An SoC based Partially Reconfigurable OFDM transmitters for Cognitive radios

Abstract

FPGAs play an important role in the implementation of modern communication systems like Cognitive radios (CR). The CRs are designed to run multiple waveforms based on environment sensing. The waveforms can be multicarrier and can have wider bandwidths and high data rate. The radio platform will be loaded with multiple executable files depending on the waveforms which will use different source coding, channel coding and modulation schemes. In the case of waveform components running on FPGA the user have to load large bit files even for small changes in the waveforms. In CRs the configuration time and power consumption plays significant role. The configuration time and power is very critical in strategic wireless radio communications. If the waveforms design is made Partially Reconfigurable then the configuration time and the Hardware usage can be saved. Orthogonal frequency-division multiplexing (OFDM) is a method of transmitting digital data on multiple carrier frequencies and which is a best transmission technology for CR systems. The paper describes the Design and Implementation of OFDM transmitters with multiple modulations, channel coding and source coding using Partial Re-configuration (PR).The PR technique allows user to swap between multiple OFDM transmitters which are using ½ BPSK, ½ QPSK, ¾ QPSK, ½ QAM and ¾ QAM during runtime by configuring a control register in FPGA. This PR based implementation of OFDM Transmitter has a common hardware, which is the Static Part and there is a configurable Dynamic part. The user has to load the bit stream for the Dynamic part only, and not the entire bit stream. A soft processor (Microblaze) is used for configuring and debugging the system.