EC310 16-week Review. Rules of Engagement Teams selected by instructor Host will read the entire...

EC31016-weekReview

Rules of Engagement Teams selected by instructor Host will read the entire questions. Only after, a team may “buzz”

by raise of hand A team must answer the question within 5 seconds after buzzing in

(must have answer at hand) If the answer is incorrect, the team will lose its turn and another

team may buzz in. No score will be deducted. No negative scores. Maximum score is 100. Once reached, that team will stand down

for others to participate. Teams will earn all points scored at the end of game.

When selecting a question, Teams must only select questions of different value, unless there are no others, but may be from different categories.

All team members will participate and will answer questions Only one round - No Daily Doubles, Double Jeopardy or Final

Jeopardy … and no partial credits!

Jeopardy!BGP / BGP

RoutingComm Sys.

EM Spectrum, Signals,

Modulation

A/D Conversion

Digital Modulation

Power Gain, SNR,

Antennas

Propagation / Electronic

Warfare

10 pts 10 pts 10 pts 10 pts 10 pts 10 pts








Briefly describe each of the following Autonomous Systems Categories:(a) Stub AS

(b) Multihomed AS

(c) Transit AS

BGP/BGP Routing 10 pts

- Has only one connection to another AS

- Has more than one connection to other ASes, but doesn’t allow data to pass through it

- Connects to more than one AS and allows traffic to pass through it

Name the four basic components of a communications system.

Comm Sys., EM Spectrum, Signals, Modulation 10 pts

TransmitterReceiver

ChannelNoise

What is the most important advantage of digital communications?

A/D Conversion 10 pts

Relative Noise Immunity – a digital system only has to decide between a finite set, e.g. binary 0 or binary 1 for a binary digital receiver, which is easier even amid of a significant noise.

What digital modulation scheme does each constellation represent?

Digital Modulation 10 pts

BPSKQPSK

8-PSK 16-PSK

8-QAM

Antenna Type

Azimuth beam pattern

Vertical beam pattern

Physical size

Dipole(vertically oriented)

Monopole (vertically oriented)

Yagi (of the driven element)

Fill in the missing information for each antenna type.

Gain, SNR, Antennas 10 pts

omnidirectional

omnidirectional

Depends on gain(it varies)

null

null

Depends on gain(it varies)

λ2

λ4

λ2

For VLF-HF communications, list and describe the basic modes of propagation

Propagation/EW 10 pts

Ground wave – EM waves that travel close to the surface of the earth

Sky wave – EM waves that travel up into the atmosphere and then bend back to earth

Space wave – EM waves that travel in a straight line (direct line-of-sight or LOS)

Describe the steps followed in BGP routing when selecting a route.


1) a BGP router first attempts to find all paths from the router to a given destination

2) it then judges these paths against the policies of the AS administrator

3) it then selects a “good enough” path to the destination that satisfies the policy constraints

What is the wavelength of a radio station whose broadcast frequency is 106.9 MHz?

λ=𝑐𝑓=

3×108𝑚𝑠

106.9×106 𝐻𝑧=𝟐 .𝟖𝟏𝒎


What is quantization error and how can it be mitigated?


Quantization error is the difference between the original analog signal and the reconstructed (stairstep) signal after A/D and D/A. Quantization error can be reduced by increasing the number of bits N for each sample. This will make the quantization intervals smaller, reducing the difference between the analog sample values and the quantization levels.

(a) Consider the frequency spectrum for an FSK signal below. Express the Bandwidth in its simplified form in terms of and .

(b) Using the equation obtained in part (a), consider the following FFT for an FSK signal. Given , what bit rate can this channel support?


𝐵𝑊 =2 (∆ 𝑓 +𝑅𝑏)

∆ 𝑓


Given the following radiation pattern, where each ring represents a 2 dB change in power What is the beamwidth? What is the sidelobe level? What is the front-to-back ratio?

~ 30º

𝑆𝐿𝐿𝑑𝐵=0𝑑𝐵− (−11𝑑𝐵 )=𝟏𝟏𝒅𝑩

𝐹𝐵𝑅𝑑𝐵=0𝑑𝐵− (−11𝑑𝐵 )=𝟏𝟏𝒅𝑩


Consider the diagram and formula below. What is the longest line-of-sight communication range between a transmitter on a DDG with an antenna 130 feet high and a receiver on a small craft with an antenna 12 feet high.

𝑑𝑇𝑜𝑡𝑎𝑙=√2 ∙130 𝑓𝑡+√2∙12 𝑓𝑡=𝟐𝟏𝒎𝒊

𝑑=√2h


What AS path would an IP packet from 12.12.12.1 take to reach 17.17.200.2?

What AS path would an IP packet from 13.13.13.3 take reach 17.17.200.2?

What AS path would an IP packet from 20.20.20.1 take to reach 17.17.200.2?

40 – 2003 – 2005

40 – 2003 – 2005

60 – 40 – 2003 – 2005

Consider the network diagram and BGp route announcement from Router 3 below, assuming no local preferences are set.

What is the time-domain expression of the following modulated signal?

𝑣𝐴𝑀 (𝑡 )=10sin (2𝜋 ∙300,000𝑡 )+5cos (2𝜋 ∙299,000𝑡 )−5 cos (2𝜋 ∙301,000𝑡 )+3cos (2𝜋 ∙298,000𝑡 )−3cos (2𝜋 ∙302,000𝑡 )


sin 𝐴 sin𝐵=12cos ( 𝐴−𝐵 )− 1

2cos ( 𝐴+𝐵 )

Consider the frequencies for a bass guitar below. What minimum sampling frequency must be exceeded in order to accurately reconstruct the signal and avoid aliasing?


Source: http://www.calvin.edu/academic/engineering/2013-14-team10/background.html

Consider the code provided for an 8-PSK system. What would be the bit stream for the phase shifts received as (0°) (225°) (45°) (90°)?

If the phase shifts are received at 20 µs intervals, what is the baud rate?

What is the bit rate?


Ans: 000111001011

Phase shift = Symbol


The signal power at the input to the receiver is 6.8 nW and the noise power at the input to the receiver is 2.4 nW. Find SNR.

A transmitter feeds a dipole antenna (gain G = 1.64) with 150 Watts of power. Calculate EIRP.

𝑆𝑁𝑅=𝑃𝑆

𝑃 𝑁

=6.8𝑛𝑊2.4𝑛𝑊

=𝟐 .𝟖𝟑

𝐸𝐼𝑅𝑃=𝑃 𝑡 𝐺𝑡=(150𝑊 ) (1.64 )=𝟐𝟒𝟔𝑾

Propagation/EW 40 pts During an operation, you discover your communications are being

jammed by an opposing force. Intelligence indicates the jammer is at 9 km from you and can generate an EIRP of 20 Watts. You cannot destroy the jammer at this time, so you decide to move closer to your source to mitigate your received J/S. The source is generating an EIRP of 10 dB. How close do you have to be from the source to achieve a received J/S of -3 dB?

, , ,

Name and describe (include negative and positive consequences) one technical solution that an AS network operator can use to combat prefix hijacking an MITM attack on BGP networks?


Filtering – Best current practices for AS network operators dictate the use of filters at AS borders to reject suspicious route announcements or alter malicious route attributes. Filters are manually established based on the routing policies of an organization. Filtering has both a business cost and computational cost associated with it.

Internet Routing Registries – These are repositories of the IP prefixes, ASNs, routing policy, network topology, and human points of contact for those ASes which choose to register their information. While this method may be effective, the downside is that these registries are only effective if the registry data is secure, complete, and accurate, which is currently not guaranteed.

Resource Public Key Infrastructure (RPKI) – Similar to the IRRs, RPKI is a repository of Internet routing information. The key difference is that it uses the X.509 certificate system to provide cryptographic assurance of (1) the association between an ASN and the IP prefixes it has been allocated, and (2) the association between an ASN and the IP prefixes it is authorized to originate.

There is nothing in RPKI which validates the route attributes, including the AS path, associated with a BGP route announcement from an AS.

Nor does it provide certainty that the AS which has registered their information used the correct ASN or set of prefixes.

Nor does it provide network topology information or human points of contact as with IRRs. Lastly, it does not mandate that network operators use this information when constructing their filters. How RPKI is applied is entirely dependent on what AS network operators choose to do with the information

available.

Consider the figure below, and calculate the following:

(a)

(b)

(c)


Consider the following analog waveform. It is to be sampled at 2 MHz and quantized with a 2-bit quantizer (input voltage range is -2.0 V to +2.0 V). Using digital bits sequentially from low to high, what is the series of transmitted bits representing the waveform?


Ans: 1111100101101001011010

11

10

01

00

11

11

10

01

01

10

10

01

01

1010

(Underlined bits are borderline)

Consider a system using 16-PSK modulation.

(a) How many bits per symbol are used (N)?

(b) If the baud is 15,000 symbols/second, what is the bit rate ?

(c) How much bandwidth does this system need?

(d) What would be the major drawback in using a higher M-ary modulation like 32-PSK?


𝑁=log2𝑆=log216=𝟒𝒃𝒊𝒕𝒔 /𝒔𝒚𝒎

𝑅𝑏=𝑅𝑆×𝑁=( 15,000 𝑠𝑦𝑚𝑠𝑒𝑐 )( 4𝑏𝑖𝑡𝑠

𝑠𝑦𝑚 )=𝟔𝟎 ,𝟎𝟎𝟎𝒃𝒑𝒔=60𝑘𝑏𝑝𝑠

𝐵𝑊 =2𝑅𝑏

𝑁=2×60,000𝑏𝑝𝑠4𝑏𝑖𝑡𝑠/ 𝑠𝑦𝑚

=𝟑𝟎 ,𝟎𝟎𝟎𝑯𝒛=30𝑘𝐻𝑧

As more symbols are added, their phases get closer making the system more susceptible to noise as correctly differentiating between symbols would be more difficult.


For the diagram below, Pin = 2 mW, AP1 = 10, AP2,dB = -4 dB, and AP3,dB = 3 dB. Calculate Pout,dBW

Note: There are different ways to approach this problem. and

Consider the Friis Free Space equation . Your cell phone transmits at a power level of 500 mW, and has an antenna gain of 2 dB. The cell tower has an antenna gain of 8 dB. Your cell phone is dual-band, so it can transmit at either 800 MHz or 1900 MHz, depending on your location. What combination of frequency and distance from the tower would yield the highest power level at the tower, 800 MHz at a distance of 8 km or 1900 MHz at a distance of 4 km? note: Justify answer by comparing power levels.


, , , ,

Hence, the cell phone transmitting at 800 MHz would yield the highest received power level at the tower even at double the distance of 8 km.

EC310 16-week Review. Rules of Engagement Teams selected by instructor Host will read the entire...

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