What's the big deal about WiMax?

There's been a lot of buzz about WiMax as Sprint Nextel rolls out its first network to use the 4G wireless technology. But what exactly is it? This FAQ will help you sort it out.

Marguerite Reardon Former senior reporter
Marguerite Reardon started as a CNET News reporter in 2004, covering cellphone services, broadband, citywide Wi-Fi, the Net neutrality debate and the consolidation of the phone companies.
Marguerite Reardon
7 min read

Sprint Nextel has made headlines all week as it's started lighting up its first 4G wireless network using a technology called WiMax. But what exactly is WiMax? And how does it fit into the future of wireless? Here's a primer to help you sort it out.

Sprint was the first major carrier in the world to announce massive deployment of mobile WiMax in 2006. The company said it would use the technology to build a fourth-generation, or 4G, wireless network that would provide true wireless broadband.

But the hyped technology hasn't been without controversy. Fast forward to the present, and Sprint's former CEO Gary Forsee, who staked his reputation and ultimately his job on WiMax's success, was forced to resign after investors protested that the company needed to focus more on keeping current 3G customers instead of building a new 4G network.

Now, Sprint is waiting to spin off its WiMax assets into a joint venture with Clearwire to help ensure that its dream of a nationwide WiMax network is realized. In the meantime, it's moving forward with initial network deployments. And this week, it launched the first mobile WiMax network called Xohm in Baltimore. More cities will follow over the coming weeks and months.

Next week, Sprint and its ecosystem of WiMax suppliers is planning a major coming out party for Xohm. With all the buzz swirling around WiMax, I thought it would be a good time for a little refresher on what the technology is and how it compares to existing technologies as well as other 4G technologies on the horizon.

What is WiMax?
The acronym WiMax stands for Worldwide Interoperability for Microwave Access. It's an IP-based wireless technology that can accommodate fixed, portable, and mobile usage models, according to the WiMax Forum. It's considered a promising next-generation wireless technology, because it supports high data rates and has a long transmission reach. Before it was standardized in 2004, there were many non-standard versions of the technology being developed throughout the world, including Korea's WiBro technology.

What can WiMax be used for?
The primary purpose of WiMax is to offer wireless broadband. Originally, it was used to provide broadband to places where there was no wired infrastructure. This is how most of the 350 deployments throughout the world use the technology today.

A mobile version of the technology was approved in 2005 by the IEEE standards body. This version, known as 802.16e, allows the technology to be embedded into laptops, tablet PCs, smartphones, and consumer electronic devices like digital cameras so they can connect to the Internet via WiMax while in motion. So for example, if you're walking down the street, riding on a train or traveling in a car, the 802.16e version of the technology will allow you to still access the Net.

The WiMax Forum claims the technology can deliver 40 Mbps of capacity per channel, which can then be split "among hundreds of businesses, thousands of residences, and thousands of mobile Internet users." Specifically, the group believes the technology can offer 30 Mbps of capacity within a typical cell radius of up to 3 kilometers.

People have called WiMax Wi-Fi on steroids. How does WiMax differ from Wi-Fi?
WiMax and Wi-Fi are both Internet protocol-based wireless technologies. And they both provide high-speed wireless access to the Internet. But that is pretty much where the similarities end.

Wi-Fi was designed to provide indoor wireless connectivity over relatively short distances. The technology is mostly used for home networks or to provide Internet connectivity in small public places like a coffee shop or library. Although there have been some attempts to "mesh" the technology and use it outside for citywide deployments. But because of its short range, these deployments require a lot of radios.

Another major differentiator between WiMax and Wi-Fi is that Wi-Fi uses unlicensed spectrum. WiMax uses licensed spectrum, typically in the 2.5MHz range. WiMax is also designed to be a carrier grade technology so there is more reliability and quality of service built into the technology than is typically available with Wi-Fi.

How does WiMax compare to 3G cellular phone services?
Like WiMax, 3G services transmit over long distances. And these services also require spectrum licenses. But in general, 3G cellular networks are slower than WiMax. What's more, these networks were fundamentally built for voice traffic. WiMax has been developed for data.

How do the speeds of 3G services compare with WiMax?
Verizon Wireless and Sprint Nextel have built their networks using a technology called EV-DO. Today's networks, which use a version of the technology called Revision A, offer theoretical download speeds of about 3.1 Mbps. But actual downloads are between about 400 Kbps and 800 Kbps.

AT&T uses a different technology, based on UMTS and called HSPDA or High Speed Data Packet Access. It can theoretically deliver download speeds of about 3.6 Mbps. But in the real world, speeds are closer to 400 Kbps to 700Kbps.

That said, the next generation of 3G for both technologies is on its way. And it offers faster speeds. Verizon and Sprint can upgrade to EV-DO Revision B, which offers a theoretical maximum download speed of more than 9 Mbps. Actual peak download speeds would likely fall around 4.0Mbps.

AT&T is currently upgrading its 3G UMTS network to HSUPA. And AT&T executives have said that as soon as next year its network could offer theoretical download speeds up to 20 Mbps. The actual speed is likely to be around 4 Mbps and 6.6 Mbps.

By comparison, WiMax can deliver theoretical download speeds to individual users around 10 Mbps to 20 Mbps. But most people using a mobile WiMax service will get between 2 Mbps and 4 Mbps of bandwidth.

Why do theoretical speeds differ from actual speeds?
There are several variables to consider when it comes to calculating performance of wireless networks. All wireless networks are a shared medium, meaning the more users on the network, the less total capacity is available for individual users. Also physics plays a role. And distance is always a factor when it comes to wireless technology. Typically, the further a wireless signal travels, the weaker it becomes, which translates into slower bandwidth speeds.

How does WiMax stack up against other 4G technologies, such as Long Term Evolution or LTE?
WiMax and LTE are the leading technology candidates for 4G networks of the future. And they actually have more similarities than differences. Both technologies are IP-based and as a result are designed for data rather than voice. And because they are IP-based they will both be able to offer consumers a true mobile broadband experience on portable devices like smartphones and consumer electronics.

Both technologies use the same fundamental technology, OFDM or orthogonal frequency-division multiplexing. So while GSM and CDMA were bitter rivals in the 2G and 3G cellular wars, WiMax and LTE are more like siblings, sharing a common parent. This means that companies, such as Motorola and Nokia, will have an easier time developing products and equipment for either network because they can re-use some technology built for one technology.

Who is deploying mobile WiMax in the U.S.?
The WiMax Forum lists more than 350 WiMax deployments throughout the world already. But most of these are fixed deployments in developing markets where WiMax is used to provide broadband to areas without fixed line infrastructure.

In the U.S. Clearwire and Sprint Nextel are building WiMax networks that will serve both mobile customers as well as fixed customers. Earlier this year, the two companies agreed to join forces to deploy a nationwide WiMax network. The companies have raised $3.2 billion in investment from several companies including, Intel and Google as well as cable providers Comcast and Time Warner Cable.

Sprint just launched the Xohm network in Baltimore this week. It will be lighting up other WiMax cities such as Washington, DC, Chicago, Philadelphia and Dallas, in the coming months.

Who is deploying LTE?
The world's largest wireless operators have committed to LTE. AT&T and Verizon Wireless in the U.S. and Vodafone, which is the largest operator in the world, said they'll use LTE. Verizon Wireless has already said it will use its newly acquired 700 Mhz spectrum to build the network.

LTE is still in its early days of development, which means it won't likely be deployed en mass until 2011 or 2012.

As for speeds, LTE is expected to be faster than the current generation of WiMax. But the IEEE is working on a new version of WiMAx called 802.16m, which should be ratified in 2009, that will provide faster speeds.

Are there any WiMax devices available today?
There are some, but not many. That said, several large companies such as Intel, Nokia, and Motorola have thrown their weight behind WiMax. And they promise to launch new components and devices to support the technology. But so far, devices with WiMax have been few and far between. Nokia has announced the N810 "Portable Internet Tablet." Samsung has announced a WiMax-capable Q1 Ultra Premium Mobile PC. And Intel will soon be including WiMax in its laptop chipsets, which should help seed the market.