A frequent prediction about mobile bandwidth demand is that 1,000 times more capacity will be needed. How that can happen is the issue.
A rough list of solutions suggests that about 10 times more capacity will be gained by new bandwidth allocations, another 10 times increase will be gained by changes in network architecture and a final 10 times improvement will be gotten from applying better signal processing, using better antenna solutions and other operational efficiencies.
So the Federal Communications Commission now is looking at whether 24 GHz spectrum can be released for mobile communications applications, part of an overall effort to free up more licensed, unlicensed and shared spectrum for communications applications.
The Notice of Inquiry occurs at the same time that Google has asked for permission to test communications across different high-frequency spectrum bands, including millimeter-wave systems operating in the 71 GHz to 76 GHz band and the 81 GHz to 86 GHz range.
Ironically, as networks get faster, consumers respond by consuming lots more data, as well.
Long Term Evolution 4G networks have a rather predictable impact on mobile data consumption: the amount of data consumed each month grows, compared to data consumption on 3G networks.
In fact, some studies also suggest that access to LTE networks also increases use of Wi-Fi.
A study of Android smartphone users by Devicescape, conducted over six months, found that 4G LTE users consumption of Wi-Fi and mobile data doubled, compared to data consumed by 3G users.
On average, 4G smartphone users consume 2.1 times more mobile data per month and twice as much Wi-Fi than their 3G counterparts.
This is due to the fact that 4G customers use their mobile device about 40 percent to 50 percent more than 3G users and consume richer content. Also, as a practical matter, one minute of use of LTE results in more consumption than one minute of 3G usage simply because more data can be transferred in the same amount of time.
A September 2014 report by Citrix found that video accounted for 52 percent of all mobile traffic, on both 4G and 3G networks.
But 4G users were 1.5 times as many requests for video over 4G LTE networks than on 3G networks, and those requests resulted in five times as much video data traffic on 4G compared with 3G.
Ironically, the more the supply, the more the demand.
But advances in computing capabilities now make possible more extensive use of spectrum that in the past has been unusable for communications purposes.
“Years ago, engineers and policymakers debated the feasibility and practicality of using spectrum above 2 GHz for mobile wireless services,” FCC Chairman Tom Wheeler noted.
More recently, 3 GHz has been seen as the highest frequency that could be used to support mobile operations.
The difference now is signal processing that allows practical communications at frequencies traditionally unusable. But cheaper signal processing now means it is possible to overcome propagation issues that have prevented use of millimeter waves for mobile or fixed communications apps.
So there now is optimism that frequencies above 24 GHz could be used to support mobile service, a previously-unthinkable option.
This matters for obvious reasons. More spectrum is needed. Also, the basic trade off–capacity and distance are inversely related–means very-high capacity is possible at millimeter wave frequencies, even if distance is limited.
Physics dictates the higher bandwidth possible at millimeter wave frequencies, even if coverage is more limited than at frequencies below 2GHz. Despite digital coding, potential bandwidth still is dictated by the number of oscillations a radio wave makes in a single unit of time.
In other words, at the peak of the cycle, coders might represent a positive bit, at the trough, a negative bit. So the total number of possible symbols depends on the frequency, or number of instances in a given unit of time that the waveform crosses between high and low states.
As the name implies, higher frequency signals have many more oscillations than lower frequency signals. Hence, more potential bandwidth, using any particular coding and modulation scheme.
The trade off is the effective distances at which such waves are useful for mobile or fixed communications, as millimeter waves are attenuated by water and, in some cases, oxygen. The trick is to use frequencies where attenuation is relatively lower, as is the case for optical communications as well.
Still, it seems highly probable that new frequencies, best suited for use in dense population areas, will be released for service, at some point.
by Gary Kim