Intra-Frequency Handover Overview

1. Intra-Frequency Handover Overview

2. Intra-Frequency Handover Procedure

3. Signaling Procedures for Intra-Frequency Handover

Characters of Intra-Frequency Handover:

z The carrier frequencies of the current cell and target cell are the same

Intra-frequency soft handover

Intra-frequency hard handover.

z Intra-frequency handover consists of two types,

Intra-frequency soft handover: more than one radio link are set up for the UE.

Intra-frequency hard handover: only one radio link is set up for the UE.

z Intra-frequency soft handover is more commonly used than intra-frequency hard handover. Intra-frequency hard handover is used only in some special scenarios, for example, when there is no Iur interface between two RNCs.

Intra-Frequency Handover Overview

Comparison between soft handover and hard handover:

Can be happened in Intra-

frequency cells or Inter-frequency cells

Only happened between Intra- frequency cells The frequencies of cells

Yes No

Interruption during handover

One Several

The number of RLs in active set after handover

Hard Handover Hard Handover Soft Handover

Soft Handover ItemItem

z The maximum number of RL is 3. This value can be changed. But this function need the UE to support. Normally, the active set supported by UE is fixed 3 and can not be changed.

Intra-Frequency Handover Overview

Intra-Frequency Soft Handover :

z Soft Handover

z Softer Handover

z Intra-Frequency soft handover is a function in which the UE is connected to several cells at the same time. Addition or release of radio links are controlled by the ACTIVE SET UPDATE procedure.

z During soft handover, a UE is in the overlapping cell coverage area of two sectors belonging to different base stations. The communications between UE and base station take place concurrently via two air interface channels from each base station separately.

z During softer handover, a UE is in the overlapping cell coverage area of two adjacent sectors of a base station. The communications between UE and base station take place concurrently via two air interface channels, one for each sector separately.

Intra-Frequency Handover Overview

Using selection combination Using maximum-ratio combination

Uplink signal

Using maximum-ratio combination Using maximum-ratio combination

Downlink signal

Occupying more Iub bandwidth Occupying less Iub bandwidth

Resource use

When the UE is in the overlapped coverage area of two neighboring cells of different NodeBs

When the UE is in the overlapped coverage area of two neighboring cells of a NodeB with combined RLs Scenario

Soft Handover Soft Handover Softer Handover

Softer Handover ItemItem

Comparison between soft handover and softer handover :

During softer handover, the uplink signaling are combined in NodeB by maximum ratio combination, but during soft

handover they are combined in RNC by selective combination

Compare to later one, the maximum ratio combination can get more gain. So the performance of maximum ratio combination is better

Since softer handover is completed in NodeB, it do not consume transport resource of Iub

Intra-Frequency Handover Overview

Intra-Frequency Hard Handover :

zNo Iur interface

zIur interface is congested

zHigh-speed Best Effort (BE) service Handover

zSoft handover fails

z Intra-frequency hard handover refers to a handover where all the old radio links are released before the new radio links are established. Compared with soft handover, intra-frequency hard handover uses fewer resources.

z The scenarios of intra-frequency hard handover are as follows:

The UE needs to perform the intra-frequency handover between two cells configured in different RNCs. No Iur interface is present between RNCs.

The UE needs to perform the intra-frequency handover between two cells configured in different RNCs. The Iur interface is congested between RNCs.

There is a high-speed Best Effort (BE) service.

Compared with soft handover, intra-frequency hard handover is used to save downlink bandwidth for a high-speed BE service.

The intra-frequency soft handover fails and intra-frequency hard handover is allowed.

When intra-frequency soft handover fails because of a congestion problem of the target cell, the RNC tries an intra-frequency hard handover with a lower service bit rate.

The INTRA_FREQUENCY_HARD_HANDOVER_SWITCHparameter in the SET CORRMALGOSWITCHcommand is used to determine whether to enable intra- frequency hard handover. By default, this switch is ON.

Contents

1. Intra-Frequency Handover

Intra-Frequency Handover Decision and Execution