Support for Femtocells in 16m
Document Number:
IEEE C802.16m-08/1430
Date Submitted:
2008-10-31
Source:
Kaibin Zhang, Gang Shen, Jimin Liu
Voice:
+86-21-50554550-8261
Alcatel Shanghai Bell Co., Ltd.
E-mail:
kaibin.zhang@alcatel-sbell.com.cn
Venue:
IEEE 802.16m-08/040-Call for Comments and Contributions on Project 802.16m System Description Document (SDD), on the topic of
TGm SDD Femtocells
Base Contribution:
N/A
Purpose:
To be discussed and adopted into the 802.16m SDD by TGm.
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Introduction
• Femtocell
– Femtocell, tiny, low-power cellular base stations, operated in
licensed frequencies.
– A femtocell installed in homes or SOHO, improves the indoor
coverage by providing the coverage up to 30m.
– Typically using existing wired broadband connection as backhaul
(cable, DSL, Ethernet)
– It is required to support Femtocell in 16m SRD
• Technical issues to be discussed in this document
– Synchronization
– Location service
– MBS
Synchronization
• Synchronization requirement in SRD
– 16m shall support frequency and timing synchronization among all BSs
• Candidate solutions to Femto BS synchronization
– Option 1: IEEE 1588
• Using Master-boundary-slave hierarchy to distribute the clock, each inbetween node is required to have the capability to recover and generate the
clock in DL
• Requires symmetric UL/DL transmission delay and less small jitter. Difficult
for home broadband connection (cable/DSL) to meet the requirement.
– Option 2: GPS
• High accuracy but poor indoor coverage
• Increase the cost of Femto
– Option 3: Synchronization with macro-cell via air interface
• First get synchronization when initiating itself
• Periodically updating
• It is recommended to accept all 3 options as the methods to
synchronize Femtocell with macro-cell/network
Location-based service
• 16m requirements on location-based service
– Handset-based position accuracy up to 50 meter
– Network-based position accuracy up to 100 meter
• Proposed solution for location-based service in Femtocells
– Employ the coordinate of the Femto BS as the reference of the
attached MS location
• Coverage of a Femtocell is typically less than 30m, it is small enough
to meet the MS location accuracy requirement
– The coordinate of a Femto BS could be obtained by measuring the
arriving time difference of signals from neighboring femto/macro
• It could be performed once a Femto BS powers on and enters the
network
MBS
• Solutions to MBS in Femtocell overlapped with macro-cell
– Option 1: Working as a normal BS, Femtocell and overlapped macro/micro
cell broadcast/multicast MBS in common MBS zone
• Comply with MBS solution for macro cells
• Traffic load on home broadband connection
– Option 2: Femtocell broadcast/multicast MBS by using radio resource
different from overlapped macro/micro-cell
• Dedicated resources allocated for Femto MBS
• High spectrum efficiency due to possible high modulation order of MBS in
Femtocell
– Option 3: Get MBS from macro-cell directly, Femto BS not involved
• Correct de-coding ensured by low modulation order of MBS
• Simple implementation & Less overhead over Femtocell backhauling
– Option 4: MBS may be sent out via unicast in Femtocell
• Any above option can be the candidate solution for MBS in Femtocell
Proposed Text For SDD
17 Support for Femtocell
17.x Synchronization
A Femto BS shall synchronize with macro/micro BS to a
common timing and frequency signal. The Femto BS may get
synchronization with macro/micro BS via air interface, or GPS,
or other clock & timing recovery protocol over backhaul
network like IEEE1588.
17.x Location based service
The coordinate of Femtocell may be regarded as the location
reference of its attached MS.
17.x MBS
Multicast & Broadcast Service may be only sent from macro BS
to MS. Femto BS may not involve into the MBS transmitting. In
this case, MS may get MBS from macro BS directly, no matter if
it is attached to Femtocell or not.