3 research outputs found
Precoder Design and Power Allocation for Downlink MIMO-NOMA via Simultaneous Triangularization
In this paper, we consider the downlink precoder design for two-user
power-domain multiple-input multiple-output (MIMO) non-orthogonal multiple
access (NOMA) systems. The proposed precoding scheme is based on simultaneous
triangularization and decomposes the MIMO-NOMA channels of the two users into
multiple single-input single-output NOMA channels, assuming low-complexity
self-interference cancellation at the users. In contrast to the precoding
schemes based on simultaneous diagonalization (SD), the proposed scheme avoids
inverting the MIMO channels of the users, thereby enhancing the ergodic rate
performance. Furthermore, we develop a power allocation algorithm based on the
convex-concave procedure, and exploit it to obtain the ergodic achievable rate
region of the proposed MIMO-NOMA scheme. Our results illustrate that the
proposed scheme outperforms baseline precoding schemes based on SD and
orthogonal multiple access for a wide range of user rates and performs close to
the dirty paper coding upper bound. The ergodic rate region can further be
improved by utilizing a hybrid scheme based on time sharing between the
proposed MIMO-NOMA scheme and point-to-point MIMO.Comment: Accepted for presentation at the 2021 IEEE Wireless Communications
and Networking Conference. This paper is the conference version of
arXiv:2006.06471 with 6pp, 2 figures, for code, see
https://gitlab.com/aravindh.krishnamoorthy/mimo-nom
Precoder Design and Statistical Power Allocation for MIMO-NOMA via User-Assisted Simultaneous Diagonalization
In this paper, we investigate the downlink precoder design for two-user
power-domain multiple-input multiple-output (MIMO) non-orthogonal multiple
access (NOMA). We propose a novel user-assisted (UA) simultaneous
diagonalization (SD) based MIMO-NOMA scheme that achieves SD of the MIMO
channels of both users through a combination of precoder design and
low-complexity self-interference cancellation at the users, thereby
considerably lowering the overall decoding complexity compared to joint
decoding. The achievable ergodic user rates of the proposed scheme are analyzed
for Rayleigh fading channels based on a finite-size random matrix theory
framework, which is further exploited to develop a statistical power allocation
algorithm. Simulation and numerical results show that the proposed UA-SD
MIMO-NOMA scheme significantly outperforms orthogonal multiple access and a
benchmark precoder design performing SD via generalized singular value
decomposition in terms of the achievable ergodic rate region for most user
rates. The ergodic rate region is further enhanced by a hybrid scheme which
performs time sharing between the proposed UA-SD MIMO-NOMA scheme and
single-user MIMO.Comment: Accepted by the IEEE Transactions on Communications, see DOI. 32
pages, 8 figures, for associated code, see
https://gitlab.com/aravindh.krishnamoorthy/mimo-nom
Uplink and Downlink MIMO-NOMA with Simultaneous Triangularization
In this paper, we consider the uplink and downlink precoder design for
two-user power-domain multiple-input multiple-output (MIMO) non-orthogonal
multiple access (NOMA) systems. We propose novel uplink and downlink precoding
and decoding schemes that lower the decoding complexity at the receiver by
decomposing the MIMO-NOMA channels of the users into multiple single-input
single-output (SISO)-NOMA channels via simultaneous triangularization (ST) of
the MIMO channels of the users and a low-complexity self-interference
cancellation at the receiver. The proposed ST MIMO-NOMA schemes avoid channel
inversion at transmitter and receiver and take advantage of the null spaces of
the MIMO channels of the users, which is beneficial for the ergodic achievable
rate performance. We characterize the maximum ergodic achievable rate regions
of the proposed uplink and downlink ST MIMO-NOMA schemes, and compare them with
respective upper bounds, baseline MIMO-NOMA precoding schemes, and orthogonal
multiple access (OMA). Our results illustrate that the proposed schemes
significantly outperform the considered baseline MIMO-NOMA precoding schemes
and OMA, and have a small gap to the respective upper bounds for most channel
conditions and user rates. Moreover, we show that a hybrid scheme, which
performs time sharing between the proposed uplink and downlink ST MIMO-NOMA and
single-user MIMO, can improve performance even further.Comment: Accepted by the IEEE Transactions on Wireless Communications. This is
the journal version of the submission arXiv:2006.04581 with 33 pages, 10
figures, and 2 tables. For associated code see
https://gitlab.com/aravindh.krishnamoorthy/mimo-nom