1. TCS 316 High Speed Information Networks UMTS Handover by Nasir Faruk Mobile Week 13 May, 2014
25/04/ :14:46

2. Content and rem.. Weeks 13 Cell Search procedure (Skipped) Handover
Softer
Soft
Hard
Sectorisation (Briefly taught last semester)
Weeks 14 ( To be skip. You met it in industry when lucky hahaha) IP
IP Mobility
Mobile IP
VoIP
25/04/ :14:46

3. Air Interface Modes UMTS Core Network Frequency Division Duplex Mode 1
Direct Sequence Mode
wray castle browser
Internet Search
XXXXXXX XXX
XXXXX XXXX
XXXX XXX XX
CDMA
UMTS Terrestrial Radio
Access network (UTRAN)
Time Division Duplex Mode 1
TD-CDMA
wray castle browser
Internet Search
XXXXXXX XXX
XXXXX XXXX
XXXX XXX XX
User Equipment (UE)
FDD Mode
User Equipment (UE)
TDD Mode
25/04/ :14:46
Figure 2

4. Handover Types Within UTRA FDD – Intra-Mode Handover
Soft
Softer
Hard (intra- or inter-frequency)
Inter Mode Handover
Handover to UTRA TDD – not implemented yet!
Inter-system Handover
In R99 means only to GSM handover
In R8 & LTE (E-UTRA or E-UTRAN) means handover to and from LTE (Long Term Evolution).
25/04/ :14:46

5. Effect on Capacity with Contiguous Coverage
Cell A
Cell B
Cell A in isolation
10 channels
Cell B in isolation
10 channels
Interference
Capacity of Cells A and B
is less than 20 because
of increased interference
25/04/ :14:46
Figure 9

6. Cell Capacity 10 users using 10 kbit/s channel
Total Cell Capacity = 100 kbit/s
2 users using
50 kbit/s channel
Total Cell Capacity = 100 kbit/s
25/04/ :14:46
Figure 10

7. Power Control at Cell Boundaries
instructs mobile
to turn power up
Increase in
interference here
Power Control
wray castle browser
Internet Search
XXXXXXX XXX
XXXXX XXXX
XXXX XXX XX
wray castle browser
Internet Search
XXXXXXX XXX
XXXXX XXXX
XXXX XXX XX
Node B 1
Node B 2
25/04/ :14:46
Figure 29

8. Necessity for Soft/Softer Handover
Essentially to avoid interference
Mobile could penetrate far into adjacent cell without being power controlled by that cell
This could be overcome by the use of very fast and frequent hard handovers
Not efficient as too much signalling involved.
25/04/ :14:46

9. Soft Handover Soft Handover – make before break Node B 1 2
wray castle browser
Internet Search
XXXXXXX XXX
XXXXX XXXX
XXXX XXX XX
Power Control
Power Control B
Soft Handover – make before break
25/04/ :14:46
Figure 30

10. WCDMA Soft Handover
Active set - the cells participating in the soft handover
Normally just 2 cells
Neighbour or monitored set
Cells that the UE continuously measures
Pilot Ec/No not strong enough to be added to the active set
25/04/ :14:46

11. UE Measurements GSM BTS Inter- system Node B Node B Micro Intra-
frequency
Inter-
frequency
RLC
Buffer
Downlink
Quality
Intra-frequency
wray castle browser
Internet Search
XXXXXXX XXX
XXXXX XXXX
XXXX XXX XX
Uplink
Traffic
Volume
Node B
Internal
TX power UE
RSSI
Local Measurement
25/04/ :14:46
Figure 21

12. Ec/No Measurement from CPICH
UTRA FDD intra-mode handover relies on the Ec/No measurement performed from the CPICH.
Quantities defined that can be measured by the terminal from the CPICH are as follows:
Received Signal Code Power (RSCP) – received power on one code after despreading defined on the pilot symbols;
Received Signal Strength Indicator (RSSI) – wideband received power within the channel bandwidth;
Ec/No = RSCP/RSSI, i.e. RSCP divided by the total power in the channel bandwidth.
25/04/ :14:46

13. WCDMA Handover Algorithm
If a neighbour cell pilot channel signal remains better than the current best cell’s pilot minus a hysteresis value for a timeout period the neighbour cell may be added to the active set.
If an active cell signal is worse than that of the current best cell minus a different hysteresis value for a short period it may be removed from the active set.
If a neighbour cell signal is better than the current worst active cell plus a third different hysteresis value for the timeout period it may replace that worst active cell.
25/04/ :14:46

14. Soft Handover Region Two-Cell Case Soft handover region A B Start End
wray castle browser
Internet Search
XXXXXXX XXX
XXXXX XXXX
XXXX XXX XX
Start
End
25/04/ :14:46
Figure 31

15. Soft Handover Region Three-Cell Case Three-way handover Required hereB A C
25/04/ :14:46
Figure 31 (continued)

16. Example of a Soft Handover
Quality
Cell A
Timer
Timer
Timer
Macro
Remove
Threshold
Macro
Add
Threshold
Timer
Macro
Replacement
Threshold
Cell B
Cell C
Time 1. 2. 3.
Full specification is in 3GPP TR V6.0.1 ( )
25/04/ :14:46

17. Soft vs Softer Handover
Softer Handover – also make before break
25/04/ :14:46

18. Softer Handover
Between two cells or sectors supported by the same Node B
UE transmits & receives from both cells simultaneously:
UE combines downlink information
Node B combines uplink information
Only one power control loop
Both soft & softer handover may occur simultaneously
Soft/softer handover at the UE & softer at the Node B
Similar to multipath reception
Two separate downlink codes
RAKE fingers need to generate two codes
25/04/ :14:46

19. Soft Handover at the RNC
Uplink data routed to RNC for combining
Better frame selected
After each interleaving period ms
Outer loop power control frame reliability indicator utilised.
25/04/ :14:46

20. Serving & Drift RNC
25/04/ :14:46

21. Serving & Drift RNC
25/04/ :14:46

22. Serving & Drift RNC
25/04/ :14:46

23. Macro and Micro Diversity
Macro Diversity Combining
at RNC for Soft Handover
RNC
Cell A
Soft
Handover
Cell B
wray castle browser
Internet Search
XXXXXXX XXX
XXXXX XXXX
XXXX XXX XX
Softer
Handover
Node B
Node B
Micro Diversity
Combining at
Node B for
Softer Handover UE
25/04/ :14:46
Figure 36

24. UMTS Hard Handover
Between two cells using different carrier frequencies
Between cells whose Nodes B are
connected to different RNCs without the Iur interface
To and from GSM
25/04/ :14:46

25. Handover and External Reselection Related Procedures
UMTS
Core Network
GSM
Core Network
RNC
BSC
Node B
micro
Node B
macro
Node B
macro
BTS
Hard Handover
Soft Handover
Hard Handover
within UTRAN
within UTRAN
outside UTRAN
Reselection
outside UTRAN
25/04/ :14:46
Figure 19

26. UMTS Handover Types - Summary
wray castle browser
Internet Search
XXXXXXX XXX
XXXXX XXXX
XXXX XXX XX
GSM
UMTS
Macro
Micro UE
Hard C B
Soft A
Hard Handover – break before
make
A = intra-frequency
B = inter-frequency
C = inter-system
25/04/ :14:46
Figure 33