Pads short PDCCH payloads with zeros, to increase their length to 12. The decoder treats the padded bits as known bits, in order to improve the error correction.

Author: robmaunder

PDCCH_decoder.m

@@ -11,8 +11,7 @@
 %   ln(P(bit=0)/P(bit=1)).
 %
 %   A should be an integer scalar. It specifies the number of bits in the
-%   information bit sequence, where A should be less than E and should be 
-%   no greater than 200.
+%   information bit sequence, where A should be in the range 1 to 140.
 %
 %   L should be a scalar integer. It specifies the list size to use during
 %   Successive Cancellation List (SCL) decoding.
@@ -43,9 +42,6 @@
 
 addpath 'components'
 
-if A < 12
-    error('polar_3gpp_matlab:UnsupportedBlockLength','A should be no less than 12.');
-end
 if A > 140
     error('polar_3gpp_matlab:UnsupportedBlockLength','A should be no greater than 140.');
 end
@@ -72,7 +68,12 @@
 P2 = 3;
 
 % Determine the number of information and CRC bits.
-K = A+P;
+if A < 12
+    % a has been padded with zeros to increase its length to 12
+    K = 12+P;
+else
+    K = A+P;
+end
 
 % Determine the number of bits used at the input and output of the polar
 % encoder kernal.
@@ -90,5 +91,18 @@
 % Get the 3GPP information bit pattern.
 info_bit_pattern = get_3GPP_info_bit_pattern(K, Q_N, rate_matching_pattern, mode);
 
-% Perform Distributed-CRC-Aided polar decoding.
-a_hat = DS1CA_polar_decoder(f_tilde,crc_polynomial_pattern,RNTI,crc_interleaver_pattern,info_bit_pattern,rate_matching_pattern,mode,L,min_sum,P2);
+if A < 12
+    % We know that a has been padded with zeros
+    a_tilde = [NaN(1,A),zeros(1,12-A)];
+    
+    % Perform Distributed-CRC-Aided polar decoding.
+    a_hat = DS1CKA_polar_decoder(f_tilde,crc_polynomial_pattern,RNTI,crc_interleaver_pattern,info_bit_pattern,rate_matching_pattern,mode,L,min_sum,P2,a_tilde);
+    
+    if ~isempty(a_hat)
+        % Remove the padding
+        a_hat = a_hat(1:A);
+    end    
+else
+    % Perform Distributed-CRC-Aided polar decoding.
+    a_hat = DS1CA_polar_decoder(f_tilde,crc_polynomial_pattern,RNTI,crc_interleaver_pattern,info_bit_pattern,rate_matching_pattern,mode,L,min_sum,P2);
+end

PDCCH_encoder.m

@@ -6,7 +6,7 @@
 %   order to obtain the encoded bit sequence e.
 %
 %   a should be a binary row vector comprising A number of bits, each
-%   having the value 0 or 1. A should be in the range 1 to 200.
+%   having the value 0 or 1. A should be in the range 1 to 140.
 %
 %   E should be an integer scalar. It specifies the number of bits in the
 %   encoded bit sequence, where E should greater than A.
@@ -39,11 +39,9 @@
 end
 
 
+
 A = length(a);
 
-if A < 12
-    error('polar_3gpp_matlab:UnsupportedBlockLength','A should be no less than 12.');
-end
 if A > 140
     error('polar_3gpp_matlab:UnsupportedBlockLength','A should be no greater than 140.');
 end
@@ -54,8 +52,14 @@
 crc_polynomial_pattern = [1 1 0 1 1 0 0 1 0 1 0 1 1 0 0 0 1 0 0 0 1 0 1 1 1];
 P = length(crc_polynomial_pattern)-1;
 
-% Determine the number of information and CRC bits.
-K = A+P; 
+% If a contains fewer than 12 bits, increase its length to 12 by padding it 
+% with zeros
+if A < 12
+    a = [a,zeros(1,12-length(a))];
+    K = 12+P;
+else
+    K = A+P;     
+end
 
 % Determine the number of bits used at the input and output of the polar
 % encoder kernal.

PUCCH_decoder.m

@@ -7,10 +7,11 @@
 %
 %   f_tilde should be a real row vector comprising G number of Logarithmic
 %   Likelihood Ratios (LLRS), each having a value obtained as LLR =
-%   ln(P(bit=0)/P(bit=1)).
+%   ln(P(bit=0)/P(bit=1)), where G should be no greater than 8192 if A<360
+%   and no greater than 16384 if A>=360.
 %
 %   A should be an integer scalar. It specifies the number of bits in the
-%   information bit sequence, where A should be less than G.
+%   information bit sequence, where A should be in the range 12 to 1706.
 %
 %   L should be a scalar integer. It specifies the list size to use during
 %   Successive Cancellation List (SCL) decoding.

PUCCH_encoder.m

@@ -5,10 +5,11 @@
 %   order to obtain the encoded bit sequence f.
 %
 %   a should be a binary row vector comprising A number of bits, each
-%   having the value 0 or 1.
+%   having the value 0 or 1, where A should be in the range 12 to 1706.
 %
-%   E should be an integer scalar. It specifies the number of bits in the
-%   encoded bit sequence, where G should be greater than A.
+%   G should be an integer scalar. It specifies the number of bits in the
+%   encoded bit sequence, where G should be no greater than 8192 if A<360
+%   and no greater than 16384 if A>=360.
 %
 %   f will be a binary row vector comprising G number of bits, each having
 %   the value 0 or 1.

components/DCKA_polar_decoder.m

@@ -1,6 +1,6 @@
 function a_hat = DCKA_polar_decoder(e_tilde, crc_polynomial_pattern, crc_interleaver_pattern, info_bit_pattern, rate_matching_pattern, mode, L, min_sum, P2, a_tilde)
 % DCKA_POLAR_DECODER Distributed-CRC-and-Known-bit-Aided (DCKA) polar decoder.
-%   a_hat = DCKA_POLAR_DECODER(e_tilde, crc_polynomial_pattern, crc_interleaver_pattern, info_bit_pattern, rate_matching_pattern, mode, L, min_sum, P2) 
+%   a_hat = DCKA_POLAR_DECODER(e_tilde, crc_polynomial_pattern, crc_interleaver_pattern, info_bit_pattern, rate_matching_pattern, mode, L, min_sum, P2, a_tilde) 
 %   decodes the encoded LLR sequence e_tilde, in order to obtain the
 %   recovered information bit sequence a_hat.
 %