3G (UMTS) HANDOVER ISSUES

Team Members: Cuong Pham & Thomas Truong

Handover in network

UMTS HandoverIntra-system Handover:Intra-frequency HOInter-frequency HOInter-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 handoverHard handover `break-before-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 handoverUE 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 handoverSofter 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 PhasesHandover detectionHandover preparationHandover 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

HO access

BTSold BSCnew

measurementresult

BSCold

Link establishment

MSCMSmeasurementreport

HO decision

HO required

BTSnew

HO request

resource allocation

ch. activation

ch. activation ackHO request ackHO commandHO commandHO command

HO completeHO completeclear commandclear command

clear complete clear complete

Hard Handoff Procedure

3G (UMTS)

Soft Handoff Procedure

UMTS Radio Access Network Architecture -

Mobility and Handover Issues RNC: Radio Network Controller

RNS: Radio Network Subsystem

RNC

Iub

RNS

CN

RNC

Iub

RNS

Iur

Iu

Node B

Node BNode B

Node BNode B

Node B

Node B

UE

UTRAN comprises several RNSsNode B can support FDD or TDD or both

RNC is responsible for handover decisions requiring signaling to the UECell offers FDD or TDD

UMTS HO AlgorithmThe 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 Algorithm1. 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

HHO AlgorithmNeighboring 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 6

Cell 7

Cell 11

Cell 10

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 UMTSVehicular Technology Conference, 2004. VTC 2004-Spring. 2004 IEEE 59 th 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 HSDPA15th 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. LandstorferDynamic Simulator for the Analysis of the Performance of WCDMA Radio Networks4thCOST 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

References6/ Hung-Hui Juan; Ching-Yao Huang;

Adaptive UMTS Handover Control Algorithm in Third Generation Wireless SystemsInformation, Communications and Signal Processing, 2005 Fifth International Conference on06-09 Dec. 2005 Page(s):607 - 612

7/ Danyan Chen; Xiaofeng Wang; Elhakeem, A.K.;Performance analysis of UMTS handover with the help of WLANQuality of Service in Heterogeneous Wired/Wireless Networks, 2005. Second International Conference on22-24 Aug. 2005 Page(s):8 pp. Digital Object Identifier 10.1109/QSHINE.2005.42

8/ Richardson, K.W.;UMTS overviewElectronics & Communication Engineering JournalVolume 12,  Issue 3,  June 2000 Page(s):93 - 100