IT300 Midterm Review

disadvantages of converting analog data to digital data

-> complexity -> processing delays -> conversion processes resulting in loss of data -> requires synchronization -> data errors caused by noise

advantages of converting analog data to digital data

-> compression -> security -> error control -> efficiency - virtual links -> noise elimination

optical signal

-> exhibit both wave-like and particle behaviors -> optical waves are immune from radio frequency interference or (rfi) -> optical signals are produced by photos -> optical signals are much higher in frequency (THz region) than rf signals (3kHz to 300GHz)

radio frequency (rf)

-> signal exhibit 'wave-like' behavior -> rf waves are produced by electrical current traveling through a conductor

dBW and dBm

-> since it is a ratio, it is unitless, but we often associate the ratio with a reference. --> i.e. a power ration can be referenced to 1 watt or 1 milliwatt

how many hertz are in one terahertz?

1E12 Hz = 1 x 10^12

how many hertz is one kilohertz?

1E3 Hz = 1 x 10^3

how many hertz is one megahertz?

1E6 Hz = 1 x 10^6

how many hertz are in one gigahertz?

1E9 Hz = 1 x 10^9

The amount of symbols n amount of bits can represent

2^n

voice grade electrical signals can be achieved with a smaller bandwidth between what two numbers?

300Hz and 3400Hz

6 GHz = _______ kHz. Answers: a. 6,000,000 kHz b. 6,000 kHz c. 600, 000 kHz d. 6E10 kHz

6,000,000 kHz (1 GHz is 1,000,000 kHz)

A communications link is an end-to-end path between communicating users through a network. Answers: True False

False

A unipolar signal crosses zero, while a bipolar signal always remains positive. Answers: True False

False

Low SNR is preferred in a communications link, since it means that the noise will also be low. Answers: True False

False

Multipath fading in an urban environment is a severe issue for unguided digital communications. Because of this, MIMO (multiple in, multiple out) antenna systems should never be used for communications in an urban setting. Answers: True False

False

Network availability takes into consideration both the amount of time that the network fails and is not functioning, as well as the time it takes to bring the network back into full service. Answers: True False

False

Optical signals are not part of the electromagnetic (EM) spectrum. Only radio frequency (RF) waves are considered part of the EM spectrum. Answers: True False

False

Orthogonal Frequency Division Multiplexing (OFDM) is a spread spectrum technology. Answers: True False

False

RF and Optical signals are both E-M waves. Therefore, you can collect an optical E-M wave using an RF antenna. Answers: True False

False

The noise floor includes thermal noise, impulse noise, intermodulation noise (IM), and cochannel interference (CCI). Link margins are only added to counter weather. Answers: True False

False

equation for watts #2

P (watts) = I^2 x R = v^2/R

equation for watts #1

P (watts) = V (volts) x I (amps)

equation for power

P (watts) = VI = I^2R = V^2/R

equation for time in seconds

T (seconds) = 1/f(Hz)

A carrier is a periodic wave that can be represented by either a sine or cosine wave. Once the carrier is combined with a message (i.e., information) wave, the modulated carrier (i.e., passband or modulated signal wave) will have a frequency bandwidth that can be viewed in the frequency domain. Answers: True False

True

A switched circuit is one in which a user maintains the physical path through a network during the period of a call. Once the user's call is complete, the communications path is made available to other users. Answers: True False

True

A virtual circuit enables the sharing of physical links by numerous users. Time division multiplexing (TDM) and packet switching techniques are ways in which virtual circuits can be created. Answers: True False

True

An E-M wave is a transverse wave in which amplitude changes in the electric and magnetic fields are perpendicular to the direction of wave propagation. Answers: True False

True

An unguided signal can be split into several transmission paths, with each path experiencing different impediments (e.g., reflection, scattering, etc.), thus causing each path to vary in length. This results in several copies of the signal reaching the receiver at slightly different times, thus leading to signal distortion. This is termed multipath fading. Answers: True False

True

By viewing a signal in the frequency domain, you can determine the both the amplitude and frequency bandwidth of the signal. Answers: True False

True

Depolarization of a transmitted signal reduces the amount of energy transfer between the RF wave and antenna. Answers: True False

True

Frequency division multiplexing (FDM) can be used for either analog or digital communication. Time division multiplexing (TDM) can only be used to multiplex digital communications. Answers: True False

True

In an unguided RF system, frequency reuse can be accomplished by transmitting two different signals at the same frequency, but with each EM signal having an orthogonal polarization from the other. Answers: True False

True

In unguided medium (free space), the electromagnetic (EM) signal wave spreads as it leaves the transmit antenna. Since the power of the EM signal resides at the surface area of the wave front, signal power is described as signal power density (i.e., watts per area). As the signal propagates away from the transmitter, power density decreases, and attenuation is experienced. Answers: True False

True

It is useful to observe an information signal in both the time and frequency domains. The time domain gives us information about the signal's amplitude over time, while the frequency domain gives us information regarding signal frequency and bandwidth. Answers: True False

True

MIMO antenna systems intentionally takes advantage of multipath using spatially diversified transmit and receive antennas, and digital signal processors (DSPs). Answers: True False

True

Only MMF cores can be constructed as step-index or graded index cores. Answers: True False

True

Radio Frequency (RF) signals propagate as an electromagnetic (EM) wave. Optical signals behave as both a wave and as a particle as it propagates. Although optical waves possess this "wave-particle duality", they are still considered EM waves. Answers: True False

True

Signal modulation is used to mix a baseband signal with a carrier wave for the purpose of relocating the modulated channel to the higher carrier frequency. Answers: True False

True

Signals on UTP guided medium are in a balanced configuration, which is how it handles RF noise. This differs from coaxial cables, which are in an unbalanced configuration. Answers: True False

True

The Antenna Reciprocity Theorem states that an antenna's RF characteristics are the same whether it is transmitting or receiving. Answers: True False

True

The OSI Data Link Layer (Layer 2) identifies the standards and specifications used to communicate within a "common network" (ex. 100BaseT Ethernet). However, the Data Link Layer does not provide end-to-end network connectivity over disparate common networks. Answers: True False

True

The greater the frequency bandwidth of a signal the greater the signal's information carrying capacity. Answers: True False

True

The time varying components of capacitance and inductance results in reactive power elements that can decrease power transfer. Answers: True False

True

Using a direct sequence spread spectrum (DSSS) technique spreads a narrow band channel so that it occupies greater frequency spectrum. By doing this, the signal has greater immunity from narrow band noise. Answers: True False

True

When considering the impact of impulse noise, we find that it is more devastating to a digital communications link, than an analog one. Therefore, error control methods should be used on all digital links. Answers: True False

True

When datagrams are exchanged using a connectionless virtual circuit, there is no guarantee that datagrams will arrive in proper sequence. It is left to the upper OSI layers to re-sequence received datagrams. Answers: True False

True

When determining the decibel value of the signal-to-noise ratio (SNR), both the signal and noise floor power must be referenced to the same power units (i.e., both referenced to 1 watt or 1 milliwatt, etc.). However, SNR is a unitless ratio. Answers: True False

True

With error control, n-k bits are added to a dataword (k-bits in length) to create a codeword (n-bits in length). Answers: True False

True

equation for volts #2

V (volts) = I (amperes) x R (ohms)

Ohm's Law

V (volts) = I (amperes) x Z (Ohms)

equation for volts #1

V (volts) = joules/coulombs

passband signal

a baseband signal that has been shifted to a higher frequency for transmission

decibel (dB)

a relative measure between two quantities, used in communication systems since it helps us to simplify calculations

ideal isotropic antenna

a theoretical, perfect omnidirectional 'point' antenna that spreads its over the surface of a perfect sphere

power density (watts per unit surface area)

a way to determine the power available to a receiving antenna

Determine the data rate possible given 64-QAM modulation where M=64, and baud rate is 4800 baud. Answers: a. 28.8 kbps b. 48 kbps c. 14.4 kbps d. 1.44 kbps

a. 28.8 kbps

34.5 watts = _______ mW Answers: a. 34,500 mW b. 15.3 dBm c. 45.37 dBW d. 34.5E-3 mW

a. 34,500 mW (1 watt = 1000 milliwatts)

Convert 300 watts to dBm Answers: a. 54.77 dBm b. 24.77 dBm c. 300 dBm d. 24.77 dBW

a. 54.77 dBm [P](dBm) = 10log10( 𝑃1𝑚𝑊)

You digitize an analog signal that has a frequency bandwidth of 20kHz, using a bit depth of 16. What data rate must be supported? Answers: a. 640 kbps b. 64 kbps c. 320 kbps d. 256 kbps

a. 640 kbps

Convert 47 dBW to dBm Answers: a. 77 dBm b. 17 dBm c. -17 dBm d. -17 dBW

a. 77 dBm

Identify the type of circuit in which the user maintains exclusive 24/7 access to the physical path. Answers: a. Dedicated Circuit b. Switched Circuit c. Virtual Circuit d. Packet Switched Circuit

a. Dedicated Circuit

Select the correct statement(s) regarding FM. Answers: a. FM is considered "envelope modulation" because the amplitude of the modulated carrier does not change with the message b. AM is better than FM regarding noise rejection c. Bessel functions are used to determine modulated carrier amplitudes in the time domain d. all statements are correct

a. FM is considered "envelope modulation" because the amplitude of the modulated carrier does not change with the message

Select the correct statement(s) regarding amplitude modulation (AM). Answers: a. If the AM Index is greater than 1 (i.e., µAM>1), then overmodulation occurs leading to signal distortion b. With AM, the message is captured as carrier frequency changes c. The AM modulated carrier bandwidth is always equal to the baseband bandwidth d. All of the above are correct

a. If the AM Index is greater than 1 (i.e., µAM>1), then overmodulation occurs leading to signal distortion

Determine the decibel values of thermal noise power (N) and thermal noise power density (No) given the following: T=298 degrees Kelvin, B = 20MHz. (note: brackets "[ ]" represent decibel values) Answers: a. [N] = -130.85dBW, [No]= -173.86dBm b. [N] = +130.85dBW, [No] = +203.86 dBm c. [N] = -127.84 dBW, [No]= -203.86 dBW d. [N] = -98.22 dBm, [No]= -173.79 dBm

a. [N] = -130.85dBW, [No]= -173.86dBm

Select the correct statement(s) regarding the difference between analog and digital signals. Answers: a. analog signals are comprised of an infinite number of amplitudes and time slices b. digital signals are only represented by discrete values of "0s" and "1s", and therefore can never convey analog information c. digital signals are more accurate than analog signals; this is why digital music sounds much better d. analog networks easily fit into the OSI Reference Model

a. analog signals are comprised of an infinite number of amplitudes and time slices

Select the correct statement(s) regarding impedance in a communications circuit. Answers: a. capacitance and inductance changes with signal frequency b. impedance is comprised of only real resistive components c. the greater the reactance in a circuit, the less the overall resistance of within the circuit d. all are correct statements

a. capacitance and inductance changes with signal frequency

A ___________ data compression technique results in some of the original data being lost. Answers: a. lossy b. lossless c. analog d. PCM

a. lossy

Given the following AM modulated signal, determine the original message, m(t): s(t) = 2.5[1+0.5 cos(2π25kHz*t)] cos(2π88MHz*t) Answers: a. m(t) = 1.25cos(2π25kHz*t) b. m(t) = 1.25cos(2π88MHz*t) c. m(t) = 2.5cos(2π25kHz*t) d. m(t) = 2.5cos(2π88MHz*t)

a. m(t) = 1.25cos(2π25kHz*t)

Identify the device that combines multiple time slots or frequency channels into an aggregate for transmission. Answers: a. multiplexer b. modem c. repeater d. switch

a. multiplexer

Select the correct statement(s) regarding connectionless and connection-oriented networks. Answers: a. packet networks support either connection-oriented or connectionless circuits b. A connection must be established prior to exchanging data when using a connectionless circuit c. packets must contain source and destination addresses in a connection-oriented circuit d. all statements are correct

a. packet networks support either connection-oriented or connectionless circuits

Identify the correct group of propagation modes and impediments which impact unguided signal transmissions. Answers: a. reflection, scattering, diffraction b. refraction, modal dispersion, direct LOS c. reflection, absorption, impedance d. crosstalk, modal dispersion, absorption

a. reflection, scattering, diffraction

Given the following parameters, select the correct equation for the amplitude modulated (AM) carrier signal. Am=2v, Ac=2.8v, fm=5000Hz, fc=10GHz, φm=0, φc=0 cos(2π10E9t) Answers: a. s(t) = 2.8[1+0.71 cos(2π5kHz*t)] cos(2π10E9t) b. s(t) = 2.8[1+1.4cos(2π5000t)] cos(2π10E6t) c. s(t) = 2[1+6.5 cos(2π3500t)] cos(2π100t) d. s(t) = 2[1+0.93 cos(2π100t)] cos(2π100E3t)

a. s(t) = 2.8[1+0.71 cos(2π5kHz*t)]

An analog signal with a bandwidth of 36MHz is sampled at a frequency (fs) of 36,000,000 samples per second during the ADC (analog-to-digital conversion) process. What is the outcome of the received signal after the DAC (digital-to-analog conversion) process? Answers: a. the signal will have experienced aliasing b. the signal will not experience aliasing c. the signal will perfectly represent the original pre-ADC analog signal d. none of the above describes the outcome

a. the signal will have experienced aliasing

Identify the correct equation that describe the relationship between a sine and cosine wave. Answers: a. v(t) = A sin (2πft + π/2) = A cos (2πft) b. v(t) = A sin (2πft) = A cos (2πft + π/2) c. v(t) = A sin (2πft ) = A cos (2πft) d. v(t) = A sin (2πft - π/2) = A cos (2πft)

a. v(t) = A sin (2πft + π/2) = A cos (2πft) formula for sine and cosine waves: m(t) = Am cos(2πfmt±φ), or m(t) = Am sin(2πfmt±φ

Information

accumulated data that provides context that can be interpreted

broadband signal

an aggregate of more than one baseband signal

Convert -10 dBW to milliwatts Answers: a. 0.1 mW b. 100 mW c. -100 mW d. -0.1 mW

b. 100 mW

10,000 kHz is equivalent to: Answers: a. 10,000kHz b. 10MHz c. 1MHz d. 1GHz

b. 10MHz

Given the following information, determine the [SNR] in decibel form: [Pr] = [S] = -70dBm, T=300oKelvin, B=36MHz Answers: a. -173.83 dB b. 28.27 dB c. -98 dB d. 98 dB

b. 28.27 dB

A signal has a frequency range from 300Hz to 3.4kHz. What is the frequency bandwidth in Hz? Answers: a. 1300E6 Hz b. 3100 Hz c. 1.6 kHz d. 130 MHz

b. 3100 Hz (3.4kHz - 300Hz = 3100Hz)

A five-bit dataword can represent how many encoded symbols (i.e., A, B, C, 1, 2, 3, etc.)? Selected Answer: Answers: a. 16 symbols b. 32 symbols c. 64 symbols d. 128 symbols

b. 32 symbols (2^5 = 32)

Given the following PM modulated signal equation, determine the frequency bandwidth. s(t)=3cos(2π13E9t + 0.4cos(2π13E3t)) Answers: a. 22kHz b. 36.4 kHz c. 72.8 kHz d. 116 kHz

b. 36.4 kHz

Determine the data rate possible given 32-QAM modulation where M=32, and baud rate is 9.6 kbps. Answers: a. 4.8 kbps b. 48 kbps c. 14.4 kbps d. 1.44 kbps

b. 48 kbps

Convert -33 dBW to milliwatts Answers: a. 3 mW b. 50 mW c. -50 mW d. -3 mW

b. 50 mW [P](dBW) = 10log10( 𝑃1𝑊)

128-QAM tells us that a single symbol equals _____ logical bits. Answers: a. 6 b. 7 c. 4 d. 3

b. 7

Which modulation method represents logical data by changing the carrier wave's frequency. Answers: a. ASK b. FSK c. PSK d. QAM

b. FSK

A modulated signal represents digital data using a set of frequencies {f1, f2, f3, f4, f5, f6, f7, f8}. What is the digital modulation technique and how many bits can a single symbol represent? Answers: a. FSK, 2 bits per symbol b. FSK, 3 bits per symbol c. PSK, 4 bits per symbol d. PSK, 2 bits per symbol

b. FSK, 3 bits per symbol

Given the following AM modulated signal, determine the occupied frequency bandwidth (note: assume double-sideband large carrier (DSB-LC): s(t) = 2.4[1+0.7 cos(2π33Hz*t)] cos(2π10GHz*t) Answers: a. Frequency bandwidth = 33 Hz b. Frequency bandwidth = 66 Hz c. Frequency bandwidth = 10GHz d. Frequency bandwidth = 20GHz

b. Frequency bandwidth = 66 Hz

What is the difference between M-ary line coding and M-ary modulation? Answers: a. there is no difference b. M-ary line coding results in a baseband signal, while M-ary modulation results in a modulated digital signal c. M-ary line coding applies to digital baseband signals, while M-ary modulation applies to analog signals d. Hartley's Law applies to M-ary line coding but not to M-ary modulation

b. M-ary line coding results in a baseband signal, while M-ary modulation results in a modulated digital signal

In selecting a line coding technique, we consider the need for receive clock synchronization, as well as the frequency bandwidth occupied by the resulting signal. What is true about the Manchester line coding technique. Answers: a. Manchester occupies less frequency spectrum (i.e., frequency bandwidth), than simpler line coding techniques such as NRZ b. Manchester ensures signal transitions for each bit sent, thus helping to ensure receive clock synchronization; however, it occupies twice the frequency bandwidth compared to NRZ c. Manchester ensures greater receive clock synchronization and efficient bandwidth usage compared to NRZ d. there are no true statements listed above

b. Manchester ensures signal transitions for each bit sent, thus helping to ensure receive clock synchronization; however, it occupies twice the frequency bandwidth compared to NRZ

Determine the decibel value of SNR given a signal power, S=-100dBm, and noise power, N=-128dBm. Answers: a. SNR = -228 dB b. SNR = 28 dB c. SNR = -28 dB d. SNR = 228 dB

b. SNR = 28 dB

What is the purpose of a transducer? Answers: a. They are used to transform potential energy (joules) into power (watts) b. Transducers are used to convert one form of signal energy into another form of signal energy. As an example, a microphone is an example of a transducer. c. Transducers are used to convert DC signals into an alternating (AC) signal d. None of the above are correct

b. Transducers are used to convert one form of signal energy into another form of signal energy. As an example, a microphone is an example of a transducer

Select the true statement regarding Amplitude Modulation (AM). Answers: a. when using DSB-LC AM modulation, the frequency bandwidth is fm b. both DSB-LC and DSB-SC have a frequency bandwidth of 2fm c. SSB modulation provides the highest quality AM signal d. there are no true statements

b. both DSB-LC and DSB-SC have a frequency bandwidth of 2fm

How do coaxial cables prevent RF interference? Answers: a. by adopting a balanced signal configuration b. by use of a properly grounded conductive shielding surrounding the signal wire c. by implementing noise cancellation techniques d. all of the above

b. by use of a properly grounded conductive shielding surrounding the signal wire

What is true about delay skew? Answers: a. delay skew is only a problem with coaxial cables b. delay skew exists in UTP cables (e.g., Cat 5E) where each wire pair is twisted at different twist ratios c. delay skew only exists in unguided systems where path reflection causes signal copies to reach the receiver at different times d. delay skew is another term for signal propagation

b. delay skew exists in UTP cables (e.g., Cat 5E) where each wire pair is twisted at different twist ratios

Given a wavelength of λ=1000 meters, determine the frequency and signal time period. Answers: a. f=30 kHz, T=3.34E-6 seconds b. f=300 kHz, T=3.34E-6 seconds c. f=3000 kHz, T=3.34E-8 seconds d. f=30,000 kHz, T=3.34E-9 seconds

b. f=300 kHz, T=3.34E-6 seconds formula used: frequency = f=1/T, where T is the period of the sinusoidal wave in seconds -> DO NOT FORGET THAT WHEN YOU FIND FREQUENCY IT IS IN HZ AND MUST BE CONVERTED TO KHZ.

Given the following parameters, select the correct equation for the amplitude modulated (AM) carrier signal. Am=6.5v, Ac=7v, fm=3500Hz, fc=100kHz, φm=0, φc=0 Answers: a. s(t) = 7[1+1.08 cos(2π3500t)] cos(2π100E3t) b. s(t) = 7[1+0.93 cos(2π3500t)] cos(2π100E3t) c. s(t) = 7[1+6.5 cos(2π3500t)] cos(2π100t) d. s(t) = 6.5[1+0.93 cos(2π100t)] cos(2π100E3t)

b. s(t) = 7[1+0.93 cos(2π3500t)] cos(2π100E3t)

Given the following message, m(t), carrier, c(t), and Kvco=4300(Hz/v), determine the FM modulated signal equation and FM index. m(t)=2.5cos(2π4000t), c(t)=3cos(2π2GHz*t). Answers: a. s(t)=2cos(2π5E6t + 1.56sin(2π3500t)), β=1.56 b. s(t)=3cos(2π2E9t + 2.68sin(2π4E3t)), β=2.68 c. s(t)=4cos(2π5E9t + 2.57sin(2π3500t)), β=2 d. s(t)=4cos(2π3500t + 2.57sin(2π5MHz*t)), β=2.57

b. s(t)=3cos(2π2E9t + 2.68sin(2π4E3t)), β=2.68

Given the following message, m(t), carrier, c(t), and Kp=0.1(rad/v), determine the PM modulated signal equation and PM index. m(t)=2cos(2π4000t), c(t)=4cos(2π8MHzt). Answers: a. s(t)=4cos(2π4E6t + 0.75cos(2π3500t)), µPM=0.75 b. s(t)=4cos(2π8E6t + 0.2cos(2π4E3t)), µPM=0.2 c. s(t)=3cos(2π4E6t + 0.75cos(2π3500t)), µPM=0.75 d. s(t)=4cos(2π4000t + 0.2cos(2π8E6t)), µPM=0.2

b. s(t)=4cos(2π8E6t + 0.2cos(2π4E3t)), µPM=0.2

What is true about the frequency bandwidth of a modulated electrical or electromagnetic (EM) signal? Answers: a. signal bandwidth is only determined by the frequency of the unmodulated carrier wave b. the baseband message bandwidth and selected modulation method determines the transmitted bandwidth of the modulated carrier c. the message/baseband bandwidth has no impact on the modulated signal bandwidth d. a and c are true

b. the baseband message bandwidth and selected modulation method determines the transmitted bandwidth of the modulated carrier

Select the correct statement(s) regarding frequency modulation (FM) bandwidth. Answers: a. the more the carrier frequency is allowed to change frequencies (Δf), the smaller the modulated signal bandwidth b. the larger the FM index, β, the larger the modulated signal bandwidth c. as you increase kvco, you decrease modulated signal bandwidth d. all statements are correct

b. the larger the FM index, β, the larger the modulated signal bandwidth

Calculate the amplitude of a sinusoidal signal at t=8E-03s given the following equation: c(t) = 5 cos(2π(60Hz)t + π/2) Answers: a. 1.67E-2 b. 5 c. -6.3E-1 d. 0.04

c. -6.3E-1 (8E-03 is equivalent to 8 x 10^-3)

Determine the maximum theoretical data rate possible given a frequency bandwidth of 22MHz, SNR=101, and M=8. Answers: a. 27 Mbps b. 91 Mbps c. 147 Mbps d. 285 Mbps

c. 147 Mbps

56 watts = ______ dBW Answers: a. 47.48 dBW b. 17.5 dBm c. 17.48 dBW d. 26 dBW

c. 17.48 dBW 10log(Power/1W) = dBW 10log(56/1) = 17.48 dBW

A signal has a frequency range from 300kHz to 10,000Hz. What is the frequency bandwidth? Answers: a. 1300E6 Hz b. 2,900 Hz c. 290 kHz d. 130 kHz

c. 290 kHz

16QAM tells us that a single symbol equals _____ logical bits. Answers: a. 2 b. 3 c. 4 d. 5

c. 4

A single symbol represents the following logical values: 00, 01, 10, 11. At a baud rate of 2400, what is the resulting bit rate using Hartley's Law? Answers: a. 1200 bps b. 2400 bps c. 4800 bps d. 9600 bps

c. 4800 bps

Convert 120E3 mW to dBm Answers: a. 30 dBm b. 20.8 dBm c. 50.8 dBm d. 80.8 dBm

c. 50.8 dBm

A DC circuit with is driven by 12 volt supply and a DC load of 200 Ohms. Calculate I (Amps) and P (Watts). Answers: a. 720 A, 60 W b. 2.4 mA, 28.8 mW c. 60 mA, 720 mW d. 12 A, 200 W

c. 60 mA, 720 mW formula used: Ohm's Law: V = I x R Power (watts) = VI = I2R = V2/R Z = R +jX where XC = 1/(2πfC), XL= 2πfL

Given the following PM modulated signal equation, determine the frequency bandwidth. s(t)=3cos(2π13E9t + 2cos(2π13E3t)) Answers: a. 22kHz b. 40kHz c. 78 kHz d. 116 kHz

c. 78 kHz

Calculate the data rate for a 9600 baud signal where each symbol can take on one of two levels (M=2) Answers: a. 2400 bps b. 4800 bps c. 9600 bps d. 9600 kbps

c. 9600 bps

What is correct regarding an ideal isotropic antenna? Answers: a. An ideal isotropic antenna is a highly efficient antenna used extensively in today's communication systems b. An ideal isotropic antenna is a specialized antenna used to direct EM signal energy towards a specific direction c. An ideal isotropic antenna is a theoretical antenna that does not exist in practice, but is useful in explaining power density and unguided EM signal attenuation d. None of the above are correct statements

c. An ideal isotropic antenna is a theoretical antenna that does not exist in practice, but is useful in explaining power density and unguided EM signal attenuation

Select the true statement regarding error control algorithms. Answers: a. ARQ is solely an error detection algorithm b. the concept of codeword and dataword is only applicable to error correction c. CRC is an error detection method that requires the use of a shared polynomial between communicating nodes d. PCM is a prime example of an error detection method

c. CRC is an error detection method that requires the use of a shared polynomial between communicating nodes

_________ is noise caused when the same frequency is used by adjacent transmitters that interfere with one another. Answers: a. Thermal noise (N) b. Intermodulation noise (IM) c. Cochannel interference (CCI) d. Impulse noise

c. Cochannel interference (CCI)

Select the correct statement(s) regarding DCE and DTE interfaces. Answers: a. DTE and DCE describes the device types (e.g., computers, switches, routers, etc.) b. distinguishing between DTE and DCE is only required for half-duplex communications c. DTE and DCE describes the interface and direction of data flow between devices; a single device may have both types of interfaces d. all statements are correct

c. DTE and DCE describes the interface and direction of data flow between devices; a single device may have both types of interfaces

Select the correct statement(s) regarding FDM and TDM. Answers: a. FDM and TDM are both identical in the way channels are aggregated; therefore their terms can be used interchangeably b. FDM aggregates channels by separating each by time slots, whereas TDM aggregates channels by frequency c. FDM separates channels in the frequency domain, whereas TDM separates time slots in the time domain d. TDM requires guard channels in between information channels, whereas FDM does not require the use of guard channels

c. FDM separates channels in the frequency domain, whereas TDM separates time slots in the time domain

A telephone is an example of: Answers: a. Simplex Communications b. Half Duplex Communications c. Full Duplex Communications d. Complex Communications

c. Full Duplex Communications

Select the correct statement(s) regarding fiber optic cable. Answers: a. The core and cladding within a fiber optic cable must have the same refractive index in order to achieve TIR (Total Internal Reflection) b. Only single mode fiber (SMF) can be constructed with either a "step" or "graded index" core c. Multimode optical fibers (MMF) are vulnerable to modal dispersion d. All statements are correct

c. Multimode optical fibers (MMF) are vulnerable to modal dispersion

Select the correct statement(s) regarding EM waves. Answers: a. EM depolarization enables frequency reuse b. RHCP and LHCP are EM waves that are considered linearly polarized c. RHCP or LHCP waves can be created by transmitting the same signal, separated by 90 degrees, using orthogonal polarizations d. all of the statements are correct

c. RHCP or LHCP waves can be created by transmitting the same signal, separated by 90 degrees, using orthogonal polarizations

Select the correct statement(s) regarding SMF and MMF fiber optic cables. Answers: a. since MMF cables support multiple modes of light, it has greater capacity and supports greater distances compared to SMF b. Both MMF and SMF can be designed with step index or graded cores c. SMF propagates a single mode of light, thus reducing signal distortion d. all of the statements are correct

c. SMF propagates a single mode of light, thus reducing signal distortion

Select the correct statement regarding acoustic and electrical signals Answers: a. Acoustic wave propagate at the speed of light (3E8 m/s) b. Electrical waves depend upon the existence of air molecules in order to propagate c. Transducers are required to turn acoustic signals into an electrical signal d. Acoustic signals are electrical signals

c. Transducers are required to turn acoustic signals into an electrical signal

Question 29 10 out of 10 points You want to capture and digitize an analog signal that has a frequency bandwidth of 5500 Hz. You select a sampling rate of 5500 samples per second. What happens to your digitized signal? Answers: a. You should be fine since your sampling rate is the same as the analog signal's bandwidth b. You cannot sample an analog signal since it is infinite and continuous c. Your digital signal will experience aliasing because you did not follow Nyquist sampling rate requirements d. None of the above

c. Your digital signal will experience aliasing because you did not follow Nyquist sampling rate requirements

Determine the decibel values of thermal noise power (N) and thermal noise power density (No) given the following: T=303 degrees Kelvin, B = 36MHz. (note: brackets "[ ]" represent decibel values) Answers: a. [N] = +128 dBW, [No]= +204dBm b. [N] = -128.22 dBW, [No] = -203.79 dBm c. [N] = -128.22 dBW, [No]= -173.79 dBm d. [N] = -98.22 dBm, [No]= -173.79 dBW

c. [N] = -128.22 dBW, [No]= -173.79 dBm

Given a receive power of 7E-5 mW and a noise power in decibels of N= 144E-13 W, determine the decibel SNR value. Answers: a. [SNR] = -173.5 dB b. [SNR] = +66.87 dB c. [SNR] = +36.87 dB d. [SNR] = +84.03 dB

c. [SNR] = +36.87 dB

Given a receive power of 80E-6 mW and a noise power in decibels of [N]= -125dBW, determine the decibel SNR value. Answers: a. [SNR] = -80e-6 dBm - 123.5 dBm = -173.5 dB b. [SNR] = -40.97Bm - (123.5 dBm) = -165.97 dB c. [SNR] = -40.97 dBm - (-95 dBm) = 54.03 dB d. [SNR] = 40.97 dBm - (-125 dBm) = +84.03 dB

c. [SNR] = -40.97 dBm - (-95 dBm) = 54.03 dB

Select the correct statement(s) regarding symbol rate (baud rate) and bit rate (bits per second). Answers: a. a single logical bit can represent one or more symbols b. symbol rate is another term for bit rate - they are the same c. a symbol can represent one or more logical bits d. all are correct statements

c. a symbol can represent one or more logical bits

Select the correct statement(s) regarding the Shannon-Hartley Capacity Theorem. Answers: a. data rate capacity is a function of carrier frequency and signal bandwidth b. the theoretical Shannon capacity identifies the lowest data rate capacity achievable; today's digital systems can reach capacities much greater than the Shannon limit. c. according to the theorem, an increase in signal bandwidth or SNR results in an increase in bit rate capacity d. all of the above are correct statements

c. according to the theorem, an increase in signal bandwidth or SNR results in an increase in bit rate capacity

Select the correct statement(s) regarding directional antenna beamwidth. Answers: a. beamwidth increases as frequency increases b. beamwidth increases as the diameter of a parabolic antennas increases c. beamwidth decreases as frequency increases d. beamwidth decreases as wavelength increases

c. beamwidth decreases as frequency increases

carrier wave has an amplitude of 2 volts, a frequency of 120 kHz, and -π/2 radian phase angle. Select the correct carrier wave equation. Answers: a. c(t) = 2 cos(2π*12kHz*t - π) b. c(t) = 2cos(2π*120E3Hz*t + π) c. c(t) = 2cos(2π*120E3Hz*t - 1.57) d. None of the above are correct

c. c(t) = 2cos(2π*120E3Hz*t - 1.57)

Select the correct statement(s) regarding packet switching. Answers: a. connectionless packet communications requires that a connection first be established prior to the exchange of data b. the packet switching concept requires the establishment of dedicated physical circuits c. connection-oriented circuits must use overhead to establish communications prior to data exchanges between nodes d. all statements are correct

c. connection-oriented circuits must use overhead to establish communications prior to data exchanges between nodes

Select the correct statement(s) regarding circuit switching. Answers: a. the circuit switching concept is only used on full mesh network architectures b. circuit switching can only be used on digital networks where each packet contains both source and destination addresses c. during a circuit switched connection, a physical path through the network is established, but only for the duration of the call d. no correct statements

c. during a circuit switched connection, a physical path through the network is established, but only for the duration of the call

The period of a carrier wave is T=0.005 seconds. Determine the frequency and wavelength of the carrier wave. Answers: a. f=20 Hz, λ=3E8 meters b. f=200 Hz, λ=1.5E7 meters c. f=200 Hz, λ=1.5E6 meters d. f=400 Hz, λ=150E3 meters

c. f=200 Hz, λ=1.5E6 meters f = 1/T = 0.005/1 = 200 Hz formula used: f=c/λ, where c = 3 x 108 m/s = 3E8 meters per second = 3*10^8/200 = 1.5E6

What makes a fiber optic (FO) cable work? Answers: a. total internal reflection (TIR) is achieved provided the core and cladding have the same refractive indices b. FO light propagation only occurs when there is line-of-sight (LOS) between the source and detector c. light propagation occurs when the refractive index of the core differs from the refractive index of the cladding d. none of the above

c. light propagation occurs when the refractive index of the core differs from the refractive index of the cladding

Given the following PM modulated signal equation, determine the original message equation, m(t). s(t)=3.2cos(2π2E9t + 0.99cos(2π5000t)), Kp=0.33 (Hz/v) Answers: a. m(t)= 4.4cos(2π5000t) b. m(t)= 4.4cos(2π2E9t) c. m(t)= 3cos(2π5000t) d. m(t)= 3.2cos(2π2E9t)

c. m(t)= 3cos(2π5000t)

Select the true statement(s) regarding a virtual circuit. Answers: a. both analog and digital networks take advantage of the virtual circuit concept b. virtual circuits require the assignment of dedicated physical links during network connection c. regarding the efficient use of physical links, virtual circuits are more efficient than analog circuits d. both a and b are true statements

c. regarding the efficient use of physical links, virtual circuits are more efficient than analog circuits

Select the correct statement(s) regarding resonant and non-resonant antennas. Answers: a. antenna resonance occurs when reactive components are equal to purely resistive components within the antenna b. all antennas used today are non-resonant antennas - i.e., resonant antennas are theoretical antennas only c. resonant antennas are purely resistive, which enables maximum energy transfer from antenna to RF wave d. all statements are correct

c. resonant antennas are purely resistive, which enables maximum energy transfer from antenna to RF wave

Given the following message, m(t), carrier, c(t), and Kp=0.07(rad/v), determine the PM modulated signal equation and PM index. m(t)=2cos(2π4000t), c(t)=4cos(2π8MHzt). Answers: a. s(t)=4cos(2π4E6t + 0.75cos(2π3500t)), µPM=0.75 b. s(t)=4cos(2π8E6t + 0.2cos(2π4E3t)), µPM=0.2 c. s(t)=4cos(2π8E6t + 0.14cos(2π4000t)), µPM=0.14 d. s(t)=4cos(2π4000t + 0.2cos(2π8E6t)), µPM=0.2

c. s(t)=4cos(2π8E6t + 0.14cos(2π4000t)), µPM=0.14

Select the correct statement(s) regarding the polarization of Radio Frequency (RF) waves. Answers: a. the magnetic field of the RF wave determines the wave's polarization b. both the magnetic and electric fields of the RF waves determine the wave's polarization c. the electric field of the RF wave determined the wave's polarization d. the RF wave is not part of the electromagnetic (EM) spectrum, and as such, has no polarization

c. the electric field of the RF wave determined the wave's polarization

What does a BER of 10-4 mean? Answers: a. there will be no errors during transmission since the BER is so low b. there is a probability of one error for every 100,000 bits transmitted c. there is a probability of one error for every 10,000 bits transmitted d. does not mean anything unless associated with a transmission data rate (bit rate)

c. there is a probability of one error for every 10,000 bits transmitted

we can modulate the signal into a higher frequency using a _______ ____

carrier wave

carrier wave

carries the information signal by modulating the information signal onto the carrier waveform

full-duplex

combination device that both transmits and receives signals (ex. telephone).

transceiver

combination device that both transmits and receives signals.

half-duplex

communicating devices share the same medium or channel and must take turns transmitting and receiving (ex. push-to-talk radio, ptt, radios).

simplex

communications only occur in a single direction (ex. Broadcast radio)

link

communications path between two nodes (a circuit will be comprised of one or more links)

Analog signal

continuous over time, infinite number of samples over time and infinite number of amplitude values per sample.

public switched telephone network (pstn)

converts acoustic voice to analog electric signals for transmission across the telephone network

Select the correct statement(s) regarding DC circuits. Answers: a. Ohm's law states that voltage equals current multiplied by resistance b. power equals energy expended over time c. power in watts equals voltage multiplied by current d. all statements are correct

correct answer: d

Determine the maximum theoretical data rate possible given a frequency bandwidth of 18MHz, SNR=99, and M=32. Answers: a. 27 Mbps b. 32 Mbps c. 120 kbps d. 119 Mbps

d. 119 Mbps

Convert 1223 milliwatts to decibels referenced to 1mW. Answers: a. 32 dBW b. 30.9 dBW c. 0.9 dBm d. 30.9 dBm

d. 30.9 dBm formula = [P](dBm) = 10log10( 𝑃1𝑚𝑊)

Given the following parameters, determine the correct sinusoidal equation for a sine wave: f=10kHz, A=3v, φ (phase angle)=+π/4 radians. Answers: a. 3sin(2π10t - π/4) b. 10sin(2π3t) c. 10sin(2π3t + π/4) d. 3sin(2π10,000t + π/4)

d. 3sin(2π10,000t + π/4)

Given the following parameters, determine the correct sinusoidal equation for a sine wave: f=10kHz, A=3v, φ (phase angle)=+π/4 radians. Answers: a. 3sin(2π10t - π/4) b. 10sin(2π3t) c. 10sin(2π3t + π/4) d. 3sin(2π10,000t + π/4)

d. 3sin(2π10,000t + π/4) **DO NOT MISS THE KHZ CONVERSION** formula of a sine wave: m(t) = Am cos(2πfmt±φ), or m(t) = Am sin(2πfmt±φ

Given the following FM modulated signal equation, determine the frequency bandwidth. s(t)=1cos(2π36GHz*t + 4sin(2π4kHz*t)) Answers: a. 36 kHz b. 4 kHz c. 1 kHz d. 40 kHz

d. 40 kHz

Determine the power density from an ideal isotropic antenna measured at a distance of 12 kilometers from the transmitting antenna, at a frequency of 100 MHz, and a transmit power of 10 watts: Answers: a. 5.53 w/m^2 b. 5.53E-2 w/m^2 c. 5.53E-8 w/m^2 d. 5.53E-9 w/m^2

d. 5.53E-9 w/m^2

Select the correct statement(s) regarding optical signals. Answers: a. Optical signals are immune from radio frequency interference (RFI) b. Optical signal operate in the THz frequency range, which can support high data throughput c. Optical signals cannot be collected using RF antennas. d. All are correct statements

d. All are correct statements

Which OSI Reference Model layer provides information regarding the proper application port that received data should be sent to? Answers: a. Physical Layer 1 b. Data Link Layer 2 c. Network Layer 3 d. Transport Layer 4

d. Transport Layer 4

Select the best definition of a virtual connection or path. Answers: a. a virtual connection is one where the signal only travels through an unguided medium b. a virtual connection is one in which a physical path is shared between two users in a half- duplex manner (e.g., push-to-talk radios) c. a virtual connection is another term for a physical connection d. a virtual connection is one in which the physical path is shared by several users, but without their knowledge that the physical path is being shared

d. a virtual connection is one in which the physical path is shared by several users, but without their knowledge that the physical path is being shared

Select the correct statement(s) regarding Hartley's Law. Answers: a. Hartley's Law gives us a relationship between baud rate (symbols per second) and data rate (bits per second) b. by increasing "M", you also increase bit rate c. by increasing baud rate, you also increase bit rate d. all are correct statements

d. all are correct statements

Select the correct statement(s) regarding electrical and electromagnetic (EM) information/signal waves. Answers: a. an electrical signal travelling through a guided conductive wire will create a surrounding EM wave that is proportional to the current b. electrical and EM signals carrying information will have an associated bandwidth that can be seen in the frequency domain c. an EM wave in the RF part of the spectrum will create a current in a receive antenna that is proportional to the RF wave d. all are correct statements

d. all are correct statements

For guided mediums, insertion loss is dependent upon which of the following? Answers: a. number of connectors and splices b. wire diameter c. signal frequency d. all of the above

d. all of the above

Identify the ways a full duplex digital connection can be achieved between users. Answers: a. by separating transmit and receive directions using separate wires, cables, or channels in each direction b. by using different modulation frequencies to separate transmit and receive directions c. by using different time slots to separate transmit and receive frequencies over a common medium d. all of the above

d. all of the above

The parabolic antenna gain equation tells us what? G=η(πD/λ)^2 Answers: a. greater antenna gain can be achieved by increasing the efficiency of the antenna b. for a parabolic antenna, increasing the physical diameter of the antenna increases antenna gain c. antenna gain increase with increased transmit or receive frequencies d. all of the above

d. all of the above

What does Friis free space loss (FSL) tell us about unguided transmission attenuation? FSL=(4πd/λ)^2 Answers: a. increased distance between transmit and receive antennas means increased free space loss attenuation b. higher frequencies attenuate more than lower frequencies c. free space loss attenuation is independent of transmit power or antenna gain d. all of the above

d. all of the above

Analog information can be converted into digital data using techniques such as PCM (pulse code modulation). Select the correct statement(s). Answers: a. in order to convert an analog signal that consists of an infinite number of values, it must be sampled using the Nyquist sampling theorem b. digitized analog signals always experience quantization loss c. signal aliasing is experienced when sampling falls below the recommended Nyquist sampling rate d. all of the above are correct

d. all of the above are correct

What needs to be considered to ensure successful communications over guided or unguided mediums? Answers: a. determining the EM noise environment in which communications will take place b. understanding the frequency and frequency bandwidth limitations associated with the assigned communication frequencies c. matching modulation or line coding methods to the characteristics of communications being established d. all of the above must be considered

d. all of the above must be considered

Which of the following determine the capacity of data in bits per second that can be supported over a transmission medium? Answers: a. RF (EM) noise environment b. M'ary modulation and or M-ary line coding methods c. the communications medium itself d. all of the above must be considered

d. all of the above must be considered

Select the correct statement(s) regarding partial mesh networks. Answers: a. the number of links connecting nodes in a partial mesh network depends upon the availability and reliability requirements of the network b. switches play an integral role in a partial mesh network, where several paths through the network are available c. redundant links and switches are used to improve the availability and reliability of partial mesh networks d. all of the statements are correct

d. all of the statements are correct

Select the correct statement(s) regarding AC signals. Answers: a. both current and voltage change over time b. AC can be represented as either a periodic or aperiodic wave c. in a sinusoidal circuit, voltage may be out-of-phase from the current waveform d. all statement are correct

d. all statement are correct

Select the correct statement(s) regarding 4B5B. Answers: a. a four bit dataword is mapped to a 5 bit codeword; this results in only half of the possible codewords being mapped to legitimate datawords b. 4B5B means that only 80% of the codeword represents information, with 20% representing overhead c. 4B5B avoids long string of logical "1s" and "0s", thus enabling use of simpler line coding techniques d. all statements are correct

d. all statements are correct

Select the correct statement(s) regarding Ohm's Law. Answers: a. voltage increases as current increases over the same resistive load, R b. with AC signals, the phase values of voltage and current may differ causing changes in circuit power (i.e., power factor) c. AC signals result in reactive time-varying values of impedance d. all statements are correct

d. all statements are correct

Select the correct statement(s) regarding digital baseband modulation. Answers: a. with digital modulation, logical "1s" and "0s" are encoded to specific values of carrier wave amplitudes, frequencies, or phase angles b. QAM is a modulation technique in which both carrier amplitude and phase angle changes represent logical data c. with QAM, two carrier waves of the same frequency, but separated by π/2 radians, are used to represent logical data d. all statements are correct

d. all statements are correct

Select the correct statement(s) regarding optical repeaters. Answers: a. with an optical repeater the data signal must go through an OEO process b. unlike amplifiers, repeaters eliminate noise from the signal c. repeaters can only be used on digital signals d. all statements are correct

d. all statements are correct

Select the correct statement(s) regarding packet switching networks. Answers: a. all packets must contain source and destination addresses in a connectionless packet switching network b. connection-oriented packet switching requires the establishment of a circuit between communicating nodes prior to the exchange of information c. connection-oriented packet switching requires greater use of overhead bits compared to connectionless data exchanges d. all statements are correct

d. all statements are correct

Select the correct statement(s) regarding spread spectrum technologies. Answers: a. both direct sequence spread spectrum (DSSS) and frequency hopping spread spectrum (FHSS) results in the signal being spread over a wider frequency bandwidth b. both direct sequence spread spectrum (DSSS) and frequency hopping spread spectrum (FHSS) requires a pseudorandom noise (PN) code and pseudorandom hop sequence, respectively, to be shared between transmitter and receiver c. the transmit power requirements using DSSS and FHSS are the same as a narrow band transmission, even though DSSS and FHSS spreads the signal across a wider frequency spectrum d. all statements are correct

d. all statements are correct

Select the correct statement(s) regarding the signal-to-noise ratio (SNR). Answers: a. SNR represents the ratio of receive power to noise floor power b. the decibel form of SNR is a unitless c. the correct equation for SNR in decibels is [SNR]dB = 10 log10(S/N) d. all statements are correct

d. all statements are correct

UTP wire pairs use balanced signaling to eliminate undesired noise components. Select the correct statement(s). Answers: a. signals propagate on both wires but appear as mirror images of each other b. balanced signals implement noise canceling techniques c. the twisting of wire pairs minimizes crosstalk d. all statements are correct

d. all statements are correct

The period of a carrier wave is T=0.0025 seconds. Determine the frequency and wavelength of the carrier wave. Answers: a. f=25 Hz, λ=3E8 meters b. f=250 Hz, λ=3E7 meters c. f=40 Hz, λ=750E6 meters d. f=400 Hz, λ=750E3 meters

d. f=400 Hz, λ=750E3 meters

Given the following FM modulated signal equation, determine the original message equation, m(t). s(t)=3 cos(2π13E9t + 1.04sin(2π13E3t)), Kvco=4500 (Hz/v) Answers: a. m(t)= 3cos(2π13E9t) b. m(t)= 1.04cos(2π13E3t) c. m(t)= 1.04cos(2π13E9t) d. m(t)= 3cos(2π13E3t)

d. m(t)= 3cos(2π13E3t)

Given the following FM modulated signal equation, determine the original message equation, m(t). s(t)= 1cos(2π2.4GHz*t + 5sin(2π7kHz*t)), Kvco=4500 (Hz/v) Answers: a. m(t)= 1.8cos(2π2.4E9t) b. m(t)= 1.8cos(2π22E3t) c. m(t)= 14.7cos(2π7kHz*t) d. m(t)= 7.78cos(2π7kHz*t)

d. m(t)= 7.78cos(2π7kHz*t)

Given the following message, m(t), carrier, c(t), and Kvco=5000(Hz/v), determine the FM modulated signal equation and FM index. m(t)=2.3cos(2π3500t), c(t)=5cos(2π4GHzt). Answers: a. s(t)=4.5cos(2π4E6t + 3sin(2π3500t)), β=3 b. s(t)=4.5cos(2π3500t + 3.5sin(2π4E6t)), β=3.5 c. s(t)=3cos(2π3500t + 4sin(2π4000t)), β=4 d. s(t)=5cos(2π4E9t + 3.28sin(2π3500t)), β=3.28

d. s(t)=5cos(2π4E9t + 3.28sin(2π3500t)), β=3.28

Select the correct statement(s) regarding DCE and DTE interfaces. Answers: a. the DCE and DTE convention describes devices and not interfaces b. to establish data flow, DTE interfaces must always be connected to other DTE interfaces, and DCE interfaces must always be connected to other DCE interfaces c. DCE and DTE device descriptions are unique to IEEE 802.3 Ethernet LANs d. the DCE and DTE convention describes the interfaces associated with devices; a single device may have both a DTE and DCE interface to enable correct data flow

d. the DCE and DTE convention describes the interfaces associated with devices; a single device may have both a DTE and DCE interface to enable correct data flow

Given the following AM modulated signal, determine the AM index. Will you begin to see distortion in the signal? s(t) = 5[1+0.5 cos(2π100t)] cos(2π160E6t) Answers: a. µAM = 1.5, you will begin to see distortion caused by overmodulation b. µAM = 5, you will begin to see distortion caused by overmodulation c. µAM = 5, you will not see distortion caused by overmodulation d. µAM = 0.5, you will not see distortion caused by overmodulation

d. µAM = 0.5, you will not see distortion caused by overmodulation

when reference to 1 watt we use?

dBW

when referenced to 1 milliwatt we use?

dBm

dedicated circuit

dedicated circuits are distinct, physical circuits dedicated to directly connecting devices across a network

Identify the correct statement(s) regarding dedicated circuits. Answers: a. because call setup is not required, dedicated circuits are very efficient b. dedicated and circuit switched concepts are identical c. dedicated circuits are used between specific locations where 24/7 connectivity is needed d. all statements are correct

dedicated circuits are used between specific locations where 24/7 connectivity is needed

physical connection

describes the physical path between communicating ends.

multiplexer

device that aggregates multiple user connections together (ex. frequency or time division multiplexers)

Digital signal

discrete binary values {0, 1} > in order to transmit {0, 1} over guided and unguided mediums, binary values must be mapped to electrical values pr EM values in field strength.

circuit

end-to-end communications path between two or more points. may consist of one or more links.

true or false: smaller wire diameter means less signal resistance

false, smaller wire diameter means greater signal resistance.

an em wave can propagate through ____ _____ and can create a signal current in another conductor

free space

a signal containing information has an associated _________ _________

frequency bandwidth

message waves contain information and has an associated _________ _________

frequency bandwidth

equation for frequency bandwidth

frequency bandwidth (bw) = f (highest frequency) - f (lowest frequency)

conductor wire diameter

gauge - awg

equation for amperes

i (amperes) = coulombs/seconds

knowledge

information that is 'actionable'

__________ enables us to separate signals in a interfering basis

modulation

circuit switch

network allocates a dedicated physical path through the network for the duration of the connection

packet switch

network allocates a virtual path through the network

connectionless packet switch

no virtual path is established prior to data being exchanged

switches

node that reads source and destination addresses, and transmits the data to the correct physical link according to the destination address

how many frequencies is a carrier wave represented by?

one frequency

equation for power density

pd = p/4*pi*d^2 (watts/m^2)

information can be captured through changes carrier wave frequency or _____

phase

fm index

provides a metric regarding the quality of the fm signal

conversion equation from degrees to radians

radians = pi(radians)/180(degrees) x (degrees)

Data

raw without context or meaning

receiver

receivers detect signal transmissions from guided or unguided mediums.

Unguided medium

signal transmission that occurs in 'free space' where it is not specifically contained (ex. air, vacuum, etc.) EM signals: > Radio frequency (RF) > Free space optics (FSO)

Guided medium

signal transmission that uses a medium which 'guides' the signal along a physical path (ex. coaxial cable, twisted pair, fiber optic cable, etc.) electrical, RF (subset of EM), and optical signals: > Conductive wires (ex. copper, gold, silver, etc.) > Fiber Optic (FO) cables (ex. glass, plastic, etc.).

virtual connection

similar to a physical connection, except that the actual path is shared between a number of users. users may not know that they are actually sharing a physical path with others. associated with digital communication.

trunk

similar to links except support multiple circuits.

both fm and pm occupy greater ________ _________ compared to am

spectral bandwidth

em signal power resides in the _______ area of a traveling wave

surface

baseband signal

the information or message from a single source (ex. computer, radio channel, etc.)

carrier frequency

the new frequency of the carrier wave, after modulation has taken place

passband

the resulting signal after modulation. can also be called a modulated carrier.

angular modulation

the term used for frequency modulation, fm, or phase modulation, pm

transmitter

transmitters send analog or digital signals through guided or unguided mediums

true or false: fm and pm techniques are not vulnerable to additive noise components in the rf environment

true

true or false: signal current that flows through a conductor creates an electromagnetic wave, which is proportional to the current

true

phase modulation or pm

unlike fm the message is represented through changes in the phase angle of the carrier wave. we need to change message amplitudes to phase angle changes

equation for a cosine wave

v(t) = A*cos(2*pi*f*t)

equation for a sine wave

v(t) = A*sin(2*pi*f*t)

connection-oriented packet switch

virtual path through the network established before data is exchanged

equation for wavelength

wavelength (represented by a lambda) = c (speed of light)/ f(hertz), where x = 10^8 m/s^7

modulation

when a carrier wave which contains no information is used to raise the signal to a higher frequency (i.e. to the carrier's frequency)

dc (direct current) vs. ac (alternating current)

with ac, frequency of electrical current impacts electrical characteristics of the circuit (e.g., higher frequency introduces higher signal resistance and time-varying reactive components)