If H > C lossless transmission impossible!
C
Channel
RH
Source
Brain Wave
Information Rate
sensation perception cognitiondata information knowledge
CognitiveBandwidth
PerceptualBandwidth
SensoryBandwidth
Information Rates
Sense Information StreamBits/s
Vision 10.000.000
Hearing 100.000
Touch 10.000
Smell 1.000
Taste 1.000
Sense Bandwidth of consciousness bits/s
vision 40
hearing 30
touch 5
Taste and smell 1
Channel=”Bandpass Filter”
Effect of degrading the speech signal by spectral filtering
The original speech signal contains significant energy up to 7 kHz
a) signal bandpass filtered (0.25 - 0.75 kHz)
b) signal bandpass filtered (1.0 – 3.0 kHz)
c) original signal
Effect of Bandpass
Bandpass System
Most long-haul transmission systems have a bandpassFrequency response
The transfer function can be written as
)(11)(
ffo
fofjQ
fH
where the resonant frequency fo and quality factor Q are
LCof
21 L
CRQ
ou l
fQB f f
The 3dB bandwidth between the lower and upper cutoff
frequencies is
=
R
L C
fl fo fu
f
1.00.707
B
Bandpass System
Since practical tuned circuits usually have 10 < Q <100,the fractional bandwidth B/fc should be kept within the range
c
B0.01 0.1
f
As a rough rue of thumb, the carrier frequencies and corresponding nominal bandwidth can be
cB 0.02f
Bandpass System
Frequency band Carrier frequency
Bandwidth
Longwave radio 100 kHz 2 kHz
Shortwave radio 5 MHz 100 kHz
VHF 100 MHz 2 MHz
Microwave 5 GHz 100 MHz
Millimeterwave 1 00 GHz 2 GHz
Optical 5x1014 Hz 1013 Hz
Selected carrier frequencies and nominal bandwidth