Lookup table for CW phase noise across timing sources. More...

#include "channel_model.h"

Public Member Functions
RealType	sample (const timing::Timing *timing, RealType time) const noexcept
	Samples phase noise for one timing source at the specified time.

RealType	phaseDifference (const timing::Timing rx_timing, RealType rx_time, const timing::Timing tx_timing, RealType tx_time) const noexcept
	Computes receiver-minus-transmitter phase noise at two propagation times.

Static Public Member Functions
static CwPhaseNoiseLookup	build (std::span< const std::shared_ptr< timing::Timing > > timings, RealType start_time, RealType end_time)
	Builds a phase-noise lookup for the requested timing sources and time range.

Public Attributes
RealType	start_time {}
	Lookup start time in seconds.

RealType	end_time {}
	Lookup end time in seconds.

RealType	dt {}
	Lookup sample spacing in seconds.

std::unordered_map< SimId, CwPhaseNoiseBuffer >	buffers
	Per-timing-source phase-noise buffers.

Detailed Description

Lookup table for CW phase noise across timing sources.

Definition at line 75 of file channel_model.h.

Member Function Documentation

◆ build()

CwPhaseNoiseLookup simulation::CwPhaseNoiseLookup::build	(	std::span< const std::shared_ptr< timing::Timing > >	timings,
		RealType	start_time,
		RealType	end_time
	)

static

Builds a phase-noise lookup for the requested timing sources and time range.

Definition at line 540 of file channel_model.cpp.

    {
        CwPhaseNoiseLookup lookup{};
        lookup.start_time = start_time;
        lookup.end_time = std::max(start_time, end_time);
 
        const RealType sample_rate = params::rate() * params::oversampleRatio();
        lookup.dt = sample_rate > 0.0 ? (1.0 / sample_rate) : 1.0;
 
        const auto sample_count =
            static_cast<std::size_t>(std::ceil((lookup.end_time - lookup.start_time) / lookup.dt) + 1.0);
        constexpr std::size_t phase_noise_warning_threshold_bytes = 500ULL * 1024ULL * 1024ULL;
        const auto bytes_per_buffer = sample_count * sizeof(RealType);
 
        for (const auto& timing : timings)
        {
            if (!timing || lookup.buffers.contains(timing->getId()))
            {
                continue;
            }
 
            CwPhaseNoiseBuffer buffer{};
            buffer.start_time = lookup.start_time;
            buffer.dt = lookup.dt;
            if (timing->isEnabled())
            {
                auto timing_clone = timing->clone();
                if (lookup.start_time > 0.0)
                {
                    const auto skip_count = static_cast<std::size_t>(std::llround(lookup.start_time / lookup.dt));
                    timing_clone->skipSamples(skip_count);
                }
                // TODO: Replace whole-simulation CW lookup generation with chunked/streaming generation.
                if (bytes_per_buffer > phase_noise_warning_threshold_bytes)
                {
                    LOG(Level::WARNING,
                        "CW phase-noise lookup for timing '{}' allocates {} bytes; large scenarios need chunked "
                        "streaming.",
                        timing->getName(), bytes_per_buffer);
                }
                buffer.samples.resize(sample_count);
                std::ranges::generate(buffer.samples, [&] { return timing_clone->getNextSample(); });
            }
 
            lookup.buffers.emplace(timing->getId(), std::move(buffer));
        }
 
        return lookup;
    }

References end_time, LOG, max, params::oversampleRatio(), params::rate(), and start_time.

Referenced by processing::pipeline::applyStreamingInterference().

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◆ phaseDifference()

RealType simulation::CwPhaseNoiseLookup::phaseDifference	(	const timing::Timing *	rx_timing,
		RealType	rx_time,
		const timing::Timing *	tx_timing,
		RealType	tx_time
	)		const

noexcept

Computes receiver-minus-transmitter phase noise at two propagation times.

Definition at line 605 of file channel_model.cpp.

    {
        return sample(tx_timing, tx_time) - sample(rx_timing, rx_time);
    }

References max.

◆ sample()

RealType simulation::CwPhaseNoiseLookup::sample	(	const timing::Timing *	timing,
		RealType	time
	)		const

noexcept

Samples phase noise for one timing source at the specified time.

Definition at line 591 of file channel_model.cpp.

    {
        if (timing == nullptr)
        {
            return 0.0;
        }
        const auto it = buffers.find(timing->getId());
        if (it == buffers.end())
        {
            return 0.0;
        }
        return it->second.sampleAt(time);
    }

References max.

Member Data Documentation

◆ buffers

std::unordered_map<SimId, CwPhaseNoiseBuffer> simulation::CwPhaseNoiseLookup::buffers

Per-timing-source phase-noise buffers.

Definition at line 80 of file channel_model.h.

◆ dt

RealType simulation::CwPhaseNoiseLookup::dt {}

Lookup sample spacing in seconds.

Definition at line 79 of file channel_model.h.

79{}; ///< Lookup sample spacing in seconds.

◆ end_time

RealType simulation::CwPhaseNoiseLookup::end_time {}

Lookup end time in seconds.

Definition at line 78 of file channel_model.h.

78{}; ///< Lookup end time in seconds.

Referenced by build().

◆ start_time

RealType simulation::CwPhaseNoiseLookup::start_time {}

Lookup start time in seconds.

Definition at line 77 of file channel_model.h.

77{}; ///< Lookup start time in seconds.