|
Actually, no timer for BS wait on HO-IND was
intended. HO-IND is not actually a response to a specific message
(MOB_BSHO-REQ or RSP). You get a race condition if you make HO-IND a response to
a message. You have to look at the relationship between MOB_MSHO-REQ,
MOB_BSHO-REQ, and MOB_BSHO-RSP carefully and you will see it. Note that the
language in the standard says that MS will send HO-IND to signal handover, not
as a response to a specific message. So BS cannot start a timer because HO-IND
is always 'unexpected'.
Thanks,
Phillip Barber
Chief
Scientist
Broadband Wireless Solutions
Huawei Technologies Co.,
LTD.
----- Original Message -----
Sent: Tuesday, June 27, 2006 10:25
PM
Subject: Re: [STDS-802-16] [HO] Usage of
"network assisted HO supported flag"
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
"Chi-Chen Lee"
<jjlee@itri.org.tw>
Sent by: chichen.lee@gmail.com
06/27/2006 08:26 PM
|
|
To
| "Malini Raghavendra"
<Malini.Raghavendra@lntinfotech.com>,
STDS-802-16@listserv.ieee.org
|
|
cc
|
|
|
Subject
| Re: [STDS-802-16] [HO] Usage of
"network assisted HO supported flag" |
|
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/
==========================================
______________________________________________________________________
______________________________________________________________________
--
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/
==========================================
______________________________________________________________________
______________________________________________________________________
|