Low-complexity Transceiver Design Research Articles

Enhancing the performance of LiFi communication with OSTBC, QAM, and OFDM: High-capacity, low-complexity transceiver design

Light fidelity (LiFi) is one of the most promising areas within wireless optical communication system. It provides many benefits, including high capacity, improved security and enhanced cost-effectiveness. However, there is still challenges which are link blockages, attenuation, interference and bandwidth restriction of modulation techniques. Orthogonal space–time block coding (OSTBC) offers a suitable solution to address link blockage by providing an alternative communication channel between the transmitter and the receiver. OSTBC has more tolerate to the practical channel impact limitation such as attenuation and interference that may occur in overlapping regions. In addition, the use of the OSTBC technique enhances the system’s ability to transfer data as the transmission rate is duplicated by the number of transmitters and receivers. This paper proposes the utilisation of a LiFi transceiver-based OSTBC that employs quadrature amplitude modulation (QAM) in conjunction with orthogonal frequency-division multiplexing (OFDM). Co-simulation tools have been done by integrated Matlab with Optisystem, were used in the design of LiFi transceiver with all assumption required. The findings reveal the capability of LiFi transceiver of transmitting rate up to 15 Gbps with maintaining a satisfactory bit error rate (BER) of 10−4 over a link range of 200 m evenin the presence of realistic channel effects. Moreover, the LiFi transceiver’s structure used does not incorporate optical amplifier components, resulting in reduced computational complexity compared to conventional LiFi transceivers. The proposed system proved its progress over the previous work under the influence of the same input effects.

Multi-antenna GFDM for resilient decentralized communications

Owing to the superior performance of generalized frequency division multiplexing (GFDM), in terms of enhanced spectral efficiency and lower out-of-band radiations, it is considered as a potential replacement of traditional orthogonal frequency division multiplexing (OFDM) for next generation wireless communication systems. However, non-orthogonal pulse shaping in GFDM gives rise to intrinsic self-interference complicating the receiver design. Moreover, its extension to multi-input multi-output (MIMO) designs for spatial diversity and enhanced reliability is also not straightforward as overlapping of transmitted symbols in time and frequency hinders the extension of conventional diversity techniques to MIMO GFDM. In this work, we consider a multi-antenna GFDM decentralized communication system and present a generic framework to achieve spatial transmit diversity along with a low complexity transceiver design. We extend our proposal by presenting a novel multi-antenna preamble that helps not only in acquisition of robust time and frequency synchronization but also in reliable estimation of time-varying frequency selective channels. Performance evaluation over realistic 3GPP simulation scenarios, confirms the attainment of full diversity order along with superior preamble-based time–frequency synchronization and channel estimation performance as compared to state of the art.

NC-OFDM-SPM: A Two-Dimensional Non-Coherent Modulation Scheme for Achieving the Coherent Performance of OFDM along with Sending an Additional Data-stream

A promising candidate solution for reducing complexity in future wireless systems is the use of non-coherent designs; however, it is very well known in the literature that non-coherent schemes perform worse than their coherent counterparts. To address this longstanding challenging trade-off, we demonstrate and prove in this work the ability of the proposed two-dimensional modulation scheme termed as non-coherent orthogonal frequency division multiplexing with subcarrier power modulation and differential phase shift keying in achieving the performance of a coherent design, while reducing complexity. Although the proposed design is non-coherent (i.e., it uses differential phase shift keying and power difference to convey information), it achieves the same bit error rate (BER) performance as conventional OFDM with coherent BPSK. Furthermore, since the proposed scheme employs two-dimensional modulations simultaneously (i.e., DPSK and subcarrier power levels), an additional data stream can be transmitted through the power subcarriers’ levels. Thus, the proposed design not only solves the trade-off between coherent and non-coherent modulations in terms of reliability by achieving the same BER, but also provides higher data rates by exploring the power domain as an additional dimension for conveying extra data bits, while maintaining low complexity transceiver design, thus making it very appealing for IoT applications.

Low Complexity Transceiver Design for FBMC-OQAM System for Future Generation Wireless Communication

Low Complexity Transceiver Design for FBMC-OQAM System for Future Generation Wireless Communication

Artificial-Noise-Aided Nonlinear Secure Transmission for Multiuser Multi-Antenna Systems With Finite-Rate Feedback

We consider a low-complexity transceiver design for secure communications of a multiuser multi-antenna system with an external multi-antenna eavesdropper. We propose to employ Tomlinson–Harashima precoder (THP) to simultaneously transmit message-bearing signals and artificial noise (AN) according to the quantized channel state information (CSI). Based on random vector quantization of the channel vectors, we obtain analytical approximations of the ergodic secrecy rate (ESR) of each legitimate receiver (LR) and the ergodic secrecy sum rate of the system with arbitrary system parameters. Based on the obtained analytical results, the near-optimal power allocation to the information signals and AN can be obtained using a numerical method. We show using an information-theoretical method that, besides the advantage in the ESR over the linear precoding scheme, THP can reduce the supported rate of the eavesdropper’s channel by preventing the eavesdropper from obtaining the legitimate channels’ (quantized) CSI. The ESR loss of each LR compared with the perfect CSI case will increase without bound for a fixed number of feedback bits. We also derive a feedback bit scaling law to solve this problem. Finally, numerical results are provided to verify our analytical results and also the advantage of the proposed secure nonlinear transceiver over the corresponding linear scheme.

Spatial Carrierless Amplitude and Phase Modulation Technique for Visible Light Communication Systems

Spatial carrierless amplitude and phase modulation (S-CAP) technique is developed in this paper as a physical layer solution to improve the spectral efficiency of the conventional CAP scheme while preserving its low-complexity transceiver design. The S-CAP technique is proposed and investigated for systems employing the visible light communication technology. An analytical expression for the joint detection of the spatial and signal bits for the user equipment experiencing line-of-sight propagation (LOS) is derived and validated via simulation. The effects of the multipath propagation and user mobility on the bit-error-rate (BER) performance of the proposed S-CAP are also investigated. It is found that the BER performance of the S-CAP in LOS is dictated by the minimum of the channel gains $h_\text {min}$ , the signal constellation points, and the channel gain dissimilarity, $\Delta |h|$ . The power factor imbalance (PFI) and multiple photodetectors (PDs) are then introduced to improve the performance and mitigate the channel impairments. The use of the PFI and PDs in LOS results in the signal-to-noise gain of 33.5 and 43 dB, respectively. The proposed scheme is thus a novel implementation of the CAP in a multiple-input–multiple-output system and demonstrates its potential as a suitable physical layer solution for the VLC technology.

Polarization Shift Keying (PolarSK): System Scheme and Performance Analysis

Single-Radio-Frequency (RF) Multiple-Input-Multiple-Output (MIMO) systems such as the spatial modulation (SM) system and the space shift keying (SSK) system have been proposed to pursue a high spectral efficiency while keeping a low cost and complexity transceiver design. Currently, polarization domain resource has been introduced to the single-RF MIMO system to reduce the size of the transmit antenna array and provide 1 bit per channel use (bpcu) multiplexing gain. Nevertheless, the polarization domain resource still has the potential to provide a higher multiplexing gain in the polarized single-RF MIMO system. In this paper, we propose a generalized polarization shift keying (PolarSK) modulation scheme for a SIMO system that uses the polarization states in the dual-polarized transmit antenna as an information-bearing unit to increase the overall spectral efficiency. At the receive end, the maximum likelihood (ML) detector is employed to demodulate the received signal. A closed form union upper bound on the average bit error probability (ABEP) of PolarSK system with the optimum maximum likelihood (ML) receiver is deduced under fading channels. To reduce the computational complexity of the receiver, a linear successive interference cancellation (SIC) detection algorithm and a sphere-decoding (SD) detection algorithm are proposed. On the basis of analytic results and simulations, performances of the proposed PolarSK systems in terms of computational complexity and ABEP are analyzed. Numerical results show that the proposed PolarSK scheme performs better than state of the art dual-polarized/uni-polarized SM schemes.

A Low-Complexity Transceiver Design in Sparse Multipath Massive MIMO Channels

In this letter, we develop a low-complexity transceiver design, referred to as semi-random beam pairing (SRBP), for sparse multipath massive MIMO channels. By exploring a sparse representation of the MIMO channel in the virtual angular domain, we generate a set of transmit-receive beam pairs in a semi-random way to support the simultaneous transmission of multiple data streams. These data streams can be easily separated at the receiver via a successive interference cancelation (SIC) technique, and the power allocation among them are optimized based on the classical waterfilling principle. The achieved degree of freedom (DoF) and capacity of the proposed approach are analyzed. Simulation results show that, compared to the conventional singular value decomposition (SVD)-based method, the proposed transceiver design can achieve near-optimal DoF and capacity with a significantly lower computational complexity.

Low-Complexity Transceiver Design for MIMO Broadcast Systems

Low-Complexity Transceiver Design for MIMO Broadcast Systems

Capacity Bounds and Low Complexity Transceiver Design for Double-Scattering MIMO Multiple Access Channels

We investigate the sum capacity and present low complexity transceiver designs for the multiple-input multiple-output (MIMO) multiple access channel (MAC) under a general class of fading, known as <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">double-scattering</i> . We assume that the receiver has perfect channel state information (CSI), while each transmitter only has access to its own statistical CSI. We show that the optimum transmit directions for each user coincide with the eigenvectors of the user's own transmit spatial correlation matrix. We also derive new closed-form upper bounds on the sum capacity of the MIMO MAC under double-scattering, which are subsequently employed to obtain low complexity power allocation policies which are easy to compute, and require each user to know only their own channel statistics. Then, we establish beamforming optimality conditions for all users. Finally, we consider the case as the number of users becomes large, in which case we demonstrate that beamforming is asymptotically optimal.