Pub Date : 2007-06-04DOI: 10.1109/WDDC.2007.4339382
V. Chakravarthy, Z. Wu, A. Shaw, M. Temple, R. Kannan, F. Garber
Several studies have revealed that spectrum congestion is primarily due to the inefficient use of spectrum versus unavailability. Cognitive radio (CR) and ultra wide band (UWB) technologies have been proposed as candidates to address this problem. Currently, a CR determines unused frequency bands and transmits overlay waveforms in these bands, while UWB transmits underlay waveforms that span the entire frequency band while coexisting with primary users. This suggests that most of the spectrum occupied by primary users is underused. This work proposes a general soft decision cognitive radio (SDCR) framework, based on a previous developed spectrally modulated, spectrally modulated (SMSE) framework, to combine benefits of overlay/underlay techniques while maximizing channel capacity. We also show that current CR and UWB implementations represent two extreme SDCR cases and that current overlay/underlay waveforms are two special cases of the general waveform platform.
{"title":"A general overlay/underlay analytic expression representing cognitive radio waveform","authors":"V. Chakravarthy, Z. Wu, A. Shaw, M. Temple, R. Kannan, F. Garber","doi":"10.1109/WDDC.2007.4339382","DOIUrl":"https://doi.org/10.1109/WDDC.2007.4339382","url":null,"abstract":"Several studies have revealed that spectrum congestion is primarily due to the inefficient use of spectrum versus unavailability. Cognitive radio (CR) and ultra wide band (UWB) technologies have been proposed as candidates to address this problem. Currently, a CR determines unused frequency bands and transmits overlay waveforms in these bands, while UWB transmits underlay waveforms that span the entire frequency band while coexisting with primary users. This suggests that most of the spectrum occupied by primary users is underused. This work proposes a general soft decision cognitive radio (SDCR) framework, based on a previous developed spectrally modulated, spectrally modulated (SMSE) framework, to combine benefits of overlay/underlay techniques while maximizing channel capacity. We also show that current CR and UWB implementations represent two extreme SDCR cases and that current overlay/underlay waveforms are two special cases of the general waveform platform.","PeriodicalId":142822,"journal":{"name":"2007 International Waveform Diversity and Design Conference","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130484078","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2007-06-04DOI: 10.1109/WDDC.2007.4339380
F. Giannetti, V. Lottici, I. Stupia
In this contribution we demonstrate that the peak-to-average power ratio (PAPR) of a multi-carrier code division multiple access (MC-CDMA) signal can be suitably minimized by resorting to a judicious strategy for the allocation of the spreading signature codes. A low-complexity implementation of the proposed strategy is presented and its performance gain over conventional random allocation strategy is numerically assessed.
{"title":"Minimum-PAPR waveform design for MC-CDMA transmissions over nonlinear channels","authors":"F. Giannetti, V. Lottici, I. Stupia","doi":"10.1109/WDDC.2007.4339380","DOIUrl":"https://doi.org/10.1109/WDDC.2007.4339380","url":null,"abstract":"In this contribution we demonstrate that the peak-to-average power ratio (PAPR) of a multi-carrier code division multiple access (MC-CDMA) signal can be suitably minimized by resorting to a judicious strategy for the allocation of the spreading signature codes. A low-complexity implementation of the proposed strategy is presented and its performance gain over conventional random allocation strategy is numerically assessed.","PeriodicalId":142822,"journal":{"name":"2007 International Waveform Diversity and Design Conference","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124664429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2007-06-04DOI: 10.1109/WDDC.2007.4339376
L. Hacini, A. Farrouki, Z. Hammoudi
Hybrid acquisition of PN codes, using order statistics and multiple antennas, is proposed for direct sequence code-division multiple-access (DS-CDMA) communications. To search for the phase alignment between the local PN code and the incoming PN sequence, the receiver employs a Constant False Alarme Rate (CFAR) detector. The proposed detection scheme utilizes the largest value of the correlation results as a test cell for each antenna element. Next, the adaptive threshold is obtained by using the remaining ordered variables. A non conventional approach is then employed to perform the non-coherent integration of the received multiple-antenna signals. Exact expression for the probability of false alarm is derived, and the performances of the considered system are studied under Rayleigh fading assumptions.
{"title":"Hybrid acquisition scheme of PN codes using order statistics-based detection and antenna diversity","authors":"L. Hacini, A. Farrouki, Z. Hammoudi","doi":"10.1109/WDDC.2007.4339376","DOIUrl":"https://doi.org/10.1109/WDDC.2007.4339376","url":null,"abstract":"Hybrid acquisition of PN codes, using order statistics and multiple antennas, is proposed for direct sequence code-division multiple-access (DS-CDMA) communications. To search for the phase alignment between the local PN code and the incoming PN sequence, the receiver employs a Constant False Alarme Rate (CFAR) detector. The proposed detection scheme utilizes the largest value of the correlation results as a test cell for each antenna element. Next, the adaptive threshold is obtained by using the remaining ordered variables. A non conventional approach is then employed to perform the non-coherent integration of the received multiple-antenna signals. Exact expression for the probability of false alarm is derived, and the performances of the considered system are studied under Rayleigh fading assumptions.","PeriodicalId":142822,"journal":{"name":"2007 International Waveform Diversity and Design Conference","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129594458","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2007-06-04DOI: 10.1109/WDDC.2007.4339428
S. Hens, S. N. Madsen
Interferometric radar systems are used by the research, commercial and military communities for applications ranging from topographic mapping to measuring subtle deformations of the Earth's surface for geophysical processes such as earthquakes, volcanoes and ice motion. These systems operate at a variety of wavelengths from 1 cm to 1 m depending on the application. As the number of users of the spectrum increases it is becoming increasingly necessary for these systems to alter their waveforms to have the necessary interoperable compatibility. In particular, notching of certain spectral bands within the radar transmit band may be required to avoid interference with critical users operating in the same band. For high accuracy applications it is necessary to account for how these waveform differences affect the interferometric phase and correlation. We have developed a formula for the effective interferometric wavelength that accounts for the effect of the transmitted waveform on the effective interferometric wavelength and the way the data is processed.
{"title":"Interferometric radar waveform design and the effective interferometric wavelength","authors":"S. Hens, S. N. Madsen","doi":"10.1109/WDDC.2007.4339428","DOIUrl":"https://doi.org/10.1109/WDDC.2007.4339428","url":null,"abstract":"Interferometric radar systems are used by the research, commercial and military communities for applications ranging from topographic mapping to measuring subtle deformations of the Earth's surface for geophysical processes such as earthquakes, volcanoes and ice motion. These systems operate at a variety of wavelengths from 1 cm to 1 m depending on the application. As the number of users of the spectrum increases it is becoming increasingly necessary for these systems to alter their waveforms to have the necessary interoperable compatibility. In particular, notching of certain spectral bands within the radar transmit band may be required to avoid interference with critical users operating in the same band. For high accuracy applications it is necessary to account for how these waveform differences affect the interferometric phase and correlation. We have developed a formula for the effective interferometric wavelength that accounts for the effect of the transmitted waveform on the effective interferometric wavelength and the way the data is processed.","PeriodicalId":142822,"journal":{"name":"2007 International Waveform Diversity and Design Conference","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134329785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2007-06-04DOI: 10.1109/WDDC.2007.4339455
Yimin D. Zhang, M. Amin
It is known that improved target characterizations can be achieved by concurrently using multiple over-the-horizon radars (OTHRs) as compared to a single OTHR operating alone. However, a key limitation with OTHR radar is the selection of an appropriate operating frequency, given the rising demand on radar waveform bandwidth commensurate with the range resolution requirements. The authors have considered concurrent operations of two OTHR systems that use the same frequency band with different chirp waveforms, and a cross-radar interference cancellation technique has been developed. The purpose of this paper is to examine the performance of cross-radar interference cancellation in the presence of multiple target returns from both auto-and cross-radar reception modes. It is shown that, the interference between target returns corresponding to the same radar is negligible, whereas the residual error of cross-radar interference cancellation in the presence of signal returns corresponding to different radars takes a low value in a typical application scenario.
{"title":"Concurrent operation and cross-radar interference cancellation of two over-the-horizon radars","authors":"Yimin D. Zhang, M. Amin","doi":"10.1109/WDDC.2007.4339455","DOIUrl":"https://doi.org/10.1109/WDDC.2007.4339455","url":null,"abstract":"It is known that improved target characterizations can be achieved by concurrently using multiple over-the-horizon radars (OTHRs) as compared to a single OTHR operating alone. However, a key limitation with OTHR radar is the selection of an appropriate operating frequency, given the rising demand on radar waveform bandwidth commensurate with the range resolution requirements. The authors have considered concurrent operations of two OTHR systems that use the same frequency band with different chirp waveforms, and a cross-radar interference cancellation technique has been developed. The purpose of this paper is to examine the performance of cross-radar interference cancellation in the presence of multiple target returns from both auto-and cross-radar reception modes. It is shown that, the interference between target returns corresponding to the same radar is negligible, whereas the residual error of cross-radar interference cancellation in the presence of signal returns corresponding to different radars takes a low value in a typical application scenario.","PeriodicalId":142822,"journal":{"name":"2007 International Waveform Diversity and Design Conference","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129397376","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2007-06-04DOI: 10.1109/WDDC.2007.4339431
L. Baldini, E. Gorgucci, F. Cuccoli, D. Giuli, M. Gherardelli
A methodology to correct reflectivity factor and differential reflectivity at C-band for rain attenuation is presented and evaluated. The methodology is based on a full self-consistency condition describing the interrelation between polarimetric measurements and attenuation or differential attenuation along the rain medium. Evaluation is performed both using C-band profiles generated from S-band radar measurements collected by the NCAR S-Pol radar as well as data collected at C-band by the Polar 55 C radar in Italy. Evaluation shows improvement in performance with respect to the available techniques. In particular, it shows the capability to remove any systematic bias that could arise from drop size distribution variability from attenuation and differential attenuation estimates.
{"title":"Evaluation of a fully self-consistent methodology to correct attenuation and differential attenuation at C-band","authors":"L. Baldini, E. Gorgucci, F. Cuccoli, D. Giuli, M. Gherardelli","doi":"10.1109/WDDC.2007.4339431","DOIUrl":"https://doi.org/10.1109/WDDC.2007.4339431","url":null,"abstract":"A methodology to correct reflectivity factor and differential reflectivity at C-band for rain attenuation is presented and evaluated. The methodology is based on a full self-consistency condition describing the interrelation between polarimetric measurements and attenuation or differential attenuation along the rain medium. Evaluation is performed both using C-band profiles generated from S-band radar measurements collected by the NCAR S-Pol radar as well as data collected at C-band by the Polar 55 C radar in Italy. Evaluation shows improvement in performance with respect to the available techniques. In particular, it shows the capability to remove any systematic bias that could arise from drop size distribution variability from attenuation and differential attenuation estimates.","PeriodicalId":142822,"journal":{"name":"2007 International Waveform Diversity and Design Conference","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116554712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2007-06-04DOI: 10.1109/WDDC.2007.4339419
M. Martorella, F. Berizzi, J. Palmer, B. Haywood, B. Bates
In recent studies the possibility of extending autofocusing techniques to fully polarimetric ISAR systems has been proposed. The image contrast and entropy based autofocusing techniques have been proposed in the last decade as some of the most common techniques for obtaining well focused single polarisation ISAR images. In this paper, the two techniques are extended and applied to fully polarimetric ISAR data. A performance analysis is then provided and compared to single polarisation ISAR using real data.
{"title":"Image contrast and entropy based autofocusing for polarimetric ISAR","authors":"M. Martorella, F. Berizzi, J. Palmer, B. Haywood, B. Bates","doi":"10.1109/WDDC.2007.4339419","DOIUrl":"https://doi.org/10.1109/WDDC.2007.4339419","url":null,"abstract":"In recent studies the possibility of extending autofocusing techniques to fully polarimetric ISAR systems has been proposed. The image contrast and entropy based autofocusing techniques have been proposed in the last decade as some of the most common techniques for obtaining well focused single polarisation ISAR images. In this paper, the two techniques are extended and applied to fully polarimetric ISAR data. A performance analysis is then provided and compared to single polarisation ISAR using real data.","PeriodicalId":142822,"journal":{"name":"2007 International Waveform Diversity and Design Conference","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124691342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2007-06-04DOI: 10.1109/WDDC.2007.4339413
S. Blunt, P. Yantham
This paper considers the embedding of a covert communication signal amongst radar backscatter by means of a tag/transponder that lies within the illuminated area of the radar. Past approaches have operated on an inter-pulse basis whereby a communication symbol/identifier is relayed to an intended receiver by imparting a Doppler-like phase-shift to each of a successive series of incident radar pulses. In contrast, the approach proposed in this paper operates on an intra-pulse basis whereby the incident radar waveform at the tag/transponder is "re-modulated" into one of a set of different waveforms each representing a different communication symbol. The particular design issues for these re-modulated waveforms are discussed and three general design methods are proposed. The effectiveness of the different methods is assessed in terms of the probability of communication error as a function of the respective powers of the embedded communication signal, the masking radar backscatter, and noise. The relative "covertness" of the resulting waveforms is also discussed.
{"title":"Waveform design for radar-embedded communications","authors":"S. Blunt, P. Yantham","doi":"10.1109/WDDC.2007.4339413","DOIUrl":"https://doi.org/10.1109/WDDC.2007.4339413","url":null,"abstract":"This paper considers the embedding of a covert communication signal amongst radar backscatter by means of a tag/transponder that lies within the illuminated area of the radar. Past approaches have operated on an inter-pulse basis whereby a communication symbol/identifier is relayed to an intended receiver by imparting a Doppler-like phase-shift to each of a successive series of incident radar pulses. In contrast, the approach proposed in this paper operates on an intra-pulse basis whereby the incident radar waveform at the tag/transponder is \"re-modulated\" into one of a set of different waveforms each representing a different communication symbol. The particular design issues for these re-modulated waveforms are discussed and three general design methods are proposed. The effectiveness of the different methods is assessed in terms of the probability of communication error as a function of the respective powers of the embedded communication signal, the masking radar backscatter, and noise. The relative \"covertness\" of the resulting waveforms is also discussed.","PeriodicalId":142822,"journal":{"name":"2007 International Waveform Diversity and Design Conference","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124081902","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2007-06-04DOI: 10.1109/WDDC.2007.4339383
E. Lock, R. Adve
Previous work in waveform diversity for distributed apertures for target detection has focused largely on orthogonal transmissions. This paper investigates an alternative approach; implementing waveform diversity based on differing slopes of the linear FM pulse to the application of target detection for a distributed radar aperture system in the presence of noise and clutter. This paper add develop the required signal model corresponding to the proposed system, accounting for the cross-coupling between the linearly FM pulses. This paper determines whether applying this type of waveform diversity will result in improved performance in the discrimination of the target from noise and interfering sources and compare the performance whether this method is a feasible solution. A crucial step is the optimization of the FM rates using sequential quadratic programming.
{"title":"Varying FM rates in adaptive processing for distributed radar apertures","authors":"E. Lock, R. Adve","doi":"10.1109/WDDC.2007.4339383","DOIUrl":"https://doi.org/10.1109/WDDC.2007.4339383","url":null,"abstract":"Previous work in waveform diversity for distributed apertures for target detection has focused largely on orthogonal transmissions. This paper investigates an alternative approach; implementing waveform diversity based on differing slopes of the linear FM pulse to the application of target detection for a distributed radar aperture system in the presence of noise and clutter. This paper add develop the required signal model corresponding to the proposed system, accounting for the cross-coupling between the linearly FM pulses. This paper determines whether applying this type of waveform diversity will result in improved performance in the discrimination of the target from noise and interfering sources and compare the performance whether this method is a feasible solution. A crucial step is the optimization of the FM rates using sequential quadratic programming.","PeriodicalId":142822,"journal":{"name":"2007 International Waveform Diversity and Design Conference","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126363051","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2007-06-04DOI: 10.1109/WDDC.2007.4339437
T. Varslot, B. Yazıcı, C. Yarman, M. Cheney, L. Scharf
A time-reversal implementation of a transmit waveform preconditioning scheme for optimal clutter rejection in radar imaging is presented. Waveform preconditioning involves determining a map on the space of transmit waveforms, and then applying this map to the waveforms before transmission. Our work applies to antenna arrays with an arbitrary number of transmit-and receive elements, and makes no assumptions about the elements being co-located. Waveform preconditioning for clutter rejection achieves efficient use of power and computational resources by distributing power properly over a frequency band and by eliminating clutter filtering in receive processing. By our time-reversal implementation we avoid the need to obtain an explicit model for the environment in order to compute the preconditioning operator.
{"title":"Time-reversal waveform preconditioning for clutter rejection","authors":"T. Varslot, B. Yazıcı, C. Yarman, M. Cheney, L. Scharf","doi":"10.1109/WDDC.2007.4339437","DOIUrl":"https://doi.org/10.1109/WDDC.2007.4339437","url":null,"abstract":"A time-reversal implementation of a transmit waveform preconditioning scheme for optimal clutter rejection in radar imaging is presented. Waveform preconditioning involves determining a map on the space of transmit waveforms, and then applying this map to the waveforms before transmission. Our work applies to antenna arrays with an arbitrary number of transmit-and receive elements, and makes no assumptions about the elements being co-located. Waveform preconditioning for clutter rejection achieves efficient use of power and computational resources by distributing power properly over a frequency band and by eliminating clutter filtering in receive processing. By our time-reversal implementation we avoid the need to obtain an explicit model for the environment in order to compute the preconditioning operator.","PeriodicalId":142822,"journal":{"name":"2007 International Waveform Diversity and Design Conference","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120938593","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：