Communication Systems I. How can information flow from point A to point B?

Communication Systems I

How can information flow frompoint A to point B?

Morse Code

Can you spell your name?

See http://morsecode.scphillips.com/jtranslator.html for a live demo

Semaphores

http://www.globalsecurity.org

Semaphore as a Signaling Tool

Semaphore as a Communication Tool

http://www.wikipedia.org

R O G E R

Nuclear Disarmament http://www.viewimages.com

Semaphore in Pop Culture

Fountain of Bits

Analog Signal Encoding

Modem Maximum Data Rate

Modem

56Kbps

ADSL Maximum Rate?

ADSL

Why is ADSL much faster?

256 Channels of 4 kHz each

How fast is ADSL?

ADSL = 256 x 4 kHz x 8 bits= 8 Mbps

ADSL2 = 12 Mbps

ADSL2+ = 25 Mbps

*ADSL2+ expands channel frequency from 1.1 to 2.2 MHz

Serial vs Parallel Transmission

Image © Quatec

Example of Serial Comm?

Example of Parallel Comm?

Which Mode is More Common?

Cost. Less cables. Smaller size. Simplicity. Keeping bits aligned in a high-

speed parallel line requires more complex electronics.

Serial

Why?

The Need for Speed

USB 1.0 (12 Mbps) USB 2.0 (480 Mbps) USB 3.0 (4.8 Gbps) Firewire 400 (400 Mbps) Firewire 800 (800 Mbps) SATA (1.5/3.0 Gbps) RS-232 (115.2 Kbps)

Synchronous vs Asynchronous

A B

A B

Synchronous uses a clock line

Asynchronous relies on a common clock on each side

RS-232 (Serial Communication) Baud Rate

Data bits

Start bit / Stop bits

Parity

RS-232 Pulses

Letter “V” ASCII = 86 (0101 01102)9600 bps, 8-N-1

Layout: Start Bit, Data Bits, Parity, Stop Bits

* Note: Rs-232 logic pulses are inverted

RS-232 Pulses

Letter “Y” ASCII = 89 (0101 10012)9600 bps, 8-Odd-1

Layout: Start Bit, Data Bits, Parity, Stop Bits

* Note: Rs-232 logic pulses are inverted

How about ASCII 0?

Layout: Start Bit, Data Bits, Parity, Stop Bits

The data transmission is unbalanced. Can cause transmission errors.

9600 bps, 8-N-1

Manchester Encoding (IEEE 802.3)

Bit 1 = Low to High

Bit 0 = High to Low

Example

Image: Wikipedia

Data = 0

Manchester Code

Encode the following transmissions using the Manchester standard

Letter “V” ASCII = 86 (0101 01102)

Letter “Y” ASCII = 89 (0101 10012)