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4G explained: A guide to LTE, WiMax, HSPA+, and more

The three flavors of 4G

What is WiMax?

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WiMax stands for “Worldwide Interoperability for Microwave Access.” It is an ITU-approved, fourth-generation mobile broadband technology that attempts to mimic the abilities of Wi-Fi wireless Internet, but over a mobile phone network using an open protocol (802.16m). Think of it as a patchwork of Wi-Fi hotspots that, instead of reaching for a few hundred feet, can stretch for miles and overlap, eliminating coverage gaps. It provides fixed and mobile Internet access for compatible devices with less interference than traditional Wi-Fi. Theoretically, a WiMax tower could provide broadband wireless Internet over a 30-mile range, though most stations currently achieve much less. Current WiMax users can realistically expect about 3Mbps to 6Mbps download speeds.

If you’ve heard of WiMax, it’s probably due to Sprint, which is working with Clearwire to develop an extensive WiMax network. It is currently available in select cities. More on this in our Sprint section later on.

What is LTE?

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LTE stands for “Long Term Evolution,” and is an ITU-approved 4G mobile broadband technology. It is a direct competitor to WiMax. LTE is more of a successor to current mobile 3G standards than WiMax. However, instead of transmitting data using microwaves, LTE uses radio waves. Theoretically it can attain speeds up to 100Mbps, though real-world speeds on Verizon’s network are around 6Mbps to 12Mbps. LTE was developed as a long-term alternative to DSL, cable, and other wired forms of Internet.

The two largest carriers in the United States, AT&T and Verizon, are both investing in LTE networks, though Verizon has already launched its network. MetroPCS is also working on a LTE network.

What’s the difference between LTE and WiMax?

WiMax is based on IEEE (Institute of Electrical and Electronics Engineers) standards, meaning it uses an open protocol that has been debated and approved by a large community of engineers. LTE, on the other hand, is a standard that was cooked up by the 3GPP (Third Generation Partnership Project), which is an organization consisting of wireless agencies and telecommunications companies. The 3GPP organization came up with 3G standard for GSM some years back, which was adopted by a majority of wireless carriers around the world (except here in the U.S. where Verizon and Sprint chose to use CDMA).

However, LTE and WiMax aren’t enemies like CDMA and GSM have been. Both technologies use OFDM (Orthogonal frequency-division multiplexing), which means that unlike competing 3G networks like CDMA and GSM, WiMax and LTE are more like siblings. They aren’t entirely incompatible. Hopefully, it will be easier and cheaper to design devices that incorporate both technologies.

Similarities: Both use SIM cards, both are backward compatible with existing CDMA and GSM networks, both use OFDM and MIMO (Multiple In, Multiple Out), both have similar speeds, and both are IP-based.

Okay, then what is HSPA+?

HSPA+ stands for “Evolved High-Speed Packet Access.” It has been touted by some carriers as a 4G mobile broadband network type, and the ITU recently changed its 4G definition to put HPSA+ under the 4G umbrella, but really, it is merely an upgrade to existing 3G GSM technologies. Think of it as a stopgap or bridge between 3G and 4G. Though it offers download speeds that can theoretically reach 84Mbps (possibly even higher in the future), it is not a next-generation network. It still uses the old interface and standards implemented years ago for 3G, and lacks the response time of LTE and WiMax. It’s like comparing a Formula 1 race car to a souped-up Toyota Camry; the Camry may move fast, but it wasn’t designed to race. HSPA+ is the definition of an old dog that has learned new tricks. LTE has a lot of small back-end improvements to its core technology that better suit it for the future, but many carriers may stick with HSPA+ for a couple years due to the savings. HSPA+ networks will likely feature download speeds from 1Mbps to 7Mbps at first, though performance may vary wildly.

T-Mobile has been a big proponent of HSPA+, touting itself as “America’s largest 4G network.” More on that below. Since it is relatively cheap and speedy to upgrade a GSM network to HSPA+, both T-Mobile and AT&T have implemented HSPA+ in a large number of major markets and are quickly rolling the service out across the country. AT&T is also developing a next-generation LTE network.