DS‐PAM UWB System Using Non‐linear Chirp Waveform

We propose a direct‐sequence pulse‐amplitude modulation (DS‐PAM) ultra‐wideband (UWB) system which employs a non‐linear chirp waveform instead of the conventional Gaussian monocycle in this paper. In the approved frequency for UWB, there exist myriad narrowband interferers. Specifically, we focus on the mutual interference between UWB systems and 802.11a WLAN. This paper offers a method to suppress this inband narrowband interference by introducing a kind of non‐linear chirp waveform. Using the proposed non‐linear chirp waveform, the effects of one or more narrowband interference sources with different frequencies can be suppressed. System performance of UWB systems in the narrowband interference environment can be improved. Computer simulations with additive white Gaussian noise successfully demonstrate an increase in performance with the proposed system as compared to traditional linear chirp systems.     

基于信道缩短的超宽带信道盲估计方法

在基于一阶统计量解圆周卷积的超宽带信道盲估计方法中,存在着要求信道长度必须小于符号周期长度的局限性.使用信道缩短技术,对实际信道的长度进行缩短,估计出缩短信道后再恢复成实际的超宽带信道,有效地解决了这个问题.仿真实验表明,在信道长度大于符号周期长度时,仍然能很好地估计出信道.     

Multiuser detection of time-hopping PPM UWB system in the presence of multipath fading

Ultra-wideband (UWB) impulse radio (IR) systems are currently being considered for several applications due to their attractive features that include low-power carrierless and ample multipath diversity. Among the various modulation and multiple-access schemes, time-hopping (TH) pulse position modulation (PPM) is a popular technique in application. Most past works rely on strict power control and perform single-user detection (matched filtering) on the desired signal. This paper aims to apply multiuser detection techniques in binary PPM (BPPM) UWB IR multiple-access systems. Moreover, we consider frequency-selective multipath fading channels to account for the wireless cellular environment. A class of linear multiuser detectors (LMDs) is applied to extract the information bits while eliminating multiuser interference (MUI) in the presence of multipath fading. Simulation results are provided to compare the performance of different LMDs.     

Multiple Access <Emphasis Type="Italic">M</Emphasis>-ary Modulation UWB System Based on Code-Selected Direct Sequence Bipolar PAM

This work presents an M-ary multiple access code-selected direct sequence (DS) ultra wideband (UWB) communication system. A high data rate multiple access UWB system can be obtained by a code selection mechanism. In the proposed system, each user is assigned a DS code set with M/2 DS code sequence and a particular DS code sequence can be selected by the log₂ (M/2) bits from the DS code set. More importantly for this M-ary UWB communication system, with the increase of the modulation level M, it allows to reduce the required transmitter power maintaining the number of users, the data transmission rate and the multiple access performance. In this paper, we also introduce the detailed algorithm to compute the bit error rate (BER) over the AWGN channel and correlation receivers.

An Ordered Successive Interference Cancellation Scheme in UWB MIMO Systems

In this letter, an ordered successive interference cancellation (OSIC) scheme is applied for multiple‐input multiple‐output (MIMO) detection in ultra‐wideband (UWB) communication systems. The error rate expression of an OSIC receiver on a log‐normal multipath fading channel is theoretically derived in a closed form solution. Its bit error rate performance is analytically compared with that of a zero forcing receiver in the UWB MIMO detection scheme followed by RAKE combining.     

基于自适应调制技术的MIMO UWB无线通信系统的研究

在对多输入多输出(MIMO)技术和超宽带(UWB)无线通信研究的基础上提出了一种基于自适应调制技术的时变多进制MIMO UWB系统。通过采用奇异值分解理论和速率分阶的方法对系统性能进行了分析,推导出了速率离散分阶情况下的功率和速率的分配公式,提出了相邻时隙平均功率控制(JTAPC)算法,并且对系统的性能进行了仿真。研究结果表明,功率控制算法的使用很大程度上提高了采用速率分阶的系统的性能,并且降低了系统实现的复杂度。     

Chirping techniques for enhancing the performance of SOA-based UWB over fiber systems: An experimental demonstration

A phaser-based processing technique was adopted in an UWB over fiber system employing SOA. The target is to simultaneously reduce the ASE noise impact and nonlinear effects inherent to optical amplification. Experimental results prove the effectiveness of chirping in terms of cross correlation and bit error rate.     

VHF/UHF UWB SAR基于通道均衡的RFI抑制方法

对工作于甚高频/超高频(VHF/UHF)波段的超宽带合成孔径雷达(UWB SAR),射频干扰(RFI)会严重恶化图像质量。该文提出了一种基于通道均衡的RFI抑制方法,它能有效地抑制雷达接收信号中的RFI分量,同时保持图像质量。实际的处理结果证实了该算法的有效性。     

基于超宽带雷达的运动人体目标跟踪成像算法

 超宽带雷达用于人体探测,在大规模城区巷战、反恐斗争和灾害救援等方面有着广阔的应用前景.传统的超宽带成像算法在识别能力及计算效率上已不能满足要求.本文针对运动人体目标场景建立系统模型,将人体运动等效为天线移动扫描,基于快速SEABED成像算法提出一种用于超宽带雷达的动目标跟踪成像算法.仿真与实验结果验证了算法的有效性和可行性,该算法对系统硬件要求低,实时性好,准确度高,能完成对运动目标速度估计及运动轨迹跟踪,并对目标边界成像.     

可见光通信自适应直流偏置光正交频分复用系统设计与性能研究

传统的直流偏置光正交频分复用(DCO-OFDM)系统通过添加直流偏置(DC)和限幅获得单极性信号,由于傅里叶逆变换(IDFT)输出时域信号的随机性,固定的直流偏置会产生较大的非线性限幅失真。该文提出设计自适应直流偏置光正交频分复用(ADCO-OFDM)系统,以双边限幅前、后符号之间的均方误差(MSE) 最小化为优化目标,求解使非线性限幅失真最小的DC。介绍了ADCO-OFDM系统原理、推导了子载波比特信噪比(SNR),建立了均方误差最小化优化模型,并给出了最优直流偏置的求解过程。采用蒙特卡罗(Monte Carlo)仿真方法分析了误码率(BER)和光功率消耗,验证了系统设计和性能分析的正确性。