Abstract:
PURPOSE: A blind-based frequency offset estimation method is provided to increase the performance in an irregular noise environment OFDM(Orthogonal Frequency Division Multiplexing) system. CONSTITUTION: A frequency offset estimation method includes a stage(S101) of receiving a reception signal in a protective range and an OFDM(Orthogonal Frequency Division Multiplexing) signal range, a stage(S102) of calculating the number of samples in the protective range the same with the number of samples in the reception signal including the same signal in the later part of the protective range and OFDM signal range, a stage(S103) summing the calculated samples, a stage(S104) of calculating an angle from the summed signal of the samples and a stage(S105) of calculating a frequency offset estimation value based on the calculated angle. [Reference numerals] (AA) Start; (BB) End; (S101) Step of receiving a reception signal in a protective range and an OFDM signal range; (S102) Step of obtaining samples amounting to the number of samples(N_G) in the protective range from the reception signal; (S103) Step of adding up the samples; (S104) Step of calculating an angle from the summed signal of the samples; (S105) Step of calculating a frequency offset estimation value from the calculated angle;
Abstract:
샘플 표준 편차를 기초로 한 다중 경로 페이딩 채널에서 OFDM 시스템을 위한 타이밍 옵셋 추정 방법 및 이러한 방법을 사용하는 장치가 개시되어 있다. 타이밍 옵셋 추정 방법은 OFDM 수신 신호를 입력으로 하는 제1 함수를 이용해 제1 타이밍 옵셋을 추정하고, 상기 제1 타이밍 옵셋을 이용하여 산출된 제1 구간에서 프리앰블 신호 및 OFDM 수신 신호를 입력으로 하는 제2 함수를 이용해 제2 타이밍 옵셋 및 제1 타이밍 매트릭을 산출하는 단계와 제2 타이밍 옵셋을 기초로 산출된 제2 구간에서 제1 타이밍 매트릭의 표준 편차값을 입력으로 하는 제3 함수를 이용해 제3 타이밍 옵셋을 산출하는 단계를 포함할 수 있다. 따라서, 타이밍 옵셋을 추정 시 신호 경로 성분의 랜덤성에 강인한 특성을 갖는다.
Abstract:
PURPOSE: A method and an apparatus of estimating a frequency offset based on training symbols in a wireless communication system are provided to improve estimation performance of the frequency offset under various noise environments including non-normal distribution noise as well as normal distribution noise. CONSTITUTION: A method of estimating a frequency offset based on training symbols in a wireless communication system comprise of: receiving signals comprising N samples(S101); obtaining N/2 samples from the received signals(S102); summing the N/2 samples(S103); finding an angle from the sum of N/2 samples(S104); and calculating an offset estimate based on the angle(S1050). [Reference numerals] (AA) Start; (BB) End; (S101) Step of receiving input signals; (S102) Step of obtaining N/2 samples from the received signals; (S103) Step of summing the N/2 samples; (S104) Step of finding an angle from the sum signal of the N/2 samples; (S105) Step of calculating an offset estimate from the found angle;
Abstract:
PURPOSE: A frequency offset estimation method and apparatus based on local optimum estimation in a wireless communication system are provided to estimate a frequency offset with high performance in various noise environments by using a frequency offset estimation method. CONSTITUTION: A frequency offset based on the initial offset of a OFDM(Orthogonal Frequency Division Multiplexing) reception signal having non-uniform noise and guard interval(GI) and local optimum estimation(LOE) section is estimated. A frequency offset having the minimum difference between the frequency offset of the each estimated LOE section and the initial offset of the each LOE section is selected as the final frequency offset. A frequency offset of the each LOE section is estimated by a predetermined equation. A non-uniform noise included in the OFDM reception signal has the Cauchy distribution. [Reference numerals] (AA) Received signal; (BB) Selecting ε^p with minimum |ε^p-ε_p|; (CC) Final estimated value
Abstract:
PURPOSE: A frequency offset estimation method using repeated training symbol in an OFDM system is provided to offer a proper standard of use by determining a frequency estimation technique corresponding to the situation. CONSTITUTION: An OFDM symbol regarding the simulation for estimating the frequency offset. The generated OFDM symbol is transmitted in AWGN(additive white Gaussian noise) environment or Rayleigh channel. The OFDM symbol is received. The frequency offset of the received OFDM symbol is estimated using each frequency offset estimation technique. The mean square error(MSE) of the estimated frequency offset is obtained. The obtained MSE using the frequency offset estimation method is compared with the signal to noise ratio. According to the compared results, the optimal frequency offset technique is decided. [Reference numerals] (AA) Generating an OFDM symbol; (BB) Transmission; (CC) Setting normalization frequency offset; (DD) Comparing accuracy and selecting an optimal technique
Abstract:
PURPOSE: A method for analyzing performance of a spectrum sensing technique based on Cyclostationarity is provided to select a spectrum sensing technique of excellent performance according to channel characteristics by comparing detection probability performance. CONSTITUTION: An OFDM(Orthogonal Frequency Division Multiplexing) symbol is obtained for an OFDM signal(S100). An autocorelation function is calculated using the symbol of the OFDM signal(S200) A CAF(Cyclic Autocorrelation Function) is calculated using the autocorelation function(S300). SCD(Spectral Correlation Density) is calculated using a cyclic autocorrelation function(S400). Test statistics are calculated(S500). The spectrum sensing performance of each techniques is determined through SNR(Signal Noise Ratio) comparison based on the test statistics of techniques(S600). [Reference numerals] (AA) Start; (BB) End; (S100) Symbol acquisition step; (S200) Autocorrelation function calculation step; (S300) CAF calculation step; (S400) SCD calculation step; (S500) Test statistics calculation step; (S600) Performance evaluation step
Abstract:
PURPOSE: An orthogonal frequency division multiplexing(OFDM) receiver which estimates timing in a multi-path fading channel, an OFDM system including the same, and a timing estimation method thereof are provided to improve timing estimation performance by eliminating timing errors. CONSTITUTION: A first timing estimation part(110) calculates a timing metric value based on an autocorrelation function of a received signal including a baseband orthogonal frequency division multiplexing(OFDM) sample signal. The first timing estimation part calculates a first timing estimation value based on the calculated timing metric value. A second timing estimation part(120) calculates a filtered timing metric value based on a cross-correlation function between the received signal and a preamble signal in a first timing estimation range based on the first timing estimation value. The second timing estimation part calculates a second timing estimation value based on the filtered timing metric value. An optimum-timing estimation part(130) calculates an optimum-timing estimation value by comparing an amplification amount.
Abstract:
PURPOSE: An orthogonal frequency division multiplexing(OFDM) blind frequency offset estimation method and an apparatus thereof are provided to use a symmetric alpha stable random variable, thereby performing reliable data transmission in an actual communication environment. CONSTITUTION: A time synchronization process with respect to a received orthogonal frequency division multiplexing(OFDM) signal is performed(S1). A k-th sample of the OFDM signal is expressed as an equation after the time synchronization process. A likelihood function is created using a CP(cyclic prefix) inserted in an OFDM symbol(S2). An optimal frequency offset value is estimated as the maximum of the likelihood function among frequency offset trial values in the equation(S3). A trial value applied in a Cauchy distribution likelihood function includes a set of trial values expressed as an equation.
Abstract:
PURPOSE: An inter-symbol interference analysis method according to the number of overlap times in an overlap based direct modulation-binary phase shift keying(DM-BPSK) chirp spread spectrum(CSS) system is provided to use an ISI(Inter-Symbol Interference) formula and simulation test result, thereby minimizing ISI in actual overlap based DM-BPSK CSS system design. CONSTITUTION: A transmission signal overlapped in a transmitter is modeled(S101). The transmission signal overlapped in the transmitter is transmitted through an AWGN(Additive White Gaussian Noise) channel(S103). The transmission signal overlapped in the transmitter is received in a receiver(S105). A real value of a down-chirp correlator output signal of the overlapped transmission signal received in the receiver is modeled(S107). An ISI(Inter-Symbol Interference) formula according to the number of overlap times is induced. A closed type bit error rate formula is induced using the induced ISI formula(S109). An ISI performance variation according to the number of overlap times is analyzed using the induced ISI formula(S111).