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Complementary beamforming: New approaches

Publication ,  Journal Article
Choi, YS; Alamouti, SM; Tarokh, V
Published in: IEEE Transactions on Communications
January 1, 2006

Smart antenna technology can greatly improve the coverage radius of wireless systems by focusing the transmitted signal (beam) toward desired users. However, beamforming has an important side effect as it creates a region, herein referred to as the complementary region, where some users in the network cannot sense the directional signals (beams). We have referred to this as the hidden beam problem in Tarokh. From a physical layer perspective, beamforming reduces cochannel interference (CCI). However, in systems that use medium access-control techniques such as the carrier-sense multiple access (CSMA) protocol in wireless local area networks, during a busy period of the channel, the users in the complementary region may wrongly decide that the medium is idle and transmit packets. This may cause CCI, unnecessary retransmissions, subsequent backoff, and increased network latency. We introduced the concept of complementary beamforming (CBF) to address this issue in Tarokh. In this paper, we propose two new methods, called "subspace complementary beamforming" (SCBF) and "complementary superposition beamforming" (CSBF). The SCBF uses dummy data to ensure a controlled level of received energy in all directions of eigenvectors unused by downlink beamforming. The technique works in multipath fading channels. The approach achieves similar results to those reported in Tarokh. However, it enables the second technique (CSBF) which can also send data content in the complementary beam. This allows passive nodes in the network to receive "broadcast" information, while the active nodes are engaged in the exchange of user-specific data. It is shown that CBF effects can be achieved simply by increasing the transmit power of only one of antenna elements when space-division multiple access is not applied. Simulations are provided in order to quantify overall network performance improvements when using CBF, confirming significant throughput and delay performance enhancements. © 2006 IEEE.

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Published In

IEEE Transactions on Communications

DOI

ISSN

0090-6778

Publication Date

January 1, 2006

Volume

54

Issue

1

Start / End Page

41 / 50

Related Subject Headings

  • 4606 Distributed computing and systems software
  • 4009 Electronics, sensors and digital hardware
  • 4006 Communications engineering
  • 1005 Communications Technologies
  • 0906 Electrical and Electronic Engineering
  • 0804 Data Format
 

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Choi, Y. S., Alamouti, S. M., & Tarokh, V. (2006). Complementary beamforming: New approaches. IEEE Transactions on Communications, 54(1), 41–50. https://doi.org/10.1109/TCOMM.2005.861674
Choi, Y. S., S. M. Alamouti, and V. Tarokh. “Complementary beamforming: New approaches.” IEEE Transactions on Communications 54, no. 1 (January 1, 2006): 41–50. https://doi.org/10.1109/TCOMM.2005.861674.
Choi YS, Alamouti SM, Tarokh V. Complementary beamforming: New approaches. IEEE Transactions on Communications. 2006 Jan 1;54(1):41–50.
Choi, Y. S., et al. “Complementary beamforming: New approaches.” IEEE Transactions on Communications, vol. 54, no. 1, Jan. 2006, pp. 41–50. Scopus, doi:10.1109/TCOMM.2005.861674.
Choi YS, Alamouti SM, Tarokh V. Complementary beamforming: New approaches. IEEE Transactions on Communications. 2006 Jan 1;54(1):41–50.

Published In

IEEE Transactions on Communications

DOI

ISSN

0090-6778

Publication Date

January 1, 2006

Volume

54

Issue

1

Start / End Page

41 / 50

Related Subject Headings

  • 4606 Distributed computing and systems software
  • 4009 Electronics, sensors and digital hardware
  • 4006 Communications engineering
  • 1005 Communications Technologies
  • 0906 Electrical and Electronic Engineering
  • 0804 Data Format