Channel Estimators for Full-Duplex Communication Using Orthogonal Pilot Sequences

Abstract

Full-duplex communication is desirable to maximize the spectral efficiency, despite the challenges it puts forth. The key challenge inhibiting the operation of radios in full-duplex mode is selfinterference. In this paper, we propose a pilot-based channel estimation to estimate both self-interference and communication channels simultaneously at both ends of a full-duplex link using orthogonal sequences. The Cramer-Rao Lower Bound for estimators of both the channels was determined and compared with the halfduplex channel estimator. We performed simulations varying sequence length and channel taps and studied the performance of the estimators. We also studied the effect of synchronization between the sequences on the performance of the estimators. Thus, providing a solution to balance the trade-off between the accuracy of the channel estimation and the overhead added to the transmissions for full-duplex communication. INDEX TERMS Channel estimation, orthogonal m-sequences, full-duplex (FDX), half-duplex (HDX), self-interference (SI), Cramer-Rao Lower Bound (CRLB).

Self-interference cancellation in underwater acoustic communications systems using orthogonal pilots in IBFD

“…The proposed orthogonal self-interference cancelation method based on mathematical proofs has no restrictions on the channel characteristics and all the channels that can be used in the OFDM system can be used in the proposed full-duplex system. Therefore, the proposed method for eliminating self-interference from Far signal is independent of the number of channel taps unlike method of [17], where the orthogonality condition is satisfied only in a certain number of channel taps.…”

“…To improve the performance of digital SIC by using the reconstructed SI signal from the SI channel obtained using an adaptive filter, they suggested using the SI signal combined with the intended signal in the estimation of the SI channel. In [17], an SIC model to estimate the SI and communication channels concurrently across a FD connection utilising orthogonal pilot sequences was proposed. The HD and FD of both channel estimators using the Cramer-Rao Lower Bound were compared.…”

Full‐duplex MIMO‐OFDM systems with imperfect estimation of CFO and time‐varying multipath channels

“…downlink to terminals) and reception (e.g. uplink to a base station) to simultaneously access a common frequency slot [1, 2 ]. The non‐orthogonal frequency allocation theoretically produces a gain of doubling the system spectral efficiency.…”

“…Unlike [1–7 ] considering either block‐fading channel estimation or the effect of imperfect synchronisation under the assumption of perfect channel estimation, this Letter addresses multiple‐input multiple‐output orthogonal frequency division multiplexing (MIMO‐OFDM) FD systems with imperfect estimation of both carrier frequency offset (CFO) and time‐varying channel responses. More specifically, time variation of multipath MIMO channels (over intended and SI links) leads to the identifiability problem of estimating a large number of unknown parameters which is much greater than the number of (known) received signal samples.…”