多天线智能分集接收系统的设计

通过对多天线分集接收技术的分析,针对多径传输引起的衰落,提出一种多天线分集接收方法。本文将智能控制处理技术与空间分集接收天线技术相结合,通过智能控制选择合并算法。通过无线遥控接收机进行实验,取得良好接收效果。     

天线分集技术在WSNs定位中的应用

针对基于接收信号强度指示（RSSI）的定位算法中根据RSSI测距误差较大的问题,提出了在锚节点上使用天线分集技术的方法。该方法在锚节点上安装2根天线,天线互成90°,采用空间分集。锚节点在接收未知节点广播信号时,选择2根天线中信号强的天线接收信号,并记录RSSI值。实验证明：在锚节点上引入天线分集技术,可以降低无线信号多径衰落的影响,提高RSSI值的稳定性,减小了测距误差,提高了定位精度。     

发射分集MC-CDMA系统空时多用户检测

该文研究了在频率选择性瑞利衰落信道中的同步多载波码分多址(MC-CDMA)系统上行链路,在移动终端处使用两个发射天线,采用基于空时分组码的发射分集,基站采用分集天线接收。考虑对应于子载波的衰落系数是信道冲激响应的离散傅里叶变换,给出了采用发射分集和接收分集的MC-CDMA系统上行链路信号模型。研究了采用发射分集和接收分集的MC-CDMA系统的解相关多用户检测、最小均方误差(MMSE)多用户检测,进行联合的多用户检测和空时码解码。仿真结果验证了上述模型及算法的有效性。     

短波广域分集技术研究

短波广域分集技术是利用多个相距较远的、通过网络互联的短波固定台站,将不同地域空间和不同极化天线所接收到的短波信号,通过实时汇聚和合并解调,有效提升短波话音通信的稳定性和可靠性。针对短波广域分集接收系统的设计,首先对其技术特点作了详尽介绍并指出其设计难点;对短波广域分集接收技术国内外当前的研究状况进行了总结和概括,最后介绍了短波广域分集接收中的关键技术并指明了其未来的发展趋势。     

LTE系统基于传输分集的信号检测的DSP实现

信号检测是长期演进( LTE)系统接收端的一项重要技术,对系统的性能有着较大的影响。在LTE系统中,接收端的天线同时接收来自发送端的多个天线端口的数据,因此接收端必须采用信号检测算法还原发送端的数据。分析与研究了基于传输分集的信号检测算法,并着重讨论了空频编码法,提出了一种简单的DSP实现方案。该方案已成功应用于TD-LTE TTCN扩展测试集仪表开发项目中。     

基于MIMO技术的无线胶囊内窥镜接收系统

本文旨在为胶囊内窥镜系统提出一种提高图像传输速率并降低误码率的方法——MIMO（Multiple Input Multiple Output）技术来提高传输可靠性。为了不增加发射端的体积和功耗,我们使用单个发送天线,而在接收端采用多个接收天线即SIMO（Single Input Multiple Output）系统,同时我们仿真了各种分集接收技术的性能,选出一种最优的接收合并方式。     

一种基于MIMO的时延估计算法

在城市峡谷和室内环境中,信号在传输过程中受多径衰落和非视距的影响,导致长期演进(LTE)系统的时延参数无法精确估计。针对该问题,提出一种基于多输入多输出(MIMO)的LTE时延参数估计算法。采用具有良好自相关特性的主同步信号作为参考信号,利用MIMO发射分集和最大比合并接收技术降低信号传输过程中的误码率,通过参考信号与接收信号进行互相关处理,获得时延估计。仿真结果表明,当累积分布概率为90%时,该算法的时延参数估计误差比参考算法提高了大约5个最小采样间隔。     

球形译码算法在信号空间分集系统中的应用研究

针对信号空间分集系统中最大似然检测算法复杂度高的问题,选用球形译码算法作为信号空间分集系统接收机检测算法,可以使接收机在接近最大似然算法检测性能的同时,降低接收机检测复杂度。为进一步降低检测复杂度,通过采用最小均方误差算法减小噪声对接收信号的干扰,来降低因搜索噪声点而产生的复杂度,并利用衰减因子k加快搜索半径收缩来达到进一步降低球形译码算法检测复杂度的目的。仿真结果表明,在信号空间分集系统中引入球形译码算法可以降低接收机检测复杂度,并且改进后的球形译码算法检测时间在低信噪比情况下约为传统球形译码算法的12%—33%。因此,球形译码算法可以有效地降低信号空间分集系统接收机检测复杂度。     

基于比特对数似然比分集的WCDMA系统性能

研究比特对数似然比（BLLR）的天线分集是误比特率性能优于传统信噪比（SNR）天线分集的一种新技术,对组合空时分组码、2D-RAKE接收机和基于BLLR分集技术的MQAMWCDMA系统在相关MIMO Nakagami衰落信道上的误比特率性能进行蒙特卡洛仿真研究,并推导了接收相关的Nakagami衰落信道上采用BLLR检测的16QAM WCDMA系统平均误比特率的解析表达式。仿真结果表明,理论推导与仿真结果相吻合。对于BLLR的广义选择合并分集技术的系统误比特率性能优于SNR的广义选择合并系统;选取的可分离路径数越多系统性能越好,而平均路径强度的衰减速率越小,误比特率性能越好。     

空间分集技术在CFBM-MC-CDMA系统中的应用研究

给出了一种简单的空时编码方案，提出了应用该方案的基于复数滤波器组调制的多载波码分多址(CF-BM-MC-CDMA)通信系统的模型。理论分析可知，采用空时编码天线发射分集技术的CFBM-MC-CDMA系统与未采用天线分集的系统相比，其多址干扰功率降低了一半。仿真结果表明，系统采用天线分集技术能显著提高其误比特率性能，在低信噪比区域，系统采用两天线分集接收的性能要比采用两天线分集发射的性能好得多。     

Nakagami衰落信道上正交信号的性能分析

推导了Nakagami衰落信道上采用联合发收天线选择和相干检测的M进制正交（双正交）信号的精确或近似平均误符号率/误比特率解析表达式。数值计算和模拟结果验证了M进制正交信号平均误符号率/误比特率近似表达式的准确性,同时阐明了Nakagami衰落系数和发收天线数对采用联合发收天线选择的M进制正交（双正交）信号平均误符号率/误比特率性能的影响。数值计算和模拟结果还表明：当收发天线总数固定时,收发两端天线数量分配越均匀,M进制正交（双正交）信号的误码性能越好。     

Performance analysis of uplink MIMO MC-CDMA systems based on linear zero-forcing V-BLAST algorithm

A structure was proposed for multiple-input-multiple-output multicarrier code divi- sion multiple access （MIMO MC-CDMA） uplink transmission system. Linear zero- forcing V-BLAST （ZF V-BLAST） algorithm and maximum ratio combining （MRC） scheme was applied to the receivers. The average bit error rate （BER） expression was derived on condition that the number of receive antennas was larger than that of transmit antennas and it was verified by simulations. Numerical results show that the number of transmit and receive antennas, as well as the number of sub- carriers, all exert significant effects on the BER performance. The space diversity and frequency diversity show different abilities to improve the BER performance. The MIMO MC-CDMA system based on linear ZF V-BLAST algorithm is capable of achieving better BER performance than that of the conventional MC-CDMA system by reducing the number of transmit antennas or increasing the number of receive antennas.     

非理想CSI下MIMO MRC系统多用户分集性能分析*

针对在无线多输入—多输出（MIMO）通信系统的发射端采用波束成形、接收端采用最大比合并的MIMO MRC系统,考虑收发端仅能获得存在信道估计误差的非理想信道信息（CSI）且系统受到共信道干扰这一条件,分析系统的多用户分集性能。导出封闭形式的信号干扰噪声比的概率分布函数表达式和以平均容量的形式给出的系统多用户分集性能表达式。数值仿真证实了理论分析的结果。研究表明,信道估计误差和共信道干扰均会降低系统的多用户分集性能,而信道估计的精度是影响系统多用户分集性能的关键因素。     

北斗系统B1频段导航信号的多路复用策略研究

针对北斗B1频段导航信号的多路复用策略及其性能进行了分析研究。根据所需复用的不同信号数量和信号间不同的相位约束关系,提出了相应的多路复用方案。根据信号间不同的功率分配比对相应的复用策略及复用效率进行评估,以期找到在复用性能上最优的方案。     

门限决策的AF中继选择协作网络性能分析

中继选择能有效地克服信道衰弱影响,提高分集效果,但全天候协作降低了系统的带宽效率。研究了Rayleigh信道条件下一种新的基于门限决策的多中继选择系统并分析了系统性能,推导了M-PSK信号多中继选择系统的SER闭式表达式和系统带宽效率表达式。实验结果显示,在低信噪比和较少候选中继场景,提高协作门限,可提高系统带宽利用率;高信噪比和较多候选中继场景,适度降低协作门限,可有效提高系统平均SER性能。     

Generalized selection combining scheme with double threshold in the soft handover region

A new diversity selection combining scheme in a multiple Base Stations (BSs) scenario is proposed, in order to minimize the impact of suddenly losing one active BS in the soft handover (SHO) region. By analyzing the average number of path estimations and the average number of combined paths, we can see that the proposed scheme has a satisfactory average bit error ratio (ABER) but with a low complexity, as compared by the conventional distributed combining schemes. Simulation results validate the superiority of the proposed scheme.     

Combined adaptive beamforming with space-time block coding for multi-antenna communications

Aiming at the multi-antenna communication systems, a downlink transmit scheme combining adaptive beamforming （ABF） with space-time block coding （STBC） is first presented, which utilizes the maximization of the output mean signal-to-noise ratio （SNR） and the minimization of the symbol error rate （SER） upper bound of the three widely used modulations as the design criteria. Then, based on the moment generating function （MGF） and the Gauss-Chebyshev integration, a simple and accurate numerical method is presented to analyze the SER performance of the system with the new transmit scheme under the three commonly used modulations. Finally, computer simulation results demonstrate the effectiveness and superiority of the proposed strategy.     

Ergodic secrecy capacity of MRC/SC in single-input multiple-output wiretap systems with imperfect channel state information

This paper investigates the secrecy performance of maximal ratio combining (MRC) and selection combining (SC) with imperfect channel state information (CSI) in the physical layer. In a single-input multipleoutput (SIMO) wiretap channel, a source transmits confidential messages to the destination equipped with M antennas using the MRC/SC scheme to process the received multiple signals. An eavesdropper equipped with N antennas also adopts the MRC/SC scheme to promote successful eavesdropping. We derive the exact and asymptotic closed-form expressions for the ergodic secrecy capacity (ESC) in two cases: (1) MRC with weighting errors, and (2) SC with outdated CSI. Moreover, two important indicators, namely high signal-to-noise ratio (SNR) slope and high SNR power offset, which govern ESC at the high SNR region, are derived. Finally, simulations are conducted to validate the accuracy of our proposed analytical models. Results indicate that ESC rises with the increase of the number of antennas and the received SNR at the destination, and fades with the increase of those at the eavesdropper. Another finding is that the high SNR slope is constant, while the high SNR power offset is correlated with the number of antennas at both the destination and the eavesdropper.     

SER analysis of PTS based techniques for PAPR reduction in OFDM systems

A major drawback of orthogonal frequency division multiplexing (OFDM) is high peak-to-average power ratio (PAPR). An OFDM signal with high PAPR requires power amplifier?s (PAs) with large linear operating ranges but such PAs are difficult to design and costly to manufacture. Therefore, to reduce PAPR various methods have been proposed. One of the existing technique to reduce PAPR is partial transmit sequences (PTS). The major drawback of this technique is that it requires transmission of side information (SI) with each OFDM symbol, which results in low bandwidth efficiency. It is hard to recover the side information from the OFDM signal received at the receiver.The two methods, which do not require SI to decode the OFDM symbol at the receiver, are multi-point square mapping combined with PTS (M-PTS) and concentric circle mapping based PTS (CCM-PTS). In this paper, the SER performance of PTS based methods namely CCM-PTS and M-PTS over AWGN channel is mathematically analyzed. The SER performance of CCM-PTS over AWGN is analyzed using two decoding techniques, namely minimum distance decoding and circular boundary decoding, whereas M-PTS is analyzed using minimum distance decoding. The simulation results for SER performance of CCM-PTS and M-PTS, over fading channel, have been presented using computer simulations and the SER performance of CCM-PTS by both the decoding techniques is compared with M-PTS. Also, a comparison of PAPR reduction capability and computational complexity of CCM-PTS and M-PTS has been presented. CCM-PTS method almost has the same PAPR reduction capability as M-PTS, but its SER performance is better than M-PTS and uses a simpler method to decode the data symbols.     

Simplified relay antenna selection with source beamforming for MIMO two-way relaying networks

A simplified relay antenna selection with source beamforming (RAS-BF) scheme is advocated for multiple-input multiple-output (MIMO) two-way relaying networks (TWRNs) employing amplify-and-forward (AF) protocol, which does not require channel estimation at the relay node and the optimal relay antenna can be simply determined by comparing the minimum received pilot signaling powers pertaining to each antenna. The theoretical analysis of system outage probability and average symbol error rate (SER) shows that full diversity order can also be achieved by the simplified scheme. Simulation results are provided to verify our theoretical results and further illustrate that the simplified scheme outperforms the outage-optimal counterpart in the presence of channel state information (CSI) imperfections.