  We present a mathematical formulation of old teleportation protocol (original
teleportation protocol introduced by Bennett et.al.) for mixed states and study
in detail the role of mixedness of the two qubit quantum channel in a
teleportation protocol. We show that maximally entangled mixed state described
by the density matrix of rank-4 will be useful as a two qubit teleportation
channel to teleport a single qubit mixed state when the teleportation channel
parameter p1 greater than 0.5. Also we discuss the case when p1 less than equal
to 0.5.
