LTE Femtocells

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LTE Femtocells

• Arrate Alonso Gómez (e0728412)
• Mobile Communications Seminar

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Overview

1. Introduction
2. Network architecture, Performance and
   Interference Management
3. Financial Analysis of a Pico-Cellular Home
   Network Deployment
4. UMB and LTE for Femtocells
5. Conclusions

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1. Introduction

• WHAT IS A FEMTOCELL?
• Small cellular base station
• Limited transmission power
• Limited user support to 8 users
• Plug Play
• Extension of the operators cellular networks

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2.Network architecture and Performance
Features of femtocells Features of femtocells
INTEROPERABILITY Transparent access Standard interfaces
SCALABILITY Integration into the core without decreasing the performance of the macrocell
POWER CONTROL In the Downlink Ensure a constant radius. In the Uplink low pre definable impact to macrocells
Key requirements for co-channel deployment of femtocells Key requirements for co-channel deployment of femtocells
Auto-Configuration In the downlink Maximum Transmit Power has to be configured In the uplink User-equipments power has to be limited
Public Access Prevents excessive interference between UEs located close to a private owned femtocells working in the same frequency range. Also prevents strong downlink interference created by UEs not connected to near femtocells.
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2.Network architecture and Performance

• DOWNLINK

Event Why?
Drop in the macrocell throughput caused by the increase of active femtocells from 10 to 100 is minimal Low transmit power of the femtocells in the downlink Wall separation
Theoretically achievable femtocell throughput is very high as the deployments are indoors ? high SIRs Small distance to the femtocell (Indoors) Wall separation
Increasing the number of femtocells from 10 to 100 does not change the downlink throughput of the femtocells Small size of each cell Wall separation

• CDF of downlink throughputs for locations within
  the central macrocell 1

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2.Network architecture and Performance

• UPLINK

Event Why?
Drop in the macrocell throughput caused by the increase of active femtocells from 10 to 100 is minimal Fast power control in the uplink for femtocells of UEs
Theoretically achievable femtocell throughput is very high as the deployments are indoors ? high SIRs High signal to interference ratios due to the small distance to the femtocell Wall separation.
Increasing the number of femtocells from 10 to 100 in the same macrocell sector, reduces the maximum allowed interference per UE is reduced by a factor of 10 ? performance of the femtocell reduced but not significantly The SIR can drop up to 10 dB, resulting in a reduction in uplink throughput.

• CDF of uplink throughputs for locations within
  the central macrocell 1

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2.Network architecture and Performance

• Interference Management

Interference Management 3G Femtocells
Planned deployment Frequency/Code reuse UNPLANNED DEPLOYMENT !!!
PROBLEM Macrocell and femtocells are working in
the same frequency range ? Co-Channel
Interference (CCI)

• SOLUTION TWO-TIER NETWORK
• Deployment in separate carriers (Split RF
  Spectrum)
• Intelligent algorithms at femtocells (Shared RF
  Spectrum)

• A femtocell based two-tier CDMA network 2

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3.Financial Analysis of a Pico-Cellular Home
Network Deployment

• Wireless Network Evolution

From a NETWORK OPERATOR POINT OF VIEW From a NETWORK OPERATOR POINT OF VIEW
Time Terms Short Term Long Term
Expense Terms Operational Expenditure Capital Expenditure

• Evaluation Scenario

Deployments to be considered Deployments to be considered
Femto-cellular deployment Randomly placed
Macro-cellular deployment Best-case scenario

• Overview of macro-cellular underlay network with
  femto-cellular home base station overlay
  deployment 3.

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3.Financial Analysis of a Pico-Cellular Home
Network Deployment

• Economic Models

Macrocell case Home-Cell Case
Capital Expenditure (CapEx) Cost per base station Core UMTS Core packet routers No equipment costs No Installation costs
Operational Expenditure (OpEX) Cost of maintenance Site running costs Backhaul costs No maintenance costs
Operational Expenditure (OpEX) Cost of maintenance Site running costs Backhaul costs HOME BROADBAND WOULD BE SUBSIDIZED BY THE OPERATOR!!
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3.Financial Analysis of a Pico-Cellular Home
Network Deployment

• Impact Analysis

Event Reason
Small fraction of HBS achieve a full coverage Randomly distributed HBS
EXAMPLE Operator with 40 market share and in
which 20 of its customers have home base
stations deployed, those home base stations alone
will satisfy approximately 80 of the total
demand.

• Fractional user coverage for different operator
  market share 3.

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3.Financial Analysis of a Pico-Cellular Home
Network Deployment

• Impact Analysis

Event Reason
Home Network CapEx and OpEx similar Both very low for the savings applied to both
Macro cellular Network OpEx dominate the total annual costs. OpEx are the most expensive cost due to its periodicity.
Macrocellular costs decrease quickly with low percentage of HBS High user coverage achievable with a relatively small fraction of HBS
Characteristic Point Total network cost
minimize at 30 HBS

• Network costs for an operator with 40 market
  share and 64 user per macrocell 3.

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4. UMB and LTE for Femtocells

• UMB and LTE OFDMA based
• Higher spectral efficiencies
• Low latency
• High peak data rate
• All-IP
• Key feature for FEMTOCELL deployments

• New generation femtocells Higher order
  modulations
• Improve self-configuration
• Improve self-provisioning
• Improve self-optimization

• Mobile operators may choose to introduce
  islands of 4G in an ocean of 3G

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5.Conclusions

• Network architecture, Performance and
  Interference Management
• Performance analysis

Macrocell Performance Femtocell Performance
Downlink (from 10 to 100 HBS) Unchanged throughput High theoretical unchanged throughput
Uplink (from 10 to 100 HBS) Unchanged throughput Performance affected but throughput still good

• CCI Management
• Normal case None overpopulated area, no CCI to
  be taken into account.
• Worst case Femto cell overpopulated urban area
• Solution Two-tier layer with shared RF spectrum
  and TH-CDMA physical layer (7x improvement).

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5.Conclusions

• Financial Analysis of a Pico-Cellular Home
  Network Deployment
• Macrocell coverage less economically viable with
  higher demand
• Deploying HBS with small fraction of users is
  finantially a better chance and also better RF
  performance.
• Femtocells not only a good solution for users but
  also for vendors (more service for nearly any
  investments)

• UMB and LTE for Femtocells
• New generation flat, low cost architectures
• Hybrid mobile network
• New broadband experience for the users

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6.References

• 1 H. Claussen., Performance of Micro- and
  co-Channel Femtocells in Hierarchical Cell
  Structure, in Proceedings 18th Annual IEEE
  International Symposium on Personal, Indoor and
  Mobile Radio Communications (PIMRC07), 2007.
• 2 V. Chandrasekhar and J.G. Andrews., Uplink
  Capacity and Interference Avoidance for
  Two-Tier Cellular Networks in Proceedings
  IEEE GLOBECOM, 2007.
• 3 H. Claussen and L.T.W. Ho and L.G. Samuel.,
  Financial Analysis of a Pico-Cellular Home
  Network Deployment, in Proceedings
  International Conference on Communications
  (ICC), 2007.
• 4 Qualcomm., Femtocells and WLAN Complement
  3G and Beyond, December 2007.

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Many thanks for your attention