TDD/CDMA移动通信系统的一种信道分配方案

未来的TD/CDMA移动通信系统中存活话音及上下行业务量不等、优先级不同的数据业务，为适应新业务的特点，充分发挥TDD/CDMA移动通信系统自身的优势，本文提出了TDD/CDMA移动通信的一种新的信道分配方案。仿真结果表明，该方案可大大降低低优先级业务的掉线概率，充分利用有限的信道资源。     

同信道干扰对多载波CDMA蜂窝系统下行信道的影响

该文主要讨论多载波CDMA蜂窝系统在下行信道中的同信道干扰问题,理论分析了同信道干扰的解析表达式,并通过计算机仿真得出了在一定的传播损耗下多载波CDMA蜂窝系统下行信道的性能。通过仿真发现,即使在有小区间同信道干扰情况下,通过简单的小区布置,多载波CDMA蜂窝系统下行信道就可以有很大的信道容量。     

OFDM系统中的子载波分配策略

正交频分复用(OFDM)技术是未来宽带无线通信中最流行的技术之一。研究了适用于多用户(OFDM)系统中的多业务间子载波自适应资源分配机制。考虑了每个用的不同业务需求,资源根据每个用户不同的服务质量要求来分配。提出了基于OFDM系统的自适应子载波重分配算法,该算法能够最大程度地灵活分配所有子载波。仿真表明,使用此算法能在很大程度上改善OFDM系统的性能。     

多载波码分多址系统联合特征码与子信道动态分配

针对多载波码分多址系统中固定的子信道分配方案不能依据信道变化进行调整，而固定的扩频码分配又降低了系统的软容量等问题，本文在上行链路盲信道估计的基础上，提出下行链路联合特征码与子信道动态分配方案．根据接人的用户数多少及各个用户的信道信息，进行联合码域与频域的动态资源分配，进一步降低了多址干扰．数值仿真结果表明，本方案收敛快，信道跟踪性能好，在相同误码率条件下系统平均发射功率可以降低3～4dB．     

Ricean衰落信道下一种正交多载波CDMA系统的性能

本文提出了一种新的多载波码分多址(MC-CDMA)系统.与传统系统相比,其主要区别是采用多个并行MC-CDMA分支,每一个分支用一组正交子载波进行调制.在每个分支上,使用相同扩频序列的不同码片调制子载波.这种系统能更有效地利用传输带宽,实现频率分集.由于该系统降低了每个子载波上的数据速率,扩频序列更容易同步.最后给出了系统在Ricean衰落信道下的性能分析.     

一种部分信道响应环境中的多用户MIMO-OFDM自适应子载波分配优化算法

该文提出一种在部分信道响应环境中利用各个用户的信道反馈信息自适应调整多用户子载波分配的优化算法,该算法考虑到实际环境中反馈信息延迟和误差引起的部分信道响应情况,结合各用户的反馈信道信息和动态子载波组分配技术,可实现有效降低自适应子载波分配运算量同时又不明显弱化系统性能的目的。仿真结果表明,该算法可改善部分信道响应带来的负面影响,同时也使子载波分配算法获得较大的简化。     

多用户自适应调制OFDM系统的高效子载波分配方案

为保证用户的子载波分配的实时高效,该文给出了一种能够满足和适应未来移动多媒体通信要求的高效频带分配方案。它是基于自适应调制的OFDM系统的。该方案使用了一种基于贪婪算法的高效算法,这种算法简单易于理解,复杂度低,仿真结果表明其性能优良,接近于最优解。     

一种低复杂度MIMO-OFDMA系统的自适应子载波分配算法

本篇论文提出一种多用户多输入多输出正交频分复用系统(MIMO-OFDMA)下行链路具有信道变化实时性的动态子载波分配算法.文中采用奇异置分解,将每个子载波的MIMO衰落信道分解为独立的并行子信道,利用子信道通对各子载波容量的求解推导出本文算法.此次优的算法在满足各个用户数据速率和BER要求的同时,能减小发射功率.仿真结果也证明了这一点.     

阵列天线多载波DS-CDMA系统基于子空间的信道估计

阵列天线多载波DS-CDMA系统在未来移动通信中具有重要的应用前景。本文研究了阵列天线多载波DS-CD MA系统基于子空间的信道盲估计方法。通过在阵列天线多载波DS-CDMA系统下构造统一的信号模型,实现了基于子空间的信道盲估计。仿真结果表明所提出的方法可有效地对阵列天线多载波DS-CDMA系统的信道参数进行估计,并可抵抗适度的远近效应。     

多载波CDMA系统

介绍了一种基于ＣＤＭＡ技术和ＯＦＤＭ的多载波ＣＤＭＡ系统,并对其三种类型进行了比较。     

多载波通信系统的实用功率分配算法

本文利用多载波通信系统的误码率、比特位数与信噪比之间的关系提出了性能良好的快速表查询法.在噪声干扰,信道衰减和一定频段上功率谱密度对子信道最大传输位数限制的条件下,得到了一种实用的离散多音频多载波通信系统的功率分配和数据位加载算法.在系统初始化过程中,该算法使系统能在满足各种约束条件下达到最优功率分配和数据位加载,比其他算法具有更高的计算效率和更大的系统性能裕量.在信道特性变化时,该算法使系统在不增加硬件的情况下能进行快速跟踪和自适应位交换.     

一种基于快跳频技术的多载波CDMA系统

为进一步提高多载波CDMA系统的频带效率与抗干扰能力,提出了一种跳频多址技术结合多载波调制的传输方案,利用跳频技术将部分子载波传输与随机交织引入到多载波传输系统中,给出了系统实现的模型,并对该传输方案的系统带宽和误码性能进行了分析。理论分析与仿真结果表明：与以往的多载波CDMA系统相比,所建议系统的结构简单,性能优异,消除了已有系统中峰均功率比高和远近效应等问题,具有较强的抗多址干扰与窄带干扰的能力,并能有效地抗信道中突发错误的能力。     

A Multicarrier CDMA System for Joint Time-Frequency Diversity Using Divided Spreading Sequence

One of the principal disadvantages of multicarrier modulation technique is the sensitivity to the frequency offset introduced by Doppler shift. This frequency offset introduces inter-carrier interference (ICI) among the multiplicity of carriers in the multicarrier modulated signal. However, Doppler spread induced by temporal channel variations can provides another means for diversity. In this paper, we propose a modified multicarrier code division multiple access (CDMA) system to exploit Doppler diversity as well as multipath diversity. The key work of our framework is a canonical time-frequency-based decomposition of the mobile wireless channel into series of independent fading channel. The decomposition naturally leads to a time-frequency generalization of the Rake receiver that exploits both multipath and Doppler diversity.     

Performance of a Multiuser Detector with Multicarrier Transmission for a DS/CDMA System

In this paper, a new multiuser detector combining decorrelating detector and multicarrier transmission scheme is proposed and analyzed in a frequency selective Rayleigh fading channel. The bit error probability and asymptotic multiuser efficiency are derived as performance measures. From numerical results, it is shown that the proposed detector achieves better BER performance and lower computational complexity compared to a conventional decorrelating detector. It is also shown that the proposed detector is robust to partial narrowband interference, and alleviates near-far problem effectively. The results in this paper can be applied to design of a wideband CDMA system.     

Femtocell双层网络中基于Q-learning的子信道分配方案

在Femtocell家庭基站(Femtocell Base Station, FBS)组成的异构网络中,为提升网络的频谱效率,FBS与Macrocell宏基站(Macrocell Base Station, MBS)一般要求是同频部署,然而同频部署会产生同信道干扰。为了实现FBS的大规模部署,降低网络同信道干扰影响变得尤为重要。该文提出一种基于Q-learning的子信道分配方案,既保证大量部署的FBS不会对MBS带来过高的跨层干扰,同时也降低了FBS之间的同层干扰。同时针对FBS稀疏部署和密集部署的场景,分别进行了算法的仿真验证,其仿真结果表明该算法降低了干扰,验证了理论的正确性。     

Blind Channel Estimation for Multi-Rate Multicarrier DS/CDMA Communications

Multi-rate multicarrier DS/CDMA is a potentially attractive multiple access method for future wireless communications networks that must support multimedia, and thus multi-rate, traffic. Several receiver structures exist for single-rate multicarrier systems, but little has been reported on multi-rate multicarrier systems. Considering that high-performance detection such as coherent demodulation needs the explicit knowledge of the channel, based on the finite-length chip waveform truncation, this paper proposes a subspace-based scheme for timing and channel estimation in multi-rate multicarrier DS/CDMA systems, which is applicable to both multicode and variable spreading factor systems. The performance of the proposed scheme for these two multi-rate systems is validated via numerical simulations. The effects of the finite-length chip waveform truncation on the performance of the proposed scheme is also analyzed theoretically.     

Performance of a Multicarrier CDMA System with Rayleigh Fading Multipath Channels

This paper examines the performance of a multicarrier CDMA system in a Rayleigh fading channel without a RAKE receiver. Since the multicarrier technique is a diversity reception technique used in the frequency domain, the signal is transmitted at different frequency bands and undergoes different fading. The superimposed signal of the multipath components after going through the mobile channel will be processed by an Fourier Transform to enter the frequency domain, where the time delays in various paths are converted to the phase shifts in the compound signal. In this paper, we use sounding bits to extract the characteristics of the mobile channel and to partly remove the multipath effect. From the simulation, it is found that the multicarrier technique is simpler than the technique used in the single carrier system with a RAKE receiver while producing a better performance than that of the RAKE receiver.     

一种基于均值反馈模型的自适应空间子信道分配算法

MIMO/OFDM是未来宽带无线通信接口的有效架构。该文针对多用户MIMO/OFDM系统,提出了一种基于均值反馈模型的自适应空间子信道分配算法,以获取最大的系统吞吐量为目标,推导了子载波分配准则,并给出了相应的算法流程。仿真结果表明,该算法具有良好的性能,有效地提高了系统的传输速率。