Sure, almost everyone is inextricably tied to a cell phone these days. But how much do we know about these phones? What technology drives them? And what can we expect in the future? Once you get past the alphabet soup of acronyms, the landscape gets intriguing.
3G IS HERE • Most people own 2.5G phones, which still get the job done (see "Perspective From The Past" ). Voice calls remain their primary application, but data services like instant messaging, SMS, and e-mail are growing in popularity. Current data rates can easily handle these functions.
Apple's iPhone uses EDGE. So do some of the BlackBerry phones. Others employ cdma2000 EV-DO. And while Internet access has been around for years using 2G and 2.5G, it never caught on in the cell-phone arena mainly due to browser, screen, and keyboard limitations. However, that's changing.
The main justification for 3G is mobile Internet access and faster e-mail. Multimedia transmissions from digital cameras, video, and audio also drive the networks to 3G. Video and audio downloads will continue to grow, as will gaming and location-based services thanks to improved GPS navigation (see "Surging Markets Drive New Wireless Technologies").
One marked change in these phones is the presence of Wi-Fi, much like Apple's iPhone. EDGE is fine for phone calls and slow-speed data. But if you need higher speeds, go to Wi-Fi. Since hotspots are everywhere these days, they are a good alternative to 3G data services. And as screens expand and browsers improve, Internet access gets more practical.
AT&T, Sprint Nextel, and Verizon already offer 3G data services. TMobile doesn't, but it does take the dual-mode phone route with built-in Wi-Fi. T-Mobile has a huge hotspot network, so this strategy works well. The company's Hotspot@Home service is an affordable option available right now.
Most 3G services are tied to the Card bus or USB modems for laptops (Fig. 1). These high-performance 3G modems give laptop road warriors fast Internet access, even in the absence of a decent Wi-Fi hotspot. Most carriers offer 3G phones, but the number of choices is small.
There are three 3G technologies: UMTS, cdma2000, and TDSCDMA (Fig. 2). The European Telecommunications Standards Institute (ETSI) defined the original 3G back in 2000, but now the Third Generation Partnership Project (3GPP) manages the standard. It became an ITU standard, with first implementations in Europe and Japan, in 2001.
The Universal Mobile Telecommunications System (UMTS) also is known as International Mobile Telecommunications 2000 (IMT-2000). Defined as the upgrade path for GSM, it's system-compatible with GSM. However, there's a different radio technology. Specifically, UMTS 3G uses wideband CDMA (WCDMA) with direct-sequence spread-spectrum (DSSS) in 5-MHz channels with frequency-division duplexing (FDD).
With such an arrangement, it's possible to get downlink data rates up to 2 Mbits/s when fixed, up to 384 kbits/s while moving slowly, and up to 144 kbits/s when moving rapidly. In the U.S., the UMTS 3G spectrum sits in the 806- to 890-MHz band, with potential for the 1.710- to 1.755-GHz and 2.1-GHz bands. In Europe, 3G uses 1900 to 2025 MHz and 2110 to 2200 MHz.
Built by Qualcomm, cdma2000 with EV-DO is a fully recognized 3G standard. The 3GPP2 is the organization, like 3GPP, that develops the cdma2000 standard.
The cdma2000 standard began as a 2.5G standard, yet it's continuously spilling into 3G's domain as a result of various upgrades. The 1xRTT version supported data rates to 144 kbits/s, while the first EV-DO versions (Rev. 0) crossed into 3G territory with a maximum downlink speed of 2.45 Mbits/s under ideal conditions. Later versions known as Rev. A and Rev. B have leaped well ahead of UMTS in some ways.
China developed Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) to fulfill its 3G needs. Instead of the spectrum-eating FDD methods that use paired chunks of spectrum with UMTS and cdma2000, its time-synchronized time-division duplex (TDD) modem only employs a single 1.6-MHz band. It also demonstrated a 384-kbit/s data rate using Analog Devices' Othello chip set, lagging behind the other 3G technologies, but future advances are expected.
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