Femtocell Activities in 3GPP2 TSG-C
TBD
31 March 2009
New Orleans, LA
Status of Femto Work in TSG-C
• cdma2000 1x air interface signaling enhancement for Femto is part of
cdma2000 1x air interface revision E specification
• Start: Q1 2008
• Baseline: Q1 2009
• Expected Publication: Q2 2009
• cdma2000 HRPD air interface signaling enhancement for Femto is ongoing as part of cdma2000 HRPD air interface revision C specification
• May reuse some enhancements from 1x
• Expected Publication in Q4 2009
• Enhanced system selection (ESS) to support femtocell selection
• Based on enhancements to the Preferred User Zone List (PUZL) in the Over-theair Service Provisioning (OTASP) spec (C.S0016)
• Stage 2 of this work was completed in Jun 2008.
• C.S0016-D Publication with enhanced PUZL scheduled for May 2009.
March 2009
1
Challenges with the Current Practice (1/2)
• While femtocell deployment is possible without any enhancements to
the air interface, the following challenges are addressed more efficiently
with the enhancements in 1x Revision E
– No prioritization of femtocell over macrocell
• Need to be able to distinguish femto pilot vs macro pilot
– Open / signaling association models increase number of idle handoffs and
registrations
• Impact on MS standby time
• Frequent registrations can lead to page loss and increase the signaling load
– MS may not select HRPD femtocell following the 1x femtocell selection
•
Select HRPD femtocell following 1x femtocell selection
– Manual search is slow and inconvenient
• Support fast and user friendly manual search by providing human-readable ID
– Macro  Femto handover encounters PN ambiguity problem
• Support seamless connected handovers
March 2009
2
Challenges with the Current Practice (2/2)
• While femtocell deployment is possible without any enhancements to
OTASP, the following challenges are addressed more efficiently
–
–
–
–
–
Acquisition of femtocells without the use of beacons
Minimize access attempts on unauthorized femtocells
Minimize repetitive system selection attempts (or loops)
Minimize impact on the design and implementation of the PRL
Maximize standby time
March 2009
3
Introduction to 1x Signaling Enhancements
• In order to more efficiently support Femto AP operations for cdma2000
1x, the following signaling messages are introduced
– Access Point Pilot Information
• Allow the femto access point (FAP) and/or basestation to broadcast the
band/channels/PN offsets of femto access points deployed in the geographical
region
– Access Point Identification
• Allow a FAP to advertise to the MS a unique identifier and other information
about the FAP that assist system selection and handoff
– Handoff Supplementary Information
• During handoff to target FAP, allow the MS to report information that
disambiguates the target FAP
Note: Development of femtocell enhancements is on-going for HRPD revision C.
March 2009
4
Enhanced System Selection (ESS) – Summary
• ESS supports efficient discovery and scanning for femtocells
– Based on enhancements to network-provisioned MS database PUZL
• New PUZL features include
– ESS support for 1x, DO and dual 1x/DO femtocells
– Support for personal femtocells, hotspots, network of hotspots or
communities
– Efficient off-frequency scans of a femto based on RF or Geo-based triggers
• Only when MS is in the vicinity of a desired femtocell
• To minimize battery power consumption and hit to stand-by time
– Manual femtocell acquisition with human-readable femto ID
– Blacklisting and white-listing of femtocells
• Blacklisting helps prevent system selection loops
• Network Provisioned
March 2009
5
Active Call Hand-in Example
•
•
•
Under the same macro BS, it is likely
that the same PN will be assigned to
many Femto APs
Macro BS needs to be able to resolve
target MSC_ID and CELL_ID for the PN
that has ambiguity
One possible solution under
consideration is that the Femto AP is
configured with unique MSC_ID and
CELL_ID. If agreed, this information
would be advertised in the APID
message. The MS includes this info with
the PSMM. The remaining standard
handoff process will route the call to the
MFIF (based on MSC_ID) and correct
femto AP (based on CELL_ID) with no
modification to A1 and IS-41 interfaces
Femto AP1
PN = b
March 2009
4. IS-41
<CELL_ID>
MSC
MFIF
Macro BS
PN = a
3. A1-Handoff
Required
<MSC_ID,
CELL_ID>
2. PSMM
+ HSIN<MSC_ID,
CELL_ID>
5. MFIF contacts
Femto AP2 for
handoff
1. APIDM
(MSC_ID, CELL_ID)
Femto AP2
PN = b
6
Femto ESS – System Selection Sequence
Mobile is associated with a Macro system
Not in any User Zone
Identify one or more
User Zones associated
with the macro-SID
from the PUZL DB
Check to see if MS has
entered the User Zones
based on the finer
definitions of the scan
regions (RF coverage
based and GEO based
entries)
Mobile finds a
macro system
Mobile is not
associated with a
system
Mobile leaves the
User Zone
Mobile is associated with a Macro system
Identified to be in one or more User Zones
Execute efficient scans
to find the femto(s)
associated with the
User Zone(s).
Continually check to
see if the trigger
conditions for the femto
system scans remain
satisfied.
Mobile enters a specific
User Zone
Mobile loses femto
coverage and tries to
acquire available macro/
femto system
Mobile finds a
femto system
Mobile is associated
with a Femto system
Scan for Macro/Femto
Channel based relative
priority
Mobile is on the most
preferred system.
Mobile finds a femto
system
March 2009
7
Working with the Broadband Forum?
• How will 3GPP2 submit items to the Broadband Forum?
• Should 3GPP2 develop a consolidated document?
– Or should each TSG (i.e., TSG-A, TSG-C, TSG-S and TSG-X) develop
individual documents for the Broadband Forum?
• What is the process for developing the Femto Auto-Config Parameters?
March 2009
8
Details
1x Signaling
March 2009
9
1. Access Point Pilot Information Message
(APPIM)
•
APPIM is broadcasted by FAPs and/or macro network
– Broadcast from FAPs allows the macro network to remain unchanged
•
APPIM includes femtocell deployment information
– Band, frequencies, and PN offsets allocated for the femtocell deployment
– Scope of allocation in the macro network, e.g., SID/NID that information would be
valid
– MS can cache the information up to LIFETIME limit specified
– To optimize overhead when this message is advertised on macro paging channel, the
message can be sent with low duty cycle and MS can go to sleep mode before
receiving this message
•
Benefits
– Helps MS distinguish between macrocells and femtocells, e.g., MS may want to only
idle handoff to FAP in the home area
– MS would not need to be pre-provisioned with such scan information especially when
in roaming conditions
– Offers flexibility in allocation of frequencies and PN offsets for femtocell deployment
– Speeds up manual / exploratory scans to discover nearby femtocells
March 2009
10
2.1 Access Point Identification Message
(APIDM)
•
Contents
–
–
–
–
–
SID, NID, and unique access point identifier
Supported association model (i.e., open/restricted/signaling-only)
MSC_ID, CELL_ID (for assisting hand-in to FAP)
Associated HRPD band class and channel
Location Information LAT, LONG, ALT, and horizontal and vertical uncertainty
•
Broadcasted by FAP at high frequency schedule
•
Benefits
– Quick identification of FAP with synergy to Enhanced System Selection (ESS)
– Association model information helps MS avoid registration on unknown femtocells
with signaling/restricted association
– Reporting MSC ID and Cell ID information identifies target FAP in macro  femto
handoff
– HRPD information enables selection of FAP for HRPD following 1X selection
March 2009
11
2.2 Access Point Identification Text Message
(APIDTM)
• Contents
– Variable length text identification of the FAP (similar to WIFI SSID)
– International encoding supported
• Broadcasted by femtocell on only normal channel at low frequency
schedule
• Benefits
– Enable user friendly manual scans to discover and identify nearby
femtocells
March 2009
12
3. Handoff Supplementary Information
Notification / Solicit
• The notification message includes mapping between PN Offset and
<CELL_ID, MSC_ID> of APs that the MS considers to handoff to
– Purpose is to disambiguate target FAP during handoff
• Same PN may be used by several FAPs under the same macro network
• CELL_ID and MSC_ID are used in Handoff Required message from macro
basestation to MSC identically to handoff in macro network
– The MS retrieves the <CELL_ID, MSC_ID> information from Access Point
Identification message
– This message can be sent along with Pilot Measurement report
• The BS may request the information using the Handoff Supplementary
Information Solicit message
March 2009
13
Details
Enhanced System Selection
March 2009
14
ESS – Preferred User Zone List (PUZL)
• User Zone (UZ) refers to a region in which femto-cell scans are
performed based on
– Geo-spatial (e.g. GPS) or RF coverage (e.g. SID/NID/AP_ID)
• PUZL consists of two parts:
– A global set of general parameters (e.g. Manual Acq Allowed)
– A list of individual User Zones (UZs).
• Each UZ has several main functions:
– Defines geo-spatial or RF regions in which a MS can execute RF Scans for
a femtocell – to use minimal battery power
– Defines the RF Scan parameters to find the femto-cell.
– Defines a set of parameters to uniquely identify a desired or undesired
femtocell.
March 2009
15
ESS – New PUZL Features
•
•
ESS support for 1x, DO and dual 1x/DO femtocells
Efficient off-frequency scans of a femto based on RF or Geo-based triggers
• Only when MS is in the vicinity of a desired femtocell
• To minimize battery power consumption and hit to stand-by time
•
•
Manual femto-cell acquisition with human-readable femto ID
White-listing and blacklisting of femtocells
• Network Provisioned
• Blacklisting helps prevent system selection loops
•
•
•
•
Handset Display Control to indicate Femto selection / connection
Prioritization of UZs in case of overlapping UZs
PUZL vs. PRL priority indication
Generalization of user zone spatial definitions:
• From current 2-D surfaces and latitude/longitude centers to include 3-D volumes and altitude
center
•
Identification of a femtocell based on the
• New broadcast message AP_ID (1x Rev. E) and
• Existing Registration Zone and/or LAT/LONG in System Parameters Message (SPM)
– A Registration Zone value is unique within a system defining a paging region (collection of sectors)
March 2009
16
ESS – Femto Usage Models
• Personal hotspot model
– Femto cells deployed in private homes and small home offices
– Each femto cell allowing access only to a small number of specific users
• Community hotspot model
– Pico or femto cells deployed in enterprises, campuses, apartment buildings,
etc.
– A network of small number of pico or femto cells all concentrated in a fairly
small geographic area allowing access only to specific group users in that
area that change infrequently.
• Distributed “network of hotspots” model
– Geographically distributed networks of pico or femto cells deployed across
hotel chains, airports, Starbucks, etc.
– Networks of pico or femto cells
March 2009
17