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3 Oct 2012
Building the World’s Largest Residential Small-Cell network
Nick Johnson – CTO, ip.access
Revised Agenda
– “Building the World’s Largest Residential Small Cell Deployment”– In which Nick Johnson, founder and CTO of ip.access will describe the lessons to be
learnt from the world’s largest femtocell deployment.
– Among the topics to be discussed:
– Network performance – finding the gold-plated needle in a haystack that spans four timezones
– Handset incompatibilities - life at the bottom of the food chain.– Interference Management and making it work at extreme scale– Partnering – choosing a partner with size, experience and motivation– The ultimate cognitive receiver - listening to the customer
Our role in the value chain
PicochipBaseband SoC + PHY s/w
Aricent3G macro stack sw
Ip.access3G Small Cell RAN
AP (HNB)AC (HNB-GW)NOS (HMS)
Field supportATT lab support
DPH-xxxASR-5K (HNB-GW)
BAC
Network Ops
CiscoIp.access
AT&T
Ref hw design3G swManuf. support
OysterCatcher™ architecture
Existing core network
Iu-CS
Iu-PS
Security Gateway
3G Access Controller
Operational Support Systems
Network Orchestration System
Iu-h/IPSec
NTP
Standard 3G phones
S8/16 AP
E16/24 AP
C4/8 AP
Northbound FM/PM/CM
Iu-h
TR-69, HTTP
NTPv4
2. Access Points (APs) continuously log internal trace.
1. AMS Configures AP Diagnostic Reporting
4. OCS processes SONiX log files
3. On Call Drop trigger, 3GAP uses HTTP(S) of SONiX Log files to NOS file server
5. OCS User Interface available for offline analysis
Before and after
Correlating signalling with the radio
Handover configuration
– Simple requirement right?– When the signal gets too weak, we hand over to a neighbour
– True, but which neighbour?– The strongest, surely.
– Well, yes, but not always– Eh?
Handover Configuration
– You can read the values from a live network using a test mobile
– But I’ll let you do that
– Two things:– 30-odd parameters – plenty of
ways of getting it wrong– Set 14 – we found many of
them
– Need good defaults – then adapt them
UE issues
– It focusses the mind when your bugs appear on YouTube
– Five stages of bug fixing:
– Denial– It’s not us, it’s the phone,
or the network, or the user
– Anger– Why didn’t they raise it
earlier, before it went critical
– Bargaining– Well, how much of it do
we really need to fix? Can we just hack it?
– Depression– Man, that’s the third field
escape this month– Acceptance
– Ok, we’ll fix it - properly
UE Issues
– Pre-standard Fast Dormancy
– A smartphone eager to enter fast dormancy would release the channel too early, especially if the LAU Accept was delayed a bit
– Process would repeat ad infinitum
– Who had to fix it? We did.
FrequencyMacrocells
Small-cell
f1 f2 f3
FrequencyMacrocells
Small cell
f1 f2
FrequencyMacrocells
Small cell
f1 f2
(a)
(b)
(c)
FrequencyMacrocells
Small cell
f1 f2
(d)
Frequency Assignment Options
– ‘Correct’ configuration depends on existing operator spectrum holdings and the way in which they are used currently
– Starting with a clear channel for femto is common where available, but is not essential
– Ultimately highest spectrum efficiency from avoiding ‘hard’rules, but adjusting according to location and loading
Interference Management - Co-channel radio effects
– Focus on the effects of the femto on the macro network:– DL: creation of a deadzone around the femto– UL: noise rise in the macro network
– and the effect of the macro on the femto network:– DL: femtocell reselection issues– UL: noise rise in the femto
FUE
F
FUE
MUE
A,G
D,J
B,H
C,I
EF
F
FUE
MUE
Femto AP
Femto UE
Macro UE
Apartments
MacroNodeB
Interference path
UE Association
F
Small-cell-to-macro downlink interference
– If the femto power is fixed, the deadzone can become large when the macro network is weak
– tune femto power according to measured macro power using Network Listen
femto only
femto+macro
macro only
AP CPICH coverage
Indoor + outdoor walk-test
Indoor walk-testpeak outdoor femto RSCP
~ -60dBm
Macrocell CPICH Coverage – ground floor
macro RSCP at position of peak outdoor RSCP ~ -80dBm
=>Ec/Io ~-20dB => blocking
Downlink CPICH setting
Power = DL-RSSI +
EcNo-target +MAPL
Power adapts to ensure the cell stays close to right-size
Uplink noise rise
– In normal CS voice operation
– Per UE noise rise in macro ~0.01dB
– In HSUPA though,– Per UE noise rise in the
macro (red arrow) can by be ~1dB
– Therefore has to be managed
– Uplink power cap– Fixed now, adaptive later
– Careful HO tuning
UL DCH Tx Power capping
It’s important to cap the UL power to ensure
this
this
doesn’t turn into
Macro to femto uplink interference - HSUPA
– With a high power macro UE in the femtocell, the uplink Ec/No will be affected, and may affect the sustainable HSUPA throughput.
– These graphs show the theoretical maximum effect, based on FRC#3 Ped A channel for 30% and 70% maximum rate respectively.
UL adaptive gain
– The system monitors UL noise and adapts receiver gain to maintain it at a constant level
– Power control adapts nearby FUE power to maintain performance
– Nearby MUEs appear attenuated, and therefore interfere less
– Dynamic behaviour is important to ensure macro is not degraded due to statically high FUE UL power
Baseband processor R
x
gain control
Concluding remarks
– We’ve created (with Picochip, Aricent, Cisco and other partners) the biggest W-CDMA residential small-cell deployment in the world
– We’ve achieved better-than-macro performance on key network KPIs
– It’s become a key part of the network strategy to manage customer satisfaction and deployment netex
– The network continues to grow strongly
– Thanks for your attention