AT&T analysis highlights differences between 28 GHz, 37/39 GHz

AT&T (NYSE: T) directed its engineers to conduct a thorough analysis on the 28 GHz and 37/39 GHz bands, and the results show what its preliminary calculations suggested: to achieve the same performance results, a carrier using 37-39 GHz spectrum will require about 50 percent more spectrum than a carrier deploying in the 28 GHz band.

AT&T argues that these types of performance factors should be taken into consideration in formulating licensing and spectrum aggregation policies. Treating both bands the same way could produce unintended results that undermine competitive and innovative 5G deployment in the U.S., the company suggests.

Conducted at AT&T Labs in Austin, Texas, by AT&T's Advanced Wireless Technology Group, the analysis included comparison of the propagation differences between the 28 and 37/39 GHz bands.

In its executive summary, AT&T notes that these two bands are particularly attractive due to the large bandwidth available. Between the two bands, current industry momentum favors 28 GHz due in part to activity in South Korea related to the 2018 Olympics. From a propagation point of view, 28 GHz has better potential given the longer wavelengths compared to 37/39 GHz, but there is significantly more bandwidth available in the 37/39 GHz, which makes it an attractive 5G option as well, AT&T says.

After a series of technical steps that AT&T spells out in its report to the commission, engineers concluded that a licensee will need somewhere between 44 percent and 66 percent more spectrum in the 39 GHz band to provide the same cell edge data rate with the same cell radius as compared to 28 GHz.

As part of the FCC's Spectrum Frontiers proceeding, AT&T also took the opportunity to urge the commission to reject calls for further investigation into potential interference that may be experienced by the incumbent satellite operators. According to AT&T, terrestrial interference can be managed through the same good faith coordination and interference mitigation techniques that have been practiced for decades. Regarding space station receiver interference, it's AT&T's position that the record is "replete" with technical analyses showing that aggregate interference from terrestrial 5G mobiles and fixed stations into a receiver several thousand miles above the earth will be nominal.

With regard to 39 GHz, AT&T said it supports StraightPath's proposal for a license swap in 39 GHz, but it argued for an even more flexible approach, noting that 39 GHz licensees should also be permitted to voluntarily swap into open licensed allocations in 37 and 38 GHz if a swap opportunity doesn't exist within the 39 GHz band.  

For more:
- see this filing and this report
- see this filing

Related articles:
AT&T adds Nokia to 5G roster
AT&T/EchoStar proposal for 28 GHz sharing gets heat from other satellite players
FCC needs to tackle a bunch of thorny issues on mmWave spectrum before unleashing it

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