Multi-symbol encapsulated OFDM system
AssigneeHer Majesty the Queen in right of Canada, as represented by the Minister of Industry, through the Communications Research Centre Canada
InventorsXianbin Wang, Yiyan Wu
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Abstract
A method and system for communication of information in OFDM format are disclosed. The method employs multi-symbol encapsulation (MSE), wherein multiple OFDM symbols are grouped together in cyclic frames having a single cyclic guard portion, for example a cyclic prefix, with multiple OFDM symbols sandwiched between each two consecutive cyclic guard portions. All OFDM symbols of one frame are equalized together at the receiver in a frequency domain using a single DFT/IDFT operation sequence. Embodiments of the MSE OFDM system are disclosed enabling high bandwidth efficiency, high tolerance to carrier frequency offset and low peak-to-average power ratio.
Claims20
An OFDM receiver for receiving a multi-symbol encapsulated (MSE) OFDM signal transmitted along a transmission channel, said MSE OFDM signal comprising a preamble sequence having a pre-determined structure, the OFDM receiver comprising:
- an A/D converter for sampling the received OFDM signal at a sampling frequency and for producing a sequence of received waveform samples;
- a synchronization and channel estimation unit adapted to identify the preamble sequence in the sequence of received waveform samples and to perform channel and frequency offset estimation from the received preamble sequence and the pre-determined structure of the preamble sequence;
- a cyclic guard removing unit adapted to identify information-bearing OFDM frames in the sequence of received waveform samples, to remove the cyclic guard portions from each identified OFDM frame and to produce a sequence of guard-removed OFDM frames;
- a channel equalizer, comprising:
- first processing means adapted to perform at least an M×N points DFT and M×N complex multiplications for converting the guard-removed OFDM frames to frequency domain, and for frequency-domain equalization to produce a sequence of equalized frame spectra;
- and,
- second processing means adapted to perform at least an M×N point inverse DFT on each equalized frame spectrum to produce a sequence of equalized guard-less OFDM frames, each comprising M OFDM symbols;
- third processing means adapted for splitting the equalized frame into M OFDM symbols, performing M N-point inverse DFTs for demodulating the equalized guard-less OFDM frames and for producing a set of M×N received m-ary symbols from each equalized OFDM frame;
- and,
- a parallel-to-serial converter adapted to convert the set of M×N received m-ary symbols into a received sequence of m-ary data symbols.
A method for an orthogonal frequency division multiplexing (OFDM) transmission comprising:
- converting an input sequence of data symbols into a sequence of OFDM frames, wherein each said OFDM frame comprises a sequence of M>1 OFDM symbols and only one cyclic guard portion, using the steps of:
- sequentially performing frequency domain multiplexing of M subsets of N>1 data symbols using an N-point inverse DFT for producing a sequence of M N-point OFDM symbols, and
- forming an OFDM frame from the sequence of M N-point OFDM symbols by appending a cyclic guard portion at an end thereof;
- and,
- performing digital-to-analog (D/A) conversion of the sequence of OFDM frames for producing an OFDM signal;
- transmitting the OFDM signal along a transmission channel;
- receiving the OFDM signal with an OFDM receiver;
- and,
- equalizing and demodulating the OFDM signal;
- wherein the step of equalizing and demodulating the OFDM signal includes the steps of:
- sampling the received OFDM signal at a sampling frequency fs to produce a sequence of waveform samples;
- identifying OFDM frames in the sequence of waveform samples;
- and, for each identified OFDM frame,
- removing P waveform samples from the OFDM frame to produce a sequence of M×N waveform samples,
- performing frequency-domain equalization of the sequence of M×N waveform samples, and
- demodulating the sequence of M×N waveform samples using M N-point DFTs for producing an output sequence of M×N m-ary data symbols;
- wherein the step of performing frequency-domain equalization comprises the steps of:
- computing a multi-symbol frequency spectrum of the sequence of M×N waveform samples using an M×N points DFT;
- performing element-by-element division of the multi-symbol frequency spectrum by a channel transfer function;
- computing an equalized multi-symbol sequence of M×N waveform samples using an inverse DFT.
Dependencies are inferred from the claim text.