There was a time, not so long ago, that 5G in millimeter wave (mmWave) spectrum was viewed with a healthy amount of skepticism, if not outright incredulity.
For example, a report in 2017 sponsored by companies in the cable industry pointed to "clear technical, operational and aesthetic challenges" in deploying 5G in mmWave spectrum.
Similarly, the Pentagon's Defense Innovation Board (DIB) warned last year that US policymakers should immediately switch their focus from 5G in mmWave and toward 5G in lower spectrum bands. "5G capability requires larger bands of spectrum, and without that additional bandwidth, the United States will not gain true 5G capability beyond the limited range that mmWave can provide," the board wrote.
After all, early mmWave 5G networks in the US didn't inspire much confidence. "Costs will likely be much higher (that is, cell radii appear smaller) and penetration rates lower than initially expected," wrote the Wall Street analysts at MoffettNathanson in early 2019 after reviewing Verizon's 5G mmWave network in Sacramento, California.
The challenges in building widespread mmWave 5G coverage are clear: With signals that can only travel a few thousand feet, thousands of mmWave transmitters would be needed to cover a single large city like Los Angeles with 5G.
A Google study for the DIB indicated it would take roughly 13 million transmitters and $400 billion to deliver 100Mbit/s to 72% of the US population using 5G in mmWave spectrum.
A widening embrace
Now, though, a growing range of countries and companies are moving to support 5G in mmWave spectrum. The development doesn't necessarily represent a complete about-face on the topic, but it certainly indicates an admission of the role that mmWave spectrum may ultimately play in 5G.
"Industrial applications using mmWave are a no brainer for private networks," noted analyst Earl Lum of EJL Wireless Research.
"To reach its full potential, 5G will use low-, mid- and highband spectrum as operators provide coverage, capacity, low latency and high-speed data throughput," Chris Pearson president of the 5G Americas trade group, told Light Reading. "The US is a leader in identifying and allocating mmWave spectrum, but there is much interest around the world as it provides great capacity for 5G services and applications."
The latest indication of global interest in mmWave 5G comes from South Korea, an early leader in 5G in midband spectrum. According to a widely cited report from the Korea Herald, the country's three main telecom operators expect to commercialize mmWave 5G sometime this year. The report, citing unnamed sources, indicated the operators would first deploy mmWave 5G in the business-to-business sector, but would wait until next year or the year after to offer mmWave 5G to consumers.
That's important considering South Korea's current midband 5G networks now carry close to a fourth of all wireless network traffic in the country, according to new figures from the country's telecoms regulator. South Korean operators launched 5G roughly a year ago using midband 3.5GHz spectrum. Transmissions in such spectrum can travel much, much further than transmissions in highband, mmWave spectrum due to the physics of propagation in such bands.
News of mmWave in interest in South Korea dovetails with similar momentum among other operators around the world. For example, operators stretching from Taiwan to Thailand to Japan to Italy to Russia have all voiced mmWave intentions of varying degrees.
A slow rollout
That said, there are still plenty of obstacles around 5G in mmWave spectrum. For example, the Global Mobile Suppliers Association (GSA) recently reported that 70% of all announced 5G devices support midband and lowband spectrum, but just 30% support 5G in mmWave spectrum.
US operators are moving forward with mmWave plans, too. Verizon, for instance, announced it would expand its mmWave 5G service to an additional 30 US cities this year. T-Mobile is bringing its "layer cake" 5G (comprising low-, mid- and highband spectrum) to cities including New York City. Verizon, T-Mobile and AT&T have spent billions of dollars in the past two years on mmWave spectrum licenses.
The momentum is building around mmWave 5G. Next, we'll see if the global recession dampens that slow-building enthusiasm.