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I know that base station can generate beamforming vector (precoding) by channel state information.

If user have multi antenna, mobile user can also do beamforming?

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  • \$\begingroup\$ To a degree. Your average cell phone is crammed like crazy so you only add as many antennas as needed to meet requirements. \$\endgroup\$
    – winny
    Commented May 22, 2022 at 8:41

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The question is somewhat unclear so I am answering what I think it is.

Yes, the mobile user in whatever network service (be it an utility cell network, home wirreless network, etc...) is highly encouraged to use whatever directional discrimination is available for both transmitting and receiving.

It is always good - it brings less noise for all users of the frequency band, less transmiter power needed, better signal to noise ratio, etc.

Then again, the mobile user is generally constrained in

  • size - multiple antennas and antenna separation may not be possible
  • electrical power - the additional hardware drains more power
  • computational power - the beamforming is an additional computational burden
  • price
  • aestetics
  • technology availability

In short, the mobile user may not use beamforming because it cannot and not because it should not.

For some networks (e.g. Starlink) the great directional discrimination is a hard requirement, so the user-side device uses hundreds of small antennas packed inside for its "beamforming".

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  • \$\begingroup\$ thanks a lot! This is what I am curious about. Then if user have more than 2 antennas, it "CAN" do beamforming. Is it right? \$\endgroup\$
    – new_be
    Commented May 22, 2022 at 10:26
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    \$\begingroup\$ Maybe. In some cases, one can do beamforming with a single antenna (by reorienting it). Mobile phone users in a bad coverage do this a lot. With two or more antennas one can at least switch between them (a basic, but important method). Further sophistications are possible if the electronics connected to these antennas are capable enough (like, e.g. phase shifting the signal between the antennas). \$\endgroup\$
    – fraxinus
    Commented May 22, 2022 at 10:30
  • \$\begingroup\$ thank you very much!! \$\endgroup\$
    – new_be
    Commented May 22, 2022 at 10:50

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