Wireless Systems Design

Wireless-Internet Access Gets Easier And More Confusing

As Cellular-Network Carriers And IEEE 802.11 Wi-Fi Hot-Spot Providers Compete For Mobile Users, It May Affect How Those Users Access and Utilize The Wireless Internet.

Picture this: You want to wirelessly access the Internet, but you're not sure which technology option is best. Should you use a 2G or 3G cellular network, or perhaps even a Wi-Fi hot spot? You also must figure out what kind of device is most suitable for your Internet-access needs. Would a laptop work just as well as a cellular handset? Or would a PDA prove more useful? These choices can cause much confusion. At the same time, they are crucial to ensuring a successful wireless experience with the Internet. Before addressing these issues in greater detail, let's consider all of the options and their associated devices.

CELLULAR-NETWORK ACCESS
The telecommunications industry has been witness to the ongoing convergence of computational and communication technologies. This trend has led to a stunning variety of options for wirelessly accessing the Internet with everything from laptops and PDAs to cell phones. Think about accessing the Internet via a cellular handset using 2G to 3G cellular-networking devices. Most users in the United States currently have 2G technology based on TDMA, CDMA, or GSM protocols. Their access to the Internet is limited to small, monochromatic text screens using a microbrowser like the Wireless Application Protocol (WAP). The average connection speed is very slow, as it ranges from 9.6 to 14.4 kbps. The only benefit is cost. Access is fairly cheap, starting from around $5 per month plus associated standard airtime fees.

For mobile-phone users, the growing availability of 2.5G and 3G wireless networks is opening up a new world of Internet experience. In this camp, access speeds range from 40 to 60 kbps. Burst speeds are near 150 kbps. This type of "near-broadband" access comes at a price that ranges from $35 to $150 per month. And high-speed Internet access is only one of the advantages of 2.5G and 3G technologies. Mobile-phone users will be amazed at many of the features that are now available in next-generation handsets. They include everything from high-resolution, color liquid-crystal-display (LCD) screens to melodic ringtones and embedded cameras.

Many of these 2.5G and 3G next-generation handsets hail from the standard lineup of vendors. Motorola's (www.motorola.com) Model A830, for example, is a 3G phone that offers a 4-K color LCD, global positioning technology, an MP3 player, and an integrated digital camera (FIG. 1). Samsung's (www.samsung.com) SPH-A500 looks more like a Star Trek communicator than a cell phone. It boasts a high-resolution, thin-film-transistor (TFT) color display. The SPH-A500 can download digital photos from Sprint's PCS Vision Camera via a short cable.

If these new devices aren't to your liking, consider accessing the Internet via one of those odd-looking combination PDA/cell-phone devices. Known as smartphones, these computationally oriented devices have many advantages. Concerning personal and business contact information and e-mail, for instance, they flaunt a unique capability that allows them to synchronize directly with the user's personal computer. They also provide the voice capabilities of a typical cell phone. Internet access is available via 2.5G and 3G cellular technology.

One example of a smartphone is Palm's (www.palm.com) Tungsten W handheld. Though it runs on a 2G GSM network, the Tungsten W can support 2.5G GPRS Internet access. Based on the Palm operating system (OS), it runs on a 33-MHz processor with 16 MB of RAM.

Another popular smartphone is the Kyocera 7135 (www.kyocera.com). Its clam-shell design incorporates a color LCD screen on the top half of the shell. A typical PDA-type Graffiti area sits on the lower part of the shell, just above the keypad. The 7135 also supports Palm's OS running on a 33-MHz processor with 16 MB of internal RAM.

Another option is the Sendo Z100 smartphone. This device utilizes the GSM/GPRS network. But it operates on Microsoft's (www.microsoft.com) Win-dows PocketPC operating system. Unlike many smartphones, this model will feature a true cell-phone shape with a physical numerical keypad, voice dialing, and other traditional cell-phone functions.

Strangely enough, many existing PDAs without cell-phone capabilities can access the Internet via very high-speed IEEE 802.11b connections. Some of these devices even support a Bluetooth hook-up to the Internet—usually as an add-on module. These PDAs act like a Wi-Fi-enabled laptop, which can connect wirelessly to the Web as long as it is near a hot spot.

Clearly, many wireless-Internet-access options are available today. The same can be said of the many devices on which these options can be utilized. It's a wonder that manufacturers haven't combined third-generation and Wi-Fi Internet-accessing capabilities in one device. Users could then connect to the Internet at high data rates near a hot spot. If they were anywhere else, they could just connect at lower data rates.

Furthermore, say you could have one device that could connect to the Internet. Why not make that device a laptop personal computer? Cellular handsets are fine for scanning headlines and checking e-mail in a hurry. But a laptop is still the closest thing to being in the office while you're on the road. Also, in terms of screen size and sheer computational power, no handset or PDA can yet match the performance of a laptop.

As it turns out, this idea has sparked some interest lately. Several vendors are now developing PC-card modems that enable Internet connections via cellular 2.5G and 3G networks. One example is Novatel Wireless (www.novatelwireless.com). Its Merlin series of PC cards provide access to GSM/GPRS, PCS, and CDMA connections. But these same PC-card modems can also provide Internet access through the use of a Wi-Fi wireless-LAN hot spot. Some cards will even let the user make cellular phone calls from a laptop.

An example of this type of multi-mode modem is Sierra Wireless' (www.sierrawireless.com) AirCard 555 (FIG. 2). This device acts like a wireless network interface card (NIC). It is being used on Verizon's CDMA 2000 1X networks for Internet access. Thanks to the device's built-in headphone jack, users can place phone calls right from a laptop or PDA.

Another alternative is Nokia's (www.nokia.com) D211. This multi-mode radio card enables "always-on" Internet access within GPRS and wireless-LAN coverage areas. It functions in EGSM 900/1800 networks, achieving data transmission rates of up to 40.2 kbps over GPRS. In the presence of a Wi-Fi-compliant wireless-network access point, the D211 can theoretically support data rates up to 11 Mbps.

HOT-SPOT ACCESS
By far, the fastest way to wirelessly access the Internet is through the use of an IEEE 802.11b, 802.11a, or draft 802.11g WLAN connection. 802.11b is the most widely used of these IEEE-standard wireless protocols. At typical connection speeds of 500 kbps, it can theoretically achieve a maximum rate of 11 Mbps in the unlicensed 2.4-GHz spectrum. In practice, the actual connection speed is usually only about half that much. But this is still much faster than 2.5G or 3G cellular-network speeds. Other WLAN standards, like 802.11a and 802.11g, will at the very least double the data rate of 802.11b.

For a typical laptop to connect to the wireless Internet, it must have a WLAN PC-modem card. It also needs to be reasonably close to an access point (AP) which, in turn, is connected to a broadband-Internet gateway via cable, DSL, or satellite. This last point is often a source of confusion. Access points themselves only provide a connection to an existing wired LAN. That LAN must be connected to a broadband gate—typically via a separate or built-in router. This gate, in turn, is connected to the Internet. Several commercial access points incorporate a router that connects directly to a DSL or cable-broadband box.

Most Wi-Fi access points have an optimum range of up to 460 ft. as long as no obstacles, such as office walls, block the signal path. To maintain a connection at extended ranges, the IEEE 802.11b specification provides lower-throughput rates of 11 Mbps at 75 to 125 ft. indoors. Outdoors, the lower-throughput rate is 11 Mbps at up to 750 ft. Again, these numbers assume no obstructions. A good rule of thumb is to keep the access point within 150 ft. of the connected laptop or PDA.

Luckily, the WLAN PC-modem cards that support 802.11b are both prolific and inexpensive. There are many common vendors of both PC cards and associated access points. To name a few, they include Proxim, SMC, and Linksys. Several companies also have introduced dual-mode cards and APs. In addition to 802.11b, they support the high-data-rate 802.11a standard. These products require dual-mode or combination-chip systems, as 802.11b and 802.11a operate at different frequencies and data protocols.

One example of dual-mode support is Proxim's (www.proxim.com) ORiNOCO 802.11a/b ComboCard. Another company, SMC Networks (www.smc.com), offers two dual-mode PC-card adapters. One adapter is for 802.11b/a, while the other is for the 802.11a/g standard. SMC's SMC2336W-AG is one of the first cards to support 802.11g, the latest "draft" IEEE WLAN standard. At 54 Mbps, this standard offers the same high data throughput as 802.11a. IEEE 802.11g operates at 2.4 GHz, however, while being backward compatible with 802.11b.

In addition, a dual-band access point that is compatible with 802.11b and 802.11a hails from Linksys (www.linksys.com), which was recently acquired by Cicso (www.cisco.com). Linksys' WAP51AB dual-band access point simultaneously communicates with 802.11b and 802.11a devices. To access the Internet, this AP must be linked to a LAN that connects to the Internet. Another option is the company's WRT51AB dual-band wireless-broadband router (FIG. 3). This router can connect directly to an Internet-accessible cable or DSL modem.

Recently, Linksys also announced the availability of an 802.11g access point. The WAP54G allows users to connect via 802.11g or 802.11b. As a result, users can maintain any existing 802.11b infrastructure.

Where can one find a hot-spot connection? As it turns out, WLAN access points are popping up as "hot spots" everywhere. Their locations range from the home office to commercial spaces like hotels, coffee shops, bookstores, and airports. Wireless-Internet access is even available from dockside boats (www.idockusa.com).

One of the better-known providers of Wi-Fi Internet access is Boingo Wireless (www.boingo.com). It boasts just over 600 Wi-Fi hot-spot locations, including Wayport's (www.wayport.com) nationwide Wi-Fi network. These hot spots are now positioned in hundreds of hotel lobbies.

Cellular providers like AT&T Wireless, T-Mobile, and Sprint also have been supporting hot-spot services. These major carriers see wireless-Internet accessibility via Wi-Fi-compatible hot spots as another source of revenue. Despite any tensions that were previously predicted, the carriers don't view Wi-Fi as competition for 2.5G and 3G cellular Internet access. For example, AT&T Wireless (www.att.com) recently announced an agreement with Wayport to offer joint high-speed data services. T-Mobile (www.voicestream.com), which is now known as VoiceStream, owns and operates the largest hot-spot network in North America. In addition, Sprint PCS is an investor in Boingo.

The cellular-network carriers' efforts to dip into the hot-spot market have seen a new twist: the creation of Cometa Networks (www.cometanetworks.com). AT&T, IBM, and Intel recently formed Cometa Networks to provide nationwide coverage for Wi-Fi hot spots. Cometa plans to offer services this year. By the end of 2004, it hopes to have deployed 20,000 hot spots across the country. Cometa Networks will compete directly with current hot-spot providers, like Boingo and Wayport.

Truly, the act of wirelessly accessing the Internet has never been easier or more confusing. Almost every mobile device provides some mechanism to access the Internet, whether that device is a cellular phone, personal digital assistant, Web tablet, or laptop computer. Now it's up to users to decide the access speed and data requirements that best suit their particular needs. Once these decisions are made, the choice of an appropriate network option and device can be fairly straightforward. Regardless of which route is taken, one thing remains certain: Future mobile devices will be even more tightly coupled to the wireless Internet.

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