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/**
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*
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* \section COPYRIGHT
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*
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* Copyright 2013-2020 Software Radio Systems Limited
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*
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* By using this file, you agree to the terms and conditions set
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* forth in the LICENSE file which can be found at the top level of
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* the distribution.
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*
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*/
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#ifndef SRSLTE_EVM_H_
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#define SRSLTE_EVM_H_
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#include "srslte/phy/modem/mod.h"
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#include "srslte/phy/modem/modem_table.h"
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#include "srslte/phy/phch/ra.h"
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#include "srslte/phy/utils/debug.h"
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#include "srslte/phy/utils/vector.h"
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/** @struct srslte_evm_buffer_t
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* This structure carries the necessary temporary data required for calculating the EVM.
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*
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* @var max_bits maximum of bits which can support
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* @var hard_bits vector that stores hard bits after decision
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* @var symbols vector that stores the modulated symbols from the hard bits
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*/
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typedef struct {
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uint32_t max_bits;
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uint8_t* hard_bits;
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cf_t* symbols;
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} srslte_evm_buffer_t;
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/**
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* Allocates the EVM calculation buffer
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* @param nof_prb that provides the maximum number of bits
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* @return EVM buffer pointer
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*/
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static inline srslte_evm_buffer_t* srslte_evm_buffer_alloc(uint32_t nof_bits)
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{
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srslte_evm_buffer_t* q = SRSLTE_MEM_ALLOC(srslte_evm_buffer_t, 1);
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// Check allocation result and number of PRB
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if (!q || !nof_bits) {
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ERROR("Malloc");
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return q;
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}
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// Zero memory the buffer fields
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SRSLTE_MEM_ZERO(q, srslte_evm_buffer_t, 1);
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// Set max number of bits
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q->max_bits = nof_bits;
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// Allocate hard bits
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q->hard_bits = srslte_vec_u8_malloc(q->max_bits);
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if (!q->hard_bits) {
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ERROR("Malloc");
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return q;
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}
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// Allocate symbols assuming BPSK
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q->symbols = srslte_vec_cf_malloc(q->max_bits);
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if (!q->symbols) {
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ERROR("Malloc");
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return q;
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}
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return q;
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}
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/**
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* Allocates the EVM calculation buffer
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* @param nof_prb that provides the maximum number of bits
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* @return EVM buffer pointer
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*/
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static inline void srslte_evm_buffer_resize(srslte_evm_buffer_t* q, uint32_t new_max_bits)
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{
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// Assert pointer and number of PRB
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if (!q || !new_max_bits) {
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ERROR("Invalid inputs");
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return;
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}
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// Return if no resize is required
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if (q->max_bits >= new_max_bits) {
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return;
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}
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// Update with greater value
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q->max_bits = new_max_bits;
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// Free hard bits if it was allocated
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if (q->hard_bits) {
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free(q->hard_bits);
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}
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// Allocate hard bits again
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q->hard_bits = srslte_vec_u8_malloc(q->max_bits);
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if (!q->hard_bits) {
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ERROR("Malloc");
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return;
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}
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// Free symbols if it was allocated
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if (q->symbols) {
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free(q->symbols);
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}
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// Allocate symbols again
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q->symbols = srslte_vec_cf_malloc(q->max_bits);
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if (!q->symbols) {
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ERROR("Malloc");
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return;
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}
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}
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/**
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* Template for hard decision taking
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*/
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#define HARD_DECISION(LLR_T, SOFTBITS, HARDBITS, NOF_SOFTBITS) \
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do { \
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/* Typecasts pointer type to minimum width */ \
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uint8_t* ptr = (uint8_t*)SOFTBITS; \
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\
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/* Big endian compensation, ptr needs to point at the MSB */ \
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ptr += sizeof(LLR_T) - 1UL; \
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\
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for (uint32_t i = 0; i < NOF_SOFTBITS / 8; i++) { \
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/* Default mask */ \
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uint8_t w = 0xff; \
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\
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/* For each soft bit, take MSB ad collocate in right position */ \
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w ^= (*ptr & 0x80); \
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ptr += sizeof(LLR_T); \
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w ^= (*ptr & 0x80) >> 1; \
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ptr += sizeof(LLR_T); \
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w ^= (*ptr & 0x80) >> 2; \
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ptr += sizeof(LLR_T); \
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w ^= (*ptr & 0x80) >> 3; \
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ptr += sizeof(LLR_T); \
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w ^= (*ptr & 0x80) >> 4; \
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ptr += sizeof(LLR_T); \
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w ^= (*ptr & 0x80) >> 5; \
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ptr += sizeof(LLR_T); \
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w ^= (*ptr & 0x80) >> 6; \
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ptr += sizeof(LLR_T); \
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w ^= (*ptr & 0x80) >> 7; \
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ptr += sizeof(LLR_T); \
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HARDBITS[i] = w; \
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} \
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if (NOF_SOFTBITS % 8) { \
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uint8_t w = 0xff; \
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for (uint32_t i = 0; i < NOF_SOFTBITS % 8; i++) { \
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w ^= (*ptr & 0x80) >> i; \
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ptr += sizeof(LLR_T); \
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} \
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HARDBITS[NOF_SOFTBITS / 8] = w; \
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} \
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} while (false)
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/**
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* Template RMS EVM calculation for different LLR
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*/
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#define EVM_RUN_TEMPLATE(LLR_T, SUFFIX) \
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static inline float srslte_evm_run_##SUFFIX(srslte_evm_buffer_t* q, \
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const srslte_modem_table_t* modem_table, \
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const cf_t* symbols, \
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const LLR_T* llr, \
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uint32_t nof_bits) \
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{ \
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float evm_rms = NAN; \
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\
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/* Return NAN if EVM buffers, modem table, LLR, symbols or bits missing*/ \
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if (!q || !modem_table || !modem_table->nbits_x_symbol || !llr || !symbols || !nof_bits) { \
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ERROR("Invalid inputs %p %p %p %p %d", q, modem_table, llr, symbols, nof_bits); \
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return evm_rms; \
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} \
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\
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/* Limit number of bits to the one supported by the buffer */ \
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nof_bits = SRSLTE_MIN(q->max_bits, nof_bits); \
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\
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/* Calculate number of symbols */ \
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uint32_t nsymbols = nof_bits / modem_table->nbits_x_symbol; \
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\
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/* Hard decision */ \
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HARD_DECISION(LLR_T, llr, q->hard_bits, nof_bits); \
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\
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/* Modulate */ \
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srslte_mod_modulate_bytes(modem_table, q->hard_bits, q->symbols, nof_bits); \
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\
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/* Compute symbol difference */ \
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srslte_vec_sub_ccc(symbols, q->symbols, q->symbols, nsymbols); \
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\
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/* Average squares */ \
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float evm_pow = srslte_vec_avg_power_cf(q->symbols, nsymbols); \
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\
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/* Convert measure to RMS */ \
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evm_rms = sqrtf(evm_pow); \
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\
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return evm_rms; \
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}
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/** @function srslte_evm_run_f
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* Calculates the Root Mean Squared EVM given a modulation table, complex symbols, floating point LLR (soft bits) and
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* the number of bits.
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*
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* @param q is the EVM buffers, need to be preallocated
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* @param modem_table points at the modulator table
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* @param symbols vector carrying the modulated complex symbols
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* @param llr softbits
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* @param nof_bits number of bits
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* @return the measured RMS EVM if no error occurs, otherwise it returns NAN
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*/
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EVM_RUN_TEMPLATE(float, f)
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/** @function srslte_evm_run_s
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* Calculates the Root Mean Squared EVM given a modulation table, complex symbols, fixed integer 16 bit LLR (soft bits)
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* and the number of bits.
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*
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* @param q is the EVM buffers, need to be preallocated
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* @param modem_table points at the modulator table
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* @param symbols vector carrying the modulated complex symbols
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* @param llr softbits
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* @param nof_bits number of bits
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* @return the measured RMS EVM if no error occurs, otherwise it returns NAN
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*/
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EVM_RUN_TEMPLATE(int16_t, s)
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/** @function srslte_evm_run_b
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* Calculates the Root Mean Squared EVM given a modulation table, complex symbols, fixed integer 8 bit LLR (soft bits)
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* and the number of bits.
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*
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* @param q is the EVM buffers, need to be preallocated
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* @param modem_table points at the modulator table
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* @param symbols vector carrying the modulated complex symbols
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* @param llr softbits
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* @param nof_bits number of bits
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* @return the measured RMS EVM if no error occurs, otherwise it returns NAN
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*/
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EVM_RUN_TEMPLATE(int8_t, b)
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#undef EVM_RUN_TEMPLATE
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#undef HARD_DECISION
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static inline void srslte_evm_free(srslte_evm_buffer_t* q)
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{
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// Check EVM buffer object exist
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if (q) {
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// Check hard bits were allocated
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if (q->hard_bits) {
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free(q->hard_bits);
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}
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// Check symbols were allocated
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if (q->symbols) {
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free(q->symbols);
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}
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// Free buffer object
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free(q);
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}
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}
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#endif // SRSLTE_EVM_H_
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