Full-duplex (FD) wireless and phased arrays are both promising
techniques that can significantly improve data rates in future wireless
networks. However, integrating FD with transmit (Tx) and receive
(Rx) phased arrays is extremely challenging, due to the large
number of self-interference (SI) channels. Previous work relies on
either RF canceller hardware or on analog/digital Tx beamforming
(TxBF) to achieve SI cancellation (SIC). However, Rx beamforming
(RxBF) and the data rate gain introduced by FD nodes employing
beamforming have not been considered yet. We study FD phased
arrays with joint TxBF and RxBF with the objective of achieving
improved FD data rates. The key idea is to carefully select the
TxBF and RxBF weights to achieve wideband RF SIC in the spatial
domain with minimal TxBF and RxBF gain losses. Essentially,
TxBF and RxBF are repurposed, thereby not requiring specialized RF
canceller circuitry. We formulate the corresponding optimization
problem and develop an iterative algorithm to obtain an approximate
solution with provable performance guarantees. Using SI
channel measurements and datasets, we extensively evaluate the
performance of the proposed approach in different use cases under
various network settings. The results show that an FD phased array
with 9/36/72 elements can cancel the total SI power to below the
noise floor with sum TxBF and RxBF gain losses of 10.6/7.2/6.9 dB,
even at Tx power level of 30 dBm. Moreover, the corresponding FD
rate gains are at least 1.33/1.66/1.68×.
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Residual self-interference cancellation and data detection in full-duplex communication systems
Residual self-interference cancellation is an important practical requirement for realizing the full potential of full-duplex (FD) communication. Traditionally, the residual self-interference is cancelled via digital processing at the baseband, which requires accurate knowledge of channel estimates of the desired and self-interference channels. In this work, we consider point-to-point FD communication and propose a superimposed signaling technique to cancel the residual self-interference and detect the data without estimating the unknown channels. We show that when the channel estimates are not available, data detection in FD communication results in ambiguity if the modulation constellation is symmetric around the origin. We demonstrate that this ambiguity can be resolved by superimposed signalling, i.e., by shifting the modulation constellation away from the origin, to create an asymmetric modulation constellation. We compare the performance of the proposed detection method to that of the conventional channel estimation-based detection method, where the unknown channels are first estimated and then the data signal is detected. Simulations show that for the same average energy over a transmission block, the bit error rate performance of the proposed detection method is better than that of the conventional method. The proposed method does not require any channel estimates and is bandwidth efficient.
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- Award ID(s):
- 1642865
- NSF-PAR ID:
- 10043841
- Date Published:
- Journal Name:
- IEEE International Conference on Communicaitons
- Page Range / eLocation ID:
- 1 to 6
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Full-duplex (FD) wireless and phased arrays are both promising techniques that can significantly improve data rates in future wireless networks. However, integrating FD with transmit (Tx) and receive (Rx) phased arrays is extremely challenging, due to the large number of self-interference (SI) channels. Previous work relies on either RF canceller hardware or on analog/digital Tx beamforming (TxBF) to achieve SI cancellation (SIC). However, Rx beamforming (RxBF) and the data rate gain introduced by FD nodes employing beamforming have not been considered yet. We study FD phased arrays with joint TxBF and RxBF with the objective of achieving improved FD data rates. The key idea is to carefully select the TxBF and RxBF weights to achieve wideband RF SIC in the spatial domain with minimal TxBF and RxBF gain losses. Essentially, TxBF and RxBF are repurposed, thereby not requiring specialized RF canceller circuitry. We formulate the corresponding optimization problem and develop an iterative algorithm to obtain an approximate solution with provable performance guarantees. Using SI channel measurements and datasets, we extensively evaluate the performance of the proposed approach in different use cases under various network settings. The results show that an FD phased array with 9/36/72 elements can cancel the total SI power to below the noise floor with sum TxBF and RxBF gain losses of 10.6/7.2/6.9 dB, even at Tx power level of 30 dBm. Moreover, the corresponding FD rate gains are at least 1.33/1.66/1.68×more » « less
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Full-duplex (FD) wireless communication refers to a communication system in which both ends of a wireless link transmit and receive data simultaneously and on the same frequency band. One of the major challenges of FD communication is self-interference (SI), which refers to the interference caused by transmitting elements of a radio to its own receiving elements. Fully digital beamforming is a technique used to conduct beamforming and has been recently repurposed to also reduce SI. However, the cost of fully digital systems (e.g., base stations) dramatically increases with the increase in the number of antennas as these systems use a separate Tx-Rx RF chain for each antenna element. Hybrid beamforming systems use a much smaller number of RF chains to feed the same number of antennas, and hence can significantly reduce the deployment cost. In this paper, we aim to quantify the performance gap between these two radio architectures in terms of SI cancellation and system capacity in FD multi-user MIMO setups. We first obtained over-the-air channel measurement data on two outdoor massive MIMO deployments over the course of three months. We next study two state-of-the-art transmit beamforming based FD systems for fully digital and hybrid architectures. We show that the hybrid beamforming system can achieve 80-97% of the fully digital system capacity, depending on the number of clients.more » « less
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/ICC.2017.7997326
