Development of Low Power Consumption OFDM Receiver based on Joint RF and Baseband Signal Processing

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Although OFDM (Orthogonal Frequency Division Multiplex) is an efficient technique capable of reducing the performance degradation due to delay spreading in multipath environment and employed as a transmission technique for terrestrial digital television broadcasting and wireless LAN (local area network), it is not capable of improving the degradation due to fading. Recently, digital terrestrial television broadcasting for handheld terminals based on OFDM has been introduced in Japan. However, the power consumption of the receiver becomes a problem. The RF (radio frequency) front-end component of the receiver requires low noise figure (NF) linear amplifier. Generally speaking, it requires high power consumption amplifier to reduce the NF. Furthermore, the baseband signal processing block including FFT processors requires huge computational cost. That is, it is difficult to reduce the power consumption in principle.In order to reduce the power consumption of the OFDM receiver, this research project has proposed an adaptive mixed signal processing, where the RF signal processing component including low NF amplifier is adaptively controlled its power consumption according to the channel condition. When the channel condition is good, the amplifier at the RF front-end is operated in low power mode, while it is switched to low NF mode if the channel condition becomes worse. In order to measure the channel condition, the baseband block measures the signal-to-noise ratios (SNR) of each OFDM sub-channel and estimates the instantaneous bit error rate from the measured SNRs.In this project, we have confirmed that the proposed mixed signal processing receiver is capable of reducing power consumption.