This document summarizes Dominick Marciano's senior project on using a rake receiver with a direct sequence spread spectrum (DSSS) communication system. The initial goal was to show that a rake receiver improves signal reception and reliability for a DSSS system. Limited experimental results provided initial evidence of this benefit. Additionally, the experiment validated that the autocorrelation function, which is fundamental to DSSS, behaves as predicted by theory. A laboratory experiment was conducted to simulate multipath signals, which were successfully decoded using a rake receiver. The results supported the theoretical prediction that a rake receiver can improve the bit error rate over a single receiver.
FPGA Design & Simulation Modeling of Baseband Data Transmission SystemIOSR Journals
Abstract: This paper describes a study on a baseband data transmission system developed for undergraduate
students studying communication engineering. Theoretical material, developed in the lectures, is briefly
covered. A practical system is presented with pre-detection filtering being employed to improve the bit error
rate. A simulation of the complete system is carried out on a Sun work station using the MATLAB simulation
package. Simulation and theoretical results are compared.
The Presentation includes Basics of Non - Uniform Quantization, Companding and different Pulse Code Modulation Techniques. Comparison of Various PCM techniques is done considering various Parameters in Communication Systems.
FPGA Design & Simulation Modeling of Baseband Data Transmission SystemIOSR Journals
Abstract: This paper describes a study on a baseband data transmission system developed for undergraduate
students studying communication engineering. Theoretical material, developed in the lectures, is briefly
covered. A practical system is presented with pre-detection filtering being employed to improve the bit error
rate. A simulation of the complete system is carried out on a Sun work station using the MATLAB simulation
package. Simulation and theoretical results are compared.
The Presentation includes Basics of Non - Uniform Quantization, Companding and different Pulse Code Modulation Techniques. Comparison of Various PCM techniques is done considering various Parameters in Communication Systems.
Hop- by- Hop Message Authentication and Wormhole Detection Mechanism in Wirel...Editor IJCATR
One of the most effective way to prevent unauthorized and corrupted message from being forward in wireless sensor
network. So to restrict these problems many authentication schemes have been developed based on symmetric key cryptosystem. But
there is high computational and communication overhead in addition to lack of scalability and resilience to node compromise attacks.
So to address these isuues polynomial based scheme[1] was introduced. But in these methods it having the threshold problem that
means to send the limited message only because to send larger number of message means the attacker can fully recover. So in my
existing system a scalable message authentication scheme based on elliptic curve cryptography. This scheme allows any node to
transmit an unlimited number of messages without suffering the threshold problem. But these method only detect the black hole and
grey hole attacks are dected but does not detect the worm hole attack. In my proposed system to detect the worm hole attack. Worm
hole attack is one of the harmful attack to which degrade the network performance. So, in the proposed system, one innovative
technique is introduced which is called an efficient wormhole detection mechanism in the wireless sensor networks. In this method,
considers the RTT between two successive nodes and those nodes‟ neighbor number which is needed to compare those values of other
successive nodes. The identification of wormhole attacks is based on the two faces. The first consideration is that the transmission time
between two wormhole attack affected nodes is considerable higher than that between two normal neighbor nodes. The second
detection mechanism is based on the fact that by introducing new links into the network, the adversary increases the number of
neighbors of the nodes within its radius. An experimental result shows that the proposed method achieves high network performance..
Acquisition of Long Pseudo Code in Dsss SignalIJMER
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
International Journal of Modern Engineering Research (IJMER) covers all the fields of engineering and science: Electrical Engineering, Mechanical Engineering, Civil Engineering, Chemical Engineering, Computer Engineering, Agricultural Engineering, Aerospace Engineering, Thermodynamics, Structural Engineering, Control Engineering, Robotics, Mechatronics, Fluid Mechanics, Nanotechnology, Simulators, Web-based Learning, Remote Laboratories, Engineering Design Methods, Education Research, Students' Satisfaction and Motivation, Global Projects, and Assessment…. And many more.
Dwpt Based FFT and Its Application to SNR Estimation in OFDM SystemsCSCJournals
In this paper, wavelet packet (WP) based FFT and its application to SNR estimation is proposed. OFDM systems demodulate data using FFT. The proposed solution computes the exact FFT using WP and its computational complexity is of the same order as FFT, i.e. O (Nlog2 N). SNR estimation is done inside wavelet packet based FFT block unlike previous SNR estimations techniques which perform SNR estimation after FFT. Wavelet packet analyzed data is used to perform SNR estimation in colored noise. The proposed estimator takes into consideration the different noise power levels of the colored noise over the OFDM sub-carriers. The OFDM band is divided into several sub-bands using wavelet packet and noise in each sub-band is considered white. The second-order statistics of the transmitted OFDM preamble are calculated in each sub-band and the power noise is estimated. The proposed estimator is compared with Reddy’s estimator for colored noise in terms of mean squared error (MSE).
قد قمت بتحميل هذه الكتب اثناء دراستى عامى 2012/2011 , وردا للجميل وحرصا منى على عدم فقدانها , قمت بتحميلها من جديد. حيث اننى قد تعلمت الكثير من كتب الدكتور / ممدوح حمزة .
والسيرة الذاتية للدكتور ممدوح حمزة
https://drive.google.com/file/d/0B8kCZNvJ2l88ZW53YnFXaVBBNHM/view
Hop- by- Hop Message Authentication and Wormhole Detection Mechanism in Wirel...Editor IJCATR
One of the most effective way to prevent unauthorized and corrupted message from being forward in wireless sensor
network. So to restrict these problems many authentication schemes have been developed based on symmetric key cryptosystem. But
there is high computational and communication overhead in addition to lack of scalability and resilience to node compromise attacks.
So to address these isuues polynomial based scheme[1] was introduced. But in these methods it having the threshold problem that
means to send the limited message only because to send larger number of message means the attacker can fully recover. So in my
existing system a scalable message authentication scheme based on elliptic curve cryptography. This scheme allows any node to
transmit an unlimited number of messages without suffering the threshold problem. But these method only detect the black hole and
grey hole attacks are dected but does not detect the worm hole attack. In my proposed system to detect the worm hole attack. Worm
hole attack is one of the harmful attack to which degrade the network performance. So, in the proposed system, one innovative
technique is introduced which is called an efficient wormhole detection mechanism in the wireless sensor networks. In this method,
considers the RTT between two successive nodes and those nodes‟ neighbor number which is needed to compare those values of other
successive nodes. The identification of wormhole attacks is based on the two faces. The first consideration is that the transmission time
between two wormhole attack affected nodes is considerable higher than that between two normal neighbor nodes. The second
detection mechanism is based on the fact that by introducing new links into the network, the adversary increases the number of
neighbors of the nodes within its radius. An experimental result shows that the proposed method achieves high network performance..
Acquisition of Long Pseudo Code in Dsss SignalIJMER
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
International Journal of Modern Engineering Research (IJMER) covers all the fields of engineering and science: Electrical Engineering, Mechanical Engineering, Civil Engineering, Chemical Engineering, Computer Engineering, Agricultural Engineering, Aerospace Engineering, Thermodynamics, Structural Engineering, Control Engineering, Robotics, Mechatronics, Fluid Mechanics, Nanotechnology, Simulators, Web-based Learning, Remote Laboratories, Engineering Design Methods, Education Research, Students' Satisfaction and Motivation, Global Projects, and Assessment…. And many more.
Dwpt Based FFT and Its Application to SNR Estimation in OFDM SystemsCSCJournals
In this paper, wavelet packet (WP) based FFT and its application to SNR estimation is proposed. OFDM systems demodulate data using FFT. The proposed solution computes the exact FFT using WP and its computational complexity is of the same order as FFT, i.e. O (Nlog2 N). SNR estimation is done inside wavelet packet based FFT block unlike previous SNR estimations techniques which perform SNR estimation after FFT. Wavelet packet analyzed data is used to perform SNR estimation in colored noise. The proposed estimator takes into consideration the different noise power levels of the colored noise over the OFDM sub-carriers. The OFDM band is divided into several sub-bands using wavelet packet and noise in each sub-band is considered white. The second-order statistics of the transmitted OFDM preamble are calculated in each sub-band and the power noise is estimated. The proposed estimator is compared with Reddy’s estimator for colored noise in terms of mean squared error (MSE).
قد قمت بتحميل هذه الكتب اثناء دراستى عامى 2012/2011 , وردا للجميل وحرصا منى على عدم فقدانها , قمت بتحميلها من جديد. حيث اننى قد تعلمت الكثير من كتب الدكتور / ممدوح حمزة .
والسيرة الذاتية للدكتور ممدوح حمزة
https://drive.google.com/file/d/0B8kCZNvJ2l88ZW53YnFXaVBBNHM/view
The typical three path propagation and anti jamming capability associated with DSSS were carried out
through the combination of Lab VIEW and MATLAB 7.8. At the transmitter, the NRZ data stream is first mapped
into BPSK symbols and then spread-out using different PN code like Hadamard code, Gold or Kasami sequences.
And we see that single user is not total utilization band. Direct Sequence Spread Spectrum (DSSS) techniques are
used same bandwidth Number of user to increase, and we see that better performance. That we can say Direct
Sequence Spread Spectrum techniques is reused to bandwidth. And we can say that in this techniques power loss is
low, anti jamming capability is less and system is more reliable. Furthermore, BPSK-Spreading transceiver should be
analyzed for their performance, multipath scenario and interference whether under AWGN channel which show that
these has been overcome effectively and attain more robust performance, when using direct sequence spread
spectrum.
A NOVEL ADAPTIVE - WAVELET BASED DETECTION ALGORITHM FOR CHIPLESS RFID SYSTEMcsandit
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chipless RFID tags. The chipless RFID tag has a frequency signature which is identical to itself.
Here a vector network analyser is used where the received backscatter signal is analysed in
frequency domain. Thus the frequency signature is decoded by comparing the wavelet
coefficients which identifies the bits accurately. Further, the detection algorithm has been
applied for the tag detection under different dynamic environments to check the robustness of
the detection algorithm. The new method doesn’t rely on calibration tags and shows robust
detection under different environments and movement.
NMR is a Powerful analytical technique used to characterize organic molecules by identifying carbon-hydrogen frameworks within molecules.
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effect precision in the chaotic dynamics used in the coupled technic and the chaotic map’s perturbation
technics used for the generation of a Pseudo-Random Number Generator (PRNGs).The use of the
pseudo- chaotic sequences coupled to the orbit perturbation method in the chaotic logistic map and the
NewPiece-Wise Linear Chaotic Map (NPWLCM). The pseudo random number generator’s originality
proposed from the perturbation of the chaotic recurrence. Furthermore the outputs of the binary sequences
with NPWLCM are reconstructed conventionally with the Bernoulli’s sequences shifts map to change the
shapes with the bitwise permetation then the results in simulation are shown in progress.After being
perturbed, the chaotic system can generate the chaotic binary sequences in uniform distribution and the
statistical properties invulnerable analysis. This generator also has many advantages in the possible useful
applications of spread spectrum digitalimages, such as sensitive secret keys, random uniform distribution
of pixels in Crypto system in secure and synchronize communication.
Enhanced Transmission and Receiver Diversity in Orthogonal Frequency Division...IJECEIAES
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Enhanced Transmission and Receiver Diversity in Orthogonal Frequency Division...
Senior Project
1. SENIOR PROJECT
Dominick Marciano
Advisor: Michael Knox
Department of Electrical Engineering
Five Metrotech Center, Brooklyn, NY
MULTIPATH DETECTION USING SPREAD
SPECTRUM RAKE RECEIVERS
MAY 17, 1997
2. ABSTRACT
The initial goal of myprojectwas to show the benefitof usingarake receiverwithadirect
sequence spreadspectrum(DSSS)communicationsystem. Due totime andequipmentconstraints,I
was able tocompile limitedresultsthatshow intuitivelythatarake receiverwill improve signal
receptionandoverall reliability. More conclusive dataachievedbyotherswillbe presented.
While recordingthe resultsof myexperimentation,Irealizedthatthisdatacan also be usedto
prove that the autocorrelationfunctiondoesworkexactlyastheorypredicts. Autocorrelationisthe
basicelementof DSSSsystems. Withoutautocorrelation,DSSSsystemscouldnotexist. Therefore,Iwill
alsodiscussDSSSsystemsandthe autocorrelationfunction.
THEORY
A systemof communicationwasneededthatwouldbe hardtodetectand alsoensure the
privacyof the data. One systemthatwas developedtomeetthese requirementsiscalleddirect
sequence spreadspectrum(DSSS). The primaryconceptbehindDSSSisspreadingof the signal. Digital
data ismultipliedbyapseudo-randomnoisecode (PN code). ThisPN code isgeneratedbya shift
registerandwill repeat. There are particularconditionsthatmustbe metin orderto ensure a goodPN
code1
. One of the propertiesisthat itmustlookrandom. The PN code musthave a muchhigher
frequencythanthe datathat is to be transmitted.
Whentwo binarypulsesare multipliedinthe time domain,we know thatthe bandwidth(BW) of
the resultantsignal inthe frequencydomainwillbe twice the BWof the of the multiplier(PN code) in
the time domain2
. So,if our data wasa voice signal,itwouldnormallyoccupyapproximately4KHz
bandwidth. But,if the voice signal ismultipliedbyaPN code thatis operatingatclock speedof 1MHz,
the resultantsignal inthe frequencydomainwillhave a2 MHz bandwidth. Therefore,the originalvoice
data has beenspreadsignificantly. Inordertoconserve energy,the amplitude of the signal must
3. decrease asthe bandwidthof the signal increasestherebymaintainingthe areaunderthe signal curve
constant.
By significantlyspreadingthe signal,the amplitude of the signal maygolow enoughthatitis less
than backgroundnoise and thereby makingitdifficulttodetect. Hidingthe signal belowbackground
noise resultsinincreasingthe privacyof the signal. Thisspreadsignal canthenbe modulatedonan RF
carrier andtransmittedbycable or wirelessly.
On the receiverend,the processisreversedinordertoretrieve the original signal (data). The
firststepisto multiplythe receivedsignalbycarrierfrequency. Thiswill removethe carriercomponent
fromthe signal sowe can work ondecodingthe original data. The nextstepisto de-spreadthe signal
by multiplyingthe signalbythe same exactPN code that was usedtospreadthe signal. Itiscritical that
the PN code on the receiverendisnotonlyidentical tothe PN code onthe transmitterend,butthey
mustproperlyalignintime.
Since the PN codes are binaryand identical,we getthe autocorrelationof the twosignalswhen
theyare multiplied. Fromknowledge of FourierTransformswe know thattwopulses(digital 1’s)
multipliedwill givearesultanttriangle shape. The autocorrelationfunctiontellsusthatwe will see this
resultwhenthe twoPN codesare perfectlyaligned. The more the PN codesare misaligned,the less
correlationwill existmakingitmore difficulttorecoverthe original data. If the PN codes are completely
misaligned,nocorrelationwill existandthere will be nodatarecovery. Throughpreviousworkitis
knownthat the lowerlimitof the signal willequal:
(# agreements − #disagreements)
PN Code Length
= −
1
15
4. for a four(4) bitshiftregister(Figure 1). PN code lengthisdeterminedsimplybythe following function:
2n
-1 where n = # of stages in the shift register
Figure 1. Autocorrelation Function - 4 Bit Shift Register
Whendealingwithwirelesscommunications,the propagationof electromagneticwavesmust
be considered. When asignal istransmittedwirelessly,itwill propagateinall directions(basicdipole
antenna). The propagatingwave maybe inline of sight(LOS) of the receiverorit may getreflectedor
refractedpriorto gettingtothe receiver. The LOSsignalswill arrive atthe receiverpriortothe
reflected/refractedsignals. The twoor more signalsare identical exceptthe reflected/refractedwaves
are a delayedversionof the LOSsignal3
. These non-LOSsignalsare referredtoasmulti-pathsignals.
Since the multipathsignalsare delayed,we now know thatwhentheyare multipliedbythe PN
code there will be little ornocorrelationandthe signal canbe discarded. However,there isnoreason
whywe can’t use these signalstoimprove ourreceptionandreliability. Theyare still exactreplicasof
the original andLOS signals. Thiscan be accomplishedbyuse of a rake receiver.
A rake receivercandetectand assistindecodingmultiple delayedsignalsbysplittingthe
receivedsignal intoasmanybranches asdesired. Eachbranch signal will getmultipliedbythe original
PN code shiftedtodifferentpointsintime. Assumingthere isasingle multipathsignalthatisdelayedby
0.5µsec (approximately150 metersof extratravel),inadditional tothe LOSsignal,the delayedsignal
can be recoveredif itismultipliedbythe original PN code delayedby0.5µsec. Now the receivercan
5. processtwo(2) copiesof the original signal. The twosignals,ormore ina real worldapplication,canbe
combinedtoincrease the signal strength4
andimprove signal clarity. Anotheroptionistoassigna
weightingfactortoeachof the decodedsignalsbasedontheirsignal level. Once thisisaccomplished,a
decisioncircuitcanbe usedto selectthe strongestsignal. If the selectedsignal islost ordegraded due
to interference orfading,the nextstrongestsignal canbe chosen. Utilizingthismethodwill
undoubtedlyimprovesystemreliability.
EXPERIMENT
Since the experimentwasconductedinalaboratoryenvironment,propagationdelayhadtobe
simulated. Inordertoachieve a1µsec delayedsignal,the transmittedsignalwouldhave totravel
approximately300 metersbefore beingreceived. Thistype of delaycouldnotbe accomplishedina
small laboratory,soI useda Hewlett-Packard11759BRF channel simulatorbetweenthe transmitterand
receiverandhardwiredthe systemtogetherwithcoaxialcable (Figure 2).
Figure 2. System used to simulate multipath signals and their recovery
6. The channel simulatoriscomputercontrolledtosplitanincomingsignal andtointroduce signal
delay. The delay toa signal issetbythe operatorandcan be variedinstepsof 0.1µsec. Due to the
designof the simulator,adelayof 0.5µsec will be introducedto anyinputsignal. Thisinternal delayof
the simulatorhadto be accountedfor inthe assemblyof the PN code generator. The simulatoralso
introducedsignificantsignalattenuation. Inorderto account forthis attenuation,anamplifierwas
addedat the outputof the simulator.
The PN code generatorusedisshowninFigure 3. It was clockedat1MHz inorderto ensure the
data was spreada significantamount. The code comingfromregister5 was usedtospreadthe data.
The spreadsignal wasinputto the channel simulatorwithadelayof 0µsec forpath #1, whichresultedin
a 0.5µsec delayinthe outputsignal due tothe internal systemdelay. Forease of calculation,an
additional 0.5µsecdelaywasintroducedtothe path#1 signal givingita total 1µsec delay. Thiswasused
as the reference signal (LOS) where t0 =0.1µsec. The same PN code generatorwasusedto decode the
receivedsignals. Thiswasdone forsimplicitybyavoidingthe needtotrack the signal andobtain
alignment. AnotherPN code generatorwasusedtosimulate the transmitteddata. ThissecondPN code
generatorwasclockedat 6KHz whichrepresentsaslightlygreaterbandwidththanthatof voice data.
7. Figure 3. PN code generator
To ensure the transmitterwasfunctioningproperly,aspectrumanalyzerwashookeduptothe
inputof the channel simulator. InFigure 4 itcan be seenthatthe bandwidthof the signal is2MHz;
whichistwice the bandwidthof the spreadingPN code andis exactlywhatisexpected. Several other
measurementswere takenandFigure 5showstwosignalscomingoutof the channel simulatorwhere
one of the signalsisdelayedby 2µsec.
8. Figure 4. Spread signal from transmitter
Figure 5. Two signals, one with a 2 microsecond delay
Usinga digital oscilloscope,itiseasytoconfirmthe operationof the entire system. InFigure 6,
the original signal isshownalongwiththe decodedsignal. Itisquite obviousthatthe signal isdecoded
and demodulatedasexpected. InFigures7through9 the delaywasprogressivelyincreaseduntilthe PN
codeswere misalignedbyexactly1bit(1µsec). It can be clearlyseen thatthe autocorrelationfunctionis
9. Figure 6. One signal recovered
Figure 7. A 0.2 microsecond delayed signal recovered
10. Figure 8. A 0.7 microsecond delayed signal recovered
Figure 9. Attempted recovery of a 1 microsecond delayed signal
11. performingasexpected. Asthe bitsbecome lessaligned,the decodedsignalbecomesmore degraded.
Whenthe two PN codesare completelymisaligned,the signalisnotdecodedatall.
To testthe abilitytodecode multipleversionsof the same signal,Isetpath#1 to a 1µsec delay
and path#2 toa 2µsec delay. Usinga 1µsec and a 2µsec delayedPN codes (registers6and 7 of the PN
code generator),bothsignalswere successfullydecoded (Figure10). It isclear that the signalsare the
same representingidentical data. The onlyitemtonote isthat the signal frompath #2 isinverteddue
to the logicimplementedandisinsignificant. Inthe final step,the signal inpath#2 wasadjustedto
preventPN alignment. Thisresultedinthe lossof signal frompath#2 withno effectonthe receptionof
the signal onpath #1 (Figure 11).
Figure 10. Two signals successfullyrecovered
12. Figure 11. Attempted detection of two signals, with one lost
RESULTS OF OTHERS
There are several differentmethodsof implementingrake receiversinaDSSSsystem. One
methodthathas beenemployedistohave a multiple stage rake receiver5
. Inthismethod,the channel
impulse response isestimatedaswell asmultipleaccessinterference. Byknowingthisinformation,it
enablesmore reliable detectionof databits. Thishelpsimprove systemsthatemploycode division
multiple access(CDMA). InFigure 12,it can be seenthatwhena 2 stage rake receiverisusedas
opposedtoa single stage receiver,the biterrorrate (BER) fora givensignal tonoise ratio(SNR) is
decreased.
13. Figure 12. BER as a function of SNR for 1 and 2 stage rake receivers in the presence of 2 multipath components
Anothermethodusesmultiplesub-carriersinthe transmitteraswell asthe receiverandis
referredtoas multiple carrierspreadspectrum(MCSS)6
. The datais splitintoparallel pathsafteritis
codedby normal DSSSmethods. Each pathis thenmultipliedbyanindividual chipof the PN code and
subsequentlymodulatedontosub-carriers. These individual pathsare thensummedintoaserial multi-
carrier signal thatwill thenbe modulatedontothe maincarrierandtransmitted. Inthe receiver,the
processisreversedtodecode the signal. InFigure 13 it can be seenthe BER vs SNR forthe MCSS system
improvesasthe numberof multipathchannelsincreases. Whenthere are onlytwo(2) multipath
signals,astandardrake receiveractuallyprovidesslightlybetterperformance. Usingastandard rake
receiver,the probabilityof errordecreasesfora givenSNRasthe numberof branchesisincreased
14. (Figure 14). Aninterestingfactisthatas the PN sequence isincreased,there isalsoadecrease inthe
probabilityof error7
.
Figure 13. Performance of DSSS and MCSS rake receivers with L multipath signals
15. Figure 14. Probability of error based on # of rake branches and PN code length
CONCLUSION
In thisexperiment,aswellasthose conductedbyothers,itisclearthat DSSS systemsbehave as
predicted. Fromthe bandwidthspreadingtothe performance of the autocorrelationfunction,thistype
of systemprovides reliablecommunication. Reliabilityisimprovedasexpectedwhenarake receiveris
usedand ithas beenshownthatBER and probabilityof errorare reduced. These resultsare both
intuitive andconclusive fromthe experimentsconducted. There are many otherimplementationsof
rake receiverswaitingtobe built. Asmore researchandexperimentationisconducted,signal reception
and reliabilitywill undoubtedlyimprove.