mirror of
https://git.rwth-aachen.de/acs/public/villas/node/
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122 lines
4.1 KiB
C++
122 lines
4.1 KiB
C++
/** Calc jitter, mean and variance of GPS vs NTP TS.
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*
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* @author Umar Farooq <umar.farooq@rwth-aachen.de>
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* @copyright 2014-2020, Institute for Automation of Complex Power Systems, EONERC
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* @license GNU General Public License (version 3)
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*
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* VILLASnode
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* any later version.
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*
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* This program 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 General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*********************************************************************************/
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/** @addtogroup hooks Hook functions
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* @{
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*/
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#include <vector>
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#include <cinttypes>
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#include <cstring>
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#include <villas/hook.hpp>
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#include <villas/timing.h>
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#include <villas/sample.h>
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#include <villas/utils.hpp>
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#define GPS_NTP_DELAY_WIN_SIZE 16
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namespace villas {
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namespace node {
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class JitterCalcHook : public Hook {
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protected:
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std::vector<int64_t> jitter_val;
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std::vector<int64_t> delay_series;
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std::vector<int64_t> moving_avg;
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std::vector<int64_t> moving_var;
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int64_t delay_mov_sum;
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int64_t delay_mov_sum_sqrd;
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int curr_count;
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public:
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JitterCalcHook(struct vpath *p, struct vnode *n, int fl, int prio, bool en = true) :
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Hook(p, n, fl, prio, en),
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jitter_val(GPS_NTP_DELAY_WIN_SIZE),
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delay_series(GPS_NTP_DELAY_WIN_SIZE),
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moving_avg(GPS_NTP_DELAY_WIN_SIZE),
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moving_var(GPS_NTP_DELAY_WIN_SIZE),
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delay_mov_sum(0),
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delay_mov_sum_sqrd(0),
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curr_count(0)
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{ }
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/**
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* Hook to calculate jitter between GTNET-SKT GPS timestamp and Villas node NTP timestamp.
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*
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* Drawbacks: No protection for out of order packets. Default positive delay assumed,
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* so GPS timestamp should be earlier than NTP timestamp. If difference b/w NTP and GPS ts
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* is high (i.e. several mins depending on GPS_NTP_DELAY_WIN_SIZE),
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* the variance value will overrun the 64bit value.
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*/
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virtual Hook::Reason process(sample *smp)
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{
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assert(state == State::STARTED);
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timespec now = time_now();
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int64_t delay_sec, delay_nsec, curr_delay_us;
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delay_sec = now.tv_sec - smp->ts.origin.tv_sec;
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delay_nsec = now.tv_nsec - smp->ts.origin.tv_nsec;
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/* Calc on microsec instead of nenosec delay as variance formula overflows otherwise.*/
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curr_delay_us = delay_sec * 1000000 + delay_nsec / 1000;
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delay_mov_sum = delay_mov_sum + curr_delay_us - delay_series[curr_count];
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moving_avg[curr_count] = delay_mov_sum / GPS_NTP_DELAY_WIN_SIZE; /* Will be valid after GPS_NTP_DELAY_WIN_SIZE initial values */
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delay_mov_sum_sqrd = delay_mov_sum_sqrd + (curr_delay_us * curr_delay_us) - (delay_series[curr_count] * delay_series[curr_count]);
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moving_var[curr_count] = (delay_mov_sum_sqrd - (delay_mov_sum * delay_mov_sum) / GPS_NTP_DELAY_WIN_SIZE) / (GPS_NTP_DELAY_WIN_SIZE - 1);
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delay_series[curr_count] = curr_delay_us; /* Update the last delay value */
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/* Jitter calc formula as used in Wireshark according to RFC3550 (RTP)
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D(i,j) = (Rj-Ri)-(Sj-Si) = (Rj-Sj)-(Ri-Si)
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J(i) = J(i-1)+(|D(i-1,i)|-J(i-1))/16
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*/
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jitter_val[(curr_count + 1) % GPS_NTP_DELAY_WIN_SIZE] = jitter_val[curr_count] + (labs(curr_delay_us) - jitter_val[curr_count]) / 16;
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logger->info("{}: jitter={} usec, moving average={} usec, moving variance={} usec", __FUNCTION__,
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jitter_val[(curr_count + 1) % GPS_NTP_DELAY_WIN_SIZE],
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moving_avg[curr_count],
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moving_var[curr_count]);
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curr_count++;
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if (curr_count >= GPS_NTP_DELAY_WIN_SIZE)
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curr_count = 0;
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return Reason::OK;
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}
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};
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/* Register hook */
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static char n[] = "jitter_calc";
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static char d[] = "Calc jitter, mean and variance of GPS vs NTP TS";
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static HookPlugin<JitterCalcHook, n, d, (int) Hook::Flags::NODE_READ | (int) Hook::Flags::PATH, 0> p;
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} /* namespace node */
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} /* namespace villas */
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/** @} */
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