Transcript IEEE C802.16m-08/1273

HO between IEEE802.16m femto cell and macro cell
IEEE 802.16 Presentation Submission Template (Rev. 9)
Document Number:
IEEE C802.16m-08/1273
Date Submitted:
2008-10-31
Source:
Chie Ming Chou, Fang-Ching (Frank) Ren, Richard Li, Chun-Yen Wang
ITRI
E-mail: [email protected] [email protected]
Venue:
TGm call for contributions on IEEE 802.16m-08/040. Specific topic : “Support for Femtocells”
Base Contribution:
N/A
Purpose:
To be discussed and adopted by TGm.
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Mobility challenges in femto cell
• Advertisements
– The density of femtocell can be much higher than that of macro cells.
– Advertisement for femto cell list is not efficient.
• Handover
– A macro-cell may cover one or several femto cells, when connection is
good enough in a macro cell, a MS may not initiate a handover process
to access a femto cell.
– Since femto cells can have closed access for a limit set of users, most
camping/handover requests by the passenger will be rejected. Such
frequent futile camping/handover attempts will increase network
signaling load and impact end user mobility performance.
2
A two-way handover
between macro cell and femto cell
• When handover from macro cell into femto cell
– Challenges listed in previous slide
• When handover from femto cell into macro cell
– Due to the confined range of a femto cell, it needs a fast HO scheme to avoid
disconnection
Macro cell 2
Macro cell 1
Femto cell 1
Femto cell 2
3
Proposal for HO from a macro cell to a
femto cell
• There are 3 steps in proposed mechanism:
– Administration of femto cell’s monitoring
– Femto cell’s monitoring
– Initiate Handover from macro cell to femto cell
• Administration of femto cell’s monitoring
– A femto cell will record the MAC address of its limit set of MSs.
• If femto cell is open access, then an identifier of no-limitation will be
used
– The femto cell shall exchange the MAC address of its limit set of
MSs to neighboring macro cells.
• A macro-cell will maintain the mapping between MAC address and
corresponding femto cell ID.
4
Proposal for HO from a macro cell to a
femto cell (con)
• Femto cell’s monitoring
– Macro cell will notify corresponding femto cell if a allowable MS coming.
• Verify the MAC address during network entry process.
– Macro cell will forward associating uplink resources allocation
information of this MS to femto cell.
• Can be notified by unicast message or force a femto cell to listen the broadcast
message of the macro cell
– After receiving allocation information, the femto cell can monitor the MS
UL data transmission and measure the received signal quality.
• Received signal quality can include RSSI, SINR, and etc.
• Initiate Handover from macro cell to femto cell
– When monitoring received signal quality is above the threshold, Femto
cell will give a request message to the macro cell
• After receiving this message, the macro cell will originate the handover
procedure to handover this MS to requested femto cell
5
Proposal for HO from a macro cell to a
femto cell (con)
Macro cell
(serving)
MS
Femto cell
Power on &
initialization
User negotiation (MAC address)
Ranging process
RNG-REQ (with MAC address)
RNG-RSP
Verify User
Notify user coming &
corresponding allocation
UL_MAP-IE (broadcast)
Data
Listen
MOB_BSHO-REQ
(with action time. Resources, adjustment)
Compare with setting
threshold
HO_NFY (with action time,
resources, & adjustment)
Handover Process
6
Proposal for HO from a femto cell to a
macro cell
• When a MS moves from femto cell to macro cell, the target macro cell
always has overlapped coverage with the femto cell.
– Scanning process of a MS can be skipped or simplified.
• The femto cell would select the strongest macro cell as the target macro cell.
• Due to the small coverage of femto cell, the link conditions between a
femto cell and a macro cell may be the same as those between MS and
macro cell.
– The serving femto-cell can provide the link condition parameters to MS such
that the MS can speed up DL/UL synchronization during HO process
• When a MS which is served by a femto cell finds the link is not good
– A MS will directly send the handover request message instead of scanning
message
– A fast synchronization without contention ranging may be applied
7
Proposal for HO from a femto cell to a
macro cell (con)
Femto-cell 1
(serving)
MS1
Macro-cell 1
(target)
Macro-cell 2
preamble
preamble
Link is not good
MOB_MSHO-REQ
HO
Initialization
HO negotiation
BSHO_IND
RNG-REQ
RNG-RSP
Data Burst
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Proposed text
17 Support for Femtocell
[insert the following text]
17.x HO process between femto cell and macro cell
17.x.1 HO from a macro cell to a femto cell
A femto cell shall exchange the MAC address of its limit set of MSs to neighboring
macro cells. A macro cell will notify corresponding femto cell if an allowable MS
performs network (re-)entry with this macro cell. The macro cell will also forward
uplink resources allocation information of this MS to femto cell. After receiving
allocation information, the femto cell can monitor the MS UL data transmission and
measure the received signal quality. If monitoring received signal quality is above
the threshold, the femto cell will give a request message to the macro cell to trigger
a BS-initiate HO process.
17.x.2 HO from a femto cell to a macro cell
When a MS which is served by a femto cell finds the link is not good, a MS will
directly send the handover request message instead of scanning message. A fast
synchronization without contention ranging may be applied.
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