Mobile & Wireless Q & A

In the past month, I've received several mobile and wireless questions from readers, and I think the answers have applicability to this UPDATE's general readership.

In the December 2, 2001, edition of Mobile & Wireless UPDATE, you wrote, "Second generation (2G) networks feature a 9.6Kbps to 20Kbps wireless data speed, 2.5G networks handle 20Kbps to 128Kbps, and 3G networks support up to 384Kbps." After reading articles about Universal Mobile Telecommunications System (UMTS), I gather that UMTS supports speeds as fast as 2Mbps. Am I missing something?

UMTS is a 3G standard that the International Telecommunications Union (ITU) developed. Part of the UMTS specification describes data rates specific to various user scenarios. These user scenarios break down into three categories: stationary (fixed) user, slow-moving user, and fast-moving user (e.g., car, bus, train). The theoretical data rate for fixed UMTS communication is 2Mbps. The 384Kbps number is specific to slow-moving users. However, these data rates are theoretical and are achieved only in perfect conditions. Also, remember that all users in a cell site must share data rates. Therefore, as the number of wireless data users increases, the actual data rates available to each user will be slower. So, 384Kbs is probably a high estimate of the data speeds we'll see with UMTS.

Why have the media devoted so little ink to the incompatibility of smart phones and Wi-Fi? What do you think of the possibility of a single CompactFlash (CF) slot on these devices to permit the use of an 802.11b card?

Great question. Smart phones' lack of support for Wi-Fi comes down to two primary reasons. First, Wi-Fi requires a lot of power to transmit data at fast data rates. If you've ever used a Wi-Fi card with a Pocket PC, you know how quickly the card can drain a battery. In case you're wondering why Bluetooth is more compatible with smart phones, Bluetooth uses about a hundredth of the power that Wi-Fi requires. Second, wireless carriers who sell smart phones want you to use their wireless data services—for example, General Packet Radio Service (GPRS) and Radio Transmission Technology (1xRTT). Wireless carriers have invested much money into upgrading their networks to support faster data rates and want to maximize the returns. The inclusion of a CF slot on smart phones is a possibility, but a Secure Digital (SD) slot is more likely. T-Mobile's Pocket PC Phone Edition has an SD slot, but it supports only file storage—not other wireless cards. Go figure!

From what I've seen, the Audiovox Thera Pocket PC on the Verizon Wireless network hasn't enjoyed the same success as the T-Mobile device because of the slowness of the current Code Division Multiple Access (CDMA) speed on Verizon's network. With GPRS, T-Mobile can keep the device continuously connected at about 40Kbps. Verizon can offer only 14.4Kbps. What are your findings?

The T-Mobile device is a true Pocket PC Phone Edition device, whereas the Thera is a regular Pocket PC device with a built-in Sierra Wireless wireless data card. Therefore, battery consumption and other features aren't optimized in the Thera. The Verizon network supports higher data rates in many regions, but Verizon is struggling to upgrade all sections of its nationwide network to its Express Network. Verizon has different network infrastructures in different regions following the mergers that formed the combined Verizon network. In many locations, the speed defaults to the lower 14.4Kbps.

I'm aware of all the Bluetooth and Wi-Fi applications in personal and office IT, but I have little knowledge of the potential applications in industrial technology. Do you know of any industrial automation companies that are applying either technology?

I don't have specific examples of industrial automation companies using Bluetooth or Wi-Fi. However, I've heard about efforts to use Bluetooth for equipment tracking similar to the way people use current Radio Frequency Identification (RFID) technologies. The advantages of using Bluetooth are the low power consumption and the low costs of Bluetooth radios.

If you have any mobile and wireless questions, send them to me at the address above. Perhaps your question will appear in this space. See you next time.

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