1
TCOM 370
April 23, 1999
Solutions to Homework 99-8
Problem 1
Prcfw_empty slot = 0.1 = e G G = 2.3
Prcfw_collided slots = 0.6
Prcfw_success = 1 0.1 0.6 = 0.3
But we know that Prcfw_success = Ge G , and if we use the value of G (=2.3) calculated using Prc

TCOM 370
Exam 1
1 Hr. 15 Min.
Closed Book
Feb. 12, 1998
One Info. Sheet Allowed
All problems equally weighted
Problem 1
(a) Define the term "full duplex" in describing data transmission links.
(b) Give two methods for achieving full duplex in data transmi

T COM 370
April 1, 1997
Exam 2
1 Hr. 15 Mins.
One Summary Sheet Allowed
Equal Points for all Four Problems
Problem 1
Binary messages of length 4 are protected by a 3-bit frame check sequence generated by a CRC
code with generator polynomial X3+X 2+1.
(a)

1 Hr. 15 Min.
Closed Book
T COM 370
Exam 2
March 24, 1998
One Info. Sheet Allowed
All problems equally weighted
Problem 1
(a) For each of the following line coding schemes, apart from synchronization
considerations, s tate one characteristic that is consi

May 8, 1997
Closed Book
T COM 370
Final Exam
1:30 - 3:30
3 Summary Sheets Allowed
Problem 1 (9)
The fastest standard for transmitting data over standard telephone lines allows transmission
from an internet service provider to a user's modem at 56 Kbps. As

TCOM370
Solutions to Homework 99-1
Problem 1
4 hops (point-to-point links) between two terminals nodes; Transmission rate 9600 bps on
all links; 24 overhead bits [Header + Trailer] for each packet; 1ms per-hop signal
propagation delay. 1 sec. Call set-up

TCOM370
Homework Set 3 Solution
Problem 1
The number of bits per character prior to transmission is 11 bits, of which 7 are
information bits, and the other 4 bits are transmission over head. Thus only
7
of the
11
transmitted bits are useful information. S

1
TCOM 370 Homework 5 Solutions March 16, 1999
Problem 1 (#3 in 1998 Exam 2)
(Hand-out in class)
Problem 2 (#1 in 1997 Exam 2)
(a) Generate the FCS using long division:
0000000 no remainder
1101000 X 6 + X 5 + X 3
X3
X 3 + X 2 +1 X 6 + X 5 + X 3
X6 + X5 +

Solutions to Homework Set 4, March 4 1999
Problem 1
(a)
00000
00
01101
01
10110
10
11011
11
Recall that for linear block codes, the minimum Hamming distance equals the
minimum Hamming weight. The minimum Hamming weight of non-zero codewords
equals 3,

1
TCOM 370
March 30, 1999
Solutions to Homework #6
Problem 1
3
(a) H =
Pn logPn = (0.5log 0.5 + 0.25log 0.25 + 0.25log 0.25) = 1.5
n =1
bits/symbol
(b)
A 1/2
B 1/4
0
0
1
C 1/4
A
B
C
1
0
10
11
or
1
01
00
(c) (i) Cant do any better since the number of bit

1
TCOM 370
April 8, 1999
Solutions to Homework #7
Problem 1
Stop-and-wait
U no error =
Tix =
N
5 10 3
Tix
Tix + 2T p
, where N = I-frame length in bits. We want:
U=
N
N + 2T p 5 10
3
=
N
N + 2 20 10
3
5 10
3
=
N
0.5
N + 200
N
100
2
N 200
Problem 2
T p

February 18, 1997
T COM 370
Exam 1
One Summary Sheet Allowed
1 Hr. 10 Mins.
Equal Points for all Problems
Problem 1
(a) List the seven layers of the ISO-defined open systems interconnection protocol architecture.
(b)
Identify the layers at which the follo