  In this paper, the outage behavior and diversity order of the mixture
transceiver architecture for multiple-input single-output broadcast channels
are analyzed. The mixture scheme groups users with closely-aligned channels and
applies superposition coding and successive interference cancellation decoding
to each group composed of users with closely-aligned channels, while applying
zero-forcing beamforming across semi-orthogonal user groups. In order to enable
such analysis, closed-form lower bounds on the achievable rates of a general
multiple-input single-output broadcast channel with superposition coding and
successive interference cancellation are newly derived. By employing
channel-adaptive user grouping and proper power allocation, which ensures that
the channel subspaces of user groups have angle larger than a certain
threshold, it is shown that the mixture transceiver architecture achieves full
diversity order in multiple-input single-output broadcast channels and
opportunistically increases the multiplexing gain while achieving full
diversity order. Furthermore, the achieved full diversity order is the same as
that of the single-user maximum ratio transmit beamforming. Hence, the mixture
scheme can provide reliable communication under channel fading for
ultra-reliable low latency communication. Numerical results validate our
analysis and show the outage superiority of the mixture scheme over
conventional transceiver designs for multiple-input single-output broadcast
channels.
