Finding the right mix of spectrum for 5G

Globally 3.5 GHz is a 5G band, but not in the U.S.

To deliver multi-gigabit-per-second throughputs associated with 5G, operators around the world are working with regulatory authorities to test and commercially deploy in an increasingly variable mix of spectrum. The key driver shaping spectral allocation hinges on balancing very high capacity associated with millimeter wave frequencies with the coverage and propagation benefits of low- and mid-band spectrum.

During the recent 5G New Horizons Wireless Symposium in Austin, Texas, Chetan Sharma, founder of Chetan Sharma Consulting, told RCR Wireless News, “I think given the nature of 5G, all about extremely high throughput capability, while you can do a significant amount of high bandwidth type applications in 28 GHz, 37 GHz and higher bands, coverage is a problem. That’s a hindrance to actually deploying it at scale. Ideally an operator will want to have deployment across all three types of bands, low, mid and high. But the mid band is considered a property where you can go really high throughputs if you have enough spectrum in that band and you can provide decent coverage.”

This mix of frequencies tracks with what Japanese operators are exploring. NTT DoCoMo, for instance, is working with Huawei and the Tobu Railway to trial 5G in the 28 GHz band. The partners previously tested out transmission in the 39 GHz band.

Kohei Sato, secretary general of Japan’s 5G Mobile Communications Promotion Forum (5GMF) said in an interview the three major bands gaining traction in Japan are 3.7 GHz, 4.5 GHz and 28 GHz. “Last year we had a lot of discussion including with the Japanese government. This is not decided yet, but within this year…the government will decide the suitable frequency bands.”

Frequencies around 3.5 GHz are drawing interest around the world given the attractive coverage and capacity associated with the mid-band. In the U.S., the 3.5 GHz is the subject of ongoing U.S. Federal Communications Commission rule making regarding a three-tiered priority access licensure scheme to open up the band, which has long supported fixed satellite and Department of Defense incumbents.

Sharma called 3.5 GHz “the ideal band that can give you little bit of coverage and capacity.” Asked if the disparity between the U.S. and the rest of the world regarding 3.5 GHz could create an long-term issues, he said, “I think is poses a problem, a challenge, in terms of scale, the types of equipment, devices that are being built, or infrastructure, that is being built on 3.5 GHz. I think when they were thinking about 3.5 and CBRS, they were really not contemplating 5G and what it might look like and what other countries might do. Over the last six or 12 months, decidedly, lots of countries have toward 3.5. I think FCC will try to figure out a way to allocate some spectrum in that vicinity. Fundamentally, I think it is a good band for 5G services.”

Watch the conversation with Sharma here. 

Watch the interview with Sato here.