Handoff in Mobile Communication

This presentation will show you how handoff works on Mobile communication

1. HELLO ! 👨 Noushad Hasan ( 2014-3-50-025) 👩 Maliha Rahman(2014-3-50-007) 👨 Sauradip Roy (2014-3-50-008) 1

2. “Hand-off in Mobile Communication”

3. What is Handoff ? Let’s start with the first set of slides

4. In   mobile communication,  handoff is the transition for any given user of signal transmission from one base station to a geographically adjacent base station as the user moves around. Each base-station transition, as well as the switching processor sequence itself, is called handoff. 4

5. 📌 Handoff Strategies Handoff is encouraged to maintain call quality as subscribers move in and out of range of base station. New voice & Control channel frequencies. Prioritizing handoff over a new call initiation by allocating unused channels of new base station. Before handoff the base station monitors the signal level for a certain period of time. Avoid unnecessary handoff by measuring the signal strength and ensuring the handoff is completed before the termination of call. 5

6. 📌 Handoff Strategies(Cont.) 6 Handoff should be performed under the following circumstances-

7. 📌 Handoff Strategies(Cont.) The call will be dropped when there is an excessive delay in MSC due to huge traffic in assigning handoff The call will be dropped if no channels are available. 7

8. Guard Channel Concept a fraction of the total available channels  in a cell is reserved exclusively for handoff request from ongoing calls which may be handed off into the cell. 📌 Prioritizing Handoff Queuing of handoff requests In such system the probability that the handoff will not be served is equal to blocking probability of new originating call.A fraction of the total available channels in a cell is reserved exclusively for handoff request from ongoing calls which may be handed off into the cell.  8

9. 📌 What happens when handoff takes place ??? 1.Signal strength falls below the threshold level. 2.Base station of the cell originates a handoff request. 3.MSC gets the information from the candidate cell. 9 When mobile is in the edge of cell- 4.MSC asks both the cell to co-ordinate with each other. 5.If the handoff is successful the mobile is asked to switch to another voice channel

10. 📌 Handoff in different cellular systems Handoff in 1G Cellular System Handoff in 2G Cellular System Signal strengths are measured and monitored by MSC Signal Strengths are monitored by mobile itself MSC decides if handoff is necessary or not. According to received power from BS the mobile decides when to handoff Huge traffic at MSC due to computational load MSC is no longer loaded with traffic since mobile takes the handoff decision 10

11. 📌 Types of Handoff Hard Handoff B reak before make. Connects to single BS at a time. Soft Handoff Make before break. Connects to multiple BS simultaneously. 11

12. How to Overcome??? 12

13. 📌 Umbrella Cell Concept for Practical Handoff Situations 13 Figure: Umbrella Cell Approach

14. 📌 Umbrella Cell Concept for Practical Handoff Situations(Cont.) The Umbrella cell concept ensures that the number of handoff’s is minimized for the high speed users and provides additional microcell channels for pedestrian users. The speed of vehicle may be evaluated by the MSC, by calculating how rapidly received signal strength varies for each reverse voice channel. If a high speed user is approaching to the base station, and its speed is decreasing, then the base station will handover the user to the microcell, without consulting with the MSC. 14

15. 📌 Cell Dragging in practical situations If a user travels away from the base station at a slow speed and the average signal strength doesn’t decay rapidly then it seems like the present cell has been dragged into the adjacent cell , it is called cell dragging. It occurs when there is a line of sight communication path between the mobile unit and the antenna most of the time. 15

16. 📌 Cell Dragging in practical situations (Cont.) This phenomenon effects these following occurrences- Low speed user line of sight to base station Strong signal changing slowly User moves into the area of an adjacent cell without handoff Creates potential interference and traffic management problems because user has travelled down into the adjacent cell This can be avoided by adjusting the handoff threshold and ratio coverage parameters carefully. 16

17. THANKS! Any questions ??? 17

18. SlidesCarnival icons are editable shapes . This means that you can: Resize them without losing quality. Change fill color and opacity. Change line color, width and style. Isn’t that nice? :) Examples: 18

19. Now you can use any emoji as an icon! And of course it resizes without losing quality and you can change the color. How? Follow Google instructions https://twitter.com/googledocs/status/730087240156643328 ✋👆👉👍👤👦👧👨👩👪💃🏃💑❤😂😉😋😒😭👶😸🐟🍒🍔💣📌📖🔨🎃🎈🎨🏈🏰🌏🔌🔑 and many more... 😉 19