Analytical evaluation of average bit error rate for the land mobile satellite channel

An analytical solution is presented showing the average bit error probability for the land mobile satellite channel. The channel is modelled as Rice and Rayleigh—lognormal fading. Modulation schemes under consideration include differentially detected PSK and non-coherently detected FSK. Results indicate that the receiver performance is highly dominated by the time share of shadowing. The ratio of the BERs in shadowed and unshadowed areas of typical measured channels and an operating point assumed to be at E_s/N_o = 10 dB is of the order of 10^?2.     

异步多径条件下空时CDMA多用户检测

本文利用最小均方误差准则,推导了异步多径条件下空时CDMA多用户检测算法,分析了多用户检测与单用户检测关系,提出空时CDMA多用户检测接收机结构。基于SAGE迭代算法进行空时多用户检测,并利用CDMA信号的有限字符特性和上行信道的导频信息对SAGE算法提出改进。仿真结果说明了本文提出的空时CDMA多用户检测算法性能。     

一种新的按位块分段快速排序算法

针对分段快速排序法因分段映射策略不理想而造成算法复杂度显著增加之问题，文章提出了一种由按位块分段、分段映射和局部快速排序所组成的新排序算法——按位块分段快速排序法（以下简称为“按位块分段快速排序”）。算法分析和实验结果都表明：在待排序数据均匀分布或正态分布的情况下，按位块分段快速排序法的时间复杂度可以达到O（N），而附加存储空间开销却仅仅为N＋M（M为分段数目，1≤M≤N），同时排序速度明显优于Quick Sort、分段快速排序、分“档”统计插入排序和Proponion Split Sort等算法。     

Java线程的深入探讨

本文主要讨论了Ｊａｖａ的线程及其特点，以及Ｊａｖａ中的同步机制。对Ｊａｖａ环境下多线程程序的开发做了探讨。     

Secure Classical Bit Commitment Using Fixed Capacity Communication Channels

If mutually mistrustful parties A and B control two or more appropriately located sites, special relativity can be used to guarantee that a pair of messages exchanged by A and B are independent. In earlier work we used this fact to define a relativistic bit commitment protocol, RBC1, in which security is maintained by exchanging a sequence of messages whose transmission rate increases exponentially in time. We define here a new relativistic protocol, RBC2, which requires only a constant transmission rate and could be practically implemented. We prove that RBC2 allows a bit commitment to be indefinitely maintained with unconditional security against all classical attacks. We examine its security against quantum attacks, and show that it is immune from the class of attacks shown by Mayers and Lo-Chau to render non-relativistic quantum bit commitment protocols insecure.     

A multi-carrier demodulator architecture for SMS/IBS

This paper describes a multi-carrier demodulator (MCD) architecture which is capable of demodulating a mixture of signals of different data rates, such as are found in present day transparent transponders. No extra restrictions are placed on the signal transmission rates, bandwidths, channel spacings, frequency stabilities, independent timing, etc. beyond what is already specified by INTELSAT and EUTELSAT. The only exception to this is that no signal should straddle the centre frequency of the existing 72 MHz bandwidth transponders. The system is a refinement of the ‘frequency domain’ filtering approach described in References 7 and 8. The main improvement is in performing the symbol timing recovery in the frquency domain before converting to the time domain. This leads to reductions in computational complexity in both the timing recovery and the frequency to time conversion process. All of these functions can be performed by standard DSP processors. Only the initial time to frequency domain transform requires ASIC technology.     

运用删截卷积码实现不等错误保护

在数字通信系统中，发送的数据序列中的比特往往具有不等的重要性。为了寻求更可靠的信息传输，人们提出了一些不等错误保护（UEP）编码方案。本文介绍了一种通过删截卷积码（CC）实现UEP编码的方案，并通过仿真分析了该UEP编码的性能。仿真结果表明，运用删截卷积码实现的UEP编码能获得较好的性能。     

Analytical calculation of the transition to complete phase synchronization in coupled oscillators

Here we present a system of coupled phase oscillators with nearest neighbors coupling, which we study for different boundary conditions. We concentrate at the transition to the total synchronization. We are able to develop exact solutions for the value of the coupling parameter when the system becomes completely synchronized, for the case of periodic boundary conditions as well as for a chain with fixed ends. We compare the results with those calculated numerically.      

QAM调制分析与其SystemView仿真实现

正交振幅调制OAM(Ouadrature Amplitude Modulation)是一种频谱利用率很高的调制方式.文章在介绍OAM调制、解调原理的基础上,深入探讨了OAM的频谱利用率和误码率性能.并在SystemView下对该系统进行了完整仿真.通过仿真观察到调制与解调信号的波形,星座图以及OAM信号功率谱密度曲线,并对仿真结果进行了分析.由分析结果可知,OAM调制系统具有很高的频谱利用率以及较好的误码率性能,因此可增大系统容量,同时也保证了系统的可靠性.     

利用声表面波抽头延迟线实现突发通信的快速同步

在突发通信系统中，同步是系统的关键技术，要求同步快、可靠、易实现、抗干扰能力强。本文介绍用声表面波抽头延迟线完成系统快速同步的方法，可满足系统对同步的要求。