Due 9/5/2012 (3pm)
ELEC 437
Problem Set #1
1. Packets arrive from source 1 as a Poisson process with rate 1 and independently from source 2 as a
Poisson process with rate 2 .
Show that the aggregate arrival process is a Poisson process with rate 1 + 2 .
2
ELEC 437: Solutions to Problem Set #3
Fall 2016
1. Non-Fully Connected Topologies (10 Points)
(a) (7pts) C > D > E > A > B
(c) is a disconnected topology. Flow A is free to transmit whenever it wants. It
does not sense Flow B at all.
(d) is a hidden ter
Due 10/05/2016 (3pm)
ELEC 437/539
Problem Set #3
1. Non-Fully Connected Topologies (10 points)
Consider the five 2-flow 802.11 topologies in Figure 1 where nodes A and B are transmitting to nodes
a and b, respectively. RTS/CTS is off. Binary expontential
ELEC 566
Homework #1
Fall, 2016; Due September 14, Wednesday
Color Centers
10 points
Color center are responsible for beautiful colors of some ancient artwork. Such color centers
are observed in many other materials as well, table salt for example. The fi
Due 9/24/2012 (3pm)
ELEC 437
Problem Set #2
1. A greedy ELEC 437 student decides to increase throughput by modifying his/her 802.11 card in two
ways: disabling binary exponential backo and changing CWmin to 4.
(a) Suppose that the greedy student is compet
Due 10/08/2012 (3pm DH 3127)
ELEC 437
Problem Set #3
(No Late Homework Accepted)
1. Three 802.11 ows. Consider the three 802.11 ows in the gure. As depicted, the middle ow is in
range with neighbors on both sides but the two outer ows are mutually out-of-
ELEC 437: Introduction to Communication Networks
Fall 2012 Midterm Exam
Instructions: Read carefully before beginning.
The time for this exam is 3 hours. The exam must be taken in a contiguous 3 hour slot
beginning when you open the envelope. It must be
ELEC 437: Solutions to Problem Set #1
Fall 2012
Each problem is worth 10 points
1. Each process consists of i.i.d. exponential arrivals. Due to the memoryless property, at any
time the next event of the aggregate process is the earliest arrival among the
ELEC 437: Solutions to Problem Set #2
Fall 2012
Each problem is worth 10 points
1. (a) (3pts) Denote BG as the backo counter of the greedy student and BN as the backo
counter of the non-greedy student. The greedy student wins the contention if BG < BN
wit
ELEC 437: Solutions to Problem Set #3
Fall 2012
Each problem is worth 10 points
1. (a) An example timeline for three ows is depicted in the gure below.
Transmission
DIFS
Backoff
SIFS
SIFS
DIFS
n1
Flow Aa
Backoff
Defer
10
0
15
8
5
time
0
DIFS
defer
Flow Bb
ELEC 437: Solutions to Problem Set #4
Fall 2012
Each problem is worth 10 points
1. Denoting the round trip time as d,
(a) Using the notation from class xmax = e(t0 +d)/ where C = et0 / . Therefore
xmax = Ced/
(b)
t2 t1
d
C et/ C dt +
qmax =
0
C ed/ et/ C
ELEC 437: Solutions to Problem Set #5
Fall 2012
Each problem is worth 10 points
1. (a) TCP throughput for two dierent values of RTT is shown in the gure.
7000
rtt=54ms
rtt=20ms
TCP throughput (pkts/s)
6000
5000
4000
3000
2000
1000
0
4
10
3
10
2
1
10
loss