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Document Sample
SIGNAL MODULATION
for
MULTIMEDIA DATA
TRANSMISSION
with special emphasis on wireless
MULTIMEDIA SYSTEMS
IREK DEFEE
• Content:
- SIGNAL MODULATION
TECHNIQUES
- RADIO WAVE PROPAGATION
- WIRELESS SYSTEMS
- WIRELESS DATA TRANSPORT
- SOURCE AND CHANNEL CODING
(WHICH WE ARE NOT COVERING)
MULTIMEDIA SYSTEMS
IREK DEFEE
SIGNAL MODULATION TECHNIQUES:
HOW TO OVERLAY BITS OR STREAMS OF
BITS ON A SIGNAL TO CARRY THEM?
FOR MULTIMEDIA TRANSMISSION WE
NEED TO TRANSFER A LOT OF DATA
THUS, WE NEED TO PACK THE DATA
EFFICIENTLY ON TRANSMISSION
CARRIER ( WHICH CAN BE RADIO WAVES,
ELECTRIC CURRENT, PHOTONS)
MULTIMEDIA SYSTEMS
IREK DEFEE
Let’s start from the beginning:
Sinusoidal Waveform
• The signal at frequency around fc:
s(t) = Acos(2pfct + q)
• To encode digital symbol of {0, 1},
– One can encode using the amplitude A
– One can encode using the phase q
– One can encode using the frequency fc
– Use some combination of amplitude, phase, or
frequency.
MULTIMEDIA SYSTEMS
IREK DEFEE
Let’s start from the beginning:
Sinusoidal Waveform
• The signal at frequency around fc:
s(t) = Acos(2pfct + q)
• To encode digital symbol of {0, 1},
– One can encode using the amplitude A
– One can encode using the phase q
– One can encode using the frequency fc
– Use some combination of amplitude, phase, or
frequency.
MULTIMEDIA SYSTEMS
IREK DEFEE
Amplitude-Shift Keying (ASK)
Change amplitude A
CARRIER
MULTIMEDIA SYSTEMS
IREK DEFEE
ASK (cont.)
• The signal is
2 Eb
s1 t cos( 2pf c t ) 0 t Tb
Tb
s2 t 0
MULTIMEDIA SYSTEMS
IREK DEFEE
Phase-shift Keying (PSK)
Change phase q
MULTIMEDIA SYSTEMS
IREK DEFEE
PSK (cont.)
• Signal is
2 Eb
s1 t cos( 2pf c t ) 0 t Tb
Tb
2 Eb
s2 t cos( 2pf c t ) 0 t Tb
Tb
MULTIMEDIA SYSTEMS
IREK DEFEE
Frequency-shift keying (FSK)
MULTIMEDIA SYSTEMS
IREK DEFEE
FSK (cont.)
• Signal is
2 Eb
s1 t cos( 2pf1t ) 0 t Tb
Tb
2 Eb
s2 t cos( 2pf 2t ) 0 t Tb
Tb
MULTIMEDIA SYSTEMS
IREK DEFEE
HOW TO PUT MORE BITS ON THE CARRIER?
1. BY USING MORE PHASE SHIFTS E.G. 8-PSK
HERE WE USE
8 PHASE
VALUES
FIGURE 1/V.29
EACH VALUE
Signal space diagram at 9600 bit/s
ENCODES
MULTIMEDIA SYSTEMS
3 BITS
IREK DEFEE
2. BY USING MORE AMPLITUDE LEVELS
AND PHASE SHIFTS – EXAMPLE 16-QAM
(Im)
90°
4
11111 11000
D
01000 00101 01010
2
10010 10101 10011 10100
00000 01111 00010 01101 C 00011
180° 0° (Re)
–4 –2 2 4
11001 11110 11010 11101
A
00111 01001 00110 01011 00100
–2
10000 10111 10001 10110
HERE EACH
01110 00001 B 01100
11100
–4
11011
PHASE/AMPLITUDE
270° T1702150-93/d03
VALUE ENCODES
NOTE – The binary numbers denote Y0n Y1n Y2 n Q3n Q4n . 5 BITS
FIGURE 3/V.32
32-point signal structure with trellis coding for 9600 bit/s
and states A B C and D used at 4800 bit/s and for training
MULTIMEDIA SYSTEMS
IREK DEFEE
128-QAM EXAMPLE -COMBINATION OF AMPLITUDE
AND PHASE ENCODES SPECIFIC BIT PATTERN
90° (Im)
0110000 0111000
8
1100000 1111001 1101000 1110001
0010011 0101001 0010111 0100001 0010101
D 6
1011101 1000011 1011111 1000111 1011011 1000101
0110101 0001101 0110100 0001111 0111100 0001011 0111101
4
1100101 1111011 1100100 1111010 1101100 1110010 1101101 1110011
0010001 0101011 0010010 0101010 0010110 0100010 0010100 0100011 0010000
2
C
1011000 1000001 1011100 1000010 1011110 1000110 1011010 1000100 1011001 1000000
0001000 0110111 0001100 0110110 0001110 0111110 0001010 0111111 0001001
-8 -6 -4 -2 2 4 6 8 (Re)
180° 1100111 1111111 1100110 1111110 1101110 1110110 1101111 1110111 0°
0011001 0101111 0011010 0101110 0011110 0100110 0011100 0100111 0011000
A -2
1010000 1001001 1010100 1001010 1010110 1001110 1010010 1001100 1010001 1001000
0000000 0110011 0000100 0110010 0000110 0111010 0000010 0111011 0000001
-4
1100011 1111101 1100010 1111100 1101010 1110100 1101011 1110101
0101101 0011011 0101100 0011111 0100100 0011101 0100101
-6 B
1010101 1001011 1010111 1001111 1010011 1001101
0000101 0110001 0000111 0111001 0000011
-8
1100001 1111000 1101001 1110000
0101000 270° 0100000 T1701310-90
Note – Binary numbers refer to Y0n , Y1n , Y2n , Q3n , Q4n , Q5n , Q6n .
A, B, C, D refer to synchronizing signal elements.
FIGURE 2-1/V.32 bis
Signal space diagram and mapping for modulation at 14 400 bit/s per second
MULTIMEDIA SYSTEMS
IREK DEFEE
EXAMPLE OF NUMBERS ENCODING BY
SPECIFIC BIT PATTERNS
45
41
408 396 394 400 414
398 375 349 339 329 326 335 347 359 386
These
37 412 371 340 314 290 279 269 265 273 281 302 322 353 390 values of
signal are
33 401 357 318 282 257 236 224 216 212 218 228 247 270 298 337 378
29 406 350 306 266 234 206 185 173 164 162 170 181 197 220 253 288 327 379
25
21
360 310 263 226 193 165 146 133 123 121 125 137 154 179 207 242 289 338 391
384 324 277 229 189 156 131 110 96 87 83 92 100 117 140 172 208 254 299 354
encoded by specific
17 355 294 243 201 160 126 98 79 64 58 54 62 71 90 112 141 180 221 271 323 387 modulation
patterns
13 392 330 274 222 177 135 102 77 55 41 35 31 37 48 65 91 118 155 198 248 303 361
9 380 316 255 203 158 119 84 60 39 24 17 15 20 30 49 72 101 138 182 230 283 348 415
5
1
367 304 244 194 148 108
362 296 238 186 142 103
75
69
50
43
28
22
13
9
6
1
4
0
8
5
21
16
38
32
63
56
93
85
127 171 219 275 336 402
122 163 213 267 328 395
on the previous
–3 365 300 240 190 144 106 73 45 25 11 3 2 7 18 36 59 88 124 166 217 272 331 397
page
–7 372 307 251 199 152 113 80 52 33 19 12 10 14 26 42 66 97 134 174 225 280 341 409
–11 388 320 261 210 167 128 94 67 47 34 27 23 29 40 57 81 111 147 187 237 291 351
–15 410 343 284 232 183 149 115 89 68 53 46 44 51 61 78 99 132 168 209 258 315 376
–19 369 311 259 214 175 139 116 95 82 74 70 76 86 104 129 157 195 235 285 342 399
–23 403 345 292 249 205 176 150 130 114 107 105 109 120 136 161 191 227 268 319 373
–27 382 332 287 250 215 184 169 153 145 143 151 159 178 202 231 264 308 358 413
–31 377 333 293 260 233 211 200 192 188 196 204 223 245 278 312 352 404
–35 383 346 313 286 262 252 241 239 246 256 276 295 325 363 407
–39 405 370 344 321 309 301 297 305 317 334 356 385
–43 411 389 374 366 364 368 381 393
–43 –39 –35 –31 –27 –23 –19 –15 –11 –7 –3 1 5 9 13 17 21 25 29 33 37 41 45
T1403000-97/d05
Figure 5/V.34 – One-quarter of the points in the superconstellation
MULTIMEDIA SYSTEMS
IREK DEFEE
• The more bits we put the better signal to
noise must be (small phase and amplitude
values are lost in noise)
How to put even more bits on a signal?
By using multicarrier modulation –
bits are overlayed on many carriers at the
same time.
MULTIMEDIA SYSTEMS
IREK DEFEE
• ONE USES MANY CHANNELS. EACH
CHANNEL IS MODULATED E.G. WITH
8 KBITS/S. WITH MANY CHANNELS
OVERALL DATA RATE GROWS
• EACH CHANNEL CAN BE
INDIVIDUALLY TUNED TO THE
TRANSMISSION BANDWIDTH, E.G.
SOME CHANNELS CAN BE SKIPPED
COMPLETELY.
MULTIMEDIA SYSTEMS
IREK DEFEE
Now we have many carriers
s1 (t) = Acos(2pf1ct + q)
s2 (t) = Acos(2pf2ct + q)
s3 (t) = Acos(2pf3ct + q)
………………………
sn (t) = Acos(2pfnct + q)
The carriers are assumed to be close to each other
A
f1c …………….. fnc
f
MULTIMEDIA SYSTEMS
IREK DEFEE
How the overall modulated signal will
look ?
In time domain In frequency domain
signals overlap they also overlap
Example of four subcarriers Spectra of individual subcarriers
We have to add additional condition for
signals in order to be able to separate them
• This condition is orthogonality
1 , i j 1 , i j
xi t x* t dt X i f X * f df
i j 0 , i j
j j
0 ,
In time domain In frequency domain
The carriers must satisfy these special conditions
Then by summing and adding upp it will be possible
to separate them
This principle is called OFDM, ORTHOGONAL
FREQUENCY DIVISION MULTIPLEX
MULTIMEDIA SYSTEMS
IREK DEFEE
• WHERE ARE THESE SIGNAL
MODULATION TECHNIQUES APPLIED?
1. PSK, QPSK – GOOD FOR WEAK SIGNALS,
APPLIED IN THE GSM MOBILE SYSTEM, ALSO IN
DIGITAL TELEVISION FROM SATELLITES
2. QAM – REQUIRES STRONGER SIGNALS,
APPLIED IN DIGITAL CABLE TELEVISION
AND IN THE EXTENSION OF GSM CALLED EDGE
3. MULTICARRIER OFDM – APPLIED IN
TERRESTRIAL DIGITAL TELEVISION, IN
WIRELESS LAN, AND IN NEW 4G MOBILE
NETWORK VERY EFFICIENT USE OF
BANDWIDTH, CAN BE ADJUSTED FOR BAD
SIGNAL PROPAGATION
MULTIMEDIA SYSTEMS
IREK DEFEE
The OFDM modulation
• It uses radio bands very effectively
• Applications in wireless networks
Digital Terrestrial Television: e.g. 8 000, 32 000
Digital Mobile Television 4 000and 8 000 carriers
Wireless LAN (802.11a/g): 52 carriers
Ultra Wide Band: many carriers in many bands
NEW 4th generation mobile system called LTE
(Long Term Evolution)- thousands of carriers
MULTIMEDIA SYSTEMS
IREK DEFEE
The OFDM modulation cntd.
• Applications in wired networks
ADSL – broadband networking over telephone lines
It seems OFDM is the winning signal modulation
technology for multimedia data transmission:
- it allows high data bandwidth and is robust
against signal loss
- it is complicated but this is not a problem with
current hardware and computer technology
MULTIMEDIA SYSTEMS
IREK DEFEE
EXAMPLE OF APPLICATION OF
OFDM :
ADSL SYSTEM
BROADBAND NETWORKING
For the home
c@Irek Defée MULTIMEDIA SYSTEMS
• NETWORKING FOR HOME HAS TO
BE CHEAP AND DISTRIBUTED ON
LARGE SCALE
• HOW TO MAKE IT?
- LAYING NEW CABLES – NOT
ECONOMICAL (MAYBE IN NEW
BUILDINGS)
- WIRELESS – BROADBAND NOT
POSSIBLE (MAYBE IN THE
FUTURE??)
c@Irek Defée MULTIMEDIA SYSTEMS
• THE ONLY REALISTIC POSSIBILITY
IS TO USE EXISTING CABLING
THERE ARE TWO TYPES OF EXTERNAL
CABLES FOR CARRYING INFORMATION
AVAILABLE IN HOMES:
TELEPHONE (ALMOST EVERYWHERE)
CABLE TV (IN MANY PLACES)
c@Irek Defée MULTIMEDIA SYSTEMS
• TELEPHONE NETWORK IS DESIGNED AS
NARROWBAND, CABLES ARE FOR
SPEECH, 4kHz BAND
BUT EVERYBODY HAS SEPARATE LINE
• CABLE TV IS DESIGNED AS BROADBAND
BUT ALL USERS SHARE
THE SAME CABLE (FOR TV SIGNAL)
IT LOOKS IMPOSSIBLE TO USE THEM
c@Irek Defée MULTIMEDIA SYSTEMS
• WITH THE OFDM TECHNOLOGY THIS
CAN CHANGE. TELEPHONE CABLE
IS NARROWBAND BUT ITS BANDWIDTH
IS NOT 4 kHz.
Bandwidth of typical telephone cable:
4kHz 1 MHz
ABOVE THE 4kHz CABLE BANDWIDTH IS VERY
VARIABLE. IT IS DIFFERENT FOR EACH CABLE AND
DEPENDS ON DISTANCE
c@Irek Defée MULTIMEDIA SYSTEMS
• UNTIL RECENTLY UNEQUALIZED
BANDWIDTH WAS NOT USEFUL,
TOO MUCH SIGNAL DEGRADATION
• NEW SIGNAL PROCESSING
TECHNIQUES ENABLE ITS USE
c@Irek Defée MULTIMEDIA SYSTEMS
ADSL
ASYMMETRIC DIGITAL SUBSCRIBER LOOP
THE TECHNIQUE FOR USING ”BAD” CABLE
BANDWIDTH BASED ON
OFDM MULTICARRIER SIGNAL MODULATION
c@Irek Defée MULTIMEDIA SYSTEMS
ADSL IN
TELEPHONE NETWORK
MODEM
D
TELEPHONE
S
EXCHANGE L
A MODEM
M
MODEM
BROADBAND
LINKS TO CUSTOMERSARE FEW KM
LINK LONG, CABLING IS NARROWBAND
ADSL MODEMS ENABLE TO
USE MORE BANDWIDTH
c@Irek Defée MULTIMEDIA SYSTEMS
MULTICARRIER MODULATION IN ADSL
f
VOICE BAND
HIGH BAND
4 kHz CARRIER CHANNELS
EACH CHANNEL IS SEPARATELY MODULATED
WITH A SIGNAL.
SIGNAL LEVEL OF EACH CHANNEL CAN BE
MATCHED TO THE GAIN AT ITS FREQUENCY
c@Irek Defée MULTIMEDIA SYSTEMS
• IN PRACTICAL SYSTEM ONE USES
256 CHANNELS. EACH CHANNEL IS
MODULATED WITH E.G. 32 KBITS/S
IN TOTAL THIS GIVES 8 Mbits/sec !!!
• EACH CHANNEL CAN BE INDIVIDUALLY
TUNED TO THE TRANSMISSION SIGNAL
LEVEL, E.G. SOME CHANNELS CAN BE
SKIPPED COMPLETELY.
c@Irek Defée MULTIMEDIA SYSTEMS
• COMPLETE SYSTEM
f
4 25 160 240 .....................1200 kHz
TEL. UPSTREAM DOWNSTREAM
DATA DATA
FROM USER TO USER
THE SYSTEM IS ASYMMETRIC, IT SENDS MORE
DATA DOWN THE LINE THAN UP (E.G. 256 kbits/s up)
BUT FOR HOME USERS THIS IS OK
c@Irek Defée MULTIMEDIA SYSTEMS
• THERE ARE VERY MANY DETAILS
IN ADSL STANDARD:
- HOW THE CARRIERS ARE MODULATED?
(QAM MODULATION)
- HOW THE MODULATION IS REALIZED?
(512-POINT FFT)
- HOW THE ERROR CORRECTION IS
PERFORMED? (FEC)
- HOW THE SIGNALS ARE
SYNCHRONIZED? (PILOT TONE)
c@Irek Defée MULTIMEDIA SYSTEMS
• THESE DETAILS CAN BE FOUND IN THE
ADSL STANDARD AND OVERVIEWS ON
THE WEB.
• ADSL IS NOW OFFERED
COMMERCIALLY ON LARGE SCALE
PRICES (ARE IN THE RANGE OF
FEW TENS OF €/m FOR 1-8 Mb/s
BANDWIDTH. THE SYSTEM WORKS
VERY RELIABLY.
c@Irek Defée MULTIMEDIA SYSTEMS
• BUT FROM PRACTICE IT IS KNOWN
THAT ADSL HAS A PROBLEM TOO:
- BANDWIDTH OFFERED DEPENDS ON
DISTANCE, CABLE QUALITY AND
MAY VARY WIDELY
c@Irek Defée MULTIMEDIA SYSTEMS
New ADSL standards
• These are ADSL2 and ADSL2+. They
provide improvements by:
- using higher signal power
- bonding several phone lines
- using greater bandwidth comparing to ADSL
(up to 2.2 MHz)
- real time channel estimation and adaptation
of bitrate to channel conditions
c@Irek Defée MULTIMEDIA SYSTEMS
ANOTHER EXAMPLE:
Proposed Ultra Wide Band Network
• Ultra Wide Band is wireless network
of very short range but with very
high data transfer rate (600 Mb/s to
1000 Mb/s and more)
This network can eliminate e.g. MONITOR
cable. Then mobile device can drive
the monitor directly.
MULTIMEDIA SYSTEMS
IREK DEFEE
UWB -Ultra Wideband Communication
• UWB system is proposed for high speed
communication between devices, to
eliminate cables:
c@Irek Defée MULTIMEDIA SYSTEMS
Where is UWB?
Look around the show for various
applications…
Video
Streaming MP3 File Transfers
Print Files
Camera
Downloads
Disk Backup
Movie …and more!
Transfers
c@Irek Defée MULTIMEDIA SYSTEMS
What Problem Does UWB
Solve?
The Customer’s Frustration with Cables:
• Tangle of cables in our Homes and Offices
• Ever increasing file sizes of content to be
downloaded and enjoyed by Consumers
• Consumers don’t want to wait long for a file to
transfer
• User Models limited by the use of Cables
• Customers to-day prefer Wireless
UWB is more than a Cable replacement technology
Create new User Models and product opportunities not possible today
with cables
BUT…..MUST Match the Security of cables
MUST be easy to use
c@Irek Defée MULTIMEDIA SYSTEMS
The Vision:
Creating new User Models and Product opportunities
Personal
Wireless Storage/Wallet
Photo Printer
Share video clips
Music & Photos
SHARE and EXCHANGE
Create New User Models
not possible in the Cabled Media Center
Photo & Video Clip World
Display Connecting PC, CE and
Mobile Segments
In Car Media center
& video Multi Channel
Speakers
c@Irek Defée MULTIMEDIA SYSTEMS
The Model that Consumers
Expect
Buy it Plug it in Use it…Easily!
• Compatible and Interoperable out of the box
• Many suppliers supporting a Common Standard at
all levels of the ecosystem
c@Irek Defée MULTIMEDIA SYSTEMS
UWB opportunity
• If Ultra Wide Band networking becomes
popular and monitors/TV’s will
get it, then there will be no need to
connect TV and monitor by cable
to their signal sources. Mobile devices
will display on them directly
MULTIMEDIA SYSTEMS
IREK DEFEE
Imagine this
Mobile devices are more and
more capable (processors,
memory, hard discs), resembling
PC from few years ago
UWB
Ultra Wide Band
Mobile device has wireless
links to keyboard and display
Bluetooth
MULTIMEDIA SYSTEMS
IREK DEFEE
Principle of UWB
• Ultra wideband system uses very broad
frequency band:
There are UWB standards proposed which are based on
several principles: One of them is MULTIBAND OFDM
with many thousands of carriers.
c@Irek Defée MULTIMEDIA SYSTEMS
UWB is Multi-band OFDM
• Central Idea #1:
– Divide the spectrum into bands that are 528 MHz wide.
Band Group #1 Band Group #2 Band Group #3 Band Group #4 Band Group #5
Band Band Band Band Band Band Band Band Band Band Band Band Band Band
#1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 #12 #13 #14
3432 3960 4488 5016 5544 6072 6600 7128 7656 8184 8712 9240 9768 10296
MHz MHz MHz MHz MHz MHz MHz MHz MHz MHz MHz MHz MHz MHz
f
• Advantages:
– Transmitter and receiver process smaller bandwidth signals.
– Instantaneous processing BW = 528 MHz.
MULTIMEDIA SYSTEMS
IREK DEFEE
Exploiting the Band Plan
• Exploit range of band group’s to separate
applications:
Band Group #1 Band Group #2
Band Band Band Band Band Band
#1 #2 #3 #4 #5 #6
3432 3960 4488 5016 5544 6072
MHz MHz MHz MHz MHz MHz
f
Longer Range Apps
Use BG #1 and #2
MULTIMEDIA SYSTEMS
IREK DEFEE
Exploiting the Band Plan
• Exploit range of band group’s to separate
Band Group #3 Band Group #4
applications: Band Band Band Band Band Band
#7 #8 #9 #10 #11 #12
3432 3960 4488 5016 5544 6072 6600 7128 7656 8184 8712 9240 9768 10296
MHz MHz MHz MHz MHz MHz MHz MHz MHz MHz MHz MHz MHz MHz
f
` Shorter Range Apps
Use BG #3 and #4
MULTIMEDIA SYSTEMS
IREK DEFEE
Overview of Multi-band OFDM
• Central Idea #2:
– Interleave OFDM symbols across all bands.
3168
Band # 1
3696
Band # 2
4224
Band # 3
4752
Time
Freq (MHz)
• Advantages:
– Exploits frequency diversity.
– Provide robustness against multi-path / interference.
– Same transmit power as if the entire band is used.
MULTIMEDIA SYSTEMS
IREK DEFEE
IMPORTANT EXAMPLE
• EDGE – ENHANCED DATA RATE FOR
GSM EXPANSION
TECHNIQUE FOR INCREASING THE BIT
RATE OF GSM SYSTEM BY USING
8-PSK.
IT IS ADOPTED FOR DATA TRANSFER
BUT REQUIRES MAJOR HARDWARE
UPGRADES IN THE SYSTEM
MULTIMEDIA SYSTEMS
IREK DEFEE
CURRENT STATUS OF UWB
• Ultra Wide Band connections were
demonstrated for television sets
• Television sets are
• becoming so thin
that that there is no place
• for connectors
• Signal can be
transmitted by wireless UWB link.
MULTIMEDIA SYSTEMS
IREK DEFEE
ANOTHER EXAMPLE
Home Communication over Powerlines
• Powerlines are everywhere, in every room
at home. There is a question if they could be used
for data transmission. After very long development
it looks that powerline communication will become
available e.g. one can see products from:
www.devolo.com
c@Irek Defée MULTIMEDIA SYSTEMS
• The system is very simple to install:
c@Irek Defée MULTIMEDIA SYSTEMS
• How this system operates?
It is based on a standard called Homeplug. For signal
transmission the band which is used is 2-28 MHz
with OFDM modulation. It has 917 carriers and
carriers can be independently modulated by
different modulations from PSK up to 1024 QAM
The maximum data rate can be up to 150 Mb/s,
practical rates are 40-85 Mb/s.
The standard has a lot of other details:
www.homeplug.org
c@Irek Defée MULTIMEDIA SYSTEMS
FURTHER EXAMPLES OF OFDM
WIRELESS SYSTEMS
1. LTE – next generation mobile system
2. WiMax – next generation network
3. WLAN – local area network
MULTIMEDIA SYSTEMS
IREK DEFEE
LTE – Next mobile system after 3G
• LTE = Long Term Evolution
• Extension of 3G network
• Higher databandwith, uses OFDM
modulation
• LTE is fully oriented to multimedia and
advanced applications -> analyze next
slide
c@Irek Defée MULTIMEDIA SYSTEMS
c@Irek Defée MULTIMEDIA SYSTEMS
LTE OFDM
• Orthogonal Frequency-Division Multiplexing
• FDM where carriers are appropriately spaced to insure
orthogonality. Notice the overlap!!
• Spectrally efficient!!
c@Irek Defée MULTIMEDIA SYSTEMS
OFDM signal in time and frequency
Please note that signals on different subcarriers (frequency axis)
carry modulation symbols (time axis). Modulation symbols
(QPSK or QAM) are separated by short breaks (guard intervals)
c@Irek Defée MULTIMEDIA SYSTEMS
LTE Parameters System to the User
– How much data can be sent to the user
– The system is very flaxible, has many parameters
1.25 MHz 2.5 MHz 5 MHz 10 MHz 15 MHz 20 MHz
Transmission BW
Sub-frame duration 0.5 ms
Sub-carrier spacing 15 kHz
Sampling frequency 1.92 MHz 3.84 MHz 7.68 MHz 15.36 MHz 23.04 MHz 30.72 MHz
(1/2 3.84 MHz) (2 3.84 MHz) (4 3.84 MHz) (6 3.84 MHz) (8 3.84 MHz)
FFT size 128 256 512 1024 1536 2048
Number of occupied 76 151 301 601 901 1201
sub-carriers†, ††
Number of 7/6
OFDM symbols
per sub frame
(Short/Long CP)
CP length Short (4.69/9) 6, (4.69/18) 6, (4.69/36) 6, (4.69/72) 6, (4.69/108) 6, (4.69/144) 6,
(μs/samples) (5.21/10) 1* (5.21/20) 1 (5.21/40) 1 (5.21/80) 1 (5.21/120) 1 (5.21/160) 1
Long (16.67/32) (16.67/64) (16.67/128) (16.67/256) (16.67/384) (16.67/512)
c@Irek Defée MULTIMEDIA SYSTEMS
LTE parameters User to the System
How much data teh user can sent
Transmission BW 1.25 2.5 MHz 5 MHz 10 MHz 15 MHz 20 MHz
MHz
Timeslot duration 0.675 ms
Sub-carrier spacing 15 kHz
Sampling frequency 1.92 3.84 MHz 7.68 MHz 15.36 23.04 30.72
MHz (2 3.84 MHz) MHz MHz MHz
(1/2 3.84 (4 3.84 (6 3.84 (8 3.84
MHz) MHz) MHz) MHz)
FFT size 128 256 512 1024 1536 2048
Number of occupied 76 151 301 601 901 1201
sub-carriers†, ††
Number of 9/8
OFDM symbols
per Timeslot
(Short/Long CP)
CP length (μs/samples) Short 7.29/14 7.29/28 7.29/56 7.29/112 7.29/168 7.29/224
Long 16.67/32 16.67/64 16.67/128 16.67/256 16.67/384 16.67/512
Timeslot Interval (samples) Short 18 36 72 144 216 288
Long 16 32 64 128 192 256
c@Irek Defée MULTIMEDIA SYSTEMS
LTE modulation structure
In the LTE the channel width and number of carriers is flexible
12 carriers form one resource block, 1 slot in time is 0.5 ms
and it carries 7 OFDM symbols, 1 subframe is 2 slots
c@Irek Defée MULTIMEDIA SYSTEMS
LTE DATA TRANSFER CAPACITY
• There are so many parameters in the system
that data transfer can be very flexibly adjusted.
One can say that practically several tens of
megabits per second is possible. Thus, LTE will
be the first wide area wireless network with full
multimedia data transfer capabilities
MULTIMEDIA SYSTEMS
IREK DEFEE
WiMax Network
• New type of networks to be deployed in the
near future
• Two types specified:
• One type of them is a substitute for ADSL,
with wireless modems – fixed network
• Antoher type is full mobile network
c@Irek Defée MULTIMEDIA SYSTEMS
WiMAX
• World Interoperability for Microwave Access
• There are two main applications of WiMAX:
1) Fixed WiMAX (IEEE 802.16-2004) - Fixed WiMAX
applications are point-to-multipoint enabling the
delivery of last mile wireless broadband access as an
alternative to cable and DSL for homes and
businesses.
2) Mobile WiMAX (IEEE 802.16e-2005) - Mobile
WiMAX offers the full mobility of cellular networks
at true broadband speeds.
c@Irek Defée MULTIMEDIA SYSTEMS
WiMAX
Fixed WiMAX Architecture
c@Irek Defée MULTIMEDIA SYSTEMS
WiMAX
Mobile WiMAX Architecture
c@Irek Defée MULTIMEDIA SYSTEMS
WiMax Basics
• WiMax allows data transport over
multiple broad frequency ranges
• WiMax’s transmission range and data
rate vary significantly depending on the
frequency bands an implementation uses
• Orthogonal frequency division
multiplexing (OFDM)
• 10 to 66 GHz range
• 75 Mbits
c@Irek Defée MULTIMEDIA SYSTEMS
WiMax frequency bands
• IEEE 802.16a
Spectrum: 2 to 11GHz
More flexible while maintaining the technology’s
data rate and transmission range
• IEEE 802.16b
5 and 6 GHz frequency
provides quality of service
priority transmission for real-time voice and video
and to offer differentiated service levels for
different traffic types
c@Irek Defée MULTIMEDIA SYSTEMS
WiMax Technical Specifications
• OFDM modulation with 256 cariers, 192 useful
• Mobile WiMax 256 to 1024 carriers
• Modulation PSK, QPSK, 16 QAM, 64 QAM
c@Irek Defée MULTIMEDIA SYSTEMS
WiMax Data Rates
• Note: there are several channel bandwidths,
many modulation types and OFDM carriers
c@Irek Defée MULTIMEDIA SYSTEMS
WiMax Technical Specifications
• Up to 280 Mbps per base stations
• Base station transmission range up to 50 km
• True broadband for portable users - providing
broadband connectivity for laptops and PDAs
with integrated WiMax technology
c@Irek Defée MULTIMEDIA SYSTEMS
WiMax radio frequency bands
• 2.3 GHz, 2.5 GHz, 3.4 GHz, 3.6 GHz,
• 5.4 GHz, 5.8 GHz and possibly others
• such as 700 MHz and 900 MHz or even up to 66 GHz
c@Irek Defée MULTIMEDIA SYSTEMS
WLAN
WIRELESS LOCAL
AREA NETWORK
c@Irek Defée MULTIMEDIA SYSTEMS
What is Wireless LAN?
c@Irek Defée MULTIMEDIA SYSTEMS
Wireless LAN Solution
• Extends the local area network
• Freedom to access the corporate network
- high-speed rates
- features comparable to those of wired
networks
• Reliable communications in network
access areas
- meeting rooms
- other corporate offices
- airports
- hotels
- remote and home offices
• Secure access to important information
- e-mail
- corporate data
- the Internet
c@Irek Defée MULTIMEDIA SYSTEMS
How Does Wireless LAN Solution Work?
Wireless LAN PC Card
• Each wireless station and access point has a wireless LAN card
• Provides an interface between an end-user device and
radio waves
+
Radio signal
Internet
Wireless LAN Access Point
• Connected to the wired network
• Acts as bridge between wireless
and wired network E-mail WWW Firewall
• Enables high-performance server server
network access
c@Irek Defée MULTIMEDIA SYSTEMS
Security solution
THE WIRELESS LAN SOLUTION
CORPORATE CAMPUS BRANCH OFFICES
COMMON AREAS
CONNECTIVITY TO CORP
MEETING ROOMS
FACILITIES, ACCESS FOR
TRAINING CENTERS
ROAD WARRIORS
TEMPORARY
OFFICES HOME OFFICE
HOT SPOTS
QUICK CONNECTION
AIRPORTS, HOTELS PORTABLE
CONVENTION CENTERS EASY START-UP
BUSINESS TOWERS
c@Irek Defée MULTIMEDIA SYSTEMS
• THERE ARE FOUR FAMILIES OF
WLAN STANDARDS:
WLAN Standard Over-the-Air Actual rate for
(OTA) Estimates data transmission
(Bitrate of signals (Data transfer)
transmitted)
802.11b OLD 11 Mbps 5 Mbps
802.11g 54 Mbps 25 Mbps (when
.11b is not present)
802.11a 54 Mbps 25 Mbps
802.11n 200+ Mbps 100 Mbps
Note: 802.11n is new and not commonly available yet
c@Irek Defée MULTIMEDIA SYSTEMS
• WLAN RADIO BANDS
IEEE 802.11g 2.4 GHz
IEEE 802.11a 5 GHz (200MHz)
IEEE 802.11n 2.4 and 5 GHz
• MODULATION:
- OFDM - (MULTICARRIER
MODULATION) IEEE 802.11a and g
c@Irek Defée MULTIMEDIA SYSTEMS
What is IEEE802.11b WLAN?
It is substitute for the Ethernet. All users
send and receive packets in the same band.
radio resources are allocated for them on
randomized basis.
The more users are on-line, the less bandwidth
is available. IEEE 802.11b bandwidth is:
11 Mb/s theoretically
5 Mb/s practically – shared by all users
Range: 15-100m (bulidings, open spaces)
c@Irek Defée MULTIMEDIA SYSTEMS
• CHANNEL BANDWIDTH
20 MHz – 52 CARRIER FREQUENCIES
48 USED FOR DATA
QPSK AND QAM MODULATION IS
USED FOR CARRIERS
GROSS BIT RATES ARE FROM 6-54 Mb/sec
USEFUL BIT RATES ABOUT HALF OF
THAT
c@Irek Defée MULTIMEDIA SYSTEMS
• THE SYSTEM DATA TRANSFER IS
ORGANISED AS TIME DIVISION
MULTIPLEX IN FRAMES
EACH FRAME HAS LENGTH OF 2 ms
AND WITHIN IT PACKETS OF DATA
SEND (48 BYTES)
c@Irek Defée MULTIMEDIA SYSTEMS
• PERFORMANCE CAN REACH
PRACTICALLY 20 Mb/sec
• THE NUMBER OF USERS:
TRANSMISSION RANGE IS 30-150 M
(TRANSMITTER POWER 0.2-1W)
THERE ARE MAX. 19 CHANNELS
• DEPENDING ON THE BANDWIDTH
THERE COULD BE ABOUT 50-70(?) USERS
FOR 1 ACCESS POINT
c@Irek Defée MULTIMEDIA SYSTEMS
The 802.11n standard
• This is new standard improving on the
older ones
• The major improvements are:
- Better OFDM modulation up to 65 Mb/s
- It can use several transmission and
receiving systems and the same time
c@Irek Defée MULTIMEDIA SYSTEMS
Multiple stream transmission in 802.11n
Here there is a scheme with 2 streams, in the 802.11n standard there
can be 2,3, or 4 streams, the bit rate will be 2x,3x,4x higher.
In the end we can have up to 100 Mb/s data transfer with 4 streams.
The standard has also optional modes of operation
(with wider channels)
The data rate then could be up to 300 Mb/s.
c@Irek Defée MULTIMEDIA SYSTEMS
Digital Terrestrial and Mobile Television
• There are 3 standards: DVB-T, DVB-T2 and DVB-H
• OFDM modulation is used with 2000, 4000, 8000…. up
to 32 000 carriers
• Each carrier can be modulated with PSK, 16-QAM,
64-QAM up to 256-QAM
• Data rates are between 20-40 Mbits/sec in single TV
channel with 8 MHz width
Digital Television is widely used in Europe
MULTIMEDIA SYSTEMS
IREK DEFEE
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