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A New Transmit Beamforming Scheme for Bidirectional Relaying

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In this paper, we study the bidirectional/two-way relaying while considering dual antennas at the relay. With detect-and-forward relaying, we propose a transmit beamforming scheme using equal gain transmission (EGT) principle in the bidirectional relaying. Analytical outage probability and symbol error probability for the proposed scheme are presented and a close match with the numerical results is observed. Through numerical results, we show that EGT based transmit beamforming performs slightly worse than the optimum transmit beamforming scheme, while EGT is simpler to implement and requires partial channel state information (CSI). We also show that EGT based transmit beamforming outperforms existing transmission schemes in the presence of CSI error .

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  1. 1.

    Note that [5] presented DF bidirectional relaying using single relay antenna while utilizing error correcting codes. In contrast, this paper does not consider error correcting codes.

  2. 2.

    In other words, the relay estimates \(x_A\) correctly. Note that only the analytical results adopt the assumption of perfect self interference cancellation. Despite this assumption, we show in Sect. 5 that the analytical results match closely with the simulation results, hence the probability of cancellation error is negligible.

  3. 3.

    A close form expression of (11) can be derived by following [11, Eq. 17].


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Author information

Correspondence to Md. Noor-A-Rahim.

Additional information

This work was supported by the NTU-NXP Intelligent Transport System Test-Bed Living Lab Fund S15-1105-RF-LLF from the Economic Development Board, Singapore.

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Noor-A-Rahim, M., Guan, Y.L. A New Transmit Beamforming Scheme for Bidirectional Relaying. Wireless Pers Commun 97, 5929–5939 (2017). https://doi.org/10.1007/s11277-017-4819-6

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  • Bidirectional relaying
  • Detect-and-forward (DF) relaying
  • CSI error