Timing control in orthogonal frequency division multiplex systems based on effective signal-to-noise ratio
First Claim
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1. A method comprising:
- using a current time reference to decode a plurality of orthogonal frequency division multiplex (OFDM) symbols in a plurality of time slots;
measuring a packet error rate of the decoded OFDM symbols;
determining an effective signal-to-noise ratio (SNR) metric from pilot tones of the demodulated OFDM symbols;
based on the determined effective SNR metric, predicting a supportable packet error rate;
comparing the measured packet error rate and the predicted packet error rate; and
based on said comparing, adjusting the current time reference before decoding a next OFDM time slot.
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Abstract
A spread-spectrum communication system provides an effective signal-to-noise ratio (SNR) of received orthogonal frequency division multiplex (OFDM) slots in the presence of timing errors. Effective SNR can serve as a diagnostic tool for determining whether there was a timing error when a measured packet error rate (PER) remains high, and a predicted PER from the effective SNR remains low. A loop can use the effective SNR to control a time reference used by an OFDM decoder.
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Citations
35 Claims
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1. A method comprising:
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using a current time reference to decode a plurality of orthogonal frequency division multiplex (OFDM) symbols in a plurality of time slots; measuring a packet error rate of the decoded OFDM symbols; determining an effective signal-to-noise ratio (SNR) metric from pilot tones of the demodulated OFDM symbols; based on the determined effective SNR metric, predicting a supportable packet error rate; comparing the measured packet error rate and the predicted packet error rate; and based on said comparing, adjusting the current time reference before decoding a next OFDM time slot. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. An apparatus configured to receive signals from a base station, the apparatus comprising:
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means for using a current time reference to decode a plurality of orthogonal frequency division multiplex (OFDM) symbols in a plurality of time slots; means for measuring a packet error rate of the decoded OFDM symbols; means for determining an effective signal-to-noise ratio (SNR) metric from pilot tones of the decoded OFDM symbols; based on the determined effective SNR metric, means for predicting a supportable packet error rate; means for comparing the measured packet error rate and the predicted packet error rate; and based on said means for comparing, means for adjusting the current time reference before decoding a next OFDM time slot. - View Dependent Claims (16)
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17. An apparatus configured to receive orthogonal frequency division multiplex (OFDM) symbols from a base station, the apparatus comprising:
a timing control module configured to; determine if a measured packet error rate of the received OFDM symbols is greater than a first threshold value; determine if a predicted packet error rate is less than a second threshold value; and if the measured packet error rate is greater than the first threshold value, and the predicted packet error rate is less than the second threshold value, then adjust a current time reference before decoding a next OFDM time slot. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A computer program product, comprising:
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a computer-readable medium comprising; code for using a current time reference to decode a plurality of orthogonal frequency division multiplex (OFDM) symbols in a plurality of time slots; code for measuring a packet error rate of the decoded OFDM symbols; code for determining an effective signal-to-noise ratio (SNR) metric from pilot tones of the demodulated OFDM symbols; code for, based on the determined effective SNR metric, predicting a supportable packet error rate; code for comparing the measured packet error rate and the predicted packet error rate; and code for, based on said comparing, adjusting the current time reference before decoding a next OFDM time slot. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35)
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Specification