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LTE Femtocells By Dr. Doug Pulley, picoChip
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LTE Femtocells By Dr. Doug Pulley, picoChip

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picoChip sponsored LTE Focus 2010, a one-day event that offered the latest views from LTE operators, analysts and technology experts on the evolution and deployment path towards LTE. …

picoChip sponsored LTE Focus 2010, a one-day event that offered the latest views from LTE operators, analysts and technology experts on the evolution and deployment path towards LTE.

Dr Doug Pulley hosted an evening seminar on 'Deploying small cell architectures for LTE'.

Can be downloaded from http://www.picochip.com/event/18/

Published in: Technology

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  • @rogerforsen - updates from Picochip or updates on Femtocells? In case of latter, see http://3g4g.blogspot.com/2013/02/small-cell-standardization-in-3gpp.html
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  • Hi, also any updates from 2010 to now, roger.forsen@tieto.com
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  • Hi Dr. Doug,,,

    I would appreciate if you can share with me the LTE Femtocell Presentation, my email=zzeennoo22@yahoo.com.
    you did a great work, many thanks for you.
    Regards,,,
    Zeene,,,
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  • 1. LTE Femtocells Dr Doug Pulley CTO & co-Founder Slide 1 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 2. Agenda picoChip, femtocells and Self Organising Networks: An Overview Why femtos for LTE? The physics Principles of SON Femtocell taxonomy Handover Interference mitigation Slide 2 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 3. picoChip, femtocells and SON An overview of the what and why of femtocells Slide 3 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 4. picoChip Fabless „Innovator of the Year‟ Semiconductor Doug Pulley picoChip CTO April 2010 company Femtocell market picoChip, Bath,UK leader 150+ employees Major development locations: UK, China picoChip, Beijing, China Slide 4 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 5. A what-o-cell? The traditional definition femtocell - noun a low-power domestic access point… …using conventional mobile technology …in licensed spectrum …generating coverage and capacity …over internet-grade backhaul …at prices comparable with Wi-Fi access points …with full operator management Generic Femto Network Architecture Slide 5 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 6. High hopes to High Street… Vodafone AT & T  Launched January 2010  National launch March 2010  Connects to Vodafone network  Connects to AT&T network  Minimum download speed 1MB per second  Supports up to 4 voice or data users at once  Up to 4 users at once (up to 32 can be registered)  Seamless call hand-over Additional Countries launching… Slide 6 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 7. 5 years of Industry Leadership  Demonstrated industry‟s first femtocell: 3GSM 2005  Coined the term „femtocell‟  First femtocell chip: PC202 in 2006  Founder members of Femto Forum Elected to Board of Directors 2007 to date Chair WG1 (Marketing) Lead author for WG2 interference study (CDMA) Co-lead author for WG2 interference study (OFDMA) Active in 3GPP RAN – co-authored TRs on HNB and HeNB  First to demonstrate end-end IOT with 3rd party gateway  Commercial carrier launches:  Vodafone, AT&T, Softbank, SFR, etc  60+ in trials Slide 7 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 8. but femtocells are not just for Christmas… Residential Metro Enterprise Rural Slide 8 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 9. Why does LTE need femtos? signal 64QAM 60% of mobile traffic in-building 16QAM QPSK wall distance LTE is not magic! Slide 9 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 10. “A game of two halves”: 3GPP Cell Specification Base station class Minimum coupling loss Wide Area 70dB Medium Range (WCDMA not LTE) 53dB Local Area 45dB H(e)NB 45dB (assumed not specified) Slide 10 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 11. Base Station Taxonomy AKA Max Tx Power Range Typical Mobility Simultaneous Users/UEs Residential Home BS ~13dBm <50m 4-8 <10km/h Femtocell ≤20dBm SISO ≤17dBm per ant MIMO Enterprise Home BS or ≤24dBm <300m 16-64 <30km/h Femtocell Local Area BS (LTE up to 80) Rural Local Area BS ≤24 or 38dBm >2m 16-64 <120 km/h Femtocell or <2000m (LTE up to 80) Medium Range BS Metro Local Area BS ≤24dBm >2 m 16-64 <120 km/h Femtocell <2000 m Slide 11 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 12. So how does a femtocell work…  plug-in and turn on  listens to network environment  adjusts: power levels; carrier; codes  self organizes into mobile network (SON)  connects through broadband  ipsec tunnel established to carrier  remote management  provides private mobile broadband cell  your coverage  your capacity And what does this mean in LTE HeNB? Slide 12 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 13. LTE Self Organising Networks: SON eNB power on (or cable connected) a-1 : configuration of IP address (A) Basic Setup and detection of OAM a-2 : authentication of eNB/NW a-3 : association to aGW Self-Configuration (pre-operational state) a-4 : downloading of eNB software (and operational parameters) (B) Initial Radio b-1 : neighbour list configuration Configuration b-2 : coverage/capacity related parameter configuration Self-Optimisation (operational state) (C) Optimization / c-1 : neighbour list optimisation Adaptation c-2 : coverage and capacity control But what if you have millions of self-installed eNBs? Slide 13 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 14. SON Functionality SON covers a number of operations:  Self Configuration  This can be a periodic event determined by the network operator.  It uses OAM data and NMM measurements for the configuration procedure  Self Optimisation  This is a continuous process where extra data us gathered from e.g. UE Measurements, to optimise parameters used in the femtocell  Aimed at optimisations for local dynamic conditions  Stays within OAM parameters  Self Healing  To deal with unusual circumstances such as frequent switching of UE between Macro and Home eNodeB.  Self Maintenance, Self Planning, Self Tuning etc.. Slide 14 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 15. Femtocell Access Point SON/RRM Technology: Where it comes from and goes to.. Deployment Modelling System Test 3GPP H(e)NB Recommendations IOT and FAP and Carrier Integration Verification FF Recommendations Slide 15 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 16. Provisioning and OA&M Zero Touch Installation Femtocell configuration via OA&M Slide 16 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 17. Zero Touch Installation OAM Configuration via TR-069 Establish secure network connection Self-configuration using NMM Plug in and turn on Start transmitting Synchronisation via NMM, GPS Register or NTP with HeNB-GW over S1AP Slide 17 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 18. Zero Touch Installation  Zero Touch Installation combines the various aspects of FAP application software in addition to other hardware functions such as NMM to allow Home eNodeB to be self configured after power up  Some aspects of Zero Touch Installation can be done on a more frequent basis such as:  OAM data arriving from network  NMM updates  Synchronisation updates  Etc.. Slide 18 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 19. Femtocell Configuration via TR-069 Alternatives using HeMS SSL/TLS TR-069 TR-069 ACS FTP File Server HeNB (TR-069 Sec GW agent) S1AP IPsec tunnel HeNB GW EPC  TR-069 used for femtocell Configuration Management  TR-196 = femtocell data model (updated to support LTE)  3GPP have defined updates to:  E-UTRAN configurable parameters  Performance Management  Fault Management Slide 19 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 20. Femtocell Synchronisation A howto Slide 20 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 21. Why is it required?  Handover  Handsets do not follow same frequency requirements as Base stations  Handsets derive accurate frequency from Base stations  If femto and macro are not synchronised, HO may fail or call is disrupted  Network Interference  There can also be issues of interference between networks, typically reducing the call quality and network capacity  Frequency accuracy also allows the femtocell to “sniff out” adjacent cell sites, ensuring good behaviour to reduce interference BS Class Frequency Accuracy Wide Area 50 ppb Local Area 100 ppb Home 250 ppb Slide 21 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 22. Available Timing References  Timing over Packet NTP  “Enhanced” NTP Master NTP INTERNET (Network Time Protocol) client NTP client  GPS signal  Indoor solutions available in the market GPS device  Broadcast information  Adjacent macro cells Radio Scan  GSM 3G Macro  WCDMA 2G Macro 4G Macro  LTE  TV Slide 22 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 23. Femtocell Handovers Outbound (femtocell to macrocell) Inbound (macrocell to femtocell) Femtocell to femtocell Slide 23 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 24. Femtocell Handover  HeNBs have been built into LTE from the beginning  The UE understands the concepts of:  HeNB name (SIB 9)  CSG IDs (SIB 1)  Open/closed access (SIB 1)  CSG physical cell ID range (SIB 4)  In connect mode handover controlled by (H)eNB based on measurements from UE and/or network loading  In idle mode, UEs have an autonomous search function to find HeNBs  Handover to UMTS, GSM and CDMA2000 also defined Slide 24 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 25. Femto-to-Macro Outbound Handover EPC S1 S1 HeNB-GW eNB HeNB HeNB  Same principle as existing macro-to-macro handover. But no X2 interface, so signalling is via S1 Slide 25 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 26. Macro-to-Femto Inbound Handover PhysCell_Id4 PhysCell_Id1 PhysCell_Id2 PhysCell_Id3  Same principle as existing macro-to-macro handover. But no X2 interface, so signalling is via S1  UE autonomously detects HeNBs.  HeNBs have an unique Physical Cell ID within the macrocell the UE is currently connected  Release 9 defines how macrocell identifies femtocells where UE is CSG member Slide 26 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 27. Femto-to-Femto Handover  Same principle as existing macro-to-macro handover  Handled entirely within the HeNB-GW, via S1 HeNB-GW S1 HeNB HeNB S1 Part of the same CSG – eg HeNB enterprise or HeNB campus  If supported X2 could be used for handover Slide 27 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 28. Interference Mitigation Keep the noise down! Slide 28 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 29. Deployment Considerations Separation between Femto AP Femto can be on a dedicated and macrocell carrier frequency or co-channel with macro layer. Shared or Dedicated carrier Neighbour macrocell Femto UE Femto AP Indoors or outdoors Macro UE Indoors or outdoors Open, Closed or Hybrid Access “Hybrid” access added in Rel-9 – allows all UEs access the femto but gives priority (higher QoS, etc) to those in the “Closed Subscriber Group” Slide 29 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 30. Interference Scenarios – Detailed Case 1  UE Registered in HeNB is radiating at a power level that can be received by the Macro eNodeB  This is received as noise by Macro eNodeB and makes it more difficult to listen to the UEs camping on it  Depending on the interference level, Macro eNodeB would tell UEs to raise their power levels Slide 30 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 31. Interference Scenarios Aggressor Victim 1 UE attached to Home eNode B Macro eNode B 2 Home eNode B UE attached to Macro eNode B 3 UE attached to Macro eNode B Home eNode B 4 Macro eNode B UE attached to Home eNode B 5 UE attached to Home eNode B Home eNode B 6 Home eNode B UE attached to Home eNode B 1 Attached 6 BS Victim 4 UE Victim 2 5 3 Slide 31 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 32. Deployment Modelling and Simulation  To determine algorithms and parameter values, extensive simulation is necessary  picoChip has developed two in-house simulation systems necessary for evaluating deployment issues:  macro/femto network co-existence  indoor femtocell performance  These have been used to provide results for activities in Femtoforum and 3GPP on WCDMA, LTE and TDSCDMA systems and benchmarked with other leaders Slide 32 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 33. Macro/Femto Coexistence Simulator  Can test many scenarios:  co-channel/adjacent channel  open, closed and hybrid acccess  Can test:  interference mitigations  RF design parameters  Can determine:  femto network performance  any macro impairments  … Slide 33 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 34. Indoor Wireless Modelling Semi-detached Apartment block Slide 34 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 35. System Modelling  Femto Houses or apartments dropped within macro coverage area 10 m 10 m 10 m house 10 m Max femto BS area 10 m 2 apartment “stripes” with multiple floors Max UE area house Slide 35 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 36. Enterprise Modelling Three femtocell deployment in larger enterprise Slide 36 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 37. Scenario 2: Femto to Macro Downlink: Macro Deadzone Femto coverage area Femto downlink SINR > threshold Neighbour macrocell Femto UE Femto AP Macro Deadzone Macro DL SINR < threshold Slide 37 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 38. Protecting the Macrocell DL  Transmissions from nearby uncontrolled HeNB results in DL interference  Most severe for macro UEs furthest from the macrocell  HeNB can mitigate by:  Enabling hybrid access, with HeNB power set to optimize total system (femtocell + macrocell) performance eg. based on measurement reports from visiting UEs  smart usage of the sub-carriers in the case the macro eNB is using fractional frequency re-use (avoid those SCs being used nearby)  smart power control where HeNB estimates pathloss from macro eNB to macro UE (by means of “sniffing”) and sets its power appropriately. Enhancement is to only provide full protection when nearby victim UEs are detected (e.g. based on Zadoff-Chu sequence properties). Slide 38 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 39. Network Monitor Mode (aka “sniffer”) DAC Transmitter Baseband DL PHY & UL DL Rx NMM ADC Receiver UL Rx Duplexer Measurement Type Purpose Co-channel RSRP Setting femto Tx power for desired coverage and Co-channel RSRQ protection of co-channel MUEs (incl. hybrid access) Adjacent-channel carrier RSRP Setting femto Tx power for protection of adjacent- Adjacent-channel ref signal Rx channel MUEs, including adjacent channel operators power Uplink Ref Signal Detection Detection of Victim UEs Read system info Tx power (for pathloss calc), CSG status, Cell ID etc. Slide 39 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 40. Setting Femto Maximum Tx Power Femto Pmax for different Co-Channel Target Deadzones 30 25 70 dB 20 60 dB 15 Femto Pmax (dBm) 50 dB 10 40 dB 5 0 -5 -10 -15 -20 -90 -80 -70 -60 -50 -40 Macro RSSI (dBm) Slide 40 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 41. Adjacent Operator Protection Femto UE receive transmit filter spectrum Some signal power from the femtocell leaks into the adjacent ACS channel, according to its ACLR ACLR and the MUE ACS Adjacent Femto Tx Channel Channel 3GPP Requirement: If the adjacent channel belongs to a different operator, the femto must limit its transmit power to minimise interference to that operator Slide 41 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 42. Protecting the Macrocell UL  Transmissions from femto UEs results in a higher level of UL interference at macro eNB  Impact most severe if HeNB close to macro eNB.  Impact increases with femto density. ◘ Femto can mitigate by: ◘ Power control of its UEs based on pathloss estimates to limit “noise rise” at macro eNB to acceptable value. Ideally make adaptive e.g. acceptable noise rise per HeNB is a function of HeNB density. Requires feedback from macro eNB (e.g. via X2 in future releases). ◘ For PUCCH control channel, femto could use different set of subcarriers than the macro. Slide 42 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 43. Use of X2  One potential issue is that there could be a large number of femtos within the macro coverage area which could lead to complexity issues at the macro eNB if each femto had an X2 interface to the macro eNB  Two possible approaches to solving this  Have an X2 “concentration” function in an X2 proxy or gateway  Only send load indications in the direction from the macro to the femtos, rather than being bidirectional Macro Macro eNB eNB Home eNB X2 Load Indications X2 Load Indications Home X2 Load Indications X2 eNB Proxy Home eNB Home eNB Slide 43 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 44. Use of X2 - benefits  System sim, average UL cell throughput for macro (lower curves) and femto (upper curves) versus femto density. Femto provides “loose”, “tight” or “adaptive” (X2 based) protection to macro. 3GPP/FF apartment block deployment model. Slide 44 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 45. Protecting the Femtocell Uplink  Transmissions from nearby uncontrolled UEs results in a higher level of UL interference  Reflected in TS36.104 tests for Dynamic Range and ACS – upper limits increased for HeNB  Femto can mitigate with dynamic control of the receiver gain  Reduce gain to temporarily accommodate higher interference  Also known as adaptive noise figure  Attached femto UEs will power up to overcome interference  Small path loss to femto means UE have plenty of power headroom Slide 45 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 46. Protecting the Femtocell Downlink (femto-femto)  Transmissions from nearby uncontrolled HeNB results in DL interference  HeNB can mitigate by using a sub-set of sub-carriers not being used by other nearby HeNB. Both centralized control (e.g. at HeNB GW) or control at individual HeNBs has been considered by RAN4 Slide 46 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 47. Interference Mitigation Summary  DL interference to UEs attached to Macro eNodeB or neighboring HeNB  Adaptive transmit power control based on measurements of co-channel and adjacent-channel macro signal strength and/or smart usage of subcarriers.  “Sniffer” (aka Network Monitor Mode) functionality in HeNB to measure Macro DL transmissions  Enhancements based on nearby victim UE detection by HeNB  Balance required femto against macro performance, which may change with hybrid access femtocells  UL interference to Macro Node B  Implement UE “power cap” based on estimate of path loss to macro eNode B  Ideally the power cap should be adaptive such that interference contribution from individual HeNB is function of HeNB density  Support for X2 between macro eNodeB and HeNB desirable in future 3GPP releases Slide 47 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 48. Dr Doug Pulley CTO & co-Founder picoChip Ltd Address: Riverside Buildings, 108 Walcot Street, Bath, BA1 5BG Email: doug.pulley@picochip.com Website: www.picochip.com Slide 48 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010
  • 49. Slide 49 l 9 September 2010 l LTE Focus - Amsterdam l © picoChip 2010