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Consider a channel whose power-density profile is made up of three impulse functions with relative power and time-delay locations.
A signal within a mobile wireless system undergoes time spreading. The symbol rate = 20 k symbols/sec.
In Figures below, P-boxes and S-boxes alternate. Is this arrangement any more secure than if all the P-boxes were first grouped together.
What is the output of the first iteration of the DES algorithm when the plaintest and the key arc each made up of zero sequences?
Consider the 10-bit plaintext sequence 0 1 0 1 1 0 1 0 0 1 and its corresponding cipher text sequence 0 1 1 1 0 1 1 0 1 O.
If the prime numbers are p = 7 and q = 11. list five allowable values for the decryption key, d.
Find the nonsuper-increasing vector to be made public. and encrypt the data vector 1 1 0 1 1.
The session key in hex notation is = 0002 0003 0002 0003 0002 0003 0002 0003, where the rightmost 4-digit group represents the sub key Z1.
The IDEA session key is encrypted using the RSA algorithm. The resulting encrypted session key (in base-10 notation)
Describe the steps used for message encryption employed by the Data Encryption Standard (DES). How different is the operation when using Triple-DES?
One might therefore think that such SS techniques might provide similar benefits against AWGN. Explain why this is not possible.
The system specifications are as follows: data and SS-code modulation is BPSK, data rate is 8,000 bits/s.
Consider a CDMA direct-sequence cellular telephone system, where each user requires an Eb/I0 of 6 dB for acceptable voice quality.
A direct-sequence spread-spectrum system uses QPSK modulation for transmitting data. It is required that the bit-error probability.
Frequency modulation (FM) and pulse code modulation (PCM) represent techniques that spread the spectrum of an information signal.
Let X be an integer variable represented with 64 bits. The probability is ½ that Xis in the range (0, 216 - 1)
Calculate the unicity distance for an encrypted Hawaiian message if the key sequence consists of a random permutation of the 12-letter alphabet.
What benefits might there be in using CDMA versus either FDMA or TDMA access schemes?
Draw a similar block diagram for a slow frequency hopping (SFH) demodulator, and explain how it would work.
Explain why a maximal-length n-stage linear feedback shift register can produce a sequence with a period no greater than 2n - 1.
Show that in a maximal-length n-stage linear feedback shift register the output stage must always be an input to the feedback network.
A total of 24 equal-power terminals are to share a frequency band through a code-division multiple access (CDMA) system.
What are the equation and graphical form of the autocorrelation function and power spectral density of the sequence?
Consider an FH/MFSK system such as the one shown in Figure. Let the PN generator be defined by a 20-stage linear feedback shift.
Find the mean and the standard deviation of the time needed to acquire a 10-megachip/s BPSK modulated PN code sequence using a serial search.