1. ECEN5553 Telecom Systems Dr
ECEN5553 Telecom Systems Dr. George Scheets Week #12 Read [24a] "The Troubled Past and Uncertain Future of Radio Interference" [24b] "Fantastic 4G" [25] "Riding the Data Tsunami in the Cloud" [26a] "Mobile's Millimeter Wave Makeover" [26b] "Telecom Experts Plot a Path to 5G" Exam #2: Results to date: Hi = 90, Lo = 74.5, Ave = 81.62, σ = 4.76 Term Paper: Due 4 November (Live Sites) Due 11 November (DL)

2. EM Waves and You Solids: Concrete Wood Glass: Similar Similar except
Effect.
MHz
GHz
THz
PHz
EHz
Glass:
Similar
except
around
visible
light &
infrared.
Metal:
Blocks
everything.
Gamma
can punch
thru thin
sheets.
source:

3. Atmospheric Absorption
source:

4. Do Cell Phones Cause Brain Cancer?
Studies in [21b] show mixed results
Some show increased chances
Some show decreased chances
World Health Organization says maybe
Laws of Physics & Frequencies Used Today
Localized "Heating" possible
1 watt cell by ear? 1/2 watt hits head.
Oklahoma Mesonet, 2:50 pm, 31 October 2011
600 watts/meter2 solar radiation falling (hazy)
Top of Dr. Scheets' head ≈ 0.03 meters2
19.2 watts of solar radiation hit top

5. Radio Transmission Want a reasonable size antenna?
λ (= velocity/frequency) needs to be small
Signal needs high frequencies
Injecting pulses directly into antennas?
Won't work well
All pulses have a lot of low frequency energy Won't radiate well
Need to shift all pulse's energy to higher frequency range

6. 1 MHz Sinusoid 1.5 1 vp 1 MHz -1.5 .000005 Spectrum Power freq (Hertz)
-1.5
Spectrum
Power
freq
(Hertz)
1,000,000

7. Binary ASK
1.5
1 MHz
-1.5
.00001
Two different Amplitudes are transmitted
10 cycles/ seconds = 1 MHz
5 cycles/symbol
200 K symbols/second = 200 K bits/second

8. Binary FSK 1.5 -1.5 .00001 Two different frequencies are transmitted
-1.5
.00001
Two different frequencies are transmitted
Symbol #1) 5 cycles/ seconds = 1 MHz
Symbol #2) 10 cycles/ seconds = 2 MHz
1.5 MHz Average (center) Frequency
2 symbols in seconds =
200 K symbols/second = 200 K bits/second

9. Binary PSK 1.5 1 MHz -1.5 .00001 Two different phases are transmitted
-1.5
.00001
Two different phases are transmitted
10 cycles/ seconds = 1 MHz
5 cycles/symbol
200 K symbols/second = 200 K bits/second

10. M-Ary Signaling
One of M possible signals transmitted each symbol interval
Tends to be used where bandwidth is tight & SNR decent at the receiver.
Each symbol can represent log2M bits
Example: In 16 FSK
one of 16 possible frequencies is transmitted every symbol interval
each symbol can represent 4 bits

11. 4-Ary ASK
1.5
1 MHz
-1.5
4 different Amplitudes are transmitted (3 shown)
4th symbol might be 0 volts for 5 μ seconds
15 cycles/ seconds = 1 MHz
5 cycles/symbol
200 K symbols/second = 400 K bits/second

12. Quadrature Amplitude Modulation (form of M-Ary Modulation)
1.5
1 MHz
-1.5
Different amplitudes and phases are transmitted
15 cycles/ seconds = 1 MHz
5 cycles/symbol
200 K symbols/second = Log2M*200 K bits/second

13. Unfiltered b Spectrum

14. Cosine & Cosine2
Cosine
Cosine2

15. Cosine & Cosine*Sine
Cosine
Sine
Cosine*Sine

16. RF Wireless Layer 1 Issues
Message mapped onto carrier wave
Binary: PSK
4-Ary: 4-PSK, a.k.a. QPSK
M-Ary: QAM (combo of ASK & PSK)
Hi frequency RF carrier
Small antenna
Less penetration
Wireless is a Hostile Environment
Compared to Guided Media (fiber, copper cable)
Noisier & received power is very weak

17. Forward Error Correction
XMTR Adds extra parity bits to the bit stream
FEC codes allow trade-off of an increase in the bit rate for a reduced RCVR Message Bit Error Rate
Cranking up transmitted signal power can do the same
Distance between legal code words sets error correcting capability
FEC codes are used on...
Cell Phones
NASA Deep Space probes
Long Haul Fiber Optic Systems
Compact Disk
...and other applications.

18. Digital Communication System
Source
Data, Digitized
audio or video.
Outputs bits.
Modulator
Converts bits
to a symbol
suitable for
channel.
FEC
Adds extra
parity bits.
Optional
FEC Decoder
Examines blocks
of bits. If possible,
corrects or
detects bit errors.
Outputs estimate of
source bit stream.
Symbol Detector
Examines
received symbol
& outputs 1
(binary) or more
(M-Ary) bits.
Channel
Attenuates,
distorts,
& adds noise
to symbols.

19. Modulator Copper Cable Electrical pulses frequently used Fiber Cable
Electrical pulses converted to optical pulses
RF Systems
High frequency sinusoid symbols used
Carrier frequency impacts antenna size
Binary versus M-Ary
M-Ary packs more bits in the bandwidth
M-Ary more susceptible to decoding errors
M-Ary used when bandwidth is tight & SNR decent

20. RF Modulator May map 1 Mbps stream from the FEC coder to...
... 1 M symbol/sec Binary ASK, PSK, or FSK signal
K symbol/sec 4-Ary ASK, PSK (a.k.a. QPSK), or FSK signal
2 bits per symbol
Would require less Bandwidth than Binary as BW proportional to symbol rate
... other M-Ary signal (QAM)

21. Receiver Symbol Detector
If Radio system
INPUT: attenuated, noisy & distorted Binary PSK, QPSK, or QAM
If copper cable
INPUT: attenuated, noisy & distorted square electrical pulses (Baseband)
If fiber
INPUT: attenuated, noisy, & distorted square optical pulses (Baseband)
OUTPUT: Baseband (square electrical pulses)

22. Receiver
FEC Decoder
INPUT: Baseband Bits Traffic we want + parity bits
OUTPUT: Baseband Bits Traffic bits
Some may be in error

23. FEC Examples Single Sample Detector (SSD)
Samples each symbol once, compares result to threshold
Matched Filter Detector (MFD)
Samples each bit multiple times and computes an average, compares average to a threshold
MFD will have lower P(BE) than SSD
MFD P(BE) gets worse as bit rate increases
Averaging time becomes shorter
Number of independent samples gets smaller

24. FEC Examples In the limit, as bit interval T approaches zero seconds
# of independent samples approaches 1
MFD P(BE) approaches SSD P(BE)
Suppose you have a system where
P(BE) = 0.1 for SSD for all bit rates
P(BE) = 0.02 for MFD at bit rate R (no FEC)
P(BE) = 0.03 for MFD at bit rate 2R (2:1 FEC)
P(BE) = 0.04 for MFD at bit rate 3R (3:1 FEC)

25. Block Diagram: Single Sample Detector & no FEC
Source
Channel Coder
Data bits
R bps
Symbol Detector:
Single Sample
Channel
P(Bit Error) = .1
R bps
If symbol detector screws up 10% of
the time, P(Bit Application Error) = 0.1

26. Example: Source Output
500 Kbps Data Bit Stream
Layer 2 protocols and above
Voice, Computer Data, or Video
T = seconds/bit
1/T = 500 K Data bps.
volts +1
time -1 T

27. Example: 2:1 FEC Coder Output
Might duplicate each application bit
for every 1 data bit input, two code bits (1 parity bit & the input application bit) are output
T = seconds/bit
1/T = 1 M Code bps.
volts +1
time -1 T

28. Example) SSD 2 bit code words
Suppose you now transmit each bit twice, and P(Code Bit Error) = .1
Legal Transmitted code words; 00, 11
Possible received code words 00, 11 (appears legal, 0 or 2 bits decoded in error) 01, 10 (clearly illegal, 1 bit decoded in error) P(No bits in error) = .9*.9 = .81 P(One bit in error) = 2*.9*.1 = .18 P(Both bits in error) = .1*.1 = .01
Decoder takes 2 Code bits at a time & outputs 1 bit of Data If illegal code word received, it can guess 0 or 1. 81% + 18%(1/2) = 90% of time the correct bit is output 1% + 18%(1/2) = 10% of time the incorrect bit is output
Same performance as No twice the bit rate

29. SSD 2:1 FEC FEC Coder: Input = 1 bit. Source Modulator Output =
Input + Parity
bit.
Source
Modulator
data
bits
R bps
Symbol rate
transmitted
must double
compared to no
FEC case, or
4-Ary signaling
must be used.
code
bits
2R bps
app.
bits
code bits
FEC Decoder:
Looks at blocks of
2 bits. Outputs
1 bit.
Symbol
Detector:
Single sample
Channel
P(data bit error) = .1
P(code bit error) = .1

30. Example) SSD 3 bit code words
Transmit each bit thrice, P(Code Bit Error) = .1
Legal Transmitted code words; 000, 111
Possible received code words 000, 111 (appears legal, 0 or 3 bits in error) 001, 010, 100 (clearly illegal, 1 or 2 bits in error) 011, 101, 110 (clearly illegal, 1 or 2 bits in error) P(No bits in error) = .9*.9*.9 = .729 P(One bit in error) = 3*.92*.1 = .243 P(Two bits in error) = 3*.9*.12 = P(Three bits in error) = .1*.1*.1 = .001
Decoder takes 3 bits at a time & outputs 1 bit. Majority Rules. 72.9% % = 97.2% of time correct bit is output .1% + 2.7% = 2.8% of time incorrect bit is output
Improved 3x the required bit rate

31. SSD 3:1 FEC Source Coder: Input = 1 bit. Source Channel Coder Output =
Input + two
parity bits.
Source
Channel Coder
data
bits
R bps
Symbol rate
transmitted
must triple
compared to no
FEC case, or
8-Ary signaling
must be used.
code
bits
3R bps
data
bits
code bits
Source Decoder:
Looks at blocks of
3 bits. Outputs
1 bit.
Symbol
Detector:
Single sample
Channel
P(data bit error) = .028
P(code bit error) = .1
3:1 FEC offers superior performance than simpler no FEC code system.

32. Example) MFD No Coding
Probability of a Bit Error will improve over that of Single Sample Detector to, say, P(Bit Error) = .02
No Coding: Transmit each Data Bit Once
Legal Transmitted data‘words’; 0, 1
Possible received data words 0, 1 (legal or 1 bit in error, no way to tell) P(Data Bit OK) = .98 P(Data Bit in error) = .02

33. Matched Filter Detector & No coding: Block Diagram
Source
Channel Coder
Symbol Detector:
Matched Filter
Channel
P(Bit Error) = .02
Matched Filter shows reduced bit errors compared to SSD
Improvement decreases as symbol rate increases

34. Example) MFD 2 bit code words
Suppose you transmit each bit twice, smaller bit width will cause P(Code Bit Error) to increase to, say 0.03
Legal Transmitted code words; 00, 11
Possible received code words 00, 11 (appears legal, 0 or 2 bits in error) 01, 10 (clearly illegal, 1 bit in error) P(No code bits in error) = .97*.97 = P(One code bit in error) = 2*.97*.03 = P(Both code bits in error) = .03*.03 = .0009
Decoder takes 2 code bits at a time and outputs 1 data bit If illegal code word received, it can guess 0 or % %(1/2) = 97% of time correct bit output .09% %(1/2) = 3% of time the incorrect bit is output
FEC makes it worse: 3% data bit error vs 2% No Coding

35. Typical FEC Performance
Coded
Plot changes as type of symbol, type of
detector, and type of FEC coder change.
P(BE)
Uncoded
Plot changes as type
of symbol, and
type of detector change.
Last example is
operating here.
There generally always is a cross-over point.
The max possible P(BE) = 1/2.
SNR

36. MFD 2:1 FEC 2R code bps Source Coder: Input = 1 bit. Source
Output =
Input + Parity
bit.
Source
Channel Coder R
data
bps R
app.
bps
2R code bps
Source Decoder:
Looks at blocks of
2 bits. Outputs
1 bit.
Symbol
Detector:
Matched
Filter
Channel
P(data bit error) = .03
P(code bit error) = .03

37. Example) MFD 3 bit code words
Transmit each bit thrice, P(Bit Error) again increases to, say 0.04, due to further increase in the bit rate.
Legal Transmitted code words; 000, 111
Possible received code words 000, 111 (appears legal, 0 or 3 bits in error) 001, 010, 100 (clearly illegal, 1 or 2 code bits in error) 011, 101, 110 (clearly illegal, 1 or 2 code bits in error) P(No code bits in error) = .96*.96*.96 = P(One code bit in error) = 3*.962*.04 = P(Two code bits in error) = 3*.96*.042 = P(Three code bits in error) = .04*.04*.04 =
Decoder takes 3 bits at a time & outputs 1 bit. Majority Rules % % = % of time correct bit is output % % = % of time incorrect bit is output
FEC makes Data BER better (.5% vs thrice the bit rate

38. MFD 3:1 FEC 3R code bps Source Coder: Input = 1 bit. Source
Output =
Input + two
parity bits.
Source
Channel Coder R
application
bps R
app.
bps
3R code bps
Source Decoder:
Looks at blocks of
3 bits. Outputs
1 bit.
Symbol
Detector:
Matched
Filter
Channel
P(app. bit error) = .005
P(code bit error) = .04

39. Typical FEC Performance
FEC allows target
P(BE) to be reached
with lower received
SNR, but a higher
bit rate must be
transmitted. Used a
lot in power limited
environments.
P(BE)
Coded
Uncoded
Different FEC codes
will have different curves!
Received SNR

40. Very Large Array Parabolics
Directional antennas. Larger size → narrower beam.
Narrower beam → energy more focused (XMTR)
Narrower beam → better at picking up weak signal (RCVR)
image source: Wikipedia

41. FAST Radio Telescope (500 m)
Direct TV Antenna (1/2 m)

42. Omni-Directional Antenna Array
Belkin Wireless
Pre-N Router
F5D8230-4
Steerable beams.
source:

43. Two Omni Array Example λ/2 fc = 300 MHz λ = 1 meter Same signal fed
to both antennas.
Beam shoots out
both sides at 90
degree angle.
(Far side not shown.)
Directivity Strength

44. Two Omni Array Example λ/2 fc = 300 MHz λ = 1 meter Signal to right
antenna delayed
by picosecond
( = 10% wavelength)
with respect to right
antenna.
Directivity Strength

45. Two Omni Array Example λ/2 fc = 300 MHz λ = 1 meter Signal to left
antenna delayed
by picosecond
( = 10% wavelength)
with respect to right
antenna.
Directivity Strength

46. Two Omni Array Example λ/2 fc = 300 MHz λ = 1 meter Signal to left
antenna delayed
by picosecond
( = 25% wavelength)
with respect to right
antenna.
Directivity Strength

47. Two Omni Array Example λ/2 fc = 300 MHz λ = 1 meter Signal to left
antenna delayed
by 1 2/3 nanosecond
( = 50% wavelength)
with respect to right
antenna.
Directivity Strength

48. I/O LAN Antenna Combinations
SISO
Common Today
SIMO, MISO, & MIMO
Starting to see use on wireless LAN's & MAN's
SIMO & MISO Can help cancel effects of multi-path
MIMO Can provide spatial diversity
Increases amount of usable RF bandwidth

49. Satcom & Flat Panel Antenna Arrays
USS Lake Champlain: Aegis Guided Missile Cruiser
image source: wikipedia