XX. In small groups, perform the following tasks.

1. Explain how Bluetooth technology is used to connect and exchange information within communications systems. You may wish to consider devices such as mobile phones, laptops, video game consoles and personal computers.

2. Email is used regularly in business, both internally and externally. Explain how emails are sent across a network.

3. Communication systems have greatly changed the workplace. In relation to the following situation, briefly describe the changes to the nature of work that have taken place: While sitting on a train on the way to her office, a worker for an accounting firm uses a laptop to check her email.

4. Define virtual communities and discuss the impact they have had on social interactions.

5. Discuss the advantages and disadvantages of electronic mail.

6. Research the term e-crime and discuss one of the areas where this form of criminal activity is having an impact on communication systems.

7. Explain the similarities and differences between the Internet, intranets and extranets.

8. Define podcasts and list three areas where this technology is emerging as a popular form of digital communication.

WRITING

XXI. Link each set of sentences to make one sentence. You may omit, change or add words as required. Then form your sentences into two paragraphs to make a description of how the hybrid satellite communications system works (See Appendix 1).

1)

The hybrid satellite communications system provides communications.

The hybrid satellite communications system provides the Internet access, to computer users.

The hybrid satellite communications system includes a satellite system.

The hybrid satellite communications system includes a terrestrial communications system.

The satellite system includes two transceivers.

2)

The first transceiver receives and transmits the first set of signals.

The signals are received from the terrestrial communications system to a plurality of user units.

3)

The second transceiver receives a second set of signals in a second frequency band from the user units.

The second transceiver transmits those signals back to the terrestrial communications system.

4)

The first set of signals are relayed by a Direct Broadcast System (DBS) satellite in a frequency band between 12.2 GHz and 129 GHz.

The second set of signals are received and transmitted by a Mobile Satellite System (MSS) satellite operating between 1.0 GHz and 3.0 GHz.

5)

The present invention is capable of using the present communications infrastructure. The infrastructure is dedicated to the satellite transmission of television via DBS satellites.

The infrastructure is dedicated to satellite cellular communications via MSS satellites.

Unit 8 revision

I. What do you know about satellites? Look at the picture and explain how the satellite in orbit operates.

II. Read the text and compare satellite Broadband to dial-up, dsl or cable in terms of speed and cost.

Satellite broadband is Internet connectivity provided by satellite, rather than dial-up, DSL (digital subscriber line) or cable service. It is linked to a dish network subscriber service and provides speeds similar to other broadband technologies. Broadband service is the premiere way to connect to the Internet. Unfortunately, not everyone can get DSL or cable service, particularly in rural areas. To be eligible for DSL, the subscriber must be within 18,000 feet (5,486.4 meters) of the phone center, though some telecommunications companies do accommodate greater distances. Companies that provide cable TV offer Internet service, but this also does not cover all areas.

For those left out, satellite broadband can be the answer. The Internet feed is beamed from satellite to a dish installed at the subscriber's home. This type of broadband can deliver speeds of 2 megabits per second (mbps) downstream, and 1 mbps upstream. Compare this to dial-up service that tops out at about 53 kilobits per second. That's about 39 times slower than satellite-based broadband. Like every technology, satellite broadband also has its disadvantages. It is more expensive to set up than DSL or cable, and weather can affect the signal. Another disadvantage is signal delay, known as high latency.

Every time a subscriber sends a command to fetch a Web page, the request must travel 22,300 miles (35,888 km) to a satellite in geostationary orbit. From there, the signal travels another 22,300 miles back to earth, to the satellite service provider, where it is routed to the internet, data is exchanged, and is then sent 22,300 miles back to the satellite. Once the satellite receives the information, the page data must travel the final 22,300 miles back to the user. The subscriber pays for that 89,200 mile (143,553 km) round trip for each request in delayed milliseconds. Some sources indicate the average latency is 500-700 ms. This unavoidable 'delay' makes satellite broadband a poor choice for activities like multiplayer online gaming. While this technology is far faster than dial-up, it is still one of the slower broadband technologies. Cable is also a faster technology, though cable speeds can be affected by local traffic loads.