WorksheetsCellular Communication System
Total questions: 19
Worksheet time: 55mins
TDMA is used instead of TDM when:
all the signals come from the same source
the signals come from different sources
TDM is used in RF communications
they mean the same thing
When calculating the maximum number of users, a limiting factor in FDM is:
the type of media used
the length of the channel
the bandwidth of each signal
all of the above
A DS-1 signal contains:
12 channels
24 channels
32 channels
64 channels
The bit-rate of a DS-1 signal over a T-1 line is:
64 kbps
256 kbps
1.536 Mbps
1.544 Mbps
Besides data bits, a DS-1 frame contains a:
timing bit
T-bit
signaling bit
framing bit
Spread-spectrum can be done by using:
computer-controlled frequency reuse
frequency-hopping
direct-sequence method
all of the above
To calculate processing gain, divide the transmitted RF bandwidth by:
the digital data bit rate
bandwidth of original baseband
the S/N ratio
the chip size
A receiver for frequency-hopping spread-spectrum would be
a narrowband receiver
a wideband receiver
a direct-conversion receiver
a CDMA receiver
CDMA:
cannot be used with frequency-hopping spread-spectrum
cannot be used with direct-sequence spread-spectrum
cannot be used on an RF channel
allows many transmitters to use a band simultaneously
Multiplexing allows many signals to (a) a channel.
In FDM, each signal uses part of the bandwidth (a) of the time.
In TDM, each signal uses all of the bandwidth (a) of the time.
Using CDMA on a radio channel, all signals can transmit (a) of the time.
A PN sequence is a (a) -random noise sequence.
The AM radio band is an example of (a) -division multiplexing.
A signal would have a bandwidth of 200 kHz and a signal – to – noise ratio of 20 dB if transmitted without spreading. It is spread using a chipping rate of 50:1. Calculate its bandwidth and a signal – to – noise ratio after spreading.
(a)
The bandwidth of a communication channel is 12.5 kHz. The S/N ratio is 25 dB. Calculate (a) the maximum theoretical data rate in bits per second, (b) the maximum theoretical channel capacity, and (c) the number of coding levels N needed to achieve the maximum speed. [For part (c), use the y x key on a scientii c calculator.]
(a)
A Frequency – hopping spread – spectrum system hops to each of 100 frequencies every 10 seconds. How long does it spend on each frequency?
(a)
Determine the carrier frequency of channel five in frequency division multiplexing.
(a)
