Wireless Networks - Chapter 2, 3, 4, 5, 6

List two types of directional antennas.

- parabolic dish - patch

What is the maximum data-transmission rate for ZigBee?

250 kbps

In a direct, point-to-point link, the Fresnel zone should never be obstructed more than ___________________

40%

Which frequency band(s) can ZigBee networks utilize?

868 MHz, 915 MHz and 2.4 GHz >>> (ISM band)

What type of security is provided for in the ZigBee specification?

encryption

To work as efficiently as a dipole, a monopole antenna requires a(n) ___________________

ground plane

When planning a wireless link, you should always prepare a ___________________ to ensure that the signal that reaches the receiver meets the minimum signal strength requirements.

link budget

The 802.15.3 standard was developed to

support multimedia

Which of the following topologies are supported by ZigBee?

tree, star, and mesh

In WPANs, the _____ layer of the protocol stack handles the different types of traffic.

Radio Frequency (RF)

___________________is a method of transmission in which the information is broken up into smaller units.

Packet switching

What is switching? What type of switching is used with telephone transmissions, andwhat type is used for data transmissions?

Switching involves moving a signal from one wire or frequency to another to create a connection. Telephone systems use a type of switching known as circuit switching. When a telephone call is made, a temporary dedicated channel is made between the caller and the recipient of the call through the switch. Data transmissions use packet switching. Packet switching requires that the data transmission be broken into smaller units then sent independently through the network to reach the destination.

In a piconet, the 802.15.3 PNC is primarily responsible for___________________

Timing

Eight binary digits grouped together form which of the following?

byte

Which of the following divides the bandwidth of the frequency channel into several time slots?

TDMA (time division multiple access)

What are the functions of NCA in Ghana?

- Grant Licenses and Authorizations for Operation of Communication Systems and Services - Ensure Fair Competition Among Licensees - Establish and Monitor Quality of Service Indicators for Service Providers - Authorize Type Approval and Enforce Equipment Standards - Coordinate Frequency Use Among Neighbouring Countries

Bluetooth divides the 2.4 GHz frequency into 79 frequencies that are spaced how far apart?

1 MHz

In the 60 GHz band used in 802.15.3c, RF channels have approximately how much bandwidth?

2 ghz

The frequencies between approximately _____ and ______ form the entire range approved by the FCC for use with UWB technology.

3.4 GHz; 10.3 GHz

How many RF channels are available in 802.15.3c?

4

The maximum data rate of WiGig is _____ Gbps.

7

A transmitter generates a 15 dBm signal and is connected to an antenna using a cable that induces a 3 dB loss. The cable has two connectors that induce a loss of 2 dB each.What is the signal level at the input of the antenna?

8 dBm

UWB can cause interference with the frequency band used in _________.

802.11a

Explain how a radio antenna works when transmitting a signal.

An antenna is a copper wire or similar device that has one end up in the air and the other end connected to the ground. When transmitting, the radio waves are directed to strike this wire. This will set up an electrical pressure (voltage) along the wire. This pressure will cause a small electrical current to flow up and down the wire. The voltage causes a movement back and forth of the electricity in the antenna at the same frequency as the radio waves. Broadcasting or sending out radio waves is accomplished by forcing the electricity in the antenna to move at the same frequency as the radio waves.

What is the name of the organization that develops and promotes Bluetooth products and consists of over 2,500 hardware and software vendors?

Bluetooth SIG

In 802.15.3, frame collisions can only happen during the _____

CAP (contention access period)

A ___________________ transmission uses spread spectrum technology and unique spreading codes for each user.

CDMA or Code Division Multiple Access.

In 802.15.3c, using _______ prevents collisions.

CSMA/CA (carrier sense multiple access with collision avoidance)

___________________divides the bandwidth of the frequency into several narrower frequencies. Each user then transmits using its own narrower frequency channel.

FDMA (frequency division multiple access)

What is the generic name of the error-correction mechanism that is used to ensure the reliability of transmissions in HR WPANs?

FEC(forward error correction)

A WiMedia device cannot request more channel time from the PNC. True or False?

False

A ZigBee coordinator cannot allocate guaranteed time slots for devices to transmit data. True or False?

False

A directional antenna typically has a low gain. True or False?

False

Bluetooth devices are usually small and mobile, so conserving power is necessary.True or False?

False

Bluetooth has seven power classes for transmitting. True or False?

False

Devices in an 802.15.3c piconet can only communicate through the PNC. True or False?

False

Infrared wireless systems require that each device needs to have only one component:either an emitter that transmits a signal or a detector that receives the signal.

False

Objects (such as walls) and interference from other sources do not affect the range of Bluetooth transmissions. True or False?

False

TDMA can carry three times the amount of data that CDMA can. True or False?

False

The American Standard Code for Information Interchange (ASCII) can represent up to 1024 characters.

False

When using the same antenna for full-duplex communications, the same frequency can be used for transmitting and receiving simultaneously. True or False?

False

The resulting output from the modulation process is known as the middle frequency(MF) signal. True

False, the resulting output from the modulation process is known as the intermediate frequency (IF) signal.

Which method of Bluetooth transmission uses two different frequencies to indicate whether the bit is a 1 or a 0?

GFSK (Gaussian frequency shift keying)

In 802.15.3, the lower levels of the protocol stack are implemented in the_____

Hardware

Explain multipath distortion and how it can be minimized.

Multipath distortion is what occurs when the same signal reflects and arrives at the receiver's antenna from several different directions and at different times. One way to minimize multipath distortion is by increasing the height of the antenna to create a clear line-of-sight. Using an amplifier at the receiver and transmitting the same signal on separate frequencies can also alleviate multipath distortion.

In the ______ power-saving mode, 802.15.3c devices must listen to the system-wide wake beacon.

PSPS(Piconet synchronized power save)

At the lowest level of the Bluetooth protocol stack is the ___________________ layer.

Radio Frequency (RF)

List and describe the three types of data flow.

Simplex - when data moves from the transmitter to the receiver only. The receiver cannot reply. Half-duplex - when data can move in both directions but not simultaneously. When one is transmitting, the other must listen until the transmission is finished. Full-duplex - data can move in both directions simultaneously

How do sky waves propagate?

Sky waves bounce up and down between the ionosphere and the surface of the earth until they reach the receiver.

How do smart antennas function?

Smart antennas are built as a collection of smaller antennas or segments that can be enabled or disabled to track the user or receiver in order to prevent the waste of RF energy and minimize interference

A Bluetooth channel consists of ___________________

a hopping sequence including up to 79 frequencies

A(n) ___________________ actively increases a signal's intensity or strength.

amplifier

Unlike a digital signal, a(n) ___________________ signal is a continuous signal with no "breaks" in it.

analog

Which type of transmission is used when human voice is modulated directly onto a carrier wave?

analog

One of the purposes of a(n) ___________________ is to emit an electromagnetic signal into air or space.

antenna

Which of the following is not a feature of Bluetooth?

asymmetric transmission

Decibel is a relative measurement that requires a(n) ___________________

comparison

When signals are sent at frequencies that are closely grouped together, an errant signal may encroach on a close frequency, causing___________________

crosstalk

Infrared wireless transmission can be either directed or ___________________

diffused

PSK is an example of

digital modulation

The simplest and most practical type of antenna is a ___________________ antenna.

dipole

A gain of 6 dB means that the signal level or strength ___________________

doubles twice

Radiotelephony or radio travels in waves known as ___________________ waves.

electromagnetic

The gain of an antenna is the measure of how ___________________ the direction of an antenna pattern is.

focused

Between the transmitting antenna and the receiving antenna, a signal will always be subject to ___________________

free space loss

The ___________________ period is when ZigBee devices have time reserved for priority transmissions.

guaranteed time slot

Which of the following is not an example of a Bluetooth communication?

hard drive to memory

The lower levels of the WPAN protocol stack are implemented in the ___________________

hardware

Which range of the electromagnetic spectrum is less susceptible to interference from sources of visible light?

infrared

The result of using a PN code is that___________________

it spreads the signal over a wider range of frequencies

A lower frequency signal uses a ___________________ antenna, whereas a higher frequency ___________________ signal uses a ___________________ antenna

longer, shorter

A(n) ___________________ combines two inputs to create a single output.

mixer

Changing a signal to encode data onto it is known as ___________________

modulation

The amount that the Bluetooth frequency varies, which is between 280 KHz and 350KHz, is called the ___________________

modulation index

A(n) ___________________ antenna transmits a signal in all directions with relatively equal intensity.

omnidirectional

Each of the following is a type of RF filter except ___________________

passband

For the best performance between transmitter and receiver, the two antennas should have the same ___________________

polarization

Which of the following topologies are supported by Bluetooth?

scatternet and piconet

The name of the process in ZigBee to ensure the same frame is not transmitted more than once is ________.

sequential freshness

What does the Federal Communications Commission do regarding the licensing of radion frequencies?

the FCC is the primary regulatory agency for telecommunications in the United States. It also regulates radio and television broadcasts, cellular, satellite and two-way radio communications.

The distance between one positive peak and the next positive peak of a wave is called ___________________

wavelength

Explain the difference between amplitude modulation, frequency modulation, and phase modulation.

The height of a carrier wave is known as the amplitude. This height can be changed so that a higher wave represents a 1 bit while a lower wave represents a 0 bit. The change in the height is known as amplitude modulation (AM). Frequency modulation (FM) changes the number of waves used to represent one cycle. When using frequency modulation, the number of waves needed to represent a 1 bit is more than the number of waves needed to represent a 0 bit. Phase modulation (PM) changes the starting point of the cycle. This change only takes place when the bits being transmitted change from a 1 bit to a 0 bit or vice versa. The change in starting point indicates that a different bit is now being sent.

What happens if someone sets up a pair of antennas that interfere with your point-to-point link between two buildings that uses an unlicensed frequency?

The issue must be resolved privately between both parties without the regulatory agencies getting involved.

List and describe the three different types of binary signaling techniques.

The return-to-zero (RZ) technique calls for the voltage to increase to represent a 1 bit but for there to be no voltage for transmitting a 0 bit. The voltage is reduced to zero before the end of the period for transmitting a 1 bit. With the non-return-to-zero (NRZ) technique the voltage signal remains at high for the entire length of the bit period. Like RZ, there is no voltage for transmitting a 0 bit. The final technique, polar non-return-to-zero (Polar NRZ), increases the voltage to represent a 1 bit but drops the voltage to a negative amount to represent a 0 bit.

List and discuss the advantages of standards.

The standards regulate and monitor the use of the licensed portion of the frequency spectrum. Most of the available Radio Frequencies are licensed to certain users in a particular area and no one else is allowed to use the same frequency in the same area of signal coverage. Standards also ensure that devices interoperate with those from other vendors, and create competition, which results in lower prices for consumers and lower manufacturing costs for manufacturers because they don't have to make large research investments. Standards also help protect consumer investment in technology by creating a migration path.

Why do computers and data transmission equipment use binary?

They are electrical devices, and electricity has only two states.

Which of the following is a feature of WPAN devices?

They are small and can operate on batteries.

A passband has both a minimum and maximum threshold.

True

CAPs are optional. True or False?

True

In WirelessHD, the PNC is usually a video source.

True

Infrared light, though invisible, has many of the characteristics of visible light.

True

Infrared wireless systems send data by the intensity of the light wave instead of whether the light signal is on or off.

True

Letters of the alphabet and symbols are stored using the ASCII code, but not numbers used in calculations.

True

The beacon carries timing information for the piconet. True or False?

True

When mixing two signals, the highest sum and the smallest difference between the carrier frequency and the range of frequencies at the other input define two limits known as the sidebands of the frequency carrier. True or False?

True

Without switching, 1,225 cables would be required to interconnect 50 telephones.True or False?

True

What is quadrature amplitude modulation (QAM) and how does it work?

Using phase modulation with 180 degree angles can result in 8 different signals. However, when phase modulation is combined with amplitude modulation a total of 16 different signals can be created. QAM is the use of the 16 different signals.

Which of the following technologies uses an RF frequency band in which signals can still get through walls?

WHDI(Wireless Home Digital Interface)

Explain the difference between bps and baud rate.

When data is transmitted using radio waves the measure of speed is usually bits per second (bps). BPS is the number of bits that can be transmitted per second. Changing signals are illustrated by a sine wave, and a baud is a change in that signal. The baud rate is the number of times that a signal changes per second.