a. Routing (i.e., determination of routes) is the function of the Network layer

Question

a. Routing (i.e., determination of routes) is the function of the Network layer , 64-QAM modems are more prone to noise than 16-QAM modems. c. Attenuation of light signal in an optical fiber depends on the wavelength of the light signal. d. The signal power of radio waves falls with increasing distance between the transmitter and the receiver. e. Customers, who use Cable-TV providers for their Internet connectivity, can experience degraded service when more customers join the same network. f. Slotted ALOHA is an example of a Contention based MAC protocol. g. Stop and Wait protocols suffer from low link utilization. h. GSM networks have a hard limit on the number of users that can be supported simultaneously. i. A codeset with Hamming distance of 10 can detect 5 bit errors j. Bit rate = (Baud rate) * (number of bits per symbol) k. Half Duplex modems allow bi-directional traffic. 1. Full Duplex modems allow bi-directional traffic. m. Simplex modems allow bi-directional traffic. n. LEO satellites have a larger footprint that the MEO satellites. o. Sped of lghti ar he same as the sped ding i amnlitude modulation and ii)

Explanation / Answer

a) Network layer is responsible for packet forwarding as well as routing. So this is TRUE

b) 64 QAM modems have the constellation points very close to each other compared to 16 QAM modems. Due to this it is more prone to noise. So this is TRUE.

c) Short wavelengths are more scattered than longer wavelengths that is the reason that attenuation depends on the wavelength of the light.
So this is TRUE.

d) Using the signal power formula, it can be clearly seen that it increases with distance. So this is TRUE

e) The system of internet over cable tv provider is based on the fact that all users do not use the internet at the same time with same intensity. So when more users do start to use concurrently, the bandwidth get divided, so internet speeds may suffer. So this is TRUE

f) In slotted aloha, many users can use the same channel. This is the property of the contention based MAC protocols. Nodes send data when they are ready and wait random time before resending in case collison occurs.
So this is TRUE

g) In stop and wait, the sender has to wait for confirmation before sending the next message, therefore, the link isn't used to be maximum capability.
So this is TRUE

h) GSM uses a combination of TDMA and FDMA. These are sharing the time or frequency over many people turn by turn. So, their capacity is limited unlike CDMA which can allow multiple access. So this is TRUE.

i) A hamming distance of 10 means there needs to be 10 changes to generate another valid code. So, any number of errors below 10 will never generate a valid code so we can point them out as errors. So, 9 bit errors can be detected. Since, 5 < 9, so this is true.
Also note that 2x -1 = 10 implies x = 5, so 5 bit errors can be detected and corrected as well.

j) Baud rate refers to the number of times the signal changes its state. So, number of bits in each symbol * the number of times it changes state gives the bit rate.

k) Half duplex means a bidirectional line where each both side can't send message at a time but each side can send turn by turn so bidirectional comunication can occur. So this is TRUE

l) Full duplex means both users can at the same time send messages and messages can travel in opposite direction at the same time over the duplex line. So it is bidirectional. So this is TRUE

m) In simplex modems, one channel is used for incoming traffic and another channel is used for outgoing traffic. Thereby, overall providing birectional traffic. So this is TRUE

n) The MEO satellites (medium Earth orbit) have a higher coverage than LEO satellites (lower Earth orbit). So, the footprint of MEO is said to be larger. So this statement is actually false.

o) Speed of light slows down with higher refractive index. Optical fibers are made out of glass so have higher refractive index than air. Therefore, speed of light is theoretically and also practically seen as a bit slower than that in air. So, this statement is also false.

If any query, ask in comments. Thank you.

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