For a while now, industry analysts, players and authorities — including GSMA and Ericsson — have been heralding the dramatic growth of mobile broadband (MBB) data traffic that will likely happen over the next 10–15 years. Meanwhile, long-term evolution (LTE) is positioned to become the dominant mobile access technology far beyond 2020, when more commercial scale 5G deployment should begin.

Since its introduction in Release 8 of the 3rd Generation Partnership Project (3GPP), LTE has improved spectral efficiency. Waveforms, modulation advancements, coding schemes (e.g., 64-QAM/256-QAM) and multiple-input and multiple-output (MIMO) antennas are pushing the limits of theoretical download data speed over the Gigabit mark. GSA announced in October 2017 they are already investing in Gigabit LTE networks with, according to Ericsson’s November report, 14 claiming to be commercial-ready.

Not all the news about LTE and MBB is rosy. In some environments, devices operate in highly noisy conditions that dramatically dampen the efficiency of technological improvements by reducing the data rate and capacity. Achieving a higher MIMO order is still a challenge for device manufacturers hosting multiple antennas in a limited space. Densifying the networks and intensifying the distribution of small cells can help, but this deployment process presents an economic challenge of effort and money for mobile network operators (MNOs).

Carrier Aggregation Drives Up MBB Demand

So far, carrier aggregation (CA) has been a successful option for overcoming MBB deployment obstacles. The more carriers that are combined (with up to 20 MHz bandwidth each), the more expansive the usable spectrum and the higher the data speed.

C-Band Spectrum Fig1

Figure 1: LTE operator investment in CA to facilitate Gigabit LTE throughput.

Therefore, MNOs can better support the increasing demand for traffic growth while limiting superfluous infrastructure investments. However, they still need to acquire additional spectrum. While 3GPP’s Release 13 allows the aggregation of a maximum of 32 carriers, the availability of the commercial network typically includes two to four and up to seven in LTE-Advanced-Pro networks.

What Is the C-Band Spectrum?

Allocating new spectrum has become a mandatory requirement for the mobile industry to improve capacity and enhance mobile broadband (eMBB). 3GPP provides various strategies to aggregate spectrum and enable eMBB for faster throughput. LTE-A-Pro, with LAA technology, adds carrier aggregation across the unlicensed spectrum in the 5 GHz (sub-6 GHz), and 5G will do the same in the millimeter wave (mmWave) range between 24 GHz and 29.5 GHz.

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

On the lower bands, the sub-6 GHz domain contributes a critical portion of the spectrum, offering a  compromise between the broad coverage of lower frequencies and the higher capacity of mmWave. Part of this spectrum is known as C-band. C-band sits between 3.4 GHz and 4.2 GHz and is emerging as a prime resource for the capacity crunch without incurring high-cost investments that would otherwise be required to upgrade the infrastructure.

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

  • Economical: Overlay the C-band on top of existing macrocellular or small-cell grids without needing new cell sites, unlike what mmWave would require.
  • Technical: Access to a range of spectrum with fewer challenging propagation conditions than mmWave. This approach reinforces transmission in a non-line-of-sight (NLOS) environment and facilitates indoor penetration on a scale like lower-frequency bands.

C-band spectrum also provides a few advantages over lower frequencies based on frequency-division-duplex (FDD-LTE) technology. As a time-division-duplex technology (TDD-LTE), C-band allows transmission and reception on the same channel, compared to FDD-LTE requirements for a paired spectrum with different frequencies and a guard band. For a TDD-LTE device, this capability eliminates the use of a dedicated diplexer to isolate transmission and receptions, therefore reducing the bill of materials (BOM) cost.

Since they are part of the same LTE 3GPP standards, FDD-LTE and TDD-LTE offer comparable performances and similar high-spectral efficiency. There is increasing industry interest in applying this technology to MBB.

Although the most used TDD spectrum is band 40, bands 42 and 43 are gaining attention, especially across Europe and Asia-Pacific. These two C-bands are licensed globally for commercial terrestrial wireless communications for LTE deployment. Moreover, it allocates a potential spectrum as much as 400 MHz between 3.4 GHz 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 Spectrum Fig 2

Figure 2: Adoption of TDD spectrum.

In the U.S. market, the Federal Communications Commission (FCC) 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) and general authorized access (GAA). These levels create new demand for operators looking to enter the mobile wireless market, facilitate a private LTE network for large enterprises, or expand capacity cost effectively.

C-Band: A Steppingstone to 5G

As an active player in the mobile broadband ecosystem, we continue collaborating technology, products and solutions in response to increasing demand for more band support while delivering higher cost and production efficiencies for Gigabit-class devices. C-band range centered around 3.5 GHz can aid the transition from 4G to 5G by providing the NLOS spectrum MBB industry players need. With these solutions, providers can offer more extensive wireless capacity and higher quality services.

Are you ready to find out what C-band can do for your organization? See how easy it is to get started with an evaluation kit from Telit. Request to qualify for your FREE evaluation kit today!

 

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