Multi-stage/hybrid BF under limited dynamic range for OFDM FD backhaul with MIMO SI nulling

Kurisummoottil Thomas, Christo; Sheemar, Chandan Kumar; Slock, Dirk TM
ISWCS 2019, 16th International Symposium on Wireless Communication Systems, Workshop Full Duplex Radio Communications for 5G and Beyond (FDB5G), 27-30 August 2019, Oulu, Finland

This paper considers a bidirectional full-duplex Multi-Input Multi-Output (MIMO) OFDM system. We consider the more realistic noise model called limited dynamic range (LDR) model which takes into account the hardware impairments in the analog sections of the transceiver chains. At the transmit side, we introduce a two stage beamformer (BF) with an inner BF of lower dimension and an outer BF of higher dimension, both BFs being at the digital (baseband) side. The inner BF in OFDM
domain handles transmission, while the outer BF in time domain handles self interference (SI). At the receive side, we propose a hybrid combiner which involves an analog phase shifter based BF, with fewer RF chains compared to the number of receive antennas and a digital (baseband) BF in OFDM domain. The analog BF helps reduce SI before analog-to-digital conversion (ADC). All BFs optimize alternatingly a weighted sum mean
squared error (WSMSE) equivalent of the weighted sum rate over uplink (UL) and downlink (DL)channels. The proposed multi-stage BF architecture allows to reduce the coupling between classical transceiver design and MIMO SI nulling, and guarantee
SI reduction during OFDM cyclic prefixes, with UL/DL possibly using different numerology or being asynchronous, allowing proper ADC operation.

Systèmes de Communication
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