共查询到20条相似文献,搜索用时 78 毫秒
1.
Low duty-cycle (LDC) algorithm is interference mitigation technique, which can reduce the average interference to the existing
radio systems by lowering pulse repetition interval or pulse occupation time. In this paper, the coexistence environment between
low data rate ultra wideband (UWB) communication system such as wireless sensor network and the existing wideband system using
orthogonal frequency division multiplexing (OFDM) such as 4th generation mobile cellular system (4G), worldwide interoperability
for microwave access (WiMAX), and field pickup unit (FPU) is considered. In order to analyze the interference mitigation capability
of LDC algorithm with impulse based UWB (LDC-UWB) system, the frame error rate (FER) of wideband OFDM system is examined for
two types of LDC-UWB system: the signal with random polarity such as binary pole signals and without random polarity such
as mono pole signals. We present that LDC algorithm is an efficient interference mitigation technique for low data rate UWB
communication via computer simulations regardless of definitions of transmitted energy of UWB communication system, and also
that the signal with random polarity is suitable for LDC-UWB system to mitigate interference to the other radio systems. We
further investigate the adequate duty-cycle of LDC-UWB system for each definition of transmitted power of UWB communication. 相似文献
2.
On the UWB system coexistence with GSM900, UMTS/WCDMA, and GPS 总被引:14,自引:0,他引:14
Hamalainen M. Hovinen V. Tesi R. Iinatti J.H.J. Latva-aho M. 《Selected Areas in Communications, IEEE Journal on》2002,20(9):1712-1721
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. 相似文献
3.
Witrisal K. Leus G. Pausini M. Krall C. 《Selected Areas in Communications, IEEE Journal on》2005,23(9):1851-1862
A discrete-time equivalent system model is derived for differential and transmitted reference (TR) ultra-wideband (UWB) impulse radio (IR) systems, operating under heavy intersymbol-interference (ISI) caused by multipath propagation. In the systems discussed, data is transmitted using differential modulation on a frame-level, i.e., among UWB pulses. Multiple pulses (frames) are used to convey a single bit. Time hopping and amplitude codes are applied for multi user communications, employing a receiver front-end that consists of a bank of pulse-pair correlators. It is shown that these UWB systems are accurately modeled by second-order discrete-time Volterra systems. This proposed nonlinear equivalent system model is the basis for developing optimal and suboptimal receivers for differential UWB communications systems under ISI. As an example, we describe a maximum likelihood sequence detector with decision feedback, to be applied at the output of the receiver front-end sampled at symbol rate, and an adaptive inverse modeling equalizer. Both methods significantly increase the robustness in presence of multipath interference at tractable complexity. 相似文献
4.
Ultra-wideband (UWB) technology has been considered to offer an innovative solution for future short-range high-speed wireless
communications. These systems use very low transmission power, spread over a bandwidth of several gigahertz. The very low
transmission power and the large bandwidth used, enable UWB radio systems to co-exist with other narrowband systems over the
same frequency band without interfering the narrowband systems. Nevertheless, these narrowband systems may cause interference
which may jam the UWB receiver completely. Since standard narrowband interference suppression techniques are not applicable,
techniques for interference suppression have to be developed. In this paper, the method of the local polynomial estimator
in time-hopping impulse radio (TH-IR) for UWB communication is considered, which should not estimate any parameter of channel.
And the narrowband interference (NBI) is modeled as a stationary process. Theoretical analysis of this algorithm reveals that
it can eliminate the narrowband interference almost completely and can be computed by simple expression. Moreover, the sampling
rate is very low. 相似文献
5.
由于高传输速率及多径效应的影响,在窄脉冲超宽带(IR-UWB)通信系统中,基于传统横向滤波器的时域均衡技术已无法对抗严重的码间干扰。通过收发两端联合设计,提出了一种以数据块为基础的基于码元的频域均衡技术,同时介绍了其应用前提和算法实现。仿真结果表明,所提方法能有效对抗超宽带通信系统中存在的码间干扰,是窄脉冲超宽带通信系统中更为现实的技术选择。 相似文献
6.
Qi Zhang Chun Sum Ng 《Communications, IEEE Transactions on》2008,56(4):608-618
Ultra-wideband (UWB) communication systems are expected to operate in a highly frequency-selective multipath fading environment. To exploit multipath diversity gains in a multiuser scenario, we developed a differentially-encoded, di-symbol time-division multiuser impulse radio (d2TD-IR) system with delay-sum autocorrelation receivers. In traditional time-division multiple access systems, each user transmits a single pulse during a symbol duration in a pre-assigned chip which is longer than maximum excess delay of the channel. However, due to the exponential decay property of UWB channel, we proposed the use of much shorter chip duration, which significantly increases the transmission rate. Because dense pulse transmission will induce multiuser interference, two time-hopping access sequences, which alternately encode the odd- and even-index symbols, are employed with delay-sum autocorrelation receivers to maximally suppress the interference. It was shown that when the chip duration is properly chosen, the proposed system outperforms the conventional time-hopping impulse radio system at high signal-to-noise ratio. This paper also proposed a method to estimate the optimal chip duration when only the average power decay profile of the UWB channel is known. 相似文献
7.
Hüseyin Arslan 《Wireless Personal Communications》2007,42(4):479-490
In this paper, a low complexity coherent joint maximum-likelihood detection receiver is developed for canceling multi-access
interference in impulse radio (IR) based ultra wideband (UWB) wireless communication systems. Unlike previous joint demodulation
receivers, where the complexity is enormous and the other users’ codes are required, the proposed approach does not need to
know the time hopping (TH) codes of the other users which makes it a very attractive solution. The performance of joint demodulation
receiver depends on the ability to estimate the channel coefficients of desired and interfering users. A novel and practical
algorithm for estimating multiple users’ channel responses is developed. The performance of the proposed algorithms are tested
through computer simulations and the results are compared with the performance of the conventional single user UWB receiver.
It is observed that the proposed joint demodulation receiver provides significant performance gains with respect to conventional
single user receiver.
This paper is presented in part in IEEE International Conference on Communications (ICC) 2004, Paris, France. 相似文献
8.
《Wireless Communications, IEEE Transactions on》2008,7(8):2964-2974
In recent years, there has been a growing interest in multiple access communication systems that spread their transmitted energy over very large bandwidths. These systems, which are referred to as ultra wide-band (UWB) systems, have various advantages over narrow-band and conventional wide-band systems. The importance of multiuser detection for achieving high data or low bit error rates in these systems has already been established in several studies. This paper presents iterative (?turbo?) multiuser detection for impulse radio (IR) UWB systems over multipath channels. While this approach is demonstrated for UWB signals, it can also be used in other systems that use similar types of signaling. When applied to the type of signals used by UWB systems, the complexity of the proposed detector can be quite low. Also, two very low complexity implementations of the iterative multiuser detection scheme are proposed based on Gaussian approximation and soft interference cancellation. The performance of these detectors is assessed using simulations that demonstrate their favorable properties. 相似文献
9.
10.
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。 相似文献
11.
Narrowband interference suppression in time-hopping impulse radio ultra-wideband communications 总被引:2,自引:0,他引:2
《Communications, IEEE Transactions on》2006,54(6):1057-1067
Ultra-wideband (UWB) technology has been considered an innovative solution for future short-range high-speed wireless communications. Interference suppression is important for the UWB devices to operate over spectrum occupied by narrowband systems. In this paper, the use of a notch filter in time-hopping impulse radio (TH-IR) for UWB communication is considered, where a Gaussian monopulse is employed with pulse position modulation. Lognormal channel fading is assumed, and a complete analytical framework is provided for the performance evaluation of using a transversal-type notch filter to reject narrowband interference (NBI). A closed-form expression of bit-error probability is derived, and the numerical results show that the use of a notch filter can improve the system performance significantly. Furthermore, a performance comparison between TH-IR and multicarrier code-division multiple-access (MC-CDMA) UWB systems is made under the conditions of the same transmit power, the same data rate, and the same bandwidth. It is shown that in the presence of NBI, the TH-IR system and MC-CDMA system achieve similar performance when both use a notch filter. 相似文献
12.
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. 相似文献
13.
14.
15.
针对多天线冲激无线电超宽带通信系统,提出了一种盲的线性接收机。在不需要信道信息的情况下,可以利用经过预编码的空时分组码给接收信号带来的特定结构,直接得到接收机系数,从而恢复出发送符号。仿真表明,随着用于估计的数据块的增加,盲接收机的性能逐渐接近于相关接收。 相似文献
16.
Time reversal is a promising technique for the improvement of UWB communication systems. Intersymbol interference (ISI) limits the system performance in such wireless systems. This paper presents a general ISI analysis for time reversal UWB communication systems. The time reversal UWB system gives good performance for rates below the coherence bandwidth but at higher data rates the performance of the system is limited by intersymbol interference and bit error rate saturates even for high signal-to-noise ratio. To mitigate the ISI effects, a single input/multiple output (SIMO) time reversal UWB system is used and its performance is analyzed. It is shown that by using a SIMO TR transceiver, ISI reduces and the system capacity increases. Transmitted signal power at SIMO time reversal decreases, therefore in low data rate SISO performance is better than SIMO, But in high rate scenario, SIMO TR suppresses the ISI better than the SISO TR and its performance is better than SISO TR. It is possible to compensate the reduced power by using a receiver with more sensitivity. 相似文献
17.
超宽带(UWB)信号极宽的带宽使超宽带系统不可避免地与其频带内已有的窄带系统产生干扰。本文针对超宽带系统提出了两种新型的具有窄带干扰(NBI)抑制能力的修正非线性chirp超宽带波形。这两种波形基于窄脉冲超宽带的通信方式设计,其能量可以在时间上均匀分布,从而避免了高峰值功率的问题。此外这两种设计方法对有用信号没有损失,只需要对波形进行时域处理即可改变相应的频域特性。仿真结果和理论分析显示,基于这两种超宽带波形的直接序列扩频二进制相移键控超宽带(DS-BPSK UWB)系统,在抑制窄带干扰方面极大优于采用传统线性chirp波形的超宽带系统。 相似文献
18.
Ultra-wideband (UWB) systems having a bandwidth on the order of gigahertz have received wide attention both in the US and in Europe. The family of UWB systems may communicate either, by generating ultra-wideband signals or with the aid of innovatively combining conventional narrowband, wideband, or broadband signals. At the time of writing, UWB systems have only been implemented using ultra-wideband signals, such as those known from impulse radio systems. Hence, in this paper, UWB systems using narrowband signals are explored as a design alternative, which are based on the well-known family of frequency-hopping (FH) spread-spectrum multiple-access techniques. In the proposed UWB system, FH is implemented using multistage frequency-hopping multiple access (MS/UWB FHMA). We highlight the principles of the synchronous MS/UWB FHMA communication system, investigate the associated spectrum assignment, and the residue number system (RNS) based FH strategy: detection of the received signal can be achieved with the aid of existing fast FH signal detection schemes. Our study shows that the RNS assisted FH strategy is capable of efficiently dividing the huge number of users supported by the synchronous MS/UWB FHMA system into a number of reduced-size user groups, where the multiuser interference only affects the users within the same group. Since the number of users in each group is only a small fraction of the total number of users supported by the synchronous MS/UWB FHMA system, advanced multiuser detection algorithms can be employed for achieving near-single-user performance at an acceptable complexity. Our results show that MS/UWB FHMA is capable of supporting an extremely high number of users, while employing relatively simple receivers. 相似文献
19.
In this paper, we consider the problem of applying the Multiple-Input-Multiple-Output (MIMO) techniques on Impulse-Radio Time-Hopping Ultra-Wideband (IR-TH-UWB) communications. In particular, we propose two novel Space-Time (ST) block codes that are suitable for UWB. The proposed encoded MIMO-UWB schemes present the main advantage of conveying the information only through the positions of the very short unipolar UWB pulses. The constraint of unipolar transmissions keeps the transceiver structures very simple since it imposes no additional constraints on the RF circuitry to control the amplitudes or the phases of the sub-nanosecond UWB pulses. Consider the case where the transmitter is equipped with P antennas and where M PPM modulation positions are available. The first proposed scheme achieves a full transmit diversity order for M ges P while transmitting at the rate of log2(M) bits Per Channel Use (PCU). The second scheme is fully diverse with any number of antennas and transmits at a rate of M log2(P)/P bits PCU. The proposed codes permit to achieve different levels of compromise between complexity and performance since scheme 1 necessitates M-dimensional Maximum-Likelihood (ML) decoding while scheme 2 necessitates MP-dimensional decoding. We also present a comprehensive analysis on the enhancement in terms of the data rate achieved at a certain communication distance based on realistic indoor channel models and on an exact system model that takes inter-pulse-interference and intersymbol- interference into consideration. 相似文献
20.
《Electromagnetic Compatibility, IEEE Transactions on》2009,51(2):372-381