In this paper, a novel timing offset estimation algorithm of low complexity is presented, which needs a few pilots. The results of simulation prove that the system performance with timing offset correction is approxim...In this paper, a novel timing offset estimation algorithm of low complexity is presented, which needs a few pilots. The results of simulation prove that the system performance with timing offset correction is approximate to that over AWGN channel.展开更多
For multiple-input multiple-output （MIMO） orthogonal frequency division multiplexing （OFDM） systems, a joint timing synchronization and frequency offset acquisition algorithm based on fractional Fourier transform ...For multiple-input multiple-output （MIMO） orthogonal frequency division multiplexing （OFDM） systems, a joint timing synchronization and frequency offset acquisition algorithm based on fractional Fourier transform （FRFT） is proposed. The linear frequency modulation signals superimposed on the data signals are used as the training signals. By performing FRFT on the received signals and searching the peak value of the FRFT results, the receiver can realize timing synchronization and frequency offset acquisition simultaneously. Compared with the existing methods, the proposed algorithm can provide better timing synchronization performance and larger frequency offset acquisition range even under multi-path channels with low signal to noise ratio. Theoretical analysis and simulation results prove this point.展开更多
Due to the neglect of the retrieval of communication parameters(including the symbol rate,the symbol timing offset,and the carrier frequency),the existing non-cooperative communication mode recognizers suffer from the...Due to the neglect of the retrieval of communication parameters(including the symbol rate,the symbol timing offset,and the carrier frequency),the existing non-cooperative communication mode recognizers suffer from the generality ability degradation and severe difficulty in distinguishing a large number of modulation modes,etc.To overcome these drawbacks,this paper proposes an efficient communication mode recognizer consisting of communication parameter estimation,the constellation diagram retrieval,and a classification network.In particular,we define a 2-D symbol synchronization metric to retrieve both the symbol rate and the symbol timing offset,whereas a constellation dispersity annealing procedure is devised to correct the carrier frequency accurately.Owing to the accurate estimation of these crucial parameters,high-regularity constellation maps can be retrieved and thus simplify the subsequent classification work.Numerical results show that the proposed communication mode recognizer acquires higher classification accuracy,stronger anti-noise robustness,and higher applicability of distinguishing multiple types,which presents the proposed scheme with vast applicable potentials in non-cooperative scenarios.展开更多
The linear transmission impairments,such as the timing offset(TO),frequency offset(FO),and chromatic dispersion(CD),are major factors of signal degradations in coherent optical fiber communication systems.The estimati...The linear transmission impairments,such as the timing offset(TO),frequency offset(FO),and chromatic dispersion(CD),are major factors of signal degradations in coherent optical fiber communication systems.The estimation and compensation of such impairments play significant roles in the receiver side digital signal processing(DSP)unit.In this paper,we propose to combat the linear impairments systematically(including TO,FO and CD)with a joint timefrequency signal processing by taking the advantage of fractional Fourier transform(FrFT).In view of geometrical analysis,TO/FO induces a shift in time/frequency coordinate and the CD leads to the rotation in the fractional domain.Both mathematical derivations and geometrical interpretations have been established to unveil the relationships between impairments and linear frequency modulated(LFM)training symbols(TSs).By considering a typical coherent optical orthogonal frequency-division multiplexing(COOFDM)transmission system,three kinds of linear impairments have been jointly estimated by simple geometric calculations using appropriately designed TS based on FrFTs.Simulation and experimental results confirmed the feasibility of time-frequency techniques with better accuracy,less complexity,and improved spectral efficiency.展开更多
Joint Radar and Communications(JRC)can implement two Radio Frequency(RF)functions using a single of resources,providing significant hardware,power and spectrum savings for wireless systems requiring both functions.Fre...Joint Radar and Communications(JRC)can implement two Radio Frequency(RF)functions using a single of resources,providing significant hardware,power and spectrum savings for wireless systems requiring both functions.Frequency-Hopping(FH)MIMO radar is a popular candidate for JRC because the achieved communication symbol rate can greatly exceed the radar pulse repetition frequency.However,practical transceiver imperfections can cause many existing theoretical designs to fail.In this work,we reveal for the first time the non-trivial impact of hardware imperfections on FH-MIMO JRC and model the impact analytically.We also design new waveforms and correspondingly develop a low-complexity algorithm to jointly estimate the hardware imperfections of unsynchronized receiver.In addition,using low-cost software-defined radios and Commercial Off-The-Shelf(COTS)products,we build the first FH-MIMO JRC experimental platform with simultaneous over-the-air radar and communication validation.Confirmed by simulation and experimental results,the proposed designs achieve high performance for both radar and communications.展开更多
Worldwide Interoperability for Microwave Access(WiMAX)trusts Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing(MIMO-OFDM)combination for the deployment of physical layer functions and for conne...Worldwide Interoperability for Microwave Access(WiMAX)trusts Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing(MIMO-OFDM)combination for the deployment of physical layer functions and for connecting the medium access control to the wireless media.Even though Orthogonal Frequency Division Multiplexing(OFDM)facilitates reliable digital broadband transmission in the fading wireless channels,the presence of synchro-nization errors in the form of Carrier Frequency Offset(CFO)and Time Offset(TO)adversely affect the performance of OFDM based physical layers.The objective of this work is to improve the accuracy of the frequency and the time offset estimation in the WiMAX physical layer.A method to enhance the synchro-nization accuracy byfine-tuning the merit factor of the preamble sequence is sug-gested in this paper.Also,a new preamble with improved synchronization accuracy is proposed for the WiMAX system.The performance of the proposed preamble is evaluated in a Rayleigh fading channel and the results of simulations show that the Mean Square Error(MSE)in offset estimation is significantly reduced and it outperforms the standard WiMAX preamble.展开更多
This paper combines the advantages of both common-view time transfer and one-way timing and proposes a new one-way timing method.Owing to the limitations in users capacity and real-time,common-view time transfer can n...This paper combines the advantages of both common-view time transfer and one-way timing and proposes a new one-way timing method.Owing to the limitations in users capacity and real-time,common-view time transfer can not provide time service simultaneously for mass users.A zero baseline experiment is carried out to validate its feasibility.Experimental results indicate this new method can achieve a timing accuracy within 5 ns.Users with requirements of rigorous time can employ this method to keep time synchronized with timing labs.展开更多
This paper analyzes the necessity of the measurement of one-way delay, and it also points out the errors caused by the time offset between measurement devices. Then we propose an algorithm to estimate time offset betw...This paper analyzes the necessity of the measurement of one-way delay, and it also points out the errors caused by the time offset between measurement devices. Then we propose an algorithm to estimate time offset between measurement devices in network. With the estimated time offset, we can correct our measuring results. Simulation shows the effectiveness of our algorithm.展开更多
This paper presents a programmable gain amplifier（PGA） circuit with a digitally assisted DC offset cancellation（DCOC） scheme for a direct conversion WLAN receiver.Implemented in a standard 0.13-μm CMOS process,th...This paper presents a programmable gain amplifier（PGA） circuit with a digitally assisted DC offset cancellation（DCOC） scheme for a direct conversion WLAN receiver.Implemented in a standard 0.13-μm CMOS process,the PGA occupies 0.39 mm2 die area and dissipates 6.5 mW power from a 1.2 V power supply.By using a single loop single digital-to-analog converter（DAC） mixed signal DC offset cancellation topology,the minimum DCOC settling time achieved is as short as 1.6μs with the PGA gain ranging from -8 to 54 dB in a 2 dB step.The DCOC loop utilizes a segmented DAC structure to lower the design complexity without sacrificing accuracy and a digital control algorithm to dynamically set the DCOC loop to fast or normal response mode,making the PGA circuit in compliance with the targeted WLAN specifications.展开更多
The article presents a novel orthogonal frequency division multiplexing （OFDM） frame synchronization method. The method uses the preamble that contains two identical halves, and the energy difference of the two simi...The article presents a novel orthogonal frequency division multiplexing （OFDM） frame synchronization method. The method uses the preamble that contains two identical halves, and the energy difference of the two similar parts of the received preamble in receiver is used to obtain the frame＇s correct starting point. Furthermore, an improvement of the proposed method is presented, which uses the preamble that can be divided into four similar portions, and the energy difference of the four similar parts of the received preamble in receiver is used to obtain the frame＇s correct starting point. The performances of the frame synchronization methods in multipath channel are compared in terms of mean square error （MSE） obtained by simulations. It can be seen from the simulation results that the proposed methods have better performances than Schmidl＇s, Minn＇s, and Park＇s method in multipath channel.展开更多
One of the biggest challenges in ultra-wideband （UWB） radio is the accurate timing acquisition for the receiver. In this article, we develop a novel data-aided synchronization algorithm for pulses amplitude modulati...One of the biggest challenges in ultra-wideband （UWB） radio is the accurate timing acquisition for the receiver. In this article, we develop a novel data-aided synchronization algorithm for pulses amplitude modulation （PAM） UWB systems Pilot and information symbols are transmitted simultaneously by an orthogonal code division multiplexing （OCDM） scheme. In the receiver, an algorithm based on the minimum average error probability （MAEP） of coherent detector is applied to estimate the timing offset. The multipath interference （MI） problem for timing offset estimation is considered. The mean-square-error （MSE） and the bit-error-rate（BER） performances of our proposed scheme are simulated. The results show that our algorithm outperforms the algorithm based on the maximum correlator output （MCO） in multipath channels.展开更多
文摘In this paper, a novel timing offset estimation algorithm of low complexity is presented, which needs a few pilots. The results of simulation prove that the system performance with timing offset correction is approximate to that over AWGN channel.
基金supported by the National Natural Science Foundation of China(60672047).
文摘For multiple-input multiple-output （MIMO） orthogonal frequency division multiplexing （OFDM） systems, a joint timing synchronization and frequency offset acquisition algorithm based on fractional Fourier transform （FRFT） is proposed. The linear frequency modulation signals superimposed on the data signals are used as the training signals. By performing FRFT on the received signals and searching the peak value of the FRFT results, the receiver can realize timing synchronization and frequency offset acquisition simultaneously. Compared with the existing methods, the proposed algorithm can provide better timing synchronization performance and larger frequency offset acquisition range even under multi-path channels with low signal to noise ratio. Theoretical analysis and simulation results prove this point.
文摘Due to the neglect of the retrieval of communication parameters(including the symbol rate,the symbol timing offset,and the carrier frequency),the existing non-cooperative communication mode recognizers suffer from the generality ability degradation and severe difficulty in distinguishing a large number of modulation modes,etc.To overcome these drawbacks,this paper proposes an efficient communication mode recognizer consisting of communication parameter estimation,the constellation diagram retrieval,and a classification network.In particular,we define a 2-D symbol synchronization metric to retrieve both the symbol rate and the symbol timing offset,whereas a constellation dispersity annealing procedure is devised to correct the carrier frequency accurately.Owing to the accurate estimation of these crucial parameters,high-regularity constellation maps can be retrieved and thus simplify the subsequent classification work.Numerical results show that the proposed communication mode recognizer acquires higher classification accuracy,stronger anti-noise robustness,and higher applicability of distinguishing multiple types,which presents the proposed scheme with vast applicable potentials in non-cooperative scenarios.
文摘The linear transmission impairments,such as the timing offset(TO),frequency offset(FO),and chromatic dispersion(CD),are major factors of signal degradations in coherent optical fiber communication systems.The estimation and compensation of such impairments play significant roles in the receiver side digital signal processing(DSP)unit.In this paper,we propose to combat the linear impairments systematically(including TO,FO and CD)with a joint timefrequency signal processing by taking the advantage of fractional Fourier transform(FrFT).In view of geometrical analysis,TO/FO induces a shift in time/frequency coordinate and the CD leads to the rotation in the fractional domain.Both mathematical derivations and geometrical interpretations have been established to unveil the relationships between impairments and linear frequency modulated(LFM)training symbols(TSs).By considering a typical coherent optical orthogonal frequency-division multiplexing(COOFDM)transmission system,three kinds of linear impairments have been jointly estimated by simple geometric calculations using appropriately designed TS based on FrFTs.Simulation and experimental results confirmed the feasibility of time-frequency techniques with better accuracy,less complexity,and improved spectral efficiency.
文摘Joint Radar and Communications(JRC)can implement two Radio Frequency(RF)functions using a single of resources,providing significant hardware,power and spectrum savings for wireless systems requiring both functions.Frequency-Hopping(FH)MIMO radar is a popular candidate for JRC because the achieved communication symbol rate can greatly exceed the radar pulse repetition frequency.However,practical transceiver imperfections can cause many existing theoretical designs to fail.In this work,we reveal for the first time the non-trivial impact of hardware imperfections on FH-MIMO JRC and model the impact analytically.We also design new waveforms and correspondingly develop a low-complexity algorithm to jointly estimate the hardware imperfections of unsynchronized receiver.In addition,using low-cost software-defined radios and Commercial Off-The-Shelf(COTS)products,we build the first FH-MIMO JRC experimental platform with simultaneous over-the-air radar and communication validation.Confirmed by simulation and experimental results,the proposed designs achieve high performance for both radar and communications.
文摘Worldwide Interoperability for Microwave Access(WiMAX)trusts Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing(MIMO-OFDM)combination for the deployment of physical layer functions and for connecting the medium access control to the wireless media.Even though Orthogonal Frequency Division Multiplexing(OFDM)facilitates reliable digital broadband transmission in the fading wireless channels,the presence of synchro-nization errors in the form of Carrier Frequency Offset(CFO)and Time Offset(TO)adversely affect the performance of OFDM based physical layers.The objective of this work is to improve the accuracy of the frequency and the time offset estimation in the WiMAX physical layer.A method to enhance the synchro-nization accuracy byfine-tuning the merit factor of the preamble sequence is sug-gested in this paper.Also,a new preamble with improved synchronization accuracy is proposed for the WiMAX system.The performance of the proposed preamble is evaluated in a Rayleigh fading channel and the results of simulations show that the Mean Square Error(MSE)in offset estimation is significantly reduced and it outperforms the standard WiMAX preamble.
基金supported by the National Natural Science Foundation of China (Grant No. 11033004)the Astronomy Joint Fund of Chinese Academy of Sciences (Grant No. 10778715)
文摘This paper combines the advantages of both common-view time transfer and one-way timing and proposes a new one-way timing method.Owing to the limitations in users capacity and real-time,common-view time transfer can not provide time service simultaneously for mass users.A zero baseline experiment is carried out to validate its feasibility.Experimental results indicate this new method can achieve a timing accuracy within 5 ns.Users with requirements of rigorous time can employ this method to keep time synchronized with timing labs.
文摘This paper analyzes the necessity of the measurement of one-way delay, and it also points out the errors caused by the time offset between measurement devices. Then we propose an algorithm to estimate time offset between measurement devices in network. With the estimated time offset, we can correct our measuring results. Simulation shows the effectiveness of our algorithm.
文摘This paper presents a programmable gain amplifier（PGA） circuit with a digitally assisted DC offset cancellation（DCOC） scheme for a direct conversion WLAN receiver.Implemented in a standard 0.13-μm CMOS process,the PGA occupies 0.39 mm2 die area and dissipates 6.5 mW power from a 1.2 V power supply.By using a single loop single digital-to-analog converter（DAC） mixed signal DC offset cancellation topology,the minimum DCOC settling time achieved is as short as 1.6μs with the PGA gain ranging from -8 to 54 dB in a 2 dB step.The DCOC loop utilizes a segmented DAC structure to lower the design complexity without sacrificing accuracy and a digital control algorithm to dynamically set the DCOC loop to fast or normal response mode,making the PGA circuit in compliance with the targeted WLAN specifications.
文摘The article presents a novel orthogonal frequency division multiplexing （OFDM） frame synchronization method. The method uses the preamble that contains two identical halves, and the energy difference of the two similar parts of the received preamble in receiver is used to obtain the frame＇s correct starting point. Furthermore, an improvement of the proposed method is presented, which uses the preamble that can be divided into four similar portions, and the energy difference of the four similar parts of the received preamble in receiver is used to obtain the frame＇s correct starting point. The performances of the frame synchronization methods in multipath channel are compared in terms of mean square error （MSE） obtained by simulations. It can be seen from the simulation results that the proposed methods have better performances than Schmidl＇s, Minn＇s, and Park＇s method in multipath channel.
基金the National Natural Science Foundation of China （60572118）.
文摘One of the biggest challenges in ultra-wideband （UWB） radio is the accurate timing acquisition for the receiver. In this article, we develop a novel data-aided synchronization algorithm for pulses amplitude modulation （PAM） UWB systems Pilot and information symbols are transmitted simultaneously by an orthogonal code division multiplexing （OCDM） scheme. In the receiver, an algorithm based on the minimum average error probability （MAEP） of coherent detector is applied to estimate the timing offset. The multipath interference （MI） problem for timing offset estimation is considered. The mean-square-error （MSE） and the bit-error-rate（BER） performances of our proposed scheme are simulated. The results show that our algorithm outperforms the algorithm based on the maximum correlator output （MCO） in multipath channels.
