By Art Reisman, CTO, www.netequalizer.com
The subject of Internet speed and how to make it go faster is always a hot topic. So that begs the question, if everybody wants their Internet to go faster, what are some of the limitations? I mean, why can’t we just achieve infinite speeds when we want them and where we want them?
Below, I’ll take on some of the fundamental gating factors of Internet speeds, primarily exploring the difference between wired and wireless connections. As we have “progressed” from a reliance on wired connections to a near-universal expectation of wireless Internet options, we’ve also put some limitations on what speeds can be reliably achieved. I’ll discuss why the wired Internet to your home will likely always be faster than the latest fourth generation (4G) wireless being touted today.
To get a basic understanding of the limitations with wireless Internet, we must first talk about frequencies. (Don’t freak out if you’re not tech savvy. We usually do a pretty good job at explaining these things using analogies that anybody can understand.) The reason why frequencies are important to this discussion is that they’re the limiting factor to speed in a wireless network.
The FCC allows cell phone companies and other wireless Internet providers to use a specific range of frequencies (channels) to transmit data. For the sake of argument, let’s just say there are 256 frequencies available to the local wireless provider in your area. So in the simplest case of the old analog world, that means a local cell tower could support 256 phone conversations at one time.
However, with the development of better digital technology in the 1980s, wireless providers have been able to juggle more than one call on each frequency. This is done by using a time sharing system where bits are transmitted over the frequency in a round-robin type fashion such that several users are sharing the channel at one time.
The wireless providers have overcome the problem of having multiple users sharing a channel by dividing it up in time slices. Essentially this means when you are talking on your cell phone or bringing up a Web page on your browser, your device pauses to let other users on the channel. Only in the best case would you have the full speed of the channel to yourself (perhaps at 3 a.m. on a deserted stretch of interstate). For example, I just looked over some of the mumbo jumbo and promises of one-gigabit speeds for 4G devices, but only in a perfect world would you be able to achieve that speed.
In the real world of wireless, we need to know two things to determine the actual data rates to the end user.
- The maximum amount of data that can be transmitted on a channel
- The number of users sharing the channel
The answer to part one is straightforward: A typical wireless provider has channel licenses for frequencies in the 800 megahertz range.
A rule of thumb for transmitting digital data over the airwaves is that you can only send bits of data at 1/2 the frequency. For example, 800 megahertz is 800 million cycles per second and 1/2 of that is 400 million cycles per second. This translates to a theoretical maximum data rate of 400 megabits. Realistically, with noise and other environmental factors, 1/10 of the original frequency is more likely. This gives us a maximum carrying capacity per channel of 80 megabits and a ballpark estimate for our answer to part one above.
However, the actual answer to variable two, the number of users sharing a channel, is a closely guarded secret among service providers. Conservatively, let’s just say you’re sharing a channel with 20 other users on a typical cell tower in a metro area. With 80 megabits to start from, this would put your individual maximum data rate at about four megabits during a period of heavy usage.
So getting back to the focus of the article, we’ve roughly worked out a realistic cap on your super-cool new 4G wireless device at four megabits. By today’s standards, this is a pretty fast connection. But remember this is a conservative benefit-of-the-doubt best case. Wireless providers are now talking about quota usage and charging severely for overages. That translates to the fact that they must be teetering on gridlock with their data networks now. There is limited frequency real estate and high demand for content data services. This is likely to only grow as more and more users adopt mobile wireless technologies.
So where should you look for the fastest and most reliable connection? Well, there’s a good chance it’s right at home. A standard fiber connection, like the one you likely have with your home network, can go much higher than four megabits. However, as with the channel sharing found with wireless, you must also share the main line coming into your central office with other users. But assuming your cable operator runs a point-to-point fiber line from their office to your home, gigabit speeds would certainly be possible, and thus wired connections to your home will always be faster than the frequency limited devices of wireless.
Related Article: Commentary on Verizon quotas
Interesting side note , in this article by Deloitte they do not mention limitations of frequency spectrum as a limiting factor to growth.