Software Radio: Simulation On Modulation Mode Recognition And Demodulation Algorithms

Software radio refers in particular to multi-purpose intellectualized wirelessapparatus by using software that defines and realizes each kind of functions, thedominant idea of its design: make wideband A/D and D/A switch as close aspossible to antenna, in basic hardware platform basis, the use of software as muchas possible to achieve wireless communications functions. Thus, the wirelesscommunications system with good versatility and the flexibility, makes the systeminterconnection and the promotion extremely convenient. Followed by analogcommunications to digital communications and fixed communications to mobilecommunications, software radio is considered to be the domain third breakthroughin wireless areas.This article mainly has carried on the simulation to the software radio receiversystem modulation recognition and the demodulation algorithm. The full textmainly divides into following several parts, as follows:1.The key technology of software radio and the main algorithm of modulationand demodulationThe main technology of software radio includes: smart antenna technology,number/analog-analog/number transformation technology, numeral frequencyconversion technology, digital signal processor (DSP) technology. Software radiofunctions of the software is one of the greatest advantages in all software, digitalsignal processing software is occupying the important position.2.Software radio modulation recognition algorithm simulationServing as wireless gateway of the software radio, in carries on beforereceiving demodulate the signals must first identify the modulation style and thesignal parameters so that the system can be automatically cut over to theappropriate software demodulate procedures for demodulating a record information.Therefore the signal modulation style automatic diagnosis is one of functionsrequired. The first decision-making based on the theory of automatic identificationsignal modulation format of the basic principles and algorithms for the simulation.Since the numeral modulation signal is more frequent than the analog modulationsignal use, this article logarithm character modulation signal carries on therecognition. Firstly 2ASK, 2PSK, 2FSK, 4ASK, 4PSK, 4FSK six signals produced,the use of radio signals by changing the form of Hilbert, extracts the signalaccording to the formula the instantaneous scope and the phase. After completesthe preparatory work, we carried on according to the algorithm to six kind ofsignals characteristic parameters withdrawn, in the simulation process oursupposition signal for the intermediate frequency modulation signal, eachobservation sample was 200 characters, the noise uses the white gaussian noise.For 500 times for each signal simulation parameters determined by thecharacteristics of each identification threshold, the threshold was based on thecharacteristics of the identification algorithm performance. The simulation resultalso indicated that, when at 20dB of SNR, signal identification of the six computerscould reach more than 95% success rate, QPSK and FSK signal identificationsuccess rate can reach 100%.3. Simulation on demodulation algorithm of software radioSimulation processes including modulation signal generation, carrier-synchronous, timesynchronous, several signal processing and so on. The all-digital receiver, the coreissue is carrier synchronization and timing synchronized with the good or badperformance will directly impact the quality of communication, so here this mainlyto two simultaneous simulation.As QPSK modulation signals contain the carrier signal is unable to useconventional phase-lock link or Narrowband filter information directly from thecarrier, so here we use the figures based on the judgement Costas phase-lock link tomake relevant carrier. Central figures Costas through nonlinear operations to themain principles of extraction I and Q contains the phase error signal information,the use of phase error to withdraw to control oscillator with the same frequency,Simulation results show that in 0.4 seconds, the error message is probably out ofphase zero, the carrier has completed simultaneously.Digital communications system is a synchronous communications systems,should enable the collection, made both flow rate and phase information codeskeep pace relations and the need to ensure synchronous signal transmission systeminformation codes have the same flow rate. Therefore, after the completion of thecarrier at the same time we also conducted simulation. Here we are using thefeedback form phase-lock link to regularly synchronized, the main tenetsphase-lock link through to the base figure to the appropriate signal processing andextraction of timing error, and this error for feedback control oscillator to beinserted within the module, which is equivalent to the 24-hour sampling again to becorrect synchronous signals. Timing error at the time of extraction is the mostimportant issue, the timing error extraction algorithms currently used mainlyearly-late gate algorithms, Mill -mill algorithms and Gardner algorithms. As wehave before independence in regular synchronous completed carrier synchronous,so here we use regularly Mill -mill algorithms to extract error message.Resumption of the synchronous signal processing to be carried out directlydemodulate signals from the original code million.According to previous reports, the software radio system receiver, the boardmust provide the carrier with symbols and synchronization functions, but the noiseand phase distortion to receivers impossible to achieve perfect carriersynchronization and symbols, incorrect carrier synchronous signals will lead to thetransmission of signals in relation to the reception of signals from phase orphase-error. Simulation of random error in the article will process has been staticphase error and synchronous error symbols of the system mistakenly spaces rates.Gauss in the final simulation of a white noise background to the wrong place thesignal to noise ratio as the function through analysis of the simulation results, was areceiver reliability assessment.4. Conclusion and prospectsSince the 1990s, a new area of mobile communications technology revolutionquietly emerging, which is characterized by a new generation of software radiotechnology communications systems research and development. Software radiowill be modular, standardized hardware modules connect to form a basic platformswitch, and through a variety of wireless communications software onto the openarchitecture of a functional.By reading a lot of this on the basis of relevant information on the preparationof software radio receiver identification algorithms for the simulation anddemodulate algorithm for software radio theory laid the theoretical foundation forfurther study. However, there are still some issues, for example, systemcompleteness is also waiting for strengthens, the signal processing algorithmperformance also may have further been optimized the space and so on. With thein-depth study, we will try to achieve software radio functions in hardwareplatform.After several years of development, software radio communications have beenfrom the military phase of the development of research studies in the field ofmodern mobile communications into a third generation mobile communications inparticular the cornerstone. Software radio has been in personal mobilecommunications, military communications, radar and electronic warfare andinformation appliances, has been widely applied. Therefore software radio will be amagnificent prospect.