Interleaver scheme in an OFDM system with multiple-stream data sources
AssigneeLucent Technologies Inc.
InventorsMohsen Sarraf, Mohammed Zarrabizadeh
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Abstract
A transmission system encodes blocks of source data with error correction codes and spreads encoded data for each source block over a range of time and frequencies. This has the effect of reducing the impact of flat fading. This is because if a portion of the encoded data corresponding to a block of source data is lost, as a result of flat fading during a time interval, other portions, transmitted at a different time, may not be affected. A receiving system may therefore recover the original block of source data based on the portions of the encoded data that were received, including error correction bits. The transmission and receiving systems may be orthogonal frequency division multiplexed (OFDM) communications systems.
Claims24
A transmission system for increasing the effectiveness of forward error correction (FEC), comprising:
- an encoder encoding blocks of source data by deriving error correction codes based on the blocks of source data and outputting a plurality of substreams of data including the error correction codes;
- a plurality of interleavers for reordering each substream;
- at least one delay unit for delaying at least one of the plurality of substreams relative to the other substreams;
- and
- a signal generation unit for modulating a plurality of subcarriers based on the interleaved substreams and upconverting the modulated subcarriers for transmission,
- wherein the plurality of subcarriers form one orthogonal frequency division multiplexed (OFDM) frame,
- wherein a separate OFDM frame includes each of the error correction codes, and
- wherein the error correction codes do not appear in consecutive OFDM frames.
A receiving system for receiving and recovering transmitted data, comprising:
- a receiver for down converting, demodulating and demultiplexing a received signal having a plurality of subcarriers into a plurality of interleaved substreams;
- at least one delay unit delaying at least one of the plurality of substreams relative to the other substreams to equalize a total delay for each substream;
- a plurality of de-interleavers for reordering each substream;
- and
- a decoder, receiving the reordered substreams, correcting errors present in the reordered substreams based on error correction data in the substreams and outputting decoded data,
- wherein the plurality of subcarriers form one orthogonal frequency division multiplexed (OFDM) frame,
- wherein a separate OFDM frame includes each of the error correction codes, and
- wherein the error correction codes do not appear in consecutive OFDM frames.
A communications system for increasing the effectiveness of forward error correction (FEC), including:
- a transmission system comprising
- an encoder encoding blocks of source data by deriving error correction codes based on the blocks of source data and outputting a plurality of transmission substreams of data including the error correction codes;
- a plurality of interleavers for reordering each transmission substream;
- at least one delay unit for delaying at least one of the plurality of transmission substreams relative to the other transmission substreams;
- and
- a signal generation unit for modulating a plurality of subcarriers based on the interleaved transmission substreams and upconverting the modulated subcarriers for transmission,
- wherein the plurality of subcarriers form one orthogonal frequency division multiplexed (OFDM) frame,
- wherein a separate OFDM frame includes each of the error correction codes, and
- wherein the error correction codes do not appear in consecutive OFDM frames;
- and
- a receiving system comprising
- a receiver for down converting, demodulating and demultiplexing the upconverted, modulated subcarriers into a plurality of interleaved, received substreams, each received substream corresponding to one of the transmission substreams;
- at least one delay unit delaying at least one of the plurality of received substreams relative to the other received substreams to equalize a total delay among the received substreams and their corresponding transmission substreams;
- a plurality of de-interleavers for reordering each received substream;
- and
- a decoder, receiving the reordered received substreams, correcting errors present in the reordered, received substreams based on error correction data in the received substreams and outputting decoded data.
A method for increasing the effectiveness of forward error correction (FEC) in a transmission system, comprising:
- encoding blocks of source data by deriving error correction codes based on the blocks of source data;
- outputting a plurality of substreams of data including the error correction codes;
- delaying at least one of the plurality of substreams relative to the other substreams;
- and
- modulating a plurality of subcarriers based on the substreams,
- wherein the plurality of subcarriers form one orthogonal frequency division multiplexed (OFDM) frame,
- wherein a separate OFDM frame includes each of the error correction codes, and
- wherein the error correction codes do not appear in consecutive OFDM frames.
A method for receiving and recovering transmitted substreams of data including error correcting codes, comprising:
- down converting a received signal having a plurality of subcarriers;
- demodulating the plurality of subcarriers into a plurality of substreams, each substream including error correction data;
- delaying at least one of the plurality of substreams relative to the other substreams to equalize a total delay among all of the substreams;
- decoding the substreams to correct errors present in the substreams based on the error correction data in the substreams;
- and
- outputting the corrected substreams,
- wherein the plurality of subcarriers form one orthogonal frequency division multiplexed (OFDM) frame,
- wherein a separate OFDM frame includes each of the error correction codes, and
- wherein the error correction codes do not appear in consecutive OFDM frames.
Dependencies are inferred from the claim text.