OFDM transmission/reception system and transmitting/receiving apparatus
First Claim
1. An orthogonal frequency division multiplexing (OFDM) transmission/reception system comprising:
- transmission means for;
setting some or all of a plurality of equidistant carrier positions as reference carrier positions;
assigning actual transmitted carriers on those of said reference carrier positions which are located in a predetermined non-equidistant pattern to yield an OFDM symbol; and
periodically transmitting said OFDM symbol as frequency reference symbols; and
receiver means for;
detecting said frequency reference symbols as a carrier reception pattern by detecting whether carriers exist or not at said reference carrier positions;
detecting a carrier frequency offset based on a difference between said reception pattern and a transmission pattern; and
compensating for frequencies of carriers in accordance with said carrier frequency offset.
1 Assignment
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Accused Products
Abstract
This invention improves the frequency acquisition range and the resistance to multipath interference. In a digital signal transmission system using OFDM, on the transmission side, some or all of a plurality of equidistant carrier positions are treated as reference carrier positions. The actual transmitted carriers are arranged in a predetermined pattern non-equidistant to the frequency carrier positions to form an OFDM symbol. This OFDM symbol is periodically transmitted as frequency reference symbols. On the reception side, the carrier arrangement pattern of the frequency reference symbols is detected, a carrier frequency offset is detected from the detected pattern offset, and the carrier frequency is compensated based on the frequency offset.
327 Citations
15 Claims
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1. An orthogonal frequency division multiplexing (OFDM) transmission/reception system comprising:
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transmission means for; setting some or all of a plurality of equidistant carrier positions as reference carrier positions; assigning actual transmitted carriers on those of said reference carrier positions which are located in a predetermined non-equidistant pattern to yield an OFDM symbol; and periodically transmitting said OFDM symbol as frequency reference symbols; and receiver means for; detecting said frequency reference symbols as a carrier reception pattern by detecting whether carriers exist or not at said reference carrier positions; detecting a carrier frequency offset based on a difference between said reception pattern and a transmission pattern; and compensating for frequencies of carriers in accordance with said carrier frequency offset. - View Dependent Claims (2, 3, 4, 5)
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6. An OFDM transmitting apparatus comprising:
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reference symbol generating means for generating data for frequency reference symbols corresponding to non-equidistant positions among carrier positions assigned at equidistances along a frequency axis; multiplexing means for multiplexing at least data for said frequency reference symbols and data for a main information symbol; OFDM modulation means for performing OFDM modulation on a plurality of carriers with an output of said multiplexing means; and quadrature modulation means for performing quadrature modulation on an output of said OFDM modulation means. - View Dependent Claims (7, 8, 9, 10)
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11. An OFDM receiving apparatus comprising:
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carrier generating means for generating carriers; quadrature demodulation means for receiving an OFDM modulation wave including a frequency reference symbol and performing quadrature demodulation of said OFDM modulation wave with the output of said carrier generating means; OFDM demodulation means for performing OFDM demodulation using an output of said quadrature demodulation means; first frequency control means for detecting a carrier frequency offset using said output of said quadrature demodulation means and supplying a first carrier compensation signal based on said carrier frequency offset to said carrier generating means; and second frequency pattern of transmitted carries using an frequency reference symbol included in an OFDM demodulation output from said OFDM demodulation means, comparing said detected carrier arrangement pattern with a predetermined carrier arrangement pattern to detect a carrier frequency offset and supplying a second carrier compensation signal based on that frequency offset to said carrier generating means. - View Dependent Claims (12, 13, 14, 15)
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Specification