5G Wireless: The ‘G’ Stands For ‘Glass’

What, exactly, do we mean when we say that a network is “wireless?”

The word’s well over a hundred years old, having been in common use even before Guglielmo Marconi founded The Wireless Telegraph And Signal Company in 1897 to exploit the then-new medium’s commercial potential. In those early days, the meaning of “wireless” was straightforward: it referred to the technology of sending signals via electromagnetic waves directly over the air with no need for electrical conductors or any other kind of hard physical connection.

Things got a bit more complicated through the twentieth century as networks took on hybrid characteristics to serve a proliferation of innovative use cases. “Wireless” began referring not just to the enabling technology for over-the-air communications, but also to the mostly-wired networks themselves that utilized wireless to extend their reach. If the final leg connecting the sender and receiver was wireless, the network itself was generally considered wireless.

Networks relying heavily on wireless interfaces for interior connections were not generally considered wireless. MCI, the upstart telephone company founded in the 1960s, disrupted incumbent AT&T by bypassing its inter-city lines with microwave repeaters — wireless transceivers that relay signals over the air. But MCI was known as a landline carrier.

Cut to the late 1980s, when viral growth of analog cellular telephony, powered by Advanced Mobile Phone System (AMPS), brought untethered voice reachability to millions of subscribers. CB radio, walkie-talkies, and other direct device-to-device solutions had been popular among hobbyists (and law enforcement agencies/first responders) for decades, but were never broadly adopted in an era when wired terrestrial telephony filled the basic communications needs for most of us. AMPS, on the other hand, became a general consumer service by leveraging its connection to the existing wired telephone network, and by its adoption of a call set-up process—number button-pushing—already familiar to everyone. Finally, a real wireless network for the masses!

Or was it?

To be sure, from the early days of installed “car phones” and those theoretically portable milk carton-sized wonders we tried without much success to carry in our pockets, the critical last hop was indeed carried over the air.

Billions of investment dollars were required to build out the enabling architecture for that last hop. The hyper-enthusiasm of the public for “cellphones” and the never-ending quest of investors for outsize returns fed on each other to create both the demand and supply required for the mainstreaming of mobile telephony. As both a social and technological phenomenon, the Great Untethering felt like a revolution, and we now know that it truly was one.

But from a purely functional point of view, basic analog cellphones were more akin to cordless landline handsets—albeit with far greater range—than they were to CB radio and walkie-talkies, both of which operate end-to-end over the air. And like their AMPS forebears, today’s cellular networks utilize wireless to extend the reach of wired networks, not to do the connecting job alone.

By the turn of the century, the AMPS analog voice protocol had largely been replaced by digital wireless transmission techniques such as TDMA and CDMA. This switchover, which would ultimately support the untethered transmission and reception of high-bandwidth data in addition to voice, ran concurrently with another revolution–the broad public adoption of wired internet. The confluence of these two technology platforms—digital wireless and public internet– created a lush environment for innovation that captured the imaginations of incumbents, entrepreneurs, financiers, and consumers, and in so doing defined an era.

Thanks to engineering breakthroughs funded by massive investment in the promise of mobile, wireless throughput increased dramatically during this period until it was no longer a showstopper for use cases requiring high data rates. Soon a new generation of enhanced applications enabled by conjoining wireless and wired data connections would evolve, applications demanding far greater wireless bandwidth than could have ever been imagined not just by Marconi and the other pioneers of analog broadcasting almost a century earlier, but also by the pioneers of analog wireless telephony removed by merely a decade or so.

These applications would of course depend upon the contemporaneous development of digital mobile devices—i.e., enhanced cellphones, or “smartphones”—capable of accommodating that bandwidth for the final, wireless leg. And for most users, it’s those devices that represent the network. That’s why despite being even more dependent than their primitive cellular forebears on wired phone and data networks, it’s the wireless aspect of today’s networks that captures the public imagination. Mobility is the magic.

But all of this wondrous untethering can only be supported by — you guessed it — ever-denser buildouts of wired arteries and capillaries to accommodate the enormous growth in core network traffic generated by the offloading of mobile data. (Entrepreneurs in the golden age of television understood that the throughput and distance limitations of electromagnetic waves over air created a business opportunity for cable carriers that would complement, and in time even replace, “free” TV.) In 2019 our “wireless” networks are in fact patchworks of multiple media interfaces.

The electrical connections over legacy copper rolled out in earlier eras of telephony and centralized computing continue to play a role. It is, however, a shrinking role. The beating heart of today’s network pulses not so much with electrons navigating wires of copper as with photons flowing through “wires” of optical fiber : glass. Glass so pure that looking through a block of it three miles thick would give you the same visibility as looking through your windshield. For mobile telecommunications networks, wireless connections are always the final link in the chain — from the nearest antenna or cell tower to your device and back. But it’s fiber that picks up data from the towers, delivers it to the core network, and carries it to another antenna from which it finally gets sent over air to the destination in your pocket.

The rollout of 5G will only accelerate network dependency on fiber, and not just at the core. Antenna density requirements for this game-changing wireless standard will necessitate the addition of hundreds of thousands, perhaps millions, of additional small-cell and micro-cell radio sites, each one connected back to the core network. More often than not, that backhaul connection will be fiber. And mobile baseband centralization (C-RAN), necessary to minimize the footprint and cost of site equipment, will demand just as many so-called “fronthaul” connections—again, mostly fiber—from the small-cell radios to baseband units.

Just as the driver who shows up at your door with the package represents the human face on the complex logistical wonder of same day delivery, it’s wireless, in the form of a gadget you can’t put down, that serves for most of us as a sort of technological proxy for the even more complex miracle that enables mobile telecommunications in the twenty-first century. But behind the scenes, there’s an incredibly elaborate infrastructure which makes these marvels possible.

For 5G, that infrastructure is made not of asphalt roads and strategically placed warehouses, but of glass fibers; from the core of the network through a labyrinth of access points, data centers, central offices, and base stations to the ubiquitous radio cells that enable our mobility. Strands of glass narrower than the width of a human hair, some of them thousands of miles long and some only inches, fed through conduits lying underground or resting at the bottom of the ocean, or hung from the poles of another era and finally stitched together at the network’s edge to allow a constant and constantly growing flood of data to be dumped off and picked up at the nearest antenna— these are the interstates, the country lanes, the city streets, and the walkways to our front door that carry our mobile digital freight.

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