Band n77 (C-Band) Deployment Guide
C-Band Deployment Technical Reference
Band n77 is the primary mid-band 5G NR spectrum globally, but deployment varies significantly by country. The US C-Band (3700 to 3980 MHz) was the most expensive spectrum ever auctioned ($81 billion at Auction 107), while other countries allocated their C-Band portions at lower cost through administrative assignment or smaller auctions. Understanding these differences is critical for equipment vendors and test system designers.
The key deployment challenge at 3.5 to 3.7 GHz is balancing coverage and capacity. Massive MIMO with 64T64R panels provides both high gain (25 dBi beamforming) and spatial multiplexing (16 beams), enabling urban cell coverage of 1.5 to 2.5 km while delivering 1 to 2 Gbps per sector. Without massive MIMO, cell edge at 3.7 GHz would be only 0.5 to 1 km.
C-Band Link Budget
TX power: 46 dBm (40W per port, 64 ports)
Antenna gain: 25 dBi (64T64R beamforming)
Cable/connector loss: 1 dB
EIRP: 70 dBm
Path Loss (COST-Hata urban macro):
PL = 137.4 + 35.2 × log10(dkm) dB at 3.7 GHz
At 1 km: PL = 137.4 dB | RSRP = −67.4 dBm
At 2 km: PL = 148.0 dB | RSRP = −78.0 dBm
Cell edge (~2.5 km): RSRP ≅ −83 dBm
Global C-Band Allocation Comparison
| Country/Region | Frequency | Total BW | Band | Status |
|---|---|---|---|---|
| United States | 3700-3980 MHz | 280 MHz | n77 | Deployed (2022) |
| Europe | 3400-3800 MHz | 400 MHz | n78 | Deployed (2019+) |
| Japan | 3600-4100 MHz | 500 MHz | n77 | Deployed (2020) |
| China | 3300-3600 MHz | 300 MHz | n78 | Deployed (2019) |
| South Korea | 3420-3700 MHz | 280 MHz | n78 | Deployed (2019) |
Frequently Asked Questions
How does US C-Band differ from international?
US uses 3700 to 3980 MHz (280 MHz, n77). Europe uses 3400 to 3800 MHz (n78). Japan: 3600 to 4100 MHz (n77). China: 3300 to 3600 MHz (n78). US was delayed by satellite relocation ($9.7B fund). FAA power restrictions near airports due to altimeter interference at 4200 to 4400 MHz.
What massive MIMO configurations are used?
Standard: 64T64R with 192 antenna elements. Panel: ~0.9m x 0.5m, 30 to 40 kg. Forms up to 16 beams via digital beamforming. Advanced: 128T128R for extreme capacity. Wavelength at 3.5 GHz (~8.5 cm) enables compact element spacing with good beamforming resolution.
What is the C-Band link budget?
TX: 46 dBm, antenna gain: 25 dBi (64T64R), EIRP: 70 dBm. At 1 km: PL = 137.4 dB, RSRP = -67.4 dBm. Cell edge (~2.5 km): RSRP = -83 dBm. 256-QAM requires -80 dBm. Urban macro coverage: 1.5 to 2.5 km with massive MIMO.