Question 1

Increasing the speed of the WLAN will cause shorter delays in waiting for reflections.

Accepted Answer

Increasing the speed of the WLAN (Wireless Local Area Network) primarily enhances data transfer rates. Delays caused by reflections, known as multipath propagation delays, are more related to the physical environment and the signal processing techniques used rather than the speed of the network itself.

Question 2

____ is not part of a frame.

Accepted Answer

Channel is not a component of a frame. Frames are data packets used in networking for communication, which include elements like length, parity for error checking, and the actual data being transmitted, but not the channel through which they are sent.

Question 3

When transmitting with FHSS, if interference is encountered on a particular frequency then that part of the signal will be retransmitted on the previous frequency of the hopping code.

Accepted Answer

In Frequency Hopping Spread Spectrum (FHSS), if interference is encountered on a particular frequency, the system does not retransmit that part of the signal on the previous frequency. Instead, it continues to hop to the next frequency in the predetermined sequence.

Question 4

What is a disadvantage of narrowband transmissions?

Accepted Answer

Narrowband transmissions are more susceptible to interference from another radio signal because they operate on a smaller range of frequencies.

Question 5

Into which layers are WLAN features isolated by IEEE standards?

Accepted Answer

WLAN features are isolated into the PHY (physical layer) and MAC (media access control) layers by IEEE standards. PMD (physical media dependent) and PLCP (physical layer convergence protocol) are sublayers within the PHY layer. MAX (medium access control extension) is not a layer defined by IEEE standards.

Question 6

How does OFDM work?

Accepted Answer

OFDM works by breaking up a signal into smaller parts and sending them in parallel on different channels to increase data transfer rates and reduce interference.

Question 7

The value of layers in the OSI reference model is that it divides networking into a series of tasks, and then illustrates how those tasks relate to each other.

Accepted Answer

The value of layers in the OSI reference model is indeed that it divides networking into a series of tasks and illustrates how those tasks relate to each other. This allows for easier troubleshooting and standardization in network communication.

Question 8

According to FCC regulations, all FHSS systems in the 900 MHz band must change frequencies through 50 channels and cannot spend more than ____ on one frequency each 20 seconds.

Accepted Answer

FCC regulations require FHSS systems in the 900 MHz band to change frequencies through 50 channels, but there is no requirement for the time spent on one frequency each 20 seconds. However, most FHSS systems limit this time to 400 milliseconds to comply with FCC regulations and to minimize interference with other devices in the same frequency band. Therefore, the best choice is C.

Question 9

Because wireless technology has advanced at such a rapid pace, the earliest WLANs are now essentially obsolete.

Accepted Answer

WLAN technology has advanced rapidly over the years, with newer and faster standards being introduced. The earliest WLANs using outdated standards such as 802.11b, which offered slower speeds and lower data rates compared to more recent standards such as 802.11ac and 802.11ax. Therefore, the earliest WLANs can be considered obsolete for practical purposes.

Question 10

____ signals by nature transmit on only one frequency or a very narrow portion of the frequencies.

Accepted Answer

Radio signals typically transmit on only one frequency or a very narrow portion of the frequencies. Broadband signals, such as those used for internet, transmit on a wide range of frequencies. Computer signals can also transmit on a wide range of frequencies, depending on the specific application. Heat is not a type of signal.

Question 11

Because a device must wait to transmit until it receives the last reflected signal, this in effect puts a ceiling limit on the overall speed of the WLAN. What is the current ceiling for WLAN speed?

Accepted Answer

The answer of Because a device must wait to transmit...

Question 12

Which system is preferred for 802.11b WLANs?

Accepted Answer

DSSS (Direct Sequence Spread Spectrum) is the preferred system for 802.11b WLANs because it provides a higher data transfer rate compared to FHSS (Frequency Hopping Spread Spectrum), which is the other option. OFDM (Orthogonal Frequency Division Multiplexing) is a more advanced system, but it is not used for 802.11b WLANs. Therefore, A) DSSS is the best choice.

Question 13

In FHSS, the amount of time needed to move from one frequency to another is the ____ time.

Accepted Answer

In FHSS, the process of moving from one frequency to another is called "hopping." Therefore, the answer is (D) hop.

Question 14

DSSS uses a bit pattern called a ____ code.

Accepted Answer

DSSS (Direct Sequence Spread Spectrum) uses a coding technique called "chipping" to spread the signal over a wider bandwidth. This involves adding a chipping code, which is a bit pattern, to each data bit to make it occupy a larger portion of the frequency spectrum.

Question 15

Bluetooth divides the 2.4 GHz frequency into ____ different frequencies spaced 1 GHz apart.

Accepted Answer

Bluetooth divides the 2.4 GHz frequency into 79 different frequencies spaced 1 MHz (not 1 GHz) apart. This allows multiple Bluetooth devices to operate in the same general area without interfering with each other.

Question 16

Which layer of the OSI reference model permits the devices on the network to hold ongoing communications across the network?

Accepted Answer

The session layer of the OSI reference model allows devices on a network to establish, maintain and terminate ongoing communication across the network.

Question 17

When was the concept used by FHSS technology developed?

Accepted Answer

The concept used by Frequency-Hopping Spread Spectrum (FHSS) technology was developed during World War II. It was notably contributed to by actress and inventor Hedy Lamarr and composer George Antheil, who patented an early version of the technology in 1942 to help in the war effort by preventing the jamming of radio-controlled torpedoes.

Question 18

Of the 52 subchannels, 32 are used for standard transmissions and 20 are used for FEC transmissions.

Accepted Answer

In a typical communication system, the division of subchannels between standard transmissions and Forward Error Correction (FEC) transmissions can vary widely depending on the specific requirements and design of the system. The statement provided does not correspond to a universally applicable configuration.

Question 19

What is the top layer of the OSI reference model?

Accepted Answer

The top layer of the OSI reference model is the application layer, which deals with providing services for user applications. This layer is responsible for user interfaces, email, file transfer, and other application-level protocols.

Question 20

IEEE has divided the ____ layer into two sublayers: Logical Link Control (LLC) and Media Access Control (MAC).

Accepted Answer

The Data Link layer is divided into Logical Link Control (LLC) and Media Access Control (MAC) sublayers according to the IEEE standard.

Quiz 4: IEEE 80211 Physical Layer Standards