چكيده به لاتين
The full-duplex (FD) communication technology leads to the construction of radio frequency receivers/transmitters to transmit and receive simultaneously at the same carrier frequency, which would improve the attainable spectral efficiency by a factor of two in compared with its counterpart half-duplex (HD) operation. The main challenge encountered in implementing an FD wireless device is the large power difference between the self-interference (SI) imposed by the device’s own signal transmission and the signal of interest received from a remote source. SI cancellation techniques classified into three categories, namely passive suppression, analog cancellation and digital cancellation.
However, due to the hardware imperfections and implementing problem such as oscillator phase noise, power amplifier nonlinearity, in-phase and quadrature-phase (I/Q) imbalance and the quantization noise of analog-to-digital converters, complete SI suppression and cancellation is so difficult and there is always residual SI in practical FD radios. Among all the SI cancellation bottlenecks, the results of several studies show that the main reason for residual SI is the phase noise of oscillators. Therefore, we develop a new scheme to jointly estimate and cancel the IQ mixer imbalance, power amplifier (PA) nonlinearities, up/down-conversion phase-noise and the SI-channel using the Generalized Complex Exponential Basis Expansion Model (GCE-BEM) in both time and frequency domains.
The GCE-BEM is derived to approximate the time-varying phase-noise and to transform the problem of estimating the time-varying phase-noise into the estimation of a set of time-invariant coefficients in the less expansion order and more accuracy. After providing a least square estimation (LS) method for SI suppression and cancellation in the analog domain, the Maximum likelihood (ML) and least square (LS) estimators based on the proposed GCE-BEM are then used in both time and frequency multiplexed pilot transmission to find GCE-BEM coefficients. One of the most important features of this study is the participation of the intended signal in the estimation process and not considering it as aggregate Gaussian noise and simultaneous estimation of the intended channel, SI channel and phase noise and non-linearity of transmitter and receiver chains effects.
First, using pilot symbols and LS estimators, and then using second order statistics of the unknown intended signal, and using an iterative algorithm-based ML estimator based on the proposed GCE-BEM, the intended signal channel simultaneously with the SI channel and phase noise and non-linearity of transmitter and receiver chains effects are estimated. Simulation results indicate that the proposed GCE-BEM based SI cancellation and suppression in both time and frequency multiplexed pilot transmission can offer a superior SI-cancellation performance with the resulting intended-signal-to-SI-and-noise ratio (SINR) very close to the intended-signal-to-noise ratio (SNR) in the less processing time and expansion order.
Finally, using the desired received signal channel estimation, the bit error rate curves (BER) related to both proposed estimators for given FD-OFDM communications are mapped.
