大容量宽带卫星通信系统的下行高效传输方法

Two Efficient Downlink Transfer Methods for Broadband Satellite Communication Systems with Large Capacity

针对基于非再生式星上处理的大容量宽带卫星通信系统下行链路采用频分复用(FDM)传输方式效率低、性能差的问题,提出并论证了两种特殊的连续波时分复用(CWTDM)方法——分帧交织叠接相加法(AFO)和准正交时分复用(QOTDM)法。首先,两种方法均先将待传输的各路基带复信号采样量化;然后,AFO方法对量化信号进行分帧叠接相加后加上帧头构成复用帧进行下行传输,QOTDM方法采用样点交织的时分复接再添加同步序列后转化为连续信号进行传输。AFO方法对信号复接、分接的处理简单;QOTDM方法复接时只需每路缓存一个样点,有利于实现更大容量的星上交换。与FDM下行传输方式相比,这两种方法的功率效率更高、链路特性更好。仿真结果表明,相较FDM传输方式,QOTDM方法的256个载波下的信干比可提高10dB,子信道隔离度可达到实用要求。

Two specific continuous wave time division multiplexing （CWTDM） methods, i. e. , adding frame overlapped （AFO） method and quasi-orthogonal time division multiplexing （QOTDM） method, are proposed to overcome the low efficiency and poor performance of the frequency division multiplexing （FDM） mode in the downlink of broadband satellite communication systems with large capacity based on the non-regenerative on-board processing （OBP）. Both the proposed methods firstly samples and quantifies various baseband complex signals to be transferred; Then the AFO method divides the frames and overlaps them with the frame header to consist a multiplexing frame to transfer in the downlink, and the QOTDM method, interleaves sample sequences using the time division multiplexing mode and then transfers the sequences in the way of continuous signals by adding a synchronous sequence. The AFO method is simple in both multiplexing and de-multiplexing, while the QOTDM method is helpful for realizing larger capacity of onboard switching since it only needs to save one complex sample for each signal in multiplexing. Compared with the FDM downlink transfer method, both the proposed methods have higher power efficiency and better link performance. results show that the ratio of signal to inference of the QOTDM method improves 10 Simulation dB in 256 carriers compared with FDM transfer method, and the sub-channels isolation level meets a practical requirement.