In this paper, novel finite-order filter designs for source and multiple full-duplex relays (FDRs) are proposed to improve the spectrum efficiency and link reliability of amplify-and-forward cooperative communication networks. In contrast to the single relay, FDRs suffer not only self-interference (SI), but inter-relay interference (IRI). By taking SI and IRI into consideration, this work aims at the joint design of the source filter, relay filters, and the linear minimum squared error (LMMSE) receiver. The finite-order filters are conducted in two stages. In the first stage, the spectrums of the source and FDRs are computed. Since the optimization problem involves the nonlinear equality constraint, we adopt the generic nonlinear equality alternating direction method of multipliers (neADMM) with a damping procedure to find the stationary solution. In the second stage, the filter coefficients are developed to approach the derived spectrums by using a weighted least square criterion. The numerical results justify the validity of the proposed designs. Interestingly, the results show that preserving a certain amount of SI at the FDRs not only reduces the implementation cost but improves the end-to-end signal-to-interference-plus-noise ratio (SINR).

This paper studies the joint common beamforming (CB) and the superposition coding (SC) design for a two-user massive multiple-input single-output (MISO) system with non-orthogonal multiple access (NOMA). Conventional beamforming design has to estimate the uplink channel state information (CSI) of the near and the far users separately. By the channel reciprocity, the CB is then constructed by combining two uplink CSIs together with certain rules. The design needs two training phases to separately estimate the CSI of the two users but combine them subsequently. In this paper, we propose a model adopting common pilots for the near and far users to estimate an uplink combined channel. In this model, only one training phase is required, and the CB is then constructed by the estimated combined channel directly. With the estimated combined channel, the joint CB and SC design is equivalent to optimizing the pilot power allocation and SC factor. However, the associated optimization is not convex. We then adopt the majorization-minimization approach to conduct the optimization problem and numerically find that the solutions meet the optimum points. Simulations verify the effectiveness of our joint design and show the superior performance not only for the transmission rate but also the reduced overhead.

This paper considers the finite-order filter design problem for the source and multiple full-duplex (FD) relays in a cooperative communication system under frequency-selective fading channels. The goal is to optimize the source and relay filters such that the end-to-end signal-to-interference-plus-noise ratio (SINR) of minimum mean-squared error decision-feedback equalizer (MMSE-DFE) can be maximized. The resultant design problem is very difficult since we need to deal with self interference (SI), inter-relay interference (IRI), and inter-symbol interference (ISI) at the same time. Novel designs are then proposed to overcome the difficulty in this work. Transforming the signals into the frequency domain and using some optimization techniques, we first theoretically derive the power spectrum of the source filter and the spectrums of the relay filters. Then, the finite-order design is developed to approach the derived spectrums. Based on the weighted least-square (WLS) criterion, the Steiglitz-McBride method is exploited to obtain the filter coefficients in finite lengths. Numerical results demonstrated that complete removal of SI may not be a good strategy; preserving a certain amount of SI at each relay instead provides better SINR performance.

Reference to the 5G network specifications defined by 3GPP, the online charging system has been greatly added and modified both in terms of interface and architecture. Since traditional online charging systems are mostly closed systems, a small number of open-source projects are no longer maintained, which makes the research in recent years extremely lacking in a suitable simulation environment. It encourages the emergence of free5GC project, which is the world's first 5G core network, developed by Taiwan independently and adopting the Apache 2.0 open-source specification. In this research, we try to implement the network function of the online charging system under the free5GC architecture and integrate it with third-party public cloud services. Adopting cloud computing, we focus on improving Charging Data Record (CDR) in computing and storage to compose a highly available and reliable B5G/6G charging system.

Orthogonally multiplexed orthogonal amplitude modulation (OMOAM) is a modulation family unifying numerous modulations date back from 1960s and also many standard-preferable modulations. By converting frequency multiplexing to time multiplexing, orthogonally time multiplexed orthogonal amplitude modulation (OTMOAM) is proposed to explore advantages over the conventional orthogonally multiplexed orthogonal amplitude modulation (OMOAM). Transmitter and receiver system models unifying both OTMOAM and OMOAM are provided, and bit error rate (BER) for both systems are also derived for flat Rayleigh fading channel. Numerical results show that OTMOAM provides lower PAPR and better BER performance in high signal-to-noise power ratio than the conventional OMOAM.

A constant-power adaptive transmission technique adopting differentially coherent orthogonally multiplexed orthogonal phase modulation (DOMOPM) signals is studied for flat fading channels. Numerical results show that the constant-power adaptive DOMOPM system significantly outperforms the constant-power adaptive noncoherent frequency shift keying system in average spectral efficiency.

Adaptive transmission technique adopting rectangularly-pulsed orthogonally multiplexed modulation (OMM) signals is studied for the flat Rayleigh fading channel. By choosing spectrally efficient OMM signals in accordance with channel status under an error rate constraint, constant-power adaptive OMM systems are shown to significantly outperform the conventional constant-power adaptive orthogonal frequency division multiplexing systems in average spectral efficiency.

An adaptive transmission technique adopting differentially coherent orthogonally multiplexed orthogonal phase modulation (DOMOPM) signals is studied for flat Nakagami-m fading channels. By choosing spectrally efficient DOMOPM signals in accordance with channel status under an error rate constraint, constant-power adaptive DOMOPM systems are shown to significantly outperform the constant-power adaptive noncoherent frequency shift keying systems in average spectral efficiency.