Datasheet

Q. How does the modem select the service to which to attach? Does it switch to a better service when one is

available?

A. Yes. For GSM networks, the modem always looks for HSPA/HSPA+ as the first choice. If HSPA/HSPA+ is not

available, the modem downshifts to the next best available radio network; that is, UMTS to EDGE and finally to

General Packet Radio Service (GPRS). If you have only EDGE service, the modem continues to scan in the

background for UMTS or HSPA service. If the UMTS or HSPA service becomes available, the modem

automatically switches to that service. For CDMA networks, the modem always looks for EVDO Rev A first,

then Rev 0, and then 1xRTT.

Q. What factors affect throughput on the 3G WWAN?

A. Several factors can affect throughput and performance:

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Congestion: 3G WWAN data services use a shared wireless medium; therefore, the number of active users

in a cell site affects throughput.

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Coverage: The distance from the cell tower affects throughput. The further you are located from the cell

tower, the lower the achievable throughput. A site survey is recommended as part of the installation process

to help ensure adequate network coverage.

●

Interference: RF noise from nearby devices can inhibit performance.

Q. Are the Cisco 3G WWAN interfaces suitable for use as primary links?

A. The 3G wireless standards for data rate and latency performance have continuously improved. Today both

Evolution-Data Optimized or Evolution-Data only EVDO and HSPA services offer fractional T1 data rates and

latency below 100 milliseconds (ms). For sites and applications that have low and intermittent data usage

(such as bank ATMs, kiosks, and gas stations), the Cisco 3G WWAN interface may be suitable.

Q. Can I run voice-over-IP (VoIP) traffic over Cisco 3G WWAN Express Cards?

A. Yes. It is recommended to use the latest 3G technology—EVDO Rev A and HSPA+/HSPA—to run VoIP over

a 3G link.

Q. Is latency a problem with the Cisco 3G solution?

A. Latencies vary by technology. Depending on the service available in your area and the applications you are

running over your link, latency may be a concern. The most advanced technologies support latencies of less

than 100 ms.