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 Voice:ITRI E-mail: {ChunYen, ccy, frank_ren, richard929, whsheen}Information and Communications Research Laboratories, @itri.org.tw195 Chung Hsing Rd., Sec.4 Chu Tung, Hsin Chu, Taiwan 310, R.O.C.

*<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, JPBase Contribution:

N/APurpose:

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 E-

MBS service(s) is announced and available to be received

– A BS within the service area is responsible to forward the associated E-MBS 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 E-MBS 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

single-BS transmission mode

multi-BS transmission mode

Zone 1Zone 2

Zone 3

Zone 4

Zone 4

Zone 5

Zone 6

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.

• E-MBS HO decision:– An E-MBS service needs HO if the target BS

does not belong to the associated E-MBS Zone

• MBS HO optimization:– 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

4

MS SBS TBS

Unicast HO REQ

E-MBS HO decision

HO preparation phase

CID and scheduling information forwarding

…GW

E-MBS service resumption

HO pre-notification

Unicast HO RSP

…

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 E-MBS 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

• 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 location-update procedure

Original preferred BS MS

Reselects a preferred BS during MS paging unavailable interval

New preferred BS

E-MBS HO decision

Location-update procedure for CID updating

GW

E-MBS service resumption

perform location update procedure to update CIDs when the MS detects a change in E-MBS Zone…

6

Original preferred BS MS

Reselects a preferred BS during MS paging unavailable interval

New preferred BS

E-MBS HO decision

GW

Location-update procedure for E-MBS service resumption

• 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 E-MBS 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

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]…

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preferred BS(SBS)MS TBS GW

E-MBS service continuity procedure of a connected-state MS

• When the MS awakes to a possible inter-MBS Zone transition by some measurements,

• it transits to connected state by network reentry procedure

Method 3

transit to connected state by network reentry procedure when the MS awakes to a possible inter-MBS Zone transition…

some measurements trigger network

reentry procedure

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

• If a BS within the guard range providessame E-MBS service by using single-BStransmission mode, it should be able to aware of the MCID used in theneighboring E-MBS Zone

• Therefore, the BS can provide themapping of MCID used in the neighboring E-MBS Zone to the CID used in current E-MBS Zone

• Besides, we propose that the timing of transmitting E-MBS data in single-BS transmission mode is always later than the timing in multi-BS transmission mode to relieve packet loss

multi-BS Tx mode

single-BS TX mode Guard range

gateway

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

Idle mode?

Unicast HO?

MBS HO decision& HO procedure

YES

NO

NOSingle BS?

YES

Using threshold 1(stricter)

Monitor RSSI during MS paging

unavailable interval

over T1?

Network reentry procedure

YES

YES

NO

Using threshold 2(looser)

over T2?

Change preferred BS & update CIDs

internally

YES

NO

NO

12

Proposed Text for SDD

• 15.1: General Concepts Add the assumptions described in page 2-3

• 15.x: Service Continuity of Enhanced-MBS15.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 ”

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