def gilberts_model(probability, frame=None, state=True):
"""
Takes a frame and distorts it based on probabilty(param);
every frame has a chance to become distorted, and to arrive correctly
P(error) + P(no error) = 100%
After error occurence, probabilities are swapped;
and swapped again after correct transmission.
errors and correct transmissions are grouped together.
e.g.
P(error) = 10%
P(no error) = 90%
*error occures*
P(error) = 90%
P(no error) = 10%
*correct transmission*
P(error) = 10%
P(no error) = 90%
:param probability:
:param frame:
:param state:
:return:
"""
probability = int(probability * 100)
if frame is None:
frame = Frame(1, np.zeros(8)) # failsafe if frame is not given
for index in range(frame.__len__()):
rand = random.randint(1, 10000)
if state: # if previous frame was sent correctly
if rand in range(1, probability +
1): # if rand is in range of probability
if frame.packet[
index] == 1: # and then changes this bit's value
frame.packet[index] = 0
else:
frame.packet[index] = 1
state = False # changing the state after error; False -> error occured
# when sending the previous frame
elif not state: # if previous frame was sent with error
if rand in range(
10000 -
probability): # if rand is in range of new probability
if frame.packet[
index] == 1: # and then changes this bit's value
frame.packet[index] = 0
else:
frame.packet[index] = 1
else:
state = True # changing the state after no error; True -> successful transmission
# when sending the prefious frame
return state, frame # returns frame, and state after transmission
