IEEE C802.16n-11/0186
Project
IEEE 802.16 Broadband Wireless Access Working Group <http://ieee802.org/16>
Title
Forwarding Between Infrastructure Stations
Date
Submitted
2011-09-12
Source(s)
Anseok Lee, Eunkyung Kim, Sungcheol
Chang, Sungkyung Kim, Won-Ik Kim,
Miyoung Yun, Hyun Lee, Chulsik Yoon,
Kwangjae Lim
E-mail:
alee@etri.re.kr
ekkim@etri.re.kr
scchang@etri.re.kr
ETRI
Re:
Call for Comments on the 802.16n Amendment Working Document < 80216n-10_0049r1.pdf >
Abstract
This provides AWD text proposals for Forwarding Between Infrastructure Stations
Purpose
To be discussed and adopted by 802.16 TGn
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
discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw material
contained herein.
The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution,
and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name
any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole
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contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.16.
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<http://standards.ieee.org/guides/bylaws/sect6-7.html#6> and
<http://standards.ieee.org/guides/opman/sect6.html#6.3>.
Further information is located at <http://standards.ieee.org/board/pat/pat-material.html> and
<http://standards.ieee.org/board/pat>.
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Forwarding Between Infrastructure Stations
Anseok Lee, Eunkyung Kim, Sungcheol Chang, Sungkyung Kim, Won-Ik Kim, Miyoung Yun, Hyun
Lee, Chulsik Yoon, Kwangjae Lim
ETRI
1. Introductions
This contribution provides AWD text proposals of Forwarding Between Infrastructure Stations. The IEEE
802.16n System Requirement Document (SRD) [1] requires Recovery from SPOF (Single Point Of Failure) and
also mandates Path Management for alternative path maintenance to support fast recovery from SPOF. This
contribution proposes the approach of Forwarding Between Infrastructure Stations for backbone connection
recovery for robustness against to SPOF.
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2. Scenarios
A disrupted network configuration includes a HR-BS has lost the connection to the backbone network
(Degraded HR-BS). In HR-Network, the Degraded HR-BS may operate as a relay station to communicate with
another Infrastructure Stations if it has direct relay link to another Infrastructure Station . Fig. 1 and Fig. 2
respectively show the degraded network configuration and the recovery from backbone loss of Degraded HR-BS
by operating as a relay station.
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HR-BS
Degraded
HR-BS
HR-MS
HR-MS
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HR-MS
Fig. 1 Degraded network configuration
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HR-MS
IEEE C802.16n-11/0186
HR-RS
(Degraded
HR-BS)
HR-BS
Primary Path
HR-MS
HR-MS
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HR-MS
HR-MS
Fig. 2 Recovery from backbone loss of Degraded HR-BS by operating as relay station
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However, when the Degraded HR-BS does not have a direct link to any of adjacent HR-BSs, Degraded HR-BS
fail to recover connection to core network and also fail to support its subordinate stations. To provide higher
reliability in HR-Network, Degraded HR-RS shall discover adjacent HR-BSs (but does not have direct link to)
through subordinate HR-MSs and make a connection (forwarding connection) to forward data to a discovered
HR-BS (Target HR-BS) through a HR-MS (Designated HR-MS). Fig. 3 shows that backbone connection
recovery using Forwarding Between Infrastructure Stations through Designated HR-MS.
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Degraded
HR-BS
HR-BS
Backbone
recovery
HR-MS
HR-MS
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HR-MS
Forwarding
Between
Infrastructure
Stations
HR-MS
Fig. 3 Backbone connection recovery by Forwarding Between Infrastructure Stations
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3. Forwarding Between Infrastructure Stations
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3.1 Discovery of Target HR-BS
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Degraded HR-BS shall request the measurement of neighboring HR-BSs to its sub-ordinate HR-MS which have
Forwarding Between Infrastructure Stations capability. The measurement requests may be delivered via
MEASURE-REQ messages from HR-BS.
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HR-MSs which have received MEASURE-REQ message shall perform the channel measurement of
neighboring HR-BS and report the result via MEASURE-RSP message. The channel measurement may also be
initiated by MM-ADV message which contains the backbone failure notification from super-ordinate HR-BS. In
this case, HR-MSs having Forwarding Between Infrastructure Stations perform measurement and report the
result via unsolicited MEASURE-RSP message to super-ordinate HR-BS.
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HR-BS
Degraded
HR-BS
MEASURE-REQ
MEASURE-REQ
MEASURE-RSP
MEASURE-RSP
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HR-MS
HR-MS
Fig. 4 Discovery of adjacent HR-BSs at Degraded HR-BS
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Degraded HR-BS shall select one of more Designated HR-MSs and correspondent Target HR-BSs for data
forwarding and backbone connection recovery based on the measurement results of sub-ordinate HR-MSs.
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3.2 HO for Alternative Connection of Designated HR-MS
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Degraded HR-BS initiates a HO procedure by transmitting HO-CMD message to each Designated HR-MS to
establish an alternative connection to a Target HR-BS.
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HR-BS
(Target HR-BS)
Degraded
HR-BS
HO_CMD
(HO for Alt. Cnt.)
HO
HR-MS
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for
.C
Alt
nt.
HR-MS
(Designated
HR-MS)
Fig. 5 HO for Alternative Connection of Designated HR-MS
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Upon receives HO-CMD message from Degraded HR-BS, Designated HR-MS shall initiate the HO procedure
to establish alternative connection to Target HR-BS. In the HO procedure, Target HR-BS cannot communicate
with the Degraded HR-BS because of the backbone connection lost and no recovery relay link at Degraded HRBS.
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After completion of network reentry to Target HR-BS, Designated HR-MS shall maintain the context of
Degraded HR-BS as a secondary connection and Degrade HR-BS shall also maintain the context of Designated
HR-MS for data forwarding to Target HR-BS.
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3.3 Switched access between HR-BSs
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Designated HR-MS shall communicate with two super-ordinate HR-BSs (Degraded HR-BS and Target HR-BS)
after completion of reentry to Target HR-BS. Designated HR-MS shall communicate with each HR-BS for a
period (Forwarding Access Period) and switch the active super-ordinate station to another HR-BS.
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At the start of Forwarding Access Period, Designated HR-MS shall transmit the Access Request via Switched
Access Control signaling header on the allocated UL resource to an the active super-ordinate station. The Access
Request shall contain the requested access time and BW request if it has uplink data to transmit.
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Secondary
connection
Degraded
HR-BS
Forwarding HR-MS
Primary
connection
Target
HR-BS
Access Request
Access Response
Communicate with
Degraded HR-BS
data delivery
Access Request (shrink)
Access Request
Access Response
Forwarding
Access Time
Access Request
Access Response
Forwarding
Access Time
data delivery
Access Request (expand)
Access Response
Access Request
Access Response
data delivery
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Fig. 6 Switched access between two HR-BSs
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Designated HR-MS shall change active HR-BS to another HR-BS when the Forwarding Access Time is expired.
To adjust (expand or shrink) remaining Forward Access Period before expiration of Forwarding Access Time,
Designated HR-MS shall send the Access Request to active super-ordinate HR-BS.
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3.4 Forwarding connection establishment
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After completion of HO for alternative connection, the Degraded HR-BS shall initiate establishment of the
forwarding connections (incoming and outgoing backbone connection) to Designated HR-MS by DSA
procedures. Designated HR-MS shall initiate the DSA procedure with Target HR-BS after completion of DSA
procedure which initiated by Degraded HR-BS. The service parameters of connections which are forwarded at
Degraded HR-BS may be delivered to Target HR-BS in DSA procedures.
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Secondary
connection
Degraded
HR-BS
Designated HR-MS
Primary
connection
Target
HR-BS
HO for Alt. Cnt.
Access Request
Access Response
DSA procedure
Access Request
Access Response
DSA procedure
Forwarding connection establishment
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Fig. 7 Forwarding connection establishment
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3.5 Backbone recovery using Forwarding Between Infrastructure Stations
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Once the forwarding connections through the Designated HR-MS are established, the Degraded HR-BS may
replace the wired backbone connection as established forwarding connections. The upper layer of Degraded HRBS shall forward SDUs from its sub-ordinate stations (outgoing traffic) to the HR-Network and CS shall classify
and map received SDUs onto the forwarding connection to Designated HR-MS. The incoming traffic for
Degraded HR-BS shall be delivered to Target HR-BS and Target HR-BS shall send the SDUs to HR-Network
and CS shall map the SDUs onto the forwarding connection to Designated HR-MS. Designated HR-MS shall
forward received SDUs on the forwarding connection to alternative HR-BS.
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Secondary
connection
Degraded
HR-BS
Designated HR-MS
Primary
connection
Target
HR-BS
Forwarding connection established
Access Reqeust
Access Response
DL (outgoing)
UL (incoming)
Access Request
Access Response
DL (incoming)
UL (outgoing)
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Fig. 8 Data forwarding using forwarding connections through Designated HR-MS
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4. Proposed Text for the 802.16n Amendment Working Document (AWD)
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The text in BLACK color: the existing text in the 802.16n Amendment Draft Standard
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The text in RED color: the removal of existing 802.16n Amendment Draft Standard Text
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The text in BLUE color: the new text added to the 802.16n Amendment Draft Standard Text
Note:
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[-------------------------------------------------Start of Text Proposal---------------------------------------------------]
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[Remedy: Accept the following modification to Section 17.3.7.2.]
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Modify section 17.3.7.2 as indicated
17.3.7.2 Robustness against SPOF
The HR-MS may transmit/receive data to/from any one infrastructure station at any given time.
The HR-MS may forward previously received data to other infrastructure stations at other times.
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17.3.7.2.4 Forwarding Between Infrastructure Stations
In HR-Networks, the HR-MS may transmit/receive data to/from any one infrastructure station at any given time.
And the HR-MS may forward previously received data to other infrastructure stations at other times. To provide
higher reliability and have robustness against SPOF, HR-Network shall support Forwarding Between
Infrastructure Stations.
The HR-BS which lost the wired backbone connection to the core network and does not have direct relay link to
any of adjacent HR-BSs shall discover Designated HR-MS which capable to establish forwarding connection to
Target HR-BS. To initiate scanning procedure, Degraded HR-BS shall transmit MEASURE-REQ message to
HR-MSs which have Forwarding Between Infrastructure Stations capability. The MEASURE-REQ message
may contain ABS ID of recommending HR-BSs if Degraded HR-BS has information of neighboring HR-BSs.
The HR-MSs which have received the MEASURE-REQ message shall perform measurement of the
neighboring HR-BSs for Designated HR-MS decision at the Degraded HR-BS. After completion of HR-MS
scanning, HR-MSs shall report the results to Degraded HR-BS by using MEASURE-RSP message. The HR-MS
scanning procedure may also be initiated by the backhaul network down notification by the MM-ADV message
from the HR-BS and the results also be reported to HR-BS by using unsolicited MEASURE-RSP message.
For establishment of forwarding connections, Degraded HR-BS shall select a Designated HR-MS from received
results and may select a Target HR-BS which is the Designated HR-MS having connectivity to. Degraded HRBS shall command HO for Alternative Connection by AAI-HO-CMD message to Designated HR-MS. The
AAI-HO-CMD message may contain ABS ID of the Target HR-BS. Upon the reception of AAI-HO-CMD
message, Designated HR-MS shall perform the reentry procedure with the Target HR-BS. The reentry procedure
to Target HR-BS follows the procedure in HO for Alternative Connection. Optimized HO is may not be applied
due to the failure of backbone connectivity at the Degraded HR-BS. After completion of HO for Alternative
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Connection, Designated HR-MS shall maintain the context of Degraded HR-BS and Degraded HR-BS shall also
maintain the context of Designated HR-MS for data forwarding.
Designated HR-MS shall start Switched Access between two HR-BSs after completion of reentry to Target HRBS. Designated HR-MS shall communicate with each active HR-BS in Forwarding Access Period. To start
Forwarding Access Period, Designated HR-MS shall send Access Request to a HR-BS via Switched Access
Control signaling header. The Access Request may contain Requested Forwarding Access Time and Bandwidth
Request Indication. Upon reception of Access Request, an active HR-BS shall respond by Access Response by
using Switched Access Control signaling header. Access Response shall contain Grant Indication and Granted
Forwarding Access Time if the request is granted. An active HR-BS may also allocate for UL resources to
Designated HR-MS if the bandwidth request is indicated in Access Request.
Designated HR-MS shall change the active HR-BS to another HR-BS when the Forwarding Access Time is
expired and attempt to start Forwarding Access Period. When Designated HR-MS or active HR-BS attempts to
change remaining Forwarding Access Time (e.g. to extend or to shrink), it shall send Access Request to active
HR-BS or Designated HR-MS.
Degrade HR-BS shall initiate establishment of forwarding connections (incoming and outgoing traffic) with
Designated HR-MS by using the DSA procedure. After completion of DSA procedure which initiated by
Degraded HR-BS, Designated HR-MS shall initiate the DSA procedure with Target HR-BS for forwarding
connection establish. The service class parameters of Degraded HR-BS shall be delivered to Target HR-BS in
DSA procedure.
In Designated HR-MS, forwarding connections with two HR-BSs are locally coupled, i.e. a DL connection with
Degraded HR-BS is coupled with a UL connection with Target HR-BS for outgoing traffic and a DL connection
with Target HR-BS is coupled with a UL connection with Degraded HR-BS for incoming traffic. Designated
HR-MS shall forward traffic on a DL connection of a HR-BS to another HR-BS (using a UL connection)
without interaction of higher-layer of Designated HR-MS.
[-------------------------------------------------End of Text Proposal----------------------------------------------------]
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References
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[2] IEEE 802.16n-11/0015, “P802.16n Amendment Working Document (AWD)”
[1] IEEE 802.16n-11/0048r1, “802.16n System Requirements Document including SARM annex”
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