Beamforming Transmission in IEEE 802.11ac under Time-Varying Channels

Algorithm 1

An algorithm for determining the optimal MCS with a given payload size.

Initialization: Calculate the set of possible numbers of OFDM symbols with initial channels and lowest MCS as follows:

     𝑆_nofdm=22+8𝐿_MO+𝐿_data𝑁_DBPS𝑁_DBPS∈𝑆_ndbps

where

𝑆_ndbps=𝑁_DBPS∣therequredSNRofMCS≤||𝐇(0)𝐇^𝐻(0)||²𝜎²

for  𝑁_OFDM∈𝑆_ndbps (select with the increasing order)

  (i) Find the feedback delay with 𝑇_DATA with 𝑁_OFDM symbols.

     𝑟_SU=2𝑇_SIFS+𝑇_VHT-CB+𝑇_DATA𝑁_OFDM

  (ii) Find 𝑁^new_DBPS𝑟_SU associated with an MCS level for which the required SNR is lower than or equal to 𝛾^varying_SU-BF𝑟_SU.

       𝛾^varying_SU-BF𝑟_SU=𝛽^2𝑟||𝐇(0)||²𝜎_𝑣²𝑟_SU+𝜎².

  (iii) Calculate the required number of OFDM symbols with 𝑁^new_DBPS𝑟_SU.

       𝑁^req_OFDM=22+8𝐿_MO+𝐿_data𝑁^new_DBPS𝑟_SU.

  (iv) If (𝑁_OFDM≥𝑁^req_OFDM),

        The optimal MCS level is given by

         𝑁_DBPS(𝛾_MCS)=𝑁^new_DBPS(𝑟_SU).

        Break

  else

   The optimal MCS level is given by 𝑁_DBPS(𝛾_MCS)=0.

  end

end