Iterative Signal Processing for Mitigation of Analog-to-Digital Converter Clipping Distortion in Multiband OFDMA Receivers

Algorithm 1

Key steps of the proposed receiver clipping compensation algorithm for Receiver A.

Initialization: for all 𝑘∈Ω_𝐴

(1) Set 𝑖=0,𝛼¹⁽⁰⁾=1 and 𝑍^𝑘(0)=0

(2) Obtain channel estimates 𝐻^𝑘(𝑖) using signal

𝑌^𝑘(𝑖)=(1/𝛼^1(𝑖))(𝑌_𝑘−𝑍^𝑘(𝑖))

(3) Channel equalization: 𝑌^𝑘(𝑖)/𝐻^𝑘(𝑖)

(4) Demap symbols 𝑌^𝑘(𝑖)/𝐻^𝑘(𝑖) to bits, deinterleave and

decode to obtain output data bits 𝐛̂^(𝑖)

Iteration: Increase 𝑖 by one and do the following steps for all

𝑘∈Ω_𝐴

(5) Create 𝑋^𝑘(𝑖) based on the coded bits 𝑐̂^{(𝑋𝑘(𝑖−1))1,…,𝑀} (hard) or

𝐿(𝑐̂^{(𝑋𝑘(𝑖−1))1,…,𝑀}) (soft)

(6) Estimate clipping levels 𝛾̂_𝐼(𝑖) and 𝛾̂_𝑄(𝑖) as well as

attenuation factor 𝛼^1(𝑖)

(7) Clip 𝐻^{𝑘(𝑖−1)}𝑋^𝑘(𝑖) according to 𝛾̂_𝐼(𝑖) and 𝛾̂_𝑄(𝑖) in time

domain to produce 𝑌^𝑘(𝑖)

(8) Calculate clipping distortion estimate

𝑍^𝑘(𝑖)=𝑌^𝑘(𝑖)−𝛼^1(𝑖)𝐻^(i𝑘−1)𝑋^(i)𝑘

(9) Remove the distortion from the received signal, that is,

𝑌^𝑘(𝑖)=(1/𝛼^1(𝑖))(𝑌_𝑘−𝑍^𝑘(𝑖))

(10) Obtain new channel estimates 𝐻^𝑘(𝑖) using signal 𝑌^𝑘(𝑖)

(11) Channel equalization: 𝑌^𝑘(𝑖)/𝐻^𝑘(𝑖)

(12) Demap symbols 𝑌^𝑘(𝑖)/𝐻^𝑘(𝑖) to bits, deinterleave and

decode to obtain output data bits 𝐛̂^(𝑖)