Optimal low-complexity self-interference cancellation for full-duplex MIMO small cells

Abstract

Self-interference (SI) significantly limits the performance of full-duplex (FD) radio devices if not properly cancelled. State-of-the-art SI cancellation (SIC) techniques at the receive chain implicitly set an upper bound on the transmit power of the device. This paper starts from this observation and proposes a transmit beamforming design for FD multiple-antenna radios that: i) leverages the inherent SIC capabilities at the receiver and the channel state information; and ii) exploits the potential of multiple antennas in terms of spatial SIC. The proposed solution not only maximizes the throughput while complying with the SIC requirements of the FD device, but also enjoys a very low complexity that allows it to outperform state-of-the-art counterparts in terms of processing time and power requirements. Numerical results show that our transmit beamforming design achieves significant gains with respect to applying zero-forcing to the SI channel when the number of transmit antennas is small to moderate, which makes it particularly appealing for FD smallcell base stations.Index Terms-Full-duplex, multiple antennas, optimal beamforming design, self-interference cancellation, small cells.

Low complexity full duplex MIMO systems: Analog canceler architectures, beamforming design, and future directions

“…First, the digital TX and RX BF design takes into explicit account the available number of analog taps 𝑁 , or number of AUX TXs 𝑁 , of the analog SI cancellation block. Although some available BF solutions [4,20,22] for FD MIMO systems consider the presence of an analog SI canceler, the details of its hardware limitations are excluded from the BF design. Second, the proposed FD MIMO framework is the only one that explicitly considers the case where 𝑁 < min{𝑀 𝑘 , 𝑁 𝑘 }, i.e., the available number of analog taps, or AUX TX RF chains, may be smaller than both the numbers of TX and RX RF chains.…”

“…We compare the presented FD MIMO designs versus the combined cancellation and spatial suppression design presented in [4] as well as the digital BF design proposed in [7]. We note that the designs presented in [20,21] were not considered in the results that follow due to the fact that they are only applicable to UpLink (UL) and Down-Link (DL) communications with 𝑑 𝑘 = 𝑑 𝑚 = 1, whereas our proposed solutions hold for 𝑑 𝑘 , 𝑑 𝑚 ≥ 1. A detailed description of the FD MIMO designs that will be compared is provided below.…”

“…The digital beamformer and analog canceler parameters are thus designed by taking into account each other's capabilities, hence, the burden of SI mitigation is split between digital BF and analog cancellation. We note that the related work [4] has considered joint design of digital BF and analog cancellation, however these and related solutions [20,21] assume underlying analog canceler hardware as in [13,6,15,16,14], which scales with the number of transceiver antennas. For the JointNull solution proposed in [22], although the number of analog cancelers does not necessarily scale with the number of antennas, the underlying architecture of the canceler (i.e., number of taps or AUX TXs) is not explicitly taken into account in the BF design.…”

Joint design of multi-tap analog cancellation and digital beamforming for reduced complexity full duplex MIMO systems

“…The digital beamformer and analog canceller parameters are thus designed by taking into account each others capabilities, hence the burden of self-interference mitigation is split between digital beamforming and analog cancellation. We note that the related work [3] has considered joint design of digital beamforming and analog cancellation, however these and related solutions [11], [12] assume underlying analog canceller hardware as in [5], [9], which scales with the number of transmit and receive antennas. As our simulation results will show, the proposed analog canceller architecture together with our novel co-design of analog cancellation and TX and RX digital beamforming is capable of achieving higher rates with less hardware compared to the State-of-the-Art (SotA) FD MIMO solutions.…”

Low Complexity Full Duplex MIMO: Novel Analog Cancellation Architectures and Transceiver Design

“…The digital beamformer and analog canceller parameters are thus designed by taking into account each others capabilities, hence the burden of SI mitigation is split between digital BF and analog cancellation. We note that the related work [4] has considered joint design of digital BF and analog cancellation, however these and related solutions [16], [17] assume underlying analog canceller hardware as in [6], [12]- [15], which scales with the number of transceiver antennas. For the JointNull solution recently proposed in [18], although the number of analog cancellers does not necessarily scale with the number of antennas, the underlying architecture of the canceller (i.e., number of taps or AUX TXs) is not taken into account in the BF design.…”