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