1. ECEN5553 Telecom Systems Dr
ECEN5553 Telecom Systems Dr. George Scheets Week #13 [27] "5G Wireless Access: Requirements and Realization" [28a] "Why Wi-Fi Stinks- and How to Fix It" [28b] "What's Next for Wi-Fi?" [28c] "Old-School Wi-Fi is Slowing Down Networks"= [29a] "What to Expect from 11ac’s Next Big Deal: Multiuser MIMO" [29b] "Worries Mount over Upcoming LTE-U Deployments Hurting Wi-Fi" [29c] "Is it Safe to Use Public Wi-Fi Networks?" [29d] "How the Wi-Fi industry is adapting to keep up with the IoT" Exam #2 Results Hi = 90.1, Low = 54.2, Ave = 78.94, σ = A > 81, B > 72, C > 59, D > 50 Term Paper: Late Fee = -1 point per working day Final Exam Monday, 5 December, 2:00 – 3:50 pm (Live) < 12 December (Distance Learning)

2. Bit Error Rate Unsatisfactory?
System designer has several options:
Use FEC codes
Increase received signal power
Crank up transmitter power out
Use directional antennas
Use more effective modulation technique
Slow down the transmitted symbol rate
Use less noisy receiver electronics

3. Techniques to Increase Bit Rate (Per Channel Basis)
Use FEC
Increase Received Signal Power
Increase transmitter power out
Use directional antennas
Change Modulation Technique
Go to higher "M" in M-ary
Build a Quieter Receiver
Slow Down Transmitted Bit Rate
Increase Available Bandwidth
Compress the Application Signal
Increases apparent bit rate

4. Voyager II Deep Space Probe
Used all of previous techniques on downlink:
2:1 FEC Coding (different code than in previous examples)
Increasingly sophisticated earth receive antennas
Binary PSK signaling
Reduced bit rates
Cryogenically cooled receiver electronics
Flight history
Launch , August 1977
Jupiter fly-by, July 1979, Message bit rate: Kbps
Saturn fly-by, August 1981, Message bit rate: 44 Kbps
Uranus fly-by, January 1986, Message bit rate: 29.9 Kbps
Neptune fly-by, August 1989, Message bit rate: 21.6 Kbps
Now well past Pluto. NASA is still in contact.

5. Pre-Cellular Mobile Telephony
source: Telecommunications by Warren Hioki, 1st Edition

6. 0th Generation Mobile Phones
Source:

7. Cellular Telephone System
source: Telecommunications by Warren Hioki, 1st Edition

8. Cellular Telephony Advantages:
Frequency Reuse
Reduced Transmitter Power Out
Reduced Multipath Problems
Reduced brain damage?
Subdividing Cells increases System Capacity
More Reliable due to cell overlap

9. Cellular Telephony Disadvantages:
More complex
More installation hassles
BS to MTSO link (Backhaul) & switching requirements can get out of hand

10. 1987 Mobile Phone
source: September 1987
Electronic Design Magazine

11. One Big Cell
30 Channels
could support
30 users

12. Seven Smaller Cells Set #2 10 Channels Can Set #1 Support 10 Channels
70 Users
with same
Channel
set.
Set #3
10 Channels

13. Mobile Traffic
Source: "The Great Spectrum Famine", IEEE Spectrum Magazine, October 2010.

14. London, 1995

15. Hidden Cell Towers
sources:
businessweek.com
mobilitydigest.com

16. Cellular Telephony - Operation Power Up & Intermittently Thereafter
Mobile tunes to strongest control channel
Mobile communicates with BS/MTSO
Local MTSO notes in database mobile is active & which cell it's in
If mobile is roaming, Home MTSO is notified, typically via SS7 or SIP Signaling

17. Cellular Telephony - Operation Mobile to Wired call
Mobile transmits # to BS/MTSO
Uses Control Channel
Unused voice RF channel is assigned
Mobile tunes to assigned channels
BS & MTSO coordinate Backhaul
MTSO places call via CO to wired unit
Could be via PSTN or VoIP

18. Cellular Telephony - Operation Wired to Mobile call
Signaling info shipped to home MTSO
Home MTSO checks database
Mobile in home area? Mobile is paged
Mobile not in home area? Signaling info is forwarded to local MTSO Local MTSO database indicates Mobile's cell Mobile is paged & tunes to assigned RF channel
End-to-End Voice channel is set up
BS & MTSO coordinate Backhaul
MTSO & CO coordinate Long Haul

19. Cellular Telephony - Operation
Handoff MTSO/BS/Mobile decides signal getting too weak Adjacent cells are polled Unused voice RF channels in the new cell is assigned Mobile tunes to assigned channel MTSO reroutes traffic: Old BS  MTSO to New BS  MTSO

20. Where is this MTSO? Could be anywhere Increased Computer Power
Co-located with a Central Office
In the Cloud
Elsewhere
Increased Computer Power
What used to be done at MTSO can now be accomplished at other locations
Widespread Internet Availability
Traffic could flow thru ISP & bypass MTSO
Depends on the carrier

21. Advanced Mobile Phone System (AMPS)
1st Generation U.S. Cellular
Analog FDMA
30 KHz FM channels
# of subscribers peaked in 1999
February 18, 2008
FCC no longer required carriers to support
Should now be called OMPS
RIP

22. 1G AMPS FDMA 1 2 3 4 Cell 1 Cell 2 AMPS time
Different channels use some of
the frequency all of the time.
frequency 1 2 3 4
Cell 1 Cell 2
AMPS
time

23. 1G Backhaul Typically a T-1 14.4 Kbps data per user Voice Backhaul
23 calls
1 signaling channel
14.4 Kbps data per user
Voice Backhaul
Moving a little data on the side

24. 2G Mobile Wireless (MAN)
Time Division Multiple Access
U.S. TDMA, 2G, gone → GSM
GSM, 2G, Data Speeds < 14.4 Kbps Obsolete
RIP

25. 2G GSM
Combo of TDM & FDM
frequency 1 4 7 10
Cell 1 Cell 2 2 5 8 11 3 6 9 12
time 1 4 7 10
etc.

26. 2G Mobile Wireless (MAN)
Time Division Multiple Access
U.S. TDMA, 2G, gone → GSM
GSM, 2G, Data Speeds < 14.4 Kbps Obsolete
Code Division Multiple Access
TIA-95 CDMA (a.k.a. IS-95 or CDMA1), 2G Data Speeds < 14.4 Kbps Obsolete
RIP

27. DSSS - Transmit Side +1 Traffic (9 Kbps) time -1 Spreading Signal
27 Kcps +1 +1 +1
time -1 -1 -1
Transmitted
Signal
27 Kcps
(mapped
onto hi freq) +1 +1 +1 +1
time -1 -1

28. Wireless RF Transmitter RCVR Front End 27 Kcps Square Pulses X
BPSK output
27 Kcps
90% of power in 54 KHz BW
centered at fc Hertz
cos(2πfct)
RCVR Front End
BPSK input
27 Kcps
+ noise
Low Pass
Filter
27 Kcps
Square Pulses
+ filtered noise X
cos(2πfct)

29. DSSS-Receiver +1 +1 +1 +1 time Received Signal 27 Kcps -1 -1
Despreading
Signal
27 Kcps +1 +1 +1
time -1 -1 -1
Recovered
Traffic
9 Kbps +1
time
DSSS-Receiver -1

30. DSSS-Receiver 2nd Signal active Received Signal #2 27 Kcps +1 +1 +1 +1
time
DSSS-Receiver
2nd Signal active -1 -1
Despreading
Signal #1
27 Kcps +1 +1 +1
time -1 -1 -1 +1 +1
Recovered
Garbage
from 2nd
signal +1
time -1 -1 -1

31. DSSS-Receiver 2 Signals active +1 Recovered Traffic 9 Kbps time -1 +1
Garbage
from 2nd
signal +1
time -1 -1 -1
Input to
Matched
Filter
Detector
(sum) +2
time
DSSS-Receiver
2 Signals active -2

32. Additional signals transmitting at the same time
Input to
Matched
Filter
Detector
(sum) +2
time -2
TBit
Receiver
Matched
Filter
Detector
Output +1
time -1
Additional signals transmitting at the same time
increase the apparent noise seen by our system.
Message (voice) BER will increase.

33. CDMA Channels use different codes. Other channels cause
Different channels use all
of the bandwidth all of the time.
CDMA
frequency
Channels use different
codes.
Other channels cause
noise-like interference.
time

34. CDMA: 3D View
frequency
code #3
code #2
code #1
time

35. Multiplexing Schemes Frequency Division Mutiplexing
Time Division Multiplexing
Statistical Multiplexing
Code Division Multiplexing

36. 2G Backhaul Still Frequently T Carrier 14.4 Kbps Data Initially
T1's, Fractional T3's, or a maybe a T3
14.4 Kbps Data Initially
< 200 Kbps data with later add ons
Primarily Voice Backhaul
Moving a little more data on the side

37. Mobile Wireless Evolution
2G: Voice! Voice!
2.5G: One eye
on data.
3G: Voice & Data
4G: Hi Speed Data
LTE
(4G)
Sprint
WiMax
Development
halted in 2005

38. 3G Mobile Wireless (MAN)
Universal Mobile Telephone Service (UMTS)
3G GSM, Data Rates from 384 Kbps to 2+ Mbps
Wideband CDMA, 5 MHz BW
High Speed Packet Access (HSPA)
3G GSM, UMTS upgrade, data < 2(4+) Mbps up(down)link
W-CDMA: more codes & higher M-Ary for data
Code Division Multiple Access 2000 (CDMA 2000)
3rd Generation
Data Rates 200 Kbps to maybe 3+ Mbps

39. 3G Backhaul T3's & SONET ATM or IP Based Mixed Traffic Environment
Some Carrier Ethernet
Mixed Traffic Environment

40. FDM FDMA 1 2 3 4 time Different channels use some of
the frequency all of the time.
frequency 1 2 3 4
time

41. Orthogonal FDM time frequency Channel 1
Channels split into sub-channels
Bits parceled out to sub-channels
Advantage:
Sub-channel bit rates can be
modified to cope with
narrow band interference
Less susceptible to multipath
time

42. FDM with Multi-path T3 bounce path XMTR direct path direct path pulses
time
bounce path
XMTR
direct path
direct path pulses
RCVR
delay
bounce path pulses
Signal sum seen by Receiver
Symbol decision intervals at Receiver.
The third bit is obliterated by multi-path. T1 T2 T3

43. OFDM with Multi-path Slower symbol rate over each subchannel. delay
bounce
direct
bounce
direct
direct
bounce
Matched filter detector will work OK. T1 T2 T3

44. Automatic ReQuest Repeat
Standard ARQ
Use "Hard Decision" symbol detector
Throw away contents of corrupted packet
Request a retransmission
TCP does this
Hybrid ARQ
Use "Soft Decision" symbol detector
Save contents of corrupted packet
Combine Results

45. Standard ARQ Hard Decision Matched Filter Bit Detector
Sample Bit Multiple Times
Compute an Average
If Average > Threshold, Call it a Logic 1
If Average < Threshold, Call it a Logic 0
Suppose flunks CRC
Suppose retrans also flunks CRC
Pretty sure of 1st, 2nd, & 5th – 8th bits
Are 3rd and 4th Bits 1's or 0's?

46. Hybrid ARQ Soft Decision Matched Filter Bit Detector
Sample Bit Multiple Times
Compute an Average
How Far From Threshold?
Barely Above? Could Say "It might be a Logic 1"
Above? Could Say "It's probably a Logic 1"
Well Above? Could Say "It's very likely a Logic 1"
Far Above? Could Say "I'm positive it’s a Logic 1"
Ditto for Voltages Below Threshold

47. Hybrid ARQ Soft Decision Matched Filter Bit Detector
Suppose flunks CRC
Suppose Average for 3rd bit barely above
Suppose Average for 4th bit barely below
Suppose retrans also flunks CRC
3rd bit average far below → Positive it's a Logic 0
4th bit average barely above → Iffy Logic 1
Byte probably is
We're pretty sure 3rd bit is a Logic 0
4th bit can't be a 1, as flunked CRC

48. 4G requires higher SNR Need more battery power Smaller Cell Sizes
source: Yuan, Y., et al, "LTE-Advanced Coverage Enhancements", IEEE Communications, October 2014

49. 4G Backhaul Frequently SONET IP & MPLS Based Bursty Data Environment
Some Carrier Ethernet
Bursty Data Environment
Hauling a little Voice over IP on the side

50. Signal power decrease is proportional to 1 / (distance)2
Data Rate Roll-Off
source: Zander, J., Mahonen, P.,
"Riding the Data Tsunami in the Cloud:
Myths and Challenges in Future Wireless Access",
IEEE Communications Magazine, March 2013.
Signal power decrease is proportional to 1 / (distance)2

51. 4G Wireless (MAN) Long Term Evolution (LTE) LTE-Advanced
OFDM, MIMO, Data Rates > 60 Mbps
Back to the Future: TDMA → CDMA → TDMA
Initially Deployed in 2011.
LTE-Advanced
Seeing initial deployment in 2013
1-2 Gbps speeds claimed on downlink
Some Trade Pub articles → Don't need a LAN
Speeds ↓ as distance from BS ↑ & BW shared
WiMax (IEEE )
OFDM, MIMO, Data Rates < Mbps
Deployed by Sprint & Clearwire. Sprint moved to LTE.
Alternative to LTE? No. Used as back haul, fixed wireless.

52. 5G Cellular IP Wireless Traffic Goals
3 Exabytes in 2010 (exabyte = 1018)
Projected to exceed 500 exabytes by 2020
4G Cannot Handle
Goals
Aggregate Data Rate (bps/unit area) 4G x 1000
Edge Rate (Worst Case speed seen by 5%) 1 Mbps → 100 Mbps
Average Round Trip Time: Reduce by x 15
Energy Use: Don't Let It Increase
source: Andrews, J;, et al, "What Will 5G Be?", IEEE Journal on Selected Areas in Communications, June 2014

53. Meeting 5G Goals Extreme Densification
Mix of few large cells and many small cells
Including pico cells (range < 100 meters)
Including femto cells (< 10 – 20 meters)
Highest Bit Rates from Smallest Cells
Increasing # of modulation techniques
Smart Radios
Improved Mobility Support
Smart Network
Seamless Merging of Large & Small Cells
source: Andrews, J;, et al, "What Will 5G Be?", IEEE Journal on Selected Areas in Communications, June 2014

54. Meeting 5G Goals Increased Bandwidth "Beach Front" BW is taken
XXX MHz and X GHz
Propagates and Penetrates Reasonably Well
Must go to Higher Carrier Frequencies
mmWave Frequencies XX to XXX GHz
Do Not Propagate as Well
Electronics Not So Good & Expensive
mmWave Not So Good for Large Cells
Potentially Good for Femto & Pico Cells

55. Meeting 5G Goals
Increased Spectral Efficiency (bps per Hz) Massive MIMO
Including 3D Beamforming
Cloud Based Control?
Backhaul
Fiber Deployments Continue
Wireless Point-to-Point Speeds Improving
mmWave more feasible for static outdoor links
Localized Caching of High BW Video
source: Andrews, J;, et al, "What Will 5G Be?", IEEE Journal on Selected Areas in Communications, June 2014

56. IEEE Comparison
Source: "IEEE ac: From Channelization to Multi-User MIMO",
IEEE Communications Magazine, October 2013

57. Sales