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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.
A direct-sequence spread-spectrum system using BPSK modulation for both the data and the code is required to support a data rate of 9600 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.
There are 11 equal-power terminals in a CDMA communication system. transmitting signals toward a central node.
If the required (Eb/N0 + I0) is 10 dB, how many equal-power users can share the band? Do not neglect receiver noise.
If the path length of the multipath wave is 100 m longer than that of the direct wave, what is the minimum chip rate necessary to reject the multipath.
A ground-to-synchronous satellite link must be closed in a jamming environment. The data rate is 1 kbit/s and the ground station has a 60-ft antenna.
Input data at 75 bits/s are channel encoded using a rate encoder. The coded bits are then modulated using 8-ary FSK.
Assume that no channel coding is used. A jam-mer operating over the same broadband bandwidth yields a received Jo = 100No.
A non coherent frequency hopping 8-ary FSK system hops at 12,000 hops/s over a bandwidth of 1 MHz. The symbol rate is 3000 symbols/s.