Spectrum Shaping Of IR-UWB Cognitive Radio System

With short-distance wireless communications using in the military affairs,industry,science,medical treatment and our daily-life, various portable individual communications equipment's and appliance wiring equipment's increasing, the source of finity spectrum is more scarcity. Sharing and highest efficiency using spectrum source is a pressing technical problem.UWB whose purpose is sharing the spectrum is a new technology. It have the features of concealment, the high transmission rate, low power consumption and so on. But because of its use of very wide bandwidth, to make it do not interfere with other communications systems, in the international, its emitted power has strictly limited. How to make UWB breakthrough this restrictions and don't increase interference to other communication system have practical significance to improve the transmission capacity of UWB.The last two years, Cognitive Radio (CR) technology leads the international field of communications extensive attention. It has become an inevitable direction of software radio and considered to be one important way of solute the shortage of spectrum. The basal thinking of CR is it can reliable cognitive spectrum environment in broadband, detect the emergence of primary users, occupy immediately available of the local spectrum and it have not harmful interference to primary users in the whole communication course. The cognitive radio technology brings a new idea for solving the problem which UWB and traditional narrow-band system coexist.IR-UWB can through adjusted Gaussian pulse's shape factor and the order of the derivative parameters to affect the power spectrum of UWB, but this redressal can't make UWB spectrum avoiding narrowband signal spectrum. So this paper suggest that through Cognitive Radio wireless signal sensing technology provid frequency parameters of narrow-band signals to adjustment the double-pulse spacing parameters, UWB Time-Hopping repetition time parameter, achieving the real-time adjustment of the spectrum UWB slot and making it always falls on narrow-band signal frequency.Through this paper, it achieves lower emitted power in narrow-band signal frequency and higher emitted power in other spectrum.It breachs FCC spectral mask and improves the transmission capacity of UWB.Main Content of this thesis:Charter 1 summarie the concept of UWB and CR, and analyzes the main problems facing of using UWB in reality and the significance of the research of IR-UWB Cognitive Radio, and explains the purpose of this research study and content.Charter 2 analyzes the effect of UWB Gaussian pulse parameters to power spectral density and the characteristics of TH-PPM UWB power spectral density. Formula and simulation results show the time-hopping interval and pulse repetition frequency affecting its power spectrum of discrete components and the location.Charter 3 introduces the interference relations between UWB signal and narrowband signal and establishs the mathematics relationship of between Narrow-band interference energy intensity and UWB intensity of the power spectral density, and show up double-pulse signal and power spectrum's expression, and analyzes UWB waveform parameters and the time-hopping parameters affecting UWB shaping of spectrum. Main Content:(1)Derivating the processing gain of matched filter UWB correlation receiver.(2)Derivating time-hopping parameters and double pulse parameters affect UWB signal spectrum, and establishes the mathematical relationship of seamless spectrum position and spectral bandwidth gap between these parameters. (3)Through simulation analysis can find the conclusions which shaping of spectrum makes the power of UWB spectrum on narrow band signal close to zero.Charter 4 starts from the detection methods of cognitive radio signal, and derivates Cycle frequency detection arithmetic, and compares with the traditional energy detecting method. Simulation analyzes the performance of energy exploration and cyclostationary signal detection based on different intensity Gaussian white noise.The basic principle of arithmetic is based on the existing communications signals choice for a stationary circle model, through the hypothesis testing of dual detection, and based on test receiving signal is cycle stationary or not judging the signal.Charter 5 is based on the chapter 2,3,4 , and point out that the interference of Narrowband system to UWB system can pass adjusting UWB signal parameters making UWB signals make the bandwidth of the spectrum slot more than narrowband signal's. Through these spectrum slot on Narrow-band signal's working frequency, it can get the purpose of decreasing the interference energy between narrowband signals and UWB signals, improving UWB transmission performance.(1) Based on the relationship of interference frequency and UWB spectrum slot position, and choices appropriate emission parameters making UWB spectrum avoiding narrow-band signal, and concludes the specific adjusted steps of TH-UWB system emission parameters which based on the cognitive condition of interference frequency.(2) Analyzing the performance of the system, and bases on the frequency interference of apperceive, we simulates the Matched filter receiver on the UWB BER which the time-hopping code based on Gauss second derivative function monopulse and double pulse.Charter 6 summarizes the conclusions of this thesis.The innovative work of this thesis:(1) Derivating The mathematics relationship between time-hopping time intervals, Pulse repetition interval parameters, double pulse interval parameters and the spectrum slot position and spectrum slot width of TH-UWB spectrum, solving the parameter problem of IR-UWB Cognitive Radio system spectrum shaping.(2)Derivating cyclostationary narrow-band signal cognitive method, establishing IR-UWB Cognitive Radio system through cyclostationary narrow-band signal detected achieves dynamic process of shaping of spectrum.