Function gen_qm4_llr

dpdk/app/test-bbdev/test_bbdev_perf.c:1720–1770

* Generate Qm LLRS for Qm==4 * Modulation, AWGN and LLR estimation from max log development */

 * Modulation, AWGN and LLR estimation from max log development
 */
static void
gen_qm4_llr(int8_t *llrs, uint32_t i, double N0, double llr_max)
{
	int qm = 4;
	int qam = 16;
	int m, k;
	double I, Q, p0, p1, llr_, b[qm], log_syml_prob[qam];
	/* 5.1.4 of TS38.211 */
	const double symbols_I[16] = {1, 1, 3, 3, 1, 1, 3, 3,
			-1, -1, -3, -3, -1, -1, -3, -3};
	const double symbols_Q[16] = {1, 3, 1, 3, -1, -3, -1, -3,
			1, 3, 1, 3, -1, -3, -1, -3};
	/* Average constellation point energy */
	N0 *= 10.0;
	for (k = 0; k < qm; k++)
		b[k] = llrs[qm * i + k] < 0 ? 1.0 : 0.0;
	/* 5.1.4 of TS38.211 */
	I = (1 - 2 * b[0]) * (2 - (1 - 2 * b[2]));
	Q = (1 - 2 * b[1]) * (2 - (1 - 2 * b[3]));
	/* AWGN channel */
	I += sqrt(N0 / 2) * randn(0);
	Q += sqrt(N0 / 2) * randn(1);
	/*
	 * Calculate the log of the probability that each of
	 * the constellation points was transmitted
	 */
	for (m = 0; m < qam; m++)
		log_syml_prob[m] = -(pow(I - symbols_I[m], 2.0)
				+ pow(Q - symbols_Q[m], 2.0)) / N0;
	/* Calculate an LLR for each of the k_64QAM bits in the set */
	for (k = 0; k < qm; k++) {
		p0 = -999999;
		p1 = -999999;
		/* For each constellation point */
		for (m = 0; m < qam; m++) {
			if ((m >> (qm - k - 1)) & 1)
				p1 = maxstar(p1, log_syml_prob[m]);
			else
				p0 = maxstar(p0, log_syml_prob[m]);
		}
		/* Calculate the LLR */
		llr_ = p0 - p1;
		llr_ *= (1 << ldpc_llr_decimals);
		llr_ = round(llr_);
		if (llr_ > llr_max)
			llr_ = llr_max;
		if (llr_ < -llr_max)
			llr_ = -llr_max;
		llrs[qm * i + k] = (int8_t) llr_;
	}
}

static void
gen_qm2_llr(int8_t *llrs, uint32_t j, double N0, double llr_max)