Module units 

Unit newtypes for the quantities that are routinely confused.

A decibel value is a Db, never a bare f64; an E_{b}/N_{0} is an EbN0 and an E_{s}/N_{0} an EsN0, so that passing one where the other is expected is a compile error. Conversions are explicit methods, never From impls that hide a formula.

The decibel conversions of plain numbers (db2lin, lin2db, db2amp, amp2db, dbm2w, w2dbm, db2np, np2db) are defined here, once: the methods of the newtypes call them, and comnum_math re-exports them (comnum_math::db2lin is this function), so that a value in dB converts to the same bits whichever way it is written.

Model

With k coded bits per symbol and a code rate R,

$$ \left.\frac{E_{s}}{N_{0}}\right|{\mathrm{dB}} = \left.\frac{E{b}}{N_{0}}\right|{\mathrm{dB}} + 10 \log{10}(k R) $$

Examples

use comnum_core::units::{Db, EbN0};
let es = EbN0(Db(4.0)).to_es_n0(2.0, 1.0);       // QPSK, uncoded
assert!((es.0.0 - 7.0103).abs() < 1e-4);
assert!((Db(3.0).to_linear() - 1.9953).abs() < 1e-4);
assert!((Db::from_linear(10.0).0 - 10.0).abs() < 1e-12);
// the newtype and the function are one conversion
assert_eq!(Db(3.0).to_linear(), comnum_core::units::db2lin(3.0));
// 2.6 information bits per symbol (a shaped or coded constellation)
let es = EbN0(Db(4.0)).to_es_n0(2.6, 1.0);
assert!((es.0.0 - (4.0 + comnum_core::units::lin2db(2.6))).abs() < 1e-12);

Structs

Db

A power ratio in decibels.

EbN0

Energy per information bit over the noise spectral density, E_{b}/N_{0}.

EsN0

Energy per symbol over the noise spectral density, E_{s}/N_{0}.

Hertz

A frequency or a rate (sample rate, symbol rate), in hertz.

Seconds

A duration, in seconds.

Functions

amp2db

Linear amplitude ratio to dB: 20 log10(x).

db2amp

Amplitude ratio in dB to linear: 10^{x/20}.

db2lin

Power ratio in dB to linear: 10^{x/10}.

db2np

Attenuation in dB per unit length to nepers (power): α_dB / (10 log10 e).

dbm2w

Power in dBm to watts: 10^{P/10} · 1 mW.

lin2db

Linear power ratio to dB: 10 log10(x).

np2db

Attenuation in nepers (power) per unit length to dB: 10 log10(e) · α.

w2dbm

Power in watts to dBm.