IEEE C802.16maint-08/344r2
Project
IEEE 802.16 Broadband Wireless Access Working Group <http://ieee802.org/16>
Title
Uncontrolled Handover
Date
Submitted
2008-11-12
Source(s)
Yerang Hur, Hyung-Joon Jeon
E-mail: yehur@posdata-usa.com
POSDATA
Steven Xu, Joseph Schumacher
Shahab Sayeedi
Motorola
Brian Shim, Yeongmoon Son
Samsung Electronics
Vladimir Yanover, Daniel Cohn
Alvarion
Philip Barber
Huawei
Re:
IEEE 802.16 Sponsor Ballot on P802.16Rev2/D7
Abstract
This proposes unexpected handover of a MS to its preferred target BS be included in the
standard so the target BS can handle it properly.
Purpose
Review and adopt proposed remedy.
Notice
Release
Patent
Policy
This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It
represents only the views of the participants listed in the “Source(s)” field above. It is offered as a basis for
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Further information is located at <http://standards.ieee.org/board/pat/pat-material.html> and
1
IEEE C802.16maint-08/344r2
<http://standards.ieee.org/board/pat>.
Uncontrolled Handover
POSDATA, Motorola, Samsung, Alvarion, Huawei
1. Introduction
Due to suboptimal radio planning conditions, link loss, or MS implementation, when a MS detects a drop, the
MS might begin ranging at a preferred BS which was not contacted by the serving BS for handover preparation.
In such a case, if the MS provides Serving BSID in RNG-REQ, the target BS might be able to handle the
unexpected handover within a reduced amount of time, comparing with the required time for full initial network
entry.
This concept is missing in IEEE P802.16Rev2 although it has been considered for some time in network. This
contribution proposes the notion of Uncontrolled HO should be included in IEEE P802.16Rev2 with the
appropriate usage of TLVs in the air link for the BS to handle such an unexpected case.
2. Proposed Text
[Modify 6.3.21.2 as indicated:]
6.3.21.2 HO process
The subclause defines the HO process in which an MS migrates from the air-interface provided by one BS to the air-interface provided
by another BS. The HO process consists of the following stages:
—
Cell reselection—MS may use neighbor BS information acquired from a decoded MOB_NBR-ADV message or may make a
request to schedule scanning intervals or sleep intervals to scan, and possibly range, neighbor BSs for the purpose of evaluating MS
interest in HO to a potential target BS. The cell reselection process need not occur in conjunction with any specific, contemplated HO
decision
—
HO Decision and Initiation—An HO begins with a decision for an MS to HO from a serving BS to a target BS. The decision
may originate either at the MS or the serving BS. The HO Decision consummates with a notification of MS intent to HO through
MOB_MSHO-REQ or MOB_BSHO-REQ message unless the MS chooses to initiate HO without notifying the serving BS or loss of
radio link to the serving BS precludes serving BS notification by the MS.
[Modify 6.3.21.2.6 as indicated:]
6.3.21.2.6 Drops during HO
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IEEE C802.16maint-08/344r2
A drop is defined as the situation where an MS has stopped communication with its serving BS (either in the DL or in the UL) before
the normal HO sequence outlined in Cell ResSelection (see 6.3.21.2.1), HO decision and initiation (see 6.3.21.2.2), HO cancellation
(see 6.3.21.2.3), Fast ranging (see 6.3.21.2.4), orand Termination with the serving BS (see 6.3.21.2.5) has been started, or the HO
process (see 6.3.21.2) was started but has not been completed. Drop is considered a particular case of HO.
An MS can detect a drop by its failure to demodulate the DL, or by exceeding the RNG-REQ retries limit allowed for the periodic
ranging mechanism. A BS can detect a drop when the Number of retries limit allowed on inviting ranging requests for the periodic
ranging mechanism is exceeded.
When the MS has detected a drop during network reentry with a target BS, it may attempt network reentry with its preferred target BS
as through Cell Reselection (see 6.3.21.2.1), which may include resuming communication with the serving BS by sending MOB_HOIND message with HO_IND type = 0b01 (HO cancel) or performing network reentry at the serving BS.
[Modify 6.3.21.2.7 as indicated:]
6.3.21.2.7 Network entry/reentry Unless otherwise indicated in this subclause, MS mobile network entry/reentry is processed
according to 6.3.9. Note that in this section, “target BS” may reference the BS that was the serving BS at the time the handover was
initiated. An MS and a target BS shall conduct ranging per 6.3.9.5 except when dedicated ranging opportunity is available, in which
case, the procedure described in 6.3.21.2.4 shall be employed. For identification of the MS, RNG-REQ message may include MS
MAC Address or HO_ID (if assigned in MOB_BSHO-REQ or MOB_BSHO-RSP). The target BS shall assign to the MS Basic CID
and Primary CID in the RNG-RSP management message. The MS shall signal the target BS of a current HO attempt by including a
serving BSID TLV and Ranging Purpose Indication TLV with Bit #0 set to 1 in the RNG-REQ management message. The MS shall
not include a Ranging Purpose Indication TLV in the RNG-REQ management message unless actually in the process of conducting an
HO (including drop during HO), location update, or network reentry from idle mode attempt.
3. References
[1] IEEE P802.16Rev2/D7. Draft Standard for Local and Metropolitan Area Networks Part 16: Air Interface for
Broadband Wireless Access Systems, October 2008.
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