Near-Far Resistant Ultra-Wideband Communications in Multiple-Access Environments

synchroniation;ultra-wideband;multiple-access interference;near-far problem

Li, Liping ; Keith Townsend, Committee Chair,Bojko Bakalov, Committee Member,Brian Hughes, Committee Co-Chair,Huaiyu Dai, Committee Member,Robert Ulman, Committee Member,Li, Liping ; Keith Townsend ; Committee Chair ; Bojko Bakalov ; Committee Member ; Brian Hughes ; Committee Co-Chair ; Huaiyu Dai ; Committee Member ; Robert Ulman ; Committee Member

University:North Carolina State University

关键词: synchroniation;    ultra-wideband;    multiple-access interference;    near-far problem;   

Others  :  https://repository.lib.ncsu.edu/bitstream/handle/1840.16/3434/etd.pdf?sequence=1&isAllowed=y

美国|英语

来源: null

【 摘 要 】

Ultra-Wideband (UWB) systems promise high data rate and accurate localization capabilitiesfor communications, imaging, sensor networks, and vehicular systems. The simpleUWB receiver structure is especially attractive to applications which require low cost andlow power consumption. However, the envisioned simple receiver designs are also fraughtwith challenges ranging from estimation of highly frequency-selective multipath channelsto synchronization of received signals consisting of very narrow pulses. In this context,transmitted reference (TR) UWB systems have been proposed in the literature as one wayto avoid computationally intensive channel estimation while still maintaining a relativelysimple receiver structure.In this dissertation, we investigate the performance of TR UWB communication systemsin multiple-access environments. We remove the commonly invoked assumption ofperfect power control and include in our analysis an additional group of users which havepower levels much higher than the desired user. The detrimental effects of high-powerusers are suppressed by chip discrimination in this dissertation. To yield a straightforwardmapping between the number of equal-power users and the variance of the resulting MAI,we incorporate the power delay profile (PDP) of the channel in the analysis, which makesthe theoretical analysis tractable. This analytical technique of using PDP is also applied toanalyze the MAI in frequency-shifted reference (FSR) UWB systems.The near-far problem also arises for synchronization when high-power users are includedin the network. In this dissertation, we propose and investigate a synchronizationprocedure which is near-far resistant. By exploiting the structure of interfering power levels,we devise an efficient suppression technique which only requires the knowledge of thespreading code of the desired user. Complexmatrix operations required by other techniquesfound in the CDMA literature are not required in our suppression process. We also proposea new dimension-based technique for the detection of the code phase based on the suppressedsignal. Simulation results validate our proposed near-far resistant synchronizationtechnique and the superior performance is shown when compared to the current literature.