Research On Signal Detection For Software Radios

Software Radio" is a new conception whose essential idea is that a communication radio is constructed by universal programmable hardware platform, which can accomplish as much radio functionality as possible by the loaded software programs. It is a huge revolution for wireless signal transmission and possesses great economic and martial values in areas of telecommunications, businesses, and so on.This paper deals with techniques of signal detection for software radios and the main research works and results are listed as follows.1. A new practical architecture of software radios is presented with examples of two hardware platforms based on different DSPs. Techniques of baseband sampling and multi-rate digital signal processing are utilized to deal with the signals. The radio portions implemented by software are started at higher IF. The platforms designed can process signals with any IF below 100MHz because of their open architectures and flexible capabilities.2. Algorithms of modulation and demodulation for different signals including AM, FM, M-DPSK, FSK, MSK etc. are studied and programmed as software modules. The modulation mode and bit rate of the adopted signal can be selected by the input arguments while the software modules keep uncharged. Data rate of signals can vary arbitrarily under 2Mb/s.3. A novel method of symbol timing recovery based on MMSE criterion is presented. It choices the sampling points with least mean square errors of demodulation as the optimum ones to make decisions. The algorithm works perfectly with less complexity and consumes less resources of DSP4. We propose a method of adaptive channel estimation and compensation, which can accurately measure the qualities of signal transmission including frequency offset, phase aberration, and amplitude fading. These values can be used to amend received signal to improve capabilities of the communication system.5. A new type of signal modulation modes fit for application of software radios -variable rate QAM - is also discussed together with its realization scheme. It adaptively changes the data rate according to qualities of the channel. This method can greatly increase spectral efficiency and system capacity.