  A key ingredient to searches for physics beyond the Standard Model in
$B^{0}_{s}$ mixing phenomena is the measurement of the
$B^{0}_{s}$-$\bar{B}^{0}_{s}$ oscillation frequency, which is equivalent to the
mass difference $\Delta m_{s}$ of the $B^{0}_{s}$ mass eigenstates. Using the
world's largest $B^{0}_{s}$ meson sample accumulated in a dataset,
corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected by the
LHCb experiment at the CERN LHC in 2011, a measurement of $\Delta m_{s}$ is
presented. A total of about 34,000 $B^{0}_{s}\rightarrowD^{-}_{s}\pi^{+}$
signal decays are reconstructed, with an average decay time resolution of 44
fs. The oscillation frequency is measured to be \mbox{$\Delta m_{s}$ = 17.768
$\pm$ 0.023 (stat) $\pm$ 0.006 (syst) ps$^{-1}$}, which is the most precise
measurement to date.
