Questions and Answers about 5G wireless

ome foreign affairs experts are advocating a crash program on 5G technology. Their reasoning is that the Chinese are building it, and so we must start making 5G chips ourselves—one pundit called it a high-tech Manhattan project—or Huawei will take over as the world's supplier of telecommunications equipment.

This might be good advice, but first we must answer basic questions about the value of 5G. Are 5G radio waves hazardous? Is 5G really a wonderful thing? Or will it be like digital radio: an overhyped, under-specced bag of burning dog poo shoved down our throats by the FCC? If 5G is not worthwhile, or if it's so hazardous the government will cripple it, then competing with China would be foolhardy.

What's the truth? As a public service I present some questions and answers about 5G.

Q. What is this "digital radio" of which you speak?

A. Digital radio (HD radio in the USA) is a complicated scheme for broadcasting digital signals in the same band as the old-fashioned analog signals, combining the unreliability of digital with the noise and variable propagation of the AM band.

To some radio users, it probably looked like a scheme by the FCC to make radio so unpopular that people stop buying radios altogether, thereby freeing up radio spectrum that the FCC could then sell at enormous profit. They would use this money to buy new carpet for their offices.

A digital radio receiver

Governments used several tricks to accomplish this: first, they invented several different incompatible versions of it for different countries. That list is far too long to list here, but one online encyclopedia has a list. Then, just when people started buying them, some countries changed the format, making all existing radios obsolete.

Listening to digital radio is a lot like putting on noise-canceling headphones. When you turn it on, the music is still there but suddenly the hiss and noise drop out. For two minutes, it's paradise. Then, as you turn your head or move two feet in any direction, the music drops out as well. A few minutes later your batteries go dead, at which point you toss your digital radio in the closet next to your digital audio tape player, your Fitbit, and that haptic touch LED lamp that had to be rebooted once a week. Then you pick up your cell phone and listen to streaming audio instead.

Q. How much RF energy will you be exposed to, and at what frequencies?

A. As chemists say, the dose makes the poison. You can't say whether 5G is dangerous without specifying the amount of exposure and the frequency. In 5G, the existing cell phone bands, allocated in discontinuous chunks ranging from 617–960, 1427–2690, and 3300–5500 MHz, all with many gaps, called Range 1, will be expanded, and a higher band, called Range 2, will be added.

With these higher frequencies, you'll have wider bandwidths and better modulation schemes (such as 256-QAM), so you'll be able to get downlink rates up to 20 Gbit/sec and uplink rates of 10 Gbit/sec. What this means in real terms is you'll probably get 100 Mbit/sec down and 50 Mbit/sec up. The receiver automatically jumps to lower bands if the signal strength is too weak.

The power transmitted by a 5G device, referred to as EIRP, or effective isotropic radiated power, is focused in a steerable beam pointed in the general direction of the base station. The base station maximum allowed transmit power isn't settled; according to current FCC rules, the maximum power is 75 dBm (31622.8 watts) per 100 MHz^[2], but satellite companies have argued for 62 dBm (1585 watts) or even 55 dBm (316 watts).

This doesn't mean they'll use a big powerful transmitter. EIRP is transmitter power × directional gain, so a tower with a 30 dBi antenna would only need 31 watts to have an EIRP of 31 kW.

These base stations are far away from the user, so exposure from a base station will be minimal. The primary source of exposure will be the handset, which is limited by FCC rules to a maximum of 43 dBm EIRP, or about 20 watts^[3]. In a typical use it'll be more like 20 dBm, or 0.1 watt. This amount of power is needed because of the higher signal bandwidth (≈100 MHz) needed for the high speeds and to overcome the strong attenuation by air and rain.

Smartphones are designed with a metallic microwave shield that blocks radiation through the screen, so little of that RF actually goes toward the user's head. That's not for your health, but to block RF generated by the screen that could degrade the radio's sensitivity. The radiation going toward the user from 5G will be even less than 0.1 watt because the beamforming antenna, which may have 8 or more elements, will direct the energy away from you.

The low power and high attenuation means the base station will need a 64- or 256-element phased array antenna to pick up your signal if you're more than 100 meters away.

Q. Are 5G radio waves harmful?

A. When terahertz radio waves (1 THz = 0.2 mm) were first studied, they were exotic and hard to produce, and there was a great anxiety about their possible human hazard. As the technology becomes more familiar, people are growing accustomed to it and less fearful.

Even so, there are many studies claiming that millimeter waves are hazardous. This article^[4] summarizes the health and safety studies that hint at risk. Unfortunately, there's massive publication bias in the field and most studies are correlative. That means it's hard to disentangle cause and effect. To be convincing, scientists would have to demonstrate a plausible biophysical mechanism by which the photons could cause injury. So far no one has ever done this.

Radio waves cause vibrations in matter, which is to say heat. But standing next to a fire or an electrical heater exposes you to radiation at much higher energies than terahertz radio waves and at orders of magnitude higher intensity. We all know standing in front of a fire for long periods of time can produce burns and cataracts due to the heating of tissue. So the big question is not about heating, but whether millimeter waves have nonthermal effects. Some studies claim these exist and can cause cataracts, injure cell membranes, damage the blood-brain barrier, interfere with melatonin production, produce oxidative stress^[3] and cause neuropsychiatric effects^[5], sometimes at ridiculously low levels of 3 nanowatts/cm. One study even claimed they could damage trees^[6]. But there is as yet no convincing evidence that nonthermal biological effects from terahertz radiation are real, let alone harmful.

From a physics point of view, a 60 GHz radio wave has a wavelength of 5.0 millimeters, far too low in energy to couple electronically to your cells or your DNA. A plausible case could be made for nonthermal effects at extremely low frequencies (3–30 Hz) similar to the natural electrical signals in our neurons.^[7] Luckily the coupling efficiency of radio waves to the human body is extremely poor, so this is mainly a risk for people with implants such as pacemakers.

Q. Do 60 GHz radio waves disrupt the ability of hemoglobin to bind oxygen?

A. No, that is silly.

Q. Will 5G deplete your cell phone battery?

A. Transmitting at 20 watts, assuming a typical transmitter efficiency of 38%, would flatten a typical 2000 mAh cell phone battery in less than ten minutes. Cell phones will also use electronic beam-steering phased array antennas and they'll have to jump to lower frequency bands to avoid dropping the call. These extra functions all take energy. There are also factors specific to Range 2. For instance, phase noise will be higher due to the higher frequencies, which will reduce spectrum efficiency, so your phone will need to compensate. Engineers are trying to make 5G more energy-efficient, but there's no doubt your battery life will be shorter than for 4G LTE, maybe a lot shorter.

Q. Will 5G Internet of Things (IoT) be secure or will it usher in a world of devices that spy on you?

A. The, uh, second thing.

Q. Will you be able to disable 5G devices in your appliances without breaking them?

A. Ah ha hahahahahahaha . . oh, you were serious, sorry.

Q. What are the disadvantages of 5G?

A. To make 5G work, companies would have to install antennas and base stations much more densely than they are now. And the attenuation at 39 GHz is much greater than at 2.6 GHz due to rain and air absorption. 5G reception in a vehicle would be difficult due to its short range. So, despite its inability to get through walls, 5G will be mostly an indoor phenomenon.

Walls and infrared-reflecting glass windows are serious obstacles to 5G. In a home or office, you'd probably need an access point in every room. This will make it much more expensive than WiFi. Thus, 5G could easily be leapfrogged by infrared laser technology, which has the same limitations but would be much faster. Lasers can easily be diffracted to cover a wide area, but so far they cannot be steered electronically (though there are potential ways of doing that).

Q. What benefits could 5G bring us?

A.The main benefits of higher frequencies are for communication between machines or devices that don't move much. It could replace bluetooth and similar technologies, but that will only happen if companies make it easy, cheap, and reliable.

For instance, a microscope or TV could transmit uncompressed images or other data to your cell phone almost instantly. The advantage is not just the speed, but the ability of devices to talk to each other securely without complicated access codes and unreliable device pairing.

It's possible that some of those scare articles out there on 5G (like the one that claims there's no such thing as coronavirus and all those poor people in Wuhan are actually dying from 5G) are actually written by people trying to convince you that 5G skeptics are loonies. There's a dirty truth here: in the future, to make good business decisions, business leaders are going to have to know some science.

As for whether 5G is better than a flaming bag of dog poo: if you're a machine and you're immobile and you can get device-to-device communication without paying a monthly fee to the phone company, then sure. Of course we won't get a choice: all cell phone makers will include it, and young people will buy it. But if all we're doing is financing toys for consumers, is it really a national emergency? It wouldn't be the first time our competitors plowed forward with dead-end technology.

People are already talking about 6G and 7G. In 6G, you'll be able to download 71 movies in a second. People are babbling about brain-to-brain communication and hologram user interfaces. With 6G, the banana in your refrigerator will have more computing power than the Apollo spacecraft. People need to step back and ask themselves: do I really want to risk getting outwitted by a banana?

New inventions are good: just imagine how disgusting our world must have been before the invention of Kleenex. But the imagined benefits of 5G—virtual reality for gamers, remote surgery, and the ability to download a movie in two seconds—would be here now if there were a market for it. There's more than enough money in corporations if they choose to do the R&D. To regain technological leadership, we don't need to imitate China. We just need to find a way to fix corporate short-term vision.

mar 05 2020, 5:01 pm. last edited mar 07, 6:09 am