Wireless Communication Technologies and Frequency Spectrum

Wireless Communication Signals

Wireless systems utilize infrared signals and radio frequency (RF) electromagnetic waves to transmit data.

Key Features of Wireless Media

• Does not require physical media for transmission.
• Propagates at the speed of light.
• Propagation characteristics vary based on frequency:
  • Surface propagation (GW)
  • Spatial propagation (SW)
  • Visual (Line-of-sight) propagation: Sensitive to natural obstacles.

The Electromagnetic Spectrum

The electromagnetic spectrum encompasses the range of all electromagnetic wave frequencies. Radio frequencies (RF) used in communication typically range from 3 Hz to 300 GHz.

Core Definitions

• Size: The maximum physical extent of a signal.
• Frequency: The rate at which a wave changes over time.
• Length: The physical length of a single period in time.

Wireless Propagation and Frequency Bands

Technologies operating above 30 MHz often require a clear line-of-sight between points.

• VHF (Very High Frequency): 30–300 MHz
• UHF (Ultra High Frequency): 300–3000 MHz
• SHF (Super High Frequency): 3–30 GHz
• EHF (Extra High Frequency): 30–300 GHz

Network Coverage Classifications

• PAN (Personal Area Network): Coverage typically under 100m.
• LAN (Local Area Network): Coverage not exceeding a few kilometers.
• MAN (Metropolitan Area Network): Coverage up to 100 km.
• WAN (Wide Area Network): Unlimited coverage (e.g., the Internet).

Wireless Network Standards and Data Rates

Mobile vs. Fixed Wireless Networks:

• W-PAN (Bluetooth): IEEE 802.15.1, 802.15.2, 802.15.3, 802.15.3a. Data rates: 1 Mbps (v1.2), 3 Mbps (v2.0).
• W-LAN (Wi-Fi): IEEE 802.11a, 802.11b, 802.11g, 802.11n. Data rates: 11 Mbps (802.11b), 54 Mbps (802.11g), up to 540 Mbps (802.11n).
• W-MAN (WiMAX): IEEE 802.16, 802.16a, 802.16c, 802.16d, 802.16e. Data rates: Up to 70 Mbps.
• W-WAN (3G/3.5G): UMTS, 3GPP, IMT-2000. Data rates: 3 Mbps (3G), up to 14 Mbps (HSDPA 3.5G).

Network Topologies and Applications

• Wi-Fi: Star topology; used for Internet, telephony, and file transfer.
• Bluetooth: Point-to-Point topology; used for file transfer.
• WiMAX: Star topology.
• 3G: Star and Tree topology; used for SMS, MMS, WAP, Internet, and digital television.

Regulatory Bands

• Licensed Bands: Regulated by national authorities (e.g., Subtel).
• Unlicensed Bands: Regulated by international bodies (e.g., ITU).