  Massive MIMO (mMIMO) enables users with different requirements to get
connected to the same base station (BS) on the same set of resources. In the
uplink of Multiuser massive MIMO (MU-mMIMO), while such heterogeneous users are
served, decoupling facilitates the use of user-specific detection schemes. In
this paper, we propose a low-complexity linear decoupling scheme called
Sequential Decoupler (SD), which aids in the parallel detection of each user's
data stream. The proposed algorithm shows significant complexity reduction.
Simulations reveal that the complexity of the proposed scheme is only 0.15% of
the conventional Singular Value Decomposition (SVD) based decoupling and is
about 47% of the pseudo-inverse based decoupling schemes when 80 users with two
antennas each are served by the BS. Also, the proposed scheme is scalable when
new users are added to the system and requires fewer operations than computing
the decoupler all over again. Further numerical analyses indicate that the
proposed scheme achieves significant complexity reduction without any
degradation in performance and is a promising low-complex alternative to the
existing decoupling schemes.
