In this corner are the Dedicated Short-Range Communications (DSRC)/Cellular Vehicle to Everything (C-V2X) proponents. In the other corner is the challenger, next-generation Wi-Fi and other unlicensed gang. What is this all about, anyway?
There is a scuffle going on around that magical 6 GHz frequency band. It started with the FCC’s proposal, of late 2018, to reallocate more than half of the 5.9 GHz band to unlicensed operations such as Wi-Fi. And it has turned into a real sparring match.
Why is this so hot? Well, 6 GHz just happens to be the top band where tolerable path loss for wireless communications exists. It is the highest sweet spot for longer-range communications and reliable performance. If we look at bands above the 6 GHz region, the issues of range, penetration and multi-path issues increase rather linearly. However, as we get past 10 GHz, elements such as atmospheric absorption come into the equation and, path loss characteristics become somewhat non-linear. However, this missive is not going to be a primer on frequency fundamentals. The real issue is that this spectrum is underutilized.
Given that the 6 GHz (and when we talk 6 GHz, it really means about 5 to 7, or so, GHz) is being put up for grabs by the FCC, there is quite a bit of excitement being generated by many sides.
It all started when the FCC, back in late 2018, began to open 1.2 GHz gigahertz of spectrum (5.925-7.125) in that band. Since then, there have been any number of proponents, and opponents, to the FCC’s plan. This is a similar slugging match as is seen in the 3.5 GHz band. If one looks at a spectrum chart, the 1.2 gigahertz of spectrum is mostly populated by fixed satellite, point-to-point microwave links, broadcast auxiliary service and cable television relay service and other fixed radio apps. There is a smattering of mobile as well.
One would think the world is coming to an end from the caterwauling going on there. Even the legislature has become involved.
Recently, a group of lawmakers sent a letter to the FCC saying they are “alarmed” by the FCC’s proposal to dink around with this spectrum. The letter came from some, 38 members of the House Committee on Transportation and Infrastructure. Their argument is that that stripping out 1.2 GHz of spectrum will have a detrimental effect on the development and deployment of safety-critical technologies. Essentially, these legislators are behind the position that the U.S. Department of Transportation (DoT) took when they addressed this with the FCC earlier. The DoT claims that allowing others to use these frequencies jeopardizes the “significant transportation safety benefits that the allocation of this band was meant to foster.”
The scenario is all too familiar. The FCC is looking to free up some spectrum for new technologies, the incumbents start whining, congress gets involved, and it becomes a free-for-all.
Is the grumbling justified? Let us go back for a moment to the 3.5 CBRS band where the CBRS Alliance tried to pull the wool over everyone’s eyes by pretending they had ownership rights to those frequencies and that they could sell them for a tidy sum. Eventually, the truth emerged, and the CBRS Alliance was sent packing with its tail between its legs.
Are the CBRS Alliance and the incumbents entitled to some compensation? Perhaps, but their initial play was a greedy money grab that, had it not been uncovered, would have put nearly $60 billion into their coffers. Giving them a paltry few million should be plenty – same with the satellite and other players for relocation. After all, they and the incumbents have been making tons of money for the last few decades.
This story is a bit different. Here, the issue is more about allowing licensed frequencies to be used in concurrence with incumbents (although that is also a part of the CBRS formula) – to use frequencies when the incumbents are not. Or use the frequencies with restrictions (such as indoor only).
However, apparently, the DoT is worried that they are going to have to give up some spectrum and they complained to their respective legislative agency to do something.
OK, enough of that. Let us unpack what the FCC is looking to do. The NPRM breaks up the 1.2 GHz as follows: 30 megahertz of the upper portion of the band for transportation and vehicle safety purposes. Repurposing the remaining lower 45 megahertz part of the band for unlicensed operations. Dedicate 20 megahertz for the deployment of C-V2X in the band, and decide on whether the remaining 10 megahertz of spectrum in the upper part of the 5.9 GHz band should be allocated for DSRC or C-V2X.
One of the issues coming out of this is that, originally, in 1999, the FCC allocated the 5.9 GHz band for DSRC under the intelligent vehicle transportation systems (ITS) program (before C-V2X came on the scene). Since C-V2X got in the game, there has been a lot of politics involved and progress has been lacking. Perhaps that is why the FCC has taken on refarming this band (it had expressed concern with the slow pace of development and deployment of vehicle safety technologies in the 5.9 GHz band). However, the legislators seem to think that the FCC is just adding to the problem since last December the FCC announced a temporary freeze on acceptance and processing of 5.9 GHz license applications.
Now, the rest of the story (to quote Paul Harvey).
Perhaps this has something to do with a recent move by Wi-Fi Forward to try and grab some underutilized spectrum for unlicensed use. Members include Google, Microsoft, Boingo, WISPA, Comcast, and Public Knowledge.
According to Wi-Fi Forward, “The 5.9 GHz band is unused in the vast majority of the country the vast majority of the time…” Enough said. They would love to see some of this spectrum rededicated to emerging technologies such as Wi-Fi 6. They go on to say, “The FCC has proposed a win-win; providing airwaves for wireless broadband and innovative automotive safety applications in a way that has garnered broad bipartisan and cross-industry support.”
Well, OK then. I can see both points of view. Vehicle-to-X communications is still fledgling. Battles are going on between the carrier-benefiting C-V2X and the IEEE standard DSRC. How this is all going to shake out is, rather, fuzzy at the moment. I can see where the DoT wants to hang onto spectrum until this shakes out.
For the emerging technologies segment, I can see them both wanting and needing more spectrum. And an elegant solution is to spectrum sharing in the high-demand frequencies. I just hope the FCC sees it the same way and finds a good compromise so everybody wins.