FPGA implementation of QAM modems using PR for reconfigurable wireless radios

Abstract

FPGAs are playing a very significant role in software defined Radios (SDR) and Cognitive radios (CR). The SDRs and CRs are capable of running different waveforms which may use different modulation techniques, source coding and channel coding. These reconfigurable radios have to load the waveforms into the FPGA based on their requirements without interrupting the system. The user has to load large bit files even for small changes in the waveforms. The configuration time and power consumption plays significant role in SDRs and CRs: for example, a virtex-7 FPGA takes 500ms to complete configuration. The Configuration time is around Sminutes in a secure SDR and CR platform. This configuration time and power is very critical in strategic wireless radio communications. The configuration time and the Hardware usage can be saved to a larger extent by designing the waveforms using Partial Re-configuration. The paper describes the Design and Implementation of 4/ 8/ 16/ 32/ 64 Quadrature Amplitude Modulation (QAM) and demodulation in FPGA using Partial Re-configuration (PR). The design allows the user to switch between these different modulation and demodulation techniques during runtime by configuring a control register in FPGA. The implementation of these QAMs uses a common hardware, which is called as the Static Part and there is a Dynamic part too. In the PR technique, the user has to load the bit stream for the Dynamic part only, and not the entire bit stream. The size of this bit file will be smaller in size compared to the bit file required to configure the entire FPGA. By designing the entire waveform using PR, the waveform can be made as part of the Platform and the configuration time and power consumption can be very much reduced.