Abstract
We address the problem of frequency synchronization in OFDM-based communications systems in the context of frequency-selective fading channels. Frequency offsets are estimated by inserting null sub-carriers into a single OFDM block. The paper clarifies issues related to acquisition range and identifiability of carrier frequency offset (CFO), and performance of estimators. A deterministic maximum likelihood estimation approach is adopted. We derive necessary and sufficient conditions on the number of null-subcarriers and their placement in order to ensure identifiability. The Cramér-Rao bound (CRB) for the CFO is derived; for a given number of null sub-carriers, the optimal placement which minimizes the CRB is derived. We show that if the number of null sub-carriers is less than half the total number of sub-carriers, performance is optimal when the null sub-carriers are equispaced.
Original language | English (US) |
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Title of host publication | Conference Record / IEEE Global Telecommunications Conference |
Pages | 202-206 |
Number of pages | 5 |
Volume | 1 |
State | Published - Dec 1 2001 |
Event | IEEE Global Telecommunicatins Conference GLOBECOM'01 - San Antonio, TX, United States Duration: Nov 25 2001 → Nov 29 2001 |
Other
Other | IEEE Global Telecommunicatins Conference GLOBECOM'01 |
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Country/Territory | United States |
City | San Antonio, TX |
Period | 11/25/01 → 11/29/01 |