History of Data Communication 1940-1989

History of Data Communication

• 1940: George Stibitz pioneered networking technology by sending computing commands over a teletype machine.
• 1943: Teletype technology enabled the transmission of punched cards at 25 bits per second.
• 1948: Teletype modems facilitated image transmission across the US.
• 1958: American Telephone and Telegraph (AT&T) improved computer modem speeds to 110 bits per second.
• 1962: AT&T introduced the Bell 103 Data Phone, allowing digital data transmission on regular phone lines. J.C.R. Licklider led the development of the ARPANET.
• 1965: Thomas Marill and Lawrence Roberts created the first wide-area computer network, a precursor to the ARPANET.
• 1977: Dennis Hayes and Dale Heatherington designed the Hayes 80-130A modem.
• 1981: The Hayes Smartmodem improved modem speed and functions, becoming affordable.
• Mid 80s: IBM PC clones, and the rise of PCI modem cards expanded network capabilities.
• 1989: Tim Berners-Lee facilitated advances in web browsing interface and online content.
• Mid 90s: Modem costs decreased, and speeds increased drastically.

Home Broadband and Communication

• 1996: Brent Townshend developed the 56K modem technology.
• Early 2000s: Analog phone lines (ISDN), ADSL, and Cable TV modems were alternatives to analog systems.
• 2002: The launch of 3G enabled widespread application services, including mobile internet.
• Mid 2000s: Wireless access became widely available and less expensive.
• 2009: 4G/LTE cellular standards provided high-speed data transmission.
• 2011-2014: High-speed fiber optic communication gained popularity.
• 2015: Network function virtualization enhanced modem functions through software.
• 2017 and Beyond: AI triggered communications and 5G advancements are shaping technology.

Digital Communication - Analog to Digital

• Signals in everyday life are usually analog in nature.
• Digital signals utilize 1s and 0s (high and low values) for transmission.
• Losses in analog signals (such as distortion, interference) are minimized in digital transmissions
• Digital signals are more reliable, manageable and easier to design and process compared to analog signals.
• Digital devices utilize common encoding techniques that make them compatible for many purposes
• Digital signals use less bandwidth
• Digital signals are easier to encode and decode when distances are long.

Advantages of Digital Communication

• Reduced effect of distortion, noise and interference
• More reliable digital circuits
• Easier to design and cheaper digital circuits
• More flexible hardware
• Reduced cross talk

Elements of Digital Communication

• Source: The original information source (e.g., sound).
• Input Transducer: Converts physical input to electrical signal (e.g., microphone).
• Source Encoder: Compresses data, removing redundant bits.
• Channel Encoder: Adds redundant bits for error correction during transmission.
• Digital Modulator: Converts the digital signal to an analog signal for transmission over a channel.
• Channel: Physical medium for transmission.
• Digital Demodulator: Converts the analog signal back to a digital format.
• Channel Decoder: Removes redundant bits added by the encoder.
• Source Decoder: Reconstructs the original data from the coded form.
• Output Transducer: Converts electrical signal to physical output (e.g., speaker).
• Output Signal: Final reproduced signal.

Modulation Techniques

• Pulse Code Modulation (PCM): Converts analog signals into binary sequences (pulses) -The process of varying one or more parameters to make a carrier signal
• Amplitude Shift Keying (ASK): Changes carrier wave amplitude to represent binary data.
• Frequency Shift Keying (FSK): Changes carrier wave frequency to represent binary data.
• Phase Shift Keying (PSK): Changes carrier wave phase to represent binary data.
• M-ary Encoding: Transmits multiple bits simultaneously by using various modulation schemes (e.g., M-ASK, M-FSK, M-PSK)

Types of Transmission Media

• Guided Media (Wired): Signals travel along a physical path.
  • Twisted Pair Cable: Inexpensive, easy to install, but susceptible to interference and limited distance.
  • Coaxial Cable: Higher bandwidth, less susceptible to interference than twisted pair but more expensive and bulky.
  • Optical Fiber Cable: Very high bandwidth, immune to interference and electromagnetic noise, but expensive and difficult to install and maintain
• Unguided Media (Wireless): Signals travel through the air.
  • Radio Waves: Omni-directional, used for long-distance communication, susceptible to interference, high attenuation.
  • Microwaves: Uni-directional, high bandwidth; used in mobile phone communication, television, and radar systems.
  • Infrared Waves: Short-range, unidirectional, used for remote controls and short-range wireless communications.
  • Stripline / Microstripline:Used in circuits and applications requiring high frequencies, like microwave circuits and antennas.

Transmission Impairment

• Attenuation: Loss of signal strength over distance.
• Distortion: Signal shape changes during transmission/mismatch to the desired bandwidth
• Noise: Random unwanted signals added to the original signal during transmission.