Unlicensed Millimeter Wave Spectrum

I haven’t seen it talked about a lot, but the FCC has set aside millimeter wave spectrum that can be used by anybody to provide broadband. That means that entities will be able to use the spectrum in rural America in areas that the big cellphone companies are likely to ignore.

The FCC set aside the V band (60 GHz) as unlicensed spectrum. This band provides 14 GHz of contiguous spectrum available for anybody to use. This is an interesting spectrum because it has a few drawbacks. This particular spectrum shares a natural harmonic with oxygen and thus is more likely to be absorbed in an open environment than other bands of millimeter wave spectrum. In practice, this will shorten bandwidth delivery distances a bit for the V band.

The FCC also established the E band (70/80 GHz) for public use. This spectrum will have a few more rules than the 60 GHz spectrum and there are light licensing requirements for the spectrum. These licenses are fairly easy to get for carriers, but it’s not so obvious that anybody else can get the spectrum. The FCC will get involved with interference issues with the spectrum – but the short carriage distances of the spectrum make interference somewhat theoretical.

There are several possible uses for the millimeter wave spectrum. First, it can be focused in a beam and used to deliver 1-2 gigabits of broadband for up to a few miles. There have been 60 GHz radios on the market for several years that operate for point-to-point connections. These are mostly used to beam gigabit broadband in places where that’s cheaper than building fiber, like on college campuses or in downtown highrises.

This spectrum can also be used as hotspots, as is being done by Verizon in cities. In the Verizon application, the millimeter wave spectrum is put on pole-mounted transmitters in downtown areas to deliver data to cellphones as fast as 1 Gbps. This can also be deployed in more traditional hot spots like coffee shops. The problem of using 60 GHz spectrum for this use is that there are almost no devices yet that can receive the signal. This isn’t going to get widespread acceptance until somebody builds this into laptops or develops a cheap dongle. My guess is that cellphone makers will ignore 60 GHz in favor or the licensed bands owned by the cellular providers.

The spectrum could also be used to create wireless fiber-to-the-curb like was demonstrated by Verizon in a few neighborhoods in Sacramento and a few other cities earlier this year. The company is delivering residential broadband at speeds of around 300 Mbps. These two frequency bands are higher than what Verizon is using and so won’t carry as far from the curb to homes, so we’ll have to wait until somebody tests this to see if it’s feasible. The big cost of this business plan will still be the cost of building the fiber to feed the transmitters.

The really interesting use of the spectrum is for indoor hot spots. The spectrum can easily deliver multiple gigabits of speed within a room, and unlike WiFi spectrum won’t go through walls and interfere with neighboring rooms. This spectrum would eliminate many of the problems with WiFi in homes and in apartment buildings – but again, this needs to first be built into laptops, sart TVs and other devices.

Unfortunately, the vendors in the industry are currently focused on developing equipment for the licensed spectrum that the big cellular companies will be using. You can’t blame the vendors for concentrating their efforts in the 24, 28, and 39 GHz ranges before looking at these alternate bands. There is always a bit of a catch 22 when introducing any new spectrum – a vendor needs to make the equipment available before anybody can try it, and vendors won’t make the equipment until they have a proven market.

Electronics for millimeter wave spectrum is not as easily created as equipment in lower frequency bands. For instance, in the lower spectrum bands, software-defined radios can easily change between nearby frequencies with no modification of hardware. However, each band of millimeter wave spectrum has different operating characteristics and specific antenna requirements and it’s not nearly as easy to shift between a 39 GHz radio and a 60 GHz radio – they requirements are different for each.

And that means that equipment vendors will need to enter the market if these spectrum bands are ever going to find widespread public use. Hopefully, vendors will find this worth their while because this is a new WiFi opportunity. Wireless vendors have made their living in the WiFi space and they need to be convinced that they have the same with these widely available spectrum bands. I believe that if some vendor builds indoor multi-gigabit routers and receivers, the users will come.

Millimeter Wireless Last Mile

MB 600 and 1200 SanFrancicso California (2015-054)I saw a webcast recently given by Siklu, an Israeli firm that makes what they call millimeter wave radios, which in the US are the V Band (57 – 64 GHz) and the E Band (71 – 66 GHz and 81 – 86 GHz). The company claims that their radios can be used to bring gigabit speeds to rural areas. Apparently a number of other people saw the same presentation because I received a number of emails and phone calls asking me if this could be a residential last mile solution.

The short answer is that their radios can do what they claim, but that this is not yet a solution for serving end-user customers in rural America. There are a number of issues that make this a poor solution today.

First, these are point-to-point radios. That means you need to hang a transmitter dish on a tower and another at each customer for this to work. Contrast this with point-to-multipoint radios where one transmitter on a tower can communicate with a few hundred customers. Anybody that has ever tried to lease space on towers knows that tower owners won’t allow a huge number of transmitters and would charge a fortune even if they did. Even for a carrier that owns towers, the idea of putting hundreds of dishes on one tower presents all sorts of logistical problems.

Then there is the issue of rain fade. These frequencies more or less die during heavy rain. Siklu claims this the average place in the US gets about 3 days per year of rain. But that’s not 3 continuous days, but the sum total over a year of an hour here and an hour there. I know here in Florida that we get evening rain storms almost daily during the summer and when we can’t go outside we turn to online entertainment.  A technology that dies when it rains would be hated here (which is how Floridians feel about satellite TV for the same reason).

The technology would fare a lot better in places where it doesn’t rain much. The only way to compensate for the rain fade is to send the signals for relatively short distances, less than half a mile, and that really reduces the usefulness in rural settings. And distances that short means spending a lot of money on fiber and on neighborhood towers.

Because of the nature of the frequencies used this is also a pure point-to-point technology. That means there can be nothing between the transmitter and receiver like leaves. Millimeter waves are really short and just about everything disrupts them.

Siklu is pushing this as a solution to bring gigabit speeds to rural customers. And it could do that if you can overcome the tower-crowding issue, the rain fade and the distance issues. But trying to bring that much bandwidth to end-users also means bringing a huge amount of bandwidth to the towers – and backhaul costs a lot more in rural areas than it does in metropolitan areas.

This finally leaves the issue of cost. Millimeter range radios from different manufacturers seem to cost $3,000 – $4,000 per pair. That sounds like a lot, but might still be cheaper than building rural fiber where there is no density. But when you add tower costs and other operating costs this technology is going to be expensive. And unlike fiber, which might last for 50 – 75 years, one would have to think the operational life of these radios is a decade at most, meaning periodic and costly replacement.

Siklu is not the only company making radios for the upper frequencies. Traditional companies like Fujitsu also make these radios along with a number of smaller companies like LightPointe and MI-Wave. But it looks like Siklu is the only one pushing this as a solution for rural broadband.

This is not to say that there are not uses for high-bandwidth point-to-point radios. The primary benefit of these radios is that they can transmit more bandwidth than traditional microwave radios. These might be a great alternative to fiber to bring bandwidth to a rural school or business (or to anybody willing to pay for a large commercial bandwidth product). This could be a great alternative to building fiber in really rough terrain or for getting big bandwidth from a valley floor up to a cellular tower on a hill. And Siklu has used these radios as backhaul for WiFi radio systems. But for all of these applications rain fade is still going to be an issue. At the distances that Siklu touts, the radios would be in service 99% of the time (two 9s). But carrier class products require four 9s (99.99%) or five 9s (99.999%) of up-time, and I find it unlikely that cellular companies or schools will tolerate the outages during storms.

I hear all of the time that wireless is going to be the solution to our rural bandwidth problem. But when you look at the practical issues associated with this and other wireless technologies in rural areas it’s easy to see that we are still a long way from having a big-bandwidth wireless technology that will work and be cost effective. These same upper frequencies will perform a lot better in urban environments where the distances are much shorter and companies like Google and Starry are probably going to make this frequency work in cities. But the life-cycle costs to make this work in the rural environment have to rival the cost of building fiber directly.

New Technology – June 2016

The InternetThere is a lot of recent news of technological breakthroughs that ought to have some an on telecom and broadband.

Faster Microwave Radios. A collaboration of researchers working for ACCESS (Advanced E Band Satellite Link Studies) in Germany has created a long-range microwave link at 6 Gbps speeds. The technology uses the very high E band frequencies at 71 – 76 GHz and in testing were able to create a data path between radios that were 23 miles apart. It’s the very short length of the radio waves at this frequency that allow for the very fast data rates.

The radios rely on transistor technology from Fraunhofer IAF, a firm that has been involved in several recent high-bandwidth radio technologies. The transmitting radio broadcasts at a high-power of 1 watt while the receivers are designed to detect and reconstruct very weak signals.

When perfected this could provide a lower cost way to provide bandwidth links to remote locations like towns situated in rough terrain or cellular and other radio towers located on mountaintops. This is a significant speed breakthrough for point-to-point microwaves at almost six times the speed of other existing microwave technologies.

Smarter Chip Processing. A team at MIT’s Computer Science and Artificial Intelligence Laboratory have developed a programming technique to make much better use of denser computer chips. In theory, a 64-core chip ought to be nearly 64 times faster than one with a single core, but in practice that has not been the case. Since most computer programs run sequentially (instructions and decision trees are examined one at a time, in order) most programs do not run much faster on denser chips.

The team created a new chip design they call Swarm that will speed up parallel processing and that will also make it easier to write the code for denser chips. In early tests, programs run on the swarm chip have been 3 to 18 times faster while also requiring as little as 10% of the code needed for normal processing.

1,000 Processor Chip. And speaking of denser chips, scientists at the University of California at Davis Department of Electrical and Computer Engineering have developed the first chip that contains over 1,000 separate processors. The chip has a maximum computation rate of 1.78 trillion instructions per second.

They are calling it the KiloCore chip and it’s both energy efficient and the highest clock rate chip ever developed. The chip uses IBM’s 32 nanometer technology. Each chip can run separate programming or they can be used in parallel. The scientists envision using a programming technique called the single-instruction-multiple-data approach that can break applications down into small discrete steps so that they can be processed simultaneously.

Faster Graphene Chips. Finally, US-Army funded researchers at MIT’s Institute for Soldier Nanotechnologies have developed a technology that could theoretically make chips as much as 1 million times faster than today. The new technology uses graphene and relies on the phenomenon that graphene can be used to slow light below the speed of electrons. This slowed-down light emits ‘plasmons’ of intense light that create what the scientists called an optic boom (similar to a sonic boom in air).

These plasmons could be used to greatly speed up the transmission speeds within computer chips. They have found that the optic booms can push data through graphene at about 1/300th the speed of light, a big improvement over photons through silicon.

The researchers have been able to create and control the plasmon bursts and are hoping to have a working graphene chip using the technology within two or three years.