QUESTION 35 How does ADSL increase network access capacity bit rate? a. By using
ID: 3706190 • Letter: Q
Question
QUESTION 35
How does ADSL increase network access capacity bit rate?
a. By using OFDM to divide the operating spectrum into overlapping subcarriers
b. By implementing M’ary modulation (e.g., QAM)
c. By adopting dynamic rate adjustable modems that automatically react to changing signal conditions
d. All of the above
10 points
QUESTION 36
NEXT describes noise caused by crosstalk. It is a more severe problem than FEXT.
True
False
a. By using OFDM to divide the operating spectrum into overlapping subcarriers
b. By implementing M’ary modulation (e.g., QAM)
c. By adopting dynamic rate adjustable modems that automatically react to changing signal conditions
d. All of the above
Explanation / Answer
How does ADSL increase network access capacity bit rate?
d. All of the above
QAM is a type of M-ary signaling.
The different waveforms numbers used in QAM depends on the modem and may vary with the quality of the
channel. 16,384-QAM is possible in ADSL modems.
A method for the automatic classification of digital modulations recognizing one of the classical single-carrier modulations called OFDM modulations such as DMT (discrete multitone) used for ADSL (asymmetric digital subscriber line).
ADSL line modems will synchronise at a line speed at a varying bitrate as ADSL is generally offered at downstream data rates from 512 Kbps to about 6 Mbps.
NEXT describes noise caused by crosstalk. It is a more severe problem than FEXT.
True.
Crosstalk noise occurs when signals are coupled between adjacent pins in connectors. Near-End Crosstalk (NEXT) is the crosstalk occurred and been detected on the same end of the cable that generated the signal. Far-End Crosstalk (FEXT) is detected at the opposite end of the cable where the signal was sent. Due to attenuation, the signals at the far end of the wire pair are weaker than the signals at the near end. NEXT noise has a high pass filter frequency response, whereas FEXT experiences channel loss. Hence, FEXT has very small magnitude and negligible effects compared to NEXT.