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Have Communications Data Rates Really Maxed Out?

May 3, 2016
The goal of most communications technologies over the past decades has been, and continues to be, increasing the data rate. But how fast can we actually go?

The goal of most communications technologies over the past decades has been, and continues to be, increasing the data rate. You can see this in the continuous data rate jumps in Ethernet and fiber-optic networks. And it is plainly obvious in wireless as well, with ongoing data rate increases in Wi-Fi and cellular equipment.

One key driver is competition amongst vendors. Buyers always want the highest speeds. Another is the constant vigilance of the standards bodies wishing to stay current. Other drivers are more traffic on the internet caused by the increase in streaming video and other heavy data usage. In wireless again, mobile video seems to be the main driver in addition to a desire to increase subscriber capacity. This is all well and good, as it keeps the industry busy and profitable. And don’t forget: You can never be too thin or too rich, and you can never have too much speed or memory capacity.

What I often wonder is, how fast can we actually go? What is the practical upper limit? And are we there yet? If not, where are we today? What are the factors that limit our ability to continually produce speed increases? Furthermore, how fast do we really need to go?

Fiber optics is where we get the fastest rates. Currently the highest capacity systems are running at 100 Gb/s. Products and systems are already in development to produce 200 and 400 Gb/s. And 1 Terahertz is readily achieved, but at a high price. Special modulation techniques and dense wavelength division multiplexing (DWDM) are making it happen. By paralleling 1 THz fibers, even higher net throughput is possible. Do we need it? Big data centers and heavy internet users say yes.

Lower rates are also more than useful. Google Fiber offers 1 Gb/s to homes in some cities, as does Verizon. Cable companies are keeping up with their hybrid fiber cable systems. Time Warner offers up to 300 Mb/s in some areas.

As for copper cable systems, 100 Gb/s is possible over very short distances. Is it needed? Yes, in data centers, as copper wiring is almost always cheaper than fiber. For shorter ranges, copper is preferred. The new G.fast systems can also deliver up to 1 Gb/s in some areas covered by DSL.

Wireless is another story. The latest Wi-Fi standards get us well into the gigabit range. Using 802.11ac in the 5-GHz band, a data rate to 1.3 Gb/s is possible. The 802.11ad WiGig technology in the 60-GHz band allows up to 7 Gb/s. That’s fast, but the range is very limited (<10 m).

Cellular data rates are not so fast. Even with the latest LTE upgrades, actual data rates come nowhere near the one gig figure. The maximum potential with LTE-Advanced is 1 Gb/s under ideal conditions that almost never occur. Data rates vary widely with local conditions, range, weather, noise, terrain, number of users, and so on. Single digit Mb/s rates are common. Some of the more up-to-date systems can get in the 15-20 Mb/s range. This is great for most cellular users, but heavy video users always want more. Real 1 Gb/s+ rates won’t be achieved until 5G comes along in 2020 and beyond.

How much speed do we really need? That depends on what you are doing. For general e-mail and internet browsing, a few Mb/s is probably adequate. You really notice a difference if you are downloading or uploading big megabit or gigabit photo files. And you can really notice the buffering on videos. This is where higher rates in the 10 to 50 Mb/s are needed. I have a 50 Mb/s Time Warner connection. I have never witnessed that speed but I see 25 Mb/s regularly. And I have not had a buffering problem with Netflix movies.

With wireless service, the current rates are probably satisfactory to all but those crazies who want to watch movies and video selfies on a 4-in. screen. More movies and video seems to be the trend however, so higher data rates are needed. I read somewhere recently that Cisco predicts that 75% of wireless traffic will be video by 2020. Higher data rates are needed to satisfy those millennials who want their instant-gratification videos.

High data rates are harder to achieve in wireless as lots of bandwidth is required and spectrum is scarce and expensive. Thanks to multicarrier methods (OFDM), multilevel modulation (QAM) and MIMO, carriers can get higher spectral efficiencies from their spectrum holdings. You will continue to see steady data rate increases. I doubt that we need 100 Mb/s or 1 Gb/s rates for our cell phones. And it is ridiculous to imagine 1Tb/s, especially in the short term.

My predictions are based on practical, consistently achievable rates, not R&D levels. We will certainly see 1 Tb/s rates on fiber in the near future. Not so with wireless. For wireless, we should see multiple gigabit rates in Wi-Fi soon, if not now. Cellular rates to peak at 50 to 100 Mb/s and finally hit 1 Gb/s on a regular basis out in 2022 or so. We are not maxed out yet, but almost there.

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