cdma_ber.ps.c

基于OPNET的卫星通信程序

/* cdma_ber.ps.c */                                                       
/* CDMA Bit-Error-Rate (BER) model for radio link Transceiver Pipeline */

#include "opnet.h"
#include "math.h"

#if defined (__cplusplus)
extern "C"
#endif
static const char*	PowI_Err_Hdr = "Error in CDMA BER computation pipeline stage (cdma_ber):";
void
cdma_ber (Packet * pkptr)
	{
	//int msgbuf[512];
	double		ber,bernew,snr,cdmasnr, proc_gain, eff_snr, cdmaeff_snr, code_rate;
	Vartype		modulation_table;
	Objid 		rx_nodeid;
	
	/** Calculate the average bit error rate affecting given packet. **/
	FIN (cdma_ber (pkptr));
	
	/* We have to make sure that the initialization is done and the extended 
	attributes are loaded */

	rx_nodeid = op_td_get_int(pkptr, OPC_TDA_RA_RX_OBJID);
	if (op_ima_obj_attr_get( rx_nodeid, "Coding_Rate",
				 &code_rate) ==
	    OPC_COMPCODE_FAILURE) 
	{
		op_sim_end (PowI_Err_Hdr, "No Coding_Rate attr",
			    OPC_NIL, OPC_NIL);
	}
	/* Determine current value of Signal-to-Noise-Ratio (SNR). */
	snr = op_td_get_dbl (pkptr, OPC_TDA_RA_SNR);
	cdmasnr = op_td_get_dbl (pkptr, OPC_TDA_RA_MAX_INDEX+1);
	
	/* Determine address of modulation table. */
	modulation_table = op_td_get_ptr (pkptr, OPC_TDA_RA_RX_MOD);

	/* Determine processing gain on channel. */
	proc_gain = op_td_get_dbl (pkptr, OPC_TDA_RA_PROC_GAIN);

	/* Calculate effective SNR incorporating processing gain. */
	eff_snr = snr + proc_gain;
	cdmaeff_snr = cdmasnr + proc_gain + 10*log10(code_rate);
	//sprintf(msgbuf,"EFF_SNR=%e\n",cdmaeff_snr);
	//op_sim_message(msgbuf, 0);
	
	/* Derive expected BER from effective SNR. */
	ber = op_tbl_mod_ber (modulation_table,cdmaeff_snr);
	
	/* Place the BER in the packet's transmission data. */
	op_td_set_dbl (pkptr, OPC_TDA_RA_BER, ber);

	FOUT
	}