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25 October 2005, Volume 26 Issue 10

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Overview

Preface

2005, 26(10):  1-1.  doi:1000-436X(2005)10-0002-05-1

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Ultra wide-band radio technology

2005, 26(10):  2-6.  doi:1000-436X(2005)10-0002-05

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Impulse-based UWB (I-UWB)system design was radically different from conventional radio system design.The history of I-UWB technology,the performance and characteristic of I-UWB system were briefly introduced,then it introduced the main topics and key technology of I-UWB in regard to signal generation techniques,propagation characteristics,modulation,antenna,receiver design,and networking protocol.Additionally,the future development of I-UWB is also in included.

academic paper

BER performance optimization of ultra wideband TH PPM in multipath environment

Guang-rong YUE,Chuan LI,Shao-qian LI

2005, 26(10):  7-12.  doi:1000-436X(2005)10-0007-06

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Aiming at the unbalanced bit error rate for different transmitted data symbol of ultra wideband (UWB)impulse radio time-hopping pulse-position-modulation (TH-PPM)in deterministic multipath environment for unreasonable parameter selection,two solutions were presented in this work.One was that the decision threshold of Rake is dynamics for different channel environment;the other was that we can improve the traditional TH PPM modulation,that is,encoding the transmitted data symbol with balance code.It is shown by theoretical analysis and computer simulation that these two methods can solve the unbalanced bit error rate of traditional TH-PPM.Comparing with dynamic threshold method,the balance encoding scheme can be implemented more easily,and is more robust to the channel time variant characteristics,the channel estimation of Rake receiver and the combination techniques.

Less complicated adaptive equalization for UWB channels

Yi-ming WANG,Hong-bo ZHU

2005, 26(10):  13-18.  doi:1000-436X(2005)10-0013-06

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A new adaptive equalization technology aiming at the intersymbol and interuser interferences in the multiuser UWB channels was presented specially for DS-UWB/TH-UWB receivers.Its computational complexity and convergence rate were compared with the traditional algorithms.The research results show that the computational complexity of this technology is less than employing RLS method solely and the convergence rate of this technology is farther off employing LMS method solely.

Performance of signal design for ultra wide band communications in indoor environments

Ning XIE,Yuan-ping ZHOU,Xiao-wei HOU,Wen-kun WEN

2005, 26(10):  19-23.  doi:1000-436X(2005)10-0019-05

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A method to optimize was proposed by the delay parameter of the pulse position modulated UWB signal in indoor environments.The system designed with the proposed method achieves an improved performance and meeted the FCC emission requirement.In particular,the BER performance is analyzed based on a mathematic model of the UWB signal and the result may provide guidance in practical applications.

Multipath model for UWB indoor LOS environments

Yang WANG,Nai-tong ZHANG,Xun TANG,Ya-nan SUN

2005, 26(10):  24-28.  doi:1000-436X(2005)10-0024-05

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A new UWB multipath model for LOS environments was proposed.The model had two deterministic clusters and stochastic arriving rays within each cluster and fitted UltRa Lab of university of Southern California indoor UWB measurements well.The model is more accurate in modeling small-scale LOS environment than traditional statistical model when considering the statistics of the mean excess delay spread,RMS delay spread and the number of significant multipaths observed in the UWB channel,also in modeling procedure it reduces complexity dramatically than traditional deterministic model.

Optimal transmissions for space-time coded OFDM UWB systems

Jun-fang WANG,Guang-xi ZHU,Jiang JIN

2005, 26(10):  29-33.  doi:1000-436X(2005)10-0029-05

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The emerging ultra-wideband (UWB)system offers a great potential for the design of high-speed short-range communications.Compared with great progress at physical layer,the corresponding medium access control (MAC)layer designs are naturally placed on the schedules.We focus on the optimal power load scheme,which is an integral part of the MAC layer protocol design,for UWB space-time coded (STC)orthogonal frequency-division multiplexing (OFDM)transmissions.Assumed the transmitter has perfect or partial channel stage information (CSI).Based on the optimization criteria of maximizing capacity,three kinds of power load schemes were presented with different tradeoff among performance,complexity and feedback bandwidth overhead.The proposed schemes are verified and compared under the channel prototype proposed by IEEE 802.15.3a Task Group.

Performance analysis of a rate adaptive multi-band ultra-wideband system based on quadrature fractal modulation scheme

Yu-hong LI,Zheng ZHOU

2005, 26(10):  34-40.  doi:1000-436X(2005)10-0034-07

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A rate adaptive multi-band ultra-wideband (UWB)system based on the quadrature fractal modulation (QFM)scheme was proposed.Exploring the use of homogeneous signals as modulating waveforms in UWB system,the signal within each 528MHz sub-band was divided into 8 different frequency bandwidths using wavelets transform and these data sequences to be transmitted were embedded into homogeneous waveforms.It is found that the use of homogeneous signals in such UWB system is quite feasible,leadings to a novel multi-rate diversity strategy.Within each 528MHz sub-band,the UWB-QFM system can provide much higher data rates than that of the UWB orthogonal frequency division multiplexing (OFDM)system.Simulation results also show that the bit error rate (BER)performance of the UWB-QFM system achieves a greatly improvement over existing UWB-OFDM system.Due to the fractal properties of the homogeneous signals,these data sequences to be transmitted can be recovered using arbitrarily short receiver signal.

Time shift TDT timing acquisition algorithm for PPM-UWB

Xin XIANG,Bin TIAN,Ke-chu YI,Lei LIU

2005, 26(10):  41-45.  doi:1000-436X(2005)10-0041-05

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It was proved that the TDT (timing with a dirty template)blind timing algorithm was only suitable for PAM-UWB systems rather than PPM-UWB systems.Furthermore,a TS-TDT (time-shift-TDT)blind timing synchronization algorithm was presented for PPM-UWB,which got synchronizing information from calculating the delay cross-correlation values by means of two correlation branches.Theoretical analysis and simulation results demonstrate that the implementation of the algorithm is of low complexity and flexible in precision control.

On the TC/MAX criterion for code acquisition and its application to UWB systems

Jiang WANG,Guang-guo BI,Zai-chen ZHANG

2005, 26(10):  46-52.  doi:1000-436X(2005)10-0046-07

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Due to the difficulty of threshold setting in code acquisition,a new hybrid criterion called TC/MAX (threshold crossing/maximum selection)was presented for code acquisition.To test the proposed criterion,the general formulation was applied to the particular case of ultra wide bandwidth (UWB)communication systems.Analysis and simulation show that the proposed scheme can improve the probability of detection significantly,compared with TC criterion.

Time-hopping sequences with two-stage few-hit zone for QS-THSS-UWB

ZHEN-YU ZHANG,FAN-XIN ZENG,LI-JIA GE

2005, 26(10):  53-59.  doi:1000-436X(2005)10-0053-07

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By combining the design of safeguard zone and traditional time-hopping (TH)sequences,we construct a class of TH sequences with two-stage few-hit zone (FHZ)suitable for quasi-synchronous time-hopping spread spectrum ultra wideband (QS-THSS-UWB)systems.The constructed sequences not only have good TH correlation properties which are very close to those of TH sequences with no-hit zone (NHZ),but also they overcome two disadvantages of the small family size and the rapidly degradation in TH correlation properties which result from the orthogonality between TH sequences with NHZ.

UWB pulse design method based on approximate prolate spheroidal wave functions

Yin LU,Hong-bo ZHU

2005, 26(10):  60-64.  doi:1000-436X(2005)10-0060-05

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Coexistence and compatibility was an important issue needed to be considered in ultra-wideband (UWB)impulse radio communications.To avoid interference,one of the effective methods was to design appropriate pulse waveform.UWB pulse design algorithm was established,the approximate solution to the prolate spheroidal wave functions (PSWF)was analyzed,a pulse design method was proposed by using the approximate prolate spheroidal wave functions (APSWF).The mathematical expression of APSWF was simple and explicit.The simulation shows that pulse based on APSWF meets the power spectral constraint of the FCC's spectral mask.The APSWF-based pulse waveform can be flexibly adjusted by this method when the spectral mask changes.

Technical Report

Novel ultra-wideband microstrip meandered-loop antenna

Wen-jun LV,Chong-hu CHENG,Hong-bo ZHU

2005, 26(10):  65-68.  doi:1000-436X(2005)10-0065-04

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A novel meandered-loop ultra-wideband antenna was proposed.The antenna was similar in configuration with a conventional wide-slot antenna,however,by employing meandered-loop structure,not only ultra-wideband performance but also compact size could be achieved.It had been investigated both numerically and experimentally for its input performance and radiation characteristics.It is observed that an operation bandwidth of over 4:1 has been achieved.Furthermore,relative stable and good omnidirectional radiation performance have also been achieved.Thus it can be determined as a useful candidate for UWB application.

Design of a subnonsecond Gauusisan pulse generator based on the RF transistor

Feng YANG,Quan XUE,Chi-hao CHEN

2005, 26(10):  69-71.  doi:1000-436X(2005)10-0069-03

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A simple and low cost subnonsecond Gaussian pulse generator was developed using RF transistor,chip resistors,and chip capacitors.The generator utilized a differential circuit to convert signal from the FPGA into a pairs of positive and negative pulses,which was then used to control the “on” and “off” states of the RF transistor,thus generating an ultra-short pulse through the charging and discharging of the capacitor.The measured results shows that output waveform have 0.8ns pulse duration and morn than 1.8V from an input wave of 25MHz repetition rate.Good agreement between the measured and calculated results is achieved.This circuits is suitable for microwave integrated circuits(MIC).

New realization scheme of pseudo-chaotic-based encoder and decoder for UWB communications

Guo-ping JIANG,Dong-dong WAN,Long XUE

2005, 26(10):  72-77.  doi:1000-436X(2005)10-0072-06

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Chaos-modulation-based ultra wide band (UWB)communication was addressed.A new structure for the pseudo-chaotic encoder was presented,and some decoding schemes were also given accordingly.The performances of such decoding schemes were compared in the AWGN channel.Simulation results verify and demonstrate the effectiveness of the proposed method.

Channel equalization performance of rake receiver in UWB systems

Liang ZHANG,Chen-yang YANG

2005, 26(10):  78-83.  doi:1000-436X(2005)10-0078-06

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Rake receiver was analyzed for its performance of channel shortening by deriving the delay spread of an equivalent channel after maximal-ratio combination.Both the relationship between the partially equalization performance of Rake receiver and the number of its taps,and the influence of channel estimation error on channel shortening performance were investigated.From the analysis,it's indicated that Rake receiver can still shorten the channel with channel estimation error,but there will be some extent of performance degradation.Moreover,the channel equalization performance of Rake receiver with lower complexity outperforms that with higher complexity in low SNR since less estimation error is introduced into Rake receiver with small number of taps.

High data rate transmissions in UWB system using orthogonal pulses

Zhao-hui LIANG,Hong-feng DU,Zheng ZHOU

2005, 26(10):  84-88.  doi:1000-436X(2005)10-0084-05

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Two orthogonal pulses based on wavelet were presented,their spectrum meet FCC spectral mask for ultra wideband (UWB)system.A novel method for high data rate transmissions in UWB system was proposed.It employs a combination of pulse polarity and orthogonal pulses shape modulation and implements high date rate by transmitting more bits simultaneously.

Novel multi-path routing scheme for UWB Ad hoc network

Ping-ping XU,Cai-yu YANG,Shu-qing SONG,Guang-guo BI

2005, 26(10):  89-96.  doi:1000-436X(2005)10-0089-08

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The routing protocols play an important role for ad hoc networks performance.As some problems with DSR,SMR,and AMR protocols were analyzed,a new routing protocol suitable for UWB Ad hoc networks was proposed in this paper.The new routing protocol utilize an act of orientation of UWB and tries to get sufficient route information and decrease the network load caused by route discovery at the same time.Simulation results show that the routing load of the new protocol is lower and throughput is higher than that of DSR.While the node's mobility increases,these advantages become more obvious.

Study on propagation properties of UWB signal waveform

Yuan-jian LIU,Ye-rong ZHANG

2005, 26(10):  97-101.  doi:1000-436X(2005)10-0097-05

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Investigating the propagation properties of Ultra-wideband (UWB)were the essential topics in UWB channel theory.Based on Fourier transformation,Various UWB pulse waveform with indoor reflection,refraction and diffraction is studied.Moreover,a novel approximate formula of n order modified Bessel function was put forward.Finally,a comparison of Fourier transformation results with time-domain accurate results shows good agreements.

Studies of pulse waveforms for UWB communications

Jun-xi ZHAO

2005, 26(10):  102-106.  doi:1000-436X(2005)10-0102-05

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The problem of designing pulse waveforms for UWB communications were investigated,and presented approaches to designing optimal pulse waveforms for UWB radio under the constraints of the FCC spectrum mask.Pulse waveforms were constructed that were quite simple and had desired properties by optimally combining different Gaussian functions,and proposed a new approach to designing flexible pulse waveforms for UWB communications based on filtering.

MAC protocols in ultra-wide band system

Ran YUE,Qin-yu ZHANG,Nai-tong ZHANG,Shi ZHENG

2005, 26(10):  107-111.  doi:1000-436X(2005)10-0107-05

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Recently,the ultra-wide band (UWB)-based technique is focused on more deeply along with the design of MAC (media access control)for its advantages.Comparing with the conventional wireless communication system,the UWB system has its unique characteristics,higher speed rate,lower PSD (power spectrum density),etc.It is therefore necessary to propose advanced MAC protocols for matching the requirements of the system.In this study,the performance of various types of MAC protocols based on UWB system is investigated.The physical structures for different MAC protocols are compared.Some special demands from UWB for MAC are analyzed.The advanced design for the MAC protocols in UWB is proposed.It may provide the implementation base for future MAC protocols.

Design of a ultra-wideband pulse generator

Yong CHENG,Yue-chen ZHOU,Chong-hu CHENG

2005, 26(10):  112-115.  doi:1000-436X(2005)10-0112-04

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A shut step recovery diode (SRD)pulse generator was presented.The circuit was fabricated on microstrip line.An ultra-short pulse which duration was around in the order of 1ns,peak-peak voltage was 10.44 V,repetition rate was 100MHz was achieved.The design of the circuit especially the tuning of the basing and matching circuit was analyzed and discussed.Measured results show that the waveform of pulse is good,and ringing level is low.The pulse generator will find applications in UWB communications system.

Short essay

MIMO capacity enhancement technique of cellular link based on mobile terminal with single antenna

Qi-mei CUI,Wen YU,Xiao-feng TAO,Ping ZHANG

2005, 26(10):  116-121.  doi:1000-436X(2005)10-0116-06

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A multiple-input-multiple-output (MIMO)capacity enhancement technique of cellular link based on mobile terminal with single antenna was proposed,which was the application of generalized virtual-MIMO architecture based on ultra wide-band (UWB)technique.The principle and benefits of G-VMIMO were detailed.Besides,the capacity enhancement of cellular link based on G-VMIMO was analyzed theoretically.The establishment of G-MIMO system was put forward,and the challenges brought by the practical application of G-VMIMO to the existing cellular networks and wireless personal area network (WPAN)were explored.Finally,computer simulation verifies the capacity enhancement and the validity of G-VMIMO.

Study of performance of UWB transmitted-reference receivers

Gang YANG,Jie KANG,Ren SHI

2005, 26(10):  122-127.  doi:1000-436X(2005)10-0122-06

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The principle and advantage were analyzed about UWB transmitted-reference (TR)receiver.Moreover,considering many UWB communications had little channel variance in the course of transmitting a few bits data,an improved TR receiver was presented by extending TR signal set to the sum of several reference signals and many data signals.The performance of this improved TR receiver and basic TR receiver were detailed analyzed in theory and simulated in the IEEE UWB multipath channel models CM1 and CM2.The results show that bit error rate and data transmission efficiency of this improved TR receiver are better than basic TR receiver,at the cost of a little rise of structure complexity.

Ternary complementary sets and its application in UWB

Shi-ji WANG,Nai-tong ZHANG

2005, 26(10):  128-132.  doi:1000-436X(2005)10-0128-05

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Ternary complementary set based UWB signaling employing a set of orthogonal chip pulses was proposed for DS-UWB.It had many advantages in indoor high-speed short range communications.First the system model of multiple access communications was founded,then ternary complementary set and its recursive construction method were analyzed,and then the performance evaluation structure of multiple access communications based the ternary complementary sets by use of the Rake receiver was put forward.Ternary complementary sets assigned to two users had good aperiodic autocorrelation functions.Hence,the multipath interference as well as multiple access interference were mitigated.Simulation results show that ternary MO complementary sets have better performances compared with other random sequences in the SV/IEEE 802.15.3a channel model.

New method of BER calculate for impulse-UWB TH-PPM multiple-access communications

Hong-bing QIU,GLin ZHEN

2005, 26(10):  133-137.  doi:1000-436X(2005)10-0133-05

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A simple derivation process was presented for the bit error rate (BER)performance analysis of the ultra wideband (UWB)time hopping (TH)multiple access impulse radio (IR)communication system employing pulse position modulation (PPM)in the additive white Gaussian noise (AWGN)channel with multiuser interference (MUI).In this derivation,the MUI was assumed a zero mean Gaussian process.The variance of the multiple access interference was computed from the statistical average of the error correlation output of the receiver correlator,which completed the correlation of the multiple access receiving signal and the local template signal in the receiver.Theoretical results are compared with simulation analysis.

Performance analysis of UWB-IR anti-intercepting communication based on chaotic mapping

Long MA,Ting-chang WANG

2005, 26(10):  138-142.  doi:1000-436X(2004)10-0138-05

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UWB-IR technology has been concerned in military communications in recent years because of its high data rate,low power consumption,low probability of detection and low probability of interception.By applying the chaos mapping into the UWB-IR was applied and proposed a novel module for chaos modulation and demodulation was proposed,which enhances both the capability of anti-detecting and the capability of anti-intercepting of the UWB-IR.Furthermore,The feasibility of this application was verified.through simulations

Analysis of optimization for properties of UWB indoor multipath channel

Luo-quan HU,Hong-bo ZHU

2005, 26(10):  143-148.  doi:1000-436X(2005)10-0143-06

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Methods of optimization were proposed for analyzing the properties of UWB indoor multipath channels,and a mathematical model for UWB channel modeling was discussed.Assumptions of stochastic bridge process and probabilistic choice were adopted.A UWB channel impulse response based on bounded Brownian bridge model (BBBM)was constructed.The judgments of effective random paths,and modeling algorithms based on the methods of optimization were presented.The results of simulation for UWB channels demonstrated that the BBBM could obtain the similar properties to the ones of experiments and UTD methods,some characteristic parameters corresponded well with the experimental values.

Investigation of acquisition of the UWB signals based on BP neural network

Zhi-hua YANG,Qin-yu ZHANG,Ping CHEN,Hong-guang XU

2005, 26(10):  149-154.  doi:1000-436X(2005)10-0149-06

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A new method based on BP neural networks was proposed here to implement the fast acquisition of UWB signals with the condition of low SNR.The BP neural network was used to match the extreme short pulse in this study.It could improve the performance of the acquisition efficiently.The feasibility and efficiency of the new method were discussed.The influence of the SNR in UWB system was analyzed.The simulation results highly indicate the usefulness of the method pointed out in this study.