Wireless Systems Design

Wi-Fi, WiMAX, and WCDMA: Complementary or Competitive?

Which one will be the winner? Wi-Fi, WiMAX, or 3G cell phones using wideband CDMA (or some variation thereof)?

In asking who the winner is, one must assume that these technologies are in competition with one another. Some see it this way, while others do not. Each of these three wireless technologies—developed at different times with different perspectives and different objectives—do seem to compete, but not head-on. Instead, what we see is more like an overlap of coverage and function.

Old Man Wi-Fi:

Wi-Fi is certainly the oldest of the three wireless technologies. It first came on the scene in the late 1990s, and has steadily been improved upon. Great standards were developed (801.11a/b/g) and the Wi-Fi Alliance came along to certify interoperability making—Wi-Fi reliable and universally compatible. Then access points and hot spots rolled out across the land, giving users very wide spread access. Now, you can access email and the Internet today wirelessly from a home network, an airport or hotel hot spot, or your company's access point. Granted, the range is short, but for most applications the 100-meter range limit is just fine. There are lots of APs around making this a non-problem.

On the whole, Wi-Fi can achieve far greater speeds than the average user needs. Even older 802.11b radios, with "only" an 11 Mbit/s maximum, can serve the needs of most users. Most users don't even understand this, but who notices when the speed is 1 Mbit/s or more anyway? You have to be downloading huge files or watching video to notice that you need more speed. 802.11a/g access points and radios give up to 54 Mbits/s if you need that extra speed, but typical rates are more like 22 Mbit/s. And that is usually fast enough.

To mitigate range and speed problems, Wi-Fi chip, router, and modem makers are adopting new methods and standards. Meshed Aps, for instance, are appearing in WLAN systems everywhere these days. They include campus meshed LANs and municipal mesh LANs. The meshed APs talk to one another to relay messages from node to node, thereby extending the range of any laptop or other device. The mesh also allows for some roaming over the mesh coverage area, making overall range longer—say, up to a mile. And the reliability of mesh makes connectivity more of a sure thing.

As for speed, the forthcoming 802.11n standard promises speeds over 100 Mbit/s. I am not sure who actually needs these kinds of speeds, but we are going to get it. The new 11n standard incorporates MIMO antenna technology that not only helps to ensure that additional speed, but also greatly improves range and reliability. There have been a slew of pre-n or draft-n 100 Mbit/s (and greater) offerings that have sold relatively well, despite the lack of a formal standard and certification program. Once the 11n IEEE standards task group gets its act together and consensus occurs, the standard will get ratified, the Wi-Fi Alliance with begin testing, and we will see an even greater flood of these fast and standardized MIMO products. But most believe that ratification won't occur until early 2008, so don't look for the big roll out of products until 2008 and beyond. In the meantime, the Wi-Fi Alliance recently announced that it would be instigating a certification testing procedure for draft-n products as part of a two phase effort to begin the certification of next generation 11n products.

Bottom line: Wi-Fi is a mature, robust technology that continues to improve and serve our needs.

WiMAX: The New Kid In Town:

While WiMAX is on the map, it is not a big reality yet. But it is on its way. The standards for this wireless technology are firm, including that of the newest 802.16e-2005 mobile version. Many chips are available, with more on the way. And products are beginning to roll out. Some are available now for backhaul and fixed operation, but the mobile version is still more or less in development. Look for mobile products in 2007 and beyond.

WiMAX serves an entirely different purpose than Wi-Fi. It was created to be the wireless alternative to cable TV and DSL broadband access. In small towns and rural areas not now served by traditional broadband suppliers WiMAX has big potential. It just may find its niche in competition with cable, DSL, and even the new fiber PONs.

As for range, think in terms of 1 to 6 miles—depending on how many basestations are built, the terrain involved, and other environmental factors. For backhaul, even greater ranges are possible with tall towers. Speed is also great but depends upon the need and application. Residential users will get at least 1 Mbit/s or more—depending upon price. Speeds up to 10 Mbit/s or so are achievable in that 1 to 6 mile range. Not bad.

But WiMAXs' real potential will be unleashed when the mobile version hits. It can achieve greater ranges and speeds in a mobile manner, meaning the radio can be traveling at up to about 75 mph. You cannot do that with a Wi-Fi enabled device.

WiMAX's real impact remains to be seen. But its potential is undeniable. We shall have to wait some more to see how it unfolds.

3G Wireless: Too Little Too Late?

How many years have we been talking about and waiting for 3G? For many of us, it’s been years and years. 3G exists today in several forms—namely Qualcomm's cdma2000 technology (ncluding the EV-DO version that gives from 500 kbit/s to over 2 Mbit/s via many Sprint Nextel or Verizon networks). Users can also get 3G’s originally planned WCDMA, the 3GPP, and ITU standard. Some Cingular and T-Mobile networks offer it now, and it is widely available in Europe and in some Asian countries. Speeds to 2 Mbit/s mobile can be achieved.

3G technologies are supposed to be for cell phones, but as experience has shown, most cell phone owners do not need such data speeds. For the most part, consumers want a good reliable phone. Text messaging is hot, but you don't need 3G speeds for that. 2.5G technologies like GSM/GPRS/EDGE and EV-DO already do that really well.

One great use of 3G is Internet and email connectivity from a laptop. We ordinarily think of Wi-Fi and hot spots for these kinds of uses. But as many people already know, there are still lots of places without a hot spot. So when you absolutely, positively have to link up, a PCMCIA card with 3G is the way to go. Fast and reliable service is available almost everywhere in the U.S. today.

For those users who desire even greater speeds, the latest addition is HSDPA/HSUPA, a technology that boosts mobile speeds to well beyond the 2 Mbit/s of plain old WCDMA. It is not widely implemented yet, but it is coming.

Which One For You?

Now as your English professor used to say, it is time to compare and contrast what you have just read. If pure speed is what you crave, Wi-Fi is the way to go. With over 100 Mbit/s on the way, it beats WiMAX and 3G hands down. The downside is that Wi-Fi’s range is always going to be limited to about 100 meters from an AP.

In addition, Wi-Fi is not a mobile technology. You cannot be in motion and expect it to work. Granted, a roaming or mobile version of the standard is in the works (802.11r), but it remains to be seen if it is competitive. Wi-Fi is a wireless technology that is mainly geared at laptops, and it already is built into most of them these days. That means Wi-Fi is a portable or nomadic technology not a mobile one. How many consumers actually need fast mobility with their laptop anyway? Commuters on a train? In a car? Nevertheless, we are already seeing cell phones with Wi-Fi built in to provide voice over IP (VoIP) when an AP is available. You can even buy an all VoIP Wi-Fi handset. But in general, Wi-Fi not a mobile choice.

WiMAX can do fixed or mobile. Its range beats Wi-Fi in all cases, and speed is more than good enough. What Intel, Motorola, and many others are hoping is that WiMAX will replace, or at least co-exist with, Wi-Fi in laptops. It gives the PC a longer range with reasonable speed. And it is fully mobile, so it makes sense for many portable and mobile applications. Interestingly, WiMAX could be the 4G cell phone of the future. Once MIMO gets into WiMAX it will give both 3G and Wi-Fi a good run.

Today, 3G gives the range and speeds of WiMAX. And there is no waiting. It is here now. It works great but it is expensive.

So who wins? I think all of these technologies will find their place in the wireless landscape. One will not replace the other—at least right away. All technologies have a life cycle (growth-maturity-decline, etc.), so we will see that play out in the future. What we probably will see are profitable individual wireless services built on all three technologies, as well as wireless combos: Wi-Fi plus WiMAX in a laptop. Wi-Fi and/or WiMAX in a cell phone. And who knows, we may just see another newer technology come along to replace, overlap or compete with these three. Is that were 802.20 fits? Stay tuned to find out.

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