CHAPTER 8 JOINT PAPR REDUCTION AND ICI CANCELLATION IN OFDM SYSTEMS

Transcription

1 CHAPTER 8 JOIT PAPR REDUCTIO AD ICI CACELLATIO I OFDM SYSTEMS Itercarrier Iterferece (ICI) is aother major issue i implemetig a OFDM system. As discussed i chapter 3, the OFDM subcarriers are arrowbad ad their frequecy separatio decreases by icreasig the umber of subcarriers. A small carrier frequecy offset (CFO) betwee the trasmitter ad receiver oscillators ca disturb the orthogoality of subcarriers ad produce ICI [75], [76]. The ICI may also be caused from Doppler effect due to relative motio betwee the trasmitter ad receiver [], [7]. Overall performace of the OFDM system affected by ICI ad AWG degrades i compariso to OFDM system affected by AWG oly. I literature, may schemes [4]-[46], [78]-[83] have bee proposed to elimiate the effect of ICI. These are divided ito four major categories, which iclude ICI cacellatio [4]-[46], CFO estimatio ad removal [78]-[8], frequecy domai equalizatio [8] ad time domai widowig [83]. I [78], the CFO estimatio is performed by usig some pilot symbols, whereas frequecy domai equalizatio scheme [8] is used to mitigate the effect of ICI, but it requires a highly complex matrix iversio. Time domai widowig scheme [83] uses a shapig filter to mitigate the effect of ICI. Khoa ad Dabe preseted the BER aalysis of OFDM system affected by ICI ad suggested to use pulse shapig scheme [8] for ICI reductio. I [4], a scheme called ICI self-cacellatio is proposed by Zhao et al., which repeats oe data symbol o two adjacet data subcarriers with phase iversio. But its CIR performace degrades at higher values of CFO ad its BW efficiecy is 5%. The CIR performace of ICI self-cacellatio was further improved by a scheme called ew ICI self-cacellatio scheme proposed by Sathaatha ad Rajatheva. I cotrast to ICI self-cacellatio, i this scheme [4] data symbols are repeated o symmetrically located subcarriers with phase iversio, which taes the advatage of the frequecy diversity of a multipath fadig chael. The CIR ad BER performaces of ICI cacellatio schemes [4], [4] are claimed to be further improved by the geeral ICI cacellatio scheme [4] proposed 66

2 by Seyedi ad Saulier, which uses widowig techique at the trasmittig ad receivig eds of OFDM system. Yeh et al. proposed a trasmissio scheme [44] ow as ICI cojugate cacellatio to mitigate the effect of ICI. I this scheme, time domai OFDM sigal ad its cojugate are trasmitted over two differet parallel paths to achieve diversity gai ad are combied at the receiver to improve the BER performace of the system. But its CIR ad BER performaces degrade i compariso to ICI self-cacellatio ad ew ICI self-cacellatio schemes at higher values of CFO. The CIR ad BER performaces of ICI cojugate cacellatio [44] are further improved by phase rotated ICI cojugate cacellatio [45] proposed by Wag ad Huag. I this scheme [45], at the trasmitter a artificial phase rotatio is produced i the time domai OFDM sigal ad its cojugate to mitigate the effect of ICI. Oe of the mai disadvatages of this scheme is that it requires CFO estimatio to fid the optimal value of artificial phase rotatio factor. I [9], a ew ICI cojugate cacellatio scheme is proposed to mitigate the effect of ICI. Lie, ICI cojugate cacellatio scheme it also ivolve a two parallel path trasmissio scheme. I this scheme [9], two OFDM sigals, oe by taig IFFT ad aother by taig FFT of frequecy domai OFDM sigal are trasmitted over two differet paths usig a multiplexig scheme. I [], a repeated correlative codig scheme is proposed, which is combiatio of ICI self-cacellatio ad correlative codig. I [46], Yu Fu et al. show through simulatio that the PAPR of OFDM sigal obtaied after applyig ICI self-cacellatio scheme is higher tha that of the OFDM sigal without ICI self-cacellatio, which idicates the requiremet of PAPR reductio i ICI self-cacellatio scheme. Motivated by this observatio, i this chapter we have performed the mathematical aalysis of PAPR of some popular ICI cacellatio schemes. Aalysis cofirms that PAPR performaces of ICI cacellatio schemes uder cosideratio are either very close to or worse tha stadard OFDM sigal without ICI cacellatio. The covetioal OFDM systems with large umber of subcarriers already have the requiremet of PAPR reductio ad ay further icrease i PAPR of OFDM sigal after ICI cacellatio maes it eve more essetial. I this chapter, we have tae three popular ICI cacellatio schemes i.e. the covetioal ICI self-cacellatio [4], ew ICI self-cacellatio [4] ad ICI cojugate cacellatio [44] ito cosideratio, ad propose a M-M mappig based PTS scheme for reducig the PAPR 67

3 of OFDM sigal, which has resulted from ICI cacellatio. M-M mappig is combied with ICI cacellatio schemes [4], [4], [44] i such a way that the CIR performace of these schemes before ad after PAPR reductio remais same, ad o SI is required at the receiver to recover the origial data sigal. The proposed scheme with ICI cacellatio [4], [4], [44] ad the proposed PAPR reductio scheme achieves both ICI cacellatio ad PAPR reductio capability ad hece it is called Joit PAPR Reductio ad ICI Cacellatio scheme. Comparisos of PAPR ad CIR performaces of ICI cacellatio schemes are performed. We have also evaluated the SER performace of ICI self-cacellatio, ew ICI self-cacellatio ad ICI cojugate cacellatio schemes with the proposed PAPR reductio mechaism over AWG ad fadig chaels usig computer simulatios. The remaiig chapter is orgaized i sectio 8. through 8.7 as follows. I sectio 8., we discuss the motivatio of PAPR reductio i ICI cacellatio schemes. PAPR aalysis of ICI cacellatio schemes uder cosideratio are give i sectio 8.. System model of the proposed joit PAPR reductio ad ICI cacellatio is give i sectio 8.3. Sectio 8.4 presets the couplig of proposed PAPR reductio scheme with ICI cacellatio schemes uder cosideratio. I order to combie ew ICI self-cacellatio scheme with proposed PAPR reductio scheme, a ew partitioig scheme is proposed i sectio 8.5. The CIR, PAPR ad SER performaces of the schemes uder cosideratio are preseted ad discussed i sectio 8.6. Fially, the chapter is cocluded i sectio MOTIVATIO OF PAPR REDUCTIO I ICI CACELLATIO SCHEMES As discussed earlier, i ICI self-cacellatio scheme, data symbols trasmitted o eve umbered subcarriers are also trasmitted o odd umbered subcarriers after phase iversio. This itroduces correlatio amog adjacet subcarriers ad results i high pea formatio. Therefore, PAPR performace of such a ICI cacellatio scheme becomes iferior i compariso to covetioal OFDM sigal without ICI self-cacellatio. This observatio, motivates us to perform the mathematical aalysis of ICI self-cacellatio scheme alog with two other popular schemes, ew ICI self-cacellatio ad cojugate cacellatio schemes, which cofirms the PAPR performace degradatio i case of ICI self-cacellatio scheme. PAPR performace degradatio of ICI self-cacellatio scheme is a prime motivatig factor for this wor to combie it with a suitable PAPR reductio scheme to improve its PAPR performace. 68

4 69 8. PAPR AALYSIS OF ICI CACELLATIO SCHEMES I this sectio, we perform the mathematical aalysis of PAPR performace for covetioal ICI self-cacellatio, ew ICI self-cacellatio ad ICI cojugate cacellatio schemes. 8.. PAPR aalysis of ICI self-cacellatio scheme [4] I ICI self-cacellatio scheme, the data symbols are modulated o the subcarriers as per (3.46), which is repeated here for coveiece ) ( ) ( (),..., (3) (), ) ( The time domai OFDM sigal after applyig ICI self-cacellatio scheme ca be writte as ; ) ( exp exp ] [, + j j x eve SC (8.) ; exp exp, j j eve ; exp exp si, j j j eve ; 4 exp exp si ] [ j j j x SC (8.) The CDF of PAPR for OFDM sigal give by (8.) ca be calculated usig (3.8) as si exp ) ( ) ( SC SC z z F z PAPR P (8.3) Therefore, the complemetary cumulative distributio fuctio (CCDF) of PAPR for OFDM sigal ( ] [ x SC ) give by (8.) ca be calculated as > si exp ) ( ) ( ) ( SC SC SC z z F z PAPR P z F (8.4) The secod term of (8.4) represets the CDF of a OFDM sigal with ICI self-cacellatio havig / subcarriers. The value of the secod term of (8.4) is foud to be lesser tha z)) exp(, therefore the CCDF of PAPR will be more tha that of the covetioal OFDM sigal havig same umber of subcarriers.

5 8.. PAPR aalysis of ew ICI self-cacellatio scheme [4] I ew ICI self-cacellatio scheme data symbols are repeated with phase iversio o symmetrically located subcarriers i a data bloc. The subcarriers data allocatio defied i (3.54) is repeated here for coveiece.,,... The time domai OFDM sigal after applyig ew ICI self-cacellatio scheme ca be writte as x SC [ ] exp j exp j ( ) ; (8.5) j j exp j + si ; (8.6) Equatio (8.6) represets a time domai OFDM sigal with / subcarriers ad CDF of PAPR for sigal ( x SC [] ) ca be calculated usig (3.8) as F SC SC ( z) P( PAPR < z) ( exp( z)) (8.7) Therefore, CCDF of PAPR for sigal x SC [] is give by F SC ( z) P( PAPR SC > z) F SC ( z) ( exp( z)) (8.8) where F SC (z) deotes the CCDF of PAPR for ew ICI self-cacellatio scheme. The CCDF of PAPR for sigal x SC [] after cosiderig a oversamplig factor L, ca be writte as F o SC ( z) ( exp( z)) L (8.9) 8..3 PAPR aalysis of ICI cojugate cacellatio scheme [44] I this scheme, time domai OFDM sigal x[] ad its cojugate sigal ( []) give by (3.) ad (3.56) respectively, are trasmitted over two parallel paths ad are combied at the receiver to mitigate the effect of ICI. Sigal x CC [] is the cojugate of x [], therefore the pea ad average power of sigal x CC [] is same as that of x []. Hece, sigals x [] ad [] x CC x CC 7

6 have same expressios for CCDF of PAPR, which is give by CC CC F ( z) P( PAPR > z) ( exp( z)) (8.) where F CC (z) deotes the CCDF of PAPR for ICI cojugate cacellatio scheme. If we cosider a oversamplig factor L, the CCDF of PAPR give by (8.) ca be writte as CC F ( z) ( exp( z)) L (8.) 8.3 SYSTEM MODEL The OFDM system model usig ICI self-cacellatio or ew ICI self-cacellatio scheme with proposed PAPR reductio mechaism is depicted i Fig. 8.. Data Iput Biary to M ary Data Coversio & Costellatio Mappig Differetial Codig ICI Cacellig Modulatio & S/P Coversio Sub bloc Formatio & IFFT Phase Optimizatio & Selectio P/S Add CP D/A & HPA Data Output Costellatio De mappig & M ary to Biary Data Coversio Differetial Decodig P/S Coversio & ICI Cacellig Demodulatio FFT A/D & S/P Chael Figure 8.: OFDM system model for ICI self-cacellatio ad ew ICI self-cacellatio with proposed PAPR reductio scheme I Fig. 8., we first covert biary data ito M-ary data ad map these data poits to M differet costellatio poits of M-ary modulatio scheme. This process is explaied i more detail i sectio 8.4. After this, differetial codig [] is used to miimize the effect of frequecy offset betwee two cosecutive OFDM symbols ad ICI self-cacellig or ew ICI self-cacellig modulatio scheme is used to elimiate the effect of ICI. The obtaied serial modulated data symbols are the coverted ito parallel streams by usig P/S coverter. A bloc of parallel modulated data symbols is partitioed ito S disjoit subblocs usig appropriate partitioig scheme. FFT operatio o each data sub-bloc is performed to obtai S partial trasmit sequeces (PTS). The obtaied PTS are multiplied with 7

7 phase rotatio factors {, j} ad the combied to avoid pea formatio. A maximum of W S- combiatios of phase factors ca be tested to get a OFDM sigal with miimum PAPR, where W is the umber of phase rotatio factors. I the proposed scheme, W ad S4, therefore, 8 iteratios per OFDM symbol are eed to fid the OFDM sigal with miimum PAPR. To reduce the umber of iteratios ad computatioal complexity, a suitable phase optimizatio techique [3]-[5] ca be utilized. After this stage the blocs are exactly same as the covetioal OFDM trasceiver discussed i chapter. At the receiver, the subcarrier demodulated sigal is passed through P/S coverter ad the ICI cacellig demodulatio is applied. I ICI cacellig demodulatio, the data recovered o two subcarriers (which were used at the trasmitter for repeatig the data symbol with phase iversio), are combied with phase iversio to improve the BER performace. After this, differetial decodig, costellatio de-mappig ad M-ary to biary data coversio are performed i a sequece to obtai the desired biary data sigal. The system model for ICI cojugate cacellatio scheme with proposed PAPR reductio mechaism (show i Fig. 8.), is similar to the system model show i Fig. 8. with slight differece. The differece arises from the structure of ICI cojugate cacellatio scheme. Here also, the biary data is first coverted ito M-ary data sigal, ad the M-M mappig is used to map it over M differet costellatio poits of M-ary modulatio scheme. Data Iput Biary to M ary Data Coversio Costellatio Mappig S/P Coversio Sub bloc Formatio & IFFT Phase Optimizatio & Selectio P/S Add CP (.)* MU D/A & HPA Chael Data Output M ary to Biary Data Coversio Costellatio De mappig ICI Cacellig Demodulatio P/S P/S FFT FFT (.)* De Mux & A/D Figure 8.: OFDM system model for ICI cojugate cacellatio with proposed PAPR reductio scheme The obtaied serial stream of modulated data symbols is coverted ito parallel streams of modulated data symbols usig S/P coverter ad the same PTS procedure, as discussed earlier for system model show i Fig.8., is used to obtai time domai OFDM sigal with 7

8 miimum PAPR. The time domai OFDM sigal ad its cojugate sigal are coverted ito aalog sigals, ad the amplified to desired sigal power level by usig D/A ad HPA, respectively. Fially, both the sigals are trasmitted over two differet paths of a commuicatio chael to mitigate the effect of ICI. At the receivig ed, the sigal correspodig to time domai OFDM sigal (without cojugate) is subcarrier demodulated as per the covetioal OFDM demodulatio scheme, whereas we eed to tae the cojugate of OFDM sigal received i respose of the trasmitted cojugate OFDM sigal, before applyig it to subcarrier demodulatio. Both the subcarrier de-modulated sigals are coverted ito serial data stream by usig P/S coverter ad added before doig M-ary demodulatio. M-ary demodulated sigal is de-mapped to M-ary data sigal usig M-M decodig, ad fially coverted to biary data. 8.4 COUPLIG OF PROPOSED PAPR REDUCTIO WITH ICI CACELLATIO SCHEMES I order to improve the PAPR performace of covetioal ICI cacellatio schemes, the proposed PTS based PAPR reductio scheme ca be coupled with ay ICI cacellatio scheme uder cosideratio. Covetioal ICI self-cacellatio, ew ICI self-cacellatio or ICI cojugate cacellatio schemes ca be coupled with proposed PAPR reductio scheme usig followig procedure: I this joit scheme, first of all biary data stream is coverted ito M-ary data stream. Based o the value of M ad modulatio scheme (PSK or QAM), M-ary data poits are iitially mapped to M differet costellatio poits of M-ary PSK or QAM modulatio scheme. I this chapter, for a example, we have used quaterary to 8-PSK mappig scheme as discussed i chapter 7, to iitially map the quaterary data poits over four differet poits of 8-PSK costellatio, usig Table 7.. After that, ICI cacellig modulatio is used to elimiate the effect of ICI ad the covetioal PTS scheme usig two phase rotatio factors {, j} is used for miimizig the PAPR of resulted OFDM sigal. But, partitios of a bloc of data symbols are performed i such a way that ICI cacellig modulatio operatio remais udisturbed. The details of the partitioig schemes useful for sub-bloc formatio i ICI self-cacellatio, ew ICI self-cacellatio ad ICI cojugate cacellatio are described i sectio 8.5. As discussed i chapter 3, i PTS based scheme, costellatio poits after multiplicatio with phase rotatio factor ( ) rotates the costellatio poits by / after multiplicatio with a phase rotatio factor j ad hece covers remaiig 4 distict 73

9 poits of 8-PSK costellatio. At the receiver, after subcarrier demodulatio, ICI cacellig demodulatio ad 8-PSK demodulatio scheme are used oe after aother to obtai quaterary data sigal. After this, 8-PSK to quaterary de-mappig scheme give i Table 7.7 is used to covert 8 differet costellatio poits ito quaterary data poits. Fially, quaterary to biary data coversio scheme is used to obtai biary data sigal. The proposed PAPR reductio scheme is completely free from the requiremet of SI i.e. SI is required at the receiver to recover the origial data sigal. Proposed PAPR reductio scheme ca be applied for ay value of M ad ay M-ary modulatio scheme. 8.5 PARTITIOIG SCHEMES FOR ICI CACELLATIO SCHEMES I order to combie M-M mappig based PTS with ICI self-cacellatio, ew ICI selfcacellatio or ICI cojugate cacellatio, it is essetial that all the subcarriers should be partitioed ito disjoit sub blocs i such a way that after multiplicatio with phase rotatio factor (correspodig to PTS), the operatio of ICI cacellig modulatio remais udisturbed Partitioig scheme for ICI self-cacellatio scheme [4] I order to eep ICI cacellig modulatio udisturbed, the adjacet subcarriers, which are used for data symbol repetitio, should lie i the same partitio. Therefore, stadard adjacet partitioig scheme [6] depicted i Fig. 8.3 ca oly be foud useful to combie M-M mappig based PTS scheme for PAPR reductio with ICI self-cacellatio scheme. I adjacet partitioig scheme, show i Fig 8.3, the two adjacet subcarriers related by +, {,,..., } remai i the same partitio ad preserve this relatio eve after multiplicatio with phase rotatio factor. 74

10 4th Partitio 3rd Partitio d Partitio st Partitio Sub-carrier Idex() Sub-carrier Idex() Sub-carrier Idex() Sub-carrier Idex() Figure 8.3: Adjacet partitioig scheme for ICI self-cacellatio, 6 ad S Partitioig scheme for ew ICI self-cacellatio scheme [4] I, ew ICI self-cacellatio scheme adjacet partitioig scheme or ay other covetioal partitioig scheme [6] caot be applied because i this scheme data symbols are repeated symmetrically with phase iversio i.e.,...,, ad, they should be ept i the same partitio for eepig ICI cacellig modulatio operatio udisturbed. I order to couple proposed PAPR reductio mechaism with ew ICI selfcacellatio scheme, i this chapter, we have proposed a ew partitioig scheme called Symmetrical Adjacet Partitioig. I symmetrical adjacet partitioig scheme, the symmetrically located subcarriers are lyig i the same sub-bloc; therefore it maitais the relatioship,, eve after multiplicatio of data,... symbols with phase rotatio factors. A example of symmetrical adjacet partitioig scheme for 6 subcarriers ad S 4 partitios is show i Fig

11 st Partitio d Partitio 5 5 Sub-carrier Idex() 5 5 Sub-carrier Idex() 3rd Partitio 5 5 Sub-carrier Idex() 4th Partitio 5 5 Sub-carrier Idex() Figure 8.4: Symmetrical adjacet partitioig scheme for ew ICI self-cacellatio, 6 ad S4 I symmetrical adjacet partitioig scheme, the frequecy domai OFDM symbol is () () () divided ito S 4 sub blocs {,, ad }, where each of the sub-bloc have r / S active subcarriers, ad the remaiig subcarriers are iactive i.e. while taig - poit IFFT of ay sub-bloc we have data symbols oly o r 4 subcarriers, ad remaiig th th r subcarriers are used for zero paddig. Therefore, the subcarriers i a s th sub- sr ( s + ) r ( s + ) r sr bloc with idices to ad + to, are ept active, while the remaiig subcarriers are used for zero paddig. The locatios of active subcarriers i a s th sub bloc are disjoit with the positios of active subcarriers of remaiig S partitios, ad therefore result i disjoit partitioig. (3) th th 76

12 8.5.3 Partitioig schemes for ICI cojugate cacellatio scheme [44] I ICI cojugate cacellatio, the data symbols are ot repeated with phase iversio o ay two subcarriers i a data bloc. Hece, ay oe of the covetioal partitioig scheme lie adjacet [6], iterleaved [6] ad proposed symmetrical adjacet partitioig schemes ca be used for sub-bloc formatio. 8.6 RESULTS AD DISCUSSIO We have cosidered a OFDM system with 56 subcarriers ad trasmissio of, OFDM symbols to evaluate the overall performace of the OFDM system. All the simulatios are carried out ad plots of theoretical results are evaluated i MATLAB eviromet. We have used CIR, PAPR ad SER performaces as a measure to verify the effectiveess of the proposed scheme. To evaluate the CIR, PAPR ad SER performaces of ICI cacellatio schemes without PAPR reductio, a QPSK modulated OFDM system is tae ito cosideratio. I order to evaluate CIR, PAPR ad SER performaces of ICI cacellatio schemes with proposed PAPR reductio mechaism, a quaterary to 8-PSK mappig based PTS-OFDM system with two phase factors {, j} ad four partitios is cosidered. The SER performaces of the schemes uder cosideratio are evaluated over both AWG ad SUI-5 fadig chael. To mitigate the effect of multipath propagatio of wireless chael, a CP of legth /3 OFDM symbol duratio is used. Fig. 8.5 shows the CIR performaces of ICI self-cacellatio, ew ICI self-cacellatio ad ICI cojugate cacellatio schemes with ad without PAPR reductio, as a fuctio of ormalized frequecy offset (ε ). I Fig. 8.5, the CIR performaces of ICI self-cacellatio, ew ICI self-cacellatio ad ICI cojugate cacellatio schemes without PAPR reductio are deoted by SC without PAPR Reductio, SC without PAPR Reductio ad CC without PAPR Reductio, respectively, whereas their performaces with PAPR reductio is deoted by SC with PAPR Reductio, SC with PAPR Reductio ad CC with PAPR Reductio, respectively. The result deoted by Stadard OFDM without ICI cacellatio represets the CIR of a OFDM sigal without ICI cacellatio. This is expected to be the worst result, but as see from Fig. 8.5, the CIR of ICI cojugate cacellatio scheme becomes worse tha stadard OFDM sigal without ICI cacellatio for ε >

13 CIR(dB) Stadard OFDM (without ICI Cacellatio) SC without PAPR Reductio SC with PAPR Reductio SC without PAPR Reductio SC with PAPR Reductio CC with PAPR Reductio CC without PAPR Reductio ormalized Frequecy Offset Figure 8.5: Compariso of CIR performace of ICI self-cacellatio, ew ICI self-cacellatio ad ICI cojugate cacellatio schemes with ad without PAPR reductio If we compare the CIR performace of ay ICI cacellatio scheme with ad without PAPR reductio the they are foud to be exactly same. This shows that ICI cacellatio schemes after couplig with proposed PAPR reductio scheme eeps ICI cacellatio operatio udisturbed. It ca be see from Fig. 8.5 that CIR performace of ew ICI self-cacellatio scheme is the best amog all three ICI cacellatio schemes uder cosideratio for ε <. 5. Forε >. 5, the CIR performace of ICI self-cacellatio is slightly better tha ew ICI self-cacellatio scheme. The CIR performace of ICI cojugate cacellatio scheme is foud to be slightly better tha ICI self-cacellatio scheme for ε <. 5. The CIR performaces of all the schemes [4]-[46] degrade with ε. Fig. 8.6 shows a compariso of PAPR performaces for ICI self-cacellatio, ew ICI selfcacellatio ad ICI cojugate cacellatio schemes with ad without PAPR reductio. The 78

14 PAPR performaces of ew ICI cojugate cacellatio [9] ad repeated correlative codig [] without PAPR reductio are also show i Fig. 8.6 ad are deoted by CC without PAPR Reductio ad Repeated Correlative Codig respectively. CCDF (Pr[PAPR>PAPR]) SC with PAPR Reductio(Sim.) CC with PAPR Reductio(Sim.) SC without PAPR Reductio(Sim.) SC without PAPR Reductio(Theo.) SC with PAPR Reductio(Sim.) CC without PAPR Reductio(Sim.) CC without PAPR Reductio(Theo.) CC without PAPR Reductio SC without PAPR Reductio(Sim.) SC without PAPR Reductio(Theo.) Repeated Correlative Codig PAPR [db] Figure 8.6: Compariso of PAPR performace of ICI self-cacellatio, ew ICI self-cacellatio ad ICI cojugate cacellatio schemes with ad without PAPR reductio I Fig. 8.6, the plot of theoretical results for CCDF of PAPR derived i sectio 8. are show. The theoretical results for ICI self-cacellatio, ew ICI self-cacellatio ad ICI cojugate cacellatio schemes without PAPR reductio are deoted by SC without PAPR Reductio (Theo.), SC without PAPR Reductio (Theo.) ad CC without PAPR Reductio (Theo.), whereas their respective simulatio results are deoted by SC without PAPR Reductio (Sim.), SC without PAPR Reductio (Sim.) ad CC without PAPR Reductio (Sim.). The theoretical results for PAPR performace cofirm the validity of their respective simulatio results. The PAPR performace of stadard OFDM sigal (ot show i graph) is exactly same as covetioal ICI cojugate cacellatio scheme. 79

15 The PAPR performaces of ew ICI self-cacellatio, ICI cojugate cacellatio ad ew ICI cojugate cacellatio schemes (without PAPR reductio), are very close. But PAPR performaces of ICI self-cacellatio ad repeated correlative codig schemes are foud to be about. db ad 3.8dB poorer tha that of stadard OFDM sigal, which cofirms the eed for PAPR reductio i these schemes. I all ICI cacellatio schemes uder cosideratio, the repeated correlative codig [] has the poorest PAPR performace, the mai reaso behid this performace degradatio is that it icreases the correlatio amog the data symbols ad leads to high pea formatio, which degrades the PAPR performace. Therefore, it [] achieves ICI cacellatio capability at the cost of icreased PAPR. If we compare, PAPR performaces of ICI self-cacellatio with ad without PAPR reductio the it is foud that the ICI self-cacellatio with proposed PAPR reductio mechaism provides.5db PAPR reductio over ICI self-cacellatio without PAPR reductio mechaism. Similarly, if we compare the PAPR performaces of ew ICI selfcacellatio with ad without PAPR reductio the it is foud that ew ICI self-cacellatio with PAPR reductio achieves about.db PAPR reductio capability. ICI cojugate cacellatio scheme with PAPR reductio mechaism also provides a PAPR reductio of.db. As see from Fig. 8.6, the PAPR performace of ew ICI self-cacellatio with PAPR reductio is the best amog all schemes uder cosideratio. Figs. 8.7 ad 8.8 show the SER performaces of stadard OFDM sigal, ICI selfcacellatio, ew ICI self-cacellatio, ICI cojugate cacellatio schemes with PAPR reductio, ew ICI cojugate cacellatio ad repeated correlative codig schemes without PAPR reductio, over AWG chael for ε. ad.. I Figs. 8.7 ad 8.8 their SER performaces are deoted by Stadard OFDM system without ICI cacellatio, SC with PAPR Reductio, SC with PAPR Reductio, CC with PAPR Reductio, CC without PAPR reductio ad Repeated Correlative Codig, respectively. It is see from Fig. 8.7, that stadard OFDM system without ICI cacellatio caot achieve a SER at a SR of 5 db, ad hece, it is foud to be usuitable for ay practical commuicatio system. The SER performace of the ICI cojugate cacellatio scheme with PAPR reductio is very much improved i compariso to stadard OFDM system without 5 ICI cacellatio, ad ca easily achieve a SER at a SR of 5 db. I Fig. 8.7, ICI self-cacellatio ad ew ICI self-cacellatio schemes with PAPR reductio are foud to have same SER performace ad require db less SR i compariso to ICI cojugate 4 cacellatio with PAPR reductio to achieve a SER. 8

16 - - SER CC without PAPR Reductio Repeated Correlative Codig SC with PAPR Reductio SC with PAPR Reductio CC with PAPR Reductio Stadard OFDM without ICI Cacellatio Eb/o(dB) Figure 8.7: Compariso of SER performace of stadard OFDM sigal, ew ICI cojugate cacellatio, Repeated correlative codig, ICI self-cacellatio, ew ICI self-cacellatio ad ICI cojugate cacellatio schemes with PAPR reductio over AWG chael for ε. The SER performaces of ew ICI cojugate cacellatio ad repeated correlative codig schemes are foud to be better tha the proposed ICI self-cacellatio, ew ICI selfcacellatio ad ICI cojugate cacellatio schemes with PAPR reductio. But, their PAPR performaces are iferior i compariso to the proposed ICI self-cacellatio, ew ICI selfcacellatio ad ICI cojugate cacellatio schemes with PAPR reductio, which restrict the usefuless of ew ICI cojugate cacellatio ad repeated correlative codig schemes. 8

17 - - SER -3-4 SC with PAPR Reductio SC with PAPR Reductio Repeated Correlative Codig CC without PAPR Reductio CC with PAPR Reductio Stadard OFDM without ICI Cacellatio Eb/o(dB) Figure 8.8: Compariso of SER performace of stadard OFDM sigal, ew ICI cojugate cacellatio, Repeated correlative codig, ICI self-cacellatio, ew ICI self-cacellatio ad ICI cojugate cacellatio schemes with PAPR reductio over AWG chael for ε. As see from Fig. 8.8, at higher values of ormalized frequecy offset ( ε.), the SER performaces of ew ICI cojugate cacellatio ad repeated correlative codig are better tha proposed ICI cojugate cacellatio with PAPR reductio. But ew ICI cojugate cacellatio scheme is ot able to achieve a SER of - at E b / o 5 db ad therefore foud usuitable for commuicatio systems, whereas repeated correlative codig ca easily achieve a SER -3 at same E b / o. But poor PAPR performace of repeated correlative codig restricts its applicatio. As see from Fig. 8.8, the proposed ICI self-cacellatio ad ew ICI cacellatio schemes with PAPR reductio are the oly two schemes, whose SER performaces are foud to be satisfactory. If we compare them the it is foud that SER performace of ICI self-cacellatio is slightly better tha the ew ICI self-cacellatio scheme. As see from Fig. 8.8, the ICI self-cacellatio scheme with PAPR reductio 8

18 requires about.7 db less E b / o i compariso to ew ICI self-cacellatio with PAPR reductio to achieve a SER -4. Figs. 8.9 ad 8. show the SER performaces of stadard OFDM system, ICI selfcacellatio, ew ICI self-cacellatio, ICI cojugate cacellatio schemes with PAPR reductio, ew ICI cojugate cacellatio ad repeated correlative codig schemes without PAPR reductio, over 3-tap SUI-5 fadig chael for ε. ad., ad these are deoted by Stadard OFDM system without ICI cacelatio, SC with PAPR Reductio, SC with PAPR Reductio, CC with PAPR Reductio, CC without PAPR Reductio ad Repeated Correlative Codig, respectively. - - SER -3-4 CC without PAPR Reductio SC with PAPR Reductio SC with PAPR Reductio CC with PAPR Reductio Repeated Correlative Codig Stadard OFDM without ICI Cacellatio Eb/o(dB) Figure 8.9: Compariso of SER performace of stadard OFDM sigal, ICI self-cacellatio, ew ICI selfcacellatio ad ICI cojugate cacellatio schemes with PAPR reductio over SUI-5 fadig chael for ε. As see from Figs. 8.9 ad 8., the SER performace of stadard OFDM sigal without ICI cacellatio over SUI-5 fadig chael is very poor, which maes it usuitable for ay commuicatio system. Over SUI-5 fadig chael, for ε., the SER performace of ICI self-cacellatio, ew ICI self-cacellatio, ICI cojugate cacellatio schemes with PAPR reductio ad ew ICI cojugate cacellatio without PAPR reductio are oly foud 83

19 suitable. But at higher values of carrier frequecy offset ( ε. ), the SER performace of ICI cojugate cacellatio scheme with PAPR reductio, repeated correlative codig ad ew ICI cojugate cacellatio scheme without PAPR reductio are ot foud suitable. Therefore, ICI self-cacellatio ad ew ICI self-cacellatio schemes with PAPR reductio are two viable choices for achievig good SER performaces at ε. ad.. As expected, ew ICI self-cacellatio scheme with PAPR reductio over fadig chael shows superior the SER performace i compariso to ICI self-cacellatio with PAPR reductio at ε. ad.. As see from Fig. 8.9, ew ICI self-cacellatio with PAPR reductio scheme over fadig chael requires about.3db less E b / o i compariso to ICI self-cacellatio with PAPR reductio scheme for achievig a SER -5, at ε., whereas this gai i E b / o is about.8 db for same SER at ε.. Therefore, we ca say that ew ICI self-cacellatio with PAPR reductio scheme has the best SER performace amog all schemes uder cosideratio. - - SER -3-4 SC with PAPR Reductio SC with PAPR Reductio CC with PAPR Reductio Repeated Correlative Codig CC without PAPR Reductio Stadard OFDM without ICI Cacellatio Eb/o(dB) Figure 8.: Compariso of SER performace of stadard OFDM sigal, ICI self-cacellatio, ew ICI selfcacellatio ad ICI cojugate cacellatio schemes with PAPR reductio over SUI-5 fadig chael for ε. 84

20 8.7 COCLUSIO I this chapter a M-M mappig based PTS scheme for reducig PAPR of covetioal ICI self-cacellatio, ew ICI self-cacellatio ad ICI cojugate cacellatio has bee proposed. The theoretical aalysis of PAPR for ICI cacellatio schemes uder cosideratio cofirms the requiremet of PAPR reductio. By the use of proposed symmetrical partitioig scheme it is possible to couple the M-M mappig based PTS scheme with ew ICI cacellatio, without disturbig the operatio of ICI cacellig modulatio. The proposed PAPR scheme after couplig with ay ICI cacellatio scheme uder cosideratio provides to.5db gai i PAPR reductio capability. The proposed joit PAPR reductio ICI cacellatio is free from SI. The SER performaces of ew ICI cojugate cacellatio, repeated correlative codig ad ICI cojugate cacellatio schemes are very poor at higher values of CFO, therefore ICI self-cacellatio with PAPR reductio ad ICI self-cacellatio with PAPR reductio are two viable choices from SER performace poit of view. The CIR, PAPR ad SER performace over AWG ad fadig chael cofirms that ew ICI self-cacellatio with M-M mappig based PTS scheme is the best choice. 85