Electronic Design

Wireless LANs And Cell Phones Lead The Way

But keep an eye on up and coming standards.

But keep an eye on up and coming standards. Personal communications usually translates to one thing: mobility — which invariably means wireless. Today, one of the key influences driving the electronics industry is wireless technology. The hottest forms of this segment are wireless local-area networks (WLANs) and cell phones. But other wireless technologies are making their presence felt in our everyday lives, and there are more to come.

The hottest wireless technology of the decade so far is wireless LANs, or more specifically, equipment based on the IEEE 802.11b 11-Mbit/s standard. Also known as Wi-Fi for wireless fidelity, 802.11b wireless LANs are being used to extend the wired LANs in the enterprise, and they have become the most popular home networking technology.

A more recent development is the growing number of 802.11b public access points called hot spots. These oases of wireless cover up to a 300-foot radius and provide a way for anyone with a laptop to connect for Internet access and e-mail. Thousands of hot spots exist now, but thousands more are on the way. Most are in airports, coffee shops, convention centers, and colleges. But major hotels are adding them, as are restaurants, bookstores, and other places where people congregate and wait. There is a major push to build more hot spots. Even the cell-phone carriers are getting involved to protect themselves against the obvious competition to 2.5G and 3G data services.

The WLAN phenomenon has been remarkable. It's the most significant development going on during our longest downturn in the electronics industry, and its popularity will continue with the adoption and use of the forthcoming faster 802.11g 54-Mbit/s standard. Many fear the overcrowding of the 2.4-GHz band, where WLANs operate. If all of those proposed hot spots are realized, this could cause a problem. Of course, there is always the 802.11a standard, which is just as fast as 802.11g but operates in the 5-GHz band. A recently proposed bill in Congress is asking for 255 MHz more space in the 5-GHz band for extended WLAN activities.

A further development is the incorporation of WLAN capability in PDAs. Eventually, it will come to cell phones, further extending the ability to roam from not only cell to cell but also hot spot to hot spot. As the volume of 802.11 chips increases, prices decline, making the technology available to even more products, including wireless printers and other peripherals. You may even see 802.11 in home entertainment equipment, such as digital music stereos.

We know that the cell-phone business is mature because the greatest volume of new phones sold are replacement phones, rather than phones sold to new subscribers. Worldwide, sales of cell phones are basically flat, save for exceptional growth in China and other parts of Asia. Sales of basestations and other infrastructures are actually down and expected to stay down, other than some upgrading of existing systems to implement the newer 2.5G technologies.

Currently, 3G still seems to be on hold in Europe and the U.S. There are pockets of testing and limited implementation, but that's it. Most of the world is focused on upgrading 2G systems to 2.5G technologies. GSM systems are adding General Packet Radio Service (GPRS) and CDMA operators are implementing 1xRTT (Qualcomm's basic-rate packet-data system, one times Radio Transmission Technology) to create new data services. Instant messaging is popular and a few brave souls now handle e-mail this way, but no one is accessing the Internet from a cell phone. Generally, the new data services aren't doing that well. People use the phone to talk, not to retrieve data. The carriers could focus their attention on improving the overall service by filling in coverage gaps and improving reliability. But that's boring.

Will we ever get 3G? Maybe. Perhaps the greatest 3G development is the forthcoming adoption of time-division synchronous code-division multiple access (TD-SCDMA) in China. Even though it may not make financial sense to implement 3G here, why not go with the latest technology in countries where no cellular system exists? In a country like China, with its huge population, the technology providing the greatest subscriber capacity at lowest cost is the winner—in this case, 3G.

In the meantime, here in the U.S. we will get faster and better—almost 3G or 2.5G services. GSM/GPRS carriers will upgrade to the Enhanced Data Rate for GSM Evolution (EDGE), which can run up to 120 kbits/s or more, depending on the carrier and the environment. Most GSM/GPRS basestations can be upgraded to EDGE with software and inexpensive hardware. EDGE handsets are not available yet, but they are on the way. Carriers using CDMA will upgrade to EV-DO (Qualcomm's faster packet-data system, Evolution-Data Only) or other variants. But most subscribers don't really need these faster data phones.

Many still hold out hope for the almost mythical UMTS W-CDMA phone that can achieve a minimum 384-kbit/s data rate and possibly as high as 2 Mbits/s. Add to that video streaming capability, music downloads, interactive gaming, and unlimited Internet access. But who needs it at least enough to pay for it?

While 3G is still way off, technology improvement will be taking place. We're beginning to see the mandated E911 systems come online so that emergency services can find us within 20 to 100 feet using GPS or triangulation-based location systems. Color cameras are popular in phones now, but no one seems to use them simply because so few people have one. Both wearable and disposable phones are available now in limited quantities.

Another wireless technology designed to free us for unlimited personal communications is Bluetooth. It has been around for years now and is seeing some growth. The primary application seems to be in wireless headsets for cell phones. It is also used to link and sync PDAs with PCs or laptops. This short-range, ad hoc networking technology is now well sorted out and finally inexpensive to use. But it still seems to be seeking a way to come into its own with some killer app other than cell-phone headsets.

A forthcoming quasi-competitor to Bluetooth is ZigBee. This short-range technology also uses the 2.4-GHz band. Like Bluetooth, it supports ad hoc networking but has significantly lower speeds (250 kbits/s max). Yet ZigBee is simpler and cheaper than Bluetooth. It targets sensor networks and other industrial monitoring and control uses. It will also be great in home security and control applications, as well as toys. Silicon vendors are readying chips for later this year and beyond. Its low cost almost guarantees ZigBee a place in our personal communication future. The 802.15.4 standard for ZigBee is working its way through the approval process.

Another wireless technology in our future is ultra wideband (UWB). The FCC blessed this weird wireless technique last year. Dozens of companies, both old and new, are working on practical and affordable nonmilitary/government-type products. UWB transmits digital data using low-power, short, uniquely shaped pulses that spread the signal over a huge bandwidth. In doing so, it basically appears as random noise to other services, virtually eliminating interference. Not only does it permit some spectrum sharing, it also provides a multiple-access mode like CDMA.

The FCC restricts UWB to the 3.1- to 10.6-GHz range at unbelievably low power (effective isotropic radiated power of -41.3 dBm/MHz), so it won't likely bother anyone else. Additionally, it has the great virtue of being able to transmit data at very high rates, much higher than that of any other short-range wireless technology. The target is 110 Mbits/s over a 10-m range with rates up to 500 Mbits/s over shorter distances. With that kind of speed, UWB is probably the ideal wireless link for video transmissions in home entertainment equipment. Over 30 companies have offered proposals for adoption as the IEEE 802.15.3a UWB personal area network (PAN) standard. That process will take a couple of years, but expect to see some actual products late this year or early next year. UWB will also be used in short-range radars for cars.

Look for further developments in short-range (less than 10 meters) wireless technologies, including IR, electromagnetic induction, and near-field radio. Sensor networks, cable elimination, and RF ID are the primary target applications.

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