Research On The Multiuser Detection And LDPC Codes Of DS-UWB Communication Systems For Space Formation Flying Applications

In recent years, with the step of space exploration goes farther, people demand ahigher level of space technology. As a result of single craft no longer meets therequirement of exploration mask, the technology of craft formation flying becomesmore and more important. The DS-UWB communication mode is suitable for spaceformation flying crafts due to its realization of multiple access communication issimplicity, large user capacity, high transmission rate and high interference resistance.In this paper, the communication link model of DS-UWB based space formation flyingcrafts communication system is established, the Multiuser Detection (MUD) technologyand Low Density Parity Code (LDPC) channel coding technology are discussed.First, the communication link model of DS-UWB based space formation flyingcrafts communication system is established and the communication link equation isgiven. On this basis, the affect of signal’s impulse waveform on transmitted power isanalyzed. The feasibility of long distance communication achieved by DS-UWBcommunication system is discussed. The simulation results show that, assume BERsatisfied the system requirement, the transmitted power rises with the order of Gaussianpulse increased and the first order Gaussian pulse has the minimum transmitted power.The communication distance of space craft can be improved by reducing theinformation transmission rate or increasing the transmitted power.Second, for the Multiple Access Interference (MAI) exiting in the DS-UWB basedspace formation flying crafts communication system, this dissertation proposed a hybridmultiuser detection based on optimum decision formula mapping and suboptimumalgorithm. The hybrid multiuser detection distinguishes the symbols affected by theMAI from the symbols which are not affected by the MAI through this two typessymbols’ different range of amplitude in the mapping space. The boundaries of this twotypes symbols’ range are determined by the output vector of suboptimum algorithm. Thesimulation results show that the hybrid multiuser detection achieves the BERperformance which approaches optimum multiuser detection. And the complexity of thedetection is linear to user number. What’s more, this detection possesses large usercapacity and the ability to resist near-far effect.The last, in order to enhance the communication reliability of space formationflying crafts, LDPC channel coding technology is researched. In this thesis, theconstruction of check matrix, coding methods and decoding algorithms of LDPC arediscussed. From the simulation results we convinced that, the performance of LDPCimproved when the code length of LDPC and iteration of decoding algorithm increased.The BER performance of DS-UWB based space formation flying crafts communication system has greatly improved and the system robustness becomes stronger since theLPDC channel coding technology is applied.