This paper presents an improved orthogonal frequency-division multiple access (OFDMA) system design aiming to reduce the power consumption and the hardware complexity of low-cost user terminals. In conventional OFDMA systems, the analog-to-digital converters (ADCs) at user side contribute a considerable part to hardware complexity and energy consumption due to high sampling rate and high resolution quantization. In the proposed design, the base station uses block diagonalization precoding to cancel the interference among K users; Each user adopts a low-cost ADC where the sampling rate is reduced to 1/K of the Nyquist rate, and the number of quantization bits can be reduced to 2~3 bits. To address the problem of inter-symbol interference due to sub-Nyquist sampling and non-linear distortion due to quantization, the generalized approximate message passing (GAMP) algorithm is adopted at each receiver. Compared with conventional OFDMA systems, the proposed design can greatly reduce the hardware complexity and the power consumption of user receivers while keep the bit error rate performance acceptable.
 

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