Frequency, Bandwidth, and Throughput

Frequency, Bandwidth, and Throughput

Frequency

• Measured in MHz (megahertz) or GHz (gigahertz).
• Represents how often an electrical signal changes state per second.
• Wired signals use a broad range of frequencies, while wireless signals must be contained within specific ranges to prevent interference.
• Higher frequency results in faster potential data transfer.

Bandwidth

• Measured in Mbps (megabits per second) or Gbps (gigabits per second).
• Represents the maximum theoretical amount of data that can be transmitted per second.
• Bandwidth, in an analogy, is like the number of lanes on a highway, more lanes allow more cars (data) to pass at once.
• Can refer to frequency range (MHz/GHz) or data transfer capacity (Mbps/Gbps).

Throughput

• Also measured in Mbps or Gbps.
• Represents the actual amount of data received per second, taking into account real-world factors like network congestion, signal interference, and data errors.
• Throughput is lower than bandwidth due to overhead and inefficiencies (e.g., network delays, noise, and packet loss).
• Throughput, in the highway analogy, is the number of cars that actually reach their destination.

Key Distinctions & Misconceptions

• Bandwidth ≠ Throughput: Bandwidth is the maximum capacity, but throughput is the real-world performance.
• Frequency does not equal bandwidth, but a higher frequency often supports higher bandwidth.
• Technological advancements (modulation & encoding) allow for more data transmission without increasing frequency or bandwidth.
• Marketing terms can be misleading where ISPs often advertise “up to” speeds that don't reflect actual throughput.

Conversions & Units

• 1 bps (bit per second) is the smallest unit of data transfer and a basic speed measurement.
• 1 Kbps (1,000 bits per second) is a Low-speed connection, e.g, 32 Kbps for low-quality audio streaming.
• 1 Mbps (1,000,000 bits per second) is a Medium-speed internet connection, e.g, Netflix HD streaming requires 3+ Mbps.
• 1 Gbps (1,000,000,000 bits per second) is a High-speed internet, suitable for UHD streaming, gaming, and multiple users.

Bits vs. Bytes

• Storage measured in bytes (B). An example is 1 GB movie file.
• Throughput is measured in bits (b). An example is 1 Gbps internet speed.
• 1 Byte = 8 bits – Pay attention to capitalization: MB (megabytes) ≠ Mb (megabits).

Summary of Transmission Flaws

• On a network, actual throughput is always less than the potential bandwidth due to transmission flaws, these consist of; noise, attenuation, and latency.

Noise (Interference)

• Noise degrades or distorts signals, causing signal loss measured in decibels (dB).
• A -3 dB loss means the signal loses half its power.
• EMI (Electromagnetic Interference) is generated by electrical devices (e.g., power lines, microwaves, fluorescent lights, thunderstorms).
• RFI (Radio Frequency Interference) is EMI caused by radio waves from broadcast signals.
• Crosstalk is signal leakage between wires, reducing data accuracy.
  • Alien Crosstalk: Occurs between different cables.
  • NEXT (Near-End Crosstalk): Occurs near the signal source.
  • FEXT (Far-End Crosstalk): Occurs at the far end of the cable.
• Use shielded cables as a solution to noise.
• Proper cable installation and separation also reduces noise.
• Signal amplification reduces noise.

Attenuation (Signal Loss Over Distance)

• As signals travel, they lose strength similar to how a voice fades over distance.
• Use repeaters (devices that regenerate signals), or switches (act as multiport repeaters) as a solution.

Latency (Delay in Transmission)

• Latency is the delay between sending and receiving data.
• Latency is caused by:
  • Cable length
  • Devices in the network (routers add more latency than switches)
  • Signal conversion (wired to wireless)
  • Processing delays (firewalls, DNS resolution)
  • Network congestion and collisions
• Latency is measured as RTT (Round Trip Time) in milliseconds.
• Related Issues:
  • Jitter (Packet Delay Variation - PDV): Packets arrive out of order, affecting real-time applications like video or VoIP.
  • Packet loss: If data packets are delayed too much, they may be discarded, requiring retransmission.
• Solutions:
  • Optimize network device settings (e.g., NIC configurations).
  • Reduce network congestion.
  • Use QoS (Quality of Service) to prioritize traffic.
• By managing noise, attenuation, and latency, network efficiency can be improved, resulting in better throughput and performance.

Simplex Communication

• Signals travel in only one direction (unidirectional).
• An example is broadcast radio, TV signals, or garage door openers.
• Rarely used in modern networking but common in specialized systems.

Half-Duplex

• Signals can travel in both directions but only one at a time.
• An example is Walkie-talkies or intercom systems, where only one person can speak at a time.
• Older Ethernet networks and hubs often use half-duplex, leading to potential collisions.

Full-Duplex (Duplex)

• Signals can travel in both directions simultaneously.
• An example is Phone calls, where both parties can talk at the same time.
• Most modern network devices use full-duplex by default for better efficiency.

NIC Configuration & Duplex Mismatch

• In Windows, NIC (Network Interface Card) settings allow configuring Speed & Duplex.
• Options include:
  • Full-Duplex
  • Half-Duplex
  • Auto-Negotiation (chooses the best available setting).
• Duplex mismatch happens when a device is set to full-duplex, but the connected device only supports half-duplex., resulting in slow or failed transmissions.

Multiplexing vs. Duplexing

• Duplexing allows communication in both directions over a medium.
• Multiplexing increases the amount of data that can be transmitted by dividing a medium into multiple channels (subchannels).
  • Used in modern networking and telecommunications to maximize bandwidth efficiency.
• By properly configuring duplex settings and using multiplexing techniques, network performance can be optimized for faster and more reliable communication.