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Microwave vs low frequency and five system protocols

Short answer

Microwave systems are distributed, use S-parameters, waveguides, and line-of-sight propagation, while low-frequency systems are lumped with Z/Y/h parameters. Five microwave systems: Wi-Fi (2.4/5 GHz, OFDM, CSMA/CA), cellular (GSM/LTE/5G, TDMA/OFDMA), satellite (C/Ku/Ka bands, transponders), terrestrial microwave links (6-38 GHz, QPSK to 4096-QAM), and Bluetooth (2.4 GHz FHSS, GFSK).

Find the unique differences between microwave and conventional low frequency systems. Mention detail specifications/protocols of any five microwave communication system.

Unique differences: microwave vs conventional LF systems

PointConventional LFMicrowave
Circuit sizeMuch smaller than λAbout λ
AnalysisLumped, KVL/KCLDistributed, Maxwell's equations and transmission lines
ParametersZ, Y, hS-parameters
GuidesWires, twisted pairCoax, waveguide, microstrip
DevicesBJT, FET, triodeKlystron, magnetron, TWT, Gunn, HEMT
Skin effect and radiationNegligibleSignificant
PropagationGround wave and sky waveLine of sight
BandwidthSmallVery large

Specifications/protocols of five microwave communication systems

1. Wi-Fi (IEEE 802.11 WLAN)

  • Bands: 2.4 GHz ISM (2.400–2.4835 GHz), 5 GHz (5.15–5.85 GHz), and 6 GHz for Wi-Fi 6E.
  • Channels: 20/40/80/160 MHz wide. At 2.4 GHz there are 13 channels 5 MHz apart, and only 1, 6 and 11 do not overlap.
  • Modulation: OFDM with BPSK up to 1024-QAM (802.11ax). 802.11b used DSSS/CCK.
  • Access: CSMA/CA with optional RTS/CTS. Duplexing is TDD.
  • Rates: 11 Mbps (b), 54 Mbps (a/g), 600 Mbps (n, MIMO), about 9.6 Gbps (ax).
  • Security: WPA2/WPA3 (AES).

2. Cellular mobile (GSM / LTE / 5G NR)

  • GSM: 900/1800 MHz, 200 kHz carriers, GMSK modulation, TDMA with 8 time slots per carrier, FDD (uplink 890–915 MHz, downlink 935–960 MHz).
  • LTE (4G): 700 MHz–2.6 GHz, 1.4–20 MHz bandwidth, OFDMA downlink and SC-FDMA uplink, up to 64-QAM, MIMO, FDD or TDD.
  • 5G NR: FR1 below 6 GHz and FR2 at 24–52 GHz (mm-wave), up to 400 MHz bandwidth, flexible numerology, massive MIMO and beamforming.
  • Architecture: mobile station, base station (BTS/eNodeB/gNB), core network. Frequency reuse in hexagonal cells, with handover between cells.

3. Satellite communication

  • Geostationary orbit at 35,786 km. The ground-to-satellite delay is about 120 ms, so one hop (up and down) takes about 240 ms.
  • Bands: C band (uplink 5.925–6.425 GHz, downlink 3.7–4.2 GHz, written 6/4 GHz), Ku band (14/12 GHz), Ka band (30/20 GHz).
  • A transponder receives the uplink, translates the frequency down, amplifies with a TWTA or SSPA, and retransmits. Typical transponder bandwidth is 36 MHz.
  • Access: FDMA, TDMA, CDMA. Example: VSAT networks with QPSK/8PSK and DVB-S2.
  • Uplink is at the higher frequency because the ground station can afford more power to overcome the greater loss.

4. Terrestrial microwave link (point-to-point backhaul)

  • Bands: 6, 7, 8, 11, 13, 15, 18, 23 and 38 GHz, with E-band at 70/80 GHz.
  • Line of sight with at least 60% of the first Fresnel zone clear. Hop length 30–50 km at 6 GHz, a few km at 23–38 GHz.
  • Modulation: adaptive QPSK up to 4096-QAM. Channel width 7–56 MHz (up to 112 MHz).
  • Duplexing: FDD with a duplexer. Protection: 1+1 hot standby, and space or frequency diversity.
  • Parabolic dishes of 0.3–3 m, 30–45 dBi gain.

5. Bluetooth (IEEE 802.15.1)

  • Band: 2.4 GHz ISM. 79 channels of 1 MHz (Classic) or 40 channels of 2 MHz (Low Energy).
  • FHSS at 1600 hops/s. Modulation GFSK (1 Mbps), with π/4-DQPSK or 8DPSK for EDR (2–3 Mbps).
  • Piconet of 1 master and up to 7 active slaves, using TDD slots of 625 µs.
  • Range: 10 m (Class 2, 2.5 mW) to 100 m (Class 1, 100 mW).

✓ Answer checked by Claude Opus 5.5 (high effort)

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