Understanding 5G Spectrum Frequency Bands

Estimated reading time: 7 minutes

The fifth generation of cellular technology (5G) represents a massive leap forward for wireless mobile communications. In terms of data rates, security and latency, 5G far surpasses these previous generations of communication platforms:   

• 4G (LTE, LTE-Advanced, LTE-Advanced Pro)   
• 3G (UMTS, WCDMA, CDMA, 1xEV-DO)  
• 2G (GSM, GPRS, CDMA, 1xRTT)  

Mass quantities of new radio spectrum have been specified to support these capabilities in the 5G standard. This spectrum consists of two parts:  

• Sub-6 GHz: frequency range 1 (FR1)  
• Millimeter wave (mmWave) bands: frequency range 2 (FR2) 

Paving the Way for 5G

In 2016, the Federal Communications Commission (FCC) adopted the Spectrum Frontiers rules. This opened up nearly 11 GHz of high-band (mmWave) spectrum for 5G, fixed wireless and other advanced services.

This move made the U.S. the first country to designate large amounts of millimeter-wave spectrum for flexible use. It set a benchmark that other regulators worldwide later followed. 

In 2020, the FCC held Auction 105, the Priority Access Licenses (PALs) auction, for the 3.5 GHz Citizens Broadband Radio Service (CBRS) band. The auction offered 22,631 county-based licenses and raised more than $4.5 billion in net bids. This helped enable shared-spectrum models supporting:  

• 5G 
• Private LTE 
• Internet of Things (IoT) 
• Enterprise networks 

The C-band auction — FCC Auction 107 — took place in late 2020 and concluded in early 2021. It raised a record-breaking $81.11 billion from major U.S. carriers for 280 MHz of mid-band spectrum (3.7-3.98 GHz), significantly boosting 5G coverage and capacity nationwide.  

Low-, Mid- and High-Band 5G Spectrum Frequencies and Their Allocations 

5G operates on three different spectrum frequency bands and will have varying effects on everyday use. 

Low-Band Spectrum 

Low-band spectrum is sub-1 GHz spectrum. Carriers primarily use low-band spectrum for 3G and LTE-Frequency Division Duplexing (FDD). It provides consumers with a broad coverage area and good building penetration. Projected peak data speeds can reach up to 400 Mbps by utilizing a 20 MHz bandwidth from one carrier.  

In the coming years, operators will reclaim low-band spectrum for 5G as 3G sunsets. This re-farming process will see operators repurpose existing spectrum frequency bands to newer technologies like 4G and 5G.

Mobile operators will support dynamic spectrum sharing (DSS), allowing 4G/LTE and 5G devices to use the spectrum. Network algorithms will balance the load. 

According to Digital Trends, T-Mobile is the leading player in the low-band spectrum market. The operator bought a large block of 600 MHz (i.e., Band n71 in 5G) spectrum during FCC auctions in 2017.  

Since that purchase, the company has built its nationwide 5G network on the spectrum block. With the Sprint merger, T-Mobile leveraged the block with another mid- and high-band spectrum to create the most extensive 5G coverage in the U.S.  

Mid-Band Spectrum 

Carriers and private companies spent billions purchasing and deploying mid-band spectrum. This spectrum, situated between 1 and 6 GHz, offers faster throughput and more bandwidth than the low-band spectrum. As Digital Trends notes, mid-band transmissions are less suitable for building penetration.   

LTE has been defined and deployed in several mid-band ranges, including Bands 42 and 43, as well as the U.S. CBRS Band 48. Whether LTE or 5G runs on a particular mid-band frequency depends on the regulatory allocation and the operator’s deployment (LTE, NR or both). Device support, therefore, depends on the device’s RF front end and which bands the vendor enabled for that market. 

Peak speeds can reach as high as 2 Gbps or more in 5G, providing more capacity for the network. 4G and 5G standards use this spectrum. Mid-band spectrum is the primary contributor to 5G coverage and capacity.  

5G New Radio (NR) introduces technologies designed to enhance spectral efficiency and manage interference more effectively than previous generations. These improvements are especially noticeable in comparable deployment scenarios, such as:  

• Higher-order multiple-input, multiple-output (MIMO) 
• Beamforming (massive MIMO) 
• Flexible numerology  
• Advanced modulation/scheduling   

However, efficiency gains are contingent on the network design (MIMO order, channelization, site density, etc.). Improved efficiency is a technical potential rather than an automatic result simply from using C-band. 

Popular Mid-Band Allocations for 5G

The 3GPP NR mid-band allocations (n77, n78 and n79) are widely used for 5G. In 3GPP NR, the FR1 (sub-6 GHz) component-carrier size is specified up to 100 MHz.

Operators commonly deploy channels in the tens of MHz up to 100 MHz in these bands. The exact channel size depends on national or regional spectrum assignments and operator strategy. 

Many modern chipsets and devices support n77 and n78 broadly. Support for n79 is also available, but it depends on the region. That broad chipset support is one reason operators promote mid-band 5G. Mid-band frequencies, including the C-band in some regions, offer a practical balance of capacity and coverage compared to low-band and mmWave. 

Private 4G and 5G networks, as well as CBRS, are also gaining popularity. These networks and the CBRS band all use the mid-band spectrum.

In these shared spectrum models, the cost of spectrum for general users is very low. However, the licensed PAL spectrum — a portion of the 3.5 GHz CBRS band auctioned off to private companies — was more valuable and expensive.   
 

High-Band Spectrum 

Most people associate high-band spectrum (i.e., mmWave or FR2) with 5G. High-band spectrum enables speeds in the tens of Gbps range at even lower latency.  

However, high-band coverage has a limited range and poor penetration of buildings. It even struggles to pass through rain. It’s considered line of sight for practical purposes.  

For mmWave mobile devices to function properly, the cell tower and the mobile device must use new antenna technology. These antennas can dynamically steer and form the radio beam between the device and the tower.

Power modulation and interferometry steer and form the beams to and from tightly packed antenna module arrays. These modules are small because the signal is in the millimeter wavelength spectrum.  

mmWave is fundamental to achieving 5G speed and latency targets. Major telecommunication companies are developing the technology to address these propagation challenges.  

Sub-6 is another significant part of the 5G high-band spectrum, offering wide coverage and moderate speeds. It is essential for widespread 5G connectivity. Although mmWave offers higher speeds and capacity within a short range, sub-6 provides broader coverage and better penetration. 

mmWave is preferable for high-capacity use cases with a clear line of sight. Sub-6 GHz is ideal for broader coverage and more general 5G high-band deployments, such as:  

• Smart city infrastructure 
• High-definition video streaming  
• Real-time online gaming 

Preparing for a 5G Future 

Commercial 5G networks are achieving viable coverage for commercial IoT deployments. Innovative solution providers can begin building future-proof mobile broadband and IoT-based designs that meet today’s consumer demands.   

At Telit Cinterion, we empower you to build future-ready solutions without compromising present-day needs. Our developer kits allow you to test our hardware, connectivity services and device management portal for your IoT solutions. From robust connectivity to scalable IoT platforms, we help you overcome today’s challenges with technology built for what’s next. 

Editor’s note: This blog was originally published on 9 May 2019 and has since been updated.