Novel DDS based OFDM transmitter structure without IFFT and interpolation filter

The traditional orthogonal frequency division multiplexing (OFDM) transmitter is implemented by inverse fast Fourier transform (IFFT), up-sampling and low pass shaping filter (LPSF), which occupy a large number of hardware resources and have long latency. To further meet the 5G and future 6G communication requirements, this paper proposes a novel direct digital synthesis (DDS) based OFDM transmitter structure that can replace these modules. Due to the strong parallelism of the system structure, it is very suitable for implementation on field programable gate array (FPGA) platform. After making two special simplifications to the primary structure, the refined structure becomes very simple compared with the traditional structures. Most attractively, the proposed structure has the following three advantages that i) the data transformation from frequency domain to time domain has zero latency, ii) the transformation length does not need to be an integer power of 2 and iii) the structure does not even need to use any multiplier, thus leading to low implementation complexity and high speed. Comparative experiments are carried out on Intel FPGA platform which show that our DDS based structure can save more than half of the resources compared with the traditional structures and can provide the same bit error rate (BER) performance under the condition without using any LPSF.