mirror of https://github.com/pvnis/srsRAN_4G.git
Initial srenb TA compensation
Xavier Arteaga
5 years ago
committed by
Xavier Arteaga
parent
d191b1c8e0
commit
ada8772f57
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/*
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* Copyright 2013-2019 Software Radio Systems Limited
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*
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* This file is part of srsLTE.
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*
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* srsLTE is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as
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* published by the Free Software Foundation, either version 3 of
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* the License, or (at your option) any later version.
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*
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* srsLTE is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* A copy of the GNU Affero General Public License can be found in
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* the LICENSE file in the top-level directory of this distribution
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* and at http://www.gnu.org/licenses/.
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*
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*/
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#ifndef SRSENB_TA_H
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#define SRSENB_TA_H
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#include "srslte/config.h"
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#include "srslte/phy/common/phy_common.h"
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#include <cmath>
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#include <vector>
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namespace srsenb {
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/**
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* Time Aligment FSM parent/callback interface for pushing n TA values
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*/
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class mac_ta_ue_interface
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{
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public:
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virtual uint32_t set_ta(int ta) = 0;
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};
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/**
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* UE's FSM for controlling Time Aligment command generation.
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*
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* Initially the FSM starts at none state which automatically transitions to Measure. Measurements are collected while
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* the FSM is in Measure state. Up to MAX_NOF_MEAS are stored. The FSM uses a minimum of MIN_NOF_MEAS measurements to
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* compute the TA average. The TA command is triggered as soon as the TA average is higher than TA_N_THRESHOLD. After
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* triggering a TA command, holds in prohibit state for PROHIBIT_PERIOD_MS before start collecting measurements.
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*
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* +------+ First call +---------+ Trigger +----------+
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* | None | ------------->| Measure |------------>| Prohibit |
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* +------+ +---------+ +----------+
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* ^ ^ |
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* | | Prohibit expires |
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* --+ +------------------------+
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*
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*
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*/
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class ta
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{
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private:
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/// Control constants
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static constexpr uint32_t MAX_NOF_MEAS = 16; ///< Maximum number of measurements to store
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static constexpr uint32_t MIN_NOF_MEAS = 4; ///< Minimum number of measurements to compute
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static constexpr uint32_t MAX_MEAS_TIME_MS = 100; ///< Maximum time of measurement
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static constexpr uint32_t PROHIBIT_PERIOD_MS = 20; ///< Time to wait from the n TA value push to measure again
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static constexpr int32_t TA_N_THRESHOLD = 1; ///< n TA value threshold
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/// Parent/callback object
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mac_ta_ue_interface* parent = nullptr;
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/// TA measure datatype
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typedef struct {
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uint32_t ts_ms; ///< Time in which the measurement was taken in ms
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float ta_us; ///< TA measurement in microseconds
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} ta_meas_t;
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uint32_t meas_t_ms = 0; ///< Time counter in milliseconds
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uint32_t meas_count = 0; ///< Number of measures in the buffer
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uint32_t meas_idx = 0; ///< Next mesurement index in the buffer
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std::vector<ta_meas_t> meas_values;
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// FSM states
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typedef enum {
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state_none = 0, ///< NO state has been set yet
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state_measure, ///< Performing measurement
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state_prohibit ///< Waiting for HARQ to transmit CE command, NO measurement shall be stored
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} state_t;
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state_t state = state_none;
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/**
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* Reset Measurement and timer counter
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*/
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void reset_measurements()
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{
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meas_t_ms = 0;
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meas_count = 0;
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meas_idx = 0;
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}
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/**
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* Averages/extrapolates n TA value
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*
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* @return the required n TA value for the current time (meas_t_ms)
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*/
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int get_ta_n()
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{
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float ta_us = 0.0f;
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// Average all measurements
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for (uint32_t i = 0; i < meas_count; i++) {
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// Write here a much fancier extrapolation algorithm
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ta_us += meas_values[i].ta_us;
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}
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if (meas_count) {
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ta_us /= static_cast<float>(meas_count);
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}
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// Return the n_ta value
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return static_cast<int>(std::roundf(ta_us * 1e-6f / SRSLTE_LTE_TS / 16.0f));
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}
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/**
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* Runs initial state none
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* @return 0
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*/
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uint32_t run_state_none()
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{
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reset_measurements();
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state = state_measure;
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return 0;
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}
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/**
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* Runs measure state
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* @return the number of enqueued MAC CE carrying TA commands
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*/
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uint32_t run_state_measure()
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{
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uint32_t ret = 0;
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// Avoid processing if no measurement or no minimum covered or maximum measuring time is reached
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if (meas_count == 0 or (meas_count < MIN_NOF_MEAS and meas_t_ms < MAX_MEAS_TIME_MS)) {
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return ret;
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}
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// Get TA command value
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int ta_n = get_ta_n();
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// Send command
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if (abs(ta_n) > TA_N_THRESHOLD) {
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// Set UE TA
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ret = parent->set_ta(ta_n);
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// Reset measurement counter
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reset_measurements();
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// Transition to prohibit state
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state = state_prohibit;
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}
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return ret;
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}
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/**
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* Runs prohibit state
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* @return 0
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*/
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uint32_t run_state_prohibit()
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{
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// Prohibit time expired
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if (meas_t_ms >= PROHIBIT_PERIOD_MS) {
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// Reset counters
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reset_measurements();
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// Go to measure
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state = state_measure;
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}
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return 0;
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}
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/**
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* Runs The internal FSM
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* @return the number of eneuqued MAC CE carrying TA commands
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*/
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uint32_t run_fsm()
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{
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switch (state) {
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case state_none:
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return run_state_none();
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case state_measure:
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return run_state_measure();
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case state_prohibit:
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return run_state_prohibit();
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default:; // Do nothing
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}
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return 0;
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}
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public:
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/**
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* TA FSM Constructor
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* @param parent_ UE MAC object with TA callback setter
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*/
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explicit ta(mac_ta_ue_interface* parent_) : parent(parent_), meas_values(MAX_NOF_MEAS)
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{
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/// Initial FSM run
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run_fsm();
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}
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/**
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* Pushes TA measurement and runs internal FSM
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*
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* @param ta_us actual TA measurement in microseconds
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* @return the number of MAC CE carrying TA
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*/
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uint32_t push_value(float ta_us)
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{
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// Put measurement if state is measurement
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if (state == state_measure) {
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// Set measurement
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meas_values[meas_idx].ts_ms = meas_t_ms;
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meas_values[meas_idx].ta_us = ta_us;
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// Increase pointer
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meas_idx = (meas_idx + 1) % static_cast<uint32_t>(meas_values.size());
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// Increase count
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if (meas_count < static_cast<uint32_t>(meas_values.size())) {
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meas_count++;
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}
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}
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// Run state machine
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return run_fsm();
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}
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/**
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* Increments internal timer 1 ms and runs internal FSM
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*
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* @param ta_us actual TA measurement in microseconds
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* @return the number of MAC CE carrying TA
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*/
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uint32_t tick()
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{
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// Increase measurement timestamp counter
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meas_t_ms++;
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// Run state machine
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return run_fsm();
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}
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};
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} // namespace srsenb
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#endif // SRSENB_TA_H
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