The author is technical director of Comrex.
American cellphone carriers turned up the heat this summer, each making bold claims that their 4G solution is better than the competition’s. Doubtless you’ve seen the ads, featuring lightning bolts, company CEOs and pretty girls in pink dresses.
For once, the United States is ahead of the curve on wireless data service, as our European and Asian friends are still mostly stuck in the 3G domain.
“4G” means different things to different folks, so for the purposes of this discussion we’ll call 4G the highest level of data service available from each of the four major carriers. There’s certainly room to argue whether some services offer enough of an incentive over 3G to qualify, but we’ll use the marketing terms for the sake of comparison.
The evolution of American wireless carriers toward 4G.
Fig. 1 shows the evolution of each of the American wireless carriers toward 4G.
Most of the carriers will tout download speeds as the main advantage to 4G, but to professionals interested in doing things like live remote streaming of audio and video (like using Comrex gear), there are other factors just as important.
If you’re sending media from the field, upload speeds are even more important than download speeds, and none of the 4G systems available are symmetrical in upload vs. download rates. Many systems deliver only a fraction of the marketed speed on the upload side.
In addition, ping time, or latency, is very important to live media streaming. If your plan is for two-way interactive audio or video, you can’t tolerate substantial delay. Overall latency can also change dramatically over a time period, resulting in what is called jitter on the network.
The best possible 4G network will deliver upload speeds well over 1Mbps, with low jitter and latency below 100 mS in each direction. With codecs that can perform an entire encode/decode cycle in less than 100 mS, total interactive delay can be kept to around the same as you would experience with a digital mobile phone.
Other factors weigh into the evaluation of 4G, of course, the most important being availability. A 4G modem isn’t useful without a signal.
But deploying 4G involves more than turning on a new radio. With increased wireless bandwidth comes the need for higher backhaul bandwidth, i.e. increasing the amount of data that must be moved from the cellular towers to the Internet gateways.
Cost is always a factor, although in the current competitive environment it’s not such a major one, since 4G is marketed to consumers. Some carriers are introducing data caps and throttling to cut costs, and not all offer automatic switchover to 3G in non-4G territory.
There are lots of variables at play so let’s tackle each carrier one at a time:
Rule the air
In terms of the criteria we’ve defined, the Verizon 4G LTE network is the one to beat. Virtually all wireless data roadmaps end at the LTE concept, and Verizon is way ahead of all others in spectrum ownership and deployment. The company announces dozens of new markets every month, and expects to have their entire network upgraded by 2014.
Verizon has been surprisingly accurate in their deployment predictions so far. Verizon also is the “Backhaul King” in many major markets, owning much of the fiber needed to connect cell sites together.
Verizon has one other major feather in its cap, which is the ownership of the cherished “Block C” of wireless spectrum nationwide, won in the great spectrum auction of 2008.
Located in the 700 MHz band and formerly used for UHF television analog channels, it has the ability to penetrate buildings much more effectively than higher frequency systems. Our early testing shows LTE working well deep within offices, elevators and basements.
Sprint was the first to market with 4G solutions, based on a competing technology called WiMax. To get to 4G quickly, Sprint partnered with (and now owns part of) the Clear WiMax network. Clear and Sprint have hit some rough patches (supposedly settled now) and that has affected deployment, which still remains spotty in many markets.
Sprint made a big announcement about their roadmap early this year which should have an impact on their services. The initiative is called “Network Vision” and is a way for them to unify the diverse spectrum they currently hold: the former Nextel push-to-talk band at the coveted 800 MHz band, the PCS band where they currently deliver 3G and voice at 1900 MHz, and the 4G WiMax band at 2500 MHz.
Network Vision involves allowing all services to operate across their various spectrums, and enhancing backhaul with point-to-point microwave links. In between the lines of their various press releases are hints the Sprint may move to LTE, which is close enough to the WiMax technology to be done relatively seamlessly. But the real advantage will come when 4G can be run on the 800 MHz band.
Our testing of WiMax shows a marked improvement over 3G for data transfer, but the high frequency limits it to “single wall penetration,” which means you’re better off near a window when using it indoors.
Likely to merge this year, AT&T and T-Mobile have similar 4G strategies, although AT&T’s roadmap is a bit longer.
Both companies have applied the 4G tag to what is an incremental upgrade to their 3G service, HSPA+, running on the same frequencies as 3G services. Our testing so far indicates an improvement in jitter and delay (to the already superior numbers of their 3G systems), but upload speeds are still somewhat limited by backhaul deployment. By “limited” I mean slightly below 1 Mbps, which is still very usable for media streaming.
An assortment of 4G-capable data modems.
The combined entity will own large chunks of spectrum in the 700 MHz and 850 MHz bands, as well as 1700 MHz and 1900 MHz. AT&T has already begun deployment of LTE in several markets in 2011, and you can expect to see that accelerate as they strive to keep up with the competition. Many of the data devices for sale now are LTE upgradeable. Within two years, this LTE network should rival Verizon’s in most of the U.S.
Our testing at Comrex shows that, given decent coverage, the jump to 4G is very much worth the investment for media streaming.
Before you sign a long-term contract, you’ll need to research which company covers your venues with which technology. But whichever network you choose, you’re sure to see a dramatic improvement in live streaming capability. As more markets come online and competition heats up further, the choices are likely to only get better.
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