Method and apparatus for transmitting common signal in hybrid beamforming

1. A method for transmitting a common signal in hybrid beamforming, comprising:

acquiring an analog common signal to be transmitted;

dividing codewords in a codebook for analog beamforming into at least two codeword groups, wherein each codeword group includes at least one codeword;

selecting different codeword groups for adjacent timeslots; for one timeslot, selecting a different codeword from the codeword group selected for the timeslot for each RF chain and obtaining an analog beamformer;

beamforming the analog common signal to be transmitted in each RF chain according to the analog beamformer; and

transmitting the beamformed analog common signal in each RF chain.

2. The method of claim 1 , wherein codewords in the codebook for analog beamforming are divided into at least two codeword groups according to users' distribution.

3. The method of claim 1 , before acquiring the analog common signal to be transmitted, further comprising:

acquiring a digital common signal for generating the analog common signal to be transmitted;

acquiring a cyclic shift for each RF chain according to a principle of using different cyclic shifts for RF chains corresponding to adjacent beams, and generating a digital beamformer using the acquired cyclic shift;

beamforming the digital common signal in each RF chain using the digital beamformer in digital baseband.

4. The method of claim 3 , further comprising:

calculating the cyclic shift according to a maximum multipath delay spread of a channel impulse response and a size of discrete Fourier transform.

5. An apparatus for transmitting a common signal in hybrid beamforming, comprising: a processor and a memory communicated with the processor; in the memory, modules that are executed by the processor are stored, comprising an analog common signal acquiring module, a codeword group dividing module, an analog beamformer obtaining module, an analog beamforming module, and a signal transmitting module, wherein

the analog common signal acquiring module, configured to acquire an analog common signal to be transmitted;

the codeword group dividing module, configured to divide codewords in a codebook for analog beamforming into at least two codeword groups, wherein each codeword group includes at least one codeword;

the analog beamformer obtaining module, configured to select different codeword groups for adjacent timeslots; for one timeslot, select a different codeword from the codeword group selected for the timeslot for each RF chain and obtain an analog beamformer;

the analog beamforming module, configured to beamform the analog common signal to be transmitted in each RF chain according to the analog beamformer; and

the signal transmitting module, configured to transmit the beamformed analog common signal in each RF chain.

6. The apparatus of claim 5 , wherein the codeword group dividing module is configured to divide codewords in the codebook for analog beamforming into at least two codeword groups according to users' distribution.

7. The apparatus of claim 5 , further comprising:

a digital common signal acquiring module, configured to acquire a digital common signal for generating the analog common signal to be transmitted;

a digital beamformer obtaining module, configured to acquire a cyclic shift for each RF chain according to a principle of using different cyclic shifts for RF chains corresponding to adjacent beams, and obtain a digital beamformer using the acquired cyclic shift;

a digital beamforming module, configured to beamform the digital common signal in each RF chain using the digital beamformer in digital baseband.

8. The apparatus of claim 7 , further comprising:

a cyclic shift calculating module, configured to calculate the cyclic shift according to a maximum multipath delay spread of a channel impulse response and a size of discrete Fourier transform, and send the cyclic shift to the digital beamformer generating module.