Information transmission system
AssigneeLucent Technologies Inc.
InventorsAdriaan Kamerman, Anjur S. Krishnakumar
Life of this patent
Estimating the term…
Abstract
A system for transmitting information over an OFDM channel using phase shift keying encoding employs a bit mapping encoder to reduce the crest factor (ratio of peak voltage to RMS voltage). For a 16 subchannel OFDM system using QPSK encoding, a first set of four symmetrically positioned pairs of subchannels is used to encode two bits of information on each subchannel. A second set of four symmetrically positioned pairs of subchannels is used to encode only one bit of information on each subchannel, with the resultant phasor for each pair of the second set of pairs of subchannels being orthogonal to the resultant phasor for one of the pairs of the first set of subchannels. With this arrangement, the crest factor is reduced.
Claims11
A method of transmitting information over an OFDM (orthogonal frequency division multiplexing) channel having a plurality of OFDM subchannels, comprising the steps of:
- determining a first phasor axis for each pair of a first set of pairs of symmetrically positioned subchannels of said OFDM subchannels, the determination being dependent on the information to be transmitted over that subchannel pair;
- determining a second phasor axis for each pair of a second set of pairs of symmetrically positioned subchannels of said OFDM subchannels, the determined second phasor axis being dependent on information to be transmitted and being orthogonal to the first phasor axis of one of said first set of pairs of subchannels;
- and
- transmitting signals dependent on the determined first and second phasor axes over said OFDM subchannels.
An apparatus for transmitting information over an OFDM (orthogonal frequency division multiplexing) channel having a plurality of OFDM subchannels, comprising:
- bit mapping means for (1) determining a first phasor axis for each of a first set of symmetrically positioned subchannels of said OFDM subchannels in dependence on the information to be transmitted over that subchannel pair, and (2) determining a second phasor axis for each pair of a second set of pairs of symmetrically positioned subchannels of said OFDM subchannels in dependence on information to be transmitted, and such as to be orthogonal to the first phasor axis of one of said first pairs of subchannels;
- and
- transmitting means for transmitting signals having the determined first and second phasor axes over said OFDM subchannels.
Dependencies are inferred from the claim text.