SDR 无线网络原理和初步试验(AM,FM).doc

SDR Implementation of Wireless Communication 1. Objective The aim of this project is to understand the principle of operation of software-defined radio (SDR), design SDR algorithms for amplitude modulation and frequency modulation, and implement real-world analogue radio communication systems using the GNU Radio software and the Universal Software Radio Peripheral (USRP) hardware. 2. Introduction With the rapid improvements in computing power of general purpose computers, it is becoming increasingly feasible to implement most of the real-time signal processing tasks for a radio communication system in software instead of dedicated hardware. This approach to radio communication is known as SDR. Figure 1 illustrates the principle of operation of SDR. The key principle of SDR operation is the theory of bandpass signalling, which states that any physical bandpass signal can be represented by its equivalent baseband complex envelope signal. At the SDR transmitter, input data is processed in software according to the chosen modulation method to produce digital samples of the complex envelope signal, then the digital signal is converted into the analogue signal by the digital-to-analog converter (DAC), and finally the analogue complex envelope signal is up-converted to the desired radio frequency band by the radio frequency (RF) front end hardware. The SDR receiver down-converts the received RF signal using the RF front end, the complex envelope signal produced is then digitised by the analog-to-digital converter (ADC), and finally the digital signal is processed by software to recover the data. Figure 1. Basic elements of SDR The roles of GNU Radio and USRP are also shown in Figure 1. GNU Radio provides a software platform for the transformation between the data and the digital complex envelope, and USRP serves as an interface linking the digital complex envelope to the analogue RF. Your task is to rapidly get yourself up to speed by going through some simple tutorials on