关于AFDM中不同均衡的仿真

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6.1 SimulationSettings

In this system, the modelling of the simulationchannel follows the dual-selective channel structure. OFDM systems use perfect channel knowledge forchannel estimation which means that the known exact channel matrix is directlyused to construct the frequency domain channel matrix. The system carrierfrequency is set as  = 4 GHz, the signal bandwidth  is 1 MHz, and the sampling rate is set to  = 2MHz, the modulation is performed using  , and select  = 256 discrete subcarrier points for multicarriertransmission. The guardwidth is set to 4 frames.

6.2 Analysisof Simulation Results6.2.1 Comparison of BER between AFDM and OFDM withdifferent equalizers

In this simulation the number of paths  is set to 3 and the maximum Doppler frequencyshift range and time shift range will be set to randomly generate the gain andtime shift frequency shift of the paths at different frame times. Simulationsdemonstrate different BER in Gaussian additive white noise environments withdifferent SNR[31].

                              

Figure 6.1 BER curves for differentequalizers and number of iterations

In this example we set  to 12,  to 4 which means the maximum possible delay is 6μs and the maximum possible Doppler shift is 15.625 KHz.

6.2.2 PerformanceEvaluation

In this simulation results, AFDM shows betterperformance than OFDM in high SNR scenario. When the SNR exceeds 24 dB, AFDM(MMSE) can achieve a BER below  of BER, while OFDM saturates its performance dueto intercoder interference (ICI) and Inter-Symbol Interference (ISI). AFDM showsbetter diversity gain and resistance to double selection fading.

MMSEoutperforms PCG in both systems. The performance of the iterative algorithmsaturates in Gaussian noise with SNR greater than 24dB and converges with MMSEalgorithm with more iterations.

Figure 6.2: Number of Iterations andMMSE Performance

In this example when the number of iterationsreaches 20, the PCG curves basically coincide with the MMSE curves, and theperformance is basically the same. MMSE, although it has better performance,also has maximum complexity, so for some small economic scenarios, theappropriate PCG method may be a more suitable choice.