Software-defined radio for OFDM transceivers

This paper presents a software-defined radio (SDR) system with reconfigurable architecture for wireless communications. As an example, adaptable orthogonal frequency division multiplexing (OFDM) transceiver for standards, such as IEEE 802.11 is studied. Specifically, the baseband software implementation by using a low-power fixed-point digital signal processor (DSP) is applied to demonstrate the concept of SDRs for different standards, and different operational modes. For simplicity, two operational modes, binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK) of OFDM baseband transceivers are implemented. The interoperability and adaptability among these operational modes of this OFDM system is discussed. Additionally, two assembly programming approaches, straight-line method and loop method, are studied experimentally for this software reconfigurable system. Both methods employ radix-2 decimation-in-time fast Fourier transform (FFT) algorithms. Furthermore, the straight-line code has significantly fewer clock cycles than the loop code OFDM transceiver, but demands the expense of a larger program memory requirement. The performance comparison of these two methods with OFDM length versus speed (clock cycles) is presented.