The aim of the paper is to build a software based radio capable of demodulating Frequency Modulated signals with the ability to receive upto four stations simultaneously. In addition convolution encoding along with Viterbi decoding is also implemented to aid in error correction capability of digital transmission systems. The initial phase is aimed at software based demodulation of multiple channels of Frequency Modulated signals. The second phase is directed towards the Error correction using convolution encoding with Viterbi decoding for streaming data encountered in digital broadcast systems. Software Radio is a way of designing software very close to the antenna. The basic feature of software radio is that software will define the transmitted waveforms, and software will demodulate the received waveforms. This paper is developed with the help of free software based radio toolkit given by a community named GNU radio. Channel coding schemes need to be used extensively in the case of transmission of digital data over the air or through any other medium. These coding schemes also called FEC (Forward Error Correction) are used in cases where the re-transmission of the data is not feasible or possible. The channel coding schemes comes to the rescue in such cases where redundant data are sent over the transmission medium along with the message. In the receiver side, this channel coded signal is decoded to get back the original data even if the channel coded signal undergoes some interference from the noise in the transmission medium. Though the channel coding has a downside of requirement to transmit additional data over the transmission medium, the advantages offered by error detection and correction mechanisms to the receiver outweighs the disadvantage of additional data transfer rate and bandwidth requirements.
Dr. Shriram K Vasudevan, Janakiraman, S., and Vasudevan, S., “SDR and Error Correction using Convolution Encoding with Viterbi Decoding”, Journal of Emerging Technologies in Web Intelligence, vol. 2, pp. 122–130, 2010.