Source code for cr.nimble._src.noise
# Copyright 2021 CR.Sparse Development Team
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import jax
import jax.numpy as jnp
from jax import random, jit
from cr.nimble import promote_arg_dtypes
from cr.nimble import arr_l2norm_sqr
[docs]def awgn_at_snr_ms(key, signal, snr):
"""Generates noise for the signal at the specified SNR based on signal energy
"""
signal = jnp.asarray(signal)
signal = promote_arg_dtypes(signal)
n = signal.size
energy = arr_l2norm_sqr(signal)
mean_energy = energy / n
mean_energy_db = 10*jnp.log10(mean_energy)
noise_mean_energy_db = mean_energy_db - snr
sigma = 10**(noise_mean_energy_db/20)
noise = sigma * random.normal(key, signal.shape)
return noise
[docs]def awgn_at_snr_std(key, signal, snr):
"""Generates noise for the signal at the specified SNR based on std ratio
Note:
Signal is expected to be zero mean
"""
signal = jnp.asarray(signal)
signal = promote_arg_dtypes(signal)
sigma_s = jnp.std(signal)
sigma_n = sigma_s*10**(-snr/20)
noise = sigma_n * random.normal(key, signal.shape)
return noise
awgn_at_snr = awgn_at_snr_ms