The Physics of Millimeter Wave Spectrum

Many of the planned used for 5G rely upon the use of millimeter wave spectrum, and like every wireless technology the characteristics of the spectrum defines both the benefits and limitations of the technology. Today I’m going to take a shot at explaining the physical characteristics of millimeter wave spectrum without using engineering jargon.

Millimeter wave spectrum falls in the range of 30 GHz to 300 GHz, although currently there has been no discussion yet in the industry of using anything higher than 100 GHz. The term millimeter wave describes the shortness of the radio waves which are only a few millimeters or less in length. The 5G industry is also using spectrum that is a little longer than millimeter waves size such as 24 GHz and 28 GHz – but these frequencies share a lot of the same operating characteristics.

There are a few reasons why millimeter wave spectrum is attractive for transmitting data. The millimeter spectrum has the capability of carrying a lot of data, which is what prompts discussion of using millimeter wave spectrum to deliver gigabit wireless service. If you think of radio in terms of waves, then the higher the frequency the greater the number of waves that are being emitted in a given period of time. For example, if each wave carries one bit of data, then a 30 GHz transmission can carry more bits in one second than a 10 GHz transmission and a lot more bits than a 30 MHz transmission. It doesn’t work exactly like that, but it’s a decent analogy.

This wave analogy also defines the biggest limitation of millimeter wave spectrum – the much shorter effective distances for using this spectrum. All radio waves naturally spread from a transmitter, and in this case thinking of waves in a swimming pool is also a good analogy. The further across the pool a wave travels, the more dispersed the strength of the wave. When you send a big wave across a swimming pool it’s still pretty big at the other end, but when you send a small wave it’s often impossible to even notice it at the other side of the pool. The small waves at millimeter length die off faster. With a higher frequency the waves are also closer together. Using the pool analogy, that means that the when waves are packed tightly together then can more easily bump into each other and become hard to distinguish as individual waves by the time they get to the other side of the pool. This is part of the reason why shorter millimeter waves don’t carry as far as other spectrum.

It would be possible to send millimeter waves further by using more power – but the FCC limits the allowed power for all radio frequencies to reduce interference and for safety reasons. High-power radio waves can be dangerous (think of the radio waves in your microwave oven). The FCC low power limitation greatly reduces the carrying distance of this short spectrum.

The delivery distance for millimeter waves can also be impacted by a number of local environmental conditions. In general, shorter radio waves are more susceptible to disruption than longer spectrum waves. All of the following can affect the strength of a millimeter wave signal:

  • Mechanical resonance. Molecules of air in the atmosphere naturally resonate (think of this as vibrating molecules) at millimeter wave frequencies, with the biggest natural interference coming at 24 GHz and 60 GHz.
  • Atmospheric absorption. The atmosphere naturally absorbs (or cancels out) millimeter waves. For example, oxygen absorption is highest at 60 GHz.
  • Millimeter waves are easily scattered. For example, the millimeter wave signal is roughly the same size as a raindrop, so rain will scatter the signal.
  • Brightness temperature. This refers to the phenomenon where millimeter waves absorb high frequency electromagnetic radiation whenever they interact with air or water molecules, and this degrades the signal.
  • Line-of-sight. Millimeter wave spectrum doesn’t pass through obstacles and will be stopped by leaves and almost everything else in the environment. This happens to some degree with all radio wavs, but at lower frequencies (with longer wavelengths) the signal can still get delivered by passing through or bouncing off objects in the environment (such as a neighboring house and still reach the receiver. However, millimeter waves are so short that they are unable to recover from collision with an object between the transmitter and receiver and thus the signal is lost upon collision with almost anything.

One interesting aspect of these spectrum is that the antennas used to transmit and receive millimeter wave spectrum are tiny and you can squeeze a dozen or more antenna into a square inch. One drawback of using millimeter wave spectrum for cellphones is that it takes a lot of power to operate multiple antennas, so this spectrum won’t be practical for cellphones until we get better batteries.

However, the primary drawback of small antennas is the small target area used to receive a signal. It doesn’t take a lot of spreading and dispersion of the signal to miss the receiver. For spectrum in the 30 GHz range the full signal strength (and maximum bandwidth achievable) to a receiver can only carry for about 300 feet. With greater distances the signal continues to spread and weaken, and the physics show that the maximum distance to get any decent bandwidth at 30 GHz is about 1,200 feet. It’s worth noting that a receiver at 1,200 feet is receiving significantly less data than one at a few hundred feet. With higher frequencies the distances are even less. For example, at 60 GHz the signal dies off after only 150 feet. At 100 GHz the signal dies off in 4 – 6 feet.

To sum all of this up, millimeter wave transmission requires a relatively open path without obstacles. Even in ideal conditions a pole-mounted 5G transmitter isn’t going to deliver decent bandwidth past about 1,200 feet, with the effective amount of bandwidth decreasing as the signal travels more than 300 feet. Higher frequencies mean even less distance. Millimeter waves will perform better in places with few obstacles (like trees) or where there is low humidity. Using millimeter wave spectrum presents a ton of challenges for cell phones – the short distances are a big limitation as well as the extra battery life needed to support extra antennas. Any carrier that talks about deploying millimeter wave in a way that doesn’t fit the basic physics is exaggerating their plans.

When Will Small ISPs Offer Wireless Loops?

I wrote last week about what it’s going to take for the big wireless companies to offer 5G fixed wireless in neighborhoods. Their biggest hurdle is going to be the availability of fiber deep inside neighborhoods. Today I look at what it would take for fiber overbuilders to integrate 5G wireless loops into their fiber networks. By definition, fiber overbuilders already build fiber deep into neighborhoods. What factors will enable fiber overbuilders to consider using wireless loops in those networks?

Affordable Technology. Number one on the list is cheaper technology. There is a long history in the wireless industry where new technologies only become affordable after at least one big company buys a lot of units. Fifteen years ago the FCC auctioned LMDS and MMDS spectrum with a lot of hoopla and promise. However, these spectrum bands were barely used because no big companies elected to use them. The reality of the manufacturing world is that prices only come down with big volumes of sales. Manufacturers need to have enough revenue to see them through several rounds of technical upgrades and tweaks, which are always needed when fine-tuning how wireless gear works in the wild.

Verizon is the only company talking about deploying a significant volume of 5G fixed wireless equipment. However, their current first-generation equipment is not 5G compliant and they won’t be deploying actual 5G gear for a few years. Time will tell if they buy enough gear to get equipment prices to an affordable level for the rest of the industry. We also must consider that Verizon might use proprietary technology that won’t be available to others. The use of proprietary hardware is creeping throughout the industry and can be seen with gear like data center switches and Comcast’s settop boxes. The rest of the industry won’t benefit if Verizon takes the proprietary approach – yet another new worry for the industry.

Life Cycle Costs. Anybody considering 5G also needs to consider the full life cycle costs of 5G versus fiber. An ISP will need to compare the life cycle cost of fiber drops and fiber electronics versus the cost of the 5G electronics. There are a couple of costs to consider:

  • We don’t know what Verizon is paying for gear, but at the early stage of the industry my guess is that 5G electronics are still expensive compared to fiber drops.
  • Fiber drops last for a long time. I would expect that most of the fiber drops built twenty years ago for Verizon FiOS are still going strong. It’s likely that 5G electronics on poles will have to replaced or upgraded every 7 – 10 years.
  • Anybody that builds fiber drops to homes knows that over time that some of those drops are abandoned as homes stop buying service. Over time there can be a sizable inventory of unused drops that aren’t driving any revenue – I’ve seen this grow to as many as 5% of total drops over time.
  • Another cost consideration is maintenance costs. We know from long experience that wireless networks require a lot more tinkering and maintenance effort than fiber networks. Fiber technology has gotten so stable that most companies know they can build fiber and not have to worry much about maintenance for the first five to ten years. Fiber technology is getting even more stable as many ISPs are moving the ONTs inside the premise. That’s going to be a hard to match with 5G wireless networks with differing temperatures and precipitation conditions.

We won’t be able to make this cost comparison until 5G electronics are widely available and after a few brave ISPs suffer through the first generation of the technology.

Spectrum. Spectrum is a huge issue. Verizon and other big ISPs are going to have access to licensed spectrum for 5G that’s not going to be available to anybody else. It’s likely that companies like Verizon will get fast speeds by bonding together multiple bands of millimeter wave spectrum while smaller providers will be limited to only unlicensed spectrum bands. The FCC is in the early stages of allocating the various bands of millimeter wave spectrum, so we don’t yet have a clear picture of the unlicensed options that will be available to smaller ISPs.

Faster speeds. There are some fiber overbuilders that already provide a gigabit product to all customers, and it’s likely over time that they will go even faster. Verizon is reporting speeds in the first 5G deployments between 300 Mbps and a gigabit, and many fiber overbuilders are not going to want a network where speeds vary by local conditions, and from customer to customer. Wireless speeds in the field using millimeter wave spectrum are never going to be as consistently reliable and predictable as a fiber-based technology.

Summary. It’s far too early to understand the potential for 5G wireless loops. If the various issues can be clarified, I’m sure that numerous small ISPs will consider 5G. The big unknowns for now are the cost of the electronics and the amount of spectrum that will be available to small ISPs. But even after those two things are known it’s going to be a complex decision for a network owner. I don’t foresee any mad rush by smaller fiber overbuilders to embrace 5G.

Are Millimeter Wave Radios Safe?

Deep inside the filing of the recent docket at the FCC that resulted in eased access to poles for 5G providers were comments that warned about the unknown health impacts of millimeter wave radiation. A group of 225 scientists from 41 countries filed comments in Dockets No. 15-79 asking that the FCC be cautious in implementing millimeter wave radiation without further scientific research into the impacts of prolonged exposure of the radiation to humans. These scientists have all published peer-reviewed papers on the topic.

As scientists are wont to do, their wording sounds cautious, but in scientific language is a stern warning: “There is scientific evidence to cause concern among independent scientists, that this new infrastructure, on top of existing electrical and wireless infrastructures, will cause more harm to mankind and nature . . . The FCC needs to critically consider the potential impact of the 5th generation wireless infrastructure on the health and safety of the U.S. population before proceeding to deploy this infrastructure.”

I looked around the web to find some of the research that’s been done in this area in the past. A quick web search showed:

·         The biggest impact of millimeter wave radiation is on the skin and 90% of the transmitted power is absorbed by the dermis and epidermis layers of the skin – meaning concerns about skin cancer.

·          A 1994 study showed that low levels of millimeter radiation created lens opacity in rats, which is linked to cataracts.

·         A 1992 Russian study found that frequencies between 53-78 GHz caused overall stress in rats that manifested by an increase in arrhythmia and other changes to heart rates.

·         A 2002 Russian study found that exposure to low level 42 GHz radiation had a profound impact on the overall immune systems in rats.

·         A 2016 Armenian study observed that millimeter wave radiation created changes in the cells of bacteria. They postulated that the radiation could do the same to humans. This study concluded that changes to bacteria could change result in increasing drug resistant.

·         Another Armenian study showed that the impact to plants might be even greater than to animals.

·         Dr. Joel Moskowitz of UC Berkeley says that the impacts of all of these other studies might be understated since 5G uses pulsed frequencies. The studies were all done using constant frequency and Dr. Moskowitz has shown that pulsed frequencies magnify the impact of radiation on organisms.

One of the handful of current uses of millimeter wave radiation is in airport scanners, which use frequencies between 24 – 30 GHz. Numerous studies have shown that the likely exposure from these scanners is safe, but made the conclusion based upon the relative short burst of exposure. The issue that has scientists concerned about 5G is continuous transmission from poles in front of homes, and perhaps eventually building some of this frequency into cellphones.

Obviously, no study has yet shown a direct health impact from pole-mounted 5G transmitters since they are just now starting to see their first deployments. The scientific evidence of the dangers of the prolonged low-level radiation has a lot of people concerned. I’ve been contacted by several groups that are starting to alert their local officials of this danger (the inbox of a blogger can be really interesting). Nationwide several local politicians have jumped on the issue.

The question these local groups are asking is if there is any way to use the health concerns to try to block 5G deployment in their neighborhoods. It looks to me like the recent FCC order for allowing small cell sites on poles doesn’t contain much ambiguity – pole owners have a federal mandate to connect the 5G devices. However, that order is being challenged in court by numerous states and cities and I imagine that the health concerns are going to be one of the issues raised in those appeals – with the primary legal tactic challenging if the FCC has the jurisdiction to override cities on pole issues.

Interestingly, Verizon has announced a timeline that seems to be going full bore on installation of 5G transmitters. The industry is usually cautious about relying on any FCC order until it’s been vetted by the courts, but perhaps Verizon is only concentrating on 5G deployment in cities that have invited them to deploy, like Sacramento. It won’t be surprising to see cities ask for an injunction against deployment until the courts decide on the issues.

The Millimeter Wave Auctions

The FCC will soon hold the auction for two bands of millimeter wave spectrum. The auction for the 28 GHz spectrum, referred to as Auction 101, will begin on November 14 and will offer 3,072 licenses in the 27.5 to 28.35 GHz band. The auction for 24 GHz, referred to as Auction 102, will follow at the end of Auction 101 and will offer 2,909 licenses in the 24.25 to 24.45 GHz and the 24.75 to 25.25 GHz bands.

This is the spectrum that will support 5G high-bandwidth products. The most unusual aspect of this auction is that the FCC is offering much wider channels than ever before, making the spectrum particularly useful for broadband deployment and also for the frequency slicing needed to serve multiple customers. The Auction 101 includes two blocks of 425 MHz and is being auctioned by County. Auction 102 will include seven blocks of 100 MHz and will be auctioned by Partial Economic Areas (PEA). PEAs divide the country into 416 zones, grouped by economic interest. They vary from the gigantic PEA that encompasses all of the New York City and the surrounding areas in Connecticut and New Jersey to PEAs that are almost entirely rural.

That means that every part of the country could see as many as seven different license holders, assuming that somebody pursues all of the spectrum. It’s likely, though, that there will be rural areas where nobody buys the spectrum. It will be interesting to look at the maps when the auctions are done.

This is the spectrum that can be used to support the fixed wireless broadband like Verizon is now deploying from poles. The spectrum has the capability of delivering big bandwidth, but for relatively short distances of 1,000 feet or more. The spectrum can also be used as a focused beam to deliver several gigabits of bandwidth for a mile to a single point, such as what Webpass is currently doing to serve downtown high-rise apartment buildings.

The industry consensus is that this spectrum will find limited use in rural areas for now since it’s hard, with existing technology, to deploy a 5G transmitter site that might only reach a few potential customers.

The FCC has released the names of the companies that will be bidding in the auction. As expected the big cellular companies are there and AT&T, Verizon and T-Mobile are bidding. Absent is Sprint, but the speculation is that they are relying on the merger with T-Mobile and have elected to sit out the auction.

The big telcos are also in the auctions with AT&T, Verizon, Frontier and Windstream all participating. Absent is CenturyLink, which further strengthens the belief that they are no longer pursuing residential broadband.

The only cable company of any size in the auction is Cox Communications. The other big companies like Comcast, Charter, Altice and many others are sitting out the auction. It doesn’t make sense for a cable company to deploy the spectrum where they are already the incumbent broadband provider. Wireless technology for end users would complete directly with their own networks. Since Cox is privately held it’s hard to know their plans, but one use of the spectrum would be to expand in the areas surrounding their current footprint or to move into new markets. It’s costly to expand their hybrid-fiber networks and 5G wireless might be a cheaper way to move into new markets.

There are some rural companies that are bidding for spectrum. It’s hard to know if the rural telcos and cooperatives on the list want to use the spectrum to enhance broadband in their own footprint or if they want to use the spectrum to expand into larger nearby markets. One of the most interesting companies taking part in both auctions is US Cellular. They are the fifth largest cellular company after the big four and serve mostly rural markets. They’ve already made public announcements about upgrading to the most current version of 4G LTE and it will be interesting to see how they use this spectrum.

Verizon’s Case for 5G, Part 2

This is a second in a series of blogs that look at Verizon’s list of ways that the company thinks they can monetize 5G. The first blog looked at medical applications. Today I look at the potential market use for 5G for retail.

Verizon’s retail vision is interesting. They picture stores that offer an individualized shopping experience that also uses augmented and virtual reality to communicate with and sell to customers. This is not a new idea and the idea of using 3D graphics and holograms in stores was one of the first future visions touted by augmented reality developers. We are just now on the verge of having technology that could make this possible.

Verizon obviously envisions using 3G bandwidth to enable these applications. Stores will want the flexibility to be able to put displays anywhere in the store, and change them at will, so doing this wirelessly would be a lot cheaper than stringing fiber all over stores. Streaming holograms requires a lot of bandwidth, so this seems like a natural application for millimeter wave spectrum. Our current cellular frequencies are not sufficient to support holograms.

The new 5G standard calls for the use of millimeter wave spectrum to deliver gigabit data paths wirelessly indoors. These frequencies don’t pass through walls, so transmitters in the ceilings could be used to beam down to displays anywhere in a store.

Verizon envisions companies using Verizon licensed spectrum. However, the FCC has already set aside several bands of millimeter wave spectrum for public use and there will soon be a whole industry developing millimeter wave routers for use as WANs – likely the same companies that today make WiFi routers. I have a hard time seeing how Verizon will have any market advantage over the many other companies that will be developing millimeter wave WANs using public spectrum.

The personalized shopping experience is a different matter. Verizon is envisioning a network that identifies customers as they enter the store, either through facial recognition, through cell phone signals, or perhaps because customers voluntarily use an app that identifies them. Verizon envisions using the 5G network tied into big data applications to enable stores to craft a unique shopping experience for each customer. For regular customers that would meaning using a profile based on their past shopping history, and for everybody else it means using a profile cobbled together from the big data all of the ISPs are gathering on everybody.

Verizon and the other big ISPs have invested in subsidiaries that can crunch big data and they are hungry to snag a piece of the advertising revenue that Google has monetized so well. Using big data to enhance the shopping experience will likely be popular with the kinds of shoppers who use in-store apps today. Customers can be offered live specials as they walk down aisles, with offers personalized to them. This could be tied into the holographic product displays and other in-store advertising systems.

However, this application could quickly get creepy if it is done for all shoppers. I know I would never visit a store a second time that recognizes me as I walk in the door and that uses a cloud-based profile of me to try to direct my shopping. Perhaps my distaste for this kind of intrusion is a generational thing and it might be attractive to younger generations of shoppers – but I would find it invasive.

There are physical issues to consider with this kind of network. I tried to use my cellphone from the rear of a grocery store yesterday and I had zero bars of data and couldn’t connect to the voice network. Dead spots can be fixed by installing one or more small cell sites inside a store to reach all parts of a store – something that will become more affordable over time.

Verizon will have an advantage if smartphones are a needed component of the customized shopping experience. But the shopping applications don’t necessarily require smartphones. For example, screens built into shopping carts could fulfill the same functions and not tie a retailer to pay Verizon.

One of the biggest hurdles I see for Verizon’s vision is that retail stores are slow adapters of new technology. This kind of application would likely start at the big nationwide chains like Target or Walmart, but it’s a decades-long sales cycle to get stores everywhere to accept this. Verizon’s vision also assumes that stores want this – but they are already competing for their own survival against online shopping and fast delivery and they might be leery about using a technology that could drive away a portion of their customer base. From what I can see, stores that provide a personal touch are the ones that are competing best with online shopping.

To summarize, Verizon is espousing a future vision of retail where the retailer can interact electronically with shoppers on a personalized basis. The first big hurdle will be convincing retailers to try the idea, because it could easily go over the top and be viewed by the public as invasive. More importantly, licensed 5G from Verizon isn’t the only technology that can deliver Verizon’s vision since there will be significant competition in the indoor millimeter wave space. This is one of those ideas that might come to pass, but there are enough hurdles to overcome that it may never become reality.

Will 5G Phones Need WiFi?

Our cellular networks have become heavily reliant on customers using WiFi. According to Cisco’s latest Virtual Network Index about 60% of the data generated from cellphones is carried over WiFi and landline broadband connections. Most of us have our cellphones set to grab WiFi networks that we are comfortable with, particularly in the home and office.

The move to use WiFi for data was pushed by the cellular companies. As recently as just a few years ago they were experiencing major congestion at cell sites. This congestion was due to a combination of cell sites using older versions of 4G technology and of inadequate backhaul data pipes feeding many cell sites. The cellular carriers and manufacturers made it easy to switch back and forth between cellular and WiFi and most people quickly got adept at minimizing data usage on the cellular network.

Many people have also started using WiFi calling. This is particularly valuable to those who live or work in a building with poor indoor cellular coverage, and WiFi calling allows a phone to process voice through the WiFi connection. But this has always been a sketchy technology and WiFi calling is often susceptible to poor voice quality and unexpected call droppage due to WiFi fluctuations. WiFi calling also doesn’t roam, so anybody walking out of the range of their WiFi router automatically drops the call.

However, recently we’ve seen possibly the start of a trend of more broadband traffic staying on the cellular network. In a recent blog I cited evidence that unlimited cellular customers are using less WiFi and are instead staying on their cellular data network even when WiFi is available. Since most people use WiFi to preserve usage on their cellular data plans, as more people feel comfortable about not hitting a data caps we ought to see many people sticking more to cellular.

5G ought to make it even easier to keep traffic on the cellular network. The new standard will make it easier to make and hold a connection to a cell site due to a big increase in the number of possible simultaneous connections available at each cell site. This should finally eliminate not being able to make a cellular connection in crowded locations.

The 5G improvements are also going to increase the available bandwidth to cellphones through the use of multiple antennas and frequencies. The expectations are that cellphone download speeds will creep up with each incremental improvement in the coming 5G networks and that speeds will slowly improve over the next decade.

Unfortunately this improved performance might not make that big of a difference within buildings with poor cellular coverage today, because for the most part the frequencies used for 5G cellular will be the same ones used today. We keep reading about the coming use of millimeter waves, but the characteristics of those frequencies, such as the short distances covered are going to best fit urban areas and it’s likely to be a long while until we see these frequencies being used everywhere in the cellular networks. Even where used, those higher frequencies will have an even harder time penetrating buildings than today’s lower frequencies.

Overall, the improvements of 5G ought to mean that cellular customers ought to be able to stay more easily with cellular networks and not need WiFi to the same extent as today. A transition to less use of WiFi will be accelerated if the cellular marketing plans continue to push unlimited or large data-cap plans.

This all has big implications on network planning. Today’s cellular networks would be instantly swamped if people stopped using WiFi. The use of cellular data is also growing at a much faster pace than the use of landline data. Those two factors together portends a blazingly fast growth in the backhaul needed for cell sites. We are likely to see geometric rates of growth, making it expensive and difficult for the cellular carriers to keep up with data demand. It’s sounding to me like being a cellular network planner might be one of the hardest jobs in the industry right now.

Gigabit LTE

Samsung just introduced Gigabit LTE into the newest Galaxy S8 phone. This is a technology with the capability to significantly increase cellular speeds, and which make me wonder if the cellular carriers will really be rushing to implement 5G for cellphones.

Gigabit LTE still operates under the 4G standards and is not an early version of 5G. There are three components of the technology:

  • Each phone has as 4X4 MIMO antenna, which is an array of four tiny antennae. Each antenna can make a separate connection to the cell tower.
  • The network must implement frequency aggregation. Both the phone and the cell tower must be able to combine the signals from the various antennas into one coherent data path.
  • Finally, the new technology utilizes the 256 QAM (Quadrature Amplitude Modulation) protocol which can cram more data into the cellular data path.

The amount of data speeds that can be delivered to a given cellphone under this technology is going to rely on a number of different factors:

  • The nearest cell site to a customer needs to be upgraded to the technology. I would speculate that this new technology will be phased in at the busiest urban cell sites first, then to busy suburban sites and then perhaps to less busy sites. It’s possible that a cellphone could make connections to multiple towers to make this work, but that’s a challenge with 4G technology and is one of the improvements promised with 5G.
  • The amount of data speed that can be delivered is going to vary widely depending upon the frequencies being used by the cellular carrier. If this uses existing cellular data frequencies, then the speed increase will be a combination of the impact of adding four data streams together, plus whatever boost comes from using 256 QAM, less the new overheads introduced during the process of merging the data streams. There is no reason that this technology could not use the higher millimeter wave spectrum, but that spectrum will use different antennae than lower frequencies.
  • The traffic volume at a given cell site is always an issue. Cell sites that are already busy with single antennae connections won’t have the spare connections available to give a cellphone more than one channel. Thus, a given connection could consist of one to four channels at any given time.
  • Until the technology gets polished, I’d have to bet that this will work a lot better with a stationary cellphone rather than one moving in a car. So expect this to work better in downtowns, convention centers, etc.
  • And as always, the strength of a connection to a given customer will vary according to how far a customer is from the cell site, the amount of local interference, the weather and all of those factors that affect radio transmissions.

I talked to a few wireless engineers and they guessed that this technology using existing cellular frequencies might create connections as fast as a few hundred Mbps in ideal conditions. But they could only speculate on the new overheads created by adding together multiple channels of cellular signal. There is no doubt that this will speed up cellular data for a customer in the right conditions, with the right phone near the right cell site. But adding four existing cellular signals together will not get close to a gigabit of speed.

It will be interesting to see how the cellular companies market this upgrade. They could call this gigabit LTE, although the speeds are likely to fall far short of a gigabit. They could also market this as 5G, and my bet is that at least a few of them will. I recall back at the introduction of 4G LTE that some carriers started marketing 3.5G as 4G, well before there were any actual 4G deployments. There has been so much buzz about 5G now for a year that the marketing departments at the cellular companies are going to want to tout that their networks are the fastest.

It’s always an open question about when we are going to hear about this. Cellular companies run a risk in touting a new technology if most bandwidth hungry users can’t yet utilize it. One would think they will want to upgrade some critical mass of cell sites before really pushing this.

It’s also going to be interesting to see how faster cellphone speeds affect the way people use broadband. Today it’s miserable to surf the web on a cellphone. In a city environment most connections are more than 10 Mbps today, but it doesn’t feel that fast because of shortfalls in the cellphone operating systems. Unless those operating systems get faster, there might not be that much noticeable different with a faster connection.

Cellphones today are already capable of streaming a single video stream, although with more bandwidth the streaming will get more reliable and will work under more adverse conditions.

The main impediment to faster cellphones really changing user habits is the data plans of the cellular carriers. Most ‘unlimited’ plans have major restrictions on using a cellphone to tether data for other devices. It’s that tethering that could make cellular data a realistic substitute for a home landline connection. My guess is until we reach a time when there are ubiquitous mini-cell sites spread everywhere that the cellular carriers are not going to let users treat cellular data the same as landline data. Until cellphones are allowed to utilize the broadband available to them, faster cellular data speeds might not have much impact on the way we use our cellphones.

5G Networks and Neighborhoods

With all of the talk about the coming 5G technology revolution I thought it might be worth taking a little time to talk about what a 5G network means for the aesthetics of neighborhoods. Just what might a street getting 5G see in new construction that is not there today?

I live in Asheville, NC and our town is hilly and has a lot of trees. Trees are a major fixture in lots of towns in America, and people plant shade trees along streets and in yards even in states where there are not many trees outside of towns.

5G is being touted as a fiber replacement, capable of delivering speeds up to a gigabit to homes and businesses. This kind of 5G (which is different than 5G cellular) is going to use the millimeter wave spectrum bands. There are a few characteristics of that spectrum that defines how a 5G network must be deployed. This spectrum has extremely short wavelengths, and that means two things. First, the signal isn’t going to travel very far before the signal dissipates and grows too weak to deliver fast data. Second, these short wavelengths don’t penetrate anything. They won’t go through leaves, walls, or even through a person walking past the transmitter – so these frequencies require a true unimpeded line-of-sight connection.

These requirements are going to be problematic on the typical residential street. Go outside your own house and see if there is a perfect line-of-sight from any one pole to your home as well as to three or four of your neighbors. The required unimpeded path means there can be no tree, shrub or other impediment between the transmitter on a pole and each home getting this service. This may not be an issue in places with few trees like Phoenix, but it sure doesn’t look very feasible on my street. On my street the only way to make this work would be by imposing a severe tree trimming regime – something that I know most people in Asheville would resist. I would never buy this service if it meant butchering my old ornamental crepe myrtle. And tree trimming must then be maintained into the future to keep new growth from blocking signal paths.

Even where this can work, this is going to mean putting up some kind of small dish on each customer location in a place that has line-of-sight to the pole transmitter. This dish can’t go just anywhere on a house in the way that satellite TV dishes can often be put in places that aren’t very noticeable. While these dishes will be small, they must go where the transmitter can always see them. That’s going to create all sorts of problems if this is not the place in the home where the existing wiring comes into the home. In my home the wiring comes into the basement in the back of the house while the best line-of-sight options are in the front – and that is going to mean some costly new wiring by an ISP, which might negate the cost advantage of the 5G.

The next consideration is back-haul – how to get the broadband signals into and out of the neighborhood. Ideally this would be done with fiber. But I can’t see somebody spending the money to string fiber in a town like Asheville, or in most residential neighborhoods just to support wireless. The high cost of stringing fiber is the primary impediment today for getting a newer network into cities.

One of the primary alternatives to stringing fiber is to feed neighborhood 5G nodes with point-to-point microwave radio shots. In a neighborhood like mine these won’t be any more practical that the 5G signal paths. The solution I see being used for this kind of back-haul is to erect tall poles of 100’ to 120’ to provide a signal path over the tops of trees. I don’t think many neighborhoods are going to want to see a network of tall poles built around them. And tall poles still suffer the same line-of-sight issues. They still have to somehow beam the signal down to the 5G transmitters – and that means a lot more tree trimming.

All of this sounds dreadful enough, but to top it off the network I’ve described would be needed for a single wireless provider. If more than one company wants to provide wireless broadband then the number of devices multiply accordingly. The whole promise of 5G is that it will allow for multiple new competitors, and that implies a town filled with multiple wireless devices on poles.

And with all of these physical deployment issues there is still the cost issue. I haven’t seen any numbers for the cost of the needed neighborhood transmitters that makes a compelling business case for 5G.

I’m the first one to say that I’ll never declare that something can’t work because over time engineers might find solutions for some of these issues. But where the technology sits today this technology is not going to work on the typical residential street that is full of shade trees and relatively short poles. And that means that much of the talk about gigabit 5G is hype – nobody is going to be building a 5G network in my neighborhood, for the same sorts of reasons they aren’t building fiber here.

Please Stop Hinting at Gigabit Cellular

SONY DSCLast week there were several press releases announcing that AT&T was working with a major corporation to provide a test of 5G technology. A few days later the industry found out that the company taking part in the test is Intel, which will be making the chips involved in the tests. Intel will apparently be beta testing early units for providing high-speed bandwidth at one of their locations.

It really bothers me every time I see one of these announcements, because the whole industry seems to have bought into the hype from companies like AT&T that conflate two totally different technologies under the name of 5G. The AT&T and Intel test is going to be for a technology to provide faster indoor wireless connections using millimeter wave spectrum in competition with WiFi.

But most of the world sees the term ‘5G’ and assumes it means the next generation of cellular technology. And that means that most people reading about the AT&T press release think that we are just a few years away from having gigabit cell phones. And we are not.

I don’t know who decided to use the term 5G for two drastically different technologies. My guess is that the confusion has been purposefully sown by AT&T and Verizon. Certainly the average consumer is more likely to pay attention if they think their cell phones will soon be blazingly fast.

But this kind of confusion has real life negative consequences. Politicians and decision makers read these articles and assume that there is a fast cellular alternative coming in a few years – and this allows them to take the issue of faster landline broadband off the plate. It’s not a hard mistake to make and I’ve even seen this same confusion from smaller telco and cable company owners who see the headlines but don’t dig deeper. I assume one reason this confusion is being promoted is that both AT&T and Verizon benefit if fewer companies are investing in fiber last-mile networks to compete with them.

The millimeter wave technology that Intel is going to alpha test is to provide gigabit speed wireless connections for very short distances. It’s a technology that can distribute gigabit speed connections around an office suite, for example. The gigabit speeds are good for about 60 feet from a transmitter which fits the indoor environment and desire for speed. But even in that environment the technology has a major limitation in that these frequencies won’t pass through almost anything. Even a wall or possibly even a cubicle divider can kill the signal. And so these early tests are probably to find the best way to scatter the bandwidth around the office to reach all the nooks and crannies found in the real world.

This technology is being called 5G because the technology will use the 5G standard, even though that standard is not yet developed. But we already know that the 5G standard will have one major benefit over WiFi. WiFi is a bandwidth sharing protocol which gives equal preference to every transmission. If one WiFi device in an office is demanding a large amount of bandwidth and another data-hungry device comes online the protocol automatically shares the bandwidth between the two devices. 5G will allow the router to guarantee the bandwidth at different levels to each device without sharing.

But this millimeter wave trial at Intel has almost nothing else in common with cellular data transmissions other than the fact that they use the same standard. Cellular networks use much lower frequencies which have been chosen because they travel a decent distance from a cell tower, and for the most part cellular frequencies are good at penetrating walls and trees and other obstacles.

Cellular networks are not going to use millimeter wave frequencies to get to cellphones. To make that work would require mini-cell sites of some sort every hundred feet or so. That can be made to work, but really is a totally impractical application in the real world unless we someday find a way to put little cell sites literally everywhere. Using these frequencies for cellular would be a niche application that might only work in a place like a conference center and the cellphone companies are not going to automatically build this technology into cellphones. It takes chip space, extra power and new antennae to add another frequency and nobody is going to add that extra cost to a cellphone until most of the world can use it – and that literally could take many decades, if ever.

Instead, the 5G standard will be used in cellphones to improve data speeds – but not at anything near to gigabit speeds. The early versions of the 5G specification have a goal of being able to deliver 50 Mbps data speeds to large numbers of phones out of a cell site. That’s a 4 – 5 times increase in cellular speeds from today and is going to make it a lot more enjoyable to browse the web from a cellphone. But 50 Mbps is very different than gigabit cellular speeds. The big companies really need have to stop implying there is going to be gigabit cellular. That is extremely misleading and is very far from the truth.

My Thoughts on AT&T AirGig

PoleBy now most of you have seen AT&T’s announcement of a new wireless technology they are calling AirGig. This is a technology that can bounce millimeter wave signals along a series of inexpensive plastic antennae perched at the top of utility poles.

The press release is unclear about the speeds that might be delivered from the technology. The press release says it has the potential to deliver multi-gigabit speeds. But at the same time it talks about delivering 4G cellular as well as 5G cellular and fixed broadband. The 4G LTE cellular standard can deliver about 15 Mbps while the 5G cellular standard (which is still being developed) is expected to eventually increase cellular speeds to about 50 Mbps. So perhaps AT&T plans to use the technology to deploy micro cell sites while also being able to deliver millimeter wave wireless broadband loops. The link above includes a short video which doesn’t clarify this issue very well.

Like any new radio technology, there is bound to be a number of issues involved with moving the technology from the lab to the field. I can only speculate at this point, but I can foresee the following as potential issues with the millimeter wave part of the technology:

  • The video implies that the antennas will be used to deliver bandwidth using a broadcast hotspot. I’m not entirely sure that the FCC will even approve this spectrum to be used in this manner – this is the same spectrum used in microwave ovens. It can be dangerous to work around for linemen climbing poles and it can create all sorts of havoc by interfering with cable TV networks and TV reception.
  • Millimeter wave spectrum does not travel very far when used as a hot spot. This spectrum has high atmospheric attenuation and is absorbed by gases in the atmosphere. When focused in a point-to-point the spectrum can work well to about half a mile. But in a hot spot mode it’s good, at best, for a few hundred feet and loses bandwidth quickly with distance traveled. The bandwidth is only going to reach to homes that are close to the pole lines.
  • Millimeter wave spectrum suffers from rain fade and during a rain storm almost all of the spectrum is scattered.
  • The spectrum doesn’t penetrate foliage, or much of anything else. So there is going to have to be a clear path between the pole unit and the user. America is a land of residential trees and even in the open plains people plant trees closely around their house as a windbreak.
  • The millimeter wave spectrum won’t penetrate walls, so this will require some sort of outdoor receiver to catch millimeter wave signals.
  • I wonder how the units will handle icing. Where cables tend to shake ice off within a few days, hardware mounted on poles can be ice-covered for months.
  • The technology seems to depend on using multiple wireless hops to go from unit to unit. Wireless hops always introduce latency into the signal and it will be interesting to see how much latency is introduced along rural pole runs.
  • For any wireless network to deliver fast speeds it has to be connected somewhere to fiber backhaul. There are still many rural counties with little or no fiber.

We have always seen that every wireless technology has practical limitations that make it suitable for some situations and not others. This technology will be no different. In places where this can work it might be an incredible new broadband solution. But there are bound to be situations where the technology will have too many problems to be practical.

I’ve seen speculation that one of the major reasons for this press release is to cause a pause to anybody thinking of building fiber. After all, why should anybody build fiber if there is cheap multi-gigabit wireless coming to every utility pole? But with all of the possible limitations mentioned above (and others that are bound to pop up in the real world) this technology may only work in some places, or it might not work well at all. This could be the technology we have all been waiting for or it could be a flop. I guess we’ll have to wait and see.