Orthogonal frequency division multiplexing receiver system

Claim 2

An orthogonal frequency division multiplexing (OFDM) receiver system comprising: a receiving section for receiving an OFDM signal, converting the same into a digital signal and compensating for phase error and for frequency error of the digitally converted OFDM signal; a pilot signal decoding section for FFT-processing the output of the receiving section, and sequentially storing pilot signals and data separately according to a rearrangement rule; a synchronizing section for receiving the output of the pilot signal decoding section, performing coarse time synchronization, coarse frequency synchronization, frame synchronization, fine frequency synchronization and fine time synchronization, estimating a phase noise and correcting the same; an equalizing and deinterleaving section for performing a channel equalization algorithm on the output of the pilot signal decoding section using a reference pilot signal of the synchronizing section, restoring the equalized symbol into the original symbol, and rearranging the symbol in the order of the original symbol; and a controller for controlling the timing of data rearrangement in the pilot signal decoding section and feed-back controlling the receiving section according to the outputs of the respective synchronization results.

Claim 3

The OFDM receiver system according to claim 1 further comprising: a first complex multiplier for supporting the respective synchronization processes; a phase memory for supplying a phase offset for the output of the first complex multiplier to the synchronizing section; a coefficient memory for storing filter coefficients for supporting the channel equalization; a symbol memory for storing received data samples supplied from the synchronizing section; and a second complex multiplier for complex-multiplying the output of the coefficient memory and the output of the symbol memory and supplying the obtained OFDM demodulated sample to the equalizing and deinterleaving section.

Claim 4

The OFDM receiver system according to claim 1 , wherein the pilot signal decoding section comprises: a fast Fourier transform (FFT) processor for FFT-processing an input signal; a rearrangement table in which the order for storing pilot signals and data separately is stored; a memory for storing pilot signals and data are separately stored among the FFT-processed signals in accordance with the storage order for the rearrangement table; and a rearrangement controller for supplying input/output timings and input/output memory addresses and controlling the memory.

Claim 5

The OFDM receiver system according to claim 2 , wherein the synchronizing section comprises: a coarse time synchronization block for calculating an estimated value for coarse time synchronization; a coarse frequency synchronization block for calculating an estimated value for coarse frequency synchronization; a fine frequency synchronization block for calculating an estimated value for fine frequency synchronization; a fine time synchronization block for calculating an estimated value for fine time synchronization; a phase noise estimation block for calculating an estimated value for phase noise estimation and correction; a first memory for temporarily storing input/output data of the coarse time synchronization block; a second memory for temporarily storing input/output data of the coarse frequency synchronization block and the fine frequency synchronization block; a third memory for storing data input/output data of the coarse frequency synchronization block, the fine frequency synchronization block, the fine time synchronization block, the phase noise estimation block and the controller; a timing adjusting block for transmitting a control signal indicative of the starting timing of a time domain symbol to the pilot signal decoding section according to signals supplied from the coarse time synchronization block and the fine time synchronization block; a first switching block for serving to perform interfacing with the second memory shared by the coarse frequency synchronization block and the fine frequency synchronization block in a time-divisional manner; a second switching block for serving interfacing with the third memory shared by the coarse frequency synchronization block, the fine frequency synchronization block, the fine time synchronization block and the phase noise estimation block in a time-divisional manner; a third switching block for serving to perform interfacing for allowing the coarse time synchronization block, the coarse frequency synchronization block, the fine frequency synchronization block and the fine time synchronization block to share the first complex multiplier in a time-divisional manner.

Claim 6

The OFDM receiver system according to claim 4 , wherein the estimated value of the coarse time synchronization is obtained by the first complex multiplier for receiving the signal output from the receiving section through the third switching block, receiving 1+0j from the pilot signal decoding section, and multiplying two complex numbers, the phase memory for receiving the complex multiplication result and generating the corresponding phase function, and the coarse time synchronization block for receiving the phase function of the phase memory and obtaining a difference value between current neighboring samples, and a difference value between the neighboring samples delayed corresponding to the useful samples, subtracting the two difference values within the range of the window size set by the first memory, accumulating the subtraction results and obtaining the sum of the i-th window to obtain the estimated value of the coarse time synchronization.

Claim 7

The OFDM receiver system according to claim 5 , wherein a signal indicative of the timing for the coarse time synchronization is controlled by the timing adjusting block, and the symbol starting point is determined by the controller by detecting a threshold value.

Claim 8

The OFDM receiver system according to claim 4 , wherein in obtaining the estimated value of the coarse frequency synchronization using the corresponding CPC sample among signals FFT-processed by the pilot signal decoding section after applying a received signal to a frequency offset set by the receiving section, the synchronizing section for coarse frequency synchronization obtains the estimated value of the coarse frequency synchronization such that the synchronizing section receives the current CPC sample from the rearrangement memory, stores the same in the second memory through the first switching block, receives the previous CPC sample delayed by one symbol from the second memory, receives, for a period of one symbol, the multiplication result on the previous CPC sample converted into the conjugate complex and the complex number of the current CPC sample by means of the first complex multiplier to then accumulate real-number parts and imaginary-number parts.

Claim 9

The OFDM receiver system according to claim 7 , wherein the estimated value is stored in the third memory through the third switching block, peak values among the stored estimated values are detected by the controller to then determine the optimal frequency offset, and the receiving section is feed-back controlled according to the determined frequency offset.

Claim 10

The OFDM receiver system according to claim 8 , wherein the peaks are detected by a first peak detecting step of tracing a frequency offset within the range of ±½ of the distance between carriers, and a second peak detecting step of tracing a frequency offset within the finer range in which the distance between carriers is narrower.

Claim 11

The OFDM receiver system according to claim 4 , wherein the frame synchronization is performed such that TPS samples FFT-processed by the pilot signal decoding section and stored in the rearrangement memory, are read out, the TPS samples are stored in the third memory through the third switching block, the TPS samples delayed by a predetermined period and output from the third memory are supplied to the controller to perform the frame synchronization using TPS frame sync words inverted for each frame.

Claim 12

The OFDM receiver system according to claim 4 , wherein in obtaining the estimated value of the fine frequency synchronization using the corresponding pilot signals among the signals FFT-processed bu the pilot signal decoding section after a received signal is converted by an initial rotation factor via the receiving section, the fine frequency synchronization is performed such that the fine frequency synchronization block receives the current CPC sample from the rearrangement memory, stores the same in the second memory through the second switching block, receives the previous CPC sample delayed by one symbol from the second memory, converts the previous CPC sample into a conjugate complex number and supplies the same to the first complex multiplier through the third switching block, the first complex multiplier multiplies the current CPC sample with the conjugate complex number of the previous CPC sample to then transmit the multiplication result to the phase memory so that the phase value corresponding to the input applied thereto is supplied to the fine frequency synchronization block, and the fine frequency synchronization block receives outputs of the phase memory and integrates the same to obtain the estimated values.

Claim 13

The OFDM receiver system according to claim 11 , wherein the estimated values of the fine frequency synchronization are stored in the third memory through the second switching block to then be supplied to the controller and loop-filtered, and the mean value thereof is obtained to readjust the rotation factor of the receiving section, thereby performing feed-back controlling operation.

Claim 14

The OFDM receiver system according to claim 4 , wherein the fine time synchronization is performed by the fine time synchronizing section using the corresponding SPC samples FFT-processed by the pilot signal decoding section and stored in the rearrangement memory, the fine time synchronizing block converts the (j+1)-th SPC sample into a conjugate complex number and supplies the same to the first complex multiplier through the third switching block, the first complex multiplier multiplies the conjugate complex number of the j-th SPC sample with the conjugate complex number of the (j+1)-th SPC sample to then transmit the multiplication result to the phase memory, the phase memory outputs a phase value corresponding to the input applied thereto and supplies the same to the fine time synchronizing section, and the fine time synchronizing block integrates the phase value output from the phase memory to obtain the estimated value of the fine time synchronization.

Claim 15

The OFDM receiver system according to claim 13 , wherein the estimated value of the fine time synchronization is stored in the third memory through the second switching block to then be supplied to the controller, and the controller feed-back controls the gains of the time adjusting block and the receiving section.

Claim 16

The OFDM receiver system according to claim 4 , wherein the phase noise estimation and correction are performed such that among the signals FFT-processed by the pilot signal decoding section, the SPC sample is supplied to the fine frequency synchronization block, the fine frequency synchronization block multiplies the SPC sample with the conjugate complex number of the reference value of the SPC sample to then output the phase noise for each reference carrier, the phase noise estimation block receives the outputs of the fine frequency synchronization block and estimates phase noises present throughout one symbol.

Claim 17

The OFDM receiver system according to claim 15 , wherein the phase noise estimated by the phase noise estimation block is converted for correcting the phase noise of actual data to then be supplied to the first complex multiplier through the third switching block, the first complex multiplier receives the data sample stored in the pilot signal decoding section and multiplies the same with the conjugate complex number of the estimated phase noise to then transmit the phase-noise removed data sample to the equalizing and deinterleaving section.

Claim 18

The OFDM receiver system according to claim 1 , wherein the equalization is performed such that received channel-distorted sample data (SPC) are stored in the symbol memory, the equalizing and deinterleaving section receives the received SPC and the SPC reference value of the corresponding SPC position from the pilot signal decoding section and performs time-axis interpolation and frequency-axis interpolation to obtain a channel transmission function, thereby acquiring equalized data sample.

Claim 19

The OFDM receiver system according to claim 1 , wherein the controller can be implemented by a DSP chip.

Claim 20

The OFDM receiver system according to claim 1 , wherein the synchronizing section can be implemented by a FPGA chip.

Claim 21

The OFDM receiver system according to claim 1 , wherein the equalizing and deinterleaving section can be implemented by a FPGA chip.