Study On Multiple Access Performance Of Ultra-Wideband Impulse Radio

The Time-Hopping(TH) code and Direct Sequence(DS) let the impulse UWB system have the multiple access ability, but the Multiple Access Interference(MAI) is unavoidable. The MAI becomes the main factor to influence the UWB system performance as the users increase. The main contents of this thesis are outlined as follows:First, the paper studies the three impulse modulation methods of ultra-wideband (UWB) system, analysis the power density of the TH-UWB system with Pulse Position Modulation (PPM), simulation the influence of the power density by the modulation parameters. Study the IEEE 802.15.3a channel model, simulation the impulse response of the CM1, CM2, CM3, CM4 channel environment.Second, analyze the multiple access interference (MAI) of the TH-PPM UWB and DS-UWB systems in the multi-path environment. An approximate expression of Bit Error Rate (BER) is arrived based on Standard Gaussian Approximation (SGA). Analyze the BER and simulation results show that increase the transmission power to improve the multi-access interference is impossible.Third, analyze the performance of the MAI of the time-hopping pulse position modulation UWB system. An expression for bit error rate is derived by characteristic function (CF) analysis. The simulation result shows that SGA technique overestimates the performance of the UWB system in the high SNR.Fourth, Analyze the BER of the TH-PPM UWB system, we provide three ways to improve the system performance. The simulation results show that the increase of transmission power, numbers of chips N in one bit, and decrease the pulse width parameter will improve the system performance, but these three methods are restricted by the system condition. The simulation of the PPM parameter 8 shows when the pulse waveform is fixed, there is exist the PPM parameter S to let the system performance optimal.