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In downlink non-orthogonal multiple access (NOMA) with multiuser clustering, a single beamforming (BF) vector precodes the superimposed signal of strong and weak users. This precoding results in an imperfect inter-cluster interference (ICI) cancellation at weak users since the BF vectors are designed based on strong users’ channels. Also, the ICI is highly increased with the number of transmit antennas, causing severe degradation in the performance of weak users and total system. In this paper, first , a new cooperative NOMA is introduced, in which weak user beam-matching (WBM) equalizer is proposed to remove the ICI at weak users by matching weak users’ channels with the designed BF vectors. The process of WBM is accomplished with the aid of device-to-device (D2D) channel state information (CSI) sharing between the nearby strong and weak users. Second , based on WBM principle, strong user beam-matching (SBM) equalizer is proposed to eliminate the generated ICI at strong users in the case of limited feedback. Third , a new power allocation strategy is proposed to improve weak users’ performance by considering the gained throughput from interference cancellation. Finally , besides the sum-rate, which is adopted as the performance metric by most of the existing NOMA works, the bit error rate (BER) of NOMA users in cooperative NOMA is calculated and compared with those in other schemes. Simulation results show that our cooperative NOMA with the proposed equalizers achieves significant sum-rate and BER improvements over other non-cooperative schemes with both perfect and limited feedback scenarios.

The extension of the digital video broadcasting second generation standard (DVB-S2X) for transmission over satellite has been introduced recently with its novel superframe structure, which is a key enabler for applying interference management techniques, such as precoding, to multibeam high throughput geosynchronous (GEO) satellite systems operating in the Ka-band. This paper presents the first full design of DVB-S2X system with multi-user-multiple-input-single-output (MU-MISO DVB-S2X), with most of its modulation and coding schemes (MODCODs), over rainy fading channels. The atmospheric impairments on the Ka-band satellite channel are considered, especially the rainfall effect, which is the most effective atmospheric impairment that degrades the system performance. Two rainy fading channels are designed, one for tropical region and the other for temperate region, using real rain data from these areas. In addition, the user scheduling influence on the bit error rate (BER) performance of MU-MISO DVB-S2X system is tested and compared with the conventional MISO DVB-S2X system. Simulation results show that the proposed system can achieve a significant improvement in terms of BER performance with at least 20 dB for 128 amplitude and phase shift keying (128APSK) MODCOD over the tropical channel and 14 dB for 32APSK MODCOD over temperate channel when the number of users is six. The enhancement in error rates proves that MU-MISO DVB-S2X system with scheduling can be the key solution for DVB-S2X system performance degradation in fading channels, especially rainy fading channels.

Digital Video Broadcasting - Satellite Second generation extension (DVB-S2X) has been introduced recently with a relatively higher number of modulation schemes and code rates (MODCODs) to satisfy the increased demand for higher data rates and qualified broadcasting services. In this paper, the performance of DVB-S2X for two frame sizes are introduced. Monte Carlo simulation is used to implement the system model with two scenarios; Additive White Gaussian Noise (AWGN) channel is used in the first scenario to validate DVB-S2X system by comparing the results with ETSI standard. In the second scenario, the system is tested with Rician channel which represents the real channel for satellite transmission. Comparisons in bit and frame error rates have been made between those two models to observe the impact for Shannon channel capacity and spectral efficiency for different (MODCODs). Moreover, this paper presents a better evaluation for DVB-S2X performance with two types of channels and MODCODs compared to the previous work.