ارزيابي عملكرد سيستم SC-FDMA در حضور انحراف هاي فركانسي

چكيده انگليسي :

Performance Evaluation of the SC FDMA System in Presense of Carrier Frequency Offset Sayyed Kazem Hashemizadeh sk hashemizadeh@ec iut ac ir Date of Submission 2012 2 12 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Mohammad Javad Omidi omidi@cc iut ac irAbstract Today the demand for multimedia wireless communications is growing at an extremely rapid pace andthis trend is expected to continue in the future The common feature of many current wireless standards forhigh rate multimedia transmission is the adoption of a multicarrier air interface based on orthogonalfrequency division multiplexing OFDM In OFDM a set of equally spaced subcarriers are used for paralleldata transmission There is currently a strong interest in extending the OFDM concept to multiusercommunication scenarios by employing orthogonal frequency division multiple access OFDMA and singlecarrier frequency division multiple access SC FDMA technologies A prominent example of this trend isthe 3GPP Long Term Evolution LTE physical layer where OFDM has been adopted as the basicmodulation technique that is new in cellular applications In an OFDMA system the available subcarriers are divided into several mutually exclusive sets assignedto different users for simultaneous transmission As in OFDMA the transmitters in an SC FDMA system usedifferent orthogonal subcarriers to transmit information symbols However they transmit the subcarrierssequentially rather than in parallel The SC FDMA has similar throughput performance and essentially thesame overall complexity as OFDMA Furthermore compared with OFDMA it has low peak to averagepower ratio PAPR property These systems inherit some disadvantages of OFDM beside its appealingfeatures Similar to OFDM OFDMA and SC FDMA are highly sensitive to carrier frequency offset CFO caused by oscillator instabilities and or wireless channel effects However the CFO is a more challenging issue on OFDMA and SC FDMA uplink systems wheredifferent users are affected by different CFOs Mutual orthogonality among the subcarriers in the presence ofCFO is lost and consequently inter carrier interference ICI and multi user interference MUI areintroduced In an SC FDMA system ICI leads to inter symbol interference ISI Currently OFDMA and SC FDMA are two competing technologies for the uplink of next generation broadband wireless systems so thestudy and comparison of these systems in different aspects are important Although the sensitivity analysis ofthe OFDM system to CFO has been investigated extensively in the literature but less studies on OFDMAuplink system have been reported and less focus has been applied to SC FDMA uplink system This thesis studies and compares OFDMA and SC FDMA systems in terms of sensitivity to CFO on theuplink In order to calculate signal to interference ratio SIR we use a simple superposition principleapproach where the effects of different users are studied separately We derive closed form mathematicalexpressions for desired signal and interference terms and consequently SIR for both OFDMA and SC FDMA systems on the uplink It is pointed out that there is a strong relation between sensitivity analysis toCFO and subcarrier allocation schemes We also prove that the derived expressions are reduced to verysimple forms in interleaved subcarrier allocation for both systems In addition the theoretical analysis areverified using Monte Carlo simulations in block interleaved and block interleaved subcarrier allocationsand upon this set of results the two systems are compared Finally a review on the important CFOcompensation methods on OFDMA and SC FDMA uplink systems is presented Keywords SC FDMA OFDMA Carrier frequency offset Inter carrier interference Multi userinterference Inter symbol interference SIR analysis CFO compensation methods

هاشمي زاده، كاظم

ارزيابي عملكرد سيستم SC-FDMA در حضور انحراف هاي فركانسي

سيستم OFDMA , تداخل هاي بين حاملي , بين كاربري و بين سمبلي , تحليل SIR , روش هاي تصحيح انحراف فركانس