1. June 12, 20141 Mobile Computing COE 446 Network Operation Tarek Sheltami KFUPM CCSE COE http://faculty.kfupm.edu.sa/coe/tarek/coe446.htm Principles of Wireless Networks K. Pahlavan and P. Krishnamurth

2. June 12, 20142 Handoff Management Architectural Issues in Handoff Handoff Decision Time Algorithms Types of Handoffs Outline

3. June 12, 20143 Handoff Management 1. Architectural Issues in Handoff Set of protocols to notify all related entities of a particular connection that a handoff has been executed and the connection has to be redefined In voice network, MT selects the BS that is serving its location When an MT moves from one point of attachment to another, the old serving point of attachment has to be informed about the change (dissociation) Other network components involved in routing mechanism have to be aware of the handoff in order to seamlessly continue the ongoing connection of the call Mobile Management

4. June 12, 20144 Handoff are classified according to the connection creation Seamless handoff and hard handoff Handoffs are classified into: 1. Network Controlled Handoff (NCHO) 2. Mobile Controlled Handoff (MCHO) 3. Mobile Assisted Handoff (MAHO) Mobile Management

5. June 12, 20145 (Cellular Digital Packet Data)

6. June 12, 20146 Handoff Management 2. Handoff Decision Time Algorithms Traditional handoff algorithms are based on the RSS. Some of them are as follows: 1. RSS 2. RSS plus Threshold 3. RSS plus Hysteresis 4. RSS, Hysteresis and Threshold 5. Algorithms plus Dwell Timer Mobile Management

7. June 12, 20147

8. 8

9. 9 Time051015202530354045 BS 1 -50-57-56-44-49-55-60-60.5-55-52 BS 2 -49-53-46-54-45-47-56-60-55-56 BS 3 -66-55-45-47-57-58-46-54-55-62 A mobile terminal is receiving signals from 3 BSs at the handoff region. The handoff decision is made at each sampling time according to the below table. The MT is initially connected with BS 1. Show the handoff transitions between BSs for each of the following algorithms: RSS RSS + -60 dBm Threshold RSS + Hysteresis 10 dBm RSS + Hsyteresis 5 dBm + -55 dBm Threshold Example

10. June 12, 201410 Time051015202530354045 BS 1 -50-57-56-44-49-55-60-60.5-55-52 BS 2 -49-53-46-54-45-47-56-60-55-56 BS 3 -66-55-45-47-57-58-46-54-55-62

11. June 12, 201411 Handoff Management 2. Handoff Decision Time Algorithms The performance of handoff algorithms measures have been considered such as call blocking probability, handoff blocking probability, delay between handoff request and execution, and call dropping probability Handoff rate is related to the ping-pong effect and algorithms are designed to minimize the number of unnecessary handoffs Mobile Management

12. June 12, 201412 Generic Handoff Management Process 1. Handoff decision is made and initiated 2. MT register with new visiting database via handoff messages 3. New visiting database communicates with the home database to get the subscriber profile and for authentication 4. Home database responds to the new visiting database with authentication of the MT 5. Home database sends messages to the old visiting database to cancel registration 6. The old visiting database flushes or redirects to the new visiting database and removes the MT from its list Mobile Management

13. June 12, 201413

14. June 12, 201414 Handoff Management Types of Handoffs: 1. Intracell, two channels 2. Intercell intradomain handoff, between two BSs associated with the same database 3. Intercell interdomain handoff, between two BSs with different database Mobile Management