Question

Answer the following:

1. What is crosstalk? How is it minimized in case of a twisted pair of wire?
2. Why are two separate frequencies used for uplink and downlink transmission in case of satellite communication?
3. Differentiate between the 2 switching techniques (Circuit Switching and Packet Switching).(4 differences)
4. What is the answer to Exercise 2.7 from Section 2 of our textbook with this change: the 4th transmission (B sends to D) does not occur?

2- pages in length, in your own words, properly cite any outside resources. Use 1" margins and Times Roman Font, 12-point, or something comparable. The paper should be well organized with proper grammar and spelling.

Be sure to properly cite any sources you use using APA format

Answer 1

Answer to Question 1

In cabling, Crosstalk refers to electro-magnetic interference from one unshielded twisted pair to another twisted pair. This generally happens when the two wires are running in parallel. One can also define crosstalk as picking up of electro-magnetic signals from other adjacent two/more unshielded twisted pair wires by electro-magnetic induction. Twisted pair wire reduces/minimizes crosstalk as when a pair of wires is twisted together, the electro-magnetic signals generated by the two wires cancel each other because they are of opposite polarity. This helps in reducing the susceptibility of interference to the adjacent wires.

Answer to Question 2

The uplink frequency is the frequency which is used for transmission of signals from earth station transmitter to the satellite.

The downlink frequency is the frequency which is used for transmission of signals from the satellite to the earth station receiver.

Electromagnetic waves can travel a certain amount of distance after which the signal strength will need to be enhanced. The signals have to cross the atmosphere which results in attenuation. The higher the frequency of the signal, the more is the signal loss and more power is needed for reliable transmission.

Now, since higher frequency leads to signal loss, then why not use lower frequency. This is because lower frequencies get reflected by atmospheric bands and cannot penetrate to get through to the satellite.

Now, a satellite is a light device which cannot support high-power transmitters on it. So, it transmits at a lower frequency (higher the frequency, higher is the transmitter power to accommodate losses) as compared to the stationary earth station which can afford to use very high-power transmitters. This is compensated by using highly sensitive receiver circuits on the earth station which is in the line-of-sight (LOS) of the satellite.

On satellites such chnages/modifications will require a significant amount of equipment and the amount of power and energy that will go into enhancing the signal strength. Mounting such a thing will make the satellite bulky and quite large. Hence, the same is done on the earth where it is easily maintained and uplink and downlink frequencies are different.

Answer to Question 3

  

Circuit Switching   Packet Switching

In circuit switching, a single connection is established between 2 points before communication takes place.	In packet switching, a packet is simply data that has been divided into smaller units along with a header, to transfer information with ease.
There are 3 phases in circuit switching i) Connection Establishment. ii) Data Transfer. iii) Connection Released.	In Packet switching directly data transfer takes place .
It is most ideal for voice communication, while also keeping the delay uniform.	It is used mainly for data transmission as the delay is not uniform.
Congestion can occur during connection establishment time, there might be a case in which the channel we are requesting is already occupied.	Congestion can occur during data transfer phase