Tactical Wireless Communications and Networks
Design Concepts and Challenges
Problems Manual
Prepared by
George F. Elmasry and Yan Grushevsky
Chapter 1
1- Assume IP host addresses area assigned at random at two separate LANs on a tactical
network. What is the probability of creating an IP address conflict using IPv4? What is
the same probability using IPv6? Include restricted IP addresses
2- Continuing with problem 1, let us consider that LANs on a tactical network are only
assigned Class C IP addresses based on IPv4 schemas. What is the probability of creating
this IP routing conflict under the same assumption of random assignment of addresses
within Class C?
3- Refer to Figure 1.4 in this chapter (Overhead with the OSI stack layers) and let us
consider the case of VoIP packets of the G.729 codec. A VoIP packet has 20 bytes of
payload and 40 bytes of UDP, RTP, and IPv4 headers. The codec transport layer creates
50 VoIP packets per second. Consider that the DLL of a tactical radio added another 80
bytes of header and trailer and the MAC frames are of size 48 bytes +5 bytes for headers
(the last MAC frame corresponding to the packet must be padded). Let us also assume
that the MAC layer adds a rate 1/(1+1/3) redundancy for recovering lost MAC frames.
Let us also assume that the physical layer adds its own redundancy of rate ½ (double the
size of the handed MAC frames). What is the final ratio of the original VoIP packet
information content (the 20 bytes of payload) to the physical layer bits?
4- Continuing with problem 3, if the transport layer creates handshaking packets of rate 2
packets per every 50 packets of VoIP packets (2 packets per second) of the same size as
VoIP packets, the network layer creates packets of average size of 60 bytes per packet
and of the rate of 5 packets per second (control traffic). Assume also that a network
management utility sends packets of average size of 180 bytes and at the rate of 6
packets per second. Can you find the same ratio of the original VoIP packet information
content to physical layer bits?
5- Continuing with problems 3 and 4, let us assume that all packets generated above the IP
layer (VoIP packets and handshaking packets) have an added encryption header of 120
bytes per packet (exclude network management and IP control traffic). Can you find the
same ratio of the original VoIP packet information content to physical layer bits?
6- What are some of the main causes of VoIP inefficiency in tactical wireless networks?
7- Unlike VoIP, with data transmission over tactical Networks, we can have a large payload
per packet making the effect of overhead much less than that of VoIP. What do you
think is the main challenge of data transmission over tactical wireless networks?
Chapter 2
1- Consider the case of M-AM (M-level Amplitude Modulation, where M is an even
number) where the number of bit transmitted per symbol is (log 2 M). The transmitted
signal is related to a data symbol xi ∈ {0, 1, … , M − 1} by si (t) = (2xi − M + 1)  (t),
where  (t) is the common signal shape to all signals. Assume the net amplitude
modulation is symmetric at each AM constellation point. Arranging the M-constellation
points on a straight line separated by a distance of d = 2a, and do the following
a. Draw the one dimensional signal space constellation for this case form s0 to
sM−1 symmetrically around the zero-power point.
b. Define the decision regions on this constellation
c. What is the energy level of each signal?
d. What is the average signal energy associated with this set?
e. Assuming a unit-energy-basis projection, and the variance noise component is
N0 /2 creating a zero mean Gaussian noise, draw the Pdfs around the decision
regions showing the probability density of error and find the conditional error
probability of the inner constellation points (as a Q-Function).
f. Continuing with 1-e, find the conditional error probability of the outer two
points of this constellation (as a Q-Function)
g. Drive the average symbol error probability (considering both inner and outer
points).
h. Considering that the relationship between signal energy and bit energy is related
as follows: Es = Eb log 2 M, proof that for large M, this M-AM constellation is
less efficient in energy utilization than binary antipodal signal by a factor of
(3 log 2 M)/(M 2 − 1).
i.
Is there an improvement in spectral efficiency since we send log 2 M bits per
symbol?
j.
Considering the use of Gray code with this constellation, and assuming that the
nearest-neighbors error are predominant, drive an approximation of the
probability of bit error with this constellation.
2- It is difficult to drive similar analysis to problem 1 above for the different QAM
constellation in Figure 2.15 of this chapter. In QAM, inner constellation points have 4
nearest neighbors, the edge points have three nearest neighbors and the corner points
have two nearest neighbors.
a. For the three constellations in Figure 2.15 of this chapter, define the three
different decision regions of each constellation (2 regions are already defined for
the 16-QAM)
b. Derive an upper bound of the probability of symbol error for QAM in general
c. For the 32-QAM, assuming signal spacing d = 2a in each dimension,
i. What are the various energies for the different points of the
constellation?
ii. How many instantiations are there for each energy level?
iii. Assuming the different energy levels are transmitted with equal
probabilities, what is the average energy expressed as a function of the
signal spacing?
iv. Express the upper bound of the probability of symbol error for QAM
(which you derived in 2-b above) in terms of bit energy
v. What is the relative efficiency in terms of dB of this 32-QAM compared to
antipodal signaling?
π
3- What is the Gray Code for the 4-PSK signals? (The phase change is multiple of 2 ).
4- Create the Gray Code labeling for the 16 QAM signal constellations in Figure 2.15 of this
chapter.
5- Referring to Equations (2-17) and (2-18) of this chapter, Drive all the steps starting from
Equation (2-17) that results in Equation (2-18) expressing the coherent antipodal
signaling with Rayleigh fading.
6- Drive the analysis on coherent orthogonal signals with Rayleigh fading leading to
Equation (2.19) of this chapter.
7- Consider a 4-ary Pulse Position Modulation (PPM), which used four rectangular pulses
each with amplitude A and pulse duration of Ts /4, where the symbol interval Ts = 2Tb
(Tb is the bit interval for 2 bits per symbol).
a. What are the Fourier Transforms of these four signals?
b. Estimate and plot the power spectrum for the 4-ary PPM
8- Referring to Figures 2.22 and 2.23 of this chapter. Let us assume that an enemy jammer
was able to accurately estimate the slot length in both cases (fast hopping and slow
hopping). If the slow hopping slot length is 6 times the length of the fast hopping slot
length, the number of frequency carriers are 8 and the frame time period allocated for
slotting repeatedly is 6Ts . Where Ts is the time to transmit a symbol.
a. Create the frequency-time grid in both cases showing all possible frequency/time
hopping slots for each case and a random hopping pattern.
b. If the enemy jammer could not follow the hopping pattern and relied on
randomly jamming one frequency per frame time. What is the probability of that
jammer hitting a slot utilized for transmission (just causing an error in the
transmission) during a frame time? Calculate this probably in both cases.
c. Continuing with b above, what do you see the benefit of fast hopping with these
kinds of jammers?
d. A sophisticated jammer can sense the transmission frequency and switch to it
with some lag of time. Let us assume that we have a sophisticated jammer that
1
only need 3 TS lag time to zoom on the transmission frequency. What is the
probability of that jammer hitting a utilized slot? What is the error pattern in
both cases?
1
e. What if the jammer’s lag time is 4 TS ? Sketch the error pattern and estimate the
average jamming rate.
f. If you are to design a frequency hopping tactical radio, what will be you limit on
how fast you will hop?
g. For this problem, if you are to design a tactical radio, what are the top factors
you would consider to overcome jammers? If you are to design a frequency
hopping jammer, what will be the top factors to consider for jamming the
signal??
Chapter 3
1Over the telegraphy channel, source symbols are expressed using the channel symbols
which can be a dot, a dash, a letter space or a word space. Channel symbols are:
 a dot: the line is closed for one unit time and then opened for one unit time
 a dash: the line is closed for three unit times and opened for one unit time
 a letter space: the line is opened for three unit times
 a word space: the line is open for six unit times
The table below shows the international Morse Code statistics for the English Alphabet used in
Telegraphy. Column two shows the international Morse code Dot-Dash combination used to
express every character (symbol) , while column three shows the time duration in terms of time
unit used to carry each symbol.
Symbol
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
Space
International Morse Code
. __
__ . . .
__ . __ .
__ . .
.
. . __ .
__ __ .
. .. .
..
. __ __ __
__ . __
. __ . .
__ __
__ .
__ __ __
. __ __ .
__ __ . __
. __ .
. ..
__
. . __
. . . __
. __ __
__ . . __
__ . __ __
__ __ . .
Symbol Duration in time units
9
13
15
11
5
13
13
11
7
17
13
13
11
9
15
15
17
11
9
7
11
13
13
15
17
15
6
Symbol Probability
0.0642
0.0127
0.0218
0.0317
0.1031
0.0208
0.0152
0.0467
0.0575
0.0008
0.0049
0.0321
0.0198
0.0574
0.0632
0.0152
0.0008
0.0484
0.0514
0.0796
0.0228
0.0083
0.0175
0.0013
0.0164
0.0005
0.1859
a- Sort the table based on symbol duration in time units. Plot a correlation between
symbol duration and symbol probability. What kind of correlation you see between
symbol probability and symbol duration in time units?
b- Find the entropy of the given English alphabet symbols
c- If you are to design an ASCII code like for these symbols, how many bits per symbol
̅ ratio of this ASCII like code?
would you need? What is the Entropy to N
d- Consider the Symbol Duration in time units’ column, what is the average time units per
symbol transmission?
e- With the telegraphy channel, how many Morse code times units are used to express
each information bit?
2- Submarine communications is challenging. A submarine Coax cable channel can send a
positive pulse, a negative pulse or a zero level during each channel symbol time. The cable
type requires that at least one zero must follow each positive or negative pulse.
a. What is the largest set of codewords of length 4 channel symbols?
b. Draw a state transition diagram of this channel showing the transition between the
three channel symbols as states.
c. Express the set of 4 channel symbols over the transition diagram in 2.c.
3- The table below shows the Franaszek code. This is a prefix code that translates a bit stream
(0 and 1 occur with the same probability) into codewords with specific characteristics.
Source Codeword
11
10
000
010
011
0010
0011
Encoded Codeword
0100
1000
000100
001000
100100
00001000
00100100
a. By inspecting the codewords, what is the least number of 0s that must follow every
1?
b. What is the maximum number of 0s that can occur in an encoded sequence?
c. What is the probability of each source code word? What is the coding rate for this
code?
4- You are given an example of octal source symbols (0, 1, 2, 3, 4, 5, 6, 7) with the following
probabilities:
1
P0 = P1 = P2 = P3 = 32;
1
P4 = P5 = 16;
1
P6 = 4;
1
P7 = 2;
a. Calculate the Entropy per octal symbol for this source
b. What is a common method (ASCII like binary) of representing this source
c. Design a variable length source code that has an average block length equals to the
entropy.
d. Encode the source octal sequence 30127 using the code you designed.
000110000000001000101
5- A computer executes the following four instructions for ADD, SUB, MPY and STO. Let us
assume we designate the codewrds (00, 01, 10, 11) to these four instructions. Let us assume
that these instructions are used independently with probabilities (3/4, 1/16, 1/16, 1/8). If
we use a code that approaches the Entropy, what is the percentage of reduction of the
average number of bits used to communicate these instructions?
6- Is the following source code uniquely decodable? Show if it is or it is not.
C0 : 101
C1 : 0011
C2 : 1001
C3 : 1110
C4 : 00001
C5 : 11001
C6 : 11100
C7 : 010100
7- The (7, 4) linear block code shown in table 3.2 of this chapter is capable of correcting one bit
error per the 7 bit received code word (minimum Hamming distance = 3). The probability of
block error is the probability of that two or more bit errors occur per code word.
a. When this code is used over a BSC with crossover probability of p, what is the
probability of block error?
b. Let us assume that there exists another hypothetical code with the same rate of 4/7
but with double the codeword size (14, 8) and with a minimum Hamming distance
of 6. When this hypothetical code is also used over the same BSC with the same
crossover probability of p, will the probability of block error be more, less, or the
same? Show why using p = 0.01 and with referencing the law of large number.
8- Referring to Section 3.2.1 of this chapter, use generation matrix in Equation (3.32) to find
the codeword corresponding to the message (1011).
9- Referring to Section 3.2.3 of this chapter and the convolutional encoder in Figure 3.10, use
the information sequence u = (10111) to:
a. Find the output sequence v (1) , and v (2) relying on shifting the bits in the figure.
b. Find the same output sequence using discrete convolution of modulo-2 using g (1) and
g (2) of this convolutional encoder.
c. Find the output code word from interlacing v (1) , and v (2)
Chapter 4
1- Patients arrive to the emergency room independently at random. Assume their arrival
follow a Poisson process (exponential inter-arrival time) and that the time spent with
the ER staff to treat each patient is exponentially distributed with an average of 20
minutes. If the average arrival rate is one patient every 30 minute. Does this ER, as an
M/M/1 queue model, reach a steady state?
2- Customers arrive at a fast food restaurant at a rate of 5 person/minute. They wait on
the service line on the average for 5 minutes before they receive their order. The
probability of a customer eating in the restaurant is 0.5 and the probability for taking
their order “to go” is 0.5. On the average, a meal takes 20 minutes to be eaten.
Calculate the average number of customers in the restaurant.
3- A queuing system is empty at time t=0, assume six packets arrive at time {1, 3, 4, 7, 8,
15}. These packets needed the service times {3.5, 4, 2, 1, 1.5, 4}.
a. Find the departure time, wait time and system time for each packet.
b. Sketch a figure similar to Figure 4.2 in this chapter showing α(t) and β(t).
c. Sketch the number of packets in the system versus time.
4- A tactical Radio subnet is capable of transmitting at a maximum rate of 50kbps. Assume
packets transmitted have a length that follows an exponential distribution with a mean
of 1000 bits. The subnet has 10 nodes each with one session generating Poisson traffic
at a rate of 150 packet/min.
(a) If the radio is designed with fixed resource allocation such that the 10 nodes are
statically allocated 10 equal capacity TDMA channels. Assume a TDMA slot transmits
10 packets. Find the average delay per packet, the average number of packets in
each node’s queue, and the average number of packets queued in the system
(subnet).
(b) If the radio is designed with statistical multiplexing (TDMA time slots are optimally
assigned on need based), find the average delay per packet, the average number of
packets in each node’s queue, and the average number of packets queued in the
system (subnet).
(c) If the radio designer used fixed resource but decided to assign half of the nodes a
time slot to transfer 5 packets while the other half is assigned a time slot to transfer
2 packets. find an approximation of the average delay per packet, the average
number of packets in each node’s queue, and the average number of packets
queued in the system (subnet).
5- Consider the M/M/m queue model in Section 4.2.2.2 of this chapter. Consider the case
when the number of servers reaches ∞ (we have an M/M/∞) case. Starting from the
global balance equations of the Markove chain representation of this queue model, find
p0 and pn . What is the average delay of this queue model?
6- Consider a system similar to the M/M/m queue model in Section 4.2.2.2 of this chapter
but is a loss system in the sense that if an arrival finds all m servers busy, it does not
enter the systems and is lost. We refer to this system as the M/M/m/m system where
the last m in this notation indicates the limit in the number of customers in the system.
This system can represent virtual circuits in a network where customers in the system
correspond to active virtual circuit sessions and the maximum number of virtual circuits
between two nodes is m circuits. Here the average service time
1
μ
is the average
duration of the virtual circuit session. The M/M/m/m model means that blocked
requests are lost (they are not waiting in the queue to be serviced).
a- Sketch the state transition diagram representation of this system.
b- Find the BLOCKING PROBABILITY. That is the steady state probability where all
circuits are busy and an arriving request for a virtual circuit is denied service.
7- Consider a simple routing problem shown in the figure below where node A sends traffic
to node B using two links with service rate μ. Packets arrive at node A according to a
Poisson process with rate λ packets per second. Packet transmission times are
exponentially distributed and independent of the inter-arrival times as in the M/M/1
system. Let us assume that the arriving traffic is divided equally among the two links.
You are given two design approaches in dividing the traffic to evaluate. The first
approach is called randomization where each packet is assigned to one of the two links
based on a fair coin flip (entirely random). The second approach is called selective
where you create a common queue for the two links and send the packet at the head of
the queue to the link that becomes idle first.
a- Which approach performs better in terms of average delay per packet? Quantify
that gain in delay.
b- What is the impact of the selective approach on the Poisson character of the arrival
process?
1
8- For the M/M/2 queue model, what is p0 , p1 and pQ when ρ = 2 , when ρ = 0.9 and
when ρ approaches 1.
Chapter 5
1- Consider the RS (31, 15) used in Link 16
a. What is the minimum Hamming distance of the code?
b. What is the code error correction capability in terms of symbols and bit (assume
no erasure).
c. Assuming erasure used with this code, what is the minimum number of symbols
must be received by the decoder to reconstruct a codeword?
2- Consider the case of an RS encoding with erasure of rate ¾ where a block of three
symbols are encoded into four symbols. The decoder can reconstruct the original three
symbols in the block upon receiving any three of the four symbols. Assume a stream of
12 source symbols being encoded as 16 symbols for sending over a channel that causes
burst error. Assume the channel causes a burst of three symbols in erasure.
a. If we have no interleaving, can the burst error be recovered?
b. Show that interleaving can ensure the recovery of any burst of three-symbol
erasure error
3- A legacy radio terminal receives a block of information every 10 microseconds. The
terminal has a decoder that checks every block of information for errors and corrects
the errors pattern if possible. The maximum number of errors it can correct is 3 errors
per block. If the block has no error, the decoder will release after 1 microsecond. If the
block has 1 error, the decoder will release it in 5 microseconds, and if the block has
more than 1 error, the decoder will release it in 20 microseconds. Information blocks
wait in the queue if the decoder is busy. Assume that the decoder is initially empty.
Assume that the first 10 blocks had the following number of errors {0, 1, 3, 1, 0, 4, 0, 1,
0, 0}.
a. Plot the number of information blocks queued in the decoder as a function of
time.
a. What is the mean number of blocks in the decoder queue?
b. Based on this sample of information blocks, what is the probability that the
decoder queue is empty?
c. Based on this sample of information blocks, what is the probability of decoder
failing to correct an error pattern in the block?
4- Legacy tactical radios such as Link 16 tend to face burst errors with high channel error
probability during periods of fading and a very small error probability during nominally
good periods. One of the challenges we face in representing these tactical radios
channel characteristics in modeling and simulation environments is creating a good
representation in state machine like for this fading pattern. A classic modeling approach
creates a discrete Markov chain representation that assigns the channel model at the
bit/symbol level to one of two states: State 0, the channel is ”good” and state 1, the
channel is ”bad”. At state 0, the bit/symbols error probability could be low (e. g. , 10−5 )
and at State 1, the channel bit/symbol error probability is high (e.g., 0.5).
a. Draw the state transition diagram for these two state Markov model showing:
 p00 as the probability that the channel is the good (0) state and transition to
the good state
 p01 as the probability that the channel is the good state and transition to the
bad (1) state
 p11 as the probability that the channel is the bad state and transition to the
bad state
 p10 as the probability that the channel is the bad state and transition to the
good state
b. From the 2-state Markov representation, drive the steady state probability
equations
c. The following values of state transition probability are found to represent some
measured mild fading channels with acceptable accuracy, find the probability
that the channel is in a good state and the probability that the channel is in a bad
state.
d. For the following values of state transition probability, find the probability that
the channel is in a good state and the probability that the channel is in a bad
state.
e. Assuming that at state 0, the bit/symbols error probability is 10−5 and at State 1,
the channel bit/symbol error probability is 0.5. Find the average error probability
in both cases given in (c) and (d).
5- One of the challenges we have with moving the battlefield to IP, is the use of IP over
legacy waveforms such as Link 16. The protocol stack below gives a conceptual view of
using IP over Link 16 to transmit data using TCP/IP relying on an adaptation layer.
TCP
𝜆1 IP packets per second
IP
Adaptation layer
𝜆16 Messages per second
Link 16
𝜇16 Messages per second
(Function of Link 16 BW)
One of the main challenges here is the low rates of Link 16 data modes considering the
demand for bandwidth of most IP applications.
a. Using the tandem queues model in the figure and assuming M/M/1
approximation for each queue, find the maximum rate of IP packets per second
to be transmitted over Link 16 as a function of Link 16 bandwidth and the Link 16
message queue length to limit the average number of link 16 messages in the
queue to 32 messages.
b. If Link 16 bandwidth allows for serving 8 messages per second, an IP packet is
divided into 7 Link 16 messages, and the average queue length for the Link 16
message queue is 32 messages. Find λ1
c. If we want to limit the link 16 message queue size to 48 messages, any message
arrives when the queue has 48 messages is dropped. Find the probability that we
drop a link 16 messages.
d. Because of the fact that breaking IP packets into Link 16 messages generate a
burst arrival of Link 16 messages at the message queue, the M/M/1 queue
model could be a bad approximation. A better approach would be to create
cross layer signaling from the Link 16 message queue to the IP layer (or the
adaptation layer referred to in the figure) in order to make the IP layer packet
arrival rate decreases from λ1 to λ2 where λ2 < λ1 , when the Link 16 queue
reaches a threshold of T1 messages. Find T in order to
i. Ensure that the link 16 message queue of size 48 messages can absorb up
to two IP packets arrival at once.
ii. Relying on M/M/1 approximation, if λ2 = 0.5 λ1 . Assume that the links 16
message queue is emptied, what is the probability of the queue reaching
4 messages in order to signal the IP layer to go back to λ1 .
Chapter 6
1- Routing through tactical networks core can use different options. Let us assume we have
the depicted in the figure below where nodes A and B communicate through a terrestrial
link followed by two satellite hops then another terrestrial link. Let us assume that the
1
terrestrial links each introduce delay of τ according to the following exponential pdf of delay
function:
1
ft (t) = τe−τt , where τ = 10 msec −1
Let us also assume that the satellite hops each introduce fixed delay of 250 msec followed
by exponential delay according to the following pdf of delay function
1
ft (t) = τe−τt , where τ = 5 msec −1
Satellite
Satellite
Terrestrial
Terrestrial
A
B
a) Find the end-to-end expected value of delay and the variance of delay between
nodes A and B assuming delays at each link are independent.
b) Let us assume that we were able to add a new terrestrial link between nodes C and
B with the same delay characteristics as the other terrestrial links as shown in the
figure. Find the end-to-end expected value of delay and the variance of delay
between nodes A and B if node C is able to route the traffic distant to node B over
the new link.
2- Consider the network topology in the figure below. Let us assume that all links has a
capacity of 10 units (the units specifying link capacity and traffic load is irrelevant). Let us
assume that all traffic is sourced at nodes 1 and 2 and is distant to node 6.
1
4
2
5
3
6
a. If the traffic load sourced at each of nodes 1 and 2 is 5 units, what is the worst
routing scenario and what is a good scenario?
b. If the traffic load sourced at each of nodes 1 and 2 is 5 and 15 units respectively, find
three different routing scenarios that you can consider “worst, bad, and best”.
3- Techniques such as ROSPF can allow the increase of the number of nodes (IP addresses)
within a MANET subnet without flooding the subnet with control traffic such as Link State
Updates (LSUs). Let us assume that we have a subnet that has a minimum control traffic
load expressed as T0 . This is an indication of the control traffic generated over the MANET
subnet regardless of the number of nodes in the subnet and regardless of the use of ROSPF
or OSPF. Let us assume that in the case of using OSPF, the control traffic generated from
OSPF is an increasing linear function of the number of nodes with a slope “a”. Let us also
assume that in the case of using ROSPF, the control traffic generated from ROSPF is an
increasing linear function of the number of nodes with a slope “b”, where b < a.
a. Sketch a plot of the control traffic as a function of the number of nodes in the
subnet for both OSPF and ROSPF cases
b. Let us assume that the subnet can only accommodate control traffic to a certain
load T1 before control traffic load can cause a catastrophic failure of the subnet
because it leaves little or no room for user traffic. Drive the increase in the number
of nodes in the subnet with the use of ROSPF as a function of T0 , T1 , a and b.
c. If the slope a is one (a 45o angle), the slope b is
1
√3
(a 30o angle), what is the increase
in the number of nodes in the subnet as a function of n1 ?
4- Let us assume that we have a case of cross layer signaling between layers 2 and 3 such that
as layer 2 capacity increases or decreases, layer 3 sends traffic to layer 2 equal to layer 2
capacity but with a lag of time. The lag of time causes some traffic shaping (layer 2 drops
traffic at some moments). Let us assume that layer 2 capacity follows a raised sinusoidal
function expressed a:
C (t) = A + L sin(t)
The offered traffic load by Layer 3 becomes
T(t) = A + L sin(t − B),
where B indicates the lag of time
a. Sketch layer 2 capacity and layer 3 load as a function of t, and show instants where
traffic will be shaped by layer 2
b. Express the shaped traffic as a function of t.
c. If lag B= 1.4 % from period of sin() function, what is the shaped traffic as a function of
t.
5- Consider Figure 6.10 in this chapter showing hop reuse for TDMA slots. Assume the same
constraints as Figure 6.10 are set forth where there is a broadcast reuse after 3 hops.
Assume that we have 64 nodes in the subnet perfectly forming an 8*8 grid with the gird
reflecting the number of hop counts.
a. Sketch this grid of 64 nodes (8*8) showing that only 16 TDMA slots can be shared
among these 64 nodes while meeting the three-hop TDMA slot reuse constraint.
b- Select a corner node, an end node and a middle node of the 8*8 grid and show for
each of these three nodes the transmitting slot STi , the receiving slots SR j , and the
neighbors ‘s neighbors transmitting slots NNTi
6- Consider a tactical node with two security classifications generating the same traffic pattern
independently with equal inter-arrival time R and transmitting over an encrypted core. You
are provisioned a certain bandwidth over the network core and you have two design
options on queuing the encrypted packets for transmission over the network core.
Option 1: Divide the provisioned bandwidth into two identical channels one for each
security enclave where each channel will serve packets with equal transmission time T,
where the equal inter-arrival time R > T.
Option 2: Statistically multiply the two traffic streams for transmission over the core where
T
the packet transmission time becomes 2.
a- Find the average system time of the packet in the two case
b- Find the difference in variance of waiting time in the queue between the two
options.
For Chapters 7-11, Students will be given a class project assignment to choose a research
paper from a peer reviewed IEEE journal or the IEEE communications magazine (military
communications issues). The student will summarize the paper and prepare a 10 minute
power point slides to present in the front of the class. Exceptions may be given to select a
MILCOM (or any other conference) paper if the conference paper has great impact, related
to the course materials, well written and presents a comprehensive problem definition and
new contributions to the field. Topics for these papers will include:
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Cognitive radios and there use in tactical networks
Open architecture in tactical networks
Bringing commercial wireless technologies to tactical networks
Gamming Theory and its applications to tactical networks
Network Operations in tactical networks