The Antenna Selection Code MATLAB is related to a downlink system with multiple antenna users, combining received signals and enabling multi-stream multiplexing. This package is linked to the scientific paper: Emil Björnson, Marios Kountouris, Mats Bengtsson, Björn Ottersten, titled, \"IEEE Transactions on Signal Processing, Vol. 61, No. 13, July 2013, Pages 3431-3446.\" The package provides a MATLAB-based simulation environment that can replicate all numerical results and figures from the paper. We encourage reproducible research! In a downlink multi-antenna system with many users, the multiplexing gain is severely limited by the number of transmitting antennas (N) and how they are used. When the total number of receiving antennas at the multi-antenna users is much larger than (N), it is possible to achieve maximal multiplexing gain with various transmitting/receiving strategies. For instance, excess receiving antennas can be used to schedule users with near-orthogonal effective channels, to multiplex multiple streams to users with well-conditioned channels, and/or to implement interference-aware receive combining. This paper aims to answer the following question: Should the (N) data streams be allocated to a few users (each with many streams) or to multiple users (each with few streams, thereby enabling receive combining)? The analysis in the paper concludes that...