A debate already is emerging about the use of 28 GHz and 39 GHz bands for linking mobile devices to 5G networks. "Samsung very interested in 28 GHz and has spent considerable time on that, but from a regulatory point of view, 39 GHz is more suitable for rule modification," Sadri said. That's because satellite services use portions of the 28 GHz band. By contrast, 39 GHz has significantly more than 1 GHz available for use.
On the technology front, systems typically have a fixed space of about 10 cm2 for an antenna. The 39 GHz band allows smaller antennas and thus could pack more of them into that space than a 28 GHz link -- an important factor given phased-array antennas with beam forming are a likely requirement.
In addition, Sadri estimates 39 GHz offers 3-5 dB signal improvement over 60 GHz. The 28 GHz band offers a benefit of only about 1.5 dB over 39 GHz.
Future research will explore such tradeoffs in more detail. Engineers will also explore techniques to work around challenges such as roaming at the high frequencies, linking millimeter and traditional services, and handling reach issues in urban areas where skyscrapers would block high-frequency signals.
— Rick Merritt, Silicon Valley Bureau Chief, EE Times