Self-Interference Cancellation and Channel Estimation in Multicarrier-Division Duplex Systems With Hybrid Beamforming

Abstract

Design of full-duplex (FD) wireless systems faces many challenges, including selfinterference cancellation (SIC), capability to provide high capacity, high flexibility for operation, best usage of resources, etc. In this paper, we propose and investigate a multicarrier-division duplex (MDD) based hybrid beamforming system operated in FD mode, which is endowed with the advantages of both time-division duplex and frequency-division duplex. It also shares some merits of FD and allows to be free of self-interference (SI) in digital domain, but faces the same challenge of SI as the FD in analog domain. Hence in this paper, we first propose an adaptive beamforming assisted SI cancellation scheme with taking into account the practical requirement of analog-to-digital conversion (ADC). It can be shown that the proposed approach is capable of jointly coping with the desired signals' transmission and SI suppression. Then, channel estimation (CEst) in MDD/MU-MIMO system is proposed by exploiting the reciprocity between the uplink and downlink subcarrier channels that is provided by MDD. Correspondingly, the orthogonality-achieving pilot symbols are designed, and the least-square (LS) CEst as well as linear minimum mean-square error (LMMSE) CEst are derived. Finally, the performance of MDD/MU-MIMO systems employing the proposed SIC method is investigated, with respect to the SI cancellation capability, sum-rate potential, CEst performance, and the effect of CEst on the achievable performance. Our studies show that MDD/MU-MIMO provides an effective option for design of future wireless transceivers. INDEX TERMS Full-duplex, multicarrier-division duplex, self-interference cancellation, hybrid beamforming, channel estimation, least square, linear minimum mean square error.

Multicarrier-Division Duplex: A Duplexing Technique for the Shift to 6G Wireless Communications

“…Once the passive and digital-domain SIC are fixed, from Figure 2, the demand on the propagation-and analog-domain SIC can be easily calculated, which is 48 dB in our considered example. To suppress this SI, the adaptive beamforming-assisted method proposed in [5] may be applied, which is capable of providing a big range of SI suppression at the cost of slight performance degradation 2 .…”

“…3. EE and SE versus BS transmit power, where DL/UL communication channels are assumed to be the 4-tap channel with each tap following the complex Gaussian distribution of CN (0, 1/4), while the SI channel is flat Rician-fading due to the short propagation distance, whose detailed mathematical expression can be found in [5], with the Rician factor being 20 dB and the array angle between transmitter and receiver being 120 • . The remaining parameters are presented in Figure 2.…”

“…A question naturally arises as to if the hardware/software technologies fail to provide the desired SIC for the practical implementation of IBFD in near future, is there a transitional alternative from HD to IBFD, which can not only inherit the main merits of IBFD but also relieve the stringent requirements of IBFD for SIC? To this end, the multicarrier-division duplex (MDD), originally proposed in [4], and recently studied in [3,5], is capable of enabling concurrent downlink (DL) and uplink (UL) transmissions in the same time slot and same frequency band, but on different subcarriers. To achieve these, in MDD systems, the subcarriers of one band are divided into two mutually exclusive subsets, namely a DL subcarrier subset and UL subcarrier subset, to support DL and UL transmissions, respectively.…”

Resource Allocation in Millimeter-Wave Multicarrier-Division Duplex Systems With Hybrid Beamforming

“…The problem (30) can be solved by the cyclic coordinate descent (CCD) algorithm via iteratively optimizing the individual elements of W W W RF , the details of which can be found in [7] and are not repeated for brevity. After obtaining the analog combiner for SIC, the optimal digital combiner for a subcarrier can be derived based on conventional MMSE approach [39].…”

“…To this end, various SI cancellation (SIC) techniques have been proposed, but most of which are however unable to provide enough SI reduction with the practical complexity for operation in largescale multiple-input multiple-output (MIMO) systems [5,6]. Therefore, to inherit the merits of IBFD while simultaneously circumvent the problem of SI, we proposed and investigated a multicarrier-division duplex multiuser MIMO (MDD/MU-MIMO) system in [7]. According to [8], MDD is a transitional technique from HD to IBFD, enabling DL and UL to work within the same time and same frequency band but on different subcarriers.…”