A hybrid approach to develop a real time COFDM based data link using TI C64xx DSP and XC5VSX95T FPGA

Abstract

Error correcting codes are combined with Orthogonal Frequency Division Multiplexing (OFDM) modulation scheme to make it capable to cater for the severe multipath frequency selective environments which cause inter symbol interference (ISI). Modern communication systems are using Coded-OFDM technology due to its excellent performance in such environments. This paper presents a real time implementation of an end-to-end COFDM based Software Defined Radio. The Baseband and IF Signal Processing Module (BISPM) uses Texas Instrument TMS 320C6455 Digital Signal Processor (DSP) and XC5VSX95T Field Programmable Gate Array (FPGA). The BISPM is reconfigurable to BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying) and 16QAM (Quadrature Amplitude Modulation) modulation schemes. Sensitivity, data throughput, signal-to-noise ratio (SNR) and synchronization results are evaluated from real time hardware platform. The prototype performance was evaluated for Additive White Gaussian Noise (AWGN) and indoor Rayleigh channel. Results show that the prototype achieves the sensitivity requirements of −80dBm (at bit error rate (BER) of 10−6) for BPSK and QPSK modulation schemes and that of −75dBm (at BER of 10−6) for 16QAM modulation scheme, which designates the prototype design specifications. Also, there was a significant improvement in the BER performance of the data link developed by a hybrid (using both DSP and FPGA) approach as compared to that of by DSP only.