Implementation of Multimode Reconfigurable OFDM Transceiver for SDR

Abstract

Multicarrier communication has replaced single carrier communication in recent times. Multicarrier communication method OFDM has become a popular choice for modern communication standards. It offers advantages like efficient use of spectral bandwidth, robustness against harsh channel environments like selective fading and elimination of Inter symbol and interchannel interference. Analog modules are constantly being replaced by digital systems due to exponential rise in their speed, computational power and size. Software defined radios (SDRs) are systems implemented on digital logic. These radio systems offer flexibility, easy upgradability and cost efficiency when compared with analog systems. A multimode OFDM transceiver is implemented on FPGA logic which supports multiple configurations like modulation schemes, FFT Size and Forward error correction rate. Modulation scheme supported by this design are BPSK, QPSK, 8-PSK and 16-QAM. FFT Packet size support of 64, 128 and 256 is provided. A forward error correction rate of 0.5 and 0.66 is also implemented in this design. Timing Synchronization at the receiver are implemented using Minn Algorithm while frequency offset estimation and compensation has been implemented using Modified Maximum Likelihood Algorithm. These modules can be loaded into FPGA logic one at a time. Channel environment defines type of module to be loaded into FPGA. These modules are loaded in FPGA using partial reconfiguration technique. Partial reconfiguration offers certain advantages over static implementation of a design. This method is area efficient, cost efficient and reduces system downtime. Our design uses 51% less area than multiplexed approach of implementation of OFDM transceiver. This implementation has an advantage of easy upgradation and modification in design for future requirements