Cross‐level PRC transmitter for TH‐PAM UWB systems

A cross‐level pre‐RAKE combining (PRC) scheme for time hopping pulse amplitude modulation ultra wideband (TH‐PAM UWB) transmitter is studied in this paper. A two‐stage cross‐level PRC (CL‐PRC) scheme is proposed. The conventional PRC schemes suppress all the chip‐wise interference. However, the proposed scheme suppresses only the specific frame‐wise inter‐symbol interference (ISI) by exploiting the characteristic that the information bits are transmitted only at ultra short time slots. This results in a low complexity pre‐equalizer without bit error rate (BER) performance degradation. Furthermore, an order selection rule is presented to achieve the tradeoff between signal‐to‐interference ratio (SIR) and computational complexity. Simulation results illustrate the superior SIR and BER performance of our proposal. Copyright © 2009 John Wiley & Sons, Ltd.     

Non‐linear Chirp UWB Ranging System with Narrowband Interference Suppression Abilities

In this letter, we analyze an ultra‐wideband ranging system based on non‐linear chirp waveforms with the ability of narrowband interference suppression. A number of non‐linear chirp waveforms are proposed and evaluated by simulation. The results verify that the proposed schemes can suppress the Narrowband interference to a certain degree.     

M‐ary Bi‐orthogonal Modulation UWB with Narrowband Interference Suppression Capability

An M‐ary bi‐orthogonal modulation scheme for ultra‐wideband (UWB) systems capable of narrowband interference (NBI) suppression is proposed in this letter. We utilize a set of bi‐orthogonal pulse series to achieve NBI suppression. Through analysis and simulation, we verify that the proposed scheme can suppress NBIs effectively.     

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.     

Coexistence of OSCR‐Based IR‐UWB System with IEEE 802.11a WLAN

Impulse radio (IR) is a competitive candidate for ultra‐wideband (UWB) systems. In this letter, we evaluated the coexistence of an IR‐UWB system based on an orthogonal sinusoidal correlation receiver (OSCR) with an IEEE 802.11a WLAN through a detailed simulation. The coexistence performance of the two systems is characterized in terms of the receiver's bit‐error rates. Then, some approaches to interference mitigation are discussed.     

UWB对IEEE802.11a WLAN的电磁干扰分析

在FCC模板和ECC模板的基础上,分析了室内环境下UWB设备对IEEE802.11a WLAN系统的电磁干扰。在IEEE802.11a系统性能恶化1dB的情况下,使用双线模型分别计算出室内环境下单个UWB设备和多个UWB设备的发射功率限制。分析结果表明,对于IEEE802.11a WLAN来说,距离最近的UWB干扰是最主要的干扰,建议以36cm的最小隔离距离为基础来限制5GHz频段处的UWB发射功率。因此ECC模板更能满足IEEE802.11a的电磁兼容要求,而FCC模板能否保证有待进一步研究。     

Suppression of IEEE 802.11a interference using SVD-based algorithm for DS-UWB systems in wireless multipath channels

IEEE 802.11a systems which operate around 5 GHz and overlap the band of UWB signals will interfere with UWB systems significantly. In this letter, a novel narrow-band interference (NBI) suppression technique based on the singular value decomposition (SVD) algorithm is proposed in direct sequence ultra-wideband (DS-UWB) systems in wireless multipath channels. SVD is used to approximate the interference which then is subtracted from the received signals. In contrast to the conventional suppression methods such as the notch filter and the maximal-ratio combining partial RAKE (MRC PRAKE) receiver, our proposed technique is simple and robust, the hardware complexity of the receiver can be reduced greatly.     

超宽带频率依赖性信道模型下的PAM和PPM性能比较

在超宽带无线通信中,频率依赖性信道扭曲了发射脉冲波形,影响了通信系统的性能.文章分析此类信道模型下脉冲位置调制和脉冲幅度调制的性能,结果表明,在频率依赖性信道中PAM调制优于PPM调制.     

基于IIR陷波的UWB窄带干扰抑制

提出了一种基于IIR陷波的UWB窄带干扰抑制方法。超宽带脉冲通过IIR陷波来降低自身特定频段的功率谱从而使UWB系统避开窄带干扰,达到与其它系统共存的目的。以高斯导脉冲为例,对所设计IIR陷波器进行仿真验证,并就陷波前、后的脉冲波形的通信性能进行比较。仿真结果表明:陷波脉冲具有良好的窄带干扰抑制能力,在实现和其他无线窄带通信系统共存的同时,具有良好的系统传输性能。     

单频信号对TH-PPM UWB通信最佳干扰分析

介绍了单频信号对TH-PPM UWB通信设备造成最佳干扰的理论分析,得出最佳干扰频率,并在AWGN信道下,用计算机仿真验证了该干扰频率的最佳性以及对UWB通信所产生的干扰效果。     

超宽带(UWB)技术及其抗干扰性能分析

介绍了跳时超宽带(TM-UWB)通信的特点,通过对比传统的RAKE接收机和MMSE-RAKE接收机性能分析了UWB的抗窄带干扰性能,结果表明超宽带在无线个人域网中(WPAN)可以和其它无线电系统共存.     

Impact of TH‐UWB interference on MB‐OFDM UWB systems: interference modeling and performance analysis

In this paper, the coexistence issue between multiband‐orthogonal frequency‐division multiplexing (MB‐OFDM) and time‐hopping ultra‐wideband (TH‐UWB) networks is widely analyzed. For this purpose, to study and model the TH‐UWB interference, an analytical framework which describes key features of the interference distribution is provided. The interference distribution is studied in the context of TH‐UWB's signaling parameters. Our results reveal that the interference distribution highly depends on its time‐hopping parameters. Therefore, choosing proper time‐hopping parameters leads to less destructive interferences. The Generalized Gaussian and the Symmetric‐α‐Stable (SαS) distributions are used to model the interference‐plus‐noise signal. The maximum likelihood and a characteristic function‐based regression‐type methods are adopted to estimate parameters of Generalized Gaussian and SαS distributions, respectively. Moreover, the interference channel effects on the impulsive behavior of the TH‐UWB signal is studied. It is shown that impulsive behavior of the faded interference signals highly depends on the channel time‐dispersiveness. Furthermore, an exact performance of a multiband‐orthogonal frequency‐division multiplexing system impaired by a TH‐UWB system is derived. The comparison of the analytical performance, the empirical simulation, and the approximation results show that both approximation methods are valid for low interference‐to‐noise‐ratio, while SαS provides a more accurate approximation for high interference‐to‐noise‐ratio. Copyright © 2015 John Wiley & Sons, Ltd.     

A Two‐Stage Radix‐4 Viterbi Decoder for Multiband OFDM UWB Systems

This letter presents a power efficient 64‐state Viterbi decoder (VD) employing a two‐stage radix‐4 add‐compare‐select architecture. A class of VD architectures is implemented, and their hardware complexity, maximum operating speed, and power consumption are compared. Implementation results show that the proposed VD architecture is suitable for multiband orthogonal frequency‐division multiplexing (MB‐OFDM) ultra‐wideband (UWB) systems, which can support the data rate of 480 Mbps even when implemented using 0.18‐μm CMOS technology.     

基于空间分集的UWB系统性能分析

将多接收天线应用于跳时(TH)二进制反极性脉冲幅度调制(2PAM)超宽带(UWB)系统中,在存在多用户干扰的环境下以提高系统的误码性能,进而达到高速率通信。分析了在SGA条件下,基于空间分集的SINR的表达式,估计了系统的误比特率,并对2PAM-TH-UWB系统的性能进行仿真。仿真结果表明,随着接收端接收天线数的增加,2PAM-TH-UWB系统误码性能提高。     

Controllable Band‐Notched Slot Antenna for UWB Communication Systems

We propose a slot antenna consisting of a rectangular slot on the ground plane, fed by a microstrip line with a rectangular‐ring‐shaped tuning stub that can be deployed in ultra‐wideband (UWB) communication systems to avoid interference with wireless local area network (WLAN) communication. Our antenna can achieve a single band‐notched property from the 5 GHz frequency to the 6 GHz frequency owing to a controllable band notch that uses L‐ and J‐shaped parasitic elements. The antenna characteristics can be modified to tune the band‐notched property (4 GHz to 5 GHz or 6 GHz to 7 GHz) and the bandwidth of the band notch (1 GHz to 2 GHz). Furthermore, the shifted notch with enhanced width of the band notch from 1 GHz to 1.5 GHz is described in this paper. The UWB slot antenna and L‐ and J‐shaped parasitic elements also provide the band‐rejection function for reference in the WiMAX (3.5 GHz) and WLAN (5 GHz to 6 GHz) regions of the spectrum. Experiment results evidence the return loss performance, radiation patterns, and antenna gains at different operational frequencies.     

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.     

Interference Evaluation of Bluetooth and IEEE 802.11b Systems

The emergence of several radio technologies, such as Bluetooth and IEEE 802.11, operating in the 2.4 GHz unlicensed ISM frequency band, may lead to signal interference and result in significant performance degradation when devices are colocated in the same environment. The main goal of this paper is to evaluate the effect of mutual interference on the performance of Bluetooth and IEEE 802.11b systems. We develop a simulation framework for modeling interference based on detailed MAC and PHY models. First, we use a simple simulation scenario to highlight the effects of parameters, such as transmission power, offered load, and traffic type. We then turn to more complex scenarios involving multiple Bluetooth piconets and WLAN devices.     

Rayleigh‐Quotient and Iterative‐Threshold‐Test‐Based Blind TOA Estimation for IR‐UWB Systems

This letter proposes a non‐coherent blind time‐of‐arrival (TOA) estimation scheme for impulse radio ultra‐wideband systems. The TOA estimation is performed in two consecutive phases: the Rayleigh‐quotient theorem‐based coarse‐signal acquisition (CSA) and the iterative‐threshold‐test‐based fine time estimation (FTE). The proposed scheme serves in a blind manner without demanding any a priori knowledge of the channel and the noise. Analysis and simulations demonstrate that the proposed scheme significantly increases the signal detection probability in CSA and ameliorates the TOA estimation accuracy in FTE.     

三维分布UWB设备对窄带无线系统干扰分析

针对超宽带(UWB)设备对其他相对窄带无线设备终端存在干扰的可能问题,通过建立的三维积分模型对无线系统终端受室内三维空间分布的多UWB设备合成干扰效果进行了分析。所提出的UWB干扰模型可以有效分析三维分布的多UWB设备对其他相对窄带无线系统的干扰,给出受干扰设备抗UWB干扰能力及UWB发射功率控制模板干扰保护强度等方面的数值评估,可作为现代化办公楼UWB设备布置及UWB功率控制研究方面的参考。     

A CMOS Frequency Synthesizer Block for MB‐OFDM UWB Systems

A CMOS frequency synthesizer block for multi‐band orthogonal frequency division multiplexing ultra‐wideband systems is proposed. The proposed frequency synthesizer adopts a double‐conversion architecture for simplicity and to mitigate spur suppression requirements for out‐of‐band interferers in 2.4 and 5 GHz bands. Moreover, the frequency synthesizer can consist of the fewest nonlinear components, such as divide‐by‐Ns and a mixer with the proposed frequency plan, leading to the generation of less spurs. To evaluate the feasibility of the proposed idea, the frequency synthesizer block is implemented in 0.18‐µm CMOS technology. The measured sideband suppression ratio is about 32 dBc, and the phase noise is ‐105 dBc/Hz at an offset of 1 MHz. The fabricated chip consumes 17.6 mA from a 1.8 V supply, and the die‐area including pads is 0.9 × 1.1 mm².