Spectrum as the Foundation of 5G
Every 5G NR deployment begins with a spectrum strategy. The available frequency band determines maximum channel bandwidth, propagation characteristics, antenna design, and ultimately the end-user experience. 3GPP defines two frequency ranges in TS 38.104 Section 5.1:
- FR1:
410 MHzto7.125 GHz(commonly called "sub-6 GHz") - FR2:
24.25 GHzto52.6 GHz(millimeter wave, extended to71 GHzin Release 17 as FR2-2)
Operators worldwide have acquired spectrum across both ranges, but deployment strategies vary dramatically based on geography, population density, and use-case targets.
Complete 5G NR Band Reference
The table below covers the most commercially significant NR bands as defined in TS 38.101-1 (FR1) and TS 38.101-2 (FR2).
| NR Band | Frequency Range | Max Channel BW | Duplex | Primary Region |
|---|---|---|---|---|
| n1 | 2110–2170 MHz (DL) | 20 MHz | FDD | Global (refarmed 3G) |
| n3 | 1805–1880 MHz (DL) | 30 MHz | FDD | Europe, Asia |
| n5 | 869–894 MHz (DL) | 10 MHz | FDD | Americas |
| n7 | 2620–2690 MHz (DL) | 20 MHz | FDD | Europe, Asia |
| n28 | 758–803 MHz (DL) | 20 MHz | FDD | APAC, Europe (700 MHz) |
| n41 | 2496–2690 MHz | 100 MHz | TDD | Americas, China |
| n77 | 3300–4200 MHz | 100 MHz | TDD | Global C-band |
| n78 | 3300–3800 MHz | 100 MHz | TDD | Europe, Asia C-band |
| n79 | 4400–5000 MHz | 100 MHz | TDD | Japan (DOCOMO, SoftBank) |
| n257 | 26.5–29.5 GHz | 400 MHz | TDD | Global mmWave |
| n258 | 24.25–27.5 GHz | 400 MHz | TDD | Europe, Asia mmWave |
| n260 | 37–40 GHz | 400 MHz | TDD | Americas |
| n261 | 27.5–28.35 GHz | 400 MHz | TDD | Americas (Verizon, AT&T) |
Band Classification by Coverage Tier
Operators typically segment their spectrum into three planning tiers:
| Tier | Bands | Typical Cell Radius | Capacity per Cell | Primary Role |
|---|---|---|---|---|
Low-band (<1 GHz) | n5, n28, n71 | 5–30 km | 30–75 Mbps | Coverage layer |
Mid-band (1–6 GHz) | n41, n77, n78 | 0.5–5 km | 200–900 Mbps | Capacity + coverage |
High-band (>24 GHz) | n257, n258, n260, n261 | 0.1–0.5 km | 1–4 Gbps | Hotspot capacity |
Sub-6 GHz vs mmWave: Link Budget Analysis
The most critical engineering trade-off in 5G planning is the balance between coverage (sub-6) and capacity (mmWave). A link budget comparison illustrates why.
Worked Example: Downlink Link Budget
Assumptions: gNB TX power43 dBm, antenna gains as specified, noise figure 7 dB, target SINR 0 dB for cell-edge.
| Parameter | n78 (3.5 GHz, 100 MHz) | n261 (28 GHz, 400 MHz) |
|---|---|---|
| TX power | 43 dBm | 35 dBm (EIRP-limited) |
| Antenna gain (gNB) | 24 dBi (64T64R) | 34 dBi (256-element) |
| Antenna gain (UE) | 0 dBi | 10 dBi (phased array) |
| EIRP | 67 dBm | 79 dBm |
Thermal noise (kTB) | -94 dBm | -88 dBm |
| Noise figure | 7 dB | 9 dB |
| Required SINR | 0 dB | 0 dB |
| Receiver sensitivity | -87 dBm | -79 dBm |
| Max allowable path loss | 154 dB | 158 dB |
| FSPL at max range | 154 dB → ~1.5 km | 158 dB → ~300 m |
Despite higher EIRP from beamforming at mmWave, the path loss exponent in urban NLOS environments (typically 3.5–4.0 per 3GPP TR 38.901 UMi model) severely limits mmWave range. Additional losses from foliage (~0.4 dB/m), building penetration (~25–40 dB for low-E glass), and rain fade (~7 dB/km at 28 GHz in heavy rain per ITU-R P.838) further constrain outdoor-to-indoor coverage.
Global Spectrum Auctions and Allocations
FCC C-Band Auction (Auction 107) — United States
The FCC's C-band auction concluded in February 2021 as the most expensive spectrum auction in history:
- Total proceeds: USD
$81.17 billion - Spectrum:
3.7–3.98 GHz(280 MHz total, released in two phases) - Top bidders: Verizon acquired
161 MHzavg nationwide for$45.5B; AT&T acquired80 MHzavg for$23.4B - Deployment deadline: Phase 1 (
3.7–3.8 GHz) cleared December 2021; Phase 2 (full 280 MHz) by December 2023
Verizon deployed its C-band holdings as n77 across 200+ markets, initially using 60 MHz channels and expanding to 100 MHz as spectrum cleared.
India 3.5 GHz Auction (2022)
India's first 5G spectrum auction in July 2022 allocated mid-band and mmWave spectrum:
- 3.3–3.67 GHz (n78): Reliance Jio acquired
700 MHzacross circles for INR88,078 crore(~USD $10.6B); Bharti Airtel acquired400 MHztotal - 26 GHz (n258): Jio acquired
800 MHz; Airtel acquired800 MHz; Adani acquired400 MHz - Total auction value: INR
1,50,173 crore(~USD $18.2B)
Jio launched commercial n78 service across 50+ cities by December 2022, reporting median DL speeds of 300–500 Mbps on 100 MHz channels with 64T64R massive MIMO.
Worked Example: Capacity Planning for C-Band Deployment
An operator deploys n78 with 100 MHz bandwidth, μ = 1 (30 kHz SCS), 64T64R massive MIMO supporting 16 MU-MIMO layers:
`
273 RBs × 12 subcarriers = 3,276 subcarriers per OFDM symbol
`
Step 2 — Throughput per slot (14 symbols, 0.5 ms):
`
3,276 × 14 × 8 bits (256-QAM) = 366,912 bits per layer per slot
`
Step 3 — With 16 spatial layers and 0.85 effective code rate:
`
366,912 × 16 × 2,000 slots/s × 0.85 = 9.97 Gbps aggregate cell capacity
`
Step 4 — Apply TDD ratio (DDDSU → 75% DL) and 70% scheduler efficiency:
`
9.97 × 0.75 × 0.70 = 5.23 Gbps practical DL cell throughput
`
This aligns with field reports from dense urban massive MIMO deployments showing 4–6 Gbps aggregate cell throughput.
Band Combination Strategies
Modern 5G devices support Carrier Aggregation (CA) across bands, specified in TS 38.101-1 Section 5.5A. Common operator-deployed combinations include:
| Operator | CA Combination | Aggregate BW | Observed Peak DL |
|---|---|---|---|
| T-Mobile US | n41 + n25 (LTE anchor) | 100 + 20 MHz | ~700 Mbps |
| SK Telecom | n78 + n78 (intra-band) | 80 + 80 MHz | ~2.5 Gbps |
| Verizon | n77 + n261 | 100 + 400 MHz | ~4.2 Gbps |
| DOCOMO | n79 + n78 | 100 + 100 MHz | ~4.1 Gbps |
Spectrum Refarming Trends
Operators globally are refarming legacy 2G/3G spectrum to NR:
- Vodafone Europe refarmed
900 MHz(n8) and2100 MHz(n1) from 3G to NR in 11 markets by Q1 2025, using Dynamic Spectrum Sharing (DSS) during the transition period. - China Mobile operates NR on
2.6 GHz(n41) refarmed from TD-LTE, deploying over 1 million n41 gNBs as of Q3 2024 — the largest single-band 5G deployment globally. - Telstra (Australia) refarmed
700 MHz(n28) for NR coverage, achieving>98%population coverage on low-band 5G.
DSS, defined in TS 38.101-3, allows LTE and NR to share the same carrier dynamically. However, DSS reduces NR throughput by 30–50% compared to dedicated NR spectrum due to LTE CRS overhead and scheduling constraints.
Propagation Modeling Considerations
3GPP TR 38.901 defines channel models for frequencies from 0.5 to 100 GHz. Key parameters by band:
| Scenario | n28 (700 MHz) | n78 (3.5 GHz) | n261 (28 GHz) |
|---|---|---|---|
| UMa LOS PL exponent | 2.2 | 2.2 | 2.0 |
| UMa NLOS PL exponent | 3.3 | 3.5 | 3.4 |
| O2I penetration (low-loss) | ~11 dB | ~17 dB | ~32 dB |
| O2I penetration (high-loss) | ~17 dB | ~26 dB | ~44 dB |
| Shadow fading std dev (NLOS) | 6 dB | 7.8 dB | 8.2 dB |
These values directly impact site density calculations. A mid-band n78 deployment typically requires 3–5x the site density of a low-band n28 deployment for equivalent outdoor coverage probability, and mmWave requires 15–25x the site density of mid-band for outdoor coverage equivalence.
Key Takeaway: Spectrum selection defines the entire 5G network architecture. Low-band provides blanket coverage with modest capacity, mid-band (C-band) offers the best balance for most urban/suburban deployments, and mmWave delivers extreme capacity in confined areas. Successful operators deploy a layered spectrum strategy using CA to combine coverage and capacity bands seamlessly. Understanding link budgets, propagation models, and band-specific constraints is essential for any RF engineer working in 5G.