Service Continuity of Enhanced-MBS
Document Number:
IEEE C802.16m-08/1011r2
Date Submitted:
2008-9-15
Source:
Chun-Yen Wang, Chun-Yuan Chiu, Fang-Ching (Frank) Ren,
Richard Li, Wern-Ho Sheen
ITRI
Information and Communications Research Laboratories,
195 Chung Hsing Rd., Sec.4 Chu Tung, Hsin Chu, Taiwan 310, R.O.C.
Voice:
E-mail: {ChunYen, ccy, frank_ren, richard929, whsheen}
@itri.org.tw
*<http://standards.ieee.org/faqs/affiliationFAQ.html>
Re : IEEE 802.16m-08/033 - Call for Contributions on Project 802.16m System Description Document (SDD), on the topic of “MAC
aspects of enhanced MBS”
Venue:
Kobe, JP
Base Contribution:
N/A
Purpose:
For discussion and approval by TGM
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Outline
• Scenario description
• Service continuity of E-MBS:
– Inter-EMBS Zone transition of a connected-state MS
– Inter-EMBS Zone transition of an idle-state MS
• From multi-BS transmission mode to
single-BS transmission mode
• From single-BS transmission mode to
single-BS (multi-BS) transmission mode
• From multi-BS transmission mode to
multi-BS transmission mode
1
Scenario Description (1)
• Assumptions:
– An E-MBS service area is the coverage of a set of BSs where some EMBS service(s) is announced and available to be received
– A BS within the service area is responsible to forward the associated EMBS data from gateway by using single-BS transmission mode or
multi-BS transmission mode
– Each BS capable of providing E-MBS service belongs to a certain EMBS Zone, identified by a unique MBS_Zone ID
– The same CID and same Security Association (SA) is used for
transmitting the content of certain E-MBS service(s) in a E-MBS Zone
– Different CIDs or different SAs may be used in different E-MBS Zones
for the same E-MBS service
2
Scenario Description (2)
– A BS is allowed to turn off the transmission of an E-MBS service if
there is no subscriber interesting for this service
– A MS can continue to receive E-MBS data within the service area
regardless of the MS operation mode (i.e., connected state/idle state)
E-MBS service area
Zone 4
Zone 1
Zone 2
single-BS transmission mode
Zone 4
multi-BS transmission mode
Zone 6
Zone 5
Zone 3
Zone 7
3
E-MBS Service Continuity of a Connected-State MS
•
Target BS decision:
– Serving BS criteria for recommendation of
target BS may include factors such as
expected MS performance at potential target
BS, BS and network loading conditions, MS
QoS requirements, and E-MBS service
availability.
•
MS
SBS
TBS
Unicast HO REQ
HO preparation phase
HO pre-notification
E-MBS HO decision:
E-MBS HO decision
– An E-MBS service needs HO if the target BS
does not belong to the associated E-MBS Zone
•
E-MBS service
resumption
MBS HO optimization:
CID and scheduling
information forwarding
…
Unicast HO RSP
…
– A MS may be able to obtain the CID and the
scheduling information used in the target BS
during the HO preparation phase to improve
service continuity
– If the target BS had turned off the
transmission of the E-MBS service, the target
BS may be noticed to resume transmitting the
E-MBS service during the HO preparation
phase
GW
4
E-MBS Service Continuity of an Idle-State MS
• During idle state, a MS may have following methods to
achieve E-MBS service continuity
– Method 1:
perform location update procedure to update CIDs when the MS
detects a change in E-MBS Zone
– Method 2:
perform location update procedure when the MS detects a change in EMBS Zone, unless the MS already has the CID mappings through a
CID pre-allocation scheme [1]
– Method 3:
transit to connected state by network reentry procedure when the MS
awakes to a possible inter-MBS Zone transition
5
Method 1
perform location update procedure to update CIDs
when the MS detects a change in E-MBS Zone…
• If the MS reselects a preferred BS
during MS paging unavailable
interval, and then
• detects the change of E-MBS Zone
by monitoring the MBS zone
identifier list which is transmitted by
the new preferred BS in the downlink
broadcast message,
• it can update its CIDs and resume
content reception through locationupdate procedure
Original
preferred BS
MS
New
preferred BS
GW
Reselects a preferred BS during
MS paging unavailable interval
E-MBS HO decision
Location-update
procedure for
CID updating
E-MBS service
resumption
6
Method 2
perform location update procedure when the MS detects a change in
E-MBS Zone, unless the MS already has the CID mappings through
a CID pre-allocation scheme[1]…
• The CID pre-allocation scheme
informs MSs within a certain E-MBS
Zone regarding the mapping of CIDs
used in the current E-MBS Zone to
new CID within a neighboring EMBS Zone
• When a MS moves to a new zone, it
can immediately (and internally)
update its CIDs and resume content
reception without the need to perform
CID update through location-update
Original
preferred BS
MS
New
preferred BS
GW
Reselects a preferred BS during
MS paging unavailable interval
E-MBS HO decision
Location-update procedure
for E-MBS service resumption
7
Method 3
transit to connected state by network reentry procedure
when the MS awakes to a possible inter-MBS Zone transition…
• When the MS awakes to a possible
inter-MBS Zone transition by some
measurements,
• it transits to connected state by
network reentry procedure
MS
preferred BS
(SBS)
TBS
GW
some measurements
trigger network
reentry procedure
E-MBS service continuity procedure
of a connected-state MS
8
CID Updating Method of an Idle-State MS:
from Multi-BS Transmission Mode to
single-BS Transmission Mode
• For a E-MBS service using multi-BS transmission mode, gateway is
responsible to schedule resource and decides a MCID for the service
• Since this resource can not be reused in a guard range due to co-channel
interference, the scheduling information should be forwarded to all BSs
within the guard range
gateway
• If a BS within the guard range provides
same E-MBS service by using single-BS
transmission mode, it should be able to
aware of the MCID used in the
neighboring E-MBS Zone
• Therefore, the BS can provide the
multi-BS Tx mode
mapping of MCID used in the
neighboring E-MBS Zone to the
Guard range
single-BS TX mode
CID used in current E-MBS Zone
• Besides, we propose that the timing of transmitting E-MBS data in singleBS transmission mode is always later than the timing in multi-BS
transmission mode to relieve packet loss
9
CID Updating Method of an Idle-State MS:
from single-BS Transmission Mode to
single-BS (Multi-BS) Transmission Mode
• For a E-MBS service using single-BS transmission mode, BS is responsible
to schedule resource and decides a CID for the service
• Therefore, its neighboring BSs are not aware of the CID used by itself for
the service unless the CID pre-allocation scheme proposed in [1] is used
• In order to avoid the overhead of the CID pre-allocation, we propose to
adopt the method 3 to achieve E-MBS service continuity for this case
(an Idle-State MS may transit to connected state by network reentry
procedure when the MS awakes to a possible inter-MBS Zone transition)
• In idle mode, a MS may reselect a preferred BS during MS paging
unavailable interval according to some measurements.
• A stricter threshold of these measurements may be used for awaking to a
possible inter-MBS Zone transition
10
CID Updating Method of an Idle-State MS:
from Multi-BS Transmission Mode to
Multi-BS Transmission Mode
• It seems like there is no reason to use different resource and CIDs in two
neighboring MBS Zones for the same MBS service, instead of combining
them to a bigger MBS Zone.
– a MS transiting from multi-BS transmission mode to multi-BS
transmission mode is an impossible case.
• If there is some rare reasons resulting in this situation, but the two
neighboring MBS Zones always adopt same CID allocated by the gateway,
– there is no need to update CID.
• If there is some rare reasons resulting in different resource and CIDs used
in two neighboring MBS Zones for the same MBS service,
– we propose to adopt the method 1 for this case.
(an Idle-State MS update its CIDs and resume content reception
through location-update procedure after detecting the change of MBS
Zone)
11
MS Operation
YES
Idle mode?
Monitor RSSI
during MS paging
unavailable interval
NO
NO
Unicast HO?
NO
Single BS?
Using threshold 2
(looser)
YES
YES
NO
Using threshold 1
(stricter)
MBS HO decision
& HO procedure
over T2?
YES
NO
over T1?
YES
Change preferred
BS & update CIDs
internally
Network reentry
procedure
12
Proposed Text for SDD
• 15.1: General Concepts
Add the assumptions described in page 2-3
• 15.x: Service Continuity of Enhanced-MBS
15.x.1: E-MBS Service Continuity of a Connected-State
MS
Add the discussion described in page 4
15.x.2: E-MBS Service Continuity of an Idle-State MS
Add the discussion described in page 5-12
13
Reference
1.
IEEE C802.16maint-08/171r9, “Improvement in MBS in
802.16REV2 ”
14