Implementation Of Successive Interference Cancellation Research Articles

On the performance of STBC-NOMA assisted overlay cognitive system under CEEs and imperfect SIC

In future wireless networks, the synergy of non-orthogonal multiple access (NOMA) and cognitive radio (CR) can provide higher spectral efficiency and increased data rate. In this context, this article studies the performance of a space-time block code-aided overlay cognitive NOMA system based on Alamouti's (2 x 1, multiple-input single-output) code under the practical consideration of channel estimation errors (CEEs) and imperfect implementation of successive interference cancellation (SIC) at the receiver. We evaluate the closed-form expressions, after approximation, for the system throughput (ST) and outage probability (OP) over Rayleigh fading channels for both the secondary and primary networks. Asymptotic expressions of the OP and ST at high signal-to-noise ratio region are also evaluated to obtain further insights into the proposed scheme. Further, the article investigates the impact of various parameters on the OP and ST of the proposed scheme. Moreover, the OP of STBC orthogonal multiple access (OMA) based overlay cognitive network is also determined and compared with the presented network. Finally, simulations are used to validate the performance analysis of the proposed network and the accuracy of the derived analytical results. The simulation result shows that the presented system achieves significant gain in terms of the OP and ST compared to the STBC-OMA based overlay cognitive system and a recently proposed scheme under imperfect SIC and CEE conditions.

Resource Optimization in Full Duplex Non-Orthogonal Multiple Access Systems

In this paper, we investigate a full duplex (FD) multi-user non-orthogonal multiple access (NoMA) communication system based on the optimization of received signal-to-interference-plus-noise ratio (SINR) per unit power. Since the communication system operates in the FD mode, co-channel interference (CCI) and self-interference (SI) dominate the system's performance. Accordingly, to combat the CCI, we adopt a game-theoretic approach and propose users' clustering algorithms and to suppress the SI, we formulate an optimization problem to maximize the power-normalized SINR (PN-SINR). While the user clustering optimization problem is constrained by: 1) the successive interference cancellation (SIC) constraint and 2) two binary constraints for the allocations of uplink (UL) and downlink (DL) users, the PN-SINR problem is constrained by: 1) total transmit power budget at the base station and UL users; 2) the fundamental condition for the implementation of successive interference cancellation in the NoMA; and 3) the minimum fairness condition for the UL users. The original PN-SINR problem is non-convex and hence is converted into an equivalent subtractive-form problem, after which we propose an iterative algorithm to find the optimal power allocation policy. Properties of all the proposed algorithms are thoroughly investigated and the numerical results are provided. Based on the channel conditions and suppression level of SI and CCI, the superiority of the proposed FD-NoMA system over half-duplex NoMA and FD orthogonal multiple access systems is verified.

Outage Probability Constrained MIMO-NOMA Designs Under Imperfect CSI

Non-orthogonal multiple access (NOMA) has been recognized as a promising multiple access scheme to be used in fifth-generation wireless networks. In this paper, multiple-input and multiple-output (MIMO) techniques are applied to NOMA systems by considering two types of imperfect channel state information—channel distribution information (CDI) and channel estimation uncertainty. Based on the two considered channel models, the power allocation and beamforming vectors are jointly designed to maximize the system utility of MIMO-NOMA, subjected to probabilistic constraints. Due to the implementation of successive interference cancellation in NOMA, the power allocation coefficients of the users in each cluster become coupled, which complicates the rate outage probability constraints and results in two challenging non-convex problems. For the optimization problem under CDI, we propose an efficient successive convex approximation (SCA) algorithm based on first-order approximation and semidefinite programming (SDP). For the optimization problem under channel estimation uncertainty, a new algorithm for the joint power allocation and receive beamforming design is developed to maximize the system utility based on SCA and an efficient 1-D search. In addition, the convergence and the feasibility are discussed for the two formulated problems. Furthermore, an efficient method to find a feasible initial solution is provided. Finally, the presented simulation results validate that the proposed two algorithms outperform MIMO-orthogonal multiple access and MIMO fixed NOMA (MIMO F-NOMA) with fixed power allocation and beamforming.

Low complexity successive interference cancellation for MIMO–OFDM systems

AbstractLayered architectures like the V‐BLAST scheme are a promising candidate to exploit the capacity advantages of multiple antenna systems leading to practical wireless communication schemes with very high data rates. The combination with orthogonal frequency division multiplexing (OFDM), called MIMO–OFDM, with per‐antenna‐coding is one of the most likely implementations of these multilayer architectures in frequency selective environments. In this paper, we present a novel, computational efficient implementation of successive interference cancellation (SIC) for coded MIMO–OFDM. It utilises a parallelised version of the Sorted QR Decomposition (SQRD) to achieve the same optimised detection order for all subcarriers, in order to exploit the error correction capability of the forward error correction code within the SIC. In comparison to other schemes known from literature, our approach requires only a fraction of computational complexity with almost the same performance. Copyright © 2007 John Wiley & Sons, Ltd.

DSP implementation of successive interference cancellation (SIC) receiver for 3GPP WCDMA uplink transmission

AbstractThe 3GPP WCDMA is a widely accepted third‐generation cellular system standard. By using nonorthogonal codes for different users, the multiple access interference (MAI) can be a limiting factor for system performance, as for other CDMA systems. Multiuser detection (MUD) is known to reduce MAI and improve CDMA system performance, but many such techniques have high complexity. Successive interference cancellation (SIC) is an effective MUD technique with relatively low complexity. We consider the software implementation of an SIC receiver for WCDMA uplink transmission on a commercially available general‐purpose multi digital signal processor (DSP) platform. This also goes in line with the recent interest in software‐defined radio. Issues addressed in this work include job partitioning and signal routing for multiprocessor implementation, design of SIC components (especially the channel estimator and the signal regenerator), determination of the precision of fixed‐point computations, consideration of the receiver's error performance and analysis of the implementation's complexity and efficiency. These issues are tightly coupled with the 3GPP WCDMA specifications. Because the employed platform only contains four DSPs, the implementation only considers up to three users. But this is sufficient for us to appreciate various DSP implementation issues of an SIC receiver. Moreover, by the nature of SIC, it is easy to extend the implementation to handle more users with an enlarged platform. Our present implementation achieves real‐time speed in the RAKE receiver part of the complete receiver. Due to the complexity in signal regeneration, the overall SIC receiver still falls short of the real‐time requirement when interference cancellation is activated. In fact, the platform employed presently cannot support real‐time processing when the number of multipaths is four or more, unless either the system architecture or the SIC algorithm is redesigned. Such and other ways of improvement are relegated to potential future work. Copyright © 2003 John Wiley & Sons, Ltd.

Implementation aspects for successive interference cancellation in DS/CDMA systems

This paper addresses the practical implementation of Successive Interference Cancellation (SIC) for DS/CDMA systems. The practical aspects of such an implementation are discussed and a convenient p...