3G (UMTS) HANDOVER
ISSUES
Team Members: Cuong Pham &
Thomas Truong
Handover in network
UMTS Handover
Intra-system Handover:
Intra-frequency HO
Inter-frequency HO
Inter-system HO
• Different radio access technologies (e.g.
UMTS and GSM/EDGE)
• Different radio access modes (e.g.
FDD/WCDMA and TDD/TD-CDMA)
Hard handover
Hard handover `breakbefore-make' is applied
when the user’s equipment
communicates with only
just one Node B.
Connection with the old
Node B is broken before
the new connection is
established
Soft handover
UE is located in the coverage
area of two or more different
Node Bs. The UE
simultaneously
communicates with two or
more Node Bs via two or
more radio channels. A
received signal in Node B is
routed to the RNC (Radio
Network Controller). The
RNC compares the signal on
the frame by- frame basis.
The best frame is selected for
the next processing; the
others frames are discarded.
Softer handover
Softer handover is
similar to soft
handover. The main
difference between
these two handovers
resides in fact that a
UE is located in the
coverage area of two
sectors of one Node B
Handover Phases
Handover detection
Handover preparation
Handover execution
Handover Detection
One of the responsibilities of the
handover entity is monitoring and
triggering the handover.
Handover Preparation
In this phase, the handover entity
requests for the other networks
resource availability information.
Handover Execution
A handover execution message is
responsible for triggering the handover
to another network and is sent by the
handover entity.
Handover Procedure
MS
BTSold
BSCold
measurement
measurement
report
result
MSC
HO decision
HO required
BSCnew
BTSnew
HO request
resource allocation
ch. activation
HO command
HO command
HO command
HO request ack ch. activation ack
HO access
Link establishment
clear command clear command
clear complete
clear complete
HO complete
HO complete
Hard Handoff Procedure
3G (UMTS)
Soft Handoff Procedure
UMTS Radio Access Network Architecture -
Mobility and Handover Issues
RNS
UE
Node B
RNC: Radio Network Controller
RNS: Radio Network Subsystem
Iub
RNC
Node B
Iu
UTRAN comprises several
RNSs
Node B can support FDD or
TDD or both
CN
Iur
Node B
Iub
Node B
RNC
Node B
RNS
RNC is responsible for
handover decisions requiring
signaling to the UE
Cell offers FDD or TDD
UMTS HO Algorithm
The algorithm samples the signal
strength of the surrounding base
stations every 1 sec.
3dB threshold for soft handover.
6dB threshold for hard handover.
The size of the Active Set is 3 signals
SHO Algorithm
Each UE is connected to its Primary_BS, and keeps
an Active_ Set (2 “closest” cells)
2.
Each UE measures the SIR received from the
surrounding cells.
3.
If (AS1_SIR – Pr_BS_SIR) >3dB OR (AS2_SIR –
Pr_BS_SIR) > 3dB
UE enters Soft Handover
UE keeps a simultaneous connection to the
Primary_BS and one or both of the Active_Set
cells
1.
HHO Algorithm
Neighboring cells replace the cells in the Active_Set if
their SIR exceeds the Active_Set cells’ SIR by 6dB.
-
-
If (AS1_SIR – Pr_BS_SIR) > 6dB for three
measurements in a row: AS1 becomes the
Primary_BS
If (AS2_SIR – Pr_BS_SIR) > 6dB for three
measurements in a row: AS2 becomes the
Primary_BS
Hard & Soft HO in UMTS
Cell 10
Cell 11
Cell 6
Cell 7
Parameters
- UE speed = 38 km/h and moving among 3
cells.
- Soft handover Threshold = 3 dB
- Traffic = 12.2 kbps
- Path loss = Vehicular
Case 1
Case 2
Case 3
Case 3
Case 4
Case 4
Average UL Transmission Power
Path Loss
Algorithm of SHO
References
1/ Sattari, N.; Pangalos, P.; Aghvami, H.;
Seamless handover between WLAN and UMTS
Vehicular Technology Conference, 2004. VTC 2004-Spring. 2004 IEEE 59th Volume 5, 17-19 May 2004
Page(s):3035 - 3038 Vol.5 Digital Object Identifier 10.1109/VETECS.2004.1391481
2/ H. Buddendick , G. Wölfle, S. Burger, and P. Wertz
Simulator for Performance Analysis in UMTS FDD Networks with HSDPA
15th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications
(PIMRC) 2004, Barcelona (Spain), Sept. 2004
3/ P. Wertz, R. Hoppe, G. Wölfle, H. Buddendick, and F.M. Landstorfer
Dynamic Simulator for the Analysis of the Performance of WCDMA Radio Networks
4thCOST 273 MCM-Meeting in Lisbon, Portugal, COST 273 TD(02)148, Sept. 2002
4/ R. Hoppe, G. Wölfle, H. Buddendick, and F.M. Landstorfer
Fast Planning of Efficient WCDMA Radio Networks
54th IEEE Vehicular Technology Conference (VTC) 2001 - Fall, Atlantic City (New Jersey,
USA), October 2001
5/ R. Hoppe, H. Buddendick, G. Wölfle, and F.M. Landstorfer
Dynamic Simulator for Studying WCDMA Radio Network Performance
53rd Vehicular Technology Conference (VTC) 2001 - Spring, Rhodos (Greece), May 2001
References
6/ Hung-Hui Juan; Ching-Yao Huang;
Adaptive UMTS Handover Control Algorithm in Third Generation
Wireless Systems
Information, Communications and Signal Processing, 2005 Fifth International
Conference on
06-09 Dec. 2005 Page(s):607 - 612
7/ Danyan Chen; Xiaofeng Wang; Elhakeem, A.K.;
Performance analysis of UMTS handover with the help of WLAN
Quality of Service in Heterogeneous Wired/Wireless Networks, 2005. Second
International Conference on
22-24 Aug. 2005 Page(s):8 pp.
Digital Object Identifier 10.1109/QSHINE.2005.42
8/ Richardson, K.W.;
UMTS overview
Electronics & Communication Engineering Journal
Volume 12, Issue 3, June 2000 Page(s):93 - 100