Florian Kaltenberger
4a930b7d0e
git-svn-id: http://svn.eurecom.fr/openair4G/trunk@5217 818b1a75-f10b-46b9-bf7c-635c3b92a50f
266 lines
6.3 KiB
C
Executable File
266 lines
6.3 KiB
C
Executable File
/*******************************************************************************
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Eurecom OpenAirInterface
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Copyright(c) 1999 - 2014 Eurecom
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This program is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free Software
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Foundation; either version 2 of the License, or (at your option) any later version
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This program is distributed in the hope it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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more details.
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You should have received a copy of the GNU General Public License along with
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this program; if not, write to the Free Software Foundation, Inc.,
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51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
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The full GNU General Public License is included in this distribution in
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the file called "COPYING".
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Contact Information
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Openair Admin: openair_admin@eurecom.fr
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Openair Tech : openair_tech@eurecom.fr
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Forums : http://forums.eurecom.fsr/openairinterface
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Address : Eurecom, 2229, route des crêtes, 06560 Valbonne Sophia Antipolis, France
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*******************************************************************************/
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/* file: ccoding_byte.c
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purpose: Encoding routines for implementing 802.11 convolutionally-coded waveforms
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author: raymond.knopp@eurecom.fr, based on similar code for 3GPP convolutional code (UMTS) by P. Humblet (2000)
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date: 10.2004
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*/
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#include "defs.h"
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unsigned short gdot11[] = { 0133, 0171 }; // {A,B}
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unsigned short gdot11_rev[] = { 0155, 0117 }; // {A,B}
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unsigned char ccodedot11_table[128];
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unsigned char ccodedot11_table_rev[128];
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/*************************************************************************
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Encodes for an arbitrary convolutional code of rate 1/2
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with a constraint length of 7 bits.
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The inputs are bit packed in octets (from MSB to LSB).
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Trellis termination is included here
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*************************************************************************/
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void
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ccodedot11_encode (unsigned int numbytes,
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unsigned char *inPtr,
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unsigned char *outPtr,
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unsigned char puncturing)
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{
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unsigned int state;
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unsigned char c, out, shiftbit =0;
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// printf("In ccodedot11_encode (%d,%p,%p,%d)\n",numbytes,inPtr,outPtr,puncturing);
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#ifdef DEBUG_CCODE
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unsigned int dummy;
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#endif //DEBUG_CCODE
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int bit_index;
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/* The input bit is shifted in position 8 of the state.
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Shiftbit will take values between 1 and 8 */
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state = 0;
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#ifdef DEBUG_CCODE
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dummy = 0;
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#endif //DEBUG_CCODE
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/* Do not increment inPtr until we read the next octet */
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bit_index=0;
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while (numbytes-- > 0) {
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c = *inPtr++;
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#ifdef DEBUG_CCODE
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printf("** %d **\n",c);
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#endif //DEBUG_CCODE
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switch (puncturing) {
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case 0: //rate 1/2
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for (shiftbit = 0; shiftbit<8;shiftbit++) {
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state >>= 1;
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if ((c&(1<<shiftbit)) != 0){
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state |= 64;
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}
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out = ccodedot11_table[state];
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*outPtr++ = out & 1;
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*outPtr++ = (out>>1)&1;
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#ifdef DEBUG_CCODE
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printf("%d: %d -> %d (%d)\n",dummy,state,out,ccodedot11_table[state]);
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dummy+=2;
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#endif //DEBUG_CCODE
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}
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break;
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case 1: // rate 3/4
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for (shiftbit = 0; shiftbit<8;shiftbit++) {
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state >>= 1;
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if ((c&(1<<shiftbit)) != 0){
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state |= 64;
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}
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out = ccodedot11_table[state];
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if (bit_index<2)
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*outPtr++ = out & 1;
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if (bit_index!=1)
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*outPtr++ = (out>>1)&1;
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#ifdef DEBUG_CCODE
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printf("%d: %d -> %d (%d)\n",dummy,state,out,ccodedot11_table[state]);
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dummy+=2;
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#endif //DEBUG_CCODE
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bit_index=(bit_index==2)?0:(bit_index+1);
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}
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break;
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case 2: // rate 2/3
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for (shiftbit = 0; shiftbit<8;shiftbit++) {
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state >>= 1;
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if ((c&(1<<shiftbit)) != 0){
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state |= 64;
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}
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out = ccodedot11_table[state];
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*outPtr++ = out & 1;
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if (bit_index==0)
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*outPtr++ = (out>>1)&1;
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#ifdef DEBUG_CCODE
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printf("%d: %d -> %d (%d)\n",dummy,state,out,ccodedot11_table[state]);
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dummy+=2;
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#endif //DEBUG_CCODE
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bit_index=(bit_index==0)?1:0;
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}
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break;
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default:
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break;
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}
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}
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/*
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// Termination - Add one NULL byte to terminate trellis
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#ifdef DEBUG_CCODE
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printf("Termination\n");
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#endif //DEBUG_CCODE
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for (shiftbit = 0; shiftbit<8;shiftbit++) {
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state >>= 1;
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out = ccodedot11_table[state];
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*outPtr++ = out & 1;
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*outPtr++ = (out>>1)&1;
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#ifdef DEBUG_CCODE
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printf("%d: %d -> %d (%d)\n",dummy,state,out,ccodedot11_table[state]);
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dummy+=2;
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#endif //DEBUG_CCODE
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printf("%d -> %d (%d)\n",state,out,ccodedot11_table[state]);
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}
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*/
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}
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/*************************************************************************
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Functions to initialize the code tables
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*************************************************************************/
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/* Basic code table initialization for constraint length 7 */
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/* Input in MSB, followed by state in 6 LSBs */
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void ccodedot11_init(void)
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{
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unsigned int i, j, k, sum;
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for (i = 0; i < 128; i++) {
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ccodedot11_table[i] = 0;
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/* Compute R output bits */
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for (j = 0; j < 2; j++) {
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sum = 0;
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for (k = 0; k < 7; k++)
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if ((i & gdot11[j]) & (1 << k))
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sum++;
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/* Write the sum modulo 2 in bit j */
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ccodedot11_table[i] |= (sum & 1) << j;
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}
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}
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}
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/* Input in LSB, followed by state in 6 MSBs */
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void ccodedot11_init_inv(void)
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{
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unsigned int i, j, k, sum;
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for (i = 0; i < 128; i++) {
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ccodedot11_table_rev[i] = 0;
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/* Compute R output bits */
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for (j = 0; j < 2; j++) {
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sum = 0;
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for (k = 0; k < 7; k++)
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if ((i & gdot11_rev[j]) & (1 << k))
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sum++;
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/* Write the sum modulo 2 in bit j */
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ccodedot11_table_rev[i] |= (sum & 1) << j;
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}
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}
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}
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/*****************************************************************/
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/**
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Test program
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******************************************************************/
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#ifdef DEBUG_CCODE
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#include <stdio.h>
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main()
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{
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unsigned char test[] = "0Thebigredfox";
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unsigned char output[512], *inPtr, *outPtr;
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unsigned int i;
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test[0] = 128;
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test[1] = 0;
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ccodedot11_init();
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inPtr = test;
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outPtr = output;
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ccodedot11_encode(16, inPtr, outPtr,0);
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for (i = 0; i < 32; i++) printf("%x ", output[i]);
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printf("\n");
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}
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#endif
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/** @}*/
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