On the UWB system coexistence with GSM900, UMTS/WCDMA, and GPS

This paper evaluates the level of interference caused by different ultra-wideband (UWB) signals to other various radio systems, as well as the performance degradation of UWB systems in the presence of narrowband interference and pulsed jamming. The in-band interference caused by a selection of UWB signals is calculated at GSM900, UMTS/wideband code-division multiple-access (WCDMA), and Global Position System (GPS) frequency bands as a function of the UWB pulsewidth. Several short-pulse waveforms, based on the Gaussian pulse, can be used to generate UWB transmission. The two UWB system concepts studied here are time hopping and direct sequence spread spectrum. Baseband binary pulse amplitude modulation is used as the data modulation scheme. Proper selection of pulse waveform and pulsewidth allows one to avoid some rejected frequency bands up to a certain limit. However, the pulse shape is also intertwined with the data rate demands. If short-pulses are used in UWB communication the high-pass filtered waveforms are preferred according to the results. The use of long pulses, however, favors the generic Gaussian waveform instead. An UWB system suffers most from narrowband systems if the narrowband interference and the nominal center frequency of the UWB signal overlap. This is proved by bit-error rate simulations in an additive white Gaussian noise (AWGN) channel with interference at global system for mobile communication (GSM) and UMTS/WCDMA frequencies.     

Performance Analysis of UWB Channels for Wireless Personal Area Networks

Ultra-wide band (UWB) communication is one of the most promising technology for high data rate networks over short-range communication. The ultra-wide bandwidth offers pulses with very short duration that provides frequency diversity and multipath resolution. Ultra-wide band (UWB) channels raise new effects in the receiver, the amplitude fading statistics being different compared to the conventional narrow band wireless channels. This review paper focuses on modeling of ultra-wide band channels, especially for simulation of personal area networks and also discusses the benefits, application potential and technical challenges in wideband communication. The concept of Orthogonal Frequency Division Multiplexing (OFDM) has recently been applied in wireless communication systems due to its high data rate transmission capability with high bandwidth efficiency and its robustness to multi-path delay. UWB OFDM communication was proposed for physical layer in the IEEE 802.15.3a standard which covers wideband communication in wireless personal area networks. Since the channel model for multicarrier UWB communication is different from that of plain ultra-wide band channel, a novel modification method in UWB channel model is proposed with specific center frequency and multipath resolution. Moreover, dynamic channel estimation is necessary before demodulation of UWB OFDM signals since the radio channel is time varying and frequency selective for wideband systems. The performance of the proposed method is statistically analyzed using LS and MMSE based channel estimation methods.     

基于认知无线电的脉冲陷波UWB窄带干扰抑制

提出了一种基于认知无线电的自适应超宽带(UWB)窄带干扰抑制方法.为了使UWB对变化的干扰环境具有自适应调节能力,引入了认知无线电技术.通过频谱感知和认知引擎技术提取窄带干扰频谱特征作为陷波器的设计依据.以高斯脉冲为例,对陷波器的陷波性能进行检验.最后,就陷波前、后脉冲的通信性能进行比较.仿真结果表明:认知陷波脉冲具有...     

Narrowband interference mitigation in body surface to external communication in UWB body area networks using first-order Hermite pulse

Ultra wideband (UWB) is the most preferred candidate for body area networks (BAN). The higher data rate and lower multipath fading makes it highly suitable for the design of BAN. However, narrowband interference (NBI) may significantly degrade the performance of UWB. The paper presents an effective method of NBI mitigation for UWB BAN. The method uses modified Hermite pulse (MHP) in lieu of Gaussian and other pulse shapes. The spectral characteristics of the MHP make them immune to interference. The performance has been tested in various body postures in the CM4 channel model of the BAN, and further validated by transmitting medical signals like electrocardiography and MRI. The results show that MHP pulse is highly immune to NBI.     

超宽带多址通信信号的功率谱分析

超宽带(UWB)多址通信是继CDMA技术之后迅速发展的一种宽带传输技术.本文在介绍了各种UWB通信调制方式后,针对产生的UWB多址信号,分析了信号特征,结合数学模型,以简明方式分析了TM-UWB与DSC-UWB多址通信信号的功率谱密度分布,它是UWB通信系统设计与用户干扰分析的基础.     

一种新的UWB通信脉冲设计

研究了基于FCC辐射遮蔽约束的超宽带无线通信系统超短脉冲波形设计方法.以具有不同形状因子和频谱搬移因子的高斯二阶微分脉冲为基函数,提出迭代组合和LMMSE（线性最小均方误差）组合的UWB（超宽带）脉冲设计方法.对采用迭代组合脉冲或高斯二阶微分脉冲的系统在高斯信道下的单链路误比特率、多址、多径等性能进行了仿真比较,验证了所提出的组合脉冲设计方法.     

超宽带通信技术干扰共存研究

本文对传统脉冲、多频带OFDM、DS-CDMA等3种超宽带方案进行了介绍,在阐述其原理及异同点的同时,对不同方案的频谱使用以及相应的抗干扰技术进行了介绍,并且研究了超宽带系统与其它系统电磁兼容共存问题,给出了不同的电磁兼容方案.     

脉冲超宽带TH-PPM多址通信的误比特率计算方法

简单地给出了脉冲超宽带(IR-UWB)TH-PPM多址通信方式在信道加性白高斯噪声(AWGN)与多址用户干扰高斯近似条件下的误比特率推导过程。从接收端相关检测时多址用户信号与本地模板信号相互作用产生误相关输出的平均出发,假定多址用户干扰是零均值的高斯过程,分析计算多用户干扰的方差,通过数值计算与系统仿真比较了所得到的结果。     

超宽带系统在窄带干扰条件下的性能研究

超宽带（Ultra Wide-Band，UWB）系统发射信号的带宽在一个非常大的频段范围内，易与已存在的窄带无线通信系统的带宽形成重叠。因此，有必要研究UWB系统在频段重合范围内的抗干扰能力。文中首先分析了直接扩频超宽带系统在最小均方误差准则检测方式下，RAKE接收机的比特误码率（Bit Error Rate，BERl，然后研究了普通窄带系统的功率谱密度，最后做出了仿真分析。结果表明，在CM1信道传播下，窄带干扰对UWB系统不会造成很大影响，而在CM2信道传播下会照成一定影响，必须通过其他通信手段如信道编码来降低BER，实现通信的可靠性。     

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.     

干扰抑制的UWB脉冲设计与性能分析

提出了一种新的带内（窄带或宽带）干扰抑制的超宽带脉冲的设计方法。采用不同幅度和延迟的高斯脉冲的组合来拟合抽样函数脉冲,实现了超宽带频谱屏蔽的高效逼近,并能够和带内的其他通信系统更好地共存。在介绍设计原理的基础上,给出了设计时域波形的具体实现及波形所对应的功率谱密度图,使其满足FCC频谱屏蔽的要求。同时,对于假设存在的带内干扰对波形进行类似的设计,使其具备抑制干扰的能力。最后,分析了TH—PSKUWB系统的传输性能,并和最佳单周期高斯波形进行了详细的比较,结果表明：其误码性能远远优于最佳单周期高斯波形。     

Application of SVD on Suppression of IEEE 802.11a Interference in TH‐PAM UWB Systems

Interference from IEEE 802.11a systems affects ultra‐wideband (UWB) systems significantly. In this letter, we suggest a novel narrow‐band interference (NBI) suppression technique based on the singular value decomposition (SVD) algorithm in time‐hopping pulse amplitude modulation (TH‐PAM) UWB systems. The SVD algorithm is used to approximate the interference which then is subtracted from the received signals. In contrast to the conventional notch filter and rake receiver, our method is more effective and the receiver complexity can be greatly reduced.     

Performance of DS‐UWB in MB‐OFDM and multi‐user interference over Nakagami‐m fading channels

The mutual interference between the two ultra wideband (UWB) technologies, which use the same frequency spectrum, will be a matter of concern in the near future. In this context, we present a performance analysis of direct‐sequence (DS) UWB communication in the presence of multiband orthogonal frequency division multiplexing (MB‐OFDM) UWB interfering transmissions. The channel fading is modeled according to Nakagami‐m distribution, and multi‐user interference is taken into account. The DS‐UWB system performance is evaluated in terms of bit error rate (BER). Specifically, using the characteristic function approach, an analytical expression for the average BER is derived conditioned on the channel impulse response. Numerical and simulation results are provided and compared for different coexistence scenarios. Copyright © 2011 John Wiley & Sons, Ltd.     

Slightly Frequency-Shifted Reference Ultra-Wideband (UWB) Radio

A promising ultra-wideband (UWB) radio technique being widely considered for low-data-rate applications, such as those often encountered in sensor networks, is the transmitted reference (TR) UWB scheme. However, the standard TR-UWB scheme, while often motivated by the simplicity of its receiver, is still dogged by implementation concerns. In particular, the receiver requires an extremely wideband delay element, which is difficult to incorporate into low-power integrated systems. In this paper, a TR scheme is proposed in which the separation between the data and reference signals, rather than being a time delay, is a slow rotation over the symbol interval. This provides a (slightly) frequency-shifted reference that, while orthogonal to the data-bearing pulse, still goes through a nearly equal channel. A detailed analysis of the proposed scheme is provided. Simulation results demonstrate the expected result that frequency shifting of the reference in the proposed manner is not effective for high-data-rate systems that experience appreciable intersymbol interference. However, for the targeted low-to-moderate data-rate applications, numerical results demonstrate that the proposed system not only achieves the primary goal of providing a much simpler receiver architecture, but also that it outperforms the standard TR-UWB system     

Performance analysis for impulse radio and direct-sequence impulse radio in narrowband interference

The impact of narrowband interference (NBI) on two ultra wideband (UWB) systems is analyzed. The two systems are impulse radio (IR) and a variation of it, termed direct-sequence IR (DS-IR). The signal-to-noise ratio (SNR) at the decision device of a correlation receiver is computed for both systems, assuming that the NBI is wide sense stationary and that the channel is frequency-selective. The SNR is expressed by means of a simple equation involving the signal and the interference spectrum. Next, a statistical model for the interference is introduced, considering the interference as the sum of a given number of sinusoidal signals with random powers and frequencies. The bit-error rate of IR and DS-IR is derived. The results are then specialized and compared with simulations in three case studies of practical interest, where the NBI is a single jammer with deterministic power and frequency, a multitone signal with random frequencies, or a grid of interfering signals with random powers.     

循环功率谱特征检测算法在认知超宽带无线通信的应用

认知超宽带无线通信技术结合了超宽带无线通信技术和认知无线电技术,信号频谱检测是认知超宽带无线通信系统的核心模块之一。循环平稳特性普遍存在于各种调制信号中,该文研究了一种新的检测算法循环功率谱特征检测算法,并以OFDM信号为例给出了软件仿真和性能分析。该检测算法能够区分有用信号,噪声信号和干扰信号,是最适合认知超宽带无线通信系统的。     

Application of convolutional error correcting codes in ultrawideband M-ary PPM signaling

The interference issues related to ultrawideband (UWB) radio pose tight restrictions on the maximum data rate of UWB radio telecommunication systems. A possible solution is to reduce the required signal to interference ratio (SIR) that gives satisfactory performance to the UWB system. In this letter, we propose coded M-ary UWB radio communication systems. Two classes of convolutional codes, namely, low-rate superorthogonal codes and high-rate punctured codes are considered for this purpose. Simulation results on the bit error rate of the proposed system indicates that the system is capable to work in lower SIR's and therefore supports higher data transmission rates in a real interference environment compared to the previously proposed UWB communication systems.     

Coexistence and interworking between UMTS and UWB: a performance evaluation of a UMTS/UWB interoperability platform

Ultra wideband (UWB) radio technology is nowadays one of the most promising technologies for medium-short range communications. It has a wide range of applications including high data rate systems and low data rate systems with location and tracking. The interoperation of UWB with Wide Area Networks (WAN) technologies is very interesting in order to extend the scope of UWB applications, but harmless coexistence between them must be assured. Extensive research is being focused to the development of efficient mitigation techniques and the collaboration between both radio services is an interesting solution when UWB is collocated in the same device with other radio technology. In this paper a UMTS/UWB interworking platform is presented, which allows remote monitoring of a UWB body area network for medical applications. The coexistence between UMTS and UWB is evaluated and cooperative mitigation techniques are proposed and implemented in the platform.     

On The Tradeoff Between Two Types of Processing Gain

One of the features characterizing almost every multiple-access (MA) communication system is the processing gain. Through the use of spreading sequences, the processing gain of random code-division multiple-access (RCDMA) systems, or any other CDMA systems, is devoted to both bandwidth expansion and orthogonalization of the signals transmitted by different users. Another type of MA system is impulse radio (IR). IR systems promise to deliver high data rates over ultra wideband (UWB) channels with low-complexity transmitters and receivers. In many aspects, IR systems are similar to time-division MA systems, and the processing gain of IR systems represents the ratio between the actual transmission time and the total time between two consecutive transmissions (on-plus-off to on ratio). While CDMA systems, which constantly excite the channel, rely on spreading sequences to orthogonalize the signals transmitted by different users, IR systems transmit a series of short pulses, and the orthogonalization between the signals transmitted by different users is achieved by the fact that most of the pulses do not collide with each other at the receiver. In this paper, a general class of MA communication systems that use both types of processing gain is presented, and both IR and RCDMA systems are demonstrated to be special cases of this more general class of systems. The bit-error rate of several receivers as a function of the ratio between the two types of processing gain is analyzed and compared under the constraint that the total processing gain of the system is large and fixed. It is demonstrated that in non-intersymbol interference (ISI) channels, there is no tradeoff between the two types of processing gain. However, in ISI channels, a tradeoff between the two types of processing gain exists. In addition, the suboptimality of RCDMA in frequency-selective channels is established.     

An IR-UWB Photonic Distribution System

Experimental results are presented for a novel distribution system for an impulse radio ultra-wideband (UWB) radio signals employing a gain-switched laser. The pulse position modulated short optical pulses with a bit rate of 1.25 Gb/s are transmitted over fiber to a remote antenna unit, where the signal is converted to the electrical domain and undergoes spectral shaping to remove unwanted components according to UWB requirements. An experimental radio terminal has also been constructed to enable bit-error-rate measurements to be carried out. These experiments show that the optical distribution system will be capable of supporting the radio part of the system.