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 `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 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 HO access BTSold BSCnew measurement result BSCold Link establishment MSC MS report HO decision HO required BTSnew HO request resource allocation ch. activation ch. activation ack HO request ack HO command HO complete clear command clear complete

Hard Handoff Procedure

3G (UMTS) Soft Handoff Procedure

UMTS Radio Access Network Architecture - Mobility and Handover Issues RNC Iub RNS CN Iur Iu Node B UE RNC: Radio Network Controller RNS: Radio Network Subsystem UTRAN comprises several RNSs Node B can support FDD or TDD or both 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) Each UE measures the SIR received from the surrounding cells. 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 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 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 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