Hello all.
For 4G to 3G we use RRC connection release with redirection even for CSFB.
And we plan to activate handover instead of RRC release.
My question is: What is the difference in the performance between HO and RRC release (4G to 3G)?
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CST will increase and it can impact user experience or call drops may increase.
Why do you want to use handovers?
We will just try it .
And I want to know expected outcome (bad or good).
Delay will increase, and it may impact the Drop rate.
As handover will involve measurements but currently its going blindly.
The advantage of HO lies in the ability to maintain the ongoing call or data session without interruption.
While RRC release with redirection involves releasing the radio resources and redirecting the user equipment to another network, which usually takes increases Call Setup Time and may cause a brief interruption in the communication, increasing the risk of Drop Call Rate.
Even if you activate PSHO toward 3G you will need to keep a critical zone where UE is redirected toward UMTS by RRC release.
You may not remove this critical coverage zone even if you add PS handover.
Firstly all RRC release with redirect toward EUTRA or UTRA are considered a normal release which will not contribute to call drop rate.
Secondly PSHO relies on event B2 which requires finding a suitable cell on 3g. If UE does not find a 3g cell with the required ECNO/RSCP it can not perform HO which may lead to call drop while RRC release with redirection is done blindly without considering 3g coverage.
Thirdly in most vendors a QCI-1 bearer is not redirected and only a QCI-9 (aka data bearer) is allowed to be redirected. This means the end user will not sense a release with redirection of QCI-9 bearer.
In summary one may not conclude that PSHO increase the chance of call drops compared to RRC release with redirection. It all depends on your mobility settings, the thresholds you choose for each event and the overall interoperability with legacy networks…
Thanks for your answer to my comments. 
My initial answer was based on the commom comparison between these 2 techniques: HO vs RRC Release with Redirect. Then, it’s possible to highlight some particular benefit of any technique depending of the experience and situations working with them.
Below are my answers on your message:
RRC release with redirect always increments the risk of failures in the current call, but vendors not consider it as “drops” due to hardware/software limitations. Generally, final operator clients are aware about this limitation, and due to it, they ask for Drive Test to check the performance of these processes
If UE doesn’t find a suitable cell on 3G, user experience will be affected with any method. Suggestion here is to set B2 thresholds with ECNO/RSCP 3G minimum access levels.
OK, but always final operator client will define if the degradation caused by interruption time is “permisible”. For that reason it was introduced PSHO technique as extra feature (Ericson case).
Agree, in the network configuration it’s possible to configure the parameters to favor more one or the other.