A novel MMSE based codebook construction for MIMO precoded spatial multiplexing with limited feedback

This paper deals with the design and performance analysis of the transmission precoder optimization for multiple-input multiple-output (MIMO) systems with limited feedback of channel state information (CSI). We assume that the receiver can get perfect channel knowledge by channel estimation while the transmitter only has partial channel knowledge from limited feedback. We present a minimum mean square error (MMSE) criterion based codebook construction algorithm for MIMO pre- coded spatial multiplexing systems under a specific average power constraint. The optimal transmitter structure is employed in this paper. Simulation results show that the MMSE criteria based codebook construction algorithm with hybrid design of power allocation and precoding can achieve better performance than that of equal power allocation based codebook of previous research.     

MIMO无线信道容量比较与分析

介绍了无线MIMO系统信道容量的计算方法,重点分析和比较了在瑞利衰落信道下,发射端已知或未知,但接收端完全未知的信道状态信息时的独立同分布的多入多出各态历经容量特性。并利用Matlab对其进行仿真。结果表明,在低信噪比时,采用自适应功率分配得到的信道容量特性要优于采用平均功率分配。并且信道容量随收、发天线数目的最小值呈线性增长。     

基于自适应排序LDPC码的OFDM系统及其性能分析

为了在正交频分复用(OFDM)系统中充分利用非正则低密度奇偶校验(LDPC)码编码比特错误概率不同的特性,提出了一种新的基于自适应排序LDPC码的OFDM传输技术.假设发射机已知信道状态信息(CSI),非正则LDPC码的编码比特根据度进行排序,并被分配到相应的子载波上,度高的比特分配到轻度衰落的子载波,度低的节点分配到深度衰落的子载波.为了降低反馈信道的开销,可以对反馈的CSI进行量化.该传输技术的性能可以由密度演进算法进行分析.分析和仿真结果表明,相对于传统的无排序LDPC码编码OFDM系统,所提出的基于自适应排序LDPC码的OFDM系统可以获得1 ~1.5dB的性能增益,并且对CSI的量化具有鲁棒性.     

有限散射信道下MIMO系统信道容量的分析

介绍了有限散射信道下MIMO系统信道容量的计算方法,重点分析了在有限散射信道下,多径分量对信道容量的影响,探讨了发射端在已知和未知信道状态信息时的最优功率分配策略。     

闭环CL-MRC跨层交互系统的性能分析

为增强无线网络的性能,提出了一种闭环CL-MRC跨层交互方案（Closed Loop-Maximal Ratio Combining cross layer scheme）。该方案是跨物理层和数据链路层两层,利用自适应调制技术和自动重传技术的交互协作,使发射端利用反馈信息自适应选择调制模式和发射权矢量,并自动重传发射数据,以达到性能增强的目的。推导了该闭环CL-MRC系统的频谱效率和中断概率的闭合表达式,同时,对比单发/单收（SISO）和开环MIMO跨层系统,闭环CL-MRC系统的性能有明显提高。     

基于统计信道状态信息的有限反馈空分多址方法

研究了在发送相关信道场景下,综合利用统计信道状态信息和瞬时信道状态信息的多波束选择算法.与传统的基于码本的传输方案不同,基于单信道质量标识反馈的多波束选择算法利用统计信道状态信息决定其最佳的波束矢量,每一时隙只反馈信道质量标识,而且该算法的性能与传统方案基本相近.为了进一步提高平均和速率,提出了基于双信道质量标识反馈的...     

Blind channel equalization algorithm based on dual unscented Kalman filter for chaotic multi-input multi-output communication systems

To reduce channel noise,fading,and inter-user interference effectively in the chaotic communication systems with multi-user,a blind channel equalization algorithm based on dual unscented Kalman filter algorithm is proposed.Assuming that the coefficients of a multi-input multi-output (MIMO) channel can be described by an autoregressive model,two separate state-space representations are used for the signals and coefficients.Then two unscented Kalman filters are used to estimate chaotic signals and channel coefficients simultaneously.The simulation results indicate that the algorithm can effectively track the coefficients of the multi-path fading channel in chaotic MIMO communication systems at a fast convergence speed.     

MIMO系统信道容量与传输性能仿真研究

MIMO技术是无线通信领域的重大突破,在不增加系统带宽的情况下,显著地提高系统的数据传输速率和通信质量。该文首先描述了MIMO系统模型,然后对MIMO系统的信道容量进行讨论和仿真分析,最后讨论空时编码技术和对基于Alamouti空时码的系统性能进行仿真分析,从而证明了MIMO系统的优越性。     

MIMO-OFDM scheme using ApFFT over 3GPP SCM channels

The all-phase fast Fourier transform (apFFT) is proposed as a digital demodulation algorithm in place of the fast Fourier transform (FFT) for orthogonal frequency division multiplexing (OFDM) based multiple-input multiple-output (MIMO) communication systems. The amplitude spectrum of apFFT-demodulated symbols is the square of that of the FFT, which helps reduce the Gaussian noise to a great extent. Moreover, the phases of apFFT symbols are not affected by the frequency shift between the transmitter and receiver oscillators. These properties particularly appeal to MIMO systems over frequency-selective fading channels. The proposed MIMO-OFDM system employing the apFFT is validated using the spatial channel model (SCM) proposed by the third generation partnership project (3GPP). The simulation results demonstrate that the performance of the proposed system after compensating for the rate loss due to zero bits inserted in the space-frequency OFDM (SF-OFDM) coding scheme, still considerably outperforms the conventional system over 3GPP SCM channels, especially under poor channel conditions.     

LTE系统中的MIMO技术

由于MIMO技术可以提高系统的信道容量,提高信息传输速率,因此该技术已成为4G的关键技术之一,文中主要论述了MIM0技术的原理和MIMO技术的不同实现方法,对LTE下行MIMO技术的接收算法进行了详细的讨论,并简要介绍了MIMO技术在LTE中的应用.     

MIMO系统信道容量分析

研究了MIMO系统中的功率分配算法,重点研究了平均功率分配法、注水功率分配法以及最小误比特率功率分配法,得到了3种功率分配法的功率分配矩阵,从而得到信道容量。并用Matlab进行仿真,得到了3种功率分配法下的信道容量与信噪比的关系。通过仿真结果可以看出,在信道状态信息已知的情况下,MIMO系统能得到更大的信道容量。并且相对于其他两种分配法而言,使用注水算法,可以显著的提高MIMO系统容量。     

LDPC based differential unitary space-frequency coding for MIMO-OFDM systems

INTRODUCTION Unitary space-time modulation (USTM) (Hochwald and Marzetta, 2000) has been shown to be ideally suited for Rayleigh flat fading channels when there is no CSI. And for continuously changing fading channels, differential unitary space-time modulation (DUSTM) was proposed in Hochwald and Sweldens (2000). However, the performance of DUSTM de-grades considerably in frequency-selective fading channels often encountered in broadband wireless communications. Hence concatena…     

A novel OFDM transmission scheme with length-adaptive Cyclic Prefix

INTRODUCTION In broadband wireless communication, thdelay spread caused by channel multi-path fadinwill usually introduce serious Inter-Symbol Interference (ISI) to the receiver. To counteract the ISIthe high-efficiency Orthogonal Frequency DivisioMultiplexing (OFDM) modulation first splits thhigh-rate data stream into a number of parallesub-streams and modulates them onto differenorthogonal sub-carriers and thus lower the symborate, and then add a Cyclic Prefix (CP) to the h…     

A novel OFDM transmission scheme with length-adaptive Cyclic Prefix

Conventional OFDM transmission system uses a fixed-length Cyclic Prefix to counteract Inter-Symbol Interferences(ISI)caused by channel delay spreading under wireless mobile environment. This may cause considerable performance deterioration when the CP length is less than the channel RMS delay spread,or may decrease the system power and spectrum efficiency when it is much larger. A novel Orthogonal Frequency Division Multiplexing(OFDM)transmission scheme is proposed in this paper to adapt the CP length to the variation of channel delay spread. AOFDM-VCPL utilizes the preamble or pilot sub-carriers of each OFDM packet to estimate the channel RMS delay spread; and then uses a criterion to calculate the CP length,which finally affects the OFDM transmitter. As illustrated in the simulation section,by deploying this scheme in a typical wireless environment,the system can transmit at data rate 11.5 Mb/s higher than conventional non-adaptive system while gaining a 0.65 dB power saving at the same BER performance.     

Time-domain training sequences design for MIMO OFDM channel estimation

This paper describes a Least Squares （LS） channel estimation scheme for MIMO OFDM systems based on time-domain training sequence. We first compute the minimum mean square error （MSE） of the LS channel estimation, and then derive the optimal criteria of the training sequence with respect to the minimum MSE. It is shown that optimal time-domain training sequence should satisfy two criteria. First, the autocorrelation of the sequence transmitted from the same antenna is an impulse function in a region longer than the channel maximum delay. Second, the cross-correlation between sequences transmitted from different antennas is zero in this region. Simulation results show that the estimator using optimal time-domain training sequences has better performance than that using optimal frequency training sequence at low signal-to-noise ratio （SNR）. To reduce the training overhead, a suboptimal training sequence is also proposed. Comparing with optimal training sequence, it has low computation complexity and high transmission efficiency at the expense of little performance degradation.     

Media-specific rate allocation in heterogeneous wireless networks

INTRODUCTION With the development of novel wireless tech- nologies and increasing available bandwidth, multi- media applications over wireless networks become attractive for both businesses and end users. Fast de- ployment of Wi-Fi HotSpots, increase in wireless coverage of remote habitable areas (Wi-Max, or wireless mesh networks), improved data services over the 2G cellular systems and the long awaited debut of 3G wireless services offer many potential and inter- operable communicatio…     

MIMO HSDPA系统中的chip级空时均衡接收方案

提出了一种频率选择性衰落环境下多输入多输出高速下行分组接入(MIMO HSDPA)系统中chip级的空时均衡接收方案, 以消除多天线和多码扩频传输时产生的严重的码间干扰和共信道间干扰; 并推导出分数采样时的空时均衡接收机以进一步提高接收机性能, 然后给出分析和接收信干噪比来设计最优权重. ITU Pedestrian A信道环境下的仿真结果验证了本文的分析和接收机优越的性能.     

多频带UWB通信系统中低复杂度迭代差分译码算法

相对于相干检测,由于在收发端不需要信道状态信息,非相干UWB通信在信噪比方面会有近3dB的性能损失.为了克服这一性能差距,提出了一种有效的基于多频带UWB系统的差分编译码方案.该方案在发射端使用2个并行级联的递归酉差分空频编码器对数据进行编码.接收端的2个分量译码器通过互相交换软度量值对数据进行译码.为了降低接收机的计算复杂度,给出一种只使用转移概率计算信息比特似然比的译码算法.仿真结果表明,在较少迭代次数下,算法性能远优于传统非相干检测,在高信噪比时,其性能甚至超过了相干检测.     

广义分布式天线系统容量解析界

首先对广义分布式天线系统的复合信道模型,如瑞利对数正态衰落信道模型,进行了分析.通过与传统多输入多输出系统的比较,对广义分布式天线系统容量进行了分析,并得出广义分布式天线系统历经容量完整的解析表达式是不可能存在的.为了有效地对广义分布式天线系统历经容量的性能进行评估,利用多元统计理论和矩阵不等式理论推导了在瑞利对数正态衰落信道模型及在发射端采用等功率分配方案下广义分布式天线系统历经容量的解析下界和解析上界.最后,通过数值仿真证明了系统的历经容量可以很好地用其解析界来表述.     

级联Turbo-SPC码的空时系统的设计

Multiple antenna wireless systems can provide larger channel capacity and enable spatial diversity to combat fading. In this paper we conduct an investigation into the design of coded space-time system obtained by serially concatenating channel code module and space-time code module with an interleaver in between. As an example, the system is constructed by employing low decoding complexity turbo-SPC （single parity check） code as outer module and linear complex field space-time code as inner module, which achieves full diversity and lossless equivalent channel capacity. Simulation results prove that our designed system performs well and it only loses 0.8 dB from multiple-input multiple-output （MIMO） capacity at BER = 10^-5 in the case of information bit length 6048. Compared with turbo code-based systems, it also has lower error floor.