IT351 - Mobile & Wireless Computing Tutorial_1

1. The ISO/OSI 7-layer reference model, or simply the OSI model, has been influential in network design for over 20 years now.

i. Use a diagram to show how a message is passed (physically and logically), using the OSI model, between two Application-layer peers that are separated by a single data link layer device (bridge).

ii. What are the main functions of the transport, network and data link layers of the OSI model?

2. Application developers who work with mobile computing environments gain a number of benefits over traditional desktop computing environments. Briefly describe three applications that are enabled by mobile computing.

3. Why can waves with a very low frequency be used for submarine communication? Why are they not used for data transmission in mobile phones and computer networks

4. Explain briefly what is meant by free space loss.

5. Although a Line-of-sight is required between a sender and receiver for radio waves with frequency > 30 MHz, mobile phones can work in big cities without such a LOS. Explain

6. Is it possible to transmit a digital signal , e.g., coded as square wave as used inside a computer using radio transmission without any loss? Why?

7. Is a directional antenna useful for mobile phones? Why? How can the gain of the antenna be improved?

8. What are the main problems of signal propagation? Why do radio waves not always follow a straight line?

9. Explain how is reflection both useful and harmful

HOME WORK:

Search the Internet and describe briefly the License-free ISM band. Explain why is the International availability of the same ISM bands important.