Pulse or digital communications – Receivers – Angle modulation
Reexamination Certificate
2007-09-04
2007-09-04
Patel, Jay K. (Department: 2611)
Pulse or digital communications
Receivers
Angle modulation
C375S322000, C375S329000
Reexamination Certificate
active
10174417
ABSTRACT:
A frequency offset estimator is employed that estimates the frequency offset in signal frames that include only binary Phase-Shift Keying (BPSK) carriers in OFDM systems. Specifically, the offset frequency estimator takes advantage of those OFDM systems in which some OFDM symbols only have carriers with either zero or the BPSK constellations. In many WLAN systems such as the system described in standard IEEE802.11a, transmission frames include only BPSK symbols, which are used for training and other services. By making use of these BPSK symbols in each frame, a very accurate estimate of frequency offset can be obtained. By advantageously employing the frequency offset estimator of this invention, a carrier recovery system can achieve high performance even under strong ISI and low SNR. In a specific embodiment of the invention, BPSK carriers spread to be on a line in a complex plane at an angle to the real axis. An estimate of the angle of the line including the BPSK carriers is then employed to obtain an estimate of the frequency offset.
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Ejaz Naheed
Lucent Technologies - Inc.
Patel Jay K.
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