Performance of pilot-assisted channel estimation without feedback for broadband ANC systems using OFDM access

Recently, broadband analog network coding (ANC) has intensively been studied due to its potential to increase the network capacity by exploiting the broadcasting nature of the wireless channel. However, channel state information (CSI) knowledge is required for self-information removal and signal detection. A low-complexity pilot-assisted channel estimation (PACE) scheme has been presented for broadband ANC, where feedback of the CSI estimates from the relay to the users is required. In this study, we propose a PACE scheme without CSI feedback from the relay for broadband ANC using orthogonal frequency-division multiplexing. In the first time slot the users transmit their respective pilots to the relay and in the second time slot the relay simply amplifies and forwards the received pilot signals to both users. Each user can then estimate all the CSI it needs for self-information removal and coherent signal detection, without requiring any feedback of the CSI estimates from the relay. We theoretically analyze the channel estimator’s mean square error (MSE) performance and evaluate the bit error rate (BER) and throughput performance of broadband ANC using the proposed PACE by computer simulation. The results show that the increase in the MSE of the proposed CE scheme causes only a slight BER performance degradation compared to the conventional PACE scheme with ideal feedback. However, the benefit of eliminating the CSI feedback can be seen in the throughput performance.