ICI mitigation in concurrent multi-band receiver due to the phase noise and IQ imbalance

Abstract

For the next generation long-term evolution (LTE) advanced mobile communication system, 100 MHz bandwidth and 1 Gbit/s data speed are needed. However, there is not enough and wide vacant frequency band. Therefore, spectrum aggregation method has been studied to extend available frequency bands. Frequency synthesiser and power amplifier of transceiver should cover this wide bandwidth. The phase noise and In-phase and quadrature (IQ) imbalance would increase, which would be a serious problem in this transceiver. Also, signal-to-noise ratio becomes degraded because of nonlinearity and the quantisation noises of the Analog-to-digital conversion (ADC) in the receiver. Uplink of LTE-advanced uses Aggregated DFT-spread (NxDFT-S) orthogonal frequency division multiplexing (OFDM) signals. Since the effect of the phase noise and IQ imbalance are more serious in the multi-band Discrete Fourier transform (DFT)-spreading OFDM system, we like to analyse the effect of inter-carrier interference in frequency domain of receiver and the degradation of bit error rate (BER) performance. Also, by the channel response in frequency domain of the uplink system, we separate phase noise and IQ imbalance effect. Finally, we like to propose a compensation method that estimates the channel exactly and removes IQ imbalance and phase noise. Simulation result shows that the proposed method achieves the 2 dB performance gain of BER = 10−4.