QAM with interference cancellation for high-speed multicode CDMA

2003 ◽  
Author(s):  
Bin Xia ◽  
Jiangzhou Wang
Keyword(s):  
Interference Cancellation ◽  
High Speed ◽  
Multicode Cdma

scholarly journals Enabling User Relaying In MCM-NOMA Under Doubly Selective Channels Using Iterative Interference Cancellation Schemes For Wireless IoT Networks

2022 ◽  
Author(s):  
Anis Amazigh Hamza ◽  
Iyad Dayoub ◽  
Ihsen Alouani ◽  
Abderrahmane Amrouche
Keyword(s):  
Interference Cancellation ◽  
High Speed ◽  
Channel State ◽  
Doubly Selective Channels ◽  
Cell Edge ◽  
Doubly Selective Channel ◽  
Selective Channel ◽  
Improvement Method ◽  
Iterative Interference Cancellation ◽  
User Interference

<div>Cell-edge users of the future cellular internet of things (IoT) with massive IoT sensors can suffer from extremely severe channel conditions, especially under very high-speed scenarios. In this paper, we present a performance improvement method for cell-edge users of multi-carrier modulation (MCM)-based non-orthogonal multiple access (NOMA) downlink systems. To this end, we consider the implementation of cooperative user relaying NOMA (CUR-NOMA) and derive its lower bound end-to-end bit error rate (E2E-BER) under doubly selective channels. In addition, the imperfect successive interference cancellation (SIC) process is analyzed, wherein two interference cancellation schemes are combined to remove the NOMA induced inter-user interference (IUI) and the doubly selective channel induced inter-carrier interference (ICI). Furthermore, numerical simulations are performed to prove the efficiency of the introduced schemes with imperfect channel state information (CSI) when compared to the theoretical perfect SIC with a perfect CSI case. </div>

scholarly journals Advancing High-Speed Transmissions over OCDMA Networks by Employing an Intelligently Structured Receiver for Noise Mitigation

2018 ◽  
Vol 8 (12) ◽  
pp. 2408 ◽  
Author(s):  
Kai-Sheng Chen ◽  
Yi-Chang Chen ◽  
Long-Guang Liao
Keyword(s):  
Interference Cancellation ◽  
High Speed ◽  
Noise Suppression ◽  
Optical Signal ◽  
Spectral Amplitude ◽  
Light Sources ◽  
Bit Rate ◽  
Noise Mitigation ◽  
Compact Structure ◽  
Code Division Multiple

We propose an intelligently structured receiver to achieve high-speed transmissions over optical code-division multiple access (OCDMA) networks. Employing spectral-amplitude coding (SAC) reduces multiuser interference (MUI) in OCDMA, but the network bit-rate is limited by phase-induced intensity noise (PIIN) coming from the incoherency of light sources. To mitigate PIIN, the receiver performs interference estimations and regenerations through consecutive stages. The MUI is removed by subtracting the estimated interference term from the received multiplexed signals. For PIIN variance, it is both dependent on and positively related to user number and bit-rate. Reducing the number of interference users allows the network to support transmissions with a higher speed under a given noise level. The proposed scheme has the advantages of all-optical signal processing and a compact structure. Additionally, the function of noise suppression is rarely studied in the existing MUI elimination schemes, such as serial interference cancellation (SIC) and parallel interference cancellation (PIC). The simulation results show the proposed receiver achieves significant increment in bit-rate than the conventional balanced detector in SAC–OCDMA networks.

scholarly journals Robust Null Broadening Beamforming Based on Covariance Matrix Reconstruction via Virtual Interference Sources

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 1865 ◽  
Author(s):  
Jian Yang ◽  
Jian Lu ◽  
Xinxin Liu ◽  
Guisheng Liao
Keyword(s):  
Interference Cancellation ◽  
High Speed ◽  
Adaptive Beamforming ◽  
Interference Signal ◽  
Reconstruction Process ◽  
Matrix Reconstruction ◽  
Noise Covariance ◽  
Interference Signals ◽  
Robust Adaptive ◽  
Set Up

When jammers move rapidly or an antenna platform travels at high speed, interference signals may move out of the null width in the array beampattern. Consequently, the interference suppression performance can be significantly degraded. To solve this problem, both the null broadening technique and robust adaptive beamforming are considered in this paper. A novel null broadening beamforming method based on reconstruction of the interference-plus-noise covariance (INC) matrix is proposed, in order to broaden the null width and offset the motion of the interfering signals. In the moving case, a single interference signal can have multiple directions of arrival, which is equivalent to the existence of multiple interference sources. In the reconstruction of the INC matrix, several virtual interference sources are set up around each of the actual jammers, such that the nulls can be broadened. Based on the reconstructed INC and signal-plus-noise covariance (SNC) matrices, the steering vector of the desired signal can be obtained by solving a new convex optimization problem. Simulation results show that the proposed beamformer can effectively broaden the null width and deepen the null depth, and its performance in interference cancellation is robust against fast-moving jammers or array platform motion. Furthermore, the null depth can be controlled by adjusting the power parameters in the reconstruction process and, if the direction of interference motion is known, the virtual interference sources can be set to achieve better performance.

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