  Merging wireless traces is a fundamental step in measurement-based studies
involving multiple packet sniffers. Existing merging tools either require a
wired infrastructure or are limited in their usability. We propose WiPal, an
offline merging tool for IEEE 802.11 traces that has been designed to be
efficient and simple to use. WiPal is flexible in the sense that it does not
require any specific services, neither from monitors (like synchronization,
access to a wired network, or embedding specific software) nor from its
software environment (e.g. an SQL server). We present WiPal's operation and
show how its features - notably, its modular design - improve both ease of use
and efficiency. Experiments on real traces show that WiPal is an order of
magnitude faster than other tools providing the same features. To our
knowledge, WiPal is the only offline trace merger that can be used by the
research community in a straightforward fashion.
