IEEE 802.21 MEDIA INDEPENDENT HANDOVER
DCN: 21-06-0631-00-0000
Title: The amendment for the Link Going Down primitive
Date Submitted: April, 20, 2006
Presented at IEEE 802.21 session #15 in San Diego
Authors or Source(s):
Zhou Yi, Liu Yuan, Guo Junxiang
Abstract: This contribution suggests an amendment to the Link
Going Down event. By using the amended event, higher layers
can take proper actions for handover preparation.
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Background
• In 802.21, a Link_Going_Down/MIH_Link_Going_Down event is often used
to indicate that current link is going to disconnect and handover should be
prepared. It is necessary for the upper layers to know the reasons for why the link
will go down. For example, when the battery level of the terminal is low and the
current link will disconnect soon, a MIH_Link_Going_Down event may be
generated in order to prepare for a handover to the module that has lower power
consumption (As an example, a GSM module usually has lower battery
consumption than a WiFi module) to lengthen the usable time of terminal.
However, the current definition of the Link_Going_Down
/MIH_Link_Going_Down has no parameter for why it has generated, so the
upper layers can not take proper actions according to the received indications.
• We propose to give an amendment to the primitive Link_Going_Down
/MIH_Link_Going_Down by adding a reason code in order to facilitate making
proper handover decisions for upper layers.
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Amendment for Link_Going_Down.indication
Name Type Valid Range Value
EventSource LINK_EVEN The origination point from where the event
T_SOURCE is generated.
MacMobileTerminal MAC Address N/A MAC Address of Mobile Terminal
MacNewPoA MAC Address N/A MAC Address of New PoA (AP)
MacOldAccessRouter MAC Address N/A MAC Address of old Access Router
MacNewAccessRouter MAC Address N/A MAC Address of new Access Router
TimeInterval Time in msecs 0-65535 Time Interval in which the link is expected
to go down. The link connectivity is
expected to be available at least for time
specified by TimeInterval . Unit: 1ms
ConfidenceLevel Percentage (0- 0-100 The confidence level for link to go down
100) within the specified time interval
Expressed in percentage (0~100)
ReasonCode Enumerated 0-255 Reason for why the link will go down, such
as explicit disconnection, no resources or
undefined reason, etc.
UniqueEventIdentifer INTEGER 0 – 65535 To be used in case of event rollback
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Amendment for Link_Going_Down.indication
The reason code for Link_Going_Down may be one or combination of the
following reasons.
Reason Code Id Reason Code Meaning
0 RC_UNSPECIFIC The link will go down because
of undefined reasons.
1 RC_EXPLICIT_DISCONNECT The link will go down because
that explicit disconnect
procedures will be initiated
either by client or network.
2 RC_NORESOURCE The link will go down because
there will be no resources to
maintain the current connection.
3 - 127 Reserved Reserved
128 - 255 RC_VENDOR_SPECIFIC Vendor Specific reason code.
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Amendment for MIH_Link_Going_Down.indication
Name Type Valid Range Value
MacMobileTerminal MAC Address N/A MAC Address of Mobile Terminal
MacNewPoA MAC Address N/A MAC Address of New PoA (AP)
MacOldAccessRouter MAC Address N/A MAC Address of old Access Router
MacNewAccessRouter MAC Address N/A MAC Address of new Access Router
TimeInterval Time in msecs 0-65535 Time Interval in which the link is
expected to go down. The link
connectivity is expected to be available
at least for time specified by
TimeInterval . Unit: 1ms
ConfidenceLevel Percentage (0-100) 0-100 The confidence level for link to go down
within the
specified time interval
Expressed in percentage (0~100)
ReasonCode Enumerated 0-255 Reason for why the link will go down,
such as explicit disconnection, no
resources, low power or undefined
reason, etc.
UniqueEventIdentifer INTEGER 0 – 65535 To be used in case of event rollback
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Amendment for MIH_Link_Going_Down.indication
The reason code for MIH_Link_Going_Down may be one or combination of
the following reasons.
Reason Code Id Reason Code Meaning
0 RC_UNSPECIFIC The link will go down because of
undefined reasons.
1 RC_EXPLICIT_DISCONNECT The link will go down because
that explicit disconnect
procedures will be initiated either
by client or network.
2 RC_NORESOURCE The link will go down because
there will be no resources to
maintain the current connection.
3 RC_LOW_POWER The link will go down because
the power is too low to maintain
the current connection.
4 - 127 Reserved Reserved
128 - 255 RC_VENDOR_SPECIFIC Vendor Specific reason code.
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Amendment for the current draft
Effect on receipt
Higher layers may take different actions on this notification. Upper layers may
prepare to initiate handovers based on the reason code and confidence level
reported as part of the event.
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More Explanation to ReasonCode
• RC_UNSPECIFIC
The link will go down because of undefined reasons.
Use Case
The reason that cause current link to disconnect may be unknown, so upper layers
are notified by the Link_Going_Down event with RC_UNSPECIFIC.
• RC_EXPLICIT_DISCONNECT
The link will go down because that explicit disconnect procedures will be initiated
either by client or network.
Use Case
As the description in the current draft, when a BS has decided to shutdown for
administrative reasons, it may send Link_Going_Down event with
RC_EXPLICIT_DISCONNECT to the MIHF in the terminal before
disconnecting the current link.
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More Explanation to ReasonCode
• RC_NORESOURCE
The link will go down because there will be no resources to maintain the current
connection.
Use Case
A BS may have connected too many ursers so that link QoS or quality parameters
(Packet Transfer Delay, Packet Loss Ratio and etc.) are degrading and can not meet
the requirements for maintaining the current connections because of insufficient
resources. The resources may include allocated bandwidth, processing capability of
BS and etc. Therefore the BS may send Link_Going_Down indications with
RC_NORESOURCE to terminals.
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More Explanation to ReasonCode
• RC_LOW_POWER (only for MIH_Link_Going_Down)
The link will go down because the power is too low to maintain the current
connection.
Use Case
Mobile terminals usually have limited battery supply, and when the battery level
is low and the current link can not be maintained, a terminal may choose a link
that has lower power consumption for handover according to the
MIH_Link_Going_Down event with RC_LOW_POWER. This will lengthen
the useable time of terminal.
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More Explanation to ReasonCode
• Reserved:
Reservation for extension in 802.21 in the furture.
• RC_VENDOR_SPECIFIC:
Vendor Specific reason codes.
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