Weighted-Combining Calibration on Multiuser MIMO Systems with Implicit Feedback

Hayato FUKUZONO; Tomoki MURAKAMI; Riichi KUDO; Yasushi TAKATORI; Masato MIZOGUCHI

doi:10.1587/transcom.E98.B.701

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Weighted-Combining Calibration on Multiuser MIMO Systems with Implicit Feedback

Hayato FUKUZONO, Tomoki MURAKAMI, Riichi KUDO, Yasushi TAKATORI, Masato MIZOGUCHI

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Summary :

Implicit feedback is an approach that utilizes uplink channel state information (CSI) for downlink transmit beamforming on multiple-input multiple-output (MIMO) systems, relying on over-the-air channel reciprocity. The implicit feedback improves throughput efficiency because overhead of CSI feedback for change of over-the-air channel responses is omitted. However, it is necessary for the implicit feedback to calibrate circuitry responses that uplink CSI includes, because actual downlink and uplink channel responses do not match due to different transmit and receive circuitry chains. This paper presents our proposed calibration scheme, weighted-combining calibration (WCC); it offers improved calibration accuracy. In WCC, an access point (AP) calculates multiple calibration coefficients from ratios of downlink and uplink CSI, and then combines coefficients with minimum mean square error (MMSE) weights. The weights are derived using a linear approximation in the high signal to noise power ratio (SNR) regime. Analytical mean square error (MSE) of calibration coefficients with WCC and calibration schemes for comparison is expressed based on the linear approximation. Computer simulations show that the analytical MSE matches simulated one if the linear approximation holds, and that WCC improves the MSE and signal to interference plus noise power ratio (SINR). Indoor experiments are performed on a multiuser MIMO system with implicit feedback based on orthogonal frequency division multiplexing (OFDM), built using measurement hardware. Experimental results verify that the channel reciprocity can be exploited on the developed multiuser MIMO-OFDM system and that WCC is also effective in indoor environments.

Publication: IEICE TRANSACTIONS on Communications Vol.E98-B No.4 pp.701-713

Publication Date: 2015/04/01

Publicized

Online ISSN: 1745-1345

DOI: 10.1587/transcom.E98.B.701

Type of Manuscript: PAPER

Category: Wireless Communication Technologies

Authors

Hayato FUKUZONO
  NTT Corporation
Tomoki MURAKAMI
  NTT Corporation
Riichi KUDO
  NTT Corporation
Yasushi TAKATORI
  NTT Corporation
Masato MIZOGUCHI
  NTT Corporation

Keyword

multiple-input multiple-output (MIMO), channel reciprocity, implicit feedback, calibration, minimum mean square error (MMSE)

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Hayato FUKUZONO, Tomoki MURAKAMI, Riichi KUDO, Yasushi TAKATORI, Masato MIZOGUCHI, "Weighted-Combining Calibration on Multiuser MIMO Systems with Implicit Feedback" in IEICE TRANSACTIONS on Communications, vol. E98-B, no. 4, pp. 701-713, April 2015, doi: 10.1587/transcom.E98.B.701.
Abstract: Implicit feedback is an approach that utilizes uplink channel state information (CSI) for downlink transmit beamforming on multiple-input multiple-output (MIMO) systems, relying on over-the-air channel reciprocity. The implicit feedback improves throughput efficiency because overhead of CSI feedback for change of over-the-air channel responses is omitted. However, it is necessary for the implicit feedback to calibrate circuitry responses that uplink CSI includes, because actual downlink and uplink channel responses do not match due to different transmit and receive circuitry chains. This paper presents our proposed calibration scheme, weighted-combining calibration (WCC); it offers improved calibration accuracy. In WCC, an access point (AP) calculates multiple calibration coefficients from ratios of downlink and uplink CSI, and then combines coefficients with minimum mean square error (MMSE) weights. The weights are derived using a linear approximation in the high signal to noise power ratio (SNR) regime. Analytical mean square error (MSE) of calibration coefficients with WCC and calibration schemes for comparison is expressed based on the linear approximation. Computer simulations show that the analytical MSE matches simulated one if the linear approximation holds, and that WCC improves the MSE and signal to interference plus noise power ratio (SINR). Indoor experiments are performed on a multiuser MIMO system with implicit feedback based on orthogonal frequency division multiplexing (OFDM), built using measurement hardware. Experimental results verify that the channel reciprocity can be exploited on the developed multiuser MIMO-OFDM system and that WCC is also effective in indoor environments.
URL: https://globals.ieice.org/en_transactions/communications/10.1587/transcom.E98.B.701/_p

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@ARTICLE{e98-b_4_701,
author={Hayato FUKUZONO, Tomoki MURAKAMI, Riichi KUDO, Yasushi TAKATORI, Masato MIZOGUCHI, },
journal={IEICE TRANSACTIONS on Communications},
title={Weighted-Combining Calibration on Multiuser MIMO Systems with Implicit Feedback},
year={2015},
volume={E98-B},
number={4},
pages={701-713},
abstract={Implicit feedback is an approach that utilizes uplink channel state information (CSI) for downlink transmit beamforming on multiple-input multiple-output (MIMO) systems, relying on over-the-air channel reciprocity. The implicit feedback improves throughput efficiency because overhead of CSI feedback for change of over-the-air channel responses is omitted. However, it is necessary for the implicit feedback to calibrate circuitry responses that uplink CSI includes, because actual downlink and uplink channel responses do not match due to different transmit and receive circuitry chains. This paper presents our proposed calibration scheme, weighted-combining calibration (WCC); it offers improved calibration accuracy. In WCC, an access point (AP) calculates multiple calibration coefficients from ratios of downlink and uplink CSI, and then combines coefficients with minimum mean square error (MMSE) weights. The weights are derived using a linear approximation in the high signal to noise power ratio (SNR) regime. Analytical mean square error (MSE) of calibration coefficients with WCC and calibration schemes for comparison is expressed based on the linear approximation. Computer simulations show that the analytical MSE matches simulated one if the linear approximation holds, and that WCC improves the MSE and signal to interference plus noise power ratio (SINR). Indoor experiments are performed on a multiuser MIMO system with implicit feedback based on orthogonal frequency division multiplexing (OFDM), built using measurement hardware. Experimental results verify that the channel reciprocity can be exploited on the developed multiuser MIMO-OFDM system and that WCC is also effective in indoor environments.},
keywords={},
doi={10.1587/transcom.E98.B.701},
ISSN={1745-1345},
month={April},}

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TY - JOUR
TI - Weighted-Combining Calibration on Multiuser MIMO Systems with Implicit Feedback
T2 - IEICE TRANSACTIONS on Communications
SP - 701
EP - 713
AU - Hayato FUKUZONO
AU - Tomoki MURAKAMI
AU - Riichi KUDO
AU - Yasushi TAKATORI
AU - Masato MIZOGUCHI
PY - 2015
DO - 10.1587/transcom.E98.B.701
JO - IEICE TRANSACTIONS on Communications
SN - 1745-1345
VL - E98-B
IS - 4
JA - IEICE TRANSACTIONS on Communications
Y1 - April 2015
AB - Implicit feedback is an approach that utilizes uplink channel state information (CSI) for downlink transmit beamforming on multiple-input multiple-output (MIMO) systems, relying on over-the-air channel reciprocity. The implicit feedback improves throughput efficiency because overhead of CSI feedback for change of over-the-air channel responses is omitted. However, it is necessary for the implicit feedback to calibrate circuitry responses that uplink CSI includes, because actual downlink and uplink channel responses do not match due to different transmit and receive circuitry chains. This paper presents our proposed calibration scheme, weighted-combining calibration (WCC); it offers improved calibration accuracy. In WCC, an access point (AP) calculates multiple calibration coefficients from ratios of downlink and uplink CSI, and then combines coefficients with minimum mean square error (MMSE) weights. The weights are derived using a linear approximation in the high signal to noise power ratio (SNR) regime. Analytical mean square error (MSE) of calibration coefficients with WCC and calibration schemes for comparison is expressed based on the linear approximation. Computer simulations show that the analytical MSE matches simulated one if the linear approximation holds, and that WCC improves the MSE and signal to interference plus noise power ratio (SINR). Indoor experiments are performed on a multiuser MIMO system with implicit feedback based on orthogonal frequency division multiplexing (OFDM), built using measurement hardware. Experimental results verify that the channel reciprocity can be exploited on the developed multiuser MIMO-OFDM system and that WCC is also effective in indoor environments.
ER -