FAQ: Wi-Fi's latest alphabet soup

Fast-paced innovation can be exhilarating, but it can also be a recipe for confusion.

Take Wi-Fi, the popular wireless-networking technology that's taken the computer and consumer electronics industries by storm. The term specifically refers to a handful of standards approved by industry groups that has made wireless networking inexpensive and nearly unbiquitous in the latest gadgets and computers. The Wi-Fi standards use unlicensed radio spectrum to transfer data between devices, such as a laptop and a wireless-networking router.

802.11b was the first of the Wi-Fi standards to become popular about five years ago. Two other standards, 802.11a and 802.11g, have joined it as Wi-Fi standards, and still another, 802.11n, is on the way, although still a way off. Some of these work together, but some don't. Each offers slightly different advantages and disadvantages. All are available in commercial products you can buy now.

Sorting out the alphabet soup can be as frustrating as untangling the ball of wires behind your PC that the standards are supposed to help replace. For example, 802.11n is still in development but manufacturers are trying to get a jump on the demand for it by developing products using a technology that 802.11n will be based on. Called MIMO, it's getting lots of buzz as some wireless-router makers tout it as the most powerful flavour of Wi-Fi to date.

Here are the basics to begin cutting through the knot.

What are the different flavours of Wi-Fi?
Wi-Fi standards are set by the Institute of Electrical and Electronics Engineers, or IEEE, and the Wi-Fi Alliance, an industry group responsible for interoperability testing. So far they have finalised and approved three standards: 802.11a, 802.11b and 802.11g.

802.11n is a proposed specification that will become a Wi-Fi standard once it's finalised by the IEEE and the Wi-Fi Alliance completes its interoperability testing. Groups have submitted various 802.11n proposals to the IEEE, but are still debating what to include in the standard. It isn't expected to be completed until late 2006, with products based on the standard coming out in early 2007.

Some companies are also touting a wireless-networking technology known as MIMO. This is not technically a variety of Wi-Fi, or even an industry standard. Rather, it is the technology that's expected to form the basis of 802.11n.

What is MIMO and what does it do?
MIMO (pronounced my-mo) stands for multiple input, multiple output and refers to the use of more than one antenna to send and receive two or more unique data streams over the same channel simultaneously in wireless devices, resulting in networks with long ranges and high throughputs. It is currently the primary basis for the proposed 802.11n standard.

In addition to multiple antennas, MIMO products use specialised software, allowing data sent from access points in multiple streams to be received and deciphered by clients. In combination, the multiple antennas and software allow data to be reliably sent and received in environments with considerable interference over relatively long distances.

MIMO products create wireless networks that can reach significantly farther than current Wi-Fi networks and still provide high data throughputs. In some cases, wireless networks using MIMO technology can reach over 300 feet and still send and receive data at 30mbps.

However, Pre-N products offer higher throughputs at the outer edges of its range, according to reviewers.

What are the pros and cons of various Wi-Fi standards?
802.11b is the oldest and currently the most widely used Wi-Fi standard. Consumers have considerable choice in gear, which is often cheaper than products supporting newerstandards such as 802.11a and 802.11g. 802.11b has lower bandwidth and shorter range compared with other types of Wi-Fi.

802.11a has higher throughput than 802.11b, but is not compatible with 802.11b or 802.11g. It has been the least popular flavour of Wi-Fi, although manufacturers are beginning to include it in products alongside 802.11b and 802.11g.

802.11g is faster than 802.11b and is compatible with it. But, like 802.11b, it is more susceptible than 802.11a to interference from common household appliances, such as cordless phones and microwave ovens, that operate in the 2.4GHz radio band.

MIMO transmits data at the highest rates, but it is not an industry standard. In addition, products based on MIMO generally cost more than devices based on 802.11a, 802.11b and 802.11g.

Can I combine products based on different Wi-Fi standards?
The 802.11g and 802.11b standards are compatible. That means if you have an 802.11b client, such as a notebook, it can connect to an 802.11g access point.

The 802.11n is also expected to be compatible with its Wi-Fi predecessors. MIMO products are already on the market and manufacturers have made it a point to make them compatible with 802.11b and 802.11g-based products.

Products based on 802.11a are not compatible with products based on other Wi-Fi standards.

Compatibility is becoming less of a problem, however, as manufacturers increasingly support all three Wi-Fi standards in their devices.

How do various Wi-Fi standards compare on speed?
The 802.11b standard offers a top data transfer speed of 11mbps under optimal conditions, but it typically achieves about half that rate in the real world.

The 802.11g and 802.11a standards top out at data transfer speeds of 54mbps under optimal conditions. Like 802.11b, they generally perform at half their top speed in real-world installations.

Manufacturers of MIMO products say throughput can reach more than 108mbps. Ultimately, the IEEE is aiming for speeds from 100mbps and higher for the 802.11n standard.

What manufacturers currently sell MIMO gear?
A number of wireless networking chipmakers, such as Airgo and Atheros, are manufacturing their own versions of MIMO parts and several gear companies have been shipping products using those chips. Belkin and Linksys use Airgo's MIMO chips in their MIMO products. Belkin calls it MIMO Pre-N, while Linksys refers to it as SRX Speed and Range eXpansion. Netgear uses two types of MIMO technologies, one from Airgo, which it calls Pre-N, and another from Atheros and Video54, which it calls RangeMax.

Early reviews of these products indicate that the less-expensive RangeMax gear is more complicated to use and can potentially interrupt other, nearby Wi-Fi networks. Pre-N products offer higher throughputs at the outer edges of their range, but they cost more.

Do consumers really need dramatic increases in throughput over wireless networks?
Sharing broadband Internet access represents the top application for Wi-Fi networks in the consumer market. Since broadband connections typically perform well below 802.11b data transfer speeds, increased speeds offered by newer specifications such as 802.11g and MIMO do not yet mean much for consumers.

The question is most relevant for MIMO, which offers substantially higher speeds than any approved Wi-Fi standard. Manufacturers initially played up MIMO's role for multimedia applications, saying consumers would want to watch videos or play music streamed from a central home device. So far, those devices have failed to take off. More recently, device makers have touted MIMO-based products for their increased range.

What is WiMax? Will it replace Wi-Fi?
WiMax, similar to Wi-Fi, is a logo marking interoperability between products using a standard approved by the IEEE -- 802.16-2004. However, unlike Wi-Fi, WiMax makes wireless broadband Internet access directly available and is viewed as an alternative to high-speed cable and digital-subscriber lines. Wi-Fi products create wireless networks allowing those who can connect to the networks to share resources, such as an Internet connection or a printer.

WiMax is essentially radio technology that promises to deliver two-way Internet access at speeds of up to 75mbps at long range. Its backers claim that WiMax can transmit data up to 30 miles between broadcast towers and can blanket areas more than a mile in radius.