Research On Indoor Communication Technology Under WDMA-UWB System Based On LDPC Encoding And Decoding

UWB communication system has been widely used in the fields of people's livelihood and military because of its advantages such as high data rate,low power spectral density,and short time pulse.The indoor environment has the characteristics of narrow and complicated scenes and many obstacles.Due to the wide bandwidth of the ultra-wideband signal,it will exhibit dense multipath phenomenon,which poses a challenge to the stability of the signal transmission.In order to improve the bit error performance of indoor communication in UWB systems,this paper adds LDPC code encoding and decoding technology to WDMA-UWB communication systems,and uses forward error correction technology to enhance the transmission quality and anti-interference ability of WDMA-UWB communication systems to reduce the bit error rate of transmission.WDMA-UWB system not only has the advantages of ultra-narrow pulses of UWB signals,high time resolution and low complexity,but also has the advantages of strong anti-interference ability and high transmission rate based on orthogonal wavelet wave division multiple access technology.It is very suitable for the needs of indoor communication.First,this paper determines the type of wavelet suitable for ultra-wideband transmission signals,builds an indoor WDMA-UWB communication link model,derives the communication link equations,models the signals at the transceiver end,and obtains the mathematical calculation formula for the received signal.Subsequently,a multi-user receiver under dense multipath channels was designed,and the four ultra-wideband channels CM1-CM4 were reconstructed using orthogonal matching tracking algorithm,and a good accuracy rate was obtained.The changes in pilot frequency and measurement number were explored.The influence of CM1-CM4 channel on the estimated mean square error,the selective Rake receiver with low bit error rate is designed according to the channel estimation result.Then perform multi-user detection,introduce a joint algorithm,determine the boundary of the optimal mapping through the sub-optimal solution vector obtained by the sub-optimal algorithm,find the wrong symbol with polarity reversal due to multiple access interference,and after a simulation experiment,the joint algorithm is found The bit error performance has been significantly improved,better than the traditional multi-user detection algorithm,very close to the performance of the OMD algorithm,taking into account both high performance and low complexity.Finally,in order to further improve the bit error performance of the communication system,the LDPC code encoding and decoding technology is introduced into the indoor WDMA-UWB communication system,and the performance gain after adding the code is investigated.The influence of parameters such as the code length of the LDPC code and the number of decoding iterations on the system's bit error performance is verified,and the performance differences brought by using different decoding algorithms are compared.The addition of LDPC code channel coding and decoding technology makes the ultra-wideband communication system very robust,and it also needs to compromise between complexity and performance.