The present invention relates to an orthogonal frequency-division multiplexing receiver, and more particular to an orthogonal frequency-division multiplexing receiver including an FFT/IFFT operating core and a scheduler. In order to simultaneously share the FFT/IFFT operating core, the scheduler manages input/output timings of FFT/IFFT operations and control signals. The FFT/IFFT operating core supports decimation-in-time (DIT) and decimation-in-frequency (DIF) FFT/IFFT operations at the same time.
1. An ODFM receiver, comprising:
an FFT/IFFT operation core; and
a scheduler, the scheduler managing input/output timings of FFT/IFFT operations and control signals for simultaneously sharing the FFT/IFFT operating core, wherein the FFF/IFFF operating core simultaneously supports a decimation-in-time (DIT) FFT/IFFT operation and a decimation-in-frequency (DIF) FFT/IFFT operation;
wherein interface specifications in the FFT/IFFT operating core interfacing with the scheduler are used for sending and receiving signals via Rx Input (RI), Sharing Input (SI), Sharing Output (SO), and Extra Output (EO) ports;
wherein for a channel estimation to simultaneously operate three FFT/IFFT operations, the single FFT/IFFT operation core is shared in an OFDM symbol for processing DIT-FFF, DIF-IFFT, DIT-FFT operations in turn, and an operating clock over 4 times of an FFT input data rate is used.
2. The ODFM receiver of claim 1 , wherein the FFT/IFFT operations received by the scheduler are divided into an acquisition state and a tracking state, and an FFT for a main OFDM symbol (FFT_MAIN) operation, an FFT for Pre-Sync CID (FFT for Co-Channel Interference detection before OFDM Sync; FFT_PRE_CID) operation, and an IFFT for integer frequency offset estimation (IFFT_IFO) operation are requested from the scheduler in the acquisition state, and an FFT_MAIN operation, an IFFT for channel estimation (IFFT_CE) operation, an FFT for channel estimation (FFT_CE operation), an IFFT for fine time synchronization (IFFT_FTSYNC) operation, an FFT for Post-Sync CID (FFT for Co-Channel Interference detection after OFDM Sync; FFT_POST_CID) operation, and an FFT for measurement of frequency Doppler (FFT_MFD) operation are requested from the scheduler in the tracking state.
3. The ODFM receiver of claim 2 , wherein the FFT_PRE_CID operation in the acquisition state is utilized for a co-channel interference estimation, and the IFFT_IFO operation is utilized for an integer frequency offset estimation, and the FFT_PRE_CID operation and the IFFT_IFO operation are performed through sharing an FFT/IFFT operating core.
4. The ODFM receiver of claim 1 , wherein for calculating an Fine symbol positioning value to processing an IFFT operation, the single FFT/IFFT operation core is shared in an OFDM symbol for processing DIT-FFT, DIF-IFFT, DIT-FFT operations in turn, and an operating clock over 6 times of an FFT input data rate is used.
5. The ODFM receiver of claim 1 , wherein when the FFT/IFFT operating core performs an operation, the scheduler makes an additional FFT operation can be performed in a nonworking interval corresponding to a working interval of an FFT size*¾.
6. The ODFM receiver of claim 5 , wherein the additional FFT operation performed through the scheduler can perform N-point FFT operations.
7. The ODFM receiver of claim 1 , wherein the RI is utilized to storage dedicated inputs, which are time-domain sample data being the same size as an FFT and being slowly input in ⅙ of an operating clock frequency.
8. The ODFM receiver of claim 1 , wherein the SI is utilized to receive shared FFT/IFFT inputs of each assigned interval.