Simulated Result For Single Carrier Modulation Computer Science Essay
This study is prepared to demo the advancement of the undertaking. The study covered the accomplishments of the work over the past four hebdomads. The major aims of this undertaking are to look into the disadvantages of OFDM systems and its channel appraisal techniques and suggest efficient manner to find channel parametric quantities with betterment, design slow attenuation channel for both level attenuation and frequence selective attenuation channel in order to prove the consequence of transmitted informations, develop algorithm to find noise discrepancy and relation between different sub-carriers and algorithm to transport stage displacement keying ( PSK ) transition strategies in order to gauge channel stage, and develop simulation environment for OFDM symbols. . Due to the presence of assorted obstructions in the extension medium transmitted signal undergoes contemplation every bit good as shadowing and refractions. Due to the absence of line of sight ( LOS ) between the sender and the receiver several obstructions even causes diffraction losingss. Due to multiple obstructions present in the extension medium transmitted signals travel through different way. In other words the signal transmitted by the sender reached at the receiving system via different waies which is called multipath extension and the set of this extension way between sender and receiving system is multipath channel where these extension waies are characterized by three parametric quantities delay, fading and stage displacement ( Stuber, 2002 ) .
2.0 Project Description
In this undertaking we are covering with the attenuation issues caused by channel damage. But in order to execute additive transition the first occupation is to extenuate the consequence of amplitude and stage displacement caused by multipath. So this research based undertaking is divided into two parts. In the first portion, amplitude and stage displacement caused by the channel is determined with the aid of pilot information. The familial signal can be either informations or image which are send through three different modeled channels which are linear white Gaussian Noise ( AWGN ) , level attenuation and frequence selective channel and for level attenuation and frequence selective attenuation public presentation is compared for slow attenuation channel instance under two environment- urban every bit good as suburb. In the 2nd portion, channel appraisal is done for extraneous frequence division multiplexing ( OFDM ) system utilizing the pilot signal. The undertaking is intended to be finished in 16 hebdomads from 1st June 2010 to 17th September 2010.
3.0 Progress Summary
Before the simulation in MATLAB is started this undertaking ab initio theoretical accounts the channel and represents the needed equations mathematically and after mathematical mold cryptography and simulation is really carried out at the same time.
3.1.0 Work done
3.1.1 Mathematical Modeling of Channels
In order to finish this undertaking European GSM ( Global System for Mobile Communication ) is used. In Europe, GSM operates in the scope of 900MHz and 1.8 GHz. For this undertaking bearer frequence of 1.8 GHz is used. In GSM, available both frontward and change by reversal frequence sets are divided into 200 KHz broad channels called ARFCNs ( Absolute Frequency Channel Numbers ) . Furthermore, Nyquist pulsations with period i.e. symbol period ( Ts ) 5µs ( micro-second ) is used. For urban environment root mean square ( RMS ) value scope 10-25µs is used ( Rappaport, 2005 ) and 10 µs is used in this undertaking for simulation during channel mold. Similarly, for sub-urban environment RMS value scope 200-310ns is used and for this undertaking 300ns is used during simulation ( Rappaport, 2005 ) .
3.1.1.1 Slow frequence selective attenuation channel
We have,
Coherence clip, Tc ? ( 1 )
Where,
degree Fahrenheit is the Doppler displacement and is given by
f = V fc / degree Celsius ( 2 )
c= 3*108 ms-1 is speed of visible radiation
fc is bearer frequence and is 1.8 GHz for GSM and
For our undertaking we assume speed of user to be 5km/hr.
So with these values we get Doppler displacement, ( degree Fahrenheit ) = 8.333Hz and,
Using this value on equation ( 1 ) , we get,
Coherence clip, Tc =21.494*10-3 s ? 21.5ms
From this we can detect that 5µs & A ; lt ; & A ; lt ; 10µs & A ; lt ; & A ; lt ; 21.5ms
i.e. Ts & A ; lt ; & A ; lt ; t & A ; lt ; & A ; lt ; Tc, where RMS value, t =10µs for urban environment.
This status clearly depicts the status for the slow frequence selective attenuation channel ( Rappaport, 2005 ) .
3.1.1.2 Slow level attenuation channel
We have,
Coherence clip, Tc ? ( 3 )
Where,
degree Fahrenheit is the Doppler displacement and is given by
f = V fc / degree Celsius ( 4 )
c= 3*108 ms-1 is speed of visible radiation
fc is bearer frequence and is 1.8 GHz for GSM and
For our undertaking we assume speed of user to be 20km/hr and 120km/hr.
So with these values we get Doppler displacement, ( f1 ) = 33.33Hz ( for speed, V1=20km/hr ) , likewise we get Doppler displacement, ( f2 ) = 200Hz ( for speed, V2=120km/hr )
Using this value on equation ( 3 ) , we get,
Coherence clip, Tc1=5.37*10-3 s ? 5.4ms for speed, V1=20km/hr, likewise
Coherence clip, Tc2=895.24*10-6 s ? 900ms for speed, V2=120km/hr.
From this we can detect for both instance that 5.4ms & A ; gt ; & A ; gt ; 5µs & A ; gt ; & A ; gt ; 300ns and 900µs & A ; gt ; & A ; gt ; 5µs & A ; gt ; & A ; gt ; 300ns
i.e. Tc1 & A ; gt ; & A ; gt ; Ts & A ; gt ; & A ; gt ; t and Tc2 & A ; gt ; & A ; gt ; Ts & A ; gt ; & A ; gt ; T, where RMS value, t = 300ns for urban environment.
This status clearly depicts the status for the slow level attenuation channel ( Rappaport, 2005 ) .
3.1.2 Statistical theoretical accounts for multipath attenuation channel
3.1.3 Slow level attenuation channel
Different multipath theoretical accounts have been suggested in order to analyze the statistical nature of the multipath attenuation channel. Among them this undertaking chooses Clarke ‘s and Gan ‘s attenuation theoretical account since it deals with sprinkling and is widely used theoretical accounts ( Akram, 2007 ) . This undertaking assumes Rayleigh melting distribution so in order to implement Rayleigh melting simulator at baseband complex Gaussian random variable is generated for each of the N/2 positive set of frequence constituents transmitted from the noise beginning and subsequently on negative frequence constituents is generated by conjugating positive frequence values thereby delegating these at negative frequence values ( Rappaport, 2005 ) .
Impulse response of N bins for a fading channel is mathematically represented as ( Rappaport, 2005 ) ,
Ea, N? [ PWB ] = E [ || N ||2 ] = Ea, N? [ iexp| ( jN? ) |2 ] = i2 ( 5 )
Where,
Ea, N? [ . ] represent the norm over all possible values of Army Intelligence and N?i
and Army Intelligence is the ith pat impulse response ( Rappaport, 2007 ) . In the level attenuation channel in channel response there is merely one pat so expectation value is given by E [ |h |2 ] =E [ |a0|2 ] =1 ( Chen, 2007 ) . The outlook value of channel impulse response with N samples is given by
E [ ||||2 ] = N*E [ |h |2 ] = N ( 6 )
If is the amplitude of complex random variable in frequence sphere ;
is the root square of Doppler power spectrum ; and
B is the RF signal spectral form after Doppler spread. Mathematically, we can associate these footings ( Chen, 2007 ) by the undermentioned equation,
E [ ||b||2 = 2.|| ||2 ( 7 )
Using the Parseval ‘s theorem for equation ( 7 ) in DFT signifier reduces B into
||b||2 = * ||B||2 ( 8 )
From eqn ( 7 ) and eqn ( 8 ) we can compose as,
E [ ||b||2 = * E [ ||b||2 = . || ||2 ( 9 )
On normalising B we get,
E [ ||||2 ] = E [ ||b||2
= 2. Tocopherol [ ||b||2 = N [ from eqn ( 6 ) ]
So,
= ( 10 )
Similarly, from eqn ( 9 ) and eqn ( 10 ) we can compose as,
= . B
This is the needed look for the channel impulse response for slow level attenuation channel ( Chen, 2007 ) .
3.1.3 Simulation consequence for SNR vs. BER for multi-carrier and individual bearer transition
One of the major parts of this undertaking is to look into the disadvantages of OFDM systems and its channel appraisal techniques and suggest efficient manner to find channel parametric quantities with betterment. Before this undertaking starts channel appraisal techniques, difference between individual bearer transition and multicarrier transition is analyzed in order to make up one’s mind why multicarrier transition is selected for our undertaking.
Fig 1: – Simulated consequence for individual bearer transition
Fig 2: – Simulated consequence for multi-carrier transition
Fig 3: – Simulated consequence for individual bearer vs. multi-carrier ( without developing spots )
In multi-carrier transition the entire information rate to be sent in the available channel is sub-divided among the sub-carriers nevertheless in the individual bearer transition the system becomes more susceptible to loss of transmitted informations due to the presence of noise and other attenuation damages present in the random wireless channel. Furthermore, in individual bearer transition it gets more susceptible to interference due to the extra bandwidth used by the bearer from other uninterrupted signal beginning ( Ahson and Ilyas, 2008 ) . These redresss can be overcome by multi-carrier transition which is besides the basic for the extraneous frequence division multiplexing ( OFDM ) . In multicarrier transition, transition strategies use extraneous wave form for modulating the subcarriers so subcarriers have overlapping spectrum thereby accomplishing the higher spectrum efficiency ( Goldsmith, 2005 ) .
Simulation consequences for individual bearer transition, multicarrier transition are shown in fig ( 1 ) and fig ( 2 ) severally. For simpleness during simulation this stage assumes binary stage displacement keying ( BPSK ) signal is generated through signal generator. Furthermore, simulated consequence is depicted in the fig ( 3 ) in order to compare the efficiency between individual bearer transition and multi-carrier transition. From this simulation we can clearly province that spot error rate ( BER ) is extremely improved in multicarrier transition.
Minimum ( BER1 )
1*10-5
Average ( BER1 )
1*10-2
Maximum ( BER1 )
0.58
Minimum ( BER2 )
1.9*10-6
Average ( BER2 )
0.39*10-3
Maximum ( BER2 )
0.49
Table 1: – Analysis of individual bearer vs. multi-carrier
3.1.3.1 Analysis of the comparing
We can take the SNR value from 0 to 30 dubnium. During the simulation it creates some random informations foremost and propagated these informations through AWGN channel where noise will be besides added. So the BER for individual bearer will be BER1=error/ ( 100*100 ) .
For multi bearer if we took 2 different bearers. So in this instance the BER will be BER2=error/ ( 100*100*2 ) .
There is another thing for an instant SNR the BER will be non same ; it will be changed harmonizing the SNR degree will be increased. Let the SNR degree is measured by M.
So the concluding BER for individual and multi bearer will be BER1= error/ ( 100*100*M ) and BER2= error/ ( 100*100*2*M ) .
3.2 Work in advancement
Statistical mold for slow frequence selective attenuation channel is in advancement. As statistical mold for slow level attenuation channel is already done, MATLAB cryptography is in advancement for the simulation of indiscriminately produced informations when sent through the slow level attenuation channel. Furthermore, coding for QPSK transition for indiscriminately produced signal is in advancement. On the other manus MATLAB cryptography for OFDM is on advancement even. In this portion consecutive high rate of transmitted information is converted into parallel low rate bomber watercourse.
3.3 Work to be done
3.3.1 Statistical mold and simulation
This undertaking is supposed to back up two sorts of informations which are indiscriminately produced informations and image file. In the first portion of the undertaking merely statistical mold of slow level attenuation channel is done. In future this undertaking has to imitate this theoretical account for both indiscriminately produced informations and image file. In add-on, statistical mold of slow frequence selective attenuation channel is still to be carried out and farther simulation is to be carried out even for both types of informations. After this these informations should be transmitted through the modeled slow-flat fading channel and frequence attenuation channel and the MATLAB cryptography and simulation portion is still to be carried out in approaching yearss. Another major work to be carried out is to pattern LMS ( least average square ) and RLS ( recursive least square ) algorithm mathematically and imitate them. On the 2nd portion of the undertaking related to OFDM, till now indiscriminately produced consecutive information is converted to parallel watercourse merely.
The major work to be done in the approaching yearss that known pilot sub-carrier should be inserted with the modulated analogue informations. After that reverse fast Fourier transform ( IFFT ) is to be performed into the obtained frequence sphere transmitted informations. Subsequently on parallel watercourse of informations is converted back to the consecutive signifier following with digital to analog ( D/A ) transition and low base on balls filter ( LPF ) . The resulted signal is transmitted over the AWGN channel along with noise. At the receiver terminal precisely rearward operation is performed as done in transmitter side. In order to gauge the channel pilot information is the utile tools. Every sub-carrier contains the pilot information so with the aid of standard symbols and the known pilot information we can gauge the channel features approximately and this work is still left to be done
3.4 Research issues encountered and get the better of
This whole undertaking is traveling on based on idle instance, mathematical look and some MATLAB simulation. So it ‘s non certain that in the industrial base is at that place any other challenges have to confront if this theory truly implement. Besides this overcome some issues occurred during the interval of undertaking period.
Small graduated table melting envelope distribution could be Ricean or Rayleigh distribution depending upon the stationary signal constituent. If there is a presence of dominant stationary signal constituent as LOS ( line of sight ) extension so the envelope of little graduated table attenuation is Ricean else if there is non the presence of dominant stationary signal constituent envelope distribution is Rayleigh ( Rappaport, 2007 ) . This undertaking assumes the Rayleigh distribution.
Different multipath theoretical accounts have been suggested in order to analyze the statistical nature of the multipath attenuation channel. Among them this undertaking chooses Clarke ‘s and Gan ‘s attenuation theoretical account since it deals with sprinkling and is widely used theoretical accounts. Channel appraisal is based on the pilot information. There are many schemes of channel appraisal utilizing pilot information. For the first instance of channel appraisal of slow attenuation modeled channel pilot information is assumed set to be certain per centum of the entire information length. We need pilot information even during the channel appraisal of the OFDM system in that instance this research issues is encountered but still non decided.
3.5 Changes
At foremost in the design we made a error. Simultaneously we applied IFFT and so once more OFDM Modulator in the sender aerial and the same thing we did reversely ( FFT and OFDM Demodulation ) in the receiving system subdivision. But so we realize that it was incorrect. IFFT automatically done the OFDM transition and we do n’t necessitate to make once more OFDM transition. Then we correct our error.
One another thing we change. At first our mark was to analyse channel appraisal of OFDM system utilizing minimal average square mistake ( MMSE ) algorithm. We realize that it will be more complicated for us. If we success to finish our chief undertaking, we will seek to gauge the channel utilizing MMSE algorithm.
The major undertaking demand to be done during the undertaking continuance of 110 working yearss is shown in Gantt chart. The undertaking is concerned with the bing jobs related to OFDM associating with development boulder clay now. Based on that, this undertaking will plan a system theoretical account to extenuate some of the disadvantages of existed OFDM jobs. The undertakings performed with milepost of the undertaking are shown in five different stages and explained as below.
3.6 Work program
The major undertaking demand to be done during the undertaking continuance of 16 hebdomads is shown in Gantt chart. The undertakings performed with milepost of the undertaking are shown in five different stages and explained as below.
3.6.1 Work Completed
Phase I: Undertaking proposal signifier of the undertaking is already made and submitted to relevant supervisor before 1st June 2010. During this stage undertaking aims, aims are analyzed and seek to happen out the donees of the undertaking.
Phase II: Literature reappraisal of the undertaking is already prepared and submitted within the deadline 17th June 2010. Researches made on yesteryear is relevant measure to be undertaken so past diaries, documents or literature reappraisal are studied in order to derive new thoughts for the hereafter program which even provides good way. These articles even indicate the possible jobs that are likely to be encountered.
3.6.2 Work on advancement and future work
Phase III: This stage is the on-going stage of this undertaking that includes the readying of the advancement study. In this stage we issue the job and addressed it immediately. In add-on, overall appraisal of the undertaking is carried out and do alterations is required.
Phase IV: Based on the research made guidelines is made how to get down the undertaking and make up one’s mind if farther research is needed or non if non maintaining nucleus thought in head it is ready to implement thoughts made via research made boulder clay now. System theoretical account and algorithm is designed. MATLAB scheduling is done for assorted algorithms used during the undertaking and simulation is carried out in changing status in order to find channel parametric quantities. QPSK transition is done during simulation. Ultimately, system public presentation is analyzed during the terminal of this stage executing simulation for three different channel theoretical accounts, AWGN channels, level attenuation channels and frequence selective attenuation channels. At the terminal of this stage concluding consequence will be demonstrated to the supervisor.
Phase V: Including all methodological analysiss, descriptions, public presentation comparings concluding certification is produced with full user usher and eventually difficult transcript of study is made ready for entry.
3.6.3 Gantt chart
3.7 Decision
In this advancement study the modeled slow level attenuation channel is presented and its channel impulse response is represented mathematically. Before making this advancement study even includes mathematical mold of channel. During this certain needed premises are made and based under this premise status for slow frequence selective attenuation channel and decelerate level attenuation channel are designed for both urban and sub-urban environment. One of the undertaking objectives is to look into the disadvantage of OFDM system and its channel appraisal techniques. So, maintaining in this head this undertaking ab initio tries to compare individual bearer transition and multi- bearer transition through MATLAB simulation because OFDM is based on multi-carrier transition.
