Pub Date : 1996-03-19DOI: 10.1109/NRSC.1996.551120
S. El-Khamy, S. Shaaban, E.A. Thabet
We present a novel technique for a multi-user communication system utilizing binary chirp modulated (CM) signals. This suggested technique is motivated by the inherent interference rejection capability of such spread-spectrum type system, specially in circumstances where immunity against Doppler shift and fading due to multipath propagation are important. The chirp signals used are selected such that they all have the same power as well as the same bandwidth. Closed form expressions, as well as approximate analytical expressions, for the cross-coherence functions between the different forms of considered chirp signals are derived. The performance of a suggested coherent receiver structure is investigated and the corresponding error rates are presented. The results show that the proposed multi-user chirp signaling technique is efficient and promising as a multiple-access technique.
{"title":"Multi-user chirp modulation signals (M-CM) for efficient multiple-access communication systems","authors":"S. El-Khamy, S. Shaaban, E.A. Thabet","doi":"10.1109/NRSC.1996.551120","DOIUrl":"https://doi.org/10.1109/NRSC.1996.551120","url":null,"abstract":"We present a novel technique for a multi-user communication system utilizing binary chirp modulated (CM) signals. This suggested technique is motivated by the inherent interference rejection capability of such spread-spectrum type system, specially in circumstances where immunity against Doppler shift and fading due to multipath propagation are important. The chirp signals used are selected such that they all have the same power as well as the same bandwidth. Closed form expressions, as well as approximate analytical expressions, for the cross-coherence functions between the different forms of considered chirp signals are derived. The performance of a suggested coherent receiver structure is investigated and the corresponding error rates are presented. The results show that the proposed multi-user chirp signaling technique is efficient and promising as a multiple-access technique.","PeriodicalId":127585,"journal":{"name":"Thirteenth National Radio Science Conference. NRSC '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117167636","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 : 1996-03-19DOI: 10.1109/NRSC.1996.551101
S. El-Khamy, N. Abdel-Kader
A simple linear transformation referred to as the equivalence theorem is used to reduce many problems of elliptical arrays, which may operate in a multipath correlated interference environment, to those of their circular equivalents. Then a preprocessing technique in conjunction with the conjugate gradient method (CGM) is used to find the optimal weights of the resultant circular array. The pattern obtained has its maximum in the direction of the desired signals. This method is extended to the case of many desired signals. Such an array is suitable to act as a smart array in multipath telecommunication channels.
{"title":"Smart elliptical arrays","authors":"S. El-Khamy, N. Abdel-Kader","doi":"10.1109/NRSC.1996.551101","DOIUrl":"https://doi.org/10.1109/NRSC.1996.551101","url":null,"abstract":"A simple linear transformation referred to as the equivalence theorem is used to reduce many problems of elliptical arrays, which may operate in a multipath correlated interference environment, to those of their circular equivalents. Then a preprocessing technique in conjunction with the conjugate gradient method (CGM) is used to find the optimal weights of the resultant circular array. The pattern obtained has its maximum in the direction of the desired signals. This method is extended to the case of many desired signals. Such an array is suitable to act as a smart array in multipath telecommunication channels.","PeriodicalId":127585,"journal":{"name":"Thirteenth National Radio Science Conference. NRSC '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117266425","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 : 1996-03-19DOI: 10.1109/NRSC.1996.551148
D. Khalil, T. Amer, H. Ragaie
We present a new beam propagation technique for the analysis of 3-dimensional (3D) integrated optical structures. This new technique depends on the use of the weighted index method to transform the 3 dimensional BPM into two coupled 2-dimensional BPM techniques. The numerical results show good agreement with the standard 3D BPM while the computational time as well as the required memory are greatly reduced.
{"title":"The weighted index beam propagation method (WIBPM)","authors":"D. Khalil, T. Amer, H. Ragaie","doi":"10.1109/NRSC.1996.551148","DOIUrl":"https://doi.org/10.1109/NRSC.1996.551148","url":null,"abstract":"We present a new beam propagation technique for the analysis of 3-dimensional (3D) integrated optical structures. This new technique depends on the use of the weighted index method to transform the 3 dimensional BPM into two coupled 2-dimensional BPM techniques. The numerical results show good agreement with the standard 3D BPM while the computational time as well as the required memory are greatly reduced.","PeriodicalId":127585,"journal":{"name":"Thirteenth National Radio Science Conference. NRSC '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116112501","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 : 1996-03-19DOI: 10.1109/NRSC.1996.551136
S. El-Khamy, E. Youssef, M. Madkour
The performance of synchronous multi-user detectors in wireless CDMA fading multipath channels, such as indoor channels for personal communications is investigated using eigen analysis via the Karhunen-Loeve transformation (KLT). A modified receiver design is introduced to eliminate the multiple-access interference (MAI) between the different users in the two cases of a single receiving antenna and multiple receiving antennas (space diversity).
{"title":"Cancellation of multiple-access interference in wireless CDMA systems using eigen receivers","authors":"S. El-Khamy, E. Youssef, M. Madkour","doi":"10.1109/NRSC.1996.551136","DOIUrl":"https://doi.org/10.1109/NRSC.1996.551136","url":null,"abstract":"The performance of synchronous multi-user detectors in wireless CDMA fading multipath channels, such as indoor channels for personal communications is investigated using eigen analysis via the Karhunen-Loeve transformation (KLT). A modified receiver design is introduced to eliminate the multiple-access interference (MAI) between the different users in the two cases of a single receiving antenna and multiple receiving antennas (space diversity).","PeriodicalId":127585,"journal":{"name":"Thirteenth National Radio Science Conference. NRSC '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122491177","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 : 1996-03-19DOI: 10.1109/NRSC.1996.551099
A. V. Kalinin, V.P. Maltcev, G. A. Kislyakov, V.S. Beagou, E. Kalinina
The interferometric (correlational) radioastronomical antenna measurements with terrestrial sources is a variant of the radioholographic method. This method, which is illustrated, requires a special two-channel correlational receiver and an additional tracking receiver. The radio source is combined with the tested source in an interferometer. As a signal source, one may use a variety of radio sources and satellites. The article presents some experimental results obtained from different antennas. The peculiarities of the measurements, using natural radio sources and satellites, are discussed.
{"title":"Radioholographic antenna measurements with extraterrestrial sources","authors":"A. V. Kalinin, V.P. Maltcev, G. A. Kislyakov, V.S. Beagou, E. Kalinina","doi":"10.1109/NRSC.1996.551099","DOIUrl":"https://doi.org/10.1109/NRSC.1996.551099","url":null,"abstract":"The interferometric (correlational) radioastronomical antenna measurements with terrestrial sources is a variant of the radioholographic method. This method, which is illustrated, requires a special two-channel correlational receiver and an additional tracking receiver. The radio source is combined with the tested source in an interferometer. As a signal source, one may use a variety of radio sources and satellites. The article presents some experimental results obtained from different antennas. The peculiarities of the measurements, using natural radio sources and satellites, are discussed.","PeriodicalId":127585,"journal":{"name":"Thirteenth National Radio Science Conference. NRSC '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128498096","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 : 1996-03-19DOI: 10.1109/NRSC.1996.551151
I. Badawy, W. El-Gammal, M. Abo-El-Khier
This paper describes a Non-Destructive Assay System for the verification of uranium fuel rods used in nuclear reactors. The system is based on gamma-ray spectroscopy technique. It employs a NaI(Tl) Detector, a Photo-multiplier tube, a Multi-channel Pulse-height Analyzer, associated electronics and a lead collimator. Two segments of well-known enrichments are used as "Standards". By selecting certain gamma-rays peaks in the uranium spectra, the U-235 enrichment can be measured. Measurements performed on the verification of fuel rods of a gave U-235 enrichment with relative accuracy of about /spl plusmn/5%. The obtained results showed that the system can be very useful for the physical inventory verification, accountability and control, of uranium fuel rods at nuclear reactors and at the fuel fabrication stage as well.
{"title":"A non-destructive assay system for the verification of uranium fuel rods","authors":"I. Badawy, W. El-Gammal, M. Abo-El-Khier","doi":"10.1109/NRSC.1996.551151","DOIUrl":"https://doi.org/10.1109/NRSC.1996.551151","url":null,"abstract":"This paper describes a Non-Destructive Assay System for the verification of uranium fuel rods used in nuclear reactors. The system is based on gamma-ray spectroscopy technique. It employs a NaI(Tl) Detector, a Photo-multiplier tube, a Multi-channel Pulse-height Analyzer, associated electronics and a lead collimator. Two segments of well-known enrichments are used as \"Standards\". By selecting certain gamma-rays peaks in the uranium spectra, the U-235 enrichment can be measured. Measurements performed on the verification of fuel rods of a gave U-235 enrichment with relative accuracy of about /spl plusmn/5%. The obtained results showed that the system can be very useful for the physical inventory verification, accountability and control, of uranium fuel rods at nuclear reactors and at the fuel fabrication stage as well.","PeriodicalId":127585,"journal":{"name":"Thirteenth National Radio Science Conference. NRSC '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126794673","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 : 1996-03-19DOI: 10.1109/NRSC.1996.551140
M. K. Ahmed, S. Ibrahem
A small signal GaAs FET model is derived based on measured s-parameters. The model parameters have been found using a computer aided optimization program, where the initial value of the circuit elements are determined in part from measured s-parameters at 1 GHz, and in part from DC measurements. By using the optimization program, it is to be noted that the final value of some circuit elements is changed by a negligible amount compared with its initial value. Some other circuit elements which have large changes between their initial and final values, can be readjusted using the second order approximation.
{"title":"Small signal GaAs MESFET model parameters extracted from measured S-parameters","authors":"M. K. Ahmed, S. Ibrahem","doi":"10.1109/NRSC.1996.551140","DOIUrl":"https://doi.org/10.1109/NRSC.1996.551140","url":null,"abstract":"A small signal GaAs FET model is derived based on measured s-parameters. The model parameters have been found using a computer aided optimization program, where the initial value of the circuit elements are determined in part from measured s-parameters at 1 GHz, and in part from DC measurements. By using the optimization program, it is to be noted that the final value of some circuit elements is changed by a negligible amount compared with its initial value. Some other circuit elements which have large changes between their initial and final values, can be readjusted using the second order approximation.","PeriodicalId":127585,"journal":{"name":"Thirteenth National Radio Science Conference. NRSC '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126444464","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 : 1996-03-19DOI: 10.1109/NRSC.1996.551134
E. Eweda, H. El-Deen Ahmed, M. A. Bassiouney, A. El-Azim El-Mahdi
At high data rates, the adaptation processor of the adaptive filter may be unable to perform the multiplications required by the adaptation algorithm each baud interval. A direct, but expensive, solution of this problem is to use parallel processing. The present paper presents a simple alternative solution that is suitable for the case of adaptive system identification. The idea of the proposed method is to make one iteration for each several baud intervals. The idea is implemented as follows. With N being the number of adaptive filter coefficients, N successive input samples and the corresponding sample of the system output are injected to the adaptation processor to perform one iteration. Input and output samples that come before the termination of this iteration are discarded by the adaptation processor. After termination of the iteration, new N input samples and the corresponding output sample are injected to the adaptation processor and the procedure is repeated. The above idea is applied to both the LMS algorithm and the sign algorithm. The effect of data discarding on the transient performance of the identification procedure is studied by computer simulations for both white and correlated inputs of the system.
{"title":"Adaptive system identification based on adaptation with data discarding","authors":"E. Eweda, H. El-Deen Ahmed, M. A. Bassiouney, A. El-Azim El-Mahdi","doi":"10.1109/NRSC.1996.551134","DOIUrl":"https://doi.org/10.1109/NRSC.1996.551134","url":null,"abstract":"At high data rates, the adaptation processor of the adaptive filter may be unable to perform the multiplications required by the adaptation algorithm each baud interval. A direct, but expensive, solution of this problem is to use parallel processing. The present paper presents a simple alternative solution that is suitable for the case of adaptive system identification. The idea of the proposed method is to make one iteration for each several baud intervals. The idea is implemented as follows. With N being the number of adaptive filter coefficients, N successive input samples and the corresponding sample of the system output are injected to the adaptation processor to perform one iteration. Input and output samples that come before the termination of this iteration are discarded by the adaptation processor. After termination of the iteration, new N input samples and the corresponding output sample are injected to the adaptation processor and the procedure is repeated. The above idea is applied to both the LMS algorithm and the sign algorithm. The effect of data discarding on the transient performance of the identification procedure is studied by computer simulations for both white and correlated inputs of the system.","PeriodicalId":127585,"journal":{"name":"Thirteenth National Radio Science Conference. NRSC '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132152186","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 : 1996-03-19DOI: 10.1109/NRSC.1996.551126
E. Abdel-Azeem, R. Seireg, S. Shaheen
Cryptography is the only powerful tool for achieving high levels of information security in a computer networks environment. The ISO have proposed five security service groups including, confidentiality, authentication, data integrity, non-repudiation, and access control. Cryptography can support implementation of all these security services, by using various cryptographic techniques, which include among other things conventional secret key algorithms, public-key algorithms, authentication procedures, and different digital signature schemes. Hash functions, in cryptography, are used for digital signature applications and authentication procedures. It is advisable, for cryptographic reasons, to sign only hashed messages. A secure hash function must be a one-way and collision-free function. Cryptographic security of hash functions could be evaluated, so far, either by conducting detailed cryptanalysis, or by using computational complexity theory. Each of these methods has its own shortcomings. A new scheme for evaluating the cryptographic security of hash functions is proposed. The proposed scheme is simple, fast, and based on a solid mathematical model offered by Markov process. The proposed scheme is used to evaluate the cryptographic security of the Message Digest MD-4 algorithm. The results are in accordance with what was conjectured and published.
{"title":"Cryptographic security evaluation of MD4 hash function","authors":"E. Abdel-Azeem, R. Seireg, S. Shaheen","doi":"10.1109/NRSC.1996.551126","DOIUrl":"https://doi.org/10.1109/NRSC.1996.551126","url":null,"abstract":"Cryptography is the only powerful tool for achieving high levels of information security in a computer networks environment. The ISO have proposed five security service groups including, confidentiality, authentication, data integrity, non-repudiation, and access control. Cryptography can support implementation of all these security services, by using various cryptographic techniques, which include among other things conventional secret key algorithms, public-key algorithms, authentication procedures, and different digital signature schemes. Hash functions, in cryptography, are used for digital signature applications and authentication procedures. It is advisable, for cryptographic reasons, to sign only hashed messages. A secure hash function must be a one-way and collision-free function. Cryptographic security of hash functions could be evaluated, so far, either by conducting detailed cryptanalysis, or by using computational complexity theory. Each of these methods has its own shortcomings. A new scheme for evaluating the cryptographic security of hash functions is proposed. The proposed scheme is simple, fast, and based on a solid mathematical model offered by Markov process. The proposed scheme is used to evaluate the cryptographic security of the Message Digest MD-4 algorithm. The results are in accordance with what was conjectured and published.","PeriodicalId":127585,"journal":{"name":"Thirteenth National Radio Science Conference. NRSC '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133246660","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 : 1996-03-19DOI: 10.1109/NRSC.1996.551145
A. Ragab, M. M. Mokhtar
A new adaptive method called off-line sliding window (OLSW) is introduced to improve the performance of slowly adaptive equalizers when they are used to equalize fast fading channels in general and mobile channels in particular. Application of the OLSW adaptive method to the DFE-RLS equalizer (a decision feedback equalizer that uses the recursive least square algorithms for adaptation) when it is used within a proposed digital mobile communication system for North America is investigated. The simulation results show beside the performance improvement, that the performance of the DFE-RLS equalizers that utilize the OLSW method is less sensitive to the tracking speed. Also, this method avoids the build up of roundoff errors over time for the RLS algorithms.
{"title":"A new iterative method for improving equalizer performance in mobile fading channels","authors":"A. Ragab, M. M. Mokhtar","doi":"10.1109/NRSC.1996.551145","DOIUrl":"https://doi.org/10.1109/NRSC.1996.551145","url":null,"abstract":"A new adaptive method called off-line sliding window (OLSW) is introduced to improve the performance of slowly adaptive equalizers when they are used to equalize fast fading channels in general and mobile channels in particular. Application of the OLSW adaptive method to the DFE-RLS equalizer (a decision feedback equalizer that uses the recursive least square algorithms for adaptation) when it is used within a proposed digital mobile communication system for North America is investigated. The simulation results show beside the performance improvement, that the performance of the DFE-RLS equalizers that utilize the OLSW method is less sensitive to the tracking speed. Also, this method avoids the build up of roundoff errors over time for the RLS algorithms.","PeriodicalId":127585,"journal":{"name":"Thirteenth National Radio Science Conference. NRSC '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127059883","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}
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