Design and implementation of pipelined MB-OFDM UWB transmitter backend modules on FPGA

In this paper, novel ideas have been proposed for designing and implementing the pipelined MB-OFDM UWB transmitter Digital Backend Modules on FPGA for a data rate of 200Mbps. The various digital backend modules are Scrambler, Convolutional Encoder, Puncturer, Interleaver, QPSK Mapping, and OFDM. The most critical block is the OFDM block because it consists of 128 point IFFT, that to work at a speed of 528MHz. This is achieved in the proposed OFDM module by using Modified Radix-2
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SDF algorithm with extensive pipelining of LPM without using parallel architecture. By the way the speed 528 MHz can be obtained with minimum hardware. Also the hardware complexity has been significantly reduced by usage of constant coefficient canonical signed digit (CSD) multipliers and accuracy has been improved by the internal word length maintained at 13bits which is 7 bits more than the input. For designing the interleaver, the initial problem faced was that the amount of registers that has to be used in designing the interleaver using bit mapping. This leads to thousands of registers in use. In the proposed interleaver, two different RAM banks which are working in tandem with different write and read addresses and clock rates are used to provide optimum results. The implementation has been performed on ALTERA STRATIX III EP3SL50F484C2 FPGA and results obtained are compliance to IEEE 802.15.3a standard.