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Re: [STDS-802-16] [HO] Usage of "network assisted HO supported flag"



Hi,

Thanks for your reply.

The first issue I concern is CAN MS not choose to send MOB_HO-IND if Network Assisted HO supported flag is set to "1", it seems that you support it.

For the case 1 you mentioned, I have different opinion, in my perception, 
MOB_HO-IND with Target BS set to 0x00000000 is just as an acknowledgment to MOB_BSHO-REQ but not an indication of handover decision. The action that "serving BS may release its resources allocated for that particular MS after receiving MOB_HO-IND with Target BS set to 0x00000000" is not specified in standard.

For the case 2
you mentioned, we should note that resource retain timer is started only after BS receives MOB_HO-IND in which HO_IND_type field specifies serving BS release. So, in case 2, if MS not send MOB_HO-IND to serving BS, how could serving BS start the resource retain timer?

For the case 3 you mentioned, it has same problem with case 2, that is if
serving BS not receives MOB_HO-IND, therefore, resource retain timer will not be started, the question is can MS always assume that it can send MOB_HO-IND with cancel in some abnormal cases such as drop or failed to handover to target BS?

This is quite tricky. The problem rises because MS can choose not to send
MOB_HO-IND when Network Assisted HO supported flag is set to "1". However, if MS always needs to send MOB_HO-IND, why we need Network Assisted HO supported flag? If uncontrolled HO is allowed (though standard states that MS shall send MOB_HO-IND in any case: release, cancel and reject), we need to solve the resource retain timer issue.

Please let me know you comment.

Thanks.

On 6/27/06, Malini Raghavendra <Malini.Raghavendra@lntinfotech.com > wrote:

Hello Mr Lee,

Here is my view on the Network Assisted HO Flag going through the specification.

The Network Assisted Flag in MOB_BSHO-REQ and MOB_BSHO-RSP messages indicates to MS
of serving BS support in specifying the candidate BSs for Handoff .

In this scenario there are 3 cases.
Case 1: When MS decides to handoff with recommended BSs of MOB_BSHO-REQ or MOB_BSHO-RSP,
as per section 6.3.2.3.55 of IEEE 802.16e-2005 MS may choose to send MOB_HO-IND as a n acknowledgment
with Target BS set to 0x00000000 which indicates the serving BS of MS deciding to handoff.
 
In which case BS may release its resources allocated for that particular MS without waiting for resource retain timer to expire.

Case 2: When MS decides to handoff but does not send MOB_HO-IND, it is like uncontrolled HO specified in NWG stage 2,
and BS shall retain its resources till the resource retain timer expiry.

Case 3. When MS does not want to handoff, it may choose to send MOB_HO-IND with reject/cancel.

Hence i think the network assisted flag is necessary to be included in the message and signifies a specific behavior in HO.

Let me know if there is any difference in opinion.

Thanks,

Malini Raghavendra
Project Lead
Communication and Embedded Systems,
Larsen &Toubro Infotech,
Bangalore,INDIA



Chi-Chen Lee <jjlee@ITRI.ORG.TW>

06/27/2006 11:28 AM
Please respond to
Chi-Chen Lee <jjlee@ITRI.ORG.TW>

To
STDS-802-16@listserv.ieee.org
cc

Subject
[STDS-802-16] [HO] Usage of "network assisted HO supported flag"







Hi,

I have one question about the usage of Network Assisted HO supported flag in MOB_BSHO-REQ message and MOB_BSHO-RSP message. In my understanding, if Network Assisted HO supported flag is set to "1" in MOB_BSHO-REQ or MOB_BSHO-RSP message, MS may perform a handover to any BS among the recommended BSs without MOB_HO-IND. However, according to section 6.3.2.3.55 of IEEE 802.16e-2005, an MS "shall" transmit a MOB_HO-IND message for final indication that it is about to perform a HO. It seems that there is conflict between the usage of MOB_HO-IND and the usage of Network Assisted HO supported flag.

There are two possibilities of the above issue:

(1) An MS shall transmit a MOB_HO-IND message for final indication even though the Network Assisted HO supported flag is set to "1", i.e. MS behavior has no difference between Network Assisted HO supported flag is set to 0 and 1. In this case, why we still need Network Assisted HO supported flag? What does it mean to MS?

(2) An MS may perform a handover to any BS among the recommended BSs without MOB_HO-IND. Note that in this case, the MS MAY send MOB_HO-IND with target BS ID = "0x00000000" as an acknowledgement to the MOB_BSHO-REQ message but may not send MOB_HO-IND during actual HO. However, this case incurs another issue: if there is no MOB_HO-IND before MS starts HO, how does the Resource retain timer work in this case? Without Resource retain timer, how can the MS decide that it can cancel HO except in the drop case?

I appreciate any comments and discussion on this issue.

thanks,


==========================================
Chi-Chen Lee
Design Engineer
Wireless System Technology Div.,
SoC Technology Center(STC),
Industrial Technology Research Institute
Tel: +886-3-5914579
Fax: +886-3-5829733
E-mail:
jjlee@itri.org.tw
http://www.stc.itri.org.tw/

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--
Cheers,


==========================================
Chi-Chen Lee
Design Engineer
Wireless System Technology Div.,
SoC Technology Center(STC),
Industrial Technology Research Institute
Tel: +886-3-5914579
Fax: +886-3-5829733
E-mail: jjlee@itri.org.tw
http://www.stc.itri.org.tw/
==========================================