A novel satellite on-board processing scheme based on photon frequency conversion is proposed for the purpose of realizing frequency conversion. For the received intermediate frequency signal, a Mach-Zehnder modulator is used to convert it into an optical signal. The modulated optical signal and an optical signal generated by a tunable laser enter the photodiode through a coupler to perform heterodyne beat frequency and generate an intermediate frequency signal of the target carrier frequency, thereby reducing the cost and power consumption of on-board processing. Simulation results show the spectrograms and constellation diagrams of frequency conversion from Q-band to V-band in 8PSK modulation format. The bit error rate(BER) obtained by simulation shows that in a satellite communication system, when the OSNR is higher than 5dB, the BER performance can meet the 2×10-2 threshold when using 8PSK modulation format, which indicates that error-free transmission can be achieved when using 20% soft-decision FEC. The Q factor obtained by simulation shows that when the OSNR is higher than 5dB, the Q factor can reach more than 6.5 when using QPSK modulation format, which indicates that reliable transmission can be achieved. Compared with existing solutions, this scheme has the advantages of lower cost, lower power consumption and more flexible frequency selection, it can also solve the inflexibility and improve the performance of radio frequency conversion in traditional scheme.
As a resolve to high complexity of user selection and different users with different requirements of QoS(Quality of Services) optimization of multi-user selection with criterion of SLNR based on QoS is proposed in this paper with maximization of SLNR(Signal-to-leakage and Noises Ratio) as standard and different settlements of scheduling for different kinds of users in MIMO (Multiple-input multiple-Output) system. The simulation compares this algorithm with round robin scheduling and leakage based user scheduling. The results show the proposed optimization is much better not only in channel capacity but also in throughput and BER (Bit error rate) than these two algorithms.
A scheme to realize the flexible photonic frequency multiplication at millimeter-wave (mm-wave) and radio over fiber (RoF) transmission has been proposed and demonstrated. To enable the generated multiple-frequency signal to have a better performance of phase preserving, we theoretically investigated the phase change during the generation and transmission and proposed an adaptive coding algorithm to reduce the impact of phase fluctuation. The coding algorithm brings the frequency multiplication and fiber transmission distance together into consideration and adjusts the phase of the signal consequently. Due to the proposed coding algorithm, the system not only realizes the flexible frequency multiplication but also eliminates the phase deviation induced by the modulation and fiber dispersion, which effectively increases the transmission distance of fiber link. In addition, it also reduces the complexity of phase retrieval at receiver side. A 50-GHz to 100-GHz RoF system with 1 Gbit / s radio signal has been implemented by numerical simulation, and the result shows that the adaptive mm-wave RoF system could realize arbitrary multiple-frequency of quadrature phase shift-keying signal from double to decuple and reliable transmission of the tenfold signal at least 50 km.
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