Abstract
A time domain sub-sampling technique that can be applied to wired or wireless orthogonal frequency division multiplexing systems is described in this paper. Focus is given on the specific conditions that allow optimal sparse information recovery. The advantage of the proposed method is that it can be implemented with very low complexity hardware, since it is based on deterministic non-iterative operations. A sub-sampling operating mode is used when sparse information is detected by the receiver and can be applied up to 75 % of the time. The power consumed by the various modules can be significantly reduced during the sub-sampling mode. These modules include the analogue/digital converter and the (inverse) Fast Fourier Transform, as well as the buffering memory used by these modules. The signal to noise ratio analysis shows that an optimal signal reception can be achieved if low order quadrature amplitude modulation and Fourier Transform size are used. Full information recovery can be achieved in some cases of wired communication. A bit error rate lower than 10−3 is measured, if fewer than 1/16 of the Fourier Transform input symbols are omitted at the receiver. A space-time block code system is also modelled, to test the proposed sub-sampling method in a wireless environment.
Highlights
Fewer samples than the ones required by the Nyquist theorem can be used for signal recovery, if the information exchanged is sparse or compressible
Deactivating Fast Fourier Transform (FFT) sub-blocks at the receiver affects more the BER than the deactivation of IFFT sub-blocks. This is due to the fact that the deactivation of larger FFT blocks than those corresponding to the selected R value leads to information loss since FFT blocks with non-identical inputs are turned off
5 Conclusions In this paper, a sub-sampling method has been proposed and evaluated for wired orthogonal frequency division multiplexing (OFDM) and space-time block coding (STBC)-OFDM wireless environments. It can be implemented with very low cost hardware in order to reduce the power consumption, the memory requirements and increase the processing speed of an OFDM system
Summary
The orthogonal frequency division multiplexing (OFDM) is used in a diversity of telecommunication standards. The sub-sampling mode is applied when sparse information exchange (the number of non-zero bits is lower than a threshold) is detected both at the transmitter and the receiver. In this case, several multiplications/additions of the transmitter IFFT and the receiver FFT can be omitted. The potential applications of this work include OFDM network infrastructures where sparse information is permanently transmitted, like for example, night surveillance cameras In this case, simpler ADC and IFFT/FFT implementations with small memory can be used by the OFDM transceivers, in order to support the proposed subsampling scheme.
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