radio_link_agent.cpp

各种视频压缩格式的网络传输的模拟信道分析

/*
 ==========================================================================================
 ITU-T Telecommunications Standardization Sector      Document:   VCEG-M77
 Study Group 16 Question 6                            Filename:   radio_link_agent.cc
 Video Coding Experts Group (VCEG)                    Generated:  02 July, 2001
 ----------------------------------------
 Thirteenth meeting: Austin, Texas, 2-4 April, 2001


 Intention: 
 ~~~~~~~~~~~~
 Simple offline software simulator for RTP/IP over 3GPP/3GPP2 bearers


 Source:
 ~~~~~~~
 Thomas Stockhammer, Guenther Liebl                  Tel:   [phone]
 Institute for Communications Engineering            Fax:   [phone]
 Munich University of Technology                     Email: {stockhammer,liebl}@ei.tum.de
 80290 Munich, Germany
 ==========================================================================================
*/

#include "radio_link_agent.h"



// constructor
RADIO_LINK_AGENT::RADIO_LINK_AGENT()
{
  int32 i;

  // basic initialization
  ModuleName = "RADIO-LINK-AGENT";

 for (i=0;i<PACKET_BUFFER_SIZE;i++)
    {
      SDU_Buffer[i].upper_layer_PDU.internal_identifier = 0;
      SDU_Buffer[i].upper_layer_PDU.size = 0;
      SDU_Buffer[i].unsent_bytes = 0;
      SDU_Buffer[i].received_bytes_counter = 0;
      SDU_Buffer[i].correct_bytes_counter = 0;
    }

  SDU_buffer_read_position = 0;
  SDU_buffer_write_position = 0;
  SDU_buffer_total_length = 0;
  SDU_buffer_unsent_length = 0;


  radio_bearer_bitrate = 0;
  frame_size = 0;
  agent_header_size = 0;
  ACK_mode = FALSE;
  fully_persistent_ARQ = FALSE;
  max_number_of_retransmissions = 0;


  for (i=0;i<FRAME_BUFFER_SIZE;i++)
    {
      Retransmit_Buffer[i].retransmission_frame = NULL;
      Retransmit_Buffer[i].retransmission_time = 0;
    }
  
  Retransmit_buffer_read_position = 0;
  Retransmit_buffer_write_position = 0;
  Retransmit_buffer_length = 0;

 
  total_frames_counter = 0;
  total_retransmitted_frames_counter = 0;
  total_dummy_frames_counter = 0;
  total_correct_payload_bits_counter = 0;
  total_bitrate = 0.;
  total_net_bitrate = 0.;
  effective_net_bitrate = 0.;

  transmission_time_interval = 0;  
  simulation_time = 0;
  send_sequence_number = 0;
  receive_sequence_number = 0;
}



// destructor
RADIO_LINK_AGENT::~RADIO_LINK_AGENT()
{

}



// initialize the radio link agent from the given parameter file
void RADIO_LINK_AGENT::initialize(FILE *ParameterFile_ptr, FILE *CommonLogFile_ptr, PACKET_DATA_AGENT *upper_layer_agent)
{
  char ack_mode, fully_persistent_arq;

  LogFile_ptr = CommonLogFile_ptr;  
  fprintf(LogFile_ptr,"%s: start initialization process\n",ModuleName);

  Upper_Layer_Agent = upper_layer_agent;

  // get the desired radio bearer bitrate from the parameter file
  fscanf(ParameterFile_ptr,"- nominal radio bearer bitrate (in kbit/s): %d\n",&radio_bearer_bitrate);
  if ( (radio_bearer_bitrate <= 0) || (radio_bearer_bitrate%8 != 0) )
    {
      fprintf(stderr,"!!error in module %s: illegal value %d for the radio bearer bitrate\n",ModuleName,radio_bearer_bitrate);
      exit(-1);
    }
   else 
     {
       fprintf(LogFile_ptr,"%s: nominal radio bearer bitrate is %d kbit/s\n",ModuleName,radio_bearer_bitrate);
     }


  // get the desired frame size of the radio link agent from the parameter file
  fscanf(ParameterFile_ptr,"- frame size (in bits): %d\n",&frame_size);
  if ( (frame_size <= 0) || (frame_size%8 != 0) )
    {
      fprintf(stderr,"!!error in module %s: illegal value %d for the frame size\n",ModuleName,frame_size);
      exit(-1);
    }
   else 
     {
       fprintf(LogFile_ptr,"%s: using radio link frames of size %d bits\n",ModuleName,frame_size);
     }

  // compute the transmission time interval
  transmission_time_interval = frame_size/radio_bearer_bitrate;
  fprintf(LogFile_ptr,"%s: using a transmission time interval of %d ms\n",ModuleName,transmission_time_interval);


  // get the header size of the radio link agent from the parameter file
  fscanf(ParameterFile_ptr,"- radio link agent header size (in bytes): %d\n",&agent_header_size);
  if ( agent_header_size <= 0 )
    {
      fprintf(stderr,"!!error in module %s: illegal value %d for the radio link agent header size\n",ModuleName,agent_header_size);
      exit(-1);
    }
   else 
     {
       fprintf(LogFile_ptr,"%s: adding %d bytes of header info to each PDU\n",ModuleName,agent_header_size);
     }


  // check, if acknowledged mode is to be used
  fscanf(ParameterFile_ptr,"- acknowledged mode (y/n): %c\n",&ack_mode);
  if ( ack_mode == 'y' )
    {
      ACK_mode = TRUE;
      fprintf(LogFile_ptr,"%s: operates in acknowledged mode\n",ModuleName);
    }
  else if ( ack_mode == 'n' )
    {
      ACK_mode = FALSE;
      fprintf(LogFile_ptr,"%s: operates in unacknowledged mode\n",ModuleName);
    }
  else
    {
      fprintf(stderr,"!!error in module %s: illegal value %c for the mode indicator\n",ModuleName,ack_mode);
      exit(-1);
    }


  // determine, whether acknowledged mode is fully-persistent or not
  fscanf(ParameterFile_ptr,"- fully-persistent ARQ (y/n): %c\n",&fully_persistent_arq);
  if ( ACK_mode && (fully_persistent_arq == 'y') )
    {
      fully_persistent_ARQ = TRUE;
      fprintf(LogFile_ptr,"%s: ARQ is fully-persistent\n",ModuleName);
    }
  else if ( ACK_mode && (fully_persistent_arq == 'n') )
    {
      fully_persistent_ARQ = FALSE;
      // get the maximum number of retransmissions per frame from the parameter file
      fscanf(ParameterFile_ptr,"- maximum number of retransmissions per frame in acknowledged mode: %d\n",&max_number_of_retransmissions);
      if ( max_number_of_retransmissions <= 0 )
        {
          fprintf(stderr,"!!error in module %s: illegal value %d for the maximum number of retransmissions\n",ModuleName,max_number_of_retransmissions);
          exit(-1);
        }
      else
        {
          fprintf(LogFile_ptr,"%s: maximum number of retransmissions per frame is limited to %d\n",ModuleName,max_number_of_retransmissions);
        }
    }
  else if ( ACK_mode )
    {
      fprintf(stderr,"!!error in module %s: illegal value %c for the persistency indiator\n",ModuleName,fully_persistent_arq);
      exit(-1);
    }


  fprintf(LogFile_ptr,"%s: end initialization process\n",ModuleName);
}



// generate a radio link frame either from retransmission buffer, SDU buffer, or new data from the upper layer agent
// if no data to be sent is available, generate a dummy frame and issue a streaming timer mismatch warning
// return value: TRUE, if there is still some unsent data somewhere in the transmitting side
//               FALSE, if all data has been sent and there are no pending retransmissions anymore
Boolean RADIO_LINK_AGENT::send_frame(RADIO_LINK_FRAME **outgoing_frame)
{
  int32 upper_layer_status;
  int32 mapped_data_size;

  // in acknowledged mode, retransmission buffer has highest priority
  if ( ACK_mode && (Retransmit_buffer_length > 0) )
    {
      // retransmission buffer contains frames to be retransmitted 
      if ( simulation_time >= Retransmit_Buffer[Retransmit_buffer_read_position].retransmission_time )
	{
	  // the first frame to be retransmitted is already due
	  (*outgoing_frame) = Retransmit_Buffer[Retransmit_buffer_read_position].retransmission_frame;
	  if ( (*outgoing_frame)->frame_type != RETRANSMIT )
	    {
	      fprintf(stderr,"!!error in module %s: illegal frame of type %d found in retransmission queue\n",ModuleName,(*outgoing_frame)->frame_type);
	      exit(-1);
	    }
          Retransmit_Buffer[Retransmit_buffer_read_position].retransmission_frame = NULL;
	  Retransmit_Buffer[Retransmit_buffer_read_position].retransmission_time = 0;
	  Retransmit_buffer_length--;
	  Retransmit_buffer_read_position++;
	  if ( Retransmit_buffer_read_position == FRAME_BUFFER_SIZE )
	    {
	      Retransmit_buffer_read_position = 0;   // wrap around circular retransmission buffer
	    }
	  (*outgoing_frame)->number_of_retransmissions++;
	  total_frames_counter++;
	  total_retransmitted_frames_counter++;
	  //printf("retransmission done at time %d\n",simulation_time);
	  simulation_time += transmission_time_interval;
	  return TRUE;
	}
    }

  // check, if the SDU buffer is empty and new SDUs have to be requested from the upper layer agent
  if ( SDU_buffer_unsent_length == 0 )
    {
      // SDU buffer is empty

      //check for buffer overflow first
      if ( SDU_buffer_total_length == PACKET_BUFFER_SIZE )
	{