HIGH RATE TRANSMIT DIVERSITY ASSISTED
SPACE SHIFT KEYING MODULATION OVER
MIMO CHANNELS
Zongdi Yue
1
, Lei Li
1
, Shu Fang
1
, Jian Wu
1
, Su Hu
1
1
University of Electronic Science and Technology of China, Chengdu, 611731, China
yuezongdi@139.com
Keywords: Multiple-Input Multiple-Output (MIMO),
Space Shift Keying (SSK), High Rate Transmit Diversity
Assisted Space Shift Keying (HT-SSK), Transmit
Diversity.
Abstract
Space shift keying (SSK) modulation is a newly emerging
transmission technology for multiple-input multiple-out-
put (MIMO) wireless systems. In this paper, we propose a
novel high rate transmit diversity assisted space shift key-
ing (HT-SSK) modulation scheme to achieve the transmit
diversity gain over SSK system with high spectrum effi-
ciency. We first apply antenna shift method at each time
slot to achieve transmit diversity with L time slots. Then,
we use the different transmit signal combinations of L
time slots to convey the additional
information
bits, where c is the number of transmit symbols in total.
Thus, the proposed HT-SSK modulation scheme achieves
higher spectrum efficiency than conventional transmit
diversity assisted space shift keying modulation scheme,
while achieves the same transmit diversity gain with small
performance loss. Simulation results show that the pro-
posed HT-SSK scheme provides significant performance
gain than SSK modulation scheme with the same spec-
trum efficiency. It also outperforms the conventional spa-
tial modulation (SM) scheme.
1 Introduction
Multiple-input multiple-output (MIMO) techniques have
attracted extensive attentions because the capability to
improve the spectrum efficiency of wireless link signifi-
cantly [1]-[4]. Conventional MIMO techniques convey
information bits by the amplitude and phase modulation
(APM) symbols. Space shift keying (SSK) modulation
[5]-[8] is regarded as an emerging trans-mission tech-
nique that introduces MIMO configuration and exploits
the spatial domain to convey information. Unlike the tra-
ditional APM based MIMO technique, SSK conveys the
source information by the indices of active antenna rather
than the conventional transmitting APM symbols. For
SSK modulation, each transmission activates just one an-
tenna and transmits a predetermined signal. This signal is
previously known at the transceiver and therefore conveys
no information bits. Thus, the source bits are fully con-
veyed by the spatial domain. The receiver of SSK system
aims to detect the activated transmit antenna index to re-
cover the information bits. With the increasing of the
transmit antennas, more information bits are conveyed by
the transmit signal. The spectrum efficiency of SSK is
bps/Hz, where
is the transmit antenna number
and it is called the M-ary SSK modulation [5]. Since SSK
transmits only one signal each time, it provides the bene-
fits such as no inter-channel interference, no inter-antenna
synchronization and reduction of radio frequency (RF)
chains compared to the conventional MIMO systems. Si-
milar to SSK, only one transmit antenna is activated dur-
ing any transmission period for spatial modulation (SM)
[9]-[12]. SM utilizes antenna indices and an APM symbol
to convey data bits together, which can be regarded as a
special case of SSK. The spectrum efficiency of SM
achieves
bps/Hz, where
is the
quadrature amplitude modulation (QAM) or PSK modula-
tion order. However, the detection complexity of SM in-
creases while its performance degrades compared with
SSK.
Both SSK modulation and SM techniques can achieve
the receive diversity gain by increasing the number of
antennas at the receiver. However, it is difficult to achieve
transmit diversity gain in SSK or SM systems directly. In
[13], the solution has its basic foundation on the transmis-
sion of signals with good time-correlation properties and
is shown that it increases two fold the diversity order for
arbitrary transmit and receive antennas. In [14], transmit
diversity assisted space shift keying (ST-SSK) is advo-
cated, which can achieve a transmit diversity gain at cost
of a moderate throughput loss. The transmit diversity gain
is achieved by sending the same data information in dif-
ferent time slot. In [15], it aims at exploiting the SM con-
cept and achieving transmit-diversity gain provided by
space-time block codes (STBC) technology. The proposed
scheme takes advantage of SM and STBC technologies to
design transmit-diversity and high rate modulation scheme.
It exploits the location-specific property of the wireless
channel and an additional dimension for data transmission.
The sophisticated concept of space time shift keying
(STSK) scheme was invented for MIMO system in [16].
The proposed STSK scheme constitutes a generalized
shift-keying architecture utilizing both the space as well as
the time dimensions. The STSK scheme utilizes Q disper-
sion matrices to obtain a flexible diversity and multiplex-
ing tradeoff. Generalized space-time shift keying (G-
STSK) architecture is proposed in [17], which acts as a