Martian Intuition

How does Sprint's Mobile Broadband service perform in Austin? Is it worth a twenty-four month commitment totaling over $1500?

In an effort to answer this question, here's a summary of my experiences & observations during this first month of going mobile.

Bandwidth & Latency

During an ssh terminal session—where characters typed are sent across the network and echoed back for display—the cellular radio link makes the network feel springy. When transmission delays occur, responses eventually snap back with a quickness.

Here's an example of a typical session with a 4-bar signal:

For 125MB of Amazon's MP3 downloads, a single-connection download started out strong, bursting up to 153KBps:

and then wobbled around 90KBps, continuing more slowly than those initial bursts.

Concurrent connections saturating the bandwidth (e.g. the iTunes Music Store default three-connection downloads) tend to maintain ~200KBps combined. Even during download-heavy traffic, the connection remained responsive for other network traffic.

Stuck in a spot with weak signal, 2-bars or less? As expected, connection latency rises & throughput drops; still usable but hardly "broadband." Concurrent connections can falter at 1-bar. I observed ssh/scp sessions stalling indefinitely with such little signal.

Stability

In some locations with either weak signal or from within a building, the PPP connection will be "ended by the remote host", within the first 20-seconds. That's a symptom of my signal being to noisy to reach the base-station. Landline/analog modems drop calls with this error when the line signal is to noisy.

Disconnecting & reconnecting can yield a dramatic improvement in connection quality. Once connected, sessions that start out as only 1xRTT (that's one 144Kbps CDMA2000 channel) may rev up to EV-DO.

Once established, the connection is reliable & stable. Not once was my connection dropped during up to 3-hour sessions. YMMV when in a moving vehicle.

Power Consumption

The official specs state:

• Voltage: 3.3V
• Typical Current - 370mA (1x), 470 mA (EV-DO)
• Maximum Current - 1000 mA (EV-DO)

That means typical EV-DO usage will drain between 1.5 & 3.3 Watts. For comparison, the power-hungry hard drive in the MacBook Pro consumes between 0.6 & 1.9 Watts.

This extra battery drain is quite noticeable, cutting an hour from my normal 3:15 of work time on a full charge. For comparison, the Mac's built-in AirPort (802.11 a|b|g|n wireless) makes no noticeable difference on battery-powered work time.

Network Address

The client IP address is dynamically allocated. It changes on every connection.

The Verdict

I'm sticking with the service. The advantages of a private, mobile internet connection outweigh the admittedly expected downsides. The uncertainty: can Sprint hang in there? It's tough times in pin-drop land. Maybe I'll get an early break from my two-year contract!