Hello Mr Lee,
Your perception of Network Assisted
HO is now same as mine.
For the issue of Serving BS releasing
the resources when Serving BS does not get MOB_HO-IND,
it can be done in following 3 ways.
The referenced sections are in 802.16e
D12 Specification.
case 1: Referring to section 6.3.22.2.5
Termination with the serving BS
Regardless of Resource retain timer,
the serving BS shall remove MAC context and MAC PDUs associated with the
MS
upon reception of a backbone message
from the target BS indicating MS Network Attachment at target BS.
Case 2 when BS detects MS drop, refer
section 6.3.22.2.6 Drops During HO
A drop is defined as the situation where
an MS has stopped communication with its serving BS (either in the
downlink, or in the uplink) before the
normal HO sequence outlined in Cell Selection and Termination with
the serving BS has been completed.
When the serving BS has detected
a drop, it shall react as if a MOB_HO-IND message has been received
with HO_IND_type indicating serving
BS release.
Case 3 when BS does not get indication
from target BS of successful HO, Refer 11.7.12.1 System Resource_Retain_Time
The Resource_Retain_Time is the duration
for MSS's connection information that will be retained in Serving
BS. BS shall start Resource_Retain_Time
timer at MSS notification of pending HO attempt through
MOB_HO-IND or by detecting an MSS
drop. The unit of this value is 100msec.
So even when there is a drop the resource
retain timer wll be used by BS to retain resource for a possible MS
coming back to Serving BS for resumption
of connection.
Another point to note, MSS has T29 and
T42 timers which aid MSS is handling MOB_HO-IND retransmissions,
A similar timer support is not given
at BS[Not in 16e D12 atleast,], so that BS can wait for a specific time
to receive MOB_HO-IND
after sending MOB_BSHO-REQ/MOB_BSHO-RSP.
This should have been defined by standards
committee as it is a common support provided for any message based protocol
handling.
Thanks,
Project Lead
Communication and Embedded Systems,
Larsen &Toubro Infotech,
Bangalore,INDIA
Hi Malini,
I like to correct my perception about the usage of Network Assisted HO
supported flag. I think the only difference between Network Assisted HO
supported flag is set to "1" or "0" is that if the
flag is set to "1", MS can send a MOB_HO-IND without specifying
a target BS ID and just using 0x000000 as target BS ID. In contrast, if
the flag is set to "0", MS must specify the target BS ID in MOB_HO-IND.
Thus, the last issue is that, in the case of "uncontrolled HO"
you mentioned, if serving BS not receives MOB_HO-IND, therefore, resource
retain timer will not be started. How can MS decide that it can send MOB_HO-IND
with cancel in some abnormal cases such as drop or failed to handover to
target BS? Or in this case, the MS should not assume the serving BS will
retain the resource allocated to the MS.
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
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/
==========================================
______________________________________________________________________
______________________________________________________________________