20. Use Of WLAN, LAN, And PAN Components, Continued

To keep the cards and their communications channels constantly active, we custom-built a small program that copied a 1.2 MB compressed file from the notebook to a dedicated server in an endless loop. Because the file fits entirely into RAM, our measurements include no distortions introduced from additional disk access. As usual, we wrote an entry to a file every ten seconds and kept that activity up until the battery ran dry and the notebook shut itself down.

Our home-brew "Network Analyzer" created constant network traffic

Discussion

Compared to simple office use (2h 43min) intensive WLAN activity reduces battery lifetime up to 36% (the Gigabyte PC Card had the biggest effect overall). The internal mini-PCI modules had less impact. For example, tests with the Broadcom unit showed a 20% loss in battery life (about 34 minutes). It was especially noteworthy to observe that Intel's "Centrino Module" reduced battery lifetime even more than the competitor's product.