| Compared with civilian ultra-wideband technology, military ultra-wideband technology isnot restrained by the power spectral density, which makes it available for longer-distance UWBcommunication through enhancing the transmission power. However, it poses an even greaterchallenge of transmission reliability at the same time. Based on the above background, weattempt to introduce cooperation technology into Code-Orthogonalized Transmitted-ReferenceUltra-Wideband (COTR-UWB) system. This new system perfectly combines the advantages ofcooperation and UWB technology. It both retains the characteristics of UWB, such as excellentconcealment, great anti-jamming ability, low transmitting power and the advantages of simpletransceiver structure, easy to implement synchronous from COTR-UWB system. Meanwhile, theintroduction of cooperation technology not only improves the quality of tactical communicationsbut also increases the propagation distance and expands signal coverage. So, the study on how tocombine Code-Orthogonalized Transmitted-Reference Ultra-Wideband with cooperative comm-unication technology to achieve high-efficiency cooperative communication will have broadprospect of research and practical significance.The main content and innovation are as follows:1. On the background of the longer-distance tactical UWB communication background, weproposed a COTR-UWB cooperative communication system which combines cooperationtechnology with transmitted-reference ultra-wideband communications. It is a systemcharacterized by excellent transmission performance, wide coverage range, great concealmentand powerful anti-interference capability, making it available for transmitting under complexelectromagnetic environment.2. We developed a COTR-UWB cooperative model according to three-node cooperativeprototype. We consider a cooperation strategy with amplify-and-forward protocol as well asmaximum-ratio combining scheme. Due to the fact that so far, there is few channel model candescribe the transmission characteristics of longer-distance UWB communication so far, weadopted multipath Rayleigh UWB channel in this model.3. To analyze the transmission performance of COTR-UWB cooperative system, we firstlyinvoked Gaussian approximation method and sampling expansion method to deduce the SERexpressions of COTR-UWB system. Besides, we compared the system’s SER performance ofthe system in cooperation condition with which in non-cooperation condition by using numericalanalysis. After that, we discussed the effect of parameters such as time-bandwidth product,instantaneous received SNR and the number of impulses on the SER performance. Simulation results showed that the cooperative communication system has excellent transmissionperformance and it gains multi-order diversity in dense multipath channels. Moreover, wecompared the analysis performance of Gaussian approximation with that of sampling expansion,and came to a conclusion that sampling expansion method can better meet the requirements ofanalytical accuracy with COTR-UWB.4. We proposed a relay selection scheme of COTR-UWB cooperative communicationsystem. In order to reduce computational complexity, we deduced an upper approximation boundwhich precisely shows the tendency of system’s SER. Then, we obtained the measurementparameter and cooperation factor based on this bound. According to those two parameters, wediscussed the relay selection criterions and gave the specific relay selection scheme of COTR-UWB cooperative system.5. Based on the COTR-UWB cooperative communication system, we discussed theemission energy allocation problem under the condition of minimized system’s SER. By solvingLagrange’s equations, we obtained the optimal energy allocation expressions of COTR-UWBcooperative system. Analysis results show that the emission energy ratios of source and relaydepend on the statistical variance of each channel. At last, we discussed the determinationproblems of energy allocation ratio and amplification in different channel conditions as well. |
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