多路DFT扩频的低峰均比OSFBC传输方法

空频分组码（SFBC）可以为MIMO系统带来发射分集增益,而单载波频分多址（SC-FDMA）系统的发送信号具有低峰均比（PAPR）,但直接传输正交SFBC（OSFBC）会出现PAPR过大的问题。为此,本文以四发射天线为例针对OSFBC提出了一种基于DFT扩频的低PAPR传输方案,通过设置多个并行DFT单元并将得到的多组频域数据等间隔交叉排列映射到子载波上,根据频域循环移位和内插的性质使时域信号等效为多条单载波信号的叠加,PAPR与同点数SC-FDMA信号大致相当。同时,本文方案未带来误码率性能的下降,能够取得的分集增益与正交空时分组码（OSTBC）相同。      

基于LTE的单载波频分多址调制技术研究

针对移动通信中,对于手持终端能耗的要求较高的特点,单载波频分多址作为一种单载波调制方式,以其与生俱来的优点,被3GPP LTE标准采用为上行调制方式。该文对单载波频分多址进行了简要的介绍,对3GPP相关标准进行解析,简要说明了在LTE上行信道中的编码调制方式和帧结构,并结合标准进行仿真,给出仿真信号频谱,在峰均比性能上与OFDM进行了对比,说明了单载波频分多址在峰均比方面与OFDM比较,可以将峰均比提高2个单位以上,满足移动通信中低功率的要求。     

上行链路无线传输中的SC-FDMA

SC-FDMA是一种改良的OFDMA,在未来的上行链路高速数据通信里是一种很有前途的技术,被选为LTE的上行链路传输方案。SC-FDMA本质上跟OFDMA有相似的复杂度,它的一个显著优点就是PAPR低。主要研究子载波映射对PAPR的影响。具体来说,分布式频分多址(DFDMA)比集中式频分多址(LFDMA)PAPR低;SC-FDMA要比OFDMA中的PAPR要低,性能更好。     

基于DFT滤波器组的多载波调制系统设计

采用DFT滤波器组来代替OFDM系统中的IDFT/DFT模块,形成基于滤波器组的收发器。设计适于多经衰落信道的DFT滤波器组收发器。其均衡与OFDM系统一样,是在接收端采用单抽头的均衡器。实验采用随机多径信道,仿真结果表明所提出的滤波器组收发器可以获得较好的频谱特性,以及较满意的SIR（信号与干扰比值）。     

DFT扩频广义多载波系统的SINR性能分析

针对离散傅立叶变换扩频的广义多载波系统(DFT-S-GMC),提出一种信干噪比(SINR)的性能分析方法.该方法基于DFT-S-GMC收发机频域等效的简化实现结构,利用信道频率响应和噪声方差,接收端采用最小均方误差(MMSE)均衡,分析得到了SINR的闭合表达式,并考虑了信道均衡后时域复用的数据块(IFBT符号)之间的残余干扰,而且,本方法很容易扩展到一发多收的情况.仿真表明,多径信道下基于该等效SINR的误块率(BLER)性能曲线能很好地匹配系统在高斯白噪声信道下的性能曲线.     

基于正交变换的广义多载波系统自适应传输方案

针对基于正交变换的广义多载波系统(OT-GMC),提出一种正交变换模式和调制编码方式联合自适应的单载波混合传输方案。该方案以最大化频谱效率为优化准则,依据接收信号的信干噪比(SINR)自适应切换正交变换模式和调制编码方式。当正交变换采用恒等变换时,对子带数据进行独立的链路自适应,提高了频谱效率。当正交变换采用离散傅里叶变换时,发射信号具有较低的峰均比,提高了发射端的功放效率。该传输方案实质上获得了单载波混合传输系统内频谱效率和峰均比的最优化折中性能。仿真表明,多径信道下该混合传输方案的吞吐量性能优于单一传输方案。     

广义多载波合成滤波器组的快速算法

近年来,移动通信业务在全球范围内发展迅猛。除了通话短信等服务外,人们要求更多的多媒体服务,能满足无所不在的各种个性化的需求。即将推出的3G系统也不能满足未来用户的实际需求,国内外移动通信领域的专家已经在进行B3G/4G系统的研究和开发工作。推导了广义多载波合成滤波器组的快速实现算法,并且结合Xilinx公司Virtex-Ⅱ系列芯片的结构特点,设计出了广义多载波合成滤波器组的FPGA实现结构。     

广义正交传输系统及其高效实现方法

基于子带变换理论构建的广义正交传输复用模型，不仅适用于TDMA、FDMA和CDMA多用户系统，也适用于像OFDM之类的多载波（MC）系统以及由OFDM与CDMA综合而成的MC-CDMA系统。该模型在结构上等效于均匀DFT滤波器组，可以采用FFT结合多相滤波器组的方式高效实现。本文实现的多载波系统具有子载波间隔可伸缩性特点，而复杂性与OFDM加窗处理相接近。在相同的仿真环境下得到的结果表明：基于软脉冲响应的多载波系统（MCSIS）误码率性能优于OFDM；对于相同衰落信道，MC-CDMA系统抗衰落特性明显优于OFDM。     

基于离散正弦变换的单载波频分多址系统及其性能分析

为分析离散傅里叶变换(DFT)与离散正弦变换(DST)对单载波频分多址(SC-FDMA)系统某些性能的影响,提出了一种基于离散正弦变换的单载波频分多址系统。给出了基于DST的SC-FD-MA系统的结构框图,接着重点推导和分析了DST IFDMA和DSTLFDMA信号的时域表达式,最后讨论了系统的峰值平均功率比(PAPR)和不同脉冲成形滤波器的冲激响应。仿真结果表明,基于DST的SC-FDMA系统比传统的基于DFT的SC-FDMA系统和正交频分多址接入(OFDMA)系统有更好的比特误码率。此外,DST SC-FDMA信号的PAPR性能接近于DFT SC-FDMA且优于OFDMA。     

基于星座符号序列局部相位旋转的低峰均功率比滤波器组多载波结构优化

针对基于离散傅里叶变换(DFT)扩频的低峰均功率比滤波器组多载波(LP-FBMC)结构需要额外传输边带信息(SI)等问题,该文提出一种基于星座符号序列局部相位旋转的无SI优化结构。考虑到SI是由LP-FBMC在发送端对4种信号传输形式进行选择而产生,结合这4种形式解调后的星座符号序列与原符号序列的关系,采用对星座符号序列进行局部相位旋转的方式避免边带信息的传输。局部旋转的方式减少了相位旋转角度的个数,降低了计算复杂度,并在接收端通过扩大相位判定范围的方式提升了相位估计的正确率。仿真结果表明,所提结构不但能保持与LP-FBMC结构相同的峰均功率比抑制性能和相近的误码率性能,而且计算复杂度相较于嵌入式SI结构降低了约20%。     

MIMO Frequency Hopping Spread Spectrum Multi-Carrier Multiple Access: A Novel Uplink System for B3G Cellular Networks

In this paper, we propose and give the performance of a novel uplink system based on the combination of multi-carrier (MC), code division multiple access (CDMA) and multiple input multiple output (MIMO) techniques. First, we describe the interests of spread-spectrum multi-carrier multiple access (SS-MC-MA) scheme for uplink, especially compared to MC-CDMA. Classically, with SS-MC-MA, each user spreads its data symbols on a specific subset of adjacent or multiplexed subcarriers, to facilitate the channel estimation and reduce complexity at the reception. In order to compensate for the lack of frequency diversity of SS-MC-MA with adjacent subcarriers, we first combine it with an orthogonal space-time block code (STBC) and demonstrate the resulting spatial diversity gain. Then, we propose to allocate the subsets to the different users by applying a frequency hopping pattern (FH). In that case, each user benefits from the frequency diversity linked to the total bandwidth as with the multiplexed subcarriers solution, while keeping the advantages of the adjacent subcarriers solution. The gain provided by the use of the frequency hopping is stressed on. Finally, the performance of this scheme is evaluated over realistic MIMO channel with channel turbo coding for systems offering asymptotic spectrum efficiency of 1, 2, 3 and 4.5 bit/s/Hz. Thus, the efficiency of the novel proposed STBC FH SS-MC-MA system as a very promising multiple access and modulation scheme for the uplink of the future wideband wireless networks is successfully demonstrated.     

DS/CDMA系统上行链路一种稳健的阵列接收方法

W G.Hou等对DS/CDMA移动通信系统上行链路提出了通过估计空间到达角（DOA）而进行波束形成的空间滤波方法,本文首先对该方法进行了从对移动台的初始DOA定位到跟踪的大量改进,使该方法对期望用户的跟踪和对干扰用户进行空域抑制更为准确和有效。然后将算法与导频位辅助LMS-DRMTA算法进行了比较,该方法比导频位辅助LMS-DRMTA算法具有更小的运算量,更好的稳定性,当扇区激活用户数较大时,该方法还具有更低的误码率（BER）,该阵列接收法更适合大容量的移动通信系统。     

OFDM-FDMA Scheme for the Uplink of a Mobile Communication System

The Orthogonal Frequency Division Multiplexing (OFDM) transmission technique can efficiently deal with multi-path propagation effects especially in broadband radio channels. It also has a high degree of system flexibility in multiple access schemes by combining the conventional TDMA, FDMA and CDMA approaches with the OFDM modulation procedure which is particularly important in the uplink of a multi-user system. In OFDM-FDMA schemes carrier synchronization and the resulting subcarrier orthogonality plays an important role to avoid any multiple access interferences (MAI) in the base station receiver. An additional technical challenge in system design is the required amplifier linearity to avoid any non-linear effects caused by a large peak-to-average ratio (PAR) of an OFDM transmission signal. A specific OFDM-FDMA uplink procedure is proposed and will be designed in this paper which can be seen as a combination of a specific subcarrier spreading scheme and subcarrier selection process. The resulting transmit signal consists of a periodic extension and multiple repetition of all modulation symbols and leads therefore to an extremely low computation complexity in the transmitter. Furthermore, the transmit signal shows simultaneously a constant envelope to avoid any non-linear effects in the amplification process. This uplink scheme can be considered as a trade off between low computation complexity and system performance. Prof. Hermann Rohling is with the Technical University Hamburg-Harburg, Germany where he has developed an international reputation in the field of OFDM transmission techniques. Previously Prof. Rohling was with the AEG Research Institute, Ulm as a researcher working in the area of digital signal processing for radar and communications applications. His research interests have included Wideband Mobile Communications especially based on Multicarrier Transmission Techniques (OFDM) for future broadband systems (4G), signal theory, digital radar signal processing, detection, estimation and differential GPS for high precision navigation. Prof. Rohling is a member of Informationstechnische Gesellschaft (ITG), German Institute of Navigation (DGON) and a senior member of IEEE. He is chairman of the August 2005 International OFDM Workshop (InOWo 2005) in Hamburg, Germany. Martin Stemick received the Dipl.-Ing. degree in electrical engineering from the Technical University Hamburg Harburg (TUHH), Germany in 2004. Currently, he is a Ph. D. student and belongs to the scientific staff of the Department of Telecommunications, TUHH, Hamburg, Germany. His research interests include wireless OFDM-systems, with a current emphasis on resource allocation and equalization techniques.     

多载波系统中一种基于预编码的改进PAPR降低方案

针对多载波系统中峰均功率比（Peak to Average Power Ratio，PAPR）普遍较高的问题，首先给出预编码技术抑制PAPR的基本思路和预编码矩阵的一般性设计规则;然后将降低信号峰值的问题转化为在信号瞬时功率均值不变的条件下最小化信号瞬时功率方差的优化问题;最后，为了使预编码矩阵能够联合改善载波的相位和发送信号的非周期自相关性以提高PAPR的抑制效果，基于梯度搜索算法提出一种将非周期自相关性和相位共同优化的算法求解上述最小化问题，通过互补误差函数（Complementary Cumulative Distribution Function，CCDF）表示对PAPR的抑制效果。仿真结果表明，该算法在不影响甚至稍微提高系统误码率性能的前提下，相比于预编码方法改善约0.8 dB。     

基于块空时分组编码DFT-S-OFDM虚拟MIMO传输方案

该文提出了一种基于块空时分组编码的DFT-S-OFDM上行链路虚拟MIMO传输方案,并给出一种低复杂度的虚拟MIMO系统接收机检测算法。仿真研究表明：基于块空时分组编码的DFT-S-OFDM虚拟MIMO传输方案可保持原DFT-S-OFDM系统低峰均比的特性,显著降低虚拟MIMO系统接收机检测门限,提高上行链路虚拟MIMO系统传输可靠性。     

A pilot-based dynamic channel assignment scheme for wireless access TDMA/FDMA systems

We propose a control architecture for implementing a dynamic channel assignment (DCA) algorithm which optimizes two-way channel quality in a TDMA portable radio system. Computer simulations are used to evaluate the performance of this DCA method. A common control frequency, which is frame-synchronized among base stations, provides (1) beacons for portables to locate base stations and obtain DCA information, (2) broadcast channels for system and alerting information, and (3) pilot signals to permit portables to evaluate downlink interference. This allows low-complexity radio ports and portables to mutually select channels to avoid interference and avoid creating excessive interference. Results from computer simulations demonstrate the good spectrum efficiency of this method and its potential for handling nonuniform traffic demand. This work is targeted toward understanding the implications to local exchange networks of wireless system alternatives that could provide access to those networks.A preliminary work with the same title was presented at the Second International Conference on Universal Personal Communications, October 12–15, 1993, Ottawa, Canada.     

一种降低多载波信号峰均比的技术

多载波信号峰均比的降低在现代功率放大器研究和设计中具有重要意义。文章基于多载波信号的包络特征,提出了一种全新的峰均比降低技术。理论分析和计算机仿真结果表明:文章所提出的技术可以较大程度的改变信号的包络分布,进而大幅度降低多载波信号的峰均比。从实验结果也可以看出,采用了这种新型多载波信号峰均比降低技术的功率放大器,线性与现有功率放大器相比得到大幅度改善。     

A Subcarriers Allocation Scheme for Cognitive Radio Systems Based on Multi-Carrier Modulation

Cognitive radio (CR) is a dynamic spectrum access technology as a solution to spectrum under-utilization problem in some licensed bands. Operating over an exceedingly wide spectrum, CR systems usually adopt multi-carrier modulation (MCM) to implement flexible channelization. Consequently, efficient channel allocation scheme becomes extremely important to an MCM based CR (MCM-CR) system. In this paper, a maximum likelihood detection model is developed to detect the presence and locations of licensed users (LUs) signals in the frequency domain. Performance of the detection model, including the optimal detection region, detection probability and false alarm probability, is analyzed. A one-order two-state Markovian chain model is proposed to predict channel status information. In particular, a novel subcarrier allocation scheme for MCM-CR systems is proposed, taking into account the confidence of channel estimation, quality of services (QoS) of rental users (RUs) and throughput. To validate the analytical results, simulations have been conducted to show effectiveness of the proposed scheme.     

基于上行时隙的新型信号检测方法研究

本文利用通信系统具有上下行时隙的特点,根据基站和用户终端发射功率的不同,提出了基于上行时隙的能量检测算法。在非授权用户系统的认知节点进行在线能量检测时,容易受到系统自身发射信号的干扰。为了减轻该影响,本文基于上行时隙进行能量检测,这样认知节点所受干扰主要来源于系统的用户终端,其带来的干扰相对较小。文中选取了TD-LTE系统作为非授权用户、雷达系统作为授权用户的认知系统开展研究,并通过MATLAB仿真证明了基于上行时隙的能量检测算法的可行性。     

A Phase Adjustment Based Partial Transmit Sequence Scheme for PAPR Reduction

The peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing signal is normally very large and is crucial for the analog amplifier in the transmitter. It is therefore necessary to reduce the PAPR before the signal is transmitted. In this paper, a PAPR reduction scheme is presented based on the partial transmit sequence (PTS) method. By allowing each subblock of data to be rotated by an arbitrary angle, a simple yet efficient phase search algorithm is proposed. With a prespecified number of iterations, the proposed method gives the best phase vector for a combination of data blocks to achieve the smallest PAPR value. Our simulation results show that the proposed scheme provides significant computational savings while yielding a performance similar to that of the conventional PTS method.