Building the World’s Largest Residential Small-Cell network
Building the World’s LargestResidential Small-Cell network Nick Johnson – CTO, ip.access 3 Oct 2012
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 chainAricent Ip.access Cisco3G macro stack sw AP (HNB) DPH-xxx ASR-5K (HNB-GW) Ip.access AC (HNB-GW) 3G Small Cell NOS (HMS) BAC AT&T RAN Field supportPicochipBaseband SoC + ATT lab supportPHY s/w Network Ops Ref hw design 3G sw Manuf. support
OysterCatcher™ architecture 2. Access Points (APs) continuously log internal trace. 3G Access Controller Iu-h Iu-CS Security Iu-h/IPSec Gateway E16/24 APStandard 1. AMS Configures AP3G phones TR-69, HTTP Diagnostic ReportingIu-PS 3. On Call Drop trigger, 3GAP uses HTTP(S) of SONiX Log files to NOS NTPv4 file server NTP Network Orchestration Existing core S8/16 AP System network 4. OCS processes SONiX log files Operational Northbound 5. OCS User Interface Support Systems availableFM/PM/CM for offline analysis C4/8 AP
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.
Frequency Assignment Options– ‘Correct’ configuration depends on Small-cell existing operator spectrum (a) holdings and the way in which they Macrocells are used currently Frequency f1 f2 f3– Starting with a clear channel for Small cell femto is common where available, (b) but is not essential Macrocells Frequency f1 f2– Ultimately highest spectrum efficiency from avoiding ‘hard’ Small cell rules, but adjusting according to (c) Macrocells location and loading Frequency f1 f2 Small cell (d) Macrocells Frequency f1 f2
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 A,G F FUE D,J Macro FUE NodeB F B, E H MUE UE Association F C,I Interferenc e path F Femto AP Apartments FUE Femto UE MUE Macro UE
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 macro only femto+macro femto only
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 doesn’t turn into this
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 Baseband Rx performance processor– Nearby MUEs appear attenuated, and therefore interfere less gain control– Dynamic behaviour is important to ensure macro is not degraded due to statically high FUE UL power
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