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

In future, lots of tasks for space exploration can be implemented by SpaceFormation Flying. To make this Space Formation Flying efficient, thecommunication between different aircrafts is a key issue. In this thesis, according tothe characteristics of this Space Formation Flying system, UWB technology isintroduced to construct a DS-UWB based Space Formation Flying communicationsystem. UWB has many advantages, such as high date rates, low hardwarecomplexity and strong ability of keeping secret. Then two key techniques arediscussed carefully in this thesis, including Multiuser Identification (MUI)technique and Multiuser Detection (MUD) technique. More specifically, the mainworks including:First, on the basis of the characteristics of this Space Formation Flying systemand its some restrictive conditions, we introduce the UWB technology and DirectSequence (DS) multiple access method to construct a DS-UWB based SpaceFormation Flying communication system. Then the transmission, diffusion,receiving problems of DS-UWB signals are studied in detail. Besides, from channelcapability and link equation views, the feasibility of UWB long-rangecommunication is discussed. Simulation results show that, the Multiple AccessInference (MAI) cannot be regarded as the Gaussian White Noise and the traditionalcorrelation receiver has a poor ability to resist the effects of MAI and Near-farEffect (NFE). Therefore, the MUI and MUD techniques are needed in this multiusersystem.Second, we investigate the MUI technique for our DS-UWB based SpaceFormation Flying communication system. After converting the problem ofestimating the number of active users to the problem of solving the maximum aposteriori (MAP) criterion, and also introducing the Artificial Fish SwarmAlgorithm (AFSA), we proposed a Population Declining AFSA (PD-AFSA) basedMUI method. Experiments show that this method can follow up the changingnumber of active users fleetly and estimate the current number of active usersaccurately.The last, in order to solve the problems of MAI and NFE in multiuser DS-UWB systems, we proposed three novel MUD algorithms motivated from optimization,error bit recognition and data fusion views. They are improved AFSA MUDalgorithm (AFSA-MUD), Decision Feedback and Error Bit Recognition (DF-EBR)based MUD algorithm, and Decision-level Fusion based MUD algorithm,respectively. Simulation results demonstrate that all these proposed MUDalgorithms can achieve the performance close to OMD, at the cost of much lowercomputational complexity. Moreover, we also clarify the merits and faults of theseMUD algorithms, and give some suggestions about their applications into the designof our DS-UWB based Space Formation Flying communication system.