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LTE_Femtocells

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LTE_Femtocells Powered By Docstoc
					Arrate Alonso Gómez (e0728412)
Mobile Communications Seminar
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
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
  2.Network architecture and
  Performance
                                         Features of femtocells
                      INTEROPERABILITY        Transparent access
                     Key requirements for co-channel deployment of femtocells
                                              Standard interfaces
Auto-Configuration                                  In the downlink: Maximum Transmit Power has to be
                     SCALABILITY             Integration into the core without
                                                        configured
                                                    In the uplink: User-equipment’s power has to be
                                              decreasing the performance of the
                                              macrocelllimited
Public Access        POWER CONTROL                 Prevents excessive interference between UEs located
                                              In the Downlink: Ensure a constant radius.
                                             In the Uplink: low pre definable impact to working in the
                                                       close to a private owned femtocells
                                              macrocells
                                                       same frequency range.
                                                    Also prevents strong downlink interference created
                                                       by UEs not connected to near femtocells.
             2.Network architecture and
                   Performance
DOWNLINK:
Event                       Why?
Drop in the macrocell       1.   Low transmit power of
throughput caused by             the femtocells in the
the increase of active           downlink
femtocells from 10 to 100   2.   Wall separation
is minimal
Theoretically achievable    1.   Small distance to the
femtocell throughput is          femtocell (Indoors)
very    high   as    the    2.   Wall separation
deployments are indoors
 high SIRs
Increasing the number       1.   Small size of each cell
of femtocells from 10 to    2.   Wall separation
100 does not change the                                    CDF of downlink throughputs for
downlink throughput of                                     locations within the central macrocell [1]
the femtocells
        2.Network architecture and
    UPLINK:
              Performance
Event                            Why?
Drop in the macrocell            Fast power control in the
throughput caused by the         uplink for femtocells of UEs
increase of active femtocells
from 10 to 100 is minimal

Theoretically      achievable    1.   High signal to interference
femtocell throughput is very          ratios due to the small
high as the deployments are           distance to the femtocell
indoors  high SIRs              2.   Wall separation.

Increasing the number of         The SIR can drop up to 10 dB,
femtocells from 10 to 100 in     resulting in a reduction in
the same macrocell sector,       uplink throughput.
reduces      the    maximum                                         CDF of uplink throughputs for locations
allowed interference per UE is                                      within the central macrocell [1]
reduced by a factor of 10 
performance of the femtocell
reduced but not significantly
           2.Network architecture and
                 Performance
 Interference Management
  Interference Management 3G       Femtocells
     Planned deployment              UNPLANNED DEPLOYMENT !!!
     Frequency/Code reuse


PROBLEM
Macrocell and femtocells are working in the same
frequency range
 Co-Channel Interference (CCI)

SOLUTION : TWO-TIER NETWORK
1. Deployment in separate carriers (Split RF
   Spectrum)
2. Intelligent algorithms at femtocells (Shared RF
   Spectrum)
                                                         A femtocell based two-tier CDMA
                                                         network [2]
     3.Financial Analysis of a Pico-
 Cellular Home Network Deployment
  Wireless Network Evolution

      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 …

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

                                 Macrocell case              Home-Cell Case
Capital Expenditure (CapEx)         Cost per base station      No equipment costs
                                    Core UMTS                  No Installation costs
                                    Core packet routers
Operational Expenditure (OpEX)      Cost of maintenance        No maintenance costs
                                    Site running costs
                                    Backhaul costs              HOME BROADBAND
                                                                 WOULD BE SUBSIDIZED BY
                                                                 THE OPERATOR!!
    3.Financial Analysis of a Pico-
Cellular Home Network Deployment
Impact Analysis
Event                     Reason
Small fraction of HBS        Randomly distributed
achieve a full coverage       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].
      3.Financial Analysis of a Pico-
  Cellular Home Network Deployment
    Impact Analysis
Event                            Reason
Home Network CapEx and               Both very low for the
OpEx similar                         savings applied to both
Macro cellular Network OpEx         OpEx are the most
dominate the total annual            expensive cost due to
costs.                               its periodicity.
Macrocellular costs decrease        High user coverage
quickly with low percentage of       achievable with a
HBS                                  relatively small fraction
                                     of HBS

 Characteristic Point:                                           Network costs for an operator with
 Total network cost minimize at 30% HBS                          40% market share and 64 user per
                                                                 macrocell [3].
 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“
                           5.Conclusions
1.   Network architecture, Performance and Interference Management
            Performance analysis                          Macrocell        Femtocell
                                                           Performance      Performance
                                    Downlink                  Unchanged       High theoretical
                                    (from 10 to 100 HBS)       throughput       unchanged
                                                                                throughput
                                    Uplink                    Unchanged       Performance
                                    (from 10 to 100 HBS)       throughput       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).
                           5.Conclusions
2.       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)

3.   UMB and LTE for Femtocells
           New generation flat, low cost architectures
           Hybrid mobile network
           New broadband experience for the users
                    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 (PIMRC’07), 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.
  Many
thanks for
   your
attention

				
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posted:2/22/2012
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