Sub-Sampled Time Domain Sparse Information in Wired OFDM and STBC-OFDM Systems

Abstract

A sub-sampling method developed for wired or wireless Orthogonal Frequency Division Multiplexing (OFDM) systems is presented. The proposed technique can be activated during the exchange of sparse data. The sub-sampling method is implemented with low cost and complexity hardware since it requires the customization of a few specific OFDM stages like channel interleaving, sampling control, etc, and does not require any iterative optimization procedure. Employing special Inverse-Fast Fourier Transform (I-FFT) input structures, the recovery of the original data from fewer samples than those required by the receiver FFT is possible without any other cost for general OFDM applications. A special detector initiates the sub-sampling mode when sparse information is exchanged like sensor data or uncompressed real-time video with stationary views like night surveillance cameras. Up to ¾ of the time, the system can operate in sub-sampling mode reducing the power consumed by the Analogue/Digital Converter (ADC), the FFT and the IFFT. Memory needed for sample storage, intermediate results and FFT/IFFT coefficients can be released in real time if the proposed architecture is adopted. A Bit Error Rate (BER) below 10−3 or full information recovery is achieved in most of the cases. An image reconstruction example is also tested in a wireless environment with Normalised Mean Square Error (NMSE) ranging from 10−5 to less than 0.1.