Android广播机制安全性研究

近年来,Android组件的安全性是研究热点,但作为Android四大组件之一的广播接收器,则鲜见有关其安全性的研究成果。在研究Android广播机制的基础上,对其安全结构与特点进行了深入分析。基于Android广播机制的安全挑战,针对性地给出相应的安全对策。最后,总结并展望今后的研究方向。     

卫星导航接收机信噪比分析

用噪声温度的概念给出了卫星导航接收机射频前端的噪声,分析A／D转换器和码环不同步带来的噪声。根据上述结论设计的卫星接收机的各项技术指标都达到了先进水平,验证了本文的合理性和正确性。     

2.5 Gbit/s光发射模块消光比与光接收误码特性

改变2．5Gbit/s光发射模块消光比（EX）,对作为标准接收用的光接收机灵敏度进行了测试。实验表明,EX小于9．0时,光接收灵敏度较差;EX大于15．0时,由于眼图中交叉点偏低或光脉冲波形畸变,可能导致光接收灵敏度恶化;EX在9．0－12．0范围时,光接收灵敏度最佳。     

基于单比特采样的IR-UWB系统采样抖动性能分析

研究了基于单比特采样接收的IR—UWB系统中采样抖动对性能的影响。论文给出了采样抖动的简化分析模型,推导了AWGN信道下全精度采样系统和单比特采样系统的误码率理论解。论文通过仿真实验验证了理论分析的正确性,并分析比较了全精度采样系统、单比特采样系统在AWCN信道与多径衰落信道下的抗采样抖动性能及其原因。     

一种信道化测频接收机的工程实现

将Ku波段射频信号下变频为1.25～1.75 GHz的中频信号,经26路功分器功分为26路信号,每路经过相互交叠的带通滤波器和检波器,当频率位于某个通道的滤波器内时,该通道检波器输出对应检波电压,将该检波电压与相邻通道检波电压和绝对电平进行比较,并将比较结果送入FPGA,由FPGA进行判断、编码,输出对应的频率编码、同时到达信号,准备好指示等。     

TD-SCDMA集群系统中部分宏分集组网前向容量分析

TD-SCDMA集群小区使用宏分集技术可以有效的克服大尺度衰落,保证信号质量。本文首先分析了在没有任何措施的前提下进行宏分集组网,但前向容量会随着宏分集基站数的增多而减少。在分析容量损失原因的基础上,我们进一步提出在终端利用Rake接收机对各路信号进行同步、相位调整,再进行最大比值合并,然后发送给用户,由此,前向容量大大提高。     

基于LDPC编码的IDMA编码和扩频均衡研究

将一种接近容量限的码型低密度奇偶校验码(LDPC)应用于交织多址接入系统,即基于LDPC编码的IDMA系统;深入研究了与此系统相关的编码和扩频的均衡问题。在高斯白噪声(AWGN)信道中,在以不同码率编码的该系统中,分别以误比特率10-6和10-3为标准,根据要达到的可靠数据和语音通信所需要的最小信噪比(SNR),阐明编码和扩频的均衡问题。仿真结果表明,在AWGN信道中,对于可靠的通信传输服务,基于LDPC编码的IDMA系统传输的最佳LD-PC编码码率在0.4和0.5之间;并且,以这种码率传输的系统相对于其他系统的优势是相当明显的。     

基于LPC2138的AES3数字音频接口设计

随着数字音频技术的不断发展,数字化音频设备已广泛应用于广播电视节目领域。鉴于专业数字音频设备越来越多地需求,以及专用接收发送设备的复杂性,本设计采用Philips公司的ARM7控制芯片LPC2138结合音响设备专用芯片,设计一个简单的AES/EBU(AES3)数字音频收发系统,实现了专业AES3数字音频的接收与发送。实验显示,在输入1 kHz,24 dBu时,本设计的总谐波失真小于0.005%,信噪比大于90 dBu。     

MIMO iterative receiver SNR estimation strategies for link to system interfacing

This paper presents link to system (L2S) interfacing technique for multiple input and multiple output (MIMO) iterative receivers. In L2S interfacing, usually the post detection signal to noise ratio (SNR)‐based frame error rate lookup tables (LUT) are used to predict the link level performance of receivers. While L2S interfacing for linear MIMO receivers can be conveniently implemented, it is more challenging for MIMO iterative receivers due to unavailability of the closed form SNR expressions. In this paper, we propose three methods for post detection SNR estimation for MIMO iterative receivers. The first is based on the QR decomposition of the channel matrix, the second relies on the residual noise calculation based on the soft symbols, and the third exploits the closed form SNR expressions for linear receivers. A link to system interface model for iterative receivers is developed for evaluating the reference curves for different modulation and coding schemes, and results are validated by comparing the simulated and predicted frame error rates. It is shown that linear and residual noise‐based SNR approximations result in a very good prediction performance whereas the performance of QR decomposition‐based method degrades for higher order modulations and coding schemes. This paper presents link to system interfacing technique for MIMO iterative receivers. A link to system interface model for iterative receivers is developed for evaluating the reference curves for different modulation and coding schemes, and results are validated by comparing the simulated and predicted frame error rates. Three post detection SNR evaluation schemes have been proposed for link to system interfacing all of which give good prediction performance especially at lower order modulation.