1. Electrical Communications Systems ECE.09.331 Spring 2008
Lecture 1a January 22, 2008
Shreekanth Mandayam
ECE Department
Rowan University

2. Plan Why are we studying ECOMMS? What is a communications system?
Technology successes, Trends and Decisions
What is a communications system?
Objectives
Block diagram
What limits our ability to communicate?
Fundamental limits - Shannon’s Theorem
Wireless communications evolution
What are we studying in this course?
Course logistics
ECOMMS Readiness QUIZ, next Monday!

3. Communications: Where are we?
4GW?
(what the consumer sees……………………………)

5. NASA – Imminent Communications Needs
The needs that ISHM helps satisfy:
Reliability & Safety
Lockheed-Martin to build Orion
Lunar Habitat

6. Decisions, decisions…..
I live in the Philadelphia metro area. What cell-phone carrier should I choose? What if travel to Europe every few weeks? Or Japan?
Verizon, AT&T, T-Mobile, ……?
I’m designing the next generation microprocessor. It’s going to be connected to Internet2. How do I design the right size the memory buffer?
I’m designing the communications protocols for the manned exploration of Mars. What’s the right bandwidth/data rate for control signal transmission?

7. What is a communications system?
Communications Systems: Systems designed to transmit and receive information
Info
Source
Sink
Comm
System

8. Block Diagram m(t) message from source n(t) noise Transmitter Tx s(t)
Info
Source
n(t)
noise
Transmitter Tx
s(t)
transmitted
signal
Receiver Rx
received
message to
sink
Channel
r(t)
received
signal
Info
Sink

9. What limits our ability to communicate?
NOISE!!!!!
Noise: an unwanted, random fluctuation in the signal
Without the effects of noise, a message with infinitesimally small power could be transmitted over infinitely large distances
ALL advances in communications technology are advances to combat the effects of noise

10. Fundamental Limit: Shannon’s Theorem (1948,1949)
Theoretical limit for error-free transmission in a communications system in the presence of noise
Source Data Rate: R [bits/sec]
Channel Capacity:
C = B log2(1 + S/N) [bits/sec]
R < C: No Error!!!

11. Mars Orbiter
(Odyssey/Mars Global Surveyer)
12k – 3.5k bps
DSN Antenna
(on Earth)
X-Band
128 kbps
Mars Rover
(Spirit/Opportunity)

12. Wireless Comm Evolution: UMTS (3G)

13. Evolution 1-G 2-G 3-G TECHNOLOGY FEATURES Late 1970’s, early 1980’s
AMPS Advanced Mobile Phone Service
-Analog voice service
- No data service
2-G
1990’s
CDMA Code Division Multiple Access
TDMA Time Division Multiple Access
GSM Global System for Mobile Communications
PDC Personal digital cellular
Digital voice service
- 9.6K to 14.4K bit/sec.
- CDMA, TDMA and PDC offer one-way data transmissions only
- Enhanced calling features like caller ID
- No always-on data connection
3-G
2000 and beyond
W-CDMA Wide-band Code Division Multiple Access
CDMA-2000 Based on the Interim Standard-95 CDMA standard
TD-SCDMA Time-division synchronous CDMA
- Superior voice quality
- Up to 2M bit/sec. always-on data
- Broadband data services like video and multimedia
- Enhanced roaming
Evolution

14. And there’s more….
Joseph M. Nowack,

15. ECOMMS: What are we studying?
Electrical Communications Systems
Measures of information and noise
Capacities for information transmission
Design of communications systems
Measures of performance
Communications circuits
Communications protocols
Hardware
INdependent
dependent

16. ECOMMS: Topics Receiver Rx Transmitter Tx s(t) Channel r(t) m(t) Noise
Wire/wireless
Antennas/
Coupling
Antennas/
Coupling
Demodulation circuits and systems
DSP
Modulation circuits and systems
DSP
Analog/digital
Protocols
Fundamental limits

17. ECOMMS: Details

18. ECOMMS: Course Logistics

19. ECOMMS Readiness Quiz NEXT MONDAY, Jan 28, 12:40 PM Room 204/206
CLOSED Book and Notes
Topics:
Complex algebra, Phasors, Fourier Series, AC Circuits
BRING YOUR CALCULATOR!

20. Summary