Analysis And Research Of OFDM Baseband System Based On YunSDR Platform

Today's era,the mobile data revolution is gradually opening the curtain.In order to meet the needs of the times,IEEE(Institute of electrical and Electronics Engineers)to promote the standardization of WLAN and wireless city network(WMAN).With the introduction of the WiFi protocol(802.11a/b/g/n)and WiMAX(802.16d/e/m),IEEE has constructed an advanced air interface technology with orthogonal frequency division multiplexing(OFDM).Such as:IEEE802.11a WLAN standard 5G band transmission OFDM signal can achieve 54Mbit/s rate.For the WLAN products,how to make the implementation of the algorithm is simpler;how to ensure that the performance of the receiver does not decline in the scope of the application or less,is the key to the success of its commercialization.Therefore,the design of the algorithm in this paper can provide some reference for its commercialization.In this paper,we studied the OFDM baseband system IEEE802.11a standard:as the number of module DAC conversion,RF modulation and demodulation,channel frequency and RF frequency and ADC sampling,the generalized channel makes signal nonlinear distortion,therefore,the receiving system through the channel compensation and bit inversion recovery the original data.The design of this system by using the frame structure characteristics of transmitter(such as training sequence and pilot,cyclic prefix)of frame synchronization(the starting point for the signal frame),carrier frequency offset compensation(carrier transceiver system to eliminate the deviation),channel estimation and equalization(eliminate the multipath effect and channel fading),constellation mapping implementation of channel compensation;and then the de interleaving,channel decoding,descrambling bit inversion(inverse basic transmitter),to restore the original data.Subsequently,the actual transceiver test experiment simulation and YunSDR platform of IEEE802.11a baseband OFDM system is built,based on comparing the actual channel and channel simulation verified the correctness and feasibility of the algorithm to estimate the baseband system.Then,according to different channel quality(multipath,frequency offset and white noise conditions),in order to balance the transmission efficiency and reliability requirements,we use the modulation and error correction encoding schemes of different data transmission rate of 6-54Mbps.And in the final of the different modulation modes(BPSK,QPSK,16QAM and 64QAM)and different convolution encoding rate(respectively:1/2,2/3,3/4)constellation error vector magnitude under the OFDM baseband system(EVM)were compared to analyze the overall performance of the OFDM baseband transceiver system built.