ECEN5553 Telecom Systems Dr. George Scheets Week #8 Readings: [18a] "Trading at the Speed of Light" [18b] "Is The U.S. Stock Market Rigged?" Optional: "Flash Boys" [16] "Voice over the Internet: A Tutorial" Outline 7 October 2015, Lecture 22 (Live) No later than 14 October (Remote DL) No Class Friday (Fall Break)

Outlines Received due 7 October (local) 14 October (remote) 44 %

Packet Switch StatMux Trunking Pure Internet (or Ethernet) Model Router Fixed Rate Traffic Bursty Data Traffic Assumptions: All Fixed Rate Traffic is packetized. All traffic is Statistically Multiplexed onto the trunk BW. SONET & OTN (Ethernet)

Internet Service Provider Backbone Router Trunks Leased Line Packet Aware StatMux, Packet Switched Network, Full Duplex Trunks. Access lines mostly attach to routers.

ATM Trunking (In Nineties, claimed as Tomorrow's Network Model) ATM Switch Fixed Rate Traffic Bursty Data Traffic Assumptions: Fixed Rate Traffic gets CBR Virtual Circuits. CBR traffic gets near-TDM like service. Data Traffic is StatMuxed onto the remaining trunk BW. SONET OC-N

ATM Backbone ATM Switch Trunks Leased Line Cell Aware StatMux/TDM, Cell Switched Network, Full Duplex Trunks. Access lines mostly attach to ATM switches, and "ATM capable" routers, FR switches, TD Muxes, & cross connects.

Circuit Switch TDM Trunking (Eighties 'Private Line' Network Model) TDM Switch Fixed Rate Traffic Bursty Data Traffic Assumptions: All Traffic receives trunk bandwidth based on peak input rates. No aggregation. Data traffic consists of many slower speed, relatively lightly loaded circuits. Fiber, Cable, & Microwave

Carrier Leased Line Backbone Cross-Connect Trunks Leased Line Byte Aware TDM, Circuit Switched Network, Full Duplex Trunks. Access lines mostly attach to routers, FR & ATM switches, TD Muxes, & cross connects of other carriers.

Hybrid TDM Trunking (Network Model for older Carriers) TDM Switch Fixed Rate Bursty Data Packet Switch Assumptions: Bursty Data Traffic is all StatMuxed onto a common fabric (such as Frame Relay). Aggregate streams are TDM cross connected onto SONET. Trunk BW assigned based on peak rates. SONET

Hybrid Network Cross-Connect Trunks Leased Line Byte Aware Fixed Rate Traffic: CSTDM bandwidth based on Peak Rates Bursty Traffic: Access lines aggregated onto higher load trunk. Packet Switch StatMux Trunks are CSTDM.

Voice Quality vs. Bit Rate Bit Rate (Kbps) Quality G.728 G.711 G G.729 G.723.1

Switched Network Carrying Capacities High Speed Trunk Carrying Capacity Circuit Switch TDM Packet Switch StatMux Cell Switch StatMux Hybrid 0% Bursty 100% Bursty 100% Fixed Rate 0% Fixed Rate Offered Traffic Mix

Switched Network Carrying Capacities Hybrid Network Carrying Capacity Circuit Switch TDM Hybrid all bursty data traffic groomed onto packet network 0% Bursty 100% Bursty 100% Fixed Rate 0% Fixed Rate Offered Traffic Mix

Switched Network Carrying Capacities Hybrid Network Carrying Capacity Hybrid no data traffic groomed onto packet network 0% Bursty 100% Bursty 100% Fixed Rate 0% Fixed Rate Offered Traffic Mix

Switched Network Carrying Capacities Hybrid Network Carrying Capacity real world network 0% Bursty 100% Bursty 100% Fixed Rate 0% Fixed Rate Offered Traffic Mix

Switched Network Carrying Capacities Convergence Carrying Capacity Circuit Switch TDM Packet Switch StatMux Cell Switch StatMux 0% Bursty 100% Bursty 100% Fixed Rate 0% Fixed Rate Offered Traffic Mix

70’s & 80’s Fixed Rate Voice Dominates Voice Data time 70’s & 80’s

Switched Network Carrying Capacities Convergence Carrying Capacity Circuit Switch TDM 0% Bursty 100% Bursty 100% Fixed Rate 0% Fixed Rate Offered Traffic Mix

Turn of the Century A Mixed Traffic Environment Voice Data time 2000

Switched Network Carrying Capacities Convergence Carrying Capacity Cell Switch StatMux 0% Bursty 100% Bursty 100% Fixed Rate 0% Fixed Rate Offered Traffic Mix

By 2005, Data Dominated Voice Data time 2005

Switched Network Carrying Capacities Convergence Carrying Capacity Packet Switch StatMux 0% Bursty 100% Bursty 100% Fixed Rate 0% Fixed Rate Offered Traffic Mix

What's the impact of Video? nVnVnVnVideo #1 since 2010, is a packet switched statmux network best? uYuYuYuYes. Most video coders are variable rate. nTnTnTnTwo changes to make the network more video friendly… uMuMuMuMight be a good idea to increase Ethernet's maximum packet size. uAuAuAuAll packets with bit errors shouldn't be dropped FVFVFVFVoice/Video dropped packet = lower quality FBFBFBFBetter quality possible if payload delivered

Carrying Capacity...  Got bursty data traffic to move? A packet switched system using statistical multiplexing will allow you to service the most users given a fixed chunk of bandwidth.  Got fixed rate traffic to move? A circuit switched system will allow you to service the most customers given a fixed chunk of bandwidth.

WAN Trends  60's - Fixed Rate Voice Dominates  Voice Network moving data on the side  Mid to Late 90's – Mixed Traffic Environment  New Carriers – ATM  Older Carriers – Hybrid  Early 00's - Mostly Bursty Traffic  Data Networks moving voice on the side  10's - Mostly Video  Data Networks moving video Data & voice on the side

Example) Coding a Microphone Output time (sec) m(t) volts (air pressure) Energy from about ,500 Hz.

A/D Convertor time (sec) m(t) volts (air pressure) Step #1) Sample the waveform at rate > 2*Max Frequency. Telephone voice is sampled at 8,000 samples/second. 1/8000 second

A/D Convertor n Legacy Wired Telephone System uses PCM n Pulse Code Modulation One of N possible equal length Code Words is assigned to each Voltage N Typically a Power of 2 Log 2 N bits per code word u Wired Phone System: N = 256 & 8 bits/word u Compact Disk: N = 65,536 & 16 bits/word

A/D Convertor. 1 bit/sample. time (sec) Example) N = 2. Assign 0 or 1 to voltage. 0 < Voltage < +5v, Assign Logic 1 -5v < Voltage < 0, Assign Logic v, output a 1 t1 Bit Stream Out =

A/D Convertor. 1 bit/sample. Example) N = 2. Assign 0 or 1 to voltage. Far side gets (13 samples) Needs to output 13 voltages. What does a 1 represent? A 0? Receive a 1? Output +2.5 v (mid-range) Receive a 0? Output -2.5 v (mid-range) Hold the voltage until next sample 0 < Voltage < +5v, Assign Logic 1 -5v < Voltage < 0, Assign Logic 0

A/D Convertor. 1 bit/sample. Input to the transmitter. Output at the receiver. Considerable Round-Off error exists v -2.5 v

time (sec) Example) N = 4. Assign 00, 01, 10 or < Voltage < 5, Assign 11 0 < Voltage < 2.5, Assign < Voltage < 0, Assign < Voltage < -2.5, Assign v, Assign 11 t1 Bit Stream Out = v -2.5 v A/D Convertor. 2 bits/sample

A/D Convertor. 2 bits/sample. Input to the transmitter. Output at the receiver. Receive 11? Output 3.75v Receive 10? Output 1.25v Receive 00? Output -1.25v Receive 01? Output -3.75v Reduced Round-Off error exists v v v v

Circuit Switched Voice (POTS)  Bandwidth ≈ 3,500 Hertz  A/D Converter  samples voice 8,000 times/second  rounds off voice to one of 256 voltage levels  transmits 8 bits per sample to far side  D/A Converter  receives 8 bit code word  outputs one of 256 voltage levels for 1/8000th second  64,000 bps (1 byte, 8000 times/second)

Compact Disk  Bandwidth ≈ 20,000 Hertz  A/D Converter  samples voice 44,100 times/second  rounds off voice to one of 65,536 voltage levels  transmits 16 bits per sample to far side  D/A Converter  receives 16 bit code word  outputs one of 65,536 voltage levels for 1/44100th second  705,600 bps

Sampling & Quantizing Examples  fs = 16 KHz  4096 quantiles  256 quantiles (approximate phone quality)  32 quantiles  4 quantiles (generally 2 levels used!)  4096 quantiles  fs = 16 KHz  fs = 8 KHz (some interference)  fs = 2 KHz  fs = 1 KHz

1/8th Second of Voice

Sources of POTS delay Local Loop PCM Coder TDM Trunk POTS TSI POTS TSI Intermediate Digital Voice Switches... TDM TrunkLocal Loop PCM Coder Trunk resources are dedicated to each voice call via TDM. Source CO Destination CO

Sources of VoIP delay Voice Coder Packet Switch Packet Switch Intermediate Packet Switches... StatMux Trunks Voice Decoder Trunk resources are randomly assigned to each voice call via Statistical Multiplexing. Packet Assembler Transmission Buffer Receiver Buffer

Voice (Video) on LAN (WAN)  More complex system than circuit switched voice  Packet Assembler  Transmitter Buffer  Receiver Buffer  End-to-End Delays > Circuit Switch TDM  Delay Variability > Circuit Switch TDM