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Carrier Frequency Offset Compensation with Successive Cancellation in Uplink OFDMA Systems. Tevfik Yucek, Student Member,IEEE,and Huseyin Arsla n,Senior Member,IEEE Wireless Communications, IEEE Transactions on Volume 6, Issue 10, October 2007 Page(s):3546 - 3551 學生 : 陳威宇 學號 :96325513. - PowerPoint PPT Presentation
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Carrier Frequency Offset Compensation with Successive Cancellation in Uplink OFDMA
Systems
Tevfik Yucek,Student Member,IEEE,and Huseyin Arslan,Senior Member,IEEE
Wireless Communications, IEEE Transactions onVolume 6, Issue 10, October 2007 Page(s):3546 - 3551
學生 :陳威宇學號 :96325513
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Outline
• Introduction• System Model• Proposed Compensation Algorithm• Numerical Results• Conclusions• Reference
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Ⅰ. Introduction
• OFDMA - orthogonal frequency division multiple access
- subcarriers -> grouped into sets & assigned to different user
• CFO - carrier frequency offset - mismatch of the oscillators in the transmitter and the receiver
• In the uplink of an OFDMA - inter-carrier interference ,ICI multiple access interference , MAI
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Introduction ICI- the leakage or interference between a user’s own subcarriers
MAI-the power leakage from user’s subcarriers
• Two main approaches,can be used to mitigate the frequency offset in the uplink of OFDMA
- feedback and compensation method
• In this paper,present SIC (successive interference cancellation) method for frequency offset compensation assuming that
- perfect timing alignment - frequency offset of all uplink users are known at the receiver
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Ⅱ . System Model• OFDMA system with D users and N subcarriers• The IDFT output of ith user can be written as
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System Model• Assuming perfect time synchronization , discrete-time model of the rec
eived signal at the BS after removal of the CP can be written as
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System Model• The DFT output can be obtained as
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System Model• Assuming , the received signal in kth subcarrier can be written as
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System Model
• Clustered subcarrier assignment scheme where subcarriers are grouped into clusters
and each clusters is assigned to a different user
- Clustered =>size K
- total number of clustered is N/K
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Ⅲ. Proposed Compensation Algorithm
• Combination A. Decorrelation - remove the ICI effect B. Successive Cancellation - solve the MAI problem
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A. Decorrelation• In the receiver , the DFT output for cth cluster ,
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Decorrelation• The decorrelator output can be calculated using (8) as
• Using and the channel knowledge , the receiver can detect the transmitted information.
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B. Successive Cancellation• The interference of cth cluster
• The uth subcarrier`s value after removal of MAI from cth cluster becomes
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Successive Cancellation• proof
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Ⅳ . Numerical Results• An uplink OFDMA system parameter
subcarrier : 256 users: 8
clusters for each user : 8 transmission bandwidth : 10 MHz
channel : A of ITU-R channel model for vehicular environments with high antenna[13]
IMT-2000 frequency offset : independent for all user
random variable with uniform distribution(-єmax ,єmax)
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Numerical Results
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Numerical Results
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Numerical Results
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Numerical Results
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Ⅴ. Conclusions
• The proposed method , a combination of decorrelator and successive cancelation , can compensate the different frequency offsets of users with manageable complexity .
• We have proposed to apply SIC to only neighboring subcarriers in order to decrease the computational complexity.
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Ⅵ . Reference• [5] J Choi; C. Lee; H. W. Jung and Y. H. Lee; “ carrier fre
quency offset compensation for uplink of ofdm-fdma systems,”IEEE Trans. Commun. ,vol.53,no.7,pp. 1155-1165,July 2005
• [9] T. Yucek , “ Self-interference handling in OFDM based wireless communication systems,” Master’s thesis , University of South Florida,Nov.2003.