94.536 Mobile Computing

Midterm, Fall 2002

Duration: 90 minutes

Instructor: T. Kunz

Name: Student number:

Answer all questions on this exam paper. Each explanation should be as brief as possible; you may also want to use diagrams where appropriate.

Question 1. Frequency Reuse (10 marks)

Briefly explain the concept of frequency reuse that underlies cellular systems. Also explain why frequency reuse is necessary.

Question 2. GSM (5 marks)

How are users authenticated in GSM? Explain all necessary steps, assuming that a user inserts his/her SIM into a new device in an unknown network and powers up the device.

Question 3. Wireless LANs (15 marks)

1. IEEE 802.11, Hiperlan, and Bluetooth are all developed to allow IP packets to be carried over a wireless media. Based on the respective MAC protocols, how likely are packet collisions for each networking technology?

2. Compare the overhead introduced by the three MAC schemes and the resulting performance at zero load, light load, and high load of the medium.

Question 4. IEEE 802.11 (15 marks)

Describe how clock synchronization and power saving is achieved in IEEE 802.11 for both Infrastructure Networks and Ad-hoc Networks.

Question 5. Bluetooth (5 marks)

Outline how connections are established and data exchanged in Bluetooth.