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sender.py
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"""
This module contains various functions related to the sender
"""
from math import comb
import numpy as np
from utils import int2list, list2int
class Sender():
"""
This class describes the sender object
"""
def __init__(self, messages, delay_tolerance, degree_not_feedback):
"""
Intialize the basic parameters of the transmission
Parameters
----------
messages : `list`
All the symbols to be transmitted
delay_tolerance : `int`
The delay tolerance or the time for which a packet is useful
degree_not_feedback : `int`
The coding degree to use if no feedback received
"""
self.feedback = None
self.feedback_packet = None
self.messages_list = messages
self.sent_list = [False] * len(messages)
self.delay_tolerance = delay_tolerance
self.degree_not_feedback = degree_not_feedback
def send_packet(self, packet_number, size, scheme='ICC'):
"""
Simulates transmission of one packet
Parameters
----------
packet_number : `int`
The current packet number
size : `int`
No. of 8 bit messages that can be in a packet
scheme : ['ICC', 'repetition']
Method to use while transmission
Returns
-------
`tuple`
The packet header and packet
"""
# Check the scheme
if scheme == 'ICC':
packet = [self.messages_list[packet_number]]
packet_header = [packet_number]
# If feedback received
if self.feedback_packet is packet_number - 1:
oldest_undelivered = self.feedback_packet - int(self.feedback[1:9], 2)
num_missing = int(self.feedback[9:], 2)
if num_missing == 0:
oldest_undelivered = self.feedback_packet + 1
if oldest_undelivered < packet_number:
packet.append(self.messages_list[oldest_undelivered])
packet_header.append(oldest_undelivered)
if num_missing > 1:
if packet_number - oldest_undelivered <= size - 1:
for i in range(oldest_undelivered + 1, oldest_undelivered + num_missing):
packet.append(self.messages_list[i])
packet_header.append(i)
elif packet_number - oldest_undelivered > size - 1 and num_missing == packet_number - oldest_undelivered:
for i in range(oldest_undelivered + 1, oldest_undelivered + size - 1):
packet.append(self.messages_list[i])
packet_header.append(i)
elif packet_number - oldest_undelivered > size - 1 and 1 < num_missing < packet_number - oldest_undelivered:
interest_list = self.messages_list[oldest_undelivered + 1:packet_number]
for _ in range(size - 2):
coded_message, coding_list = self.code(interest_list, packet_number, oldest_undelivered, num_missing)
packet.append(coded_message)
packet_header.append(coding_list)
else:
if self.feedback:
oldest_undelivered = self.feedback_packet - int(self.feedback[1:9], 2)
num_missing = int(self.feedback[9:], 2)
if num_missing == 0:
oldest_undelivered = self.feedback_packet + 1
else:
oldest_undelivered = 0
z = min(packet_number - oldest_undelivered, self.delay_tolerance)
interest_list = self.messages_list[packet_number - z:packet_number]
if z <= size-1:
for i, pack in enumerate(interest_list):
packet.append(pack)
packet_header.append(i + packet_number - z)
else:
for _ in range(size-1):
coded_message, coding_list = self.code(interest_list=interest_list, oldest_undelivered=oldest_undelivered,
packet_number=packet_number, distribution='uniform')
packet.append(coded_message)
packet_header.append(coding_list)
elif scheme=='repetition':
# Fixing the feedback
if self.feedback is not None and self.feedback_packet is not None:
num_missing = int(self.feedback[9:], 2)
oldest_undelivered = self.feedback_packet - int(self.feedback[1:9], 2) if num_missing != 0 else self.feedback_packet + 1
else:
num_missing = 0
oldest_undelivered = 0
# Adding the current element in the pakcet
packet = [self.messages_list[packet_number]]
packet_header = [packet_number]
size -= 1
if self.feedback_packet is packet_number - 1:
if oldest_undelivered == packet_number:
pass
else:
packet.append(self.messages_list[oldest_undelivered])
packet_header.append(oldest_undelivered)
size -= 1
if num_missing > 1 and size > 0:
window_size = packet_number - oldest_undelivered - 1
for i in range(1, min(window_size, size)+1):
packet.append(self.messages_list[packet_number - i])
self.sent_list[packet_number - i] = True
packet_header.append(packet_number-i)
else:
window_size = min(self.delay_tolerance, packet_number - oldest_undelivered)
for i in range(1, min(window_size, size)+1):
packet.append(self.messages_list[packet_number - i])
self.sent_list[packet_number - i] = True
packet_header.append(packet_number-i)
return(packet_header, packet)
def code(self, interest_list=None, packet_number=None, oldest_undelivered=None, num_missing=None, distribution=None):
"""
Code a set of symbols by XORing to form a new symbol
Parameters
----------
interest_list : `list`
The interest window where the symbols are still useful
packet_number : `int`
The current packet number
oldest_undelivered : `int`
The oldest undelivered packet of interest
num_missing : `int`
The number of missing packets
distribution : [None, 'uniform']
If 'uniform' then the degree is chosen from a uniform distribution else the
windowed coding method of degree selection is used
Returns
------
`tuple`
The coded message and the symbols with which it is created
"""
if distribution == 'uniform':
z = min(packet_number - oldest_undelivered, self.delay_tolerance)
coding_degree = min(self.degree_not_feedback, z)
base_index = packet_number - z
else:
probs = [(num_missing - 1) * comb(packet_number - oldest_undelivered - num_missing, d - 1) /
comb(packet_number - oldest_undelivered - 1, d) for d in range(1, packet_number - oldest_undelivered - num_missing + 2)]
coding_degree = probs.index(max(probs)) + 1
base_index = oldest_undelivered + 1
coded_message = int('000000000', 2)
coding_list = []
for _ in range(coding_degree):
# Dont repeat
idx = np.random.randint(0,len(interest_list))
while(idx in coding_list):
idx = np.random.randint(0,len(interest_list))
coded_message = coded_message ^ list2int(interest_list[idx])
coding_list.append(base_index + idx)
coded_message = int2list(coded_message, 8)
return (coded_message, coding_list)
def store_feedback(self, packet_number, feedback):
"""
Store the received feedback
"""
self.feedback = feedback
self.feedback_packet = packet_number