The Telecommunications TIG
Prof. Mary Ann IngramMarch 30, 2004
Overview
Define Digital Telecomunication Networks
Curriculum Research Examples Conclusion
Analog vs. Digital
Information, such as voice, can be converted into a continuously varying analog voltage, using a microphone for example, and be transmitted
How telephones and cell phones used to operate
Alternatively, the analog information can be quantized, and transmitted using digital modulation
Digital Communications At any particular time, only one of
a few waveform choices are transmitted
A noisy version of the waveform is received
The receiver compares the noisy waveform to the clean ones it has stored and decides on the clean one that has the closest match
The Advantage of Digital
In a well-designed system, the receiver usually makes the right choice The noise is eliminated!
Observed
Stored
A Pervasive Technology
Cellular Telephone Satellite Broadcasting Digital Subscriber Line Cable Wireless Local Area Networks Internet CDs and DVDs
At Georgia Tech…
We focus on digital communications in the Telecommunications Technical Interest Group (TIG)
Communication Networks
Networks are organized into standardized layers, to allow for interoperability
7-Layer OSI (International Organ-ization for Standardization) Model
Layer Responsibilities
1. Physical Basic hardware components for networks. i.e. RS-232 specification
2. Data Link Frame format, Transmitting frames over the net. i.e. bit/byte stuffing, checksum
3. Network Address assignment, Packet's forwarding methods
4. Transport Transfer correctness
5. Session Establishing a communication session, Security, Authentication i.e. passwords
6. Presentation Computers represent data in different ways (char, integer) thus the protocol need to translate the data to and from the local node.
7. Application Specifications for applications using the network, how to send a request, how to specify a filename over the net, how to respond to a request etc..
Packets Each layer contains packets The payload on one layer is the payload
& header from the previous layer
Header Payload
Header Payload layer i
layer i+1
Protocols
A protocol is a set of rules for operation at a given layer
Generally, a protocol operates only on the header and is indifferent to the payload
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Overview
Define Digital Telecomunication Networks
Curriculum Research Examples Conclusion
UG Elective Courses PHY
ECE 4601, Communications Systems ECE 4602, Communications Systems Lab
NET ECE 4604, Networking Design and Simulation ECE 4894 Advanced Internetworking ECE 4823 Wireless Communications ECE 4823 Intro to Wireless and Mobile
Networking
Telecom Grad Courses -PHY
ECE 6601 - Random Processes ECE 6602 - Digital Communications ECE 6603 - Advanced Digital Communications ECE 6604 - Personal and Mobile
Communications ECE 6605 - Information Theory ECE 6606 - Coding Theory and Applications Hybrid Fiber-Coax Communication Systems Space-Time Processing for Communication
ECE 6607 - Computer Communication Networks ECE 6608 - Performance Analysis of Comm
Networks ECE 6609 - ATM Networks ECE 6610 - Wireless Networks ECE 7611 - Advanced Communication Theory Computer Network Security Multimedia Communication Cryptography: Theory and Practice
Telecom Grad Courses -NET
Overview
Define Digital Telecomunication Networks
Curriculum Research Examples Conclusion
Research Examples
CD and DVD optical recording Ground stations for low earth orbit
(LEO) satellites High-speed wireless prototype
Apr 9, 2023 18
Binary and Nonbinary optical recording
• Increased storage capacity of CD and DVD- from theory to commercialization
• Binary and M-ary in optical recording• Much of the technology developed in Prof. McLaughlin’s group
Signal fromBinary CD, DVD
M-ary CD, DVD
CD and DVD:Information encoded in transitions Our system:
Information encoded in amplitude
Status
• Our ASIC integrated on CD and DVD platforms 3x increase on CD (R, RW) 2x increase on DVD for (R, RW, ROM) 2x increase on Blu-ray for R, RW Recently announced results from dual layer ML DVD-16 GB feasibility in ROM
Chip available through Sanyo
Technology gaining acceptance in optical data storage community
Sony, Pioneer, Ricoh, Panasonic, Mitsubishi, Philips, Yamaha, TDK and others have efforts ML Alliance
Satellite Communications with Adaptive and Phased Array Antennas
11m Dish – System costs $ 2- 4 million
Single satellites Satellite tracking
cumbersome (mechanical)
Avoidance of other signals good (thin main lobe)
Located near poles Staff of 8
Single-Line of Site (LOS)-path signal
Problem with Current Ground Stations for LEOs
Adaptive Array Ground Station
01001110010101011000110101
AdaptiveProcessor
Smaller phased array elements low on cost curve
Located anywhere No staff Electronically
steered
1. Prior to the pass: antenna with cement blocks to prevent it from blowing over. Atlanta skyline in the background. The antenna had a significant vertical wobble (ground plane) due to wind. 2. Students observing EO-1 signal spectrum.
3. Prior to pass, checking spectra of know interference.
System noise floor
Analyzer noise floor
Sirius and XM Radio interference, 1,000,000 times stronger than EO-1 signal.
In test 1, 11-19-03: EO-1 spectrum detected on analyzer
In test 2, 11-25-03:
EO-1 signal digitized, fast fourier transform performed and EO-1 spectrum observed on computer screen.
4. Detected EO-1 spectrum during pass
Georgia Tech:Successful Smart Antenna Tests at Georgia Tech 11-19-03 and 11-25-03
Yamacraw Wireless System Prototype
State and Industry-funded project to build a “gigabit per second” wireless link for wireless LAN applications
Based on MIMO and OFDM
Trans. TM
1
Rec.RM
1
Multiple-input-multiple-output (MIMO)
Orthogonal Frequency Division Multiplexing (OFDM)
f
Yamacraw Network Testbed
End Host
MAC Capture PC
Software radio cage
Software radio cage
Local Client PC
TransportProtocol
Wirelesschannels
Ethernet Ethernet
array array
MAC Capture PC
End Host
TransportProtocol
FPDP FPDP
Physical Layer Architecture 4x4 Open-Loop MIMO 64 QAM over 20 MHz Each pair of MIMO channels gets 8-to-2
selection diversity
OFDMDemod
SinkSpace-Frequency
filter
P-to-S
4N*code rateForward
ErrorCorrection
4N
8-to-2Switch
N
N
N
N Receiver
FPGA
RF-to-IF
RF-to-IF
RF-to-IF
RF-to-IF
OFDMDemod
OFDMDemod
OFDMDemod
Matrix Inversion on FPGA (in progress)
8-to-2Switch
Fourantennas activated
micro-controller
micro-controller
PEAK DATA RATES
CURRENT OFFLINE PROCESSING:
25 MHz*(200/256) subcarriers * 6 bits/symbol * 4 channels = 468 Mb/s
GOAL AT END OF PROJECT (Upper Limit)50 MHz*(200/256) subcarriers * 6 bits/symbol
* 4 channels = 937 Mb/s*Actual real-time implementation speed will depend on
processing and hardware limitations
MIMO OFDM Wireless Tests
Waveform:
25 Ms/s (Goal is 40 –50 Ms/s), 4x4 MIMO, 64-QAM
Channel Estimates (1 x 4)
OFDM Waveform
Constellation
8-to-2 Switch and Microcontroller Selection diversity maximizes average
SNR over band for each MIMO channel
Two 8-element antenna arrays shown with diversity switch boards
4x4 MIMO With Selection Diversity
MIMO Signal Sources and 4-port Transmit Antenna
Subcarrier Allocation MAC Protocol
Physical layer Physical layer
Transmit packets accordingto the resource allocation results
Receive packets accordingto the resource allocation results
Construct resourcemapping table
Receivedpackets
Optimum subcarrierbit-allocation
Dynamic resourceallocation
Admissioncontrol
time slots
bits persubcarrier
power
Newpackets
Packets to beretransmitted
Transmission request
Admissionrequest
Need ARQ ?
Yes
No
Piggyback
Piggybackedtransmissionrequest
Transmissionrequest
What request ?
Admissionrequest
in frame mapping subframe
in downlink controlsubframe
in uplinkcontrolsubframe
in subframesfor services
time slots
bits persubcarrier
powerallocated resources
allocated resources
Mobile Terminal Side Base Station Side
State for guaranteedand controlled-loadservices
State for all services
TCP-G
MACCACConnection request (bandwidth, conn_id)
Transmit (data)
Connection admitted(fid)
Connection tear-down request(fid)
Connection tear-down complete(fid)
Connection request (fid, bandwidth)
PCAP
ETH MAC
PHY1 PHY2
APPLIC PC SRT SRT
APPLIC
GTCP
PHY1
RAW SOCKETS
ETHERNET
PCAP
MAC ETH
PHY2 PHY1
APPLIC
GTCP
PHY1
RAW SOCKETS
ETHERNET
APPLIC PC
Connection tear-down request(conn_id)
SRT: Software Radio Test-bed
Reliable Transport Protocal with Guaranteed Services
GTCP has been implemented in user level both on Linux and Windows platforms
GTCP interaction with MAC defined using a set of interfaces, shown:=>
GTCP-software radio integration plan:=>
Overview
Define Digital Telecomunication Networks
Curriculum Research Examples Conclusion
Conclusions
Telecommunication technology is everywhere in our lives
Many courses on UG and GRAD levels
Active and exciting research area