The next big thing in wireless networking is here. Almost. Early indications are that 802.11g is going to be a hot technology. Early adopters will include home and small-office users who have not yet committed to a wireless standard, followed by businesses looking to upgrade their 802.11b LANs.
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Why? Because 802.11g products support data rates of up to 54 megabits per second (versus 11 Mbps for the now-common 802.11b products) while still maintaining the range that 802.11b users have grown accustomed to expecting. That bandwidth is enough to handle many concurrent users (important in a business environment) or even streaming video (which opens up uses for wireless in the home). Whats more, since 802.11g access points and routers are backward-compatible with existing Wi-Fi– certified 802.11b client products, businesses can migrate to 802.11g without abandoning their 802.11b installed bases.
Should you sign up, you ask? Theres just one problem: Despite the availability of 802.11g products in the market (such as the ones we test here from Buffalo Technology, D-Link Systems, and Linksys Group), the final 802.11g standard has not yet been set by the IEEE governing body. That has led to a host of worries, from questions about interoperability to fears that should early, non-standards-compliant products fail to work as advertised, consumers will be put off when standard 802.11g products arrive later this year.
Marketplace confusion is a valid concern. Each of the manufacturers with products out now acknowledges that those products are “pre-standard” and “draft-compliant.” The question is, which draft? In the second week of January, for example, the 802.11g task group voted to ratify a new version, labeled 6.1. Various groups within the IEEE will still hold additional rounds of balloting, so its unlikely that the 802.11g draft will become a standard much before May or June of this year.
Equipment makers are making sure that when the standard is finally ratified, theyll be able to upgrade their routers/access points and network adapters to compliance using a firmware flash or driver update. Buffalo goes so far as to guarantee upgradability; otherwise it will replace the draft-compliant products with fully compliant ones.
In fact, while we were reviewing these products, both Buffalo and Linksys supplied us with firmware patches to solve problems with legacy 802.11b clients. So at the very least, early adopters need to be prepared to maintain their clients and infrastructure components with occasional patches until the standard is finalized.
Why
“G”?”>
Why “G”?
With the availability of affordable 802.11b products and fast 802.11a products (also with data rates up to 54 Mbps), you may wonder why we need yet another wireless networking category anyway. Well, 802.11g is the standard for high-speed networking in the 2.4-GHz band—the same as the radio spectrum in which 802.11b products operate—and hence can deliver speed and backward compatibility.
802.11g products use the same transmission techniques employed by 802.11a products, which operate in the 5-GHz spectrum. This transmission method, called OFDM (orthogonal frequency division multiplexing) provides eight data rates: 6, 9, 12, 18, 24, 36, 48, and 54 Mbps.
In real-world use, you can expect to achieve maximum throughputs in the range of 18 to 22 Mbps. 802.11a products, meanwhile, provide similar performance but at distances significantly shorter than those at which 802.11g or 802.11b products transmit. That means a business needs to deploy more access points to cover a given area.
Its anybodys guess what the arrival of 802.11g products means for the still-new 802.11a universe. In the near future, we expect to see improved performance of 802.11a products, thanks to a second generation of chipsets. Most likely “a”-only products will remain a small portion of the wireless market; and theyll be deployed in environments where there is a high density of clients and maximum throughput is a must.
That said, soon equipment makers will start rolling out combination “a/g” cards. These cards will provide connectivity to virtually any IEEE standards-based wireless network, though at a higher cost than single-standard equipment.
Getting
“G” to Work”>
Getting “G” to Work
The 802.11g task force had to overcome significant engineering challenges when it was establishing the standard. The biggest challenge was to ensure high-speed performance while providing backward compatibility with the large installed base of 802.11b networking products, which share the same radio spectrum.
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Indeed, the major issues with 802.11g products concern interoperability, both with legacy 802.11b clients and among different makes of equipment. To deal with legacy 802.11b products, the 802.11g draft specifies a protected mode. 802.11g, as previously noted, uses OFDM, whereas 802.11b uses DSSS (direct sequence spread spectrum). Unfortunately, radios using these different transmission methods dont “hear” one another.
To solve this problem, the IEEE is relying on a mechanism that was part of the original 802.11 specification: CTS/RTS (clear to send/request to send). Think of it as a wireless handshaking mechanism, much as in the old RS-232 serial days. In protected mode (or mixed mode, as its also called), the access point uses CTS/RTS to give clients access to the airwaves.
Other changes also have to take place to ensure interoperability between “b” and “g” clients. The slot time, the time between packets, is increased from 9 microseconds (used by 802.11g clients operating in a pure “g” environment) to 20 microseconds (the slot time used by 802.11b clients). This means that 802.11g clients operating in a mixed-mode environment (with its associated overhead) will have poorer throughput than those operating in a “g”-only mode—even if the 802.11b clients present arent sending any traffic.
How We Tested
How We Tested
In this roundup of early pre-standard products, we tested the Buffalo AirStation WBR-G54, the D-Link AirPlus Xtreme G DI-624, and the Linksys Wireless-G WRT54G routers, as well as each companys 802.11g network card. Note that each of the products has a “G” and perhaps a “54” in its name. So even though theres no 802.11g standard yet—and 54 Mbps is also the maximum signaling rate used in 802.11a products—the naming convention for these products may confuse consumers if the spec is updated.
Two manufacturers are currently supplying chipsets. The 54G chipset, made by Broadcom, is found in the Buffalo and Linksys products, and the Prism chipset, made by Intersil, is used in the D-Link products.
Because of the interoperability issues identified above, weve added a significant number of tests to our traditional wireless testing suite; these measure performance in various modes and interoperability among vendors and legacy 802.11b clients. All of our tests were performed using NetIQs Chariot, a respected network performance analysis tool (www.netiq.com).
For starters, we tested 802.11g network throughput at various distances. We tested with only one client and used 802.11g-only mode (not mixed mode).
The Buffalo and Linksys routers can be set to G-Turbo mode. In this mode, a router would never go into protected mode, and 802.11b clients would never “see” the router. This mode locks out 802.11b users (and hence isnt an option for businesses with an investment in 802.11b clients), but it yields the maximum speed the products are capable of producing.
As the chart on page 42 shows, throughput at close distances ranged from about 16 to 21 Mbps. As expected, it dropped off with distance. At 80 feet, for example, throughput was only slightly better than half what it was at close distances. But true to the grand scheme, 802.11g performance tracked closely with that from the most recent 802.11a equipment we tested (“Dual-Band Wireless Cards Are Not All the Same,” First Looks, December 24, 2002).
Our second test was designed to evaluate the best possible performance of an 802.11g client on a network running in mixed mode (the most likely scenario).
We configured the router for mixed-mode operation and checked performance at a close distance using an 802.11g client. With no 802.11b client present, the client and router should have turned in the same performance as they did in “g”-only mode. We then booted up a notebook with an Orinoco 802.11b card and associated it to the router. The association of an 802.11b should force the wireless router into protected mode. For this test, we sent traffic only to the 802.11g client.
In this scenario, performance is reduced by the overhead of the protection mechanism that ensures that “b” and “g” clients can coexist. We dont chart the results here, since they generally tracked with the 802.11g-only results, but with a 10 to 20 percent reduction in throughput at any given distance.
Our third test (also not charted) was designed to measure performance in protected mode with traffic being sent to both 802.11g and 802.11b clients. For this test, we used one 802.11g client and one 802.11b client (the Orinoco) at close distances. Since both clients had equal access to the network, youd expect their individual throughput figures to be approximately the same, given that they were sending the same amount of data in each packet.
Indeed, thats the performance we saw with both the Buffalo and Linksys products. Each client was getting about 3 Mbps of throughput, yielding a total network performance that was slightly better than 6 Mbps. (Of course, as you increase the number of “g” clients on the network, the total network performance improves, since the higher throughput of each additional “g” client will pull up the average).
Unlike the Buffalo and Linksys products, the D-Link router/ NIC combination was show- ing about a 5:1 preference in performance for the “b” client. D-Link is aware of this issue, and a patch, not available by our deadline, should address the problem.
Our final tests (shown on the second chart) focused on vendor interoperability. For these tests, we created a devils matrix and tested each manufacturers card against the other manufacturers wireless routers. We tested for 802.11g performance at close distances. For routers that supported multiple configurable modes, we also tested several legacy cards in both mixed and Wi-Fi–only modes.
This test matrix yielded some interesting results. Most important, each manufacturers network card was able to connect successfully to every other manufacturers router and deliver acceptable throughput.
Initially, however, we did experience difficulty with an 802.11b legacy Cisco Aironet 350 card associating with either the Buffalo or the Linksys router configured for automatic mode. Each vendor provided a firmware patch that resolved the problem. After we updated the products, both legacy 802.11b clients turned in expected performance using all routers.
All Aboard
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All Aboard?
Each of the products has a configuration utility for installing the client adapter. You can use either the supplied client configuration utility or let Windows XP manage your wireless connection.
Each of the routers has a Web browser interface that simplifies configuration, and each Web interface provides a mechanism for easily updating the routers firmware—a feature youll need once a standard is ratified. Linksys stands out from the others for its excellent installation wizards.
That said, since the products we reviewed do not yet seem fully finished, we decided not to award an Editors Choice in this roundup. We would advise most buyers to wait until the standard is set before committing, if only to avoid the hassle of flashing firmware in a couple months.
But if you need the increased performance that 802.11g offers—and you need it sooner rather than later—you might want to consider the prestandard products. Just be willing to check the manufacturers Web sites regularly for patches.