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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.
Assume that the system does not use channel coding. Also assume that the propagation losses are the same for the system and the jammer.
A communicator intends to use frequency hopping at a hop rate of 10.000 hops/s to avoid a threat of repeat-back jamming.
Consider an airborne repeat-back jammer as shown in Figure. The communicator is using a FH/SS system.
Spread-spectrum techniques can be used to meet government regulations regarding flux (power) density radiating the surface of the earth.
A group of stations share a 56-kbitsls pure ALOHA channel. Each station outputs a packet on the average of once every 10s.
A group of three stations share a 56-kbitsls pure ALOHA channel. The average bit rate transmitted from each of the three station is R1 = 7.5 kbits/s.
Verify that for a pure ALOHA access scheme, the normalized throughput is bounded by 112e and that this maximum.
Let N = Nn + Nn+1, where Nn and Nn+1 are as defined in Problem. Write an expression for the pdf of N, and give an interpretation for N.
The average station makes 30 requests per hour, where each request is for one slot of 500-µs duration. Calculate the normalized total traffic on the channel.
Consider the arrival scenario of Figure; the location of the packet arrival times arc permissible as shown under pure ALOHA, but not under slotted ALOHA.
What is the probability of exactly two collisions before a successful transmission?
Measurements of a slotted-ALOHA channel show that 20% of the slots are idle. What is the normalized total traffic on the channel?
Show that the sum of two Poisson processes, with rates ?1 and ?2, is also a Poisson process, with rate ?, = ?1 + ?2.
A 10-MHz transponder is occupied by 200 identical carriers, half servicing stations with G/T = 40 dB/K, the other half servicing stations with GIT = 37 dB/K.
Compute the efficiency of the communications resource (CR) for the case of 1, 2, 5, 10, 20, 50, and 100 slots per frame.
Consider a token-ring network operating at a transmission rate of 10 Mbitsls over a cable having a propagation velocity of 200 mins.
Is there any theoretical capacity advantage in providing users with FDMA service versus TDMA service?
Demonstrate that p(f) given above is in fact a probability density function, and com-pute the mean and variance of f.