B0s oscillation measurement with the CMS detector

We discuss here the performances for oscillation measurement expected at the Large Hadron Collider ( LHC) with the Compact Muon Solenoid ( CMS) experiment. The CMS tracker performances are described with emphasis on the secondary vertex measurement. Two independent methods for the oscillation measurement are then investigated. The first one ( 'direct') is tagging the charge of the b quark at the production and at the decay in the channel B0s -> Ds Pi, while the second one ( 'indirect') is making use of the lifetime measurement of the B0s and of the CP states separation in the channel B0s -> J/psi phi.