ECEN5553 Telecom Systems Dr. George Scheets Week #13 [30a] "The Bring Your Own Device Delima" [30b] "Is It Still Possible to do Phone Phreaking? Yes, with Android on LTE" [31a] "Next Generation WiFi: As Fast as We'll Need?" [31b] "What to Expect from 11ac’s Next Big Deal: Multiuser MIMO" [32a] "Is it Safe to Use Public Wi-Fi Networks?" [32b] "Worries Mount over Upcoming LTE-U Deployments Hurting Wi-Fi" [32c] "How to Configure Wi-Fi Channels for Top Network Performance" Term Paper (Late Fee = -1 point per working day) 81, B > 70, C > 61, D > 52

Final Exam n Comprehensive, 1 hour & 50 minutes n Work 5 of 7 pages n pages will be from the Fall '14 final n 85-90% Notes 10-15% Readings n Use the space provided! # Facts should be > number of points etc. Start Reviewing Now!

Syllabus Grade Break Points n A > 410 points (90%) n B > 364 points (80%) n C > 319 points (70%) n D > 273 points (60%) n > 410 points? Guaranteed an A n > 364 but 364 but < 410? Guaranteed a B, etc. n Otherwise, at mercy of Court

Fall 2014 Break Points n A > 391 points (86%) n B > 346 points (76%) n C > 300 points (66%) n D > 255 points (56%) n Fall 2015 points likely not the same. u Probably in same vicinity u Won't know for sure until everything's graded

Techniques to Improve BER n Use FEC n Increase Received Signal Power u Increase transmitter power out u Use directional antennas n Change Modulation Technique u Go to lower "M" in M-ary n Build a Quieter Receiver n Slow Down Transmitted Bit Rate

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

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

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

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

Cellular Telephony - Operation Wired to Mobile call n Signaling info shipped to home MTSO n Home MTSO checks database u Mobile in home area? Mobile is paged u 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 n End-to-End Voice channel is set up u BS & MTSO coordinate Backhaul u MTSO & CO coordinate Long Haul

Cellular Telephony - Operation n 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

Wireless MAN Data source: Telecommunications by Warren Hioki, 1st Edition To World

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

1G AMPS FDMA frequency time Different channels use some of the frequency all of the time Cell 1 Cell 2 AMPS

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

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

2G GSM frequency time Combo of TDM & FDM etc Cell 1 Cell 2

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

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

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

time Despreading Signal 27 Kcps Received Signal 27 Kcps time Recovered Traffic 9 Kbps DSSS-Receiver

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

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

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

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

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

Multiplexing Schemes n Frequency Division Mutiplexing n Time Division Multiplexing n Statistical Multiplexing n Code Division Multiplexing

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

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

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

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

FDM FDMA frequency time Different channels use some of the frequency all of the time. 1324

Orthogonal FDM frequency time 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 Channel 1

FDM with Multi-path XMTR RCVR direct path bounce path direct path pulses bounce path pulses Signal sum seen by Receiver T2T3 Symbol decision intervals at Receiver. The third bit is obliterated by multi-path. T3 time delay T1

OFDM with Multi-path direct T3 bounce direct bounce direct bounce T2T1 Matched filter detector will work OK. delay Slower symbol rate over each subchannel.

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

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

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

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

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

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

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

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

5G Cellular n IP Wireless Traffic u 3 Exabytes in 2010 (exabyte = ) u Projected to exceed 500 exabytes by 2020 u 4G Cannot Handle n Goals u Aggregate Data Rate (bps/unit area) 4G x 1000 u Edge Rate (Worst Case speed seen by 5%) 1 Mbps → 100 Mbps u Average Round Trip Time: Reduce by x 15 u 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

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

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

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

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

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WiFi Speed vs. Distance source: 13 May 2002 Network World

Flow Chart (Simplified) Packet to Send? ACK received? No Yes No Yes No Binary Exponential Back-off Used (Similar to 802.3) Min Wait: 0 Max Wait: 51.2 msec Back-off Media Quiet? Yes Transmit No Quiet for IFS? Yes No