分布式天线系统中的系统下行误符号率分析

首先建立了包含快衰落、阴影衰落和路径损耗的复合衰落信道模型,对分布式天线采用覆盖式（BT）传输策略,推导出给定移动台位置的小区下行点对点链路误符号率表达式.并在高信噪比条件下,通过给出移动台在小区的任意分布图,推导出小区下行平均误符号率的近似闭合表达式.仿真结果表明,所推导的近似表达式可很好地反应系统的实际性能.     

分布式MIMO系统小区平均遍历容量分析

针对分布式MIMO系统的圆形小区平均遍历容量展开研究.文章首先建立了包含快衰落、阴影衰落和路径损耗的复合衰落信道模型;然后,对分布式天线采用覆盖式（BT）传输策略,并在高信噪比条件下,导出给定移动台位置时,区上、下行点对点链路遍历容量表达式.最后,考虑移动台在小区内任意分布特点,进一步推导出小区平均遍历容量闭合近似表达式.仿真结果表明,所推导的近似表达式可很好的反应系统的实际性能.导的近似表达式可很好的反应系统的实际性能.     

分布式天线系统中的下行容量分析

针对分布式天线系统(DAS)的下行容量问题展开研究。首先建立了包含路径损耗、阴影衰落和瑞利衰落的复合信道模型;然后,基于该信道模型,分别对各态历经容量和中断容量进行了分析。考虑到小区内移动台的分布特点,在选择分集传输策略下,推导了各态历经容量和中断容量的近似解析表达式。仿真结果表明,所推导的2个近似解析表达式均能准确地评估分布式天线系统的系统性能。     

分布式天线系统中的系统下行中断概率分析

本文针对分布式天线系统的系统下行中断概率问题展开研究.文章首先建立了包含路径损耗、阴影衰落和瑞利衰落的复合信道模型.接着,在接收端采用最大比合并的方式接收信号,并运用矩生成函数推导出输出信噪比的概率密度函数.然后,对分布式天线采用选择传输策略,并分析出给定移动台位置时的中断概率的表达式.最后,考虑小区内移动台任意分布特...     

复合衰落信道下分布式MIMO系统下行中断概率分析

针对复合衰落信道模型下分布式MIMO系统下行中断概率问题,首先建立了一个综合考虑Nakagami-m衰落、路径损耗和阴影衰落的复合衰落信道模型;然后针对存在中心基站的分布式MIMO系统,提出了一种更符合实际应用环境的准均匀小区移动台分布模型;接着利用矩生成函数、Gauss-Hermite积分公式和Simpson积分公式等数学手段推导了任意移动台分布下、单小区内系统平均下行中断概率闭合表达式;最后将准均匀移动台分布模型应用到该中断概率闭合表达式,并通过MATLAB仿真证明了所推导得到的闭合表达式及小区分布模型的合理性。     

Rayleigh信道下的多小区下行链路性能分析

针对存在来自相邻蜂窝小区的同信道、不同功率信道干扰的单用户下行链路场景,分析了基站和用户均为单天线时的系统性能.系统模型为两个基站、两个用户,基站与用户均为单天线.在期望信号和干扰信号均为Rayleigh分布时,运用基于概率密度函数性能分析法推导了系统中断概率;基于瞬时信干噪比(SINR)的推导,并对瞬时误符号率(SER)取平均的方法推导了平均误符号率(ASER)的闭合表达式和用户的接收SINR的n阶矩;根据用户接收平均SINR的n阶矩表达式,推导并分析了用户接收平均SINR的衰落量(AF)性能.计算机仿真了在不同干扰功率下多小区系统的中断概率、ASER的性能以及AF性能.仿真结果表明:单小区和多小区系统的中断概率、ASER和AF的解析曲线均与数值仿真结果一致.系统性能随着干扰基站功率的降低而提升,系统性能随发送功率的增加增益明显.     

分布式天线系统MIMO信道容量分析

结合了分布式天线系统和MIMO信道特点的分布式MIMO系统可以改善覆盖特性,提高系统容量。提出了包含路径损耗、快衰落和阴影衰落的两层分集分布式MIMO系统。对MIMO信道容量的分析表明,分布式MIMO系统具有良好的信道容量均匀覆盖特性。与传统集中式天线系统相比,分布式MIMO系统可以获得更好的小区平均信道容量。对下行信道容量的数值分析表明,由于“充水”方式功率分配可以充分利用MIMO信道信息,此时的分布式MIMO系统可以比等功率分配条件下的分布式天线系统多获得0.25bit/(s·Hz)每发送天线的信道容量增量。     

分布式天线系统中的系统上行中断概率分析

中断概率是无线通信系统的一个重要指标。该文针对分布式天线系统中的系统中断概率问题进行了研究。首先,建立了包含路径损耗、阴影衰落和瑞利衰落的复合信道模型;然后,在该信道模型下推导出给定移动台位置时的信噪比;接着,基于选择合并策略,分析出给定移动台位置时系统上行传输的中断概率表达式;最后,考虑到小区内移动台任意分布特点,文章给出系统上行中断概率闭合理论表达式。仿真结果表明,所提的系统上行中断概率理论表达式与仿真结果十分吻合。     

基于分布式天线的无线通信系统中信道分配问题

分布式无线通信系统(DWCS)是不同于传统蜂窝系统的一种崭新的系统,而它的信道分配问题是使整个系统发挥优势的关键之一.本文分析了传统蜂窝系统和DWCS中的信道分配的内容和意义,并给出了在DWCS中信道分配方面所要解决的几个关键的问题.     

基于分布式天线无线通信系统的信道选择策略

分布式天线系统是不同于传统蜂窝系统的一种崭新的系统,其信道分配问题是整个系统发挥优势的关键之一。所考察的信道选择策略就是基于该系统,考虑选择四根天线的情况,用CDMA多址方式,采用动态信道分配方案对信道资源进行分配,描述了DWCS系统的信道分配过程和信道选择策略,并且对于随机、最大SIR和最小SIR等方案进行仿真分析。在小业务下,最小SIR由于使得信道分配达到最大紧致,充分利用资源,阻塞率最低,在大业务下,随机和最大SIR性能更好些。同时也给出了不同的SIR门限时的系统阻塞率。     

Capacity analysis of distributed antenna systems in MIMO Nakagami fading multicell environment

In this paper, the downlink capacity analysis of distributed antenna systems (DAS) with multiple receive antennas in Nakagami-m fading multicell environment is presented. According to the performance analysis, and using mathematical manipulation, we derive the probability density function (PDF) of the effective signal to interference plus noise ratio of the system. Based on the obtained PDF, an exact closed-form expression of DAS capacity is derived. This expression includes the existing capacity expression as a special case, and avoids the error in the latter. Thus, it can provide good theoretical performance evaluation for downlink DAS. Computer simulation shows that the theoretical analysis is in good agreement with simulation result. Moreover, the increase of receive antenna and/or Nakagami fading parameter m can improve the capacity effectively.     

Robust frequency offset estimation for pilot symbol assisted packetCDMA with MIMO antenna systems

We propose frequency offset estimation and combining techniques for pilot symbol assisted (PSA) packet downlink code-division multiple access (CDMA) with multiple-input and multiple-output (MIMO) antenna systems. Orthogonal Walsh codes are used for dedicated pilot symbols at the transmit antennas. The discrete Fourier transform (DFT)-based frequency offset estimation is used for simple implementation. In addition, simple interpolation is also used for resolution improvement of the DFT. When identical frequency offset is assumed, the frequency offset estimates for each single-input single-output (SISO) sub-stream (i.e., transmit/receive antenna pair) can be combined at the receiver. Simulation results show that the estimation and combining techniques proposed deliver improvement in the frequency offset estimation performance     

分布式MIMO系统发送天线选择与预编码联合设计

为了抑制多用户分布式多入多出(MIMO)系统中的同道干扰(CCI),使系统同时服务于更多用户,提出一种发送天线选择与预编码的联合设计方法。该方法立足于分布式MIMO系统基站端天线较多的特点,将下行发送天线选择与信漏噪比(SLNR)预编码相结合,通过为用户选择不同天线,从根本上减少CCI;在为每个用户选择天线时,先以信道子矩阵的迹为依据进行端口选择,再采用逐减的方法选择使SLNR损失值最小的天线,以保证每个用户对其他用户的干扰尽量小,从而达到进一步抑制CCI的目的。复杂度分析和仿真结果表明,该方法在具有较低复杂度同时,其容量性能仍可逼近最优算法;较之单纯的SLNR预编码,在相同的容量性能约束下,其能够有效增加系统同时服务的用户数。     

Threshold-based frame error rate analysis of MIMO systems over quasistatic fading channels

Proper selection of a signal-to-noise ratio threshold largely determines the tightness of an approximation to the frame error rate of a system over a quasistatic fading channel. It is demonstrated that the expression for the optimal threshold value, which has been established for singleinput single-output (SISO) channels, remains unchanged for the general case of multiple-input multiple-output (MIMO) channels.     

Uncoded symbol error rate estimation: methods and analysis

In wireless communications systems, channel quality estimates are often used to provide a measure of the quality of service or to enable resource allocation techniques that improve system capacity and/or user quality. The uncoded bit or symbol error rate (SER) is specified as a channel quality metric in second and third generation cellular systems (e.g., general packet radio service (GPRS), enhanced general packet radio service (EGPRS), and universal mobile telecommunications system (UMTS). Nonetheless, techniques to estimate the uncoded SER are typically outside the scope of these wireless standards and are not specified. In this paper, we analyze the performance of a number of uncoded SER estimation techniques, including a novel technique in which we use the soft information of the received symbols to obtain a fast and accurate estimate of the uncoded SER. The technique we introduce has been found to outperform, in terms of accuracy and required estimation interval, conventional hard-decision based techniques that use test-patterns, or use a decode/re-encode/compare approach . Our technique also outperforms the brute-force technique, which is to send a known test-pattern, demodulate it at the receiver, and count the observed discrepancies.     

Capacity analysis in CDMA distributed antenna systems

In this letter, the effect of maximal ratio combining (MRC)-based macrodiversity on the reverse-link and forward-link capacity in code division multiple access (CDMA)-distributed antenna systems is analyzed. The concept of virtual cell is illustrated, and the analytical outage probability expressions are derived. The present investigation shows that on the reverse link, the interference can be suppressed greatly with macrodiversity, which leads to a significant increase in capacity. However, on the forward-link, it is proven that if simulcasting is used in CDMA-distributed antenna systems, the forward-link capacity cannot increase with macrodiversity whatever power allocation scheme is adopted. Based on the analysis of the cause of capacity loss, a new transmission scheme is further presented and the optimal power allocation scheme is derived. It is shown that, in this case, the forward-link capacity increases rapidly with the number of involved distributed antennas.