Transmit Antenna Selection with Precoding for Spatial Modulation MIMO Systems
Kaili Zheng, Shu Fang, Yu Zeng, Yanqiu Zhang
Department of National Key Laboratory on Communications
University of Electronic Science and Technology of China
Chengdu, China
e-mail: fangshu@uestc.edu.cn
Abstract—Spatial Modulation (SM) is an efficient transmission
technique for multiple input multiple output (MIMO) wireless
systems, which is proposed to implement MIMO systems with
low complexity and cost. In order to obtain transmit diversity
gain, transmit antenna selection (TAS) technique is adopted in
SM systems to achieve better performance. In this paper, we
present a novel transmit antenna selection method with
precoding for multiple input multiple output SM-MIMO
systems, denoted as TASP. The proposed TASP scheme is
totally different from the existing TAS schemes. Because it is
not just a common TAS scheme, but it can also combine with
all of the existing TAS schemes to further improve their
performance. The simulation results show that the proposed
TASP scheme brings a clear superiority in performance than
conventional space shift keying (SSK), SM and the capacity
optimized antenna selection (COAS) scheme. It also shows
performance improvement when combining with other TAS
schemes.
Keywords-spatial modulation; MIMO; TAS; precoding;
transmit diversity gain
Spatial modulation (SM) is a type of efficient modulation
scheme which is proposed as a low-complexity and low-cost
implementation of multiple-input multiple-output (MIMO)
communication systems. It employs space shift keying (SSK)
with amplitude-phase modulation (APM) techniques in
conjunction to enhance the spectrum efficiency [1]. In
conventional SM systems, only one transmit antenna is
activated for emitting an APM symbol each time. And the
information bits are partially conveyed by the antenna index
of the activated antenna and partially conveyed by the APM
symbol. At the receiver side, the maximum-likelihood (ML)
detection is adopted as an optimal criterion to estimate the
index of the activated transmit antenna and the emitted APM
symbol jointly for recovering the information bits [2].
For further improving the transmission performance of
SM, several types of transmit antenna selection (TAS)
criteria are investigated in SM-MIMO systems. Combining
with effective TAS methods, the transmission performance
of SM-MIMO systems can be enhanced significantly. A
norm-based TAS criterion was proposed to obtain transmit
diversity gain in [3]. In [4], a closed form expression for the
outage probability of SM-MIMO systems with norm-based
TAS was validated. In [5], the author presented a novel TAS
scheme named transmission optimized spatial modulation
(TOSM) which aims to minimize the average bit error
probability. In [6], a novel TAS criterion based on the
optimization of the Euclidean distance of the received
constellation points named Euclidean distance antenna
selection (EDAS) was proposed, which can achieve a high
diversity gain. Besides, a capacity optimized antenna
selection (COAS) scheme was also proposed in [6], where
the transmit antennas are selected with the maximum
Frobenius norm of the channel vector corresponding to each
transmit antenna. The achievable transmit diversity order of
SM employing EDAS was quantified in [7]. Due to the high
complexity, an efficient method termed as QR
decomposition-based TAS (QRD-TAS) was proposed for
further reduction in complexity of EDAS in [8]. Different
with directly optimizing the Euclidean distance, the author
proposed a low-complexity singular value decomposition-
based TAS (SVD-TAS) method for maximizing the lower
bound of the Euclidean distance in [9]. For striking a flexible
tradeoff in terms of the BER attained and the complexity
imposed, an error-vector magnitude based TAS (EVM-TAS)
was proposed in [10].
In this paper, we propose a novel TAS scheme with
precoding technique named TASP. Unlike the classic TAS
schemes, the proposed TASP is quite different in the way of
operation process. The conventional TAS schemes always
select an optimal transmit antenna subset among the total
transmit antennas before spatial modulation operation.
However, the proposed TASP scheme selects an optimal
transmit antenna subset after spatial modulation operation.
This characteristic makes it possible to combine TASP with
the existing TAS algorithms to further enhance the
transmission performance. Because for TASP, before spatial
modulation, conventional TAS schemes for transmit antenna
selection could be adopted. It means TASP is very flexible
that it can either work as a common TAS scheme or be
further combined with other TAS schemes. When working as
a common TAS scheme, TASP can significantly improve the
BER performance for conventional SM. And when
combining with other existing TAS schemes, the proposed
TASP scheme can further strengthen their improvement of
BER performance.
The contributions of this paper are as follows. Firstly, we
present a novel transmit antenna selection scheme with
precoding called TASP for SM-MIMO systems, which is
different from the existing TAS schemes. Secondly, we
analyze the optimal ML detection for the proposed TASP