Communication Engineering Set 10

Answer: eighth

Explaination:
in an ascii character set, seven bits are reserved for character representation while the eighth bit is a parity bit.

Answer: log x

Explaination:
if the size of the character set is x, then [log x] bits are needed for representation in a standard encoding.

Answer: false

Explaination:
the code length depends on the frequency of occurrence of characters. the more frequent the character occurs, the less is the length of the code.

Answer: 011

Explaination:
by recording the path of the node from root to leaf, the code word for character ‘a’ is found to be 011.

Answer: 110

Explaination:
by recording the path of the node from root to leaf, assigning left branch as 0 and right branch as 1, the codeword for c is 110.

Answer: ∑fidi

Explaination:
if character ci is at depth di and occurs at frequency fi, the cost of the codeword obtained is ∑fidi.

Answer: true

Explaination:
an optimal tree will always

Answer: prefix encoding

Explaination:
even if the character codes are of different lengths, the encoding where no character code is the prefix of another character code is called prefix encoding.

Answer: o(c log c)

Explaination:
if we maintain the trees in a priority queue, ordered by weight, then the running time is given by o(c log c).

Answer: o(c2)

Explaination:
if the implementation of the priority queue is done using linked lists, the running time of huffman algorithm is o(c2).

Answer: band stop filter

Explaination:
notch filter is a band stop filter that allows most frequencies to pass through it, except frequencies in a specific range. it is just opposite of a band-pass filter. high pass filter allows higher frequencies to pass while low pass filter allows lower frequencies to pass through it.

Answer: periodic signal

Explaination:
periodic signal is that which repeats itself after a regular interval. sin wave is a periodic function since it’s value can be determined at any point of time, as it repeats itself at a regular interval. aperiodic signal does not repeat itself at regular interval of time. random signals are the signals which have uncertain values at any time. while deterministic signals are the signals which are constant over a period of time.

Answer: acts as a medium to send message signals from transmitter to receiver

Explaination:
channel acts as a medium to transmit message signal from source transmitter to the destination receiver.

Answer: false

Explaination:
periodic signal is a signal which repeats itself after a regular interval. while aperiodic signal does not repeat itself at regular interval of time.

Answer: in the channel

Explaination:
noise is an unwanted signal that gets mixed with the transmitted signal while passing through the channel. the noise interferes with the signal and provides distortion in received signal. the transmitting antenna transmits modulated message signal while the receiving antenna receives the transmitted signal. regeneration of information refers to demodulating the received signal to produce the original message signal.

Answer: protocol

Explaination:
protocol is a set of rules that looks after data communication, by acting as an agreement between communication devices. channel is the transmission medium or the path through which information travels. modem is a device that modulates and demodulates data.

Answer: high selectivity and sensitivity

Explaination:
the main advantage of superheterodyning is that it provides high selectivity and sensitivity. it’s bandwidth remains same. it has high adjacent channel rejection and high fidelity.

Answer: flicker noise

Explaination:
flicker noise is a type of electronic noise which is generated due to fluctuations in the density of carrier. it’s also known as 1/f as it’s power spectral density increases with a decrease in frequency or increase in offset from a signal.

Answer: frequency-domain plot

Explaination:
relationship between amplitude and frequency is represented by a frequency-domain plot. also, it represents the

Answer: f(x) = f(-x)

Explaination:
geometrically a function f(x) is even, if plot of the function is symmetric over y-axis. algebraically, for any function f(x) to be even, f(x) = f(-x).

Answer: rs/2

Explaination:
theoretical minimum nyquist bandwidth needed for the baseband transmission of rs symbols per second without isi is rs/2.

Answer: c = w log2 ( 1+s/n )

Explaination:
the capacity relationship from shannon-hartley capacity theorem is given by c = w log2 ( 1+s/n ).

Answer: eb/n0

Explaination:
there exists a limiting value for eb/n0 below which they can be no error free communication at any information rate. this eb/n0 is called as shannon limit.

Answer: amount of information at the output

Explaination:
entropy is defined as the average amount of information per source output.

Answer: conditional entropy

Explaination:
shannon uses a correction factor called equivocation to account for uncertainty in the received signal. it is defined as the conditional entropy of the message x given y.