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dc.contributor.advisorSaadat Mehr, Aryanen_US
dc.creatorKhizir, Zobayer Abdullahen_US
dc.date.accessioned2009-08-05T20:56:50Zen_US
dc.date.accessioned2013-01-04T04:51:08Z
dc.date.available2010-08-13T08:00:00Zen_US
dc.date.available2013-01-04T04:51:08Z
dc.date.created2009en_US
dc.date.issued2009en_US
dc.date.submitted2009en_US
dc.identifier.urihttp://hdl.handle.net/10388/etd-08052009-205650en_US
dc.description.abstractOrthogonal Frequency Division Multiplexing (OFDM) is a multicarrier modulation technique which is robust against multipath fading and very easy to implement in transmitters and receivers using the inverse fast Fourier transform and the fast Fourier transform. A guard interval using cyclic prefix is inserted in each OFDM symbol to avoid the inter-symbol interference. This guard interval should be at least equal to, or longer than the maximum delay spread of the channel to combat against inter-symbol interference properly. In coherent detection, channel estimation is required for the data detection of OFDM systems to equalize the channel effects. One of the popular techniques is to insert pilot tones (reference signals) in OFDM symbols. In conventional method, pilot tones are inserted into every OFDM symbols. Channel capacity is wasted due to the transmission of a large number of pilot tones. To overcome this transmission loss, incoherent data detection is introduced in OFDM systems, where it is not needed to estimate the channel at first. We use differential modulation based incoherent detection in this thesis for the data detection of OFDM systems. Data can be encoded in the relative phase of consecutive OFDM symbols (inter-frame modulation) or in the relative phase of an OFDM symbol in adjacent subcarriers (in-frame modulation). We use higher order differential modulation for in-frame modulation to compare the improvement of bit error rate. It should be noted that the single differential modulation scheme uses only one pilot tone, whereas the double differential uses two pilot tones and so on. Thus overhead due to the extra pilot tones in conventional methods are minimized and the detection delay is reduced. It has been observed that the single differential scheme works better in low SNRs (Signal to Noise Ratios) with low channel taps and the double differential works better at higher SNRs. Simulation results show that higher order differential modulation schemes don¡¯t have any further advantages. For inter-frame modulation, we use single differential modulation where only one OFDM symbol is used as a reference symbol. Except the reference symbol, no other overhead is required. We also perform channel estimation using differential modulation. Channel estimation using differential modulation is very easy and channel coefficients can be estimated very accurately without increasing any computational complexity. Our simulation results show that the mean square channel estimation error is about ¡¼10¡½^(-2) at an SNR of 30 dB for double differential in-frame modulation scheme, whereas channel estimation error is about ¡¼10¡½^(-4) for single differential inter-frame modulation. Incoherent data detection using classical DPSK (Differential Phase Shift Keying) causes an SNR loss of approximately 3 dB compared to coherent detection. But in our method, differential detection can estimate the channel coefficients very accurately and our estimated channel can be used in simple coherent detection to improve the system performance and minimize the SNR loss that happens in conventional method.en_US
dc.language.isoen_USen_US
dc.subjectIncoherent Detectionen_US
dc.subjectData Detectionen_US
dc.subjectDifferential Modulationen_US
dc.subjectCoherent Detectionen_US
dc.subjectChannel Estimationen_US
dc.subjectBERen_US
dc.subjectPilot Tonesen_US
dc.subjectOFDMen_US
dc.subjectOFDM Systemsen_US
dc.titleData Detection and Channel Estimation of OFDM Systems Using Differential Modulationen_US
thesis.degree.departmentElectrical Engineeringen_US
thesis.degree.disciplineElectrical Engineeringen_US
thesis.degree.grantorUniversity of Saskatchewanen_US
thesis.degree.levelMastersen_US
thesis.degree.nameMaster of Science (M.Sc.)en_US
dc.type.materialtexten_US
dc.type.genreThesisen_US
dc.contributor.committeeMemberFotouhi, Rezaen_US
dc.contributor.committeeMemberKasap, Safa O.en_US
dc.contributor.committeeMemberDinh, Anh vanen_US


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