C-Band Spectrum: 5G Delivering the Next Level of Experience

The C-band spectrum sits between 3.4 and 4.2 gigahertz (GHz), balancing coverage and capacity. This makes it ideal for enhancing 5G networks.

Industry analysts and authorities — including GSMA and Ericsson — have heralded mobile broadband (MBB) data traffic growth for years. 4G Long-Term Evolution (LTE) continues as a stable, ubiquitous broadband technology. However, newer 5G deployments have progressively rolled out on a commercial scale.

LTE has significantly improved spectral efficiency since its introduction. Advancements in waveforms, modulation and MIMO antennas have pushed download speeds over the gigabit mark.

Despite these improvements, challenges remained in reaching the limits of spectrum capacity and legacy network design. These were addressed in the 3GPP Release (Rel) 15 5G standard with many new enhancements, such as:

• C-band and mmWave spectrum
• Radio design
• Network architecture

With its ability to balance high speed and expansive coverage, C-band is poised to revolutionize 5G deployment. It ensures a seamless transition from LTE and addressing the growing demand for mobile data.

This blog delves into the importance of C-band spectrum for 5G. Let’s explore how carrier aggregation, FCC auctions and technical benefits make it a cornerstone for modern mobile networks. You’ll discover:

• How C-band is shaping the future of connectivity
• The deployment challenges this spectrum overcomes
• How it provides a robust foundation for next-generation mobile broadband services

Carrier Aggregation Drives MBB Demand

So far, carrier aggregation (CA) has been a successful option for overcoming MBB deployment obstacles. The more combined carriers, the more expansive the usable spectrum and the higher the data speed. 

MNOs can better support the increasing demand for traffic growth while limiting superfluous infrastructure investments. However, they still need to acquire additional spectrum.

What Is the C-Band Spectrum?

Allocating new spectrum has become mandatory for the mobile industry to improve capacity and enhance mobile broadband (eMBB). 5G wireless technology accommodates millimeter wave (mmWave) spectrum between 24 and 29.5 GHz. 

However, because of its wavelength, propagation at these high frequencies is complex. It often requires line-of-sight (LOS) conditions between the base station and the device. These conditions require highly directional beams and massive MIMO antennas that track users in real time. 

The sub-6 GHz domain contributes a critical portion of the spectrum on the lower bands. It offers a balanced compromise between the broad coverage of lower frequencies and the higher capacity of mmWave. Part of this spectrum is known as C-band.

FCC Auction of C-Band Spectrum  

In 2021, the Federal Communications Commission (FCC) facilitated the world’s most expensive mid-band 5G spectrum auction. MNOs bid against each other to acquire licensed spectrum. The 257 bidders were attracted by:

• Smaller license areas offering lower entry prices
• The availability of dynamic spectrum sharing
• The prospect of new or improved business cases with private 5G and fixed wireless access

In the end, 228 licensees walked away with licenses. When the auction closed, the FCC raised around $4.6 billion at an average price of $0.22 per MHz-POP. MNOs spent around $81 billion on public C-band spectrum. Verizon, AT&T, and T-Mobile spent $45 billion, $23 billion and $9 billion, respectively.

The FCC also allocated a similar spectrum in Band 48. This band has a range of 150 MHz from 3.55 GHz to 3.7 GHz to create the Citizens Broadband Radio System (CBRS). Three primary user tiers share access:

• Incumbent
• Priority access license (PAL)
• General authorized access (GAA)

These levels create demand for operators looking to:  

• Enter the mobile wireless market  
• Facilitate private 5G and LTE networks for large enterprises  
• Expand capacity cost-effectively 

MNOs, including new incumbents like cable operators and others, spent $4.6 billion on private CBRS spectrum. The CBRS C-band PAL auction had better results than expected.

While the bandwidth and spectrum portions are smaller, licensees can still get decent speed. They can achieve a greater speed boost if they deploy the full C-band. 

C-Band Spectrum and 5G

C-band saved 5G by closing the gap between sub-6 GHz and mmWave. While mmWave offers high speeds, it is expensive and difficult to deploy at a massive scale.

However, C-band is much easier to deploy and can achieve similar speeds and performance. It is a compromise as it provides a sufficient boost to capacity, performance and speed without investment in mmWave.

The benefit of C-band, compared to mmWave, can be assessed from two different viewpoints: 

• Economic: Overlay the C-band on existing macrocellular or small-cell grids without needing new cell sites, unlike mmWave. 
• Technical: Access to a spectrum range with fewer challenging propagation conditions than mmWave. This approach reinforces transmission in a non-line-of-sight (NLOS) environment. In addition, it facilitates indoor penetration on a scale like lower-frequency bands. Sub-6 GHz user equipment (UE) is more cost-effective compared to mmWave.

Interest increased in private 5G in the C-band spectrum. Companies worldwide plan to use private 5G network slicing to enable various use cases (e.g., cameras and factory equipment) that require high-bandwidth broadband. These factories and manufacturing warehouses can leverage a self-contained 5G private network in the C-band spectrum because the bandwidth is 100 MHz.

What Are the Benefits of C-Band Spectrum?

C-band spectrum provides advantages over lower frequencies based on frequency-division-duplex (FDD-LTE) technology. C-band is a time-division-duplex technology (TDD). TDD throughput per megahertz of spectrum is lower than FDD. However, the carrier bandwidth in TDD can be up to 100 MHz in sub-6 GHz 5G operations (versus 20 MHz in FDD).

TDD also allows transmission and reception on the same channel. On the other hand, FDD requires a paired spectrum with different frequencies and a guard band. For a TDD device, this capability eliminates using a dedicated diplexer to isolate transmission and reception. In addition, it reduces the cost of the bill of materials (BOM).

The most used TDD spectrum is Band 40. However, Bands 42 and 43 are gaining attention, especially across Europe and Asia-Pacific. These two C-bands are licensed worldwide for commercial terrestrial cellular deployment.

Moreover, it allocates a potential spectrum of 400 MHz between 3.4 and 3.8 GHz. This spectrum generates frequency to support applications that require high data throughput (e.g., smartphones and industrial and home gateways). 

C-Band: A Steppingstone for 5G

As the most cost-effective expansion spectrum for 5G, C-band quickly became its most popular band. About 75% of MNOs set one of the three C-bands (i.e., n77, n78 and n79) as their primary 5G band.

Telit Cinterion was among the first to certify our 5G modules on C-band with leading MNOs. Today, we continue to refine and update our technology, products and solutions in response to evolving market demands. 

We also deliver higher efficiencies in cost and production for MBB devices. The C-band range around 3.5 GHz can aid 5G by providing the NLOS spectrum industry players need.

Speak to our IoT experts to discover what C-band can do for your next MBB device.

Editor’s Note: This post was first published on 16 January 2019 and has since been updated.