5 research outputs found
Differential Reflecting Modulation for Reconfigurable Intelligent Surface Based Communications
Reconfigurable intelligent surface (RIS) based communications have emerged as
a new paradigm. This letter proposes a differential reflecting modulation (DRM)
scheme for RIS based communication systems. In DRM, information bits are
jointly carried by the activation permutations of the reflecting patterns and
the phases of the transmitted signals, leading to that DRM can work without any
channel state information (CSI) at the transmitter, RIS or receiver. In other
words, DRM can release the intricate and resource-consuming channel estimation
in the transmission process. Simulation results show that the proposed DRM pays
an acceptable SNR penalty compared to non-differential modulation with coherent
detection.Comment: Reconfigurable intelligent surface, differential reflecting
modulation, accepted by IEEE Communications Letter
Signal Shaping for Generalized Spatial Modulation and Generalized Quadrature Spatial Modulation
This paper investigates generic signal shaping methods for
multiple-data-stream generalized spatial modulation (GenSM) and generalized
quadrature spatial modulation (GenQSM) based on the maximizing the minimum
Euclidean distance (MMED) criterion. Three cases with different channel state
information at the transmitter (CSIT) are considered, including no CSIT,
statistical CSIT and perfect CSIT. A unified optimization problem is formulated
to find the optimal transmit vector set under size, power and sparsity
constraints. We propose an optimization-based signal shaping (OBSS) approach by
solving the formulated problem directly and a codebook-based signal shaping
(CBSS) approach by finding sub-optimal solutions in discrete space. In the OBSS
approach, we reformulate the original problem to optimize the signal
constellations used for each transmit antenna combination (TAC). Both the size
and entry of all signal constellations are optimized. Specifically, we suggest
the use of a recursive design for size optimization. The entry optimization is
formulated as a non-convex large-scale quadratically constrained quadratic
programming (QCQP) problem and can be solved by existing optimization
techniques with rather high complexity. To reduce the complexity, we propose
the CBSS approach using a codebook generated by quadrature amplitude modulation
(QAM) symbols and a low-complexity selection algorithm to choose the optimal
transmit vector set. Simulation results show that the OBSS approach exhibits
the optimal performance in comparison with existing benchmarks. However, the
OBSS approach is impractical for large-size signal shaping and adaptive signal
shaping with instantaneous CSIT due to the demand of high computational
complexity. As a low-complexity approach, CBSS shows comparable performance and
can be easily implemented in large-size systems.Comment: Summited to IEEE TW
Reflecting Modulation
Reconfigurable intelligent surface (RIS) has emerged as a promising technique
for future wireless communication networks. How to reliably transmit
information in a RIS-based communication system arouses much interest. This
paper proposes a reflecting modulation (RM) scheme for RIS-based
communications, where both the reflecting patterns and transmit signals can
carry information. Depending on that the transmitter and RIS jointly or
independently deliver information, RM is further classified into two
categories: jointly mapped RM (JRM) and separately mapped RM (SRM). JRM and SRM
are naturally superior to existing schemes, because the transmit signal
vectors, reflecting patterns, and bit mapping methods of JRM and SRM are more
flexibly designed. To enhance transmission reliability, this paper proposes a
discrete optimization-based joint signal mapping, shaping, and reflecting
(DJMSR) design for JRM and SRM to minimize the bit error rate (BER) with a
given transmit signal candidate set and a given reflecting pattern candidate
set. To further improve the performance, this paper optimizes multiple
reflecting patterns and their associated transmit signal sets in continuous
fields for JRM and SRM. Numerical results show that JRM and SRM with the
proposed system optimization methods considerably outperform existing schemes
in BER.Comment: accepted for publication in IEEE JSAC SI titled Wireless Networks
Empowered by Reconfigurable Intelligent Surface
Adaptive Spatial Modulation for Visible Light Communications with an Arbitrary Number of Transmitters
As a power and bandwidth efficient modulation scheme, the optical spatial
modulation (SM) technique has recently drawn increased attention in the field
of visible light communications (VLC). To guarantee the number of bits mapped
by the transmitter's index at each timeslot is an integer, the number of
transmitters (i.e., light-emitting diodes) in the SM based VLC system is often
set be a power of two. To break the limitation on the required number of
transmitters and provide more design flexibility, this paper investigates the
SM based VLC with an arbitrary number of transmitters. Initially, a channel
adaptive bit mapping (CABM) scheme is proposed, which includes three steps: bit
mapping in space domain, bit mapping in signal domain, and the channel adaptive
mapping. The proposed CABM scheme allows operation with an arbitrary number of
transmitters, and is verified to be an efficient scheme through numerical
results. Based on the CABM scheme, the information-theoretical aspects of the
SM based VLC are analyzed. The theoretical expression of the mutual information
is first analyzed. However, it is very hard to evaluate system performance. To
obtain more insights, a lower bound of the mutual information is derived, which
is in closedform. Both theoretical analysis and numerical results show that the
gap between the mutual information and its lower bound is small. Finally, to
further improve the system performance, the precoding scheme is proposed for
the SM based VLC. Numerical results show that the system performance improves
dramatically when using the proposed precoding scheme.Comment: Accepted by IEEE Access, 201
Signal Shaping for Non-Uniform Beamspace Modulated mmWave Hybrid MIMO Communications
This paper investigates adaptive signal shaping methods for millimeter wave
(mmWave) multiple-input multiple-output (MIMO) communications based on the
maximizing the minimum Euclidean distance (MMED) criterion. In this work, we
utilize the indices of analog precoders to carry information and optimize the
symbol vector sets used for each analog precoder activation state.
Specifically, we firstly propose a joint optimization based signal shaping
(JOSS) approach, in which the symbol vector sets used for all analog precoder
activation states are jointly optimized by solving a series of quadratically
constrained quadratic programming (QCQP) problems. JOSS exhibits good
performance, however, with a high computational complexity. To reduce the
computational complexity, we then propose a full precoding based signal shaping
(FPSS) method and a diagonal precoding based signal shaping (DPSS) method,
where the full or diagonal digital precoders for all analog precoder activation
states are optimized by solving two small-scale QCQP problems. Simulation
results show that the proposed signal shaping methods can provide considerable
performance gain in reliability in comparison with existing mmWave transmission
solutions.Comment: To appear in IEEE TW