Industry Insights

Ensuring 5G New Radio Peaceful Coexistence

2019-04-03  |  5 min read 

Spectrum is a key enabler for 5G New Radio (NR) data throughput and capacity gains. However, it’s not as simple as just adding new operating bands.  Operating bands at different frequencies can experience interference issues, especially in the mid- and high-bands, that can impact your ability to provide peaceful coexistence with neighboring bands.  Adding 5G NR to an already crowded and congested spectrum increases the potential for interference.

I came across this coexistence poster that provides 5 tips to successful 5G NR coexistence. Hopefully you’ll find this useful for your 5G NR development.

1. 5G COEXISTENCE WITH LTE

5G NR needs to coexist with LTE, in adjacent bands and sometimes within the same frequency bands. 5G NR bandwidth parts (BWP) enable LTE and 5G NR signals to  hare a carrier, introducing new challenges with interference due to closely spaced and sometimes overlapping signals.

Tip: Reduce interference by increasing guard band at higher frequencies, and by using advanced sub-band filtering. Test for coexistence interference using different time  and frequency resources.

2. 5G COEXISTENCE WITH UNLICENSED SPECTRUM

Techniques such as licensed-assisted access (LAA) enable use of unlicensed spectrum through aggregation of a secondary channel. The evolution of LAA will be addressed in 5G NR Release-16 through “NR-based access to unlicensed spectrum”, resulting in potential coexistence issues with incumbents like Wi-Fi and other wireless technologies.

Tip: Test for fair coexistence between 5G NR and legacy systems by evaluating coexistence with NR operation in unlicensed bands and LTE-based LAA. Also ensure resources are properly negotiated with incumbent Radio Access Technologies (RATs).

5G Coexistence with unlicensed spectrum

3. 5G IN-DEVICE COEXISTENCE (IDC)

Multiple radio transceivers in a device can interfere with other receivers in the same device that are operating either in adjacent or sub-harmonic frequencies.

Tip: Carefully evaluate in-band and out-of-band emissions using wideband spectrum measurements such as adjacent channel leakage ratio (ACLR) and spectrum emissions mask (SEM) to gain insight into the signal’s interference possibilities. Ensuring sufficient filtering can mitigate potential issues.

4. 5G IN-BAND AND OUT-OF-BAND EMISSIONS

Performance of a device transmitter at the edge of the band and outside the band can cause interference with other wireless communications systems. In-band and out-of-band emissions must be understood to minimize interference within the band and in adjacent frequency bands.

Tip: Evaluate unwanted emissions from harmonics, intermodulation spurs, and spectral regrowth to understand how the 5G NR signal will interact with other radio signals. View the signal’s constellation diagram and EVM of the demodulated signal and EVM per subcarrier to predict good or poor coexistence.

5G In-band and out-of-band emissions

5. 5G SPECTRUM SHARING WITH SATELLITE AND RADAR SYSTEMS

5G will utilize shared spectrum in sub-6 GHz and in millimeter-wave frequencies where a device must coexist with other wireless communications systems such as  satellite and radar. 5G NR FR2 overlaps with fixed-satellite services earth station uplinks at 27.5 to 29.5 GHz and FSS downlinks at 37.5 to 40 GHz. Coexistence will require spectrum sharing techniques such as spectrum shaping, power control, beam forming and spectrum sensing.

Tip: Use network emulation tools to simulate real-world behavior and validate a device’s ability to detect coexistence traffic and allocate and reallocate spectrum dynamically without impacting quality-of-service.

I hope you found these tips as useful as I did.  5G NR operation in mid-band and high-band will introduce many more coexistence challenges than in the past.  Having the hardware and software tools that allow you to explore the higher frequencies, wider channel bandwidths, and changing channel conditions expected in 5G NR are essential.  The following screenshot shows a measurement of a demodulated 5G compliant signal alongside an LTE signal displaying multiple aspects of each signal’s evaluated quality. With a side-by-side view, you can see results of each carrier and interactions that may not otherwise be visible.

Side-by-side view of 5G NR and LTE signal

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