LTE Redirection - Definition & Explaination

[MyVi78]

Hi all,

Could anyone here help to explain what does "Redirection" means for LTE? Does it only apply for iRAT HOs only or is there another meaning to redirection?

It's something new to me and I'd like to seek some clarification here.

Thanks

[wahaha]

If i am not mistaken, there is a info about LTE redirection which is more to CSFB.

CS fallback to UMTS
To perform CS fallback to UMTS, RRC Connection Release with redirection information
is the least-effort solution because all the network and UE will support RRC Connection
Release procedure. In this solution, if the UE starts a CS call setup request via an extended
service request, or receives a CS paging, the UE’s RRC Connection in the LTE system
is released and the UE is redirected to the UMTS system. In this redirection information,
the eNodeB can indicate a target frequency. Then the UE moves to the target RAT and
searches for a suitable cell by utilizing the frequency information in the RRC Connection
Release. Once the UE finds a suitable cell, it starts from IDLE and acquires necessary
system information blocks to access the cell.

You may share your info from here whether you know about "Redirection" when reading on CSFB documents?

[lihanbok]

Hi wahaha (http://www.finetopix.com/member.php?51389-wahaha),
Do you have any document about LTE Redirection. Could you please share it. Thanks a lot.

BR,
Lihanbok.

[MyVi78]

If i am not mistaken, there is a info about LTE redirection which is more to CSFB.

CS fallback to UMTS
To perform CS fallback to UMTS, RRC Connection Release with redirection information
is the least-effort solution because all the network and UE will support RRC Connection
Release procedure. In this solution, if the UE starts a CS call setup request via an extended
service request, or receives a CS paging, the UE’s RRC Connection in the LTE system
is released and the UE is redirected to the UMTS system. In this redirection information,
the eNodeB can indicate a target frequency. Then the UE moves to the target RAT and
searches for a suitable cell by utilizing the frequency information in the RRC Connection
Release. Once the UE finds a suitable cell, it starts from IDLE and acquires necessary
system information blocks to access the cell.

You may share your info from here whether you know about "Redirection" when reading on CSFB documents?

I agree when you mentioned UE will perform RRC Connection Release procedure when moving from LTE to UMTS and vice versa by indicating the target freq., ie. LTE=>UMTS(UARFCN), UMTS=>LTE(EUARFCN), then start from idle before finding the sys information blocks.

What's the difference between using redirection compared to using hard HO? As I understand, redirection is not a standard protocol?

[wahaha]

I think redirection here is more to Voice service. When is using CSFB strategy for voice, UE will fall back from LTE to GSM/UMTS network when start to originating a call.
RRC Connection Release with redirection information, means release LTE resource and switch to UMTS or GSM network. (if i'm not mistaken)

For handover, it will happen when UE coverage become poor from serving cell which need to handover to intra cell or neighbour cells (eNodeB or NodeB) to avoid drop call.

My previous post info is based on the following link info:

http://books.google.com.my/books?id=X9XwEOxYnAkC&pg=PA163&lpg=PA163&dq=release+redirection+lte&source=bl&ots=S2g_laBvvr&sig=KZvHQ0aHCAvmajbpjFCobBtdZgo&hl=en&sa=X&ei=p1i4T7nUOpHxrQev473qBw&ved=0CFcQ6AEwBg#v=onepage&q=release%20redirection%20lte&f=false

[wahaha]

I think redirection here is more to Voice service. When is using CSFB strategy for voice, UE will fall back from LTE to GSM/UMTS network when start to originating a call.
RRC Connection Release with redirection information, means release LTE resource and switch to UMTS or GSM network. (if i'm not mistaken)

For handover, it will happen when UE coverage become poor from serving cell which need to handover to intra cell or neighbour cells (eNodeB or NodeB) to avoid drop call.

My previous post info is based on the following link info:

http://books.google.com.my/books?id=X9XwEOxYnAkC&pg=PA163&lpg=PA163&dq=release+redirection+lte&source=bl&ots=S2g_laBvvr&sig=KZvHQ0aHCAvmajbpjFCobBtdZgo&hl=en&sa=X&ei=p1i4T7nUOpHxrQev473qBw&ved=0CFcQ6AEwBg#v=onepage&q=release%20redirection%20lte&f=false

[wahaha]

Hope attached document from LG can help you to understand about LTE redirection concept.
You are welcome to share your point of view or documents about it :)

[MyVi78]

Hmm...so redirection is basically CS voice fall back from LTE to UMTS/GSM. However, if I'm not mistaken there is a redirection from UMTS to LTE. Any ideas on this?

Not too sure but I'll check again this week.

PS: Can't share the docs I currently have as it's from //H, thus encrypted.... :(

[wahaha]

I think UMTS to LTE is refer to cell reselection. Anyway, i also waiting for your further feedback about it.
Hope you can share your documents about it too :)

[MyVi78]

Ok. It seems there is redirection for both CS and PS. For CS, it's CS FB as mentioned by wahaha while for PS it's more like an additional option that we could set in eNodeB to trigger either PS HO or PS redirection (4G-3G & 3G-4G).

Still can't find any layer 3 flowchart for PS redirection...

[wahaha]

For PS redirection, i think it will be needed when UE is out of LTE coverage and switch to roaming partner's 2G/3G network (assume the operator LTE coverage is small).
Can you share your document for our reading? :)

Thanks.

For LTE signaling flow, maybe you can further info in the following link:

http://www.finetopix.com/showthread.php?29507-LTE-Signaling-Flow&p=181332#post181332

[hamody2005]

Does the redirection work from LTE to CDMA

CSFB from LTE to CDMA